resolver.c

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/*
 * Copyright (C) 2004-2015  Internet Systems Consortium, Inc. ("ISC")
 * Copyright (C) 1999-2003  Internet Software Consortium.
 *
 * Permission to use, copy, modify, and/or distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES WITH
 * REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
 * AND FITNESS.  IN NO EVENT SHALL ISC BE LIABLE FOR ANY SPECIAL, DIRECT,
 * INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
 * LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE
 * OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
 * PERFORMANCE OF THIS SOFTWARE.
 */

/*! \file */

#include <config.h>
#include <ctype.h>

#include <isc/counter.h>
#include <isc/log.h>
#include <isc/platform.h>
#include <isc/print.h>
#include <isc/string.h>
#include <isc/random.h>
#include <isc/socket.h>
#include <isc/stats.h>
#include <isc/task.h>
#include <isc/timer.h>
#include <isc/util.h>

#ifdef AES_SIT
#include <isc/aes.h>
#else
#include <isc/hmacsha.h>
#endif

#include <dns/acl.h>
#include <dns/adb.h>
#include <dns/badcache.h>
#include <dns/cache.h>
#include <dns/db.h>
#include <dns/dispatch.h>
#include <dns/ds.h>
#include <dns/edns.h>
#include <dns/events.h>
#include <dns/forward.h>
#include <dns/keytable.h>
#include <dns/log.h>
#include <dns/message.h>
#include <dns/ncache.h>
#include <dns/nsec.h>
#include <dns/nsec3.h>
#include <dns/opcode.h>
#include <dns/peer.h>
#include <dns/rbt.h>
#include <dns/rcode.h>
#include <dns/rdata.h>
#include <dns/rdataclass.h>
#include <dns/rdatalist.h>
#include <dns/rdataset.h>
#include <dns/rdatastruct.h>
#include <dns/rdatatype.h>
#include <dns/resolver.h>
#include <dns/result.h>
#include <dns/rootns.h>
#include <dns/stats.h>
#include <dns/tsig.h>
#include <dns/validator.h>

#ifdef WANT_QUERYTRACE
#define RTRACE(m)       isc_log_write(dns_lctx, \
                                      DNS_LOGCATEGORY_RESOLVER, \
                                      DNS_LOGMODULE_RESOLVER, \
                                      ISC_LOG_DEBUG(3), \
                                      "res %p: %s", res, (m))
#define RRTRACE(r, m)   isc_log_write(dns_lctx, \
                                      DNS_LOGCATEGORY_RESOLVER, \
                                      DNS_LOGMODULE_RESOLVER, \
                                      ISC_LOG_DEBUG(3), \
                                      "res %p: %s", (r), (m))
#define FCTXTRACE(m) \
                        isc_log_write(dns_lctx, \
                                      DNS_LOGCATEGORY_RESOLVER, \
                                      DNS_LOGMODULE_RESOLVER, \
                                      ISC_LOG_DEBUG(3), \
                                      "fctx %p(%s): %s", \
                                      fctx, fctx->info, (m))
#define FCTXTRACE2(m1, m2) \
                        isc_log_write(dns_lctx, \
                                      DNS_LOGCATEGORY_RESOLVER, \
                                      DNS_LOGMODULE_RESOLVER, \
                                      ISC_LOG_DEBUG(3), \
                                      "fctx %p(%s): %s %s", \
                                      fctx, fctx->info, (m1), (m2))
#define FCTXTRACE3(m, res) \
                        isc_log_write(dns_lctx, \
                                      DNS_LOGCATEGORY_RESOLVER, \
                                      DNS_LOGMODULE_RESOLVER, \
                                      ISC_LOG_DEBUG(3), \
                                      "fctx %p(%s): [result: %s] %s", \
                                      fctx, fctx->info, \
                                      isc_result_totext(res), (m))
#define FCTXTRACE4(m1, m2, res) \
                        isc_log_write(dns_lctx, \
                                      DNS_LOGCATEGORY_RESOLVER, \
                                      DNS_LOGMODULE_RESOLVER, \
                                      ISC_LOG_DEBUG(3), \
                                      "fctx %p(%s): [result: %s] %s %s", \
                                      fctx, fctx->info, \
                                      isc_result_totext(res), (m1), (m2))
#define FTRACE(m)       isc_log_write(dns_lctx, \
                                      DNS_LOGCATEGORY_RESOLVER, \
                                      DNS_LOGMODULE_RESOLVER, \
                                      ISC_LOG_DEBUG(3), \
                                      "fetch %p (fctx %p(%s)): %s", \
                                      fetch, fetch->private, \
                                      fetch->private->info, (m))
#define QTRACE(m)       isc_log_write(dns_lctx, \
                                      DNS_LOGCATEGORY_RESOLVER, \
                                      DNS_LOGMODULE_RESOLVER, \
                                      ISC_LOG_DEBUG(3), \
                                      "resquery %p (fctx %p(%s)): %s", \
                                      query, query->fctx, \
                                      query->fctx->info, (m))
#else
#define RTRACE(m) do { UNUSED(m); } while (0)
#define RRTRACE(r, m) do { UNUSED(r); UNUSED(m); } while (0)
#define FCTXTRACE(m) do { UNUSED(m); } while (0)
#define FCTXTRACE2(m1, m2) do { UNUSED(m1); UNUSED(m2); } while (0)
#define FCTXTRACE3(m1, res) do { UNUSED(m1); UNUSED(res); } while (0)
#define FCTXTRACE4(m1, m2, res) \
        do { UNUSED(m1); UNUSED(m2); UNUSED(res); } while (0)
#define FTRACE(m) do { UNUSED(m); } while (0)
#define QTRACE(m) do { UNUSED(m); } while (0)
#endif /* WANT_QUERYTRACE */

#define US_PER_SEC 1000000U
/*
 * The maximum time we will wait for a single query.
 */
#define MAX_SINGLE_QUERY_TIMEOUT 9U
#define MAX_SINGLE_QUERY_TIMEOUT_US (MAX_SINGLE_QUERY_TIMEOUT*US_PER_SEC)

/*
 * We need to allow a individual query time to complete / timeout.
 */
#define MINIMUM_QUERY_TIMEOUT (MAX_SINGLE_QUERY_TIMEOUT + 1U)

/* The default time in seconds for the whole query to live. */
#ifndef DEFAULT_QUERY_TIMEOUT
#define DEFAULT_QUERY_TIMEOUT MINIMUM_QUERY_TIMEOUT
#endif

#ifndef MAXIMUM_QUERY_TIMEOUT
#define MAXIMUM_QUERY_TIMEOUT 30 /* The maximum time in seconds for the whole query to live. */
#endif

/* The default maximum number of recursions to follow before giving up. */
#ifndef DEFAULT_RECURSION_DEPTH
#define DEFAULT_RECURSION_DEPTH 7
#endif

/* The default maximum number of iterative queries to allow before giving up. */
#ifndef DEFAULT_MAX_QUERIES
#define DEFAULT_MAX_QUERIES 75
#endif

/*%
 * Maximum EDNS0 input packet size.
 */
#define RECV_BUFFER_SIZE                4096            /* XXXRTH  Constant. */

/*%
 * This defines the maximum number of timeouts we will permit before we
 * disable EDNS0 on the query.
 */
#define MAX_EDNS0_TIMEOUTS      3

#define DNS_RESOLVER_BADCACHESIZE 1021
#define DNS_RESOLVER_BADCACHETTL(fctx) \
        (((fctx)->res->lame_ttl > 30 ) ? (fctx)->res->lame_ttl : 30)

typedef struct fetchctx fetchctx_t;

typedef struct query {
        /* Locked by task event serialization. */
        unsigned int                    magic;
        fetchctx_t *                    fctx;
        isc_mem_t *                     mctx;
        dns_dispatchmgr_t *             dispatchmgr;
        dns_dispatch_t *                dispatch;
        isc_boolean_t                   exclusivesocket;
        dns_adbaddrinfo_t *             addrinfo;
        isc_socket_t *                  tcpsocket;
        isc_time_t                      start;
        dns_messageid_t                 id;
        dns_dispentry_t *               dispentry;
        ISC_LINK(struct query)          link;
        isc_buffer_t                    buffer;
        isc_buffer_t                    *tsig;
        dns_tsigkey_t                   *tsigkey;
        isc_socketevent_t               sendevent;
        isc_dscp_t                      dscp;
        int                             ednsversion;
        unsigned int                    options;
        unsigned int                    attributes;
        unsigned int                    sends;
        unsigned int                    connects;
        unsigned int                    udpsize;
        unsigned char                   data[512];
} resquery_t;

struct tried {
        isc_sockaddr_t                  addr;
        unsigned int                    count;
        ISC_LINK(struct tried)          link;
};

#define QUERY_MAGIC                     ISC_MAGIC('Q', '!', '!', '!')
#define VALID_QUERY(query)              ISC_MAGIC_VALID(query, QUERY_MAGIC)

#define RESQUERY_ATTR_CANCELED          0x02

#define RESQUERY_CONNECTING(q)          ((q)->connects > 0)
#define RESQUERY_CANCELED(q)            (((q)->attributes & \
                                          RESQUERY_ATTR_CANCELED) != 0)
#define RESQUERY_SENDING(q)             ((q)->sends > 0)

typedef enum {
        fetchstate_init = 0,            /*%< Start event has not run yet. */
        fetchstate_active,
        fetchstate_done                 /*%< FETCHDONE events posted. */
} fetchstate;

typedef enum {
        badns_unreachable = 0,
        badns_response,
        badns_validation
} badnstype_t;

struct fetchctx {
        /*% Not locked. */
        unsigned int                    magic;
        dns_resolver_t *                res;
        dns_name_t                      name;
        dns_rdatatype_t                 type;
        unsigned int                    options;
        unsigned int                    bucketnum;
        char *                          info;
        isc_mem_t *                     mctx;

        /*% Locked by appropriate bucket lock. */
        fetchstate                      state;
        isc_boolean_t                   want_shutdown;
        isc_boolean_t                   cloned;
        isc_boolean_t                   spilled;
        unsigned int                    references;
        isc_event_t                     control_event;
        ISC_LINK(struct fetchctx)       link;
        ISC_LIST(dns_fetchevent_t)      events;
        /*% Locked by task event serialization. */
        dns_name_t                      domain;
        dns_rdataset_t                  nameservers;
        unsigned int                    attributes;
        isc_timer_t *                   timer;
        isc_time_t                      expires;
        isc_interval_t                  interval;
        dns_message_t *                 qmessage;
        dns_message_t *                 rmessage;
        ISC_LIST(resquery_t)            queries;
        dns_adbfindlist_t               finds;
        dns_adbfind_t *                 find;
        dns_adbfindlist_t               altfinds;
        dns_adbfind_t *                 altfind;
        dns_adbaddrinfolist_t           forwaddrs;
        dns_adbaddrinfolist_t           altaddrs;
        dns_forwarderlist_t             forwarders;
        dns_fwdpolicy_t                 fwdpolicy;
        isc_sockaddrlist_t              bad;
        ISC_LIST(struct tried)          edns;
        ISC_LIST(struct tried)          edns512;
        isc_sockaddrlist_t              bad_edns;
        dns_validator_t *               validator;
        ISC_LIST(dns_validator_t)       validators;
        dns_db_t *                      cache;
        dns_adb_t *                     adb;
        isc_boolean_t                   ns_ttl_ok;
        isc_uint32_t                    ns_ttl;
        isc_counter_t *                 qc;

        /*%
         * The number of events we're waiting for.
         */
        unsigned int                    pending;

        /*%
         * The number of times we've "restarted" the current
         * nameserver set.  This acts as a failsafe to prevent
         * us from pounding constantly on a particular set of
         * servers that, for whatever reason, are not giving
         * us useful responses, but are responding in such a
         * way that they are not marked "bad".
         */
        unsigned int                    restarts;

        /*%
         * The number of timeouts that have occurred since we
         * last successfully received a response packet.  This
         * is used for EDNS0 black hole detection.
         */
        unsigned int                    timeouts;

        /*%
         * Look aside state for DS lookups.
         */
        dns_name_t                      nsname;
        dns_fetch_t *                   nsfetch;
        dns_rdataset_t                  nsrrset;

        /*%
         * Number of queries that reference this context.
         */
        unsigned int                    nqueries;

        /*%
         * The reason to print when logging a successful
         * response to a query.
         */
        const char *                    reason;

        /*%
         * Random numbers to use for mixing up server addresses.
         */
        isc_uint32_t                    rand_buf;
        isc_uint32_t                    rand_bits;

        /*%
         * Fetch-local statistics for detailed logging.
         */
        isc_result_t                    result; /*%< fetch result  */
        isc_result_t                    vresult; /*%< validation result  */
        int                             exitline;
        isc_time_t                      start;
        isc_uint64_t                    duration;
        isc_boolean_t                   logged;
        unsigned int                    querysent;
        unsigned int                    referrals;
        unsigned int                    lamecount;
        unsigned int                    neterr;
        unsigned int                    badresp;
        unsigned int                    adberr;
        unsigned int                    findfail;
        unsigned int                    valfail;
        isc_boolean_t                   timeout;
        dns_adbaddrinfo_t               *addrinfo;
        isc_sockaddr_t                  *client;
        unsigned int                    depth;
};

#define FCTX_MAGIC                      ISC_MAGIC('F', '!', '!', '!')
#define VALID_FCTX(fctx)                ISC_MAGIC_VALID(fctx, FCTX_MAGIC)

#define FCTX_ATTR_HAVEANSWER            0x0001
#define FCTX_ATTR_GLUING                0x0002
#define FCTX_ATTR_ADDRWAIT              0x0004
#define FCTX_ATTR_SHUTTINGDOWN          0x0008
#define FCTX_ATTR_WANTCACHE             0x0010
#define FCTX_ATTR_WANTNCACHE            0x0020
#define FCTX_ATTR_NEEDEDNS0             0x0040
#define FCTX_ATTR_TRIEDFIND             0x0080
#define FCTX_ATTR_TRIEDALT              0x0100

#define HAVE_ANSWER(f)          (((f)->attributes & FCTX_ATTR_HAVEANSWER) != \
                                 0)
#define GLUING(f)               (((f)->attributes & FCTX_ATTR_GLUING) != \
                                 0)
#define ADDRWAIT(f)             (((f)->attributes & FCTX_ATTR_ADDRWAIT) != \
                                 0)
#define SHUTTINGDOWN(f)         (((f)->attributes & FCTX_ATTR_SHUTTINGDOWN) \
                                 != 0)
#define WANTCACHE(f)            (((f)->attributes & FCTX_ATTR_WANTCACHE) != 0)
#define WANTNCACHE(f)           (((f)->attributes & FCTX_ATTR_WANTNCACHE) != 0)
#define NEEDEDNS0(f)            (((f)->attributes & FCTX_ATTR_NEEDEDNS0) != 0)
#define TRIEDFIND(f)            (((f)->attributes & FCTX_ATTR_TRIEDFIND) != 0)
#define TRIEDALT(f)             (((f)->attributes & FCTX_ATTR_TRIEDALT) != 0)

typedef struct {
        dns_adbaddrinfo_t *             addrinfo;
        fetchctx_t *                    fctx;
} dns_valarg_t;

struct dns_fetch {
        unsigned int                    magic;
        isc_mem_t *                     mctx;
        fetchctx_t *                    private;
};

#define DNS_FETCH_MAGIC                 ISC_MAGIC('F', 't', 'c', 'h')
#define DNS_FETCH_VALID(fetch)          ISC_MAGIC_VALID(fetch, DNS_FETCH_MAGIC)

typedef struct fctxbucket {
        isc_task_t *                    task;
        isc_mutex_t                     lock;
        ISC_LIST(fetchctx_t)            fctxs;
        isc_boolean_t                   exiting;
        isc_mem_t *                     mctx;
} fctxbucket_t;

typedef struct alternate {
        isc_boolean_t                   isaddress;
        union   {
                isc_sockaddr_t          addr;
                struct {
                        dns_name_t      name;
                        in_port_t       port;
                } _n;
        } _u;
        ISC_LINK(struct alternate)      link;
} alternate_t;

struct dns_resolver {
        /* Unlocked. */
        unsigned int                    magic;
        isc_mem_t *                     mctx;
        isc_mutex_t                     lock;
        isc_mutex_t                     nlock;
        isc_mutex_t                     primelock;
        dns_rdataclass_t                rdclass;
        isc_socketmgr_t *               socketmgr;
        isc_timermgr_t *                timermgr;
        isc_taskmgr_t *                 taskmgr;
        dns_view_t *                    view;
        isc_boolean_t                   frozen;
        unsigned int                    options;
        dns_dispatchmgr_t *             dispatchmgr;
        dns_dispatchset_t *             dispatches4;
        isc_boolean_t                   exclusivev4;
        dns_dispatchset_t *             dispatches6;
        isc_dscp_t                      querydscp4;
        isc_dscp_t                      querydscp6;
        isc_boolean_t                   exclusivev6;
        unsigned int                    nbuckets;
        fctxbucket_t *                  buckets;
        isc_uint32_t                    lame_ttl;
        ISC_LIST(alternate_t)           alternates;
        isc_uint16_t                    udpsize;
#if USE_ALGLOCK
        isc_rwlock_t                    alglock;
#endif
        dns_rbt_t *                     algorithms;
        dns_rbt_t *                     digests;
#if USE_MBSLOCK
        isc_rwlock_t                    mbslock;
#endif
        dns_rbt_t *                     mustbesecure;
        unsigned int                    spillatmax;
        unsigned int                    spillatmin;
        isc_timer_t *                   spillattimer;
        isc_boolean_t                   zero_no_soa_ttl;
        unsigned int                    query_timeout;
        unsigned int                    maxdepth;
        unsigned int                    maxqueries;

        /* Locked by lock. */
        unsigned int                    references;
        isc_boolean_t                   exiting;
        isc_eventlist_t                 whenshutdown;
        unsigned int                    activebuckets;
        isc_boolean_t                   priming;
        unsigned int                    spillat;        /* clients-per-query */

        dns_badcache_t  *               badcache;        /* Bad cache. */

        /* Locked by primelock. */
        dns_fetch_t *                   primefetch;
        /* Locked by nlock. */
        unsigned int                    nfctx;
};

#define RES_MAGIC                       ISC_MAGIC('R', 'e', 's', '!')
#define VALID_RESOLVER(res)             ISC_MAGIC_VALID(res, RES_MAGIC)

/*%
 * Private addrinfo flags.  These must not conflict with DNS_FETCHOPT_NOEDNS0
 * (0x008) which we also use as an addrinfo flag.
 */
#define FCTX_ADDRINFO_MARK              0x0001
#define FCTX_ADDRINFO_FORWARDER         0x1000
#define FCTX_ADDRINFO_TRIED             0x2000
#define FCTX_ADDRINFO_EDNSOK            0x4000
#define FCTX_ADDRINFO_NOSIT             0x8000

#define UNMARKED(a)                     (((a)->flags & FCTX_ADDRINFO_MARK) \
                                         == 0)
#define ISFORWARDER(a)                  (((a)->flags & \
                                         FCTX_ADDRINFO_FORWARDER) != 0)
#define TRIED(a)                        (((a)->flags & \
                                         FCTX_ADDRINFO_TRIED) != 0)
#define NOSIT(a)                        (((a)->flags & \
                                         FCTX_ADDRINFO_NOSIT) != 0)
#define EDNSOK(a)                       (((a)->flags & \
                                         FCTX_ADDRINFO_EDNSOK) != 0)


#define NXDOMAIN(r) (((r)->attributes & DNS_RDATASETATTR_NXDOMAIN) != 0)
#define NEGATIVE(r) (((r)->attributes & DNS_RDATASETATTR_NEGATIVE) != 0)

static void destroy(dns_resolver_t *res);
static void empty_bucket(dns_resolver_t *res);
static isc_result_t resquery_send(resquery_t *query);
static void resquery_response(isc_task_t *task, isc_event_t *event);
static void resquery_connected(isc_task_t *task, isc_event_t *event);
static void fctx_try(fetchctx_t *fctx, isc_boolean_t retrying,
                     isc_boolean_t badcache);
static void fctx_destroy(fetchctx_t *fctx);
static isc_boolean_t fctx_unlink(fetchctx_t *fctx);
static isc_result_t ncache_adderesult(dns_message_t *message,
                                      dns_db_t *cache, dns_dbnode_t *node,
                                      dns_rdatatype_t covers,
                                      isc_stdtime_t now, dns_ttl_t maxttl,
                                      isc_boolean_t optout,
                                      isc_boolean_t secure,
                                      dns_rdataset_t *ardataset,
                                      isc_result_t *eresultp);
static void validated(isc_task_t *task, isc_event_t *event);
static isc_boolean_t maybe_destroy(fetchctx_t *fctx, isc_boolean_t locked);
static void add_bad(fetchctx_t *fctx, dns_adbaddrinfo_t *addrinfo,
                    isc_result_t reason, badnstype_t badtype);
static inline isc_result_t findnoqname(fetchctx_t *fctx, dns_name_t *name,
                                       dns_rdatatype_t type,
                                       dns_name_t **noqname);
static void fctx_increference(fetchctx_t *fctx);
static isc_boolean_t fctx_decreference(fetchctx_t *fctx);

/*%
 * Increment resolver-related statistics counters.
 */
static inline void
inc_stats(dns_resolver_t *res, isc_statscounter_t counter) {
        if (res->view->resstats != NULL)
                isc_stats_increment(res->view->resstats, counter);
}

static inline void
dec_stats(dns_resolver_t *res, isc_statscounter_t counter) {
        if (res->view->resstats != NULL)
                isc_stats_decrement(res->view->resstats, counter);
}

static isc_result_t
valcreate(fetchctx_t *fctx, dns_adbaddrinfo_t *addrinfo, dns_name_t *name,
          dns_rdatatype_t type, dns_rdataset_t *rdataset,
          dns_rdataset_t *sigrdataset, unsigned int valoptions,
          isc_task_t *task)
{
        dns_validator_t *validator = NULL;
        dns_valarg_t *valarg;
        isc_result_t result;

        valarg = isc_mem_get(fctx->mctx, sizeof(*valarg));
        if (valarg == NULL)
                return (ISC_R_NOMEMORY);

        valarg->fctx = fctx;
        valarg->addrinfo = addrinfo;

        if (!ISC_LIST_EMPTY(fctx->validators))
                INSIST((valoptions & DNS_VALIDATOR_DEFER) != 0);

        result = dns_validator_create(fctx->res->view, name, type, rdataset,
                                      sigrdataset, fctx->rmessage,
                                      valoptions, task, validated, valarg,
                                      &validator);
        if (result == ISC_R_SUCCESS) {
                inc_stats(fctx->res, dns_resstatscounter_val);
                if ((valoptions & DNS_VALIDATOR_DEFER) == 0) {
                        INSIST(fctx->validator == NULL);
                        fctx->validator = validator;
                }
                ISC_LIST_APPEND(fctx->validators, validator, link);
        } else
                isc_mem_put(fctx->mctx, valarg, sizeof(*valarg));
        return (result);
}

static isc_boolean_t
rrsig_fromchildzone(fetchctx_t *fctx, dns_rdataset_t *rdataset) {
        dns_namereln_t namereln;
        dns_rdata_rrsig_t rrsig;
        dns_rdata_t rdata = DNS_RDATA_INIT;
        int order;
        isc_result_t result;
        unsigned int labels;

        for (result = dns_rdataset_first(rdataset);
             result == ISC_R_SUCCESS;
             result = dns_rdataset_next(rdataset)) {
                dns_rdataset_current(rdataset, &rdata);
                result = dns_rdata_tostruct(&rdata, &rrsig, NULL);
                RUNTIME_CHECK(result == ISC_R_SUCCESS);
                namereln = dns_name_fullcompare(&rrsig.signer, &fctx->domain,
                                                &order, &labels);
                if (namereln == dns_namereln_subdomain)
                        return (ISC_TRUE);
                dns_rdata_reset(&rdata);
        }
        return (ISC_FALSE);
}

static isc_boolean_t
fix_mustbedelegationornxdomain(dns_message_t *message, fetchctx_t *fctx) {
        dns_name_t *name;
        dns_name_t *domain = &fctx->domain;
        dns_rdataset_t *rdataset;
        dns_rdatatype_t type;
        isc_result_t result;
        isc_boolean_t keep_auth = ISC_FALSE;

        if (message->rcode == dns_rcode_nxdomain)
                return (ISC_FALSE);

        /*
         * A DS RRset can appear anywhere in a zone, even for a delegation-only
         * zone.  So a response to an explicit query for this type should be
         * excluded from delegation-only fixup.
         *
         * SOA, NS, and DNSKEY can only exist at a zone apex, so a postive
         * response to a query for these types can never violate the
         * delegation-only assumption: if the query name is below a
         * zone cut, the response should normally be a referral, which should
         * be accepted; if the query name is below a zone cut but the server
         * happens to have authority for the zone of the query name, the
         * response is a (non-referral) answer.  But this does not violate
         * delegation-only because the query name must be in a different zone
         * due to the "apex-only" nature of these types.  Note that if the
         * remote server happens to have authority for a child zone of a
         * delegation-only zone, we may still incorrectly "fix" the response
         * with NXDOMAIN for queries for other types.  Unfortunately it's
         * generally impossible to differentiate this case from violation of
         * the delegation-only assumption.  Once the resolver learns the
         * correct zone cut, possibly via a separate query for an "apex-only"
         * type, queries for other types will be resolved correctly.
         *
         * A query for type ANY will be accepted if it hits an exceptional
         * type above in the answer section as it should be from a child
         * zone.
         *
         * Also accept answers with RRSIG records from the child zone.
         * Direct queries for RRSIG records should not be answered from
         * the parent zone.
         */

        if (message->counts[DNS_SECTION_ANSWER] != 0 &&
            (fctx->type == dns_rdatatype_ns ||
             fctx->type == dns_rdatatype_ds ||
             fctx->type == dns_rdatatype_soa ||
             fctx->type == dns_rdatatype_any ||
             fctx->type == dns_rdatatype_rrsig ||
             fctx->type == dns_rdatatype_dnskey)) {
                result = dns_message_firstname(message, DNS_SECTION_ANSWER);
                while (result == ISC_R_SUCCESS) {
                        name = NULL;
                        dns_message_currentname(message, DNS_SECTION_ANSWER,
                                                &name);
                        for (rdataset = ISC_LIST_HEAD(name->list);
                             rdataset != NULL;
                             rdataset = ISC_LIST_NEXT(rdataset, link)) {
                                if (!dns_name_equal(name, &fctx->name))
                                        continue;
                                type = rdataset->type;
                                /*
                                 * RRsig from child?
                                 */
                                if (type == dns_rdatatype_rrsig &&
                                    rrsig_fromchildzone(fctx, rdataset))
                                        return (ISC_FALSE);
                                /*
                                 * Direct query for apex records or DS.
                                 */
                                if (fctx->type == type &&
                                    (type == dns_rdatatype_ds ||
                                     type == dns_rdatatype_ns ||
                                     type == dns_rdatatype_soa ||
                                     type == dns_rdatatype_dnskey))
                                        return (ISC_FALSE);
                                /*
                                 * Indirect query for apex records or DS.
                                 */
                                if (fctx->type == dns_rdatatype_any &&
                                    (type == dns_rdatatype_ns ||
                                     type == dns_rdatatype_ds ||
                                     type == dns_rdatatype_soa ||
                                     type == dns_rdatatype_dnskey))
                                        return (ISC_FALSE);
                        }
                        result = dns_message_nextname(message,
                                                      DNS_SECTION_ANSWER);
                }
        }

        /*
         * A NODATA response to a DS query?
         */
        if (fctx->type == dns_rdatatype_ds &&
            message->counts[DNS_SECTION_ANSWER] == 0)
                return (ISC_FALSE);

        /* Look for referral or indication of answer from child zone? */
        if (message->counts[DNS_SECTION_AUTHORITY] == 0)
                goto munge;

        result = dns_message_firstname(message, DNS_SECTION_AUTHORITY);
        while (result == ISC_R_SUCCESS) {
                name = NULL;
                dns_message_currentname(message, DNS_SECTION_AUTHORITY, &name);
                for (rdataset = ISC_LIST_HEAD(name->list);
                     rdataset != NULL;
                     rdataset = ISC_LIST_NEXT(rdataset, link)) {
                        type = rdataset->type;
                        if (type == dns_rdatatype_soa &&
                            dns_name_equal(name, domain))
                                keep_auth = ISC_TRUE;

                        if (type != dns_rdatatype_ns &&
                            type != dns_rdatatype_soa &&
                            type != dns_rdatatype_rrsig)
                                continue;

                        if (type == dns_rdatatype_rrsig) {
                                if (rrsig_fromchildzone(fctx, rdataset))
                                        return (ISC_FALSE);
                                else
                                        continue;
                        }

                        /* NS or SOA records. */
                        if (dns_name_equal(name, domain)) {
                                /*
                                 * If a query for ANY causes a negative
                                 * response, we can be sure that this is
                                 * an empty node.  For other type of queries
                                 * we cannot differentiate an empty node
                                 * from a node that just doesn't have that
                                 * type of record.  We only accept the former
                                 * case.
                                 */
                                if (message->counts[DNS_SECTION_ANSWER] == 0 &&
                                    fctx->type == dns_rdatatype_any)
                                        return (ISC_FALSE);
                        } else if (dns_name_issubdomain(name, domain)) {
                                /* Referral or answer from child zone. */
                                return (ISC_FALSE);
                        }
                }
                result = dns_message_nextname(message, DNS_SECTION_AUTHORITY);
        }

 munge:
        message->rcode = dns_rcode_nxdomain;
        message->counts[DNS_SECTION_ANSWER] = 0;
        if (!keep_auth)
                message->counts[DNS_SECTION_AUTHORITY] = 0;
        message->counts[DNS_SECTION_ADDITIONAL] = 0;
        return (ISC_TRUE);
}

static inline isc_result_t
fctx_starttimer(fetchctx_t *fctx) {
        /*
         * Start the lifetime timer for fctx.
         *
         * This is also used for stopping the idle timer; in that
         * case we must purge events already posted to ensure that
         * no further idle events are delivered.
         */
        return (isc_timer_reset(fctx->timer, isc_timertype_once,
                                &fctx->expires, NULL, ISC_TRUE));
}

static inline void
fctx_stoptimer(fetchctx_t *fctx) {
        isc_result_t result;

        /*
         * We don't return a result if resetting the timer to inactive fails
         * since there's nothing to be done about it.  Resetting to inactive
         * should never fail anyway, since the code as currently written
         * cannot fail in that case.
         */
        result = isc_timer_reset(fctx->timer, isc_timertype_inactive,
                                  NULL, NULL, ISC_TRUE);
        if (result != ISC_R_SUCCESS) {
                UNEXPECTED_ERROR(__FILE__, __LINE__,
                                 "isc_timer_reset(): %s",
                                 isc_result_totext(result));
        }
}


static inline isc_result_t
fctx_startidletimer(fetchctx_t *fctx, isc_interval_t *interval) {
        /*
         * Start the idle timer for fctx.  The lifetime timer continues
         * to be in effect.
         */
        return (isc_timer_reset(fctx->timer, isc_timertype_once,
                                &fctx->expires, interval, ISC_FALSE));
}

/*
 * Stopping the idle timer is equivalent to calling fctx_starttimer(), but
 * we use fctx_stopidletimer for readability in the code below.
 */
#define fctx_stopidletimer      fctx_starttimer

static inline void
resquery_destroy(resquery_t **queryp) {
        dns_resolver_t *res;
        isc_boolean_t empty;
        resquery_t *query;
        fetchctx_t *fctx;
        unsigned int bucket;

        REQUIRE(queryp != NULL);
        query = *queryp;
        REQUIRE(!ISC_LINK_LINKED(query, link));

        INSIST(query->tcpsocket == NULL);

        fctx = query->fctx;
        res = fctx->res;
        bucket = fctx->bucketnum;

        fctx->nqueries--;

        LOCK(&res->buckets[bucket].lock);
        empty = fctx_decreference(query->fctx);
        UNLOCK(&res->buckets[bucket].lock);

        query->magic = 0;
        isc_mem_put(query->mctx, query, sizeof(*query));
        *queryp = NULL;

        if (empty)
                empty_bucket(res);
}

static void
fctx_cancelquery(resquery_t **queryp, dns_dispatchevent_t **deventp,
                 isc_time_t *finish, isc_boolean_t no_response)
{
        fetchctx_t *fctx;
        resquery_t *query;
        unsigned int rtt, rttms;
        unsigned int factor;
        dns_adbfind_t *find;
        dns_adbaddrinfo_t *addrinfo;
        isc_socket_t *sock;
        isc_stdtime_t now;

        query = *queryp;
        fctx = query->fctx;

        FCTXTRACE("cancelquery");

        REQUIRE(!RESQUERY_CANCELED(query));

        query->attributes |= RESQUERY_ATTR_CANCELED;

        /*
         * Should we update the RTT?
         */
        if (finish != NULL || no_response) {
                if (finish != NULL) {
                        /*
                         * We have both the start and finish times for this
                         * packet, so we can compute a real RTT.
                         */
                        rtt = (unsigned int)isc_time_microdiff(finish,
                                                               &query->start);
                        factor = DNS_ADB_RTTADJDEFAULT;

                        rttms = rtt / 1000;
                        if (rttms < DNS_RESOLVER_QRYRTTCLASS0) {
                                inc_stats(fctx->res,
                                          dns_resstatscounter_queryrtt0);
                        } else if (rttms < DNS_RESOLVER_QRYRTTCLASS1) {
                                inc_stats(fctx->res,
                                          dns_resstatscounter_queryrtt1);
                        } else if (rttms < DNS_RESOLVER_QRYRTTCLASS2) {
                                inc_stats(fctx->res,
                                          dns_resstatscounter_queryrtt2);
                        } else if (rttms < DNS_RESOLVER_QRYRTTCLASS3) {
                                inc_stats(fctx->res,
                                          dns_resstatscounter_queryrtt3);
                        } else if (rttms < DNS_RESOLVER_QRYRTTCLASS4) {
                                inc_stats(fctx->res,
                                          dns_resstatscounter_queryrtt4);
                        } else {
                                inc_stats(fctx->res,
                                          dns_resstatscounter_queryrtt5);
                        }
                } else {
                        isc_uint32_t value;
                        isc_uint32_t mask;
                        /*
                         * We don't have an RTT for this query.  Maybe the
                         * packet was lost, or maybe this server is very
                         * slow.  We don't know.  Increase the RTT.
                         */
                        INSIST(no_response);
                        isc_random_get(&value);
                        if (query->addrinfo->srtt > 800000)
                                mask = 0x3fff;
                        else if (query->addrinfo->srtt > 400000)
                                mask = 0x7fff;
                        else if (query->addrinfo->srtt > 200000)
                                mask = 0xffff;
                        else if (query->addrinfo->srtt > 100000)
                                mask = 0x1ffff;
                        else if (query->addrinfo->srtt > 50000)
                                mask = 0x3ffff;
                        else if (query->addrinfo->srtt > 25000)
                                mask = 0x7ffff;
                        else
                                mask = 0xfffff;
                        if ((query->options & DNS_FETCHOPT_NOEDNS0) == 0)
                                dns_adb_ednsto(fctx->adb, query->addrinfo,
                                               query->udpsize);
                        else
                                dns_adb_timeout(fctx->adb, query->addrinfo);

                        /*
                         * Don't adjust timeout on EDNS queries unless we have
                         * seen a EDNS response.
                         */
                        if ((query->options & DNS_FETCHOPT_NOEDNS0) == 0 &&
                            !EDNSOK(query->addrinfo)) {
                                mask >>= 2;
                        }
                        rtt = query->addrinfo->srtt + (value & mask);
                        if (rtt > MAX_SINGLE_QUERY_TIMEOUT_US)
                                rtt = MAX_SINGLE_QUERY_TIMEOUT_US;
                        /*
                         * Replace the current RTT with our value.
                         */
                        factor = DNS_ADB_RTTADJREPLACE;
                }
                dns_adb_adjustsrtt(fctx->adb, query->addrinfo, rtt, factor);
        }

        /* Remember that the server has been tried. */
        if (!TRIED(query->addrinfo)) {
                dns_adb_changeflags(fctx->adb, query->addrinfo,
                                    FCTX_ADDRINFO_TRIED, FCTX_ADDRINFO_TRIED);
        }

        /*
         * Age RTTs of servers not tried.
         */
        isc_stdtime_get(&now);
        if (finish != NULL)
                for (addrinfo = ISC_LIST_HEAD(fctx->forwaddrs);
                     addrinfo != NULL;
                     addrinfo = ISC_LIST_NEXT(addrinfo, publink))
                        if (UNMARKED(addrinfo))
                                dns_adb_agesrtt(fctx->adb, addrinfo, now);

        if (finish != NULL && TRIEDFIND(fctx))
                for (find = ISC_LIST_HEAD(fctx->finds);
                     find != NULL;
                     find = ISC_LIST_NEXT(find, publink))
                        for (addrinfo = ISC_LIST_HEAD(find->list);
                             addrinfo != NULL;
                             addrinfo = ISC_LIST_NEXT(addrinfo, publink))
                                if (UNMARKED(addrinfo))
                                        dns_adb_agesrtt(fctx->adb, addrinfo,
                                                        now);

        if (finish != NULL && TRIEDALT(fctx)) {
                for (addrinfo = ISC_LIST_HEAD(fctx->altaddrs);
                     addrinfo != NULL;
                     addrinfo = ISC_LIST_NEXT(addrinfo, publink))
                        if (UNMARKED(addrinfo))
                                dns_adb_agesrtt(fctx->adb, addrinfo, now);
                for (find = ISC_LIST_HEAD(fctx->altfinds);
                     find != NULL;
                     find = ISC_LIST_NEXT(find, publink))
                        for (addrinfo = ISC_LIST_HEAD(find->list);
                             addrinfo != NULL;
                             addrinfo = ISC_LIST_NEXT(addrinfo, publink))
                                if (UNMARKED(addrinfo))
                                        dns_adb_agesrtt(fctx->adb, addrinfo,
                                                        now);
        }

        /*
         * Check for any outstanding socket events.  If they exist, cancel
         * them and let the event handlers finish the cleanup.  The resolver
         * only needs to worry about managing the connect and send events;
         * the dispatcher manages the recv events.
         */
        if (RESQUERY_CONNECTING(query)) {
                /*
                 * Cancel the connect.
                 */
                if (query->tcpsocket != NULL) {
                        isc_socket_cancel(query->tcpsocket, NULL,
                                          ISC_SOCKCANCEL_CONNECT);
                } else if (query->dispentry != NULL) {
                        INSIST(query->exclusivesocket);
                        sock = dns_dispatch_getentrysocket(query->dispentry);
                        if (sock != NULL)
                                isc_socket_cancel(sock, NULL,
                                                  ISC_SOCKCANCEL_CONNECT);
                }
        } else if (RESQUERY_SENDING(query)) {
                /*
                 * Cancel the pending send.
                 */
                if (query->exclusivesocket && query->dispentry != NULL)
                        sock = dns_dispatch_getentrysocket(query->dispentry);
                else
                        sock = dns_dispatch_getsocket(query->dispatch);
                if (sock != NULL)
                        isc_socket_cancel(sock, NULL, ISC_SOCKCANCEL_SEND);
        }

        if (query->dispentry != NULL)
                dns_dispatch_removeresponse(&query->dispentry, deventp);

        ISC_LIST_UNLINK(fctx->queries, query, link);

        if (query->tsig != NULL)
                isc_buffer_free(&query->tsig);

        if (query->tsigkey != NULL)
                dns_tsigkey_detach(&query->tsigkey);

        if (query->dispatch != NULL)
                dns_dispatch_detach(&query->dispatch);

        if (! (RESQUERY_CONNECTING(query) || RESQUERY_SENDING(query)))
                /*
                 * It's safe to destroy the query now.
                 */
                resquery_destroy(&query);
}

static void
fctx_cancelqueries(fetchctx_t *fctx, isc_boolean_t no_response) {
        resquery_t *query, *next_query;

        FCTXTRACE("cancelqueries");

        for (query = ISC_LIST_HEAD(fctx->queries);
             query != NULL;
             query = next_query) {
                next_query = ISC_LIST_NEXT(query, link);
                fctx_cancelquery(&query, NULL, NULL, no_response);
        }
}

static void
fctx_cleanupfinds(fetchctx_t *fctx) {
        dns_adbfind_t *find, *next_find;

        REQUIRE(ISC_LIST_EMPTY(fctx->queries));

        for (find = ISC_LIST_HEAD(fctx->finds);
             find != NULL;
             find = next_find) {
                next_find = ISC_LIST_NEXT(find, publink);
                ISC_LIST_UNLINK(fctx->finds, find, publink);
                dns_adb_destroyfind(&find);
        }
        fctx->find = NULL;
}

static void
fctx_cleanupaltfinds(fetchctx_t *fctx) {
        dns_adbfind_t *find, *next_find;

        REQUIRE(ISC_LIST_EMPTY(fctx->queries));

        for (find = ISC_LIST_HEAD(fctx->altfinds);
             find != NULL;
             find = next_find) {
                next_find = ISC_LIST_NEXT(find, publink);
                ISC_LIST_UNLINK(fctx->altfinds, find, publink);
                dns_adb_destroyfind(&find);
        }
        fctx->altfind = NULL;
}

static void
fctx_cleanupforwaddrs(fetchctx_t *fctx) {
        dns_adbaddrinfo_t *addr, *next_addr;

        REQUIRE(ISC_LIST_EMPTY(fctx->queries));

        for (addr = ISC_LIST_HEAD(fctx->forwaddrs);
             addr != NULL;
             addr = next_addr) {
                next_addr = ISC_LIST_NEXT(addr, publink);
                ISC_LIST_UNLINK(fctx->forwaddrs, addr, publink);
                dns_adb_freeaddrinfo(fctx->adb, &addr);
        }
}

static void
fctx_cleanupaltaddrs(fetchctx_t *fctx) {
        dns_adbaddrinfo_t *addr, *next_addr;

        REQUIRE(ISC_LIST_EMPTY(fctx->queries));

        for (addr = ISC_LIST_HEAD(fctx->altaddrs);
             addr != NULL;
             addr = next_addr) {
                next_addr = ISC_LIST_NEXT(addr, publink);
                ISC_LIST_UNLINK(fctx->altaddrs, addr, publink);
                dns_adb_freeaddrinfo(fctx->adb, &addr);
        }
}

static inline void
fctx_stopeverything(fetchctx_t *fctx, isc_boolean_t no_response) {
        FCTXTRACE("stopeverything");
        fctx_cancelqueries(fctx, no_response);
        fctx_cleanupfinds(fctx);
        fctx_cleanupaltfinds(fctx);
        fctx_cleanupforwaddrs(fctx);
        fctx_cleanupaltaddrs(fctx);
        fctx_stoptimer(fctx);
}

static inline void
fctx_sendevents(fetchctx_t *fctx, isc_result_t result, int line) {
        dns_fetchevent_t *event, *next_event;
        isc_task_t *task;
        unsigned int count = 0;
        isc_interval_t i;
        isc_boolean_t logit = ISC_FALSE;
        isc_time_t now;
        unsigned int old_spillat;
        unsigned int new_spillat = 0;   /* initialized to silence
                                           compiler warnings */

        /*
         * Caller must be holding the appropriate bucket lock.
         */
        REQUIRE(fctx->state == fetchstate_done);

        FCTXTRACE("sendevents");

        /*
         * Keep some record of fetch result for logging later (if required).
         */
        fctx->result = result;
        fctx->exitline = line;
        TIME_NOW(&now);
        fctx->duration = isc_time_microdiff(&now, &fctx->start);

        for (event = ISC_LIST_HEAD(fctx->events);
             event != NULL;
             event = next_event) {
                next_event = ISC_LIST_NEXT(event, ev_link);
                ISC_LIST_UNLINK(fctx->events, event, ev_link);
                task = event->ev_sender;
                event->ev_sender = fctx;
                event->vresult = fctx->vresult;
                if (!HAVE_ANSWER(fctx))
                        event->result = result;

                INSIST(result != ISC_R_SUCCESS ||
                       dns_rdataset_isassociated(event->rdataset) ||
                       fctx->type == dns_rdatatype_any ||
                       fctx->type == dns_rdatatype_rrsig ||
                       fctx->type == dns_rdatatype_sig);

                /*
                 * Negative results must be indicated in event->result.
                 */
                if (dns_rdataset_isassociated(event->rdataset) &&
                    NEGATIVE(event->rdataset)) {
                        INSIST(event->result == DNS_R_NCACHENXDOMAIN ||
                               event->result == DNS_R_NCACHENXRRSET);
                }

                isc_task_sendanddetach(&task, ISC_EVENT_PTR(&event));
                count++;
        }

        if ((fctx->attributes & FCTX_ATTR_HAVEANSWER) != 0 &&
            fctx->spilled &&
            (count < fctx->res->spillatmax || fctx->res->spillatmax == 0)) {
                LOCK(&fctx->res->lock);
                if (count == fctx->res->spillat && !fctx->res->exiting) {
                        old_spillat = fctx->res->spillat;
                        fctx->res->spillat += 5;
                        if (fctx->res->spillat > fctx->res->spillatmax &&
                            fctx->res->spillatmax != 0)
                                fctx->res->spillat = fctx->res->spillatmax;
                        new_spillat = fctx->res->spillat;
                        if (new_spillat != old_spillat) {
                                logit = ISC_TRUE;
                        }
                        isc_interval_set(&i, 20 * 60, 0);
                        result = isc_timer_reset(fctx->res->spillattimer,
                                                 isc_timertype_ticker, NULL,
                                                 &i, ISC_TRUE);
                        RUNTIME_CHECK(result == ISC_R_SUCCESS);
                }
                UNLOCK(&fctx->res->lock);
                if (logit)
                        isc_log_write(dns_lctx, DNS_LOGCATEGORY_RESOLVER,
                                      DNS_LOGMODULE_RESOLVER, ISC_LOG_NOTICE,
                                      "clients-per-query increased to %u",
                                      new_spillat);
        }
}

static inline void
log_edns(fetchctx_t *fctx) {
        char domainbuf[DNS_NAME_FORMATSIZE];

        if (fctx->reason == NULL)
                return;

        /*
         * We do not know if fctx->domain is the actual domain the record
         * lives in or a parent domain so we have a '?' after it.
         */
        dns_name_format(&fctx->domain, domainbuf, sizeof(domainbuf));
        isc_log_write(dns_lctx, DNS_LOGCATEGORY_EDNS_DISABLED,
                      DNS_LOGMODULE_RESOLVER, ISC_LOG_INFO,
                      "success resolving '%s' (in '%s'?) after %s",
                      fctx->info, domainbuf, fctx->reason);

        fctx->reason = NULL;
}

static void
fctx_done(fetchctx_t *fctx, isc_result_t result, int line) {
        dns_resolver_t *res;
        isc_boolean_t no_response = ISC_FALSE;

        REQUIRE(line >= 0);

        FCTXTRACE("done");

        res = fctx->res;

        if (result == ISC_R_SUCCESS) {
                /*%
                 * Log any deferred EDNS timeout messages.
                 */
                log_edns(fctx);
                no_response = ISC_TRUE;
        }

        fctx->reason = NULL;
        fctx_stopeverything(fctx, no_response);

        LOCK(&res->buckets[fctx->bucketnum].lock);

        fctx->state = fetchstate_done;
        fctx->attributes &= ~FCTX_ATTR_ADDRWAIT;
        fctx_sendevents(fctx, result, line);

        UNLOCK(&res->buckets[fctx->bucketnum].lock);
}

static void
process_sendevent(resquery_t *query, isc_event_t *event) {
        isc_socketevent_t *sevent = (isc_socketevent_t *)event;
        isc_boolean_t destroy_query = ISC_FALSE;
        isc_boolean_t retry = ISC_FALSE;
        isc_result_t result;
        fetchctx_t *fctx;

        fctx = query->fctx;

        if (RESQUERY_CANCELED(query)) {
                if (query->sends == 0 && query->connects == 0) {
                        /*
                         * This query was canceled while the
                         * isc_socket_sendto/connect() was in progress.
                         */
                        if (query->tcpsocket != NULL)
                                isc_socket_detach(&query->tcpsocket);
                        destroy_query = ISC_TRUE;
                }
        } else {
                switch (sevent->result) {
                case ISC_R_SUCCESS:
                        break;

                case ISC_R_HOSTUNREACH:
                case ISC_R_NETUNREACH:
                case ISC_R_NOPERM:
                case ISC_R_ADDRNOTAVAIL:
                case ISC_R_CONNREFUSED:
                        FCTXTRACE3("query canceled in sendevent(): "
                                   "no route to host; no response",
                                   sevent->result);

                        /*
                         * No route to remote.
                         */
                        add_bad(fctx, query->addrinfo, sevent->result,
                                badns_unreachable);
                        fctx_cancelquery(&query, NULL, NULL, ISC_TRUE);
                        retry = ISC_TRUE;
                        break;

                default:
                        FCTXTRACE3("query canceled in sendevent() due to "
                                   "unexpected event result; responding",
                                   sevent->result);

                        fctx_cancelquery(&query, NULL, NULL, ISC_FALSE);
                        break;
                }
        }

        if (event->ev_type == ISC_SOCKEVENT_CONNECT)
                isc_event_free(&event);

        if (retry) {
                /*
                 * Behave as if the idle timer has expired.  For TCP
                 * this may not actually reflect the latest timer.
                 */
                fctx->attributes &= ~FCTX_ATTR_ADDRWAIT;
                result = fctx_stopidletimer(fctx);
                if (result != ISC_R_SUCCESS)
                        fctx_done(fctx, result, __LINE__);
                else
                        fctx_try(fctx, ISC_TRUE, ISC_FALSE);
        }

        if (destroy_query)
                resquery_destroy(&query);
}

static void
resquery_udpconnected(isc_task_t *task, isc_event_t *event) {
        resquery_t *query = event->ev_arg;

        REQUIRE(event->ev_type == ISC_SOCKEVENT_CONNECT);

        QTRACE("udpconnected");

        UNUSED(task);

        INSIST(RESQUERY_CONNECTING(query));

        query->connects--;

        process_sendevent(query, event);
}

static void
resquery_senddone(isc_task_t *task, isc_event_t *event) {
        resquery_t *query = event->ev_arg;

        REQUIRE(event->ev_type == ISC_SOCKEVENT_SENDDONE);

        QTRACE("senddone");

        /*
         * XXXRTH
         *
         * Currently we don't wait for the senddone event before retrying
         * a query.  This means that if we get really behind, we may end
         * up doing extra work!
         */

        UNUSED(task);

        INSIST(RESQUERY_SENDING(query));

        query->sends--;

        process_sendevent(query, event);
}

static inline isc_result_t
fctx_addopt(dns_message_t *message, unsigned int version,
            isc_uint16_t udpsize, dns_ednsopt_t *ednsopts, size_t count)
{
        dns_rdataset_t *rdataset = NULL;
        isc_result_t result;

        result = dns_message_buildopt(message, &rdataset, version, udpsize,
                                      DNS_MESSAGEEXTFLAG_DO, ednsopts, count);
        if (result != ISC_R_SUCCESS)
                return (result);
        return (dns_message_setopt(message, rdataset));
}

static inline void
fctx_setretryinterval(fetchctx_t *fctx, unsigned int rtt) {
        unsigned int seconds;
        unsigned int us;

        /*
         * We retry every .8 seconds the first two times through the address
         * list, and then we do exponential back-off.
         */
        if (fctx->restarts < 3)
                us = 800000;
        else
                us = (800000 << (fctx->restarts - 2));

        /*
         * Add a fudge factor to the expected rtt based on the current
         * estimate.
         */
        if (rtt < 50000)
                rtt += 50000;
        else if (rtt < 100000)
                rtt += 100000;
        else
                rtt += 200000;

        /*
         * Always wait for at least the expected rtt.
         */
        if (us < rtt)
                us = rtt;

        /*
         * But don't ever wait for more than 10 seconds.
         */
        if (us > MAX_SINGLE_QUERY_TIMEOUT_US)
                us = MAX_SINGLE_QUERY_TIMEOUT_US;

        seconds = us / US_PER_SEC;
        us -= seconds * US_PER_SEC;
        isc_interval_set(&fctx->interval, seconds, us * 1000);
}

static isc_result_t
fctx_query(fetchctx_t *fctx, dns_adbaddrinfo_t *addrinfo,
           unsigned int options)
{
        dns_resolver_t *res;
        isc_task_t *task;
        isc_result_t result;
        resquery_t *query;
        isc_sockaddr_t addr;
        isc_boolean_t have_addr = ISC_FALSE;
        unsigned int srtt;
        isc_dscp_t dscp = -1;

        FCTXTRACE("query");

        res = fctx->res;
        task = res->buckets[fctx->bucketnum].task;

        srtt = addrinfo->srtt;

        /*
         * A forwarder needs to make multiple queries. Give it at least
         * a second to do these in.
         */
        if (ISFORWARDER(addrinfo) && srtt < 1000000)
                srtt = 1000000;

        fctx_setretryinterval(fctx, srtt);
        result = fctx_startidletimer(fctx, &fctx->interval);
        if (result != ISC_R_SUCCESS)
                return (result);

        INSIST(ISC_LIST_EMPTY(fctx->validators));

        dns_message_reset(fctx->rmessage, DNS_MESSAGE_INTENTPARSE);

        query = isc_mem_get(fctx->mctx, sizeof(*query));
        if (query == NULL) {
                result = ISC_R_NOMEMORY;
                goto stop_idle_timer;
        }
        query->mctx = fctx->mctx;
        query->options = options;
        query->attributes = 0;
        query->sends = 0;
        query->connects = 0;
        query->dscp = addrinfo->dscp;
        /*
         * Note that the caller MUST guarantee that 'addrinfo' will remain
         * valid until this query is canceled.
         */
        query->addrinfo = addrinfo;
        TIME_NOW(&query->start);

        /*
         * If this is a TCP query, then we need to make a socket and
         * a dispatch for it here.  Otherwise we use the resolver's
         * shared dispatch.
         */
        query->dispatchmgr = res->dispatchmgr;
        query->dispatch = NULL;
        query->exclusivesocket = ISC_FALSE;
        query->tcpsocket = NULL;
        if (res->view->peers != NULL) {
                dns_peer_t *peer = NULL;
                isc_netaddr_t dstip;
                isc_boolean_t usetcp = ISC_FALSE;
                isc_netaddr_fromsockaddr(&dstip, &addrinfo->sockaddr);
                result = dns_peerlist_peerbyaddr(res->view->peers,
                                                 &dstip, &peer);
                if (result == ISC_R_SUCCESS) {
                        result = dns_peer_getquerysource(peer, &addr);
                        if (result == ISC_R_SUCCESS)
                                have_addr = ISC_TRUE;
                        result = dns_peer_getquerydscp(peer, &dscp);
                        if (result == ISC_R_SUCCESS)
                                query->dscp = dscp;
                        result = dns_peer_getforcetcp(peer, &usetcp);
                        if (result == ISC_R_SUCCESS && usetcp)
                                query->options |= DNS_FETCHOPT_TCP;
                }
        }

        dscp = -1;
        if ((query->options & DNS_FETCHOPT_TCP) != 0) {
                int pf;

                pf = isc_sockaddr_pf(&addrinfo->sockaddr);
                if (!have_addr) {
                        switch (pf) {
                        case PF_INET:
                                result = dns_dispatch_getlocaladdress(
                                              res->dispatches4->dispatches[0],
                                              &addr);
                                dscp = dns_resolver_getquerydscp4(fctx->res);
                                break;
                        case PF_INET6:
                                result = dns_dispatch_getlocaladdress(
                                              res->dispatches6->dispatches[0],
                                              &addr);
                                dscp = dns_resolver_getquerydscp6(fctx->res);
                                break;
                        default:
                                result = ISC_R_NOTIMPLEMENTED;
                                break;
                        }
                        if (result != ISC_R_SUCCESS)
                                goto cleanup_query;
                }
                isc_sockaddr_setport(&addr, 0);
                if (query->dscp == -1)
                        query->dscp = dscp;

                result = isc_socket_create(res->socketmgr, pf,
                                           isc_sockettype_tcp,
                                           &query->tcpsocket);
                if (result != ISC_R_SUCCESS)
                        goto cleanup_query;

#ifndef BROKEN_TCP_BIND_BEFORE_CONNECT
                result = isc_socket_bind(query->tcpsocket, &addr, 0);
                if (result != ISC_R_SUCCESS)
                        goto cleanup_socket;
#endif
                /*
                 * A dispatch will be created once the connect succeeds.
                 */
        } else {
                if (have_addr) {
                        unsigned int attrs, attrmask;
                        attrs = DNS_DISPATCHATTR_UDP;
                        switch (isc_sockaddr_pf(&addr)) {
                        case AF_INET:
                                attrs |= DNS_DISPATCHATTR_IPV4;
                                dscp = dns_resolver_getquerydscp4(fctx->res);
                                break;
                        case AF_INET6:
                                attrs |= DNS_DISPATCHATTR_IPV6;
                                dscp = dns_resolver_getquerydscp6(fctx->res);
                                break;
                        default:
                                result = ISC_R_NOTIMPLEMENTED;
                                goto cleanup_query;
                        }
                        attrmask = DNS_DISPATCHATTR_UDP;
                        attrmask |= DNS_DISPATCHATTR_TCP;
                        attrmask |= DNS_DISPATCHATTR_IPV4;
                        attrmask |= DNS_DISPATCHATTR_IPV6;
                        result = dns_dispatch_getudp(res->dispatchmgr,
                                                     res->socketmgr,
                                                     res->taskmgr, &addr,
                                                     4096, 20000, 32768, 16411,
                                                     16433, attrs, attrmask,
                                                     &query->dispatch);
                        if (result != ISC_R_SUCCESS)
                                goto cleanup_query;
                } else {
                        switch (isc_sockaddr_pf(&addrinfo->sockaddr)) {
                        case PF_INET:
                                dns_dispatch_attach(
                                    dns_resolver_dispatchv4(res),
                                    &query->dispatch);
                                query->exclusivesocket = res->exclusivev4;
                                dscp = dns_resolver_getquerydscp4(fctx->res);
                                break;
                        case PF_INET6:
                                dns_dispatch_attach(
                                    dns_resolver_dispatchv6(res),
                                    &query->dispatch);
                                query->exclusivesocket = res->exclusivev6;
                                dscp = dns_resolver_getquerydscp6(fctx->res);
                                break;
                        default:
                                result = ISC_R_NOTIMPLEMENTED;
                                goto cleanup_query;
                        }
                }

                if (query->dscp == -1)
                        query->dscp = dscp;
                /*
                 * We should always have a valid dispatcher here.  If we
                 * don't support a protocol family, then its dispatcher
                 * will be NULL, but we shouldn't be finding addresses for
                 * protocol types we don't support, so the dispatcher
                 * we found should never be NULL.
                 */
                INSIST(query->dispatch != NULL);
        }

        query->dispentry = NULL;
        fctx_increference(fctx);
        query->fctx = fctx;
        query->tsig = NULL;
        query->tsigkey = NULL;
        ISC_LINK_INIT(query, link);
        query->magic = QUERY_MAGIC;

        if ((query->options & DNS_FETCHOPT_TCP) != 0) {
                /*
                 * Connect to the remote server.
                 *
                 * XXXRTH  Should we attach to the socket?
                 */
                if (query->dscp != -1)
                        isc_socket_dscp(query->tcpsocket, query->dscp);
                result = isc_socket_connect(query->tcpsocket,
                                            &addrinfo->sockaddr, task,
                                            resquery_connected, query);
                if (result != ISC_R_SUCCESS)
                        goto cleanup_socket;
                query->connects++;
                QTRACE("connecting via TCP");
        } else {
                result = resquery_send(query);
                if (result != ISC_R_SUCCESS)
                        goto cleanup_dispatch;
        }

        fctx->querysent++;

        ISC_LIST_APPEND(fctx->queries, query, link);
        query->fctx->nqueries++;
        if (isc_sockaddr_pf(&addrinfo->sockaddr) == PF_INET)
                inc_stats(res, dns_resstatscounter_queryv4);
        else
                inc_stats(res, dns_resstatscounter_queryv6);
        if (res->view->resquerystats != NULL)
                dns_rdatatypestats_increment(res->view->resquerystats,
                                             fctx->type);

        return (ISC_R_SUCCESS);

 cleanup_socket:
        isc_socket_detach(&query->tcpsocket);

 cleanup_dispatch:
        if (query->dispatch != NULL)
                dns_dispatch_detach(&query->dispatch);

 cleanup_query:
        if (query->connects == 0) {
                query->magic = 0;
                isc_mem_put(fctx->mctx, query, sizeof(*query));
        }

 stop_idle_timer:
        RUNTIME_CHECK(fctx_stopidletimer(fctx) == ISC_R_SUCCESS);

        return (result);
}

static isc_boolean_t
bad_edns(fetchctx_t *fctx, isc_sockaddr_t *address) {
        isc_sockaddr_t *sa;

        for (sa = ISC_LIST_HEAD(fctx->bad_edns);
             sa != NULL;
             sa = ISC_LIST_NEXT(sa, link)) {
                if (isc_sockaddr_equal(sa, address))
                        return (ISC_TRUE);
        }

        return (ISC_FALSE);
}

static void
add_bad_edns(fetchctx_t *fctx, isc_sockaddr_t *address) {
        isc_sockaddr_t *sa;

        if (bad_edns(fctx, address))
                return;

        sa = isc_mem_get(fctx->mctx, sizeof(*sa));
        if (sa == NULL)
                return;

        *sa = *address;
        ISC_LIST_INITANDAPPEND(fctx->bad_edns, sa, link);
}

static struct tried *
triededns(fetchctx_t *fctx, isc_sockaddr_t *address) {
        struct tried *tried;

        for (tried = ISC_LIST_HEAD(fctx->edns);
             tried != NULL;
             tried = ISC_LIST_NEXT(tried, link)) {
                if (isc_sockaddr_equal(&tried->addr, address))
                        return (tried);
        }

        return (NULL);
}

static void
add_triededns(fetchctx_t *fctx, isc_sockaddr_t *address) {
        struct tried *tried;

        tried = triededns(fctx, address);
        if (tried != NULL) {
                tried->count++;
                return;
        }

        tried = isc_mem_get(fctx->mctx, sizeof(*tried));
        if (tried == NULL)
                return;

        tried->addr = *address;
        tried->count = 1;
        ISC_LIST_INITANDAPPEND(fctx->edns, tried, link);
}

static struct tried *
triededns512(fetchctx_t *fctx, isc_sockaddr_t *address) {
        struct tried *tried;

        for (tried = ISC_LIST_HEAD(fctx->edns512);
             tried != NULL;
             tried = ISC_LIST_NEXT(tried, link)) {
                if (isc_sockaddr_equal(&tried->addr, address))
                        return (tried);
        }

        return (NULL);
}

static void
add_triededns512(fetchctx_t *fctx, isc_sockaddr_t *address) {
        struct tried *tried;

        tried = triededns512(fctx, address);
        if (tried != NULL) {
                tried->count++;
                return;
        }

        tried = isc_mem_get(fctx->mctx, sizeof(*tried));
        if (tried == NULL)
                return;

        tried->addr = *address;
        tried->count = 1;
        ISC_LIST_INITANDAPPEND(fctx->edns512, tried, link);
}

#ifdef ISC_PLATFORM_USESIT
static void
compute_cc(resquery_t *query, unsigned char *sit, size_t len) {
#ifdef AES_SIT
        unsigned char digest[ISC_AES_BLOCK_LENGTH];
        unsigned char input[16];
        isc_netaddr_t netaddr;
        unsigned int i;

        INSIST(len >= 8U);

        isc_netaddr_fromsockaddr(&netaddr, &query->addrinfo->sockaddr);
        switch (netaddr.family) {
        case AF_INET:
                memmove(input, (unsigned char *)&netaddr.type.in, 4);
                memset(input + 4, 0, 12);
                break;
        case AF_INET6:
                memmove(input, (unsigned char *)&netaddr.type.in6, 16);
                break;
        }
        isc_aes128_crypt(query->fctx->res->view->secret, input, digest);
        for (i = 0; i < 8; i++)
                digest[i] ^= digest[i + 8];
        memmove(sit, digest, 8);
#endif
#ifdef HMAC_SHA1_SIT
        unsigned char digest[ISC_SHA1_DIGESTLENGTH];
        isc_netaddr_t netaddr;
        isc_hmacsha1_t hmacsha1;

        INSIST(len >= 8U);

        isc_hmacsha1_init(&hmacsha1, query->fctx->res->view->secret,
                          ISC_SHA1_DIGESTLENGTH);
        isc_netaddr_fromsockaddr(&netaddr, &query->addrinfo->sockaddr);
        switch (netaddr.family) {
        case AF_INET:
                isc_hmacsha1_update(&hmacsha1,
                                    (unsigned char *)&netaddr.type.in, 4);
                break;
        case AF_INET6:
                isc_hmacsha1_update(&hmacsha1,
                                    (unsigned char *)&netaddr.type.in6, 16);
                break;
        }
        isc_hmacsha1_sign(&hmacsha1, digest, sizeof(digest));
        memmove(sit, digest, 8);
        isc_hmacsha1_invalidate(&hmacsha1);
#endif
#ifdef HMAC_SHA256_SIT
        unsigned char digest[ISC_SHA256_DIGESTLENGTH];
        isc_netaddr_t netaddr;
        isc_hmacsha256_t hmacsha256;

        INSIST(len >= 8U);

        isc_hmacsha256_init(&hmacsha256, query->fctx->res->view->secret,
                            ISC_SHA256_DIGESTLENGTH);
        isc_netaddr_fromsockaddr(&netaddr, &query->addrinfo->sockaddr);
        switch (netaddr.family) {
        case AF_INET:
                isc_hmacsha256_update(&hmacsha256,
                                      (unsigned char *)&netaddr.type.in, 4);
                break;
        case AF_INET6:
                isc_hmacsha256_update(&hmacsha256,
                                      (unsigned char *)&netaddr.type.in6, 16);
                break;
        }
        isc_hmacsha256_sign(&hmacsha256, digest, sizeof(digest));
        memmove(sit, digest, 8);
        isc_hmacsha256_invalidate(&hmacsha256);
#endif
}
#endif

static isc_result_t
issecuredomain(dns_view_t *view, dns_name_t *name, dns_rdatatype_t type,
               isc_stdtime_t now, isc_boolean_t checknta,
               isc_boolean_t *issecure)
{
        dns_name_t suffix;
        unsigned int labels;

        /*
         * For DS variants we need to check fom the parent domain,
         * since there may be a negative trust anchor for the name,
         * while the enclosing domain where the DS record lives is
         * under a secure entry point.
         */
        labels = dns_name_countlabels(name);
        if (dns_rdatatype_atparent(type) && labels > 1) {
                dns_name_init(&suffix, NULL);
                dns_name_getlabelsequence(name, 1, labels - 1, &suffix);
                name = &suffix;
        }

        return (dns_view_issecuredomain(view, name, now, checknta, issecure));
}

static isc_boolean_t
wouldvalidate(fetchctx_t *fctx) {
        isc_boolean_t secure_domain;
        isc_result_t result;
        isc_stdtime_t now;

        if (!fctx->res->view->enablevalidation)
                return (ISC_FALSE);

        if (fctx->res->view->dlv != NULL)
                return (ISC_TRUE);

        isc_stdtime_get(&now);
        result = dns_view_issecuredomain(fctx->res->view, &fctx->name,
                                         now, ISC_TRUE, &secure_domain);
        if (result != ISC_R_SUCCESS)
                return (ISC_FALSE);
        return (secure_domain);
}

static isc_result_t
resquery_send(resquery_t *query) {
        fetchctx_t *fctx;
        isc_result_t result;
        dns_name_t *qname = NULL;
        dns_rdataset_t *qrdataset = NULL;
        isc_region_t r;
        dns_resolver_t *res;
        isc_task_t *task;
        isc_socket_t *sock;
        isc_buffer_t tcpbuffer;
        isc_sockaddr_t *address;
        isc_buffer_t *buffer;
        isc_netaddr_t ipaddr;
        dns_tsigkey_t *tsigkey = NULL;
        dns_peer_t *peer = NULL;
        isc_boolean_t useedns;
        dns_compress_t cctx;
        isc_boolean_t cleanup_cctx = ISC_FALSE;
        isc_boolean_t secure_domain;
        isc_boolean_t connecting = ISC_FALSE;
        dns_ednsopt_t ednsopts[DNS_EDNSOPTIONS];
        unsigned ednsopt = 0;
        isc_uint16_t hint = 0, udpsize = 0;     /* No EDNS */

        fctx = query->fctx;
        QTRACE("send");

        res = fctx->res;
        task = res->buckets[fctx->bucketnum].task;
        address = NULL;

        if ((query->options & DNS_FETCHOPT_TCP) != 0) {
                /*
                 * Reserve space for the TCP message length.
                 */
                isc_buffer_init(&tcpbuffer, query->data, sizeof(query->data));
                isc_buffer_init(&query->buffer, query->data + 2,
                                sizeof(query->data) - 2);
                buffer = &tcpbuffer;
        } else {
                isc_buffer_init(&query->buffer, query->data,
                                sizeof(query->data));
                buffer = &query->buffer;
        }

        result = dns_message_gettempname(fctx->qmessage, &qname);
        if (result != ISC_R_SUCCESS)
                goto cleanup_temps;
        result = dns_message_gettemprdataset(fctx->qmessage, &qrdataset);
        if (result != ISC_R_SUCCESS)
                goto cleanup_temps;

        /*
         * Get a query id from the dispatch.
         */
        result = dns_dispatch_addresponse2(query->dispatch,
                                           &query->addrinfo->sockaddr,
                                           task,
                                           resquery_response,
                                           query,
                                           &query->id,
                                           &query->dispentry,
                                           res->socketmgr);
        if (result != ISC_R_SUCCESS)
                goto cleanup_temps;

        fctx->qmessage->opcode = dns_opcode_query;

        /*
         * Set up question.
         */
        dns_name_init(qname, NULL);
        dns_name_clone(&fctx->name, qname);
        dns_rdataset_init(qrdataset);
        dns_rdataset_makequestion(qrdataset, res->rdclass, fctx->type);
        ISC_LIST_APPEND(qname->list, qrdataset, link);
        dns_message_addname(fctx->qmessage, qname, DNS_SECTION_QUESTION);
        qname = NULL;
        qrdataset = NULL;

        /*
         * Set RD if the client has requested that we do a recursive query,
         * or if we're sending to a forwarder.
         */
        if ((query->options & DNS_FETCHOPT_RECURSIVE) != 0 ||
            ISFORWARDER(query->addrinfo))
                fctx->qmessage->flags |= DNS_MESSAGEFLAG_RD;

        /*
         * Set CD if the client says not to validate, or if the
         * question is under a secure entry point and this is a
         * recursive/forward query -- unless the client said not to.
         */
        if ((query->options & DNS_FETCHOPT_NOCDFLAG) != 0)
                /* Do nothing */
                ;
        else if ((query->options & DNS_FETCHOPT_NOVALIDATE) != 0)
                fctx->qmessage->flags |= DNS_MESSAGEFLAG_CD;
        else if (res->view->enablevalidation &&
                 ((fctx->qmessage->flags & DNS_MESSAGEFLAG_RD) != 0))
        {
                isc_boolean_t checknta =
                        ISC_TF((query->options & DNS_FETCHOPT_NONTA) == 0);
                result = issecuredomain(res->view, &fctx->name, fctx->type,
                                        isc_time_seconds(&query->start),
                                        checknta, &secure_domain);
                if (result != ISC_R_SUCCESS)
                        secure_domain = ISC_FALSE;
                if (res->view->dlv != NULL)
                        secure_domain = ISC_TRUE;
                if (secure_domain)
                        fctx->qmessage->flags |= DNS_MESSAGEFLAG_CD;
        }

        /*
         * We don't have to set opcode because it defaults to query.
         */
        fctx->qmessage->id = query->id;

        /*
         * Convert the question to wire format.
         */
        result = dns_compress_init(&cctx, -1, fctx->res->mctx);
        if (result != ISC_R_SUCCESS)
                goto cleanup_message;
        cleanup_cctx = ISC_TRUE;

        result = dns_message_renderbegin(fctx->qmessage, &cctx,
                                         &query->buffer);
        if (result != ISC_R_SUCCESS)
                goto cleanup_message;

        result = dns_message_rendersection(fctx->qmessage,
                                           DNS_SECTION_QUESTION, 0);
        if (result != ISC_R_SUCCESS)
                goto cleanup_message;

        peer = NULL;
        isc_netaddr_fromsockaddr(&ipaddr, &query->addrinfo->sockaddr);
        (void) dns_peerlist_peerbyaddr(fctx->res->view->peers, &ipaddr, &peer);

        /*
         * The ADB does not know about servers with "edns no".  Check this,
         * and then inform the ADB for future use.
         */
        if ((query->addrinfo->flags & DNS_FETCHOPT_NOEDNS0) == 0 &&
            peer != NULL &&
            dns_peer_getsupportedns(peer, &useedns) == ISC_R_SUCCESS &&
            !useedns)
        {
                query->options |= DNS_FETCHOPT_NOEDNS0;
                dns_adb_changeflags(fctx->adb, query->addrinfo,
                                    DNS_FETCHOPT_NOEDNS0,
                                    DNS_FETCHOPT_NOEDNS0);
        }

        /* Sync NOEDNS0 flag in addrinfo->flags and options now. */
        if ((query->addrinfo->flags & DNS_FETCHOPT_NOEDNS0) != 0)
                query->options |= DNS_FETCHOPT_NOEDNS0;

        /* See if response history indicates that EDNS is not supported. */
        if ((query->options & DNS_FETCHOPT_NOEDNS0) == 0 &&
            dns_adb_noedns(fctx->adb, query->addrinfo))
                query->options |= DNS_FETCHOPT_NOEDNS0;

        if (fctx->timeout && (query->options & DNS_FETCHOPT_NOEDNS0) == 0) {
                isc_sockaddr_t *sockaddr = &query->addrinfo->sockaddr;
                struct tried *tried;

                if (fctx->timeouts > (MAX_EDNS0_TIMEOUTS * 2) &&
                    (!EDNSOK(query->addrinfo) || !wouldvalidate(fctx))) {
                        query->options |= DNS_FETCHOPT_NOEDNS0;
                        fctx->reason = "disabling EDNS";
                } else if ((tried = triededns512(fctx, sockaddr)) != NULL &&
                    tried->count >= 2U &&
                    (!EDNSOK(query->addrinfo) || !wouldvalidate(fctx))) {
                        query->options |= DNS_FETCHOPT_NOEDNS0;
                        fctx->reason = "disabling EDNS";
                } else if ((tried = triededns(fctx, sockaddr)) != NULL) {
                        if (tried->count == 1U) {
                                hint = dns_adb_getudpsize(fctx->adb,
                                                          query->addrinfo);
                        } else if (tried->count >= 2U) {
                                query->options |= DNS_FETCHOPT_EDNS512;
                                fctx->reason = "reducing the advertised EDNS "
                                               "UDP packet size to 512 octets";
                        }
                }
        }
        fctx->timeout = ISC_FALSE;

        /*
         * Use EDNS0, unless the caller doesn't want it, or we know that
         * the remote server doesn't like it.
         */
        if ((query->options & DNS_FETCHOPT_NOEDNS0) == 0) {
                if ((query->addrinfo->flags & DNS_FETCHOPT_NOEDNS0) == 0) {
                        unsigned int version = DNS_EDNS_VERSION;
                        unsigned int flags = query->addrinfo->flags;
                        isc_boolean_t reqnsid = res->view->requestnsid;
#ifdef ISC_PLATFORM_USESIT
                        isc_boolean_t reqsit = res->view->requestsit;
                        unsigned char sit[64];
#endif

                        if ((flags & FCTX_ADDRINFO_EDNSOK) != 0 &&
                            (query->options & DNS_FETCHOPT_EDNS512) == 0) {
                                udpsize = dns_adb_probesize2(fctx->adb,
                                                             query->addrinfo,
                                                             fctx->timeouts);
                                if (udpsize > res->udpsize)
                                        udpsize = res->udpsize;
                        }

                        if (peer != NULL)
                                (void)dns_peer_getudpsize(peer, &udpsize);

                        if (udpsize == 0U && res->udpsize == 512U)
                                udpsize = 512;

                        /*
                         * Was the size forced to 512 in the configuration?
                         */
                        if (udpsize == 512U)
                            query->options |= DNS_FETCHOPT_EDNS512;

                        /*
                         * We have talked to this server before.
                         */
                        if (hint != 0U)
                                udpsize = hint;

                        /*
                         * We know nothing about the peer's capabilities
                         * so start with minimal EDNS UDP size.
                         */
                        if (udpsize == 0U)
                                udpsize = 512;

                        if ((flags & DNS_FETCHOPT_EDNSVERSIONSET) != 0) {
                                version = flags & DNS_FETCHOPT_EDNSVERSIONMASK;
                                version >>= DNS_FETCHOPT_EDNSVERSIONSHIFT;
                        }

                        /* Request NSID/SIT/VERSION for current peer? */
                        if (peer != NULL) {
                                isc_uint8_t ednsversion;
                                (void) dns_peer_getrequestnsid(peer, &reqnsid);
#ifdef ISC_PLATFORM_USESIT
                                (void) dns_peer_getrequestsit(peer, &reqsit);
#endif
                                result = dns_peer_getednsversion(peer,
                                                                 &ednsversion);
                                if (result == ISC_R_SUCCESS &&
                                    ednsversion < version)
                                        version = ednsversion;
                        }
#ifdef ISC_PLATFORM_USESIT
                        if (NOSIT(query->addrinfo))
                                reqsit = ISC_FALSE;
#endif
                        if (reqnsid) {
                                INSIST(ednsopt < DNS_EDNSOPTIONS);
                                ednsopts[ednsopt].code = DNS_OPT_NSID;
                                ednsopts[ednsopt].length = 0;
                                ednsopts[ednsopt].value = NULL;
                                ednsopt++;
                        }
#ifdef ISC_PLATFORM_USESIT
#if DNS_EDNS_VERSION > 0
                        /*
                         * Some EDNS(0) servers don't ignore unknown options
                         * as it was not a explict requirement of RFC 2671.
                         * Only send SIT to EDNS(1) servers.
                         */
                        if (version < 1)
                                reqsit = ISC_FALSE;
#endif
                        if (reqsit) {
                                INSIST(ednsopt < DNS_EDNSOPTIONS);
                                ednsopts[ednsopt].code = DNS_OPT_SIT;
                                ednsopts[ednsopt].length = (isc_uint16_t)
                                        dns_adb_getsit(fctx->adb,
                                                       query->addrinfo,
                                                       sit, sizeof(sit));
                                if (ednsopts[ednsopt].length != 0) {
                                        ednsopts[ednsopt].value = sit;
                                        inc_stats(fctx->res,
                                                  dns_resstatscounter_sitout);
                                } else {
                                        compute_cc(query, sit, sizeof(sit));
                                        ednsopts[ednsopt].value = sit;
                                        ednsopts[ednsopt].length = 8;
                                        inc_stats(fctx->res,
                                                  dns_resstatscounter_sitcc);
                                }
                                ednsopt++;
                        }
#endif
                        query->ednsversion = version;
                        result = fctx_addopt(fctx->qmessage, version,
                                             udpsize, ednsopts, ednsopt);
                        if (reqnsid && result == ISC_R_SUCCESS) {
                                query->options |= DNS_FETCHOPT_WANTNSID;
                        } else if (result != ISC_R_SUCCESS) {
                                /*
                                 * We couldn't add the OPT, but we'll press on.
                                 * We're not using EDNS0, so set the NOEDNS0
                                 * bit.
                                 */
                                query->options |= DNS_FETCHOPT_NOEDNS0;
                                query->ednsversion = -1;
                                udpsize = 0;
                        }
                } else {
                        /*
                         * We know this server doesn't like EDNS0, so we
                         * won't use it.  Set the NOEDNS0 bit since we're
                         * not using EDNS0.
                         */
                        query->options |= DNS_FETCHOPT_NOEDNS0;
                        query->ednsversion = -1;
                }
        } else
                query->ednsversion = -1;

        /*
         * Record the UDP EDNS size choosen.
         */
        query->udpsize = udpsize;

        /*
         * If we need EDNS0 to do this query and aren't using it, we lose.
         */
        if (NEEDEDNS0(fctx) && (query->options & DNS_FETCHOPT_NOEDNS0) != 0) {
                result = DNS_R_SERVFAIL;
                goto cleanup_message;
        }

        if (udpsize > 512U)
                add_triededns(fctx, &query->addrinfo->sockaddr);

        if (udpsize == 512U)
                add_triededns512(fctx, &query->addrinfo->sockaddr);

        /*
         * Clear CD if EDNS is not in use.
         */
        if ((query->options & DNS_FETCHOPT_NOEDNS0) != 0)
                fctx->qmessage->flags &= ~DNS_MESSAGEFLAG_CD;

        /*
         * Add TSIG record tailored to the current recipient.
         */
        result = dns_view_getpeertsig(fctx->res->view, &ipaddr, &tsigkey);
        if (result != ISC_R_SUCCESS && result != ISC_R_NOTFOUND)
                goto cleanup_message;

        if (tsigkey != NULL) {
                result = dns_message_settsigkey(fctx->qmessage, tsigkey);
                dns_tsigkey_detach(&tsigkey);
                if (result != ISC_R_SUCCESS)
                        goto cleanup_message;
        }

        result = dns_message_rendersection(fctx->qmessage,
                                           DNS_SECTION_ADDITIONAL, 0);
        if (result != ISC_R_SUCCESS)
                goto cleanup_message;

        result = dns_message_renderend(fctx->qmessage);
        if (result != ISC_R_SUCCESS)
                goto cleanup_message;

        dns_compress_invalidate(&cctx);
        cleanup_cctx = ISC_FALSE;

        if (dns_message_gettsigkey(fctx->qmessage) != NULL) {
                dns_tsigkey_attach(dns_message_gettsigkey(fctx->qmessage),
                                   &query->tsigkey);
                result = dns_message_getquerytsig(fctx->qmessage,
                                                  fctx->res->mctx,
                                                  &query->tsig);
                if (result != ISC_R_SUCCESS)
                        goto cleanup_message;
        }

        /*
         * If using TCP, write the length of the message at the beginning
         * of the buffer.
         */
        if ((query->options & DNS_FETCHOPT_TCP) != 0) {
                isc_buffer_usedregion(&query->buffer, &r);
                isc_buffer_putuint16(&tcpbuffer, (isc_uint16_t)r.length);
                isc_buffer_add(&tcpbuffer, r.length);
        }

        /*
         * Log the outgoing packet.
         */
        dns_message_logfmtpacket2(fctx->qmessage, "sending packet to",
                                  &query->addrinfo->sockaddr,
                                  DNS_LOGCATEGORY_RESOLVER,
                                  DNS_LOGMODULE_PACKETS,
                                  &dns_master_style_comment,
                                  ISC_LOG_DEBUG(11),
                                  fctx->res->mctx);

        /*
         * We're now done with the query message.
         */
        dns_message_reset(fctx->qmessage, DNS_MESSAGE_INTENTRENDER);

        if (query->exclusivesocket)
                sock = dns_dispatch_getentrysocket(query->dispentry);
        else
                sock = dns_dispatch_getsocket(query->dispatch);
        /*
         * Send the query!
         */
        if ((query->options & DNS_FETCHOPT_TCP) == 0) {
                address = &query->addrinfo->sockaddr;
                if (query->exclusivesocket) {
                        result = isc_socket_connect(sock, address, task,
                                                    resquery_udpconnected,
                                                    query);
                        if (result != ISC_R_SUCCESS)
                                goto cleanup_message;
                        connecting = ISC_TRUE;
                        query->connects++;
                }
        }
        isc_buffer_usedregion(buffer, &r);

        /*
         * XXXRTH  Make sure we don't send to ourselves!  We should probably
         *              prune out these addresses when we get them from the ADB.
         */
        memset(&query->sendevent, 0, sizeof(query->sendevent));
        ISC_EVENT_INIT(&query->sendevent, sizeof(query->sendevent), 0, NULL,
                       ISC_SOCKEVENT_SENDDONE, resquery_senddone, query,
                       NULL, NULL, NULL);

        if (query->dscp == -1) {
                query->sendevent.attributes &= ~ISC_SOCKEVENTATTR_DSCP;
                query->sendevent.dscp = 0;
        } else {
                query->sendevent.attributes |= ISC_SOCKEVENTATTR_DSCP;
                query->sendevent.dscp = query->dscp;
                if ((query->options & DNS_FETCHOPT_TCP) != 0)
                        isc_socket_dscp(sock, query->dscp);
        }

        result = isc_socket_sendto2(sock, &r, task, address, NULL,
                                    &query->sendevent, 0);
        if (result != ISC_R_SUCCESS) {
                if (connecting) {
                        /*
                         * This query is still connecting.
                         * Mark it as canceled so that it will just be
                         * cleaned up when the connected event is received.
                         * Keep fctx around until the event is processed.
                         */
                        query->fctx->nqueries++;
                        query->attributes |= RESQUERY_ATTR_CANCELED;
                }
                goto cleanup_message;
        }

        query->sends++;

        QTRACE("sent");

        return (ISC_R_SUCCESS);

 cleanup_message:
        if (cleanup_cctx)
                dns_compress_invalidate(&cctx);

        dns_message_reset(fctx->qmessage, DNS_MESSAGE_INTENTRENDER);

        /*
         * Stop the dispatcher from listening.
         */
        dns_dispatch_removeresponse(&query->dispentry, NULL);

 cleanup_temps:
        if (qname != NULL)
                dns_message_puttempname(fctx->qmessage, &qname);
        if (qrdataset != NULL)
                dns_message_puttemprdataset(fctx->qmessage, &qrdataset);

        return (result);
}

static void
resquery_connected(isc_task_t *task, isc_event_t *event) {
        isc_socketevent_t *sevent = (isc_socketevent_t *)event;
        resquery_t *query = event->ev_arg;
        isc_boolean_t retry = ISC_FALSE;
        isc_interval_t interval;
        isc_result_t result;
        unsigned int attrs;
        fetchctx_t *fctx;

        REQUIRE(event->ev_type == ISC_SOCKEVENT_CONNECT);
        REQUIRE(VALID_QUERY(query));

        QTRACE("connected");

        UNUSED(task);

        /*
         * XXXRTH
         *
         * Currently we don't wait for the connect event before retrying
         * a query.  This means that if we get really behind, we may end
         * up doing extra work!
         */

        query->connects--;
        fctx = query->fctx;

        if (RESQUERY_CANCELED(query)) {
                /*
                 * This query was canceled while the connect() was in
                 * progress.
                 */
                isc_socket_detach(&query->tcpsocket);
                resquery_destroy(&query);
        } else {
                switch (sevent->result) {
                case ISC_R_SUCCESS:

                        /*
                         * Extend the idle timer for TCP.  20 seconds
                         * should be long enough for a TCP connection to be
                         * established, a single DNS request to be sent,
                         * and the response received.
                         */
                        isc_interval_set(&interval, 20, 0);
                        result = fctx_startidletimer(query->fctx, &interval);
                        if (result != ISC_R_SUCCESS) {
                                FCTXTRACE("query canceled: idle timer failed; "
                                          "responding");

                                fctx_cancelquery(&query, NULL, NULL, ISC_FALSE);
                                fctx_done(fctx, result, __LINE__);
                                break;
                        }
                        /*
                         * We are connected.  Create a dispatcher and
                         * send the query.
                         */
                        attrs = 0;
                        attrs |= DNS_DISPATCHATTR_TCP;
                        attrs |= DNS_DISPATCHATTR_PRIVATE;
                        attrs |= DNS_DISPATCHATTR_CONNECTED;
                        if (isc_sockaddr_pf(&query->addrinfo->sockaddr) ==
                            AF_INET)
                                attrs |= DNS_DISPATCHATTR_IPV4;
                        else
                                attrs |= DNS_DISPATCHATTR_IPV6;
                        attrs |= DNS_DISPATCHATTR_MAKEQUERY;

                        result = dns_dispatch_createtcp(query->dispatchmgr,
                                                     query->tcpsocket,
                                                     query->fctx->res->taskmgr,
                                                     4096, 2, 1, 1, 3, attrs,
                                                     &query->dispatch);

                        /*
                         * Regardless of whether dns_dispatch_create()
                         * succeeded or not, we don't need our reference
                         * to the socket anymore.
                         */
                        isc_socket_detach(&query->tcpsocket);

                        if (result == ISC_R_SUCCESS)
                                result = resquery_send(query);

                        if (result != ISC_R_SUCCESS) {
                                FCTXTRACE("query canceled: "
                                          "resquery_send() failed; responding");

                                fctx_cancelquery(&query, NULL, NULL, ISC_FALSE);
                                fctx_done(fctx, result, __LINE__);
                        }
                        break;

                case ISC_R_NETUNREACH:
                case ISC_R_HOSTUNREACH:
                case ISC_R_CONNREFUSED:
                case ISC_R_NOPERM:
                case ISC_R_ADDRNOTAVAIL:
                case ISC_R_CONNECTIONRESET:
                        FCTXTRACE3("query canceled in connected(): "
                                   "no route to host; no response",
                                   sevent->result);

                        /*
                         * No route to remote.
                         */
                        isc_socket_detach(&query->tcpsocket);
                        fctx_cancelquery(&query, NULL, NULL, ISC_TRUE);
                        retry = ISC_TRUE;
                        break;

                default:
                        FCTXTRACE3("query canceled in connected() due to "
                                   "unexpected event result; responding",
                                   sevent->result);

                        isc_socket_detach(&query->tcpsocket);
                        fctx_cancelquery(&query, NULL, NULL, ISC_FALSE);
                        break;
                }
        }

        isc_event_free(&event);

        if (retry) {
                /*
                 * Behave as if the idle timer has expired.  For TCP
                 * connections this may not actually reflect the latest timer.
                 */
                fctx->attributes &= ~FCTX_ATTR_ADDRWAIT;
                result = fctx_stopidletimer(fctx);
                if (result != ISC_R_SUCCESS)
                        fctx_done(fctx, result, __LINE__);
                else
                        fctx_try(fctx, ISC_TRUE, ISC_FALSE);
        }
}

static void
fctx_finddone(isc_task_t *task, isc_event_t *event) {
        fetchctx_t *fctx;
        dns_adbfind_t *find;
        dns_resolver_t *res;
        isc_boolean_t want_try = ISC_FALSE;
        isc_boolean_t want_done = ISC_FALSE;
        isc_boolean_t bucket_empty = ISC_FALSE;
        unsigned int bucketnum;
        isc_boolean_t dodestroy = ISC_FALSE;

        find = event->ev_sender;
        fctx = event->ev_arg;
        REQUIRE(VALID_FCTX(fctx));
        res = fctx->res;

        UNUSED(task);

        FCTXTRACE("finddone");

        bucketnum = fctx->bucketnum;
        LOCK(&res->buckets[bucketnum].lock);

        INSIST(fctx->pending > 0);
        fctx->pending--;

        if (ADDRWAIT(fctx)) {
                /*
                 * The fetch is waiting for a name to be found.
                 */
                INSIST(!SHUTTINGDOWN(fctx));
                fctx->attributes &= ~FCTX_ATTR_ADDRWAIT;
                if (event->ev_type == DNS_EVENT_ADBMOREADDRESSES) {
                        want_try = ISC_TRUE;
                } else {
                        fctx->findfail++;
                        if (fctx->pending == 0) {
                                /*
                                 * We've got nothing else to wait for and don't
                                 * know the answer.  There's nothing to do but
                                 * fail the fctx.
                                 */
                                want_done = ISC_TRUE;
                        }
                }
        } else if (SHUTTINGDOWN(fctx) && fctx->pending == 0 &&
                   fctx->nqueries == 0 && ISC_LIST_EMPTY(fctx->validators)) {

                if (fctx->references == 0) {
                        bucket_empty = fctx_unlink(fctx);
                        dodestroy = ISC_TRUE;
                }
        }
        UNLOCK(&res->buckets[bucketnum].lock);

        isc_event_free(&event);
        dns_adb_destroyfind(&find);

        if (want_try) {
                fctx_try(fctx, ISC_TRUE, ISC_FALSE);
        } else if (want_done) {
                FCTXTRACE("fetch failed in finddone(); return ISC_R_FAILURE");
                fctx_done(fctx, ISC_R_FAILURE, __LINE__);
        } else if (dodestroy) {
                fctx_destroy(fctx);
                if (bucket_empty)
                        empty_bucket(res);
        }
}


static inline isc_boolean_t
bad_server(fetchctx_t *fctx, isc_sockaddr_t *address) {
        isc_sockaddr_t *sa;

        for (sa = ISC_LIST_HEAD(fctx->bad);
             sa != NULL;
             sa = ISC_LIST_NEXT(sa, link)) {
                if (isc_sockaddr_equal(sa, address))
                        return (ISC_TRUE);
        }

        return (ISC_FALSE);
}

static inline isc_boolean_t
mark_bad(fetchctx_t *fctx) {
        dns_adbfind_t *curr;
        dns_adbaddrinfo_t *addrinfo;
        isc_boolean_t all_bad = ISC_TRUE;

        /*
         * Mark all known bad servers, so we don't try to talk to them
         * again.
         */

        /*
         * Mark any bad nameservers.
         */
        for (curr = ISC_LIST_HEAD(fctx->finds);
             curr != NULL;
             curr = ISC_LIST_NEXT(curr, publink)) {
                for (addrinfo = ISC_LIST_HEAD(curr->list);
                     addrinfo != NULL;
                     addrinfo = ISC_LIST_NEXT(addrinfo, publink)) {
                        if (bad_server(fctx, &addrinfo->sockaddr))
                                addrinfo->flags |= FCTX_ADDRINFO_MARK;
                        else
                                all_bad = ISC_FALSE;
                }
        }

        /*
         * Mark any bad forwarders.
         */
        for (addrinfo = ISC_LIST_HEAD(fctx->forwaddrs);
             addrinfo != NULL;
             addrinfo = ISC_LIST_NEXT(addrinfo, publink)) {
                if (bad_server(fctx, &addrinfo->sockaddr))
                        addrinfo->flags |= FCTX_ADDRINFO_MARK;
                else
                        all_bad = ISC_FALSE;
        }

        /*
         * Mark any bad alternates.
         */
        for (curr = ISC_LIST_HEAD(fctx->altfinds);
             curr != NULL;
             curr = ISC_LIST_NEXT(curr, publink)) {
                for (addrinfo = ISC_LIST_HEAD(curr->list);
                     addrinfo != NULL;
                     addrinfo = ISC_LIST_NEXT(addrinfo, publink)) {
                        if (bad_server(fctx, &addrinfo->sockaddr))
                                addrinfo->flags |= FCTX_ADDRINFO_MARK;
                        else
                                all_bad = ISC_FALSE;
                }
        }

        for (addrinfo = ISC_LIST_HEAD(fctx->altaddrs);
             addrinfo != NULL;
             addrinfo = ISC_LIST_NEXT(addrinfo, publink)) {
                if (bad_server(fctx, &addrinfo->sockaddr))
                        addrinfo->flags |= FCTX_ADDRINFO_MARK;
                else
                        all_bad = ISC_FALSE;
        }

        return (all_bad);
}

static void
add_bad(fetchctx_t *fctx, dns_adbaddrinfo_t *addrinfo, isc_result_t reason,
        badnstype_t badtype)
{
        char namebuf[DNS_NAME_FORMATSIZE];
        char addrbuf[ISC_SOCKADDR_FORMATSIZE];
        char classbuf[64];
        char typebuf[64];
        char code[64];
        isc_buffer_t b;
        isc_sockaddr_t *sa;
        const char *spc = "";
        isc_sockaddr_t *address = &addrinfo->sockaddr;

        if (reason == DNS_R_LAME)
                fctx->lamecount++;
        else {
                switch (badtype) {
                case badns_unreachable:
                        fctx->neterr++;
                        break;
                case badns_response:
                        fctx->badresp++;
                        break;
                case badns_validation:
                        break;  /* counted as 'valfail' */
                }
        }

        if (bad_server(fctx, address)) {
                /*
                 * We already know this server is bad.
                 */
                return;
        }

        FCTXTRACE("add_bad");

        sa = isc_mem_get(fctx->mctx, sizeof(*sa));
        if (sa == NULL)
                return;
        *sa = *address;
        ISC_LIST_INITANDAPPEND(fctx->bad, sa, link);

        if (reason == DNS_R_LAME)       /* already logged */
                return;

        if (reason == DNS_R_UNEXPECTEDRCODE &&
            fctx->rmessage->rcode == dns_rcode_servfail &&
            ISFORWARDER(addrinfo))
                return;

        if (reason == DNS_R_UNEXPECTEDRCODE) {
                isc_buffer_init(&b, code, sizeof(code) - 1);
                dns_rcode_totext(fctx->rmessage->rcode, &b);
                code[isc_buffer_usedlength(&b)] = '\0';
                spc = " ";
        } else if (reason == DNS_R_UNEXPECTEDOPCODE) {
                isc_buffer_init(&b, code, sizeof(code) - 1);
                dns_opcode_totext((dns_opcode_t)fctx->rmessage->opcode, &b);
                code[isc_buffer_usedlength(&b)] = '\0';
                spc = " ";
        } else {
                code[0] = '\0';
        }
        dns_name_format(&fctx->name, namebuf, sizeof(namebuf));
        dns_rdatatype_format(fctx->type, typebuf, sizeof(typebuf));
        dns_rdataclass_format(fctx->res->rdclass, classbuf, sizeof(classbuf));
        isc_sockaddr_format(address, addrbuf, sizeof(addrbuf));
        isc_log_write(dns_lctx, DNS_LOGCATEGORY_LAME_SERVERS,
                      DNS_LOGMODULE_RESOLVER, ISC_LOG_INFO,
                      "%s%s%s resolving '%s/%s/%s': %s",
                      code, spc, dns_result_totext(reason),
                      namebuf, typebuf, classbuf, addrbuf);
}

/*
 * Sort addrinfo list by RTT.
 */
static void
sort_adbfind(dns_adbfind_t *find) {
        dns_adbaddrinfo_t *best, *curr;
        dns_adbaddrinfolist_t sorted;

        /* Lame N^2 bubble sort. */
        ISC_LIST_INIT(sorted);
        while (!ISC_LIST_EMPTY(find->list)) {
                best = ISC_LIST_HEAD(find->list);
                curr = ISC_LIST_NEXT(best, publink);
                while (curr != NULL) {
                        if (curr->srtt < best->srtt)
                                best = curr;
                        curr = ISC_LIST_NEXT(curr, publink);
                }
                ISC_LIST_UNLINK(find->list, best, publink);
                ISC_LIST_APPEND(sorted, best, publink);
        }
        find->list = sorted;
}

/*
 * Sort a list of finds by server RTT.
 */
static void
sort_finds(dns_adbfindlist_t *findlist) {
        dns_adbfind_t *best, *curr;
        dns_adbfindlist_t sorted;
        dns_adbaddrinfo_t *addrinfo, *bestaddrinfo;

        /* Sort each find's addrinfo list by SRTT. */
        for (curr = ISC_LIST_HEAD(*findlist);
             curr != NULL;
             curr = ISC_LIST_NEXT(curr, publink))
                sort_adbfind(curr);

        /* Lame N^2 bubble sort. */
        ISC_LIST_INIT(sorted);
        while (!ISC_LIST_EMPTY(*findlist)) {
                best = ISC_LIST_HEAD(*findlist);
                bestaddrinfo = ISC_LIST_HEAD(best->list);
                INSIST(bestaddrinfo != NULL);
                curr = ISC_LIST_NEXT(best, publink);
                while (curr != NULL) {
                        addrinfo = ISC_LIST_HEAD(curr->list);
                        INSIST(addrinfo != NULL);
                        if (addrinfo->srtt < bestaddrinfo->srtt) {
                                best = curr;
                                bestaddrinfo = addrinfo;
                        }
                        curr = ISC_LIST_NEXT(curr, publink);
                }
                ISC_LIST_UNLINK(*findlist, best, publink);
                ISC_LIST_APPEND(sorted, best, publink);
        }
        *findlist = sorted;
}

static void
findname(fetchctx_t *fctx, dns_name_t *name, in_port_t port,
         unsigned int options, unsigned int flags, isc_stdtime_t now,
         isc_boolean_t *need_alternate)
{
        dns_adbaddrinfo_t *ai;
        dns_adbfind_t *find;
        dns_resolver_t *res;
        isc_boolean_t unshared;
        isc_result_t result;

        res = fctx->res;
        unshared = ISC_TF((fctx->options & DNS_FETCHOPT_UNSHARED) != 0);
        /*
         * If this name is a subdomain of the query domain, tell
         * the ADB to start looking using zone/hint data. This keeps us
         * from getting stuck if the nameserver is beneath the zone cut
         * and we don't know its address (e.g. because the A record has
         * expired).
         */
        if (dns_name_issubdomain(name, &fctx->domain))
                options |= DNS_ADBFIND_STARTATZONE;
        options |= DNS_ADBFIND_GLUEOK;
        options |= DNS_ADBFIND_HINTOK;

        /*
         * See what we know about this address.
         */
        find = NULL;
        result = dns_adb_createfind2(fctx->adb,
                                     res->buckets[fctx->bucketnum].task,
                                     fctx_finddone, fctx, name,
                                     &fctx->name, fctx->type,
                                     options, now, NULL,
                                     res->view->dstport,
                                     fctx->depth + 1, fctx->qc, &find);
        if (result != ISC_R_SUCCESS) {
                if (result == DNS_R_ALIAS) {
                        char namebuf[DNS_NAME_FORMATSIZE];

                        /*
                         * XXXRTH  Follow the CNAME/DNAME chain?
                         */
                        dns_adb_destroyfind(&find);
                        fctx->adberr++;
                        dns_name_format(name, namebuf, sizeof(namebuf));
                        isc_log_write(dns_lctx, DNS_LOGCATEGORY_CNAME,
                                      DNS_LOGMODULE_RESOLVER, ISC_LOG_INFO,
                                      "skipping nameserver '%s' because it "
                                      "is a CNAME, while resolving '%s'",
                                      namebuf, fctx->info);
                }
        } else if (!ISC_LIST_EMPTY(find->list)) {
                /*
                 * We have at least some of the addresses for the
                 * name.
                 */
                INSIST((find->options & DNS_ADBFIND_WANTEVENT) == 0);
                if (flags != 0 || port != 0) {
                        for (ai = ISC_LIST_HEAD(find->list);
                             ai != NULL;
                             ai = ISC_LIST_NEXT(ai, publink)) {
                                ai->flags |= flags;
                                if (port != 0)
                                        isc_sockaddr_setport(&ai->sockaddr,
                                                             port);
                        }
                }
                if ((flags & FCTX_ADDRINFO_FORWARDER) != 0)
                        ISC_LIST_APPEND(fctx->altfinds, find, publink);
                else
                        ISC_LIST_APPEND(fctx->finds, find, publink);
        } else {
                /*
                 * We don't know any of the addresses for this
                 * name.
                 */
                if ((find->options & DNS_ADBFIND_WANTEVENT) != 0) {
                        /*
                         * We're looking for them and will get an
                         * event about it later.
                         */
                        fctx->pending++;
                        /*
                         * Bootstrap.
                         */
                        if (need_alternate != NULL &&
                            !*need_alternate && unshared &&
                            ((res->dispatches4 == NULL &&
                              find->result_v6 != DNS_R_NXDOMAIN) ||
                             (res->dispatches6 == NULL &&
                              find->result_v4 != DNS_R_NXDOMAIN)))
                                *need_alternate = ISC_TRUE;
                } else {
                        if ((find->options & DNS_ADBFIND_LAMEPRUNED) != 0)
                                fctx->lamecount++; /* cached lame server */
                        else
                                fctx->adberr++; /* unreachable server, etc. */

                        /*
                         * If we know there are no addresses for
                         * the family we are using then try to add
                         * an alternative server.
                         */
                        if (need_alternate != NULL && !*need_alternate &&
                            ((res->dispatches4 == NULL &&
                              find->result_v6 == DNS_R_NXRRSET) ||
                             (res->dispatches6 == NULL &&
                              find->result_v4 == DNS_R_NXRRSET)))
                                *need_alternate = ISC_TRUE;
                        dns_adb_destroyfind(&find);
                }
        }
}

static isc_boolean_t
isstrictsubdomain(dns_name_t *name1, dns_name_t *name2) {
        int order;
        unsigned int nlabels;
        dns_namereln_t namereln;

        namereln = dns_name_fullcompare(name1, name2, &order, &nlabels);
        return (ISC_TF(namereln == dns_namereln_subdomain));
}

static isc_result_t
fctx_getaddresses(fetchctx_t *fctx, isc_boolean_t badcache) {
        dns_rdata_t rdata = DNS_RDATA_INIT;
        isc_result_t result;
        dns_resolver_t *res;
        isc_stdtime_t now;
        unsigned int stdoptions = 0;
        dns_forwarder_t *fwd;
        dns_adbaddrinfo_t *ai;
        isc_boolean_t all_bad;
        dns_rdata_ns_t ns;
        isc_boolean_t need_alternate = ISC_FALSE;

        FCTXTRACE("getaddresses");

        /*
         * Don't pound on remote servers.  (Failsafe!)
         */
        fctx->restarts++;
        if (fctx->restarts > 100) {
                FCTXTRACE("too many restarts");
                return (DNS_R_SERVFAIL);
        }

        res = fctx->res;

        if (fctx->depth > res->maxdepth) {
                isc_log_write(dns_lctx, DNS_LOGCATEGORY_RESOLVER,
                              DNS_LOGMODULE_RESOLVER, ISC_LOG_DEBUG(3),
                              "too much NS indirection resolving '%s'",
                              fctx->info);
                return (DNS_R_SERVFAIL);
        }

        /*
         * Forwarders.
         */

        INSIST(ISC_LIST_EMPTY(fctx->forwaddrs));
        INSIST(ISC_LIST_EMPTY(fctx->altaddrs));

        /*
         * If this fctx has forwarders, use them; otherwise use any
         * selective forwarders specified in the view; otherwise use the
         * resolver's forwarders (if any).
         */
        fwd = ISC_LIST_HEAD(fctx->forwarders);
        if (fwd == NULL) {
                dns_forwarders_t *forwarders = NULL;
                dns_name_t *name = &fctx->name;
                dns_name_t suffix;
                unsigned int labels;
                dns_fixedname_t fixed;
                dns_name_t *domain;

                /*
                 * DS records are found in the parent server.
                 * Strip label to get the correct forwarder (if any).
                 */
                if (dns_rdatatype_atparent(fctx->type) &&
                    dns_name_countlabels(name) > 1) {
                        dns_name_init(&suffix, NULL);
                        labels = dns_name_countlabels(name);
                        dns_name_getlabelsequence(name, 1, labels - 1, &suffix);
                        name = &suffix;
                }

                dns_fixedname_init(&fixed);
                domain = dns_fixedname_name(&fixed);
                result = dns_fwdtable_find2(fctx->res->view->fwdtable, name,
                                            domain, &forwarders);
                if (result == ISC_R_SUCCESS) {
                        fwd = ISC_LIST_HEAD(forwarders->fwdrs);
                        fctx->fwdpolicy = forwarders->fwdpolicy;
                        if (fctx->fwdpolicy == dns_fwdpolicy_only &&
                            isstrictsubdomain(domain, &fctx->domain)) {
                                dns_name_free(&fctx->domain, fctx->mctx);
                                dns_name_init(&fctx->domain, NULL);
                                result = dns_name_dup(domain, fctx->mctx,
                                                      &fctx->domain);
                                if (result != ISC_R_SUCCESS)
                                        return (result);
                        }
                }
        }

        while (fwd != NULL) {
                if ((isc_sockaddr_pf(&fwd->addr) == AF_INET &&
                         fctx->res->dispatches4 == NULL) ||
                    (isc_sockaddr_pf(&fwd->addr) == AF_INET6 &&
                        fctx->res->dispatches6 == NULL)) {
                                fwd = ISC_LIST_NEXT(fwd, link);
                                continue;
                }
                ai = NULL;
                result = dns_adb_findaddrinfo(fctx->adb, &fwd->addr, &ai, 0);
                if (result == ISC_R_SUCCESS) {
                        dns_adbaddrinfo_t *cur;
                        ai->flags |= FCTX_ADDRINFO_FORWARDER;
                        ai->dscp = fwd->dscp;
                        cur = ISC_LIST_HEAD(fctx->forwaddrs);
                        while (cur != NULL && cur->srtt < ai->srtt)
                                cur = ISC_LIST_NEXT(cur, publink);
                        if (cur != NULL)
                                ISC_LIST_INSERTBEFORE(fctx->forwaddrs, cur,
                                                      ai, publink);
                        else
                                ISC_LIST_APPEND(fctx->forwaddrs, ai, publink);
                }
                fwd = ISC_LIST_NEXT(fwd, link);
        }

        /*
         * If the forwarding policy is "only", we don't need the addresses
         * of the nameservers.
         */
        if (fctx->fwdpolicy == dns_fwdpolicy_only)
                goto out;

        /*
         * Normal nameservers.
         */

        stdoptions = DNS_ADBFIND_WANTEVENT | DNS_ADBFIND_EMPTYEVENT;
        if (fctx->restarts == 1) {
                /*
                 * To avoid sending out a flood of queries likely to
                 * result in NXRRSET, we suppress fetches for address
                 * families we don't have the first time through,
                 * provided that we have addresses in some family we
                 * can use.
                 *
                 * We don't want to set this option all the time, since
                 * if fctx->restarts > 1, we've clearly been having trouble
                 * with the addresses we had, so getting more could help.
                 */
                stdoptions |= DNS_ADBFIND_AVOIDFETCHES;
        }
        if (res->dispatches4 != NULL)
                stdoptions |= DNS_ADBFIND_INET;
        if (res->dispatches6 != NULL)
                stdoptions |= DNS_ADBFIND_INET6;

        if ((stdoptions & DNS_ADBFIND_ADDRESSMASK) == 0)
                return (DNS_R_SERVFAIL);

        isc_stdtime_get(&now);

        INSIST(ISC_LIST_EMPTY(fctx->finds));
        INSIST(ISC_LIST_EMPTY(fctx->altfinds));

        for (result = dns_rdataset_first(&fctx->nameservers);
             result == ISC_R_SUCCESS;
             result = dns_rdataset_next(&fctx->nameservers))
        {
                dns_rdataset_current(&fctx->nameservers, &rdata);
                /*
                 * Extract the name from the NS record.
                 */
                result = dns_rdata_tostruct(&rdata, &ns, NULL);
                if (result != ISC_R_SUCCESS)
                        continue;

                findname(fctx, &ns.name, 0, stdoptions, 0, now,
                         &need_alternate);
                dns_rdata_reset(&rdata);
                dns_rdata_freestruct(&ns);
        }
        if (result != ISC_R_NOMORE)
                return (result);

        /*
         * Do we need to use 6 to 4?
         */
        if (need_alternate) {
                int family;
                alternate_t *a;
                family = (res->dispatches6 != NULL) ? AF_INET6 : AF_INET;
                for (a = ISC_LIST_HEAD(fctx->res->alternates);
                     a != NULL;
                     a = ISC_LIST_NEXT(a, link)) {
                        if (!a->isaddress) {
                                findname(fctx, &a->_u._n.name, a->_u._n.port,
                                         stdoptions, FCTX_ADDRINFO_FORWARDER,
                                         now, NULL);
                                continue;
                        }
                        if (isc_sockaddr_pf(&a->_u.addr) != family)
                                continue;
                        ai = NULL;
                        result = dns_adb_findaddrinfo(fctx->adb, &a->_u.addr,
                                                      &ai, 0);
                        if (result == ISC_R_SUCCESS) {
                                dns_adbaddrinfo_t *cur;
                                ai->flags |= FCTX_ADDRINFO_FORWARDER;
                                cur = ISC_LIST_HEAD(fctx->altaddrs);
                                while (cur != NULL && cur->srtt < ai->srtt)
                                        cur = ISC_LIST_NEXT(cur, publink);
                                if (cur != NULL)
                                        ISC_LIST_INSERTBEFORE(fctx->altaddrs,
                                                              cur, ai, publink);
                                else
                                        ISC_LIST_APPEND(fctx->altaddrs, ai,
                                                        publink);
                        }
                }
        }

 out:
        /*
         * Mark all known bad servers.
         */
        all_bad = mark_bad(fctx);

        /*
         * How are we doing?
         */
        if (all_bad) {
                /*
                 * We've got no addresses.
                 */
                if (fctx->pending > 0) {
                        /*
                         * We're fetching the addresses, but don't have any
                         * yet.   Tell the caller to wait for an answer.
                         */
                        result = DNS_R_WAIT;
                } else {
                        isc_time_t expire;
                        isc_interval_t i;
                        /*
                         * We've lost completely.  We don't know any
                         * addresses, and the ADB has told us it can't get
                         * them.
                         */
                        FCTXTRACE("no addresses");
                        isc_interval_set(&i, DNS_RESOLVER_BADCACHETTL(fctx), 0);
                        result = isc_time_nowplusinterval(&expire, &i);
                        if (badcache &&
                            (fctx->type == dns_rdatatype_dnskey ||
                             fctx->type == dns_rdatatype_dlv ||
                             fctx->type == dns_rdatatype_ds) &&
                             result == ISC_R_SUCCESS)
                                dns_resolver_addbadcache(fctx->res,
                                                         &fctx->name,
                                                         fctx->type, &expire);
                        result = ISC_R_FAILURE;
                }
        } else {
                /*
                 * We've found some addresses.  We might still be looking
                 * for more addresses.
                 */
                sort_finds(&fctx->finds);
                sort_finds(&fctx->altfinds);
                result = ISC_R_SUCCESS;
        }

        return (result);
}

static inline void
possibly_mark(fetchctx_t *fctx, dns_adbaddrinfo_t *addr) {
        isc_netaddr_t na;
        char buf[ISC_NETADDR_FORMATSIZE];
        isc_sockaddr_t *sa;
        isc_boolean_t aborted = ISC_FALSE;
        isc_boolean_t bogus;
        dns_acl_t *blackhole;
        isc_netaddr_t ipaddr;
        dns_peer_t *peer = NULL;
        dns_resolver_t *res;
        const char *msg = NULL;

        sa = &addr->sockaddr;

        res = fctx->res;
        isc_netaddr_fromsockaddr(&ipaddr, sa);
        blackhole = dns_dispatchmgr_getblackhole(res->dispatchmgr);
        (void) dns_peerlist_peerbyaddr(res->view->peers, &ipaddr, &peer);

        if (blackhole != NULL) {
                int match;

                if (dns_acl_match(&ipaddr, NULL, blackhole,
                                  &res->view->aclenv,
                                  &match, NULL) == ISC_R_SUCCESS &&
                    match > 0)
                        aborted = ISC_TRUE;
        }

        if (peer != NULL &&
            dns_peer_getbogus(peer, &bogus) == ISC_R_SUCCESS &&
            bogus)
                aborted = ISC_TRUE;

        if (!isc_log_wouldlog(dns_lctx, ISC_LOG_DEBUG(3)))
                return;

        if (aborted) {
                addr->flags |= FCTX_ADDRINFO_MARK;
                msg = "ignoring blackholed / bogus server: ";
        } else if (isc_sockaddr_ismulticast(sa)) {
                addr->flags |= FCTX_ADDRINFO_MARK;
                msg = "ignoring multicast address: ";
        } else if (isc_sockaddr_isexperimental(sa)) {
                addr->flags |= FCTX_ADDRINFO_MARK;
                msg = "ignoring experimental address: ";
        } else if (sa->type.sa.sa_family != AF_INET6) {
                return;
        } else if (IN6_IS_ADDR_V4MAPPED(&sa->type.sin6.sin6_addr)) {
                addr->flags |= FCTX_ADDRINFO_MARK;
                msg = "ignoring IPv6 mapped IPV4 address: ";
        } else if (IN6_IS_ADDR_V4COMPAT(&sa->type.sin6.sin6_addr)) {
                addr->flags |= FCTX_ADDRINFO_MARK;
                msg = "ignoring IPv6 compatibility IPV4 address: ";
        } else
                return;

        isc_netaddr_fromsockaddr(&na, sa);
        isc_netaddr_format(&na, buf, sizeof(buf));
        FCTXTRACE2(msg, buf);
}

static inline dns_adbaddrinfo_t *
fctx_nextaddress(fetchctx_t *fctx) {
        dns_adbfind_t *find, *start;
        dns_adbaddrinfo_t *addrinfo;
        dns_adbaddrinfo_t *faddrinfo;

        /*
         * Return the next untried address, if any.
         */

        /*
         * Find the first unmarked forwarder (if any).
         */
        for (addrinfo = ISC_LIST_HEAD(fctx->forwaddrs);
             addrinfo != NULL;
             addrinfo = ISC_LIST_NEXT(addrinfo, publink)) {
                if (!UNMARKED(addrinfo))
                        continue;
                possibly_mark(fctx, addrinfo);
                if (UNMARKED(addrinfo)) {
                        addrinfo->flags |= FCTX_ADDRINFO_MARK;
                        fctx->find = NULL;
                        return (addrinfo);
                }
        }

        /*
         * No forwarders.  Move to the next find.
         */

        fctx->attributes |= FCTX_ATTR_TRIEDFIND;

        find = fctx->find;
        if (find == NULL)
                find = ISC_LIST_HEAD(fctx->finds);
        else {
                find = ISC_LIST_NEXT(find, publink);
                if (find == NULL)
                        find = ISC_LIST_HEAD(fctx->finds);
        }

        /*
         * Find the first unmarked addrinfo.
         */
        addrinfo = NULL;
        if (find != NULL) {
                start = find;
                do {
                        for (addrinfo = ISC_LIST_HEAD(find->list);
                             addrinfo != NULL;
                             addrinfo = ISC_LIST_NEXT(addrinfo, publink)) {
                                if (!UNMARKED(addrinfo))
                                        continue;
                                possibly_mark(fctx, addrinfo);
                                if (UNMARKED(addrinfo)) {
                                        addrinfo->flags |= FCTX_ADDRINFO_MARK;
                                        break;
                                }
                        }
                        if (addrinfo != NULL)
                                break;
                        find = ISC_LIST_NEXT(find, publink);
                        if (find == NULL)
                                find = ISC_LIST_HEAD(fctx->finds);
                } while (find != start);
        }

        fctx->find = find;
        if (addrinfo != NULL)
                return (addrinfo);

        /*
         * No nameservers left.  Try alternates.
         */

        fctx->attributes |= FCTX_ATTR_TRIEDALT;

        find = fctx->altfind;
        if (find == NULL)
                find = ISC_LIST_HEAD(fctx->altfinds);
        else {
                find = ISC_LIST_NEXT(find, publink);
                if (find == NULL)
                        find = ISC_LIST_HEAD(fctx->altfinds);
        }

        /*
         * Find the first unmarked addrinfo.
         */
        addrinfo = NULL;
        if (find != NULL) {
                start = find;
                do {
                        for (addrinfo = ISC_LIST_HEAD(find->list);
                             addrinfo != NULL;
                             addrinfo = ISC_LIST_NEXT(addrinfo, publink)) {
                                if (!UNMARKED(addrinfo))
                                        continue;
                                possibly_mark(fctx, addrinfo);
                                if (UNMARKED(addrinfo)) {
                                        addrinfo->flags |= FCTX_ADDRINFO_MARK;
                                        break;
                                }
                        }
                        if (addrinfo != NULL)
                                break;
                        find = ISC_LIST_NEXT(find, publink);
                        if (find == NULL)
                                find = ISC_LIST_HEAD(fctx->altfinds);
                } while (find != start);
        }

        faddrinfo = addrinfo;

        /*
         * See if we have a better alternate server by address.
         */

        for (addrinfo = ISC_LIST_HEAD(fctx->altaddrs);
             addrinfo != NULL;
             addrinfo = ISC_LIST_NEXT(addrinfo, publink)) {
                if (!UNMARKED(addrinfo))
                        continue;
                possibly_mark(fctx, addrinfo);
                if (UNMARKED(addrinfo) &&
                    (faddrinfo == NULL ||
                     addrinfo->srtt < faddrinfo->srtt)) {
                        if (faddrinfo != NULL)
                                faddrinfo->flags &= ~FCTX_ADDRINFO_MARK;
                        addrinfo->flags |= FCTX_ADDRINFO_MARK;
                        break;
                }
        }

        if (addrinfo == NULL) {
                addrinfo = faddrinfo;
                fctx->altfind = find;
        }

        return (addrinfo);
}

static void
fctx_try(fetchctx_t *fctx, isc_boolean_t retrying, isc_boolean_t badcache) {
        isc_result_t result;
        dns_adbaddrinfo_t *addrinfo;

        FCTXTRACE("try");

        REQUIRE(!ADDRWAIT(fctx));

        /* We've already exceeded maximum query count */
        if (isc_counter_used(fctx->qc) > fctx->res->maxqueries) {
                isc_log_write(dns_lctx, DNS_LOGCATEGORY_RESOLVER,
                              DNS_LOGMODULE_RESOLVER, ISC_LOG_DEBUG(3),
                              "exceeded max queries resolving '%s'",
                              fctx->info);
                fctx_done(fctx, DNS_R_SERVFAIL, __LINE__);
                return;
        }

        addrinfo = fctx_nextaddress(fctx);
        if (addrinfo == NULL) {
                /*
                 * We have no more addresses.  Start over.
                 */
                fctx_cancelqueries(fctx, ISC_TRUE);
                fctx_cleanupfinds(fctx);
                fctx_cleanupaltfinds(fctx);
                fctx_cleanupforwaddrs(fctx);
                fctx_cleanupaltaddrs(fctx);
                result = fctx_getaddresses(fctx, badcache);
                if (result == DNS_R_WAIT) {
                        /*
                         * Sleep waiting for addresses.
                         */
                        FCTXTRACE("addrwait");
                        fctx->attributes |= FCTX_ATTR_ADDRWAIT;
                        return;
                } else if (result != ISC_R_SUCCESS) {
                        /*
                         * Something bad happened.
                         */
                        fctx_done(fctx, result, __LINE__);
                        return;
                }

                addrinfo = fctx_nextaddress(fctx);
                /*
                 * While we may have addresses from the ADB, they
                 * might be bad ones.  In this case, return SERVFAIL.
                 */
                if (addrinfo == NULL) {
                        fctx_done(fctx, DNS_R_SERVFAIL, __LINE__);
                        return;
                }
        }

        if (dns_name_countlabels(&fctx->domain) > 2) {
                result = isc_counter_increment(fctx->qc);
                if (result != ISC_R_SUCCESS) {
                        isc_log_write(dns_lctx, DNS_LOGCATEGORY_RESOLVER,
                                      DNS_LOGMODULE_RESOLVER, ISC_LOG_DEBUG(3),
                                      "exceeded max queries resolving '%s'",
                                      fctx->info);
                        fctx_done(fctx, DNS_R_SERVFAIL, __LINE__);
                        return;
                }
        }

        result = fctx_query(fctx, addrinfo, fctx->options);
        if (result != ISC_R_SUCCESS)
                fctx_done(fctx, result, __LINE__);
        else if (retrying)
                inc_stats(fctx->res, dns_resstatscounter_retry);
}

static isc_boolean_t
fctx_unlink(fetchctx_t *fctx) {
        dns_resolver_t *res;
        unsigned int bucketnum;

        /*
         * Caller must be holding the bucket lock.
         */

        REQUIRE(VALID_FCTX(fctx));
        REQUIRE(fctx->state == fetchstate_done ||
                fctx->state == fetchstate_init);
        REQUIRE(ISC_LIST_EMPTY(fctx->events));
        REQUIRE(ISC_LIST_EMPTY(fctx->queries));
        REQUIRE(ISC_LIST_EMPTY(fctx->finds));
        REQUIRE(ISC_LIST_EMPTY(fctx->altfinds));
        REQUIRE(fctx->pending == 0);
        REQUIRE(fctx->references == 0);
        REQUIRE(ISC_LIST_EMPTY(fctx->validators));

        FCTXTRACE("unlink");

        res = fctx->res;
        bucketnum = fctx->bucketnum;

        ISC_LIST_UNLINK(res->buckets[bucketnum].fctxs, fctx, link);

        LOCK(&res->nlock);
        res->nfctx--;
        UNLOCK(&res->nlock);
        dec_stats(res, dns_resstatscounter_nfetch);

        if (res->buckets[bucketnum].exiting &&
            ISC_LIST_EMPTY(res->buckets[bucketnum].fctxs))
                return (ISC_TRUE);

        return (ISC_FALSE);
}

static void
fctx_destroy(fetchctx_t *fctx) {
        isc_sockaddr_t *sa, *next_sa;
        struct tried *tried;

        REQUIRE(VALID_FCTX(fctx));
        REQUIRE(fctx->state == fetchstate_done ||
                fctx->state == fetchstate_init);
        REQUIRE(ISC_LIST_EMPTY(fctx->events));
        REQUIRE(ISC_LIST_EMPTY(fctx->queries));
        REQUIRE(ISC_LIST_EMPTY(fctx->finds));
        REQUIRE(ISC_LIST_EMPTY(fctx->altfinds));
        REQUIRE(fctx->pending == 0);
        REQUIRE(fctx->references == 0);
        REQUIRE(ISC_LIST_EMPTY(fctx->validators));
        REQUIRE(!ISC_LINK_LINKED(fctx, link));

        FCTXTRACE("destroy");

        /*
         * Free bad.
         */
        for (sa = ISC_LIST_HEAD(fctx->bad);
             sa != NULL;
             sa = next_sa) {
                next_sa = ISC_LIST_NEXT(sa, link);
                ISC_LIST_UNLINK(fctx->bad, sa, link);
                isc_mem_put(fctx->mctx, sa, sizeof(*sa));
        }

        for (tried = ISC_LIST_HEAD(fctx->edns);
             tried != NULL;
             tried = ISC_LIST_HEAD(fctx->edns)) {
                ISC_LIST_UNLINK(fctx->edns, tried, link);
                isc_mem_put(fctx->mctx, tried, sizeof(*tried));
        }

        for (tried = ISC_LIST_HEAD(fctx->edns512);
             tried != NULL;
             tried = ISC_LIST_HEAD(fctx->edns512)) {
                ISC_LIST_UNLINK(fctx->edns512, tried, link);
                isc_mem_put(fctx->mctx, tried, sizeof(*tried));
        }

        for (sa = ISC_LIST_HEAD(fctx->bad_edns);
             sa != NULL;
             sa = next_sa) {
                next_sa = ISC_LIST_NEXT(sa, link);
                ISC_LIST_UNLINK(fctx->bad_edns, sa, link);
                isc_mem_put(fctx->mctx, sa, sizeof(*sa));
        }

        isc_counter_detach(&fctx->qc);
        isc_timer_detach(&fctx->timer);
        dns_message_destroy(&fctx->rmessage);
        dns_message_destroy(&fctx->qmessage);
        if (dns_name_countlabels(&fctx->domain) > 0)
                dns_name_free(&fctx->domain, fctx->mctx);
        if (dns_rdataset_isassociated(&fctx->nameservers))
                dns_rdataset_disassociate(&fctx->nameservers);
        dns_name_free(&fctx->name, fctx->mctx);
        dns_db_detach(&fctx->cache);
        dns_adb_detach(&fctx->adb);
        isc_mem_free(fctx->mctx, fctx->info);
        isc_mem_putanddetach(&fctx->mctx, fctx, sizeof(*fctx));
}

/*
 * Fetch event handlers.
 */

static void
fctx_timeout(isc_task_t *task, isc_event_t *event) {
        fetchctx_t *fctx = event->ev_arg;
        isc_timerevent_t *tevent = (isc_timerevent_t *)event;
        resquery_t *query;

        REQUIRE(VALID_FCTX(fctx));

        UNUSED(task);

        FCTXTRACE("timeout");

        inc_stats(fctx->res, dns_resstatscounter_querytimeout);

        if (event->ev_type == ISC_TIMEREVENT_LIFE) {
                fctx->reason = NULL;
                fctx_done(fctx, ISC_R_TIMEDOUT, __LINE__);
        } else {
                isc_result_t result;

                fctx->timeouts++;
                fctx->timeout = ISC_TRUE;

                /*
                 * We could cancel the running queries here, or we could let
                 * them keep going.  Since we normally use separate sockets for
                 * different queries, we adopt the former approach to reduce
                 * the number of open sockets: cancel the oldest query if it
                 * expired after the query had started (this is usually the
                 * case but is not always so, depending on the task schedule
                 * timing).
                 */
                query = ISC_LIST_HEAD(fctx->queries);
                if (query != NULL &&
                    isc_time_compare(&tevent->due, &query->start) >= 0)
                {
                        FCTXTRACE("query timed out; no response");
                        fctx_cancelquery(&query, NULL, NULL, ISC_TRUE);
                }
                fctx->attributes &= ~FCTX_ATTR_ADDRWAIT;

                /*
                 * Our timer has triggered.  Reestablish the fctx lifetime
                 * timer.
                 */
                result = fctx_starttimer(fctx);
                if (result != ISC_R_SUCCESS)
                        fctx_done(fctx, result, __LINE__);
                else
                        /*
                         * Keep trying.
                         */
                        fctx_try(fctx, ISC_TRUE, ISC_FALSE);
        }

        isc_event_free(&event);
}

static void
fctx_shutdown(fetchctx_t *fctx) {
        isc_event_t *cevent;

        /*
         * Start the shutdown process for fctx, if it isn't already underway.
         */

        FCTXTRACE("shutdown");

        /*
         * The caller must be holding the appropriate bucket lock.
         */

        if (fctx->want_shutdown)
                return;

        fctx->want_shutdown = ISC_TRUE;

        /*
         * Unless we're still initializing (in which case the
         * control event is still outstanding), we need to post
         * the control event to tell the fetch we want it to
         * exit.
         */
        if (fctx->state != fetchstate_init) {
                cevent = &fctx->control_event;
                isc_task_send(fctx->res->buckets[fctx->bucketnum].task,
                              &cevent);
        }
}

static void
fctx_doshutdown(isc_task_t *task, isc_event_t *event) {
        fetchctx_t *fctx = event->ev_arg;
        isc_boolean_t bucket_empty = ISC_FALSE;
        dns_resolver_t *res;
        unsigned int bucketnum;
        dns_validator_t *validator;
        isc_boolean_t dodestroy = ISC_FALSE;

        REQUIRE(VALID_FCTX(fctx));

        UNUSED(task);

        res = fctx->res;
        bucketnum = fctx->bucketnum;

        FCTXTRACE("doshutdown");

        /*
         * An fctx that is shutting down is no longer in ADDRWAIT mode.
         */
        fctx->attributes &= ~FCTX_ATTR_ADDRWAIT;

        /*
         * Cancel all pending validators.  Note that this must be done
         * without the bucket lock held, since that could cause deadlock.
         */
        validator = ISC_LIST_HEAD(fctx->validators);
        while (validator != NULL) {
                dns_validator_cancel(validator);
                validator = ISC_LIST_NEXT(validator, link);
        }

        if (fctx->nsfetch != NULL)
                dns_resolver_cancelfetch(fctx->nsfetch);

        /*
         * Shut down anything that is still running on behalf of this
         * fetch.  To avoid deadlock with the ADB, we must do this
         * before we lock the bucket lock.
         */
        fctx_stopeverything(fctx, ISC_FALSE);

        LOCK(&res->buckets[bucketnum].lock);

        fctx->attributes |= FCTX_ATTR_SHUTTINGDOWN;

        INSIST(fctx->state == fetchstate_active ||
               fctx->state == fetchstate_done);
        INSIST(fctx->want_shutdown);

        if (fctx->state != fetchstate_done) {
                fctx->state = fetchstate_done;
                fctx_sendevents(fctx, ISC_R_CANCELED, __LINE__);
        }

        if (fctx->references == 0 && fctx->pending == 0 &&
            fctx->nqueries == 0 && ISC_LIST_EMPTY(fctx->validators)) {
                bucket_empty = fctx_unlink(fctx);
                dodestroy = ISC_TRUE;
        }

        UNLOCK(&res->buckets[bucketnum].lock);

        if (dodestroy) {
                fctx_destroy(fctx);
                if (bucket_empty)
                        empty_bucket(res);
        }
}

static void
fctx_start(isc_task_t *task, isc_event_t *event) {
        fetchctx_t *fctx = event->ev_arg;
        isc_boolean_t done = ISC_FALSE, bucket_empty = ISC_FALSE;
        dns_resolver_t *res;
        unsigned int bucketnum;
        isc_boolean_t dodestroy = ISC_FALSE;

        REQUIRE(VALID_FCTX(fctx));

        UNUSED(task);

        res = fctx->res;
        bucketnum = fctx->bucketnum;

        FCTXTRACE("start");

        LOCK(&res->buckets[bucketnum].lock);

        INSIST(fctx->state == fetchstate_init);
        if (fctx->want_shutdown) {
                /*
                 * We haven't started this fctx yet, and we've been requested
                 * to shut it down.
                 */
                fctx->attributes |= FCTX_ATTR_SHUTTINGDOWN;
                fctx->state = fetchstate_done;
                fctx_sendevents(fctx, ISC_R_CANCELED, __LINE__);
                /*
                 * Since we haven't started, we INSIST that we have no
                 * pending ADB finds and no pending validations.
                 */
                INSIST(fctx->pending == 0);
                INSIST(fctx->nqueries == 0);
                INSIST(ISC_LIST_EMPTY(fctx->validators));
                if (fctx->references == 0) {
                        /*
                         * It's now safe to destroy this fctx.
                         */
                        bucket_empty = fctx_unlink(fctx);
                        dodestroy = ISC_TRUE;
                }
                done = ISC_TRUE;
        } else {
                /*
                 * Normal fctx startup.
                 */
                fctx->state = fetchstate_active;
                /*
                 * Reset the control event for later use in shutting down
                 * the fctx.
                 */
                ISC_EVENT_INIT(event, sizeof(*event), 0, NULL,
                               DNS_EVENT_FETCHCONTROL, fctx_doshutdown, fctx,
                               NULL, NULL, NULL);
        }

        UNLOCK(&res->buckets[bucketnum].lock);

        if (!done) {
                isc_result_t result;

                INSIST(!dodestroy);

                /*
                 * All is well.  Start working on the fetch.
                 */
                result = fctx_starttimer(fctx);
                if (result != ISC_R_SUCCESS)
                        fctx_done(fctx, result, __LINE__);
                else
                        fctx_try(fctx, ISC_FALSE, ISC_FALSE);
        } else if (dodestroy) {
                        fctx_destroy(fctx);
                if (bucket_empty)
                        empty_bucket(res);
        }
}

/*
 * Fetch Creation, Joining, and Cancelation.
 */

static inline isc_result_t
fctx_join(fetchctx_t *fctx, isc_task_t *task, isc_sockaddr_t *client,
          dns_messageid_t id, isc_taskaction_t action, void *arg,
          dns_rdataset_t *rdataset, dns_rdataset_t *sigrdataset,
          dns_fetch_t *fetch)
{
        isc_task_t *clone;
        dns_fetchevent_t *event;

        FCTXTRACE("join");

        /*
         * We store the task we're going to send this event to in the
         * sender field.  We'll make the fetch the sender when we actually
         * send the event.
         */
        clone = NULL;
        isc_task_attach(task, &clone);
        event = (dns_fetchevent_t *)
                isc_event_allocate(fctx->res->mctx, clone, DNS_EVENT_FETCHDONE,
                                   action, arg, sizeof(*event));
        if (event == NULL) {
                isc_task_detach(&clone);
                return (ISC_R_NOMEMORY);
        }
        event->result = DNS_R_SERVFAIL;
        event->qtype = fctx->type;
        event->db = NULL;
        event->node = NULL;
        event->rdataset = rdataset;
        event->sigrdataset = sigrdataset;
        event->fetch = fetch;
        event->client = client;
        event->id = id;
        dns_fixedname_init(&event->foundname);

        /*
         * Make sure that we can store the sigrdataset in the
         * first event if it is needed by any of the events.
         */
        if (event->sigrdataset != NULL)
                ISC_LIST_PREPEND(fctx->events, event, ev_link);
        else
                ISC_LIST_APPEND(fctx->events, event, ev_link);
        fctx->references++;
        fctx->client = client;

        fetch->magic = DNS_FETCH_MAGIC;
        fetch->private = fctx;

        return (ISC_R_SUCCESS);
}

static inline void
log_ns_ttl(fetchctx_t *fctx, const char *where) {
        char namebuf[DNS_NAME_FORMATSIZE];
        char domainbuf[DNS_NAME_FORMATSIZE];

        dns_name_format(&fctx->name, namebuf, sizeof(namebuf));
        dns_name_format(&fctx->domain, domainbuf, sizeof(domainbuf));
        isc_log_write(dns_lctx, DNS_LOGCATEGORY_RESOLVER,
                      DNS_LOGMODULE_RESOLVER, ISC_LOG_DEBUG(10),
                      "log_ns_ttl: fctx %p: %s: %s (in '%s'?): %u %u",
                      fctx, where, namebuf, domainbuf,
                      fctx->ns_ttl_ok, fctx->ns_ttl);
}

static isc_result_t
fctx_create(dns_resolver_t *res, dns_name_t *name, dns_rdatatype_t type,
            dns_name_t *domain, dns_rdataset_t *nameservers,
            unsigned int options, unsigned int bucketnum, unsigned int depth,
            isc_counter_t *qc, fetchctx_t **fctxp)
{
        fetchctx_t *fctx;
        isc_result_t result;
        isc_result_t iresult;
        isc_interval_t interval;
        dns_fixedname_t fixed;
        unsigned int findoptions = 0;
        char buf[DNS_NAME_FORMATSIZE + DNS_RDATATYPE_FORMATSIZE];
        char typebuf[DNS_RDATATYPE_FORMATSIZE];
        isc_mem_t *mctx;

        /*
         * Caller must be holding the lock for bucket number 'bucketnum'.
         */
        REQUIRE(fctxp != NULL && *fctxp == NULL);

        mctx = res->buckets[bucketnum].mctx;
        fctx = isc_mem_get(mctx, sizeof(*fctx));
        if (fctx == NULL)
                return (ISC_R_NOMEMORY);

        fctx->qc = NULL;
        if (qc != NULL) {
                isc_counter_attach(qc, &fctx->qc);
        } else {
                result = isc_counter_create(res->mctx,
                                            res->maxqueries, &fctx->qc);
                if (result != ISC_R_SUCCESS)
                        goto cleanup_fetch;
        }

        /*
         * Make fctx->info point to a copy of a formatted string
         * "name/type".
         */
        dns_name_format(name, buf, sizeof(buf));
        dns_rdatatype_format(type, typebuf, sizeof(typebuf));
        strcat(buf, "/");       /* checked */
        strcat(buf, typebuf);   /* checked */
        fctx->info = isc_mem_strdup(mctx, buf);
        if (fctx->info == NULL) {
                result = ISC_R_NOMEMORY;
                goto cleanup_counter;
        }

        FCTXTRACE("create");
        dns_name_init(&fctx->name, NULL);
        result = dns_name_dup(name, mctx, &fctx->name);
        if (result != ISC_R_SUCCESS)
                goto cleanup_info;
        dns_name_init(&fctx->domain, NULL);
        dns_rdataset_init(&fctx->nameservers);

        fctx->type = type;
        fctx->options = options;
        /*
         * Note!  We do not attach to the task.  We are relying on the
         * resolver to ensure that this task doesn't go away while we are
         * using it.
         */
        fctx->res = res;
        fctx->references = 0;
        fctx->bucketnum = bucketnum;
        fctx->state = fetchstate_init;
        fctx->want_shutdown = ISC_FALSE;
        fctx->cloned = ISC_FALSE;
        fctx->depth = depth;
        ISC_LIST_INIT(fctx->queries);
        ISC_LIST_INIT(fctx->finds);
        ISC_LIST_INIT(fctx->altfinds);
        ISC_LIST_INIT(fctx->forwaddrs);
        ISC_LIST_INIT(fctx->altaddrs);
        ISC_LIST_INIT(fctx->forwarders);
        fctx->fwdpolicy = dns_fwdpolicy_none;
        ISC_LIST_INIT(fctx->bad);
        ISC_LIST_INIT(fctx->edns);
        ISC_LIST_INIT(fctx->edns512);
        ISC_LIST_INIT(fctx->bad_edns);
        ISC_LIST_INIT(fctx->validators);
        fctx->validator = NULL;
        fctx->find = NULL;
        fctx->altfind = NULL;
        fctx->pending = 0;
        fctx->restarts = 0;
        fctx->querysent = 0;
        fctx->referrals = 0;
        TIME_NOW(&fctx->start);
        fctx->timeouts = 0;
        fctx->lamecount = 0;
        fctx->adberr = 0;
        fctx->neterr = 0;
        fctx->badresp = 0;
        fctx->findfail = 0;
        fctx->valfail = 0;
        fctx->result = ISC_R_FAILURE;
        fctx->vresult = ISC_R_SUCCESS;
        fctx->exitline = -1;    /* sentinel */
        fctx->logged = ISC_FALSE;
        fctx->attributes = 0;
        fctx->spilled = ISC_FALSE;
        fctx->nqueries = 0;
        fctx->reason = NULL;
        fctx->rand_buf = 0;
        fctx->rand_bits = 0;
        fctx->timeout = ISC_FALSE;
        fctx->addrinfo = NULL;
        fctx->client = NULL;
        fctx->ns_ttl = 0;
        fctx->ns_ttl_ok = ISC_FALSE;

        dns_name_init(&fctx->nsname, NULL);
        fctx->nsfetch = NULL;
        dns_rdataset_init(&fctx->nsrrset);

        if (domain == NULL) {
                dns_forwarders_t *forwarders = NULL;
                unsigned int labels;
                dns_name_t *fwdname = name;
                dns_name_t suffix;

                /*
                 * DS records are found in the parent server. Strip one
                 * leading label from the name (to be used in finding
                 * the forwarder).
                 */
                if (dns_rdatatype_atparent(fctx->type) &&
                    dns_name_countlabels(name) > 1) {
                        dns_name_init(&suffix, NULL);
                        labels = dns_name_countlabels(name);
                        dns_name_getlabelsequence(name, 1, labels - 1, &suffix);
                        fwdname = &suffix;
                }

                /* Find the forwarder for this name. */
                dns_fixedname_init(&fixed);
                domain = dns_fixedname_name(&fixed);
                result = dns_fwdtable_find2(fctx->res->view->fwdtable, fwdname,
                                            domain, &forwarders);
                if (result == ISC_R_SUCCESS)
                        fctx->fwdpolicy = forwarders->fwdpolicy;

                if (fctx->fwdpolicy != dns_fwdpolicy_only) {
                        /*
                         * The caller didn't supply a query domain and
                         * nameservers, and we're not in forward-only mode,
                         * so find the best nameservers to use.
                         */
                        if (dns_rdatatype_atparent(fctx->type))
                                findoptions |= DNS_DBFIND_NOEXACT;
                        result = dns_view_findzonecut(res->view, name,
                                                      domain, 0, findoptions,
                                                      ISC_TRUE,
                                                      &fctx->nameservers,
                                                      NULL);
                        if (result != ISC_R_SUCCESS)
                                goto cleanup_name;

                        result = dns_name_dup(domain, mctx, &fctx->domain);
                        if (result != ISC_R_SUCCESS) {
                                dns_rdataset_disassociate(&fctx->nameservers);
                                goto cleanup_name;
                        }
                        fctx->ns_ttl = fctx->nameservers.ttl;
                        fctx->ns_ttl_ok = ISC_TRUE;
                } else {
                        /*
                         * We're in forward-only mode.  Set the query domain.
                         */
                        result = dns_name_dup(domain, mctx, &fctx->domain);
                        if (result != ISC_R_SUCCESS)
                                goto cleanup_name;
                }
        } else {
                result = dns_name_dup(domain, mctx, &fctx->domain);
                if (result != ISC_R_SUCCESS)
                        goto cleanup_name;
                dns_rdataset_clone(nameservers, &fctx->nameservers);
                fctx->ns_ttl = fctx->nameservers.ttl;
                fctx->ns_ttl_ok = ISC_TRUE;
        }

        log_ns_ttl(fctx, "fctx_create");

        INSIST(dns_name_issubdomain(&fctx->name, &fctx->domain));

        fctx->qmessage = NULL;
        result = dns_message_create(mctx, DNS_MESSAGE_INTENTRENDER,
                                    &fctx->qmessage);

        if (result != ISC_R_SUCCESS)
                goto cleanup_domain;

        fctx->rmessage = NULL;
        result = dns_message_create(mctx, DNS_MESSAGE_INTENTPARSE,
                                    &fctx->rmessage);

        if (result != ISC_R_SUCCESS)
                goto cleanup_qmessage;

        /*
         * Compute an expiration time for the entire fetch.
         */
        isc_interval_set(&interval, res->query_timeout, 0);
        iresult = isc_time_nowplusinterval(&fctx->expires, &interval);
        if (iresult != ISC_R_SUCCESS) {
                UNEXPECTED_ERROR(__FILE__, __LINE__,
                                 "isc_time_nowplusinterval: %s",
                                 isc_result_totext(iresult));
                result = ISC_R_UNEXPECTED;
                goto cleanup_rmessage;
        }

        /*
         * Default retry interval initialization.  We set the interval now
         * mostly so it won't be uninitialized.  It will be set to the
         * correct value before a query is issued.
         */
        isc_interval_set(&fctx->interval, 2, 0);

        /*
         * Create an inactive timer.  It will be made active when the fetch
         * is actually started.
         */
        fctx->timer = NULL;
        iresult = isc_timer_create(res->timermgr, isc_timertype_inactive,
                                   NULL, NULL,
                                   res->buckets[bucketnum].task, fctx_timeout,
                                   fctx, &fctx->timer);
        if (iresult != ISC_R_SUCCESS) {
                UNEXPECTED_ERROR(__FILE__, __LINE__,
                                 "isc_timer_create: %s",
                                 isc_result_totext(iresult));
                result = ISC_R_UNEXPECTED;
                goto cleanup_rmessage;
        }

        /*
         * Attach to the view's cache and adb.
         */
        fctx->cache = NULL;
        dns_db_attach(res->view->cachedb, &fctx->cache);
        fctx->adb = NULL;
        dns_adb_attach(res->view->adb, &fctx->adb);
        fctx->mctx = NULL;
        isc_mem_attach(mctx, &fctx->mctx);

        ISC_LIST_INIT(fctx->events);
        ISC_LINK_INIT(fctx, link);
        fctx->magic = FCTX_MAGIC;

        ISC_LIST_APPEND(res->buckets[bucketnum].fctxs, fctx, link);

        LOCK(&res->nlock);
        res->nfctx++;
        UNLOCK(&res->nlock);
        inc_stats(res, dns_resstatscounter_nfetch);

        *fctxp = fctx;

        return (ISC_R_SUCCESS);

 cleanup_rmessage:
        dns_message_destroy(&fctx->rmessage);

 cleanup_qmessage:
        dns_message_destroy(&fctx->qmessage);

 cleanup_domain:
        if (dns_name_countlabels(&fctx->domain) > 0)
                dns_name_free(&fctx->domain, mctx);
        if (dns_rdataset_isassociated(&fctx->nameservers))
                dns_rdataset_disassociate(&fctx->nameservers);

 cleanup_name:
        dns_name_free(&fctx->name, mctx);

 cleanup_info:
        isc_mem_free(mctx, fctx->info);

 cleanup_counter:
        isc_counter_detach(&fctx->qc);

 cleanup_fetch:
        isc_mem_put(mctx, fctx, sizeof(*fctx));

        return (result);
}

/*
 * Handle Responses
 */
static inline isc_boolean_t
is_lame(fetchctx_t *fctx) {
        dns_message_t *message = fctx->rmessage;
        dns_name_t *name;
        dns_rdataset_t *rdataset;
        isc_result_t result;

        if (message->rcode != dns_rcode_noerror &&
            message->rcode != dns_rcode_nxdomain)
                return (ISC_FALSE);

        if (message->counts[DNS_SECTION_ANSWER] != 0)
                return (ISC_FALSE);

        if (message->counts[DNS_SECTION_AUTHORITY] == 0)
                return (ISC_FALSE);

        result = dns_message_firstname(message, DNS_SECTION_AUTHORITY);
        while (result == ISC_R_SUCCESS) {
                name = NULL;
                dns_message_currentname(message, DNS_SECTION_AUTHORITY, &name);
                for (rdataset = ISC_LIST_HEAD(name->list);
                     rdataset != NULL;
                     rdataset = ISC_LIST_NEXT(rdataset, link)) {
                        dns_namereln_t namereln;
                        int order;
                        unsigned int labels;
                        if (rdataset->type != dns_rdatatype_ns)
                                continue;
                        namereln = dns_name_fullcompare(name, &fctx->domain,
                                                        &order, &labels);
                        if (namereln == dns_namereln_equal &&
                            (message->flags & DNS_MESSAGEFLAG_AA) != 0)
                                return (ISC_FALSE);
                        if (namereln == dns_namereln_subdomain)
                                return (ISC_FALSE);
                        return (ISC_TRUE);
                }
                result = dns_message_nextname(message, DNS_SECTION_AUTHORITY);
        }

        return (ISC_FALSE);
}

static inline void
log_lame(fetchctx_t *fctx, dns_adbaddrinfo_t *addrinfo) {
        char namebuf[DNS_NAME_FORMATSIZE];
        char domainbuf[DNS_NAME_FORMATSIZE];
        char addrbuf[ISC_SOCKADDR_FORMATSIZE];

        dns_name_format(&fctx->name, namebuf, sizeof(namebuf));
        dns_name_format(&fctx->domain, domainbuf, sizeof(domainbuf));
        isc_sockaddr_format(&addrinfo->sockaddr, addrbuf, sizeof(addrbuf));
        isc_log_write(dns_lctx, DNS_LOGCATEGORY_LAME_SERVERS,
                      DNS_LOGMODULE_RESOLVER, ISC_LOG_INFO,
                      "lame server resolving '%s' (in '%s'?): %s",
                      namebuf, domainbuf, addrbuf);
}

static inline void
log_formerr(fetchctx_t *fctx, const char *format, ...) {
        char nsbuf[ISC_SOCKADDR_FORMATSIZE];
        char clbuf[ISC_SOCKADDR_FORMATSIZE];
        const char *clmsg = "";
        char msgbuf[2048];
        va_list args;

        va_start(args, format);
        vsnprintf(msgbuf, sizeof(msgbuf), format, args);
        va_end(args);

        isc_sockaddr_format(&fctx->addrinfo->sockaddr, nsbuf, sizeof(nsbuf));

        if (fctx->client != NULL) {
                clmsg = " for client ";
                isc_sockaddr_format(fctx->client, clbuf, sizeof(clbuf));
        } else {
                clbuf[0] = '\0';
        }

        isc_log_write(dns_lctx, DNS_LOGCATEGORY_RESOLVER,
                      DNS_LOGMODULE_RESOLVER, ISC_LOG_NOTICE,
                      "DNS format error from %s resolving %s%s%s: %s",
                      nsbuf, fctx->info, clmsg, clbuf, msgbuf);
}

static inline isc_result_t
same_question(fetchctx_t *fctx) {
        isc_result_t result;
        dns_message_t *message = fctx->rmessage;
        dns_name_t *name;
        dns_rdataset_t *rdataset;

        /*
         * Caller must be holding the fctx lock.
         */

        /*
         * XXXRTH  Currently we support only one question.
         */
        if (message->counts[DNS_SECTION_QUESTION] != 1) {
                log_formerr(fctx, "too many questions");
                return (DNS_R_FORMERR);
        }

        result = dns_message_firstname(message, DNS_SECTION_QUESTION);
        if (result != ISC_R_SUCCESS)
                return (result);
        name = NULL;
        dns_message_currentname(message, DNS_SECTION_QUESTION, &name);
        rdataset = ISC_LIST_HEAD(name->list);
        INSIST(rdataset != NULL);
        INSIST(ISC_LIST_NEXT(rdataset, link) == NULL);

        if (fctx->type != rdataset->type ||
            fctx->res->rdclass != rdataset->rdclass ||
            !dns_name_equal(&fctx->name, name)) {
                char namebuf[DNS_NAME_FORMATSIZE];
                char class[DNS_RDATACLASS_FORMATSIZE];
                char type[DNS_RDATATYPE_FORMATSIZE];

                dns_name_format(name, namebuf, sizeof(namebuf));
                dns_rdataclass_format(rdataset->rdclass, class, sizeof(class));
                dns_rdatatype_format(rdataset->type, type, sizeof(type));
                log_formerr(fctx, "question section mismatch: got %s/%s/%s",
                            namebuf, class, type);
                return (DNS_R_FORMERR);
        }

        return (ISC_R_SUCCESS);
}

static void
clone_results(fetchctx_t *fctx) {
        dns_fetchevent_t *event, *hevent;
        isc_result_t result;
        dns_name_t *name, *hname;

        FCTXTRACE("clone_results");

        /*
         * Set up any other events to have the same data as the first
         * event.
         *
         * Caller must be holding the appropriate lock.
         */

        fctx->cloned = ISC_TRUE;
        hevent = ISC_LIST_HEAD(fctx->events);
        if (hevent == NULL)
                return;
        hname = dns_fixedname_name(&hevent->foundname);
        for (event = ISC_LIST_NEXT(hevent, ev_link);
             event != NULL;
             event = ISC_LIST_NEXT(event, ev_link)) {
                name = dns_fixedname_name(&event->foundname);
                result = dns_name_copy(hname, name, NULL);
                if (result != ISC_R_SUCCESS)
                        event->result = result;
                else
                        event->result = hevent->result;
                dns_db_attach(hevent->db, &event->db);
                dns_db_attachnode(hevent->db, hevent->node, &event->node);
                INSIST(hevent->rdataset != NULL);
                INSIST(event->rdataset != NULL);
                if (dns_rdataset_isassociated(hevent->rdataset))
                        dns_rdataset_clone(hevent->rdataset, event->rdataset);
                INSIST(! (hevent->sigrdataset == NULL &&
                          event->sigrdataset != NULL));
                if (hevent->sigrdataset != NULL &&
                    dns_rdataset_isassociated(hevent->sigrdataset) &&
                    event->sigrdataset != NULL)
                        dns_rdataset_clone(hevent->sigrdataset,
                                           event->sigrdataset);
        }
}

#define CACHE(r)        (((r)->attributes & DNS_RDATASETATTR_CACHE) != 0)
#define ANSWER(r)       (((r)->attributes & DNS_RDATASETATTR_ANSWER) != 0)
#define ANSWERSIG(r)    (((r)->attributes & DNS_RDATASETATTR_ANSWERSIG) != 0)
#define EXTERNAL(r)     (((r)->attributes & DNS_RDATASETATTR_EXTERNAL) != 0)
#define CHAINING(r)     (((r)->attributes & DNS_RDATASETATTR_CHAINING) != 0)
#define CHASE(r)        (((r)->attributes & DNS_RDATASETATTR_CHASE) != 0)
#define CHECKNAMES(r)   (((r)->attributes & DNS_RDATASETATTR_CHECKNAMES) != 0)


/*
 * Destroy '*fctx' if it is ready to be destroyed (i.e., if it has
 * no references and is no longer waiting for any events).
 *
 * Requires:
 *      '*fctx' is shutting down.
 *
 * Returns:
 *      true if the resolver is exiting and this is the last fctx in the bucket.
 */
static isc_boolean_t
maybe_destroy(fetchctx_t *fctx, isc_boolean_t locked) {
        unsigned int bucketnum;
        isc_boolean_t bucket_empty = ISC_FALSE;
        dns_resolver_t *res = fctx->res;
        dns_validator_t *validator, *next_validator;
        isc_boolean_t dodestroy = ISC_FALSE;

        REQUIRE(SHUTTINGDOWN(fctx));

        bucketnum = fctx->bucketnum;
        if (!locked)
                LOCK(&res->buckets[bucketnum].lock);
        if (fctx->pending != 0 || fctx->nqueries != 0)
                goto unlock;

        for (validator = ISC_LIST_HEAD(fctx->validators);
             validator != NULL; validator = next_validator) {
                next_validator = ISC_LIST_NEXT(validator, link);
                dns_validator_cancel(validator);
        }

        if (fctx->references == 0 && ISC_LIST_EMPTY(fctx->validators)) {
                bucket_empty = fctx_unlink(fctx);
                dodestroy = ISC_TRUE;
        }
 unlock:
        if (!locked)
                UNLOCK(&res->buckets[bucketnum].lock);
        if (dodestroy)
                fctx_destroy(fctx);
        return (bucket_empty);
}

/*
 * The validator has finished.
 */
static void
validated(isc_task_t *task, isc_event_t *event) {
        dns_adbaddrinfo_t *addrinfo;
        dns_dbnode_t *node = NULL;
        dns_dbnode_t *nsnode = NULL;
        dns_fetchevent_t *hevent;
        dns_name_t *name;
        dns_rdataset_t *ardataset = NULL;
        dns_rdataset_t *asigrdataset = NULL;
        dns_rdataset_t *rdataset;
        dns_rdataset_t *sigrdataset;
        dns_resolver_t *res;
        dns_valarg_t *valarg;
        dns_validatorevent_t *vevent;
        fetchctx_t *fctx;
        isc_boolean_t chaining;
        isc_boolean_t negative;
        isc_boolean_t sentresponse;
        isc_result_t eresult = ISC_R_SUCCESS;
        isc_result_t result = ISC_R_SUCCESS;
        isc_stdtime_t now;
        isc_uint32_t ttl;
        unsigned options;
        isc_uint32_t bucketnum;

        UNUSED(task); /* for now */

        REQUIRE(event->ev_type == DNS_EVENT_VALIDATORDONE);
        valarg = event->ev_arg;
        fctx = valarg->fctx;
        res = fctx->res;
        addrinfo = valarg->addrinfo;
        REQUIRE(VALID_FCTX(fctx));
        REQUIRE(!ISC_LIST_EMPTY(fctx->validators));

        vevent = (dns_validatorevent_t *)event;
        fctx->vresult = vevent->result;

        FCTXTRACE("received validation completion event");

        bucketnum = fctx->bucketnum;
        LOCK(&res->buckets[bucketnum].lock);

        ISC_LIST_UNLINK(fctx->validators, vevent->validator, link);
        fctx->validator = NULL;

        /*
         * Destroy the validator early so that we can
         * destroy the fctx if necessary.
         */
        dns_validator_destroy(&vevent->validator);
        isc_mem_put(fctx->mctx, valarg, sizeof(*valarg));

        negative = ISC_TF(vevent->rdataset == NULL);

        sentresponse = ISC_TF((fctx->options & DNS_FETCHOPT_NOVALIDATE) != 0);

        /*
         * If shutting down, ignore the results.  Check to see if we're
         * done waiting for validator completions and ADB pending events; if
         * so, destroy the fctx.
         */
        if (SHUTTINGDOWN(fctx) && !sentresponse) {
                isc_boolean_t bucket_empty;
                bucket_empty = maybe_destroy(fctx, ISC_TRUE);
                UNLOCK(&res->buckets[bucketnum].lock);
                if (bucket_empty)
                        empty_bucket(res);
                goto cleanup_event;
        }

        isc_stdtime_get(&now);

        /*
         * If chaining, we need to make sure that the right result code is
         * returned, and that the rdatasets are bound.
         */
        if (vevent->result == ISC_R_SUCCESS &&
            !negative &&
            vevent->rdataset != NULL &&
            CHAINING(vevent->rdataset))
        {
                if (vevent->rdataset->type == dns_rdatatype_cname)
                        eresult = DNS_R_CNAME;
                else {
                        INSIST(vevent->rdataset->type == dns_rdatatype_dname);
                        eresult = DNS_R_DNAME;
                }
                chaining = ISC_TRUE;
        } else
                chaining = ISC_FALSE;

        /*
         * Either we're not shutting down, or we are shutting down but want
         * to cache the result anyway (if this was a validation started by
         * a query with cd set)
         */

        hevent = ISC_LIST_HEAD(fctx->events);
        if (hevent != NULL) {
                if (!negative && !chaining &&
                    (fctx->type == dns_rdatatype_any ||
                     fctx->type == dns_rdatatype_rrsig ||
                     fctx->type == dns_rdatatype_sig)) {
                        /*
                         * Don't bind rdatasets; the caller
                         * will iterate the node.
                         */
                } else {
                        ardataset = hevent->rdataset;
                        asigrdataset = hevent->sigrdataset;
                }
        }

        if (vevent->result != ISC_R_SUCCESS) {
                FCTXTRACE("validation failed");
                inc_stats(res, dns_resstatscounter_valfail);
                fctx->valfail++;
                fctx->vresult = vevent->result;
                if (fctx->vresult != DNS_R_BROKENCHAIN) {
                        result = ISC_R_NOTFOUND;
                        if (vevent->rdataset != NULL)
                                result = dns_db_findnode(fctx->cache,
                                                         vevent->name,
                                                         ISC_TRUE, &node);
                        if (result == ISC_R_SUCCESS)
                                (void)dns_db_deleterdataset(fctx->cache, node,
                                                             NULL,
                                                            vevent->type, 0);
                        if (result == ISC_R_SUCCESS &&
                             vevent->sigrdataset != NULL)
                                (void)dns_db_deleterdataset(fctx->cache, node,
                                                            NULL,
                                                            dns_rdatatype_rrsig,
                                                            vevent->type);
                        if (result == ISC_R_SUCCESS)
                                dns_db_detachnode(fctx->cache, &node);
                }
                if (fctx->vresult == DNS_R_BROKENCHAIN && !negative) {
                        /*
                         * Cache the data as pending for later validation.
                         */
                        result = ISC_R_NOTFOUND;
                        if (vevent->rdataset != NULL)
                                result = dns_db_findnode(fctx->cache,
                                                         vevent->name,
                                                         ISC_TRUE, &node);
                        if (result == ISC_R_SUCCESS) {
                                (void)dns_db_addrdataset(fctx->cache, node,
                                                         NULL, now,
                                                         vevent->rdataset, 0,
                                                         NULL);
                        }
                        if (result == ISC_R_SUCCESS &&
                            vevent->sigrdataset != NULL)
                                (void)dns_db_addrdataset(fctx->cache, node,
                                                         NULL, now,
                                                         vevent->sigrdataset,
                                                         0, NULL);
                        if (result == ISC_R_SUCCESS)
                                dns_db_detachnode(fctx->cache, &node);
                }
                result = fctx->vresult;
                add_bad(fctx, addrinfo, result, badns_validation);
                isc_event_free(&event);
                UNLOCK(&res->buckets[bucketnum].lock);
                INSIST(fctx->validator == NULL);
                fctx->validator = ISC_LIST_HEAD(fctx->validators);
                if (fctx->validator != NULL)
                        dns_validator_send(fctx->validator);
                else if (sentresponse)
                        fctx_done(fctx, result, __LINE__); /* Locks bucket. */
                else if (result == DNS_R_BROKENCHAIN) {
                        isc_result_t tresult;
                        isc_time_t expire;
                        isc_interval_t i;

                        isc_interval_set(&i, DNS_RESOLVER_BADCACHETTL(fctx), 0);
                        tresult = isc_time_nowplusinterval(&expire, &i);
                        if (negative &&
                            (fctx->type == dns_rdatatype_dnskey ||
                             fctx->type == dns_rdatatype_dlv ||
                             fctx->type == dns_rdatatype_ds) &&
                             tresult == ISC_R_SUCCESS)
                                dns_resolver_addbadcache(res, &fctx->name,
                                                         fctx->type, &expire);
                        fctx_done(fctx, result, __LINE__); /* Locks bucket. */
                } else
                        fctx_try(fctx, ISC_TRUE, ISC_TRUE); /* Locks bucket. */
                return;
        }


        if (negative) {
                dns_rdatatype_t covers;
                FCTXTRACE("nonexistence validation OK");

                inc_stats(res, dns_resstatscounter_valnegsuccess);

                /*
                 * Cache DS NXDOMAIN seperately to other types.
                 */
                if (fctx->rmessage->rcode == dns_rcode_nxdomain &&
                    fctx->type != dns_rdatatype_ds)
                        covers = dns_rdatatype_any;
                else
                        covers = fctx->type;

                result = dns_db_findnode(fctx->cache, vevent->name, ISC_TRUE,
                                         &node);
                if (result != ISC_R_SUCCESS)
                        goto noanswer_response;

                /*
                 * If we are asking for a SOA record set the cache time
                 * to zero to facilitate locating the containing zone of
                 * a arbitrary zone.
                 */
                ttl = res->view->maxncachettl;
                if (fctx->type == dns_rdatatype_soa &&
                    covers == dns_rdatatype_any && res->zero_no_soa_ttl)
                        ttl = 0;

                result = ncache_adderesult(fctx->rmessage, fctx->cache, node,
                                           covers, now, ttl, vevent->optout,
                                           vevent->secure, ardataset, &eresult);
                if (result != ISC_R_SUCCESS)
                        goto noanswer_response;
                goto answer_response;
        } else
                inc_stats(res, dns_resstatscounter_valsuccess);

        FCTXTRACE("validation OK");

        if (vevent->proofs[DNS_VALIDATOR_NOQNAMEPROOF] != NULL) {
                result = dns_rdataset_addnoqname(vevent->rdataset,
                                   vevent->proofs[DNS_VALIDATOR_NOQNAMEPROOF]);
                RUNTIME_CHECK(result == ISC_R_SUCCESS);
                INSIST(vevent->sigrdataset != NULL);
                vevent->sigrdataset->ttl = vevent->rdataset->ttl;
                if (vevent->proofs[DNS_VALIDATOR_CLOSESTENCLOSER] != NULL) {
                        result = dns_rdataset_addclosest(vevent->rdataset,
                                 vevent->proofs[DNS_VALIDATOR_CLOSESTENCLOSER]);
                        RUNTIME_CHECK(result == ISC_R_SUCCESS);
                }
        } else if (vevent->rdataset->trust == dns_trust_answer &&
                   vevent->rdataset->type != dns_rdatatype_rrsig)
        {
                isc_result_t tresult;
                dns_name_t *noqname = NULL;
                tresult = findnoqname(fctx, vevent->name,
                                      vevent->rdataset->type, &noqname);
                if (tresult == ISC_R_SUCCESS && noqname != NULL) {
                        tresult = dns_rdataset_addnoqname(vevent->rdataset,
                                                          noqname);
                        RUNTIME_CHECK(tresult == ISC_R_SUCCESS);
                }
        }

        /*
         * The data was already cached as pending data.
         * Re-cache it as secure and bind the cached
         * rdatasets to the first event on the fetch
         * event list.
         */
        result = dns_db_findnode(fctx->cache, vevent->name, ISC_TRUE, &node);
        if (result != ISC_R_SUCCESS)
                goto noanswer_response;

        options = 0;
        if ((fctx->options & DNS_FETCHOPT_PREFETCH) != 0)
                options = DNS_DBADD_PREFETCH;
        result = dns_db_addrdataset(fctx->cache, node, NULL, now,
                                    vevent->rdataset, options, ardataset);
        if (result != ISC_R_SUCCESS &&
            result != DNS_R_UNCHANGED)
                goto noanswer_response;
        if (ardataset != NULL && NEGATIVE(ardataset)) {
                if (NXDOMAIN(ardataset))
                        eresult = DNS_R_NCACHENXDOMAIN;
                else
                        eresult = DNS_R_NCACHENXRRSET;
        } else if (vevent->sigrdataset != NULL) {
                result = dns_db_addrdataset(fctx->cache, node, NULL, now,
                                            vevent->sigrdataset, 0,
                                            asigrdataset);
                if (result != ISC_R_SUCCESS &&
                    result != DNS_R_UNCHANGED)
                        goto noanswer_response;
        }

        if (sentresponse) {
                isc_boolean_t bucket_empty = ISC_FALSE;
                /*
                 * If we only deferred the destroy because we wanted to cache
                 * the data, destroy now.
                 */
                dns_db_detachnode(fctx->cache, &node);
                if (SHUTTINGDOWN(fctx))
                        bucket_empty = maybe_destroy(fctx, ISC_TRUE);
                UNLOCK(&res->buckets[bucketnum].lock);
                if (bucket_empty)
                        empty_bucket(res);
                goto cleanup_event;
        }

        if (!ISC_LIST_EMPTY(fctx->validators)) {
                INSIST(!negative);
                INSIST(fctx->type == dns_rdatatype_any ||
                       fctx->type == dns_rdatatype_rrsig ||
                       fctx->type == dns_rdatatype_sig);
                /*
                 * Don't send a response yet - we have
                 * more rdatasets that still need to
                 * be validated.
                 */
                dns_db_detachnode(fctx->cache, &node);
                UNLOCK(&res->buckets[bucketnum].lock);
                dns_validator_send(ISC_LIST_HEAD(fctx->validators));
                goto cleanup_event;
        }

 answer_response:
        /*
         * Cache any NS/NSEC records that happened to be validated.
         */
        result = dns_message_firstname(fctx->rmessage, DNS_SECTION_AUTHORITY);
        while (result == ISC_R_SUCCESS) {
                name = NULL;
                dns_message_currentname(fctx->rmessage, DNS_SECTION_AUTHORITY,
                                        &name);
                for (rdataset = ISC_LIST_HEAD(name->list);
                     rdataset != NULL;
                     rdataset = ISC_LIST_NEXT(rdataset, link)) {
                        if ((rdataset->type != dns_rdatatype_ns &&
                             rdataset->type != dns_rdatatype_nsec) ||
                            rdataset->trust != dns_trust_secure)
                                continue;
                        for (sigrdataset = ISC_LIST_HEAD(name->list);
                             sigrdataset != NULL;
                             sigrdataset = ISC_LIST_NEXT(sigrdataset, link)) {
                                if (sigrdataset->type != dns_rdatatype_rrsig ||
                                    sigrdataset->covers != rdataset->type)
                                        continue;
                                break;
                        }
                        if (sigrdataset == NULL ||
                            sigrdataset->trust != dns_trust_secure)
                                continue;
                        result = dns_db_findnode(fctx->cache, name, ISC_TRUE,
                                                 &nsnode);
                        if (result != ISC_R_SUCCESS)
                                continue;

                        result = dns_db_addrdataset(fctx->cache, nsnode, NULL,
                                                    now, rdataset, 0, NULL);
                        if (result == ISC_R_SUCCESS)
                                result = dns_db_addrdataset(fctx->cache, nsnode,
                                                            NULL, now,
                                                            sigrdataset, 0,
                                                            NULL);
                        dns_db_detachnode(fctx->cache, &nsnode);
                        if (result != ISC_R_SUCCESS)
                                continue;
                }
                result = dns_message_nextname(fctx->rmessage,
                                              DNS_SECTION_AUTHORITY);
        }

        result = ISC_R_SUCCESS;

        /*
         * Respond with an answer, positive or negative,
         * as opposed to an error.  'node' must be non-NULL.
         */

        fctx->attributes |= FCTX_ATTR_HAVEANSWER;

        if (hevent != NULL) {
                /*
                 * Negative results must be indicated in event->result.
                 */
                if (dns_rdataset_isassociated(hevent->rdataset) &&
                    NEGATIVE(hevent->rdataset)) {
                        INSIST(eresult == DNS_R_NCACHENXDOMAIN ||
                               eresult == DNS_R_NCACHENXRRSET);
                }
                hevent->result = eresult;
                RUNTIME_CHECK(dns_name_copy(vevent->name,
                              dns_fixedname_name(&hevent->foundname), NULL)
                              == ISC_R_SUCCESS);
                dns_db_attach(fctx->cache, &hevent->db);
                dns_db_transfernode(fctx->cache, &node, &hevent->node);
                clone_results(fctx);
        }

 noanswer_response:
        if (node != NULL)
                dns_db_detachnode(fctx->cache, &node);

        UNLOCK(&res->buckets[bucketnum].lock);
        fctx_done(fctx, result, __LINE__); /* Locks bucket. */

 cleanup_event:
        INSIST(node == NULL);
        isc_event_free(&event);
}

static void
fctx_log(void *arg, int level, const char *fmt, ...) {
        char msgbuf[2048];
        va_list args;
        fetchctx_t *fctx = arg;

        va_start(args, fmt);
        vsnprintf(msgbuf, sizeof(msgbuf), fmt, args);
        va_end(args);

        isc_log_write(dns_lctx, DNS_LOGCATEGORY_RESOLVER,
                      DNS_LOGMODULE_RESOLVER, level,
                      "fctx %p(%s): %s", fctx, fctx->info, msgbuf);
}

static inline isc_result_t
findnoqname(fetchctx_t *fctx, dns_name_t *name, dns_rdatatype_t type,
            dns_name_t **noqnamep)
{
        dns_rdataset_t *nrdataset, *next, *sigrdataset;
        dns_rdata_rrsig_t rrsig;
        isc_result_t result;
        unsigned int labels;
        dns_section_t section;
        dns_name_t *zonename;
        dns_fixedname_t fzonename;
        dns_name_t *closest;
        dns_fixedname_t fclosest;
        dns_name_t *nearest;
        dns_fixedname_t fnearest;
        dns_rdatatype_t found = dns_rdatatype_none;
        dns_name_t *noqname = NULL;

        FCTXTRACE("findnoqname");

        REQUIRE(noqnamep != NULL && *noqnamep == NULL);

        /*
         * Find the SIG for this rdataset, if we have it.
         */
        for (sigrdataset = ISC_LIST_HEAD(name->list);
             sigrdataset != NULL;
             sigrdataset = ISC_LIST_NEXT(sigrdataset, link)) {
                if (sigrdataset->type == dns_rdatatype_rrsig &&
                    sigrdataset->covers == type)
                        break;
        }

        if (sigrdataset == NULL)
                return (ISC_R_NOTFOUND);

        labels = dns_name_countlabels(name);

        for (result = dns_rdataset_first(sigrdataset);
             result == ISC_R_SUCCESS;
             result = dns_rdataset_next(sigrdataset)) {
                dns_rdata_t rdata = DNS_RDATA_INIT;
                dns_rdataset_current(sigrdataset, &rdata);
                result = dns_rdata_tostruct(&rdata, &rrsig, NULL);
                RUNTIME_CHECK(result == ISC_R_SUCCESS);
                /* Wildcard has rrsig.labels < labels - 1. */
                if (rrsig.labels + 1U >= labels)
                        continue;
                break;
        }

        if (result == ISC_R_NOMORE)
                return (ISC_R_NOTFOUND);
        if (result != ISC_R_SUCCESS)
                return (result);

        dns_fixedname_init(&fzonename);
        zonename = dns_fixedname_name(&fzonename);
        dns_fixedname_init(&fclosest);
        closest = dns_fixedname_name(&fclosest);
        dns_fixedname_init(&fnearest);
        nearest = dns_fixedname_name(&fnearest);

#define NXND(x) ((x) == ISC_R_SUCCESS)

        section = DNS_SECTION_AUTHORITY;
        for (result = dns_message_firstname(fctx->rmessage, section);
             result == ISC_R_SUCCESS;
             result = dns_message_nextname(fctx->rmessage, section)) {
                dns_name_t *nsec = NULL;
                dns_message_currentname(fctx->rmessage, section, &nsec);
                for (nrdataset = ISC_LIST_HEAD(nsec->list);
                      nrdataset != NULL; nrdataset = next) {
                        isc_boolean_t data = ISC_FALSE, exists = ISC_FALSE;
                        isc_boolean_t optout = ISC_FALSE, unknown = ISC_FALSE;
                        isc_boolean_t setclosest = ISC_FALSE;
                        isc_boolean_t setnearest = ISC_FALSE;

                        next = ISC_LIST_NEXT(nrdataset, link);
                        if (nrdataset->type != dns_rdatatype_nsec &&
                            nrdataset->type != dns_rdatatype_nsec3)
                                continue;

                        if (nrdataset->type == dns_rdatatype_nsec &&
                            NXND(dns_nsec_noexistnodata(type, name, nsec,
                                                        nrdataset, &exists,
                                                        &data, NULL, fctx_log,
                                                        fctx)))
                        {
                                if (!exists) {
                                        noqname = nsec;
                                        found = dns_rdatatype_nsec;
                                }
                        }

                        if (nrdataset->type == dns_rdatatype_nsec3 &&
                            NXND(dns_nsec3_noexistnodata(type, name, nsec,
                                                         nrdataset, zonename,
                                                         &exists, &data,
                                                         &optout, &unknown,
                                                         &setclosest,
                                                         &setnearest,
                                                         closest, nearest,
                                                         fctx_log, fctx)))
                        {
                                if (!exists && setnearest) {
                                        noqname = nsec;
                                        found = dns_rdatatype_nsec3;
                                }
                        }
                }
        }
        if (result == ISC_R_NOMORE)
                result = ISC_R_SUCCESS;
        if (noqname != NULL) {
                for (sigrdataset = ISC_LIST_HEAD(noqname->list);
                     sigrdataset != NULL;
                     sigrdataset = ISC_LIST_NEXT(sigrdataset, link)) {
                        if (sigrdataset->type == dns_rdatatype_rrsig &&
                            sigrdataset->covers == found)
                                break;
                }
                if (sigrdataset != NULL)
                        *noqnamep = noqname;
        }
        return (result);
}

static inline isc_result_t
cache_name(fetchctx_t *fctx, dns_name_t *name, dns_adbaddrinfo_t *addrinfo,
           isc_stdtime_t now)
{
        dns_rdataset_t *rdataset, *sigrdataset;
        dns_rdataset_t *addedrdataset, *ardataset, *asigrdataset;
        dns_rdataset_t *valrdataset = NULL, *valsigrdataset = NULL;
        dns_dbnode_t *node, **anodep;
        dns_db_t **adbp;
        dns_name_t *aname;
        dns_resolver_t *res;
        isc_boolean_t need_validation, secure_domain, have_answer;
        isc_result_t result, eresult;
        dns_fetchevent_t *event;
        unsigned int options;
        isc_task_t *task;
        isc_boolean_t fail;
        unsigned int valoptions = 0;
        isc_boolean_t checknta = ISC_TRUE;

        /*
         * The appropriate bucket lock must be held.
         */

        res = fctx->res;
        need_validation = ISC_FALSE;
        POST(need_validation);
        secure_domain = ISC_FALSE;
        have_answer = ISC_FALSE;
        eresult = ISC_R_SUCCESS;
        task = res->buckets[fctx->bucketnum].task;

        /*
         * Is DNSSEC validation required for this name?
         */
        if ((fctx->options & DNS_FETCHOPT_NONTA) != 0) {
                valoptions |= DNS_VALIDATOR_NONTA;
                checknta = ISC_FALSE;
        }

        if (res->view->enablevalidation) {
                result = issecuredomain(res->view, name, fctx->type,
                                        now, checknta, &secure_domain);
                if (result != ISC_R_SUCCESS)
                        return (result);

                if (!secure_domain && res->view->dlv != NULL) {
                        valoptions |= DNS_VALIDATOR_DLV;
                        secure_domain = ISC_TRUE;
                }
        }

        if ((fctx->options & DNS_FETCHOPT_NOCDFLAG) != 0)
                valoptions |= DNS_VALIDATOR_NOCDFLAG;

        if ((fctx->options & DNS_FETCHOPT_NOVALIDATE) != 0)
                need_validation = ISC_FALSE;
        else
                need_validation = secure_domain;

        adbp = NULL;
        aname = NULL;
        anodep = NULL;
        ardataset = NULL;
        asigrdataset = NULL;
        event = NULL;
        if ((name->attributes & DNS_NAMEATTR_ANSWER) != 0 &&
            !need_validation) {
                have_answer = ISC_TRUE;
                event = ISC_LIST_HEAD(fctx->events);
                if (event != NULL) {
                        adbp = &event->db;
                        aname = dns_fixedname_name(&event->foundname);
                        result = dns_name_copy(name, aname, NULL);
                        if (result != ISC_R_SUCCESS)
                                return (result);
                        anodep = &event->node;
                        /*
                         * If this is an ANY, SIG or RRSIG query, we're not
                         * going to return any rdatasets, unless we encountered
                         * a CNAME or DNAME as "the answer".  In this case,
                         * we're going to return DNS_R_CNAME or DNS_R_DNAME
                         * and we must set up the rdatasets.
                         */
                        if ((fctx->type != dns_rdatatype_any &&
                             fctx->type != dns_rdatatype_rrsig &&
                             fctx->type != dns_rdatatype_sig) ||
                            (name->attributes & DNS_NAMEATTR_CHAINING) != 0) {
                                ardataset = event->rdataset;
                                asigrdataset = event->sigrdataset;
                        }
                }
        }

        /*
         * Find or create the cache node.
         */
        node = NULL;
        result = dns_db_findnode(fctx->cache, name, ISC_TRUE, &node);
        if (result != ISC_R_SUCCESS)
                return (result);

        /*
         * Cache or validate each cacheable rdataset.
         */
        fail = ISC_TF((fctx->res->options & DNS_RESOLVER_CHECKNAMESFAIL) != 0);
        for (rdataset = ISC_LIST_HEAD(name->list);
             rdataset != NULL;
             rdataset = ISC_LIST_NEXT(rdataset, link)) {
                if (!CACHE(rdataset))
                        continue;
                if (CHECKNAMES(rdataset)) {
                        char namebuf[DNS_NAME_FORMATSIZE];
                        char typebuf[DNS_RDATATYPE_FORMATSIZE];
                        char classbuf[DNS_RDATATYPE_FORMATSIZE];

                        dns_name_format(name, namebuf, sizeof(namebuf));
                        dns_rdatatype_format(rdataset->type, typebuf,
                                             sizeof(typebuf));
                        dns_rdataclass_format(rdataset->rdclass, classbuf,
                                              sizeof(classbuf));
                        isc_log_write(dns_lctx, DNS_LOGCATEGORY_RESOLVER,
                                      DNS_LOGMODULE_RESOLVER, ISC_LOG_NOTICE,
                                      "check-names %s %s/%s/%s",
                                      fail ? "failure" : "warning",
                                      namebuf, typebuf, classbuf);
                        if (fail) {
                                if (ANSWER(rdataset)) {
                                        dns_db_detachnode(fctx->cache, &node);
                                        return (DNS_R_BADNAME);
                                }
                                continue;
                        }
                }

                /*
                 * Enforce the configure maximum cache TTL.
                 */
                if (rdataset->ttl > res->view->maxcachettl)
                        rdataset->ttl = res->view->maxcachettl;

                /*
                 * Mark the rdataset as being prefetch eligible.
                 */
                if (rdataset->ttl > fctx->res->view->prefetch_eligible)
                        rdataset->attributes |= DNS_RDATASETATTR_PREFETCH;

                /*
                 * Find the SIG for this rdataset, if we have it.
                 */
                for (sigrdataset = ISC_LIST_HEAD(name->list);
                     sigrdataset != NULL;
                     sigrdataset = ISC_LIST_NEXT(sigrdataset, link)) {
                        if (sigrdataset->type == dns_rdatatype_rrsig &&
                            sigrdataset->covers == rdataset->type)
                                break;
                }

                /*
                 * If this RRset is in a secure domain, is in bailiwick,
                 * and is not glue, attempt DNSSEC validation.  (We do not
                 * attempt to validate glue or out-of-bailiwick data--even
                 * though there might be some performance benefit to doing
                 * so--because it makes it simpler and safer to ensure that
                 * records from a secure domain are only cached if validated
                 * within the context of a query to the domain that owns
                 * them.)
                 */
                if (secure_domain && rdataset->trust != dns_trust_glue &&
                    !EXTERNAL(rdataset)) {
                        dns_trust_t trust;

                        /*
                         * RRSIGs are validated as part of validating the
                         * type they cover.
                         */
                        if (rdataset->type == dns_rdatatype_rrsig)
                                continue;

                        if (sigrdataset == NULL) {
                                if (!ANSWER(rdataset) && need_validation) {
                                        /*
                                         * Ignore non-answer rdatasets that
                                         * are missing signatures.
                                         */
                                        continue;
                                }
                        }

                        /*
                         * Normalize the rdataset and sigrdataset TTLs.
                         */
                        if (sigrdataset != NULL) {
                                rdataset->ttl = ISC_MIN(rdataset->ttl,
                                                        sigrdataset->ttl);
                                sigrdataset->ttl = rdataset->ttl;
                        }

                        /*
                         * Mark the rdataset as being prefetch eligible.
                         */
                        if (rdataset->ttl > fctx->res->view->prefetch_eligible)
                                rdataset->attributes |= DNS_RDATASETATTR_PREFETCH;


                        /*
                         * Cache this rdataset/sigrdataset pair as
                         * pending data.  Track whether it was additional
                         * or not.
                         */
                        if (rdataset->trust == dns_trust_additional)
                                trust = dns_trust_pending_additional;
                        else
                                trust = dns_trust_pending_answer;

                        rdataset->trust = trust;
                        if (sigrdataset != NULL)
                                sigrdataset->trust = trust;
                        if (!need_validation || !ANSWER(rdataset)) {
                                options = 0;
                                if (ANSWER(rdataset) &&
                                   rdataset->type != dns_rdatatype_rrsig) {
                                        isc_result_t tresult;
                                        dns_name_t *noqname = NULL;
                                        tresult = findnoqname(fctx, name,
                                                              rdataset->type,
                                                              &noqname);
                                        if (tresult == ISC_R_SUCCESS &&
                                            noqname != NULL) {
                                                tresult =
                                                     dns_rdataset_addnoqname(
                                                            rdataset, noqname);
                                                RUNTIME_CHECK(tresult ==
                                                              ISC_R_SUCCESS);
                                        }
                                }
                                if ((fctx->options & DNS_FETCHOPT_PREFETCH) != 0)
                                                options = DNS_DBADD_PREFETCH;
                                addedrdataset = ardataset;
                                result = dns_db_addrdataset(fctx->cache, node,
                                                            NULL, now, rdataset,
                                                            options,
                                                            addedrdataset);
                                if (result == DNS_R_UNCHANGED) {
                                        result = ISC_R_SUCCESS;
                                        if (!need_validation &&
                                            ardataset != NULL &&
                                            NEGATIVE(ardataset)) {
                                                /*
                                                 * The answer in the cache is
                                                 * better than the answer we
                                                 * found, and is a negative
                                                 * cache entry, so we must set
                                                 * eresult appropriately.
                                                 */
                                                if (NXDOMAIN(ardataset))
                                                        eresult =
                                                           DNS_R_NCACHENXDOMAIN;
                                                else
                                                        eresult =
                                                           DNS_R_NCACHENXRRSET;
                                                /*
                                                 * We have a negative response
                                                 * from the cache so don't
                                                 * attempt to add the RRSIG
                                                 * rrset.
                                                 */
                                                continue;
                                        }
                                }
                                if (result != ISC_R_SUCCESS)
                                        break;
                                if (sigrdataset != NULL) {
                                        addedrdataset = asigrdataset;
                                        result = dns_db_addrdataset(fctx->cache,
                                                                node, NULL, now,
                                                                sigrdataset,
                                                                options,
                                                                addedrdataset);
                                        if (result == DNS_R_UNCHANGED)
                                                result = ISC_R_SUCCESS;
                                        if (result != ISC_R_SUCCESS)
                                                break;
                                } else if (!ANSWER(rdataset))
                                        continue;
                        }

                        if (ANSWER(rdataset) && need_validation) {
                                if (fctx->type != dns_rdatatype_any &&
                                    fctx->type != dns_rdatatype_rrsig &&
                                    fctx->type != dns_rdatatype_sig) {
                                        /*
                                         * This is The Answer.  We will
                                         * validate it, but first we cache
                                         * the rest of the response - it may
                                         * contain useful keys.
                                         */
                                        INSIST(valrdataset == NULL &&
                                               valsigrdataset == NULL);
                                        valrdataset = rdataset;
                                        valsigrdataset = sigrdataset;
                                } else {
                                        /*
                                         * This is one of (potentially)
                                         * multiple answers to an ANY
                                         * or SIG query.  To keep things
                                         * simple, we just start the
                                         * validator right away rather
                                         * than caching first and
                                         * having to remember which
                                         * rdatasets needed validation.
                                         */
                                        result = valcreate(fctx, addrinfo,
                                                           name, rdataset->type,
                                                           rdataset,
                                                           sigrdataset,
                                                           valoptions, task);
                                        /*
                                         * Defer any further validations.
                                         * This prevents multiple validators
                                         * from manipulating fctx->rmessage
                                         * simultaneously.
                                         */
                                        valoptions |= DNS_VALIDATOR_DEFER;
                                }
                        } else if (CHAINING(rdataset)) {
                                if (rdataset->type == dns_rdatatype_cname)
                                        eresult = DNS_R_CNAME;
                                else {
                                        INSIST(rdataset->type ==
                                               dns_rdatatype_dname);
                                        eresult = DNS_R_DNAME;
                                }
                        }
                } else if (!EXTERNAL(rdataset)) {
                        /*
                         * It's OK to cache this rdataset now.
                         */
                        if (ANSWER(rdataset))
                                addedrdataset = ardataset;
                        else if (ANSWERSIG(rdataset))
                                addedrdataset = asigrdataset;
                        else
                                addedrdataset = NULL;
                        if (CHAINING(rdataset)) {
                                if (rdataset->type == dns_rdatatype_cname)
                                        eresult = DNS_R_CNAME;
                                else {
                                        INSIST(rdataset->type ==
                                               dns_rdatatype_dname);
                                        eresult = DNS_R_DNAME;
                                }
                        }
                        if (rdataset->trust == dns_trust_glue &&
                            (rdataset->type == dns_rdatatype_ns ||
                             (rdataset->type == dns_rdatatype_rrsig &&
                              rdataset->covers == dns_rdatatype_ns))) {
                                /*
                                 * If the trust level is 'dns_trust_glue'
                                 * then we are adding data from a referral
                                 * we got while executing the search algorithm.
                                 * New referral data always takes precedence
                                 * over the existing cache contents.
                                 */
                                options = DNS_DBADD_FORCE;
                        } else if ((fctx->options & DNS_FETCHOPT_PREFETCH) != 0)
                                options = DNS_DBADD_PREFETCH;
                        else
                                options = 0;

                        if (ANSWER(rdataset) &&
                           rdataset->type != dns_rdatatype_rrsig) {
                                isc_result_t tresult;
                                dns_name_t *noqname = NULL;
                                tresult = findnoqname(fctx, name,
                                                      rdataset->type, &noqname);
                                if (tresult == ISC_R_SUCCESS &&
                                    noqname != NULL) {
                                        tresult = dns_rdataset_addnoqname(
                                                            rdataset, noqname);
                                        RUNTIME_CHECK(tresult == ISC_R_SUCCESS);
                                }
                        }

                        /*
                         * Now we can add the rdataset.
                         */
                        result = dns_db_addrdataset(fctx->cache,
                                                    node, NULL, now,
                                                    rdataset,
                                                    options,
                                                    addedrdataset);

                        if (result == DNS_R_UNCHANGED) {
                                if (ANSWER(rdataset) &&
                                    ardataset != NULL &&
                                    NEGATIVE(ardataset)) {
                                        /*
                                         * The answer in the cache is better
                                         * than the answer we found, and is
                                         * a negative cache entry, so we
                                         * must set eresult appropriately.
                                         */
                                        if (NXDOMAIN(ardataset))
                                                eresult = DNS_R_NCACHENXDOMAIN;
                                        else
                                                eresult = DNS_R_NCACHENXRRSET;
                                }
                                result = ISC_R_SUCCESS;
                        } else if (result != ISC_R_SUCCESS)
                                break;
                }
        }

        if (valrdataset != NULL) {
                dns_rdatatype_t vtype = fctx->type;
                if (CHAINING(valrdataset)) {
                        if (valrdataset->type == dns_rdatatype_cname)
                                vtype = dns_rdatatype_cname;
                        else
                                vtype = dns_rdatatype_dname;
                }
                result = valcreate(fctx, addrinfo, name, vtype, valrdataset,
                                   valsigrdataset, valoptions, task);
        }

        if (result == ISC_R_SUCCESS && have_answer) {
                fctx->attributes |= FCTX_ATTR_HAVEANSWER;
                if (event != NULL) {
                        /*
                         * Negative results must be indicated in event->result.
                         */
                        if (dns_rdataset_isassociated(event->rdataset) &&
                            NEGATIVE(event->rdataset)) {
                                INSIST(eresult == DNS_R_NCACHENXDOMAIN ||
                                       eresult == DNS_R_NCACHENXRRSET);
                        }
                        event->result = eresult;
                        dns_db_attach(fctx->cache, adbp);
                        dns_db_transfernode(fctx->cache, &node, anodep);
                        clone_results(fctx);
                }
        }

        if (node != NULL)
                dns_db_detachnode(fctx->cache, &node);

        return (result);
}

static inline isc_result_t
cache_message(fetchctx_t *fctx, dns_adbaddrinfo_t *addrinfo, isc_stdtime_t now)
{
        isc_result_t result;
        dns_section_t section;
        dns_name_t *name;

        FCTXTRACE("cache_message");

        fctx->attributes &= ~FCTX_ATTR_WANTCACHE;

        LOCK(&fctx->res->buckets[fctx->bucketnum].lock);

        for (section = DNS_SECTION_ANSWER;
             section <= DNS_SECTION_ADDITIONAL;
             section++) {
                result = dns_message_firstname(fctx->rmessage, section);
                while (result == ISC_R_SUCCESS) {
                        name = NULL;
                        dns_message_currentname(fctx->rmessage, section,
                                                &name);
                        if ((name->attributes & DNS_NAMEATTR_CACHE) != 0) {
                                result = cache_name(fctx, name, addrinfo, now);
                                if (result != ISC_R_SUCCESS)
                                        break;
                        }
                        result = dns_message_nextname(fctx->rmessage, section);
                }
                if (result != ISC_R_NOMORE)
                        break;
        }
        if (result == ISC_R_NOMORE)
                result = ISC_R_SUCCESS;

        UNLOCK(&fctx->res->buckets[fctx->bucketnum].lock);

        return (result);
}

/*
 * Do what dns_ncache_addoptout() does, and then compute an appropriate eresult.
 */
static isc_result_t
ncache_adderesult(dns_message_t *message, dns_db_t *cache, dns_dbnode_t *node,
                  dns_rdatatype_t covers, isc_stdtime_t now, dns_ttl_t maxttl,
                  isc_boolean_t optout, isc_boolean_t secure,
                  dns_rdataset_t *ardataset, isc_result_t *eresultp)
{
        isc_result_t result;
        dns_rdataset_t rdataset;

        if (ardataset == NULL) {
                dns_rdataset_init(&rdataset);
                ardataset = &rdataset;
        }
        if (secure)
                result = dns_ncache_addoptout(message, cache, node, covers,
                                              now, maxttl, optout, ardataset);
        else
                result = dns_ncache_add(message, cache, node, covers, now,
                                        maxttl, ardataset);
        if (result == DNS_R_UNCHANGED || result == ISC_R_SUCCESS) {
                /*
                 * If the cache now contains a negative entry and we
                 * care about whether it is DNS_R_NCACHENXDOMAIN or
                 * DNS_R_NCACHENXRRSET then extract it.
                 */
                if (NEGATIVE(ardataset)) {
                        /*
                         * The cache data is a negative cache entry.
                         */
                        if (NXDOMAIN(ardataset))
                                *eresultp = DNS_R_NCACHENXDOMAIN;
                        else
                                *eresultp = DNS_R_NCACHENXRRSET;
                } else {
                        /*
                         * Either we don't care about the nature of the
                         * cache rdataset (because no fetch is interested
                         * in the outcome), or the cache rdataset is not
                         * a negative cache entry.  Whichever case it is,
                         * we can return success.
                         *
                         * XXXRTH  There's a CNAME/DNAME problem here.
                         */
                        *eresultp = ISC_R_SUCCESS;
                }
                result = ISC_R_SUCCESS;
        }
        if (ardataset == &rdataset && dns_rdataset_isassociated(ardataset))
                dns_rdataset_disassociate(ardataset);

        return (result);
}

static inline isc_result_t
ncache_message(fetchctx_t *fctx, dns_adbaddrinfo_t *addrinfo,
               dns_rdatatype_t covers, isc_stdtime_t now)
{
        isc_result_t result, eresult;
        dns_name_t *name;
        dns_resolver_t *res;
        dns_db_t **adbp;
        dns_dbnode_t *node, **anodep;
        dns_rdataset_t *ardataset;
        isc_boolean_t need_validation, secure_domain;
        dns_name_t *aname;
        dns_fetchevent_t *event;
        isc_uint32_t ttl;
        unsigned int valoptions = 0;
        isc_boolean_t checknta = ISC_TRUE;

        FCTXTRACE("ncache_message");

        fctx->attributes &= ~FCTX_ATTR_WANTNCACHE;

        res = fctx->res;
        need_validation = ISC_FALSE;
        POST(need_validation);
        secure_domain = ISC_FALSE;
        eresult = ISC_R_SUCCESS;
        name = &fctx->name;
        node = NULL;

        /*
         * XXXMPA remove when we follow cnames and adjust the setting
         * of FCTX_ATTR_WANTNCACHE in noanswer_response().
         */
        INSIST(fctx->rmessage->counts[DNS_SECTION_ANSWER] == 0);

        /*
         * Is DNSSEC validation required for this name?
         */
        if ((fctx->options & DNS_FETCHOPT_NONTA) != 0) {
                valoptions |= DNS_VALIDATOR_NONTA;
                checknta = ISC_FALSE;
        }

        if (fctx->res->view->enablevalidation) {
                result = issecuredomain(res->view, name, fctx->type,
                                        now, checknta, &secure_domain);
                if (result != ISC_R_SUCCESS)
                        return (result);

                if (!secure_domain && res->view->dlv != NULL) {
                        valoptions |= DNS_VALIDATOR_DLV;
                        secure_domain = ISC_TRUE;
                }
        }

        if ((fctx->options & DNS_FETCHOPT_NOCDFLAG) != 0)
                valoptions |= DNS_VALIDATOR_NOCDFLAG;

        if ((fctx->options & DNS_FETCHOPT_NOVALIDATE) != 0)
                need_validation = ISC_FALSE;
        else
                need_validation = secure_domain;

        if (secure_domain) {
                /*
                 * Mark all rdatasets as pending.
                 */
                dns_rdataset_t *trdataset;
                dns_name_t *tname;

                result = dns_message_firstname(fctx->rmessage,
                                               DNS_SECTION_AUTHORITY);
                while (result == ISC_R_SUCCESS) {
                        tname = NULL;
                        dns_message_currentname(fctx->rmessage,
                                                DNS_SECTION_AUTHORITY,
                                                &tname);
                        for (trdataset = ISC_LIST_HEAD(tname->list);
                             trdataset != NULL;
                             trdataset = ISC_LIST_NEXT(trdataset, link))
                                trdataset->trust = dns_trust_pending_answer;
                        result = dns_message_nextname(fctx->rmessage,
                                                      DNS_SECTION_AUTHORITY);
                }
                if (result != ISC_R_NOMORE)
                        return (result);

        }

        if (need_validation) {
                /*
                 * Do negative response validation.
                 */
                result = valcreate(fctx, addrinfo, name, fctx->type,
                                   NULL, NULL, valoptions,
                                   res->buckets[fctx->bucketnum].task);
                /*
                 * If validation is necessary, return now.  Otherwise continue
                 * to process the message, letting the validation complete
                 * in its own good time.
                 */
                return (result);
        }

        LOCK(&res->buckets[fctx->bucketnum].lock);

        adbp = NULL;
        aname = NULL;
        anodep = NULL;
        ardataset = NULL;
        if (!HAVE_ANSWER(fctx)) {
                event = ISC_LIST_HEAD(fctx->events);
                if (event != NULL) {
                        adbp = &event->db;
                        aname = dns_fixedname_name(&event->foundname);
                        result = dns_name_copy(name, aname, NULL);
                        if (result != ISC_R_SUCCESS)
                                goto unlock;
                        anodep = &event->node;
                        ardataset = event->rdataset;
                }
        } else
                event = NULL;

        result = dns_db_findnode(fctx->cache, name, ISC_TRUE, &node);
        if (result != ISC_R_SUCCESS)
                goto unlock;

        /*
         * If we are asking for a SOA record set the cache time
         * to zero to facilitate locating the containing zone of
         * a arbitrary zone.
         */
        ttl = fctx->res->view->maxncachettl;
        if (fctx->type == dns_rdatatype_soa &&
            covers == dns_rdatatype_any &&
            fctx->res->zero_no_soa_ttl)
                ttl = 0;

        result = ncache_adderesult(fctx->rmessage, fctx->cache, node,
                                   covers, now, ttl, ISC_FALSE,
                                   ISC_FALSE, ardataset, &eresult);
        if (result != ISC_R_SUCCESS)
                goto unlock;

        if (!HAVE_ANSWER(fctx)) {
                fctx->attributes |= FCTX_ATTR_HAVEANSWER;
                if (event != NULL) {
                        event->result = eresult;
                        dns_db_attach(fctx->cache, adbp);
                        dns_db_transfernode(fctx->cache, &node, anodep);
                        clone_results(fctx);
                }
        }

 unlock:
        UNLOCK(&res->buckets[fctx->bucketnum].lock);

        if (node != NULL)
                dns_db_detachnode(fctx->cache, &node);

        return (result);
}

static inline void
mark_related(dns_name_t *name, dns_rdataset_t *rdataset,
             isc_boolean_t external, isc_boolean_t gluing)
{
        name->attributes |= DNS_NAMEATTR_CACHE;
        if (gluing) {
                rdataset->trust = dns_trust_glue;
                /*
                 * Glue with 0 TTL causes problems.  We force the TTL to
                 * 1 second to prevent this.
                 */
                if (rdataset->ttl == 0)
                        rdataset->ttl = 1;
        } else
                rdataset->trust = dns_trust_additional;
        /*
         * Avoid infinite loops by only marking new rdatasets.
         */
        if (!CACHE(rdataset)) {
                name->attributes |= DNS_NAMEATTR_CHASE;
                rdataset->attributes |= DNS_RDATASETATTR_CHASE;
        }
        rdataset->attributes |= DNS_RDATASETATTR_CACHE;
        if (external)
                rdataset->attributes |= DNS_RDATASETATTR_EXTERNAL;
}

static isc_result_t
check_section(void *arg, dns_name_t *addname, dns_rdatatype_t type,
              dns_section_t section)
{
        fetchctx_t *fctx = arg;
        isc_result_t result;
        dns_name_t *name;
        dns_rdataset_t *rdataset;
        isc_boolean_t external;
        dns_rdatatype_t rtype;
        isc_boolean_t gluing;

        REQUIRE(VALID_FCTX(fctx));

#if CHECK_FOR_GLUE_IN_ANSWER
        if (section == DNS_SECTION_ANSWER && type != dns_rdatatype_a)
                return (ISC_R_SUCCESS);
#endif

        if (GLUING(fctx))
                gluing = ISC_TRUE;
        else
                gluing = ISC_FALSE;
        name = NULL;
        rdataset = NULL;
        result = dns_message_findname(fctx->rmessage, section, addname,
                                      dns_rdatatype_any, 0, &name, NULL);
        if (result == ISC_R_SUCCESS) {
                external = ISC_TF(!dns_name_issubdomain(name, &fctx->domain));
                if (type == dns_rdatatype_a) {
                        for (rdataset = ISC_LIST_HEAD(name->list);
                             rdataset != NULL;
                             rdataset = ISC_LIST_NEXT(rdataset, link)) {
                                if (rdataset->type == dns_rdatatype_rrsig)
                                        rtype = rdataset->covers;
                                else
                                        rtype = rdataset->type;
                                if (rtype == dns_rdatatype_a ||
                                    rtype == dns_rdatatype_aaaa)
                                        mark_related(name, rdataset, external,
                                                     gluing);
                        }
                } else {
                        result = dns_message_findtype(name, type, 0,
                                                      &rdataset);
                        if (result == ISC_R_SUCCESS) {
                                mark_related(name, rdataset, external, gluing);
                                /*
                                 * Do we have its SIG too?
                                 */
                                rdataset = NULL;
                                result = dns_message_findtype(name,
                                                      dns_rdatatype_rrsig,
                                                      type, &rdataset);
                                if (result == ISC_R_SUCCESS)
                                        mark_related(name, rdataset, external,
                                                     gluing);
                        }
                }
        }

        return (ISC_R_SUCCESS);
}

static isc_result_t
check_related(void *arg, dns_name_t *addname, dns_rdatatype_t type) {
        return (check_section(arg, addname, type, DNS_SECTION_ADDITIONAL));
}

#ifndef CHECK_FOR_GLUE_IN_ANSWER
#define CHECK_FOR_GLUE_IN_ANSWER 0
#endif
#if CHECK_FOR_GLUE_IN_ANSWER
static isc_result_t
check_answer(void *arg, dns_name_t *addname, dns_rdatatype_t type) {
        return (check_section(arg, addname, type, DNS_SECTION_ANSWER));
}
#endif

static void
chase_additional(fetchctx_t *fctx) {
        isc_boolean_t rescan;
        dns_section_t section = DNS_SECTION_ADDITIONAL;
        isc_result_t result;

 again:
        rescan = ISC_FALSE;

        for (result = dns_message_firstname(fctx->rmessage, section);
             result == ISC_R_SUCCESS;
             result = dns_message_nextname(fctx->rmessage, section)) {
                dns_name_t *name = NULL;
                dns_rdataset_t *rdataset;
                dns_message_currentname(fctx->rmessage, DNS_SECTION_ADDITIONAL,
                                        &name);
                if ((name->attributes & DNS_NAMEATTR_CHASE) == 0)
                        continue;
                name->attributes &= ~DNS_NAMEATTR_CHASE;
                for (rdataset = ISC_LIST_HEAD(name->list);
                     rdataset != NULL;
                     rdataset = ISC_LIST_NEXT(rdataset, link)) {
                        if (CHASE(rdataset)) {
                                rdataset->attributes &= ~DNS_RDATASETATTR_CHASE;
                                (void)dns_rdataset_additionaldata(rdataset,
                                                                  check_related,
                                                                  fctx);
                                rescan = ISC_TRUE;
                        }
                }
        }
        if (rescan)
                goto again;
}

static inline isc_result_t
cname_target(dns_rdataset_t *rdataset, dns_name_t *tname) {
        isc_result_t result;
        dns_rdata_t rdata = DNS_RDATA_INIT;
        dns_rdata_cname_t cname;

        result = dns_rdataset_first(rdataset);
        if (result != ISC_R_SUCCESS)
                return (result);
        dns_rdataset_current(rdataset, &rdata);
        result = dns_rdata_tostruct(&rdata, &cname, NULL);
        if (result != ISC_R_SUCCESS)
                return (result);
        dns_name_init(tname, NULL);
        dns_name_clone(&cname.cname, tname);
        dns_rdata_freestruct(&cname);

        return (ISC_R_SUCCESS);
}

static inline isc_result_t
dname_target(fetchctx_t *fctx, dns_rdataset_t *rdataset, dns_name_t *qname,
             dns_name_t *oname, dns_fixedname_t *fixeddname)
{
        isc_result_t result;
        dns_rdata_t rdata = DNS_RDATA_INIT;
        unsigned int nlabels;
        int order;
        dns_namereln_t namereln;
        dns_rdata_dname_t dname;
        dns_fixedname_t prefix;

        /*
         * Get the target name of the DNAME.
         */
        result = dns_rdataset_first(rdataset);
        if (result != ISC_R_SUCCESS)
                return (result);
        dns_rdataset_current(rdataset, &rdata);
        result = dns_rdata_tostruct(&rdata, &dname, NULL);
        if (result != ISC_R_SUCCESS)
                return (result);

        /*
         * Get the prefix of qname.
         */
        namereln = dns_name_fullcompare(qname, oname, &order, &nlabels);
        if (namereln != dns_namereln_subdomain) {
                char qbuf[DNS_NAME_FORMATSIZE];
                char obuf[DNS_NAME_FORMATSIZE];

                dns_rdata_freestruct(&dname);
                dns_name_format(qname, qbuf, sizeof(qbuf));
                dns_name_format(oname, obuf, sizeof(obuf));
                log_formerr(fctx, "unrelated DNAME in answer: "
                                   "%s is not in %s", qbuf, obuf);
                return (DNS_R_FORMERR);
        }
        dns_fixedname_init(&prefix);
        dns_name_split(qname, nlabels, dns_fixedname_name(&prefix), NULL);
        dns_fixedname_init(fixeddname);
        result = dns_name_concatenate(dns_fixedname_name(&prefix),
                                      &dname.dname,
                                      dns_fixedname_name(fixeddname), NULL);
        dns_rdata_freestruct(&dname);
        return (result);
}

static isc_boolean_t
is_answeraddress_allowed(dns_view_t *view, dns_name_t *name,
                         dns_rdataset_t *rdataset)
{
        isc_result_t result;
        dns_rdata_t rdata = DNS_RDATA_INIT;
        struct in_addr ina;
        struct in6_addr in6a;
        isc_netaddr_t netaddr;
        char addrbuf[ISC_NETADDR_FORMATSIZE];
        char namebuf[DNS_NAME_FORMATSIZE];
        char classbuf[64];
        char typebuf[64];
        int match;

        /* By default, we allow any addresses. */
        if (view->denyansweracl == NULL)
                return (ISC_TRUE);

        /*
         * If the owner name matches one in the exclusion list, either exactly
         * or partially, allow it.
         */
        if (view->answeracl_exclude != NULL) {
                dns_rbtnode_t *node = NULL;

                result = dns_rbt_findnode(view->answeracl_exclude, name, NULL,
                                          &node, NULL, 0, NULL, NULL);

                if (result == ISC_R_SUCCESS || result == DNS_R_PARTIALMATCH)
                        return (ISC_TRUE);
        }

        /*
         * Otherwise, search the filter list for a match for each address
         * record.  If a match is found, the address should be filtered,
         * so should the entire answer.
         */
        for (result = dns_rdataset_first(rdataset);
             result == ISC_R_SUCCESS;
             result = dns_rdataset_next(rdataset)) {
                dns_rdata_reset(&rdata);
                dns_rdataset_current(rdataset, &rdata);
                if (rdataset->type == dns_rdatatype_a) {
                        INSIST(rdata.length == sizeof(ina.s_addr));
                        memmove(&ina.s_addr, rdata.data, sizeof(ina.s_addr));
                        isc_netaddr_fromin(&netaddr, &ina);
                } else {
                        INSIST(rdata.length == sizeof(in6a.s6_addr));
                        memmove(in6a.s6_addr, rdata.data, sizeof(in6a.s6_addr));
                        isc_netaddr_fromin6(&netaddr, &in6a);
                }

                result = dns_acl_match(&netaddr, NULL, view->denyansweracl,
                                       &view->aclenv, &match, NULL);

                if (result == ISC_R_SUCCESS && match > 0) {
                        isc_netaddr_format(&netaddr, addrbuf, sizeof(addrbuf));
                        dns_name_format(name, namebuf, sizeof(namebuf));
                        dns_rdatatype_format(rdataset->type, typebuf,
                                             sizeof(typebuf));
                        dns_rdataclass_format(rdataset->rdclass, classbuf,
                                              sizeof(classbuf));
                        isc_log_write(dns_lctx, DNS_LOGCATEGORY_RESOLVER,
                                      DNS_LOGMODULE_RESOLVER, ISC_LOG_NOTICE,
                                      "answer address %s denied for %s/%s/%s",
                                      addrbuf, namebuf, typebuf, classbuf);
                        return (ISC_FALSE);
                }
        }

        return (ISC_TRUE);
}

static isc_boolean_t
is_answertarget_allowed(dns_view_t *view, dns_name_t *name,
                        dns_rdatatype_t type, dns_name_t *tname,
                        dns_name_t *domain)
{
        isc_result_t result;
        dns_rbtnode_t *node = NULL;
        char qnamebuf[DNS_NAME_FORMATSIZE];
        char tnamebuf[DNS_NAME_FORMATSIZE];
        char classbuf[64];
        char typebuf[64];

        /* By default, we allow any target name. */
        if (view->denyanswernames == NULL)
                return (ISC_TRUE);

        /*
         * If the owner name matches one in the exclusion list, either exactly
         * or partially, allow it.
         */
        if (view->answernames_exclude != NULL) {
                result = dns_rbt_findnode(view->answernames_exclude, name, NULL,
                                          &node, NULL, 0, NULL, NULL);
                if (result == ISC_R_SUCCESS || result == DNS_R_PARTIALMATCH)
                        return (ISC_TRUE);
        }

        /*
         * If the target name is a subdomain of the search domain, allow it.
         */
        if (dns_name_issubdomain(tname, domain))
                return (ISC_TRUE);

        /*
         * Otherwise, apply filters.
         */
        result = dns_rbt_findnode(view->denyanswernames, tname, NULL, &node,
                                  NULL, 0, NULL, NULL);
        if (result == ISC_R_SUCCESS || result == DNS_R_PARTIALMATCH) {
                dns_name_format(name, qnamebuf, sizeof(qnamebuf));
                dns_name_format(tname, tnamebuf, sizeof(tnamebuf));
                dns_rdatatype_format(type, typebuf, sizeof(typebuf));
                dns_rdataclass_format(view->rdclass, classbuf,
                                      sizeof(classbuf));
                isc_log_write(dns_lctx, DNS_LOGCATEGORY_RESOLVER,
                              DNS_LOGMODULE_RESOLVER, ISC_LOG_NOTICE,
                              "%s target %s denied for %s/%s",
                              typebuf, tnamebuf, qnamebuf, classbuf);
                return (ISC_FALSE);
        }

        return (ISC_TRUE);
}

static void
trim_ns_ttl(fetchctx_t *fctx, dns_name_t *name, dns_rdataset_t *rdataset) {
        char ns_namebuf[DNS_NAME_FORMATSIZE];
        char namebuf[DNS_NAME_FORMATSIZE];
        char tbuf[DNS_RDATATYPE_FORMATSIZE];

        if (fctx->ns_ttl_ok && rdataset->ttl > fctx->ns_ttl) {
                dns_name_format(name, ns_namebuf, sizeof(ns_namebuf));
                dns_name_format(&fctx->name, namebuf, sizeof(namebuf));
                dns_rdatatype_format(fctx->type, tbuf, sizeof(tbuf));

                isc_log_write(dns_lctx, DNS_LOGCATEGORY_RESOLVER,
                              DNS_LOGMODULE_RESOLVER, ISC_LOG_DEBUG(10),
                              "fctx %p: trimming ttl of %s/NS for %s/%s: "
                              "%u -> %u", fctx, ns_namebuf, namebuf, tbuf,
                              rdataset->ttl, fctx->ns_ttl);
                rdataset->ttl = fctx->ns_ttl;
        }
}

/*
 * Handle a no-answer response (NXDOMAIN, NXRRSET, or referral).
 * If look_in_options has LOOK_FOR_NS_IN_ANSWER then we look in the answer
 * section for the NS RRset if the query type is NS; if it has
 * LOOK_FOR_GLUE_IN_ANSWER we look for glue incorrectly returned in the answer
 * section for A and AAAA queries.
 */
#define LOOK_FOR_NS_IN_ANSWER 0x1
#define LOOK_FOR_GLUE_IN_ANSWER 0x2

static isc_result_t
noanswer_response(fetchctx_t *fctx, dns_name_t *oqname,
                  unsigned int look_in_options)
{
        isc_result_t result;
        dns_message_t *message;
        dns_name_t *name, *qname, *ns_name, *soa_name, *ds_name, *save_name;
        dns_rdataset_t *rdataset, *ns_rdataset;
        isc_boolean_t aa, negative_response;
        dns_rdatatype_t type, save_type;
        dns_section_t section;

        FCTXTRACE("noanswer_response");

        if ((look_in_options & LOOK_FOR_NS_IN_ANSWER) != 0) {
                INSIST(fctx->type == dns_rdatatype_ns);
                section = DNS_SECTION_ANSWER;
        } else
                section = DNS_SECTION_AUTHORITY;

        message = fctx->rmessage;

        /*
         * Setup qname.
         */
        if (oqname == NULL) {
                /*
                 * We have a normal, non-chained negative response or
                 * referral.
                 */
                if ((message->flags & DNS_MESSAGEFLAG_AA) != 0)
                        aa = ISC_TRUE;
                else
                        aa = ISC_FALSE;
                qname = &fctx->name;
        } else {
                /*
                 * We're being invoked by answer_response() after it has
                 * followed a CNAME/DNAME chain.
                 */
                qname = oqname;
                aa = ISC_FALSE;
                /*
                 * If the current qname is not a subdomain of the query
                 * domain, there's no point in looking at the authority
                 * section without doing DNSSEC validation.
                 *
                 * Until we do that validation, we'll just return success
                 * in this case.
                 */
                if (!dns_name_issubdomain(qname, &fctx->domain))
                        return (ISC_R_SUCCESS);
        }

        /*
         * We have to figure out if this is a negative response, or a
         * referral.
         */

        /*
         * Sometimes we can tell if its a negative response by looking at
         * the message header.
         */
        negative_response = ISC_FALSE;
        if (message->rcode == dns_rcode_nxdomain ||
            (message->counts[DNS_SECTION_ANSWER] == 0 &&
             message->counts[DNS_SECTION_AUTHORITY] == 0))
                negative_response = ISC_TRUE;

        /*
         * Process the authority section.
         */
        ns_name = NULL;
        ns_rdataset = NULL;
        soa_name = NULL;
        ds_name = NULL;
        save_name = NULL;
        save_type = dns_rdatatype_none;
        result = dns_message_firstname(message, section);
        while (result == ISC_R_SUCCESS) {
                name = NULL;
                dns_message_currentname(message, section, &name);
                if (dns_name_issubdomain(name, &fctx->domain)) {
                        /*
                         * Look for NS/SOA RRsets first.
                         */
                        for (rdataset = ISC_LIST_HEAD(name->list);
                             rdataset != NULL;
                             rdataset = ISC_LIST_NEXT(rdataset, link)) {
                                type = rdataset->type;
                                if (type == dns_rdatatype_rrsig)
                                        type = rdataset->covers;
                                if (((type == dns_rdatatype_ns ||
                                      type == dns_rdatatype_soa) &&
                                     !dns_name_issubdomain(qname, name))) {
                                        char qbuf[DNS_NAME_FORMATSIZE];
                                        char nbuf[DNS_NAME_FORMATSIZE];
                                        char tbuf[DNS_RDATATYPE_FORMATSIZE];
                                        dns_rdatatype_format(type, tbuf,
                                                             sizeof(tbuf));
                                        dns_name_format(name, nbuf,
                                                             sizeof(nbuf));
                                        dns_name_format(qname, qbuf,
                                                             sizeof(qbuf));
                                        log_formerr(fctx,
                                                    "unrelated %s %s in "
                                                    "%s authority section",
                                                    tbuf, nbuf, qbuf);
                                        goto nextname;
                                }
                                if (type == dns_rdatatype_ns) {
                                        /*
                                         * NS or RRSIG NS.
                                         *
                                         * Only one set of NS RRs is allowed.
                                         */
                                        if (rdataset->type ==
                                            dns_rdatatype_ns) {
                                                if (ns_name != NULL &&
                                                    name != ns_name) {
                                                        log_formerr(fctx,
                                                                "multiple NS "
                                                                "RRsets in "
                                                                "authority "
                                                                "section");
                                                        return (DNS_R_FORMERR);
                                                }
                                                ns_name = name;
                                                ns_rdataset = rdataset;
                                        }
                                        name->attributes |=
                                                DNS_NAMEATTR_CACHE;
                                        rdataset->attributes |=
                                                DNS_RDATASETATTR_CACHE;
                                        rdataset->trust = dns_trust_glue;
                                }
                                if (type == dns_rdatatype_soa) {
                                        /*
                                         * SOA, or RRSIG SOA.
                                         *
                                         * Only one SOA is allowed.
                                         */
                                        if (rdataset->type ==
                                            dns_rdatatype_soa) {
                                                if (soa_name != NULL &&
                                                    name != soa_name) {
                                                        log_formerr(fctx,
                                                                "multiple SOA "
                                                                "RRs in "
                                                                "authority "
                                                                "section");
                                                        return (DNS_R_FORMERR);
                                                }
                                                soa_name = name;
                                        }
                                        name->attributes |=
                                                DNS_NAMEATTR_NCACHE;
                                        rdataset->attributes |=
                                                DNS_RDATASETATTR_NCACHE;
                                        if (aa)
                                                rdataset->trust =
                                                    dns_trust_authauthority;
                                        else if (ISFORWARDER(fctx->addrinfo))
                                                rdataset->trust =
                                                        dns_trust_answer;
                                        else
                                                rdataset->trust =
                                                        dns_trust_additional;
                                }
                        }
                }
 nextname:
                result = dns_message_nextname(message, section);
                if (result == ISC_R_NOMORE)
                        break;
                else if (result != ISC_R_SUCCESS)
                        return (result);
        }

        log_ns_ttl(fctx, "noanswer_response");

        if (ns_rdataset != NULL && dns_name_equal(&fctx->domain, ns_name) &&
            !dns_name_equal(ns_name, dns_rootname))
                trim_ns_ttl(fctx, ns_name, ns_rdataset);

        /*
         * A negative response has a SOA record (Type 2)
         * and a optional NS RRset (Type 1) or it has neither
         * a SOA or a NS RRset (Type 3, handled above) or
         * rcode is NXDOMAIN (handled above) in which case
         * the NS RRset is allowed (Type 4).
         */
        if (soa_name != NULL)
                negative_response = ISC_TRUE;

        result = dns_message_firstname(message, section);
        while (result == ISC_R_SUCCESS) {
                name = NULL;
                dns_message_currentname(message, section, &name);
                if (dns_name_issubdomain(name, &fctx->domain)) {
                        for (rdataset = ISC_LIST_HEAD(name->list);
                             rdataset != NULL;
                             rdataset = ISC_LIST_NEXT(rdataset, link)) {
                                type = rdataset->type;
                                if (type == dns_rdatatype_rrsig)
                                        type = rdataset->covers;
                                if (type == dns_rdatatype_nsec ||
                                    type == dns_rdatatype_nsec3) {
                                        /*
                                         * NSEC or RRSIG NSEC.
                                         */
                                        if (negative_response) {
                                                name->attributes |=
                                                        DNS_NAMEATTR_NCACHE;
                                                rdataset->attributes |=
                                                        DNS_RDATASETATTR_NCACHE;
                                        } else if (type == dns_rdatatype_nsec) {
                                                name->attributes |=
                                                        DNS_NAMEATTR_CACHE;
                                                rdataset->attributes |=
                                                        DNS_RDATASETATTR_CACHE;
                                        }
                                        if (aa)
                                                rdataset->trust =
                                                    dns_trust_authauthority;
                                        else if (ISFORWARDER(fctx->addrinfo))
                                                rdataset->trust =
                                                        dns_trust_answer;
                                        else
                                                rdataset->trust =
                                                        dns_trust_additional;
                                        /*
                                         * No additional data needs to be
                                         * marked.
                                         */
                                } else if (type == dns_rdatatype_ds) {
                                        /*
                                         * DS or SIG DS.
                                         *
                                         * These should only be here if
                                         * this is a referral, and there
                                         * should only be one DS RRset.
                                         */
                                        if (ns_name == NULL) {
                                                log_formerr(fctx,
                                                            "DS with no "
                                                            "referral");
                                                return (DNS_R_FORMERR);
                                        }
                                        if (rdataset->type ==
                                            dns_rdatatype_ds) {
                                                if (ds_name != NULL &&
                                                    name != ds_name) {
                                                        log_formerr(fctx,
                                                                "DS doesn't "
                                                                "match "
                                                                "referral "
                                                                "(NS)");
                                                        return (DNS_R_FORMERR);
                                                }
                                                ds_name = name;
                                        }
                                        name->attributes |=
                                                DNS_NAMEATTR_CACHE;
                                        rdataset->attributes |=
                                                DNS_RDATASETATTR_CACHE;
                                        if (aa)
                                                rdataset->trust =
                                                    dns_trust_authauthority;
                                        else if (ISFORWARDER(fctx->addrinfo))
                                                rdataset->trust =
                                                        dns_trust_answer;
                                        else
                                                rdataset->trust =
                                                        dns_trust_additional;
                                }
                        }
                } else {
                        save_name = name;
                        save_type = ISC_LIST_HEAD(name->list)->type;
                }
                result = dns_message_nextname(message, section);
                if (result == ISC_R_NOMORE)
                        break;
                else if (result != ISC_R_SUCCESS)
                        return (result);
        }

        /*
         * Trigger lookups for DNS nameservers.
         */
        if (negative_response && message->rcode == dns_rcode_noerror &&
            fctx->type == dns_rdatatype_ds && soa_name != NULL &&
            dns_name_equal(soa_name, qname) &&
            !dns_name_equal(qname, dns_rootname))
                return (DNS_R_CHASEDSSERVERS);

        /*
         * Did we find anything?
         */
        if (!negative_response && ns_name == NULL) {
                /*
                 * Nope.
                 */
                if (oqname != NULL) {
                        /*
                         * We've already got a partial CNAME/DNAME chain,
                         * and haven't found else anything useful here, but
                         * no error has occurred since we have an answer.
                         */
                        return (ISC_R_SUCCESS);
                } else {
                        /*
                         * The responder is insane.
                         */
                        if (save_name == NULL) {
                                log_formerr(fctx, "invalid response");
                                return (DNS_R_FORMERR);
                        }
                        if (!dns_name_issubdomain(save_name, &fctx->domain)) {
                                char nbuf[DNS_NAME_FORMATSIZE];
                                char dbuf[DNS_NAME_FORMATSIZE];
                                char tbuf[DNS_RDATATYPE_FORMATSIZE];

                                dns_rdatatype_format(save_type, tbuf,
                                        sizeof(tbuf));
                                dns_name_format(save_name, nbuf, sizeof(nbuf));
                                dns_name_format(&fctx->domain, dbuf,
                                        sizeof(dbuf));

                                log_formerr(fctx, "Name %s (%s) not subdomain"
                                        " of zone %s -- invalid response",
                                        nbuf, tbuf, dbuf);
                        } else {
                                log_formerr(fctx, "invalid response");
                        }
                        return (DNS_R_FORMERR);
                }
        }

        /*
         * If we found both NS and SOA, they should be the same name.
         */
        if (ns_name != NULL && soa_name != NULL && ns_name != soa_name) {
                log_formerr(fctx, "NS/SOA mismatch");
                return (DNS_R_FORMERR);
        }

        /*
         * Do we have a referral?  (We only want to follow a referral if
         * we're not following a chain.)
         */
        if (!negative_response && ns_name != NULL && oqname == NULL) {
                /*
                 * We already know ns_name is a subdomain of fctx->domain.
                 * If ns_name is equal to fctx->domain, we're not making
                 * progress.  We return DNS_R_FORMERR so that we'll keep
                 * trying other servers.
                 */
                if (dns_name_equal(ns_name, &fctx->domain)) {
                        log_formerr(fctx, "non-improving referral");
                        return (DNS_R_FORMERR);
                }

                /*
                 * If the referral name is not a parent of the query
                 * name, consider the responder insane.
                 */
                if (! dns_name_issubdomain(&fctx->name, ns_name)) {
                        /* Logged twice */
                        log_formerr(fctx, "referral to non-parent");
                        FCTXTRACE("referral to non-parent");
                        return (DNS_R_FORMERR);
                }

                /*
                 * Mark any additional data related to this rdataset.
                 * It's important that we do this before we change the
                 * query domain.
                 */
                INSIST(ns_rdataset != NULL);
                fctx->attributes |= FCTX_ATTR_GLUING;
                (void)dns_rdataset_additionaldata(ns_rdataset, check_related,
                                                  fctx);
#if CHECK_FOR_GLUE_IN_ANSWER
                /*
                 * Look in the answer section for "glue" that is incorrectly
                 * returned as a answer.  This is needed if the server also
                 * minimizes the response size by not adding records to the
                 * additional section that are in the answer section or if
                 * the record gets dropped due to message size constraints.
                 */
                if ((look_in_options & LOOK_FOR_GLUE_IN_ANSWER) != 0 &&
                    (fctx->type == dns_rdatatype_aaaa ||
                     fctx->type == dns_rdatatype_a))
                        (void)dns_rdataset_additionaldata(ns_rdataset,
                                                          check_answer, fctx);
#endif
                fctx->attributes &= ~FCTX_ATTR_GLUING;
                /*
                 * NS rdatasets with 0 TTL cause problems.
                 * dns_view_findzonecut() will not find them when we
                 * try to follow the referral, and we'll SERVFAIL
                 * because the best nameservers are now above QDOMAIN.
                 * We force the TTL to 1 second to prevent this.
                 */
                if (ns_rdataset->ttl == 0)
                        ns_rdataset->ttl = 1;
                /*
                 * Set the current query domain to the referral name.
                 *
                 * XXXRTH  We should check if we're in forward-only mode, and
                 *              if so we should bail out.
                 */
                INSIST(dns_name_countlabels(&fctx->domain) > 0);
                dns_name_free(&fctx->domain, fctx->mctx);
                if (dns_rdataset_isassociated(&fctx->nameservers))
                        dns_rdataset_disassociate(&fctx->nameservers);
                dns_name_init(&fctx->domain, NULL);
                result = dns_name_dup(ns_name, fctx->mctx, &fctx->domain);
                if (result != ISC_R_SUCCESS)
                        return (result);
                fctx->attributes |= FCTX_ATTR_WANTCACHE;
                fctx->ns_ttl_ok = ISC_FALSE;
                log_ns_ttl(fctx, "DELEGATION");
                return (DNS_R_DELEGATION);
        }

        /*
         * Since we're not doing a referral, we don't want to cache any
         * NS RRs we may have found.
         */
        if (ns_name != NULL)
                ns_name->attributes &= ~DNS_NAMEATTR_CACHE;

        if (negative_response && oqname == NULL)
                fctx->attributes |= FCTX_ATTR_WANTNCACHE;

        return (ISC_R_SUCCESS);
}

static isc_result_t
answer_response(fetchctx_t *fctx) {
        isc_result_t result;
        dns_message_t *message;
        dns_name_t *name, *qname, tname, *ns_name;
        dns_rdataset_t *rdataset, *ns_rdataset;
        isc_boolean_t done, external, chaining, aa, found, want_chaining;
        isc_boolean_t have_answer, found_cname, found_type, wanted_chaining;
        unsigned int aflag;
        dns_rdatatype_t type;
        dns_fixedname_t dname, fqname;
        dns_view_t *view;

        FCTXTRACE("answer_response");

        message = fctx->rmessage;

        /*
         * Examine the answer section, marking those rdatasets which are
         * part of the answer and should be cached.
         */

        done = ISC_FALSE;
        found_cname = ISC_FALSE;
        found_type = ISC_FALSE;
        chaining = ISC_FALSE;
        have_answer = ISC_FALSE;
        want_chaining = ISC_FALSE;
        POST(want_chaining);
        if ((message->flags & DNS_MESSAGEFLAG_AA) != 0)
                aa = ISC_TRUE;
        else
                aa = ISC_FALSE;
        qname = &fctx->name;
        type = fctx->type;
        view = fctx->res->view;
        result = dns_message_firstname(message, DNS_SECTION_ANSWER);
        while (!done && result == ISC_R_SUCCESS) {
                name = NULL;
                dns_message_currentname(message, DNS_SECTION_ANSWER, &name);
                external = ISC_TF(!dns_name_issubdomain(name, &fctx->domain));
                if (dns_name_equal(name, qname)) {
                        wanted_chaining = ISC_FALSE;
                        for (rdataset = ISC_LIST_HEAD(name->list);
                             rdataset != NULL;
                             rdataset = ISC_LIST_NEXT(rdataset, link)) {
                                found = ISC_FALSE;
                                want_chaining = ISC_FALSE;
                                aflag = 0;
                                if (rdataset->type == dns_rdatatype_nsec3) {
                                        /*
                                         * NSEC3 records are not allowed to
                                         * appear in the answer section.
                                         */
                                        log_formerr(fctx, "NSEC3 in answer");
                                        return (DNS_R_FORMERR);
                                }

                                /*
                                 * Apply filters, if given, on answers to reject
                                 * a malicious attempt of rebinding.
                                 */
                                if ((rdataset->type == dns_rdatatype_a ||
                                     rdataset->type == dns_rdatatype_aaaa) &&
                                    !is_answeraddress_allowed(view, name,
                                                              rdataset)) {
                                        return (DNS_R_SERVFAIL);
                                }

                                if (rdataset->type == type && !found_cname) {
                                        /*
                                         * We've found an ordinary answer.
                                         */
                                        found = ISC_TRUE;
                                        found_type = ISC_TRUE;
                                        done = ISC_TRUE;
                                        aflag = DNS_RDATASETATTR_ANSWER;
                                } else if (type == dns_rdatatype_any) {
                                        /*
                                         * We've found an answer matching
                                         * an ANY query.  There may be
                                         * more.
                                         */
                                        found = ISC_TRUE;
                                        aflag = DNS_RDATASETATTR_ANSWER;
                                } else if (rdataset->type == dns_rdatatype_rrsig
                                           && rdataset->covers == type
                                           && !found_cname) {
                                        /*
                                         * We've found a signature that
                                         * covers the type we're looking for.
                                         */
                                        found = ISC_TRUE;
                                        found_type = ISC_TRUE;
                                        aflag = DNS_RDATASETATTR_ANSWERSIG;
                                } else if (rdataset->type ==
                                           dns_rdatatype_cname
                                           && !found_type) {
                                        /*
                                         * We're looking for something else,
                                         * but we found a CNAME.
                                         *
                                         * Getting a CNAME response for some
                                         * query types is an error, see
                                         * RFC 4035, Section 2.5.
                                         */
                                        if (type == dns_rdatatype_rrsig ||
                                            type == dns_rdatatype_key ||
                                            type == dns_rdatatype_nsec) {
                                                char buf[DNS_RDATATYPE_FORMATSIZE];
                                                dns_rdatatype_format(fctx->type,
                                                              buf, sizeof(buf));
                                                log_formerr(fctx,
                                                            "CNAME response "
                                                            "for %s RR", buf);
                                                return (DNS_R_FORMERR);
                                        }
                                        found = ISC_TRUE;
                                        found_cname = ISC_TRUE;
                                        want_chaining = ISC_TRUE;
                                        aflag = DNS_RDATASETATTR_ANSWER;
                                        result = cname_target(rdataset,
                                                              &tname);
                                        if (result != ISC_R_SUCCESS)
                                                return (result);
                                        /* Apply filters on the target name. */
                                        if (!is_answertarget_allowed(view,
                                                        name,
                                                        rdataset->type,
                                                        &tname,
                                                        &fctx->domain)) {
                                                return (DNS_R_SERVFAIL);
                                        }
                                } else if (rdataset->type == dns_rdatatype_rrsig
                                           && rdataset->covers ==
                                           dns_rdatatype_cname
                                           && !found_type) {
                                        /*
                                         * We're looking for something else,
                                         * but we found a SIG CNAME.
                                         */
                                        found = ISC_TRUE;
                                        found_cname = ISC_TRUE;
                                        aflag = DNS_RDATASETATTR_ANSWERSIG;
                                }

                                if (found) {
                                        /*
                                         * We've found an answer to our
                                         * question.
                                         */
                                        name->attributes |=
                                                DNS_NAMEATTR_CACHE;
                                        rdataset->attributes |=
                                                DNS_RDATASETATTR_CACHE;
                                        rdataset->trust = dns_trust_answer;
                                        if (!chaining) {
                                                /*
                                                 * This data is "the" answer
                                                 * to our question only if
                                                 * we're not chaining (i.e.
                                                 * if we haven't followed
                                                 * a CNAME or DNAME).
                                                 */
                                                INSIST(!external);
                                                if (aflag ==
                                                    DNS_RDATASETATTR_ANSWER)
                                                        have_answer = ISC_TRUE;
                                                name->attributes |=
                                                        DNS_NAMEATTR_ANSWER;
                                                rdataset->attributes |= aflag;
                                                if (aa)
                                                        rdataset->trust =
                                                          dns_trust_authanswer;
                                        } else if (external) {
                                                /*
                                                 * This data is outside of
                                                 * our query domain, and
                                                 * may not be cached.
                                                 */
                                                rdataset->attributes |=
                                                    DNS_RDATASETATTR_EXTERNAL;
                                        }

                                        /*
                                         * Mark any additional data related
                                         * to this rdataset.
                                         */
                                        (void)dns_rdataset_additionaldata(
                                                        rdataset,
                                                        check_related,
                                                        fctx);

                                        /*
                                         * CNAME chaining.
                                         */
                                        if (want_chaining) {
                                                wanted_chaining = ISC_TRUE;
                                                name->attributes |=
                                                        DNS_NAMEATTR_CHAINING;
                                                rdataset->attributes |=
                                                    DNS_RDATASETATTR_CHAINING;
                                                qname = &tname;
                                        }
                                }
                                /*
                                 * We could add an "else" clause here and
                                 * log that we're ignoring this rdataset.
                                 */
                        }
                        /*
                         * If wanted_chaining is true, we've done
                         * some chaining as the result of processing
                         * this node, and thus we need to set
                         * chaining to true.
                         *
                         * We don't set chaining inside of the
                         * rdataset loop because doing that would
                         * cause us to ignore the signatures of
                         * CNAMEs.
                         */
                        if (wanted_chaining)
                                chaining = ISC_TRUE;
                } else {
                        /*
                         * Look for a DNAME (or its SIG).  Anything else is
                         * ignored.
                         */
                        wanted_chaining = ISC_FALSE;
                        for (rdataset = ISC_LIST_HEAD(name->list);
                             rdataset != NULL;
                             rdataset = ISC_LIST_NEXT(rdataset, link)) {
                                isc_boolean_t found_dname = ISC_FALSE;
                                dns_name_t *dname_name;

                                found = ISC_FALSE;
                                aflag = 0;
                                if (rdataset->type == dns_rdatatype_dname) {
                                        /*
                                         * We're looking for something else,
                                         * but we found a DNAME.
                                         *
                                         * If we're not chaining, then the
                                         * DNAME should not be external.
                                         */
                                        if (!chaining && external) {
                                                log_formerr(fctx,
                                                            "external DNAME");
                                                return (DNS_R_FORMERR);
                                        }
                                        found = ISC_TRUE;
                                        want_chaining = ISC_TRUE;
                                        POST(want_chaining);
                                        aflag = DNS_RDATASETATTR_ANSWER;
                                        result = dname_target(fctx, rdataset,
                                                              qname, name,
                                                              &dname);
                                        if (result == ISC_R_NOSPACE) {
                                                /*
                                                 * We can't construct the
                                                 * DNAME target.  Do not
                                                 * try to continue.
                                                 */
                                                want_chaining = ISC_FALSE;
                                                POST(want_chaining);
                                        } else if (result != ISC_R_SUCCESS)
                                                return (result);
                                        else
                                                found_dname = ISC_TRUE;

                                        dname_name = dns_fixedname_name(&dname);
                                        if (!is_answertarget_allowed(view,
                                                        qname,
                                                        rdataset->type,
                                                        dname_name,
                                                        &fctx->domain)) {
                                                return (DNS_R_SERVFAIL);
                                        }
                                } else if (rdataset->type == dns_rdatatype_rrsig
                                           && rdataset->covers ==
                                           dns_rdatatype_dname) {
                                        /*
                                         * We've found a signature that
                                         * covers the DNAME.
                                         */
                                        found = ISC_TRUE;
                                        aflag = DNS_RDATASETATTR_ANSWERSIG;
                                }

                                if (found) {
                                        /*
                                         * We've found an answer to our
                                         * question.
                                         */
                                        name->attributes |=
                                                DNS_NAMEATTR_CACHE;
                                        rdataset->attributes |=
                                                DNS_RDATASETATTR_CACHE;
                                        rdataset->trust = dns_trust_answer;
                                        if (!chaining) {
                                                /*
                                                 * This data is "the" answer
                                                 * to our question only if
                                                 * we're not chaining.
                                                 */
                                                INSIST(!external);
                                                if (aflag ==
                                                    DNS_RDATASETATTR_ANSWER)
                                                        have_answer = ISC_TRUE;
                                                name->attributes |=
                                                        DNS_NAMEATTR_ANSWER;
                                                rdataset->attributes |= aflag;
                                                if (aa)
                                                        rdataset->trust =
                                                          dns_trust_authanswer;
                                        } else if (external) {
                                                rdataset->attributes |=
                                                    DNS_RDATASETATTR_EXTERNAL;
                                        }

                                        /*
                                         * DNAME chaining.
                                         */
                                        if (found_dname) {
                                                /*
                                                 * Copy the dname into the
                                                 * qname fixed name.
                                                 *
                                                 * Although we check for
                                                 * failure of the copy
                                                 * operation, in practice it
                                                 * should never fail since
                                                 * we already know that the
                                                 * result fits in a fixedname.
                                                 */
                                                dns_fixedname_init(&fqname);
                                                result = dns_name_copy(
                                                  dns_fixedname_name(&dname),
                                                  dns_fixedname_name(&fqname),
                                                  NULL);
                                                if (result != ISC_R_SUCCESS)
                                                        return (result);
                                                wanted_chaining = ISC_TRUE;
                                                name->attributes |=
                                                        DNS_NAMEATTR_CHAINING;
                                                rdataset->attributes |=
                                                    DNS_RDATASETATTR_CHAINING;
                                                qname = dns_fixedname_name(
                                                                   &fqname);
                                        }
                                }
                        }
                        if (wanted_chaining)
                                chaining = ISC_TRUE;
                }
                result = dns_message_nextname(message, DNS_SECTION_ANSWER);
        }
        if (result == ISC_R_NOMORE)
                result = ISC_R_SUCCESS;
        if (result != ISC_R_SUCCESS)
                return (result);

        /*
         * We should have found an answer.
         */
        if (!have_answer) {
                log_formerr(fctx, "reply has no answer");
                return (DNS_R_FORMERR);
        }

        /*
         * This response is now potentially cacheable.
         */
        fctx->attributes |= FCTX_ATTR_WANTCACHE;

        /*
         * Did chaining end before we got the final answer?
         */
        if (chaining) {
                /*
                 * Yes.  This may be a negative reply, so hand off
                 * authority section processing to the noanswer code.
                 * If it isn't a noanswer response, no harm will be
                 * done.
                 */
                return (noanswer_response(fctx, qname, 0));
        }

        /*
         * We didn't end with an incomplete chain, so the rcode should be
         * "no error".
         */
        if (message->rcode != dns_rcode_noerror) {
                log_formerr(fctx, "CNAME/DNAME chain complete, but RCODE "
                                  "indicates error");
                return (DNS_R_FORMERR);
        }

        /*
         * Examine the authority section (if there is one).
         *
         * We expect there to be only one owner name for all the rdatasets
         * in this section, and we expect that it is not external.
         */
        done = ISC_FALSE;
        ns_name = NULL;
        ns_rdataset = NULL;
        result = dns_message_firstname(message, DNS_SECTION_AUTHORITY);
        while (!done && result == ISC_R_SUCCESS) {
                name = NULL;
                dns_message_currentname(message, DNS_SECTION_AUTHORITY, &name);
                external = ISC_TF(!dns_name_issubdomain(name, &fctx->domain));
                if (!external) {
                        /*
                         * We expect to find NS or SIG NS rdatasets, and
                         * nothing else.
                         */
                        for (rdataset = ISC_LIST_HEAD(name->list);
                             rdataset != NULL;
                             rdataset = ISC_LIST_NEXT(rdataset, link)) {
                                if (rdataset->type == dns_rdatatype_ns ||
                                    (rdataset->type == dns_rdatatype_rrsig &&
                                     rdataset->covers == dns_rdatatype_ns)) {
                                        name->attributes |=
                                                DNS_NAMEATTR_CACHE;
                                        rdataset->attributes |=
                                                DNS_RDATASETATTR_CACHE;
                                        if (aa && !chaining)
                                                rdataset->trust =
                                                    dns_trust_authauthority;
                                        else
                                                rdataset->trust =
                                                    dns_trust_additional;

                                        if (rdataset->type == dns_rdatatype_ns) {
                                                ns_name = name;
                                                ns_rdataset = rdataset;
                                        }
                                        /*
                                         * Mark any additional data related
                                         * to this rdataset.
                                         */
                                        (void)dns_rdataset_additionaldata(
                                                        rdataset,
                                                        check_related,
                                                        fctx);
                                        done = ISC_TRUE;
                                }
                        }
                }
                result = dns_message_nextname(message, DNS_SECTION_AUTHORITY);
        }
        if (result == ISC_R_NOMORE)
                result = ISC_R_SUCCESS;

        log_ns_ttl(fctx, "answer_response");

        if (ns_rdataset != NULL && dns_name_equal(&fctx->domain, ns_name) &&
            !dns_name_equal(ns_name, dns_rootname))
                trim_ns_ttl(fctx, ns_name, ns_rdataset);

        return (result);
}

static void
fctx_increference(fetchctx_t *fctx) {
        REQUIRE(VALID_FCTX(fctx));

        LOCK(&fctx->res->buckets[fctx->bucketnum].lock);
        fctx->references++;
        UNLOCK(&fctx->res->buckets[fctx->bucketnum].lock);
}

static isc_boolean_t
fctx_decreference(fetchctx_t *fctx) {
        isc_boolean_t bucket_empty = ISC_FALSE;

        REQUIRE(VALID_FCTX(fctx));

        INSIST(fctx->references > 0);
        fctx->references--;
        if (fctx->references == 0) {
                /*
                 * No one cares about the result of this fetch anymore.
                 */
                if (fctx->pending == 0 && fctx->nqueries == 0 &&
                    ISC_LIST_EMPTY(fctx->validators) && SHUTTINGDOWN(fctx)) {
                        /*
                         * This fctx is already shutdown; we were just
                         * waiting for the last reference to go away.
                         */
                        bucket_empty = fctx_unlink(fctx);
                        fctx_destroy(fctx);
                } else {
                        /*
                         * Initiate shutdown.
                         */
                        fctx_shutdown(fctx);
                }
        }
        return (bucket_empty);
}

static void
resume_dslookup(isc_task_t *task, isc_event_t *event) {
        dns_fetchevent_t *fevent;
        dns_resolver_t *res;
        fetchctx_t *fctx;
        isc_result_t result;
        isc_boolean_t bucket_empty;
        isc_boolean_t locked = ISC_FALSE;
        unsigned int bucketnum;
        dns_rdataset_t nameservers;
        dns_fixedname_t fixed;
        dns_name_t *domain;

        REQUIRE(event->ev_type == DNS_EVENT_FETCHDONE);
        fevent = (dns_fetchevent_t *)event;
        fctx = event->ev_arg;
        REQUIRE(VALID_FCTX(fctx));
        res = fctx->res;

        UNUSED(task);
        FCTXTRACE("resume_dslookup");

        if (fevent->node != NULL)
                dns_db_detachnode(fevent->db, &fevent->node);
        if (fevent->db != NULL)
                dns_db_detach(&fevent->db);

        dns_rdataset_init(&nameservers);

        bucketnum = fctx->bucketnum;
        if (fevent->result == ISC_R_CANCELED) {
                dns_resolver_destroyfetch(&fctx->nsfetch);
                fctx_done(fctx, ISC_R_CANCELED, __LINE__);
        } else if (fevent->result == ISC_R_SUCCESS) {

                FCTXTRACE("resuming DS lookup");

                dns_resolver_destroyfetch(&fctx->nsfetch);
                if (dns_rdataset_isassociated(&fctx->nameservers))
                        dns_rdataset_disassociate(&fctx->nameservers);
                dns_rdataset_clone(fevent->rdataset, &fctx->nameservers);
                fctx->ns_ttl = fctx->nameservers.ttl;
                fctx->ns_ttl_ok = ISC_TRUE;
                log_ns_ttl(fctx, "resume_dslookup");
                dns_name_free(&fctx->domain, fctx->mctx);
                dns_name_init(&fctx->domain, NULL);
                result = dns_name_dup(&fctx->nsname, fctx->mctx, &fctx->domain);
                if (result != ISC_R_SUCCESS) {
                        fctx_done(fctx, DNS_R_SERVFAIL, __LINE__);
                        goto cleanup;
                }
                /*
                 * Try again.
                 */
                fctx_try(fctx, ISC_TRUE, ISC_FALSE);
        } else {
                unsigned int n;
                dns_rdataset_t *nsrdataset = NULL;

                /*
                 * Retrieve state from fctx->nsfetch before we destroy it.
                 */
                dns_fixedname_init(&fixed);
                domain = dns_fixedname_name(&fixed);
                dns_name_copy(&fctx->nsfetch->private->domain, domain, NULL);
                if (dns_name_equal(&fctx->nsname, domain)) {
                        fctx_done(fctx, DNS_R_SERVFAIL, __LINE__);
                        dns_resolver_destroyfetch(&fctx->nsfetch);
                        goto cleanup;
                }
                if (dns_rdataset_isassociated(
                    &fctx->nsfetch->private->nameservers)) {
                        dns_rdataset_clone(
                            &fctx->nsfetch->private->nameservers,
                            &nameservers);
                        nsrdataset = &nameservers;
                } else
                        domain = NULL;
                dns_resolver_destroyfetch(&fctx->nsfetch);
                n = dns_name_countlabels(&fctx->nsname);
                dns_name_getlabelsequence(&fctx->nsname, 1, n - 1,
                                          &fctx->nsname);

                if (dns_rdataset_isassociated(fevent->rdataset))
                        dns_rdataset_disassociate(fevent->rdataset);
                FCTXTRACE("continuing to look for parent's NS records");
                result = dns_resolver_createfetch(fctx->res, &fctx->nsname,
                                                  dns_rdatatype_ns, domain,
                                                  nsrdataset, NULL,
                                                  fctx->options, task,
                                                  resume_dslookup, fctx,
                                                  &fctx->nsrrset, NULL,
                                                  &fctx->nsfetch);
                if (result != ISC_R_SUCCESS)
                        fctx_done(fctx, result, __LINE__);
                else {
                        LOCK(&res->buckets[bucketnum].lock);
                        locked = ISC_TRUE;
                        fctx->references++;
                }
        }

 cleanup:
        if (dns_rdataset_isassociated(&nameservers))
                dns_rdataset_disassociate(&nameservers);
        if (dns_rdataset_isassociated(fevent->rdataset))
                dns_rdataset_disassociate(fevent->rdataset);
        INSIST(fevent->sigrdataset == NULL);
        isc_event_free(&event);
        if (!locked)
                LOCK(&res->buckets[bucketnum].lock);
        bucket_empty = fctx_decreference(fctx);
        UNLOCK(&res->buckets[bucketnum].lock);
        if (bucket_empty)
                empty_bucket(res);
}

static inline void
checknamessection(dns_message_t *message, dns_section_t section) {
        isc_result_t result;
        dns_name_t *name;
        dns_rdata_t rdata = DNS_RDATA_INIT;
        dns_rdataset_t *rdataset;

        for (result = dns_message_firstname(message, section);
             result == ISC_R_SUCCESS;
             result = dns_message_nextname(message, section))
        {
                name = NULL;
                dns_message_currentname(message, section, &name);
                for (rdataset = ISC_LIST_HEAD(name->list);
                     rdataset != NULL;
                     rdataset = ISC_LIST_NEXT(rdataset, link)) {
                        for (result = dns_rdataset_first(rdataset);
                             result == ISC_R_SUCCESS;
                             result = dns_rdataset_next(rdataset)) {
                                dns_rdataset_current(rdataset, &rdata);
                                if (!dns_rdata_checkowner(name, rdata.rdclass,
                                                          rdata.type,
                                                          ISC_FALSE) ||
                                    !dns_rdata_checknames(&rdata, name, NULL))
                                {
                                        rdataset->attributes |=
                                                DNS_RDATASETATTR_CHECKNAMES;
                                }
                                dns_rdata_reset(&rdata);
                        }
                }
        }
}

static void
checknames(dns_message_t *message) {

        checknamessection(message, DNS_SECTION_ANSWER);
        checknamessection(message, DNS_SECTION_AUTHORITY);
        checknamessection(message, DNS_SECTION_ADDITIONAL);
}

/*
 * Log server NSID at log level 'level'
 */
static void
log_nsid(isc_buffer_t *opt, size_t nsid_len, resquery_t *query,
         int level, isc_mem_t *mctx)
{
        static const char hex[17] = "0123456789abcdef";
        char addrbuf[ISC_SOCKADDR_FORMATSIZE];
        isc_uint16_t buflen, i;
        unsigned char *p, *nsid;
        unsigned char *buf = NULL, *pbuf = NULL;

        /* Allocate buffer for storing hex version of the NSID */
        buflen = (isc_uint16_t)nsid_len * 2 + 1;
        buf = isc_mem_get(mctx, buflen);
        if (buf == NULL)
                goto cleanup;
        pbuf = isc_mem_get(mctx, nsid_len + 1);
        if (pbuf == NULL)
                goto cleanup;

        /* Convert to hex */
        p = buf;
        nsid = isc_buffer_current(opt);
        for (i = 0; i < nsid_len; i++) {
                *p++ = hex[(nsid[i] >> 4) & 0xf];
                *p++ = hex[nsid[i] & 0xf];
        }
        *p = '\0';

        /* Make printable version */
        p = pbuf;
        for (i = 0; i < nsid_len; i++) {
                if (isprint(nsid[i]))
                        *p++ = nsid[i];
                else
                        *p++ = '.';
        }
        *p = '\0';

        isc_sockaddr_format(&query->addrinfo->sockaddr, addrbuf,
                            sizeof(addrbuf));
        isc_log_write(dns_lctx, DNS_LOGCATEGORY_RESOLVER,
                      DNS_LOGMODULE_RESOLVER, level,
                      "received NSID %s (\"%s\") from %s", buf, pbuf, addrbuf);
 cleanup:
        if (pbuf != NULL)
                isc_mem_put(mctx, pbuf, nsid_len + 1);
        if (buf != NULL)
                isc_mem_put(mctx, buf, buflen);
}

static isc_boolean_t
iscname(fetchctx_t *fctx) {
        isc_result_t result;

        result = dns_message_findname(fctx->rmessage, DNS_SECTION_ANSWER,
                                      &fctx->name, dns_rdatatype_cname, 0,
                                      NULL, NULL);
        return (result == ISC_R_SUCCESS ? ISC_TRUE : ISC_FALSE);
}

static isc_boolean_t
betterreferral(fetchctx_t *fctx) {
        isc_result_t result;
        dns_name_t *name;
        dns_rdataset_t *rdataset;
        dns_message_t *message = fctx->rmessage;

        for (result = dns_message_firstname(message, DNS_SECTION_AUTHORITY);
             result == ISC_R_SUCCESS;
             result = dns_message_nextname(message, DNS_SECTION_AUTHORITY)) {
                name = NULL;
                dns_message_currentname(message, DNS_SECTION_AUTHORITY, &name);
                if (!isstrictsubdomain(name, &fctx->domain))
                        continue;
                for (rdataset = ISC_LIST_HEAD(name->list);
                     rdataset != NULL;
                     rdataset = ISC_LIST_NEXT(rdataset, link))
                        if (rdataset->type == dns_rdatatype_ns)
                                return (ISC_TRUE);
        }
        return (ISC_FALSE);
}

static void
process_opt(resquery_t *query, dns_rdataset_t *opt) {
        dns_rdata_t rdata;
        isc_buffer_t optbuf;
        isc_result_t result;
        isc_uint16_t optcode;
        isc_uint16_t optlen;
#ifdef ISC_PLATFORM_USESIT
        unsigned char *sit;
        dns_adbaddrinfo_t *addrinfo;
        unsigned char cookie[8];
#endif

        result = dns_rdataset_first(opt);
        if (result == ISC_R_SUCCESS) {
                dns_rdata_init(&rdata);
                dns_rdataset_current(opt, &rdata);
                isc_buffer_init(&optbuf, rdata.data, rdata.length);
                isc_buffer_add(&optbuf, rdata.length);
                while (isc_buffer_remaininglength(&optbuf) >= 4) {
                        optcode = isc_buffer_getuint16(&optbuf);
                        optlen = isc_buffer_getuint16(&optbuf);
                        INSIST(optlen <= isc_buffer_remaininglength(&optbuf));
                        switch (optcode) {
                        case DNS_OPT_NSID:
                                if (query->options & DNS_FETCHOPT_WANTNSID)
                                        log_nsid(&optbuf, optlen, query,
                                                 ISC_LOG_DEBUG(3),
                                                 query->fctx->res->mctx);
                                isc_buffer_forward(&optbuf, optlen);
                                break;
#ifdef ISC_PLATFORM_USESIT
                        case DNS_OPT_SIT:
                                sit = isc_buffer_current(&optbuf);
                                compute_cc(query, cookie, sizeof(cookie));
                                INSIST(query->fctx->rmessage->sitbad == 0 &&
                                       query->fctx->rmessage->sitok == 0);
                                if (optlen >= 8U &&
                                    memcmp(cookie, sit, 8) == 0) {
                                        query->fctx->rmessage->sitok = 1;
                                        inc_stats(query->fctx->res,
                                                  dns_resstatscounter_sitok);
                                        addrinfo = query->addrinfo;
                                        dns_adb_setsit(query->fctx->adb,
                                                       addrinfo, sit, optlen);
                                } else
                                        query->fctx->rmessage->sitbad = 1;
                                isc_buffer_forward(&optbuf, optlen);
                                inc_stats(query->fctx->res,
                                          dns_resstatscounter_sitin);
                                break;
#endif
                        default:
                                isc_buffer_forward(&optbuf, optlen);
                                break;
                        }
                }
                INSIST(isc_buffer_remaininglength(&optbuf) == 0U);
        }
}

static void
resquery_response(isc_task_t *task, isc_event_t *event) {
        isc_result_t result = ISC_R_SUCCESS;
        resquery_t *query = event->ev_arg;
        dns_dispatchevent_t *devent = (dns_dispatchevent_t *)event;
        isc_boolean_t keep_trying, get_nameservers, resend;
        isc_boolean_t truncated;
        dns_message_t *message;
        dns_rdataset_t *opt;
        fetchctx_t *fctx;
        dns_name_t *fname;
        dns_fixedname_t foundname;
        isc_stdtime_t now;
        isc_time_t tnow, *finish;
        dns_adbaddrinfo_t *addrinfo;
        unsigned int options;
        unsigned int findoptions;
        isc_result_t broken_server;
        badnstype_t broken_type = badns_response;
        isc_boolean_t no_response;

        REQUIRE(VALID_QUERY(query));
        fctx = query->fctx;
        options = query->options;
        REQUIRE(VALID_FCTX(fctx));
        REQUIRE(event->ev_type == DNS_EVENT_DISPATCH);

        QTRACE("response");

        if (isc_sockaddr_pf(&query->addrinfo->sockaddr) == PF_INET)
                inc_stats(fctx->res, dns_resstatscounter_responsev4);
        else
                inc_stats(fctx->res, dns_resstatscounter_responsev6);

        (void)isc_timer_touch(fctx->timer);

        keep_trying = ISC_FALSE;
        broken_server = ISC_R_SUCCESS;
        get_nameservers = ISC_FALSE;
        resend = ISC_FALSE;
        truncated = ISC_FALSE;
        finish = NULL;
        no_response = ISC_FALSE;

        if (fctx->res->exiting) {
                result = ISC_R_SHUTTINGDOWN;
                FCTXTRACE("resolver shutting down");
                goto done;
        }

        fctx->timeouts = 0;
        fctx->timeout = ISC_FALSE;
        fctx->addrinfo = query->addrinfo;

        /*
         * XXXRTH  We should really get the current time just once.  We
         *              need a routine to convert from an isc_time_t to an
         *              isc_stdtime_t.
         */
        TIME_NOW(&tnow);
        finish = &tnow;
        isc_stdtime_get(&now);

        /*
         * Did the dispatcher have a problem?
         */
        if (devent->result != ISC_R_SUCCESS) {
                if (devent->result == ISC_R_EOF &&
                    (query->options & DNS_FETCHOPT_NOEDNS0) == 0) {
                        /*
                         * The problem might be that they
                         * don't understand EDNS0.  Turn it
                         * off and try again.
                         */
                        options |= DNS_FETCHOPT_NOEDNS0;
                        resend = ISC_TRUE;
                        add_bad_edns(fctx, &query->addrinfo->sockaddr);
                } else {
                        /*
                         * There's no hope for this query.
                         */
                        keep_trying = ISC_TRUE;

                        /*
                         * If this is a network error on an exclusive query
                         * socket, mark the server as bad so that we won't try
                         * it for this fetch again.  Also adjust finish and
                         * no_response so that we penalize this address in SRTT
                         * adjustment later.
                         */
                        if (query->exclusivesocket &&
                            (devent->result == ISC_R_HOSTUNREACH ||
                             devent->result == ISC_R_NETUNREACH ||
                             devent->result == ISC_R_CONNREFUSED ||
                             devent->result == ISC_R_CANCELED)) {
                                    broken_server = devent->result;
                                    broken_type = badns_unreachable;
                                    finish = NULL;
                                    no_response = ISC_TRUE;
                        }
                }
                FCTXTRACE3("dispatcher failure", devent->result);
                goto done;
        }

        message = fctx->rmessage;

        if (query->tsig != NULL) {
                result = dns_message_setquerytsig(message, query->tsig);
                if (result != ISC_R_SUCCESS) {
                        FCTXTRACE3("unable to set query tsig", result);
                        goto done;
                }
        }

        if (query->tsigkey) {
                result = dns_message_settsigkey(message, query->tsigkey);
                if (result != ISC_R_SUCCESS) {
                        FCTXTRACE3("unable to set tsig key", result);
                        goto done;
                }
        }

        if ((options & DNS_FETCHOPT_TCP) == 0) {
                if ((options & DNS_FETCHOPT_NOEDNS0) == 0)
                        dns_adb_setudpsize(fctx->adb, query->addrinfo,
                                   isc_buffer_usedlength(&devent->buffer));
                else
                        dns_adb_plainresponse(fctx->adb, query->addrinfo);
        }
        result = dns_message_parse(message, &devent->buffer, 0);
        if (result != ISC_R_SUCCESS) {
                FCTXTRACE3("message failed to parse", result);
                switch (result) {
                case ISC_R_UNEXPECTEDEND:
                        if (!message->question_ok ||
                            (message->flags & DNS_MESSAGEFLAG_TC) == 0 ||
                            (options & DNS_FETCHOPT_TCP) != 0) {
                                /*
                                 * Either the message ended prematurely,
                                 * and/or wasn't marked as being truncated,
                                 * and/or this is a response to a query we
                                 * sent over TCP.  In all of these cases,
                                 * something is wrong with the remote
                                 * server and we don't want to retry using
                                 * TCP.
                                 */
                                if ((query->options & DNS_FETCHOPT_NOEDNS0)
                                    == 0) {
                                        /*
                                         * The problem might be that they
                                         * don't understand EDNS0.  Turn it
                                         * off and try again.
                                         */
                                        options |= DNS_FETCHOPT_NOEDNS0;
                                        resend = ISC_TRUE;
                                        add_bad_edns(fctx,
                                                    &query->addrinfo->sockaddr);
                                        inc_stats(fctx->res,
                                                 dns_resstatscounter_edns0fail);
                                } else {
                                        broken_server = result;
                                        keep_trying = ISC_TRUE;
                                }
                                goto done;
                        }
                        /*
                         * We defer retrying via TCP for a bit so we can
                         * check out this message further.
                         */
                        truncated = ISC_TRUE;
                        break;
                case DNS_R_FORMERR:
                        if ((query->options & DNS_FETCHOPT_NOEDNS0) == 0) {
                                /*
                                 * The problem might be that they
                                 * don't understand EDNS0.  Turn it
                                 * off and try again.
                                 */
                                options |= DNS_FETCHOPT_NOEDNS0;
                                resend = ISC_TRUE;
                                add_bad_edns(fctx, &query->addrinfo->sockaddr);
                                inc_stats(fctx->res,
                                                 dns_resstatscounter_edns0fail);
                        } else {
                                broken_server = DNS_R_UNEXPECTEDRCODE;
                                keep_trying = ISC_TRUE;
                        }
                        goto done;
                default:
                        /*
                         * Something bad has happened.
                         */
                        goto done;
                }
        }

        /*
         * Log the incoming packet.
         */
        dns_message_logfmtpacket2(message, "received packet from",
                                  &query->addrinfo->sockaddr,
                                  DNS_LOGCATEGORY_RESOLVER,
                                  DNS_LOGMODULE_PACKETS,
                                  &dns_master_style_comment,
                                  ISC_LOG_DEBUG(10),
                                  fctx->res->mctx);
        /*
         * Process receive opt record.
         */
        opt = dns_message_getopt(message);
        if (opt != NULL)
                process_opt(query, opt);

#ifdef notyet
#ifdef ISC_PLATFORM_USESIT
        if (message->sitbad) {
                /*
                 * If the SIT is bad assume it is a attack and retry.
                 */
                resend = ISC_TRUE;
                /* XXXMPA log it */
                FCTXTRACE("bad sit");
                goto done;
        }
#endif
#endif

        /*
         * If the message is signed, check the signature.  If not, this
         * returns success anyway.
         */
        result = dns_message_checksig(message, fctx->res->view);
        if (result != ISC_R_SUCCESS) {
                FCTXTRACE3("signature check failed", result);
                goto done;
        }

        /*
         * The dispatcher should ensure we only get responses with QR set.
         */
        INSIST((message->flags & DNS_MESSAGEFLAG_QR) != 0);
        /*
         * INSIST() that the message comes from the place we sent it to,
         * since the dispatch code should ensure this.
         *
         * INSIST() that the message id is correct (this should also be
         * ensured by the dispatch code).
         */

        /*
         * We have an affirmative response to the query and we have
         * previously got a response from this server which indicated
         * EDNS may not be supported so we can now cache the lack of
         * EDNS support.
         */
        if (opt == NULL && !EDNSOK(query->addrinfo) &&
            (message->rcode == dns_rcode_noerror ||
             message->rcode == dns_rcode_nxdomain ||
             message->rcode == dns_rcode_refused ||
             message->rcode == dns_rcode_yxdomain) &&
             bad_edns(fctx, &query->addrinfo->sockaddr)) {
                dns_message_logpacket2(message,
                                       "received packet (bad edns) from",
                                       &query->addrinfo->sockaddr,
                                       DNS_LOGCATEGORY_RESOLVER,
                                       DNS_LOGMODULE_RESOLVER,
                                       ISC_LOG_DEBUG(3),
                                       fctx->res->mctx);
                dns_adb_changeflags(fctx->adb, query->addrinfo,
                                    DNS_FETCHOPT_NOEDNS0,
                                    DNS_FETCHOPT_NOEDNS0);
        } else if (opt == NULL && (message->flags & DNS_MESSAGEFLAG_TC) == 0 &&
                   !EDNSOK(query->addrinfo) &&
                   (message->rcode == dns_rcode_noerror ||
                    message->rcode == dns_rcode_nxdomain) &&
                   (query->options & DNS_FETCHOPT_NOEDNS0) == 0) {
                /*
                 * We didn't get a OPT record in response to a EDNS query.
                 *
                 * Old versions of named incorrectly drop the OPT record
                 * when there is a signed, truncated response so we check
                 * that TC is not set.
                 *
                 * Record that the server is not talking EDNS.  While this
                 * should be safe to do for any rcode we limit it to NOERROR
                 * and NXDOMAIN.
                 */
                dns_message_logpacket2(message, "received packet (no opt) from",
                                       &query->addrinfo->sockaddr,
                                       DNS_LOGCATEGORY_RESOLVER,
                                       DNS_LOGMODULE_RESOLVER,
                                       ISC_LOG_DEBUG(3),
                                       fctx->res->mctx);
                dns_adb_changeflags(fctx->adb, query->addrinfo,
                                    DNS_FETCHOPT_NOEDNS0,
                                    DNS_FETCHOPT_NOEDNS0);
        }

        /*
         * If we get a non error EDNS response record the fact so we
         * won't fallback to plain DNS in the future for this server.
         */
        if (opt != NULL && !EDNSOK(query->addrinfo) &&
            (query->options & DNS_FETCHOPT_NOEDNS0) == 0 &&
            (message->rcode == dns_rcode_noerror ||
             message->rcode == dns_rcode_nxdomain ||
             message->rcode == dns_rcode_refused ||
             message->rcode == dns_rcode_yxdomain)) {
                dns_adb_changeflags(fctx->adb, query->addrinfo,
                                    FCTX_ADDRINFO_EDNSOK,
                                    FCTX_ADDRINFO_EDNSOK);
        }

        /*
         * Deal with truncated responses by retrying using TCP.
         */
        if ((message->flags & DNS_MESSAGEFLAG_TC) != 0)
                truncated = ISC_TRUE;

        if (truncated) {
                inc_stats(fctx->res, dns_resstatscounter_truncated);
                if ((options & DNS_FETCHOPT_TCP) != 0) {
                        broken_server = DNS_R_TRUNCATEDTCP;
                        keep_trying = ISC_TRUE;
                } else {
                        options |= DNS_FETCHOPT_TCP;
                        resend = ISC_TRUE;
                }
                FCTXTRACE3("message truncated", result);
                goto done;
        }

        /*
         * Is it a query response?
         */
        if (message->opcode != dns_opcode_query) {
                /* XXXRTH Log */
                broken_server = DNS_R_UNEXPECTEDOPCODE;
                keep_trying = ISC_TRUE;
                FCTXTRACE("invalid message opcode");
                goto done;
        }

        /*
         * Update statistics about erroneous responses.
         */
        if (message->rcode != dns_rcode_noerror) {
                switch (message->rcode) {
                case dns_rcode_nxdomain:
                        inc_stats(fctx->res, dns_resstatscounter_nxdomain);
                        break;
                case dns_rcode_servfail:
                        inc_stats(fctx->res, dns_resstatscounter_servfail);
                        break;
                case dns_rcode_formerr:
                        inc_stats(fctx->res, dns_resstatscounter_formerr);
                        break;
                case dns_rcode_refused:
                        inc_stats(fctx->res, dns_resstatscounter_refused);
                        break;
                case dns_rcode_badvers:
                        inc_stats(fctx->res, dns_resstatscounter_badvers);
                        break;
                default:
                        inc_stats(fctx->res, dns_resstatscounter_othererror);
                        break;
                }
        }

        /*
         * Is the remote server broken, or does it dislike us?
         */
        if (message->rcode != dns_rcode_noerror &&
            message->rcode != dns_rcode_nxdomain) {
                isc_buffer_t b;
                char code[64];
#ifdef ISC_PLATFORM_USESIT
                unsigned char sit[64];

                /*
                 * Some servers do not ignore unknown EDNS options.
                 */
                if (!NOSIT(query->addrinfo) &&
                    (message->rcode == dns_rcode_formerr ||
                     message->rcode == dns_rcode_notimp ||
                     message->rcode == dns_rcode_refused) &&
                     dns_adb_getsit(fctx->adb, query->addrinfo,
                                   sit, sizeof(sit)) == 0U) {
                        dns_adb_changeflags(fctx->adb, query->addrinfo,
                                            FCTX_ADDRINFO_NOSIT,
                                            FCTX_ADDRINFO_NOSIT);
                        resend = ISC_TRUE;
                } else
#endif
                if (((message->rcode == dns_rcode_formerr ||
                      message->rcode == dns_rcode_notimp) ||
                     (message->rcode == dns_rcode_servfail &&
                      dns_message_getopt(message) == NULL)) &&
                    (query->options & DNS_FETCHOPT_NOEDNS0) == 0) {
                        /*
                         * It's very likely they don't like EDNS0.
                         * If the response code is SERVFAIL, also check if the
                         * response contains an OPT RR and don't cache the
                         * failure since it can be returned for various other
                         * reasons.
                         *
                         * XXXRTH  We should check if the question
                         *              we're asking requires EDNS0, and
                         *              if so, we should bail out.
                         */
                        options |= DNS_FETCHOPT_NOEDNS0;
                        resend = ISC_TRUE;
                        /*
                         * Remember that they may not like EDNS0.
                         */
                        add_bad_edns(fctx, &query->addrinfo->sockaddr);
                        inc_stats(fctx->res, dns_resstatscounter_edns0fail);
                } else if (message->rcode == dns_rcode_formerr) {
                        if (ISFORWARDER(query->addrinfo)) {
                                /*
                                 * This forwarder doesn't understand us,
                                 * but other forwarders might.  Keep trying.
                                 */
                                broken_server = DNS_R_REMOTEFORMERR;
                                keep_trying = ISC_TRUE;
                        } else {
                                /*
                                 * The server doesn't understand us.  Since
                                 * all servers for a zone need similar
                                 * capabilities, we assume that we will get
                                 * FORMERR from all servers, and thus we
                                 * cannot make any more progress with this
                                 * fetch.
                                 */
                                log_formerr(fctx, "server sent FORMERR");
                                result = DNS_R_FORMERR;
                        }
                } else if (message->rcode == dns_rcode_yxdomain) {
                        /*
                         * DNAME mapping failed because the new name
                         * was too long.  There's no chance of success
                         * for this fetch.
                         */
                        result = DNS_R_YXDOMAIN;
                } else if (message->rcode == dns_rcode_badvers) {
                        unsigned int flags, mask;
                        unsigned int version;
#if defined(ISC_PLATFORM_USESIT) && DNS_EDNS_VERSION == 0
                        /*
                         * Some servers return BADVERS to unknown
                         * EDNS options.  This cannot be long term
                         * strategy.  Do not disable SIT if we have
                         * already have received a SIT from this
                         * server.
                         */
                        if (dns_adb_getsit(fctx->adb, query->addrinfo,
                                           sit, sizeof(sit)) == 0U) {
                                dns_adb_changeflags(fctx->adb, query->addrinfo,
                                                    FCTX_ADDRINFO_NOSIT,
                                                    FCTX_ADDRINFO_NOSIT);
                        }
#endif

                        resend = ISC_TRUE;
                        INSIST(opt != NULL);
                        version = (opt->ttl >> 16) & 0xff;
                        flags = (version << DNS_FETCHOPT_EDNSVERSIONSHIFT) |
                                DNS_FETCHOPT_EDNSVERSIONSET;
                        mask = DNS_FETCHOPT_EDNSVERSIONMASK |
                               DNS_FETCHOPT_EDNSVERSIONSET;
                        /*
                         * Record that we got a good EDNS response.
                         */
                        if (query->ednsversion > (int)version &&
                            !EDNSOK(query->addrinfo)) {
                                dns_adb_changeflags(fctx->adb, query->addrinfo,
                                                    FCTX_ADDRINFO_EDNSOK,
                                                    FCTX_ADDRINFO_EDNSOK);
                        }
                        /*
                         * XXXMPA we should really test against the version of
                         * EDNS we sent in the request.  Some servers return
                         * BADVERS for unknown EDNS options.
                         * RFC 2671 was not clear that they should be ignored.
                         * RFC 6891 is clear that that they should be ignored.
                         * If we are supporting EDNS > 0 then perform strict
                         * version checking of badvers responses.  We won't
                         * be sending SIT etc. in that case.
                         */
#if DNS_EDNS_VERSION == 0
                         /* Avoids a compiler warning with < 0 */
                        if (version <= DNS_EDNS_VERSION)
#else
                        if (version < DNS_EDNS_VERSION)
#endif
                        {
                                dns_adb_changeflags(fctx->adb, query->addrinfo,
                                                    flags, mask);
                        } else {
                                broken_server = DNS_R_BADVERS;
                                keep_trying = ISC_TRUE;
                        }
                } else {
                        /*
                         * XXXRTH log.
                         */
                        broken_server = DNS_R_UNEXPECTEDRCODE;
                        INSIST(broken_server != ISC_R_SUCCESS);
                        keep_trying = ISC_TRUE;
                }

                isc_buffer_init(&b, code, sizeof(code) - 1);
                dns_rcode_totext(fctx->rmessage->rcode, &b);
                code[isc_buffer_usedlength(&b)] = '\0';
                FCTXTRACE2("remote server broken: returned ", code);
                goto done;
        }

        /*
         * Is the question the same as the one we asked?
         */
        result = same_question(fctx);
        if (result != ISC_R_SUCCESS) {
                /* XXXRTH Log */
                if (result == DNS_R_FORMERR)
                        keep_trying = ISC_TRUE;
                FCTXTRACE3("response did not match question", result);
                goto done;
        }

        /*
         * Is the server lame?
         */
        if (fctx->res->lame_ttl != 0 && !ISFORWARDER(query->addrinfo) &&
            is_lame(fctx)) {
                inc_stats(fctx->res, dns_resstatscounter_lame);
                log_lame(fctx, query->addrinfo);
                result = dns_adb_marklame(fctx->adb, query->addrinfo,
                                          &fctx->name, fctx->type,
                                          now + fctx->res->lame_ttl);
                if (result != ISC_R_SUCCESS)
                        isc_log_write(dns_lctx, DNS_LOGCATEGORY_RESOLVER,
                                      DNS_LOGMODULE_RESOLVER, ISC_LOG_ERROR,
                                      "could not mark server as lame: %s",
                                      isc_result_totext(result));
                broken_server = DNS_R_LAME;
                keep_trying = ISC_TRUE;
                FCTXTRACE("lame server");
                goto done;
        }

        /*
         * Enforce delegations only zones like NET and COM.
         */
        if (!ISFORWARDER(query->addrinfo) &&
            dns_view_isdelegationonly(fctx->res->view, &fctx->domain) &&
            !dns_name_equal(&fctx->domain, &fctx->name) &&
            fix_mustbedelegationornxdomain(message, fctx)) {
                char namebuf[DNS_NAME_FORMATSIZE];
                char domainbuf[DNS_NAME_FORMATSIZE];
                char addrbuf[ISC_SOCKADDR_FORMATSIZE];
                char classbuf[64];
                char typebuf[64];

                dns_name_format(&fctx->name, namebuf, sizeof(namebuf));
                dns_name_format(&fctx->domain, domainbuf, sizeof(domainbuf));
                dns_rdatatype_format(fctx->type, typebuf, sizeof(typebuf));
                dns_rdataclass_format(fctx->res->rdclass, classbuf,
                                      sizeof(classbuf));
                isc_sockaddr_format(&query->addrinfo->sockaddr, addrbuf,
                                    sizeof(addrbuf));

                isc_log_write(dns_lctx, DNS_LOGCATEGORY_DELEGATION_ONLY,
                             DNS_LOGMODULE_RESOLVER, ISC_LOG_NOTICE,
                             "enforced delegation-only for '%s' (%s/%s/%s) "
                             "from %s",
                             domainbuf, namebuf, typebuf, classbuf, addrbuf);
        }

        if ((fctx->res->options & DNS_RESOLVER_CHECKNAMES) != 0)
                checknames(message);

        /*
         * Clear cache bits.
         */
        fctx->attributes &= ~(FCTX_ATTR_WANTNCACHE | FCTX_ATTR_WANTCACHE);

        /*
         * Did we get any answers?
         */
        if (message->counts[DNS_SECTION_ANSWER] > 0 &&
            (message->rcode == dns_rcode_noerror ||
             message->rcode == dns_rcode_nxdomain)) {
                /*
                 * [normal case]
                 * We've got answers.  If it has an authoritative answer or an
                 * answer from a forwarder, we're done.
                 */
                if ((message->flags & DNS_MESSAGEFLAG_AA) != 0 ||
                    ISFORWARDER(query->addrinfo))
                {
                        result = answer_response(fctx);
                        if (result != ISC_R_SUCCESS)
                                FCTXTRACE3("answer_response (AA/fwd)", result);
                } else if (iscname(fctx) &&
                         fctx->type != dns_rdatatype_any &&
                         fctx->type != dns_rdatatype_cname)
                {
                        /*
                         * A BIND8 server could return a non-authoritative
                         * answer when a CNAME is followed.  We should treat
                         * it as a valid answer.
                         */
                        result = answer_response(fctx);
                        if (result != ISC_R_SUCCESS)
                                FCTXTRACE3("answer_response (!ANY/!CNAME)",
                                           result);
                } else if (fctx->type != dns_rdatatype_ns &&
                           !betterreferral(fctx)) {
                        /*
                         * Lame response !!!.
                         */
                        result = answer_response(fctx);
                        if (result != ISC_R_SUCCESS)
                                FCTXTRACE3("answer_response (!NS)", result);
                } else {
                        if (fctx->type == dns_rdatatype_ns) {
                                /*
                                 * A BIND 8 server could incorrectly return a
                                 * non-authoritative answer to an NS query
                                 * instead of a referral. Since this answer
                                 * lacks the SIGs necessary to do DNSSEC
                                 * validation, we must invoke the following
                                 * special kludge to treat it as a referral.
                                 */
                                result = noanswer_response(fctx, NULL,
                                                   LOOK_FOR_NS_IN_ANSWER);
                                if (result != ISC_R_SUCCESS)
                                        FCTXTRACE3("noanswer_response (NS)",
                                                   result);
                        } else {
                                /*
                                 * Some other servers may still somehow include
                                 * an answer when it should return a referral
                                 * with an empty answer.  Check to see if we can
                                 * treat this as a referral by ignoring the
                                 * answer.  Further more, there may be an
                                 * implementation that moves A/AAAA glue records
                                 * to the answer section for that type of
                                 * delegation when the query is for that glue
                                 * record.  LOOK_FOR_GLUE_IN_ANSWER will handle
                                 * such a corner case.
                                 */
                                result = noanswer_response(fctx, NULL,
                                                   LOOK_FOR_GLUE_IN_ANSWER);
                                if (result != ISC_R_SUCCESS)
                                        FCTXTRACE3("noanswer_response", result);
                        }
                        if (result != DNS_R_DELEGATION) {
                                /*
                                 * At this point, AA is not set, the response
                                 * is not a referral, and the server is not a
                                 * forwarder.  It is technically lame and it's
                                 * easier to treat it as such than to figure out
                                 * some more elaborate course of action.
                                 */
                                broken_server = DNS_R_LAME;
                                keep_trying = ISC_TRUE;
                                goto done;
                        }
                        goto force_referral;
                }
                if (result != ISC_R_SUCCESS) {
                        if (result == DNS_R_FORMERR)
                                keep_trying = ISC_TRUE;
                        goto done;
                }
        } else if (message->counts[DNS_SECTION_AUTHORITY] > 0 ||
                   message->rcode == dns_rcode_noerror ||
                   message->rcode == dns_rcode_nxdomain) {
                /*
                 * NXDOMAIN, NXRDATASET, or referral.
                 */
                result = noanswer_response(fctx, NULL, 0);
                switch (result) {
                case ISC_R_SUCCESS:
                case DNS_R_CHASEDSSERVERS:
                        break;
                case DNS_R_DELEGATION:
 force_referral:
                        /*
                         * We don't have the answer, but we know a better
                         * place to look.
                         */
                        get_nameservers = ISC_TRUE;
                        keep_trying = ISC_TRUE;
                        /*
                         * We have a new set of name servers, and it
                         * has not experienced any restarts yet.
                         */
                        fctx->restarts = 0;

                        /*
                         * Update local statistics counters collected for each
                         * new zone.
                         */
                        fctx->referrals++;
                        fctx->querysent = 0;
                        fctx->lamecount = 0;
                        fctx->neterr = 0;
                        fctx->badresp = 0;
                        fctx->adberr = 0;

                        result = ISC_R_SUCCESS;
                        break;
                default:
                        /*
                         * Something has gone wrong.
                         */
                        if (result == DNS_R_FORMERR)
                                keep_trying = ISC_TRUE;
                        FCTXTRACE3("noanswer_response", result);
                        goto done;
                }
        } else {
                /*
                 * The server is insane.
                 */
                /* XXXRTH Log */
                broken_server = DNS_R_UNEXPECTEDRCODE;
                keep_trying = ISC_TRUE;
                FCTXTRACE("broken server: unexpected rcode");
                goto done;
        }

        /*
         * Follow additional section data chains.
         */
        chase_additional(fctx);

        /*
         * Cache the cacheable parts of the message.  This may also cause
         * work to be queued to the DNSSEC validator.
         */
        if (WANTCACHE(fctx)) {
                result = cache_message(fctx, query->addrinfo, now);
                if (result != ISC_R_SUCCESS) {
                        FCTXTRACE3("cache_message complete", result);
                        goto done;
                }
        }

        /*
         * Ncache the negatively cacheable parts of the message.  This may
         * also cause work to be queued to the DNSSEC validator.
         */
        if (WANTNCACHE(fctx)) {
                dns_rdatatype_t covers;

                /*
                 * Cache DS NXDOMAIN seperately to other types.
                 */
                if (message->rcode == dns_rcode_nxdomain &&
                    fctx->type != dns_rdatatype_ds)
                        covers = dns_rdatatype_any;
                else
                        covers = fctx->type;

                /*
                 * Cache any negative cache entries in the message.
                 */
                result = ncache_message(fctx, query->addrinfo, covers, now);
                if (result != ISC_R_SUCCESS)
                        FCTXTRACE3("ncache_message complete", result);
        }

 done:
        /*
         * Remember the query's addrinfo, in case we need to mark the
         * server as broken.
         */
        addrinfo = query->addrinfo;

        FCTXTRACE4("query canceled in response(); ",
                   no_response ? "no response" : "responding",
                   result);

        /*
         * Cancel the query.
         *
         * XXXRTH  Don't cancel the query if waiting for validation?
         */
        fctx_cancelquery(&query, &devent, finish, no_response);

        if (keep_trying) {
                if (result == DNS_R_FORMERR)
                        broken_server = DNS_R_FORMERR;
                if (broken_server != ISC_R_SUCCESS) {
                        /*
                         * Add this server to the list of bad servers for
                         * this fctx.
                         */
                        add_bad(fctx, addrinfo, broken_server, broken_type);
                }

                if (get_nameservers) {
                        dns_name_t *name;
                        dns_fixedname_init(&foundname);
                        fname = dns_fixedname_name(&foundname);
                        if (result != ISC_R_SUCCESS) {
                                fctx_done(fctx, DNS_R_SERVFAIL, __LINE__);
                                return;
                        }
                        findoptions = 0;
                        if (dns_rdatatype_atparent(fctx->type))
                                findoptions |= DNS_DBFIND_NOEXACT;
                        if ((options & DNS_FETCHOPT_UNSHARED) == 0)
                                name = &fctx->name;
                        else
                                name = &fctx->domain;
                        result = dns_view_findzonecut(fctx->res->view,
                                                      name, fname,
                                                      now, findoptions,
                                                      ISC_TRUE,
                                                      &fctx->nameservers,
                                                      NULL);
                        if (result != ISC_R_SUCCESS) {
                                FCTXTRACE("couldn't find a zonecut");
                                fctx_done(fctx, DNS_R_SERVFAIL, __LINE__);
                                return;
                        }
                        if (!dns_name_issubdomain(fname, &fctx->domain)) {
                                /*
                                 * The best nameservers are now above our
                                 * QDOMAIN.
                                 */
                                FCTXTRACE("nameservers now above QDOMAIN");
                                fctx_done(fctx, DNS_R_SERVFAIL, __LINE__);
                                return;
                        }
                        dns_name_free(&fctx->domain, fctx->mctx);
                        dns_name_init(&fctx->domain, NULL);
                        result = dns_name_dup(fname, fctx->mctx, &fctx->domain);
                        if (result != ISC_R_SUCCESS) {
                                fctx_done(fctx, DNS_R_SERVFAIL, __LINE__);
                                return;
                        }
                        fctx->ns_ttl = fctx->nameservers.ttl;
                        fctx->ns_ttl_ok = ISC_TRUE;
                        fctx_cancelqueries(fctx, ISC_TRUE);
                        fctx_cleanupfinds(fctx);
                        fctx_cleanupaltfinds(fctx);
                        fctx_cleanupforwaddrs(fctx);
                        fctx_cleanupaltaddrs(fctx);
                }
                /*
                 * Try again.
                 */
                fctx_try(fctx, !get_nameservers, ISC_FALSE);
        } else if (resend) {
                /*
                 * Resend (probably with changed options).
                 */
                FCTXTRACE("resend");
                inc_stats(fctx->res, dns_resstatscounter_retry);
                result = fctx_query(fctx, addrinfo, options);
                if (result != ISC_R_SUCCESS)
                        fctx_done(fctx, result, __LINE__);
        } else if (result == ISC_R_SUCCESS && !HAVE_ANSWER(fctx)) {
                /*
                 * All has gone well so far, but we are waiting for the
                 * DNSSEC validator to validate the answer.
                 */
                FCTXTRACE("wait for validator");
                fctx_cancelqueries(fctx, ISC_TRUE);
                /*
                 * We must not retransmit while the validator is working;
                 * it has references to the current rmessage.
                 */
                result = fctx_stopidletimer(fctx);
                if (result != ISC_R_SUCCESS)
                        fctx_done(fctx, result, __LINE__);
        } else if (result == DNS_R_CHASEDSSERVERS) {
                unsigned int n;
                add_bad(fctx, addrinfo, result, broken_type);
                fctx_cancelqueries(fctx, ISC_TRUE);
                fctx_cleanupfinds(fctx);
                fctx_cleanupforwaddrs(fctx);

                n = dns_name_countlabels(&fctx->name);
                dns_name_getlabelsequence(&fctx->name, 1, n - 1, &fctx->nsname);

                FCTXTRACE("suspending DS lookup to find parent's NS records");

                result = dns_resolver_createfetch(fctx->res, &fctx->nsname,
                                                  dns_rdatatype_ns,
                                                  NULL, NULL, NULL,
                                                  fctx->options, task,
                                                  resume_dslookup, fctx,
                                                  &fctx->nsrrset, NULL,
                                                  &fctx->nsfetch);
                if (result != ISC_R_SUCCESS)
                        fctx_done(fctx, result, __LINE__);
                else {
                        fctx_increference(fctx);
                        result = fctx_stopidletimer(fctx);
                        if (result != ISC_R_SUCCESS)
                                fctx_done(fctx, result, __LINE__);
                }
        } else {
                /*
                 * We're done.
                 */
                fctx_done(fctx, result, __LINE__);
        }
}


/***
 *** Resolver Methods
 ***/
static void
destroy(dns_resolver_t *res) {
        unsigned int i;
        alternate_t *a;

        REQUIRE(res->references == 0);
        REQUIRE(!res->priming);
        REQUIRE(res->primefetch == NULL);

        RTRACE("destroy");

        INSIST(res->nfctx == 0);

        DESTROYLOCK(&res->primelock);
        DESTROYLOCK(&res->nlock);
        DESTROYLOCK(&res->lock);
        for (i = 0; i < res->nbuckets; i++) {
                INSIST(ISC_LIST_EMPTY(res->buckets[i].fctxs));
                isc_task_shutdown(res->buckets[i].task);
                isc_task_detach(&res->buckets[i].task);
                DESTROYLOCK(&res->buckets[i].lock);
                isc_mem_detach(&res->buckets[i].mctx);
        }
        isc_mem_put(res->mctx, res->buckets,
                    res->nbuckets * sizeof(fctxbucket_t));
        if (res->dispatches4 != NULL)
                dns_dispatchset_destroy(&res->dispatches4);
        if (res->dispatches6 != NULL)
                dns_dispatchset_destroy(&res->dispatches6);
        while ((a = ISC_LIST_HEAD(res->alternates)) != NULL) {
                ISC_LIST_UNLINK(res->alternates, a, link);
                if (!a->isaddress)
                        dns_name_free(&a->_u._n.name, res->mctx);
                isc_mem_put(res->mctx, a, sizeof(*a));
        }
        dns_resolver_reset_algorithms(res);
        dns_resolver_reset_ds_digests(res);
        dns_badcache_destroy(&res->badcache);
        dns_resolver_resetmustbesecure(res);
#if USE_ALGLOCK
        isc_rwlock_destroy(&res->alglock);
#endif
#if USE_MBSLOCK
        isc_rwlock_destroy(&res->mbslock);
#endif
        isc_timer_detach(&res->spillattimer);
        res->magic = 0;
        isc_mem_put(res->mctx, res, sizeof(*res));
}

static void
send_shutdown_events(dns_resolver_t *res) {
        isc_event_t *event, *next_event;
        isc_task_t *etask;

        /*
         * Caller must be holding the resolver lock.
         */

        for (event = ISC_LIST_HEAD(res->whenshutdown);
             event != NULL;
             event = next_event) {
                next_event = ISC_LIST_NEXT(event, ev_link);
                ISC_LIST_UNLINK(res->whenshutdown, event, ev_link);
                etask = event->ev_sender;
                event->ev_sender = res;
                isc_task_sendanddetach(&etask, &event);
        }
}

static void
empty_bucket(dns_resolver_t *res) {
        RTRACE("empty_bucket");

        LOCK(&res->lock);

        INSIST(res->activebuckets > 0);
        res->activebuckets--;
        if (res->activebuckets == 0)
                send_shutdown_events(res);

        UNLOCK(&res->lock);
}

static void
spillattimer_countdown(isc_task_t *task, isc_event_t *event) {
        dns_resolver_t *res = event->ev_arg;
        isc_result_t result;
        unsigned int count;
        isc_boolean_t logit = ISC_FALSE;

        REQUIRE(VALID_RESOLVER(res));

        UNUSED(task);

        LOCK(&res->lock);
        INSIST(!res->exiting);
        if (res->spillat > res->spillatmin) {
                res->spillat--;
                logit = ISC_TRUE;
        }
        if (res->spillat <= res->spillatmin) {
                result = isc_timer_reset(res->spillattimer,
                                         isc_timertype_inactive, NULL,
                                         NULL, ISC_TRUE);
                RUNTIME_CHECK(result == ISC_R_SUCCESS);
        }
        count = res->spillat;
        UNLOCK(&res->lock);
        if (logit)
                isc_log_write(dns_lctx, DNS_LOGCATEGORY_RESOLVER,
                              DNS_LOGMODULE_RESOLVER, ISC_LOG_NOTICE,
                              "clients-per-query decreased to %u", count);

        isc_event_free(&event);
}

isc_result_t
dns_resolver_create(dns_view_t *view,
                    isc_taskmgr_t *taskmgr,
                    unsigned int ntasks, unsigned int ndisp,
                    isc_socketmgr_t *socketmgr,
                    isc_timermgr_t *timermgr,
                    unsigned int options,
                    dns_dispatchmgr_t *dispatchmgr,
                    dns_dispatch_t *dispatchv4,
                    dns_dispatch_t *dispatchv6,
                    dns_resolver_t **resp)
{
        dns_resolver_t *res;
        isc_result_t result = ISC_R_SUCCESS;
        unsigned int i, buckets_created = 0;
        isc_task_t *task = NULL;
        char name[16];
        unsigned dispattr;

        /*
         * Create a resolver.
         */

        REQUIRE(DNS_VIEW_VALID(view));
        REQUIRE(ntasks > 0);
        REQUIRE(ndisp > 0);
        REQUIRE(resp != NULL && *resp == NULL);
        REQUIRE(dispatchmgr != NULL);
        REQUIRE(dispatchv4 != NULL || dispatchv6 != NULL);

        res = isc_mem_get(view->mctx, sizeof(*res));
        if (res == NULL)
                return (ISC_R_NOMEMORY);
        RTRACE("create");
        res->mctx = view->mctx;
        res->rdclass = view->rdclass;
        res->socketmgr = socketmgr;
        res->timermgr = timermgr;
        res->taskmgr = taskmgr;
        res->dispatchmgr = dispatchmgr;
        res->view = view;
        res->options = options;
        res->lame_ttl = 0;
        ISC_LIST_INIT(res->alternates);
        res->udpsize = RECV_BUFFER_SIZE;
        res->algorithms = NULL;
        res->digests = NULL;
        res->badcache = NULL;
        dns_badcache_init(res->mctx, DNS_RESOLVER_BADCACHESIZE,
                          &res->badcache);
        res->mustbesecure = NULL;
        res->spillatmin = res->spillat = 10;
        res->spillatmax = 100;
        res->spillattimer = NULL;
        res->zero_no_soa_ttl = ISC_FALSE;
        res->query_timeout = DEFAULT_QUERY_TIMEOUT;
        res->maxdepth = DEFAULT_RECURSION_DEPTH;
        res->maxqueries = DEFAULT_MAX_QUERIES;
        res->nbuckets = ntasks;
        if (view->resstats != NULL)
                isc_stats_set(view->resstats, ntasks,
                              dns_resstatscounter_buckets);
        res->activebuckets = ntasks;
        res->buckets = isc_mem_get(view->mctx,
                                   ntasks * sizeof(fctxbucket_t));
        if (res->buckets == NULL) {
                result = ISC_R_NOMEMORY;
                goto cleanup_res;
        }
        for (i = 0; i < ntasks; i++) {
                result = isc_mutex_init(&res->buckets[i].lock);
                if (result != ISC_R_SUCCESS)
                        goto cleanup_buckets;
                res->buckets[i].task = NULL;
                result = isc_task_create(taskmgr, 0, &res->buckets[i].task);
                if (result != ISC_R_SUCCESS) {
                        DESTROYLOCK(&res->buckets[i].lock);
                        goto cleanup_buckets;
                }
                res->buckets[i].mctx = NULL;
                snprintf(name, sizeof(name), "res%u", i);
#ifdef ISC_PLATFORM_USETHREADS
                /*
                 * Use a separate memory context for each bucket to reduce
                 * contention among multiple threads.  Do this only when
                 * enabling threads because it will be require more memory.
                 */
                result = isc_mem_create(0, 0, &res->buckets[i].mctx);
                if (result != ISC_R_SUCCESS) {
                        isc_task_detach(&res->buckets[i].task);
                        DESTROYLOCK(&res->buckets[i].lock);
                        goto cleanup_buckets;
                }
                isc_mem_setname(res->buckets[i].mctx, name, NULL);
#else
                isc_mem_attach(view->mctx, &res->buckets[i].mctx);
#endif
                isc_task_setname(res->buckets[i].task, name, res);
                ISC_LIST_INIT(res->buckets[i].fctxs);
                res->buckets[i].exiting = ISC_FALSE;
                buckets_created++;
        }

        res->dispatches4 = NULL;
        if (dispatchv4 != NULL) {
                dns_dispatchset_create(view->mctx, socketmgr, taskmgr,
                                       dispatchv4, &res->dispatches4, ndisp);
                dispattr = dns_dispatch_getattributes(dispatchv4);
                res->exclusivev4 =
                        ISC_TF((dispattr & DNS_DISPATCHATTR_EXCLUSIVE) != 0);
        }

        res->dispatches6 = NULL;
        if (dispatchv6 != NULL) {
                dns_dispatchset_create(view->mctx, socketmgr, taskmgr,
                                       dispatchv6, &res->dispatches6, ndisp);
                dispattr = dns_dispatch_getattributes(dispatchv6);
                res->exclusivev6 =
                        ISC_TF((dispattr & DNS_DISPATCHATTR_EXCLUSIVE) != 0);
        }

        res->querydscp4 = -1;
        res->querydscp6 = -1;
        res->references = 1;
        res->exiting = ISC_FALSE;
        res->frozen = ISC_FALSE;
        ISC_LIST_INIT(res->whenshutdown);
        res->priming = ISC_FALSE;
        res->primefetch = NULL;
        res->nfctx = 0;

        result = isc_mutex_init(&res->lock);
        if (result != ISC_R_SUCCESS)
                goto cleanup_dispatches;

        result = isc_mutex_init(&res->nlock);
        if (result != ISC_R_SUCCESS)
                goto cleanup_lock;

        result = isc_mutex_init(&res->primelock);
        if (result != ISC_R_SUCCESS)
                goto cleanup_nlock;

        task = NULL;
        result = isc_task_create(taskmgr, 0, &task);
        if (result != ISC_R_SUCCESS)
                goto cleanup_primelock;
        isc_task_setname(task, "resolver_task", NULL);

        result = isc_timer_create(timermgr, isc_timertype_inactive, NULL, NULL,
                                  task, spillattimer_countdown, res,
                                  &res->spillattimer);
        isc_task_detach(&task);
        if (result != ISC_R_SUCCESS)
                goto cleanup_primelock;

#if USE_ALGLOCK
        result = isc_rwlock_init(&res->alglock, 0, 0);
        if (result != ISC_R_SUCCESS)
                goto cleanup_spillattimer;
#endif
#if USE_MBSLOCK
        result = isc_rwlock_init(&res->mbslock, 0, 0);
        if (result != ISC_R_SUCCESS)
                goto cleanup_alglock;
#endif

        res->magic = RES_MAGIC;

        *resp = res;

        return (ISC_R_SUCCESS);

#if USE_MBSLOCK
 cleanup_alglock:
#if USE_ALGLOCK
        isc_rwlock_destroy(&res->alglock);
#endif
#endif
#if USE_ALGLOCK || USE_MBSLOCK
 cleanup_spillattimer:
        isc_timer_detach(&res->spillattimer);
#endif

 cleanup_primelock:
        DESTROYLOCK(&res->primelock);

 cleanup_nlock:
        DESTROYLOCK(&res->nlock);

 cleanup_lock:
        DESTROYLOCK(&res->lock);

 cleanup_dispatches:
        if (res->dispatches6 != NULL)
                dns_dispatchset_destroy(&res->dispatches6);
        if (res->dispatches4 != NULL)
                dns_dispatchset_destroy(&res->dispatches4);

 cleanup_buckets:
        for (i = 0; i < buckets_created; i++) {
                isc_mem_detach(&res->buckets[i].mctx);
                DESTROYLOCK(&res->buckets[i].lock);
                isc_task_shutdown(res->buckets[i].task);
                isc_task_detach(&res->buckets[i].task);
        }
        isc_mem_put(view->mctx, res->buckets,
                    res->nbuckets * sizeof(fctxbucket_t));

 cleanup_res:
        isc_mem_put(view->mctx, res, sizeof(*res));

        return (result);
}

static void
prime_done(isc_task_t *task, isc_event_t *event) {
        dns_resolver_t *res;
        dns_fetchevent_t *fevent;
        dns_fetch_t *fetch;
        dns_db_t *db = NULL;

        REQUIRE(event->ev_type == DNS_EVENT_FETCHDONE);
        fevent = (dns_fetchevent_t *)event;
        res = event->ev_arg;
        REQUIRE(VALID_RESOLVER(res));

        UNUSED(task);

        LOCK(&res->lock);

        INSIST(res->priming);
        res->priming = ISC_FALSE;
        LOCK(&res->primelock);
        fetch = res->primefetch;
        res->primefetch = NULL;
        UNLOCK(&res->primelock);

        UNLOCK(&res->lock);

        if (fevent->result == ISC_R_SUCCESS &&
            res->view->cache != NULL && res->view->hints != NULL) {
                dns_cache_attachdb(res->view->cache, &db);
                dns_root_checkhints(res->view, res->view->hints, db);
                dns_db_detach(&db);
        }

        if (fevent->node != NULL)
                dns_db_detachnode(fevent->db, &fevent->node);
        if (fevent->db != NULL)
                dns_db_detach(&fevent->db);
        if (dns_rdataset_isassociated(fevent->rdataset))
                dns_rdataset_disassociate(fevent->rdataset);
        INSIST(fevent->sigrdataset == NULL);

        isc_mem_put(res->mctx, fevent->rdataset, sizeof(*fevent->rdataset));

        isc_event_free(&event);
        dns_resolver_destroyfetch(&fetch);
}

void
dns_resolver_prime(dns_resolver_t *res) {
        isc_boolean_t want_priming = ISC_FALSE;
        dns_rdataset_t *rdataset;
        isc_result_t result;

        REQUIRE(VALID_RESOLVER(res));
        REQUIRE(res->frozen);

        RTRACE("dns_resolver_prime");

        LOCK(&res->lock);

        if (!res->exiting && !res->priming) {
                INSIST(res->primefetch == NULL);
                res->priming = ISC_TRUE;
                want_priming = ISC_TRUE;
        }

        UNLOCK(&res->lock);

        if (want_priming) {
                /*
                 * To avoid any possible recursive locking problems, we
                 * start the priming fetch like any other fetch, and holding
                 * no resolver locks.  No one else will try to start it
                 * because we're the ones who set res->priming to true.
                 * Any other callers of dns_resolver_prime() while we're
                 * running will see that res->priming is already true and
                 * do nothing.
                 */
                RTRACE("priming");
                rdataset = isc_mem_get(res->mctx, sizeof(*rdataset));
                if (rdataset == NULL) {
                        LOCK(&res->lock);
                        INSIST(res->priming);
                        INSIST(res->primefetch == NULL);
                        res->priming = ISC_FALSE;
                        UNLOCK(&res->lock);
                        return;
                }
                dns_rdataset_init(rdataset);
                LOCK(&res->primelock);
                result = dns_resolver_createfetch(res, dns_rootname,
                                                  dns_rdatatype_ns,
                                                  NULL, NULL, NULL, 0,
                                                  res->buckets[0].task,
                                                  prime_done,
                                                  res, rdataset, NULL,
                                                  &res->primefetch);
                UNLOCK(&res->primelock);
                if (result != ISC_R_SUCCESS) {
                        LOCK(&res->lock);
                        INSIST(res->priming);
                        res->priming = ISC_FALSE;
                        UNLOCK(&res->lock);
                }
        }
}

void
dns_resolver_freeze(dns_resolver_t *res) {
        /*
         * Freeze resolver.
         */

        REQUIRE(VALID_RESOLVER(res));

        res->frozen = ISC_TRUE;
}

void
dns_resolver_attach(dns_resolver_t *source, dns_resolver_t **targetp) {
        REQUIRE(VALID_RESOLVER(source));
        REQUIRE(targetp != NULL && *targetp == NULL);

        RRTRACE(source, "attach");
        LOCK(&source->lock);
        REQUIRE(!source->exiting);

        INSIST(source->references > 0);
        source->references++;
        INSIST(source->references != 0);
        UNLOCK(&source->lock);

        *targetp = source;
}

void
dns_resolver_whenshutdown(dns_resolver_t *res, isc_task_t *task,
                          isc_event_t **eventp)
{
        isc_task_t *clone;
        isc_event_t *event;

        REQUIRE(VALID_RESOLVER(res));
        REQUIRE(eventp != NULL);

        event = *eventp;
        *eventp = NULL;

        LOCK(&res->lock);

        if (res->exiting && res->activebuckets == 0) {
                /*
                 * We're already shutdown.  Send the event.
                 */
                event->ev_sender = res;
                isc_task_send(task, &event);
        } else {
                clone = NULL;
                isc_task_attach(task, &clone);
                event->ev_sender = clone;
                ISC_LIST_APPEND(res->whenshutdown, event, ev_link);
        }

        UNLOCK(&res->lock);
}

void
dns_resolver_shutdown(dns_resolver_t *res) {
        unsigned int i;
        fetchctx_t *fctx;
        isc_result_t result;

        REQUIRE(VALID_RESOLVER(res));

        RTRACE("shutdown");

        LOCK(&res->lock);

        if (!res->exiting) {
                RTRACE("exiting");
                res->exiting = ISC_TRUE;

                for (i = 0; i < res->nbuckets; i++) {
                        LOCK(&res->buckets[i].lock);
                        for (fctx = ISC_LIST_HEAD(res->buckets[i].fctxs);
                             fctx != NULL;
                             fctx = ISC_LIST_NEXT(fctx, link))
                                fctx_shutdown(fctx);
                        if (res->dispatches4 != NULL && !res->exclusivev4) {
                                dns_dispatchset_cancelall(res->dispatches4,
                                                          res->buckets[i].task);
                        }
                        if (res->dispatches6 != NULL && !res->exclusivev6) {
                                dns_dispatchset_cancelall(res->dispatches6,
                                                          res->buckets[i].task);
                        }
                        res->buckets[i].exiting = ISC_TRUE;
                        if (ISC_LIST_EMPTY(res->buckets[i].fctxs)) {
                                INSIST(res->activebuckets > 0);
                                res->activebuckets--;
                        }
                        UNLOCK(&res->buckets[i].lock);
                }
                if (res->activebuckets == 0)
                        send_shutdown_events(res);
                result = isc_timer_reset(res->spillattimer,
                                         isc_timertype_inactive, NULL,
                                         NULL, ISC_TRUE);
                RUNTIME_CHECK(result == ISC_R_SUCCESS);
        }

        UNLOCK(&res->lock);
}

void
dns_resolver_detach(dns_resolver_t **resp) {
        dns_resolver_t *res;
        isc_boolean_t need_destroy = ISC_FALSE;

        REQUIRE(resp != NULL);
        res = *resp;
        REQUIRE(VALID_RESOLVER(res));

        RTRACE("detach");

        LOCK(&res->lock);

        INSIST(res->references > 0);
        res->references--;
        if (res->references == 0) {
                INSIST(res->exiting && res->activebuckets == 0);
                need_destroy = ISC_TRUE;
        }

        UNLOCK(&res->lock);

        if (need_destroy)
                destroy(res);

        *resp = NULL;
}

static inline isc_boolean_t
fctx_match(fetchctx_t *fctx, dns_name_t *name, dns_rdatatype_t type,
           unsigned int options)
{
        /*
         * Don't match fetch contexts that are shutting down.
         */
        if (fctx->cloned || fctx->state == fetchstate_done ||
            ISC_LIST_EMPTY(fctx->events))
                return (ISC_FALSE);

        if (fctx->type != type || fctx->options != options)
                return (ISC_FALSE);
        return (dns_name_equal(&fctx->name, name));
}

static inline void
log_fetch(dns_name_t *name, dns_rdatatype_t type) {
        char namebuf[DNS_NAME_FORMATSIZE];
        char typebuf[DNS_RDATATYPE_FORMATSIZE];
        int level = ISC_LOG_DEBUG(1);

        /*
         * If there's no chance of logging it, don't render (format) the
         * name and RDATA type (further below), and return early.
         */
        if (! isc_log_wouldlog(dns_lctx, level))
                return;

        dns_name_format(name, namebuf, sizeof(namebuf));
        dns_rdatatype_format(type, typebuf, sizeof(typebuf));

        isc_log_write(dns_lctx, DNS_LOGCATEGORY_RESOLVER,
                      DNS_LOGMODULE_RESOLVER, level,
                      "fetch: %s/%s", namebuf, typebuf);
}

isc_result_t
dns_resolver_createfetch(dns_resolver_t *res, dns_name_t *name,
                         dns_rdatatype_t type,
                         dns_name_t *domain, dns_rdataset_t *nameservers,
                         dns_forwarders_t *forwarders,
                         unsigned int options, isc_task_t *task,
                         isc_taskaction_t action, void *arg,
                         dns_rdataset_t *rdataset,
                         dns_rdataset_t *sigrdataset,
                         dns_fetch_t **fetchp)
{
        return (dns_resolver_createfetch3(res, name, type, domain,
                                          nameservers, forwarders, NULL, 0,
                                          options, 0, NULL, task, action, arg,
                                          rdataset, sigrdataset, fetchp));
}

isc_result_t
dns_resolver_createfetch2(dns_resolver_t *res, dns_name_t *name,
                          dns_rdatatype_t type,
                          dns_name_t *domain, dns_rdataset_t *nameservers,
                          dns_forwarders_t *forwarders,
                          isc_sockaddr_t *client, dns_messageid_t id,
                          unsigned int options, isc_task_t *task,
                          isc_taskaction_t action, void *arg,
                          dns_rdataset_t *rdataset,
                          dns_rdataset_t *sigrdataset,
                          dns_fetch_t **fetchp)
{
        return (dns_resolver_createfetch3(res, name, type, domain,
                                          nameservers, forwarders, client, id,
                                          options, 0, NULL, task, action, arg,
                                          rdataset, sigrdataset, fetchp));
}

isc_result_t
dns_resolver_createfetch3(dns_resolver_t *res, dns_name_t *name,
                          dns_rdatatype_t type,
                          dns_name_t *domain, dns_rdataset_t *nameservers,
                          dns_forwarders_t *forwarders,
                          isc_sockaddr_t *client, dns_messageid_t id,
                          unsigned int options, unsigned int depth,
                          isc_counter_t *qc, isc_task_t *task,
                          isc_taskaction_t action, void *arg,
                          dns_rdataset_t *rdataset,
                          dns_rdataset_t *sigrdataset,
                          dns_fetch_t **fetchp)
{
        dns_fetch_t *fetch;
        fetchctx_t *fctx = NULL;
        isc_result_t result = ISC_R_SUCCESS;
        unsigned int bucketnum;
        isc_boolean_t new_fctx = ISC_FALSE;
        isc_event_t *event;
        unsigned int count = 0;
        unsigned int spillat;
        unsigned int spillatmin;
        isc_boolean_t dodestroy = ISC_FALSE;

        UNUSED(forwarders);

        REQUIRE(VALID_RESOLVER(res));
        REQUIRE(res->frozen);
        /* XXXRTH  Check for meta type */
        if (domain != NULL) {
                REQUIRE(DNS_RDATASET_VALID(nameservers));
                REQUIRE(nameservers->type == dns_rdatatype_ns);
        } else
                REQUIRE(nameservers == NULL);
        REQUIRE(forwarders == NULL);
        REQUIRE(!dns_rdataset_isassociated(rdataset));
        REQUIRE(sigrdataset == NULL ||
                !dns_rdataset_isassociated(sigrdataset));
        REQUIRE(fetchp != NULL && *fetchp == NULL);

        log_fetch(name, type);

        /*
         * XXXRTH  use a mempool?
         */
        fetch = isc_mem_get(res->mctx, sizeof(*fetch));
        if (fetch == NULL)
                return (ISC_R_NOMEMORY);
        fetch->mctx = NULL;
        isc_mem_attach(res->mctx, &fetch->mctx);

        bucketnum = dns_name_fullhash(name, ISC_FALSE) % res->nbuckets;

        LOCK(&res->lock);
        spillat = res->spillat;
        spillatmin = res->spillatmin;
        UNLOCK(&res->lock);
        LOCK(&res->buckets[bucketnum].lock);

        if (res->buckets[bucketnum].exiting) {
                result = ISC_R_SHUTTINGDOWN;
                goto unlock;
        }

        if ((options & DNS_FETCHOPT_UNSHARED) == 0) {
                for (fctx = ISC_LIST_HEAD(res->buckets[bucketnum].fctxs);
                     fctx != NULL;
                     fctx = ISC_LIST_NEXT(fctx, link)) {
                        if (fctx_match(fctx, name, type, options))
                                break;
                }
        }

        /*
         * Is this a duplicate?
         */
        if (fctx != NULL && client != NULL) {
                dns_fetchevent_t *fevent;
                for (fevent = ISC_LIST_HEAD(fctx->events);
                     fevent != NULL;
                     fevent = ISC_LIST_NEXT(fevent, ev_link)) {
                        if (fevent->client != NULL && fevent->id == id &&
                            isc_sockaddr_equal(fevent->client, client)) {
                                result = DNS_R_DUPLICATE;
                                goto unlock;
                        }
                        count++;
                }
        }
        if (count >= spillatmin && spillatmin != 0) {
                INSIST(fctx != NULL);
                if (count >= spillat)
                        fctx->spilled = ISC_TRUE;
                if (fctx->spilled) {
                        result = DNS_R_DROP;
                        goto unlock;
                }
        }

        if (fctx == NULL) {
                result = fctx_create(res, name, type, domain, nameservers,
                                     options, bucketnum, depth, qc, &fctx);
                if (result != ISC_R_SUCCESS)
                        goto unlock;
                new_fctx = ISC_TRUE;
        } else if (fctx->depth > depth)
                fctx->depth = depth;

        result = fctx_join(fctx, task, client, id, action, arg,
                           rdataset, sigrdataset, fetch);
        if (new_fctx) {
                if (result == ISC_R_SUCCESS) {
                        /*
                         * Launch this fctx.
                         */
                        event = &fctx->control_event;
                        ISC_EVENT_INIT(event, sizeof(*event), 0, NULL,
                                       DNS_EVENT_FETCHCONTROL,
                                       fctx_start, fctx, NULL,
                                       NULL, NULL);
                        isc_task_send(res->buckets[bucketnum].task, &event);
                } else {
                        /*
                         * We don't care about the result of fctx_unlink()
                         * since we know we're not exiting.
                         */
                        (void)fctx_unlink(fctx);
                        dodestroy = ISC_TRUE;
                }
        }

 unlock:
        UNLOCK(&res->buckets[bucketnum].lock);

        if (dodestroy)
                fctx_destroy(fctx);

        if (result == ISC_R_SUCCESS) {
                FTRACE("created");
                *fetchp = fetch;
        } else
                isc_mem_putanddetach(&fetch->mctx, fetch, sizeof(*fetch));

        return (result);
}

void
dns_resolver_cancelfetch(dns_fetch_t *fetch) {
        fetchctx_t *fctx;
        dns_resolver_t *res;
        dns_fetchevent_t *event, *next_event;
        isc_task_t *etask;

        REQUIRE(DNS_FETCH_VALID(fetch));
        fctx = fetch->private;
        REQUIRE(VALID_FCTX(fctx));
        res = fctx->res;

        FTRACE("cancelfetch");

        LOCK(&res->buckets[fctx->bucketnum].lock);

        /*
         * Find the completion event for this fetch (as opposed
         * to those for other fetches that have joined the same
         * fctx) and send it with result = ISC_R_CANCELED.
         */
        event = NULL;
        if (fctx->state != fetchstate_done) {
                for (event = ISC_LIST_HEAD(fctx->events);
                     event != NULL;
                     event = next_event) {
                        next_event = ISC_LIST_NEXT(event, ev_link);
                        if (event->fetch == fetch) {
                                ISC_LIST_UNLINK(fctx->events, event, ev_link);
                                break;
                        }
                }
        }
        if (event != NULL) {
                etask = event->ev_sender;
                event->ev_sender = fctx;
                event->result = ISC_R_CANCELED;
                isc_task_sendanddetach(&etask, ISC_EVENT_PTR(&event));
        }
        /*
         * The fctx continues running even if no fetches remain;
         * the answer is still cached.
         */

        UNLOCK(&res->buckets[fctx->bucketnum].lock);
}

void
dns_resolver_destroyfetch(dns_fetch_t **fetchp) {
        dns_fetch_t *fetch;
        dns_resolver_t *res;
        dns_fetchevent_t *event, *next_event;
        fetchctx_t *fctx;
        unsigned int bucketnum;
        isc_boolean_t bucket_empty;

        REQUIRE(fetchp != NULL);
        fetch = *fetchp;
        REQUIRE(DNS_FETCH_VALID(fetch));
        fctx = fetch->private;
        REQUIRE(VALID_FCTX(fctx));
        res = fctx->res;

        FTRACE("destroyfetch");

        bucketnum = fctx->bucketnum;
        LOCK(&res->buckets[bucketnum].lock);

        /*
         * Sanity check: the caller should have gotten its event before
         * trying to destroy the fetch.
         */
        event = NULL;
        if (fctx->state != fetchstate_done) {
                for (event = ISC_LIST_HEAD(fctx->events);
                     event != NULL;
                     event = next_event) {
                        next_event = ISC_LIST_NEXT(event, ev_link);
                        RUNTIME_CHECK(event->fetch != fetch);
                }
        }

        bucket_empty = fctx_decreference(fctx);

        UNLOCK(&res->buckets[bucketnum].lock);

        isc_mem_putanddetach(&fetch->mctx, fetch, sizeof(*fetch));
        *fetchp = NULL;

        if (bucket_empty)
                empty_bucket(res);
}

void
dns_resolver_logfetch(dns_fetch_t *fetch, isc_log_t *lctx,
                      isc_logcategory_t *category, isc_logmodule_t *module,
                      int level, isc_boolean_t duplicateok)
{
        fetchctx_t *fctx;
        dns_resolver_t *res;
        char domainbuf[DNS_NAME_FORMATSIZE];

        REQUIRE(DNS_FETCH_VALID(fetch));
        fctx = fetch->private;
        REQUIRE(VALID_FCTX(fctx));
        res = fctx->res;

        LOCK(&res->buckets[fctx->bucketnum].lock);

        INSIST(fctx->exitline >= 0);
        if (!fctx->logged || duplicateok) {
                dns_name_format(&fctx->domain, domainbuf, sizeof(domainbuf));
                isc_log_write(lctx, category, module, level,
                              "fetch completed at %s:%d for %s in "
                              "%" ISC_PRINT_QUADFORMAT "u."
                              "%06" ISC_PRINT_QUADFORMAT "u: %s/%s "
                              "[domain:%s,referral:%u,restart:%u,qrysent:%u,"
                              "timeout:%u,lame:%u,neterr:%u,badresp:%u,"
                              "adberr:%u,findfail:%u,valfail:%u]",
                              __FILE__, fctx->exitline, fctx->info,
                              fctx->duration / US_PER_SEC,
                              fctx->duration % US_PER_SEC,
                              isc_result_totext(fctx->result),
                              isc_result_totext(fctx->vresult), domainbuf,
                              fctx->referrals, fctx->restarts,
                              fctx->querysent, fctx->timeouts, fctx->lamecount,
                              fctx->neterr, fctx->badresp, fctx->adberr,
                              fctx->findfail, fctx->valfail);
                fctx->logged = ISC_TRUE;
        }

        UNLOCK(&res->buckets[fctx->bucketnum].lock);
}

dns_dispatchmgr_t *
dns_resolver_dispatchmgr(dns_resolver_t *resolver) {
        REQUIRE(VALID_RESOLVER(resolver));
        return (resolver->dispatchmgr);
}

dns_dispatch_t *
dns_resolver_dispatchv4(dns_resolver_t *resolver) {
        REQUIRE(VALID_RESOLVER(resolver));
        return (dns_dispatchset_get(resolver->dispatches4));
}

dns_dispatch_t *
dns_resolver_dispatchv6(dns_resolver_t *resolver) {
        REQUIRE(VALID_RESOLVER(resolver));
        return (dns_dispatchset_get(resolver->dispatches6));
}

isc_socketmgr_t *
dns_resolver_socketmgr(dns_resolver_t *resolver) {
        REQUIRE(VALID_RESOLVER(resolver));
        return (resolver->socketmgr);
}

isc_taskmgr_t *
dns_resolver_taskmgr(dns_resolver_t *resolver) {
        REQUIRE(VALID_RESOLVER(resolver));
        return (resolver->taskmgr);
}

isc_uint32_t
dns_resolver_getlamettl(dns_resolver_t *resolver) {
        REQUIRE(VALID_RESOLVER(resolver));
        return (resolver->lame_ttl);
}

void
dns_resolver_setlamettl(dns_resolver_t *resolver, isc_uint32_t lame_ttl) {
        REQUIRE(VALID_RESOLVER(resolver));
        resolver->lame_ttl = lame_ttl;
}

unsigned int
dns_resolver_nrunning(dns_resolver_t *resolver) {
        unsigned int n;
        LOCK(&resolver->nlock);
        n = resolver->nfctx;
        UNLOCK(&resolver->nlock);
        return (n);
}

isc_result_t
dns_resolver_addalternate(dns_resolver_t *resolver, isc_sockaddr_t *alt,
                          dns_name_t *name, in_port_t port) {
        alternate_t *a;
        isc_result_t result;

        REQUIRE(VALID_RESOLVER(resolver));
        REQUIRE(!resolver->frozen);
        REQUIRE((alt == NULL) ^ (name == NULL));

        a = isc_mem_get(resolver->mctx, sizeof(*a));
        if (a == NULL)
                return (ISC_R_NOMEMORY);
        if (alt != NULL) {
                a->isaddress = ISC_TRUE;
                a->_u.addr = *alt;
        } else {
                a->isaddress = ISC_FALSE;
                a->_u._n.port = port;
                dns_name_init(&a->_u._n.name, NULL);
                result = dns_name_dup(name, resolver->mctx, &a->_u._n.name);
                if (result != ISC_R_SUCCESS) {
                        isc_mem_put(resolver->mctx, a, sizeof(*a));
                        return (result);
                }
        }
        ISC_LINK_INIT(a, link);
        ISC_LIST_APPEND(resolver->alternates, a, link);

        return (ISC_R_SUCCESS);
}

void
dns_resolver_setudpsize(dns_resolver_t *resolver, isc_uint16_t udpsize) {
        REQUIRE(VALID_RESOLVER(resolver));
        resolver->udpsize = udpsize;
}

isc_uint16_t
dns_resolver_getudpsize(dns_resolver_t *resolver) {
        REQUIRE(VALID_RESOLVER(resolver));
        return (resolver->udpsize);
}

void
dns_resolver_flushbadcache(dns_resolver_t *resolver, dns_name_t *name) {
        if (name != NULL)
                dns_badcache_flushname(resolver->badcache, name);
        else
                dns_badcache_flush(resolver->badcache);
}

void
dns_resolver_flushbadnames(dns_resolver_t *resolver, dns_name_t *name) {
        dns_badcache_flushtree(resolver->badcache, name);
}

void
dns_resolver_addbadcache(dns_resolver_t *resolver, dns_name_t *name,
                         dns_rdatatype_t type, isc_time_t *expire)
{
        (void) dns_badcache_add(resolver->badcache, name, type,
                                ISC_FALSE, 0, expire);
}

isc_boolean_t
dns_resolver_getbadcache(dns_resolver_t *resolver, dns_name_t *name,
                         dns_rdatatype_t type, isc_time_t *now)
{
        return (dns_badcache_find(resolver->badcache, name, type, NULL, now));
}

void
dns_resolver_printbadcache(dns_resolver_t *resolver, FILE *fp) {
        (void) dns_badcache_print(resolver->badcache, "Bad cache", fp);
}

static void
free_algorithm(void *node, void *arg) {
        unsigned char *algorithms = node;
        isc_mem_t *mctx = arg;

        isc_mem_put(mctx, algorithms, *algorithms);
}

void
dns_resolver_reset_algorithms(dns_resolver_t *resolver) {

        REQUIRE(VALID_RESOLVER(resolver));

#if USE_ALGLOCK
        RWLOCK(&resolver->alglock, isc_rwlocktype_write);
#endif
        if (resolver->algorithms != NULL)
                dns_rbt_destroy(&resolver->algorithms);
#if USE_ALGLOCK
        RWUNLOCK(&resolver->alglock, isc_rwlocktype_write);
#endif
}

isc_result_t
dns_resolver_disable_algorithm(dns_resolver_t *resolver, dns_name_t *name,
                               unsigned int alg)
{
        unsigned int len, mask;
        unsigned char *new;
        unsigned char *algorithms;
        isc_result_t result;
        dns_rbtnode_t *node = NULL;

        /*
         * Whether an algorithm is disabled (or not) is stored in a
         * per-name bitfield that is stored as the node data of an
         * RBT.
         */

        REQUIRE(VALID_RESOLVER(resolver));
        if (alg > 255)
                return (ISC_R_RANGE);

#if USE_ALGLOCK
        RWLOCK(&resolver->alglock, isc_rwlocktype_write);
#endif
        if (resolver->algorithms == NULL) {
                result = dns_rbt_create(resolver->mctx, free_algorithm,
                                        resolver->mctx, &resolver->algorithms);
                if (result != ISC_R_SUCCESS)
                        goto cleanup;
        }

        len = alg/8 + 2;
        mask = 1 << (alg%8);

        result = dns_rbt_addnode(resolver->algorithms, name, &node);

        if (result == ISC_R_SUCCESS || result == ISC_R_EXISTS) {
                algorithms = node->data;
                /*
                 * If algorithms is set, algorithms[0] contains its
                 * length.
                 */
                if (algorithms == NULL || len > *algorithms) {
                        /*
                         * If no bitfield exists in the node data, or if
                         * it is not long enough, allocate a new
                         * bitfield and copy the old (smaller) bitfield
                         * into it if one exists.
                         */
                        new = isc_mem_get(resolver->mctx, len);
                        if (new == NULL) {
                                result = ISC_R_NOMEMORY;
                                goto cleanup;
                        }
                        memset(new, 0, len);
                        if (algorithms != NULL)
                                memmove(new, algorithms, *algorithms);
                        new[len-1] |= mask;
                        /* new[0] should contain the length of new. */
                        *new = len;
                        node->data = new;
                        /* Free the older bitfield. */
                        if (algorithms != NULL)
                                isc_mem_put(resolver->mctx, algorithms,
                                            *algorithms);
                } else
                        algorithms[len-1] |= mask;
        }
        result = ISC_R_SUCCESS;
 cleanup:
#if USE_ALGLOCK
        RWUNLOCK(&resolver->alglock, isc_rwlocktype_write);
#endif
        return (result);
}

isc_boolean_t
dns_resolver_algorithm_supported(dns_resolver_t *resolver, dns_name_t *name,
                                 unsigned int alg)
{
        unsigned int len, mask;
        unsigned char *algorithms;
        void *data = NULL;
        isc_result_t result;
        isc_boolean_t found = ISC_FALSE;

        REQUIRE(VALID_RESOLVER(resolver));

#if USE_ALGLOCK
        RWLOCK(&resolver->alglock, isc_rwlocktype_read);
#endif
        if (resolver->algorithms == NULL)
                goto unlock;
        result = dns_rbt_findname(resolver->algorithms, name, 0, NULL, &data);
        if (result == ISC_R_SUCCESS || result == DNS_R_PARTIALMATCH) {
                len = alg/8 + 2;
                mask = 1 << (alg%8);
                algorithms = data;
                if (len <= *algorithms && (algorithms[len-1] & mask) != 0)
                        found = ISC_TRUE;
        }
 unlock:
#if USE_ALGLOCK
        RWUNLOCK(&resolver->alglock, isc_rwlocktype_read);
#endif
        if (found)
                return (ISC_FALSE);
        return (dst_algorithm_supported(alg));
}

static void
free_digest(void *node, void *arg) {
        unsigned char *digests = node;
        isc_mem_t *mctx = arg;

        isc_mem_put(mctx, digests, *digests);
}

void
dns_resolver_reset_ds_digests(dns_resolver_t *resolver) {

        REQUIRE(VALID_RESOLVER(resolver));

#if USE_ALGLOCK
        RWLOCK(&resolver->alglock, isc_rwlocktype_write);
#endif
        if (resolver->digests != NULL)
                dns_rbt_destroy(&resolver->digests);
#if USE_ALGLOCK
        RWUNLOCK(&resolver->alglock, isc_rwlocktype_write);
#endif
}

isc_result_t
dns_resolver_disable_ds_digest(dns_resolver_t *resolver, dns_name_t *name,
                               unsigned int digest_type)
{
        unsigned int len, mask;
        unsigned char *new;
        unsigned char *digests;
        isc_result_t result;
        dns_rbtnode_t *node = NULL;

        /*
         * Whether a digest is disabled (or not) is stored in a per-name
         * bitfield that is stored as the node data of an RBT.
         */

        REQUIRE(VALID_RESOLVER(resolver));
        if (digest_type > 255)
                return (ISC_R_RANGE);

#if USE_ALGLOCK
        RWLOCK(&resolver->alglock, isc_rwlocktype_write);
#endif
        if (resolver->digests == NULL) {
                result = dns_rbt_create(resolver->mctx, free_digest,
                                        resolver->mctx, &resolver->digests);
                if (result != ISC_R_SUCCESS)
                        goto cleanup;
        }

        len = digest_type/8 + 2;
        mask = 1 << (digest_type%8);

        result = dns_rbt_addnode(resolver->digests, name, &node);

        if (result == ISC_R_SUCCESS || result == ISC_R_EXISTS) {
                digests = node->data;
                /* If digests is set, digests[0] contains its length. */
                if (digests == NULL || len > *digests) {
                        /*
                         * If no bitfield exists in the node data, or if
                         * it is not long enough, allocate a new
                         * bitfield and copy the old (smaller) bitfield
                         * into it if one exists.
                         */
                        new = isc_mem_get(resolver->mctx, len);
                        if (new == NULL) {
                                result = ISC_R_NOMEMORY;
                                goto cleanup;
                        }
                        memset(new, 0, len);
                        if (digests != NULL)
                                memmove(new, digests, *digests);
                        new[len-1] |= mask;
                        /* new[0] should contain the length of new. */
                        *new = len;
                        node->data = new;
                        /* Free the older bitfield. */
                        if (digests != NULL)
                                isc_mem_put(resolver->mctx, digests,
                                            *digests);
                } else
                        digests[len-1] |= mask;
        }
        result = ISC_R_SUCCESS;
 cleanup:
#if USE_ALGLOCK
        RWUNLOCK(&resolver->alglock, isc_rwlocktype_write);
#endif
        return (result);
}

isc_boolean_t
dns_resolver_ds_digest_supported(dns_resolver_t *resolver, dns_name_t *name,
                                 unsigned int digest_type)
{
        unsigned int len, mask;
        unsigned char *digests;
        void *data = NULL;
        isc_result_t result;
        isc_boolean_t found = ISC_FALSE;

        REQUIRE(VALID_RESOLVER(resolver));

#if USE_ALGLOCK
        RWLOCK(&resolver->alglock, isc_rwlocktype_read);
#endif
        if (resolver->digests == NULL)
                goto unlock;
        result = dns_rbt_findname(resolver->digests, name, 0, NULL, &data);
        if (result == ISC_R_SUCCESS || result == DNS_R_PARTIALMATCH) {
                len = digest_type/8 + 2;
                mask = 1 << (digest_type%8);
                digests = data;
                if (len <= *digests && (digests[len-1] & mask) != 0)
                        found = ISC_TRUE;
        }
 unlock:
#if USE_ALGLOCK
        RWUNLOCK(&resolver->alglock, isc_rwlocktype_read);
#endif
        if (found)
                return (ISC_FALSE);
        return (dst_ds_digest_supported(digest_type));
}

void
dns_resolver_resetmustbesecure(dns_resolver_t *resolver) {

        REQUIRE(VALID_RESOLVER(resolver));

#if USE_MBSLOCK
        RWLOCK(&resolver->mbslock, isc_rwlocktype_write);
#endif
        if (resolver->mustbesecure != NULL)
                dns_rbt_destroy(&resolver->mustbesecure);
#if USE_MBSLOCK
        RWUNLOCK(&resolver->mbslock, isc_rwlocktype_write);
#endif
}

static isc_boolean_t yes = ISC_TRUE, no = ISC_FALSE;

isc_result_t
dns_resolver_setmustbesecure(dns_resolver_t *resolver, dns_name_t *name,
                             isc_boolean_t value)
{
        isc_result_t result;

        REQUIRE(VALID_RESOLVER(resolver));

#if USE_MBSLOCK
        RWLOCK(&resolver->mbslock, isc_rwlocktype_write);
#endif
        if (resolver->mustbesecure == NULL) {
                result = dns_rbt_create(resolver->mctx, NULL, NULL,
                                        &resolver->mustbesecure);
                if (result != ISC_R_SUCCESS)
                        goto cleanup;
        }
        result = dns_rbt_addname(resolver->mustbesecure, name,
                                 value ? &yes : &no);
 cleanup:
#if USE_MBSLOCK
        RWUNLOCK(&resolver->mbslock, isc_rwlocktype_write);
#endif
        return (result);
}

isc_boolean_t
dns_resolver_getmustbesecure(dns_resolver_t *resolver, dns_name_t *name) {
        void *data = NULL;
        isc_boolean_t value = ISC_FALSE;
        isc_result_t result;

        REQUIRE(VALID_RESOLVER(resolver));

#if USE_MBSLOCK
        RWLOCK(&resolver->mbslock, isc_rwlocktype_read);
#endif
        if (resolver->mustbesecure == NULL)
                goto unlock;
        result = dns_rbt_findname(resolver->mustbesecure, name, 0, NULL, &data);
        if (result == ISC_R_SUCCESS || result == DNS_R_PARTIALMATCH)
                value = *(isc_boolean_t*)data;
 unlock:
#if USE_MBSLOCK
        RWUNLOCK(&resolver->mbslock, isc_rwlocktype_read);
#endif
        return (value);
}

void
dns_resolver_getclientsperquery(dns_resolver_t *resolver, isc_uint32_t *cur,
                                isc_uint32_t *min, isc_uint32_t *max)
{
        REQUIRE(VALID_RESOLVER(resolver));

        LOCK(&resolver->lock);
        if (cur != NULL)
                *cur = resolver->spillat;
        if (min != NULL)
                *min = resolver->spillatmin;
        if (max != NULL)
                *max = resolver->spillatmax;
        UNLOCK(&resolver->lock);
}

void
dns_resolver_setclientsperquery(dns_resolver_t *resolver, isc_uint32_t min,
                                isc_uint32_t max)
{
        REQUIRE(VALID_RESOLVER(resolver));

        LOCK(&resolver->lock);
        resolver->spillatmin = resolver->spillat = min;
        resolver->spillatmax = max;
        UNLOCK(&resolver->lock);
}

isc_boolean_t
dns_resolver_getzeronosoattl(dns_resolver_t *resolver) {
        REQUIRE(VALID_RESOLVER(resolver));

        return (resolver->zero_no_soa_ttl);
}

void
dns_resolver_setzeronosoattl(dns_resolver_t *resolver, isc_boolean_t state) {
        REQUIRE(VALID_RESOLVER(resolver));

        resolver->zero_no_soa_ttl = state;
}

unsigned int
dns_resolver_getoptions(dns_resolver_t *resolver) {
        REQUIRE(VALID_RESOLVER(resolver));

        return (resolver->options);
}

unsigned int
dns_resolver_gettimeout(dns_resolver_t *resolver) {
        REQUIRE(VALID_RESOLVER(resolver));

        return (resolver->query_timeout);
}

void
dns_resolver_settimeout(dns_resolver_t *resolver, unsigned int seconds) {
        REQUIRE(VALID_RESOLVER(resolver));

        if (seconds == 0)
                seconds = DEFAULT_QUERY_TIMEOUT;
        if (seconds > MAXIMUM_QUERY_TIMEOUT)
                seconds = MAXIMUM_QUERY_TIMEOUT;
        if (seconds < MINIMUM_QUERY_TIMEOUT)
                seconds =  MINIMUM_QUERY_TIMEOUT;

        resolver->query_timeout = seconds;
}

void
dns_resolver_setquerydscp4(dns_resolver_t *resolver, isc_dscp_t dscp) {
        REQUIRE(VALID_RESOLVER(resolver));

        resolver->querydscp4 = dscp;
}

isc_dscp_t
dns_resolver_getquerydscp4(dns_resolver_t *resolver) {
        REQUIRE(VALID_RESOLVER(resolver));
        return (resolver->querydscp4);
}

void
dns_resolver_setquerydscp6(dns_resolver_t *resolver, isc_dscp_t dscp) {
        REQUIRE(VALID_RESOLVER(resolver));

        resolver->querydscp6 = dscp;
}

isc_dscp_t
dns_resolver_getquerydscp6(dns_resolver_t *resolver) {
        REQUIRE(VALID_RESOLVER(resolver));
        return (resolver->querydscp6);
}

void
dns_resolver_setmaxdepth(dns_resolver_t *resolver, unsigned int maxdepth) {
        REQUIRE(VALID_RESOLVER(resolver));
        resolver->maxdepth = maxdepth;
}

unsigned int
dns_resolver_getmaxdepth(dns_resolver_t *resolver) {
        REQUIRE(VALID_RESOLVER(resolver));
        return (resolver->maxdepth);
}

void
dns_resolver_setmaxqueries(dns_resolver_t *resolver, unsigned int queries) {
        REQUIRE(VALID_RESOLVER(resolver));
        resolver->maxqueries = queries;
}

unsigned int
dns_resolver_getmaxqueries(dns_resolver_t *resolver) {
        REQUIRE(VALID_RESOLVER(resolver));
        return (resolver->maxqueries);
}

---