nta.c

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/*
 * Copyright (C) 2014, 2015  Internet Systems Consortium, Inc. ("ISC")
 *
 * 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 <isc/buffer.h>
#include <isc/log.h>
#include <isc/mem.h>
#include <isc/print.h>
#include <isc/rwlock.h>
#include <isc/string.h>
#include <isc/task.h>
#include <isc/time.h>
#include <isc/timer.h>
#include <isc/util.h>

#include <dns/db.h>
#include <dns/log.h>
#include <dns/nta.h>
#include <dns/fixedname.h>
#include <dns/name.h>
#include <dns/rbt.h>
#include <dns/rdataset.h>
#include <dns/resolver.h>
#include <dns/result.h>
#include <dns/time.h>

struct dns_nta {
        unsigned int            magic;
        isc_refcount_t          refcount;
        dns_ntatable_t          *ntatable;
        isc_boolean_t           forced;
        isc_timer_t             *timer;
        dns_fetch_t             *fetch;
        dns_rdataset_t          rdataset;
        dns_rdataset_t          sigrdataset;
        dns_fixedname_t         fn;
        dns_name_t              *name;
        isc_stdtime_t           expiry;
};

#define NTA_MAGIC               ISC_MAGIC('N', 'T', 'A', 'n')
#define VALID_NTA(nn)           ISC_MAGIC_VALID(nn, NTA_MAGIC)

/*
 * Obtain a reference to the nta object.  Released by
 * nta_detach.
 */
static void
nta_ref(dns_nta_t *nta) {
        isc_refcount_increment(&nta->refcount, NULL);
}

static void
nta_detach(isc_mem_t *mctx, dns_nta_t **ntap) {
        unsigned int refs;
        dns_nta_t *nta = *ntap;

        REQUIRE(VALID_NTA(nta));

        *ntap = NULL;
        isc_refcount_decrement(&nta->refcount, &refs);
        if (refs == 0) {
                nta->magic = 0;
                if (nta->timer != NULL) {
                        (void) isc_timer_reset(nta->timer,
                                               isc_timertype_inactive,
                                               NULL, NULL, ISC_TRUE);
                        isc_timer_detach(&nta->timer);
                }
                isc_refcount_destroy(&nta->refcount);
                if (dns_rdataset_isassociated(&nta->rdataset))
                        dns_rdataset_disassociate(&nta->rdataset);
                if (dns_rdataset_isassociated(&nta->sigrdataset))
                        dns_rdataset_disassociate(&nta->sigrdataset);
                if (nta->fetch != NULL) {
                        dns_resolver_cancelfetch(nta->fetch);
                        dns_resolver_destroyfetch(&nta->fetch);
                }
                isc_mem_put(mctx, nta, sizeof(dns_nta_t));
        }
}

static void
free_nta(void *data, void *arg) {
        dns_nta_t *nta = (dns_nta_t *) data;
        isc_mem_t *mctx = (isc_mem_t *) arg;

        nta_detach(mctx, &nta);
}

isc_result_t
dns_ntatable_create(dns_view_t *view,
                    isc_taskmgr_t *taskmgr, isc_timermgr_t *timermgr,
                    dns_ntatable_t **ntatablep)
{
        dns_ntatable_t *ntatable;
        isc_result_t result;

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

        ntatable = isc_mem_get(view->mctx, sizeof(*ntatable));
        if (ntatable == NULL)
                return (ISC_R_NOMEMORY);

        ntatable->task = NULL;
        result = isc_task_create(taskmgr, 0, &ntatable->task);
        if (result != ISC_R_SUCCESS)
                goto cleanup_ntatable;
        isc_task_setname(ntatable->task, "ntatable", ntatable);

        ntatable->table = NULL;
        result = dns_rbt_create(view->mctx, free_nta, view->mctx,
                                &ntatable->table);
        if (result != ISC_R_SUCCESS)
                goto cleanup_task;

        result = isc_rwlock_init(&ntatable->rwlock, 0, 0);
        if (result != ISC_R_SUCCESS)
                goto cleanup_rbt;

        ntatable->timermgr = timermgr;
        ntatable->taskmgr = taskmgr;

        ntatable->view = view;
        ntatable->references = 1;

        ntatable->magic = NTATABLE_MAGIC;
        *ntatablep = ntatable;

        return (ISC_R_SUCCESS);

   cleanup_rbt:
        dns_rbt_destroy(&ntatable->table);

   cleanup_task:
        isc_task_detach(&ntatable->task);

   cleanup_ntatable:
        isc_mem_put(ntatable->view->mctx, ntatable, sizeof(*ntatable));

        return (result);
}

void
dns_ntatable_attach(dns_ntatable_t *source, dns_ntatable_t **targetp) {
        REQUIRE(VALID_NTATABLE(source));
        REQUIRE(targetp != NULL && *targetp == NULL);

        RWLOCK(&source->rwlock, isc_rwlocktype_write);

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

        RWUNLOCK(&source->rwlock, isc_rwlocktype_write);

        *targetp = source;
}

void
dns_ntatable_detach(dns_ntatable_t **ntatablep) {
        isc_boolean_t destroy = ISC_FALSE;
        dns_ntatable_t *ntatable;

        REQUIRE(ntatablep != NULL && VALID_NTATABLE(*ntatablep));

        ntatable = *ntatablep;
        *ntatablep = NULL;

        RWLOCK(&ntatable->rwlock, isc_rwlocktype_write);
        INSIST(ntatable->references > 0);
        ntatable->references--;
        if (ntatable->references == 0)
                destroy = ISC_TRUE;
        RWUNLOCK(&ntatable->rwlock, isc_rwlocktype_write);

        if (destroy) {
                dns_rbt_destroy(&ntatable->table);
                isc_rwlock_destroy(&ntatable->rwlock);
                if (ntatable->task != NULL)
                        isc_task_detach(&ntatable->task);
                ntatable->timermgr = NULL;
                ntatable->taskmgr = NULL;
                ntatable->magic = 0;
                isc_mem_put(ntatable->view->mctx, ntatable, sizeof(*ntatable));
        }
}

static void
fetch_done(isc_task_t *task, isc_event_t *event) {
        dns_fetchevent_t *devent = (dns_fetchevent_t *)event;
        dns_nta_t *nta = devent->ev_arg;
        isc_result_t eresult = devent->result;
        dns_ntatable_t *ntatable = nta->ntatable;
        dns_view_t *view = ntatable->view;
        isc_stdtime_t now;

        UNUSED(task);

        if (dns_rdataset_isassociated(&nta->rdataset))
                dns_rdataset_disassociate(&nta->rdataset);
        if (dns_rdataset_isassociated(&nta->sigrdataset))
                dns_rdataset_disassociate(&nta->sigrdataset);
        if (nta->fetch == devent->fetch)
                nta->fetch = NULL;
        dns_resolver_destroyfetch(&devent->fetch);

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

        isc_event_free(&event);
        isc_stdtime_get(&now);

        switch (eresult) {
        case ISC_R_SUCCESS:
        case DNS_R_NCACHENXDOMAIN:
        case DNS_R_NXDOMAIN:
        case DNS_R_NCACHENXRRSET:
        case DNS_R_NXRRSET:
                nta->expiry = now;
                break;
        default:
                break;
        }

        /*
         * If we're expiring before the next recheck, we might
         * as well stop the timer now.
         */
        if (nta->timer != NULL && nta->expiry - now < ntatable->recheck)
                (void) isc_timer_reset(nta->timer, isc_timertype_inactive,
                                       NULL, NULL, ISC_TRUE);
        nta_detach(view->mctx, &nta);
}

static void
checkbogus(isc_task_t *task, isc_event_t *event) {
        dns_nta_t *nta = event->ev_arg;
        dns_ntatable_t *ntatable = nta->ntatable;
        dns_view_t *view = ntatable->view;
        isc_result_t result;

        if (nta->fetch != NULL) {
                dns_resolver_cancelfetch(nta->fetch);
                nta->fetch = NULL;
        }
        if (dns_rdataset_isassociated(&nta->rdataset))
                dns_rdataset_disassociate(&nta->rdataset);
        if (dns_rdataset_isassociated(&nta->sigrdataset))
                dns_rdataset_disassociate(&nta->sigrdataset);

        isc_event_free(&event);

        nta_ref(nta);
        result = dns_resolver_createfetch(view->resolver, nta->name,
                                          dns_rdatatype_nsec,
                                          NULL, NULL, NULL,
                                          DNS_FETCHOPT_NONTA,
                                          task, fetch_done, nta,
                                          &nta->rdataset,
                                          &nta->sigrdataset,
                                          &nta->fetch);
        if (result != ISC_R_SUCCESS)
                nta_detach(view->mctx, &nta);
}

static isc_result_t
settimer(dns_ntatable_t *ntatable, dns_nta_t *nta, isc_uint32_t lifetime) {
        isc_result_t result;
        isc_interval_t interval;
        dns_view_t *view;

        REQUIRE(VALID_NTATABLE(ntatable));
        REQUIRE(VALID_NTA(nta));

        if (ntatable->timermgr == NULL)
                return (ISC_R_SUCCESS);

        view = ntatable->view;
        if (view->nta_recheck == 0 || lifetime <= view->nta_recheck)
                return (ISC_R_SUCCESS);

        isc_interval_set(&interval, view->nta_recheck, 0);
        result = isc_timer_create(ntatable->timermgr, isc_timertype_ticker,
                                  NULL, &interval, ntatable->task,
                                  checkbogus, nta, &nta->timer);
        return (result);
}

static isc_result_t
nta_create(dns_ntatable_t *ntatable, dns_name_t *name, dns_nta_t **target) {
        isc_result_t result;
        dns_nta_t *nta = NULL;
        dns_view_t *view;

        REQUIRE(VALID_NTATABLE(ntatable));
        REQUIRE(target != NULL && *target == NULL);

        view = ntatable->view;

        nta = isc_mem_get(view->mctx, sizeof(dns_nta_t));
        if (nta == NULL)
                return (ISC_R_NOMEMORY);

        nta->ntatable = ntatable;
        nta->expiry = 0;
        nta->timer = NULL;
        nta->fetch = NULL;
        dns_rdataset_init(&nta->rdataset);
        dns_rdataset_init(&nta->sigrdataset);

        result = isc_refcount_init(&nta->refcount, 1);
        if (result != ISC_R_SUCCESS) {
                isc_mem_put(view->mctx, nta, sizeof(dns_nta_t));
                return (result);
        }

        dns_fixedname_init(&nta->fn);
        nta->name = dns_fixedname_name(&nta->fn);
        dns_name_copy(name, nta->name, NULL);

        nta->magic = NTA_MAGIC;

        *target = nta;
        return (ISC_R_SUCCESS);
}

isc_result_t
dns_ntatable_add(dns_ntatable_t *ntatable, dns_name_t *name,
                 isc_boolean_t force, isc_stdtime_t now,
                 isc_uint32_t lifetime)
{
        isc_result_t result;
        dns_nta_t *nta = NULL;
        dns_rbtnode_t *node;
        dns_view_t *view;

        REQUIRE(VALID_NTATABLE(ntatable));

        view = ntatable->view;

        result = nta_create(ntatable, name, &nta);
        if (result != ISC_R_SUCCESS)
                return (result);

        nta->expiry = now + lifetime;
        nta->forced = force;

        RWLOCK(&ntatable->rwlock, isc_rwlocktype_write);

        node = NULL;
        result = dns_rbt_addnode(ntatable->table, name, &node);
        if (result == ISC_R_SUCCESS) {
                if (!force)
                        (void)settimer(ntatable, nta, lifetime);
                node->data = nta;
                nta = NULL;
        } else if (result == ISC_R_EXISTS) {
                dns_nta_t *n = node->data;
                if (n == NULL) {
                        if (!force)
                                (void)settimer(ntatable, nta, lifetime);
                        node->data = nta;
                        nta = NULL;
                } else {
                        n->expiry = nta->expiry;
                        nta_detach(view->mctx, &nta);
                }
                result = ISC_R_SUCCESS;
        }

        RWUNLOCK(&ntatable->rwlock, isc_rwlocktype_write);

        if (nta != NULL)
                nta_detach(view->mctx, &nta);

        return (result);
}

/*
 * Caller must hold a write lock on rwlock.
 */
static isc_result_t
delete(dns_ntatable_t *ntatable, dns_name_t *name) {
        isc_result_t result;
        dns_rbtnode_t *node = NULL;

        REQUIRE(VALID_NTATABLE(ntatable));
        REQUIRE(name != NULL);

        result = dns_rbt_findnode(ntatable->table, name, NULL, &node, NULL,
                                  DNS_RBTFIND_NOOPTIONS, NULL, NULL);
        if (result == ISC_R_SUCCESS) {
                if (node->data != NULL)
                        result = dns_rbt_deletenode(ntatable->table,
                                                    node, ISC_FALSE);
                else
                        result = ISC_R_NOTFOUND;
        } else if (result == DNS_R_PARTIALMATCH)
                result = ISC_R_NOTFOUND;

        return (result);
}

isc_result_t
dns_ntatable_delete(dns_ntatable_t *ntatable, dns_name_t *name) {
        isc_result_t result;

        RWLOCK(&ntatable->rwlock, isc_rwlocktype_write);
        result = delete(ntatable, name);
        RWUNLOCK(&ntatable->rwlock, isc_rwlocktype_write);

        return (result);
}

isc_boolean_t
dns_ntatable_covered(dns_ntatable_t *ntatable, isc_stdtime_t now,
                     dns_name_t *name, dns_name_t *anchor)
{
        isc_result_t result;
        dns_fixedname_t fn;
        dns_rbtnode_t *node;
        dns_name_t *foundname;
        dns_nta_t *nta = NULL;
        isc_boolean_t answer = ISC_FALSE;
        isc_rwlocktype_t locktype = isc_rwlocktype_read;

        REQUIRE(ntatable == NULL || VALID_NTATABLE(ntatable));
        REQUIRE(dns_name_isabsolute(name));

        if (ntatable == NULL)
                return (ISC_FALSE);

        dns_fixedname_init(&fn);
        foundname = dns_fixedname_name(&fn);

 relock:
        RWLOCK(&ntatable->rwlock, locktype);
 again:
        node = NULL;
        result = dns_rbt_findnode(ntatable->table, name, foundname, &node, NULL,
                                  DNS_RBTFIND_NOOPTIONS, NULL, NULL);
        if (result == DNS_R_PARTIALMATCH) {
                if (dns_name_issubdomain(foundname, anchor))
                        result = ISC_R_SUCCESS;
        }
        if (result == ISC_R_SUCCESS) {
                nta = (dns_nta_t *) node->data;
                answer = ISC_TF(nta->expiry >= now);
        }

        /* Deal with expired NTA */
        if (result == ISC_R_SUCCESS && !answer) {
                char nb[DNS_NAME_FORMATSIZE];

                if (locktype == isc_rwlocktype_read) {
                        RWUNLOCK(&ntatable->rwlock, locktype);
                        locktype = isc_rwlocktype_write;
                        goto relock;
                }

                dns_name_format(foundname, nb, sizeof(nb));
                isc_log_write(dns_lctx, DNS_LOGCATEGORY_DNSSEC,
                              DNS_LOGMODULE_NTA, ISC_LOG_INFO,
                              "deleting expired NTA at %s", nb);

                if (nta->timer != NULL) {
                        (void) isc_timer_reset(nta->timer,
                                               isc_timertype_inactive,
                                               NULL, NULL, ISC_TRUE);
                        isc_timer_detach(&nta->timer);
                }

                result = delete(ntatable, foundname);
                if (result != ISC_R_SUCCESS) {
                        isc_log_write(dns_lctx, DNS_LOGCATEGORY_DNSSEC,
                                      DNS_LOGMODULE_NTA, ISC_LOG_INFO,
                                      "deleting NTA failed: %s",
                                      isc_result_totext(result));
                }
                goto again;
        }
        RWUNLOCK(&ntatable->rwlock, locktype);

        return (answer);
}

static isc_result_t
putstr(isc_buffer_t **b, const char *str) {
        isc_result_t result;

        result = isc_buffer_reserve(b, strlen(str));
        if (result != ISC_R_SUCCESS)
                return (result);

        isc_buffer_putstr(*b, str);
        return (ISC_R_SUCCESS);
}

isc_result_t
dns_ntatable_totext(dns_ntatable_t *ntatable, isc_buffer_t **buf) {
        isc_result_t result;
        dns_rbtnode_t *node;
        dns_rbtnodechain_t chain;
        isc_boolean_t first = ISC_TRUE;
        isc_stdtime_t now;

        REQUIRE(VALID_NTATABLE(ntatable));

        isc_stdtime_get(&now);

        RWLOCK(&ntatable->rwlock, isc_rwlocktype_read);
        dns_rbtnodechain_init(&chain, ntatable->view->mctx);
        result = dns_rbtnodechain_first(&chain, ntatable->table, NULL, NULL);
        if (result != ISC_R_SUCCESS && result != DNS_R_NEWORIGIN) {
                if (result == ISC_R_NOTFOUND)
                        result = ISC_R_SUCCESS;
                goto cleanup;
        }
        for (;;) {
                dns_rbtnodechain_current(&chain, NULL, NULL, &node);
                if (node->data != NULL) {
                        dns_nta_t *n = (dns_nta_t *) node->data;
                        char nbuf[DNS_NAME_FORMATSIZE];
                        char tbuf[ISC_FORMATHTTPTIMESTAMP_SIZE];
                        char obuf[DNS_NAME_FORMATSIZE +
                                  ISC_FORMATHTTPTIMESTAMP_SIZE +
                                  sizeof("expired:  \n")];
                        dns_fixedname_t fn;
                        dns_name_t *name;
                        isc_time_t t;

                        dns_fixedname_init(&fn);
                        name = dns_fixedname_name(&fn);
                        dns_rbt_fullnamefromnode(node, name);
                        dns_name_format(name, nbuf, sizeof(nbuf));
                        isc_time_set(&t, n->expiry, 0);
                        isc_time_formattimestamp(&t, tbuf, sizeof(tbuf));

                        snprintf(obuf, sizeof(obuf), "%s%s: %s %s",
                                 first ? "" : "\n", nbuf,
                                 n->expiry < now ? "expired" : "expiry",
                                 tbuf);
                        first = ISC_FALSE;
                        result = putstr(buf, obuf);
                        if (result != ISC_R_SUCCESS)
                                goto cleanup;
                }
                result = dns_rbtnodechain_next(&chain, NULL, NULL);
                if (result != ISC_R_SUCCESS && result != DNS_R_NEWORIGIN) {
                        if (result == ISC_R_NOMORE)
                                result = ISC_R_SUCCESS;
                        break;
                }
        }

   cleanup:
        dns_rbtnodechain_invalidate(&chain);
        RWUNLOCK(&ntatable->rwlock, isc_rwlocktype_read);
        return (result);
}

#if 0
isc_result_t
dns_ntatable_dump(dns_ntatable_t *ntatable, FILE *fp) {
        isc_result_t result;
        dns_rbtnode_t *node;
        dns_rbtnodechain_t chain;
        isc_stdtime_t now;

        REQUIRE(VALID_NTATABLE(ntatable));

        isc_stdtime_get(&now);

        RWLOCK(&ntatable->rwlock, isc_rwlocktype_read);
        dns_rbtnodechain_init(&chain, ntatable->view->mctx);
        result = dns_rbtnodechain_first(&chain, ntatable->table, NULL, NULL);
        if (result != ISC_R_SUCCESS && result != DNS_R_NEWORIGIN)
                goto cleanup;
        for (;;) {
                dns_rbtnodechain_current(&chain, NULL, NULL, &node);
                if (node->data != NULL) {
                        dns_nta_t *n = (dns_nta_t *) node->data;
                        char nbuf[DNS_NAME_FORMATSIZE], tbuf[80];
                        dns_fixedname_t fn;
                        dns_name_t *name;
                        isc_time_t t;

                        dns_fixedname_init(&fn);
                        name = dns_fixedname_name(&fn);
                        dns_rbt_fullnamefromnode(node, name);
                        dns_name_format(name, nbuf, sizeof(nbuf));
                        isc_time_set(&t, n->expiry, 0);
                        isc_time_formattimestamp(&t, tbuf, sizeof(tbuf));
                        fprintf(fp, "%s: %s %s\n", nbuf,
                                n->expiry < now ? "expired" : "expiry",
                                tbuf);
                }
                result = dns_rbtnodechain_next(&chain, NULL, NULL);
                if (result != ISC_R_SUCCESS && result != DNS_R_NEWORIGIN) {
                        if (result == ISC_R_NOMORE)
                                result = ISC_R_SUCCESS;
                        break;
                }
        }

   cleanup:
        dns_rbtnodechain_invalidate(&chain);
        RWUNLOCK(&ntatable->rwlock, isc_rwlocktype_read);
        return (result);
}
#endif

isc_result_t
dns_ntatable_dump(dns_ntatable_t *ntatable, FILE *fp) {
        isc_result_t result;
        isc_buffer_t *text = NULL;
        int len = 4096;

        result = isc_buffer_allocate(ntatable->view->mctx, &text, len);
        if (result != ISC_R_SUCCESS)
                return (result);

        result = dns_ntatable_totext(ntatable, &text);

        if (isc_buffer_usedlength(text) != 0) {
                (void) putstr(&text, "\n");
        } else if (result == ISC_R_SUCCESS) {
                (void) putstr(&text, "none");
        } else {
                (void) putstr(&text, "could not dump NTA table: ");
                (void) putstr(&text, isc_result_totext(result));
        }

        fprintf(fp, "%.*s", (int) isc_buffer_usedlength(text),
                (char *) isc_buffer_base(text));
        isc_buffer_free(&text);
        return (result);
}

isc_result_t
dns_ntatable_save(dns_ntatable_t *ntatable, FILE *fp) {
        isc_result_t result;
        dns_rbtnode_t *node;
        dns_rbtnodechain_t chain;
        isc_stdtime_t now;
        isc_boolean_t written = ISC_FALSE;

        REQUIRE(VALID_NTATABLE(ntatable));

        isc_stdtime_get(&now);

        RWLOCK(&ntatable->rwlock, isc_rwlocktype_read);
        dns_rbtnodechain_init(&chain, ntatable->view->mctx);
        result = dns_rbtnodechain_first(&chain, ntatable->table, NULL, NULL);
        if (result != ISC_R_SUCCESS && result != DNS_R_NEWORIGIN)
                goto cleanup;

        for (;;) {
                dns_rbtnodechain_current(&chain, NULL, NULL, &node);
                if (node->data != NULL) {
                        dns_nta_t *n = (dns_nta_t *) node->data;
                        if (now <= n->expiry) {
                                isc_buffer_t b;
                                char nbuf[DNS_NAME_FORMATSIZE + 1], tbuf[80];
                                dns_fixedname_t fn;
                                dns_name_t *name;

                                dns_fixedname_init(&fn);
                                name = dns_fixedname_name(&fn);
                                dns_rbt_fullnamefromnode(node, name);

                                isc_buffer_init(&b, nbuf, sizeof(nbuf));
                                result = dns_name_totext(name, ISC_FALSE, &b);
                                if (result != ISC_R_SUCCESS)
                                        goto skip;

                                /* Zero terminate. */
                                isc_buffer_putuint8(&b, 0);

                                isc_buffer_init(&b, tbuf, sizeof(tbuf));
                                dns_time32_totext(n->expiry, &b);

                                /* Zero terminate. */
                                isc_buffer_putuint8(&b, 0);

                                fprintf(fp, "%s %s %s\n", nbuf,
                                        n->forced ? "forced" : "regular",
                                        tbuf);
                                written = ISC_TRUE;
                        }
                }
        skip:
                result = dns_rbtnodechain_next(&chain, NULL, NULL);
                if (result != ISC_R_SUCCESS && result != DNS_R_NEWORIGIN) {
                        if (result == ISC_R_NOMORE)
                                result = ISC_R_SUCCESS;
                        break;
                }
        }

   cleanup:
        dns_rbtnodechain_invalidate(&chain);
        RWUNLOCK(&ntatable->rwlock, isc_rwlocktype_read);

        if (result != ISC_R_SUCCESS)
                return (result);
        else
                return (written ? ISC_R_SUCCESS : ISC_R_NOTFOUND);
}

---