bin/named/query.c

	query.c revision 84d821c5218f61a8e66463da92eedf4b26f7ce0a
/*
 * Copyright (C) 1999  Internet Software Consortium.
 *
 * Permission to use, copy, modify, and 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 INTERNET SOFTWARE CONSORTIUM DISCLAIMS
 * ALL WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL INTERNET SOFTWARE
 * CONSORTIUM 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.
 */

#include <config.h>

#include <isc/assertions.h>
#include <isc/buffer.h>
#include <isc/mem.h>
#include <isc/mutex.h>
#include <isc/result.h>
#include <isc/task.h>
#include <isc/timer.h>
#include <isc/event.h>

#include <dns/db.h>
#include <dns/dbtable.h>
#include <dns/dispatch.h>
#include <dns/events.h>
#include <dns/fixedname.h>
#include <dns/message.h>
#include <dns/name.h>
#include <dns/rdata.h>
#include <dns/rdataset.h>
#include <dns/rdatasetiter.h>
#include <dns/view.h>

#include <named/client.h>
#include <named/globals.h>
#include <named/query.h>

#include "../../isc/util.h"     /* XXX */

#define PARTIALANSWER(c)    (((c)->query.attributes & \
                  NS_QUERYATTR_PARTIALANSWER) != 0)

static inline void
query_reset(ns_client_t *client, isc_boolean_t everything) {
    isc_dynbuffer_t *dbuf, *dbuf_next;

    for (dbuf = ISC_LIST_HEAD(client->query.namebufs);
         dbuf != NULL;
         dbuf = dbuf_next) {
        dbuf_next = ISC_LIST_NEXT(dbuf, link);
        if (dbuf_next != NULL || everything) {
            ISC_LIST_UNLINK(client->query.namebufs, dbuf, link);
            isc_dynbuffer_free(client->mctx, &dbuf);
        }
    }
    /*
     * We don't need to free items from these two lists because they
     * will be taken care of when the message is reset.
     */
    ISC_LIST_INIT(client->query.tmpnames);
    ISC_LIST_INIT(client->query.tmprdatasets);
    client->query.attributes = (NS_QUERYATTR_RECURSIONOK|
                    NS_QUERYATTR_CACHEOK);
    client->query.qname = NULL;
    client->query.origqname = NULL;
    client->query.dboptions = 0;
}

static void
query_next(ns_client_t *client, isc_result_t result) {
    (void)result;
    query_reset(client, ISC_FALSE);
}

void
ns_query_free(ns_client_t *client) {
    query_reset(client, ISC_TRUE);
}

static inline isc_result_t
query_newnamebuf(ns_client_t *client) {
    isc_dynbuffer_t *dbuf;
    isc_result_t result;

    REQUIRE(NS_CLIENT_VALID(client));

    dbuf = NULL;
    result = isc_dynbuffer_allocate(client->mctx, &dbuf, 1024,
                    ISC_BUFFERTYPE_BINARY);
    if (result != ISC_R_SUCCESS)
        return (result);
    ISC_LIST_APPEND(client->query.namebufs, dbuf, link);

    return (ISC_R_SUCCESS);
}

static inline isc_dynbuffer_t *
query_getnamebuf(ns_client_t *client) {
    isc_dynbuffer_t *dbuf;
    isc_result_t result;
    isc_region_t r;

    if (ISC_LIST_EMPTY(client->query.namebufs)) {
        result = query_newnamebuf(client);
        if (result != ISC_R_SUCCESS)
            return (NULL);
    }

    dbuf = ISC_LIST_TAIL(client->query.namebufs);
    INSIST(dbuf != NULL);
    isc_buffer_available(&dbuf->buffer, &r);
    if (r.length < 255) {
        result = query_newnamebuf(client);
        if (result != ISC_R_SUCCESS)
            return (NULL);
        dbuf = ISC_LIST_TAIL(client->query.namebufs);
        isc_buffer_available(&dbuf->buffer, &r);
        INSIST(r.length >= 255);
    }
    return (dbuf);
}

static inline void
query_keepname(ns_client_t *client, dns_name_t *name, isc_dynbuffer_t *dbuf) {
    isc_region_t r;

    /*
     * 'name' is using space in 'dbuf', but 'dbuf' has not yet been
     * adjusted to take account of that.  We do the adjustment.
     */

    REQUIRE((client->query.attributes & NS_QUERYATTR_NAMEBUFUSED) != 0);

    dns_name_toregion(name, &r);
    isc_buffer_add(&dbuf->buffer, r.length);
    dns_name_setbuffer(name, NULL);
    client->query.attributes &= ~NS_QUERYATTR_NAMEBUFUSED;
}

static inline void
query_releasename(ns_client_t *client, dns_name_t **namep) {
    dns_name_t *name = *namep;

    ISC_LIST_APPEND(client->query.tmpnames, name, link);
    if (dns_name_hasbuffer(name)) {
        INSIST((client->query.attributes & NS_QUERYATTR_NAMEBUFUSED)
               != 0);
        client->query.attributes &= ~NS_QUERYATTR_NAMEBUFUSED;
    }
    *namep = NULL;
}

static inline dns_name_t *
query_newname(ns_client_t *client, isc_dynbuffer_t *dbuf,
          isc_buffer_t *nbuf)
{
    dns_name_t *name;
    isc_region_t r;
    isc_result_t result;

    REQUIRE((client->query.attributes & NS_QUERYATTR_NAMEBUFUSED) == 0);

    name = ISC_LIST_HEAD(client->query.tmpnames);
    if (name == NULL) {
        result = dns_message_gettempname(client->message, &name);
        if (result != ISC_R_SUCCESS)
            return (NULL);
    } else
        ISC_LIST_UNLINK(client->query.tmpnames, name, link);
    isc_buffer_available(&dbuf->buffer, &r);
    isc_buffer_init(nbuf, r.base, r.length, ISC_BUFFERTYPE_BINARY);
    dns_name_init(name, NULL);
    dns_name_setbuffer(name, nbuf);
    client->query.attributes |= NS_QUERYATTR_NAMEBUFUSED;

    return (name);
}

static inline dns_rdataset_t *
query_newrdataset(ns_client_t *client) {
    dns_rdataset_t *rdataset;
    isc_result_t result;

    rdataset = ISC_LIST_HEAD(client->query.tmprdatasets);
    if (rdataset == NULL) {
        result = dns_message_gettemprdataset(client->message,
                             &rdataset);
        if (result != ISC_R_SUCCESS)
            return (NULL);
    } else
        ISC_LIST_UNLINK(client->query.tmprdatasets, rdataset, link);
    dns_rdataset_init(rdataset);

    return (rdataset);
}

isc_result_t
ns_query_init(ns_client_t *client) {
    ISC_LIST_INIT(client->query.namebufs);
    query_reset(client, ISC_FALSE);
    return (query_newnamebuf(client));
}

static isc_result_t
query_addadditional(void *arg, dns_name_t *name, dns_rdatatype_t type) {
    ns_client_t *client = arg;
    isc_result_t result, eresult;
    dns_dbnode_t *node;
    dns_db_t *db;
    dns_name_t *fname, *mname;
    dns_rdataset_t *rdataset;
    dns_section_t section;
    isc_dynbuffer_t *dbuf;
    isc_buffer_t b;

    REQUIRE(NS_CLIENT_VALID(client));
    REQUIRE(type != dns_rdatatype_any);
    /* XXXRTH  Other requirements. */

    /*
     * XXXRTH  Should special case 'A' type.  If type is 'A', we should
     *     look for A6 and AAAA too.
     */

    /*
     * Initialization.
     */
    eresult = ISC_R_SUCCESS;
    fname = NULL;
    rdataset = NULL;
    db = NULL;
    node = NULL;

    /*
     * Get some resources...
     */
    dbuf = query_getnamebuf(client);
    if (dbuf == NULL)
        goto cleanup;
    fname = query_newname(client, dbuf, &b);
    rdataset = query_newrdataset(client);
    if (fname == NULL || rdataset == NULL)
        goto cleanup;

    /*
     * Find a database to answer the query.
     */
    result = dns_dbtable_find(client->view->dbtable, name, &db);
    if (result != ISC_R_SUCCESS && result != DNS_R_PARTIALMATCH)
        goto cleanup;

    /*
     * Now look for an answer in the database.
     */
    node = NULL;
    result = dns_db_find(db, name, NULL, type, client->query.dboptions,
                 0, &node, fname, rdataset);
    switch (result) {
    case DNS_R_SUCCESS:
    case DNS_R_GLUE:
        break;
    default:
        goto cleanup;
    }

    query_keepname(client, fname, dbuf);

    /*
     * Suppress duplicates.
     */
    for (section = DNS_SECTION_ANSWER;
         section <= DNS_SECTION_ADDITIONAL;
         section++) {
        mname = NULL;
        result = dns_message_findname(client->message, section,
                          name, type, &mname, NULL);
        if (result == ISC_R_SUCCESS) {
            /*
             * We've already got this RRset in the response.
             */
            goto cleanup;
        }
    }
    ISC_LIST_APPEND(fname->list, rdataset, link);
    rdataset = NULL;

    dns_message_addname(client->message, fname, DNS_SECTION_ADDITIONAL);
    fname = NULL;

    /*
     * In a few cases, we want to add additional data for additional
     * data.  It's simpler to just deal with special cases here than
     * to try to create a general purpose mechanism and allow the
     * rdata implementations to do it themselves.
     *
     * This involves recursion, but the depth is limited.  The
     * most complex case is adding a SRV rdataset, which involves
     * recursing to add address records, which in turn can cause
     * recursion to add KEYs.
     */
    if (type == dns_rdatatype_a || type == dns_rdatatype_aaaa ||
        type == dns_rdatatype_a6) {
        /*
         * RFC 2535 section 3.5 says that when A or AAAA records are
         * retrieved as additional data, any KEY RRs for the owner name
         * should be added to the additional data section.  We include
         * A6 in the list of types with such treatment.
         *
         * XXXRTH  We should lower the priority here.  Alternatively,
         * we could raise the priority of glue records.
         */
        eresult = query_addadditional(client, name, dns_rdatatype_key);
    } else if (type == dns_rdatatype_srv) {
        /*
         * If we're adding SRV records to the additional data
         * section, it's helpful if we add the SRV additional data
         * as well.
         */
        eresult = dns_rdataset_additionaldata(rdataset,
                              query_addadditional,
                              client);
    }

 cleanup:
    if (rdataset != NULL) {
        if (rdataset->methods != NULL)
            dns_rdataset_disassociate(rdataset);
        ISC_LIST_APPEND(client->query.tmprdatasets, rdataset, link);
    }
    if (fname != NULL)
        query_releasename(client, &fname);
    if (node != NULL)
        dns_db_detachnode(db, &node);
    if (db != NULL)
        dns_db_detach(&db);

    return (eresult);
}

static inline void
query_addrdataset(ns_client_t *client, dns_name_t *fname,
          dns_rdataset_t *rdataset)
{
    dns_rdatatype_t type = rdataset->type;

    ISC_LIST_APPEND(fname->list, rdataset, link);
    /*
     * We don't care if dns_rdataset_additionaldata() fails.
     */
    (void)dns_rdataset_additionaldata(rdataset, query_addadditional,
                      client);
    /*
     * RFC 2535 section 3.5 says that when NS, SOA, A, or AAAA records
     * are retrieved, any KEY RRs for the owner name should be added
     * to the additional data section.  We include A6 in the list of
     * types with such treatment.
     *
     * We don't care if query_additional() fails.
     */
    if (type == dns_rdatatype_ns || type == dns_rdatatype_soa ||
        type == dns_rdatatype_a || type == dns_rdatatype_aaaa ||
        type == dns_rdatatype_a6) {
        /*
         * XXXRTH  We should lower the priority here.  Alternatively,
         * we could raise the priority of glue records.
         */
        (void)query_addadditional(client, fname, dns_rdatatype_key);
    }
}

#define ANSWERED(rds)   (((rds)->attributes & DNS_RDATASETATTR_ANSWERED) != 0)

static inline void
query_addrrset(ns_client_t *client, dns_name_t **namep,
           dns_rdataset_t **rdatasetp, isc_dynbuffer_t *dbuf,
           dns_section_t section)
{
    dns_name_t *name, *mname;
    dns_rdataset_t *rdataset, *mrdataset;
    isc_result_t result;

    name = *namep;
    rdataset = *rdatasetp;
    mname = NULL;
    mrdataset = NULL;
    result = dns_message_findname(client->message, section,
                      name, rdataset->type,
                      &mname, &mrdataset);
    if (result == ISC_R_SUCCESS) {
        /*
         * We've already got an RRset of the given name and type.
         * There's nothing else to do;
         */
        return;
    }

    if (result == DNS_R_NXDOMAIN) {
        /*
         * The name doesn't exist.
         */
        if (dbuf != NULL)
            query_keepname(client, name, dbuf);
        dns_message_addname(client->message, name, section);
        *namep = NULL;
        mname = name;
    } else
        RUNTIME_CHECK(result == DNS_R_NXRDATASET);

    query_addrdataset(client, mname, rdataset);
    *rdatasetp = NULL;
}

static inline isc_result_t
query_addsoa(ns_client_t *client, dns_db_t *db) {
    dns_name_t *name, *fname;
    dns_dbnode_t *node;
    isc_result_t result, eresult;
    dns_fixedname_t foundname;
    dns_rdataset_t *rdataset;

    /*
     * Initialization.
     */
    eresult = ISC_R_SUCCESS;
    name = NULL;
    rdataset = NULL;
    node = NULL;
    dns_fixedname_init(&foundname);
    fname = dns_fixedname_name(&foundname);

    /*
     * Get resources and make 'name' be the database origin.
     */
    result = dns_message_gettempname(client->message, &name);
    if (result != ISC_R_SUCCESS)
        return (result);
    dns_name_init(name, NULL);
    dns_name_clone(dns_db_origin(db), name);
    rdataset = query_newrdataset(client);
    if (rdataset == NULL) {
        eresult = DNS_R_SERVFAIL;
        goto cleanup;
    }

    /*
     * Find the SOA.
     */
    result = dns_db_find(db, name, NULL, dns_rdatatype_soa, 0, 0, &node,
                 fname, rdataset);
    if (result != ISC_R_SUCCESS) {
        /*
         * This is bad.  We tried to get the SOA RR at the zone top
         * and it didn't work!
         *
         * The note above about temporary leakage applies here too.
         */
        eresult = DNS_R_SERVFAIL;
    } else
        query_addrrset(client, &name, &rdataset, NULL,
                   DNS_SECTION_AUTHORITY);

 cleanup:
    if (rdataset != NULL) {
        if (rdataset->methods != NULL)
            dns_rdataset_disassociate(rdataset);
        ISC_LIST_APPEND(client->query.tmprdatasets, rdataset, link);
    }
    if (name != NULL)
        query_releasename(client, &name);
    if (node != NULL)
        dns_db_detachnode(db, &node);

    return (eresult);
}

static inline isc_result_t
query_checktype(dns_rdatatype_t type) {

    /*
     * XXXRTH  SIG is here only temporarily.
     *     OPT still needs to be added.
     *     Should get help with this from rdata.c
     */
    switch (type) {
    case dns_rdatatype_sig:
        return (DNS_R_NOTIMP);
    case dns_rdatatype_tkey:
        return (DNS_R_NOTIMP);
    case dns_rdatatype_tsig:
        return (DNS_R_FORMERR);
    case dns_rdatatype_ixfr:
    case dns_rdatatype_axfr:
    case dns_rdatatype_mailb:
    case dns_rdatatype_maila:
        return (DNS_R_REFUSED);
    default:
        break;
    }

    return (ISC_R_SUCCESS);
}

#define MAX_RESTARTS 16

#define QUERY_ERROR(r) \
do { \
    eresult = r; \
    want_restart = ISC_FALSE; \
} while (0)

static void
query_find(ns_client_t *client) {
    dns_db_t *db;
    dns_dbnode_t *node;
    dns_rdatatype_t qtype, type;
    dns_name_t *fname, *tname, *prefix;
    dns_rdataset_t *rdataset, *qrdataset, *trdataset;
    dns_rdata_t rdata;
    dns_rdatasetiter_t *rdsiter;
    isc_boolean_t use_cache, recursion_ok, want_restart;
    isc_boolean_t auth, is_zone;
    unsigned int restarts, qcount, n, nlabels, nbits;
    dns_namereln_t namereln;
    int order;
    isc_dynbuffer_t *dbuf;
    isc_region_t r;
    isc_buffer_t b;
    isc_result_t result, eresult;
    dns_fixedname_t fixed;

    /*
     * One-time initialization.
     *
     * It's especially important to initialize anything that the cleanup
     * code might cleanup.
     */

    eresult = ISC_R_SUCCESS;
    restarts = 0;
    use_cache = ISC_FALSE;
    recursion_ok = ISC_FALSE;
    fname = NULL;
    rdataset = NULL;
    node = NULL;
    db = NULL;

    if (client->view->cachedb == NULL ||
        client->view->resolver == NULL) {
        use_cache = ISC_FALSE;
        recursion_ok = ISC_FALSE;
    }

 restart:
    want_restart = ISC_FALSE;
    auth = ISC_FALSE;

    /*
     * First we must find the right database.
     */
    result = dns_dbtable_find(client->view->dbtable,
                  client->query.qname, &db);
    if (result == ISC_R_NOTFOUND) {
        /*
         * We're not directly authoritative for this query name, nor
         * is it a subdomain of any zone for which we're
         * authoritative.
         */
        if (!use_cache) {
            /*
             * If we can't use the cache, either because we
             * don't have one or because its use has been
             * disallowed, there's no more progress we can make
             * on this query.
             */
            QUERY_ERROR(DNS_R_REFUSED);
            goto cleanup;
        }
        INSIST(client->view->cachedb != NULL);
        dns_db_attach(client->view->cachedb, &db);
    } else if (result != ISC_R_SUCCESS && result != DNS_R_PARTIALMATCH) {
        /*
         * Something is broken.
         */
        QUERY_ERROR(DNS_R_SERVFAIL);
        goto cleanup;
    }

    is_zone = dns_db_iszone(db);
    if (is_zone)
        auth = ISC_TRUE;

    /*
     * Find the first unanswered type in the question section.
     */
    qcount = 0;
    qrdataset = NULL;
    qtype = dns_rdatatype_null;
    for (trdataset = ISC_LIST_HEAD(client->query.origqname->list);
         trdataset != NULL;
         trdataset = ISC_LIST_NEXT(trdataset, link)) {
        if (!ANSWERED(trdataset)) {
            if (qrdataset == NULL) {
                qrdataset = trdataset;
                qtype = trdataset->type;
            }
            qcount++;
        }
    }
    /*
     * We had better have found something!
     */
    INSIST(qrdataset != NULL && qcount > 0);
    /*
     * If there's more than one question, we'll retrieve the node and
     * iterate it, trying to find answers.
     */
    if (qcount == 1)
        type = qtype;
    else {
        type = dns_rdatatype_any;
        /* XXXRTH */
        QUERY_ERROR(DNS_R_NOTIMP);
        goto cleanup;
    }

    /*
     * See if the type is OK.
     */
    result = query_checktype(qtype);
    if (result != ISC_R_SUCCESS) {
        QUERY_ERROR(result);
        goto cleanup;
    }

    /*
     * We'll need some resources...
     */
    dbuf = query_getnamebuf(client);
    if (dbuf == NULL) {
        QUERY_ERROR(DNS_R_SERVFAIL);
        goto cleanup;
    }
    fname = query_newname(client, dbuf, &b);
    rdataset = query_newrdataset(client);
    if (fname == NULL || rdataset == NULL) {
        QUERY_ERROR(DNS_R_SERVFAIL);
        goto cleanup;
    }

 db_find:
    /*
     * Now look for an answer in the database.
     */
    result = dns_db_find(db, client->query.qname, NULL, type, 0, 0, &node,
                 fname, rdataset);
    switch (result) {
    case DNS_R_SUCCESS:
    case DNS_R_ZONECUT:
        /*
         * These cases are handled in the main line below.
         */
        break;
    case DNS_R_DELEGATION:
        if (is_zone) {
            /*
             * We're authoritative for an ancestor of QNAME.
             */
            if (!use_cache) {
                /*
                 * We don't have a cache, so this is the best
                 * answer.
                 */
                query_addrrset(client, &fname, &rdataset, dbuf,
                           DNS_SECTION_AUTHORITY);
            } else {
                /*
                 * We might have a better answer or delegation
                 * in the cache.  We'll remember the current
                 * values of fname and rdataset, and then
                 * go looking for QNAME in the cache.  If we
                 * find something better, we'll use it instead.
                 */
                QUERY_ERROR(DNS_R_NOTIMP);
                goto cleanup;
            }
        } else {
            INSIST(recursion_ok);

            /*
             * Recurse using the best delegation.
             */
            QUERY_ERROR(DNS_R_NOTIMP);
        }
        goto cleanup;
    case DNS_R_GLUE:
        auth = ISC_FALSE;
        break;
    case DNS_R_NXRDATASET:
        INSIST(is_zone);
        /*
         * Add SOA.
         */
        query_releasename(client, &fname);
        result = query_addsoa(client, db);
        if (result != ISC_R_SUCCESS) {
            QUERY_ERROR(result);
            goto cleanup;
        }
        /*
         * XXXRTH  Add NXT record here.
         */
        goto cleanup;
    case DNS_R_NXDOMAIN:
        if (restarts > 0) {
            /*
             * We hit a dead end following a CNAME or DNAME.
             */
            goto cleanup;
        }
        INSIST(is_zone);
        /*
         * Set message rcode.
         */
        client->message->rcode = dns_rcode_nxdomain;
        /*
         * Add SOA.
         */
        query_releasename(client, &fname);
        result = query_addsoa(client, db);
        if (result != ISC_R_SUCCESS) {
            QUERY_ERROR(result);
            goto cleanup;
        }
        /*
         * XXXRTH  Add NXT chain here.
         */
        goto cleanup;
    case DNS_R_NOTFOUND:
        QUERY_ERROR(DNS_R_NOTIMP);
        goto cleanup;
    case DNS_R_CNAME:
        /*
         * Keep a copy of the rdataset.  We have to do this because
         * query_addrrset may clear 'rdataset' (to prevent the
         * cleanup code from cleaning it up).
         */
        trdataset = rdataset;
        /*
         * Add the CNAME to the answer section.
         */
        query_addrrset(client, &fname, &rdataset, dbuf,
                   DNS_SECTION_ANSWER);
        /*
         * We set the PARTIALANSWER attribute so that if anything goes
         * wrong later on, we'll return what we've got so far.
         */
        client->query.attributes |= NS_QUERYATTR_PARTIALANSWER;
        /*
         * Reset qname to be the target name of the CNAME and restart
         * the query.
         */
        tname = NULL;
        result = dns_message_gettempname(client->message, &tname);
        if (result != ISC_R_SUCCESS)
            goto cleanup;
        result = dns_rdataset_first(trdataset);
        if (result != ISC_R_SUCCESS)
            goto cleanup;
        dns_rdataset_current(trdataset, &rdata);
        r.base = rdata.data;
        r.length = rdata.length;
        dns_name_init(tname, NULL);
        dns_name_fromregion(tname, &r);
        client->query.qname = tname;
        want_restart = ISC_TRUE;
        goto cleanup;
    case DNS_R_DNAME:
        /*
         * Compare the current qname to the found name.  We need
         * to know how many labels and bits are in common because
         * we're going to have to split qname later on.
         */
        namereln = dns_name_fullcompare(client->query.qname, fname,
                        &order, &nlabels, &nbits);
        INSIST(namereln == dns_namereln_subdomain);
        /*
         * Keep a copy of the rdataset.  We have to do this because
         * query_addrrset may clear 'rdataset' (to prevent the
         * cleanup code from cleaning it up).
         */
        trdataset = rdataset;
        /*
         * Add the DNAME to the answer section.
         */
        query_addrrset(client, &fname, &rdataset, dbuf,
                   DNS_SECTION_ANSWER);
        /*
         * We set the PARTIALANSWER attribute so that if anything goes
         * wrong later on, we'll return what we've got so far.
         */
        client->query.attributes |= NS_QUERYATTR_PARTIALANSWER;
        /*
         * Get the target name of the DNAME.
         */
        tname = NULL;
        result = dns_message_gettempname(client->message, &tname);
        if (result != ISC_R_SUCCESS)
            goto cleanup;
        result = dns_rdataset_first(trdataset);
        if (result != ISC_R_SUCCESS)
            goto cleanup;
        dns_rdataset_current(trdataset, &rdata);
        r.base = rdata.data;
        r.length = rdata.length;
        dns_name_init(tname, NULL);
        dns_name_fromregion(tname, &r);
        /*
         * Construct the new qname and restart the query.
         */
        dns_fixedname_init(&fixed);
        prefix = dns_fixedname_name(&fixed);
        result = dns_name_split(client->query.qname, nlabels, nbits,
                    prefix, NULL);
        if (result != ISC_R_SUCCESS)
            goto cleanup;
        if (fname != NULL)
            query_releasename(client, &fname);
        dbuf = query_getnamebuf(client);
        if (dbuf == NULL)
            goto cleanup;
        fname = query_newname(client, dbuf, &b);
        if (fname == NULL)
            goto cleanup;
        fname->buffer->length = 20;
        result = dns_name_concatenate(prefix, tname, fname, NULL);
        if (result != ISC_R_SUCCESS) {
            if (result == ISC_R_NOSPACE) {
                /*
                 * draft-ietf-dnsind-dname-03.txt, section
                 * 4.1, subsection 3c says we should
                 * return YXDOMAIN if the constructed
                 * name would be too long.
                 */
                client->message->rcode = dns_rcode_yxdomain;
            }
            goto cleanup;
        }
        query_keepname(client, fname, dbuf);
        client->query.qname = fname;
        fname = NULL;
        want_restart = ISC_TRUE;
        goto cleanup;
    default:
        /*
         * Something has gone wrong.
         */
        QUERY_ERROR(DNS_R_SERVFAIL);
        goto cleanup;
    }

    if (type == dns_rdatatype_any) {
        /*
         * XXXRTH  Need to handle zonecuts with special case
         * code.
         */
        n = 0;
        rdsiter = NULL;
        result = dns_db_allrdatasets(db, node, NULL, 0, &rdsiter);
        if (result != ISC_R_SUCCESS) {
            QUERY_ERROR(DNS_R_SERVFAIL);
            goto cleanup;
        }
        result = dns_rdatasetiter_first(rdsiter);
        while (result == ISC_R_SUCCESS) {
            dns_rdatasetiter_current(rdsiter, rdataset);
            tname = fname;
            query_addrrset(client, &tname, &rdataset, dbuf,
                       DNS_SECTION_ANSWER);
            n++;
            /*
             * We shouldn't ever fail to add 'rdataset' because
             * it's already in the answer.
             */
            INSIST(rdataset == NULL);
            /*
             * We set dbuf to NULL because we only want the
             * query_keepname() call in query_addrrset() to be
             * called once.
             */
            dbuf = NULL;
            result = dns_message_gettemprdataset(client->message,
                                 &rdataset);
            if (result == ISC_R_SUCCESS) {
                dns_rdataset_init(rdataset);
                result = dns_rdatasetiter_next(rdsiter);
            }
        }
        /*
         * If we added at least one RRset, then we must clear fname,
         * otherwise the cleanup code might cause it to be reused.
         */
        if (n > 0)
            fname = NULL;
        dns_rdatasetiter_destroy(&rdsiter);
        if (result != DNS_R_NOMORE) {
            QUERY_ERROR(DNS_R_SERVFAIL);
            goto cleanup;
        }
    } else {
        /*
         * This is the "normal" case -- an ordinary question to which
         * we know the answer.
         */
        query_addrrset(client, &fname, &rdataset, dbuf,
                   DNS_SECTION_ANSWER);
        /*
         * Remember that we've answered this question.
         */
        qrdataset->attributes |= DNS_RDATASETATTR_ANSWERED;
    }

    /*
     * XXXRTH  Handle additional questions above.  Find all the question
     *         types we can from the node we found, and (if recursion is
     *     OK) launch queries for any types we don't have answers to.
     *
     *     Special case:  they make an ANY query as well as some
     *         other type.  Perhaps ANY should be disallowed in a
     *         multiple question query?
     */

 cleanup:
    if (rdataset != NULL) {
        if (rdataset->methods != NULL)
            dns_rdataset_disassociate(rdataset);
        ISC_LIST_APPEND(client->query.tmprdatasets, rdataset, link);
    }
    if (fname != NULL)
        query_releasename(client, &fname);
    if (node != NULL)
        dns_db_detachnode(db, &node);
    if (db != NULL)
        dns_db_detach(&db);

    if (restarts == 0 && !auth) {
        /*
         * We're not authoritative, so we must ensure the AA bit
         * isn't set.
         */
        client->message->flags &= ~DNS_MESSAGEFLAG_AA;
    }

    if (want_restart && restarts < MAX_RESTARTS) {
        restarts++;
        goto restart;
    }

    if (eresult != ISC_R_SUCCESS && !PARTIALANSWER(client))
        ns_client_error(client, eresult);
    else
        ns_client_send(client);
}

/*
 * XXXRTH  Problem areas.
 *
 * If we're authoritative for both a parent and a child, the
 * child is non-secure, and we are asked for the KEY of the
 * nonsecure child, we need to get it from the parent.
 * If we're not auth for the parent, then we have to go
 * looking for it in the cache.  How do we even know who
 * the parent is?  We probably won't find this KEY when doing
 * additional data KEY retrievals, but that's probably OK,
 * since it's a SHOULD not a MUST.  We don't want to be doing
 * tons of work just to fill out additional data.
 *
 * Similar problems occur with NXT queries, since there can
 * be NXT records at a delegation point in both the parent
 * and the child.  RFC 2535 section 5.5 says that on explicit
 * query we should return both, if available.  That seems
 * to imply we shouldn't recurse to get the missing one
 * if only one is available.  Is that right?
 */

void
ns_query_start(ns_client_t *client) {
    isc_result_t result;
    dns_message_t *message = client->message;
    dns_rdataset_t *rdataset;

    /*
     * Ensure that appropriate cleanups occur.
     */
    client->next = query_next;

    /*
     * XXXRTH  Deal with allow-query and allow-recursion here.
     */

    /*
     * If the client doesn't want recursion, turn it off.
     */
    if ((message->flags & DNS_MESSAGEFLAG_RD) == 0)
        client->query.attributes &= ~NS_QUERYATTR_RECURSIONOK;

    /*
     * Get the question name.
     */
    result = dns_message_firstname(message, DNS_SECTION_QUESTION);
    if (result != ISC_R_SUCCESS) {
        ns_client_error(client, result);
        return;
    }
    dns_message_currentname(message, DNS_SECTION_QUESTION,
                &client->query.qname);
    client->query.origqname = client->query.qname;
    result = dns_message_nextname(message, DNS_SECTION_QUESTION);
    if (result != ISC_R_NOMORE) {
        if (result == ISC_R_SUCCESS) {
            /*
             * There's more than one QNAME in the question
             * section.
             */
            ns_client_error(client, DNS_R_FORMERR);
        } else
            ns_client_error(client, result);
        return;
    }

    /*
     * Check for illegal meta-classes and meta-types in
     * multiple question queries (edns1 section 5.1).
     */
    if (message->counts[DNS_SECTION_QUESTION] > 1) {
        if (dns_rdataclass_ismeta(message->rdclass)) {
            ns_client_error(client, DNS_R_FORMERR);
            return;
        }
        for (rdataset = ISC_LIST_HEAD(client->query.qname->list);
             rdataset != NULL;
             rdataset = ISC_LIST_NEXT(rdataset, link)) {
            if (dns_rdatatype_ismeta(rdataset->type)) {
                ns_client_error(client, DNS_R_FORMERR);
                return;
            }
        }
    }

    /*
     * Check for meta-queries like IXFR and AXFR.
     */
    if (message->counts[DNS_SECTION_QUESTION] == 1) {
        rdataset = ISC_LIST_HEAD(client->query.qname->list);
        INSIST(rdataset != NULL);
        if (dns_rdatatype_ismeta(rdataset->type)) {
            switch (rdataset->type) {
            case dns_rdatatype_any:
                break; /* Let query_find handle it. */
            case dns_rdatatype_ixfr:
            case dns_rdatatype_axfr:
#ifdef notyet
                ns_xfr_start(client, rdataset->type);
                return;
#endif
            case dns_rdatatype_maila:
            case dns_rdatatype_mailb:
                ns_client_error(client, DNS_R_NOTIMP);
                return;
            default: /* TSIG, etc. */
                ns_client_error(client, DNS_R_FORMERR);
                return;
            }
        }
    }

    /* This is an ordinary query. */

    result = dns_message_reply(message, ISC_TRUE);
    if (result != ISC_R_SUCCESS) {
        ns_client_next(client, result);
        return;
    }

    /*
     * Assume authoritative response until it is known to be
     * otherwise.
     */
    message->flags |= DNS_MESSAGEFLAG_AA;

    query_find(client);
}