Fix a number of core kernel issues related to HAMMER operation.

[dragonfly.git] / contrib / dhcp-3.0 / common / dns.c

/* dns.c

   Domain Name Service subroutines. */

/*
 * Copyright (c) 2004 by Internet Systems Consortium, Inc. ("ISC")
 * Copyright (c) 2001-2003 by 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 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.
 *
 *   Internet Systems Consortium, Inc.
 *   950 Charter Street
 *   Redwood City, CA 94063
 *   <info@isc.org>
 *   http://www.isc.org/
 *
 * This software has been written for Internet Systems Consortium
 * by Ted Lemon in cooperation with Nominum, Inc.
 * To learn more about Internet Systems Consortium, see
 * ``http://www.isc.org/''.  To learn more about Nominum, Inc., see
 * ``http://www.nominum.com''.
 */

#ifndef lint
static char copyright[] =
"$Id: dns.c,v 1.35.2.16 2004/06/17 20:54:38 dhankins Exp $ Copyright (c) 2004 Internet Systems Consortium.  All rights reserved.\n";
#endif /* not lint */

#include "dhcpd.h"
#include "arpa/nameser.h"
#include "dst/md5.h"

/* This file is kind of a crutch for the BIND 8 nsupdate code, which has
 * itself been cruelly hacked from its original state.   What this code
 * does is twofold: first, it maintains a database of zone cuts that can
 * be used to figure out which server should be contacted to update any
 * given domain name.   Secondly, it maintains a set of named TSIG keys,
 * and associates those keys with zones.   When an update is requested for
 * a particular zone, the key associated with that zone is used for the
 * update.
 *
 * The way this works is that you define the domain name to which an
 * SOA corresponds, and the addresses of some primaries for that domain name:
 *
 *      zone FOO.COM {
 *        primary 10.0.17.1;
 *        secondary 10.0.22.1, 10.0.23.1;
 *        key "FOO.COM Key";
 *      }
 *
 * If an update is requested for GAZANGA.TOPANGA.FOO.COM, then the name
 * server looks in its database for a zone record for "GAZANGA.TOPANGA.FOO.COM",
 * doesn't find it, looks for one for "TOPANGA.FOO.COM", doesn't find *that*,
 * looks for "FOO.COM", finds it. So it
 * attempts the update to the primary for FOO.COM.   If that times out, it
 * tries the secondaries.   You can list multiple primaries if you have some
 * kind of magic name server that supports that.   You shouldn't list
 * secondaries that don't know how to forward updates (e.g., BIND 8 doesn't
 * support update forwarding, AFAIK).   If no TSIG key is listed, the update
 * is attempted without TSIG.
 *
 * The DHCP server tries to find an existing zone for any given name by
 * trying to look up a local zone structure for each domain containing
 * that name, all the way up to '.'.   If it finds one cached, it tries
 * to use that one to do the update.   That's why it tries to update
 * "FOO.COM" above, even though theoretically it should try GAZANGA...
 * and TOPANGA... first.
 *
 * If the update fails with a predefined or cached zone (we'll get to
 * those in a second), then it tries to find a more specific zone.   This
 * is done by looking first for an SOA for GAZANGA.TOPANGA.FOO.COM.   Then
 * an SOA for TOPANGA.FOO.COM is sought.   If during this search a predefined
 * or cached zone is found, the update fails - there's something wrong
 * somewhere.
 *
 * If a more specific zone _is_ found, that zone is cached for the length of
 * its TTL in the same database as that described above.   TSIG updates are
 * never done for cached zones - if you want TSIG updates you _must_
 * write a zone definition linking the key to the zone.   In cases where you
 * know for sure what the key is but do not want to hardcode the IP addresses
 * of the primary or secondaries, a zone declaration can be made that doesn't
 * include any primary or secondary declarations.   When the DHCP server
 * encounters this while hunting up a matching zone for a name, it looks up
 * the SOA, fills in the IP addresses, and uses that record for the update.
 * If the SOA lookup returns NXRRSET, a warning is printed and the zone is
 * discarded, TSIG key and all.   The search for the zone then continues as if
 * the zone record hadn't been found.   Zones without IP addresses don't
 * match when initially hunting for a predefined or cached zone to update.
 *
 * When an update is attempted and no predefined or cached zone is found
 * that matches any enclosing domain of the domain being updated, the DHCP
 * server goes through the same process that is done when the update to a
 * predefined or cached zone fails - starting with the most specific domain
 * name (GAZANGA.TOPANGA.FOO.COM) and moving to the least specific (the root),
 * it tries to look up an SOA record.   When it finds one, it creates a cached
 * zone and attempts an update, and gives up if the update fails.
 *
 * TSIG keys are defined like this:
 *
 *      key "FOO.COM Key" {
 *              algorithm HMAC-MD5.SIG-ALG.REG.INT;
 *              secret <Base64>;
 *      }
 *
 * <Base64> is a number expressed in base64 that represents the key.
 * It's also permissible to use a quoted string here - this will be
 * translated as the ASCII bytes making up the string, and will not
 * include any NUL termination.  The key name can be any text string,
 * and the key type must be one of the key types defined in the draft
 * or by the IANA.  Currently only the HMAC-MD5... key type is
 * supported.
 */

dns_zone_hash_t *dns_zone_hash;

#if defined (NSUPDATE)
isc_result_t find_tsig_key (ns_tsig_key **key, const char *zname,
                            struct dns_zone *zone)
{
        isc_result_t status;
        ns_tsig_key *tkey;

        if (!zone)
                return ISC_R_NOTFOUND;

        if (!zone -> key) {
                return ISC_R_KEY_UNKNOWN;
        }
        
        if ((!zone -> key -> name ||
             strlen (zone -> key -> name) > NS_MAXDNAME) ||
            (!zone -> key -> algorithm ||
             strlen (zone -> key -> algorithm) > NS_MAXDNAME) ||
            (!zone -> key) ||
            (!zone -> key -> key) ||
            (zone -> key -> key -> len == 0)) {
                return ISC_R_INVALIDKEY;
        }
        tkey = dmalloc (sizeof *tkey, MDL);
        if (!tkey) {
              nomem:
                return ISC_R_NOMEMORY;
        }
        memset (tkey, 0, sizeof *tkey);
        tkey -> data = dmalloc (zone -> key -> key -> len, MDL);
        if (!tkey -> data) {
                dfree (tkey, MDL);
                goto nomem;
        }
        strcpy (tkey -> name, zone -> key -> name);
        strcpy (tkey -> alg, zone -> key -> algorithm);
        memcpy (tkey -> data,
                zone -> key -> key -> value, zone -> key -> key -> len);
        tkey -> len = zone -> key -> key -> len;
        *key = tkey;
        return ISC_R_SUCCESS;
}

void tkey_free (ns_tsig_key **key)
{
        if ((*key) -> data)
                dfree ((*key) -> data, MDL);
        dfree ((*key), MDL);
        *key = (ns_tsig_key *)0;
}
#endif

isc_result_t enter_dns_zone (struct dns_zone *zone)
{
        struct dns_zone *tz = (struct dns_zone *)0;

        if (dns_zone_hash) {
                dns_zone_hash_lookup (&tz,
                                      dns_zone_hash, zone -> name, 0, MDL);
                if (tz == zone) {
                        dns_zone_dereference (&tz, MDL);
                        return ISC_R_SUCCESS;
                }
                if (tz) {
                        dns_zone_hash_delete (dns_zone_hash,
                                              zone -> name, 0, MDL);
                        dns_zone_dereference (&tz, MDL);
                }
        } else {
                if (!dns_zone_new_hash (&dns_zone_hash, 1, MDL))
                        return ISC_R_NOMEMORY;
        }
        dns_zone_hash_add (dns_zone_hash, zone -> name, 0, zone, MDL);
        return ISC_R_SUCCESS;
}

isc_result_t dns_zone_lookup (struct dns_zone **zone, const char *name)
{
        struct dns_zone *tz = (struct dns_zone *)0;
        int len;
        char *tname = (char *)0;
        isc_result_t status;

        if (!dns_zone_hash)
                return ISC_R_NOTFOUND;

        len = strlen (name);
        if (name [len - 1] != '.') {
                tname = dmalloc ((unsigned)len + 2, MDL);
                if (!tname)
                        return ISC_R_NOMEMORY;;
                strcpy (tname, name);
                tname [len] = '.';
                tname [len + 1] = 0;
                name = tname;
        }
        if (!dns_zone_hash_lookup (zone, dns_zone_hash, name, 0, MDL))
                status = ISC_R_NOTFOUND;
        else
                status = ISC_R_SUCCESS;

        if (tname)
                dfree (tname, MDL);
        return status;
}

int dns_zone_dereference (ptr, file, line)
        struct dns_zone **ptr;
        const char *file;
        int line;
{
        int i;
        struct dns_zone *dns_zone;

        if (!ptr || !*ptr) {
                log_error ("%s(%d): null pointer", file, line);
#if defined (POINTER_DEBUG)
                abort ();
#else
                return 0;
#endif
        }

        dns_zone = *ptr;
        *ptr = (struct dns_zone *)0;
        --dns_zone -> refcnt;
        rc_register (file, line, ptr, dns_zone, dns_zone -> refcnt, 1, RC_MISC);
        if (dns_zone -> refcnt > 0)
                return 1;

        if (dns_zone -> refcnt < 0) {
                log_error ("%s(%d): negative refcnt!", file, line);
#if defined (DEBUG_RC_HISTORY)
                dump_rc_history (dns_zone);
#endif
#if defined (POINTER_DEBUG)
                abort ();
#else
                return 0;
#endif
        }

        if (dns_zone -> name)
                dfree (dns_zone -> name, file, line);
        if (dns_zone -> key)
                omapi_auth_key_dereference (&dns_zone -> key, file, line);
        if (dns_zone -> primary)
                option_cache_dereference (&dns_zone -> primary, file, line);
        if (dns_zone -> secondary)
                option_cache_dereference (&dns_zone -> secondary, file, line);
        dfree (dns_zone, file, line);
        return 1;
}

#if defined (NSUPDATE)
isc_result_t find_cached_zone (const char *dname, ns_class class,
                               char *zname, size_t zsize,
                               struct in_addr *addrs,
                               int naddrs, int *naddrout,
                               struct dns_zone **zcookie)
{
        isc_result_t status = ISC_R_NOTFOUND;
        const char *np;
        struct dns_zone *zone = (struct dns_zone *)0;
        struct data_string nsaddrs;
        int ix;

        /* The absence of the zcookie pointer indicates that we
           succeeded previously, but the update itself failed, meaning
           that we shouldn't use the cached zone. */
        if (!zcookie)
                return ISC_R_NOTFOUND;

        /* We can't look up a null zone. */
        if (!dname || !*dname)
                return ISC_R_INVALIDARG;

        /* For each subzone, try to find a cached zone. */
        for (np = dname; np; np = strchr (np, '.')) {
                np++;
                status = dns_zone_lookup (&zone, np);
                if (status == ISC_R_SUCCESS)
                        break;
        }

        if (status != ISC_R_SUCCESS)
                return status;

        /* Make sure the zone is valid. */
        if (zone -> timeout && zone -> timeout < cur_time) {
                dns_zone_dereference (&zone, MDL);
                return ISC_R_CANCELED;
        }

        /* Make sure the zone name will fit. */
        if (strlen (zone -> name) > zsize) {
                dns_zone_dereference (&zone, MDL);
                return ISC_R_NOSPACE;
        }
        strcpy (zname, zone -> name);

        memset (&nsaddrs, 0, sizeof nsaddrs);
        ix = 0;

        if (zone -> primary) {
                if (evaluate_option_cache (&nsaddrs, (struct packet *)0,
                                           (struct lease *)0,
                                           (struct client_state *)0,
                                           (struct option_state *)0,
                                           (struct option_state *)0,
                                           &global_scope,
                                           zone -> primary, MDL)) {
                        int ip = 0;
                        while (ix < naddrs) {
                                if (ip + 4 > nsaddrs.len)
                                        break;
                                memcpy (&addrs [ix], &nsaddrs.data [ip], 4);
                                ip += 4;
                                ix++;
                        }
                        data_string_forget (&nsaddrs, MDL);
                }
        }
        if (zone -> secondary) {
                if (evaluate_option_cache (&nsaddrs, (struct packet *)0,
                                           (struct lease *)0,
                                           (struct client_state *)0,
                                           (struct option_state *)0,
                                           (struct option_state *)0,
                                           &global_scope,
                                           zone -> secondary, MDL)) {
                        int ip = 0;
                        while (ix < naddrs) {
                                if (ip + 4 > nsaddrs.len)
                                        break;
                                memcpy (&addrs [ix], &nsaddrs.data [ip], 4);
                                ip += 4;
                                ix++;
                        }
                        data_string_forget (&nsaddrs, MDL);
                }
        }

        /* It's not an error for zcookie to have a value here - actually,
           it's quite likely, because res_nupdate cycles through all the
           names in the update looking for their zones. */
        if (!*zcookie)
                dns_zone_reference (zcookie, zone, MDL);
        dns_zone_dereference (&zone, MDL);
        if (naddrout)
                *naddrout = ix;
        return ISC_R_SUCCESS;
}

void forget_zone (struct dns_zone **zone)
{
        dns_zone_dereference (zone, MDL);
}

void repudiate_zone (struct dns_zone **zone)
{
        /* XXX Currently we're not differentiating between a cached
           XXX zone and a zone that's been repudiated, which means
           XXX that if we reap cached zones, we blow away repudiated
           XXX zones.   This isn't a big problem since we're not yet
           XXX caching zones... :'} */

        (*zone) -> timeout = cur_time - 1;
        dns_zone_dereference (zone, MDL);
}

void cache_found_zone (ns_class class,
                       char *zname, struct in_addr *addrs, int naddrs)
{
        isc_result_t status = ISC_R_NOTFOUND;
        struct dns_zone *zone = (struct dns_zone *)0;
        struct data_string nsaddrs;
        int ix = strlen (zname);

        if (zname [ix - 1] == '.')
                ix = 0;

        /* See if there's already such a zone. */
        if (dns_zone_lookup (&zone, zname) == ISC_R_SUCCESS) {
                /* If it's not a dynamic zone, leave it alone. */
                if (!zone -> timeout)
                        return;
                /* Address may have changed, so just blow it away. */
                if (zone -> primary)
                        option_cache_dereference (&zone -> primary, MDL);
                if (zone -> secondary)
                        option_cache_dereference (&zone -> secondary, MDL);
        } else if (!dns_zone_allocate (&zone, MDL))
                return;

        if (!zone -> name) {
                zone -> name =
                        dmalloc (strlen (zname) + 1 + (ix != 0), MDL);
                if (!zone -> name) {
                        dns_zone_dereference (&zone, MDL);
                        return;
                }
                strcpy (zone -> name, zname);
                /* Add a trailing '.' if it was missing. */
                if (ix) {
                        zone -> name [ix] = '.';
                        zone -> name [ix + 1] = 0;
                }
        }

        /* XXX Need to get the lower-level code to push the actual zone
           XXX TTL up to us. */
        zone -> timeout = cur_time + 1800;
        
        if (!option_cache_allocate (&zone -> primary, MDL)) {
                dns_zone_dereference (&zone, MDL);
                return;
        }
        if (!buffer_allocate (&zone -> primary -> data.buffer,
                              naddrs * sizeof (struct in_addr), MDL)) {
                dns_zone_dereference (&zone, MDL);
                return;
        }
        memcpy (zone -> primary -> data.buffer -> data,
                addrs, naddrs * sizeof *addrs);
        zone -> primary -> data.data =
                &zone -> primary -> data.buffer -> data [0];
        zone -> primary -> data.len = naddrs * sizeof *addrs;

        enter_dns_zone (zone);
}

/* Have to use TXT records for now. */
#define T_DHCID T_TXT

int get_dhcid (struct data_string *id,
               int type, const u_int8_t *data, unsigned len)
{
        unsigned char buf[MD5_DIGEST_LENGTH];
        MD5_CTX md5;
        int i;

        /* Types can only be 0..(2^16)-1. */
        if (type < 0 || type > 65535)
                return 0;

        /* Hexadecimal MD5 digest plus two byte type and NUL. */
        if (!buffer_allocate (&id -> buffer,
                              (MD5_DIGEST_LENGTH * 2) + 3, MDL))
                return 0;
        id -> data = id -> buffer -> data;

        /*
         * DHCP clients and servers should use the following forms of client
         * identification, starting with the most preferable, and finishing
         * with the least preferable.  If the client does not send any of these
         * forms of identification, the DHCP/DDNS interaction is not defined by
         * this specification.  The most preferable form of identification is
         * the Globally Unique Identifier Option [TBD].  Next is the DHCP
         * Client Identifier option.  Last is the client's link-layer address,
         * as conveyed in its DHCPREQUEST message.  Implementors should note
         * that the link-layer address cannot be used if there are no
         * significant bytes in the chaddr field of the DHCP client's request,
         * because this does not constitute a unique identifier.
         *   -- "Interaction between DHCP and DNS"
         *      <draft-ietf-dhc-dhcp-dns-12.txt>
         *      M. Stapp, Y. Rekhter
         */

        /* Put the type in the first two bytes. */
        id -> buffer -> data [0] = "0123456789abcdef" [type >> 4];
        id -> buffer -> data [1] = "0123456789abcdef" [type % 15];

        /* Mash together an MD5 hash of the identifier. */
        MD5_Init (&md5);
        MD5_Update (&md5, data, len);
        MD5_Final (buf, &md5);

        /* Convert into ASCII. */
        for (i = 0; i < MD5_DIGEST_LENGTH; i++) {
                id -> buffer -> data [i * 2 + 2] =
                        "0123456789abcdef" [(buf [i] >> 4) & 0xf];
                id -> buffer -> data [i * 2 + 3] =
                        "0123456789abcdef" [buf [i] & 0xf];
        }
        id -> len = MD5_DIGEST_LENGTH * 2 + 2;
        id -> buffer -> data [id -> len] = 0;
        id -> terminated = 1;

        return 1;
}

/* Now for the DDNS update code that is shared between client and
   server... */

isc_result_t ddns_update_a (struct data_string *ddns_fwd_name,
                            struct iaddr ddns_addr,
                            struct data_string *ddns_dhcid,
                            unsigned long ttl, int rrsetp)
{
        ns_updque updqueue;
        ns_updrec *updrec;
        isc_result_t result;
        char ddns_address [16];

        if (ddns_addr.len != 4)
                return ISC_R_INVALIDARG;

        /* %Audit% Cannot exceed 16 bytes. %2004.06.17,Safe% */
        sprintf (ddns_address, "%u.%u.%u.%u",
                  ddns_addr.iabuf[0], ddns_addr.iabuf[1],
                  ddns_addr.iabuf[2], ddns_addr.iabuf[3]);

        /*
         * When a DHCP client or server intends to update an A RR, it first
         * prepares a DNS UPDATE query which includes as a prerequisite the
         * assertion that the name does not exist.  The update section of the
         * query attempts to add the new name and its IP address mapping (an A
         * RR), and the DHCID RR with its unique client-identity.
         *   -- "Interaction between DHCP and DNS"
         */

        ISC_LIST_INIT (updqueue);

        /*
         * A RR does not exist.
         */
        updrec = minires_mkupdrec (S_PREREQ,
                                   (const char *)ddns_fwd_name -> data,
                                   C_IN, T_A, 0);
        if (!updrec) {
                result = ISC_R_NOMEMORY;
                goto error;
        }

        updrec -> r_data = (unsigned char *)0;
        updrec -> r_size = 0;
        updrec -> r_opcode = rrsetp ? NXRRSET : NXDOMAIN;

        ISC_LIST_APPEND (updqueue, updrec, r_link);


        /*
         * Add A RR.
         */
        updrec = minires_mkupdrec (S_UPDATE,
                                   (const char *)ddns_fwd_name -> data,
                                   C_IN, T_A, ttl);
        if (!updrec) {
                result = ISC_R_NOMEMORY;
                goto error;
        }

        updrec -> r_data = (unsigned char *)ddns_address;
        updrec -> r_size = strlen (ddns_address);
        updrec -> r_opcode = ADD;

        ISC_LIST_APPEND (updqueue, updrec, r_link);


        /*
         * Add DHCID RR.
         */
        updrec = minires_mkupdrec (S_UPDATE,
                                   (const char *)ddns_fwd_name -> data,
                                   C_IN, T_DHCID, ttl);
        if (!updrec) {
                result = ISC_R_NOMEMORY;
                goto error;
        }

        updrec -> r_data = ddns_dhcid -> data;
        updrec -> r_size = ddns_dhcid -> len;
        updrec -> r_opcode = ADD;

        ISC_LIST_APPEND (updqueue, updrec, r_link);


        /*
         * Attempt to perform the update.
         */
        result = minires_nupdate (&resolver_state, ISC_LIST_HEAD (updqueue));

#ifdef DEBUG_DNS_UPDATES
        print_dns_status ((int)result, &updqueue);
#endif

        /*
         * If this update operation succeeds, the updater can conclude that it
         * has added a new name whose only RRs are the A and DHCID RR records.
         * The A RR update is now complete (and a client updater is finished,
         * while a server might proceed to perform a PTR RR update).
         *   -- "Interaction between DHCP and DNS"
         */

        if (result == ISC_R_SUCCESS) {
                log_info ("Added new forward map from %.*s to %s",
                          (int)ddns_fwd_name -> len,
                          (const char *)ddns_fwd_name -> data, ddns_address);
                goto error;
        }


        /*
         * If the first update operation fails with YXDOMAIN, the updater can
         * conclude that the intended name is in use.  The updater then
         * attempts to confirm that the DNS name is not being used by some
         * other host. The updater prepares a second UPDATE query in which the
         * prerequisite is that the desired name has attached to it a DHCID RR
         * whose contents match the client identity.  The update section of
         * this query deletes the existing A records on the name, and adds the
         * A record that matches the DHCP binding and the DHCID RR with the
         * client identity.
         *   -- "Interaction between DHCP and DNS"
         */

        if (result != (rrsetp ? ISC_R_YXRRSET : ISC_R_YXDOMAIN)) {
                log_error ("Unable to add forward map from %.*s to %s: %s",
                           (int)ddns_fwd_name -> len,
                           (const char *)ddns_fwd_name -> data, ddns_address,
                           isc_result_totext (result));
                goto error;
        }

        while (!ISC_LIST_EMPTY (updqueue)) {
                updrec = ISC_LIST_HEAD (updqueue);
                ISC_LIST_UNLINK (updqueue, updrec, r_link);
                minires_freeupdrec (updrec);
        }

        /*
         * DHCID RR exists, and matches client identity.
         */
        updrec = minires_mkupdrec (S_PREREQ,
                                   (const char *)ddns_fwd_name -> data,
                                   C_IN, T_DHCID, 0);
        if (!updrec) {
                result = ISC_R_NOMEMORY;
                goto error;
        }

        updrec -> r_data = ddns_dhcid -> data;
        updrec -> r_size = ddns_dhcid -> len;
        updrec -> r_opcode = YXRRSET;

        ISC_LIST_APPEND (updqueue, updrec, r_link);


        /*
         * Delete A RRset.
         */
        updrec = minires_mkupdrec (S_UPDATE,
                                   (const char *)ddns_fwd_name -> data,
                                   C_IN, T_A, 0);
        if (!updrec) {
                result = ISC_R_NOMEMORY;
                goto error;
        }

        updrec -> r_data = (unsigned char *)0;
        updrec -> r_size = 0;
        updrec -> r_opcode = DELETE;

        ISC_LIST_APPEND (updqueue, updrec, r_link);


        /*
         * Add A RR.
         */
        updrec = minires_mkupdrec (S_UPDATE,
                                   (const char *)ddns_fwd_name -> data,
                                   C_IN, T_A, ttl);
        if (!updrec) {
                result = ISC_R_NOMEMORY;
                goto error;
        }

        updrec -> r_data = (unsigned char *)ddns_address;
        updrec -> r_size = strlen (ddns_address);
        updrec -> r_opcode = ADD;

        ISC_LIST_APPEND (updqueue, updrec, r_link);


        /*
         * Attempt to perform the update.
         */
        result = minires_nupdate (&resolver_state, ISC_LIST_HEAD (updqueue));

        if (result != ISC_R_SUCCESS) {
                if (result == YXRRSET || result == YXDOMAIN ||
                    result == NXRRSET || result == NXDOMAIN)
                        log_error ("Forward map from %.*s to %s already in use",
                                   (int)ddns_fwd_name -> len,
                                   (const char *)ddns_fwd_name -> data,
                                   ddns_address);
                else
                        log_error ("Can't update forward map %.*s to %s: %s",
                                   (int)ddns_fwd_name -> len,
                                   (const char *)ddns_fwd_name -> data,
                                   ddns_address, isc_result_totext (result));

        } else {
                log_info ("Added new forward map from %.*s to %s",
                          (int)ddns_fwd_name -> len,
                          (const char *)ddns_fwd_name -> data, ddns_address);
        }
#if defined (DEBUG_DNS_UPDATES)
        print_dns_status ((int)result, &updqueue);
#endif

        /*
         * If this query succeeds, the updater can conclude that the current
         * client was the last client associated with the domain name, and that
         * the name now contains the updated A RR. The A RR update is now
         * complete (and a client updater is finished, while a server would
         * then proceed to perform a PTR RR update).
         *   -- "Interaction between DHCP and DNS"
         */

        /*
         * If the second query fails with NXRRSET, the updater must conclude
         * that the client's desired name is in use by another host.  At this
         * juncture, the updater can decide (based on some administrative
         * configuration outside of the scope of this document) whether to let
         * the existing owner of the name keep that name, and to (possibly)
         * perform some name disambiguation operation on behalf of the current
         * client, or to replace the RRs on the name with RRs that represent
         * the current client. If the configured policy allows replacement of
         * existing records, the updater submits a query that deletes the
         * existing A RR and the existing DHCID RR, adding A and DHCID RRs that
         * represent the IP address and client-identity of the new client.
         *   -- "Interaction between DHCP and DNS"
         */

  error:
        while (!ISC_LIST_EMPTY (updqueue)) {
                updrec = ISC_LIST_HEAD (updqueue);
                ISC_LIST_UNLINK (updqueue, updrec, r_link);
                minires_freeupdrec (updrec);
        }

        return result;
}

isc_result_t ddns_remove_a (struct data_string *ddns_fwd_name,
                            struct iaddr ddns_addr,
                            struct data_string *ddns_dhcid)
{
        ns_updque updqueue;
        ns_updrec *updrec;
        isc_result_t result = SERVFAIL;
        char ddns_address [16];

        if (ddns_addr.len != 4)
                return ISC_R_INVALIDARG;

        /* %Audit% Cannot exceed 16 bytes. %2004.06.17,Safe% */
        sprintf (ddns_address, "%u.%u.%u.%u",
                  ddns_addr.iabuf[0], ddns_addr.iabuf[1],
                  ddns_addr.iabuf[2], ddns_addr.iabuf[3]);

        /*
         * The entity chosen to handle the A record for this client (either the
         * client or the server) SHOULD delete the A record that was added when
         * the lease was made to the client.
         *
         * In order to perform this delete, the updater prepares an UPDATE
         * query which contains two prerequisites.  The first prerequisite
         * asserts that the DHCID RR exists whose data is the client identity
         * described in Section 4.3. The second prerequisite asserts that the
         * data in the A RR contains the IP address of the lease that has
         * expired or been released.
         *   -- "Interaction between DHCP and DNS"
         */

        ISC_LIST_INIT (updqueue);

        /*
         * DHCID RR exists, and matches client identity.
         */
        updrec = minires_mkupdrec (S_PREREQ,
                                   (const char *)ddns_fwd_name -> data,
                                   C_IN, T_DHCID,0);
        if (!updrec) {
                result = ISC_R_NOMEMORY;
                goto error;
        }

        updrec -> r_data = ddns_dhcid -> data;
        updrec -> r_size = ddns_dhcid -> len;
        updrec -> r_opcode = YXRRSET;

        ISC_LIST_APPEND (updqueue, updrec, r_link);


        /*
         * A RR matches the expiring lease.
         */
        updrec = minires_mkupdrec (S_PREREQ,
                                   (const char *)ddns_fwd_name -> data,
                                   C_IN, T_A, 0);
        if (!updrec) {
                result = ISC_R_NOMEMORY;
                goto error;
        }

        updrec -> r_data = (unsigned char *)ddns_address;
        updrec -> r_size = strlen (ddns_address);
        updrec -> r_opcode = YXRRSET;

        ISC_LIST_APPEND (updqueue, updrec, r_link);


        /*
         * Delete appropriate A RR.
         */
        updrec = minires_mkupdrec (S_UPDATE,
                                   (const char *)ddns_fwd_name -> data,
                                   C_IN, T_A, 0);
        if (!updrec) {
                result = ISC_R_NOMEMORY;
                goto error;
        }

        updrec -> r_data = (unsigned char *)ddns_address;
        updrec -> r_size = strlen (ddns_address);
        updrec -> r_opcode = DELETE;

        ISC_LIST_APPEND (updqueue, updrec, r_link);

        /*
         * Attempt to perform the update.
         */
        result = minires_nupdate (&resolver_state, ISC_LIST_HEAD (updqueue));
        print_dns_status ((int)result, &updqueue);

        /*
         * If the query fails, the updater MUST NOT delete the DNS name.  It
         * may be that the host whose lease on the server has expired has moved
         * to another network and obtained a lease from a different server,
         * which has caused the client's A RR to be replaced. It may also be
         * that some other client has been configured with a name that matches
         * the name of the DHCP client, and the policy was that the last client
         * to specify the name would get the name.  In this case, the DHCID RR
         * will no longer match the updater's notion of the client-identity of
         * the host pointed to by the DNS name.
         *   -- "Interaction between DHCP and DNS"
         */

        if (result != ISC_R_SUCCESS) {
                /* If the rrset isn't there, we didn't need to do the
                   delete, which is success. */
                if (result == ISC_R_NXRRSET || result == ISC_R_NXDOMAIN)
                        result = ISC_R_SUCCESS; 
                goto error;
        }

        while (!ISC_LIST_EMPTY (updqueue)) {
                updrec = ISC_LIST_HEAD (updqueue);
                ISC_LIST_UNLINK (updqueue, updrec, r_link);
                minires_freeupdrec (updrec);
        }

        /* If the deletion of the A succeeded, and there are no A records
           left for this domain, then we can blow away the DHCID record
           as well.   We can't blow away the DHCID record above because
           it's possible that more than one A has been added to this
           domain name. */
        ISC_LIST_INIT (updqueue);

        /*
         * A RR does not exist.
         */
        updrec = minires_mkupdrec (S_PREREQ,
                                   (const char *)ddns_fwd_name -> data,
                                   C_IN, T_A, 0);
        if (!updrec) {
                result = ISC_R_NOMEMORY;
                goto error;
        }

        updrec -> r_data = (unsigned char *)0;
        updrec -> r_size = 0;
        updrec -> r_opcode = NXRRSET;

        ISC_LIST_APPEND (updqueue, updrec, r_link);

        /*
         * Delete appropriate DHCID RR.
         */
        updrec = minires_mkupdrec (S_UPDATE,
                                  (const char *)ddns_fwd_name -> data,
                                   C_IN, T_DHCID, 0);
        if (!updrec) {
                result = ISC_R_NOMEMORY;
                goto error;
        }

        updrec -> r_data = ddns_dhcid -> data;
        updrec -> r_size = ddns_dhcid -> len;
        updrec -> r_opcode = DELETE;

        ISC_LIST_APPEND (updqueue, updrec, r_link);

        /*
         * Attempt to perform the update.
         */
        result = minires_nupdate (&resolver_state, ISC_LIST_HEAD (updqueue));
        print_dns_status ((int)result, &updqueue);

        /* Fall through. */
  error:

        while (!ISC_LIST_EMPTY (updqueue)) {
                updrec = ISC_LIST_HEAD (updqueue);
                ISC_LIST_UNLINK (updqueue, updrec, r_link);
                minires_freeupdrec (updrec);
        }

        return result;
}


#endif /* NSUPDATE */

HASH_FUNCTIONS (dns_zone, const char *, struct dns_zone, dns_zone_hash_t,
                dns_zone_reference, dns_zone_dereference)