[thirdparty/dhcp.git] / common / dns.c

/* dns.c

   Domain Name Service subroutines. */

/*
 * Copyright (c) 2004-2019 by Internet Systems Consortium, Inc. ("ISC")
 * Copyright (c) 2001-2003 by Internet Software Consortium
 *
 * This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/.
 *
 * 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.
 *   PO Box 360
 *   Newmarket, NH 03857 USA
 *   <info@isc.org>
 *   https://www.isc.org/
 *
 */

/*! \file common/dns.c
 */
#include "dhcpd.h"
#include "arpa/nameser.h"
#include <isc/md5.h>
#include <isc/sha2.h>
#include <dns/result.h>

/*
 * This file contains code to connect the DHCP code to the libdns modules.
 * As part of that function 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.  Included in the zone information may be a pointer
 * to a key in which case that key is used for the update.  If no zone
 * is found then the DNS code determines the zone on its own.
 *
 * 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.
 *
 * You can also include IPv6 addresses via the primary6 and secondary6
 * options.  The search order for the addresses is primary, primary6,
 * secondary and lastly secondary6, with a limit on the number of
 * addresses used.  Currently this limit is 3.
 *
 * 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 zone the zone is marked as bad
 * and another search of the predefined zones is done.  If no predefined
 * zone is found finding a zone is left to the DNS module via examination
 * of SOA records.  If the DNS module finds a zone it may cache the zone
 * but the zone won't be cached here.
 *
 * TSIG updates are not performed on zones found by the DNS module - 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 zone to update.
 *
 * When an update is attempted and no predefined 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 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.
 *
 * 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.
 *
 * The DDNS processing has been split into two areas.  One is the
 * control code that determines what should be done.  That code is found
 * in the client or server directories.  The other is the common code
 * that performs functions such as properly formatting the arguments.
 * That code is found in this file.  The basic processing flow for a
 * DDNS update is:
 * In the client or server code determine what needs to be done and
 * collect the necesary information then pass it to a function from
 * this file.
 * In this code lookup the zone and extract the zone and key information
 * (if available) and prepare the arguments for the DNS module.
 * When the DNS module completes its work (times out or gets a reply)
 * it will trigger another function here which does generic processing
 * and then passes control back to the code from the server or client.
 * The server or client code then determines the next step which may
 * result in another call to this module in which case the process repeats.
 */

dns_zone_hash_t *dns_zone_hash;

/*
 * DHCP dns structures
 * Normally the relationship between these structures isn't one to one
 * but in the DHCP case it (mostly) is.  To make the allocations, frees,
 * and passing of the memory easier we make a single structure with all
 * the pieces.
 *
 * The maximum size of the data buffer should be large enough for any
 * items DHCP will generate
 */

typedef struct dhcp_ddns_rdata {
        dns_rdata_t     rdata;
        dns_rdatalist_t rdatalist;
        dns_rdataset_t  rdataset;
} dhcp_ddns_data_t;

/* Function pointer type for functions which build DDNS update contents */
typedef isc_result_t (*builder_func_t)(dhcp_ddns_cb_t *ddns_cb,
                                        dhcp_ddns_data_t *dataspace,
                                        dns_name_t *pname, dns_name_t *uname);

#if defined (NSUPDATE)
#if defined (DNS_ZONE_LOOKUP)

/*
 * The structure used to find a nameserver if there wasn't a zone entry.
 * Currently we assume we won't have many of these outstanding at any
 * time so we go with a simple linked list.
 * In use find_zone_start() will fill in the oname with the name
 * requested by the DDNS code.  zname will point to it and be
 * advanced as labels are removed.  If the DNS client code returns
 * a set of name servers eventp and rdataset will be set.  Then
 * the code will walk through the nameservers in namelist and
 * find addresses that are stored in addrs and addrs6.
 */

typedef struct dhcp_ddns_ns {
        struct dhcp_ddns_ns *next;
        struct data_string oname;     /* the original name for DDNS */
        char *zname;                  /* a pointer into the original name for
                                         the zone we are checking */
        dns_clientresevent_t *eventp; /* pointer to the event that provided the
                                         namelist, we can't free the eventp
                                         until we free the namelist */
        dns_name_t *ns_name;          /* current name server we are examining */
        dns_rdataset_t *rdataset;
        dns_rdatatype_t rdtype;       /* type of address we want */

        struct in_addr addrs[DHCP_MAXNS];   /* space for v4 addresses */
        struct in6_addr addrs6[DHCP_MAXNS]; /* space for v6 addresses */
        int num_addrs;
        int num_addrs6;
        int ttl;

        void *transaction;             /* transaction id for DNS calls */
} dhcp_ddns_ns_t;

/*
 * The list of DDNS names for which we are attempting to find a name server.
 * This list is used for finding the name server, it doesn't include the
 * information necessary to do the DDNS request after finding a name server.
 * The code attempts to minimize duplicate requests by examining the list
 * to see if we are already trying to find a substring of the new request.
 * For example imagine the first request is "a.b.c.d.e." and the server has
 * already discarded the first two lables and is trying "c.d.e.".  If the
 * next request is for "x.y.c.d.e." the code assumes the in progress
 * request is sufficient and doesn't add a new request for the second name.
 * If the next request was for "x.y.z.d.e." the code doesn't assume they
 * will use the same nameserver and starts a second request.
 * This strategy will not eliminate all duplicates but is simple and
 * should be sufficient.
 */
dhcp_ddns_ns_t *dns_outstanding_ns = NULL;

/*
 * Routines to manipulate the list of outstanding searches
 *
 * add_to_ns_queue() - adds the given control block to the queue
 *
 * remove_from_ns_queue() - removes the given control block from
 * the queue
 *
 * find_in_ns_queue() compares the name from the given control
 * block with the control blocks in the queue.  It returns
 * success if a matching entry is found.  In order to match
 * the entry already on the queue must be shorter than the
 * incoming name must match the ending substring of the name.
 */

void
add_to_ns_queue(dhcp_ddns_ns_t *ns_cb)
{
        ns_cb->next = dns_outstanding_ns;
        dns_outstanding_ns = ns_cb;
}


void
remove_from_ns_queue(dhcp_ddns_ns_t *ns_cb)
{
        dhcp_ddns_ns_t **foo;

        foo = &dns_outstanding_ns;
        while (*foo) {
                if (*foo == ns_cb) {
                        *foo = ns_cb->next;
                        break;
                }
                foo = &((*foo)->next);
        }
        ns_cb->next = NULL;
}

isc_result_t
find_in_ns_queue(dhcp_ddns_ns_t *ns_cb)
{
        dhcp_ddns_ns_t *temp_cb;
        int in_len, temp_len;

        in_len = strlen(ns_cb->zname);

        for(temp_cb = dns_outstanding_ns;
            temp_cb != NULL;
            temp_cb = temp_cb->next) {
                temp_len = strlen(temp_cb->zname);
                if (temp_len > in_len)
                        continue;
                if (strcmp(temp_cb->zname,
                           ns_cb->zname + (in_len - temp_len)) == 0)
                        return(ISC_R_SUCCESS);
        }
        return(ISC_R_NOTFOUND);
}

void cache_found_zone (dhcp_ddns_ns_t *);
#endif

void ddns_interlude(isc_task_t *, isc_event_t *);

#if defined (TRACING)
/*
 * Code to support tracing DDNS packets.  We trace packets going to and
 * coming from the libdns code but don't try to track the packets
 * exchanged between the libdns code and the dns server(s) it contacts.
 *
 * The code is split into two sets of routines
 *  input refers to messages received from the dns module
 *  output refers to messages sent to the dns module
 * Currently there are three routines in each set
 *  write is used to write information about the message to the trace file
 *        this routine is called directly from the proper place in the code.
 *  read is used to read information about a message from the trace file
 *       this routine is called from the trace loop as it reads through
 *       the file and is registered via the trace_type_register routine.
 *       When playing back a trace file we shall absorb records of output
 *       messages as part of processing the write function, therefore
 *       any output messages we encounter are flagged as errors.
 *  stop isn't currently used in this code but is needed for the register
 *       routine.
 *
 * We pass a pointer to a control block to the dns module which it returns
 * to use as part of the result.  As the pointer may vary between traces
 * we need to map between those from the trace file and the new ones during
 * playback.
 *
 * The mapping is complicated a little as a pointer could be 4 or 8 bytes
 * long.  We treat the old pointer as an 8 byte quantity and pad and compare
 * as necessary.
 */

/*
 * Structure used to map old pointers to new pointers.
 * Old pointers are 8 bytes long as we don't know if the trace was
 * done on a 64 bit or 32 bit machine.
 */
#define TRACE_PTR_LEN 8

typedef struct dhcp_ddns_map {
        char  old_pointer[TRACE_PTR_LEN];
        void *new_pointer;
        struct dhcp_ddns_map *next;
} dhcp_ddns_map_t;

/* The starting point for the map structure */
static dhcp_ddns_map_t *ddns_map;

trace_type_t *trace_ddns_input;
trace_type_t *trace_ddns_output;

/*
 * The data written to the trace file is:
 * 32 bits result from dns
 * 64 bits pointer of cb
 */

void
trace_ddns_input_write(dhcp_ddns_cb_t *ddns_cb, isc_result_t result)
{
        trace_iov_t iov[2];
        u_int32_t old_result;
        char old_pointer[TRACE_PTR_LEN];

        old_result = htonl((u_int32_t)result);
        memset(old_pointer, 0, TRACE_PTR_LEN);
        memcpy(old_pointer, &ddns_cb, sizeof(ddns_cb));

        iov[0].len = sizeof(old_result);
        iov[0].buf = (char *)&old_result;
        iov[1].len = TRACE_PTR_LEN;
        iov[1].buf = old_pointer;
        trace_write_packet_iov(trace_ddns_input, 2, iov, MDL);
}

/*
 * Process the result and pointer from the trace file.
 * We use the pointer map to find the proper pointer for this instance.
 * Then we need to construct an event to pass along to the interlude
 * function.
 */
static void
trace_ddns_input_read(trace_type_t *ttype, unsigned length,
                                  char *buf)
{
        u_int32_t old_result;
        char old_pointer[TRACE_PTR_LEN];
        dns_clientupdateevent_t *eventp;
        void *new_pointer;
        dhcp_ddns_map_t *ddns_map_ptr;

        if (length < (sizeof(old_result) + TRACE_PTR_LEN)) {
                log_error("trace_ddns_input_read: data too short");
                return;
        }

        memcpy(&old_result, buf, sizeof(old_result));
        memcpy(old_pointer, buf + sizeof(old_result), TRACE_PTR_LEN);

        /* map the old pointer to a new pointer */
        for (ddns_map_ptr = ddns_map;
             ddns_map_ptr != NULL;
             ddns_map_ptr = ddns_map_ptr->next) {
                if ((ddns_map_ptr->new_pointer != NULL) &&
                    memcmp(ddns_map_ptr->old_pointer,
                           old_pointer, TRACE_PTR_LEN) == 0) {
                        new_pointer = ddns_map_ptr->new_pointer;
                        ddns_map_ptr->new_pointer = NULL;
                        memset(ddns_map_ptr->old_pointer, 0, TRACE_PTR_LEN);
                        break;
                }
        }
        if (ddns_map_ptr == NULL) {
                log_error("trace_dns_input_read: unable to map cb pointer");
                return;
        }

        eventp = (dns_clientupdateevent_t *)
                isc_event_allocate(dhcp_gbl_ctx.mctx,
                                   dhcp_gbl_ctx.task,
                                   0,
                                   ddns_interlude,
                                   new_pointer,
                                   sizeof(dns_clientupdateevent_t));
        if (eventp == NULL) {
                log_error("trace_ddns_input_read: unable to allocate event");
                return;
        }
        eventp->result = ntohl(old_result);


        ddns_interlude(dhcp_gbl_ctx.task, (isc_event_t *)eventp);

        return;
}

static void
trace_ddns_input_stop(trace_type_t *ttype)
{
}

/*
 * We use the same arguments as for the dns startupdate function to
 * allows us to choose between the two via a macro.  If tracing isn't
 * in use we simply call the dns function directly.
 *
 * If we are doing playback we read the next packet from the file
 * and compare the type.  If it matches we extract the results and pointer
 * from the trace file.  The results are returned to the caller as if
 * they had called the dns routine.  The pointer is used to construct a
 * map for when the "reply" is processed.
 *
 * The data written to trace file is:
 * 32 bits result
 * 64 bits pointer of cb (DDNS Control block)
 * contents of cb
 */

isc_result_t
trace_ddns_output_write(dns_client_t *client, dns_rdataclass_t rdclass,
                        dns_name_t *zonename, dns_namelist_t *prerequisites,
                        dns_namelist_t *updates, isc_sockaddrlist_t *servers,
                        dns_tsec_t *tsec, unsigned int options,
                        isc_task_t *task, isc_taskaction_t action, void *arg,
                        dns_clientupdatetrans_t **transp)
{
        isc_result_t result;
        u_int32_t old_result;
        char old_pointer[TRACE_PTR_LEN];
        dhcp_ddns_map_t *ddns_map_ptr;

        if (trace_playback() != 0) {
                /* We are doing playback, extract the entry from the file */
                unsigned buflen = 0;
                char *inbuf = NULL;

                result = trace_get_packet(&trace_ddns_output,
                                          &buflen, &inbuf);
                if (result != ISC_R_SUCCESS) {
                        log_error("trace_ddns_output_write: no input found");
                        return (ISC_R_FAILURE);
                }
                if (buflen < (sizeof(old_result) + TRACE_PTR_LEN)) {
                        log_error("trace_ddns_output_write: data too short");
                        dfree(inbuf, MDL);
                        return (ISC_R_FAILURE);
                }
                memcpy(&old_result, inbuf, sizeof(old_result));
                result = ntohl(old_result);
                memcpy(old_pointer, inbuf + sizeof(old_result), TRACE_PTR_LEN);
                dfree(inbuf, MDL);

                /* add the pointer to the pointer map */
                for (ddns_map_ptr = ddns_map;
                     ddns_map_ptr != NULL;
                     ddns_map_ptr = ddns_map_ptr->next) {
                        if (ddns_map_ptr->new_pointer == NULL) {
                                break;
                        }
                }

                /*
                 * If we didn't find an empty entry, allocate an entry and
                 * link it into the list.  The list isn't ordered.
                 */
                if (ddns_map_ptr == NULL) {
                        ddns_map_ptr = dmalloc(sizeof(*ddns_map_ptr), MDL);
                        if (ddns_map_ptr == NULL) {
                                log_error("trace_ddns_output_write: "
                                          "unable to allocate map entry");
                                return(ISC_R_FAILURE);
                                }
                        ddns_map_ptr->next = ddns_map;
                        ddns_map = ddns_map_ptr;
                }

                memcpy(ddns_map_ptr->old_pointer, old_pointer, TRACE_PTR_LEN);
                ddns_map_ptr->new_pointer = arg;
        }
        else {
                /* We aren't doing playback, make the actual call */
                result = dns_client_startupdate(client, rdclass, zonename,
                                                prerequisites, updates,
                                                servers, tsec, options,
                                                task, action, arg, transp);
        }

        if (trace_record() != 0) {
                /* We are recording, save the information to the file */
                trace_iov_t iov[3];
                old_result = htonl((u_int32_t)result);
                memset(old_pointer, 0, TRACE_PTR_LEN);
                memcpy(old_pointer, &arg, sizeof(arg));
                iov[0].len = sizeof(old_result);
                iov[0].buf = (char *)&old_result;
                iov[1].len = TRACE_PTR_LEN;
                iov[1].buf = old_pointer;

                /* Write out the entire cb, in case we want to look at it */
                iov[2].len = sizeof(dhcp_ddns_cb_t);
                iov[2].buf = (char *)arg;

                trace_write_packet_iov(trace_ddns_output, 3, iov, MDL);
        }

        return(result);
}

static void
trace_ddns_output_read(trace_type_t *ttype, unsigned length,
                                   char *buf)
{
        log_error("unaccounted for ddns output.");
}

static void
trace_ddns_output_stop(trace_type_t *ttype)
{
}

void
trace_ddns_init()
{
        trace_ddns_output = trace_type_register("ddns-output", NULL,
                                                trace_ddns_output_read,
                                                trace_ddns_output_stop, MDL);
        trace_ddns_input  = trace_type_register("ddns-input", NULL,
                                                trace_ddns_input_read,
                                                trace_ddns_input_stop, MDL);
        ddns_map = NULL;
}

#define ddns_update trace_ddns_output_write
#else
#define ddns_update dns_client_startupdate
#endif /* TRACING */

#define zone_resolve dns_client_startresolve

/*
 * Code to allocate and free a dddns control block.  This block is used
 * to pass and track the information associated with a DDNS update request.
 */
dhcp_ddns_cb_t *
ddns_cb_alloc(const char *file, int line)
{
        dhcp_ddns_cb_t *ddns_cb;
        int i;

        ddns_cb = dmalloc(sizeof(*ddns_cb), file, line);
        if (ddns_cb != NULL) {
                ISC_LIST_INIT(ddns_cb->zone_server_list);
                for (i = 0; i < DHCP_MAXNS; i++) {
                        ISC_LINK_INIT(&ddns_cb->zone_addrs[i], link);
                }
        }

#if defined (DEBUG_DNS_UPDATES)
        log_info("%s(%d): Allocating ddns_cb=%p", file, line, ddns_cb);
#endif

        return(ddns_cb);
}

void
ddns_cb_free(dhcp_ddns_cb_t *ddns_cb, const char *file, int line)
{
#if defined (DEBUG_DNS_UPDATES)
        log_info("%s(%d): freeing ddns_cb=%p", file, line, ddns_cb);
#endif

        data_string_forget(&ddns_cb->fwd_name, file, line);
        data_string_forget(&ddns_cb->rev_name, file, line);
        data_string_forget(&ddns_cb->dhcid, file, line);

        if (ddns_cb->zone != NULL) {
                forget_zone((struct dns_zone **)&ddns_cb->zone);
        }

        /* Should be freed by now, check just in case. */
        if (ddns_cb->transaction != NULL) {
                log_error("Impossible memory leak at %s:%d (attempt to free "
                          "DDNS Control Block before transaction).", MDL);
        }

        /* Should be freed by now, check just in case. */
        if (ddns_cb->fixed6_ia) {
                log_error("Possible memory leak at %s:%d (attempt to free "
                          "DDNS Control Block before fxed6_ia).", MDL);
        }

        dfree(ddns_cb, file, line);
}

void
ddns_cb_forget_zone(dhcp_ddns_cb_t *ddns_cb)
{
        int i;

        forget_zone(&ddns_cb->zone);
        ddns_cb->zone_name[0] = 0;
        ISC_LIST_INIT(ddns_cb->zone_server_list);
        for (i = 0; i < DHCP_MAXNS; i++) {
                ISC_LINK_INIT(&ddns_cb->zone_addrs[i], link);
        }
}
#endif

isc_result_t remove_dns_zone (struct dns_zone *zone)
{
        struct dns_zone *tz = NULL;

        if (dns_zone_hash) {
                dns_zone_hash_lookup(&tz, dns_zone_hash, zone->name, 0, MDL);
                if (tz != NULL) {
                        dns_zone_hash_delete(dns_zone_hash, tz->name, 0, MDL);
                        dns_zone_dereference(&tz, MDL);
                }
        }

        return (ISC_R_SUCCESS);
}

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, DNS_HASH_SIZE, 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)
{
        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 if ((*zone)->timeout && (*zone)->timeout < cur_time) {
                dns_zone_hash_delete(dns_zone_hash, (*zone)->name, 0, MDL);
                dns_zone_dereference(zone, 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;
{
        struct dns_zone *dns_zone;

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

        dns_zone = *ptr;
        *ptr = NULL;
        --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);
        if (dns_zone->primary6)
                option_cache_dereference(&dns_zone->primary6, file, line);
        if (dns_zone->secondary6)
                option_cache_dereference(&dns_zone->secondary6, file, line);
        dfree(dns_zone, file, line);
        return (1);
}

#if defined (NSUPDATE)
#if defined (DNS_ZONE_LOOKUP)

/* Helper function to copy the address from an rdataset to
 * the nameserver control block.  Mostly to avoid really long
 * lines in the nested for loops
 */
void
zone_addr_to_ns(dhcp_ddns_ns_t *ns_cb,
                dns_rdataset_t *rdataset)
{
        dns_rdata_t rdata;
        dns_rdata_in_a_t a;
        dns_rdata_in_aaaa_t aaaa;

        dns_rdata_init(&rdata);
        dns_rdataset_current(rdataset, &rdata);
        switch (rdataset->type) {
        case dns_rdatatype_a:
                (void) dns_rdata_tostruct(&rdata, &a, NULL);
                memcpy(&ns_cb->addrs[ns_cb->num_addrs], &a.in_addr, 4);
                ns_cb->num_addrs++;
                dns_rdata_freestruct(&a);
                break;
        case dns_rdatatype_aaaa:
                (void) dns_rdata_tostruct(&rdata, &aaaa, NULL);
                memcpy(&ns_cb->addrs6[ns_cb->num_addrs6], &aaaa.in6_addr, 16);
                ns_cb->num_addrs6++;
                dns_rdata_freestruct(&aaaa);
                break;
        default:
                break;
        }

        if ((ns_cb->ttl == 0) || (ns_cb->ttl > rdataset->ttl))
                ns_cb->ttl = rdataset->ttl;
}

/*
 * The following three routines co-operate to find the addresses of
 * the nameservers to use for a zone if we don't have a zone statement.
 * We strongly suggest the use of a zone statement to avoid problmes
 * and to allow for the use of TSIG and therefore better security, but
 * include this functionality for those that don't want such statements.
 *
 * find_zone_start(ddns_cb, direction)
 * This is the first of the routines, it is called from the rest of
 * the ddns code when we have received a request for DDNS for a name
 * and don't have a zone entry that would cover that name.  The name
 * is in the ddns_cb as specified by the direction (forward or reverse).
 * The start function pulls the name out and constructs the name server
 * block then starts the process by calling the DNS client code.
 *
 * find_zone_ns(taskp, eventp)
 * This is the second step of the process.  The DNS client code will
 * call this when it has gotten a response or timed out.  If the response
 * doesn't have a list of nameservers we remove another label from the
 * zone name and try again.  If the response does include a list of
 * nameservers we start walking through the list attempting to get
 * addresses for the nameservers.
 *
 * find_zone_addrs(taskp, eventp)
 * This is the third step of the process.  In find_zone_ns we got
 * a list of nameserves and started walking through them.  This continues
 * the walk and if we get back any addresses it adds them to our list.
 * When we get enough addresses or run out of nameservers we construct
 * a zone entry and insert it into the zone hash for the rest of the
 * DDNS code to use.
 */
void
find_zone_addrs(isc_task_t *taskp,
                isc_event_t *eventp)
{
        dns_clientresevent_t *ddns_event = (dns_clientresevent_t *)eventp;
        dhcp_ddns_ns_t *ns_cb = (dhcp_ddns_ns_t *)eventp->ev_arg;
        dns_name_t *ns_name = NULL;
        dns_rdataset_t *rdataset;
        isc_result_t result;
        dns_name_t *name;
        dns_rdata_t rdata = DNS_RDATA_INIT;
        dns_rdata_ns_t ns;


        /* the transaction is done, get rid of the tag */
        dns_client_destroyrestrans(&ns_cb->transaction);

        /* If we succeeded we try and extract the addresses, if we can
         * and we have enough we are done.  If we didn't succeed or
         * we don't have enough addresses afterwards we drop through
         * and try the next item on the list.
         */
        if (ddns_event->result == ISC_R_SUCCESS) {

                for (name = ISC_LIST_HEAD(ddns_event->answerlist);
                     name != NULL;
                     name = ISC_LIST_NEXT(name, link)) {

                        for (rdataset = ISC_LIST_HEAD(name->list);
                             rdataset != NULL;
                             rdataset = ISC_LIST_NEXT(rdataset, link)) {

                                for (result = dns_rdataset_first(rdataset);
                                     result == ISC_R_SUCCESS;
                                     result = dns_rdataset_next(rdataset)) {

                                        /* add address to cb */
                                        zone_addr_to_ns(ns_cb, rdataset);

                                        /* We are done if we have
                                         * enough addresses
                                         */
                                        if (ns_cb->num_addrs +
                                            ns_cb->num_addrs6 >= DHCP_MAXNS)
                                                goto done;
                                }
                        }
                }
        }

        /* We need more addresses.
         * We restart the loop we were in before.
         */

        for (ns_name = ns_cb->ns_name;
             ns_name != NULL;
             ns_name = ISC_LIST_NEXT(ns_name, link)) {

                if (ns_name == ns_cb->ns_name) {
                        /* first time through, use saved state */
                        rdataset = ns_cb->rdataset;
                } else {
                        rdataset = ISC_LIST_HEAD(ns_name->list);
                }

                for (;
                     rdataset != NULL;
                     rdataset = ISC_LIST_NEXT(rdataset, link)) {

                        if (rdataset->type != dns_rdatatype_ns)
                                continue;
                        dns_rdata_init(&rdata);

                        if (rdataset == ns_cb->rdataset) {
                                /* first time through use the saved state */
                                if (ns_cb->rdtype == dns_rdatatype_a) {
                                        ns_cb->rdtype = dns_rdatatype_aaaa;
                                } else {
                                        ns_cb->rdtype = dns_rdatatype_a;
                                        if (dns_rdataset_next(rdataset) !=
                                            ISC_R_SUCCESS)
                                                continue;
                                }
                        } else {
                                if ((!dns_rdataset_isassociated(rdataset)) ||
                                    (dns_rdataset_first(rdataset) !=
                                     ISC_R_SUCCESS))
                                        continue;
                        }

                        dns_rdataset_current(rdataset, &rdata);
                        if (dns_rdata_tostruct(&rdata, &ns, NULL) !=
                            ISC_R_SUCCESS)
                                continue;

                        /* Save our current state */
                        ns_cb->ns_name = ns_name;
                        ns_cb->rdataset = rdataset;

                        /* And call out to DNS */
                        result = zone_resolve(dhcp_gbl_ctx.dnsclient, &ns.name,
                                              dns_rdataclass_in,
                                              ns_cb->rdtype,
                                              DNS_CLIENTRESOPT_NODNSSEC,
                                              dhcp_gbl_ctx.task,
                                              find_zone_addrs,
                                              (void *)ns_cb,
                                              &ns_cb->transaction);

                        /* do we need to clean this? */
                        dns_rdata_freestruct(&ns);

                        if (result == ISC_R_SUCCESS)
                                /* we have started the next step, cleanup
                                 * the structures associated with this call
                                 * but leave the cb for the next round
                                 */
                                goto cleanup;

                        log_error("find_zone_ns: unable to continue "
                                  "resolve: %s %s",
                                  ns_cb->zname,
                                  isc_result_totext(result));

                        /* The call to start a resolve transaction failed,
                         * should we try to continue with any other names?
                         * For now let's not, but let's use whatever we
                         * may already have.
                         */
                        goto done;
                }
        }

 done:
        /* we've either gotten our max number of addresses or
         * run out of nameservers to try.  Convert the cb into
         * a zone and insert it into the zone hash.  Then
         * we need to clean up the saved state.
         */
        if ((ns_cb->num_addrs != 0) ||
            (ns_cb->num_addrs6 != 0))
                cache_found_zone(ns_cb);

        dns_client_freeresanswer(dhcp_gbl_ctx.dnsclient,
                                 &ns_cb->eventp->answerlist);
        isc_event_free((isc_event_t **)&ns_cb->eventp);

        remove_from_ns_queue(ns_cb);
        data_string_forget(&ns_cb->oname, MDL);
        dfree(ns_cb, MDL);

 cleanup:
        /* cleanup any of the new state information */

        dns_client_freeresanswer(dhcp_gbl_ctx.dnsclient,
                                 &ddns_event->answerlist);
        isc_event_free(&eventp);

        return;

}

/*
 * Routine to continue the process of finding a nameserver via the DNS
 * This is routine is called when we are still trying to get a list
 * of nameservers to process.
 */

void
find_zone_ns(isc_task_t *taskp,
             isc_event_t *eventp)
{
        dns_clientresevent_t *ddns_event = (dns_clientresevent_t *)eventp;
        dhcp_ddns_ns_t *ns_cb = (dhcp_ddns_ns_t *)eventp->ev_arg;
        dns_fixedname_t zname0;
        dns_name_t *zname = NULL, *ns_name = NULL;
        dns_rdataset_t *rdataset;
        isc_result_t result;
        dns_rdata_t rdata = DNS_RDATA_INIT;
        dns_rdata_ns_t ns;

        /* the transaction is done, get rid of the tag */
        dns_client_destroyrestrans(&ns_cb->transaction);

        if (ddns_event->result != ISC_R_SUCCESS) {
                /* We didn't find any nameservers, try again */

                /* Remove a label and continue */
                ns_cb->zname = strchr(ns_cb->zname, '.');
                if ((ns_cb->zname == NULL) ||
                    (ns_cb->zname[1] == 0)) {
                        /* No more labels, all done */
                        goto cleanup;
                }
                ns_cb->zname++;

                /* Create a DNS version of the zone name and call the
                 * resolver code */
                if (((result = dhcp_isc_name((unsigned char *)ns_cb->zname,
                                             &zname0, &zname))
                     != ISC_R_SUCCESS) ||
                    ((result = zone_resolve(dhcp_gbl_ctx.dnsclient,
                                            zname, dns_rdataclass_in,
                                            dns_rdatatype_ns,
                                            DNS_CLIENTRESOPT_NODNSSEC,
                                            dhcp_gbl_ctx.task,
                                            find_zone_ns,
                                            (void *)ns_cb,
                                            &ns_cb->transaction))
                     != ISC_R_SUCCESS)) {
                        log_error("find_zone_ns: Unable to build "
                                  "name or start resolve: %s %s",
                                  ns_cb->zname,
                                  isc_result_totext(result));
                        goto cleanup;
                }

                /* we have successfully started the next iteration
                 * of this step, clean up from the call and continue */
                dns_client_freeresanswer(dhcp_gbl_ctx.dnsclient,
                                         &ddns_event->answerlist);
                isc_event_free(&eventp);
                return;
        }

        /* We did get a set of nameservers, save the information and
         * start trying to get addresses
         */
        ns_cb->eventp = ddns_event;
        for (ns_name = ISC_LIST_HEAD(ddns_event->answerlist);
             ns_name != NULL;
             ns_name = ISC_LIST_NEXT(ns_name, link)) {

                for (rdataset = ISC_LIST_HEAD(ns_name->list);
                     rdataset != NULL;
                     rdataset = ISC_LIST_NEXT(rdataset, link)) {

                        if (rdataset->type != dns_rdatatype_ns)
                                continue;

                        if ((!dns_rdataset_isassociated(rdataset)) ||
                            (dns_rdataset_first(rdataset) !=
                             ISC_R_SUCCESS))
                                continue;

                        dns_rdataset_current(rdataset, &rdata);
                        if (dns_rdata_tostruct(&rdata, &ns, NULL) !=
                            ISC_R_SUCCESS)
                                continue;

                        /* Save our current state */
                        ns_cb->ns_name = ns_name;
                        ns_cb->rdataset = rdataset;

                        /* And call out to DNS */
                        result = zone_resolve(dhcp_gbl_ctx.dnsclient, &ns.name,
                                              dns_rdataclass_in,
                                              ns_cb->rdtype,
                                              DNS_CLIENTRESOPT_NODNSSEC,
                                              dhcp_gbl_ctx.task,
                                              find_zone_addrs,
                                              (void *)ns_cb,
                                              &ns_cb->transaction);

                        /* do we need to clean this? */
                        dns_rdata_freestruct(&ns);

                        if (result == ISC_R_SUCCESS)
                                /* We have successfully started the next step
                                 * we don't cleanup the eventp block as we are
                                 * still using it.
                                 */
                                return;

                        log_error("find_zone_ns: unable to continue "
                                  "resolve: %s %s",
                                  ns_cb->zname,
                                  isc_result_totext(result));

                        /* The call to start a resolve transaction failed,
                         * should we try to continue with any other names?
                         * For now let's not
                         */
                        goto cleanup;
                }
        }

 cleanup:
        /* When we add a queue to manage the DDNS
         * requests we will need to remove any that
         * were waiting for this resolution */

        dns_client_freeresanswer(dhcp_gbl_ctx.dnsclient,
                                 &ddns_event->answerlist);
        isc_event_free(&eventp);

        remove_from_ns_queue(ns_cb);

        data_string_forget(&ns_cb->oname, MDL);
        dfree(ns_cb, MDL);
        return;

}

/*
 * Start the process of finding nameservers via the DNS because
 * we don't have a zone entry already.
 * We construct a control block and fill in the DDNS name.  As
 * the process continues we shall move the zname pointer to
 * indicate which labels we are still using.  The rest of
 * the control block will be filled in as we continue processing.
 */
isc_result_t
find_zone_start(dhcp_ddns_cb_t *ddns_cb, int direction)
{
        isc_result_t status = ISC_R_NOTFOUND;
        dhcp_ddns_ns_t *ns_cb;
        dns_fixedname_t zname0;
        dns_name_t *zname = NULL;

        /*
         * We don't validate np as that was already done in find_cached_zone()
         */

        /* Allocate the control block for this request */
        ns_cb = dmalloc(sizeof(*ns_cb), MDL);
        if (ns_cb == NULL) {
                log_error("find_zone_start: unable to allocate cb");
                return(ISC_R_FAILURE);
        }
        ns_cb->rdtype = dns_rdatatype_a;

        /* Copy the data string so the NS lookup is independent of the DDNS */
        if (direction == FIND_FORWARD) {
                data_string_copy(&ns_cb->oname,  &ddns_cb->fwd_name, MDL);
        } else {
                data_string_copy(&ns_cb->oname,  &ddns_cb->rev_name, MDL);
        }
        ns_cb->zname = (char *)ns_cb->oname.data;

        /*
         * Check the dns_outstanding_ns queue to see if we are
         * already processing something that would cover this name
         */
        if (find_in_ns_queue(ns_cb) == ISC_R_SUCCESS) {
                data_string_forget(&ns_cb->oname, MDL);
                dfree(ns_cb, MDL);
                return (ISC_R_SUCCESS);
        }

        /* Create a DNS version of the zone name and call the
         * resolver code */
        if (((status = dhcp_isc_name((unsigned char *)ns_cb->zname,
                                     &zname0, &zname))
             != ISC_R_SUCCESS) ||
            ((status = zone_resolve(dhcp_gbl_ctx.dnsclient,
                                    zname, dns_rdataclass_in,
                                    dns_rdatatype_ns,
                                    DNS_CLIENTRESOPT_NODNSSEC,
                                    dhcp_gbl_ctx.task,
                                    find_zone_ns,
                                    (void *)ns_cb,
                                    &ns_cb->transaction))
             != ISC_R_SUCCESS)) {
                log_error("find_zone_start: Unable to build "
                          "name or start resolve: %s %s",
                          ns_cb->zname,
                          isc_result_totext(status));

                /* We failed to start the process, clean up */
                data_string_forget(&ns_cb->oname, MDL);
                dfree(ns_cb, MDL);
        } else {
                /* We started the process, attach the control block
                 * to the queue */
                add_to_ns_queue(ns_cb);
        }

        return (status);
}
#endif

isc_result_t
find_cached_zone(dhcp_ddns_cb_t *ddns_cb, int direction)
{
        isc_result_t status = ISC_R_NOTFOUND;
        const char *np;
        struct dns_zone *zone = NULL;
        struct data_string nsaddrs;
        struct in_addr zone_addr;
        struct in6_addr zone_addr6;
        int ix;

        if (direction == FIND_FORWARD) {
                np = (const char *)ddns_cb->fwd_name.data;
        } else {
                np = (const char *)ddns_cb->rev_name.data;
        }

        /* We can't look up a null zone. */
        if ((np == NULL) || (*np == '\0')) {
                return (DHCP_R_INVALIDARG);
        }

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

                np = strchr(np, '.');
                if (np == NULL)
                        break;
                np++;
        }

        if (status != ISC_R_SUCCESS)
                return (status);

        /* Make sure the zone is valid, we've already gotten
         * rid of expired dynamic zones.  Check to see if
         * we repudiated this zone.  If so give up.
         */
        if ((zone->flags & DNS_ZONE_INACTIVE) != 0) {
                dns_zone_dereference(&zone, MDL);
                return (ISC_R_FAILURE);
        }

        /* Make sure the zone name will fit. */
        if (strlen(zone->name) >= sizeof(ddns_cb->zone_name)) {
                dns_zone_dereference(&zone, MDL);
                return (ISC_R_NOSPACE);
        }
        strcpy((char *)&ddns_cb->zone_name[0], zone->name);

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

        if (zone->primary) {
                if (evaluate_option_cache(&nsaddrs, NULL, NULL, NULL,
                                          NULL, NULL, &global_scope,
                                          zone->primary, MDL)) {
                        int ip = 0;
                        while (ix < DHCP_MAXNS) {
                                if (ip + 4 > nsaddrs.len)
                                        break;
                                memcpy(&zone_addr, &nsaddrs.data[ip], 4);
                                isc_sockaddr_fromin(&ddns_cb->zone_addrs[ix],
                                                    &zone_addr,
                                                    NS_DEFAULTPORT);
                                ISC_LIST_APPEND(ddns_cb->zone_server_list,
                                                &ddns_cb->zone_addrs[ix],
                                                link);
                                ip += 4;
                                ix++;
                        }
                        data_string_forget(&nsaddrs, MDL);
                }
        }

        if (zone->primary6) {
                if (evaluate_option_cache(&nsaddrs, NULL, NULL, NULL,
                                          NULL, NULL, &global_scope,
                                          zone->primary6, MDL)) {
                        int ip = 0;
                        while (ix < DHCP_MAXNS) {
                                if (ip + 16 > nsaddrs.len)
                                        break;
                                memcpy(&zone_addr6, &nsaddrs.data[ip], 16);
                                isc_sockaddr_fromin6(&ddns_cb->zone_addrs[ix],
                                                    &zone_addr6,
                                                    NS_DEFAULTPORT);
                                ISC_LIST_APPEND(ddns_cb->zone_server_list,
                                                &ddns_cb->zone_addrs[ix],
                                                link);
                                ip += 16;
                                ix++;
                        }
                        data_string_forget(&nsaddrs, MDL);
                }
        }

        if (zone->secondary) {
                if (evaluate_option_cache(&nsaddrs, NULL, NULL, NULL,
                                          NULL, NULL, &global_scope,
                                          zone->secondary, MDL)) {
                        int ip = 0;
                        while (ix < DHCP_MAXNS) {
                                if (ip + 4 > nsaddrs.len)
                                        break;
                                memcpy(&zone_addr, &nsaddrs.data[ip], 4);
                                isc_sockaddr_fromin(&ddns_cb->zone_addrs[ix],
                                                    &zone_addr,
                                                    NS_DEFAULTPORT);
                                ISC_LIST_APPEND(ddns_cb->zone_server_list,
                                                &ddns_cb->zone_addrs[ix],
                                                link);
                                ip += 4;
                                ix++;
                        }
                        data_string_forget (&nsaddrs, MDL);
                }
        }

        if (zone->secondary6) {
                if (evaluate_option_cache(&nsaddrs, NULL, NULL, NULL,
                                          NULL, NULL, &global_scope,
                                          zone->secondary6, MDL)) {
                        int ip = 0;
                        while (ix < DHCP_MAXNS) {
                                if (ip + 16 > nsaddrs.len)
                                        break;
                                memcpy(&zone_addr6, &nsaddrs.data[ip], 16);
                                isc_sockaddr_fromin6(&ddns_cb->zone_addrs[ix],
                                                    &zone_addr6,
                                                    NS_DEFAULTPORT);
                                ISC_LIST_APPEND(ddns_cb->zone_server_list,
                                                &ddns_cb->zone_addrs[ix],
                                                link);
                                ip += 16;
                                ix++;
                        }
                        data_string_forget (&nsaddrs, MDL);
                }
        }

        dns_zone_reference(&ddns_cb->zone, zone, MDL);
        dns_zone_dereference (&zone, MDL);
        return ISC_R_SUCCESS;
}

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

void repudiate_zone (struct dns_zone **zone)
{
        /* verify that we have a pointer at least */
        if ((zone == NULL) || (*zone == NULL)) {
                log_info("Null argument to repudiate zone");
                return;
        }

        (*zone)->flags |= DNS_ZONE_INACTIVE;
        dns_zone_dereference(zone, MDL);
}

#if defined (DNS_ZONE_LOOKUP)
void cache_found_zone(dhcp_ddns_ns_t *ns_cb)
{
        struct dns_zone *zone = NULL;
        int len, remove_zone = 0;

        /* See if there's already such a zone. */
        if (dns_zone_lookup(&zone, ns_cb->zname) == ISC_R_SUCCESS) {
                /* If it's not a dynamic zone, leave it alone. */
                if (zone->timeout == 0) {
                        goto cleanup;
                }

                /* Remove any old addresses in case they've changed */
                if (zone->primary)
                        option_cache_dereference(&zone->primary, MDL);
                if (zone->primary6)
                        option_cache_dereference(&zone->primary6, MDL);

                /* Set the flag to remove the zone from the hash if
                   we have problems */
                remove_zone = 1;
        } else if (dns_zone_allocate(&zone, MDL) == 0) {
                return;
        } else {
                /* We've just allocated the zone, now we need
                 * to allocate space for the name and addresses
                 */

                /* allocate space for the name */
                len = strlen(ns_cb->zname);
                zone->name = dmalloc(len + 2, MDL);
                if (zone->name == NULL) {
                        goto cleanup;
                }

                /* Copy the name and add a trailing '.' if necessary */
                strcpy(zone->name, ns_cb->zname);
                if (zone->name[len-1] != '.') {
                        zone->name[len] = '.';
                        zone->name[len+1] = 0;
                }
        }

        zone->timeout = cur_time + ns_cb->ttl;

        if (ns_cb->num_addrs != 0) {
                len = ns_cb->num_addrs * sizeof(struct in_addr);
                if ((!option_cache_allocate(&zone->primary, MDL)) ||
                    (!buffer_allocate(&zone->primary->data.buffer,
                                      len, MDL))) {
                        if (remove_zone == 1)
                                remove_dns_zone(zone);
                        goto cleanup;
                }
                memcpy(zone->primary->data.buffer->data, ns_cb->addrs, len);
                zone->primary->data.data =
                        &zone->primary->data.buffer->data[0];
                zone->primary->data.len = len;
        }
        if (ns_cb->num_addrs6 != 0) {
                len = ns_cb->num_addrs6 * sizeof(struct in6_addr);
                if ((!option_cache_allocate(&zone->primary6, MDL)) ||
                    (!buffer_allocate(&zone->primary6->data.buffer,
                                      len, MDL))) {
                        if (remove_zone == 1)
                                remove_dns_zone(zone);
                        goto cleanup;
                }
                memcpy(zone->primary6->data.buffer->data, ns_cb->addrs6, len);
                zone->primary6->data.data =
                        &zone->primary6->data.buffer->data[0];
                zone->primary6->data.len = len;
        }

        enter_dns_zone(zone);

 cleanup:
        dns_zone_dereference(&zone, MDL);
        return;
}
#endif

/*!
 * \brief Create an id for a client
 *
 * This function is used to create an id for a client to use with DDNS
 * This version of the function is for the standard style, RFC 4701
 *
 * This function takes information from the type and data fields and
 * mangles it into a dhcid string which it places in ddns_cb.  It also
 * sets a field in ddns_cb to specify the class that should be used
 * when sending the dhcid, in this case it is a DHCID record so we use
 * dns_rdatatype_dhcid
 *
 * The DHCID we construct is:
 *  2 bytes - identifier type (see 4701 and IANA)
 *  1 byte  - digest type, currently only SHA256 (1)
 *  n bytes - digest, length depends on digest type, currently 32 for
 *            SHA256
 *
 * What we base the digest on is up to the calling code for an id type of
 * 0 - 1 octet htype followed by hlen octets of chaddr from v4 client request
 * 1 - data octets from a dhcpv4 client's client identifier option
 * 2 - the client DUID from a v4 or v6 client's client id option
 * This identifier is concatenated with the fqdn and the result is digested.
 */
int get_std_dhcid(dhcp_ddns_cb_t *ddns_cb,
                  int type,
                  const u_int8_t *identifier,
                  unsigned id_len)
{
        struct data_string *id = &ddns_cb->dhcid;
        isc_sha256_t sha256;
        unsigned char buf[ISC_SHA256_DIGESTLENGTH];
        unsigned char fwd_buf[256];
        unsigned fwd_buflen = 0;

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

        /* We need to convert the fwd name to wire representation */
        if (MRns_name_pton((char *)ddns_cb->fwd_name.data, fwd_buf, 256) == -1)
                return (0);
        while(fwd_buf[fwd_buflen] != 0) {
                fwd_buflen += fwd_buf[fwd_buflen] + 1;
        }
        fwd_buflen++;

        if (!buffer_allocate(&id->buffer,
                             ISC_SHA256_DIGESTLENGTH + 2 + 1,
                             MDL))
                return (0);
        id->data = id->buffer->data;

        /* The two first bytes contain the type identifier. */
        putUShort(id->buffer->data, (unsigned)type);

        /* The next is the digest type, SHA-256 is 1 */
        putUChar(id->buffer->data + 2, 1u);

        /* Computing the digest */
        isc_sha256_init(&sha256);
        isc_sha256_update(&sha256, identifier, id_len);
        isc_sha256_update(&sha256, fwd_buf, fwd_buflen);
        isc_sha256_final(buf, &sha256);

        memcpy(id->buffer->data + 3, &buf, ISC_SHA256_DIGESTLENGTH);

        id->len = ISC_SHA256_DIGESTLENGTH + 2 + 1;

        return (1);
}

/*!
 *
 * \brief Create an id for a client
 *
 * This function is used to create an id for a client to use with DDNS
 * This version of the function is for the interim style.  It is retained
 * to allow users to continue using the interim style but they should
 * switch to the standard style (which uses get_std_dhcid) for better
 * interoperability.
 *
 * This function takes information from the type and data fields and
 * mangles it into a dhcid string which it places in ddns_cb.  It also
 * sets a field in ddns_cb to specify the class that should be used
 * when sending the dhcid, in this case it is a txt record so we use
 * dns_rdata_type_txt
 *
 * NOTE WELL: this function has issues with how it calculates the
 * dhcid, they can't be changed now as that would break the records
 * already in use.
 */

int get_int_dhcid (dhcp_ddns_cb_t *ddns_cb,
                   int type,
                   const u_int8_t *data,
                   unsigned len)
{
        struct data_string *id = &ddns_cb->dhcid;
        unsigned char buf[ISC_MD5_DIGESTLENGTH];
        isc_md5_t 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, NUL,
         * and one byte for length for dns.
         */
        if (!buffer_allocate(&id -> buffer,
                             (ISC_MD5_DIGESTLENGTH * 2) + 4, MDL))
                return (0);
        id->data = id->buffer->data;

        /*
         * We put the length into the first byte to turn
         * this into a dns text string.  This avoid needing to
         * copy the string to add the byte later.
         */
        id->buffer->data[0] = ISC_MD5_DIGESTLENGTH * 2 + 2;

        /* Put the type in the next two bytes. */
        id->buffer->data[1] = "0123456789abcdef"[(type >> 4) & 0xf];
        /* This should have been [type & 0xf] but now that
         * it is in use we need to leave it this way in order
         * to avoid disturbing customer's lease files
         */
        id->buffer->data[2] = "0123456789abcdef"[type % 15];

        /* Mash together an MD5 hash of the identifier. */
        isc_md5_init(&md5);
        isc_md5_update(&md5, data, len);
        isc_md5_final(&md5, buf);

        /* Convert into ASCII. */
        for (i = 0; i < ISC_MD5_DIGESTLENGTH; i++) {
                id->buffer->data[i * 2 + 3] =
                        "0123456789abcdef"[(buf[i] >> 4) & 0xf];
                id->buffer->data[i * 2 + 4] =
                        "0123456789abcdef"[buf[i] & 0xf];
        }

        id->len = ISC_MD5_DIGESTLENGTH * 2 + 3;
        id->buffer->data[id->len] = 0;
        id->terminated = 1;

        return (1);
}

int get_dhcid(dhcp_ddns_cb_t *ddns_cb,
              int type,
              const u_int8_t *identifier,
              unsigned id_len)
{
        if (ddns_cb->dhcid_class == dns_rdatatype_dhcid)
                return get_std_dhcid(ddns_cb, type, identifier, id_len);
        else
                return get_int_dhcid(ddns_cb, type, identifier, id_len);
}

/*
 * The dhcid (text version) that we pass to DNS includes a length byte
 * at the start but the text we store in the lease doesn't include the
 * length byte.  The following routines are to convert between the two
 * styles.
 *
 * When converting from a dhcid to a leaseid we reuse the buffer and
 * simply adjust the data pointer and length fields in the data string.
 * This avoids any prolems with allocating space.
 */

void
dhcid_tolease(struct data_string *dhcid,
              struct data_string *leaseid)
{
        /* copy the data string then update the fields */
        data_string_copy(leaseid, dhcid, MDL);
        leaseid->data++;
        leaseid->len--;
}

isc_result_t
dhcid_fromlease(struct data_string *dhcid,
                struct data_string *leaseid)
{
        if (!buffer_allocate(&dhcid->buffer, leaseid->len + 2, MDL)) {
                return(ISC_R_FAILURE);
        }

        dhcid->data = dhcid->buffer->data;

        dhcid->buffer->data[0] = leaseid->len;
        memcpy(dhcid->buffer->data + 1, leaseid->data, leaseid->len);
        dhcid->len = leaseid->len + 1;
        if (leaseid->terminated == 1) {
                dhcid->buffer->data[dhcid->len] = 0;
                dhcid->terminated = 1;
        }

        return(ISC_R_SUCCESS);
}

/*
 * Construct the dataset for this item.
 * This is a fairly simple arrangement as the operations we do are simple.
 * If there is data we simply have the rdata point to it - the formatting
 * must be correct already.  We then link the rdatalist to the rdata and
 * create a rdataset from the rdatalist.
 */

static isc_result_t
make_dns_dataset(dns_rdataclass_t  dataclass,
                 dns_rdatatype_t   datatype,
                 dhcp_ddns_data_t *dataspace,
                 unsigned char    *data,
                 int               datalen,
                 int               ttl)
{
        dns_rdata_t *rdata = &dataspace->rdata;
        dns_rdatalist_t *rdatalist = &dataspace->rdatalist;
        dns_rdataset_t *rdataset = &dataspace->rdataset;

        isc_region_t region;

        /* set up the rdata */
        dns_rdata_init(rdata);

        if (data == NULL) {
                /* No data, set up the rdata fields we care about */
                rdata->flags = DNS_RDATA_UPDATE;
                rdata->type = datatype;
                rdata->rdclass = dataclass;
        } else {
                switch(datatype) {
                case dns_rdatatype_a:
                case dns_rdatatype_aaaa:
                case dns_rdatatype_txt:
                case dns_rdatatype_dhcid:
                case dns_rdatatype_ptr:
                        /* The data must be in the right format we simply
                         * need to supply it via the correct structure */
                        region.base   = data;
                        region.length = datalen;
                        dns_rdata_fromregion(rdata, dataclass, datatype,
                                             &region);
                        break;
                default:
                        return(DHCP_R_INVALIDARG);
                        break;
                }
        }

        /* setup the datalist and attach the rdata to it */
        dns_rdatalist_init(rdatalist);
        rdatalist->type = datatype;
        rdatalist->rdclass = dataclass;
        rdatalist->ttl = ttl;
        ISC_LIST_APPEND(rdatalist->rdata, rdata, link);

        /* convert the datalist to a dataset */
        dns_rdataset_init(rdataset);
        dns_rdatalist_tordataset(rdatalist, rdataset);

        return(ISC_R_SUCCESS);
}

#if defined (DEBUG_DNS_UPDATES)
static void log_call(char *text, dns_name_t* pname, dns_name_t* uname) {
    char buf1[512];
    char buf2[512];
    if (pname) {
        dns_name_format(pname, buf1, 512);
    } else {
        *buf1=0;
    }

    if (uname) {
        dns_name_format(uname, buf2, 512);
    } else {
        *buf2=0;
    }

    log_info ("DDNS: %s: pname:[%s] uname:[%s]", text, buf1, buf2);
}
#endif


/*
 * 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"
 *
 * There are two cases, one for the server and one for the client.
 *
 * For the server the first step will have a request of:
 * The name is not in use
 * Add an A RR
 * Add a DHCID RR
 *
 * For the client the first step will have a request of:
 * The A RR does not exist
 * Add an A RR
 * Add a DHCID RR
 */

static isc_result_t
build_fwd_add1(dhcp_ddns_cb_t   *ddns_cb,
                     dhcp_ddns_data_t *dataspace,
                     dns_name_t       *pname,
                     dns_name_t       *uname)
{
        isc_result_t result;

#if defined (DEBUG_DNS_UPDATES)
        log_call("build_fwd_add1", pname, uname);
#endif

        /* Construct the prerequisite list */
        if ((ddns_cb->flags & DDNS_INCLUDE_RRSET) != 0) {
                /* The A RR shouldn't exist */
                result = make_dns_dataset(dns_rdataclass_none,
                                          ddns_cb->address_type,
                                          dataspace, NULL, 0, 0);
        } else {
                /* The name is not in use */
                result = make_dns_dataset(dns_rdataclass_none,
                                          dns_rdatatype_any,
                                          dataspace, NULL, 0, 0);
        }
        if (result != ISC_R_SUCCESS) {
                return(result);
        }
        ISC_LIST_APPEND(pname->list, &dataspace->rdataset, link);
        dataspace++;

        /* Construct the update list */
        /* Add the A RR */
        result = make_dns_dataset(dns_rdataclass_in, ddns_cb->address_type,
                                  dataspace,
                                  (unsigned char *)ddns_cb->address.iabuf,
                                  ddns_cb->address.len, ddns_cb->ttl);
        if (result != ISC_R_SUCCESS) {
                return(result);
        }
        ISC_LIST_APPEND(uname->list, &dataspace->rdataset, link);
        dataspace++;

        /* Add the DHCID RR */
        result = make_dns_dataset(dns_rdataclass_in, ddns_cb->dhcid_class,
                                  dataspace,
                                  (unsigned char *)ddns_cb->dhcid.data,
                                  ddns_cb->dhcid.len, ddns_cb->ttl);
        if (result != ISC_R_SUCCESS) {
                return(result);
        }
        ISC_LIST_APPEND(uname->list, &dataspace->rdataset, link);

        return(ISC_R_SUCCESS);
}

/*
 * 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"
 *
 * The message for the second step depends on if we are doing conflict
 * resolution.  If we are we include the prerequisite.  The prerequiste
 * will either:
 *  A. require the data value of the DHCID RR to match that of the client
 * or
 *  B. required only that the DHCID RR of the configured class (DHCID or
 * TXT) exist
 *
 * based on whether DDNS_GUARD_ID_MUST_MATCH is on (default) or off.
 *
 * The prerequisite is omitted if conflict detection is off.
 *
 * If not we delete the DHCID in addition to all A rrsets.
 *
 * Conflict resolution:
 * DHCID RR exists, and matches client identity.
 * Delete A RRset.
 * Add A RR.
 *
 * Conflict override:
 * Delete DHCID RRs.
 * Add DHCID RR
 * Delete A RRset.
 * Add A RR.
 */

static isc_result_t
build_fwd_add2(dhcp_ddns_cb_t   *ddns_cb,
                     dhcp_ddns_data_t *dataspace,
                     dns_name_t       *pname,
                     dns_name_t       *uname)
{
        isc_result_t result = ISC_R_SUCCESS;

#if defined (DEBUG_DNS_UPDATES)
        log_call("build_fwd_add2", pname, uname);
#endif

        /*
         * If we are doing conflict detection we use a prereq list.
         * If not we delete the DHCID in addition to all A rrsets.
         */
        if (ddns_cb->flags & DDNS_CONFLICT_DETECTION) {
                /* Construct the prereq list */
                /* The DHCID RR exists and optionally matches the client's
                 * identity.  If matching is turned off, we use the presence
                 * of a DHCID RR to signal that this is a dynamic entry and
                 * thus eligible for us to overwrite.  If matching is on
                 * then we can only replace the entries if they belong to
                 * this client. */
                unsigned char *match_id = NULL;
                int match_id_len = 0;
                int match_class = dns_rdataclass_any;
                if (ddns_cb->flags & DDNS_GUARD_ID_MUST_MATCH) {
                        match_id = (unsigned char*)(ddns_cb->dhcid.data);
                        match_id_len = ddns_cb->dhcid.len;
                        match_class = dns_rdataclass_in;
                }

                result = make_dns_dataset(match_class,
                                          ddns_cb->dhcid_class,
                                          dataspace,
                                          match_id, match_id_len, 0);
                if (result != ISC_R_SUCCESS) {
                        return(result);
                }
                ISC_LIST_APPEND(pname->list, &dataspace->rdataset, link);
                dataspace++;
        } else {
                /* Start constructing the update list.
                 * Conflict detection override: delete DHCID RRs */
                result = make_dns_dataset(dns_rdataclass_any,
                                          ddns_cb->dhcid_class,
                                          dataspace, NULL, 0, 0);
                if (result != ISC_R_SUCCESS) {
                        return(result);
                }
                ISC_LIST_APPEND(uname->list, &dataspace->rdataset, link);
                dataspace++;

                /* Add current DHCID RR, always include client id */
                result = make_dns_dataset(dns_rdataclass_in,
                                          ddns_cb->dhcid_class,
                                          dataspace,
                                          (unsigned char *)ddns_cb->dhcid.data,
                                          ddns_cb->dhcid.len, ddns_cb->ttl);
                if (result != ISC_R_SUCCESS) {
                        return(result);
                }
                ISC_LIST_APPEND(uname->list, &dataspace->rdataset, link);
                dataspace++;
        }

        /* Start or continue constructing the update list */
        /* Delete the address RRset */
        result = make_dns_dataset(dns_rdataclass_any, ddns_cb->address_type,
                                  dataspace, NULL, 0, 0);
        if (result != ISC_R_SUCCESS) {
                return(result);
        }
        ISC_LIST_APPEND(uname->list, &dataspace->rdataset, link);
        dataspace++;

        /* Add the address RR */
        result = make_dns_dataset(dns_rdataclass_in, ddns_cb->address_type,
                                  dataspace,
                                  (unsigned char *)ddns_cb->address.iabuf,
                                  ddns_cb->address.len, ddns_cb->ttl);
        if (result != ISC_R_SUCCESS) {
                return(result);
        }
        ISC_LIST_APPEND(uname->list, &dataspace->rdataset, link);

        return(ISC_R_SUCCESS);
}

/*
 * Creates the DNS foward update add used for DSMM add attempt #3 and
 * ddns-other-guard-is-dynamic is off
 *
 *
 * If the second update failed with NXRRSET, this indicates that:
 *
 * 1. our FQDN is in use
 * 2  no guard record (DHCID RR) for that FQDN, of our class (and optionally
 * client id) exists
 *
 * In Dual Stack Mixed Mode, we need to attempt a third add, to distinguish
 * between static entries that we cannot modify and dynamic entries belonging
 * to the "other" side of dual stack.  The prerequisites for this add are:
 *
 * 1. No address record of my type exists
 * 2. No guard record of my type exists
 * 3. A guard record of the other type exists
 *
 * and updates which will add the new address and guard record:
 *
 * prereq nxrrset <name> <addr_t>           # no address record of my type
 * prereq nxrrset <name> <guard_t>          # no guard record of my type
 * prereq yxrrset <name> <other_guard_t>    # other guard type does exist
 * update add <name> <addr_t> <address>     # add the new address record
 * update add <name> <guard_t> <client-id>  # add the new address record
 */
static isc_result_t
build_dsmm_fwd_add3(dhcp_ddns_cb_t   *ddns_cb,
                     dhcp_ddns_data_t *dataspace,
                     dns_name_t       *pname,
                     dns_name_t       *uname)
{
        isc_result_t result = ISC_R_SUCCESS;

#if defined (DEBUG_DNS_UPDATES)
        log_call("build_fwd_add3", pname, uname);
#endif
        /* Construct the prereq list */
        /* No address record of my type exists */
        result = make_dns_dataset(dns_rdataclass_none,
                                  ddns_cb->address_type,
                                  dataspace, NULL, 0, 0);
        if (result != ISC_R_SUCCESS) {
                return(result);
        }
        ISC_LIST_APPEND(pname->list, &dataspace->rdataset, link);
        dataspace++;

        /* No guard record of my type exists */
        result = make_dns_dataset(dns_rdataclass_none,
                                  ddns_cb->dhcid_class,
                                  dataspace, NULL, 0, 0);
        if (result != ISC_R_SUCCESS) {
                return(result);
        }
        ISC_LIST_APPEND(pname->list, &dataspace->rdataset, link);
        dataspace++;

        /* Guard record of the other type DOES exist */
        result = make_dns_dataset(dns_rdataclass_any,
                                  ddns_cb->other_dhcid_class,
                                  dataspace, NULL, 0, 0);
        if (result != ISC_R_SUCCESS) {
                return(result);
        }
        ISC_LIST_APPEND(pname->list, &dataspace->rdataset, link);
        dataspace++;

        /* Start constructing the update list. */
        /* Add the address RR */
        result = make_dns_dataset(dns_rdataclass_in, ddns_cb->address_type,
                                  dataspace,
                                  (unsigned char *)ddns_cb->address.iabuf,
                                  ddns_cb->address.len, ddns_cb->ttl);
        if (result != ISC_R_SUCCESS) {
                return(result);
        }
        ISC_LIST_APPEND(uname->list, &dataspace->rdataset, link);
        dataspace++;

        /* Add current DHCID RR */
        result = make_dns_dataset(dns_rdataclass_in, ddns_cb->dhcid_class,
                                  dataspace,
                                  (unsigned char *)ddns_cb->dhcid.data,
                                  ddns_cb->dhcid.len, ddns_cb->ttl);
        if (result != ISC_R_SUCCESS) {
                return(result);
        }
        ISC_LIST_APPEND(uname->list, &dataspace->rdataset, link);

        return(ISC_R_SUCCESS);
}

/*
 * Creates the DNS foward update add used for DSMM add attempt #3 and
 * ddns-other-guard-is-dynamic is ON
 *
 * If the second update failed with NXRRSET, this indicates that:
 *
 * 1. our FQDN is in use
 * 2  no guard record (DHCID RR) for that FQDN, of our class (and optionally
 * client id) exists
 *
 * When we're In Dual Stack Mixed Mode and ddns-other-guard-is-dynamic is ON
 * we need only determine if a guard record of the other type exists, to know
 * if we can add/replace and address record of our type.   In other words,
 * the presence of a dynamic entry belonging to the "other" stack means
 * all entries for this name should be dynamic and we overwrite an unguarded
 * address record of our type.
 *
 * The udpate will contain a single prequisite for a guard record of the
 * other type, an update to delete any address records of our type, and
 * updates to add the address and guard records:
 *
 * prereq yxrrset <name> <other_guard_t>   # other guard type exists
 * update delete <name> <addr_t>           # delete existing address record
 *                                         # (if one)
 * update add <name> <addr_t> <address>    # add new address record
 * update add <name> <guard_t> <client-id> # add new guard record
 */
static isc_result_t
build_dsmm_fwd_add3_other(dhcp_ddns_cb_t   *ddns_cb,
                     dhcp_ddns_data_t *dataspace,
                     dns_name_t       *pname,
                     dns_name_t       *uname)
{
        isc_result_t result = ISC_R_SUCCESS;

#if defined (DEBUG_DNS_UPDATES)
        log_call("build_fwd_add3_other", pname, uname);
#endif
        /* Construct the prereq list */

        // If ID matching is on, a result of NXRRSET from add2 means
        // either there is no guard of my type, or there is but
        // it does not match this client.  We need to distinguish
        // between those two cases here and only allow this add
        // if there is no guard of my type.
        if (ddns_cb->flags & DDNS_GUARD_ID_MUST_MATCH) {
                /* No guard record of my type exists */
                result = make_dns_dataset(dns_rdataclass_none,
                                          ddns_cb->dhcid_class,
                                          dataspace, NULL, 0, 0);
                if (result != ISC_R_SUCCESS) {
                        return(result);
                }

                ISC_LIST_APPEND(pname->list, &dataspace->rdataset, link);
                dataspace++;
        }

        /* A guard record of the other type exists */
        result = make_dns_dataset(dns_rdataclass_any,
                                  ddns_cb->other_dhcid_class,
                                  dataspace, NULL, 0, 0);
        if (result != ISC_R_SUCCESS) {
                return(result);
        }
        ISC_LIST_APPEND(pname->list, &dataspace->rdataset, link);
        dataspace++;

        /* Start constructing the update list. */
        /* Delete the existing address record of my type (if one) */
        result = make_dns_dataset(dns_rdataclass_any,
                                  ddns_cb->address_type,
                                  dataspace, NULL, 0, 0);
        if (result != ISC_R_SUCCESS) {
                return(result);
        }
        ISC_LIST_APPEND(uname->list, &dataspace->rdataset, link);
        dataspace++;

        /* Add the address RR */
        result = make_dns_dataset(dns_rdataclass_in, ddns_cb->address_type,
                                  dataspace,
                                  (unsigned char *)ddns_cb->address.iabuf,
                                  ddns_cb->address.len, ddns_cb->ttl);
        if (result != ISC_R_SUCCESS) {
                return(result);
        }
        ISC_LIST_APPEND(uname->list, &dataspace->rdataset, link);
        dataspace++;

        /* Add current DHCID RR */
        result = make_dns_dataset(dns_rdataclass_in, ddns_cb->dhcid_class,
                                  dataspace,
                                  (unsigned char *)ddns_cb->dhcid.data,
                                  ddns_cb->dhcid.len, ddns_cb->ttl);
        if (result != ISC_R_SUCCESS) {
                return(result);
        }
        ISC_LIST_APPEND(uname->list, &dataspace->rdataset, link);

        return(ISC_R_SUCCESS);
}

/*
 * The entity chosen to handle the A record for this client (either the
 * client or the server) SHOULD delete the A (or AAAA) record that was
 * added when the lease was made to the client.
 *
 * If we are doing conflict resolution, the udpate will contain a prequisite
 * that will either:
 *  A. require that a guard record of the configure class (DHCID or TXT) with
 *  a data value matching that the client exist (per RFC 4703)
 * or
 *  B. require only that the guard record of the configured class exist
 *
 * based on whether DDNS_GUARD_ID_MUST_MATCH is on (default) or off.
 *
 * The prerequisite is omitted if conflict detection is off.
 *
 */
static isc_result_t
build_fwd_rem1(dhcp_ddns_cb_t   *ddns_cb,
                     dhcp_ddns_data_t *dataspace,
                     dns_name_t       *pname,
                     dns_name_t       *uname)
{
        isc_result_t result = ISC_R_SUCCESS;

#if defined (DEBUG_DNS_UPDATES)
        log_call("build_fwd_rem1", pname, uname);
#endif

        /* If we're doing conflict detection, add the guard record pre-req */
        if (ddns_cb->flags & DDNS_CONFLICT_DETECTION) {
                /* Construct the prereq list */
                /* The guard record exists and optionally matches the client's
                 * identity.  If matching is turned off, we use the presence
                 * of a DHCID RR to signal that this is a dynamic entry and
                 * thus eligible for us to overwrite.  If matching is on
                 * then we can only delete the entries if they belong to
                 * this client. */
                unsigned char *match_id = NULL;
                int match_id_len = 0;
                int match_class = dns_rdataclass_any;
                if (ddns_cb->flags & DDNS_GUARD_ID_MUST_MATCH) {
                        match_id = (unsigned char*)(ddns_cb->dhcid.data);
                        match_id_len = ddns_cb->dhcid.len;
                        match_class = dns_rdataclass_in;
                }

                result = make_dns_dataset(match_class,
                                          ddns_cb->dhcid_class,
                                          dataspace,
                                          match_id, match_id_len, 0);
                if (result != ISC_R_SUCCESS) {
                        return(result);
                }
                ISC_LIST_APPEND(pname->list, &dataspace->rdataset, link);
                dataspace++;
        }

        /* Construct the update list */
        /* Delete A RRset */
        result = make_dns_dataset(dns_rdataclass_none, ddns_cb->address_type,
                                  dataspace,
                                  (unsigned char *)ddns_cb->address.iabuf,
                                  ddns_cb->address.len, 0);
        if (result != ISC_R_SUCCESS) {
                return(result);
        }
        ISC_LIST_APPEND(uname->list, &dataspace->rdataset, link);

        return(ISC_R_SUCCESS);
}

/*
 * If the deletion of the A succeeded, and there are no A or AAAA
 * 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 record has been added
 * to this domain name.
 *
 * Second query has:
 * A RR does not exist.
 * AAAA RR does not exist.
 * Delete appropriate DHCID RR.
 */
static isc_result_t
build_fwd_rem2(dhcp_ddns_cb_t   *ddns_cb,
                     dhcp_ddns_data_t *dataspace,
                     dns_name_t       *pname,
                     dns_name_t       *uname)
{
        isc_result_t result;
        unsigned char *match_id = NULL;
        int match_id_len = 0;
        int match_class = dns_rdataclass_any;

#if defined (DEBUG_DNS_UPDATES)
        log_call("build_fwd_rem2", pname, uname);
#endif

        /* Construct the prereq list */
        /* The A RR does not exist */
        result = make_dns_dataset(dns_rdataclass_none, dns_rdatatype_a,
                                  dataspace, NULL, 0, 0);
        if (result != ISC_R_SUCCESS) {
                return(result);
        }
        ISC_LIST_APPEND(pname->list, &dataspace->rdataset, link);
        dataspace++;

        /* The AAAA RR does not exist */
        result = make_dns_dataset(dns_rdataclass_none, dns_rdatatype_aaaa,
                                  dataspace, NULL, 0, 0);
        if (result != ISC_R_SUCCESS) {
                return(result);
        }
        ISC_LIST_APPEND(pname->list, &dataspace->rdataset, link);
        dataspace++;

        /* Construct the update list */
        /* Delete DHCID RR */

        /* We'll specify the client id in the guard record delete if
         * matching is enabled, otherwise we leave it off. */
        if (ddns_cb->flags & DDNS_GUARD_ID_MUST_MATCH) {
                match_id = (unsigned char*)(ddns_cb->dhcid.data);
                match_id_len = ddns_cb->dhcid.len;
                match_class = dns_rdataclass_none;
        }

        result = make_dns_dataset(match_class, ddns_cb->dhcid_class,
                                  dataspace,
                                  match_id, match_id_len, 0);
        if (result != ISC_R_SUCCESS) {
                return(result);
        }
        ISC_LIST_APPEND(uname->list, &dataspace->rdataset, link);

        return(ISC_R_SUCCESS);
}

/*
 * Constructs the second stage forward remove, when the first stage
 * succeeds and DSMM is enabled, and ddns-other-guard-is-dynamic is OFF
 *
 * Normal conflict detection requires that the guard record of the
 * configured type only be deleted if there are no address records of
 * any type.  In Dual Stack Mixed Mode, we are only concerned with whether
 * there any records or our configured address type remaining.
 *
 * This update consists of a single prequisite that there be no address
 * records of our type followed by a delete of the guard record of our type
 * and optionally matching client-id.
 *
 * prereq nxrrset name <addr_t>     # no records of this address type exist
 * update delete name <guard_t> <client_id>  # delete the existing guard record
 */
static isc_result_t
build_fwd_rem2_dsmm (dhcp_ddns_cb_t   *ddns_cb,
                     dhcp_ddns_data_t *dataspace,
                     dns_name_t       *pname,
                     dns_name_t       *uname)
{
        isc_result_t result;
        unsigned char *match_id = NULL;
        int match_id_len = 0;
        int match_class = dns_rdataclass_any;

#if defined (DEBUG_DNS_UPDATES)
        log_call("build_fwd_rem2_dsmm", pname, uname);
#endif

        /* Construct the prereq list */
        /* The address RR does not exist */
        result = make_dns_dataset(dns_rdataclass_none,
                                  ddns_cb->address_type,
                                  dataspace, NULL, 0, 0);
        if (result != ISC_R_SUCCESS) {
                return(result);
        }
        ISC_LIST_APPEND(pname->list, &dataspace->rdataset, link);
        dataspace++;

        /* Construct the update list */
        /* Delete DHCID RR */

        /* We'll specify the client id in the guard record delete if
         * matching is enabled, otherwise we leave it off. */
        if (ddns_cb->flags & DDNS_GUARD_ID_MUST_MATCH) {
                match_id = (unsigned char*)(ddns_cb->dhcid.data);
                match_id_len = ddns_cb->dhcid.len;
                match_class = dns_rdataclass_none;
        }

        result = make_dns_dataset(match_class, ddns_cb->dhcid_class,
                                  dataspace,
                                  match_id, match_id_len, 0);
        if (result != ISC_R_SUCCESS) {
                return(result);
        }
        ISC_LIST_APPEND(uname->list, &dataspace->rdataset, link);

        return(ISC_R_SUCCESS);
}

/*
 * Constructs the second stage forward remove, when the first stage
 * succeeds and DSMM is enabled and ddns-other-guard-is-dynamic is ON
 *
 * This update addresses the case when an address record of our type exists
 * without a guard record of our type, yet a dynamic entry of the other type
 * exists.  The presence of a guard of the other type indicates that all
 * entries for this name should be treated as dynamic, thus permitting us to
 * remove the address record of our type.
 *
 * prereq nxrrset <name> <guard_t>        # my guard type does not exist
 * prereq yxrrset <name> <other_guard_t>  # other guard type does exist
 * update delete <name> <addr_t> address  # delete the existing address record
 *
 */
static isc_result_t
build_fwd_rem2_dsmm_other(dhcp_ddns_cb_t   *ddns_cb,
                     dhcp_ddns_data_t *dataspace,
                     dns_name_t       *pname,
                     dns_name_t       *uname)
{
        isc_result_t result;

#if defined (DEBUG_DNS_UPDATES)
        log_call("build_fwd_rem2_dsmm_other", pname, uname);
#endif

        /* Construct the prereq list */
        /* No guard record of my type exists */
        result = make_dns_dataset(dns_rdataclass_none, ddns_cb->dhcid_class,
                                  dataspace, NULL, 0, 0);
        if (result != ISC_R_SUCCESS) {
                return(result);
        }
        ISC_LIST_APPEND(pname->list, &dataspace->rdataset, link);
        dataspace++;

        /* Guard record of the OTHER type DOES exist */
        result = make_dns_dataset(dns_rdataclass_any,
                                  ddns_cb->other_dhcid_class,
                                  dataspace, NULL, 0, 0);
        if (result != ISC_R_SUCCESS) {
                return(result);
        }
        ISC_LIST_APPEND(pname->list, &dataspace->rdataset, link);
        dataspace++;

        /* Construct the update list */
        /* Delete the address RRset */
        result = make_dns_dataset(dns_rdataclass_none, ddns_cb->address_type,
                                  dataspace,
                                  (unsigned char *)ddns_cb->address.iabuf,
                                  ddns_cb->address.len, 0);
        if (result != ISC_R_SUCCESS) {
                return(result);
        }
        ISC_LIST_APPEND(uname->list, &dataspace->rdataset, link);

        return(ISC_R_SUCCESS);
}

/*
 * This routine converts from the task action call into something
 * easier to work with.  It also handles the common case of a signature
 * or zone not being correct.
 */
void ddns_interlude(isc_task_t  *taskp,
                    isc_event_t *eventp)
{
        dhcp_ddns_cb_t *ddns_cb = (dhcp_ddns_cb_t *)eventp->ev_arg;
        dns_clientupdateevent_t *ddns_event = (dns_clientupdateevent_t *)eventp;
        isc_result_t eresult = ddns_event->result;
        isc_result_t result;

        /* We've extracted the information we want from it, get rid of
         * the event block.*/
        isc_event_free(&eventp);

#if defined (TRACING)
        if (trace_record()) {
                trace_ddns_input_write(ddns_cb, eresult);
        }
#endif

#if defined (DEBUG_DNS_UPDATES)
        print_dns_status(DDNS_PRINT_INBOUND, ddns_cb, eresult);
#endif

        /* This transaction is complete, clear the value */
        dns_client_destroyupdatetrans(&ddns_cb->transaction);

        /* If we cancelled or tried to cancel the operation we just
         * need to clean up. */
        if ((eresult == ISC_R_CANCELED) ||
            ((ddns_cb->flags & DDNS_ABORT) != 0)) {
#if defined (DEBUG_DNS_UPDATES)
                log_info("DDNS: completeing transaction cancellation cb=%p, "
                         "flags=%x, %s",
                         ddns_cb, ddns_cb->flags, isc_result_totext(eresult));
#endif
                if ((ddns_cb->flags & DDNS_ABORT) == 0) {
                        log_info("DDNS: cleaning up lease pointer for a cancel "
                                 "cb=%p", ddns_cb);
                        /*
                         * We shouldn't actually be able to get here but
                         * we are.  This means we haven't cleaned up
                         * the lease pointer so we need to do that before
                         * freeing the cb.
                         */
                        ddns_cb->cur_func(ddns_cb, eresult);
                        return;
                }

                if (ddns_cb->next_op != NULL) {
                        /* if necessary cleanup up next op block */
                        ddns_cb_free(ddns_cb->next_op, MDL);
                }
                ddns_cb_free(ddns_cb, MDL);
                return;
        }

        /* If we had a problem with our key or zone try again */
        if ((eresult == DNS_R_NOTAUTH) ||
            (eresult == DNS_R_NOTZONE)) {
                int i;
                /* Our zone information was questionable,
                 * repudiate it and try again */
                log_error("DDNS: bad zone information, repudiating zone %s",
                          ddns_cb->zone_name);
                repudiate_zone(&ddns_cb->zone);
                ddns_cb->zone_name[0]    = 0;
                ISC_LIST_INIT(ddns_cb->zone_server_list);
                for (i = 0; i < DHCP_MAXNS; i++) {
                        ISC_LINK_INIT(&ddns_cb->zone_addrs[i], link);
                }

                if ((ddns_cb->state == DDNS_STATE_ADD_PTR) ||
                    (ddns_cb->state == DDNS_STATE_REM_PTR)) {
                        result = ddns_modify_ptr(ddns_cb, MDL);
                } else {
                        result = ddns_modify_fwd(ddns_cb, MDL);
                }

                if (result != ISC_R_SUCCESS) {
                        /* if we couldn't redo the query log it and
                         * let the next function clean it up */
                        log_info("DDNS: Failed to retry after zone failure");
                        ddns_cb->cur_func(ddns_cb, result);
                }
                return;
        } else {
                /* pass it along to be processed */
                ddns_cb->cur_func(ddns_cb, eresult);
        }

        return;
}

/*
 * This routine does the generic work for sending a ddns message to
 * modify the forward record (A or AAAA) and calls one of a set of
 * routines to build the specific message.
 */

isc_result_t
ddns_modify_fwd(dhcp_ddns_cb_t *ddns_cb, const char *file, int line)
{
        isc_result_t result;
        dns_tsec_t *tsec_key = NULL;

#if defined (DEBUG_DNS_UPDATES)
        log_info("DDNS: ddns_modify_fwd");
#endif

        unsigned char *clientname;
        dhcp_ddns_data_t *dataspace = NULL;
        dns_namelist_t prereqlist, updatelist;
        dns_fixedname_t zname0, pname0, uname0;
        dns_name_t *zname = NULL, *pname, *uname;

        isc_sockaddrlist_t *zlist = NULL;

        /* Creates client context if we need to */
        result = dns_client_init();
        if (result != ISC_R_SUCCESS) {
                return result;
        }

        /* Get a pointer to the clientname to make things easier. */
        clientname = (unsigned char *)ddns_cb->fwd_name.data;

        /* Extract and validate the type of the address. */
        if (ddns_cb->address.len == 4) {
                ddns_cb->address_type = dns_rdatatype_a;
        } else if (ddns_cb->address.len == 16) {
                ddns_cb->address_type = dns_rdatatype_aaaa;
        } else {
                return DHCP_R_INVALIDARG;
        }

        /*
         * If we already have a zone use it, otherwise try to lookup the
         * zone in our cache.  If we find one we will have a pointer to
         * the zone that needs to be dereferenced when we are done with it.
         * If we don't find one that is okay we'll let the DNS code try and
         * find the information for us.
         */

        if (ddns_cb->zone == NULL) {
                result = find_cached_zone(ddns_cb, FIND_FORWARD);
#if defined (DNS_ZONE_LOOKUP)
                if (result == ISC_R_NOTFOUND) {
                        /*
                         * We didn't find a cached zone, see if we can
                         * can find a nameserver and create a zone.
                         */
                        if (find_zone_start(ddns_cb, FIND_FORWARD)
                            == ISC_R_SUCCESS) {
                                /*
                                 * We have started the process to find a zone
                                 * queue the ddns_cb for processing after we
                                 * create the zone
                                 */
                                /* sar - not yet implemented, currently we just
                                 * arrange for things to get cleaned up
                                 */
                                goto cleanup;
                        }
                }
#endif
                if (result != ISC_R_SUCCESS)
                        goto cleanup;
        }

        /*
         * If we have a zone try to get any information we need
         * from it - name, addresses and the key.  The address
         * and key may be empty the name can't be.
         */
        if (ddns_cb->zone) {
                /* Set up the zone name for use by DNS */
                result = dhcp_isc_name(ddns_cb->zone_name, &zname0, &zname);
                if (result != ISC_R_SUCCESS) {
                        log_error("Unable to build name for zone for "
                                  "fwd update: %s %s",
                                  ddns_cb->zone_name,
                                  isc_result_totext(result));
                        goto cleanup;
                }

                if (!(ISC_LIST_EMPTY(ddns_cb->zone_server_list))) {
                        /* If we have any addresses get them */
                        zlist = &ddns_cb->zone_server_list;
                }


                if (ddns_cb->zone->key != NULL) {
                        /*
                         * Not having a key is fine, having a key
                         * but not a tsec is odd so we warn the user.
                         */
                        /*sar*/
                        /* should we do the warning? */
                        tsec_key = ddns_cb->zone->key->tsec_key;
                        if (tsec_key == NULL) {
                                log_error("No tsec for use with key %s",
                                          ddns_cb->zone->key->name);
                        }
                }
        }

        /* Set up the DNS names for the prereq and update lists */
        if (((result = dhcp_isc_name(clientname, &pname0, &pname))
             != ISC_R_SUCCESS) ||
            ((result = dhcp_isc_name(clientname, &uname0, &uname))
             != ISC_R_SUCCESS)) {
                log_error("Unable to build name for fwd update: %s %s",
                          clientname, isc_result_totext(result));
                goto cleanup;
        }

        /* Allocate the various isc dns library structures we may require. */
        dataspace = isc_mem_get(dhcp_gbl_ctx.mctx, sizeof(*dataspace) * 4);
        if (dataspace == NULL) {
                log_error("Unable to allocate memory for fwd update");
                result = ISC_R_NOMEMORY;
                goto cleanup;
        }

        ISC_LIST_INIT(prereqlist);
        ISC_LIST_INIT(updatelist);

        switch(ddns_cb->state) {
        case DDNS_STATE_ADD_FW_NXDOMAIN:
                result = build_fwd_add1(ddns_cb, dataspace, pname, uname);
                if (result != ISC_R_SUCCESS) {
                        goto cleanup;
                }
                ISC_LIST_APPEND(prereqlist, pname, link);
                break;

        case DDNS_STATE_ADD_FW_YXDHCID:
                result = build_fwd_add2(ddns_cb, dataspace, pname, uname);
                if (result != ISC_R_SUCCESS) {
                        goto cleanup;
                }

                /* If we are doing conflict detection we have entries
                 * in the pname list and we need to attach it to the
                 * prereqlist */

                if (ddns_cb->flags & DDNS_CONFLICT_DETECTION) {
                        ISC_LIST_APPEND(prereqlist, pname, link);
                }

                break;

        case DDNS_STATE_DSMM_FW_ADD3: {
                /* We should only be here if we're doing DSMM */
                builder_func_t builder;
                if (ddns_cb->flags & DDNS_OTHER_GUARD_IS_DYNAMIC) {
                        builder = build_dsmm_fwd_add3_other;
                } else {
                        builder = build_dsmm_fwd_add3;
                }

                result = (*builder)(ddns_cb, dataspace, pname, uname);
                if (result != ISC_R_SUCCESS) {
                        goto cleanup;
                }

                ISC_LIST_APPEND(prereqlist, pname, link);
                break;
                }

        case DDNS_STATE_REM_FW_YXDHCID:
                result = build_fwd_rem1(ddns_cb, dataspace, pname, uname);
                if (result != ISC_R_SUCCESS) {
                        goto cleanup;
                }
                ISC_LIST_APPEND(prereqlist, pname, link);
                break;

        case DDNS_STATE_REM_FW_NXRR: {
                builder_func_t builder;

                if (ddns_cb->flags & DDNS_DUAL_STACK_MIXED_MODE) {
                        builder = build_fwd_rem2_dsmm;
                } else {
                        builder = build_fwd_rem2;
                }

                result = (*builder)(ddns_cb, dataspace, pname, uname);
                if (result != ISC_R_SUCCESS) {
                        goto cleanup; }
                ISC_LIST_APPEND(prereqlist, pname, link);
                break;
                }

        case DDNS_STATE_REM_FW_DSMM_OTHER: {
                result = build_fwd_rem2_dsmm_other(ddns_cb, dataspace,
                                                  pname, uname);
                if (result != ISC_R_SUCCESS) {
                        goto cleanup; }
                ISC_LIST_APPEND(prereqlist, pname, link);
                break;
                }

        default:
                log_error("ddns_modify_fwd: Invalid state: %d", ddns_cb->state);
                result = DHCP_R_INVALIDARG;
                goto cleanup;
                break;
        }

        /*
         * We always have an update list but may not have a prereqlist
         * if we are doing conflict override.
         */
        ISC_LIST_APPEND(updatelist, uname, link);

        /* send the message, cleanup and return the result */
        result = ddns_update(dhcp_gbl_ctx.dnsclient,
                             dns_rdataclass_in, zname,
                             &prereqlist, &updatelist,
                             zlist, tsec_key,
                             DNS_CLIENTUPDOPT_ALLOWRUN,
                             dhcp_gbl_ctx.task,
                             ddns_interlude,
                             (void *)ddns_cb,
                             &ddns_cb->transaction);
        if (result == ISC_R_FAMILYNOSUPPORT) {
                log_info("Unable to perform DDNS update, "
                         "address family not supported");
        }

#if defined (DEBUG_DNS_UPDATES)
        print_dns_status(DDNS_PRINT_OUTBOUND, ddns_cb, result);
#endif

 cleanup:
#if defined (DEBUG_DNS_UPDATES)
        if (result != ISC_R_SUCCESS) {
                log_info("DDNS: %s(%d): error in ddns_modify_fwd %s for %p",
                         file, line, isc_result_totext(result), ddns_cb);
        }
#endif

        if (dataspace != NULL) {
                isc_mem_put(dhcp_gbl_ctx.mctx, dataspace,
                            sizeof(*dataspace) * 4);
        }
        return(result);
}


isc_result_t
ddns_modify_ptr(dhcp_ddns_cb_t *ddns_cb, const char *file, int line)
{
        isc_result_t result;
        dns_tsec_t *tsec_key  = NULL;
        unsigned char *ptrname;
        dhcp_ddns_data_t *dataspace = NULL;
        dns_namelist_t updatelist;
        dns_fixedname_t zname0, uname0;
        dns_name_t *zname = NULL, *uname;
        isc_sockaddrlist_t *zlist = NULL;
        unsigned char buf[256];
        int buflen;

#if defined (DEBUG_DNS_UPDATES)
        log_info("DDNS: ddns_modify_ptr");
#endif

        /* Creates client context if we need to */
        result = dns_client_init();
        if (result != ISC_R_SUCCESS) {
                return result;
        }

        /*
         * Try to lookup the zone in the zone cache.  As with the forward
         * case it's okay if we don't have one, the DNS code will try to
         * find something also if we succeed we will need to dereference
         * the zone later.  Unlike with the forward case we assume we won't
         * have a pre-existing zone.
         */
        result = find_cached_zone(ddns_cb, FIND_REVERSE);

#if defined (DNS_ZONE_LOOKUP)
        if (result == ISC_R_NOTFOUND) {
                /*
                 * We didn't find a cached zone, see if we can
                 * can find a nameserver and create a zone.
                 */
                if (find_zone_start(ddns_cb, FIND_REVERSE) == ISC_R_SUCCESS) {
                        /*
                         * We have started the process to find a zone
                         * queue the ddns_cb for processing after we
                         * create the zone
                         */
                        /* sar - not yet implemented, currently we just
                         * arrange for things to get cleaned up
                         */
                        goto cleanup;
                }
        }
#endif
        if (result != ISC_R_SUCCESS)
                goto cleanup;


        if ((result == ISC_R_SUCCESS) &&
            !(ISC_LIST_EMPTY(ddns_cb->zone_server_list))) {
                /* Set up the zone name for use by DNS */
                result = dhcp_isc_name(ddns_cb->zone_name, &zname0, &zname);
                if (result != ISC_R_SUCCESS) {
                        log_error("Unable to build name for zone for "
                                  "fwd update: %s %s",
                                  ddns_cb->zone_name,
                                  isc_result_totext(result));
                        goto cleanup;
                }
                /* If we have any addresses get them */
                if (!(ISC_LIST_EMPTY(ddns_cb->zone_server_list))) {
                        zlist = &ddns_cb->zone_server_list;
                }

                /*
                 * If we now have a zone try to get the key, NULL is okay,
                 * having a key but not a tsec is odd so we warn.
                 */
                /*sar*/
                /* should we do the warning if we have a key but no tsec? */
                if ((ddns_cb->zone != NULL) && (ddns_cb->zone->key != NULL)) {
                        tsec_key = ddns_cb->zone->key->tsec_key;
                        if (tsec_key == NULL) {
                                log_error("No tsec for use with key %s",
                                          ddns_cb->zone->key->name);
                        }
                }
        }

        /* We must have a name for the update list */
        /* Get a pointer to the ptrname to make things easier. */
        ptrname = (unsigned char *)ddns_cb->rev_name.data;

        if ((result = dhcp_isc_name(ptrname, &uname0, &uname))
             != ISC_R_SUCCESS) {
                log_error("Unable to build name for fwd update: %s %s",
                          ptrname, isc_result_totext(result));
                goto cleanup;
        }

        /*
         * Allocate the various isc dns library structures we may require.
         * Allocating one blob avoids being halfway through the process
         * and being unable to allocate as well as making the free easy.
         */
        dataspace = isc_mem_get(dhcp_gbl_ctx.mctx, sizeof(*dataspace) * 2);
        if (dataspace == NULL) {
                log_error("Unable to allocate memory for fwd update");
                result = ISC_R_NOMEMORY;
                goto cleanup;
        }

        ISC_LIST_INIT(updatelist);

        /*
         * Construct the update list
         * We always delete what's currently there
         * Delete PTR RR.
         */
        result = make_dns_dataset(dns_rdataclass_any, dns_rdatatype_ptr,
                                  &dataspace[0], NULL, 0, 0);
        if (result != ISC_R_SUCCESS) {
                goto cleanup;
        }
        ISC_LIST_APPEND(uname->list, &dataspace[0].rdataset, link);

        /*
         * If we are updating the pointer we then add the new one
         * Add PTR RR.
         */
        if (ddns_cb->state == DDNS_STATE_ADD_PTR) {
                /*
                 * Need to convert pointer into on the wire representation
                 */
                if (MRns_name_pton((char *)ddns_cb->fwd_name.data,
                                   buf, 256) == -1) {
                        goto cleanup;
                }
                buflen = 0;
                while (buf[buflen] != 0) {
                        buflen += buf[buflen] + 1;
                }
                buflen++;

                result = make_dns_dataset(dns_rdataclass_in,
                                          dns_rdatatype_ptr,
                                          &dataspace[1],
                                          buf, buflen, ddns_cb->ttl);
                if (result != ISC_R_SUCCESS) {
                        goto cleanup;
                }
                ISC_LIST_APPEND(uname->list, &dataspace[1].rdataset, link);
        }

        ISC_LIST_APPEND(updatelist, uname, link);

        /*sar*/
        /*
         * for now I'll cleanup the dataset immediately, it would be
         * more efficient to keep it around in case the signaturure failed
         * and we wanted to retry it.
         */
        /* send the message, cleanup and return the result */
        result = ddns_update((dns_client_t *)dhcp_gbl_ctx.dnsclient,
                             dns_rdataclass_in, zname,
                             NULL, &updatelist,
                             zlist, tsec_key,
                             DNS_CLIENTUPDOPT_ALLOWRUN,
                             dhcp_gbl_ctx.task,
                             ddns_interlude, (void *)ddns_cb,
                             &ddns_cb->transaction);
        if (result == ISC_R_FAMILYNOSUPPORT) {
                log_info("Unable to perform DDNS update, "
                         "address family not supported");
        }

#if defined (DEBUG_DNS_UPDATES)
        print_dns_status(DDNS_PRINT_OUTBOUND, ddns_cb, result);
#endif

 cleanup:
#if defined (DEBUG_DNS_UPDATES)
        if (result != ISC_R_SUCCESS) {
                log_info("DDNS: %s(%d): error in ddns_modify_ptr %s for %p",
                         file, line, isc_result_totext(result), ddns_cb);
        }
#endif

        if (dataspace != NULL) {
                isc_mem_put(dhcp_gbl_ctx.mctx, dataspace,
                            sizeof(*dataspace) * 2);
        }
        return(result);
}

void
ddns_cancel(dhcp_ddns_cb_t *ddns_cb, const char *file, int line) {
        ddns_cb->flags |= DDNS_ABORT;
        if (ddns_cb->transaction != NULL) {
                dns_client_cancelupdate((dns_clientupdatetrans_t *)
                                        ddns_cb->transaction);
        }
        ddns_cb->lease = NULL;

#if defined (DEBUG_DNS_UPDATES)
        log_info("DDNS: %s(%d): cancelling transaction for  %p",
                 file, line,  ddns_cb);
#endif
}

#endif /* NSUPDATE */

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

#if defined (NSUPDATE)
#if defined (DEBUG_DNS_UPDATES)
/* Defines a type for creating list of labeled integers */
typedef struct {
        int val;
        char *name;
} LabeledInt;

char*
ddns_state_name(int state) {
        static LabeledInt ints[] = {
                { DDNS_STATE_CLEANUP, "DDNS_STATE_CLEANUP" },
                { DDNS_STATE_ADD_FW_NXDOMAIN, "DDNS_STATE_ADD_FW_NXDOMAIN" },
                { DDNS_STATE_ADD_FW_YXDHCID, "DDNS_STATE_ADD_FW_YXDHCID" },
                { DDNS_STATE_ADD_PTR, "DDNS_STATE_ADD_PTR" },
                { DDNS_STATE_DSMM_FW_ADD3, "DDNS_STATE_DSMM_FW_ADD3" },
                { DDNS_STATE_REM_FW_YXDHCID, "DDNS_STATE_REM_FW_YXDHCID" },
                { DDNS_STATE_REM_FW_NXRR, "DDNS_STATE_FW_NXRR" },
                { DDNS_STATE_REM_PTR, "DDNS_STATE_REM_PTR" },
                { -1, "unknown" },
        };

        LabeledInt* li = ints;
        while (li->val != -1 && li->val != state) {
                ++li;
        }

        return (li->name);
}

int
add_nstring(char **orig, char *max, char *add, int add_len) {
        if (*orig && (*orig + add_len < max)) {
                strncpy(*orig, add, add_len);
                *orig += add_len;
                **orig = 0;
                return (0);
        }

        return (-1);
}

int
add_string(char **orig, char *max, char *add) {
        return (add_nstring(orig, max, add, strlen(add)));
}

/*
 * direction outbound (messages to the dns server)
 *           inbound  (messages from the dns server)
 * ddns_cb is the control block associated with the message
 * result is the result from the dns code.  For outbound calls
 * it is from the call to pass the message to the dns library.
 * For inbound calls it is from the event returned by the library.
 *
 * For outbound messages we print whatever we think is interesting
 * from the control block.
 * For inbound messages we only print the transaction id pointer
 * and the result and expect that the user will match them up as
 * necessary.  Note well: the transaction information is opaque to
 * us so we simply print the pointer to it.  This should be sufficient
 * to match requests and replys in a short sequence but is awkward
 * when trying to use it for longer sequences.
 */
void
print_dns_status (int direction,
                  struct dhcp_ddns_cb *ddns_cb,
                  isc_result_t result)
{
        char obuf[1024];
        char *s = obuf, *end = &obuf[sizeof(obuf)-2];
        char *en;
        const char *result_str;
        char ddns_address[
                sizeof("ffff:ffff:ffff:ffff:ffff:ffff:255.255.255.255")];

        if (direction == DDNS_PRINT_INBOUND) {
                log_info("DDNS reply: id ptr %p, result: %s",
                         ddns_cb->transaction, isc_result_totext(result));
                return;
        }

        /*
         * To avoid having to figure out if any of the strings
         * aren't NULL terminated, just 0 the whole string
         */
        memset(obuf, 0, 1024);

        en = "DDNS request: id ptr ";
        if (s + strlen(en) + 16 < end) {
                sprintf(s, "%s%p", en, ddns_cb->transaction);
                s += strlen(s);
        } else {
                goto bailout;
        }

        en = ddns_state_name(ddns_cb->state);

        switch (ddns_cb->state) {
        case DDNS_STATE_ADD_FW_NXDOMAIN:
        case DDNS_STATE_ADD_FW_YXDHCID:
        case DDNS_STATE_REM_FW_YXDHCID:
        case DDNS_STATE_REM_FW_NXRR:
        case DDNS_STATE_DSMM_FW_ADD3:
                strcpy(ddns_address, piaddr(ddns_cb->address));
                if (s + strlen(en) + strlen(ddns_address) +
                    ddns_cb->fwd_name.len + 7 < end) {
                        sprintf(s, " %s %s for %.*s", en, ddns_address,
                                ddns_cb->fwd_name.len,
                                ddns_cb->fwd_name.data);
                        s += strlen(s);
                } else {
                        goto bailout;
                }
                break;

        case DDNS_STATE_ADD_PTR:
        case DDNS_STATE_REM_PTR:
                if (s + strlen(en) + ddns_cb->fwd_name.len +
                    ddns_cb->rev_name.len + 7 < end) {
                        sprintf(s, " %s %.*s for %.*s", en,
                                ddns_cb->fwd_name.len,
                                ddns_cb->fwd_name.data,
                                ddns_cb->rev_name.len,
                                ddns_cb->rev_name.data);
                        s += strlen(s);
                } else {
                        goto bailout;
                }
                break;

        case DDNS_STATE_CLEANUP:
        default:
                if (s + strlen(en) < end) {
                        sprintf(s, "%s", en);
                        s += strlen(s);
                } else {
                        goto bailout;
                }
                break;
        }

        en = " zone: ";
        if (s + strlen(en) + strlen((char *)ddns_cb->zone_name) < end) {
                sprintf(s, "%s%s", en, ddns_cb->zone_name);
                s += strlen(s);
        } else {
                goto bailout;
        }

        /* @todo replace with format that matches bind9 zone file */
        if (ddns_cb->dhcid_class == dns_rdatatype_dhcid) {
                char *idbuf = NULL;
                if (add_string(&s, end, "dhcid: [")) {
                        goto bailout;
                }

                idbuf = buf_to_hex(ddns_cb->dhcid.data,
                                   ddns_cb->dhcid.len, MDL);
                if (idbuf) {
                        int ret = add_string(&s, end, idbuf);
                        dfree(idbuf, MDL);
                        if (!ret) {
                                goto bailout;
                        }
                }

                if (add_string(&s, end, "]")) {
                        goto bailout;
                }
        } else {
                /* 1st byte of a txt dhcid is length, so we skip printing it
                 * In the event it's empty, we end up not adding anything */
                int skip_length_byte = (ddns_cb->dhcid.len > 0 ? 1 : 0);
                if (add_string (&s, end, "txt: [") ||
                    add_nstring (&s, end,
                                (char *)ddns_cb->dhcid.data + skip_length_byte,
                                 ddns_cb->dhcid.len - skip_length_byte) ||
                    add_string (&s, end, "]")) {
                        goto bailout;
                }
        }

        en = " ttl: ";
        if (s + strlen(en) + 10 < end) {
                sprintf(s, "%s%ld", en, ddns_cb->ttl);
                s += strlen(s);
        } else {
                goto bailout;
        }

        en = " result: ";
        result_str = isc_result_totext(result);
        if (s + strlen(en) + strlen(result_str) < end) {
                sprintf(s, "%s%s", en, result_str);
                s += strlen(s);
        } else {
                goto bailout;
        }

 bailout:
        /*
         * We either finished building the string or ran out
         * of space, print whatever we have in case it is useful
         */
        log_info("%s", obuf);

        return;
}
#endif /* DEBUG_DNS_UPDATES */
#endif /* NSUPDATE */