Import bind-9.3.4

[dragonfly.git] / contrib / bind-9.3 / bin / named / update.c

/*
 * Copyright (C) 2004-2006  Internet Systems Consortium, Inc. ("ISC")
 * Copyright (C) 1999-2003  Internet Software Consortium.
 *
 * Permission to use, copy, modify, and distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES WITH
 * REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
 * AND FITNESS.  IN NO EVENT SHALL ISC BE LIABLE FOR ANY SPECIAL, DIRECT,
 * INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
 * LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE
 * OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
 * PERFORMANCE OF THIS SOFTWARE.
 */

/* $Id: update.c,v 1.88.2.5.2.29 2006/01/06 00:01:42 marka Exp $ */

#include <config.h>

#include <isc/print.h>
#include <isc/string.h>
#include <isc/taskpool.h>
#include <isc/util.h>

#include <dns/db.h>
#include <dns/dbiterator.h>
#include <dns/diff.h>
#include <dns/dnssec.h>
#include <dns/events.h>
#include <dns/fixedname.h>
#include <dns/journal.h>
#include <dns/message.h>
#include <dns/nsec.h>
#include <dns/rdataclass.h>
#include <dns/rdataset.h>
#include <dns/rdatasetiter.h>
#include <dns/rdatastruct.h>
#include <dns/rdatatype.h>
#include <dns/soa.h>
#include <dns/ssu.h>
#include <dns/view.h>
#include <dns/zone.h>
#include <dns/zt.h>

#include <named/client.h>
#include <named/log.h>
#include <named/update.h>

/*
 * This module implements dynamic update as in RFC2136.
 */

/*
  XXX TODO:
  - document strict minimality
*/

/**************************************************************************/

/*
 * Log level for tracing dynamic update protocol requests.
 */
#define LOGLEVEL_PROTOCOL       ISC_LOG_INFO

/*
 * Log level for low-level debug tracing.
 */
#define LOGLEVEL_DEBUG          ISC_LOG_DEBUG(8)

/*
 * Check an operation for failure.  These macros all assume that
 * the function using them has a 'result' variable and a 'failure'
 * label.
 */
#define CHECK(op) \
        do { result = (op);                                      \
               if (result != ISC_R_SUCCESS) goto failure;        \
        } while (0)

/*
 * Fail unconditionally with result 'code', which must not
 * be ISC_R_SUCCESS.  The reason for failure presumably has
 * been logged already.
 *
 * The test against ISC_R_SUCCESS is there to keep the Solaris compiler
 * from complaining about "end-of-loop code not reached".
 */

#define FAIL(code) \
        do {                                                    \
                result = (code);                                \
                if (result != ISC_R_SUCCESS) goto failure;      \
        } while (0)

/*
 * Fail unconditionally and log as a client error.
 * The test against ISC_R_SUCCESS is there to keep the Solaris compiler
 * from complaining about "end-of-loop code not reached".
 */
#define FAILC(code, msg) \
        do {                                                    \
                const char *_what = "failed";                   \
                result = (code);                                \
                switch (result) {                               \
                case DNS_R_NXDOMAIN:                            \
                case DNS_R_YXDOMAIN:                            \
                case DNS_R_YXRRSET:                             \
                case DNS_R_NXRRSET:                             \
                        _what = "unsuccessful";                 \
                }                                               \
                update_log(client, zone, LOGLEVEL_PROTOCOL,     \
                              "update %s: %s (%s)", _what,      \
                              msg, isc_result_totext(result));  \
                if (result != ISC_R_SUCCESS) goto failure;      \
        } while (0)

#define FAILN(code, name, msg) \
        do {                                                            \
                const char *_what = "failed";                           \
                result = (code);                                        \
                switch (result) {                                       \
                case DNS_R_NXDOMAIN:                                    \
                case DNS_R_YXDOMAIN:                                    \
                case DNS_R_YXRRSET:                                     \
                case DNS_R_NXRRSET:                                     \
                        _what = "unsuccessful";                         \
                }                                                       \
                if (isc_log_wouldlog(ns_g_lctx, LOGLEVEL_PROTOCOL)) {   \
                        char _nbuf[DNS_NAME_FORMATSIZE];                \
                        dns_name_format(name, _nbuf, sizeof(_nbuf));    \
                        update_log(client, zone, LOGLEVEL_PROTOCOL,     \
                                   "update %s: %s: %s (%s)", _what, _nbuf, \
                                   msg, isc_result_totext(result));     \
                }                                                       \
                if (result != ISC_R_SUCCESS) goto failure;              \
        } while (0)

#define FAILNT(code, name, type, msg) \
        do {                                                            \
                const char *_what = "failed";                           \
                result = (code);                                        \
                switch (result) {                                       \
                case DNS_R_NXDOMAIN:                                    \
                case DNS_R_YXDOMAIN:                                    \
                case DNS_R_YXRRSET:                                     \
                case DNS_R_NXRRSET:                                     \
                        _what = "unsuccessful";                         \
                }                                                       \
                if (isc_log_wouldlog(ns_g_lctx, LOGLEVEL_PROTOCOL)) {   \
                        char _nbuf[DNS_NAME_FORMATSIZE];                \
                        char _tbuf[DNS_RDATATYPE_FORMATSIZE];           \
                        dns_name_format(name, _nbuf, sizeof(_nbuf));    \
                        dns_rdatatype_format(type, _tbuf, sizeof(_tbuf)); \
                        update_log(client, zone, LOGLEVEL_PROTOCOL,     \
                                   "update %s: %s/%s: %s (%s)",         \
                                   _what, _nbuf, _tbuf, msg,            \
                                   isc_result_totext(result));          \
                }                                                       \
                if (result != ISC_R_SUCCESS) goto failure;              \
        } while (0)
/*
 * Fail unconditionally and log as a server error.
 * The test against ISC_R_SUCCESS is there to keep the Solaris compiler
 * from complaining about "end-of-loop code not reached".
 */
#define FAILS(code, msg) \
        do {                                                    \
                result = (code);                                \
                update_log(client, zone, LOGLEVEL_PROTOCOL,     \
                              "error: %s: %s",                  \
                              msg, isc_result_totext(result));  \
                if (result != ISC_R_SUCCESS) goto failure;      \
        } while (0)

/**************************************************************************/

typedef struct rr rr_t;

struct rr {
        /* dns_name_t name; */
        isc_uint32_t            ttl;
        dns_rdata_t             rdata;
};

typedef struct update_event update_event_t;

struct update_event {
        ISC_EVENT_COMMON(update_event_t);
        dns_zone_t              *zone;
        isc_result_t            result;
        dns_message_t           *answer;
};

/**************************************************************************/
/*
 * Forward declarations.
 */

static void update_action(isc_task_t *task, isc_event_t *event);
static void updatedone_action(isc_task_t *task, isc_event_t *event);
static isc_result_t send_forward_event(ns_client_t *client, dns_zone_t *zone);
static void forward_done(isc_task_t *task, isc_event_t *event);

/**************************************************************************/

static void
update_log(ns_client_t *client, dns_zone_t *zone,
           int level, const char *fmt, ...) ISC_FORMAT_PRINTF(4, 5);

static void
update_log(ns_client_t *client, dns_zone_t *zone,
           int level, const char *fmt, ...)
{
        va_list ap;
        char message[4096];
        char namebuf[DNS_NAME_FORMATSIZE];
        char classbuf[DNS_RDATACLASS_FORMATSIZE];

        if (client == NULL || zone == NULL)
                return;

        if (isc_log_wouldlog(ns_g_lctx, level) == ISC_FALSE)
                return;

        dns_name_format(dns_zone_getorigin(zone), namebuf,
                        sizeof(namebuf));
        dns_rdataclass_format(dns_zone_getclass(zone), classbuf,
                              sizeof(classbuf));

        va_start(ap, fmt);
        vsnprintf(message, sizeof(message), fmt, ap);
        va_end(ap);

        ns_client_log(client, NS_LOGCATEGORY_UPDATE, NS_LOGMODULE_UPDATE,
                      level, "updating zone '%s/%s': %s",
                      namebuf, classbuf, message);
}

static isc_result_t
checkupdateacl(ns_client_t *client, dns_acl_t *acl, const char *message,
               dns_name_t *zonename, isc_boolean_t slave)
{
        char namebuf[DNS_NAME_FORMATSIZE];
        char classbuf[DNS_RDATACLASS_FORMATSIZE];
        int level = ISC_LOG_ERROR;
        const char *msg = "denied";
        isc_result_t result;

        if (slave && acl == NULL) {
                result = DNS_R_NOTIMP;
                level = ISC_LOG_DEBUG(3);
                msg = "disabled";
        } else
                result = ns_client_checkaclsilent(client, acl, ISC_FALSE);

        if (result == ISC_R_SUCCESS) {
                level = ISC_LOG_DEBUG(3);
                msg = "approved";
        }

        dns_name_format(zonename, namebuf, sizeof(namebuf));
        dns_rdataclass_format(client->view->rdclass, classbuf,
                              sizeof(classbuf));

        ns_client_log(client, NS_LOGCATEGORY_UPDATE_SECURITY,
                              NS_LOGMODULE_UPDATE, level, "%s '%s/%s' %s",
                              message, namebuf, classbuf, msg);
        return (result);
}

/*
 * Update a single RR in version 'ver' of 'db' and log the
 * update in 'diff'.
 *
 * Ensures:
 *   '*tuple' == NULL.  Either the tuple is freed, or its
 *         ownership has been transferred to the diff.
 */
static isc_result_t
do_one_tuple(dns_difftuple_t **tuple,
             dns_db_t *db, dns_dbversion_t *ver,
             dns_diff_t *diff)
{
        dns_diff_t temp_diff;
        isc_result_t result;

        /*
         * Create a singleton diff.
         */
        dns_diff_init(diff->mctx, &temp_diff);
        ISC_LIST_APPEND(temp_diff.tuples, *tuple, link);

        /*
         * Apply it to the database.
         */
        result = dns_diff_apply(&temp_diff, db, ver);
        ISC_LIST_UNLINK(temp_diff.tuples, *tuple, link);
        if (result != ISC_R_SUCCESS) {
                dns_difftuple_free(tuple);
                return (result);
        }

        /*
         * Merge it into the current pending journal entry.
         */
        dns_diff_appendminimal(diff, tuple);

        /*
         * Do not clear temp_diff.
         */
        return (ISC_R_SUCCESS);
}

/*
 * Perform the updates in 'updates' in version 'ver' of 'db' and log the
 * update in 'diff'.
 *
 * Ensures:
 *   'updates' is empty.
 */
static isc_result_t
do_diff(dns_diff_t *updates, dns_db_t *db, dns_dbversion_t *ver,
        dns_diff_t *diff)
{
        isc_result_t result;
        while (! ISC_LIST_EMPTY(updates->tuples)) {
                dns_difftuple_t *t = ISC_LIST_HEAD(updates->tuples);
                ISC_LIST_UNLINK(updates->tuples, t, link);
                CHECK(do_one_tuple(&t, db, ver, diff));
        }
        return (ISC_R_SUCCESS);

 failure:
        dns_diff_clear(diff);
        return (result);
}

static isc_result_t
update_one_rr(dns_db_t *db, dns_dbversion_t *ver, dns_diff_t *diff,
              dns_diffop_t op, dns_name_t *name,
              dns_ttl_t ttl, dns_rdata_t *rdata)
{
        dns_difftuple_t *tuple = NULL;
        isc_result_t result;
        result = dns_difftuple_create(diff->mctx, op,
                                      name, ttl, rdata, &tuple);
        if (result != ISC_R_SUCCESS)
                return (result);
        return (do_one_tuple(&tuple, db, ver, diff));
}

/**************************************************************************/
/*
 * Callback-style iteration over rdatasets and rdatas.
 *
 * foreach_rrset() can be used to iterate over the RRsets
 * of a name and call a callback function with each
 * one.  Similarly, foreach_rr() can be used to iterate
 * over the individual RRs at name, optionally restricted
 * to RRs of a given type.
 *
 * The callback functions are called "actions" and take
 * two arguments: a void pointer for passing arbitrary
 * context information, and a pointer to the current RRset
 * or RR.  By convention, their names end in "_action".
 */

/*
 * XXXRTH  We might want to make this public somewhere in libdns.
 */

/*
 * Function type for foreach_rrset() iterator actions.
 */
typedef isc_result_t rrset_func(void *data, dns_rdataset_t *rrset);

/*
 * Function type for foreach_rr() iterator actions.
 */
typedef isc_result_t rr_func(void *data, rr_t *rr);

/*
 * Internal context struct for foreach_node_rr().
 */
typedef struct {
        rr_func *       rr_action;
        void *          rr_action_data;
} foreach_node_rr_ctx_t;

/*
 * Internal helper function for foreach_node_rr().
 */
static isc_result_t
foreach_node_rr_action(void *data, dns_rdataset_t *rdataset) {
        isc_result_t result;
        foreach_node_rr_ctx_t *ctx = data;
        for (result = dns_rdataset_first(rdataset);
             result == ISC_R_SUCCESS;
             result = dns_rdataset_next(rdataset))
        {
                rr_t rr = { 0, DNS_RDATA_INIT };
                
                dns_rdataset_current(rdataset, &rr.rdata);
                rr.ttl = rdataset->ttl;
                result = (*ctx->rr_action)(ctx->rr_action_data, &rr);
                if (result != ISC_R_SUCCESS)
                        return (result);
        }
        if (result != ISC_R_NOMORE)
                return (result);
        return (ISC_R_SUCCESS);
}

/*
 * For each rdataset of 'name' in 'ver' of 'db', call 'action'
 * with the rdataset and 'action_data' as arguments.  If the name
 * does not exist, do nothing.
 *
 * If 'action' returns an error, abort iteration and return the error.
 */
static isc_result_t
foreach_rrset(dns_db_t *db,
              dns_dbversion_t *ver,
              dns_name_t *name,
              rrset_func *action,
              void *action_data)
{
        isc_result_t result;
        dns_dbnode_t *node;
        dns_rdatasetiter_t *iter;

        node = NULL;
        result = dns_db_findnode(db, name, ISC_FALSE, &node);
        if (result == ISC_R_NOTFOUND)
                return (ISC_R_SUCCESS);
        if (result != ISC_R_SUCCESS)
                return (result);

        iter = NULL;
        result = dns_db_allrdatasets(db, node, ver,
                                     (isc_stdtime_t) 0, &iter);
        if (result != ISC_R_SUCCESS)
                goto cleanup_node;

        for (result = dns_rdatasetiter_first(iter);
             result == ISC_R_SUCCESS;
             result = dns_rdatasetiter_next(iter))
        {
                dns_rdataset_t rdataset;

                dns_rdataset_init(&rdataset);
                dns_rdatasetiter_current(iter, &rdataset);

                result = (*action)(action_data, &rdataset);

                dns_rdataset_disassociate(&rdataset);
                if (result != ISC_R_SUCCESS)
                        goto cleanup_iterator;
        }
        if (result == ISC_R_NOMORE)
                result = ISC_R_SUCCESS;

 cleanup_iterator:
        dns_rdatasetiter_destroy(&iter);

 cleanup_node:
        dns_db_detachnode(db, &node);

        return (result);
}

/*
 * For each RR of 'name' in 'ver' of 'db', call 'action'
 * with the RR and 'action_data' as arguments.  If the name
 * does not exist, do nothing.
 *
 * If 'action' returns an error, abort iteration
 * and return the error.
 */
static isc_result_t
foreach_node_rr(dns_db_t *db,
            dns_dbversion_t *ver,
            dns_name_t *name,
            rr_func *rr_action,
            void *rr_action_data)
{
        foreach_node_rr_ctx_t ctx;
        ctx.rr_action = rr_action;
        ctx.rr_action_data = rr_action_data;
        return (foreach_rrset(db, ver, name,
                              foreach_node_rr_action, &ctx));
}


/*
 * For each of the RRs specified by 'db', 'ver', 'name', 'type',
 * (which can be dns_rdatatype_any to match any type), and 'covers', call
 * 'action' with the RR and 'action_data' as arguments. If the name
 * does not exist, or if no RRset of the given type exists at the name,
 * do nothing.
 *
 * If 'action' returns an error, abort iteration and return the error.
 */
static isc_result_t
foreach_rr(dns_db_t *db,
           dns_dbversion_t *ver,
           dns_name_t *name,
           dns_rdatatype_t type,
           dns_rdatatype_t covers,
           rr_func *rr_action,
           void *rr_action_data)
{

        isc_result_t result;
        dns_dbnode_t *node;
        dns_rdataset_t rdataset;

        if (type == dns_rdatatype_any)
                return (foreach_node_rr(db, ver, name,
                                        rr_action, rr_action_data));

        node = NULL;
        result = dns_db_findnode(db, name, ISC_FALSE, &node);
        if (result == ISC_R_NOTFOUND)
                return (ISC_R_SUCCESS);
        if (result != ISC_R_SUCCESS)
                return (result);

        dns_rdataset_init(&rdataset);
        result = dns_db_findrdataset(db, node, ver, type, covers,
                                     (isc_stdtime_t) 0, &rdataset, NULL);
        if (result == ISC_R_NOTFOUND) {
                result = ISC_R_SUCCESS;
                goto cleanup_node;
        }
        if (result != ISC_R_SUCCESS)
                goto cleanup_node;

        for (result = dns_rdataset_first(&rdataset);
             result == ISC_R_SUCCESS;
             result = dns_rdataset_next(&rdataset))
        {
                rr_t rr = { 0, DNS_RDATA_INIT };
                dns_rdataset_current(&rdataset, &rr.rdata);
                rr.ttl = rdataset.ttl;
                result = (*rr_action)(rr_action_data, &rr);
                if (result != ISC_R_SUCCESS)
                        goto cleanup_rdataset;
        }
        if (result != ISC_R_NOMORE)
                goto cleanup_rdataset;
        result = ISC_R_SUCCESS;

 cleanup_rdataset:
        dns_rdataset_disassociate(&rdataset);
 cleanup_node:
        dns_db_detachnode(db, &node);

        return (result);
}

/**************************************************************************/
/*
 * Various tests on the database contents (for prerequisites, etc).
 */

/*
 * Function type for predicate functions that compare a database RR 'db_rr'
 * against an update RR 'update_rr'.
 */
typedef isc_boolean_t rr_predicate(dns_rdata_t *update_rr, dns_rdata_t *db_rr);

/*
 * Helper function for rrset_exists().
 */
static isc_result_t
rrset_exists_action(void *data, rr_t *rr) {
        UNUSED(data);
        UNUSED(rr);
        return (ISC_R_EXISTS);
}

/*
 * Utility macro for RR existence checking functions.
 *
 * If the variable 'result' has the value ISC_R_EXISTS or
 * ISC_R_SUCCESS, set *exists to ISC_TRUE or ISC_FALSE,
 * respectively, and return success.
 *
 * If 'result' has any other value, there was a failure.
 * Return the failure result code and do not set *exists.
 *
 * This would be more readable as "do { if ... } while(0)",
 * but that form generates tons of warnings on Solaris 2.6.
 */
#define RETURN_EXISTENCE_FLAG                           \
        return ((result == ISC_R_EXISTS) ?              \
                (*exists = ISC_TRUE, ISC_R_SUCCESS) :   \
                ((result == ISC_R_SUCCESS) ?            \
                 (*exists = ISC_FALSE, ISC_R_SUCCESS) : \
                 result))

/*
 * Set '*exists' to true iff an rrset of the given type exists,
 * to false otherwise.
 */
static isc_result_t
rrset_exists(dns_db_t *db, dns_dbversion_t *ver,
             dns_name_t *name, dns_rdatatype_t type, dns_rdatatype_t covers,
             isc_boolean_t *exists)
{
        isc_result_t result;
        result = foreach_rr(db, ver, name, type, covers,
                            rrset_exists_action, NULL);
        RETURN_EXISTENCE_FLAG;
}

/*
 * Helper function for cname_incompatible_rrset_exists.
 */
static isc_result_t
cname_compatibility_action(void *data, dns_rdataset_t *rrset) {
        UNUSED(data);
        if (rrset->type != dns_rdatatype_cname &&
            ! dns_rdatatype_isdnssec(rrset->type))
                return (ISC_R_EXISTS);
        return (ISC_R_SUCCESS);
}

/*
 * Check whether there is an rrset incompatible with adding a CNAME RR,
 * i.e., anything but another CNAME (which can be replaced) or a
 * DNSSEC RR (which can coexist).
 *
 * If such an incompatible rrset exists, set '*exists' to ISC_TRUE.
 * Otherwise, set it to ISC_FALSE.
 */
static isc_result_t
cname_incompatible_rrset_exists(dns_db_t *db, dns_dbversion_t *ver,
                                dns_name_t *name, isc_boolean_t *exists) {
        isc_result_t result;
        result = foreach_rrset(db, ver, name,
                               cname_compatibility_action, NULL);
        RETURN_EXISTENCE_FLAG;
}

/*
 * Helper function for rr_count().
 */
static isc_result_t
count_rr_action(void *data, rr_t *rr) {
        int *countp = data;
        UNUSED(rr);
        (*countp)++;
        return (ISC_R_SUCCESS);
}

/*
 * Count the number of RRs of 'type' belonging to 'name' in 'ver' of 'db'.
 */
static isc_result_t
rr_count(dns_db_t *db, dns_dbversion_t *ver, dns_name_t *name,
         dns_rdatatype_t type, dns_rdatatype_t covers, int *countp)
{
        *countp = 0;
        return (foreach_rr(db, ver, name, type, covers,
                           count_rr_action, countp));
}

/*
 * Context struct and helper function for name_exists().
 */

static isc_result_t
name_exists_action(void *data, dns_rdataset_t *rrset) {
        UNUSED(data);
        UNUSED(rrset);
        return (ISC_R_EXISTS);
}

/*
 * Set '*exists' to true iff the given name exists, to false otherwise.
 */
static isc_result_t
name_exists(dns_db_t *db, dns_dbversion_t *ver, dns_name_t *name,
            isc_boolean_t *exists)
{
        isc_result_t result;
        result = foreach_rrset(db, ver, name,
                               name_exists_action, NULL);
        RETURN_EXISTENCE_FLAG;
}

typedef struct {
        dns_name_t *name, *signer;
        dns_ssutable_t *table;
} ssu_check_t;

static isc_result_t
ssu_checkrule(void *data, dns_rdataset_t *rrset) {
        ssu_check_t *ssuinfo = data;
        isc_boolean_t result;

        /*
         * If we're deleting all records, it's ok to delete RRSIG and NSEC even
         * if we're normally not allowed to.
         */
        if (rrset->type == dns_rdatatype_rrsig ||
            rrset->type == dns_rdatatype_nsec)
                return (ISC_R_SUCCESS);
        result = dns_ssutable_checkrules(ssuinfo->table, ssuinfo->signer,
                                         ssuinfo->name, rrset->type);
        return (result == ISC_TRUE ? ISC_R_SUCCESS : ISC_R_FAILURE);
}

static isc_boolean_t
ssu_checkall(dns_db_t *db, dns_dbversion_t *ver, dns_name_t *name,
             dns_ssutable_t *ssutable, dns_name_t *signer)
{
        isc_result_t result;
        ssu_check_t ssuinfo;

        ssuinfo.name = name;
        ssuinfo.table = ssutable;
        ssuinfo.signer = signer;
        result = foreach_rrset(db, ver, name, ssu_checkrule, &ssuinfo);
        return (ISC_TF(result == ISC_R_SUCCESS));
}

/**************************************************************************/
/*
 * Checking of "RRset exists (value dependent)" prerequisites.
 *
 * In the RFC2136 section 3.2.5, this is the pseudocode involving
 * a variable called "temp", a mapping of <name, type> tuples to rrsets.
 *
 * Here, we represent the "temp" data structure as (non-minimial) "dns_diff_t"
 * where each typle has op==DNS_DIFFOP_EXISTS.
 */


/*
 * Append a tuple asserting the existence of the RR with
 * 'name' and 'rdata' to 'diff'.
 */
static isc_result_t
temp_append(dns_diff_t *diff, dns_name_t *name, dns_rdata_t *rdata) {
        isc_result_t result;
        dns_difftuple_t *tuple = NULL;

        REQUIRE(DNS_DIFF_VALID(diff));
        CHECK(dns_difftuple_create(diff->mctx, DNS_DIFFOP_EXISTS,
                                      name, 0, rdata, &tuple));
        ISC_LIST_APPEND(diff->tuples, tuple, link);
 failure:
        return (result);
}

/*
 * Compare two rdatasets represented as sorted lists of tuples.
 * All list elements must have the same owner name and type.
 * Return ISC_R_SUCCESS if the rdatasets are equal, rcode(dns_rcode_nxrrset)
 * if not.
 */
static isc_result_t
temp_check_rrset(dns_difftuple_t *a, dns_difftuple_t *b) {
        for (;;) {
                if (a == NULL || b == NULL)
                        break;
                INSIST(a->op == DNS_DIFFOP_EXISTS &&
                       b->op == DNS_DIFFOP_EXISTS);
                INSIST(a->rdata.type == b->rdata.type);
                INSIST(dns_name_equal(&a->name, &b->name));
                if (dns_rdata_compare(&a->rdata, &b->rdata) != 0)
                        return (DNS_R_NXRRSET);
                a = ISC_LIST_NEXT(a, link);
                b = ISC_LIST_NEXT(b, link);
        }
        if (a != NULL || b != NULL)
                return (DNS_R_NXRRSET);
        return (ISC_R_SUCCESS);
}

/*
 * A comparison function defining the sorting order for the entries
 * in the "temp" data structure.  The major sort key is the owner name,
 * followed by the type and rdata.
 */
static int
temp_order(const void *av, const void *bv) {
        dns_difftuple_t const * const *ap = av;
        dns_difftuple_t const * const *bp = bv;
        dns_difftuple_t const *a = *ap;
        dns_difftuple_t const *b = *bp;
        int r;
        r = dns_name_compare(&a->name, &b->name);
        if (r != 0)
                return (r);
        r = (b->rdata.type - a->rdata.type);
        if (r != 0)
                return (r);
        r = dns_rdata_compare(&a->rdata, &b->rdata);
        return (r);
}

/*
 * Check the "RRset exists (value dependent)" prerequisite information
 * in 'temp' against the contents of the database 'db'.
 *
 * Return ISC_R_SUCCESS if the prerequisites are satisfied,
 * rcode(dns_rcode_nxrrset) if not.
 *
 * 'temp' must be pre-sorted.
 */

static isc_result_t
temp_check(isc_mem_t *mctx, dns_diff_t *temp, dns_db_t *db,
           dns_dbversion_t *ver, dns_name_t *tmpname, dns_rdatatype_t *typep)
{
        isc_result_t result;
        dns_name_t *name;
        dns_dbnode_t *node;
        dns_difftuple_t *t;
        dns_diff_t trash;

        dns_diff_init(mctx, &trash);

        /*
         * For each name and type in the prerequisites,
         * construct a sorted rdata list of the corresponding
         * database contents, and compare the lists.
         */
        t = ISC_LIST_HEAD(temp->tuples);
        while (t != NULL) {
                name = &t->name;
                (void)dns_name_copy(name, tmpname, NULL);
                *typep = t->rdata.type;

                /* A new unique name begins here. */
                node = NULL;
                result = dns_db_findnode(db, name, ISC_FALSE, &node);
                if (result == ISC_R_NOTFOUND)
                        return (DNS_R_NXRRSET);
                if (result != ISC_R_SUCCESS)
                        return (result);

                /* A new unique type begins here. */
                while (t != NULL && dns_name_equal(&t->name, name)) {
                        dns_rdatatype_t type, covers;
                        dns_rdataset_t rdataset;
                        dns_diff_t d_rrs; /* Database RRs with
                                                this name and type */
                        dns_diff_t u_rrs; /* Update RRs with
                                                this name and type */

                        *typep = type = t->rdata.type;
                        if (type == dns_rdatatype_rrsig ||
                            type == dns_rdatatype_sig)
                                covers = dns_rdata_covers(&t->rdata);
                        else
                                covers = 0;

                        /*
                         * Collect all database RRs for this name and type
                         * onto d_rrs and sort them.
                         */
                        dns_rdataset_init(&rdataset);
                        result = dns_db_findrdataset(db, node, ver, type,
                                                     covers, (isc_stdtime_t) 0,
                                                     &rdataset, NULL);
                        if (result != ISC_R_SUCCESS) {
                                dns_db_detachnode(db, &node);
                                return (DNS_R_NXRRSET);
                        }

                        dns_diff_init(mctx, &d_rrs);
                        dns_diff_init(mctx, &u_rrs);

                        for (result = dns_rdataset_first(&rdataset);
                             result == ISC_R_SUCCESS;
                             result = dns_rdataset_next(&rdataset))
                        {
                                dns_rdata_t rdata = DNS_RDATA_INIT;
                                dns_rdataset_current(&rdataset, &rdata);
                                result = temp_append(&d_rrs, name, &rdata);
                                if (result != ISC_R_SUCCESS)
                                        goto failure;
                        }
                        if (result != ISC_R_NOMORE)
                                goto failure;
                        result = dns_diff_sort(&d_rrs, temp_order);
                        if (result != ISC_R_SUCCESS)
                                goto failure;

                        /*
                         * Collect all update RRs for this name and type
                         * onto u_rrs.  No need to sort them here -
                         * they are already sorted.
                         */
                        while (t != NULL &&
                               dns_name_equal(&t->name, name) &&
                               t->rdata.type == type)
                        {
                                dns_difftuple_t *next =
                                        ISC_LIST_NEXT(t, link);
                                ISC_LIST_UNLINK(temp->tuples, t, link);
                                ISC_LIST_APPEND(u_rrs.tuples, t, link);
                                t = next;
                        }

                        /* Compare the two sorted lists. */
                        result = temp_check_rrset(ISC_LIST_HEAD(u_rrs.tuples),
                                                  ISC_LIST_HEAD(d_rrs.tuples));
                        if (result != ISC_R_SUCCESS)
                                goto failure;

                        /*
                         * We are done with the tuples, but we can't free
                         * them yet because "name" still points into one
                         * of them.  Move them on a temporary list.
                         */
                        ISC_LIST_APPENDLIST(trash.tuples, u_rrs.tuples, link);
                        ISC_LIST_APPENDLIST(trash.tuples, d_rrs.tuples, link);
                        dns_rdataset_disassociate(&rdataset);

                        continue;

                    failure:
                        dns_diff_clear(&d_rrs);
                        dns_diff_clear(&u_rrs);
                        dns_diff_clear(&trash);
                        dns_rdataset_disassociate(&rdataset);
                        dns_db_detachnode(db, &node);
                        return (result);
                }

                dns_db_detachnode(db, &node);
        }

        dns_diff_clear(&trash);
        return (ISC_R_SUCCESS);
}

/**************************************************************************/
/*
 * Conditional deletion of RRs.
 */

/*
 * Context structure for delete_if().
 */

typedef struct {
        rr_predicate *predicate;
        dns_db_t *db;
        dns_dbversion_t *ver;
        dns_diff_t *diff;
        dns_name_t *name;
        dns_rdata_t *update_rr;
} conditional_delete_ctx_t;

/*
 * Predicate functions for delete_if().
 */

/*
 * Return true iff 'db_rr' is neither a SOA nor an NS RR nor
 * an RRSIG nor a NSEC.
 */
static isc_boolean_t
type_not_soa_nor_ns_p(dns_rdata_t *update_rr, dns_rdata_t *db_rr) {
        UNUSED(update_rr);
        return ((db_rr->type != dns_rdatatype_soa &&
                 db_rr->type != dns_rdatatype_ns &&
                 db_rr->type != dns_rdatatype_rrsig &&
                 db_rr->type != dns_rdatatype_nsec) ?
                ISC_TRUE : ISC_FALSE);
}

/*
 * Return true iff 'db_rr' is neither a RRSIG nor a NSEC.
 */
static isc_boolean_t
type_not_dnssec(dns_rdata_t *update_rr, dns_rdata_t *db_rr) {
        UNUSED(update_rr);
        return ((db_rr->type != dns_rdatatype_rrsig &&
                 db_rr->type != dns_rdatatype_nsec) ?
                ISC_TRUE : ISC_FALSE);
}

/*
 * Return true always.
 */
static isc_boolean_t
true_p(dns_rdata_t *update_rr, dns_rdata_t *db_rr) {
        UNUSED(update_rr);
        UNUSED(db_rr);
        return (ISC_TRUE);
}

/*
 * Return true iff the two RRs have identical rdata.
 */
static isc_boolean_t
rr_equal_p(dns_rdata_t *update_rr, dns_rdata_t *db_rr) {
        /*
         * XXXRTH  This is not a problem, but we should consider creating
         *         dns_rdata_equal() (that used dns_name_equal()), since it
         *         would be faster.  Not a priority.
         */
        return (dns_rdata_compare(update_rr, db_rr) == 0 ?
                ISC_TRUE : ISC_FALSE);
}

/*
 * Return true iff 'update_rr' should replace 'db_rr' according
 * to the special RFC2136 rules for CNAME, SOA, and WKS records.
 *
 * RFC2136 does not mention NSEC or DNAME, but multiple NSECs or DNAMEs
 * make little sense, so we replace those, too.
 */
static isc_boolean_t
replaces_p(dns_rdata_t *update_rr, dns_rdata_t *db_rr) {
        if (db_rr->type != update_rr->type)
                return (ISC_FALSE);
        if (db_rr->type == dns_rdatatype_cname)
                return (ISC_TRUE);
        if (db_rr->type == dns_rdatatype_dname)
                return (ISC_TRUE);
        if (db_rr->type == dns_rdatatype_soa)
                return (ISC_TRUE);
        if (db_rr->type == dns_rdatatype_nsec)
                return (ISC_TRUE);
        if (db_rr->type == dns_rdatatype_wks) {
                /*
                 * Compare the address and protocol fields only.  These
                 * form the first five bytes of the RR data.  Do a
                 * raw binary comparison; unpacking the WKS RRs using
                 * dns_rdata_tostruct() might be cleaner in some ways,
                 * but it would require us to pass around an mctx.
                 */
                INSIST(db_rr->length >= 5 && update_rr->length >= 5);
                return (memcmp(db_rr->data, update_rr->data, 5) == 0 ?
                        ISC_TRUE : ISC_FALSE);
        }
        return (ISC_FALSE);
}

/*
 * Internal helper function for delete_if().
 */
static isc_result_t
delete_if_action(void *data, rr_t *rr) {
        conditional_delete_ctx_t *ctx = data;
        if ((*ctx->predicate)(ctx->update_rr, &rr->rdata)) {
                isc_result_t result;
                result = update_one_rr(ctx->db, ctx->ver, ctx->diff,
                                       DNS_DIFFOP_DEL, ctx->name,
                                       rr->ttl, &rr->rdata);
                return (result);
        } else {
                return (ISC_R_SUCCESS);
        }
}

/*
 * Conditionally delete RRs.  Apply 'predicate' to the RRs
 * specified by 'db', 'ver', 'name', and 'type' (which can
 * be dns_rdatatype_any to match any type).  Delete those
 * RRs for which the predicate returns true, and log the
 * deletions in 'diff'.
 */
static isc_result_t
delete_if(rr_predicate *predicate,
          dns_db_t *db,
          dns_dbversion_t *ver,
          dns_name_t *name,
          dns_rdatatype_t type,
          dns_rdatatype_t covers,
          dns_rdata_t *update_rr,
          dns_diff_t *diff)
{
        conditional_delete_ctx_t ctx;
        ctx.predicate = predicate;
        ctx.db = db;
        ctx.ver = ver;
        ctx.diff = diff;
        ctx.name = name;
        ctx.update_rr = update_rr;
        return (foreach_rr(db, ver, name, type, covers,
                           delete_if_action, &ctx));
}

/**************************************************************************/
/*
 * Prepare an RR for the addition of the new RR 'ctx->update_rr',
 * with TTL 'ctx->update_rr_ttl', to its rdataset, by deleting
 * the RRs if it is replaced by the new RR or has a conflicting TTL.
 * The necessary changes are appended to ctx->del_diff and ctx->add_diff;
 * we need to do all deletions before any additions so that we don't run
 * into transient states with conflicting TTLs.
 */

typedef struct {
        dns_db_t *db;
        dns_dbversion_t *ver;
        dns_diff_t *diff;
        dns_name_t *name;
        dns_rdata_t *update_rr;
        dns_ttl_t update_rr_ttl;
        isc_boolean_t ignore_add;
        dns_diff_t del_diff;
        dns_diff_t add_diff;
} add_rr_prepare_ctx_t;

static isc_result_t
add_rr_prepare_action(void *data, rr_t *rr) {
        isc_result_t result = ISC_R_SUCCESS;    
        add_rr_prepare_ctx_t *ctx = data;
        dns_difftuple_t *tuple = NULL;
        isc_boolean_t equal;

        /*
         * If the update RR is a "duplicate" of the update RR,
         * the update should be silently ignored.
         */
        equal = ISC_TF(dns_rdata_compare(&rr->rdata, ctx->update_rr) == 0);
        if (equal && rr->ttl == ctx->update_rr_ttl) {
                ctx->ignore_add = ISC_TRUE;
                return (ISC_R_SUCCESS);
        }

        /*
         * If this RR is "equal" to the update RR, it should
         * be deleted before the update RR is added.
         */
        if (replaces_p(ctx->update_rr, &rr->rdata)) {
                CHECK(dns_difftuple_create(ctx->del_diff.mctx,
                                           DNS_DIFFOP_DEL, ctx->name,
                                           rr->ttl,
                                           &rr->rdata,
                                           &tuple));
                dns_diff_append(&ctx->del_diff, &tuple);
                return (ISC_R_SUCCESS);
        }

        /*
         * If this RR differs in TTL from the update RR,
         * its TTL must be adjusted.
         */
        if (rr->ttl != ctx->update_rr_ttl) {
                CHECK(dns_difftuple_create(ctx->del_diff.mctx,
                                           DNS_DIFFOP_DEL, ctx->name,
                                           rr->ttl,
                                           &rr->rdata,
                                           &tuple));
                dns_diff_append(&ctx->del_diff, &tuple);
                if (!equal) {
                        CHECK(dns_difftuple_create(ctx->add_diff.mctx,
                                                   DNS_DIFFOP_ADD, ctx->name,
                                                   ctx->update_rr_ttl,
                                                   &rr->rdata,
                                                   &tuple));
                        dns_diff_append(&ctx->add_diff, &tuple);
                }
        }
 failure:
        return (result);
}

/**************************************************************************/
/*
 * Miscellaneous subroutines.
 */

/*
 * Extract a single update RR from 'section' of dynamic update message
 * 'msg', with consistency checking.
 *
 * Stores the owner name, rdata, and TTL of the update RR at 'name',
 * 'rdata', and 'ttl', respectively.
 */
static void
get_current_rr(dns_message_t *msg, dns_section_t section,
               dns_rdataclass_t zoneclass,
               dns_name_t **name, dns_rdata_t *rdata, dns_rdatatype_t *covers,
               dns_ttl_t *ttl,
               dns_rdataclass_t *update_class)
{
        dns_rdataset_t *rdataset;
        isc_result_t result;
        dns_message_currentname(msg, section, name);
        rdataset = ISC_LIST_HEAD((*name)->list);
        INSIST(rdataset != NULL);
        INSIST(ISC_LIST_NEXT(rdataset, link) == NULL);
        *covers = rdataset->covers;
        *ttl = rdataset->ttl;
        result = dns_rdataset_first(rdataset);
        INSIST(result == ISC_R_SUCCESS);
        dns_rdataset_current(rdataset, rdata);
        INSIST(dns_rdataset_next(rdataset) == ISC_R_NOMORE);
        *update_class = rdata->rdclass;
        rdata->rdclass = zoneclass;
}

/*
 * Increment the SOA serial number of database 'db', version 'ver'.
 * Replace the SOA record in the database, and log the
 * change in 'diff'.
 */

        /*
         * XXXRTH  Failures in this routine will be worth logging, when
         *         we have a logging system.  Failure to find the zonename
         *         or the SOA rdataset warrant at least an UNEXPECTED_ERROR().
         */

static isc_result_t
increment_soa_serial(dns_db_t *db, dns_dbversion_t *ver,
                     dns_diff_t *diff, isc_mem_t *mctx)
{
        dns_difftuple_t *deltuple = NULL;
        dns_difftuple_t *addtuple = NULL;
        isc_uint32_t serial;
        isc_result_t result;

        CHECK(dns_db_createsoatuple(db, ver, mctx, DNS_DIFFOP_DEL, &deltuple));
        CHECK(dns_difftuple_copy(deltuple, &addtuple));
        addtuple->op = DNS_DIFFOP_ADD;

        serial = dns_soa_getserial(&addtuple->rdata);

        /* RFC1982 */
        serial = (serial + 1) & 0xFFFFFFFF;
        if (serial == 0)
                serial = 1;

        dns_soa_setserial(serial, &addtuple->rdata);
        CHECK(do_one_tuple(&deltuple, db, ver, diff));
        CHECK(do_one_tuple(&addtuple, db, ver, diff));
        result = ISC_R_SUCCESS;

 failure:
        if (addtuple != NULL)
                dns_difftuple_free(&addtuple);
        if (deltuple != NULL)
                dns_difftuple_free(&deltuple);
        return (result);
}

/*
 * Check that the new SOA record at 'update_rdata' does not
 * illegally cause the SOA serial number to decrease or stay
 * unchanged relative to the existing SOA in 'db'.
 *
 * Sets '*ok' to ISC_TRUE if the update is legal, ISC_FALSE if not.
 *
 * William King points out that RFC2136 is inconsistent about
 * the case where the serial number stays unchanged:
 *
 *   section 3.4.2.2 requires a server to ignore a SOA update request
 *   if the serial number on the update SOA is less_than_or_equal to
 *   the zone SOA serial.
 *
 *   section 3.6 requires a server to ignore a SOA update request if
 *   the serial is less_than the zone SOA serial.
 *
 * Paul says 3.4.2.2 is correct.
 *
 */
static isc_result_t
check_soa_increment(dns_db_t *db, dns_dbversion_t *ver,
                    dns_rdata_t *update_rdata,
                    isc_boolean_t *ok)
{
        isc_uint32_t db_serial;
        isc_uint32_t update_serial;
        isc_result_t result;

        update_serial = dns_soa_getserial(update_rdata);

        result = dns_db_getsoaserial(db, ver, &db_serial);
        if (result != ISC_R_SUCCESS)
                return (result);

        if (DNS_SERIAL_GE(db_serial, update_serial)) {
                *ok = ISC_FALSE;
        } else {
                *ok = ISC_TRUE;
        }

        return (ISC_R_SUCCESS);

}

/**************************************************************************/
/*
 * Incremental updating of NSECs and RRSIGs.
 */

#define MAXZONEKEYS 32  /* Maximum number of zone keys supported. */

/*
 * We abuse the dns_diff_t type to represent a set of domain names
 * affected by the update.
 */
static isc_result_t
namelist_append_name(dns_diff_t *list, dns_name_t *name) {
        isc_result_t result;
        dns_difftuple_t *tuple = NULL;
        static dns_rdata_t dummy_rdata = { NULL, 0, 0, 0, 0,
                                           { (void*)(-1), (void*)(-1) } };
        CHECK(dns_difftuple_create(list->mctx, DNS_DIFFOP_EXISTS, name, 0,
                                   &dummy_rdata, &tuple));
        dns_diff_append(list, &tuple);
 failure:
        return (result);
}

static isc_result_t
namelist_append_subdomain(dns_db_t *db, dns_name_t *name, dns_diff_t *affected)
{
        isc_result_t result;
        dns_fixedname_t fixedname;
        dns_name_t *child;
        dns_dbiterator_t *dbit = NULL;

        dns_fixedname_init(&fixedname);
        child = dns_fixedname_name(&fixedname);

        CHECK(dns_db_createiterator(db, ISC_FALSE, &dbit));

        for (result = dns_dbiterator_seek(dbit, name);
             result == ISC_R_SUCCESS;
             result = dns_dbiterator_next(dbit))
        {
                dns_dbnode_t *node = NULL;
                CHECK(dns_dbiterator_current(dbit, &node, child));
                dns_db_detachnode(db, &node);
                if (! dns_name_issubdomain(child, name))
                        break;
                CHECK(namelist_append_name(affected, child));
        }
        if (result == ISC_R_NOMORE)
                result = ISC_R_SUCCESS;
 failure:
        if (dbit != NULL)
                dns_dbiterator_destroy(&dbit);
        return (result);
}



/*
 * Helper function for non_nsec_rrset_exists().
 */
static isc_result_t
is_non_nsec_action(void *data, dns_rdataset_t *rrset) {
        UNUSED(data);
        if (!(rrset->type == dns_rdatatype_nsec ||
              (rrset->type == dns_rdatatype_rrsig &&
               rrset->covers == dns_rdatatype_nsec)))
                return (ISC_R_EXISTS);
        return (ISC_R_SUCCESS);
}

/*
 * Check whether there is an rrset other than a NSEC or RRSIG NSEC,
 * i.e., anything that justifies the continued existence of a name
 * after a secure update.
 *
 * If such an rrset exists, set '*exists' to ISC_TRUE.
 * Otherwise, set it to ISC_FALSE.
 */
static isc_result_t
non_nsec_rrset_exists(dns_db_t *db, dns_dbversion_t *ver,
                     dns_name_t *name, isc_boolean_t *exists)
{
        isc_result_t result;
        result = foreach_rrset(db, ver, name,
                               is_non_nsec_action, NULL);
        RETURN_EXISTENCE_FLAG;
}

/*
 * A comparison function for sorting dns_diff_t:s by name.
 */
static int
name_order(const void *av, const void *bv) {
        dns_difftuple_t const * const *ap = av;
        dns_difftuple_t const * const *bp = bv;
        dns_difftuple_t const *a = *ap;
        dns_difftuple_t const *b = *bp;
        return (dns_name_compare(&a->name, &b->name));
}

static isc_result_t
uniqify_name_list(dns_diff_t *list) {
        isc_result_t result;
        dns_difftuple_t *p, *q;

        CHECK(dns_diff_sort(list, name_order));

        p = ISC_LIST_HEAD(list->tuples);
        while (p != NULL) {
                do {
                        q = ISC_LIST_NEXT(p, link);
                        if (q == NULL || ! dns_name_equal(&p->name, &q->name))
                                break;
                        ISC_LIST_UNLINK(list->tuples, q, link);
                        dns_difftuple_free(&q);
                } while (1);
                p = ISC_LIST_NEXT(p, link);
        }
 failure:
        return (result);
}


static isc_result_t
is_glue(dns_db_t *db, dns_dbversion_t *ver, dns_name_t *name,
        isc_boolean_t *flag)
{
        isc_result_t result;
        dns_fixedname_t foundname;
        dns_fixedname_init(&foundname);
        result = dns_db_find(db, name, ver, dns_rdatatype_any,
                             DNS_DBFIND_GLUEOK | DNS_DBFIND_NOWILD,
                             (isc_stdtime_t) 0, NULL,
                             dns_fixedname_name(&foundname),
                             NULL, NULL);
        if (result == ISC_R_SUCCESS) {
                *flag = ISC_FALSE;
                return (ISC_R_SUCCESS);
        } else if (result == DNS_R_ZONECUT) {
                /*
                 * We are at the zonecut.  The name will have an NSEC, but
                 * non-delegation will be omitted from the type bit map.
                 */
                *flag = ISC_FALSE;
                return (ISC_R_SUCCESS);
        } else if (result == DNS_R_GLUE || result == DNS_R_DNAME) {
                *flag = ISC_TRUE;
                return (ISC_R_SUCCESS);
        } else {
                return (result);
        }
}

/*
 * Find the next/previous name that has a NSEC record.
 * In other words, skip empty database nodes and names that
 * have had their NSECs removed because they are obscured by
 * a zone cut.
 */
static isc_result_t
next_active(ns_client_t *client, dns_zone_t *zone, dns_db_t *db,
            dns_dbversion_t *ver, dns_name_t *oldname, dns_name_t *newname,
            isc_boolean_t forward)
{
        isc_result_t result;
        dns_dbiterator_t *dbit = NULL;
        isc_boolean_t has_nsec;
        unsigned int wraps = 0;

        CHECK(dns_db_createiterator(db, ISC_FALSE, &dbit));

        CHECK(dns_dbiterator_seek(dbit, oldname));
        do {
                dns_dbnode_t *node = NULL;

                if (forward)
                        result = dns_dbiterator_next(dbit);
                else
                        result = dns_dbiterator_prev(dbit);
                if (result == ISC_R_NOMORE) {
                        /*
                         * Wrap around.
                         */
                        if (forward)
                                CHECK(dns_dbiterator_first(dbit));
                        else
                                CHECK(dns_dbiterator_last(dbit));
                        wraps++;
                        if (wraps == 2) {
                                update_log(client, zone, ISC_LOG_ERROR,
                                           "secure zone with no NSECs");
                                result = DNS_R_BADZONE;
                                goto failure;
                        }
                }
                CHECK(dns_dbiterator_current(dbit, &node, newname));
                dns_db_detachnode(db, &node);

                /*
                 * The iterator may hold the tree lock, and
                 * rrset_exists() calls dns_db_findnode() which
                 * may try to reacquire it.  To avoid deadlock
                 * we must pause the iterator first.
                 */
                CHECK(dns_dbiterator_pause(dbit));
                CHECK(rrset_exists(db, ver, newname,
                                   dns_rdatatype_nsec, 0, &has_nsec));

        } while (! has_nsec);
 failure:
        if (dbit != NULL)
                dns_dbiterator_destroy(&dbit);

        return (result);
}

/*
 * Add a NSEC record for "name", recording the change in "diff".
 * The existing NSEC is removed.
 */
static isc_result_t
add_nsec(ns_client_t *client, dns_zone_t *zone, dns_db_t *db,
         dns_dbversion_t *ver, dns_name_t *name, dns_ttl_t nsecttl,
         dns_diff_t *diff)
{
        isc_result_t result;
        dns_dbnode_t *node = NULL;
        unsigned char buffer[DNS_NSEC_BUFFERSIZE];
        dns_rdata_t rdata = DNS_RDATA_INIT;
        dns_difftuple_t *tuple = NULL;
        dns_fixedname_t fixedname;
        dns_name_t *target;

        dns_fixedname_init(&fixedname);
        target = dns_fixedname_name(&fixedname);

        /*
         * Find the successor name, aka NSEC target.
         */
        CHECK(next_active(client, zone, db, ver, name, target, ISC_TRUE));

        /*
         * Create the NSEC RDATA.
         */
        CHECK(dns_db_findnode(db, name, ISC_FALSE, &node));
        dns_rdata_init(&rdata);
        CHECK(dns_nsec_buildrdata(db, ver, node, target, buffer, &rdata));
        dns_db_detachnode(db, &node);

        /*
         * Delete the old NSEC and record the change.
         */
        CHECK(delete_if(true_p, db, ver, name, dns_rdatatype_nsec, 0,
                        NULL, diff));
        /*
         * Add the new NSEC and record the change.
         */
        CHECK(dns_difftuple_create(diff->mctx, DNS_DIFFOP_ADD, name,
                                   nsecttl, &rdata, &tuple));
        CHECK(do_one_tuple(&tuple, db, ver, diff));
        INSIST(tuple == NULL);

 failure:
        if (node != NULL)
                dns_db_detachnode(db, &node);
        return (result);
}

/*
 * Add a placeholder NSEC record for "name", recording the change in "diff".
 */
static isc_result_t
add_placeholder_nsec(dns_db_t *db, dns_dbversion_t *ver, dns_name_t *name,
                    dns_diff_t *diff) {
        isc_result_t result;
        dns_difftuple_t *tuple = NULL;
        isc_region_t r;
        unsigned char data[1] = { 0 }; /* The root domain, no bits. */
        dns_rdata_t rdata = DNS_RDATA_INIT;

        r.base = data;
        r.length = sizeof(data);
        dns_rdata_fromregion(&rdata, dns_db_class(db), dns_rdatatype_nsec, &r);
        CHECK(dns_difftuple_create(diff->mctx, DNS_DIFFOP_ADD, name, 0,
                                   &rdata, &tuple));
        CHECK(do_one_tuple(&tuple, db, ver, diff));
 failure:
        return (result);
}

static isc_result_t
find_zone_keys(dns_zone_t *zone, dns_db_t *db, dns_dbversion_t *ver,
               isc_mem_t *mctx, unsigned int maxkeys,
               dst_key_t **keys, unsigned int *nkeys)
{
        isc_result_t result;
        dns_dbnode_t *node = NULL;
        const char *directory = dns_zone_getkeydirectory(zone);
        CHECK(dns_db_findnode(db, dns_db_origin(db), ISC_FALSE, &node));
        CHECK(dns_dnssec_findzonekeys2(db, ver, node, dns_db_origin(db),
                                       directory, mctx, maxkeys, keys, nkeys));
 failure:
        if (node != NULL)
                dns_db_detachnode(db, &node);
        return (result);
}

/*
 * Add RRSIG records for an RRset, recording the change in "diff".
 */
static isc_result_t
add_sigs(dns_db_t *db, dns_dbversion_t *ver, dns_name_t *name,
         dns_rdatatype_t type, dns_diff_t *diff, dst_key_t **keys,
         unsigned int nkeys, isc_mem_t *mctx, isc_stdtime_t inception,
         isc_stdtime_t expire)
{
        isc_result_t result;
        dns_dbnode_t *node = NULL;
        dns_rdataset_t rdataset;
        dns_rdata_t sig_rdata = DNS_RDATA_INIT;
        isc_buffer_t buffer;
        unsigned char data[1024]; /* XXX */
        unsigned int i;

        dns_rdataset_init(&rdataset);
        isc_buffer_init(&buffer, data, sizeof(data));

        /* Get the rdataset to sign. */
        CHECK(dns_db_findnode(db, name, ISC_FALSE, &node));
        CHECK(dns_db_findrdataset(db, node, ver, type, 0,
                                  (isc_stdtime_t) 0,
                                  &rdataset, NULL));
        dns_db_detachnode(db, &node);

        for (i = 0; i < nkeys; i++) {
                /* Calculate the signature, creating a RRSIG RDATA. */
                CHECK(dns_dnssec_sign(name, &rdataset, keys[i],
                                      &inception, &expire,
                                      mctx, &buffer, &sig_rdata));

                /* Update the database and journal with the RRSIG. */
                /* XXX inefficient - will cause dataset merging */
                CHECK(update_one_rr(db, ver, diff, DNS_DIFFOP_ADD, name,
                                    rdataset.ttl, &sig_rdata));
                dns_rdata_reset(&sig_rdata);
        }

 failure:
        if (dns_rdataset_isassociated(&rdataset))
                dns_rdataset_disassociate(&rdataset);
        if (node != NULL)
                dns_db_detachnode(db, &node);
        return (result);
}

/*
 * Update RRSIG and NSEC records affected by an update.  The original
 * update, including the SOA serial update but exluding the RRSIG & NSEC
 * changes, is in "diff" and has already been applied to "newver" of "db".
 * The database version prior to the update is "oldver".
 *
 * The necessary RRSIG and NSEC changes will be applied to "newver"
 * and added (as a minimal diff) to "diff".
 *
 * The RRSIGs generated will be valid for 'sigvalidityinterval' seconds.
 */
static isc_result_t
update_signatures(ns_client_t *client, dns_zone_t *zone, dns_db_t *db,
                  dns_dbversion_t *oldver, dns_dbversion_t *newver,
                  dns_diff_t *diff, isc_uint32_t sigvalidityinterval)
{
        isc_result_t result;
        dns_difftuple_t *t;
        dns_diff_t diffnames;
        dns_diff_t affected;
        dns_diff_t sig_diff;
        dns_diff_t nsec_diff;
        dns_diff_t nsec_mindiff;
        isc_boolean_t flag;
        dst_key_t *zone_keys[MAXZONEKEYS];
        unsigned int nkeys = 0;
        unsigned int i;
        isc_stdtime_t now, inception, expire;
        dns_ttl_t nsecttl;
        dns_rdata_soa_t soa;
        dns_rdata_t rdata = DNS_RDATA_INIT;
        dns_rdataset_t rdataset;
        dns_dbnode_t *node = NULL;

        dns_diff_init(client->mctx, &diffnames);
        dns_diff_init(client->mctx, &affected);

        dns_diff_init(client->mctx, &sig_diff);
        dns_diff_init(client->mctx, &nsec_diff);
        dns_diff_init(client->mctx, &nsec_mindiff);

        result = find_zone_keys(zone, db, newver, client->mctx,
                                MAXZONEKEYS, zone_keys, &nkeys);
        if (result != ISC_R_SUCCESS) {
                update_log(client, zone, ISC_LOG_ERROR,
                           "could not get zone keys for secure dynamic update");
                goto failure;
        }

        isc_stdtime_get(&now);
        inception = now - 3600; /* Allow for some clock skew. */
        expire = now + sigvalidityinterval;

        /*
         * Get the NSEC's TTL from the SOA MINIMUM field.
         */
        CHECK(dns_db_findnode(db, dns_db_origin(db), ISC_FALSE, &node));
        dns_rdataset_init(&rdataset);
        CHECK(dns_db_findrdataset(db, node, newver, dns_rdatatype_soa, 0,
                                  (isc_stdtime_t) 0, &rdataset, NULL));
        CHECK(dns_rdataset_first(&rdataset));
        dns_rdataset_current(&rdataset, &rdata);
        CHECK(dns_rdata_tostruct(&rdata, &soa, NULL));
        nsecttl = soa.minimum;
        dns_rdataset_disassociate(&rdataset);
        dns_db_detachnode(db, &node);

        /*
         * Find all RRsets directly affected by the update, and
         * update their RRSIGs.  Also build a list of names affected
         * by the update in "diffnames".
         */
        CHECK(dns_diff_sort(diff, temp_order));

        t = ISC_LIST_HEAD(diff->tuples);
        while (t != NULL) {
                dns_name_t *name = &t->name;
                /* Now "name" is a new, unique name affected by the update. */

                CHECK(namelist_append_name(&diffnames, name));

                while (t != NULL && dns_name_equal(&t->name, name)) {
                        dns_rdatatype_t type;
                        type = t->rdata.type;

                        /*
                         * Now "name" and "type" denote a new unique RRset
                         * affected by the update.
                         */

                        /* Don't sign RRSIGs. */
                        if (type == dns_rdatatype_rrsig)
                                goto skip;

                        /*
                         * Delete all old RRSIGs covering this type, since they
                         * are all invalid when the signed RRset has changed.
                         * We may not be able to recreate all of them - tough.
                         */
                        CHECK(delete_if(true_p, db, newver, name,
                                        dns_rdatatype_rrsig, type,
                                        NULL, &sig_diff));

                        /*
                         * If this RRset still exists after the update,
                         * add a new signature for it.
                         */
                        CHECK(rrset_exists(db, newver, name, type, 0, &flag));
                        if (flag) {
                                CHECK(add_sigs(db, newver, name, type,
                                               &sig_diff, zone_keys, nkeys,
                                               client->mctx, inception,
                                               expire));
                        }
                skip:
                        /* Skip any other updates to the same RRset. */
                        while (t != NULL &&
                               dns_name_equal(&t->name, name) &&
                               t->rdata.type == type)
                        {
                                t = ISC_LIST_NEXT(t, link);
                        }
                }
        }

        /* Remove orphaned NSECs and RRSIG NSECs. */
        for (t = ISC_LIST_HEAD(diffnames.tuples);
             t != NULL;
             t = ISC_LIST_NEXT(t, link))
        {
                CHECK(non_nsec_rrset_exists(db, newver, &t->name, &flag));
                if (! flag) {
                        CHECK(delete_if(true_p, db, newver, &t->name,
                                        dns_rdatatype_any, 0,
                                        NULL, &sig_diff));
                }
        }

        /*
         * When a name is created or deleted, its predecessor needs to
         * have its NSEC updated.
         */
        for (t = ISC_LIST_HEAD(diffnames.tuples);
             t != NULL;
             t = ISC_LIST_NEXT(t, link))
        {
                isc_boolean_t existed, exists;
                dns_fixedname_t fixedname;
                dns_name_t *prevname;

                dns_fixedname_init(&fixedname);
                prevname = dns_fixedname_name(&fixedname);

                CHECK(name_exists(db, oldver, &t->name, &existed));
                CHECK(name_exists(db, newver, &t->name, &exists));
                if (exists == existed)
                        continue;

                /*
                 * Find the predecessor.
                 * When names become obscured or unobscured in this update
                 * transaction, we may find the wrong predecessor because
                 * the NSECs have not yet been updated to reflect the delegation
                 * change.  This should not matter because in this case,
                 * the correct predecessor is either the delegation node or
                 * a newly unobscured node, and those nodes are on the
                 * "affected" list in any case.
                 */
                CHECK(next_active(client, zone, db, newver,
                                  &t->name, prevname, ISC_FALSE));
                CHECK(namelist_append_name(&affected, prevname));
        }

        /*
         * Find names potentially affected by delegation changes
         * (obscured by adding an NS or DNAME, or unobscured by
         * removing one).
         */
        for (t = ISC_LIST_HEAD(diffnames.tuples);
             t != NULL;
             t = ISC_LIST_NEXT(t, link))
        {
                isc_boolean_t ns_existed, dname_existed;
                isc_boolean_t ns_exists, dname_exists;

                CHECK(rrset_exists(db, oldver, &t->name, dns_rdatatype_ns, 0,
                                   &ns_existed));
                CHECK(rrset_exists(db, oldver, &t->name, dns_rdatatype_dname, 0,
                                   &dname_existed));
                CHECK(rrset_exists(db, newver, &t->name, dns_rdatatype_ns, 0,
                                   &ns_exists));
                CHECK(rrset_exists(db, newver, &t->name, dns_rdatatype_dname, 0,
                                   &dname_exists));
                if ((ns_exists || dname_exists) == (ns_existed || dname_existed))
                        continue;
                /*
                 * There was a delegation change.  Mark all subdomains
                 * of t->name as potentially needing a NSEC update.
                 */
                CHECK(namelist_append_subdomain(db, &t->name, &affected));
        }

        ISC_LIST_APPENDLIST(affected.tuples, diffnames.tuples, link);
        INSIST(ISC_LIST_EMPTY(diffnames.tuples));

        CHECK(uniqify_name_list(&affected));

        /*
         * Determine which names should have NSECs, and delete/create
         * NSECs to make it so.  We don't know the final NSEC targets yet,
         * so we just create placeholder NSECs with arbitrary contents
         * to indicate that their respective owner names should be part of
         * the NSEC chain.
         */
        for (t = ISC_LIST_HEAD(affected.tuples);
             t != NULL;
             t = ISC_LIST_NEXT(t, link))
        {
                isc_boolean_t exists;
                CHECK(name_exists(db, newver, &t->name, &exists));
                if (! exists)
                        continue;
                CHECK(is_glue(db, newver, &t->name, &flag));
                if (flag) {
                        /*
                         * This name is obscured.  Delete any
                         * existing NSEC record.
                         */
                        CHECK(delete_if(true_p, db, newver, &t->name,
                                        dns_rdatatype_nsec, 0,
                                        NULL, &nsec_diff));
                } else {
                        /*
                         * This name is not obscured.  It should have a NSEC.
                         */
                        CHECK(rrset_exists(db, newver, &t->name,
                                           dns_rdatatype_nsec, 0, &flag));
                        if (! flag)
                                CHECK(add_placeholder_nsec(db, newver, &t->name,
                                                          diff));
                }
        }

        /*
         * Now we know which names are part of the NSEC chain.
         * Make them all point at their correct targets.
         */
        for (t = ISC_LIST_HEAD(affected.tuples);
             t != NULL;
             t = ISC_LIST_NEXT(t, link))
        {
                CHECK(rrset_exists(db, newver, &t->name,
                                   dns_rdatatype_nsec, 0, &flag));
                if (flag) {
                        /*
                         * There is a NSEC, but we don't know if it is correct.
                         * Delete it and create a correct one to be sure.
                         * If the update was unnecessary, the diff minimization
                         * will take care of eliminating it from the journal,
                         * IXFRs, etc.
                         *
                         * The RRSIG bit should always be set in the NSECs
                         * we generate, because they will all get RRSIG NSECs.
                         * (XXX what if the zone keys are missing?).
                         * Because the RRSIG NSECs have not necessarily been
                         * created yet, the correctness of the bit mask relies
                         * on the assumption that NSECs are only created if
                         * there is other data, and if there is other data,
                         * there are other RRSIGs.
                         */
                        CHECK(add_nsec(client, zone, db, newver, &t->name,
                                       nsecttl, &nsec_diff));
                }
        }

        /*
         * Minimize the set of NSEC updates so that we don't
         * have to regenerate the RRSIG NSECs for NSECs that were
         * replaced with identical ones.
         */
        while ((t = ISC_LIST_HEAD(nsec_diff.tuples)) != NULL) {
                ISC_LIST_UNLINK(nsec_diff.tuples, t, link);
                dns_diff_appendminimal(&nsec_mindiff, &t);
        }

        /* Update RRSIG NSECs. */
        for (t = ISC_LIST_HEAD(nsec_mindiff.tuples);
             t != NULL;
             t = ISC_LIST_NEXT(t, link))
        {
                if (t->op == DNS_DIFFOP_DEL) {
                        CHECK(delete_if(true_p, db, newver, &t->name,
                                        dns_rdatatype_rrsig, dns_rdatatype_nsec,
                                        NULL, &sig_diff));
                } else if (t->op == DNS_DIFFOP_ADD) {
                        CHECK(add_sigs(db, newver, &t->name, dns_rdatatype_nsec,
                                       &sig_diff, zone_keys, nkeys,
                                       client->mctx, inception, expire));
                } else {
                        INSIST(0);
                }
        }

        /* Record our changes for the journal. */
        while ((t = ISC_LIST_HEAD(sig_diff.tuples)) != NULL) {
                ISC_LIST_UNLINK(sig_diff.tuples, t, link);
                dns_diff_appendminimal(diff, &t);
        }
        while ((t = ISC_LIST_HEAD(nsec_mindiff.tuples)) != NULL) {
                ISC_LIST_UNLINK(nsec_mindiff.tuples, t, link);
                dns_diff_appendminimal(diff, &t);
        }

        INSIST(ISC_LIST_EMPTY(sig_diff.tuples));
        INSIST(ISC_LIST_EMPTY(nsec_diff.tuples));
        INSIST(ISC_LIST_EMPTY(nsec_mindiff.tuples));

 failure:
        dns_diff_clear(&sig_diff);
        dns_diff_clear(&nsec_diff);
        dns_diff_clear(&nsec_mindiff);

        dns_diff_clear(&affected);
        dns_diff_clear(&diffnames);

        for (i = 0; i < nkeys; i++)
                dst_key_free(&zone_keys[i]);

        return (result);
}


/**************************************************************************/
/*
 * The actual update code in all its glory.  We try to follow
 * the RFC2136 pseudocode as closely as possible.
 */

static isc_result_t
send_update_event(ns_client_t *client, dns_zone_t *zone) {
        isc_result_t result = ISC_R_SUCCESS;
        update_event_t *event = NULL;
        isc_task_t *zonetask = NULL;
        ns_client_t *evclient;

        event = (update_event_t *)
                isc_event_allocate(client->mctx, client, DNS_EVENT_UPDATE,
                                   update_action, NULL, sizeof(*event));
        if (event == NULL)
                FAIL(ISC_R_NOMEMORY);
        event->zone = zone;
        event->result = ISC_R_SUCCESS;

        evclient = NULL;
        ns_client_attach(client, &evclient);
        INSIST(client->nupdates == 0);
        client->nupdates++;
        event->ev_arg = evclient;

        dns_zone_gettask(zone, &zonetask);
        isc_task_send(zonetask, ISC_EVENT_PTR(&event));

 failure:
        if (event != NULL)
                isc_event_free(ISC_EVENT_PTR(&event));
        return (result);
}

static void
respond(ns_client_t *client, isc_result_t result) {
        isc_result_t msg_result;

        msg_result = dns_message_reply(client->message, ISC_TRUE);
        if (msg_result != ISC_R_SUCCESS)
                goto msg_failure;
        client->message->rcode = dns_result_torcode(result);

        ns_client_send(client);
        return;

 msg_failure:
        isc_log_write(ns_g_lctx, NS_LOGCATEGORY_UPDATE, NS_LOGMODULE_UPDATE,
                      ISC_LOG_ERROR,
                      "could not create update response message: %s",
                      isc_result_totext(msg_result));
        ns_client_next(client, msg_result);
}

void
ns_update_start(ns_client_t *client, isc_result_t sigresult) {
        dns_message_t *request = client->message;
        isc_result_t result;
        dns_name_t *zonename;
        dns_rdataset_t *zone_rdataset;
        dns_zone_t *zone = NULL;

        /*
         * Interpret the zone section.
         */
        result = dns_message_firstname(request, DNS_SECTION_ZONE);
        if (result != ISC_R_SUCCESS)
                FAILC(DNS_R_FORMERR,
                      "update zone section empty");

        /*
         * The zone section must contain exactly one "question", and
         * it must be of type SOA.
         */
        zonename = NULL;
        dns_message_currentname(request, DNS_SECTION_ZONE, &zonename);
        zone_rdataset = ISC_LIST_HEAD(zonename->list);
        if (zone_rdataset->type != dns_rdatatype_soa)
                FAILC(DNS_R_FORMERR,
                      "update zone section contains non-SOA");
        if (ISC_LIST_NEXT(zone_rdataset, link) != NULL)
                FAILC(DNS_R_FORMERR,
                      "update zone section contains multiple RRs");

        /* The zone section must have exactly one name. */
        result = dns_message_nextname(request, DNS_SECTION_ZONE);
        if (result != ISC_R_NOMORE)
                FAILC(DNS_R_FORMERR,
                      "update zone section contains multiple RRs");

        result = dns_zt_find(client->view->zonetable, zonename, 0, NULL,
                             &zone);
        if (result != ISC_R_SUCCESS)
                FAILC(DNS_R_NOTAUTH,
                      "not authoritative for update zone");

        switch(dns_zone_gettype(zone)) {
        case dns_zone_master:
                /*
                 * We can now fail due to a bad signature as we now know
                 * that we are the master.
                 */
                if (sigresult != ISC_R_SUCCESS)
                        FAIL(sigresult);
                CHECK(send_update_event(client, zone));
                break;
        case dns_zone_slave:
                CHECK(checkupdateacl(client, dns_zone_getforwardacl(zone),
                                     "update forwarding", zonename, ISC_TRUE));
                CHECK(send_forward_event(client, zone));
                break;
        default:
                FAILC(DNS_R_NOTAUTH,
                      "not authoritative for update zone");
        }
        return;

 failure:
        /*
         * We failed without having sent an update event to the zone.
         * We are still in the client task context, so we can
         * simply give an error response without switching tasks.
         */
        respond(client, result);
        if (zone != NULL)
                dns_zone_detach(&zone);
}

/*
 * DS records are not allowed to exist without corresponding NS records,
 * draft-ietf-dnsext-delegation-signer-11.txt, 2.2 Protocol Change,
 * "DS RRsets MUST NOT appear at non-delegation points or at a zone's apex".
 */

static isc_result_t
remove_orphaned_ds(dns_db_t *db, dns_dbversion_t *newver, dns_diff_t *diff) {
        isc_result_t result;
        isc_boolean_t ns_exists, ds_exists;
        dns_difftuple_t *t;

        for (t = ISC_LIST_HEAD(diff->tuples);
             t != NULL;
             t = ISC_LIST_NEXT(t, link)) {
                if (t->op != DNS_DIFFOP_DEL ||
                    t->rdata.type != dns_rdatatype_ns)
                        continue;
                CHECK(rrset_exists(db, newver, &t->name, dns_rdatatype_ns, 0,
                                   &ns_exists));
                if (ns_exists)
                        continue;
                CHECK(rrset_exists(db, newver, &t->name, dns_rdatatype_ds, 0,
                                   &ds_exists));
                if (!ds_exists)
                        continue;
                CHECK(delete_if(true_p, db, newver, &t->name,
                                dns_rdatatype_ds, 0, NULL, diff));
        }
        return (ISC_R_SUCCESS);

 failure:
        return (result);
}

static void
update_action(isc_task_t *task, isc_event_t *event) {
        update_event_t *uev = (update_event_t *) event;
        dns_zone_t *zone = uev->zone;
        ns_client_t *client = (ns_client_t *)event->ev_arg;

        isc_result_t result;
        dns_db_t *db = NULL;
        dns_dbversion_t *oldver = NULL;
        dns_dbversion_t *ver = NULL;
        dns_diff_t diff;        /* Pending updates. */
        dns_diff_t temp;        /* Pending RR existence assertions. */
        isc_boolean_t soa_serial_changed = ISC_FALSE;
        isc_mem_t *mctx = client->mctx;
        dns_rdatatype_t covers;
        dns_message_t *request = client->message;
        dns_rdataclass_t zoneclass;
        dns_name_t *zonename;
        dns_ssutable_t *ssutable = NULL;
        dns_fixedname_t tmpnamefixed;
        dns_name_t *tmpname = NULL;

        INSIST(event->ev_type == DNS_EVENT_UPDATE);

        dns_diff_init(mctx, &diff);
        dns_diff_init(mctx, &temp);

        CHECK(dns_zone_getdb(zone, &db));
        zonename = dns_db_origin(db);
        zoneclass = dns_db_class(db);
        dns_zone_getssutable(zone, &ssutable);
        dns_db_currentversion(db, &oldver);
        CHECK(dns_db_newversion(db, &ver));

        /*
         * Check prerequisites.
         */

        for (result = dns_message_firstname(request, DNS_SECTION_PREREQUISITE);
             result == ISC_R_SUCCESS;
             result = dns_message_nextname(request, DNS_SECTION_PREREQUISITE))
        {
                dns_name_t *name = NULL;
                dns_rdata_t rdata = DNS_RDATA_INIT;
                dns_ttl_t ttl;
                dns_rdataclass_t update_class;
                isc_boolean_t flag;

                get_current_rr(request, DNS_SECTION_PREREQUISITE, zoneclass,
                               &name, &rdata, &covers, &ttl, &update_class);

                if (ttl != 0)
                        FAILC(DNS_R_FORMERR, "prerequisite TTL is not zero");

                if (! dns_name_issubdomain(name, zonename))
                        FAILN(DNS_R_NOTZONE, name,
                                "prerequisite name is out of zone");

                if (update_class == dns_rdataclass_any) {
                        if (rdata.length != 0)
                                FAILC(DNS_R_FORMERR,
                                      "class ANY prerequisite "
                                      "RDATA is not empty");
                        if (rdata.type == dns_rdatatype_any) {
                                CHECK(name_exists(db, ver, name, &flag));
                                if (! flag) {
                                        FAILN(DNS_R_NXDOMAIN, name,
                                              "'name in use' prerequisite "
                                              "not satisfied");
                                }
                        } else {
                                CHECK(rrset_exists(db, ver, name,
                                                   rdata.type, covers, &flag));
                                if (! flag) {
                                        /* RRset does not exist. */
                                        FAILNT(DNS_R_NXRRSET, name, rdata.type,
                                        "'rrset exists (value independent)' "
                                        "prerequisite not satisfied");
                                }
                        }
                } else if (update_class == dns_rdataclass_none) {
                        if (rdata.length != 0)
                                FAILC(DNS_R_FORMERR,
                                      "class NONE prerequisite "
                                      "RDATA is not empty");
                        if (rdata.type == dns_rdatatype_any) {
                                CHECK(name_exists(db, ver, name, &flag));
                                if (flag) {
                                        FAILN(DNS_R_YXDOMAIN, name,
                                              "'name not in use' prerequisite "
                                              "not satisfied");
                                }
                        } else {
                                CHECK(rrset_exists(db, ver, name,
                                                   rdata.type, covers, &flag));
                                if (flag) {
                                        /* RRset exists. */
                                        FAILNT(DNS_R_YXRRSET, name, rdata.type,
                                               "'rrset does not exist' "
                                               "prerequisite not satisfied");
                                }
                        }
                } else if (update_class == zoneclass) {
                        /* "temp<rr.name, rr.type> += rr;" */
                        result = temp_append(&temp, name, &rdata);
                        if (result != ISC_R_SUCCESS) {
                                UNEXPECTED_ERROR(__FILE__, __LINE__,
                                         "temp entry creation failed: %s",
                                                 dns_result_totext(result));
                                FAIL(ISC_R_UNEXPECTED);
                        }
                } else {
                        FAILC(DNS_R_FORMERR, "malformed prerequisite");
                }
        }
        if (result != ISC_R_NOMORE)
                FAIL(result);


        /*
         * Perform the final check of the "rrset exists (value dependent)"
         * prerequisites.
         */
        if (ISC_LIST_HEAD(temp.tuples) != NULL) {
                dns_rdatatype_t type;

                /*
                 * Sort the prerequisite records by owner name,
                 * type, and rdata.
                 */
                result = dns_diff_sort(&temp, temp_order);
                if (result != ISC_R_SUCCESS)
                        FAILC(result, "'RRset exists (value dependent)' "
                              "prerequisite not satisfied");

                dns_fixedname_init(&tmpnamefixed);
                tmpname = dns_fixedname_name(&tmpnamefixed);
                result = temp_check(mctx, &temp, db, ver, tmpname, &type);
                if (result != ISC_R_SUCCESS)
                        FAILNT(result, tmpname, type,
                               "'RRset exists (value dependent)' "
                               "prerequisite not satisfied");
        }

        update_log(client, zone, LOGLEVEL_DEBUG,
                   "prerequisites are OK");

        /*
         * Check Requestor's Permissions.  It seems a bit silly to do this
         * only after prerequisite testing, but that is what RFC2136 says.
         */
        result = ISC_R_SUCCESS;
        if (ssutable == NULL)
                CHECK(checkupdateacl(client, dns_zone_getupdateacl(zone),
                                     "update", zonename, ISC_FALSE));
        else if (client->signer == NULL)
                CHECK(checkupdateacl(client, NULL, "update", zonename,
                                     ISC_FALSE));
        
        if (dns_zone_getupdatedisabled(zone))
                FAILC(DNS_R_REFUSED, "dynamic update temporarily disabled");

        /*
         * Perform the Update Section Prescan.
         */

        for (result = dns_message_firstname(request, DNS_SECTION_UPDATE);
             result == ISC_R_SUCCESS;
             result = dns_message_nextname(request, DNS_SECTION_UPDATE))
        {
                dns_name_t *name = NULL;
                dns_rdata_t rdata = DNS_RDATA_INIT;
                dns_ttl_t ttl;
                dns_rdataclass_t update_class;
                get_current_rr(request, DNS_SECTION_UPDATE, zoneclass,
                               &name, &rdata, &covers, &ttl, &update_class);

                if (! dns_name_issubdomain(name, zonename))
                        FAILC(DNS_R_NOTZONE,
                              "update RR is outside zone");
                if (update_class == zoneclass) {
                        /*
                         * Check for meta-RRs.  The RFC2136 pseudocode says
                         * check for ANY|AXFR|MAILA|MAILB, but the text adds
                         * "or any other QUERY metatype"
                         */
                        if (dns_rdatatype_ismeta(rdata.type)) {
                                FAILC(DNS_R_FORMERR,
                                      "meta-RR in update");
                        }
                        result = dns_zone_checknames(zone, name, &rdata);
                        if (result != ISC_R_SUCCESS)
                                FAIL(DNS_R_REFUSED);
                } else if (update_class == dns_rdataclass_any) {
                        if (ttl != 0 || rdata.length != 0 ||
                            (dns_rdatatype_ismeta(rdata.type) &&
                             rdata.type != dns_rdatatype_any))
                                FAILC(DNS_R_FORMERR,
                                      "meta-RR in update");
                } else if (update_class == dns_rdataclass_none) {
                        if (ttl != 0 ||
                            dns_rdatatype_ismeta(rdata.type))
                                FAILC(DNS_R_FORMERR,
                                      "meta-RR in update");
                } else {
                        update_log(client, zone, ISC_LOG_WARNING,
                                   "update RR has incorrect class %d",
                                   update_class);
                        FAIL(DNS_R_FORMERR);
                }
                /*
                 * draft-ietf-dnsind-simple-secure-update-01 says
                 * "Unlike traditional dynamic update, the client
                 * is forbidden from updating NSEC records."
                 */
                if (dns_db_issecure(db)) {
                        if (rdata.type == dns_rdatatype_nsec) {
                                FAILC(DNS_R_REFUSED,
                                      "explicit NSEC updates are not allowed "
                                      "in secure zones");
                        }
                        else if (rdata.type == dns_rdatatype_rrsig) {
                                FAILC(DNS_R_REFUSED,
                                      "explicit RRSIG updates are currently not "
                                      "supported in secure zones");
                        }
                }

                if (ssutable != NULL && client->signer != NULL) {
                        if (rdata.type != dns_rdatatype_any) {
                                if (!dns_ssutable_checkrules(ssutable,
                                                             client->signer,
                                                             name, rdata.type))
                                        FAILC(DNS_R_REFUSED,
                                              "rejected by secure update");
                        }
                        else {
                                if (!ssu_checkall(db, ver, name, ssutable,
                                                  client->signer))
                                        FAILC(DNS_R_REFUSED,
                                              "rejected by secure update");
                        }
                }
        }
        if (result != ISC_R_NOMORE)
                FAIL(result);

        update_log(client, zone, LOGLEVEL_DEBUG,
                   "update section prescan OK");

        /*
         * Process the Update Section.
         */

        for (result = dns_message_firstname(request, DNS_SECTION_UPDATE);
             result == ISC_R_SUCCESS;
             result = dns_message_nextname(request, DNS_SECTION_UPDATE))
        {
                dns_name_t *name = NULL;
                dns_rdata_t rdata = DNS_RDATA_INIT;
                dns_ttl_t ttl;
                dns_rdataclass_t update_class;
                isc_boolean_t flag;

                get_current_rr(request, DNS_SECTION_UPDATE, zoneclass,
                               &name, &rdata, &covers, &ttl, &update_class);

                if (update_class == zoneclass) {

                        /*
                         * RFC 1123 doesn't allow MF and MD in master zones.                             */
                        if (rdata.type == dns_rdatatype_md ||
                            rdata.type == dns_rdatatype_mf) {
                                char typebuf[DNS_RDATATYPE_FORMATSIZE];

                                dns_rdatatype_format(rdata.type, typebuf,
                                                     sizeof(typebuf));
                                update_log(client, zone, LOGLEVEL_PROTOCOL,
                                           "attempt to add %s ignored",
                                           typebuf);
                                continue;
                        }
                        if (rdata.type == dns_rdatatype_ns &&
                            dns_name_iswildcard(name)) {
                                update_log(client, zone,
                                           LOGLEVEL_PROTOCOL,
                                           "attempt to add wildcard NS record"
                                           "ignored");
                                continue;
                        }
                        if (rdata.type == dns_rdatatype_cname) {
                                CHECK(cname_incompatible_rrset_exists(db, ver,
                                                                      name,
                                                                      &flag));
                                if (flag) {
                                        update_log(client, zone,
                                                   LOGLEVEL_PROTOCOL,
                                                   "attempt to add CNAME "
                                                   "alongside non-CNAME "
                                                   "ignored");
                                        continue;
                                }
                        } else {
                                CHECK(rrset_exists(db, ver, name,
                                                   dns_rdatatype_cname, 0,
                                                   &flag));
                                if (flag &&
                                    ! dns_rdatatype_isdnssec(rdata.type))
                                {
                                        update_log(client, zone,
                                                   LOGLEVEL_PROTOCOL,
                                                   "attempt to add non-CNAME "
                                                   "alongside CNAME ignored");
                                        continue;
                                }
                        }
                        if (rdata.type == dns_rdatatype_soa) {
                                isc_boolean_t ok;
                                CHECK(rrset_exists(db, ver, name,
                                                   dns_rdatatype_soa, 0,
                                                   &flag));
                                if (! flag) {
                                        update_log(client, zone,
                                                   LOGLEVEL_PROTOCOL,
                                                   "attempt to create 2nd "
                                                   "SOA ignored");
                                        continue;
                                }
                                CHECK(check_soa_increment(db, ver, &rdata,
                                                          &ok));
                                if (! ok) {
                                        update_log(client, zone,
                                                   LOGLEVEL_PROTOCOL,
                                                   "SOA update failed to "
                                                   "increment serial, "
                                                   "ignoring it");
                                        continue;
                                }
                                soa_serial_changed = ISC_TRUE;
                        }

                        if (isc_log_wouldlog(ns_g_lctx, LOGLEVEL_PROTOCOL)) {
                                char namestr[DNS_NAME_FORMATSIZE];
                                char typestr[DNS_RDATATYPE_FORMATSIZE];
                                dns_name_format(name, namestr,
                                                sizeof(namestr));
                                dns_rdatatype_format(rdata.type, typestr,
                                                     sizeof(typestr));
                                update_log(client, zone,
                                           LOGLEVEL_PROTOCOL,
                                           "adding an RR at '%s' %s",
                                           namestr, typestr);
                        }

                        /* Prepare the affected RRset for the addition. */
                        {
                                add_rr_prepare_ctx_t ctx;
                                ctx.db = db;
                                ctx.ver = ver;
                                ctx.diff = &diff;
                                ctx.name = name;
                                ctx.update_rr = &rdata;
                                ctx.update_rr_ttl = ttl;
                                ctx.ignore_add = ISC_FALSE;
                                dns_diff_init(mctx, &ctx.del_diff);
                                dns_diff_init(mctx, &ctx.add_diff);
                                CHECK(foreach_rr(db, ver, name, rdata.type,
                                                 covers, add_rr_prepare_action,
                                                 &ctx));

                                if (ctx.ignore_add) {
                                        dns_diff_clear(&ctx.del_diff);
                                        dns_diff_clear(&ctx.add_diff);
                                } else {
                                        CHECK(do_diff(&ctx.del_diff, db, ver, &diff));
                                        CHECK(do_diff(&ctx.add_diff, db, ver, &diff));
                                        CHECK(update_one_rr(db, ver, &diff,
                                                            DNS_DIFFOP_ADD,
                                                            name, ttl, &rdata));
                                }
                        }
                } else if (update_class == dns_rdataclass_any) {
                        if (rdata.type == dns_rdatatype_any) {
                                if (isc_log_wouldlog(ns_g_lctx,
                                                     LOGLEVEL_PROTOCOL))
                                {
                                        char namestr[DNS_NAME_FORMATSIZE];
                                        dns_name_format(name, namestr,
                                                        sizeof(namestr));
                                        update_log(client, zone,
                                                   LOGLEVEL_PROTOCOL,
                                                   "delete all rrsets from "
                                                   "name '%s'", namestr);
                                }
                                if (dns_name_equal(name, zonename)) {
                                        CHECK(delete_if(type_not_soa_nor_ns_p,
                                                        db, ver, name,
                                                        dns_rdatatype_any, 0,
                                                        &rdata, &diff));
                                } else {
                                        CHECK(delete_if(type_not_dnssec,
                                                        db, ver, name,
                                                        dns_rdatatype_any, 0,
                                                        &rdata, &diff));
                                }
                        } else if (dns_name_equal(name, zonename) &&
                                   (rdata.type == dns_rdatatype_soa ||
                                    rdata.type == dns_rdatatype_ns)) {
                                update_log(client, zone,
                                           LOGLEVEL_PROTOCOL,
                                           "attempt to delete all SOA "
                                           "or NS records ignored");
                                continue;
                        } else {
                                if (isc_log_wouldlog(ns_g_lctx,
                                                     LOGLEVEL_PROTOCOL))
                                {
                                        char namestr[DNS_NAME_FORMATSIZE];
                                        char typestr[DNS_RDATATYPE_FORMATSIZE];
                                        dns_name_format(name, namestr,
                                                        sizeof(namestr));
                                        dns_rdatatype_format(rdata.type,
                                                             typestr,
                                                             sizeof(typestr));
                                        update_log(client, zone,
                                                   LOGLEVEL_PROTOCOL,
                                                   "deleting rrset at '%s' %s",
                                                   namestr, typestr);
                                }
                                CHECK(delete_if(true_p, db, ver, name,
                                                rdata.type, covers, &rdata,
                                                &diff));
                        }
                } else if (update_class == dns_rdataclass_none) {
                        /*
                         * The (name == zonename) condition appears in
                         * RFC2136 3.4.2.4 but is missing from the pseudocode.
                         */
                        if (dns_name_equal(name, zonename)) {
                                if (rdata.type == dns_rdatatype_soa) {
                                        update_log(client, zone,
                                                   LOGLEVEL_PROTOCOL,
                                                   "attempt to delete SOA "
                                                   "ignored");
                                        continue;
                                }
                                if (rdata.type == dns_rdatatype_ns) {
                                        int count;
                                        CHECK(rr_count(db, ver, name,
                                                       dns_rdatatype_ns,
                                                       0, &count));
                                        if (count == 1) {
                                                update_log(client, zone,
                                                           LOGLEVEL_PROTOCOL,
                                                           "attempt to "
                                                           "delete last "
                                                           "NS ignored");
                                                continue;
                                        }
                                }
                        }
                        update_log(client, zone,
                                   LOGLEVEL_PROTOCOL,
                                   "deleting an RR");
                        CHECK(delete_if(rr_equal_p, db, ver, name,
                                        rdata.type, covers, &rdata, &diff));
                }
        }
        if (result != ISC_R_NOMORE)
                FAIL(result);

        /*
         * If any changes were made, increment the SOA serial number,
         * update RRSIGs and NSECs (if zone is secure), and write the update
         * to the journal.
         */
        if (! ISC_LIST_EMPTY(diff.tuples)) {
                char *journalfile;
                dns_journal_t *journal;

                /*
                 * Increment the SOA serial, but only if it was not
                 * changed as a result of an update operation.
                 */
                if (! soa_serial_changed) {
                        CHECK(increment_soa_serial(db, ver, &diff, mctx));
                }

                CHECK(remove_orphaned_ds(db, ver, &diff));

                if (dns_db_issecure(db)) {
                        result = update_signatures(client, zone, db, oldver,
                                                   ver, &diff,
                                         dns_zone_getsigvalidityinterval(zone));
                        if (result != ISC_R_SUCCESS) {
                                update_log(client, zone,
                                           ISC_LOG_ERROR,
                                           "RRSIG/NSEC update failed: %s",
                                           isc_result_totext(result));
                                goto failure;
                        }
                }

                journalfile = dns_zone_getjournal(zone);
                if (journalfile != NULL) {
                        update_log(client, zone, LOGLEVEL_DEBUG,
                                   "writing journal %s", journalfile);

                        journal = NULL;
                        result = dns_journal_open(mctx, journalfile,
                                                  ISC_TRUE, &journal);
                        if (result != ISC_R_SUCCESS)
                                FAILS(result, "journal open failed");

                        result = dns_journal_write_transaction(journal, &diff);
                        if (result != ISC_R_SUCCESS) {
                                dns_journal_destroy(&journal);
                                FAILS(result, "journal write failed");
                        }

                        dns_journal_destroy(&journal);
                }

                /*
                 * XXXRTH  Just a note that this committing code will have
                 *         to change to handle databases that need two-phase
                 *         commit, but this isn't a priority.
                 */
                update_log(client, zone, LOGLEVEL_DEBUG,
                           "committing update transaction");
                dns_db_closeversion(db, &ver, ISC_TRUE);

                /*
                 * Mark the zone as dirty so that it will be written to disk.
                 */
                dns_zone_markdirty(zone);

                /*
                 * Notify slaves of the change we just made.
                 */
                dns_zone_notify(zone);
        } else {
                update_log(client, zone, LOGLEVEL_DEBUG, "redundant request");
                dns_db_closeversion(db, &ver, ISC_TRUE);
        }
        result = ISC_R_SUCCESS;
        goto common;

 failure:
        /*
         * The reason for failure should have been logged at this point.
         */
        if (ver != NULL) {
                update_log(client, zone, LOGLEVEL_DEBUG, 
                           "rolling back");
                dns_db_closeversion(db, &ver, ISC_FALSE);
        }

 common:
        dns_diff_clear(&temp);
        dns_diff_clear(&diff);

        if (oldver != NULL)
                dns_db_closeversion(db, &oldver, ISC_FALSE);

        if (db != NULL)
                dns_db_detach(&db);

        if (ssutable != NULL)
                dns_ssutable_detach(&ssutable);

        if (zone != NULL)
                dns_zone_detach(&zone);

        isc_task_detach(&task);
        uev->result = result;
        uev->ev_type = DNS_EVENT_UPDATEDONE;
        uev->ev_action = updatedone_action;
        isc_task_send(client->task, &event);
        INSIST(event == NULL);
}

static void
updatedone_action(isc_task_t *task, isc_event_t *event) {
        update_event_t *uev = (update_event_t *) event;
        ns_client_t *client = (ns_client_t *) event->ev_arg;

        UNUSED(task);

        INSIST(event->ev_type == DNS_EVENT_UPDATEDONE);
        INSIST(task == client->task);

        INSIST(client->nupdates > 0);
        client->nupdates--;
        respond(client, uev->result);
        isc_event_free(&event);
        ns_client_detach(&client);
}

/*
 * Update forwarding support.
 */

static void
forward_fail(isc_task_t *task, isc_event_t *event) {
        ns_client_t *client = (ns_client_t *)event->ev_arg;

        UNUSED(task);

        INSIST(client->nupdates > 0);
        client->nupdates--;
        respond(client, DNS_R_SERVFAIL);
        isc_event_free(&event);
        ns_client_detach(&client);
}


static void
forward_callback(void *arg, isc_result_t result, dns_message_t *answer) {
        update_event_t *uev = arg;
        ns_client_t *client = uev->ev_arg;

        if (result != ISC_R_SUCCESS) {
                INSIST(answer == NULL);
                uev->ev_type = DNS_EVENT_UPDATEDONE;
                uev->ev_action = forward_fail;
        } else {
                uev->ev_type = DNS_EVENT_UPDATEDONE;
                uev->ev_action = forward_done;
                uev->answer = answer;
        }
        isc_task_send(client->task, ISC_EVENT_PTR(&uev));
}

static void
forward_done(isc_task_t *task, isc_event_t *event) {
        update_event_t *uev = (update_event_t *) event;
        ns_client_t *client = (ns_client_t *)event->ev_arg;

        UNUSED(task);

        INSIST(client->nupdates > 0);
        client->nupdates--;
        ns_client_sendraw(client, uev->answer);
        dns_message_destroy(&uev->answer);
        isc_event_free(&event);
        ns_client_detach(&client);
}

static void
forward_action(isc_task_t *task, isc_event_t *event) {
        update_event_t *uev = (update_event_t *) event;
        dns_zone_t *zone = uev->zone;
        ns_client_t *client = (ns_client_t *)event->ev_arg;
        isc_result_t result;

        result = dns_zone_forwardupdate(zone, client->message,
                                        forward_callback, event);
        if (result != ISC_R_SUCCESS) {
                uev->ev_type = DNS_EVENT_UPDATEDONE;
                uev->ev_action = forward_fail;
                isc_task_send(client->task, &event);
        }
        dns_zone_detach(&zone);
        isc_task_detach(&task);
}

static isc_result_t
send_forward_event(ns_client_t *client, dns_zone_t *zone) {
        isc_result_t result = ISC_R_SUCCESS;
        update_event_t *event = NULL;
        isc_task_t *zonetask = NULL;
        ns_client_t *evclient;

        event = (update_event_t *)
                isc_event_allocate(client->mctx, client, DNS_EVENT_UPDATE,
                                   forward_action, NULL, sizeof(*event));
        if (event == NULL)
                FAIL(ISC_R_NOMEMORY);
        event->zone = zone;
        event->result = ISC_R_SUCCESS;

        evclient = NULL;
        ns_client_attach(client, &evclient);
        INSIST(client->nupdates == 0);
        client->nupdates++;
        event->ev_arg = evclient;

        dns_zone_gettask(zone, &zonetask);
        isc_task_send(zonetask, ISC_EVENT_PTR(&event));

 failure:
        if (event != NULL)
                isc_event_free(ISC_EVENT_PTR(&event));
        return (result);
}