lib/dns/sdb.c

	sdb.c revision c0d2891f6e08fcf5379dfb9a1bf8fbbb63f1952a
/*
 * Copyright (C) 2004  Internet Systems Consortium, Inc. ("ISC")
 * Copyright (C) 2000, 2001, 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: sdb.c,v 1.46 2004/07/22 03:58:07 marka Exp $ */

#include <config.h>

#include <string.h>

#include <isc/buffer.h>
#include <isc/lex.h>
#include <isc/log.h>
#include <isc/magic.h>
#include <isc/mem.h>
#include <isc/once.h>
#include <isc/print.h>
#include <isc/region.h>
#include <isc/util.h>

#include <dns/callbacks.h>
#include <dns/db.h>
#include <dns/dbiterator.h>
#include <dns/fixedname.h>
#include <dns/log.h>
#include <dns/rdata.h>
#include <dns/rdatalist.h>
#include <dns/rdataset.h>
#include <dns/rdatasetiter.h>
#include <dns/rdatatype.h>
#include <dns/result.h>
#include <dns/sdb.h>
#include <dns/types.h>

#include "rdatalist_p.h"

struct dns_sdbimplementation {
    const dns_sdbmethods_t      *methods;
    void                *driverdata;
    unsigned int            flags;
    isc_mem_t           *mctx;
    isc_mutex_t         driverlock;
    dns_dbimplementation_t      *dbimp;
};

struct dns_sdb {
    /* Unlocked */
    dns_db_t            common;
    char                *zone;
    dns_sdbimplementation_t     *implementation;
    void                *dbdata;
    isc_mutex_t         lock;
    /* Locked */
    unsigned int            references;
};

struct dns_sdblookup {
    /* Unlocked */
    unsigned int            magic;
    dns_sdb_t           *sdb;
    ISC_LIST(dns_rdatalist_t)   lists;
    ISC_LIST(isc_buffer_t)      buffers;
    dns_name_t          *name;
    ISC_LINK(dns_sdblookup_t)   link;
    isc_mutex_t         lock;
    dns_rdatacallbacks_t        callbacks;
    /* Locked */
    unsigned int            references;
};

typedef struct dns_sdblookup dns_sdbnode_t;

struct dns_sdballnodes {
    dns_dbiterator_t        common;
    ISC_LIST(dns_sdbnode_t)     nodelist;
    dns_sdbnode_t           *current;
    dns_sdbnode_t           *origin;
};

typedef dns_sdballnodes_t sdb_dbiterator_t;

typedef struct sdb_rdatasetiter {
    dns_rdatasetiter_t      common;
    dns_rdatalist_t         *current;
} sdb_rdatasetiter_t;

#define SDB_MAGIC       ISC_MAGIC('S', 'D', 'B', '-')

/*
 * Note that "impmagic" is not the first four bytes of the struct, so
 * ISC_MAGIC_VALID cannot be used.
 */
#define VALID_SDB(sdb)      ((sdb) != NULL && \
                 (sdb)->common.impmagic == SDB_MAGIC)

#define SDBLOOKUP_MAGIC     ISC_MAGIC('S','D','B','L')
#define VALID_SDBLOOKUP(sdbl)   ISC_MAGIC_VALID(sdbl, SDBLOOKUP_MAGIC)
#define VALID_SDBNODE(sdbn) VALID_SDBLOOKUP(sdbn)

/* These values are taken from RFC 1537 */
#define SDB_DEFAULT_REFRESH (60 * 60 * 8)
#define SDB_DEFAULT_RETRY   (60 * 60 * 2)
#define SDB_DEFAULT_EXPIRE  (60 * 60 * 24 * 7)
#define SDB_DEFAULT_MINIMUM (60 * 60 * 24)

/* This is a reasonable value */
#define SDB_DEFAULT_TTL     (60 * 60 * 24)

#define MAYBE_LOCK(sdb)                         \
    do {                                \
        unsigned int flags = sdb->implementation->flags;    \
        if ((flags & DNS_SDBFLAG_THREADSAFE) == 0)      \
            LOCK(&sdb->implementation->driverlock);     \
    } while (0)

#define MAYBE_UNLOCK(sdb)                       \
    do {                                \
        unsigned int flags = sdb->implementation->flags;    \
        if ((flags & DNS_SDBFLAG_THREADSAFE) == 0)      \
            UNLOCK(&sdb->implementation->driverlock);   \
    } while (0)

static int dummy;

static isc_result_t dns_sdb_create(isc_mem_t *mctx, dns_name_t *origin,
                   dns_dbtype_t type, dns_rdataclass_t rdclass,
                   unsigned int argc, char *argv[],
                   void *driverarg, dns_db_t **dbp);

static isc_result_t findrdataset(dns_db_t *db, dns_dbnode_t *node,
                 dns_dbversion_t *version,
                 dns_rdatatype_t type, dns_rdatatype_t covers,
                 isc_stdtime_t now, dns_rdataset_t *rdataset,
                 dns_rdataset_t *sigrdataset);

static isc_result_t createnode(dns_sdb_t *sdb, dns_sdbnode_t **nodep);

static void destroynode(dns_sdbnode_t *node);

static void detachnode(dns_db_t *db, dns_dbnode_t **targetp);


static void list_tordataset(dns_rdatalist_t *rdatalist,
                dns_db_t *db, dns_dbnode_t *node,
                dns_rdataset_t *rdataset);

static void     dbiterator_destroy(dns_dbiterator_t **iteratorp);
static isc_result_t dbiterator_first(dns_dbiterator_t *iterator);
static isc_result_t dbiterator_last(dns_dbiterator_t *iterator);
static isc_result_t dbiterator_seek(dns_dbiterator_t *iterator,
                    dns_name_t *name);
static isc_result_t dbiterator_prev(dns_dbiterator_t *iterator);
static isc_result_t dbiterator_next(dns_dbiterator_t *iterator);
static isc_result_t dbiterator_current(dns_dbiterator_t *iterator,
                       dns_dbnode_t **nodep,
                       dns_name_t *name);
static isc_result_t dbiterator_pause(dns_dbiterator_t *iterator);
static isc_result_t dbiterator_origin(dns_dbiterator_t *iterator,
                      dns_name_t *name);

static dns_dbiteratormethods_t dbiterator_methods = {
    dbiterator_destroy,
    dbiterator_first,
    dbiterator_last,
    dbiterator_seek,
    dbiterator_prev,
    dbiterator_next,
    dbiterator_current,
    dbiterator_pause,
    dbiterator_origin
};

static void     rdatasetiter_destroy(dns_rdatasetiter_t **iteratorp);
static isc_result_t rdatasetiter_first(dns_rdatasetiter_t *iterator);
static isc_result_t rdatasetiter_next(dns_rdatasetiter_t *iterator);
static void     rdatasetiter_current(dns_rdatasetiter_t *iterator,
                         dns_rdataset_t *rdataset);

static dns_rdatasetitermethods_t rdatasetiter_methods = {
    rdatasetiter_destroy,
    rdatasetiter_first,
    rdatasetiter_next,
    rdatasetiter_current
};

/*
 * Functions used by implementors of simple databases
 */
isc_result_t
dns_sdb_register(const char *drivername, const dns_sdbmethods_t *methods,
         void *driverdata, unsigned int flags, isc_mem_t *mctx,
         dns_sdbimplementation_t **sdbimp)
{
    dns_sdbimplementation_t *imp;
    isc_result_t result;

    REQUIRE(drivername != NULL);
    REQUIRE(methods != NULL);
    REQUIRE(methods->lookup != NULL);
    REQUIRE(mctx != NULL);
    REQUIRE(sdbimp != NULL && *sdbimp == NULL);
    REQUIRE((flags & ~(DNS_SDBFLAG_RELATIVEOWNER |
               DNS_SDBFLAG_RELATIVERDATA |
               DNS_SDBFLAG_THREADSAFE)) == 0);

    imp = isc_mem_get(mctx, sizeof(dns_sdbimplementation_t));
    if (imp == NULL)
        return (ISC_R_NOMEMORY);
    imp->methods = methods;
    imp->driverdata = driverdata;
    imp->flags = flags;
    imp->mctx = NULL;
    isc_mem_attach(mctx, &imp->mctx);
    result = isc_mutex_init(&imp->driverlock);
    if (result != ISC_R_SUCCESS) {
        UNEXPECTED_ERROR(__FILE__, __LINE__,
                 "isc_mutex_init() failed: %s",
                 isc_result_totext(result));
        goto cleanup_mctx;
    }

    imp->dbimp = NULL;
    result = dns_db_register(drivername, dns_sdb_create, imp, mctx,
                 &imp->dbimp);
    if (result != ISC_R_SUCCESS)
        goto cleanup_mutex;
    *sdbimp = imp;

    return (ISC_R_SUCCESS);

 cleanup_mutex:
    DESTROYLOCK(&imp->driverlock);
 cleanup_mctx:
    isc_mem_put(mctx, imp, sizeof(dns_sdbimplementation_t));
    return (result);
}

void
dns_sdb_unregister(dns_sdbimplementation_t **sdbimp) {
    dns_sdbimplementation_t *imp;
    isc_mem_t *mctx;

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

    imp = *sdbimp;
    dns_db_unregister(&imp->dbimp);
    DESTROYLOCK(&imp->driverlock);

    mctx = imp->mctx;
    isc_mem_put(mctx, imp, sizeof(dns_sdbimplementation_t));
    isc_mem_detach(&mctx);

    *sdbimp = NULL;
}

static inline unsigned int
initial_size(unsigned int len) {
    unsigned int size;
    for (size = 64; size < (64 * 1024); size *= 2)
        if (len < size)
            return (size);
    return (64 * 1024);
}

isc_result_t
dns_sdb_putrdata(dns_sdblookup_t *lookup, dns_rdatatype_t typeval, dns_ttl_t ttl,
         const unsigned char *rdatap, unsigned int rdlen)
{
    dns_rdatalist_t *rdatalist;
    dns_rdata_t *rdata;
    isc_buffer_t *rdatabuf = NULL;
    isc_result_t result;
    isc_mem_t *mctx;
    isc_region_t region;

    mctx = lookup->sdb->common.mctx;

    rdatalist = ISC_LIST_HEAD(lookup->lists);
    while (rdatalist != NULL) {
        if (rdatalist->type == typeval)
            break;
        rdatalist = ISC_LIST_NEXT(rdatalist, link);
    }

    if (rdatalist == NULL) {
        rdatalist = isc_mem_get(mctx, sizeof(dns_rdatalist_t));
        if (rdatalist == NULL)
            return (ISC_R_NOMEMORY);
        rdatalist->rdclass = lookup->sdb->common.rdclass;
        rdatalist->type = typeval;
        rdatalist->covers = 0;
        rdatalist->ttl = ttl;
        ISC_LIST_INIT(rdatalist->rdata);
        ISC_LINK_INIT(rdatalist, link);
        ISC_LIST_APPEND(lookup->lists, rdatalist, link);
    } else
        if (rdatalist->ttl != ttl)
            return (DNS_R_BADTTL);

    rdata = isc_mem_get(mctx, sizeof(dns_rdata_t));
    if (rdata == NULL)
        return (ISC_R_NOMEMORY);

    result = isc_buffer_allocate(mctx, &rdatabuf, rdlen);
    if (result != ISC_R_SUCCESS)
        goto failure;
    DE_CONST(rdatap, region.base);
    region.length = rdlen;
    isc_buffer_copyregion(rdatabuf, &region);
    isc_buffer_usedregion(rdatabuf, &region);
    dns_rdata_init(rdata);
    dns_rdata_fromregion(rdata, rdatalist->rdclass, rdatalist->type,
                 &region);
    ISC_LIST_APPEND(rdatalist->rdata, rdata, link);
    ISC_LIST_APPEND(lookup->buffers, rdatabuf, link);
    rdata = NULL;

 failure:
    if (rdata != NULL)
        isc_mem_put(mctx, rdata, sizeof(dns_rdata_t));
    return (result);
}


isc_result_t
dns_sdb_putrr(dns_sdblookup_t *lookup, const char *type, dns_ttl_t ttl,
          const char *data)
{
    unsigned int datalen;
    dns_rdatatype_t typeval;
    isc_textregion_t r;
    isc_lex_t *lex = NULL;
    isc_result_t result;
    unsigned char *p = NULL;
    unsigned int size = 0; /* Init to suppress compiler warning */
    isc_mem_t *mctx;
    dns_sdbimplementation_t *imp;
    dns_name_t *origin;
    isc_buffer_t b;
    isc_buffer_t rb;

    REQUIRE(VALID_SDBLOOKUP(lookup));
    REQUIRE(type != NULL);
    REQUIRE(data != NULL);

    mctx = lookup->sdb->common.mctx;

    DE_CONST(type, r.base);
    r.length = strlen(type);
    result = dns_rdatatype_fromtext(&typeval, &r);
    if (result != ISC_R_SUCCESS)
        return (result);

    imp = lookup->sdb->implementation;
    if ((imp->flags & DNS_SDBFLAG_RELATIVERDATA) != 0)
        origin = &lookup->sdb->common.origin;
    else
        origin = dns_rootname;

    result = isc_lex_create(mctx, 64, &lex);
    if (result != ISC_R_SUCCESS)
        goto failure;

    datalen = strlen(data);
    size = initial_size(datalen);
    for (;;) {
        isc_buffer_init(&b, data, datalen);
        isc_buffer_add(&b, datalen);
        result = isc_lex_openbuffer(lex, &b);
        if (result != ISC_R_SUCCESS)
            goto failure;

        p = isc_mem_get(mctx, size);
        if (p == NULL) {
            result = ISC_R_NOMEMORY;
            goto failure;
        }
        isc_buffer_init(&rb, p, size);
        result = dns_rdata_fromtext(NULL,
                        lookup->sdb->common.rdclass,
                        typeval, lex,
                        origin, 0,
                        mctx, &rb,
                        &lookup->callbacks);
        if (result != ISC_R_NOSPACE)
            break;

        isc_mem_put(mctx, p, size);
        p = NULL;
        size *= 2;
    } while (result == ISC_R_NOSPACE);

    if (result != ISC_R_SUCCESS)
        goto failure;

    result = dns_sdb_putrdata(lookup, typeval, ttl,
                  isc_buffer_base(&rb),
                  isc_buffer_usedlength(&rb));
 failure:
    if (p != NULL)
        isc_mem_put(mctx, p, size);
    if (lex != NULL)
        isc_lex_destroy(&lex);

    return (result);
}

static isc_result_t
getnode(dns_sdballnodes_t *allnodes, const char *name, dns_sdbnode_t **nodep) {
    dns_name_t *newname, *origin;
    dns_fixedname_t fnewname;
    dns_sdb_t *sdb = (dns_sdb_t *)allnodes->common.db;
    dns_sdbimplementation_t *imp = sdb->implementation;
    dns_sdbnode_t *sdbnode;
    isc_mem_t *mctx = sdb->common.mctx;
    isc_buffer_t b;
    isc_result_t result;

    dns_fixedname_init(&fnewname);
    newname = dns_fixedname_name(&fnewname);

    if ((imp->flags & DNS_SDBFLAG_RELATIVERDATA) != 0)
        origin = &sdb->common.origin;
    else
        origin = dns_rootname;
    isc_buffer_init(&b, name, strlen(name));
    isc_buffer_add(&b, strlen(name));

    result = dns_name_fromtext(newname, &b, origin, ISC_FALSE, NULL);
    if (result != ISC_R_SUCCESS)
        return (result);

    if (allnodes->common.relative_names) {
        /* All names are relative to the root */
        unsigned int nlabels = dns_name_countlabels(newname);
        dns_name_getlabelsequence(newname, 0, nlabels - 1, newname);
    }

    sdbnode = ISC_LIST_HEAD(allnodes->nodelist);
    if (sdbnode == NULL || !dns_name_equal(sdbnode->name, newname)) {
        sdbnode = NULL;
        result = createnode(sdb, &sdbnode);
        if (result != ISC_R_SUCCESS)
            return (result);
        sdbnode->name = isc_mem_get(mctx, sizeof(dns_name_t));
        if (sdbnode->name == NULL) {
            destroynode(sdbnode);
            return (ISC_R_NOMEMORY);
        }
        dns_name_init(sdbnode->name, NULL);
        result = dns_name_dup(newname, mctx, sdbnode->name);
        if (result != ISC_R_SUCCESS) {
            isc_mem_put(mctx, sdbnode->name, sizeof(dns_name_t));
            destroynode(sdbnode);
            return (result);
        }
        ISC_LIST_PREPEND(allnodes->nodelist, sdbnode, link);
        if (allnodes->origin == NULL &&
            dns_name_equal(newname, &sdb->common.origin))
            allnodes->origin = sdbnode;
    }
    *nodep = sdbnode;
    return (ISC_R_SUCCESS);
}

isc_result_t
dns_sdb_putnamedrr(dns_sdballnodes_t *allnodes, const char *name,
           const char *type, dns_ttl_t ttl, const char *data)
{
    isc_result_t result;
    dns_sdbnode_t *sdbnode = NULL;
    result = getnode(allnodes, name, &sdbnode);
    if (result != ISC_R_SUCCESS)
        return (result);
    return (dns_sdb_putrr(sdbnode, type, ttl, data));
}

isc_result_t
dns_sdb_putnamedrdata(dns_sdballnodes_t *allnodes, const char *name,
              dns_rdatatype_t type, dns_ttl_t ttl,
              const void *rdata, unsigned int rdlen)
{
    isc_result_t result;
    dns_sdbnode_t *sdbnode = NULL;
    result = getnode(allnodes, name, &sdbnode);
    if (result != ISC_R_SUCCESS)
        return (result);
    return (dns_sdb_putrdata(sdbnode, type, ttl, rdata, rdlen));
}

isc_result_t
dns_sdb_putsoa(dns_sdblookup_t *lookup, const char *mname, const char *rname,
           isc_uint32_t serial)
{
    char str[2 * DNS_NAME_MAXTEXT + 5 * (sizeof("2147483647")) + 7];
    int n;

    REQUIRE(mname != NULL);
    REQUIRE(rname != NULL);

    n = snprintf(str, sizeof(str), "%s %s %u %u %u %u %u",
             mname, rname, serial,
             SDB_DEFAULT_REFRESH, SDB_DEFAULT_RETRY,
             SDB_DEFAULT_EXPIRE, SDB_DEFAULT_MINIMUM);
    if (n >= (int)sizeof(str) || n < 0)
        return (ISC_R_NOSPACE);
    return (dns_sdb_putrr(lookup, "SOA", SDB_DEFAULT_TTL, str));
}

/*
 * DB routines
 */

static void
attach(dns_db_t *source, dns_db_t **targetp) {
    dns_sdb_t *sdb = (dns_sdb_t *) source;

    REQUIRE(VALID_SDB(sdb));

    LOCK(&sdb->lock);
    REQUIRE(sdb->references > 0);
    sdb->references++;
    UNLOCK(&sdb->lock);

    *targetp = source;
}

static void
destroy(dns_sdb_t *sdb) {
    isc_mem_t *mctx;
    dns_sdbimplementation_t *imp = sdb->implementation;

    mctx = sdb->common.mctx;

    if (imp->methods->destroy != NULL) {
        MAYBE_LOCK(sdb);
        imp->methods->destroy(sdb->zone, imp->driverdata,
                      &sdb->dbdata);
        MAYBE_UNLOCK(sdb);
    }

    isc_mem_free(mctx, sdb->zone);
    DESTROYLOCK(&sdb->lock);

    sdb->common.magic = 0;
    sdb->common.impmagic = 0;

    dns_name_free(&sdb->common.origin, mctx);

    isc_mem_put(mctx, sdb, sizeof(dns_sdb_t));
    isc_mem_detach(&mctx);
}

static void
detach(dns_db_t **dbp) {
    dns_sdb_t *sdb = (dns_sdb_t *)(*dbp);
    isc_boolean_t need_destroy = ISC_FALSE;

    REQUIRE(VALID_SDB(sdb));
    LOCK(&sdb->lock);
    REQUIRE(sdb->references > 0);
    sdb->references--;
    if (sdb->references == 0)
        need_destroy = ISC_TRUE;
    UNLOCK(&sdb->lock);

    if (need_destroy)
        destroy(sdb);

    *dbp = NULL;
}

static isc_result_t
beginload(dns_db_t *db, dns_addrdatasetfunc_t *addp, dns_dbload_t **dbloadp) {
    UNUSED(db);
    UNUSED(addp);
    UNUSED(dbloadp);
    return (ISC_R_NOTIMPLEMENTED);
}

static isc_result_t
endload(dns_db_t *db, dns_dbload_t **dbloadp) {
    UNUSED(db);
    UNUSED(dbloadp);
    return (ISC_R_NOTIMPLEMENTED);
}

static isc_result_t
dump(dns_db_t *db, dns_dbversion_t *version, const char *filename) {
    UNUSED(db);
    UNUSED(version);
    UNUSED(filename);
    return (ISC_R_NOTIMPLEMENTED);
}

static void
currentversion(dns_db_t *db, dns_dbversion_t **versionp) {
    REQUIRE(versionp != NULL && *versionp == NULL);

    UNUSED(db);

    *versionp = (void *) &dummy;
    return;
}

static isc_result_t
newversion(dns_db_t *db, dns_dbversion_t **versionp) {
    UNUSED(db);
    UNUSED(versionp);

    return (ISC_R_NOTIMPLEMENTED);
}

static void
attachversion(dns_db_t *db, dns_dbversion_t *source,
          dns_dbversion_t **targetp)
{
    REQUIRE(source != NULL && source == (void *) &dummy);
    REQUIRE(targetp != NULL && *targetp == NULL);

    UNUSED(db);
    *targetp = source;
    return;
}

static void
closeversion(dns_db_t *db, dns_dbversion_t **versionp, isc_boolean_t commit) {
    REQUIRE(versionp != NULL && *versionp == (void *) &dummy);
    REQUIRE(commit == ISC_FALSE);

    UNUSED(db);
    UNUSED(commit);

    *versionp = NULL;
}

static isc_result_t
createnode(dns_sdb_t *sdb, dns_sdbnode_t **nodep) {
    dns_sdbnode_t *node;
    isc_result_t result;

    node = isc_mem_get(sdb->common.mctx, sizeof(dns_sdbnode_t));
    if (node == NULL)
        return (ISC_R_NOMEMORY);

    node->sdb = NULL;
    attach((dns_db_t *)sdb, (dns_db_t **)&node->sdb);
    ISC_LIST_INIT(node->lists);
    ISC_LIST_INIT(node->buffers);
    ISC_LINK_INIT(node, link);
    node->name = NULL;
    result = isc_mutex_init(&node->lock);
    if (result != ISC_R_SUCCESS) {
        UNEXPECTED_ERROR(__FILE__, __LINE__,
                 "isc_mutex_init() failed: %s",
                 isc_result_totext(result));
        isc_mem_put(sdb->common.mctx, node, sizeof(dns_sdbnode_t));
        return (ISC_R_UNEXPECTED);
    }
    dns_rdatacallbacks_init(&node->callbacks);
    node->references = 1;
    node->magic = SDBLOOKUP_MAGIC;

    *nodep = node;
    return (ISC_R_SUCCESS);
}

static void
destroynode(dns_sdbnode_t *node) {
    dns_rdatalist_t *list;
    dns_rdata_t *rdata;
    isc_buffer_t *b;
    dns_sdb_t *sdb;
    isc_mem_t *mctx;

    sdb = node->sdb;
    mctx = sdb->common.mctx;

    while (!ISC_LIST_EMPTY(node->lists)) {
        list = ISC_LIST_HEAD(node->lists);
        while (!ISC_LIST_EMPTY(list->rdata)) {
            rdata = ISC_LIST_HEAD(list->rdata);
            ISC_LIST_UNLINK(list->rdata, rdata, link);
            isc_mem_put(mctx, rdata, sizeof(dns_rdata_t));
        }
        ISC_LIST_UNLINK(node->lists, list, link);
        isc_mem_put(mctx, list, sizeof(dns_rdatalist_t));
    }

    while (!ISC_LIST_EMPTY(node->buffers)) {
        b = ISC_LIST_HEAD(node->buffers);
        ISC_LIST_UNLINK(node->buffers, b, link);
        isc_buffer_free(&b);
    }

    if (node->name != NULL) {
        dns_name_free(node->name, mctx);
        isc_mem_put(mctx, node->name, sizeof(dns_name_t));
    }
    DESTROYLOCK(&node->lock);
    node->magic = 0;
    isc_mem_put(mctx, node, sizeof(dns_sdbnode_t));
    detach((dns_db_t **) (void *)&sdb);
}

static isc_result_t
findnode(dns_db_t *db, dns_name_t *name, isc_boolean_t create,
     dns_dbnode_t **nodep)
{
    dns_sdb_t *sdb = (dns_sdb_t *)db;
    dns_sdbnode_t *node = NULL;
    isc_result_t result;
    isc_buffer_t b;
    char namestr[DNS_NAME_MAXTEXT + 1];
    isc_boolean_t isorigin;
    dns_sdbimplementation_t *imp;

    REQUIRE(VALID_SDB(sdb));
    REQUIRE(create == ISC_FALSE);
    REQUIRE(nodep != NULL && *nodep == NULL);

    UNUSED(name);
    UNUSED(create);

    imp = sdb->implementation;

    isc_buffer_init(&b, namestr, sizeof(namestr));
    if ((imp->flags & DNS_SDBFLAG_RELATIVEOWNER) != 0) {
        dns_name_t relname;
        unsigned int labels;

        labels = dns_name_countlabels(name) -
             dns_name_countlabels(&db->origin);
        dns_name_init(&relname, NULL);
        dns_name_getlabelsequence(name, 0, labels, &relname);
        result = dns_name_totext(&relname, ISC_TRUE, &b);
        if (result != ISC_R_SUCCESS)
            return (result);
    } else {
        result = dns_name_totext(name, ISC_TRUE, &b);
        if (result != ISC_R_SUCCESS)
            return (result);
    }
    isc_buffer_putuint8(&b, 0);

    result = createnode(sdb, &node);
    if (result != ISC_R_SUCCESS)
        return (result);

    isorigin = dns_name_equal(name, &sdb->common.origin);

    MAYBE_LOCK(sdb);
    result = imp->methods->lookup(sdb->zone, namestr, sdb->dbdata, node);
    MAYBE_UNLOCK(sdb);
    if (result != ISC_R_SUCCESS &&
        !(result == ISC_R_NOTFOUND &&
          isorigin && imp->methods->authority != NULL))
    {
        destroynode(node);
        return (result);
    }

    if (isorigin && imp->methods->authority != NULL) {
        MAYBE_LOCK(sdb);
        result = imp->methods->authority(sdb->zone, sdb->dbdata, node);
        MAYBE_UNLOCK(sdb);
        if (result != ISC_R_SUCCESS) {
            destroynode(node);
            return (result);
        }
    }

    *nodep = node;
    return (ISC_R_SUCCESS);
}

static isc_result_t
find(dns_db_t *db, dns_name_t *name, dns_dbversion_t *version,
     dns_rdatatype_t type, unsigned int options, isc_stdtime_t now,
     dns_dbnode_t **nodep, dns_name_t *foundname,
     dns_rdataset_t *rdataset, dns_rdataset_t *sigrdataset)
{
    dns_sdb_t *sdb = (dns_sdb_t *)db;
    dns_dbnode_t *node = NULL;
    dns_fixedname_t fname;
    dns_rdataset_t xrdataset;
    dns_name_t *xname;
    unsigned int nlabels, olabels;
    isc_result_t result;
    unsigned int i;

    REQUIRE(VALID_SDB(sdb));
    REQUIRE(nodep == NULL || *nodep == NULL);
    REQUIRE(version == NULL || version == (void *) &dummy);

    UNUSED(options);
    UNUSED(sdb);

    if (!dns_name_issubdomain(name, &db->origin))
        return (DNS_R_NXDOMAIN);

    olabels = dns_name_countlabels(&db->origin);
    nlabels = dns_name_countlabels(name);

    dns_fixedname_init(&fname);
    xname = dns_fixedname_name(&fname);

    if (rdataset == NULL) {
        dns_rdataset_init(&xrdataset);
        rdataset = &xrdataset;
    }

    result = DNS_R_NXDOMAIN;

    for (i = olabels; i <= nlabels; i++) {
        /*
         * Unless this is an explicit lookup at the origin, don't
         * look at the origin.
         */
        if (i == olabels && i != nlabels)
            continue;

        /*
         * Look up the next label.
         */
        dns_name_getlabelsequence(name, nlabels - i, i, xname);
        result = findnode(db, xname, ISC_FALSE, &node);
        if (result != ISC_R_SUCCESS) {
            result = DNS_R_NXDOMAIN;
            continue;
        }

        /*
         * Look for a DNAME at the current label, unless this is
         * the qname.
         */
        if (i < nlabels) {
            result = findrdataset(db, node, version,
                          dns_rdatatype_dname,
                          0, now, rdataset, sigrdataset);
            if (result == ISC_R_SUCCESS) {
                result = DNS_R_DNAME;
                break;
            }
        }

        /*
         * Look for an NS at the current label, unless this is the
         * origin or glue is ok.
         */
        if (i != olabels && (options & DNS_DBFIND_GLUEOK) == 0) {
            result = findrdataset(db, node, version,
                          dns_rdatatype_ns,
                          0, now, rdataset, sigrdataset);
            if (result == ISC_R_SUCCESS) {
                if (i == nlabels && type == dns_rdatatype_any)
                {
                    result = DNS_R_ZONECUT;
                    dns_rdataset_disassociate(rdataset);
                    if (sigrdataset != NULL)
                        dns_rdataset_disassociate
                                (sigrdataset);
                } else
                    result = DNS_R_DELEGATION;
                break;
            }
        }

        /*
         * If the current name is not the qname, add another label
         * and try again.
         */
        if (i < nlabels) {
            destroynode(node);
            node = NULL;
            continue;
        }

        /*
         * If we're looking for ANY, we're done.
         */
        if (type == dns_rdatatype_any) {
            result = ISC_R_SUCCESS;
            break;
        }

        /*
         * Look for the qtype.
         */
        result = findrdataset(db, node, version, type,
                      0, now, rdataset, sigrdataset);
        if (result == ISC_R_SUCCESS)
            break;

        /*
         * Look for a CNAME
         */
        if (type != dns_rdatatype_cname) {
            result = findrdataset(db, node, version,
                          dns_rdatatype_cname,
                          0, now, rdataset, sigrdataset);
            if (result == ISC_R_SUCCESS) {
                result = DNS_R_CNAME;
                break;
            }
        }

        result = DNS_R_NXRRSET;
        break;
    }

    if (rdataset == &xrdataset && dns_rdataset_isassociated(rdataset))
        dns_rdataset_disassociate(rdataset);

    if (foundname != NULL) {
        isc_result_t xresult;

        xresult = dns_name_copy(xname, foundname, NULL);
        if (xresult != ISC_R_SUCCESS) {
            destroynode(node);
            if (dns_rdataset_isassociated(rdataset))
                dns_rdataset_disassociate(rdataset);
            return (DNS_R_BADDB);
        }
    }

    if (nodep != NULL)
        *nodep = node;
    else if (node != NULL)
        detachnode(db, &node);

    return (result);
}

static isc_result_t
findzonecut(dns_db_t *db, dns_name_t *name, unsigned int options,
        isc_stdtime_t now, dns_dbnode_t **nodep, dns_name_t *foundname,
        dns_rdataset_t *rdataset, dns_rdataset_t *sigrdataset)
{
    UNUSED(db);
    UNUSED(name);
    UNUSED(options);
    UNUSED(now);
    UNUSED(nodep);
    UNUSED(foundname);
    UNUSED(rdataset);
    UNUSED(sigrdataset);

    return (ISC_R_NOTIMPLEMENTED);
}

static void
attachnode(dns_db_t *db, dns_dbnode_t *source, dns_dbnode_t **targetp) {
    dns_sdb_t *sdb = (dns_sdb_t *)db;
    dns_sdbnode_t *node = (dns_sdbnode_t *)source;

    REQUIRE(VALID_SDB(sdb));

    UNUSED(sdb);

    LOCK(&node->lock);
    INSIST(node->references > 0);
    node->references++;
    INSIST(node->references != 0);      /* Catch overflow. */
    UNLOCK(&node->lock);

    *targetp = source;
}

static void
detachnode(dns_db_t *db, dns_dbnode_t **targetp) {
    dns_sdb_t *sdb = (dns_sdb_t *)db;
    dns_sdbnode_t *node;
    isc_boolean_t need_destroy = ISC_FALSE;

    REQUIRE(VALID_SDB(sdb));
    REQUIRE(targetp != NULL && *targetp != NULL);

    UNUSED(sdb);

    node = (dns_sdbnode_t *)(*targetp);

    LOCK(&node->lock);
    INSIST(node->references > 0);
    node->references--;
    if (node->references == 0)
        need_destroy = ISC_TRUE;
    UNLOCK(&node->lock);

    if (need_destroy)
        destroynode(node);

    *targetp = NULL;
}

static isc_result_t
expirenode(dns_db_t *db, dns_dbnode_t *node, isc_stdtime_t now) {
    UNUSED(db);
    UNUSED(node);
    UNUSED(now);
    INSIST(0);
    return (ISC_R_UNEXPECTED);
}

static void
printnode(dns_db_t *db, dns_dbnode_t *node, FILE *out) {
    UNUSED(db);
    UNUSED(node);
    UNUSED(out);
    return;
}

static isc_result_t
createiterator(dns_db_t *db, isc_boolean_t relative_names,
           dns_dbiterator_t **iteratorp)
{
    dns_sdb_t *sdb = (dns_sdb_t *)db;
    sdb_dbiterator_t *sdbiter;
    dns_sdbimplementation_t *imp = sdb->implementation;
    isc_result_t result;

    REQUIRE(VALID_SDB(sdb));

    if (imp->methods->allnodes == NULL)
        return (ISC_R_NOTIMPLEMENTED);

    sdbiter = isc_mem_get(sdb->common.mctx, sizeof(sdb_dbiterator_t));
    if (sdbiter == NULL)
        return (ISC_R_NOMEMORY);

    sdbiter->common.methods = &dbiterator_methods;
    sdbiter->common.db = NULL;
    dns_db_attach(db, &sdbiter->common.db);
    sdbiter->common.relative_names = relative_names;
    sdbiter->common.magic = DNS_DBITERATOR_MAGIC;
    ISC_LIST_INIT(sdbiter->nodelist);
    sdbiter->current = NULL;
    sdbiter->origin = NULL;

    MAYBE_LOCK(sdb);
    result = imp->methods->allnodes(sdb->zone, sdb->dbdata, sdbiter);
    MAYBE_UNLOCK(sdb);
    if (result != ISC_R_SUCCESS) {
        dbiterator_destroy((dns_dbiterator_t **) (void *)&sdbiter);
        return (result);
    }

    if (sdbiter->origin != NULL) {
        ISC_LIST_UNLINK(sdbiter->nodelist, sdbiter->origin, link);
        ISC_LIST_PREPEND(sdbiter->nodelist, sdbiter->origin, link);
    }

    *iteratorp = (dns_dbiterator_t *)sdbiter;

    return (ISC_R_SUCCESS);
}

static isc_result_t
findrdataset(dns_db_t *db, dns_dbnode_t *node, dns_dbversion_t *version,
         dns_rdatatype_t type, dns_rdatatype_t covers,
         isc_stdtime_t now, dns_rdataset_t *rdataset,
         dns_rdataset_t *sigrdataset)
{
    dns_rdatalist_t *list;
    dns_sdbnode_t *sdbnode = (dns_sdbnode_t *)node;

    REQUIRE(VALID_SDBNODE(node));

    UNUSED(db);
    UNUSED(version);
    UNUSED(covers);
    UNUSED(now);
    UNUSED(sigrdataset);

    if (type == dns_rdatatype_rrsig)
        return (ISC_R_NOTIMPLEMENTED);

    list = ISC_LIST_HEAD(sdbnode->lists);
    while (list != NULL) {
        if (list->type == type)
            break;
        list = ISC_LIST_NEXT(list, link);
    }
    if (list == NULL)
        return (ISC_R_NOTFOUND);

    list_tordataset(list, db, node, rdataset);

    return (ISC_R_SUCCESS);
}

static isc_result_t
allrdatasets(dns_db_t *db, dns_dbnode_t *node, dns_dbversion_t *version,
         isc_stdtime_t now, dns_rdatasetiter_t **iteratorp)
{
    sdb_rdatasetiter_t *iterator;

    REQUIRE(version == NULL || version == &dummy);

    UNUSED(version);
    UNUSED(now);

    iterator = isc_mem_get(db->mctx, sizeof(sdb_rdatasetiter_t));
    if (iterator == NULL)
        return (ISC_R_NOMEMORY);

    iterator->common.magic = DNS_RDATASETITER_MAGIC;
    iterator->common.methods = &rdatasetiter_methods;
    iterator->common.db = db;
    iterator->common.node = NULL;
    attachnode(db, node, &iterator->common.node);
    iterator->common.version = version;
    iterator->common.now = now;

    *iteratorp = (dns_rdatasetiter_t *)iterator;

    return (ISC_R_SUCCESS);
}

static isc_result_t
addrdataset(dns_db_t *db, dns_dbnode_t *node, dns_dbversion_t *version,
        isc_stdtime_t now, dns_rdataset_t *rdataset, unsigned int options,
        dns_rdataset_t *addedrdataset)
{
    UNUSED(db);
    UNUSED(node);
    UNUSED(version);
    UNUSED(now);
    UNUSED(rdataset);
    UNUSED(options);
    UNUSED(addedrdataset);

    return (ISC_R_NOTIMPLEMENTED);
}

static isc_result_t
subtractrdataset(dns_db_t *db, dns_dbnode_t *node, dns_dbversion_t *version,
         dns_rdataset_t *rdataset, unsigned int options,
         dns_rdataset_t *newrdataset)
{
    UNUSED(db);
    UNUSED(node);
    UNUSED(version);
    UNUSED(rdataset);
    UNUSED(options);
    UNUSED(newrdataset);

    return (ISC_R_NOTIMPLEMENTED);
}

static isc_result_t
deleterdataset(dns_db_t *db, dns_dbnode_t *node, dns_dbversion_t *version,
           dns_rdatatype_t type, dns_rdatatype_t covers)
{
    UNUSED(db);
    UNUSED(node);
    UNUSED(version);
    UNUSED(type);
    UNUSED(covers);

    return (ISC_R_NOTIMPLEMENTED);
}

static isc_boolean_t
issecure(dns_db_t *db) {
    UNUSED(db);

    return (ISC_FALSE);
}

static unsigned int
nodecount(dns_db_t *db) {
    UNUSED(db);

    return (0);
}

static isc_boolean_t
ispersistent(dns_db_t *db) {
    UNUSED(db);
    return (ISC_TRUE);
}

static void
overmem(dns_db_t *db, isc_boolean_t overmem) {
    UNUSED(db);
    UNUSED(overmem);
}

static void
settask(dns_db_t *db, isc_task_t *task) {
    UNUSED(db);
    UNUSED(task);
}


static dns_dbmethods_t sdb_methods = {
    attach,
    detach,
    beginload,
    endload,
    dump,
    currentversion,
    newversion,
    attachversion,
    closeversion,
    findnode,
    find,
    findzonecut,
    attachnode,
    detachnode,
    expirenode,
    printnode,
    createiterator,
    findrdataset,
    allrdatasets,
    addrdataset,
    subtractrdataset,
    deleterdataset,
    issecure,
    nodecount,
    ispersistent,
    overmem,
    settask
};

static isc_result_t
dns_sdb_create(isc_mem_t *mctx, dns_name_t *origin, dns_dbtype_t type,
           dns_rdataclass_t rdclass, unsigned int argc, char *argv[],
           void *driverarg, dns_db_t **dbp)
{
    dns_sdb_t *sdb;
    isc_result_t result;
    char zonestr[DNS_NAME_MAXTEXT + 1];
    isc_buffer_t b;
    dns_sdbimplementation_t *imp;

    REQUIRE(driverarg != NULL);

    imp = driverarg;

    if (type != dns_dbtype_zone)
        return (ISC_R_NOTIMPLEMENTED);

    sdb = isc_mem_get(mctx, sizeof(dns_sdb_t));
    if (sdb == NULL)
        return (ISC_R_NOMEMORY);
    memset(sdb, 0, sizeof(dns_sdb_t));

    dns_name_init(&sdb->common.origin, NULL);
    sdb->common.attributes = 0;
    sdb->common.methods = &sdb_methods;
    sdb->common.rdclass = rdclass;
    sdb->common.mctx = NULL;
    sdb->implementation = imp;

    isc_mem_attach(mctx, &sdb->common.mctx);

    result = isc_mutex_init(&sdb->lock);
    if (result != ISC_R_SUCCESS) {
        UNEXPECTED_ERROR(__FILE__, __LINE__,
                 "isc_mutex_init() failed: %s",
                 isc_result_totext(result));
        result = ISC_R_UNEXPECTED;
        goto cleanup_mctx;
    }

    result = dns_name_dupwithoffsets(origin, mctx, &sdb->common.origin);
    if (result != ISC_R_SUCCESS)
        goto cleanup_lock;

    isc_buffer_init(&b, zonestr, sizeof(zonestr));
    result = dns_name_totext(origin, ISC_TRUE, &b);
    if (result != ISC_R_SUCCESS)
        goto cleanup_origin;
    isc_buffer_putuint8(&b, 0);

    sdb->zone = isc_mem_strdup(mctx, zonestr);
    if (sdb->zone == NULL) {
        result = ISC_R_NOMEMORY;
        goto cleanup_origin;
    }

    sdb->dbdata = NULL;
    if (imp->methods->create != NULL) {
        MAYBE_LOCK(sdb);
        result = imp->methods->create(sdb->zone, argc, argv,
                          imp->driverdata, &sdb->dbdata);
        MAYBE_UNLOCK(sdb);
        if (result != ISC_R_SUCCESS)
            goto cleanup_zonestr;
    }

    sdb->references = 1;

    sdb->common.magic = DNS_DB_MAGIC;
    sdb->common.impmagic = SDB_MAGIC;

    *dbp = (dns_db_t *)sdb;

    return (ISC_R_SUCCESS);

 cleanup_zonestr:
    isc_mem_free(mctx, sdb->zone);
 cleanup_origin:
    dns_name_free(&sdb->common.origin, mctx);
 cleanup_lock:
    isc_mutex_destroy(&sdb->lock);
 cleanup_mctx:
    isc_mem_put(mctx, sdb, sizeof(dns_sdb_t));
    isc_mem_detach(&mctx);

    return (result);
}


/*
 * Rdataset Methods
 */

static void
disassociate(dns_rdataset_t *rdataset) {
    dns_dbnode_t *node = rdataset->private5;
    dns_sdbnode_t *sdbnode = (dns_sdbnode_t *) node;
    dns_db_t *db = (dns_db_t *) sdbnode->sdb;

    detachnode(db, &node);
    isc__rdatalist_disassociate(rdataset);
}

static void
rdataset_clone(dns_rdataset_t *source, dns_rdataset_t *target) {
    dns_dbnode_t *node = source->private5;
    dns_sdbnode_t *sdbnode = (dns_sdbnode_t *) node;
    dns_db_t *db = (dns_db_t *) sdbnode->sdb;
    dns_dbnode_t *tempdb = NULL;

    isc__rdatalist_clone(source, target);
    attachnode(db, node, &tempdb);
    source->private5 = tempdb;
}

static dns_rdatasetmethods_t methods = {
    disassociate,
    isc__rdatalist_first,
    isc__rdatalist_next,
    isc__rdatalist_current,
    rdataset_clone,
    isc__rdatalist_count,
    isc__rdatalist_addnoqname,
    isc__rdatalist_getnoqname
};

static void
list_tordataset(dns_rdatalist_t *rdatalist,
        dns_db_t *db, dns_dbnode_t *node,
        dns_rdataset_t *rdataset)
{
    /*
     * The sdb rdataset is an rdatalist with some additions.
     *  - private1 & private2 are used by the rdatalist.
     *  - private3 & private 4 are unused.
     *  - private5 is the node.
     */

    /* This should never fail. */
    RUNTIME_CHECK(dns_rdatalist_tordataset(rdatalist, rdataset) ==
              ISC_R_SUCCESS);

    rdataset->methods = &methods;
    dns_db_attachnode(db, node, &rdataset->private5);
}

/*
 * Database Iterator Methods
 */
static void
dbiterator_destroy(dns_dbiterator_t **iteratorp) {
    sdb_dbiterator_t *sdbiter = (sdb_dbiterator_t *)(*iteratorp);
    dns_sdb_t *sdb = (dns_sdb_t *)sdbiter->common.db;

    while (!ISC_LIST_EMPTY(sdbiter->nodelist)) {
        dns_sdbnode_t *node;
        node = ISC_LIST_HEAD(sdbiter->nodelist);
        ISC_LIST_UNLINK(sdbiter->nodelist, node, link);
        destroynode(node);
    }

    dns_db_detach(&sdbiter->common.db);
    isc_mem_put(sdb->common.mctx, sdbiter, sizeof(sdb_dbiterator_t));

    *iteratorp = NULL;
}

static isc_result_t
dbiterator_first(dns_dbiterator_t *iterator) {
    sdb_dbiterator_t *sdbiter = (sdb_dbiterator_t *)iterator;

    sdbiter->current = ISC_LIST_HEAD(sdbiter->nodelist);
    if (sdbiter->current == NULL)
        return (ISC_R_NOMORE);
    else
        return (ISC_R_SUCCESS);
}

static isc_result_t
dbiterator_last(dns_dbiterator_t *iterator) {
    sdb_dbiterator_t *sdbiter = (sdb_dbiterator_t *)iterator;

    sdbiter->current = ISC_LIST_TAIL(sdbiter->nodelist);
    if (sdbiter->current == NULL)
        return (ISC_R_NOMORE);
    else
        return (ISC_R_SUCCESS);
}

static isc_result_t
dbiterator_seek(dns_dbiterator_t *iterator, dns_name_t *name) {
    sdb_dbiterator_t *sdbiter = (sdb_dbiterator_t *)iterator;

    sdbiter->current = ISC_LIST_HEAD(sdbiter->nodelist);
    while (sdbiter->current != NULL)
        if (dns_name_equal(sdbiter->current->name, name))
            return (ISC_R_SUCCESS);
    return (ISC_R_NOTFOUND);
}

static isc_result_t
dbiterator_prev(dns_dbiterator_t *iterator) {
    sdb_dbiterator_t *sdbiter = (sdb_dbiterator_t *)iterator;

    sdbiter->current = ISC_LIST_PREV(sdbiter->current, link);
    if (sdbiter->current == NULL)
        return (ISC_R_NOMORE);
    else
        return (ISC_R_SUCCESS);
}

static isc_result_t
dbiterator_next(dns_dbiterator_t *iterator) {
    sdb_dbiterator_t *sdbiter = (sdb_dbiterator_t *)iterator;

    sdbiter->current = ISC_LIST_NEXT(sdbiter->current, link);
    if (sdbiter->current == NULL)
        return (ISC_R_NOMORE);
    else
        return (ISC_R_SUCCESS);
}

static isc_result_t
dbiterator_current(dns_dbiterator_t *iterator, dns_dbnode_t **nodep,
           dns_name_t *name)
{
    sdb_dbiterator_t *sdbiter = (sdb_dbiterator_t *)iterator;

    attachnode(iterator->db, sdbiter->current, nodep);
    if (name != NULL)
        return (dns_name_copy(sdbiter->current->name, name, NULL));
    return (ISC_R_SUCCESS);
}

static isc_result_t
dbiterator_pause(dns_dbiterator_t *iterator) {
    UNUSED(iterator);
    return (ISC_R_SUCCESS);
}

static isc_result_t
dbiterator_origin(dns_dbiterator_t *iterator, dns_name_t *name) {
    UNUSED(iterator);
    return (dns_name_copy(dns_rootname, name, NULL));
}

/*
 * Rdataset Iterator Methods
 */

static void
rdatasetiter_destroy(dns_rdatasetiter_t **iteratorp) {
    sdb_rdatasetiter_t *sdbiterator = (sdb_rdatasetiter_t *)(*iteratorp);
    detachnode(sdbiterator->common.db, &sdbiterator->common.node);
    isc_mem_put(sdbiterator->common.db->mctx, sdbiterator,
            sizeof(sdb_rdatasetiter_t));
    *iteratorp = NULL;
}

static isc_result_t
rdatasetiter_first(dns_rdatasetiter_t *iterator) {
    sdb_rdatasetiter_t *sdbiterator = (sdb_rdatasetiter_t *)iterator;
    dns_sdbnode_t *sdbnode = (dns_sdbnode_t *)iterator->node;

    if (ISC_LIST_EMPTY(sdbnode->lists))
        return (ISC_R_NOMORE);
    sdbiterator->current = ISC_LIST_HEAD(sdbnode->lists);
    return (ISC_R_SUCCESS);
}

static isc_result_t
rdatasetiter_next(dns_rdatasetiter_t *iterator) {
    sdb_rdatasetiter_t *sdbiterator = (sdb_rdatasetiter_t *)iterator;

    sdbiterator->current = ISC_LIST_NEXT(sdbiterator->current, link);
    if (sdbiterator->current == NULL)
        return (ISC_R_NOMORE);
    else
        return (ISC_R_SUCCESS);
}

static void
rdatasetiter_current(dns_rdatasetiter_t *iterator, dns_rdataset_t *rdataset) {
    sdb_rdatasetiter_t *sdbiterator = (sdb_rdatasetiter_t *)iterator;

    list_tordataset(sdbiterator->current, iterator->db, iterator->node,
            rdataset);
}