ISC BIND version 9.2.2rc1

1 files changed, 787 insertions, 0 deletions

diff --git a/usr.sbin/bind/lib/dns/db.c b/usr.sbin/bind/lib/dns/db.c
new file mode 100644
index 00000000000..357db1dd0a7
--- /dev/null
+++ b/usr.sbin/bind/lib/dns/db.c
@@ -0,0 +1,787 @@
+/*
+ * Copyright (C) 1999-2001  Internet Software Consortium.
+ *
+ * Permission to use, copy, modify, and distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND INTERNET SOFTWARE CONSORTIUM
+ * DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL
+ * INTERNET SOFTWARE CONSORTIUM BE LIABLE FOR ANY SPECIAL, DIRECT,
+ * INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING
+ * FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT,
+ * NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION
+ * WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ */
+
+/* $ISC: db.c,v 1.69.2.1 2001/09/04 23:09:33 gson Exp $ */
+
+/***
+ *** Imports
+ ***/
+
+#include <config.h>
+
+#include <isc/buffer.h>
+#include <isc/mem.h>
+#include <isc/once.h>
+#include <isc/rwlock.h>
+#include <isc/string.h>
+#include <isc/util.h>
+
+#include <dns/callbacks.h>
+#include <dns/db.h>
+#include <dns/log.h>
+#include <dns/master.h>
+#include <dns/rdata.h>
+#include <dns/rdataset.h>
+#include <dns/result.h>
+
+/***
+ *** Private Types
+ ***/
+
+struct dns_dbimplementation {
+	const char *				name;
+	dns_dbcreatefunc_t			create;
+	isc_mem_t *				mctx;
+	void *					driverarg;
+	ISC_LINK(dns_dbimplementation_t)	link;
+};
+
+/***
+ *** Supported DB Implementations Registry
+ ***/
+
+/*
+ * Built in database implementations are registered here.
+ */
+
+#include "rbtdb.h"
+#include "rbtdb64.h"
+
+static ISC_LIST(dns_dbimplementation_t) implementations;
+static isc_rwlock_t implock;
+static isc_once_t once = ISC_ONCE_INIT;
+
+static dns_dbimplementation_t rbtimp;
+static dns_dbimplementation_t rbt64imp;
+
+static void
+initialize(void) {
+	RUNTIME_CHECK(isc_rwlock_init(&implock, 0, 0) == ISC_R_SUCCESS);
+
+	rbtimp.name = "rbt";
+	rbtimp.create = dns_rbtdb_create;
+	rbtimp.mctx = NULL;
+	rbtimp.driverarg = NULL;
+	ISC_LINK_INIT(&rbtimp, link);
+
+	rbt64imp.name = "rbt64";
+	rbt64imp.create = dns_rbtdb64_create;
+	rbt64imp.mctx = NULL;
+	rbt64imp.driverarg = NULL;
+	ISC_LINK_INIT(&rbt64imp, link);
+
+	ISC_LIST_INIT(implementations);
+	ISC_LIST_APPEND(implementations, &rbtimp, link);
+	ISC_LIST_APPEND(implementations, &rbt64imp, link);
+}
+
+static inline dns_dbimplementation_t *
+impfind(const char *name) {
+	dns_dbimplementation_t *imp;
+
+	for (imp = ISC_LIST_HEAD(implementations); 
+	     imp != NULL;
+	     imp = ISC_LIST_NEXT(imp, link))
+		if (strcasecmp(name, imp->name) == 0)
+			return (imp);
+	return (NULL);
+}
+
+
+/***
+ *** Basic DB Methods
+ ***/
+
+isc_result_t
+dns_db_create(isc_mem_t *mctx, const char *db_type, dns_name_t *origin,
+	      dns_dbtype_t type, dns_rdataclass_t rdclass,
+	      unsigned int argc, char *argv[], dns_db_t **dbp)
+{
+	dns_dbimplementation_t *impinfo;
+
+	RUNTIME_CHECK(isc_once_do(&once, initialize) == ISC_R_SUCCESS);
+
+	/*
+	 * Create a new database using implementation 'db_type'.
+	 */
+
+	REQUIRE(dbp != NULL && *dbp == NULL);
+	REQUIRE(dns_name_isabsolute(origin));
+
+	RWLOCK(&implock, isc_rwlocktype_read);
+	impinfo = impfind(db_type);
+	if (impinfo != NULL) {
+		isc_result_t result;
+		result = ((impinfo->create)(mctx, origin, type,
+					    rdclass, argc, argv,
+					    impinfo->driverarg, dbp));
+		RWUNLOCK(&implock, isc_rwlocktype_read);
+		return (result);
+	}
+
+	RWUNLOCK(&implock, isc_rwlocktype_read);
+
+	isc_log_write(dns_lctx, DNS_LOGCATEGORY_DATABASE,
+		      DNS_LOGMODULE_DB, ISC_LOG_ERROR,
+		      "unsupported database type '%s'", db_type);
+
+	return (ISC_R_NOTFOUND);
+}
+
+void
+dns_db_attach(dns_db_t *source, dns_db_t **targetp) {
+
+	/*
+	 * Attach *targetp to source.
+	 */
+
+	REQUIRE(DNS_DB_VALID(source));
+	REQUIRE(targetp != NULL && *targetp == NULL);
+
+	(source->methods->attach)(source, targetp);
+
+	ENSURE(*targetp == source);
+}
+
+void
+dns_db_detach(dns_db_t **dbp) {
+
+	/*
+	 * Detach *dbp from its database.
+	 */
+
+	REQUIRE(dbp != NULL);
+	REQUIRE(DNS_DB_VALID(*dbp));
+
+	((*dbp)->methods->detach)(dbp);
+
+	ENSURE(*dbp == NULL);
+}
+
+isc_result_t
+dns_db_ondestroy(dns_db_t *db, isc_task_t *task, isc_event_t **eventp)
+{
+	REQUIRE(DNS_DB_VALID(db));
+
+	return (isc_ondestroy_register(&db->ondest, task, eventp));
+}
+
+
+isc_boolean_t
+dns_db_iscache(dns_db_t *db) {
+
+	/*
+	 * Does 'db' have cache semantics?
+	 */
+
+	REQUIRE(DNS_DB_VALID(db));
+
+	if ((db->attributes & DNS_DBATTR_CACHE) != 0)
+		return (ISC_TRUE);
+
+	return (ISC_FALSE);
+}
+
+isc_boolean_t
+dns_db_iszone(dns_db_t *db) {
+
+	/*
+	 * Does 'db' have zone semantics?
+	 */
+
+	REQUIRE(DNS_DB_VALID(db));
+
+	if ((db->attributes & (DNS_DBATTR_CACHE|DNS_DBATTR_STUB)) == 0)
+		return (ISC_TRUE);
+
+	return (ISC_FALSE);
+}
+
+isc_boolean_t
+dns_db_isstub(dns_db_t *db) {
+
+	/*
+	 * Does 'db' have stub semantics?
+	 */
+
+	REQUIRE(DNS_DB_VALID(db));
+
+	if ((db->attributes & DNS_DBATTR_STUB) != 0)
+		return (ISC_TRUE);
+
+	return (ISC_FALSE);
+}
+
+isc_boolean_t
+dns_db_issecure(dns_db_t *db) {
+
+	/*
+	 * Is 'db' secure?
+	 */
+
+	REQUIRE(DNS_DB_VALID(db));
+	REQUIRE((db->attributes & DNS_DBATTR_CACHE) == 0);
+
+	return ((db->methods->issecure)(db));
+}
+
+isc_boolean_t
+dns_db_ispersistent(dns_db_t *db) {
+
+	/*
+	 * Is 'db' persistent?
+	 */
+
+	REQUIRE(DNS_DB_VALID(db));
+
+	return ((db->methods->ispersistent)(db));
+}
+
+dns_name_t *
+dns_db_origin(dns_db_t *db) {
+	/*
+	 * The origin of the database.
+	 */
+
+	REQUIRE(DNS_DB_VALID(db));
+
+	return (&db->origin);
+}
+
+dns_rdataclass_t
+dns_db_class(dns_db_t *db) {
+	/*
+	 * The class of the database.
+	 */
+
+	REQUIRE(DNS_DB_VALID(db));
+
+	return (db->rdclass);
+}
+
+isc_result_t
+dns_db_beginload(dns_db_t *db, dns_addrdatasetfunc_t *addp,
+		 dns_dbload_t **dbloadp) {
+	/*
+	 * Begin loading 'db'.
+	 */
+
+	REQUIRE(DNS_DB_VALID(db));
+	REQUIRE(addp != NULL && *addp == NULL);
+	REQUIRE(dbloadp != NULL && *dbloadp == NULL);
+
+	return ((db->methods->beginload)(db, addp, dbloadp));
+}
+
+isc_result_t
+dns_db_endload(dns_db_t *db, dns_dbload_t **dbloadp) {
+	/*
+	 * Finish loading 'db'.
+	 */
+
+	REQUIRE(DNS_DB_VALID(db));
+	REQUIRE(dbloadp != NULL && *dbloadp != NULL);
+
+	return ((db->methods->endload)(db, dbloadp));
+}
+
+isc_result_t
+dns_db_load(dns_db_t *db, const char *filename) {
+	isc_result_t result, eresult;
+	dns_rdatacallbacks_t callbacks;
+	unsigned int options = 0;
+
+	/*
+	 * Load master file 'filename' into 'db'.
+	 */
+
+	REQUIRE(DNS_DB_VALID(db));
+
+	if ((db->attributes & DNS_DBATTR_CACHE) != 0)
+		options |= DNS_MASTER_AGETTL;
+
+	dns_rdatacallbacks_init(&callbacks);
+
+	result = dns_db_beginload(db, &callbacks.add, &callbacks.add_private);
+	if (result != ISC_R_SUCCESS)
+		return (result);
+	result = dns_master_loadfile(filename, &db->origin, &db->origin,
+				     db->rdclass, options,
+				     &callbacks, db->mctx);
+	eresult = dns_db_endload(db, &callbacks.add_private);
+	/*
+	 * We always call dns_db_endload(), but we only want to return its
+	 * result if dns_master_loadfile() succeeded.  If dns_master_loadfile()
+	 * failed, we want to return the result code it gave us.
+	 */
+	if (eresult != ISC_R_SUCCESS &&
+	    (result == ISC_R_SUCCESS || result == DNS_R_SEENINCLUDE))
+		result = eresult;
+
+	return (result);
+}
+
+isc_result_t
+dns_db_dump(dns_db_t *db, dns_dbversion_t *version, const char *filename) {
+	/*
+	 * Dump 'db' into master file 'filename'.
+	 */
+
+	REQUIRE(DNS_DB_VALID(db));
+
+	return ((db->methods->dump)(db, version, filename));
+}
+
+/***
+ *** Version Methods
+ ***/
+
+void
+dns_db_currentversion(dns_db_t *db, dns_dbversion_t **versionp) {
+
+	/*
+	 * Open the current version for reading.
+	 */
+
+	REQUIRE(DNS_DB_VALID(db));
+	REQUIRE((db->attributes & DNS_DBATTR_CACHE) == 0);
+	REQUIRE(versionp != NULL && *versionp == NULL);
+
+	(db->methods->currentversion)(db, versionp);
+}
+
+isc_result_t
+dns_db_newversion(dns_db_t *db, dns_dbversion_t **versionp) {
+
+	/*
+	 * Open a new version for reading and writing.
+	 */
+
+	REQUIRE(DNS_DB_VALID(db));
+	REQUIRE((db->attributes & DNS_DBATTR_CACHE) == 0);
+	REQUIRE(versionp != NULL && *versionp == NULL);
+
+	return ((db->methods->newversion)(db, versionp));
+}
+
+void
+dns_db_attachversion(dns_db_t *db, dns_dbversion_t *source,
+		     dns_dbversion_t **targetp)
+{
+	/*
+	 * Attach '*targetp' to 'source'.
+	 */
+
+	REQUIRE(DNS_DB_VALID(db));
+	REQUIRE((db->attributes & DNS_DBATTR_CACHE) == 0);
+	REQUIRE(source != NULL);
+	REQUIRE(targetp != NULL && *targetp == NULL);
+
+	(db->methods->attachversion)(db, source, targetp);
+
+	ENSURE(*targetp != NULL);
+}
+
+void
+dns_db_closeversion(dns_db_t *db, dns_dbversion_t **versionp,
+		    isc_boolean_t commit)
+{
+
+	/*
+	 * Close version '*versionp'.
+	 */
+
+	REQUIRE(DNS_DB_VALID(db));
+	REQUIRE((db->attributes & DNS_DBATTR_CACHE) == 0);
+	REQUIRE(versionp != NULL && *versionp != NULL);
+
+	(db->methods->closeversion)(db, versionp, commit);
+
+	ENSURE(*versionp == NULL);
+}
+
+/***
+ *** Node Methods
+ ***/
+
+isc_result_t
+dns_db_findnode(dns_db_t *db, dns_name_t *name,
+		isc_boolean_t create, dns_dbnode_t **nodep)
+{
+
+	/*
+	 * Find the node with name 'name'.
+	 */
+
+	REQUIRE(DNS_DB_VALID(db));
+	REQUIRE(dns_name_issubdomain(name, &db->origin));
+	REQUIRE(nodep != NULL && *nodep == NULL);
+
+	return ((db->methods->findnode)(db, name, create, nodep));
+}
+
+isc_result_t
+dns_db_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)
+{
+
+	/*
+	 * Find the best match for 'name' and 'type' in version 'version'
+	 * of 'db'.
+	 */
+
+	REQUIRE(DNS_DB_VALID(db));
+	REQUIRE(type != dns_rdatatype_sig);
+	REQUIRE(nodep == NULL || (nodep != NULL && *nodep == NULL));
+	REQUIRE(dns_name_hasbuffer(foundname));
+	REQUIRE(rdataset == NULL ||
+		(DNS_RDATASET_VALID(rdataset) &&
+		 ! dns_rdataset_isassociated(rdataset)));
+	REQUIRE(sigrdataset == NULL ||
+		(DNS_RDATASET_VALID(sigrdataset) &&
+		 ! dns_rdataset_isassociated(sigrdataset)));
+
+	return ((db->methods->find)(db, name, version, type, options, now,
+				    nodep, foundname, rdataset, sigrdataset));
+}
+
+isc_result_t
+dns_db_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)
+{
+	/*
+	 * Find the deepest known zonecut which encloses 'name' in 'db'.
+	 */
+
+	REQUIRE(DNS_DB_VALID(db));
+	REQUIRE((db->attributes & DNS_DBATTR_CACHE) != 0);
+	REQUIRE(nodep == NULL || (nodep != NULL && *nodep == NULL));
+	REQUIRE(dns_name_hasbuffer(foundname));
+	REQUIRE(sigrdataset == NULL ||
+		(DNS_RDATASET_VALID(sigrdataset) &&
+		 ! dns_rdataset_isassociated(sigrdataset)));
+
+	return ((db->methods->findzonecut)(db, name, options, now, nodep,
+					   foundname, rdataset, sigrdataset));
+}
+
+void
+dns_db_attachnode(dns_db_t *db, dns_dbnode_t *source, dns_dbnode_t **targetp) {
+
+	/*
+	 * Attach *targetp to source.
+	 */
+
+	REQUIRE(DNS_DB_VALID(db));
+	REQUIRE(source != NULL);
+	REQUIRE(targetp != NULL && *targetp == NULL);
+
+	(db->methods->attachnode)(db, source, targetp);
+}
+
+void
+dns_db_detachnode(dns_db_t *db, dns_dbnode_t **nodep) {
+
+	/*
+	 * Detach *nodep from its node.
+	 */
+
+	REQUIRE(DNS_DB_VALID(db));
+	REQUIRE(nodep != NULL && *nodep != NULL);
+
+	(db->methods->detachnode)(db, nodep);
+
+	ENSURE(*nodep == NULL);
+}
+
+isc_result_t
+dns_db_expirenode(dns_db_t *db, dns_dbnode_t *node, isc_stdtime_t now) {
+
+	/*
+	 * Mark as stale all records at 'node' which expire at or before 'now'.
+	 */
+
+	REQUIRE(DNS_DB_VALID(db));
+	REQUIRE((db->attributes & DNS_DBATTR_CACHE) != 0);
+	REQUIRE(node != NULL);
+
+	return ((db->methods->expirenode)(db, node, now));
+}
+
+void
+dns_db_printnode(dns_db_t *db, dns_dbnode_t *node, FILE *out) {
+	/*
+	 * Print a textual representation of the contents of the node to
+	 * 'out'.
+	 */
+
+	REQUIRE(DNS_DB_VALID(db));
+	REQUIRE(node != NULL);
+
+	(db->methods->printnode)(db, node, out);
+}
+
+/***
+ *** DB Iterator Creation
+ ***/
+
+isc_result_t
+dns_db_createiterator(dns_db_t *db, isc_boolean_t relative_names,
+		      dns_dbiterator_t **iteratorp)
+{
+	/*
+	 * Create an iterator for version 'version' of 'db'.
+	 */
+
+	REQUIRE(DNS_DB_VALID(db));
+	REQUIRE(iteratorp != NULL && *iteratorp == NULL);
+
+	return (db->methods->createiterator(db, relative_names, iteratorp));
+}
+
+/***
+ *** Rdataset Methods
+ ***/
+
+isc_result_t
+dns_db_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)
+{
+	/*
+	 * Search for an rdataset of type 'type' at 'node' that are in version
+	 * 'version' of 'db'.  If found, make 'rdataset' refer to it.
+	 */
+
+	REQUIRE(DNS_DB_VALID(db));
+	REQUIRE(node != NULL);
+	REQUIRE(DNS_RDATASET_VALID(rdataset));
+	REQUIRE(! dns_rdataset_isassociated(rdataset));
+	REQUIRE(covers == 0 || type == dns_rdatatype_sig);
+	REQUIRE(type != dns_rdatatype_any);
+	REQUIRE(sigrdataset == NULL ||
+		(DNS_RDATASET_VALID(sigrdataset) &&
+		 ! dns_rdataset_isassociated(sigrdataset)));
+
+	return ((db->methods->findrdataset)(db, node, version, type, covers,
+					    now, rdataset, sigrdataset));
+}
+
+isc_result_t
+dns_db_allrdatasets(dns_db_t *db, dns_dbnode_t *node, dns_dbversion_t *version,
+		    isc_stdtime_t now, dns_rdatasetiter_t **iteratorp)
+{
+	/*
+	 * Make '*iteratorp' an rdataset iteratator for all rdatasets at
+	 * 'node' in version 'version' of 'db'.
+	 */
+
+	REQUIRE(DNS_DB_VALID(db));
+	REQUIRE(iteratorp != NULL && *iteratorp == NULL);
+
+	return ((db->methods->allrdatasets)(db, node, version, now,
+					    iteratorp));
+}
+
+isc_result_t
+dns_db_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)
+{
+	/*
+	 * Add 'rdataset' to 'node' in version 'version' of 'db'.
+	 */
+
+	REQUIRE(DNS_DB_VALID(db));
+	REQUIRE(node != NULL);
+	REQUIRE(((db->attributes & DNS_DBATTR_CACHE) == 0 && version != NULL)||
+		((db->attributes & DNS_DBATTR_CACHE) != 0 &&
+		 version == NULL && (options & DNS_DBADD_MERGE) == 0));
+	REQUIRE((options & DNS_DBADD_EXACT) == 0 ||
+		(options & DNS_DBADD_MERGE) != 0);
+	REQUIRE(DNS_RDATASET_VALID(rdataset));
+	REQUIRE(dns_rdataset_isassociated(rdataset));
+	REQUIRE(rdataset->rdclass == db->rdclass);
+	REQUIRE(addedrdataset == NULL ||
+		(DNS_RDATASET_VALID(addedrdataset) &&
+		 ! dns_rdataset_isassociated(addedrdataset)));
+
+	return ((db->methods->addrdataset)(db, node, version, now, rdataset,
+					   options, addedrdataset));
+}
+
+isc_result_t
+dns_db_subtractrdataset(dns_db_t *db, dns_dbnode_t *node,
+			dns_dbversion_t *version, dns_rdataset_t *rdataset,
+			unsigned int options, dns_rdataset_t *newrdataset)
+{
+	/*
+	 * Remove any rdata in 'rdataset' from 'node' in version 'version' of
+	 * 'db'.
+	 */
+
+	REQUIRE(DNS_DB_VALID(db));
+	REQUIRE(node != NULL);
+	REQUIRE((db->attributes & DNS_DBATTR_CACHE) == 0 && version != NULL);
+	REQUIRE(DNS_RDATASET_VALID(rdataset));
+	REQUIRE(dns_rdataset_isassociated(rdataset));
+	REQUIRE(rdataset->rdclass == db->rdclass);
+	REQUIRE(newrdataset == NULL ||
+		(DNS_RDATASET_VALID(newrdataset) &&
+		 ! dns_rdataset_isassociated(newrdataset)));
+
+	return ((db->methods->subtractrdataset)(db, node, version, rdataset,
+						options, newrdataset));
+}
+
+isc_result_t
+dns_db_deleterdataset(dns_db_t *db, dns_dbnode_t *node,
+		      dns_dbversion_t *version, dns_rdatatype_t type,
+		      dns_rdatatype_t covers)
+{
+	/*
+	 * Make it so that no rdataset of type 'type' exists at 'node' in
+	 * version version 'version' of 'db'.
+	 */
+
+	REQUIRE(DNS_DB_VALID(db));
+	REQUIRE(node != NULL);
+	REQUIRE(((db->attributes & DNS_DBATTR_CACHE) == 0 && version != NULL)||
+		((db->attributes & DNS_DBATTR_CACHE) != 0 && version == NULL));
+
+	return ((db->methods->deleterdataset)(db, node, version,
+					      type, covers));
+}
+
+void 
+dns_db_overmem(dns_db_t *db, isc_boolean_t overmem) {
+
+	REQUIRE(DNS_DB_VALID(db));
+
+	(db->methods->overmem)(db, overmem);
+}
+
+isc_result_t
+dns_db_getsoaserial(dns_db_t *db, dns_dbversion_t *ver, isc_uint32_t *serialp)
+{
+	isc_result_t result;
+	dns_dbnode_t *node = NULL;
+	dns_rdataset_t rdataset;
+	dns_rdata_t rdata = DNS_RDATA_INIT;
+	isc_buffer_t buffer;
+
+	REQUIRE(dns_db_iszone(db) || dns_db_isstub(db));
+
+	result = dns_db_findnode(db, dns_db_origin(db), ISC_FALSE, &node);
+	if (result != ISC_R_SUCCESS)
+		return (result);
+
+	dns_rdataset_init(&rdataset);
+	result = dns_db_findrdataset(db, node, ver, dns_rdatatype_soa, 0,
+				     (isc_stdtime_t)0, &rdataset, NULL);
+ 	if (result != ISC_R_SUCCESS)
+		goto freenode;
+
+	result = dns_rdataset_first(&rdataset);
+ 	if (result != ISC_R_SUCCESS)
+		goto freerdataset;
+	dns_rdataset_current(&rdataset, &rdata);
+	result = dns_rdataset_next(&rdataset);
+	INSIST(result == ISC_R_NOMORE);
+
+	INSIST(rdata.length > 20);
+	isc_buffer_init(&buffer, rdata.data, rdata.length);
+	isc_buffer_add(&buffer, rdata.length);
+	isc_buffer_forward(&buffer, rdata.length - 20);
+	*serialp = isc_buffer_getuint32(&buffer);
+
+	result = ISC_R_SUCCESS;
+
+ freerdataset:
+	dns_rdataset_disassociate(&rdataset);
+
+ freenode:
+	dns_db_detachnode(db, &node);
+	return (result);
+}
+
+unsigned int
+dns_db_nodecount(dns_db_t *db) {
+	REQUIRE(DNS_DB_VALID(db));
+
+	return ((db->methods->nodecount)(db));
+}
+
+isc_result_t
+dns_db_register(const char *name, dns_dbcreatefunc_t create, void *driverarg,
+		isc_mem_t *mctx, dns_dbimplementation_t **dbimp)
+{
+	dns_dbimplementation_t *imp;
+
+	REQUIRE(name != NULL);
+	REQUIRE(dbimp != NULL && *dbimp == NULL);
+
+	RUNTIME_CHECK(isc_once_do(&once, initialize) == ISC_R_SUCCESS);
+
+	RWLOCK(&implock, isc_rwlocktype_write);
+	imp = impfind(name);
+	if (imp != NULL) {
+		RWUNLOCK(&implock, isc_rwlocktype_write);
+		return (ISC_R_EXISTS);
+	}
+	
+	imp = isc_mem_get(mctx, sizeof(dns_dbimplementation_t));
+	if (imp == NULL) {
+		RWUNLOCK(&implock, isc_rwlocktype_write);
+		return (ISC_R_NOMEMORY);
+	}
+	imp->name = name;
+	imp->create = create;
+	imp->mctx = NULL;
+	imp->driverarg = driverarg;
+	isc_mem_attach(mctx, &imp->mctx);
+	ISC_LINK_INIT(imp, link);
+	ISC_LIST_APPEND(implementations, imp, link);
+	RWUNLOCK(&implock, isc_rwlocktype_write);
+
+	*dbimp = imp;
+
+	return (ISC_R_SUCCESS);
+}
+
+void
+dns_db_unregister(dns_dbimplementation_t **dbimp) {
+	dns_dbimplementation_t *imp;
+	isc_mem_t *mctx;
+
+	REQUIRE(dbimp != NULL && *dbimp != NULL);
+
+	RUNTIME_CHECK(isc_once_do(&once, initialize) == ISC_R_SUCCESS);
+
+	imp = *dbimp;
+	RWLOCK(&implock, isc_rwlocktype_write);
+	ISC_LIST_UNLINK(implementations, imp, link);
+	mctx = imp->mctx;
+	isc_mem_put(mctx, imp, sizeof(dns_dbimplementation_t));
+	isc_mem_detach(&mctx);
+	RWUNLOCK(&implock, isc_rwlocktype_write);
+}