Adding upstream version 1:9.18.19.upstream/1%9.18.19

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 10241 insertions, 0 deletions

diff --git a/lib/dns/rbtdb.c b/lib/dns/rbtdb.c
new file mode 100644
index 0000000..5d36466
--- /dev/null
+++ b/lib/dns/rbtdb.c
@@ -0,0 +1,10241 @@
+/*
+ * Copyright (C) Internet Systems Consortium, Inc. ("ISC")
+ *
+ * SPDX-License-Identifier: MPL-2.0
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, you can obtain one at https://mozilla.org/MPL/2.0/.
+ *
+ * See the COPYRIGHT file distributed with this work for additional
+ * information regarding copyright ownership.
+ */
+
+/*! \file */
+
+#include <ctype.h>
+#include <inttypes.h>
+#include <stdbool.h>
+#include <sys/mman.h>
+
+#include <isc/atomic.h>
+#include <isc/crc64.h>
+#include <isc/event.h>
+#include <isc/file.h>
+#include <isc/hash.h>
+#include <isc/heap.h>
+#include <isc/hex.h>
+#include <isc/mem.h>
+#include <isc/mutex.h>
+#include <isc/once.h>
+#include <isc/print.h>
+#include <isc/random.h>
+#include <isc/refcount.h>
+#include <isc/result.h>
+#include <isc/rwlock.h>
+#include <isc/serial.h>
+#include <isc/stdio.h>
+#include <isc/string.h>
+#include <isc/task.h>
+#include <isc/time.h>
+#include <isc/util.h>
+
+#include <dns/callbacks.h>
+#include <dns/db.h>
+#include <dns/dbiterator.h>
+#include <dns/events.h>
+#include <dns/fixedname.h>
+#include <dns/log.h>
+#include <dns/masterdump.h>
+#include <dns/nsec.h>
+#include <dns/nsec3.h>
+#include <dns/rbt.h>
+#include <dns/rdata.h>
+#include <dns/rdataset.h>
+#include <dns/rdatasetiter.h>
+#include <dns/rdataslab.h>
+#include <dns/rdatastruct.h>
+#include <dns/stats.h>
+#include <dns/time.h>
+#include <dns/view.h>
+#include <dns/zone.h>
+#include <dns/zonekey.h>
+
+#include "rbtdb.h"
+
+#define RBTDB_MAGIC ISC_MAGIC('R', 'B', 'D', '4')
+
+#define CHECK(op)                            \
+	do {                                 \
+		result = (op);               \
+		if (result != ISC_R_SUCCESS) \
+			goto failure;        \
+	} while (0)
+
+/*%
+ * Note that "impmagic" is not the first four bytes of the struct, so
+ * ISC_MAGIC_VALID cannot be used.
+ */
+#define VALID_RBTDB(rbtdb) \
+	((rbtdb) != NULL && (rbtdb)->common.impmagic == RBTDB_MAGIC)
+
+typedef uint32_t rbtdb_serial_t;
+typedef uint32_t rbtdb_rdatatype_t;
+
+#define RBTDB_RDATATYPE_BASE(type) ((dns_rdatatype_t)((type)&0xFFFF))
+#define RBTDB_RDATATYPE_EXT(type)  ((dns_rdatatype_t)((type) >> 16))
+#define RBTDB_RDATATYPE_VALUE(base, ext)              \
+	((rbtdb_rdatatype_t)(((uint32_t)ext) << 16) | \
+	 (((uint32_t)base) & 0xffff))
+
+#define RBTDB_RDATATYPE_SIGNSEC \
+	RBTDB_RDATATYPE_VALUE(dns_rdatatype_rrsig, dns_rdatatype_nsec)
+#define RBTDB_RDATATYPE_SIGNSEC3 \
+	RBTDB_RDATATYPE_VALUE(dns_rdatatype_rrsig, dns_rdatatype_nsec3)
+#define RBTDB_RDATATYPE_SIGNS \
+	RBTDB_RDATATYPE_VALUE(dns_rdatatype_rrsig, dns_rdatatype_ns)
+#define RBTDB_RDATATYPE_SIGCNAME \
+	RBTDB_RDATATYPE_VALUE(dns_rdatatype_rrsig, dns_rdatatype_cname)
+#define RBTDB_RDATATYPE_SIGDNAME \
+	RBTDB_RDATATYPE_VALUE(dns_rdatatype_rrsig, dns_rdatatype_dname)
+#define RBTDB_RDATATYPE_SIGDS \
+	RBTDB_RDATATYPE_VALUE(dns_rdatatype_rrsig, dns_rdatatype_ds)
+#define RBTDB_RDATATYPE_SIGSOA \
+	RBTDB_RDATATYPE_VALUE(dns_rdatatype_rrsig, dns_rdatatype_soa)
+#define RBTDB_RDATATYPE_NCACHEANY RBTDB_RDATATYPE_VALUE(0, dns_rdatatype_any)
+
+#define RBTDB_INITLOCK(l)    isc_rwlock_init((l), 0, 0)
+#define RBTDB_DESTROYLOCK(l) isc_rwlock_destroy(l)
+#define RBTDB_LOCK(l, t)     RWLOCK((l), (t))
+#define RBTDB_UNLOCK(l, t)   RWUNLOCK((l), (t))
+
+/*
+ * Since node locking is sensitive to both performance and memory footprint,
+ * we need some trick here.  If we have both high-performance rwlock and
+ * high performance and small-memory reference counters, we use rwlock for
+ * node lock and isc_refcount for node references.  In this case, we don't have
+ * to protect the access to the counters by locks.
+ * Otherwise, we simply use ordinary mutex lock for node locking, and use
+ * simple integers as reference counters which is protected by the lock.
+ * In most cases, we can simply use wrapper macros such as NODE_LOCK and
+ * NODE_UNLOCK.  In some other cases, however, we need to protect reference
+ * counters first and then protect other parts of a node as read-only data.
+ * Special additional macros, NODE_STRONGLOCK(), NODE_WEAKLOCK(), etc, are also
+ * provided for these special cases.  When we can use the efficient backend
+ * routines, we should only protect the "other members" by NODE_WEAKLOCK(read).
+ * Otherwise, we should use NODE_STRONGLOCK() to protect the entire critical
+ * section including the access to the reference counter.
+ * Note that we cannot use NODE_LOCK()/NODE_UNLOCK() wherever the protected
+ * section is also protected by NODE_STRONGLOCK().
+ */
+typedef isc_rwlock_t nodelock_t;
+
+#define NODE_INITLOCK(l)    isc_rwlock_init((l), 0, 0)
+#define NODE_DESTROYLOCK(l) isc_rwlock_destroy(l)
+#define NODE_LOCK(l, t)	    RWLOCK((l), (t))
+#define NODE_UNLOCK(l, t)   RWUNLOCK((l), (t))
+#define NODE_TRYUPGRADE(l)  isc_rwlock_tryupgrade(l)
+#define NODE_DOWNGRADE(l)   isc_rwlock_downgrade(l)
+
+/*%
+ * Whether to rate-limit updating the LRU to avoid possible thread contention.
+ * Updating LRU requires write locking, so we don't do it every time the
+ * record is touched - only after some time passes.
+ */
+#ifndef DNS_RBTDB_LIMITLRUUPDATE
+#define DNS_RBTDB_LIMITLRUUPDATE 1
+#endif
+
+/*% Time after which we update LRU for glue records, 5 minutes */
+#define DNS_RBTDB_LRUUPDATE_GLUE 300
+/*% Time after which we update LRU for all other records, 10 minutes */
+#define DNS_RBTDB_LRUUPDATE_REGULAR 600
+
+/*
+ * Allow clients with a virtual time of up to 5 minutes in the past to see
+ * records that would have otherwise have expired.
+ */
+#define RBTDB_VIRTUAL 300
+
+struct noqname {
+	dns_name_t name;
+	void *neg;
+	void *negsig;
+	dns_rdatatype_t type;
+};
+
+typedef struct rdatasetheader {
+	/*%
+	 * Locked by the owning node's lock.
+	 */
+	rbtdb_serial_t serial;
+	dns_ttl_t rdh_ttl;
+	rbtdb_rdatatype_t type;
+	atomic_uint_least16_t attributes;
+	dns_trust_t trust;
+	atomic_uint_fast32_t last_refresh_fail_ts;
+	struct noqname *noqname;
+	struct noqname *closest;
+	unsigned int resign_lsb : 1;
+	/*%<
+	 * We don't use the LIST macros, because the LIST structure has
+	 * both head and tail pointers, and is doubly linked.
+	 */
+
+	struct rdatasetheader *next;
+	/*%<
+	 * If this is the top header for an rdataset, 'next' points
+	 * to the top header for the next rdataset (i.e., the next type).
+	 * Otherwise, it points up to the header whose down pointer points
+	 * at this header.
+	 */
+
+	struct rdatasetheader *down;
+	/*%<
+	 * Points to the header for the next older version of
+	 * this rdataset.
+	 */
+
+	atomic_uint_fast32_t count;
+	/*%<
+	 * Monotonously increased every time this rdataset is bound so that
+	 * it is used as the base of the starting point in DNS responses
+	 * when the "cyclic" rrset-order is required.
+	 */
+
+	dns_rbtnode_t *node;
+	isc_stdtime_t last_used;
+	ISC_LINK(struct rdatasetheader) link;
+
+	unsigned int heap_index;
+	/*%<
+	 * Used for TTL-based cache cleaning.
+	 */
+	isc_stdtime_t resign;
+	/*%<
+	 * Case vector.  If the bit is set then the corresponding
+	 * character in the owner name needs to be AND'd with 0x20,
+	 * rendering that character upper case.
+	 */
+	unsigned char upper[32];
+} rdatasetheader_t;
+
+typedef ISC_LIST(rdatasetheader_t) rdatasetheaderlist_t;
+typedef ISC_LIST(dns_rbtnode_t) rbtnodelist_t;
+
+#define RDATASET_ATTR_NONEXISTENT 0x0001
+/*%< May be potentially served as stale data. */
+#define RDATASET_ATTR_STALE	     0x0002
+#define RDATASET_ATTR_IGNORE	     0x0004
+#define RDATASET_ATTR_RETAIN	     0x0008
+#define RDATASET_ATTR_NXDOMAIN	     0x0010
+#define RDATASET_ATTR_RESIGN	     0x0020
+#define RDATASET_ATTR_STATCOUNT	     0x0040
+#define RDATASET_ATTR_OPTOUT	     0x0080
+#define RDATASET_ATTR_NEGATIVE	     0x0100
+#define RDATASET_ATTR_PREFETCH	     0x0200
+#define RDATASET_ATTR_CASESET	     0x0400
+#define RDATASET_ATTR_ZEROTTL	     0x0800
+#define RDATASET_ATTR_CASEFULLYLOWER 0x1000
+/*%< Ancient - awaiting cleanup. */
+#define RDATASET_ATTR_ANCIENT	   0x2000
+#define RDATASET_ATTR_STALE_WINDOW 0x4000
+
+/*
+ * XXX
+ * When the cache will pre-expire data (due to memory low or other
+ * situations) before the rdataset's TTL has expired, it MUST
+ * respect the RETAIN bit and not expire the data until its TTL is
+ * expired.
+ */
+
+#define EXISTS(header)                                 \
+	((atomic_load_acquire(&(header)->attributes) & \
+	  RDATASET_ATTR_NONEXISTENT) == 0)
+#define NONEXISTENT(header)                            \
+	((atomic_load_acquire(&(header)->attributes) & \
+	  RDATASET_ATTR_NONEXISTENT) != 0)
+#define IGNORE(header)                                 \
+	((atomic_load_acquire(&(header)->attributes) & \
+	  RDATASET_ATTR_IGNORE) != 0)
+#define RETAIN(header)                                 \
+	((atomic_load_acquire(&(header)->attributes) & \
+	  RDATASET_ATTR_RETAIN) != 0)
+#define NXDOMAIN(header)                               \
+	((atomic_load_acquire(&(header)->attributes) & \
+	  RDATASET_ATTR_NXDOMAIN) != 0)
+#define STALE(header)                                                          \
+	((atomic_load_acquire(&(header)->attributes) & RDATASET_ATTR_STALE) != \
+	 0)
+#define STALE_WINDOW(header)                           \
+	((atomic_load_acquire(&(header)->attributes) & \
+	  RDATASET_ATTR_STALE_WINDOW) != 0)
+#define RESIGN(header)                                 \
+	((atomic_load_acquire(&(header)->attributes) & \
+	  RDATASET_ATTR_RESIGN) != 0)
+#define OPTOUT(header)                                 \
+	((atomic_load_acquire(&(header)->attributes) & \
+	  RDATASET_ATTR_OPTOUT) != 0)
+#define NEGATIVE(header)                               \
+	((atomic_load_acquire(&(header)->attributes) & \
+	  RDATASET_ATTR_NEGATIVE) != 0)
+#define PREFETCH(header)                               \
+	((atomic_load_acquire(&(header)->attributes) & \
+	  RDATASET_ATTR_PREFETCH) != 0)
+#define CASESET(header)                                \
+	((atomic_load_acquire(&(header)->attributes) & \
+	  RDATASET_ATTR_CASESET) != 0)
+#define ZEROTTL(header)                                \
+	((atomic_load_acquire(&(header)->attributes) & \
+	  RDATASET_ATTR_ZEROTTL) != 0)
+#define CASEFULLYLOWER(header)                         \
+	((atomic_load_acquire(&(header)->attributes) & \
+	  RDATASET_ATTR_CASEFULLYLOWER) != 0)
+#define ANCIENT(header)                                \
+	((atomic_load_acquire(&(header)->attributes) & \
+	  RDATASET_ATTR_ANCIENT) != 0)
+#define STATCOUNT(header)                              \
+	((atomic_load_acquire(&(header)->attributes) & \
+	  RDATASET_ATTR_STATCOUNT) != 0)
+#define STALE_TTL(header, rbtdb) (NXDOMAIN(header) ? 0 : rbtdb->serve_stale_ttl)
+
+#define RDATASET_ATTR_GET(header, attribute) \
+	(atomic_load_acquire(&(header)->attributes) & attribute)
+#define RDATASET_ATTR_SET(header, attribute) \
+	atomic_fetch_or_release(&(header)->attributes, attribute)
+#define RDATASET_ATTR_CLR(header, attribute) \
+	atomic_fetch_and_release(&(header)->attributes, ~(attribute))
+
+#define ACTIVE(header, now)             \
+	(((header)->rdh_ttl > (now)) || \
+	 ((header)->rdh_ttl == (now) && ZEROTTL(header)))
+
+#define DEFAULT_NODE_LOCK_COUNT	    7 /*%< Should be prime. */
+#define RBTDB_GLUE_TABLE_INIT_BITS  2U
+#define RBTDB_GLUE_TABLE_MAX_BITS   32U
+#define RBTDB_GLUE_TABLE_OVERCOMMIT 3
+
+#define GOLDEN_RATIO_32 0x61C88647
+#define HASHSIZE(bits)	(UINT64_C(1) << (bits))
+
+static uint32_t
+hash_32(uint32_t val, unsigned int bits) {
+	REQUIRE(bits <= RBTDB_GLUE_TABLE_MAX_BITS);
+	/* High bits are more random. */
+	return (val * GOLDEN_RATIO_32 >> (32 - bits));
+}
+
+#define EXPIREDOK(rbtiterator) \
+	(((rbtiterator)->common.options & DNS_DB_EXPIREDOK) != 0)
+
+#define STALEOK(rbtiterator) \
+	(((rbtiterator)->common.options & DNS_DB_STALEOK) != 0)
+
+/*%
+ * Number of buckets for cache DB entries (locks, LRU lists, TTL heaps).
+ * There is a tradeoff issue about configuring this value: if this is too
+ * small, it may cause heavier contention between threads; if this is too large,
+ * LRU purge algorithm won't work well (entries tend to be purged prematurely).
+ * The default value should work well for most environments, but this can
+ * also be configurable at compilation time via the
+ * DNS_RBTDB_CACHE_NODE_LOCK_COUNT variable.  This value must be larger than
+ * 1 due to the assumption of overmem_purge().
+ */
+#ifdef DNS_RBTDB_CACHE_NODE_LOCK_COUNT
+#if DNS_RBTDB_CACHE_NODE_LOCK_COUNT <= 1
+#error "DNS_RBTDB_CACHE_NODE_LOCK_COUNT must be larger than 1"
+#else /* if DNS_RBTDB_CACHE_NODE_LOCK_COUNT <= 1 */
+#define DEFAULT_CACHE_NODE_LOCK_COUNT DNS_RBTDB_CACHE_NODE_LOCK_COUNT
+#endif /* if DNS_RBTDB_CACHE_NODE_LOCK_COUNT <= 1 */
+#else  /* ifdef DNS_RBTDB_CACHE_NODE_LOCK_COUNT */
+#define DEFAULT_CACHE_NODE_LOCK_COUNT 17
+#endif /* DNS_RBTDB_CACHE_NODE_LOCK_COUNT */
+
+typedef struct {
+	nodelock_t lock;
+	/* Protected in the refcount routines. */
+	isc_refcount_t references;
+	/* Locked by lock. */
+	bool exiting;
+} rbtdb_nodelock_t;
+
+typedef struct rbtdb_changed {
+	dns_rbtnode_t *node;
+	bool dirty;
+	ISC_LINK(struct rbtdb_changed) link;
+} rbtdb_changed_t;
+
+typedef ISC_LIST(rbtdb_changed_t) rbtdb_changedlist_t;
+
+typedef enum { dns_db_insecure, dns_db_partial, dns_db_secure } dns_db_secure_t;
+
+typedef struct dns_rbtdb dns_rbtdb_t;
+
+/* Reason for expiring a record from cache */
+typedef enum { expire_lru, expire_ttl, expire_flush } expire_t;
+
+typedef struct rbtdb_glue rbtdb_glue_t;
+
+typedef struct rbtdb_glue_table_node {
+	struct rbtdb_glue_table_node *next;
+	dns_rbtnode_t *node;
+	rbtdb_glue_t *glue_list;
+} rbtdb_glue_table_node_t;
+
+typedef enum {
+	rdataset_ttl_fresh,
+	rdataset_ttl_stale,
+	rdataset_ttl_ancient
+} rdataset_ttl_t;
+
+typedef struct rbtdb_version {
+	/* Not locked */
+	rbtdb_serial_t serial;
+	dns_rbtdb_t *rbtdb;
+	/*
+	 * Protected in the refcount routines.
+	 * XXXJT: should we change the lock policy based on the refcount
+	 * performance?
+	 */
+	isc_refcount_t references;
+	/* Locked by database lock. */
+	bool writer;
+	bool commit_ok;
+	rbtdb_changedlist_t changed_list;
+	rdatasetheaderlist_t resigned_list;
+	ISC_LINK(struct rbtdb_version) link;
+	dns_db_secure_t secure;
+	bool havensec3;
+	/* NSEC3 parameters */
+	dns_hash_t hash;
+	uint8_t flags;
+	uint16_t iterations;
+	uint8_t salt_length;
+	unsigned char salt[DNS_NSEC3_SALTSIZE];
+
+	/*
+	 * records and xfrsize are covered by rwlock.
+	 */
+	isc_rwlock_t rwlock;
+	uint64_t records;
+	uint64_t xfrsize;
+
+	isc_rwlock_t glue_rwlock;
+	size_t glue_table_bits;
+	size_t glue_table_nodecount;
+	rbtdb_glue_table_node_t **glue_table;
+} rbtdb_version_t;
+
+typedef ISC_LIST(rbtdb_version_t) rbtdb_versionlist_t;
+
+struct dns_rbtdb {
+	/* Unlocked. */
+	dns_db_t common;
+	/* Locks the data in this struct */
+	isc_rwlock_t lock;
+	/* Locks the tree structure (prevents nodes appearing/disappearing) */
+	isc_rwlock_t tree_lock;
+	/* Locks for individual tree nodes */
+	unsigned int node_lock_count;
+	rbtdb_nodelock_t *node_locks;
+	dns_rbtnode_t *origin_node;
+	dns_rbtnode_t *nsec3_origin_node;
+	dns_stats_t *rrsetstats;     /* cache DB only */
+	isc_stats_t *cachestats;     /* cache DB only */
+	isc_stats_t *gluecachestats; /* zone DB only */
+	/* Locked by lock. */
+	unsigned int active;
+	isc_refcount_t references;
+	unsigned int attributes;
+	rbtdb_serial_t current_serial;
+	rbtdb_serial_t least_serial;
+	rbtdb_serial_t next_serial;
+	rbtdb_version_t *current_version;
+	rbtdb_version_t *future_version;
+	rbtdb_versionlist_t open_versions;
+	isc_task_t *task;
+	dns_dbnode_t *soanode;
+	dns_dbnode_t *nsnode;
+
+	/*
+	 * Maximum length of time to keep using a stale answer past its
+	 * normal TTL expiry.
+	 */
+	dns_ttl_t serve_stale_ttl;
+
+	/*
+	 * The time after a failed lookup, where stale answers from cache
+	 * may be used directly in a DNS response without attempting a
+	 * new iterative lookup.
+	 */
+	uint32_t serve_stale_refresh;
+
+	/*
+	 * This is a linked list used to implement the LRU cache.  There will
+	 * be node_lock_count linked lists here.  Nodes in bucket 1 will be
+	 * placed on the linked list rdatasets[1].
+	 */
+	rdatasetheaderlist_t *rdatasets;
+
+	/*%
+	 * Temporary storage for stale cache nodes and dynamically deleted
+	 * nodes that await being cleaned up.
+	 */
+	rbtnodelist_t *deadnodes;
+
+	/*
+	 * Heaps.  These are used for TTL based expiry in a cache,
+	 * or for zone resigning in a zone DB.  hmctx is the memory
+	 * context to use for the heap (which differs from the main
+	 * database memory context in the case of a cache).
+	 */
+	isc_mem_t *hmctx;
+	isc_heap_t **heaps;
+
+	/* Locked by tree_lock. */
+	dns_rbt_t *tree;
+	dns_rbt_t *nsec;
+	dns_rbt_t *nsec3;
+
+	/* Unlocked */
+	unsigned int quantum;
+};
+
+#define RBTDB_ATTR_LOADED  0x01
+#define RBTDB_ATTR_LOADING 0x02
+
+#define KEEPSTALE(rbtdb) ((rbtdb)->serve_stale_ttl > 0)
+
+/*%
+ * Search Context
+ */
+typedef struct {
+	dns_rbtdb_t *rbtdb;
+	rbtdb_version_t *rbtversion;
+	rbtdb_serial_t serial;
+	unsigned int options;
+	dns_rbtnodechain_t chain;
+	bool copy_name;
+	bool need_cleanup;
+	bool wild;
+	dns_rbtnode_t *zonecut;
+	rdatasetheader_t *zonecut_rdataset;
+	rdatasetheader_t *zonecut_sigrdataset;
+	dns_fixedname_t zonecut_name;
+	isc_stdtime_t now;
+} rbtdb_search_t;
+
+/*%
+ * Load Context
+ */
+typedef struct {
+	dns_rbtdb_t *rbtdb;
+	isc_stdtime_t now;
+} rbtdb_load_t;
+
+static void
+delete_callback(void *data, void *arg);
+static void
+rdataset_disassociate(dns_rdataset_t *rdataset);
+static isc_result_t
+rdataset_first(dns_rdataset_t *rdataset);
+static isc_result_t
+rdataset_next(dns_rdataset_t *rdataset);
+static void
+rdataset_current(dns_rdataset_t *rdataset, dns_rdata_t *rdata);
+static void
+rdataset_clone(dns_rdataset_t *source, dns_rdataset_t *target);
+static unsigned int
+rdataset_count(dns_rdataset_t *rdataset);
+static isc_result_t
+rdataset_getnoqname(dns_rdataset_t *rdataset, dns_name_t *name,
+		    dns_rdataset_t *neg, dns_rdataset_t *negsig);
+static isc_result_t
+rdataset_getclosest(dns_rdataset_t *rdataset, dns_name_t *name,
+		    dns_rdataset_t *neg, dns_rdataset_t *negsig);
+static bool
+need_headerupdate(rdatasetheader_t *header, isc_stdtime_t now);
+static void
+update_header(dns_rbtdb_t *rbtdb, rdatasetheader_t *header, isc_stdtime_t now);
+static void
+expire_header(dns_rbtdb_t *rbtdb, rdatasetheader_t *header, bool tree_locked,
+	      expire_t reason);
+static void
+overmem_purge(dns_rbtdb_t *rbtdb, unsigned int locknum_start, size_t purgesize,
+	      bool tree_locked);
+static void
+resign_insert(dns_rbtdb_t *rbtdb, int idx, rdatasetheader_t *newheader);
+static void
+resign_delete(dns_rbtdb_t *rbtdb, rbtdb_version_t *version,
+	      rdatasetheader_t *header);
+static void
+prune_tree(isc_task_t *task, isc_event_t *event);
+static void
+rdataset_settrust(dns_rdataset_t *rdataset, dns_trust_t trust);
+static void
+rdataset_expire(dns_rdataset_t *rdataset);
+static void
+rdataset_clearprefetch(dns_rdataset_t *rdataset);
+static void
+rdataset_setownercase(dns_rdataset_t *rdataset, const dns_name_t *name);
+static void
+rdataset_getownercase(const dns_rdataset_t *rdataset, dns_name_t *name);
+static isc_result_t
+rdataset_addglue(dns_rdataset_t *rdataset, dns_dbversion_t *version,
+		 dns_message_t *msg);
+static void
+free_gluetable(rbtdb_version_t *version);
+static isc_result_t
+nodefullname(dns_db_t *db, dns_dbnode_t *node, dns_name_t *name);
+
+static dns_rdatasetmethods_t rdataset_methods = { rdataset_disassociate,
+						  rdataset_first,
+						  rdataset_next,
+						  rdataset_current,
+						  rdataset_clone,
+						  rdataset_count,
+						  NULL, /* addnoqname */
+						  rdataset_getnoqname,
+						  NULL, /* addclosest */
+						  rdataset_getclosest,
+						  rdataset_settrust,
+						  rdataset_expire,
+						  rdataset_clearprefetch,
+						  rdataset_setownercase,
+						  rdataset_getownercase,
+						  rdataset_addglue };
+
+static dns_rdatasetmethods_t slab_methods = {
+	rdataset_disassociate,
+	rdataset_first,
+	rdataset_next,
+	rdataset_current,
+	rdataset_clone,
+	rdataset_count,
+	NULL, /* addnoqname */
+	NULL, /* getnoqname */
+	NULL, /* addclosest */
+	NULL, /* getclosest */
+	NULL, /* settrust */
+	NULL, /* expire */
+	NULL, /* clearprefetch */
+	NULL, /* setownercase */
+	NULL, /* getownercase */
+	NULL  /* addglue */
+};
+
+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
+};
+
+typedef struct rbtdb_rdatasetiter {
+	dns_rdatasetiter_t common;
+	rdatasetheader_t *current;
+} rbtdb_rdatasetiter_t;
+
+/*
+ * Note that these iterators, unless created with either DNS_DB_NSEC3ONLY or
+ * DNS_DB_NONSEC3, will transparently move between the last node of the
+ * "regular" RBT ("chain" field) and the root node of the NSEC3 RBT
+ * ("nsec3chain" field) of the database in question, as if the latter was a
+ * successor to the former in lexical order.  The "current" field always holds
+ * the address of either "chain" or "nsec3chain", depending on which RBT is
+ * being traversed at given time.
+ */
+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, const 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
+};
+
+#define DELETION_BATCH_MAX 64
+
+/*
+ * If 'paused' is true, then the tree lock is not being held.
+ */
+typedef struct rbtdb_dbiterator {
+	dns_dbiterator_t common;
+	bool paused;
+	bool new_origin;
+	isc_rwlocktype_t tree_locked;
+	isc_result_t result;
+	dns_fixedname_t name;
+	dns_fixedname_t origin;
+	dns_rbtnodechain_t chain;
+	dns_rbtnodechain_t nsec3chain;
+	dns_rbtnodechain_t *current;
+	dns_rbtnode_t *node;
+	dns_rbtnode_t *deletions[DELETION_BATCH_MAX];
+	int delcnt;
+	bool nsec3only;
+	bool nonsec3;
+} rbtdb_dbiterator_t;
+
+#define IS_STUB(rbtdb)	(((rbtdb)->common.attributes & DNS_DBATTR_STUB) != 0)
+#define IS_CACHE(rbtdb) (((rbtdb)->common.attributes & DNS_DBATTR_CACHE) != 0)
+
+static void
+free_rbtdb(dns_rbtdb_t *rbtdb, bool log, isc_event_t *event);
+static void
+overmem(dns_db_t *db, bool over);
+static void
+setnsec3parameters(dns_db_t *db, rbtdb_version_t *version);
+static void
+setownercase(rdatasetheader_t *header, const dns_name_t *name);
+
+/*%
+ * 'init_count' is used to initialize 'newheader->count' which inturn
+ * is used to determine where in the cycle rrset-order cyclic starts.
+ * We don't lock this as we don't care about simultaneous updates.
+ *
+ * Note:
+ *      Both init_count and header->count can be UINT32_MAX.
+ *      The count on the returned rdataset however can't be as
+ *      that indicates that the database does not implement cyclic
+ *      processing.
+ */
+static atomic_uint_fast32_t init_count = 0;
+
+/*
+ * Locking
+ *
+ * If a routine is going to lock more than one lock in this module, then
+ * the locking must be done in the following order:
+ *
+ *      Tree Lock
+ *
+ *      Node Lock       (Only one from the set may be locked at one time by
+ *                       any caller)
+ *
+ *      Database Lock
+ *
+ * Failure to follow this hierarchy can result in deadlock.
+ */
+
+/*
+ * Deleting Nodes
+ *
+ * For zone databases the node for the origin of the zone MUST NOT be deleted.
+ */
+
+/* Fixed RRSet helper macros */
+
+#define DNS_RDATASET_LENGTH 2;
+
+#if DNS_RDATASET_FIXED
+#define DNS_RDATASET_ORDER 2
+#define DNS_RDATASET_COUNT (count * 4)
+#else /* !DNS_RDATASET_FIXED */
+#define DNS_RDATASET_ORDER 0
+#define DNS_RDATASET_COUNT 0
+#endif /* DNS_RDATASET_FIXED */
+
+/*
+ * DB Routines
+ */
+
+static void
+attach(dns_db_t *source, dns_db_t **targetp) {
+	dns_rbtdb_t *rbtdb = (dns_rbtdb_t *)source;
+
+	REQUIRE(VALID_RBTDB(rbtdb));
+
+	isc_refcount_increment(&rbtdb->references);
+
+	*targetp = source;
+}
+
+static void
+free_rbtdb_callback(isc_task_t *task, isc_event_t *event) {
+	dns_rbtdb_t *rbtdb = event->ev_arg;
+
+	UNUSED(task);
+
+	free_rbtdb(rbtdb, true, event);
+}
+
+static void
+update_cachestats(dns_rbtdb_t *rbtdb, isc_result_t result) {
+	INSIST(IS_CACHE(rbtdb));
+
+	if (rbtdb->cachestats == NULL) {
+		return;
+	}
+
+	switch (result) {
+	case DNS_R_COVERINGNSEC:
+		isc_stats_increment(rbtdb->cachestats,
+				    dns_cachestatscounter_coveringnsec);
+		FALLTHROUGH;
+	case ISC_R_SUCCESS:
+	case DNS_R_CNAME:
+	case DNS_R_DNAME:
+	case DNS_R_DELEGATION:
+	case DNS_R_NCACHENXDOMAIN:
+	case DNS_R_NCACHENXRRSET:
+		isc_stats_increment(rbtdb->cachestats,
+				    dns_cachestatscounter_hits);
+		break;
+	default:
+		isc_stats_increment(rbtdb->cachestats,
+				    dns_cachestatscounter_misses);
+	}
+}
+
+static bool
+do_stats(rdatasetheader_t *header) {
+	return (EXISTS(header) && STATCOUNT(header));
+}
+
+static void
+update_rrsetstats(dns_rbtdb_t *rbtdb, const rbtdb_rdatatype_t htype,
+		  const uint_least16_t hattributes, const bool increment) {
+	dns_rdatastatstype_t statattributes = 0;
+	dns_rdatastatstype_t base = 0;
+	dns_rdatastatstype_t type;
+	rdatasetheader_t *header = &(rdatasetheader_t){
+		.type = htype,
+		.attributes = hattributes,
+	};
+
+	if (!do_stats(header)) {
+		return;
+	}
+
+	/* At the moment we count statistics only for cache DB */
+	INSIST(IS_CACHE(rbtdb));
+
+	if (NEGATIVE(header)) {
+		if (NXDOMAIN(header)) {
+			statattributes = DNS_RDATASTATSTYPE_ATTR_NXDOMAIN;
+		} else {
+			statattributes = DNS_RDATASTATSTYPE_ATTR_NXRRSET;
+			base = RBTDB_RDATATYPE_EXT(header->type);
+		}
+	} else {
+		base = RBTDB_RDATATYPE_BASE(header->type);
+	}
+
+	if (STALE(header)) {
+		statattributes |= DNS_RDATASTATSTYPE_ATTR_STALE;
+	}
+	if (ANCIENT(header)) {
+		statattributes |= DNS_RDATASTATSTYPE_ATTR_ANCIENT;
+	}
+
+	type = DNS_RDATASTATSTYPE_VALUE(base, statattributes);
+	if (increment) {
+		dns_rdatasetstats_increment(rbtdb->rrsetstats, type);
+	} else {
+		dns_rdatasetstats_decrement(rbtdb->rrsetstats, type);
+	}
+}
+
+static void
+set_ttl(dns_rbtdb_t *rbtdb, rdatasetheader_t *header, dns_ttl_t newttl) {
+	int idx;
+	isc_heap_t *heap;
+	dns_ttl_t oldttl;
+
+	if (!IS_CACHE(rbtdb)) {
+		header->rdh_ttl = newttl;
+		return;
+	}
+
+	oldttl = header->rdh_ttl;
+	header->rdh_ttl = newttl;
+
+	/*
+	 * It's possible the rbtdb is not a cache.  If this is the case,
+	 * we will not have a heap, and we move on.  If we do, though,
+	 * we might need to adjust things.
+	 */
+	if (header->heap_index == 0 || newttl == oldttl) {
+		return;
+	}
+	idx = header->node->locknum;
+	if (rbtdb->heaps == NULL || rbtdb->heaps[idx] == NULL) {
+		return;
+	}
+	heap = rbtdb->heaps[idx];
+
+	if (newttl < oldttl) {
+		isc_heap_increased(heap, header->heap_index);
+	} else {
+		isc_heap_decreased(heap, header->heap_index);
+	}
+}
+
+/*%
+ * These functions allow the heap code to rank the priority of each
+ * element.  It returns true if v1 happens "sooner" than v2.
+ */
+static bool
+ttl_sooner(void *v1, void *v2) {
+	rdatasetheader_t *h1 = v1;
+	rdatasetheader_t *h2 = v2;
+
+	return (h1->rdh_ttl < h2->rdh_ttl);
+}
+
+/*%
+ * Return which RRset should be resigned sooner.  If the RRsets have the
+ * same signing time, prefer the other RRset over the SOA RRset.
+ */
+static bool
+resign_sooner(void *v1, void *v2) {
+	rdatasetheader_t *h1 = v1;
+	rdatasetheader_t *h2 = v2;
+
+	return (h1->resign < h2->resign ||
+		(h1->resign == h2->resign && h1->resign_lsb < h2->resign_lsb) ||
+		(h1->resign == h2->resign && h1->resign_lsb == h2->resign_lsb &&
+		 h2->type == RBTDB_RDATATYPE_SIGSOA));
+}
+
+/*%
+ * This function sets the heap index into the header.
+ */
+static void
+set_index(void *what, unsigned int idx) {
+	rdatasetheader_t *h = what;
+
+	h->heap_index = idx;
+}
+
+/*%
+ * Work out how many nodes can be deleted in the time between two
+ * requests to the nameserver.  Smooth the resulting number and use it
+ * as a estimate for the number of nodes to be deleted in the next
+ * iteration.
+ */
+static unsigned int
+adjust_quantum(unsigned int old, isc_time_t *start) {
+	unsigned int pps = dns_pps; /* packets per second */
+	unsigned int interval;
+	uint64_t usecs;
+	isc_time_t end;
+	unsigned int nodes;
+
+	if (pps < 100) {
+		pps = 100;
+	}
+	isc_time_now(&end);
+
+	interval = 1000000 / pps; /* interval in usec */
+	if (interval == 0) {
+		interval = 1;
+	}
+	usecs = isc_time_microdiff(&end, start);
+	if (usecs == 0) {
+		/*
+		 * We were unable to measure the amount of time taken.
+		 * Double the nodes deleted next time.
+		 */
+		old *= 2;
+		if (old > 1000) {
+			old = 1000;
+		}
+		return (old);
+	}
+	nodes = old * interval;
+	nodes /= (unsigned int)usecs;
+	if (nodes == 0) {
+		nodes = 1;
+	} else if (nodes > 1000) {
+		nodes = 1000;
+	}
+
+	/* Smooth */
+	nodes = (nodes + old * 3) / 4;
+
+	if (nodes != old) {
+		isc_log_write(dns_lctx, DNS_LOGCATEGORY_DATABASE,
+			      DNS_LOGMODULE_CACHE, ISC_LOG_DEBUG(1),
+			      "adjust_quantum: old=%d, new=%d", old, nodes);
+	}
+
+	return (nodes);
+}
+
+static void
+free_rbtdb(dns_rbtdb_t *rbtdb, bool log, isc_event_t *event) {
+	unsigned int i;
+	isc_result_t result;
+	char buf[DNS_NAME_FORMATSIZE];
+	dns_rbt_t **treep;
+	isc_time_t start;
+
+	if (IS_CACHE(rbtdb) && rbtdb->common.rdclass == dns_rdataclass_in) {
+		overmem((dns_db_t *)rbtdb, (bool)-1);
+	}
+
+	REQUIRE(rbtdb->current_version != NULL || EMPTY(rbtdb->open_versions));
+	REQUIRE(rbtdb->future_version == NULL);
+
+	if (rbtdb->current_version != NULL) {
+		isc_refcount_decrementz(&rbtdb->current_version->references);
+		UNLINK(rbtdb->open_versions, rbtdb->current_version, link);
+		isc_rwlock_destroy(&rbtdb->current_version->glue_rwlock);
+		isc_refcount_destroy(&rbtdb->current_version->references);
+		isc_rwlock_destroy(&rbtdb->current_version->rwlock);
+		isc_mem_put(rbtdb->common.mctx, rbtdb->current_version,
+			    sizeof(rbtdb_version_t));
+	}
+
+	/*
+	 * We assume the number of remaining dead nodes is reasonably small;
+	 * the overhead of unlinking all nodes here should be negligible.
+	 */
+	for (i = 0; i < rbtdb->node_lock_count; i++) {
+		dns_rbtnode_t *node;
+
+		node = ISC_LIST_HEAD(rbtdb->deadnodes[i]);
+		while (node != NULL) {
+			ISC_LIST_UNLINK(rbtdb->deadnodes[i], node, deadlink);
+			node = ISC_LIST_HEAD(rbtdb->deadnodes[i]);
+		}
+	}
+
+	if (event == NULL) {
+		rbtdb->quantum = (rbtdb->task != NULL) ? 100 : 0;
+	}
+
+	for (;;) {
+		/*
+		 * pick the next tree to (start to) destroy
+		 */
+		treep = &rbtdb->tree;
+		if (*treep == NULL) {
+			treep = &rbtdb->nsec;
+			if (*treep == NULL) {
+				treep = &rbtdb->nsec3;
+				/*
+				 * we're finished after clear cutting
+				 */
+				if (*treep == NULL) {
+					break;
+				}
+			}
+		}
+
+		isc_time_now(&start);
+		result = dns_rbt_destroy2(treep, rbtdb->quantum);
+		if (result == ISC_R_QUOTA) {
+			INSIST(rbtdb->task != NULL);
+			if (rbtdb->quantum != 0) {
+				rbtdb->quantum = adjust_quantum(rbtdb->quantum,
+								&start);
+			}
+			if (event == NULL) {
+				event = isc_event_allocate(
+					rbtdb->common.mctx, NULL,
+					DNS_EVENT_FREESTORAGE,
+					free_rbtdb_callback, rbtdb,
+					sizeof(isc_event_t));
+			}
+			isc_task_send(rbtdb->task, &event);
+			return;
+		}
+		INSIST(result == ISC_R_SUCCESS && *treep == NULL);
+	}
+
+	if (event != NULL) {
+		isc_event_free(&event);
+	}
+	if (log) {
+		if (dns_name_dynamic(&rbtdb->common.origin)) {
+			dns_name_format(&rbtdb->common.origin, buf,
+					sizeof(buf));
+		} else {
+			strlcpy(buf, "<UNKNOWN>", sizeof(buf));
+		}
+		isc_log_write(dns_lctx, DNS_LOGCATEGORY_DATABASE,
+			      DNS_LOGMODULE_CACHE, ISC_LOG_DEBUG(1),
+			      "done free_rbtdb(%s)", buf);
+	}
+	if (dns_name_dynamic(&rbtdb->common.origin)) {
+		dns_name_free(&rbtdb->common.origin, rbtdb->common.mctx);
+	}
+	for (i = 0; i < rbtdb->node_lock_count; i++) {
+		isc_refcount_destroy(&rbtdb->node_locks[i].references);
+		NODE_DESTROYLOCK(&rbtdb->node_locks[i].lock);
+	}
+
+	/*
+	 * Clean up LRU / re-signing order lists.
+	 */
+	if (rbtdb->rdatasets != NULL) {
+		for (i = 0; i < rbtdb->node_lock_count; i++) {
+			INSIST(ISC_LIST_EMPTY(rbtdb->rdatasets[i]));
+		}
+		isc_mem_put(rbtdb->common.mctx, rbtdb->rdatasets,
+			    rbtdb->node_lock_count *
+				    sizeof(rdatasetheaderlist_t));
+	}
+	/*
+	 * Clean up dead node buckets.
+	 */
+	if (rbtdb->deadnodes != NULL) {
+		for (i = 0; i < rbtdb->node_lock_count; i++) {
+			INSIST(ISC_LIST_EMPTY(rbtdb->deadnodes[i]));
+		}
+		isc_mem_put(rbtdb->common.mctx, rbtdb->deadnodes,
+			    rbtdb->node_lock_count * sizeof(rbtnodelist_t));
+	}
+	/*
+	 * Clean up heap objects.
+	 */
+	if (rbtdb->heaps != NULL) {
+		for (i = 0; i < rbtdb->node_lock_count; i++) {
+			isc_heap_destroy(&rbtdb->heaps[i]);
+		}
+		isc_mem_put(rbtdb->hmctx, rbtdb->heaps,
+			    rbtdb->node_lock_count * sizeof(isc_heap_t *));
+	}
+
+	if (rbtdb->rrsetstats != NULL) {
+		dns_stats_detach(&rbtdb->rrsetstats);
+	}
+	if (rbtdb->cachestats != NULL) {
+		isc_stats_detach(&rbtdb->cachestats);
+	}
+	if (rbtdb->gluecachestats != NULL) {
+		isc_stats_detach(&rbtdb->gluecachestats);
+	}
+
+	isc_mem_put(rbtdb->common.mctx, rbtdb->node_locks,
+		    rbtdb->node_lock_count * sizeof(rbtdb_nodelock_t));
+	isc_rwlock_destroy(&rbtdb->tree_lock);
+	isc_refcount_destroy(&rbtdb->references);
+	if (rbtdb->task != NULL) {
+		isc_task_detach(&rbtdb->task);
+	}
+
+	RBTDB_DESTROYLOCK(&rbtdb->lock);
+	rbtdb->common.magic = 0;
+	rbtdb->common.impmagic = 0;
+	isc_mem_detach(&rbtdb->hmctx);
+
+	INSIST(ISC_LIST_EMPTY(rbtdb->common.update_listeners));
+
+	isc_mem_putanddetach(&rbtdb->common.mctx, rbtdb, sizeof(*rbtdb));
+}
+
+static void
+maybe_free_rbtdb(dns_rbtdb_t *rbtdb) {
+	bool want_free = false;
+	unsigned int i;
+	unsigned int inactive = 0;
+
+	/* XXX check for open versions here */
+
+	if (rbtdb->soanode != NULL) {
+		dns_db_detachnode((dns_db_t *)rbtdb, &rbtdb->soanode);
+	}
+	if (rbtdb->nsnode != NULL) {
+		dns_db_detachnode((dns_db_t *)rbtdb, &rbtdb->nsnode);
+	}
+
+	/*
+	 * The current version's glue table needs to be freed early
+	 * so the nodes are dereferenced before we check the active
+	 * node count below.
+	 */
+	if (rbtdb->current_version != NULL) {
+		free_gluetable(rbtdb->current_version);
+	}
+
+	/*
+	 * Even though there are no external direct references, there still
+	 * may be nodes in use.
+	 */
+	for (i = 0; i < rbtdb->node_lock_count; i++) {
+		NODE_LOCK(&rbtdb->node_locks[i].lock, isc_rwlocktype_write);
+		rbtdb->node_locks[i].exiting = true;
+		if (isc_refcount_current(&rbtdb->node_locks[i].references) == 0)
+		{
+			inactive++;
+		}
+		NODE_UNLOCK(&rbtdb->node_locks[i].lock, isc_rwlocktype_write);
+	}
+
+	if (inactive != 0) {
+		RBTDB_LOCK(&rbtdb->lock, isc_rwlocktype_write);
+		rbtdb->active -= inactive;
+		if (rbtdb->active == 0) {
+			want_free = true;
+		}
+		RBTDB_UNLOCK(&rbtdb->lock, isc_rwlocktype_write);
+		if (want_free) {
+			char buf[DNS_NAME_FORMATSIZE];
+			if (dns_name_dynamic(&rbtdb->common.origin)) {
+				dns_name_format(&rbtdb->common.origin, buf,
+						sizeof(buf));
+			} else {
+				strlcpy(buf, "<UNKNOWN>", sizeof(buf));
+			}
+			isc_log_write(dns_lctx, DNS_LOGCATEGORY_DATABASE,
+				      DNS_LOGMODULE_CACHE, ISC_LOG_DEBUG(1),
+				      "calling free_rbtdb(%s)", buf);
+			free_rbtdb(rbtdb, true, NULL);
+		}
+	}
+}
+
+static void
+detach(dns_db_t **dbp) {
+	REQUIRE(dbp != NULL && VALID_RBTDB((dns_rbtdb_t *)(*dbp)));
+	dns_rbtdb_t *rbtdb = (dns_rbtdb_t *)(*dbp);
+	*dbp = NULL;
+
+	if (isc_refcount_decrement(&rbtdb->references) == 1) {
+		maybe_free_rbtdb(rbtdb);
+	}
+}
+
+static void
+currentversion(dns_db_t *db, dns_dbversion_t **versionp) {
+	dns_rbtdb_t *rbtdb = (dns_rbtdb_t *)db;
+	rbtdb_version_t *version;
+
+	REQUIRE(VALID_RBTDB(rbtdb));
+
+	RBTDB_LOCK(&rbtdb->lock, isc_rwlocktype_read);
+	version = rbtdb->current_version;
+	isc_refcount_increment(&version->references);
+	RBTDB_UNLOCK(&rbtdb->lock, isc_rwlocktype_read);
+
+	*versionp = (dns_dbversion_t *)version;
+}
+
+static rbtdb_version_t *
+allocate_version(isc_mem_t *mctx, rbtdb_serial_t serial,
+		 unsigned int references, bool writer) {
+	rbtdb_version_t *version;
+	size_t size;
+
+	version = isc_mem_get(mctx, sizeof(*version));
+	version->serial = serial;
+
+	isc_refcount_init(&version->references, references);
+	isc_rwlock_init(&version->glue_rwlock, 0, 0);
+
+	version->glue_table_bits = RBTDB_GLUE_TABLE_INIT_BITS;
+	version->glue_table_nodecount = 0U;
+
+	size = HASHSIZE(version->glue_table_bits) *
+	       sizeof(version->glue_table[0]);
+	version->glue_table = isc_mem_get(mctx, size);
+	memset(version->glue_table, 0, size);
+
+	version->writer = writer;
+	version->commit_ok = false;
+	ISC_LIST_INIT(version->changed_list);
+	ISC_LIST_INIT(version->resigned_list);
+	ISC_LINK_INIT(version, link);
+
+	return (version);
+}
+
+static isc_result_t
+newversion(dns_db_t *db, dns_dbversion_t **versionp) {
+	dns_rbtdb_t *rbtdb = (dns_rbtdb_t *)db;
+	rbtdb_version_t *version;
+
+	REQUIRE(VALID_RBTDB(rbtdb));
+	REQUIRE(versionp != NULL && *versionp == NULL);
+	REQUIRE(rbtdb->future_version == NULL);
+
+	RBTDB_LOCK(&rbtdb->lock, isc_rwlocktype_write);
+	RUNTIME_CHECK(rbtdb->next_serial != 0); /* XXX Error? */
+	version = allocate_version(rbtdb->common.mctx, rbtdb->next_serial, 1,
+				   true);
+	version->rbtdb = rbtdb;
+	version->commit_ok = true;
+	version->secure = rbtdb->current_version->secure;
+	version->havensec3 = rbtdb->current_version->havensec3;
+	if (version->havensec3) {
+		version->flags = rbtdb->current_version->flags;
+		version->iterations = rbtdb->current_version->iterations;
+		version->hash = rbtdb->current_version->hash;
+		version->salt_length = rbtdb->current_version->salt_length;
+		memmove(version->salt, rbtdb->current_version->salt,
+			version->salt_length);
+	} else {
+		version->flags = 0;
+		version->iterations = 0;
+		version->hash = 0;
+		version->salt_length = 0;
+		memset(version->salt, 0, sizeof(version->salt));
+	}
+	isc_rwlock_init(&version->rwlock, 0, 0);
+	RWLOCK(&rbtdb->current_version->rwlock, isc_rwlocktype_read);
+	version->records = rbtdb->current_version->records;
+	version->xfrsize = rbtdb->current_version->xfrsize;
+	RWUNLOCK(&rbtdb->current_version->rwlock, isc_rwlocktype_read);
+	rbtdb->next_serial++;
+	rbtdb->future_version = version;
+	RBTDB_UNLOCK(&rbtdb->lock, isc_rwlocktype_write);
+
+	*versionp = version;
+
+	return (ISC_R_SUCCESS);
+}
+
+static void
+attachversion(dns_db_t *db, dns_dbversion_t *source,
+	      dns_dbversion_t **targetp) {
+	dns_rbtdb_t *rbtdb = (dns_rbtdb_t *)db;
+	rbtdb_version_t *rbtversion = source;
+
+	REQUIRE(VALID_RBTDB(rbtdb));
+	INSIST(rbtversion != NULL && rbtversion->rbtdb == rbtdb);
+
+	isc_refcount_increment(&rbtversion->references);
+
+	*targetp = rbtversion;
+}
+
+static rbtdb_changed_t *
+add_changed(dns_rbtdb_t *rbtdb, rbtdb_version_t *version, dns_rbtnode_t *node) {
+	rbtdb_changed_t *changed;
+
+	/*
+	 * Caller must be holding the node lock if its reference must be
+	 * protected by the lock.
+	 */
+
+	changed = isc_mem_get(rbtdb->common.mctx, sizeof(*changed));
+
+	RBTDB_LOCK(&rbtdb->lock, isc_rwlocktype_write);
+
+	REQUIRE(version->writer);
+
+	if (changed != NULL) {
+		isc_refcount_increment(&node->references);
+		changed->node = node;
+		changed->dirty = false;
+		ISC_LIST_INITANDAPPEND(version->changed_list, changed, link);
+	} else {
+		version->commit_ok = false;
+	}
+
+	RBTDB_UNLOCK(&rbtdb->lock, isc_rwlocktype_write);
+
+	return (changed);
+}
+
+static void
+free_noqname(isc_mem_t *mctx, struct noqname **noqname) {
+	if (dns_name_dynamic(&(*noqname)->name)) {
+		dns_name_free(&(*noqname)->name, mctx);
+	}
+	if ((*noqname)->neg != NULL) {
+		isc_mem_put(mctx, (*noqname)->neg,
+			    dns_rdataslab_size((*noqname)->neg, 0));
+	}
+	if ((*noqname)->negsig != NULL) {
+		isc_mem_put(mctx, (*noqname)->negsig,
+			    dns_rdataslab_size((*noqname)->negsig, 0));
+	}
+	isc_mem_put(mctx, *noqname, sizeof(**noqname));
+	*noqname = NULL;
+}
+
+static void
+init_rdataset(dns_rbtdb_t *rbtdb, rdatasetheader_t *h) {
+	ISC_LINK_INIT(h, link);
+	h->heap_index = 0;
+	atomic_init(&h->attributes, 0);
+	atomic_init(&h->last_refresh_fail_ts, 0);
+
+	STATIC_ASSERT((sizeof(h->attributes) == 2),
+		      "The .attributes field of rdatasetheader_t needs to be "
+		      "16-bit int type exactly.");
+
+#if TRACE_HEADER
+	if (IS_CACHE(rbtdb) && rbtdb->common.rdclass == dns_rdataclass_in) {
+		fprintf(stderr, "initialized header: %p\n", h);
+	}
+#else  /* if TRACE_HEADER */
+	UNUSED(rbtdb);
+#endif /* if TRACE_HEADER */
+}
+
+static void
+update_newheader(rdatasetheader_t *newh, rdatasetheader_t *old) {
+	if (CASESET(old)) {
+		uint_least16_t attr = RDATASET_ATTR_GET(
+			old,
+			(RDATASET_ATTR_CASESET | RDATASET_ATTR_CASEFULLYLOWER));
+		RDATASET_ATTR_SET(newh, attr);
+		memmove(newh->upper, old->upper, sizeof(old->upper));
+	}
+}
+
+static rdatasetheader_t *
+new_rdataset(dns_rbtdb_t *rbtdb, isc_mem_t *mctx) {
+	rdatasetheader_t *h;
+
+	h = isc_mem_get(mctx, sizeof(*h));
+
+#if TRACE_HEADER
+	if (IS_CACHE(rbtdb) && rbtdb->common.rdclass == dns_rdataclass_in) {
+		fprintf(stderr, "allocated header: %p\n", h);
+	}
+#endif /* if TRACE_HEADER */
+	memset(h->upper, 0xeb, sizeof(h->upper));
+	init_rdataset(rbtdb, h);
+	h->rdh_ttl = 0;
+	return (h);
+}
+
+static void
+free_rdataset(dns_rbtdb_t *rbtdb, isc_mem_t *mctx, rdatasetheader_t *rdataset) {
+	unsigned int size;
+	int idx;
+
+	update_rrsetstats(rbtdb, rdataset->type,
+			  atomic_load_acquire(&rdataset->attributes), false);
+
+	idx = rdataset->node->locknum;
+	if (ISC_LINK_LINKED(rdataset, link)) {
+		INSIST(IS_CACHE(rbtdb));
+		ISC_LIST_UNLINK(rbtdb->rdatasets[idx], rdataset, link);
+	}
+
+	if (rdataset->heap_index != 0) {
+		isc_heap_delete(rbtdb->heaps[idx], rdataset->heap_index);
+	}
+	rdataset->heap_index = 0;
+
+	if (rdataset->noqname != NULL) {
+		free_noqname(mctx, &rdataset->noqname);
+	}
+	if (rdataset->closest != NULL) {
+		free_noqname(mctx, &rdataset->closest);
+	}
+
+	if (NONEXISTENT(rdataset)) {
+		size = sizeof(*rdataset);
+	} else {
+		size = dns_rdataslab_size((unsigned char *)rdataset,
+					  sizeof(*rdataset));
+	}
+
+	isc_mem_put(mctx, rdataset, size);
+}
+
+static void
+rollback_node(dns_rbtnode_t *node, rbtdb_serial_t serial) {
+	rdatasetheader_t *header, *dcurrent;
+	bool make_dirty = false;
+
+	/*
+	 * Caller must hold the node lock.
+	 */
+
+	/*
+	 * We set the IGNORE attribute on rdatasets with serial number
+	 * 'serial'.  When the reference count goes to zero, these rdatasets
+	 * will be cleaned up; until that time, they will be ignored.
+	 */
+	for (header = node->data; header != NULL; header = header->next) {
+		if (header->serial == serial) {
+			RDATASET_ATTR_SET(header, RDATASET_ATTR_IGNORE);
+			make_dirty = true;
+		}
+		for (dcurrent = header->down; dcurrent != NULL;
+		     dcurrent = dcurrent->down)
+		{
+			if (dcurrent->serial == serial) {
+				RDATASET_ATTR_SET(dcurrent,
+						  RDATASET_ATTR_IGNORE);
+				make_dirty = true;
+			}
+		}
+	}
+	if (make_dirty) {
+		node->dirty = 1;
+	}
+}
+
+static void
+mark_header_ancient(dns_rbtdb_t *rbtdb, rdatasetheader_t *header) {
+	uint_least16_t attributes = atomic_load_acquire(&header->attributes);
+	uint_least16_t newattributes = 0;
+
+	/*
+	 * If we are already ancient there is nothing to do.
+	 */
+	do {
+		if ((attributes & RDATASET_ATTR_ANCIENT) != 0) {
+			return;
+		}
+		newattributes = attributes | RDATASET_ATTR_ANCIENT;
+	} while (!atomic_compare_exchange_weak_acq_rel(
+		&header->attributes, &attributes, newattributes));
+
+	/*
+	 * Decrement the stats counter for the appropriate RRtype.
+	 * If the STALE attribute is set, this will decrement the
+	 * stale type counter, otherwise it decrements the active
+	 * stats type counter.
+	 */
+	update_rrsetstats(rbtdb, header->type, attributes, false);
+	header->node->dirty = 1;
+
+	/* Increment the stats counter for the ancient RRtype. */
+	update_rrsetstats(rbtdb, header->type, newattributes, true);
+}
+
+static void
+mark_header_stale(dns_rbtdb_t *rbtdb, rdatasetheader_t *header) {
+	uint_least16_t attributes = atomic_load_acquire(&header->attributes);
+	uint_least16_t newattributes = 0;
+
+	INSIST((attributes & RDATASET_ATTR_ZEROTTL) == 0);
+
+	/*
+	 * If we are already stale there is nothing to do.
+	 */
+	do {
+		if ((attributes & RDATASET_ATTR_STALE) != 0) {
+			return;
+		}
+		newattributes = attributes | RDATASET_ATTR_STALE;
+	} while (!atomic_compare_exchange_weak_acq_rel(
+		&header->attributes, &attributes, newattributes));
+
+	/* Decrement the stats counter for the appropriate RRtype.
+	 * If the ANCIENT attribute is set (although it is very
+	 * unlikely that an RRset goes from ANCIENT to STALE), this
+	 * will decrement the ancient stale type counter, otherwise it
+	 * decrements the active stats type counter.
+	 */
+
+	update_rrsetstats(rbtdb, header->type, attributes, false);
+	update_rrsetstats(rbtdb, header->type, newattributes, true);
+}
+
+static void
+clean_stale_headers(dns_rbtdb_t *rbtdb, isc_mem_t *mctx,
+		    rdatasetheader_t *top) {
+	rdatasetheader_t *d, *down_next;
+
+	for (d = top->down; d != NULL; d = down_next) {
+		down_next = d->down;
+		free_rdataset(rbtdb, mctx, d);
+	}
+	top->down = NULL;
+}
+
+static void
+clean_cache_node(dns_rbtdb_t *rbtdb, dns_rbtnode_t *node) {
+	rdatasetheader_t *current, *top_prev, *top_next;
+	isc_mem_t *mctx = rbtdb->common.mctx;
+
+	/*
+	 * Caller must be holding the node lock.
+	 */
+
+	top_prev = NULL;
+	for (current = node->data; current != NULL; current = top_next) {
+		top_next = current->next;
+		clean_stale_headers(rbtdb, mctx, current);
+		/*
+		 * If current is nonexistent, ancient, or stale and
+		 * we are not keeping stale, we can clean it up.
+		 */
+		if (NONEXISTENT(current) || ANCIENT(current) ||
+		    (STALE(current) && !KEEPSTALE(rbtdb)))
+		{
+			if (top_prev != NULL) {
+				top_prev->next = current->next;
+			} else {
+				node->data = current->next;
+			}
+			free_rdataset(rbtdb, mctx, current);
+		} else {
+			top_prev = current;
+		}
+	}
+	node->dirty = 0;
+}
+
+static void
+clean_zone_node(dns_rbtdb_t *rbtdb, dns_rbtnode_t *node,
+		rbtdb_serial_t least_serial) {
+	rdatasetheader_t *current, *dcurrent, *down_next, *dparent;
+	rdatasetheader_t *top_prev, *top_next;
+	isc_mem_t *mctx = rbtdb->common.mctx;
+	bool still_dirty = false;
+
+	/*
+	 * Caller must be holding the node lock.
+	 */
+	REQUIRE(least_serial != 0);
+
+	top_prev = NULL;
+	for (current = node->data; current != NULL; current = top_next) {
+		top_next = current->next;
+
+		/*
+		 * First, we clean up any instances of multiple rdatasets
+		 * with the same serial number, or that have the IGNORE
+		 * attribute.
+		 */
+		dparent = current;
+		for (dcurrent = current->down; dcurrent != NULL;
+		     dcurrent = down_next)
+		{
+			down_next = dcurrent->down;
+			INSIST(dcurrent->serial <= dparent->serial);
+			if (dcurrent->serial == dparent->serial ||
+			    IGNORE(dcurrent))
+			{
+				if (down_next != NULL) {
+					down_next->next = dparent;
+				}
+				dparent->down = down_next;
+				free_rdataset(rbtdb, mctx, dcurrent);
+			} else {
+				dparent = dcurrent;
+			}
+		}
+
+		/*
+		 * We've now eliminated all IGNORE datasets with the possible
+		 * exception of current, which we now check.
+		 */
+		if (IGNORE(current)) {
+			down_next = current->down;
+			if (down_next == NULL) {
+				if (top_prev != NULL) {
+					top_prev->next = current->next;
+				} else {
+					node->data = current->next;
+				}
+				free_rdataset(rbtdb, mctx, current);
+				/*
+				 * current no longer exists, so we can
+				 * just continue with the loop.
+				 */
+				continue;
+			} else {
+				/*
+				 * Pull up current->down, making it the new
+				 * current.
+				 */
+				if (top_prev != NULL) {
+					top_prev->next = down_next;
+				} else {
+					node->data = down_next;
+				}
+				down_next->next = top_next;
+				free_rdataset(rbtdb, mctx, current);
+				current = down_next;
+			}
+		}
+
+		/*
+		 * We now try to find the first down node less than the
+		 * least serial.
+		 */
+		dparent = current;
+		for (dcurrent = current->down; dcurrent != NULL;
+		     dcurrent = down_next)
+		{
+			down_next = dcurrent->down;
+			if (dcurrent->serial < least_serial) {
+				break;
+			}
+			dparent = dcurrent;
+		}
+
+		/*
+		 * If there is a such an rdataset, delete it and any older
+		 * versions.
+		 */
+		if (dcurrent != NULL) {
+			do {
+				down_next = dcurrent->down;
+				INSIST(dcurrent->serial <= least_serial);
+				free_rdataset(rbtdb, mctx, dcurrent);
+				dcurrent = down_next;
+			} while (dcurrent != NULL);
+			dparent->down = NULL;
+		}
+
+		/*
+		 * Note.  The serial number of 'current' might be less than
+		 * least_serial too, but we cannot delete it because it is
+		 * the most recent version, unless it is a NONEXISTENT
+		 * rdataset.
+		 */
+		if (current->down != NULL) {
+			still_dirty = true;
+			top_prev = current;
+		} else {
+			/*
+			 * If this is a NONEXISTENT rdataset, we can delete it.
+			 */
+			if (NONEXISTENT(current)) {
+				if (top_prev != NULL) {
+					top_prev->next = current->next;
+				} else {
+					node->data = current->next;
+				}
+				free_rdataset(rbtdb, mctx, current);
+			} else {
+				top_prev = current;
+			}
+		}
+	}
+	if (!still_dirty) {
+		node->dirty = 0;
+	}
+}
+
+/*
+ * tree_lock(write) must be held.
+ */
+static void
+delete_node(dns_rbtdb_t *rbtdb, dns_rbtnode_t *node) {
+	dns_rbtnode_t *nsecnode;
+	dns_fixedname_t fname;
+	dns_name_t *name;
+	isc_result_t result = ISC_R_UNEXPECTED;
+
+	INSIST(!ISC_LINK_LINKED(node, deadlink));
+
+	if (isc_log_wouldlog(dns_lctx, ISC_LOG_DEBUG(1))) {
+		char printname[DNS_NAME_FORMATSIZE];
+		isc_log_write(dns_lctx, DNS_LOGCATEGORY_DATABASE,
+			      DNS_LOGMODULE_CACHE, ISC_LOG_DEBUG(1),
+			      "delete_node(): %p %s (bucket %d)", node,
+			      dns_rbt_formatnodename(node, printname,
+						     sizeof(printname)),
+			      node->locknum);
+	}
+
+	switch (node->nsec) {
+	case DNS_RBT_NSEC_NORMAL:
+		result = dns_rbt_deletenode(rbtdb->tree, node, false);
+		break;
+	case DNS_RBT_NSEC_HAS_NSEC:
+		/*
+		 * Though this may be wasteful, it has to be done before
+		 * node is deleted.
+		 */
+		name = dns_fixedname_initname(&fname);
+		dns_rbt_fullnamefromnode(node, name);
+		/*
+		 * Delete the corresponding node from the auxiliary NSEC
+		 * tree before deleting from the main tree.
+		 */
+		nsecnode = NULL;
+		result = dns_rbt_findnode(rbtdb->nsec, name, NULL, &nsecnode,
+					  NULL, DNS_RBTFIND_EMPTYDATA, NULL,
+					  NULL);
+		if (result != ISC_R_SUCCESS) {
+			isc_log_write(dns_lctx, DNS_LOGCATEGORY_DATABASE,
+				      DNS_LOGMODULE_CACHE, ISC_LOG_WARNING,
+				      "delete_node: "
+				      "dns_rbt_findnode(nsec): %s",
+				      isc_result_totext(result));
+		} else {
+			result = dns_rbt_deletenode(rbtdb->nsec, nsecnode,
+						    false);
+			if (result != ISC_R_SUCCESS) {
+				isc_log_write(
+					dns_lctx, DNS_LOGCATEGORY_DATABASE,
+					DNS_LOGMODULE_CACHE, ISC_LOG_WARNING,
+					"delete_node(): "
+					"dns_rbt_deletenode(nsecnode): %s",
+					isc_result_totext(result));
+			}
+		}
+		result = dns_rbt_deletenode(rbtdb->tree, node, false);
+		break;
+	case DNS_RBT_NSEC_NSEC:
+		result = dns_rbt_deletenode(rbtdb->nsec, node, false);
+		break;
+	case DNS_RBT_NSEC_NSEC3:
+		result = dns_rbt_deletenode(rbtdb->nsec3, node, false);
+		break;
+	}
+	if (result != ISC_R_SUCCESS) {
+		isc_log_write(dns_lctx, DNS_LOGCATEGORY_DATABASE,
+			      DNS_LOGMODULE_CACHE, ISC_LOG_WARNING,
+			      "delete_node(): "
+			      "dns_rbt_deletenode: %s",
+			      isc_result_totext(result));
+	}
+}
+
+/*
+ * Caller must be holding the node lock.
+ */
+static void
+new_reference(dns_rbtdb_t *rbtdb, dns_rbtnode_t *node,
+	      isc_rwlocktype_t locktype) {
+	if (locktype == isc_rwlocktype_write && ISC_LINK_LINKED(node, deadlink))
+	{
+		ISC_LIST_UNLINK(rbtdb->deadnodes[node->locknum], node,
+				deadlink);
+	}
+	if (isc_refcount_increment0(&node->references) == 0) {
+		/* this is the first reference to the node */
+		isc_refcount_increment0(
+			&rbtdb->node_locks[node->locknum].references);
+	}
+}
+
+/*%
+ * The tree lock must be held for the result to be valid.
+ */
+static bool
+is_leaf(dns_rbtnode_t *node) {
+	return (node->parent != NULL && node->parent->down == node &&
+		node->left == NULL && node->right == NULL);
+}
+
+static void
+send_to_prune_tree(dns_rbtdb_t *rbtdb, dns_rbtnode_t *node,
+		   isc_rwlocktype_t locktype) {
+	isc_event_t *ev;
+	dns_db_t *db;
+
+	ev = isc_event_allocate(rbtdb->common.mctx, NULL, DNS_EVENT_RBTPRUNE,
+				prune_tree, node, sizeof(isc_event_t));
+	new_reference(rbtdb, node, locktype);
+	db = NULL;
+	attach((dns_db_t *)rbtdb, &db);
+	ev->ev_sender = db;
+	isc_task_send(rbtdb->task, &ev);
+}
+
+/*%
+ * Clean up dead nodes.  These are nodes which have no references, and
+ * have no data.  They are dead but we could not or chose not to delete
+ * them when we deleted all the data at that node because we did not want
+ * to wait for the tree write lock.
+ *
+ * The caller must hold a tree write lock and bucketnum'th node (write) lock.
+ */
+static void
+cleanup_dead_nodes(dns_rbtdb_t *rbtdb, int bucketnum) {
+	dns_rbtnode_t *node;
+	int count = 10; /* XXXJT: should be adjustable */
+
+	node = ISC_LIST_HEAD(rbtdb->deadnodes[bucketnum]);
+	while (node != NULL && count > 0) {
+		ISC_LIST_UNLINK(rbtdb->deadnodes[bucketnum], node, deadlink);
+
+		/*
+		 * We might have reactivated this node without a tree write
+		 * lock, so we couldn't remove this node from deadnodes then
+		 * and we have to do it now.
+		 */
+		if (isc_refcount_current(&node->references) != 0 ||
+		    node->data != NULL)
+		{
+			node = ISC_LIST_HEAD(rbtdb->deadnodes[bucketnum]);
+			count--;
+			continue;
+		}
+
+		if (is_leaf(node) && rbtdb->task != NULL) {
+			send_to_prune_tree(rbtdb, node, isc_rwlocktype_write);
+		} else if (node->down == NULL && node->data == NULL) {
+			/*
+			 * Not a interior node and not needing to be
+			 * reactivated.
+			 */
+			delete_node(rbtdb, node);
+		} else if (node->data == NULL) {
+			/*
+			 * A interior node without data. Leave linked to
+			 * to be cleaned up when node->down becomes NULL.
+			 */
+			ISC_LIST_APPEND(rbtdb->deadnodes[bucketnum], node,
+					deadlink);
+		}
+		node = ISC_LIST_HEAD(rbtdb->deadnodes[bucketnum]);
+		count--;
+	}
+}
+
+/*
+ * This function is assumed to be called when a node is newly referenced
+ * and can be in the deadnode list.  In that case the node must be retrieved
+ * from the list because it is going to be used.  In addition, if the caller
+ * happens to hold a write lock on the tree, it's a good chance to purge dead
+ * nodes.
+ * Note: while a new reference is gained in multiple places, there are only very
+ * few cases where the node can be in the deadnode list (only empty nodes can
+ * have been added to the list).
+ */
+static void
+reactivate_node(dns_rbtdb_t *rbtdb, dns_rbtnode_t *node,
+		isc_rwlocktype_t treelocktype) {
+	isc_rwlocktype_t locktype = isc_rwlocktype_read;
+	nodelock_t *nodelock = &rbtdb->node_locks[node->locknum].lock;
+	bool maybe_cleanup = false;
+
+	POST(locktype);
+
+	NODE_LOCK(nodelock, locktype);
+
+	/*
+	 * Check if we can possibly cleanup the dead node.  If so, upgrade
+	 * the node lock below to perform the cleanup.
+	 */
+	if (!ISC_LIST_EMPTY(rbtdb->deadnodes[node->locknum]) &&
+	    treelocktype == isc_rwlocktype_write)
+	{
+		maybe_cleanup = true;
+	}
+
+	if (ISC_LINK_LINKED(node, deadlink) || maybe_cleanup) {
+		/*
+		 * Upgrade the lock and test if we still need to unlink.
+		 */
+		NODE_UNLOCK(nodelock, locktype);
+		locktype = isc_rwlocktype_write;
+		POST(locktype);
+		NODE_LOCK(nodelock, locktype);
+		if (ISC_LINK_LINKED(node, deadlink)) {
+			ISC_LIST_UNLINK(rbtdb->deadnodes[node->locknum], node,
+					deadlink);
+		}
+		if (maybe_cleanup) {
+			cleanup_dead_nodes(rbtdb, node->locknum);
+		}
+	}
+
+	new_reference(rbtdb, node, locktype);
+
+	NODE_UNLOCK(nodelock, locktype);
+}
+
+/*
+ * Caller must be holding the node lock; either the "strong", read or write
+ * lock.  Note that the lock must be held even when node references are
+ * atomically modified; in that case the decrement operation itself does not
+ * have to be protected, but we must avoid a race condition where multiple
+ * threads are decreasing the reference to zero simultaneously and at least
+ * one of them is going to free the node.
+ *
+ * This function returns true if and only if the node reference decreases
+ * to zero.
+ *
+ * NOTE: Decrementing the reference count of a node to zero does not mean it
+ * will be immediately freed.
+ */
+static bool
+decrement_reference(dns_rbtdb_t *rbtdb, dns_rbtnode_t *node,
+		    rbtdb_serial_t least_serial, isc_rwlocktype_t nlock,
+		    isc_rwlocktype_t tlock, bool pruning) {
+	isc_result_t result;
+	bool write_locked;
+	bool locked = tlock != isc_rwlocktype_none;
+	rbtdb_nodelock_t *nodelock;
+	int bucket = node->locknum;
+	bool no_reference = true;
+	uint_fast32_t refs;
+
+	nodelock = &rbtdb->node_locks[bucket];
+
+#define KEEP_NODE(n, r, l)                                  \
+	((n)->data != NULL || ((l) && (n)->down != NULL) || \
+	 (n) == (r)->origin_node || (n) == (r)->nsec3_origin_node)
+
+	/* Handle easy and typical case first. */
+	if (!node->dirty && KEEP_NODE(node, rbtdb, locked)) {
+		if (isc_refcount_decrement(&node->references) == 1) {
+			refs = isc_refcount_decrement(&nodelock->references);
+			INSIST(refs > 0);
+			return (true);
+		} else {
+			return (false);
+		}
+	}
+
+	/* Upgrade the lock? */
+	if (nlock == isc_rwlocktype_read) {
+		NODE_UNLOCK(&nodelock->lock, isc_rwlocktype_read);
+		NODE_LOCK(&nodelock->lock, isc_rwlocktype_write);
+	}
+
+	if (isc_refcount_decrement(&node->references) > 1) {
+		/* Restore the lock? */
+		if (nlock == isc_rwlocktype_read) {
+			NODE_DOWNGRADE(&nodelock->lock);
+		}
+		return (false);
+	}
+
+	if (node->dirty) {
+		if (IS_CACHE(rbtdb)) {
+			clean_cache_node(rbtdb, node);
+		} else {
+			if (least_serial == 0) {
+				/*
+				 * Caller doesn't know the least serial.
+				 * Get it.
+				 */
+				RBTDB_LOCK(&rbtdb->lock, isc_rwlocktype_read);
+				least_serial = rbtdb->least_serial;
+				RBTDB_UNLOCK(&rbtdb->lock, isc_rwlocktype_read);
+			}
+			clean_zone_node(rbtdb, node, least_serial);
+		}
+	}
+
+	/*
+	 * Attempt to switch to a write lock on the tree.  If this fails,
+	 * we will add this node to a linked list of nodes in this locking
+	 * bucket which we will free later.
+	 */
+	if (tlock != isc_rwlocktype_write) {
+		/*
+		 * Locking hierarchy notwithstanding, we don't need to free
+		 * the node lock before acquiring the tree write lock because
+		 * we only do a trylock.
+		 */
+		if (tlock == isc_rwlocktype_read) {
+			result = isc_rwlock_tryupgrade(&rbtdb->tree_lock);
+		} else {
+			result = isc_rwlock_trylock(&rbtdb->tree_lock,
+						    isc_rwlocktype_write);
+		}
+		RUNTIME_CHECK(result == ISC_R_SUCCESS ||
+			      result == ISC_R_LOCKBUSY);
+
+		write_locked = (result == ISC_R_SUCCESS);
+	} else {
+		write_locked = true;
+	}
+
+	refs = isc_refcount_decrement(&nodelock->references);
+	INSIST(refs > 0);
+
+	if (KEEP_NODE(node, rbtdb, locked || write_locked)) {
+		goto restore_locks;
+	}
+
+#undef KEEP_NODE
+
+	if (write_locked) {
+		/*
+		 * We can now delete the node.
+		 */
+
+		/*
+		 * If this node is the only one in the level it's in, deleting
+		 * this node may recursively make its parent the only node in
+		 * the parent level; if so, and if no one is currently using
+		 * the parent node, this is almost the only opportunity to
+		 * clean it up.  But the recursive cleanup is not that trivial
+		 * since the child and parent may be in different lock buckets,
+		 * which would cause a lock order reversal problem.  To avoid
+		 * the trouble, we'll dispatch a separate event for batch
+		 * cleaning.  We need to check whether we're deleting the node
+		 * as a result of pruning to avoid infinite dispatching.
+		 * Note: pruning happens only when a task has been set for the
+		 * rbtdb.  If the user of the rbtdb chooses not to set a task,
+		 * it's their responsibility to purge stale leaves (e.g. by
+		 * periodic walk-through).
+		 */
+		if (!pruning && is_leaf(node) && rbtdb->task != NULL) {
+			send_to_prune_tree(rbtdb, node, isc_rwlocktype_write);
+			no_reference = false;
+		} else {
+			delete_node(rbtdb, node);
+		}
+	} else {
+		INSIST(node->data == NULL);
+		if (!ISC_LINK_LINKED(node, deadlink)) {
+			ISC_LIST_APPEND(rbtdb->deadnodes[bucket], node,
+					deadlink);
+		}
+	}
+
+restore_locks:
+	/* Restore the lock? */
+	if (nlock == isc_rwlocktype_read) {
+		NODE_DOWNGRADE(&nodelock->lock);
+	}
+
+	/*
+	 * Relock a read lock, or unlock the write lock if no lock was held.
+	 */
+	if (tlock == isc_rwlocktype_none) {
+		if (write_locked) {
+			RWUNLOCK(&rbtdb->tree_lock, isc_rwlocktype_write);
+		}
+	}
+
+	if (tlock == isc_rwlocktype_read) {
+		if (write_locked) {
+			isc_rwlock_downgrade(&rbtdb->tree_lock);
+		}
+	}
+
+	return (no_reference);
+}
+
+/*
+ * Prune the tree by recursively cleaning-up single leaves.  In the worst
+ * case, the number of iteration is the number of tree levels, which is at
+ * most the maximum number of domain name labels, i.e, 127.  In practice, this
+ * should be much smaller (only a few times), and even the worst case would be
+ * acceptable for a single event.
+ */
+static void
+prune_tree(isc_task_t *task, isc_event_t *event) {
+	dns_rbtdb_t *rbtdb = event->ev_sender;
+	dns_rbtnode_t *node = event->ev_arg;
+	dns_rbtnode_t *parent;
+	unsigned int locknum;
+
+	UNUSED(task);
+
+	isc_event_free(&event);
+
+	RWLOCK(&rbtdb->tree_lock, isc_rwlocktype_write);
+	locknum = node->locknum;
+	NODE_LOCK(&rbtdb->node_locks[locknum].lock, isc_rwlocktype_write);
+	do {
+		parent = node->parent;
+		decrement_reference(rbtdb, node, 0, isc_rwlocktype_write,
+				    isc_rwlocktype_write, true);
+
+		if (parent != NULL && parent->down == NULL) {
+			/*
+			 * node was the only down child of the parent and has
+			 * just been removed.  We'll then need to examine the
+			 * parent.  Keep the lock if possible; otherwise,
+			 * release the old lock and acquire one for the parent.
+			 */
+			if (parent->locknum != locknum) {
+				NODE_UNLOCK(&rbtdb->node_locks[locknum].lock,
+					    isc_rwlocktype_write);
+				locknum = parent->locknum;
+				NODE_LOCK(&rbtdb->node_locks[locknum].lock,
+					  isc_rwlocktype_write);
+			}
+
+			/*
+			 * We need to gain a reference to the node before
+			 * decrementing it in the next iteration.
+			 */
+			if (ISC_LINK_LINKED(parent, deadlink)) {
+				ISC_LIST_UNLINK(rbtdb->deadnodes[locknum],
+						parent, deadlink);
+			}
+			new_reference(rbtdb, parent, isc_rwlocktype_write);
+		} else {
+			parent = NULL;
+		}
+
+		node = parent;
+	} while (node != NULL);
+	NODE_UNLOCK(&rbtdb->node_locks[locknum].lock, isc_rwlocktype_write);
+	RWUNLOCK(&rbtdb->tree_lock, isc_rwlocktype_write);
+
+	detach((dns_db_t **)&rbtdb);
+}
+
+static void
+make_least_version(dns_rbtdb_t *rbtdb, rbtdb_version_t *version,
+		   rbtdb_changedlist_t *cleanup_list) {
+	/*
+	 * Caller must be holding the database lock.
+	 */
+
+	rbtdb->least_serial = version->serial;
+	*cleanup_list = version->changed_list;
+	ISC_LIST_INIT(version->changed_list);
+}
+
+static void
+cleanup_nondirty(rbtdb_version_t *version, rbtdb_changedlist_t *cleanup_list) {
+	rbtdb_changed_t *changed, *next_changed;
+
+	/*
+	 * If the changed record is dirty, then
+	 * an update created multiple versions of
+	 * a given rdataset.  We keep this list
+	 * until we're the least open version, at
+	 * which point it's safe to get rid of any
+	 * older versions.
+	 *
+	 * If the changed record isn't dirty, then
+	 * we don't need it anymore since we're
+	 * committing and not rolling back.
+	 *
+	 * The caller must be holding the database lock.
+	 */
+	for (changed = HEAD(version->changed_list); changed != NULL;
+	     changed = next_changed)
+	{
+		next_changed = NEXT(changed, link);
+		if (!changed->dirty) {
+			UNLINK(version->changed_list, changed, link);
+			APPEND(*cleanup_list, changed, link);
+		}
+	}
+}
+
+static void
+iszonesecure(dns_db_t *db, rbtdb_version_t *version, dns_dbnode_t *origin) {
+	dns_rdataset_t keyset;
+	dns_rdataset_t nsecset, signsecset;
+	bool haszonekey = false;
+	bool hasnsec = false;
+	isc_result_t result;
+
+	dns_rdataset_init(&keyset);
+	result = dns_db_findrdataset(db, origin, version, dns_rdatatype_dnskey,
+				     0, 0, &keyset, NULL);
+	if (result == ISC_R_SUCCESS) {
+		result = dns_rdataset_first(&keyset);
+		while (result == ISC_R_SUCCESS) {
+			dns_rdata_t keyrdata = DNS_RDATA_INIT;
+			dns_rdataset_current(&keyset, &keyrdata);
+			if (dns_zonekey_iszonekey(&keyrdata)) {
+				haszonekey = true;
+				break;
+			}
+			result = dns_rdataset_next(&keyset);
+		}
+		dns_rdataset_disassociate(&keyset);
+	}
+	if (!haszonekey) {
+		version->secure = dns_db_insecure;
+		version->havensec3 = false;
+		return;
+	}
+
+	dns_rdataset_init(&nsecset);
+	dns_rdataset_init(&signsecset);
+	result = dns_db_findrdataset(db, origin, version, dns_rdatatype_nsec, 0,
+				     0, &nsecset, &signsecset);
+	if (result == ISC_R_SUCCESS) {
+		if (dns_rdataset_isassociated(&signsecset)) {
+			hasnsec = true;
+			dns_rdataset_disassociate(&signsecset);
+		}
+		dns_rdataset_disassociate(&nsecset);
+	}
+
+	setnsec3parameters(db, version);
+
+	/*
+	 * Do we have a valid NSEC/NSEC3 chain?
+	 */
+	if (version->havensec3 || hasnsec) {
+		version->secure = dns_db_secure;
+	} else {
+		version->secure = dns_db_insecure;
+	}
+}
+
+/*%<
+ * Walk the origin node looking for NSEC3PARAM records.
+ * Cache the nsec3 parameters.
+ */
+static void
+setnsec3parameters(dns_db_t *db, rbtdb_version_t *version) {
+	dns_rbtnode_t *node;
+	dns_rdata_nsec3param_t nsec3param;
+	dns_rdata_t rdata = DNS_RDATA_INIT;
+	isc_region_t region;
+	isc_result_t result;
+	rdatasetheader_t *header, *header_next;
+	unsigned char *raw; /* RDATASLAB */
+	unsigned int count, length;
+	dns_rbtdb_t *rbtdb = (dns_rbtdb_t *)db;
+
+	RWLOCK(&rbtdb->tree_lock, isc_rwlocktype_read);
+	version->havensec3 = false;
+	node = rbtdb->origin_node;
+	NODE_LOCK(&(rbtdb->node_locks[node->locknum].lock),
+		  isc_rwlocktype_read);
+	for (header = node->data; header != NULL; header = header_next) {
+		header_next = header->next;
+		do {
+			if (header->serial <= version->serial &&
+			    !IGNORE(header))
+			{
+				if (NONEXISTENT(header)) {
+					header = NULL;
+				}
+				break;
+			} else {
+				header = header->down;
+			}
+		} while (header != NULL);
+
+		if (header != NULL &&
+		    (header->type == dns_rdatatype_nsec3param))
+		{
+			/*
+			 * Find A NSEC3PARAM with a supported algorithm.
+			 */
+			raw = (unsigned char *)header + sizeof(*header);
+			count = raw[0] * 256 + raw[1]; /* count */
+			raw += DNS_RDATASET_COUNT + DNS_RDATASET_LENGTH;
+			while (count-- > 0U) {
+				length = raw[0] * 256 + raw[1];
+				raw += DNS_RDATASET_ORDER + DNS_RDATASET_LENGTH;
+				region.base = raw;
+				region.length = length;
+				raw += length;
+				dns_rdata_fromregion(
+					&rdata, rbtdb->common.rdclass,
+					dns_rdatatype_nsec3param, &region);
+				result = dns_rdata_tostruct(&rdata, &nsec3param,
+							    NULL);
+				INSIST(result == ISC_R_SUCCESS);
+				dns_rdata_reset(&rdata);
+
+				if (nsec3param.hash != DNS_NSEC3_UNKNOWNALG &&
+				    !dns_nsec3_supportedhash(nsec3param.hash))
+				{
+					continue;
+				}
+
+				if (nsec3param.flags != 0) {
+					continue;
+				}
+
+				memmove(version->salt, nsec3param.salt,
+					nsec3param.salt_length);
+				version->hash = nsec3param.hash;
+				version->salt_length = nsec3param.salt_length;
+				version->iterations = nsec3param.iterations;
+				version->flags = nsec3param.flags;
+				version->havensec3 = true;
+				/*
+				 * Look for a better algorithm than the
+				 * unknown test algorithm.
+				 */
+				if (nsec3param.hash != DNS_NSEC3_UNKNOWNALG) {
+					goto unlock;
+				}
+			}
+		}
+	}
+unlock:
+	NODE_UNLOCK(&(rbtdb->node_locks[node->locknum].lock),
+		    isc_rwlocktype_read);
+	RWUNLOCK(&rbtdb->tree_lock, isc_rwlocktype_read);
+}
+
+static void
+cleanup_dead_nodes_callback(isc_task_t *task, isc_event_t *event) {
+	dns_rbtdb_t *rbtdb = event->ev_arg;
+	bool again = false;
+	unsigned int locknum;
+
+	RWLOCK(&rbtdb->tree_lock, isc_rwlocktype_write);
+	for (locknum = 0; locknum < rbtdb->node_lock_count; locknum++) {
+		NODE_LOCK(&rbtdb->node_locks[locknum].lock,
+			  isc_rwlocktype_write);
+		cleanup_dead_nodes(rbtdb, locknum);
+		if (ISC_LIST_HEAD(rbtdb->deadnodes[locknum]) != NULL) {
+			again = true;
+		}
+		NODE_UNLOCK(&rbtdb->node_locks[locknum].lock,
+			    isc_rwlocktype_write);
+	}
+	RWUNLOCK(&rbtdb->tree_lock, isc_rwlocktype_write);
+	if (again) {
+		isc_task_send(task, &event);
+	} else {
+		isc_event_free(&event);
+		if (isc_refcount_decrement(&rbtdb->references) == 1) {
+			(void)isc_refcount_current(&rbtdb->references);
+			maybe_free_rbtdb(rbtdb);
+		}
+	}
+}
+
+static void
+closeversion(dns_db_t *db, dns_dbversion_t **versionp, bool commit) {
+	dns_rbtdb_t *rbtdb = (dns_rbtdb_t *)db;
+	rbtdb_version_t *version, *cleanup_version, *least_greater;
+	bool rollback = false;
+	rbtdb_changedlist_t cleanup_list;
+	rdatasetheaderlist_t resigned_list;
+	rbtdb_changed_t *changed, *next_changed;
+	rbtdb_serial_t serial, least_serial;
+	dns_rbtnode_t *rbtnode;
+	rdatasetheader_t *header;
+
+	REQUIRE(VALID_RBTDB(rbtdb));
+	version = (rbtdb_version_t *)*versionp;
+	INSIST(version->rbtdb == rbtdb);
+
+	cleanup_version = NULL;
+	ISC_LIST_INIT(cleanup_list);
+	ISC_LIST_INIT(resigned_list);
+
+	if (isc_refcount_decrement(&version->references) > 1) {
+		/* typical and easy case first */
+		if (commit) {
+			RBTDB_LOCK(&rbtdb->lock, isc_rwlocktype_read);
+			INSIST(!version->writer);
+			RBTDB_UNLOCK(&rbtdb->lock, isc_rwlocktype_read);
+		}
+		goto end;
+	}
+
+	/*
+	 * Update the zone's secure status in version before making
+	 * it the current version.
+	 */
+	if (version->writer && commit && !IS_CACHE(rbtdb)) {
+		iszonesecure(db, version, rbtdb->origin_node);
+	}
+
+	RBTDB_LOCK(&rbtdb->lock, isc_rwlocktype_write);
+	serial = version->serial;
+	if (version->writer) {
+		if (commit) {
+			unsigned cur_ref;
+			rbtdb_version_t *cur_version;
+
+			INSIST(version->commit_ok);
+			INSIST(version == rbtdb->future_version);
+			/*
+			 * The current version is going to be replaced.
+			 * Release the (likely last) reference to it from the
+			 * DB itself and unlink it from the open list.
+			 */
+			cur_version = rbtdb->current_version;
+			cur_ref = isc_refcount_decrement(
+				&cur_version->references);
+			if (cur_ref == 1) {
+				(void)isc_refcount_current(
+					&cur_version->references);
+				if (cur_version->serial == rbtdb->least_serial)
+				{
+					INSIST(EMPTY(
+						cur_version->changed_list));
+				}
+				UNLINK(rbtdb->open_versions, cur_version, link);
+			}
+			if (EMPTY(rbtdb->open_versions)) {
+				/*
+				 * We're going to become the least open
+				 * version.
+				 */
+				make_least_version(rbtdb, version,
+						   &cleanup_list);
+			} else {
+				/*
+				 * Some other open version is the
+				 * least version.  We can't cleanup
+				 * records that were changed in this
+				 * version because the older versions
+				 * may still be in use by an open
+				 * version.
+				 *
+				 * We can, however, discard the
+				 * changed records for things that
+				 * we've added that didn't exist in
+				 * prior versions.
+				 */
+				cleanup_nondirty(version, &cleanup_list);
+			}
+			/*
+			 * If the (soon to be former) current version
+			 * isn't being used by anyone, we can clean
+			 * it up.
+			 */
+			if (cur_ref == 1) {
+				cleanup_version = cur_version;
+				APPENDLIST(version->changed_list,
+					   cleanup_version->changed_list, link);
+			}
+			/*
+			 * Become the current version.
+			 */
+			version->writer = false;
+			rbtdb->current_version = version;
+			rbtdb->current_serial = version->serial;
+			rbtdb->future_version = NULL;
+
+			/*
+			 * Keep the current version in the open list, and
+			 * gain a reference for the DB itself (see the DB
+			 * creation function below).  This must be the only
+			 * case where we need to increment the counter from
+			 * zero and need to use isc_refcount_increment0().
+			 */
+			INSIST(isc_refcount_increment0(&version->references) ==
+			       0);
+			PREPEND(rbtdb->open_versions, rbtdb->current_version,
+				link);
+			resigned_list = version->resigned_list;
+			ISC_LIST_INIT(version->resigned_list);
+		} else {
+			/*
+			 * We're rolling back this transaction.
+			 */
+			cleanup_list = version->changed_list;
+			ISC_LIST_INIT(version->changed_list);
+			resigned_list = version->resigned_list;
+			ISC_LIST_INIT(version->resigned_list);
+			rollback = true;
+			cleanup_version = version;
+			rbtdb->future_version = NULL;
+		}
+	} else {
+		if (version != rbtdb->current_version) {
+			/*
+			 * There are no external or internal references
+			 * to this version and it can be cleaned up.
+			 */
+			cleanup_version = version;
+
+			/*
+			 * Find the version with the least serial
+			 * number greater than ours.
+			 */
+			least_greater = PREV(version, link);
+			if (least_greater == NULL) {
+				least_greater = rbtdb->current_version;
+			}
+
+			INSIST(version->serial < least_greater->serial);
+			/*
+			 * Is this the least open version?
+			 */
+			if (version->serial == rbtdb->least_serial) {
+				/*
+				 * Yes.  Install the new least open
+				 * version.
+				 */
+				make_least_version(rbtdb, least_greater,
+						   &cleanup_list);
+			} else {
+				/*
+				 * Add any unexecuted cleanups to
+				 * those of the least greater version.
+				 */
+				APPENDLIST(least_greater->changed_list,
+					   version->changed_list, link);
+			}
+		} else if (version->serial == rbtdb->least_serial) {
+			INSIST(EMPTY(version->changed_list));
+		}
+		UNLINK(rbtdb->open_versions, version, link);
+	}
+	least_serial = rbtdb->least_serial;
+	RBTDB_UNLOCK(&rbtdb->lock, isc_rwlocktype_write);
+
+	if (cleanup_version != NULL) {
+		INSIST(EMPTY(cleanup_version->changed_list));
+		free_gluetable(cleanup_version);
+		isc_rwlock_destroy(&cleanup_version->glue_rwlock);
+		isc_rwlock_destroy(&cleanup_version->rwlock);
+		isc_mem_put(rbtdb->common.mctx, cleanup_version,
+			    sizeof(*cleanup_version));
+	}
+
+	/*
+	 * Commit/rollback re-signed headers.
+	 */
+	for (header = HEAD(resigned_list); header != NULL;
+	     header = HEAD(resigned_list))
+	{
+		nodelock_t *lock;
+
+		ISC_LIST_UNLINK(resigned_list, header, link);
+
+		lock = &rbtdb->node_locks[header->node->locknum].lock;
+		NODE_LOCK(lock, isc_rwlocktype_write);
+		if (rollback && !IGNORE(header)) {
+			resign_insert(rbtdb, header->node->locknum, header);
+		}
+		decrement_reference(rbtdb, header->node, least_serial,
+				    isc_rwlocktype_write, isc_rwlocktype_none,
+				    false);
+		NODE_UNLOCK(lock, isc_rwlocktype_write);
+	}
+
+	if (!EMPTY(cleanup_list)) {
+		isc_event_t *event = NULL;
+		isc_rwlocktype_t tlock = isc_rwlocktype_none;
+
+		if (rbtdb->task != NULL) {
+			event = isc_event_allocate(rbtdb->common.mctx, NULL,
+						   DNS_EVENT_RBTDEADNODES,
+						   cleanup_dead_nodes_callback,
+						   rbtdb, sizeof(isc_event_t));
+		}
+		if (event == NULL) {
+			/*
+			 * We acquire a tree write lock here in order to make
+			 * sure that stale nodes will be removed in
+			 * decrement_reference().  If we didn't have the lock,
+			 * those nodes could miss the chance to be removed
+			 * until the server stops.  The write lock is
+			 * expensive, but this event should be rare enough
+			 * to justify the cost.
+			 */
+			RWLOCK(&rbtdb->tree_lock, isc_rwlocktype_write);
+			tlock = isc_rwlocktype_write;
+		}
+
+		for (changed = HEAD(cleanup_list); changed != NULL;
+		     changed = next_changed)
+		{
+			nodelock_t *lock;
+
+			next_changed = NEXT(changed, link);
+			rbtnode = changed->node;
+			lock = &rbtdb->node_locks[rbtnode->locknum].lock;
+
+			NODE_LOCK(lock, isc_rwlocktype_write);
+			/*
+			 * This is a good opportunity to purge any dead nodes,
+			 * so use it.
+			 */
+			if (event == NULL) {
+				cleanup_dead_nodes(rbtdb, rbtnode->locknum);
+			}
+
+			if (rollback) {
+				rollback_node(rbtnode, serial);
+			}
+			decrement_reference(rbtdb, rbtnode, least_serial,
+					    isc_rwlocktype_write, tlock, false);
+
+			NODE_UNLOCK(lock, isc_rwlocktype_write);
+
+			isc_mem_put(rbtdb->common.mctx, changed,
+				    sizeof(*changed));
+		}
+		if (event != NULL) {
+			isc_refcount_increment(&rbtdb->references);
+			isc_task_send(rbtdb->task, &event);
+		} else {
+			RWUNLOCK(&rbtdb->tree_lock, isc_rwlocktype_write);
+		}
+	}
+
+end:
+	*versionp = NULL;
+}
+
+/*
+ * Add the necessary magic for the wildcard name 'name'
+ * to be found in 'rbtdb'.
+ *
+ * In order for wildcard matching to work correctly in
+ * zone_find(), we must ensure that a node for the wildcarding
+ * level exists in the database, and has its 'find_callback'
+ * and 'wild' bits set.
+ *
+ * E.g. if the wildcard name is "*.sub.example." then we
+ * must ensure that "sub.example." exists and is marked as
+ * a wildcard level.
+ *
+ * tree_lock(write) must be held.
+ */
+static isc_result_t
+add_wildcard_magic(dns_rbtdb_t *rbtdb, const dns_name_t *name, bool lock) {
+	isc_result_t result;
+	dns_name_t foundname;
+	dns_offsets_t offsets;
+	unsigned int n;
+	dns_rbtnode_t *node = NULL;
+
+	dns_name_init(&foundname, offsets);
+	n = dns_name_countlabels(name);
+	INSIST(n >= 2);
+	n--;
+	dns_name_getlabelsequence(name, 1, n, &foundname);
+	result = dns_rbt_addnode(rbtdb->tree, &foundname, &node);
+	if (result != ISC_R_SUCCESS && result != ISC_R_EXISTS) {
+		return (result);
+	}
+	if (result == ISC_R_SUCCESS) {
+		node->nsec = DNS_RBT_NSEC_NORMAL;
+	}
+	node->find_callback = 1;
+	if (lock) {
+		NODE_LOCK(&rbtdb->node_locks[node->locknum].lock,
+			  isc_rwlocktype_write);
+	}
+	node->wild = 1;
+	if (lock) {
+		NODE_UNLOCK(&rbtdb->node_locks[node->locknum].lock,
+			    isc_rwlocktype_write);
+	}
+	return (ISC_R_SUCCESS);
+}
+
+/*
+ * tree_lock(write) must be held.
+ */
+static isc_result_t
+add_empty_wildcards(dns_rbtdb_t *rbtdb, const dns_name_t *name, bool lock) {
+	isc_result_t result;
+	dns_name_t foundname;
+	dns_offsets_t offsets;
+	unsigned int n, l, i;
+
+	dns_name_init(&foundname, offsets);
+	n = dns_name_countlabels(name);
+	l = dns_name_countlabels(&rbtdb->common.origin);
+	i = l + 1;
+	while (i < n) {
+		dns_rbtnode_t *node = NULL; /* dummy */
+		dns_name_getlabelsequence(name, n - i, i, &foundname);
+		if (dns_name_iswildcard(&foundname)) {
+			result = add_wildcard_magic(rbtdb, &foundname, lock);
+			if (result != ISC_R_SUCCESS) {
+				return (result);
+			}
+			result = dns_rbt_addnode(rbtdb->tree, &foundname,
+						 &node);
+			if (result != ISC_R_SUCCESS && result != ISC_R_EXISTS) {
+				return (result);
+			}
+			if (result == ISC_R_SUCCESS) {
+				node->nsec = DNS_RBT_NSEC_NORMAL;
+			}
+		}
+		i++;
+	}
+	return (ISC_R_SUCCESS);
+}
+
+static isc_result_t
+findnodeintree(dns_rbtdb_t *rbtdb, dns_rbt_t *tree, const dns_name_t *name,
+	       bool create, dns_dbnode_t **nodep) {
+	dns_rbtnode_t *node = NULL;
+	dns_name_t nodename;
+	isc_result_t result;
+	isc_rwlocktype_t locktype = isc_rwlocktype_read;
+
+	INSIST(tree == rbtdb->tree || tree == rbtdb->nsec3);
+
+	dns_name_init(&nodename, NULL);
+	RWLOCK(&rbtdb->tree_lock, locktype);
+	result = dns_rbt_findnode(tree, name, NULL, &node, NULL,
+				  DNS_RBTFIND_EMPTYDATA, NULL, NULL);
+	if (result != ISC_R_SUCCESS) {
+		RWUNLOCK(&rbtdb->tree_lock, locktype);
+		if (!create) {
+			if (result == DNS_R_PARTIALMATCH) {
+				result = ISC_R_NOTFOUND;
+			}
+			return (result);
+		}
+		/*
+		 * It would be nice to try to upgrade the lock instead of
+		 * unlocking then relocking.
+		 */
+		locktype = isc_rwlocktype_write;
+		RWLOCK(&rbtdb->tree_lock, locktype);
+		node = NULL;
+		result = dns_rbt_addnode(tree, name, &node);
+		if (result == ISC_R_SUCCESS) {
+			dns_rbt_namefromnode(node, &nodename);
+			node->locknum = node->hashval % rbtdb->node_lock_count;
+			if (tree == rbtdb->tree) {
+				add_empty_wildcards(rbtdb, name, true);
+
+				if (dns_name_iswildcard(name)) {
+					result = add_wildcard_magic(rbtdb, name,
+								    true);
+					if (result != ISC_R_SUCCESS) {
+						RWUNLOCK(&rbtdb->tree_lock,
+							 locktype);
+						return (result);
+					}
+				}
+			}
+			if (tree == rbtdb->nsec3) {
+				node->nsec = DNS_RBT_NSEC_NSEC3;
+			}
+		} else if (result != ISC_R_EXISTS) {
+			RWUNLOCK(&rbtdb->tree_lock, locktype);
+			return (result);
+		}
+	}
+
+	if (tree == rbtdb->nsec3) {
+		INSIST(node->nsec == DNS_RBT_NSEC_NSEC3);
+	}
+
+	reactivate_node(rbtdb, node, locktype);
+
+	RWUNLOCK(&rbtdb->tree_lock, locktype);
+
+	*nodep = (dns_dbnode_t *)node;
+
+	return (ISC_R_SUCCESS);
+}
+
+static isc_result_t
+findnode(dns_db_t *db, const dns_name_t *name, bool create,
+	 dns_dbnode_t **nodep) {
+	dns_rbtdb_t *rbtdb = (dns_rbtdb_t *)db;
+
+	REQUIRE(VALID_RBTDB(rbtdb));
+
+	return (findnodeintree(rbtdb, rbtdb->tree, name, create, nodep));
+}
+
+static isc_result_t
+findnsec3node(dns_db_t *db, const dns_name_t *name, bool create,
+	      dns_dbnode_t **nodep) {
+	dns_rbtdb_t *rbtdb = (dns_rbtdb_t *)db;
+
+	REQUIRE(VALID_RBTDB(rbtdb));
+
+	return (findnodeintree(rbtdb, rbtdb->nsec3, name, create, nodep));
+}
+
+static isc_result_t
+zone_zonecut_callback(dns_rbtnode_t *node, dns_name_t *name, void *arg) {
+	rbtdb_search_t *search = arg;
+	rdatasetheader_t *header, *header_next;
+	rdatasetheader_t *dname_header, *sigdname_header, *ns_header;
+	rdatasetheader_t *found;
+	isc_result_t result;
+	dns_rbtnode_t *onode;
+
+	/*
+	 * We only want to remember the topmost zone cut, since it's the one
+	 * that counts, so we'll just continue if we've already found a
+	 * zonecut.
+	 */
+	if (search->zonecut != NULL) {
+		return (DNS_R_CONTINUE);
+	}
+
+	found = NULL;
+	result = DNS_R_CONTINUE;
+	onode = search->rbtdb->origin_node;
+
+	NODE_LOCK(&(search->rbtdb->node_locks[node->locknum].lock),
+		  isc_rwlocktype_read);
+
+	/*
+	 * Look for an NS or DNAME rdataset active in our version.
+	 */
+	ns_header = NULL;
+	dname_header = NULL;
+	sigdname_header = NULL;
+	for (header = node->data; header != NULL; header = header_next) {
+		header_next = header->next;
+		if (header->type == dns_rdatatype_ns ||
+		    header->type == dns_rdatatype_dname ||
+		    header->type == RBTDB_RDATATYPE_SIGDNAME)
+		{
+			do {
+				if (header->serial <= search->serial &&
+				    !IGNORE(header))
+				{
+					/*
+					 * Is this a "this rdataset doesn't
+					 * exist" record?
+					 */
+					if (NONEXISTENT(header)) {
+						header = NULL;
+					}
+					break;
+				} else {
+					header = header->down;
+				}
+			} while (header != NULL);
+			if (header != NULL) {
+				if (header->type == dns_rdatatype_dname) {
+					dname_header = header;
+				} else if (header->type ==
+					   RBTDB_RDATATYPE_SIGDNAME)
+				{
+					sigdname_header = header;
+				} else if (node != onode ||
+					   IS_STUB(search->rbtdb))
+				{
+					/*
+					 * We've found an NS rdataset that
+					 * isn't at the origin node.  We check
+					 * that they're not at the origin node,
+					 * because otherwise we'd erroneously
+					 * treat the zone top as if it were
+					 * a delegation.
+					 */
+					ns_header = header;
+				}
+			}
+		}
+	}
+
+	/*
+	 * Did we find anything?
+	 */
+	if (!IS_CACHE(search->rbtdb) && !IS_STUB(search->rbtdb) &&
+	    ns_header != NULL)
+	{
+		/*
+		 * Note that NS has precedence over DNAME if both exist
+		 * in a zone.  Otherwise DNAME take precedence over NS.
+		 */
+		found = ns_header;
+		search->zonecut_sigrdataset = NULL;
+	} else if (dname_header != NULL) {
+		found = dname_header;
+		search->zonecut_sigrdataset = sigdname_header;
+	} else if (ns_header != NULL) {
+		found = ns_header;
+		search->zonecut_sigrdataset = NULL;
+	}
+
+	if (found != NULL) {
+		/*
+		 * We increment the reference count on node to ensure that
+		 * search->zonecut_rdataset will still be valid later.
+		 */
+		new_reference(search->rbtdb, node, isc_rwlocktype_read);
+		search->zonecut = node;
+		search->zonecut_rdataset = found;
+		search->need_cleanup = true;
+		/*
+		 * Since we've found a zonecut, anything beneath it is
+		 * glue and is not subject to wildcard matching, so we
+		 * may clear search->wild.
+		 */
+		search->wild = false;
+		if ((search->options & DNS_DBFIND_GLUEOK) == 0) {
+			/*
+			 * If the caller does not want to find glue, then
+			 * this is the best answer and the search should
+			 * stop now.
+			 */
+			result = DNS_R_PARTIALMATCH;
+		} else {
+			dns_name_t *zcname;
+
+			/*
+			 * The search will continue beneath the zone cut.
+			 * This may or may not be the best match.  In case it
+			 * is, we need to remember the node name.
+			 */
+			zcname = dns_fixedname_name(&search->zonecut_name);
+			dns_name_copy(name, zcname);
+			search->copy_name = true;
+		}
+	} else {
+		/*
+		 * There is no zonecut at this node which is active in this
+		 * version.
+		 *
+		 * If this is a "wild" node and the caller hasn't disabled
+		 * wildcard matching, remember that we've seen a wild node
+		 * in case we need to go searching for wildcard matches
+		 * later on.
+		 */
+		if (node->wild && (search->options & DNS_DBFIND_NOWILD) == 0) {
+			search->wild = true;
+		}
+	}
+
+	NODE_UNLOCK(&(search->rbtdb->node_locks[node->locknum].lock),
+		    isc_rwlocktype_read);
+
+	return (result);
+}
+
+static void
+bind_rdataset(dns_rbtdb_t *rbtdb, dns_rbtnode_t *node, rdatasetheader_t *header,
+	      isc_stdtime_t now, isc_rwlocktype_t locktype,
+	      dns_rdataset_t *rdataset) {
+	unsigned char *raw; /* RDATASLAB */
+	bool stale = STALE(header);
+	bool ancient = ANCIENT(header);
+
+	/*
+	 * Caller must be holding the node reader lock.
+	 * XXXJT: technically, we need a writer lock, since we'll increment
+	 * the header count below.  However, since the actual counter value
+	 * doesn't matter, we prioritize performance here.  (We may want to
+	 * use atomic increment when available).
+	 */
+
+	if (rdataset == NULL) {
+		return;
+	}
+
+	new_reference(rbtdb, node, locktype);
+
+	INSIST(rdataset->methods == NULL); /* We must be disassociated. */
+
+	/*
+	 * Mark header stale or ancient if the RRset is no longer active.
+	 */
+	if (!ACTIVE(header, now)) {
+		dns_ttl_t stale_ttl = header->rdh_ttl +
+				      STALE_TTL(header, rbtdb);
+		/*
+		 * If this data is in the stale window keep it and if
+		 * DNS_DBFIND_STALEOK is not set we tell the caller to
+		 * skip this record.  We skip the records with ZEROTTL
+		 * (these records should not be cached anyway).
+		 */
+
+		if (KEEPSTALE(rbtdb) && stale_ttl > now) {
+			stale = true;
+		} else {
+			/*
+			 * We are not keeping stale, or it is outside the
+			 * stale window. Mark ancient, i.e. ready for cleanup.
+			 */
+			ancient = true;
+		}
+	}
+
+	rdataset->methods = &rdataset_methods;
+	rdataset->rdclass = rbtdb->common.rdclass;
+	rdataset->type = RBTDB_RDATATYPE_BASE(header->type);
+	rdataset->covers = RBTDB_RDATATYPE_EXT(header->type);
+	rdataset->ttl = header->rdh_ttl - now;
+	rdataset->trust = header->trust;
+
+	if (NEGATIVE(header)) {
+		rdataset->attributes |= DNS_RDATASETATTR_NEGATIVE;
+	}
+	if (NXDOMAIN(header)) {
+		rdataset->attributes |= DNS_RDATASETATTR_NXDOMAIN;
+	}
+	if (OPTOUT(header)) {
+		rdataset->attributes |= DNS_RDATASETATTR_OPTOUT;
+	}
+	if (PREFETCH(header)) {
+		rdataset->attributes |= DNS_RDATASETATTR_PREFETCH;
+	}
+
+	if (stale && !ancient) {
+		dns_ttl_t stale_ttl = header->rdh_ttl +
+				      STALE_TTL(header, rbtdb);
+		if (stale_ttl > now) {
+			rdataset->ttl = stale_ttl - now;
+		} else {
+			rdataset->ttl = 0;
+		}
+		if (STALE_WINDOW(header)) {
+			rdataset->attributes |= DNS_RDATASETATTR_STALE_WINDOW;
+		}
+		rdataset->attributes |= DNS_RDATASETATTR_STALE;
+	} else if (IS_CACHE(rbtdb) && !ACTIVE(header, now)) {
+		rdataset->attributes |= DNS_RDATASETATTR_ANCIENT;
+		rdataset->ttl = header->rdh_ttl;
+	}
+
+	rdataset->private1 = rbtdb;
+	rdataset->private2 = node;
+	raw = (unsigned char *)header + sizeof(*header);
+	rdataset->private3 = raw;
+	rdataset->count = atomic_fetch_add_relaxed(&header->count, 1);
+	if (rdataset->count == UINT32_MAX) {
+		rdataset->count = 0;
+	}
+
+	/*
+	 * Reset iterator state.
+	 */
+	rdataset->privateuint4 = 0;
+	rdataset->private5 = NULL;
+
+	/*
+	 * Add noqname proof.
+	 */
+	rdataset->private6 = header->noqname;
+	if (rdataset->private6 != NULL) {
+		rdataset->attributes |= DNS_RDATASETATTR_NOQNAME;
+	}
+	rdataset->private7 = header->closest;
+	if (rdataset->private7 != NULL) {
+		rdataset->attributes |= DNS_RDATASETATTR_CLOSEST;
+	}
+
+	/*
+	 * Copy out re-signing information.
+	 */
+	if (RESIGN(header)) {
+		rdataset->attributes |= DNS_RDATASETATTR_RESIGN;
+		rdataset->resign = (header->resign << 1) | header->resign_lsb;
+	} else {
+		rdataset->resign = 0;
+	}
+}
+
+static isc_result_t
+setup_delegation(rbtdb_search_t *search, dns_dbnode_t **nodep,
+		 dns_name_t *foundname, dns_rdataset_t *rdataset,
+		 dns_rdataset_t *sigrdataset) {
+	dns_name_t *zcname;
+	rbtdb_rdatatype_t type;
+	dns_rbtnode_t *node;
+
+	REQUIRE(search != NULL);
+	REQUIRE(search->zonecut != NULL);
+	REQUIRE(search->zonecut_rdataset != NULL);
+
+	/*
+	 * The caller MUST NOT be holding any node locks.
+	 */
+
+	node = search->zonecut;
+	type = search->zonecut_rdataset->type;
+
+	/*
+	 * If we have to set foundname, we do it before anything else.
+	 * If we were to set foundname after we had set nodep or bound the
+	 * rdataset, then we'd have to undo that work if dns_name_copy()
+	 * failed.  By setting foundname first, there's nothing to undo if
+	 * we have trouble.
+	 */
+	if (foundname != NULL && search->copy_name) {
+		zcname = dns_fixedname_name(&search->zonecut_name);
+		dns_name_copy(zcname, foundname);
+	}
+	if (nodep != NULL) {
+		/*
+		 * Note that we don't have to increment the node's reference
+		 * count here because we're going to use the reference we
+		 * already have in the search block.
+		 */
+		*nodep = node;
+		search->need_cleanup = false;
+	}
+	if (rdataset != NULL) {
+		NODE_LOCK(&(search->rbtdb->node_locks[node->locknum].lock),
+			  isc_rwlocktype_read);
+		bind_rdataset(search->rbtdb, node, search->zonecut_rdataset,
+			      search->now, isc_rwlocktype_read, rdataset);
+		if (sigrdataset != NULL && search->zonecut_sigrdataset != NULL)
+		{
+			bind_rdataset(search->rbtdb, node,
+				      search->zonecut_sigrdataset, search->now,
+				      isc_rwlocktype_read, sigrdataset);
+		}
+		NODE_UNLOCK(&(search->rbtdb->node_locks[node->locknum].lock),
+			    isc_rwlocktype_read);
+	}
+
+	if (type == dns_rdatatype_dname) {
+		return (DNS_R_DNAME);
+	}
+	return (DNS_R_DELEGATION);
+}
+
+static bool
+valid_glue(rbtdb_search_t *search, dns_name_t *name, rbtdb_rdatatype_t type,
+	   dns_rbtnode_t *node) {
+	unsigned char *raw; /* RDATASLAB */
+	unsigned int count, size;
+	dns_name_t ns_name;
+	bool valid = false;
+	dns_offsets_t offsets;
+	isc_region_t region;
+	rdatasetheader_t *header;
+
+	/*
+	 * No additional locking is required.
+	 */
+
+	/*
+	 * Valid glue types are A, AAAA, A6.  NS is also a valid glue type
+	 * if it occurs at a zone cut, but is not valid below it.
+	 */
+	if (type == dns_rdatatype_ns) {
+		if (node != search->zonecut) {
+			return (false);
+		}
+	} else if (type != dns_rdatatype_a && type != dns_rdatatype_aaaa &&
+		   type != dns_rdatatype_a6)
+	{
+		return (false);
+	}
+
+	header = search->zonecut_rdataset;
+	raw = (unsigned char *)header + sizeof(*header);
+	count = raw[0] * 256 + raw[1];
+	raw += DNS_RDATASET_COUNT + DNS_RDATASET_LENGTH;
+
+	while (count > 0) {
+		count--;
+		size = raw[0] * 256 + raw[1];
+		raw += DNS_RDATASET_ORDER + DNS_RDATASET_LENGTH;
+		region.base = raw;
+		region.length = size;
+		raw += size;
+		/*
+		 * XXX Until we have rdata structures, we have no choice but
+		 * to directly access the rdata format.
+		 */
+		dns_name_init(&ns_name, offsets);
+		dns_name_fromregion(&ns_name, &region);
+		if (dns_name_compare(&ns_name, name) == 0) {
+			valid = true;
+			break;
+		}
+	}
+
+	return (valid);
+}
+
+static bool
+activeempty(rbtdb_search_t *search, dns_rbtnodechain_t *chain,
+	    const dns_name_t *name) {
+	dns_fixedname_t fnext;
+	dns_fixedname_t forigin;
+	dns_name_t *next;
+	dns_name_t *origin;
+	dns_name_t prefix;
+	dns_rbtdb_t *rbtdb;
+	dns_rbtnode_t *node;
+	isc_result_t result;
+	bool answer = false;
+	rdatasetheader_t *header;
+
+	rbtdb = search->rbtdb;
+
+	dns_name_init(&prefix, NULL);
+	next = dns_fixedname_initname(&fnext);
+	origin = dns_fixedname_initname(&forigin);
+
+	result = dns_rbtnodechain_next(chain, NULL, NULL);
+	while (result == ISC_R_SUCCESS || result == DNS_R_NEWORIGIN) {
+		node = NULL;
+		result = dns_rbtnodechain_current(chain, &prefix, origin,
+						  &node);
+		if (result != ISC_R_SUCCESS) {
+			break;
+		}
+		NODE_LOCK(&(rbtdb->node_locks[node->locknum].lock),
+			  isc_rwlocktype_read);
+		for (header = node->data; header != NULL; header = header->next)
+		{
+			if (header->serial <= search->serial &&
+			    !IGNORE(header) && EXISTS(header))
+			{
+				break;
+			}
+		}
+		NODE_UNLOCK(&(rbtdb->node_locks[node->locknum].lock),
+			    isc_rwlocktype_read);
+		if (header != NULL) {
+			break;
+		}
+		result = dns_rbtnodechain_next(chain, NULL, NULL);
+	}
+	if (result == ISC_R_SUCCESS) {
+		result = dns_name_concatenate(&prefix, origin, next, NULL);
+	}
+	if (result == ISC_R_SUCCESS && dns_name_issubdomain(next, name)) {
+		answer = true;
+	}
+	return (answer);
+}
+
+static bool
+activeemptynode(rbtdb_search_t *search, const dns_name_t *qname,
+		dns_name_t *wname) {
+	dns_fixedname_t fnext;
+	dns_fixedname_t forigin;
+	dns_fixedname_t fprev;
+	dns_name_t *next;
+	dns_name_t *origin;
+	dns_name_t *prev;
+	dns_name_t name;
+	dns_name_t rname;
+	dns_name_t tname;
+	dns_rbtdb_t *rbtdb;
+	dns_rbtnode_t *node;
+	dns_rbtnodechain_t chain;
+	bool check_next = true;
+	bool check_prev = true;
+	bool answer = false;
+	isc_result_t result;
+	rdatasetheader_t *header;
+	unsigned int n;
+
+	rbtdb = search->rbtdb;
+
+	dns_name_init(&name, NULL);
+	dns_name_init(&tname, NULL);
+	dns_name_init(&rname, NULL);
+	next = dns_fixedname_initname(&fnext);
+	prev = dns_fixedname_initname(&fprev);
+	origin = dns_fixedname_initname(&forigin);
+
+	/*
+	 * Find if qname is at or below a empty node.
+	 * Use our own copy of the chain.
+	 */
+
+	chain = search->chain;
+	do {
+		node = NULL;
+		result = dns_rbtnodechain_current(&chain, &name, origin, &node);
+		if (result != ISC_R_SUCCESS) {
+			break;
+		}
+		NODE_LOCK(&(rbtdb->node_locks[node->locknum].lock),
+			  isc_rwlocktype_read);
+		for (header = node->data; header != NULL; header = header->next)
+		{
+			if (header->serial <= search->serial &&
+			    !IGNORE(header) && EXISTS(header))
+			{
+				break;
+			}
+		}
+		NODE_UNLOCK(&(rbtdb->node_locks[node->locknum].lock),
+			    isc_rwlocktype_read);
+		if (header != NULL) {
+			break;
+		}
+		result = dns_rbtnodechain_prev(&chain, NULL, NULL);
+	} while (result == ISC_R_SUCCESS || result == DNS_R_NEWORIGIN);
+	if (result == ISC_R_SUCCESS) {
+		result = dns_name_concatenate(&name, origin, prev, NULL);
+	}
+	if (result != ISC_R_SUCCESS) {
+		check_prev = false;
+	}
+
+	result = dns_rbtnodechain_next(&chain, NULL, NULL);
+	while (result == ISC_R_SUCCESS || result == DNS_R_NEWORIGIN) {
+		node = NULL;
+		result = dns_rbtnodechain_current(&chain, &name, origin, &node);
+		if (result != ISC_R_SUCCESS) {
+			break;
+		}
+		NODE_LOCK(&(rbtdb->node_locks[node->locknum].lock),
+			  isc_rwlocktype_read);
+		for (header = node->data; header != NULL; header = header->next)
+		{
+			if (header->serial <= search->serial &&
+			    !IGNORE(header) && EXISTS(header))
+			{
+				break;
+			}
+		}
+		NODE_UNLOCK(&(rbtdb->node_locks[node->locknum].lock),
+			    isc_rwlocktype_read);
+		if (header != NULL) {
+			break;
+		}
+		result = dns_rbtnodechain_next(&chain, NULL, NULL);
+	}
+	if (result == ISC_R_SUCCESS) {
+		result = dns_name_concatenate(&name, origin, next, NULL);
+	}
+	if (result != ISC_R_SUCCESS) {
+		check_next = false;
+	}
+
+	dns_name_clone(qname, &rname);
+
+	/*
+	 * Remove the wildcard label to find the terminal name.
+	 */
+	n = dns_name_countlabels(wname);
+	dns_name_getlabelsequence(wname, 1, n - 1, &tname);
+
+	do {
+		if ((check_prev && dns_name_issubdomain(prev, &rname)) ||
+		    (check_next && dns_name_issubdomain(next, &rname)))
+		{
+			answer = true;
+			break;
+		}
+		/*
+		 * Remove the left hand label.
+		 */
+		n = dns_name_countlabels(&rname);
+		dns_name_getlabelsequence(&rname, 1, n - 1, &rname);
+	} while (!dns_name_equal(&rname, &tname));
+	return (answer);
+}
+
+static isc_result_t
+find_wildcard(rbtdb_search_t *search, dns_rbtnode_t **nodep,
+	      const dns_name_t *qname) {
+	unsigned int i, j;
+	dns_rbtnode_t *node, *level_node, *wnode;
+	rdatasetheader_t *header;
+	isc_result_t result = ISC_R_NOTFOUND;
+	dns_name_t name;
+	dns_name_t *wname;
+	dns_fixedname_t fwname;
+	dns_rbtdb_t *rbtdb;
+	bool done, wild, active;
+	dns_rbtnodechain_t wchain;
+
+	/*
+	 * Caller must be holding the tree lock and MUST NOT be holding
+	 * any node locks.
+	 */
+
+	/*
+	 * Examine each ancestor level.  If the level's wild bit
+	 * is set, then construct the corresponding wildcard name and
+	 * search for it.  If the wildcard node exists, and is active in
+	 * this version, we're done.  If not, then we next check to see
+	 * if the ancestor is active in this version.  If so, then there
+	 * can be no possible wildcard match and again we're done.  If not,
+	 * continue the search.
+	 */
+
+	rbtdb = search->rbtdb;
+	i = search->chain.level_matches;
+	done = false;
+	node = *nodep;
+	do {
+		NODE_LOCK(&(rbtdb->node_locks[node->locknum].lock),
+			  isc_rwlocktype_read);
+
+		/*
+		 * First we try to figure out if this node is active in
+		 * the search's version.  We do this now, even though we
+		 * may not need the information, because it simplifies the
+		 * locking and code flow.
+		 */
+		for (header = node->data; header != NULL; header = header->next)
+		{
+			if (header->serial <= search->serial &&
+			    !IGNORE(header) && EXISTS(header) &&
+			    !ANCIENT(header))
+			{
+				break;
+			}
+		}
+		if (header != NULL) {
+			active = true;
+		} else {
+			active = false;
+		}
+
+		if (node->wild) {
+			wild = true;
+		} else {
+			wild = false;
+		}
+
+		NODE_UNLOCK(&(rbtdb->node_locks[node->locknum].lock),
+			    isc_rwlocktype_read);
+
+		if (wild) {
+			/*
+			 * Construct the wildcard name for this level.
+			 */
+			dns_name_init(&name, NULL);
+			dns_rbt_namefromnode(node, &name);
+			wname = dns_fixedname_initname(&fwname);
+			result = dns_name_concatenate(dns_wildcardname, &name,
+						      wname, NULL);
+			j = i;
+			while (result == ISC_R_SUCCESS && j != 0) {
+				j--;
+				level_node = search->chain.levels[j];
+				dns_name_init(&name, NULL);
+				dns_rbt_namefromnode(level_node, &name);
+				result = dns_name_concatenate(wname, &name,
+							      wname, NULL);
+			}
+			if (result != ISC_R_SUCCESS) {
+				break;
+			}
+
+			wnode = NULL;
+			dns_rbtnodechain_init(&wchain);
+			result = dns_rbt_findnode(
+				rbtdb->tree, wname, NULL, &wnode, &wchain,
+				DNS_RBTFIND_EMPTYDATA, NULL, NULL);
+			if (result == ISC_R_SUCCESS) {
+				nodelock_t *lock;
+
+				/*
+				 * We have found the wildcard node.  If it
+				 * is active in the search's version, we're
+				 * done.
+				 */
+				lock = &rbtdb->node_locks[wnode->locknum].lock;
+				NODE_LOCK(lock, isc_rwlocktype_read);
+				for (header = wnode->data; header != NULL;
+				     header = header->next)
+				{
+					if (header->serial <= search->serial &&
+					    !IGNORE(header) && EXISTS(header) &&
+					    !ANCIENT(header))
+					{
+						break;
+					}
+				}
+				NODE_UNLOCK(lock, isc_rwlocktype_read);
+				if (header != NULL ||
+				    activeempty(search, &wchain, wname))
+				{
+					if (activeemptynode(search, qname,
+							    wname))
+					{
+						return (ISC_R_NOTFOUND);
+					}
+					/*
+					 * The wildcard node is active!
+					 *
+					 * Note: result is still ISC_R_SUCCESS
+					 * so we don't have to set it.
+					 */
+					*nodep = wnode;
+					break;
+				}
+			} else if (result != ISC_R_NOTFOUND &&
+				   result != DNS_R_PARTIALMATCH)
+			{
+				/*
+				 * An error has occurred.  Bail out.
+				 */
+				break;
+			}
+		}
+
+		if (active) {
+			/*
+			 * The level node is active.  Any wildcarding
+			 * present at higher levels has no
+			 * effect and we're done.
+			 */
+			result = ISC_R_NOTFOUND;
+			break;
+		}
+
+		if (i > 0) {
+			i--;
+			node = search->chain.levels[i];
+		} else {
+			done = true;
+		}
+	} while (!done);
+
+	return (result);
+}
+
+static bool
+matchparams(rdatasetheader_t *header, rbtdb_search_t *search) {
+	dns_rdata_t rdata = DNS_RDATA_INIT;
+	dns_rdata_nsec3_t nsec3;
+	unsigned char *raw; /* RDATASLAB */
+	unsigned int rdlen, count;
+	isc_region_t region;
+	isc_result_t result;
+
+	REQUIRE(header->type == dns_rdatatype_nsec3);
+
+	raw = (unsigned char *)header + sizeof(*header);
+	count = raw[0] * 256 + raw[1]; /* count */
+	raw += DNS_RDATASET_COUNT + DNS_RDATASET_LENGTH;
+
+	while (count-- > 0) {
+		rdlen = raw[0] * 256 + raw[1];
+		raw += DNS_RDATASET_ORDER + DNS_RDATASET_LENGTH;
+		region.base = raw;
+		region.length = rdlen;
+		dns_rdata_fromregion(&rdata, search->rbtdb->common.rdclass,
+				     dns_rdatatype_nsec3, &region);
+		raw += rdlen;
+		result = dns_rdata_tostruct(&rdata, &nsec3, NULL);
+		INSIST(result == ISC_R_SUCCESS);
+		if (nsec3.hash == search->rbtversion->hash &&
+		    nsec3.iterations == search->rbtversion->iterations &&
+		    nsec3.salt_length == search->rbtversion->salt_length &&
+		    memcmp(nsec3.salt, search->rbtversion->salt,
+			   nsec3.salt_length) == 0)
+		{
+			return (true);
+		}
+		dns_rdata_reset(&rdata);
+	}
+	return (false);
+}
+
+/*
+ * Find node of the NSEC/NSEC3 record that is 'name'.
+ */
+static isc_result_t
+previous_closest_nsec(dns_rdatatype_t type, rbtdb_search_t *search,
+		      dns_name_t *name, dns_name_t *origin,
+		      dns_rbtnode_t **nodep, dns_rbtnodechain_t *nsecchain,
+		      bool *firstp) {
+	dns_fixedname_t ftarget;
+	dns_name_t *target;
+	dns_rbtnode_t *nsecnode;
+	isc_result_t result;
+
+	REQUIRE(nodep != NULL && *nodep == NULL);
+	REQUIRE(type == dns_rdatatype_nsec3 || firstp != NULL);
+
+	if (type == dns_rdatatype_nsec3) {
+		result = dns_rbtnodechain_prev(&search->chain, NULL, NULL);
+		if (result != ISC_R_SUCCESS && result != DNS_R_NEWORIGIN) {
+			return (result);
+		}
+		result = dns_rbtnodechain_current(&search->chain, name, origin,
+						  nodep);
+		return (result);
+	}
+
+	target = dns_fixedname_initname(&ftarget);
+
+	for (;;) {
+		if (*firstp) {
+			/*
+			 * Construct the name of the second node to check.
+			 * It is the first node sought in the NSEC tree.
+			 */
+			*firstp = false;
+			dns_rbtnodechain_init(nsecchain);
+			result = dns_name_concatenate(name, origin, target,
+						      NULL);
+			if (result != ISC_R_SUCCESS) {
+				return (result);
+			}
+			nsecnode = NULL;
+			result = dns_rbt_findnode(
+				search->rbtdb->nsec, target, NULL, &nsecnode,
+				nsecchain, DNS_RBTFIND_EMPTYDATA, NULL, NULL);
+			if (result == ISC_R_SUCCESS) {
+				/*
+				 * Since this was the first loop, finding the
+				 * name in the NSEC tree implies that the first
+				 * node checked in the main tree had an
+				 * unacceptable NSEC record.
+				 * Try the previous node in the NSEC tree.
+				 */
+				result = dns_rbtnodechain_prev(nsecchain, name,
+							       origin);
+				if (result == DNS_R_NEWORIGIN) {
+					result = ISC_R_SUCCESS;
+				}
+			} else if (result == ISC_R_NOTFOUND ||
+				   result == DNS_R_PARTIALMATCH)
+			{
+				result = dns_rbtnodechain_current(
+					nsecchain, name, origin, NULL);
+				if (result == ISC_R_NOTFOUND) {
+					result = ISC_R_NOMORE;
+				}
+			}
+		} else {
+			/*
+			 * This is a second or later trip through the auxiliary
+			 * tree for the name of a third or earlier NSEC node in
+			 * the main tree.  Previous trips through the NSEC tree
+			 * must have found nodes in the main tree with NSEC
+			 * records.  Perhaps they lacked signature records.
+			 */
+			result = dns_rbtnodechain_prev(nsecchain, name, origin);
+			if (result == DNS_R_NEWORIGIN) {
+				result = ISC_R_SUCCESS;
+			}
+		}
+		if (result != ISC_R_SUCCESS) {
+			return (result);
+		}
+
+		/*
+		 * Construct the name to seek in the main tree.
+		 */
+		result = dns_name_concatenate(name, origin, target, NULL);
+		if (result != ISC_R_SUCCESS) {
+			return (result);
+		}
+
+		*nodep = NULL;
+		result = dns_rbt_findnode(search->rbtdb->tree, target, NULL,
+					  nodep, &search->chain,
+					  DNS_RBTFIND_EMPTYDATA, NULL, NULL);
+		if (result == ISC_R_SUCCESS) {
+			return (result);
+		}
+
+		/*
+		 * There should always be a node in the main tree with the
+		 * same name as the node in the auxiliary NSEC tree, except for
+		 * nodes in the auxiliary tree that are awaiting deletion.
+		 */
+		if (result != DNS_R_PARTIALMATCH && result != ISC_R_NOTFOUND) {
+			isc_log_write(dns_lctx, DNS_LOGCATEGORY_DATABASE,
+				      DNS_LOGMODULE_CACHE, ISC_LOG_ERROR,
+				      "previous_closest_nsec(): %s",
+				      isc_result_totext(result));
+			return (DNS_R_BADDB);
+		}
+	}
+}
+
+/*
+ * Find the NSEC/NSEC3 which is or before the current point on the
+ * search chain.  For NSEC3 records only NSEC3 records that match the
+ * current NSEC3PARAM record are considered.
+ */
+static isc_result_t
+find_closest_nsec(rbtdb_search_t *search, dns_dbnode_t **nodep,
+		  dns_name_t *foundname, dns_rdataset_t *rdataset,
+		  dns_rdataset_t *sigrdataset, dns_rbt_t *tree,
+		  dns_db_secure_t secure) {
+	dns_rbtnode_t *node, *prevnode;
+	rdatasetheader_t *header, *header_next, *found, *foundsig;
+	dns_rbtnodechain_t nsecchain;
+	bool empty_node;
+	isc_result_t result;
+	dns_fixedname_t fname, forigin;
+	dns_name_t *name, *origin;
+	dns_rdatatype_t type;
+	rbtdb_rdatatype_t sigtype;
+	bool wraps;
+	bool first = true;
+	bool need_sig = (secure == dns_db_secure);
+
+	if (tree == search->rbtdb->nsec3) {
+		type = dns_rdatatype_nsec3;
+		sigtype = RBTDB_RDATATYPE_SIGNSEC3;
+		wraps = true;
+	} else {
+		type = dns_rdatatype_nsec;
+		sigtype = RBTDB_RDATATYPE_SIGNSEC;
+		wraps = false;
+	}
+
+	/*
+	 * Use the auxiliary tree only starting with the second node in the
+	 * hope that the original node will be right much of the time.
+	 */
+	name = dns_fixedname_initname(&fname);
+	origin = dns_fixedname_initname(&forigin);
+again:
+	node = NULL;
+	prevnode = NULL;
+	result = dns_rbtnodechain_current(&search->chain, name, origin, &node);
+	if (result != ISC_R_SUCCESS) {
+		return (result);
+	}
+	do {
+		NODE_LOCK(&(search->rbtdb->node_locks[node->locknum].lock),
+			  isc_rwlocktype_read);
+		found = NULL;
+		foundsig = NULL;
+		empty_node = true;
+		for (header = node->data; header != NULL; header = header_next)
+		{
+			header_next = header->next;
+			/*
+			 * Look for an active, extant NSEC or RRSIG NSEC.
+			 */
+			do {
+				if (header->serial <= search->serial &&
+				    !IGNORE(header))
+				{
+					/*
+					 * Is this a "this rdataset doesn't
+					 * exist" record?
+					 */
+					if (NONEXISTENT(header)) {
+						header = NULL;
+					}
+					break;
+				} else {
+					header = header->down;
+				}
+			} while (header != NULL);
+			if (header != NULL) {
+				/*
+				 * We now know that there is at least one
+				 * active rdataset at this node.
+				 */
+				empty_node = false;
+				if (header->type == type) {
+					found = header;
+					if (foundsig != NULL) {
+						break;
+					}
+				} else if (header->type == sigtype) {
+					foundsig = header;
+					if (found != NULL) {
+						break;
+					}
+				}
+			}
+		}
+		if (!empty_node) {
+			if (found != NULL && search->rbtversion->havensec3 &&
+			    found->type == dns_rdatatype_nsec3 &&
+			    !matchparams(found, search))
+			{
+				empty_node = true;
+				found = NULL;
+				foundsig = NULL;
+				result = previous_closest_nsec(
+					type, search, name, origin, &prevnode,
+					NULL, NULL);
+			} else if (found != NULL &&
+				   (foundsig != NULL || !need_sig))
+			{
+				/*
+				 * We've found the right NSEC/NSEC3 record.
+				 *
+				 * Note: for this to really be the right
+				 * NSEC record, it's essential that the NSEC
+				 * records of any nodes obscured by a zone
+				 * cut have been removed; we assume this is
+				 * the case.
+				 */
+				result = dns_name_concatenate(name, origin,
+							      foundname, NULL);
+				if (result == ISC_R_SUCCESS) {
+					if (nodep != NULL) {
+						new_reference(
+							search->rbtdb, node,
+							isc_rwlocktype_read);
+						*nodep = node;
+					}
+					bind_rdataset(search->rbtdb, node,
+						      found, search->now,
+						      isc_rwlocktype_read,
+						      rdataset);
+					if (foundsig != NULL) {
+						bind_rdataset(
+							search->rbtdb, node,
+							foundsig, search->now,
+							isc_rwlocktype_read,
+							sigrdataset);
+					}
+				}
+			} else if (found == NULL && foundsig == NULL) {
+				/*
+				 * This node is active, but has no NSEC or
+				 * RRSIG NSEC.  That means it's glue or
+				 * other obscured zone data that isn't
+				 * relevant for our search.  Treat the
+				 * node as if it were empty and keep looking.
+				 */
+				empty_node = true;
+				result = previous_closest_nsec(
+					type, search, name, origin, &prevnode,
+					&nsecchain, &first);
+			} else {
+				/*
+				 * We found an active node, but either the
+				 * NSEC or the RRSIG NSEC is missing.  This
+				 * shouldn't happen.
+				 */
+				result = DNS_R_BADDB;
+			}
+		} else {
+			/*
+			 * This node isn't active.  We've got to keep
+			 * looking.
+			 */
+			result = previous_closest_nsec(type, search, name,
+						       origin, &prevnode,
+						       &nsecchain, &first);
+		}
+		NODE_UNLOCK(&(search->rbtdb->node_locks[node->locknum].lock),
+			    isc_rwlocktype_read);
+		node = prevnode;
+		prevnode = NULL;
+	} while (empty_node && result == ISC_R_SUCCESS);
+
+	if (!first) {
+		dns_rbtnodechain_invalidate(&nsecchain);
+	}
+
+	if (result == ISC_R_NOMORE && wraps) {
+		result = dns_rbtnodechain_last(&search->chain, tree, NULL,
+					       NULL);
+		if (result == ISC_R_SUCCESS || result == DNS_R_NEWORIGIN) {
+			wraps = false;
+			goto again;
+		}
+	}
+
+	/*
+	 * If the result is ISC_R_NOMORE, then we got to the beginning of
+	 * the database and didn't find a NSEC record.  This shouldn't
+	 * happen.
+	 */
+	if (result == ISC_R_NOMORE) {
+		result = DNS_R_BADDB;
+	}
+
+	return (result);
+}
+
+static isc_result_t
+zone_find(dns_db_t *db, const 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_rbtnode_t *node = NULL;
+	isc_result_t result;
+	rbtdb_search_t search;
+	bool cname_ok = true;
+	bool close_version = false;
+	bool maybe_zonecut = false;
+	bool at_zonecut = false;
+	bool wild;
+	bool empty_node;
+	rdatasetheader_t *header, *header_next, *found, *nsecheader;
+	rdatasetheader_t *foundsig, *cnamesig, *nsecsig;
+	rbtdb_rdatatype_t sigtype;
+	bool active;
+	nodelock_t *lock;
+	dns_rbt_t *tree;
+
+	search.rbtdb = (dns_rbtdb_t *)db;
+
+	REQUIRE(VALID_RBTDB(search.rbtdb));
+	INSIST(version == NULL ||
+	       ((rbtdb_version_t *)version)->rbtdb == (dns_rbtdb_t *)db);
+
+	/*
+	 * We don't care about 'now'.
+	 */
+	UNUSED(now);
+
+	/*
+	 * If the caller didn't supply a version, attach to the current
+	 * version.
+	 */
+	if (version == NULL) {
+		currentversion(db, &version);
+		close_version = true;
+	}
+
+	search.rbtversion = version;
+	search.serial = search.rbtversion->serial;
+	search.options = options;
+	search.copy_name = false;
+	search.need_cleanup = false;
+	search.wild = false;
+	search.zonecut = NULL;
+	dns_fixedname_init(&search.zonecut_name);
+	dns_rbtnodechain_init(&search.chain);
+	search.now = 0;
+
+	/*
+	 * 'wild' will be true iff. we've matched a wildcard.
+	 */
+	wild = false;
+
+	RWLOCK(&search.rbtdb->tree_lock, isc_rwlocktype_read);
+
+	/*
+	 * Search down from the root of the tree.  If, while going down, we
+	 * encounter a callback node, zone_zonecut_callback() will search the
+	 * rdatasets at the zone cut for active DNAME or NS rdatasets.
+	 */
+	tree = (options & DNS_DBFIND_FORCENSEC3) != 0 ? search.rbtdb->nsec3
+						      : search.rbtdb->tree;
+	result = dns_rbt_findnode(tree, name, foundname, &node, &search.chain,
+				  DNS_RBTFIND_EMPTYDATA, zone_zonecut_callback,
+				  &search);
+
+	if (result == DNS_R_PARTIALMATCH) {
+	partial_match:
+		if (search.zonecut != NULL) {
+			result = setup_delegation(&search, nodep, foundname,
+						  rdataset, sigrdataset);
+			goto tree_exit;
+		}
+
+		if (search.wild) {
+			/*
+			 * At least one of the levels in the search chain
+			 * potentially has a wildcard.  For each such level,
+			 * we must see if there's a matching wildcard active
+			 * in the current version.
+			 */
+			result = find_wildcard(&search, &node, name);
+			if (result == ISC_R_SUCCESS) {
+				dns_name_copy(name, foundname);
+				wild = true;
+				goto found;
+			} else if (result != ISC_R_NOTFOUND) {
+				goto tree_exit;
+			}
+		}
+
+		active = false;
+		if ((options & DNS_DBFIND_FORCENSEC3) == 0) {
+			/*
+			 * The NSEC3 tree won't have empty nodes,
+			 * so it isn't necessary to check for them.
+			 */
+			dns_rbtnodechain_t chain = search.chain;
+			active = activeempty(&search, &chain, name);
+		}
+
+		/*
+		 * If we're here, then the name does not exist, is not
+		 * beneath a zonecut, and there's no matching wildcard.
+		 */
+		if ((search.rbtversion->secure == dns_db_secure &&
+		     !search.rbtversion->havensec3) ||
+		    (search.options & DNS_DBFIND_FORCENSEC) != 0 ||
+		    (search.options & DNS_DBFIND_FORCENSEC3) != 0)
+		{
+			result = find_closest_nsec(&search, nodep, foundname,
+						   rdataset, sigrdataset, tree,
+						   search.rbtversion->secure);
+			if (result == ISC_R_SUCCESS) {
+				result = active ? DNS_R_EMPTYNAME
+						: DNS_R_NXDOMAIN;
+			}
+		} else {
+			result = active ? DNS_R_EMPTYNAME : DNS_R_NXDOMAIN;
+		}
+		goto tree_exit;
+	} else if (result != ISC_R_SUCCESS) {
+		goto tree_exit;
+	}
+
+found:
+	/*
+	 * We have found a node whose name is the desired name, or we
+	 * have matched a wildcard.
+	 */
+
+	if (search.zonecut != NULL) {
+		/*
+		 * If we're beneath a zone cut, we don't want to look for
+		 * CNAMEs because they're not legitimate zone glue.
+		 */
+		cname_ok = false;
+	} else {
+		/*
+		 * The node may be a zone cut itself.  If it might be one,
+		 * make sure we check for it later.
+		 *
+		 * DS records live above the zone cut in ordinary zone so
+		 * we want to ignore any referral.
+		 *
+		 * Stub zones don't have anything "above" the delegation so
+		 * we always return a referral.
+		 */
+		if (node->find_callback &&
+		    ((node != search.rbtdb->origin_node &&
+		      !dns_rdatatype_atparent(type)) ||
+		     IS_STUB(search.rbtdb)))
+		{
+			maybe_zonecut = true;
+		}
+	}
+
+	/*
+	 * Certain DNSSEC types are not subject to CNAME matching
+	 * (RFC4035, section 2.5 and RFC3007).
+	 *
+	 * We don't check for RRSIG, because we don't store RRSIG records
+	 * directly.
+	 */
+	if (type == dns_rdatatype_key || type == dns_rdatatype_nsec) {
+		cname_ok = false;
+	}
+
+	/*
+	 * We now go looking for rdata...
+	 */
+
+	lock = &search.rbtdb->node_locks[node->locknum].lock;
+	NODE_LOCK(lock, isc_rwlocktype_read);
+
+	found = NULL;
+	foundsig = NULL;
+	sigtype = RBTDB_RDATATYPE_VALUE(dns_rdatatype_rrsig, type);
+	nsecheader = NULL;
+	nsecsig = NULL;
+	cnamesig = NULL;
+	empty_node = true;
+	for (header = node->data; header != NULL; header = header_next) {
+		header_next = header->next;
+		/*
+		 * Look for an active, extant rdataset.
+		 */
+		do {
+			if (header->serial <= search.serial && !IGNORE(header))
+			{
+				/*
+				 * Is this a "this rdataset doesn't
+				 * exist" record?
+				 */
+				if (NONEXISTENT(header)) {
+					header = NULL;
+				}
+				break;
+			} else {
+				header = header->down;
+			}
+		} while (header != NULL);
+		if (header != NULL) {
+			/*
+			 * We now know that there is at least one active
+			 * rdataset at this node.
+			 */
+			empty_node = false;
+
+			/*
+			 * Do special zone cut handling, if requested.
+			 */
+			if (maybe_zonecut && header->type == dns_rdatatype_ns) {
+				/*
+				 * We increment the reference count on node to
+				 * ensure that search->zonecut_rdataset will
+				 * still be valid later.
+				 */
+				new_reference(search.rbtdb, node,
+					      isc_rwlocktype_read);
+				search.zonecut = node;
+				search.zonecut_rdataset = header;
+				search.zonecut_sigrdataset = NULL;
+				search.need_cleanup = true;
+				maybe_zonecut = false;
+				at_zonecut = true;
+				/*
+				 * It is not clear if KEY should still be
+				 * allowed at the parent side of the zone
+				 * cut or not.  It is needed for RFC3007
+				 * validated updates.
+				 */
+				if ((search.options & DNS_DBFIND_GLUEOK) == 0 &&
+				    type != dns_rdatatype_nsec &&
+				    type != dns_rdatatype_key)
+				{
+					/*
+					 * Glue is not OK, but any answer we
+					 * could return would be glue.  Return
+					 * the delegation.
+					 */
+					found = NULL;
+					break;
+				}
+				if (found != NULL && foundsig != NULL) {
+					break;
+				}
+			}
+
+			/*
+			 * If the NSEC3 record doesn't match the chain
+			 * we are using behave as if it isn't here.
+			 */
+			if (header->type == dns_rdatatype_nsec3 &&
+			    !matchparams(header, &search))
+			{
+				NODE_UNLOCK(lock, isc_rwlocktype_read);
+				goto partial_match;
+			}
+			/*
+			 * If we found a type we were looking for,
+			 * remember it.
+			 */
+			if (header->type == type || type == dns_rdatatype_any ||
+			    (header->type == dns_rdatatype_cname && cname_ok))
+			{
+				/*
+				 * We've found the answer!
+				 */
+				found = header;
+				if (header->type == dns_rdatatype_cname &&
+				    cname_ok)
+				{
+					/*
+					 * We may be finding a CNAME instead
+					 * of the desired type.
+					 *
+					 * If we've already got the CNAME RRSIG,
+					 * use it, otherwise change sigtype
+					 * so that we find it.
+					 */
+					if (cnamesig != NULL) {
+						foundsig = cnamesig;
+					} else {
+						sigtype =
+							RBTDB_RDATATYPE_SIGCNAME;
+					}
+				}
+				/*
+				 * If we've got all we need, end the search.
+				 */
+				if (!maybe_zonecut && foundsig != NULL) {
+					break;
+				}
+			} else if (header->type == sigtype) {
+				/*
+				 * We've found the RRSIG rdataset for our
+				 * target type.  Remember it.
+				 */
+				foundsig = header;
+				/*
+				 * If we've got all we need, end the search.
+				 */
+				if (!maybe_zonecut && found != NULL) {
+					break;
+				}
+			} else if (header->type == dns_rdatatype_nsec &&
+				   !search.rbtversion->havensec3)
+			{
+				/*
+				 * Remember a NSEC rdataset even if we're
+				 * not specifically looking for it, because
+				 * we might need it later.
+				 */
+				nsecheader = header;
+			} else if (header->type == RBTDB_RDATATYPE_SIGNSEC &&
+				   !search.rbtversion->havensec3)
+			{
+				/*
+				 * If we need the NSEC rdataset, we'll also
+				 * need its signature.
+				 */
+				nsecsig = header;
+			} else if (cname_ok &&
+				   header->type == RBTDB_RDATATYPE_SIGCNAME)
+			{
+				/*
+				 * If we get a CNAME match, we'll also need
+				 * its signature.
+				 */
+				cnamesig = header;
+			}
+		}
+	}
+
+	if (empty_node) {
+		/*
+		 * We have an exact match for the name, but there are no
+		 * active rdatasets in the desired version.  That means that
+		 * this node doesn't exist in the desired version, and that
+		 * we really have a partial match.
+		 */
+		if (!wild) {
+			NODE_UNLOCK(lock, isc_rwlocktype_read);
+			goto partial_match;
+		}
+	}
+
+	/*
+	 * If we didn't find what we were looking for...
+	 */
+	if (found == NULL) {
+		if (search.zonecut != NULL) {
+			/*
+			 * We were trying to find glue at a node beneath a
+			 * zone cut, but didn't.
+			 *
+			 * Return the delegation.
+			 */
+			NODE_UNLOCK(lock, isc_rwlocktype_read);
+			result = setup_delegation(&search, nodep, foundname,
+						  rdataset, sigrdataset);
+			goto tree_exit;
+		}
+		/*
+		 * The desired type doesn't exist.
+		 */
+		result = DNS_R_NXRRSET;
+		if (search.rbtversion->secure == dns_db_secure &&
+		    !search.rbtversion->havensec3 &&
+		    (nsecheader == NULL || nsecsig == NULL))
+		{
+			/*
+			 * The zone is secure but there's no NSEC,
+			 * or the NSEC has no signature!
+			 */
+			if (!wild) {
+				result = DNS_R_BADDB;
+				goto node_exit;
+			}
+
+			NODE_UNLOCK(lock, isc_rwlocktype_read);
+			result = find_closest_nsec(&search, nodep, foundname,
+						   rdataset, sigrdataset,
+						   search.rbtdb->tree,
+						   search.rbtversion->secure);
+			if (result == ISC_R_SUCCESS) {
+				result = DNS_R_EMPTYWILD;
+			}
+			goto tree_exit;
+		}
+		if ((search.options & DNS_DBFIND_FORCENSEC) != 0 &&
+		    nsecheader == NULL)
+		{
+			/*
+			 * There's no NSEC record, and we were told
+			 * to find one.
+			 */
+			result = DNS_R_BADDB;
+			goto node_exit;
+		}
+		if (nodep != NULL) {
+			new_reference(search.rbtdb, node, isc_rwlocktype_read);
+			*nodep = node;
+		}
+		if ((search.rbtversion->secure == dns_db_secure &&
+		     !search.rbtversion->havensec3) ||
+		    (search.options & DNS_DBFIND_FORCENSEC) != 0)
+		{
+			bind_rdataset(search.rbtdb, node, nsecheader, 0,
+				      isc_rwlocktype_read, rdataset);
+			if (nsecsig != NULL) {
+				bind_rdataset(search.rbtdb, node, nsecsig, 0,
+					      isc_rwlocktype_read, sigrdataset);
+			}
+		}
+		if (wild) {
+			foundname->attributes |= DNS_NAMEATTR_WILDCARD;
+		}
+		goto node_exit;
+	}
+
+	/*
+	 * We found what we were looking for, or we found a CNAME.
+	 */
+
+	if (type != found->type && type != dns_rdatatype_any &&
+	    found->type == dns_rdatatype_cname)
+	{
+		/*
+		 * We weren't doing an ANY query and we found a CNAME instead
+		 * of the type we were looking for, so we need to indicate
+		 * that result to the caller.
+		 */
+		result = DNS_R_CNAME;
+	} else if (search.zonecut != NULL) {
+		/*
+		 * If we're beneath a zone cut, we must indicate that the
+		 * result is glue, unless we're actually at the zone cut
+		 * and the type is NSEC or KEY.
+		 */
+		if (search.zonecut == node) {
+			/*
+			 * It is not clear if KEY should still be
+			 * allowed at the parent side of the zone
+			 * cut or not.  It is needed for RFC3007
+			 * validated updates.
+			 */
+			if (type == dns_rdatatype_nsec ||
+			    type == dns_rdatatype_nsec3 ||
+			    type == dns_rdatatype_key)
+			{
+				result = ISC_R_SUCCESS;
+			} else if (type == dns_rdatatype_any) {
+				result = DNS_R_ZONECUT;
+			} else {
+				result = DNS_R_GLUE;
+			}
+		} else {
+			result = DNS_R_GLUE;
+		}
+		/*
+		 * We might have found data that isn't glue, but was occluded
+		 * by a dynamic update.  If the caller cares about this, they
+		 * will have told us to validate glue.
+		 *
+		 * XXX We should cache the glue validity state!
+		 */
+		if (result == DNS_R_GLUE &&
+		    (search.options & DNS_DBFIND_VALIDATEGLUE) != 0 &&
+		    !valid_glue(&search, foundname, type, node))
+		{
+			NODE_UNLOCK(lock, isc_rwlocktype_read);
+			result = setup_delegation(&search, nodep, foundname,
+						  rdataset, sigrdataset);
+			goto tree_exit;
+		}
+	} else {
+		/*
+		 * An ordinary successful query!
+		 */
+		result = ISC_R_SUCCESS;
+	}
+
+	if (nodep != NULL) {
+		if (!at_zonecut) {
+			new_reference(search.rbtdb, node, isc_rwlocktype_read);
+		} else {
+			search.need_cleanup = false;
+		}
+		*nodep = node;
+	}
+
+	if (type != dns_rdatatype_any) {
+		bind_rdataset(search.rbtdb, node, found, 0, isc_rwlocktype_read,
+			      rdataset);
+		if (foundsig != NULL) {
+			bind_rdataset(search.rbtdb, node, foundsig, 0,
+				      isc_rwlocktype_read, sigrdataset);
+		}
+	}
+
+	if (wild) {
+		foundname->attributes |= DNS_NAMEATTR_WILDCARD;
+	}
+
+node_exit:
+	NODE_UNLOCK(lock, isc_rwlocktype_read);
+
+tree_exit:
+	RWUNLOCK(&search.rbtdb->tree_lock, isc_rwlocktype_read);
+
+	/*
+	 * If we found a zonecut but aren't going to use it, we have to
+	 * let go of it.
+	 */
+	if (search.need_cleanup) {
+		node = search.zonecut;
+		INSIST(node != NULL);
+		lock = &(search.rbtdb->node_locks[node->locknum].lock);
+
+		NODE_LOCK(lock, isc_rwlocktype_read);
+		decrement_reference(search.rbtdb, node, 0, isc_rwlocktype_read,
+				    isc_rwlocktype_none, false);
+		NODE_UNLOCK(lock, isc_rwlocktype_read);
+	}
+
+	if (close_version) {
+		closeversion(db, &version, false);
+	}
+
+	dns_rbtnodechain_reset(&search.chain);
+
+	return (result);
+}
+
+static isc_result_t
+zone_findzonecut(dns_db_t *db, const dns_name_t *name, unsigned int options,
+		 isc_stdtime_t now, dns_dbnode_t **nodep, dns_name_t *foundname,
+		 dns_name_t *dcname, dns_rdataset_t *rdataset,
+		 dns_rdataset_t *sigrdataset) {
+	UNUSED(db);
+	UNUSED(name);
+	UNUSED(options);
+	UNUSED(now);
+	UNUSED(nodep);
+	UNUSED(foundname);
+	UNUSED(dcname);
+	UNUSED(rdataset);
+	UNUSED(sigrdataset);
+
+	FATAL_ERROR("zone_findzonecut() called!");
+
+	UNREACHABLE();
+	return (ISC_R_NOTIMPLEMENTED);
+}
+
+static bool
+check_stale_header(dns_rbtnode_t *node, rdatasetheader_t *header,
+		   isc_rwlocktype_t *locktype, nodelock_t *lock,
+		   rbtdb_search_t *search, rdatasetheader_t **header_prev) {
+	if (!ACTIVE(header, search->now)) {
+		dns_ttl_t stale = header->rdh_ttl +
+				  STALE_TTL(header, search->rbtdb);
+		/*
+		 * If this data is in the stale window keep it and if
+		 * DNS_DBFIND_STALEOK is not set we tell the caller to
+		 * skip this record.  We skip the records with ZEROTTL
+		 * (these records should not be cached anyway).
+		 */
+
+		RDATASET_ATTR_CLR(header, RDATASET_ATTR_STALE_WINDOW);
+		if (!ZEROTTL(header) && KEEPSTALE(search->rbtdb) &&
+		    stale > search->now)
+		{
+			mark_header_stale(search->rbtdb, header);
+			*header_prev = header;
+			/*
+			 * If DNS_DBFIND_STALESTART is set then it means we
+			 * failed to resolve the name during recursion, in
+			 * this case we mark the time in which the refresh
+			 * failed.
+			 */
+			if ((search->options & DNS_DBFIND_STALESTART) != 0) {
+				atomic_store_release(
+					&header->last_refresh_fail_ts,
+					search->now);
+			} else if ((search->options &
+				    DNS_DBFIND_STALEENABLED) != 0 &&
+				   search->now <
+					   (atomic_load_acquire(
+						    &header->last_refresh_fail_ts) +
+					    search->rbtdb->serve_stale_refresh))
+			{
+				/*
+				 * If we are within interval between last
+				 * refresh failure time + 'stale-refresh-time',
+				 * then don't skip this stale entry but use it
+				 * instead.
+				 */
+				RDATASET_ATTR_SET(header,
+						  RDATASET_ATTR_STALE_WINDOW);
+				return (false);
+			} else if ((search->options &
+				    DNS_DBFIND_STALETIMEOUT) != 0)
+			{
+				/*
+				 * We want stale RRset due to timeout, so we
+				 * don't skip it.
+				 */
+				return (false);
+			}
+			return ((search->options & DNS_DBFIND_STALEOK) == 0);
+		}
+
+		/*
+		 * This rdataset is stale.  If no one else is using the
+		 * node, we can clean it up right now, otherwise we mark
+		 * it as ancient, and the node as dirty, so it will get
+		 * cleaned up later.
+		 */
+		if ((header->rdh_ttl < search->now - RBTDB_VIRTUAL) &&
+		    (*locktype == isc_rwlocktype_write ||
+		     NODE_TRYUPGRADE(lock) == ISC_R_SUCCESS))
+		{
+			/*
+			 * We update the node's status only when we can
+			 * get write access; otherwise, we leave others
+			 * to this work.  Periodical cleaning will
+			 * eventually take the job as the last resort.
+			 * We won't downgrade the lock, since other
+			 * rdatasets are probably stale, too.
+			 */
+			*locktype = isc_rwlocktype_write;
+
+			if (isc_refcount_current(&node->references) == 0) {
+				isc_mem_t *mctx;
+
+				/*
+				 * header->down can be non-NULL if the
+				 * refcount has just decremented to 0
+				 * but decrement_reference() has not
+				 * performed clean_cache_node(), in
+				 * which case we need to purge the stale
+				 * headers first.
+				 */
+				mctx = search->rbtdb->common.mctx;
+				clean_stale_headers(search->rbtdb, mctx,
+						    header);
+				if (*header_prev != NULL) {
+					(*header_prev)->next = header->next;
+				} else {
+					node->data = header->next;
+				}
+				free_rdataset(search->rbtdb, mctx, header);
+			} else {
+				mark_header_ancient(search->rbtdb, header);
+				*header_prev = header;
+			}
+		} else {
+			*header_prev = header;
+		}
+		return (true);
+	}
+	return (false);
+}
+
+static isc_result_t
+cache_zonecut_callback(dns_rbtnode_t *node, dns_name_t *name, void *arg) {
+	rbtdb_search_t *search = arg;
+	rdatasetheader_t *header, *header_prev, *header_next;
+	rdatasetheader_t *dname_header, *sigdname_header;
+	isc_result_t result;
+	nodelock_t *lock;
+	isc_rwlocktype_t locktype;
+
+	/* XXX comment */
+
+	REQUIRE(search->zonecut == NULL);
+
+	/*
+	 * Keep compiler silent.
+	 */
+	UNUSED(name);
+
+	lock = &(search->rbtdb->node_locks[node->locknum].lock);
+	locktype = isc_rwlocktype_read;
+	NODE_LOCK(lock, locktype);
+
+	/*
+	 * Look for a DNAME or RRSIG DNAME rdataset.
+	 */
+	dname_header = NULL;
+	sigdname_header = NULL;
+	header_prev = NULL;
+	for (header = node->data; header != NULL; header = header_next) {
+		header_next = header->next;
+		if (check_stale_header(node, header, &locktype, lock, search,
+				       &header_prev))
+		{
+			/* Do nothing. */
+		} else if (header->type == dns_rdatatype_dname &&
+			   EXISTS(header) && !ANCIENT(header))
+		{
+			dname_header = header;
+			header_prev = header;
+		} else if (header->type == RBTDB_RDATATYPE_SIGDNAME &&
+			   EXISTS(header) && !ANCIENT(header))
+		{
+			sigdname_header = header;
+			header_prev = header;
+		} else {
+			header_prev = header;
+		}
+	}
+
+	if (dname_header != NULL &&
+	    (!DNS_TRUST_PENDING(dname_header->trust) ||
+	     (search->options & DNS_DBFIND_PENDINGOK) != 0))
+	{
+		/*
+		 * We increment the reference count on node to ensure that
+		 * search->zonecut_rdataset will still be valid later.
+		 */
+		new_reference(search->rbtdb, node, locktype);
+		search->zonecut = node;
+		search->zonecut_rdataset = dname_header;
+		search->zonecut_sigrdataset = sigdname_header;
+		search->need_cleanup = true;
+		result = DNS_R_PARTIALMATCH;
+	} else {
+		result = DNS_R_CONTINUE;
+	}
+
+	NODE_UNLOCK(lock, locktype);
+
+	return (result);
+}
+
+static isc_result_t
+find_deepest_zonecut(rbtdb_search_t *search, dns_rbtnode_t *node,
+		     dns_dbnode_t **nodep, dns_name_t *foundname,
+		     dns_rdataset_t *rdataset, dns_rdataset_t *sigrdataset) {
+	unsigned int i;
+	dns_rbtnode_t *level_node;
+	rdatasetheader_t *header, *header_prev, *header_next;
+	rdatasetheader_t *found, *foundsig;
+	isc_result_t result = ISC_R_NOTFOUND;
+	dns_name_t name;
+	dns_rbtdb_t *rbtdb;
+	bool done;
+	nodelock_t *lock;
+	isc_rwlocktype_t locktype;
+
+	/*
+	 * Caller must be holding the tree lock.
+	 */
+
+	rbtdb = search->rbtdb;
+	i = search->chain.level_matches;
+	done = false;
+	do {
+		locktype = isc_rwlocktype_read;
+		lock = &rbtdb->node_locks[node->locknum].lock;
+		NODE_LOCK(lock, locktype);
+
+		/*
+		 * Look for NS and RRSIG NS rdatasets.
+		 */
+		found = NULL;
+		foundsig = NULL;
+		header_prev = NULL;
+		for (header = node->data; header != NULL; header = header_next)
+		{
+			header_next = header->next;
+			if (check_stale_header(node, header, &locktype, lock,
+					       search, &header_prev))
+			{
+				/* Do nothing. */
+			} else if (EXISTS(header) && !ANCIENT(header)) {
+				/*
+				 * We've found an extant rdataset.  See if
+				 * we're interested in it.
+				 */
+				if (header->type == dns_rdatatype_ns) {
+					found = header;
+					if (foundsig != NULL) {
+						break;
+					}
+				} else if (header->type ==
+					   RBTDB_RDATATYPE_SIGNS)
+				{
+					foundsig = header;
+					if (found != NULL) {
+						break;
+					}
+				}
+				header_prev = header;
+			} else {
+				header_prev = header;
+			}
+		}
+
+		if (found != NULL) {
+			/*
+			 * If we have to set foundname, we do it before
+			 * anything else.  If we were to set foundname after
+			 * we had set nodep or bound the rdataset, then we'd
+			 * have to undo that work if dns_name_concatenate()
+			 * failed.  By setting foundname first, there's
+			 * nothing to undo if we have trouble.
+			 */
+			if (foundname != NULL) {
+				dns_name_init(&name, NULL);
+				dns_rbt_namefromnode(node, &name);
+				dns_name_copy(&name, foundname);
+				while (i > 0) {
+					i--;
+					level_node = search->chain.levels[i];
+					dns_name_init(&name, NULL);
+					dns_rbt_namefromnode(level_node, &name);
+					result = dns_name_concatenate(
+						foundname, &name, foundname,
+						NULL);
+					if (result != ISC_R_SUCCESS) {
+						if (nodep != NULL) {
+							*nodep = NULL;
+						}
+						goto node_exit;
+					}
+				}
+			}
+			result = DNS_R_DELEGATION;
+			if (nodep != NULL) {
+				new_reference(search->rbtdb, node, locktype);
+				*nodep = node;
+			}
+			bind_rdataset(search->rbtdb, node, found, search->now,
+				      locktype, rdataset);
+			if (foundsig != NULL) {
+				bind_rdataset(search->rbtdb, node, foundsig,
+					      search->now, locktype,
+					      sigrdataset);
+			}
+			if (need_headerupdate(found, search->now) ||
+			    (foundsig != NULL &&
+			     need_headerupdate(foundsig, search->now)))
+			{
+				if (locktype != isc_rwlocktype_write) {
+					NODE_UNLOCK(lock, locktype);
+					NODE_LOCK(lock, isc_rwlocktype_write);
+					locktype = isc_rwlocktype_write;
+					POST(locktype);
+				}
+				if (need_headerupdate(found, search->now)) {
+					update_header(search->rbtdb, found,
+						      search->now);
+				}
+				if (foundsig != NULL &&
+				    need_headerupdate(foundsig, search->now))
+				{
+					update_header(search->rbtdb, foundsig,
+						      search->now);
+				}
+			}
+		}
+
+	node_exit:
+		NODE_UNLOCK(lock, locktype);
+
+		if (found == NULL && i > 0) {
+			i--;
+			node = search->chain.levels[i];
+		} else {
+			done = true;
+		}
+	} while (!done);
+
+	return (result);
+}
+
+/*
+ * Look for a potentially covering NSEC in the cache where `name`
+ * is known not to exist.  This uses the auxiliary NSEC tree to find
+ * the potential NSEC owner. If found, we update 'foundname', 'nodep',
+ * 'rdataset' and 'sigrdataset', and return DNS_R_COVERINGNSEC.
+ * Otherwise, return ISC_R_NOTFOUND.
+ */
+static isc_result_t
+find_coveringnsec(rbtdb_search_t *search, const dns_name_t *name,
+		  dns_dbnode_t **nodep, isc_stdtime_t now,
+		  dns_name_t *foundname, dns_rdataset_t *rdataset,
+		  dns_rdataset_t *sigrdataset) {
+	dns_fixedname_t fprefix, forigin, ftarget, fixed;
+	dns_name_t *prefix = NULL, *origin = NULL;
+	dns_name_t *target = NULL, *fname = NULL;
+	dns_rbtnode_t *node = NULL;
+	dns_rbtnodechain_t chain;
+	isc_result_t result;
+	isc_rwlocktype_t locktype;
+	nodelock_t *lock = NULL;
+	rbtdb_rdatatype_t matchtype, sigmatchtype;
+	rdatasetheader_t *found = NULL, *foundsig = NULL;
+	rdatasetheader_t *header = NULL;
+	rdatasetheader_t *header_next = NULL, *header_prev = NULL;
+
+	/*
+	 * Look for the node in the auxilary tree.
+	 */
+	dns_rbtnodechain_init(&chain);
+	target = dns_fixedname_initname(&ftarget);
+	result = dns_rbt_findnode(search->rbtdb->nsec, name, target, &node,
+				  &chain, DNS_RBTFIND_EMPTYDATA, NULL, NULL);
+	if (result != DNS_R_PARTIALMATCH) {
+		dns_rbtnodechain_reset(&chain);
+		return (ISC_R_NOTFOUND);
+	}
+
+	prefix = dns_fixedname_initname(&fprefix);
+	origin = dns_fixedname_initname(&forigin);
+	target = dns_fixedname_initname(&ftarget);
+	fname = dns_fixedname_initname(&fixed);
+
+	locktype = isc_rwlocktype_read;
+	matchtype = RBTDB_RDATATYPE_VALUE(dns_rdatatype_nsec, 0);
+	sigmatchtype = RBTDB_RDATATYPE_VALUE(dns_rdatatype_rrsig,
+					     dns_rdatatype_nsec);
+
+	/*
+	 * Extract predecessor from chain.
+	 */
+	result = dns_rbtnodechain_current(&chain, prefix, origin, NULL);
+	dns_rbtnodechain_reset(&chain);
+	if (result != ISC_R_SUCCESS && result != DNS_R_NEWORIGIN) {
+		return (ISC_R_NOTFOUND);
+	}
+
+	result = dns_name_concatenate(prefix, origin, target, NULL);
+	if (result != ISC_R_SUCCESS) {
+		return (ISC_R_NOTFOUND);
+	}
+
+	/*
+	 * Lookup the predecessor in the main tree.
+	 */
+	node = NULL;
+	result = dns_rbt_findnode(search->rbtdb->tree, target, fname, &node,
+				  NULL, DNS_RBTFIND_EMPTYDATA, NULL, NULL);
+	if (result != ISC_R_SUCCESS) {
+		return (ISC_R_NOTFOUND);
+	}
+
+	lock = &(search->rbtdb->node_locks[node->locknum].lock);
+	NODE_LOCK(lock, locktype);
+	for (header = node->data; header != NULL; header = header_next) {
+		header_next = header->next;
+		if (check_stale_header(node, header, &locktype, lock, search,
+				       &header_prev))
+		{
+			continue;
+		}
+		if (NONEXISTENT(header) ||
+		    RBTDB_RDATATYPE_BASE(header->type) == 0)
+		{
+			header_prev = header;
+			continue;
+		}
+		if (header->type == matchtype) {
+			found = header;
+			if (foundsig != NULL) {
+				break;
+			}
+		} else if (header->type == sigmatchtype) {
+			foundsig = header;
+			if (found != NULL) {
+				break;
+			}
+		}
+		header_prev = header;
+	}
+	if (found != NULL) {
+		bind_rdataset(search->rbtdb, node, found, now, locktype,
+			      rdataset);
+		if (foundsig != NULL) {
+			bind_rdataset(search->rbtdb, node, foundsig, now,
+				      locktype, sigrdataset);
+		}
+		new_reference(search->rbtdb, node, locktype);
+
+		dns_name_copy(fname, foundname);
+
+		*nodep = node;
+		result = DNS_R_COVERINGNSEC;
+	} else {
+		result = ISC_R_NOTFOUND;
+	}
+	NODE_UNLOCK(lock, locktype);
+	return (result);
+}
+
+static isc_result_t
+cache_find(dns_db_t *db, const 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_rbtnode_t *node = NULL;
+	isc_result_t result;
+	rbtdb_search_t search;
+	bool cname_ok = true;
+	bool found_noqname = false;
+	bool all_negative = true;
+	bool empty_node;
+	nodelock_t *lock;
+	isc_rwlocktype_t locktype;
+	rdatasetheader_t *header, *header_prev, *header_next;
+	rdatasetheader_t *found, *nsheader;
+	rdatasetheader_t *foundsig, *nssig, *cnamesig;
+	rdatasetheader_t *update, *updatesig;
+	rdatasetheader_t *nsecheader, *nsecsig;
+	rbtdb_rdatatype_t sigtype, negtype;
+
+	UNUSED(version);
+
+	search.rbtdb = (dns_rbtdb_t *)db;
+
+	REQUIRE(VALID_RBTDB(search.rbtdb));
+	REQUIRE(version == NULL);
+
+	if (now == 0) {
+		isc_stdtime_get(&now);
+	}
+
+	search.rbtversion = NULL;
+	search.serial = 1;
+	search.options = options;
+	search.copy_name = false;
+	search.need_cleanup = false;
+	search.wild = false;
+	search.zonecut = NULL;
+	search.zonecut_rdataset = NULL;
+	search.zonecut_sigrdataset = NULL;
+	dns_fixedname_init(&search.zonecut_name);
+	dns_rbtnodechain_init(&search.chain);
+	search.now = now;
+	update = NULL;
+	updatesig = NULL;
+
+	RWLOCK(&search.rbtdb->tree_lock, isc_rwlocktype_read);
+
+	/*
+	 * Search down from the root of the tree.  If, while going down, we
+	 * encounter a callback node, cache_zonecut_callback() will search the
+	 * rdatasets at the zone cut for a DNAME rdataset.
+	 */
+	result = dns_rbt_findnode(search.rbtdb->tree, name, foundname, &node,
+				  &search.chain, DNS_RBTFIND_EMPTYDATA,
+				  cache_zonecut_callback, &search);
+
+	if (result == DNS_R_PARTIALMATCH) {
+		/*
+		 * If dns_rbt_findnode discovered a covering DNAME skip
+		 * looking for a covering NSEC.
+		 */
+		if ((search.options & DNS_DBFIND_COVERINGNSEC) != 0 &&
+		    (search.zonecut_rdataset == NULL ||
+		     search.zonecut_rdataset->type != dns_rdatatype_dname))
+		{
+			result = find_coveringnsec(&search, name, nodep, now,
+						   foundname, rdataset,
+						   sigrdataset);
+			if (result == DNS_R_COVERINGNSEC) {
+				goto tree_exit;
+			}
+		}
+		if (search.zonecut != NULL) {
+			result = setup_delegation(&search, nodep, foundname,
+						  rdataset, sigrdataset);
+			goto tree_exit;
+		} else {
+		find_ns:
+			result = find_deepest_zonecut(&search, node, nodep,
+						      foundname, rdataset,
+						      sigrdataset);
+			goto tree_exit;
+		}
+	} else if (result != ISC_R_SUCCESS) {
+		goto tree_exit;
+	}
+
+	/*
+	 * Certain DNSSEC types are not subject to CNAME matching
+	 * (RFC4035, section 2.5 and RFC3007).
+	 *
+	 * We don't check for RRSIG, because we don't store RRSIG records
+	 * directly.
+	 */
+	if (type == dns_rdatatype_key || type == dns_rdatatype_nsec) {
+		cname_ok = false;
+	}
+
+	/*
+	 * We now go looking for rdata...
+	 */
+
+	lock = &(search.rbtdb->node_locks[node->locknum].lock);
+	locktype = isc_rwlocktype_read;
+	NODE_LOCK(lock, locktype);
+
+	found = NULL;
+	foundsig = NULL;
+	sigtype = RBTDB_RDATATYPE_VALUE(dns_rdatatype_rrsig, type);
+	negtype = RBTDB_RDATATYPE_VALUE(0, type);
+	nsheader = NULL;
+	nsecheader = NULL;
+	nssig = NULL;
+	nsecsig = NULL;
+	cnamesig = NULL;
+	empty_node = true;
+	header_prev = NULL;
+	for (header = node->data; header != NULL; header = header_next) {
+		header_next = header->next;
+		if (check_stale_header(node, header, &locktype, lock, &search,
+				       &header_prev))
+		{
+			/* Do nothing. */
+		} else if (EXISTS(header) && !ANCIENT(header)) {
+			/*
+			 * We now know that there is at least one active
+			 * non-stale rdataset at this node.
+			 */
+			empty_node = false;
+			if (header->noqname != NULL &&
+			    header->trust == dns_trust_secure)
+			{
+				found_noqname = true;
+			}
+			if (!NEGATIVE(header)) {
+				all_negative = false;
+			}
+
+			/*
+			 * If we found a type we were looking for, remember
+			 * it.
+			 */
+			if (header->type == type ||
+			    (type == dns_rdatatype_any &&
+			     RBTDB_RDATATYPE_BASE(header->type) != 0) ||
+			    (cname_ok && header->type == dns_rdatatype_cname))
+			{
+				/*
+				 * We've found the answer.
+				 */
+				found = header;
+				if (header->type == dns_rdatatype_cname &&
+				    cname_ok && cnamesig != NULL)
+				{
+					/*
+					 * If we've already got the
+					 * CNAME RRSIG, use it.
+					 */
+					foundsig = cnamesig;
+				}
+			} else if (header->type == sigtype) {
+				/*
+				 * We've found the RRSIG rdataset for our
+				 * target type.  Remember it.
+				 */
+				foundsig = header;
+			} else if (header->type == RBTDB_RDATATYPE_NCACHEANY ||
+				   header->type == negtype)
+			{
+				/*
+				 * We've found a negative cache entry.
+				 */
+				found = header;
+			} else if (header->type == dns_rdatatype_ns) {
+				/*
+				 * Remember a NS rdataset even if we're
+				 * not specifically looking for it, because
+				 * we might need it later.
+				 */
+				nsheader = header;
+			} else if (header->type == RBTDB_RDATATYPE_SIGNS) {
+				/*
+				 * If we need the NS rdataset, we'll also
+				 * need its signature.
+				 */
+				nssig = header;
+			} else if (header->type == dns_rdatatype_nsec) {
+				nsecheader = header;
+			} else if (header->type == RBTDB_RDATATYPE_SIGNSEC) {
+				nsecsig = header;
+			} else if (cname_ok &&
+				   header->type == RBTDB_RDATATYPE_SIGCNAME)
+			{
+				/*
+				 * If we get a CNAME match, we'll also need
+				 * its signature.
+				 */
+				cnamesig = header;
+			}
+			header_prev = header;
+		} else {
+			header_prev = header;
+		}
+	}
+
+	if (empty_node) {
+		/*
+		 * We have an exact match for the name, but there are no
+		 * extant rdatasets.  That means that this node doesn't
+		 * meaningfully exist, and that we really have a partial match.
+		 */
+		NODE_UNLOCK(lock, locktype);
+		if ((search.options & DNS_DBFIND_COVERINGNSEC) != 0) {
+			result = find_coveringnsec(&search, name, nodep, now,
+						   foundname, rdataset,
+						   sigrdataset);
+			if (result == DNS_R_COVERINGNSEC) {
+				goto tree_exit;
+			}
+		}
+		goto find_ns;
+	}
+
+	/*
+	 * If we didn't find what we were looking for...
+	 */
+	if (found == NULL ||
+	    (DNS_TRUST_ADDITIONAL(found->trust) &&
+	     ((options & DNS_DBFIND_ADDITIONALOK) == 0)) ||
+	    (found->trust == dns_trust_glue &&
+	     ((options & DNS_DBFIND_GLUEOK) == 0)) ||
+	    (DNS_TRUST_PENDING(found->trust) &&
+	     ((options & DNS_DBFIND_PENDINGOK) == 0)))
+	{
+		/*
+		 * Return covering NODATA NSEC record.
+		 */
+		if ((search.options & DNS_DBFIND_COVERINGNSEC) != 0 &&
+		    nsecheader != NULL)
+		{
+			if (nodep != NULL) {
+				new_reference(search.rbtdb, node, locktype);
+				*nodep = node;
+			}
+			bind_rdataset(search.rbtdb, node, nsecheader,
+				      search.now, locktype, rdataset);
+			if (need_headerupdate(nsecheader, search.now)) {
+				update = nsecheader;
+			}
+			if (nsecsig != NULL) {
+				bind_rdataset(search.rbtdb, node, nsecsig,
+					      search.now, locktype,
+					      sigrdataset);
+				if (need_headerupdate(nsecsig, search.now)) {
+					updatesig = nsecsig;
+				}
+			}
+			result = DNS_R_COVERINGNSEC;
+			goto node_exit;
+		}
+
+		/*
+		 * This name was from a wild card.  Look for a covering NSEC.
+		 */
+		if (found == NULL && (found_noqname || all_negative) &&
+		    (search.options & DNS_DBFIND_COVERINGNSEC) != 0)
+		{
+			NODE_UNLOCK(lock, locktype);
+			result = find_coveringnsec(&search, name, nodep, now,
+						   foundname, rdataset,
+						   sigrdataset);
+			if (result == DNS_R_COVERINGNSEC) {
+				goto tree_exit;
+			}
+			goto find_ns;
+		}
+
+		/*
+		 * If there is an NS rdataset at this node, then this is the
+		 * deepest zone cut.
+		 */
+		if (nsheader != NULL) {
+			if (nodep != NULL) {
+				new_reference(search.rbtdb, node, locktype);
+				*nodep = node;
+			}
+			bind_rdataset(search.rbtdb, node, nsheader, search.now,
+				      locktype, rdataset);
+			if (need_headerupdate(nsheader, search.now)) {
+				update = nsheader;
+			}
+			if (nssig != NULL) {
+				bind_rdataset(search.rbtdb, node, nssig,
+					      search.now, locktype,
+					      sigrdataset);
+				if (need_headerupdate(nssig, search.now)) {
+					updatesig = nssig;
+				}
+			}
+			result = DNS_R_DELEGATION;
+			goto node_exit;
+		}
+
+		/*
+		 * Go find the deepest zone cut.
+		 */
+		NODE_UNLOCK(lock, locktype);
+		goto find_ns;
+	}
+
+	/*
+	 * We found what we were looking for, or we found a CNAME.
+	 */
+
+	if (nodep != NULL) {
+		new_reference(search.rbtdb, node, locktype);
+		*nodep = node;
+	}
+
+	if (NEGATIVE(found)) {
+		/*
+		 * We found a negative cache entry.
+		 */
+		if (NXDOMAIN(found)) {
+			result = DNS_R_NCACHENXDOMAIN;
+		} else {
+			result = DNS_R_NCACHENXRRSET;
+		}
+	} else if (type != found->type && type != dns_rdatatype_any &&
+		   found->type == dns_rdatatype_cname)
+	{
+		/*
+		 * We weren't doing an ANY query and we found a CNAME instead
+		 * of the type we were looking for, so we need to indicate
+		 * that result to the caller.
+		 */
+		result = DNS_R_CNAME;
+	} else {
+		/*
+		 * An ordinary successful query!
+		 */
+		result = ISC_R_SUCCESS;
+	}
+
+	if (type != dns_rdatatype_any || result == DNS_R_NCACHENXDOMAIN ||
+	    result == DNS_R_NCACHENXRRSET)
+	{
+		bind_rdataset(search.rbtdb, node, found, search.now, locktype,
+			      rdataset);
+		if (need_headerupdate(found, search.now)) {
+			update = found;
+		}
+		if (!NEGATIVE(found) && foundsig != NULL) {
+			bind_rdataset(search.rbtdb, node, foundsig, search.now,
+				      locktype, sigrdataset);
+			if (need_headerupdate(foundsig, search.now)) {
+				updatesig = foundsig;
+			}
+		}
+	}
+
+node_exit:
+	if ((update != NULL || updatesig != NULL) &&
+	    locktype != isc_rwlocktype_write)
+	{
+		NODE_UNLOCK(lock, locktype);
+		NODE_LOCK(lock, isc_rwlocktype_write);
+		locktype = isc_rwlocktype_write;
+		POST(locktype);
+	}
+	if (update != NULL && need_headerupdate(update, search.now)) {
+		update_header(search.rbtdb, update, search.now);
+	}
+	if (updatesig != NULL && need_headerupdate(updatesig, search.now)) {
+		update_header(search.rbtdb, updatesig, search.now);
+	}
+
+	NODE_UNLOCK(lock, locktype);
+
+tree_exit:
+	RWUNLOCK(&search.rbtdb->tree_lock, isc_rwlocktype_read);
+
+	/*
+	 * If we found a zonecut but aren't going to use it, we have to
+	 * let go of it.
+	 */
+	if (search.need_cleanup) {
+		node = search.zonecut;
+		INSIST(node != NULL);
+		lock = &(search.rbtdb->node_locks[node->locknum].lock);
+
+		NODE_LOCK(lock, isc_rwlocktype_read);
+		decrement_reference(search.rbtdb, node, 0, isc_rwlocktype_read,
+				    isc_rwlocktype_none, false);
+		NODE_UNLOCK(lock, isc_rwlocktype_read);
+	}
+
+	dns_rbtnodechain_reset(&search.chain);
+
+	update_cachestats(search.rbtdb, result);
+	return (result);
+}
+
+static isc_result_t
+cache_findzonecut(dns_db_t *db, const dns_name_t *name, unsigned int options,
+		  isc_stdtime_t now, dns_dbnode_t **nodep,
+		  dns_name_t *foundname, dns_name_t *dcname,
+		  dns_rdataset_t *rdataset, dns_rdataset_t *sigrdataset) {
+	dns_rbtnode_t *node = NULL;
+	nodelock_t *lock;
+	isc_result_t result;
+	rbtdb_search_t search;
+	rdatasetheader_t *header, *header_prev, *header_next;
+	rdatasetheader_t *found, *foundsig;
+	unsigned int rbtoptions = DNS_RBTFIND_EMPTYDATA;
+	isc_rwlocktype_t locktype;
+	bool dcnull = (dcname == NULL);
+
+	search.rbtdb = (dns_rbtdb_t *)db;
+
+	REQUIRE(VALID_RBTDB(search.rbtdb));
+
+	if (now == 0) {
+		isc_stdtime_get(&now);
+	}
+
+	search.rbtversion = NULL;
+	search.serial = 1;
+	search.options = options;
+	search.copy_name = false;
+	search.need_cleanup = false;
+	search.wild = false;
+	search.zonecut = NULL;
+	dns_fixedname_init(&search.zonecut_name);
+	dns_rbtnodechain_init(&search.chain);
+	search.now = now;
+
+	if (dcnull) {
+		dcname = foundname;
+	}
+
+	if ((options & DNS_DBFIND_NOEXACT) != 0) {
+		rbtoptions |= DNS_RBTFIND_NOEXACT;
+	}
+
+	RWLOCK(&search.rbtdb->tree_lock, isc_rwlocktype_read);
+
+	/*
+	 * Search down from the root of the tree.
+	 */
+	result = dns_rbt_findnode(search.rbtdb->tree, name, dcname, &node,
+				  &search.chain, rbtoptions, NULL, &search);
+
+	if (result == DNS_R_PARTIALMATCH) {
+		result = find_deepest_zonecut(&search, node, nodep, foundname,
+					      rdataset, sigrdataset);
+		goto tree_exit;
+	} else if (result != ISC_R_SUCCESS) {
+		goto tree_exit;
+	} else if (!dcnull) {
+		dns_name_copy(dcname, foundname);
+	}
+
+	/*
+	 * We now go looking for an NS rdataset at the node.
+	 */
+
+	lock = &(search.rbtdb->node_locks[node->locknum].lock);
+	locktype = isc_rwlocktype_read;
+	NODE_LOCK(lock, locktype);
+
+	found = NULL;
+	foundsig = NULL;
+	header_prev = NULL;
+	for (header = node->data; header != NULL; header = header_next) {
+		header_next = header->next;
+		if (check_stale_header(node, header, &locktype, lock, &search,
+				       &header_prev))
+		{
+			/*
+			 * The function dns_rbt_findnode found us the a matching
+			 * node for 'name' and stored the result in 'dcname'.
+			 * This is the deepest known zonecut in our database.
+			 * However, this node may be stale and if serve-stale
+			 * is not enabled (in other words 'stale-answer-enable'
+			 * is set to no), this node may not be used as a
+			 * zonecut we know about. If so, find the deepest
+			 * zonecut from this node up and return that instead.
+			 */
+			NODE_UNLOCK(lock, locktype);
+			result = find_deepest_zonecut(&search, node, nodep,
+						      foundname, rdataset,
+						      sigrdataset);
+			dns_name_copy(foundname, dcname);
+			goto tree_exit;
+		} else if (EXISTS(header) && !ANCIENT(header)) {
+			/*
+			 * If we found a type we were looking for, remember
+			 * it.
+			 */
+			if (header->type == dns_rdatatype_ns) {
+				/*
+				 * Remember a NS rdataset even if we're
+				 * not specifically looking for it, because
+				 * we might need it later.
+				 */
+				found = header;
+			} else if (header->type == RBTDB_RDATATYPE_SIGNS) {
+				/*
+				 * If we need the NS rdataset, we'll also
+				 * need its signature.
+				 */
+				foundsig = header;
+			}
+			header_prev = header;
+		} else {
+			header_prev = header;
+		}
+	}
+
+	if (found == NULL) {
+		/*
+		 * No NS records here.
+		 */
+		NODE_UNLOCK(lock, locktype);
+		result = find_deepest_zonecut(&search, node, nodep, foundname,
+					      rdataset, sigrdataset);
+		goto tree_exit;
+	}
+
+	if (nodep != NULL) {
+		new_reference(search.rbtdb, node, locktype);
+		*nodep = node;
+	}
+
+	bind_rdataset(search.rbtdb, node, found, search.now, locktype,
+		      rdataset);
+	if (foundsig != NULL) {
+		bind_rdataset(search.rbtdb, node, foundsig, search.now,
+			      locktype, sigrdataset);
+	}
+
+	if (need_headerupdate(found, search.now) ||
+	    (foundsig != NULL && need_headerupdate(foundsig, search.now)))
+	{
+		if (locktype != isc_rwlocktype_write) {
+			NODE_UNLOCK(lock, locktype);
+			NODE_LOCK(lock, isc_rwlocktype_write);
+			locktype = isc_rwlocktype_write;
+			POST(locktype);
+		}
+		if (need_headerupdate(found, search.now)) {
+			update_header(search.rbtdb, found, search.now);
+		}
+		if (foundsig != NULL && need_headerupdate(foundsig, search.now))
+		{
+			update_header(search.rbtdb, foundsig, search.now);
+		}
+	}
+
+	NODE_UNLOCK(lock, locktype);
+
+tree_exit:
+	RWUNLOCK(&search.rbtdb->tree_lock, isc_rwlocktype_read);
+
+	INSIST(!search.need_cleanup);
+
+	dns_rbtnodechain_reset(&search.chain);
+
+	if (result == DNS_R_DELEGATION) {
+		result = ISC_R_SUCCESS;
+	}
+
+	return (result);
+}
+
+static void
+attachnode(dns_db_t *db, dns_dbnode_t *source, dns_dbnode_t **targetp) {
+	dns_rbtdb_t *rbtdb = (dns_rbtdb_t *)db;
+	dns_rbtnode_t *node = (dns_rbtnode_t *)source;
+
+	REQUIRE(VALID_RBTDB(rbtdb));
+	REQUIRE(targetp != NULL && *targetp == NULL);
+
+	isc_refcount_increment(&node->references);
+
+	*targetp = source;
+}
+
+static void
+detachnode(dns_db_t *db, dns_dbnode_t **targetp) {
+	dns_rbtdb_t *rbtdb = (dns_rbtdb_t *)db;
+	dns_rbtnode_t *node;
+	bool want_free = false;
+	bool inactive = false;
+	rbtdb_nodelock_t *nodelock;
+
+	REQUIRE(VALID_RBTDB(rbtdb));
+	REQUIRE(targetp != NULL && *targetp != NULL);
+
+	node = (dns_rbtnode_t *)(*targetp);
+	nodelock = &rbtdb->node_locks[node->locknum];
+
+	NODE_LOCK(&nodelock->lock, isc_rwlocktype_read);
+
+	if (decrement_reference(rbtdb, node, 0, isc_rwlocktype_read,
+				isc_rwlocktype_none, false))
+	{
+		if (isc_refcount_current(&nodelock->references) == 0 &&
+		    nodelock->exiting)
+		{
+			inactive = true;
+		}
+	}
+
+	NODE_UNLOCK(&nodelock->lock, isc_rwlocktype_read);
+
+	*targetp = NULL;
+
+	if (inactive) {
+		RBTDB_LOCK(&rbtdb->lock, isc_rwlocktype_write);
+		rbtdb->active--;
+		if (rbtdb->active == 0) {
+			want_free = true;
+		}
+		RBTDB_UNLOCK(&rbtdb->lock, isc_rwlocktype_write);
+		if (want_free) {
+			char buf[DNS_NAME_FORMATSIZE];
+			if (dns_name_dynamic(&rbtdb->common.origin)) {
+				dns_name_format(&rbtdb->common.origin, buf,
+						sizeof(buf));
+			} else {
+				strlcpy(buf, "<UNKNOWN>", sizeof(buf));
+			}
+			isc_log_write(dns_lctx, DNS_LOGCATEGORY_DATABASE,
+				      DNS_LOGMODULE_CACHE, ISC_LOG_DEBUG(1),
+				      "calling free_rbtdb(%s)", buf);
+			free_rbtdb(rbtdb, true, NULL);
+		}
+	}
+}
+
+static isc_result_t
+expirenode(dns_db_t *db, dns_dbnode_t *node, isc_stdtime_t now) {
+	dns_rbtdb_t *rbtdb = (dns_rbtdb_t *)db;
+	dns_rbtnode_t *rbtnode = node;
+	rdatasetheader_t *header;
+	bool force_expire = false;
+	/*
+	 * These are the category and module used by the cache cleaner.
+	 */
+	bool log = false;
+	isc_logcategory_t *category = DNS_LOGCATEGORY_DATABASE;
+	isc_logmodule_t *module = DNS_LOGMODULE_CACHE;
+	int level = ISC_LOG_DEBUG(2);
+	char printname[DNS_NAME_FORMATSIZE];
+
+	REQUIRE(VALID_RBTDB(rbtdb));
+
+	/*
+	 * Caller must hold a tree lock.
+	 */
+
+	if (now == 0) {
+		isc_stdtime_get(&now);
+	}
+
+	if (isc_mem_isovermem(rbtdb->common.mctx)) {
+		/*
+		 * Force expire with 25% probability.
+		 * XXXDCL Could stand to have a better policy, like LRU.
+		 */
+		force_expire = (rbtnode->down == NULL &&
+				(isc_random32() % 4) == 0);
+
+		/*
+		 * Note that 'log' can be true IFF overmem is also true.
+		 * overmem can currently only be true for cache
+		 * databases -- hence all of the "overmem cache" log strings.
+		 */
+		log = isc_log_wouldlog(dns_lctx, level);
+		if (log) {
+			isc_log_write(
+				dns_lctx, category, module, level,
+				"overmem cache: %s %s",
+				force_expire ? "FORCE" : "check",
+				dns_rbt_formatnodename(rbtnode, printname,
+						       sizeof(printname)));
+		}
+	}
+
+	/*
+	 * We may not need write access, but this code path is not performance
+	 * sensitive, so it should be okay to always lock as a writer.
+	 */
+	NODE_LOCK(&rbtdb->node_locks[rbtnode->locknum].lock,
+		  isc_rwlocktype_write);
+
+	for (header = rbtnode->data; header != NULL; header = header->next) {
+		if (header->rdh_ttl + STALE_TTL(header, rbtdb) <=
+		    now - RBTDB_VIRTUAL)
+		{
+			/*
+			 * We don't check if refcurrent(rbtnode) == 0 and try
+			 * to free like we do in cache_find(), because
+			 * refcurrent(rbtnode) must be non-zero.  This is so
+			 * because 'node' is an argument to the function.
+			 */
+			mark_header_ancient(rbtdb, header);
+			if (log) {
+				isc_log_write(dns_lctx, category, module, level,
+					      "overmem cache: ancient %s",
+					      printname);
+			}
+		} else if (force_expire) {
+			if (!RETAIN(header)) {
+				set_ttl(rbtdb, header, 0);
+				mark_header_ancient(rbtdb, header);
+			} else if (log) {
+				isc_log_write(dns_lctx, category, module, level,
+					      "overmem cache: "
+					      "reprieve by RETAIN() %s",
+					      printname);
+			}
+		} else if (isc_mem_isovermem(rbtdb->common.mctx) && log) {
+			isc_log_write(dns_lctx, category, module, level,
+				      "overmem cache: saved %s", printname);
+		}
+	}
+
+	NODE_UNLOCK(&rbtdb->node_locks[rbtnode->locknum].lock,
+		    isc_rwlocktype_write);
+
+	return (ISC_R_SUCCESS);
+}
+
+static void
+overmem(dns_db_t *db, bool over) {
+	/* This is an empty callback.  See adb.c:water() */
+
+	UNUSED(db);
+	UNUSED(over);
+
+	return;
+}
+
+static void
+printnode(dns_db_t *db, dns_dbnode_t *node, FILE *out) {
+	dns_rbtdb_t *rbtdb = (dns_rbtdb_t *)db;
+	dns_rbtnode_t *rbtnode = node;
+	bool first;
+	uint32_t refs;
+
+	REQUIRE(VALID_RBTDB(rbtdb));
+
+	NODE_LOCK(&rbtdb->node_locks[rbtnode->locknum].lock,
+		  isc_rwlocktype_read);
+
+	refs = isc_refcount_current(&rbtnode->references);
+	fprintf(out, "node %p, %" PRIu32 " references, locknum = %u\n", rbtnode,
+		refs, rbtnode->locknum);
+	if (rbtnode->data != NULL) {
+		rdatasetheader_t *current, *top_next;
+
+		for (current = rbtnode->data; current != NULL;
+		     current = top_next)
+		{
+			top_next = current->next;
+			first = true;
+			fprintf(out, "\ttype %u", current->type);
+			do {
+				uint_least16_t attributes = atomic_load_acquire(
+					&current->attributes);
+				if (!first) {
+					fprintf(out, "\t");
+				}
+				first = false;
+				fprintf(out,
+					"\tserial = %lu, ttl = %u, "
+					"trust = %u, attributes = %" PRIuLEAST16
+					", "
+					"resign = %u\n",
+					(unsigned long)current->serial,
+					current->rdh_ttl, current->trust,
+					attributes,
+					(current->resign << 1) |
+						current->resign_lsb);
+				current = current->down;
+			} while (current != NULL);
+		}
+	} else {
+		fprintf(out, "(empty)\n");
+	}
+
+	NODE_UNLOCK(&rbtdb->node_locks[rbtnode->locknum].lock,
+		    isc_rwlocktype_read);
+}
+
+static isc_result_t
+createiterator(dns_db_t *db, unsigned int options,
+	       dns_dbiterator_t **iteratorp) {
+	dns_rbtdb_t *rbtdb = (dns_rbtdb_t *)db;
+	rbtdb_dbiterator_t *rbtdbiter;
+
+	REQUIRE(VALID_RBTDB(rbtdb));
+
+	rbtdbiter = isc_mem_get(rbtdb->common.mctx, sizeof(*rbtdbiter));
+
+	rbtdbiter->common.methods = &dbiterator_methods;
+	rbtdbiter->common.db = NULL;
+	dns_db_attach(db, &rbtdbiter->common.db);
+	rbtdbiter->common.relative_names = ((options & DNS_DB_RELATIVENAMES) !=
+					    0);
+	rbtdbiter->common.magic = DNS_DBITERATOR_MAGIC;
+	rbtdbiter->common.cleaning = false;
+	rbtdbiter->paused = true;
+	rbtdbiter->tree_locked = isc_rwlocktype_none;
+	rbtdbiter->result = ISC_R_SUCCESS;
+	dns_fixedname_init(&rbtdbiter->name);
+	dns_fixedname_init(&rbtdbiter->origin);
+	rbtdbiter->node = NULL;
+	rbtdbiter->delcnt = 0;
+	rbtdbiter->nsec3only = ((options & DNS_DB_NSEC3ONLY) != 0);
+	rbtdbiter->nonsec3 = ((options & DNS_DB_NONSEC3) != 0);
+	memset(rbtdbiter->deletions, 0, sizeof(rbtdbiter->deletions));
+	dns_rbtnodechain_init(&rbtdbiter->chain);
+	dns_rbtnodechain_init(&rbtdbiter->nsec3chain);
+	if (rbtdbiter->nsec3only) {
+		rbtdbiter->current = &rbtdbiter->nsec3chain;
+	} else {
+		rbtdbiter->current = &rbtdbiter->chain;
+	}
+
+	*iteratorp = (dns_dbiterator_t *)rbtdbiter;
+
+	return (ISC_R_SUCCESS);
+}
+
+static isc_result_t
+zone_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_rbtdb_t *rbtdb = (dns_rbtdb_t *)db;
+	dns_rbtnode_t *rbtnode = (dns_rbtnode_t *)node;
+	rdatasetheader_t *header, *header_next, *found, *foundsig;
+	rbtdb_serial_t serial;
+	rbtdb_version_t *rbtversion = version;
+	bool close_version = false;
+	rbtdb_rdatatype_t matchtype, sigmatchtype;
+
+	REQUIRE(VALID_RBTDB(rbtdb));
+	REQUIRE(type != dns_rdatatype_any);
+	INSIST(rbtversion == NULL || rbtversion->rbtdb == rbtdb);
+
+	if (rbtversion == NULL) {
+		currentversion(db, (dns_dbversion_t **)(void *)(&rbtversion));
+		close_version = true;
+	}
+	serial = rbtversion->serial;
+	now = 0;
+
+	NODE_LOCK(&rbtdb->node_locks[rbtnode->locknum].lock,
+		  isc_rwlocktype_read);
+
+	found = NULL;
+	foundsig = NULL;
+	matchtype = RBTDB_RDATATYPE_VALUE(type, covers);
+	if (covers == 0) {
+		sigmatchtype = RBTDB_RDATATYPE_VALUE(dns_rdatatype_rrsig, type);
+	} else {
+		sigmatchtype = 0;
+	}
+
+	for (header = rbtnode->data; header != NULL; header = header_next) {
+		header_next = header->next;
+		do {
+			if (header->serial <= serial && !IGNORE(header)) {
+				/*
+				 * Is this a "this rdataset doesn't
+				 * exist" record?
+				 */
+				if (NONEXISTENT(header)) {
+					header = NULL;
+				}
+				break;
+			} else {
+				header = header->down;
+			}
+		} while (header != NULL);
+		if (header != NULL) {
+			/*
+			 * We have an active, extant rdataset.  If it's a
+			 * type we're looking for, remember it.
+			 */
+			if (header->type == matchtype) {
+				found = header;
+				if (foundsig != NULL) {
+					break;
+				}
+			} else if (header->type == sigmatchtype) {
+				foundsig = header;
+				if (found != NULL) {
+					break;
+				}
+			}
+		}
+	}
+	if (found != NULL) {
+		bind_rdataset(rbtdb, rbtnode, found, now, isc_rwlocktype_read,
+			      rdataset);
+		if (foundsig != NULL) {
+			bind_rdataset(rbtdb, rbtnode, foundsig, now,
+				      isc_rwlocktype_read, sigrdataset);
+		}
+	}
+
+	NODE_UNLOCK(&rbtdb->node_locks[rbtnode->locknum].lock,
+		    isc_rwlocktype_read);
+
+	if (close_version) {
+		closeversion(db, (dns_dbversion_t **)(void *)(&rbtversion),
+			     false);
+	}
+
+	if (found == NULL) {
+		return (ISC_R_NOTFOUND);
+	}
+
+	return (ISC_R_SUCCESS);
+}
+
+static isc_result_t
+cache_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_rbtdb_t *rbtdb = (dns_rbtdb_t *)db;
+	dns_rbtnode_t *rbtnode = (dns_rbtnode_t *)node;
+	rdatasetheader_t *header, *header_next, *found, *foundsig;
+	rbtdb_rdatatype_t matchtype, sigmatchtype, negtype;
+	isc_result_t result;
+	nodelock_t *lock;
+	isc_rwlocktype_t locktype;
+
+	REQUIRE(VALID_RBTDB(rbtdb));
+	REQUIRE(type != dns_rdatatype_any);
+
+	UNUSED(version);
+
+	result = ISC_R_SUCCESS;
+
+	if (now == 0) {
+		isc_stdtime_get(&now);
+	}
+
+	lock = &rbtdb->node_locks[rbtnode->locknum].lock;
+	locktype = isc_rwlocktype_read;
+	NODE_LOCK(lock, locktype);
+
+	found = NULL;
+	foundsig = NULL;
+	matchtype = RBTDB_RDATATYPE_VALUE(type, covers);
+	negtype = RBTDB_RDATATYPE_VALUE(0, type);
+	if (covers == 0) {
+		sigmatchtype = RBTDB_RDATATYPE_VALUE(dns_rdatatype_rrsig, type);
+	} else {
+		sigmatchtype = 0;
+	}
+
+	for (header = rbtnode->data; header != NULL; header = header_next) {
+		header_next = header->next;
+		if (!ACTIVE(header, now)) {
+			if ((header->rdh_ttl + STALE_TTL(header, rbtdb) <
+			     now - RBTDB_VIRTUAL) &&
+			    (locktype == isc_rwlocktype_write ||
+			     NODE_TRYUPGRADE(lock) == ISC_R_SUCCESS))
+			{
+				/*
+				 * We update the node's status only when we
+				 * can get write access.
+				 */
+				locktype = isc_rwlocktype_write;
+
+				/*
+				 * We don't check if refcurrent(rbtnode) == 0
+				 * and try to free like we do in cache_find(),
+				 * because refcurrent(rbtnode) must be
+				 * non-zero.  This is so because 'node' is an
+				 * argument to the function.
+				 */
+				mark_header_ancient(rbtdb, header);
+			}
+		} else if (EXISTS(header) && !ANCIENT(header)) {
+			if (header->type == matchtype) {
+				found = header;
+			} else if (header->type == RBTDB_RDATATYPE_NCACHEANY ||
+				   header->type == negtype)
+			{
+				found = header;
+			} else if (header->type == sigmatchtype) {
+				foundsig = header;
+			}
+		}
+	}
+	if (found != NULL) {
+		bind_rdataset(rbtdb, rbtnode, found, now, locktype, rdataset);
+		if (!NEGATIVE(found) && foundsig != NULL) {
+			bind_rdataset(rbtdb, rbtnode, foundsig, now, locktype,
+				      sigrdataset);
+		}
+	}
+
+	NODE_UNLOCK(lock, locktype);
+
+	if (found == NULL) {
+		return (ISC_R_NOTFOUND);
+	}
+
+	if (NEGATIVE(found)) {
+		/*
+		 * We found a negative cache entry.
+		 */
+		if (NXDOMAIN(found)) {
+			result = DNS_R_NCACHENXDOMAIN;
+		} else {
+			result = DNS_R_NCACHENXRRSET;
+		}
+	}
+
+	update_cachestats(rbtdb, result);
+
+	return (result);
+}
+
+static isc_result_t
+allrdatasets(dns_db_t *db, dns_dbnode_t *node, dns_dbversion_t *version,
+	     unsigned int options, isc_stdtime_t now,
+	     dns_rdatasetiter_t **iteratorp) {
+	dns_rbtdb_t *rbtdb = (dns_rbtdb_t *)db;
+	dns_rbtnode_t *rbtnode = (dns_rbtnode_t *)node;
+	rbtdb_version_t *rbtversion = version;
+	rbtdb_rdatasetiter_t *iterator;
+
+	REQUIRE(VALID_RBTDB(rbtdb));
+
+	iterator = isc_mem_get(rbtdb->common.mctx, sizeof(*iterator));
+
+	if ((db->attributes & DNS_DBATTR_CACHE) == 0) {
+		now = 0;
+		if (rbtversion == NULL) {
+			currentversion(
+				db, (dns_dbversion_t **)(void *)(&rbtversion));
+		} else {
+			INSIST(rbtversion->rbtdb == rbtdb);
+
+			(void)isc_refcount_increment(&rbtversion->references);
+		}
+	} else {
+		if (now == 0) {
+			isc_stdtime_get(&now);
+		}
+		rbtversion = NULL;
+	}
+
+	iterator->common.magic = DNS_RDATASETITER_MAGIC;
+	iterator->common.methods = &rdatasetiter_methods;
+	iterator->common.db = db;
+	iterator->common.node = node;
+	iterator->common.version = (dns_dbversion_t *)rbtversion;
+	iterator->common.options = options;
+	iterator->common.now = now;
+
+	isc_refcount_increment(&rbtnode->references);
+
+	iterator->current = NULL;
+
+	*iteratorp = (dns_rdatasetiter_t *)iterator;
+
+	return (ISC_R_SUCCESS);
+}
+
+static bool
+cname_and_other_data(dns_rbtnode_t *node, rbtdb_serial_t serial) {
+	rdatasetheader_t *header, *header_next;
+	bool cname, other_data;
+	dns_rdatatype_t rdtype;
+
+	/*
+	 * The caller must hold the node lock.
+	 */
+
+	/*
+	 * Look for CNAME and "other data" rdatasets active in our version.
+	 */
+	cname = false;
+	other_data = false;
+	for (header = node->data; header != NULL; header = header_next) {
+		header_next = header->next;
+		if (header->type == dns_rdatatype_cname) {
+			/*
+			 * Look for an active extant CNAME.
+			 */
+			do {
+				if (header->serial <= serial && !IGNORE(header))
+				{
+					/*
+					 * Is this a "this rdataset doesn't
+					 * exist" record?
+					 */
+					if (NONEXISTENT(header)) {
+						header = NULL;
+					}
+					break;
+				} else {
+					header = header->down;
+				}
+			} while (header != NULL);
+			if (header != NULL) {
+				cname = true;
+			}
+		} else {
+			/*
+			 * Look for active extant "other data".
+			 *
+			 * "Other data" is any rdataset whose type is not
+			 * KEY, NSEC, SIG or RRSIG.
+			 */
+			rdtype = RBTDB_RDATATYPE_BASE(header->type);
+			if (rdtype != dns_rdatatype_key &&
+			    rdtype != dns_rdatatype_sig &&
+			    rdtype != dns_rdatatype_nsec &&
+			    rdtype != dns_rdatatype_rrsig)
+			{
+				/*
+				 * Is it active and extant?
+				 */
+				do {
+					if (header->serial <= serial &&
+					    !IGNORE(header))
+					{
+						/*
+						 * Is this a "this rdataset
+						 * doesn't exist" record?
+						 */
+						if (NONEXISTENT(header)) {
+							header = NULL;
+						}
+						break;
+					} else {
+						header = header->down;
+					}
+				} while (header != NULL);
+				if (header != NULL) {
+					other_data = true;
+				}
+			}
+		}
+	}
+
+	if (cname && other_data) {
+		return (true);
+	}
+
+	return (false);
+}
+
+static void
+resign_insert(dns_rbtdb_t *rbtdb, int idx, rdatasetheader_t *newheader) {
+	INSIST(!IS_CACHE(rbtdb));
+	INSIST(newheader->heap_index == 0);
+	INSIST(!ISC_LINK_LINKED(newheader, link));
+
+	isc_heap_insert(rbtdb->heaps[idx], newheader);
+}
+
+/*
+ * node write lock must be held.
+ */
+static void
+resign_delete(dns_rbtdb_t *rbtdb, rbtdb_version_t *version,
+	      rdatasetheader_t *header) {
+	/*
+	 * Remove the old header from the heap
+	 */
+	if (header != NULL && header->heap_index != 0) {
+		isc_heap_delete(rbtdb->heaps[header->node->locknum],
+				header->heap_index);
+		header->heap_index = 0;
+		if (version != NULL) {
+			new_reference(rbtdb, header->node,
+				      isc_rwlocktype_write);
+			ISC_LIST_APPEND(version->resigned_list, header, link);
+		}
+	}
+}
+
+static uint64_t
+recordsize(rdatasetheader_t *header, unsigned int namelen) {
+	return (dns_rdataslab_rdatasize((unsigned char *)header,
+					sizeof(*header)) +
+		sizeof(dns_ttl_t) + sizeof(dns_rdatatype_t) +
+		sizeof(dns_rdataclass_t) + namelen);
+}
+
+static void
+update_recordsandxfrsize(bool add, rbtdb_version_t *rbtversion,
+			 rdatasetheader_t *header, unsigned int namelen) {
+	unsigned char *hdr = (unsigned char *)header;
+	size_t hdrsize = sizeof(*header);
+
+	RWLOCK(&rbtversion->rwlock, isc_rwlocktype_write);
+	if (add) {
+		rbtversion->records += dns_rdataslab_count(hdr, hdrsize);
+		rbtversion->xfrsize += recordsize(header, namelen);
+	} else {
+		rbtversion->records -= dns_rdataslab_count(hdr, hdrsize);
+		rbtversion->xfrsize -= recordsize(header, namelen);
+	}
+	RWUNLOCK(&rbtversion->rwlock, isc_rwlocktype_write);
+}
+
+/*
+ * write lock on rbtnode must be held.
+ */
+static isc_result_t
+add32(dns_rbtdb_t *rbtdb, dns_rbtnode_t *rbtnode, const dns_name_t *nodename,
+      rbtdb_version_t *rbtversion, rdatasetheader_t *newheader,
+      unsigned int options, bool loading, dns_rdataset_t *addedrdataset,
+      isc_stdtime_t now) {
+	rbtdb_changed_t *changed = NULL;
+	rdatasetheader_t *topheader = NULL, *topheader_prev = NULL;
+	rdatasetheader_t *header = NULL, *sigheader = NULL;
+	unsigned char *merged = NULL;
+	isc_result_t result;
+	bool header_nx;
+	bool newheader_nx;
+	bool merge;
+	dns_rdatatype_t rdtype, covers;
+	rbtdb_rdatatype_t negtype, sigtype;
+	dns_trust_t trust;
+	int idx;
+
+	/*
+	 * Add an rdatasetheader_t to a node.
+	 */
+
+	/*
+	 * Caller must be holding the node lock.
+	 */
+
+	if ((options & DNS_DBADD_MERGE) != 0) {
+		REQUIRE(rbtversion != NULL);
+		merge = true;
+	} else {
+		merge = false;
+	}
+
+	if ((options & DNS_DBADD_FORCE) != 0) {
+		trust = dns_trust_ultimate;
+	} else {
+		trust = newheader->trust;
+	}
+
+	if (rbtversion != NULL && !loading) {
+		/*
+		 * We always add a changed record, even if no changes end up
+		 * being made to this node, because it's harmless and
+		 * simplifies the code.
+		 */
+		changed = add_changed(rbtdb, rbtversion, rbtnode);
+		if (changed == NULL) {
+			free_rdataset(rbtdb, rbtdb->common.mctx, newheader);
+			return (ISC_R_NOMEMORY);
+		}
+	}
+
+	newheader_nx = NONEXISTENT(newheader) ? true : false;
+	topheader_prev = NULL;
+	sigheader = NULL;
+	negtype = 0;
+	if (rbtversion == NULL && !newheader_nx) {
+		rdtype = RBTDB_RDATATYPE_BASE(newheader->type);
+		covers = RBTDB_RDATATYPE_EXT(newheader->type);
+		sigtype = RBTDB_RDATATYPE_VALUE(dns_rdatatype_rrsig, covers);
+		if (NEGATIVE(newheader)) {
+			/*
+			 * We're adding a negative cache entry.
+			 */
+			if (covers == dns_rdatatype_any) {
+				/*
+				 * If we're adding an negative cache entry
+				 * which covers all types (NXDOMAIN,
+				 * NODATA(QTYPE=ANY)),
+				 *
+				 * We make all other data ancient so that the
+				 * only rdataset that can be found at this
+				 * node is the negative cache entry.
+				 */
+				for (topheader = rbtnode->data;
+				     topheader != NULL;
+				     topheader = topheader->next)
+				{
+					set_ttl(rbtdb, topheader, 0);
+					mark_header_ancient(rbtdb, topheader);
+				}
+				goto find_header;
+			}
+			/*
+			 * Otherwise look for any RRSIGs of the given
+			 * type so they can be marked ancient later.
+			 */
+			for (topheader = rbtnode->data; topheader != NULL;
+			     topheader = topheader->next)
+			{
+				if (topheader->type == sigtype) {
+					sigheader = topheader;
+				}
+			}
+			negtype = RBTDB_RDATATYPE_VALUE(covers, 0);
+		} else {
+			/*
+			 * We're adding something that isn't a
+			 * negative cache entry.  Look for an extant
+			 * non-ancient NXDOMAIN/NODATA(QTYPE=ANY) negative
+			 * cache entry.  If we're adding an RRSIG, also
+			 * check for an extant non-ancient NODATA ncache
+			 * entry which covers the same type as the RRSIG.
+			 */
+			for (topheader = rbtnode->data; topheader != NULL;
+			     topheader = topheader->next)
+			{
+				if ((topheader->type ==
+				     RBTDB_RDATATYPE_NCACHEANY) ||
+				    (newheader->type == sigtype &&
+				     topheader->type ==
+					     RBTDB_RDATATYPE_VALUE(0, covers)))
+				{
+					break;
+				}
+			}
+			if (topheader != NULL && EXISTS(topheader) &&
+			    ACTIVE(topheader, now))
+			{
+				/*
+				 * Found one.
+				 */
+				if (trust < topheader->trust) {
+					/*
+					 * The NXDOMAIN/NODATA(QTYPE=ANY)
+					 * is more trusted.
+					 */
+					free_rdataset(rbtdb, rbtdb->common.mctx,
+						      newheader);
+					if (addedrdataset != NULL) {
+						bind_rdataset(
+							rbtdb, rbtnode,
+							topheader, now,
+							isc_rwlocktype_write,
+							addedrdataset);
+					}
+					return (DNS_R_UNCHANGED);
+				}
+				/*
+				 * The new rdataset is better.  Expire the
+				 * ncache entry.
+				 */
+				set_ttl(rbtdb, topheader, 0);
+				mark_header_ancient(rbtdb, topheader);
+				topheader = NULL;
+				goto find_header;
+			}
+			negtype = RBTDB_RDATATYPE_VALUE(0, rdtype);
+		}
+	}
+
+	for (topheader = rbtnode->data; topheader != NULL;
+	     topheader = topheader->next)
+	{
+		if (topheader->type == newheader->type ||
+		    topheader->type == negtype)
+		{
+			break;
+		}
+		topheader_prev = topheader;
+	}
+
+find_header:
+	/*
+	 * If header isn't NULL, we've found the right type.  There may be
+	 * IGNORE rdatasets between the top of the chain and the first real
+	 * data.  We skip over them.
+	 */
+	header = topheader;
+	while (header != NULL && IGNORE(header)) {
+		header = header->down;
+	}
+	if (header != NULL) {
+		header_nx = NONEXISTENT(header) ? true : false;
+
+		/*
+		 * Deleting an already non-existent rdataset has no effect.
+		 */
+		if (header_nx && newheader_nx) {
+			free_rdataset(rbtdb, rbtdb->common.mctx, newheader);
+			return (DNS_R_UNCHANGED);
+		}
+
+		/*
+		 * Trying to add an rdataset with lower trust to a cache
+		 * DB has no effect, provided that the cache data isn't
+		 * stale. If the cache data is stale, new lower trust
+		 * data will supersede it below. Unclear what the best
+		 * policy is here.
+		 */
+		if (rbtversion == NULL && trust < header->trust &&
+		    (ACTIVE(header, now) || header_nx))
+		{
+			free_rdataset(rbtdb, rbtdb->common.mctx, newheader);
+			if (addedrdataset != NULL) {
+				bind_rdataset(rbtdb, rbtnode, header, now,
+					      isc_rwlocktype_write,
+					      addedrdataset);
+			}
+			return (DNS_R_UNCHANGED);
+		}
+
+		/*
+		 * Don't merge if a nonexistent rdataset is involved.
+		 */
+		if (merge && (header_nx || newheader_nx)) {
+			merge = false;
+		}
+
+		/*
+		 * If 'merge' is true, we'll try to create a new rdataset
+		 * that is the union of 'newheader' and 'header'.
+		 */
+		if (merge) {
+			unsigned int flags = 0;
+			INSIST(rbtversion->serial >= header->serial);
+			merged = NULL;
+			result = ISC_R_SUCCESS;
+
+			if ((options & DNS_DBADD_EXACT) != 0) {
+				flags |= DNS_RDATASLAB_EXACT;
+			}
+			/*
+			 * TTL use here is irrelevant to the cache;
+			 * merge is only done with zonedbs.
+			 */
+			if ((options & DNS_DBADD_EXACTTTL) != 0 &&
+			    newheader->rdh_ttl != header->rdh_ttl)
+			{
+				result = DNS_R_NOTEXACT;
+			} else if (newheader->rdh_ttl != header->rdh_ttl) {
+				flags |= DNS_RDATASLAB_FORCE;
+			}
+			if (result == ISC_R_SUCCESS) {
+				result = dns_rdataslab_merge(
+					(unsigned char *)header,
+					(unsigned char *)newheader,
+					(unsigned int)(sizeof(*newheader)),
+					rbtdb->common.mctx,
+					rbtdb->common.rdclass,
+					(dns_rdatatype_t)header->type, flags,
+					&merged);
+			}
+			if (result == ISC_R_SUCCESS) {
+				/*
+				 * If 'header' has the same serial number as
+				 * we do, we could clean it up now if we knew
+				 * that our caller had no references to it.
+				 * We don't know this, however, so we leave it
+				 * alone.  It will get cleaned up when
+				 * clean_zone_node() runs.
+				 */
+				free_rdataset(rbtdb, rbtdb->common.mctx,
+					      newheader);
+				newheader = (rdatasetheader_t *)merged;
+				init_rdataset(rbtdb, newheader);
+				update_newheader(newheader, header);
+				if (loading && RESIGN(newheader) &&
+				    RESIGN(header) &&
+				    resign_sooner(header, newheader))
+				{
+					newheader->resign = header->resign;
+					newheader->resign_lsb =
+						header->resign_lsb;
+				}
+			} else {
+				free_rdataset(rbtdb, rbtdb->common.mctx,
+					      newheader);
+				return (result);
+			}
+		}
+		/*
+		 * Don't replace existing NS, A and AAAA RRsets in the
+		 * cache if they are already exist. This prevents named
+		 * being locked to old servers. Don't lower trust of
+		 * existing record if the update is forced. Nothing
+		 * special to be done w.r.t stale data; it gets replaced
+		 * normally further down.
+		 */
+		if (IS_CACHE(rbtdb) && ACTIVE(header, now) &&
+		    header->type == dns_rdatatype_ns && !header_nx &&
+		    !newheader_nx && header->trust >= newheader->trust &&
+		    dns_rdataslab_equalx((unsigned char *)header,
+					 (unsigned char *)newheader,
+					 (unsigned int)(sizeof(*newheader)),
+					 rbtdb->common.rdclass,
+					 (dns_rdatatype_t)header->type))
+		{
+			/*
+			 * Honour the new ttl if it is less than the
+			 * older one.
+			 */
+			if (header->rdh_ttl > newheader->rdh_ttl) {
+				set_ttl(rbtdb, header, newheader->rdh_ttl);
+			}
+			if (header->noqname == NULL &&
+			    newheader->noqname != NULL)
+			{
+				header->noqname = newheader->noqname;
+				newheader->noqname = NULL;
+			}
+			if (header->closest == NULL &&
+			    newheader->closest != NULL)
+			{
+				header->closest = newheader->closest;
+				newheader->closest = NULL;
+			}
+			free_rdataset(rbtdb, rbtdb->common.mctx, newheader);
+			if (addedrdataset != NULL) {
+				bind_rdataset(rbtdb, rbtnode, header, now,
+					      isc_rwlocktype_write,
+					      addedrdataset);
+			}
+			return (ISC_R_SUCCESS);
+		}
+		/*
+		 * If we have will be replacing a NS RRset force its TTL
+		 * to be no more than the current NS RRset's TTL.  This
+		 * ensures the delegations that are withdrawn are honoured.
+		 */
+		if (IS_CACHE(rbtdb) && ACTIVE(header, now) &&
+		    header->type == dns_rdatatype_ns && !header_nx &&
+		    !newheader_nx && header->trust <= newheader->trust)
+		{
+			if (newheader->rdh_ttl > header->rdh_ttl) {
+				newheader->rdh_ttl = header->rdh_ttl;
+			}
+		}
+		if (IS_CACHE(rbtdb) && ACTIVE(header, now) &&
+		    (options & DNS_DBADD_PREFETCH) == 0 &&
+		    (header->type == dns_rdatatype_a ||
+		     header->type == dns_rdatatype_aaaa ||
+		     header->type == dns_rdatatype_ds ||
+		     header->type == RBTDB_RDATATYPE_SIGDS) &&
+		    !header_nx && !newheader_nx &&
+		    header->trust >= newheader->trust &&
+		    dns_rdataslab_equal((unsigned char *)header,
+					(unsigned char *)newheader,
+					(unsigned int)(sizeof(*newheader))))
+		{
+			/*
+			 * Honour the new ttl if it is less than the
+			 * older one.
+			 */
+			if (header->rdh_ttl > newheader->rdh_ttl) {
+				set_ttl(rbtdb, header, newheader->rdh_ttl);
+			}
+			if (header->noqname == NULL &&
+			    newheader->noqname != NULL)
+			{
+				header->noqname = newheader->noqname;
+				newheader->noqname = NULL;
+			}
+			if (header->closest == NULL &&
+			    newheader->closest != NULL)
+			{
+				header->closest = newheader->closest;
+				newheader->closest = NULL;
+			}
+			free_rdataset(rbtdb, rbtdb->common.mctx, newheader);
+			if (addedrdataset != NULL) {
+				bind_rdataset(rbtdb, rbtnode, header, now,
+					      isc_rwlocktype_write,
+					      addedrdataset);
+			}
+			return (ISC_R_SUCCESS);
+		}
+		INSIST(rbtversion == NULL ||
+		       rbtversion->serial >= topheader->serial);
+		if (loading) {
+			newheader->down = NULL;
+			idx = newheader->node->locknum;
+			if (IS_CACHE(rbtdb)) {
+				if (ZEROTTL(newheader)) {
+					ISC_LIST_APPEND(rbtdb->rdatasets[idx],
+							newheader, link);
+				} else {
+					ISC_LIST_PREPEND(rbtdb->rdatasets[idx],
+							 newheader, link);
+				}
+				INSIST(rbtdb->heaps != NULL);
+				isc_heap_insert(rbtdb->heaps[idx], newheader);
+			} else if (RESIGN(newheader)) {
+				resign_insert(rbtdb, idx, newheader);
+				/*
+				 * Don't call resign_delete as we don't need
+				 * to reverse the delete.  The free_rdataset
+				 * call below will clean up the heap entry.
+				 */
+			}
+
+			/*
+			 * There are no other references to 'header' when
+			 * loading, so we MAY clean up 'header' now.
+			 * Since we don't generate changed records when
+			 * loading, we MUST clean up 'header' now.
+			 */
+			if (topheader_prev != NULL) {
+				topheader_prev->next = newheader;
+			} else {
+				rbtnode->data = newheader;
+			}
+			newheader->next = topheader->next;
+			if (rbtversion != NULL && !header_nx) {
+				update_recordsandxfrsize(false, rbtversion,
+							 header,
+							 nodename->length);
+			}
+			free_rdataset(rbtdb, rbtdb->common.mctx, header);
+		} else {
+			idx = newheader->node->locknum;
+			if (IS_CACHE(rbtdb)) {
+				INSIST(rbtdb->heaps != NULL);
+				isc_heap_insert(rbtdb->heaps[idx], newheader);
+				if (ZEROTTL(newheader)) {
+					ISC_LIST_APPEND(rbtdb->rdatasets[idx],
+							newheader, link);
+				} else {
+					ISC_LIST_PREPEND(rbtdb->rdatasets[idx],
+							 newheader, link);
+				}
+			} else if (RESIGN(newheader)) {
+				resign_insert(rbtdb, idx, newheader);
+				resign_delete(rbtdb, rbtversion, header);
+			}
+			if (topheader_prev != NULL) {
+				topheader_prev->next = newheader;
+			} else {
+				rbtnode->data = newheader;
+			}
+			newheader->next = topheader->next;
+			newheader->down = topheader;
+			topheader->next = newheader;
+			rbtnode->dirty = 1;
+			if (changed != NULL) {
+				changed->dirty = true;
+			}
+			if (rbtversion == NULL) {
+				set_ttl(rbtdb, header, 0);
+				mark_header_ancient(rbtdb, header);
+				if (sigheader != NULL) {
+					set_ttl(rbtdb, sigheader, 0);
+					mark_header_ancient(rbtdb, sigheader);
+				}
+			}
+			if (rbtversion != NULL && !header_nx) {
+				update_recordsandxfrsize(false, rbtversion,
+							 header,
+							 nodename->length);
+			}
+		}
+	} else {
+		/*
+		 * No non-IGNORED rdatasets of the given type exist at
+		 * this node.
+		 */
+
+		/*
+		 * If we're trying to delete the type, don't bother.
+		 */
+		if (newheader_nx) {
+			free_rdataset(rbtdb, rbtdb->common.mctx, newheader);
+			return (DNS_R_UNCHANGED);
+		}
+
+		idx = newheader->node->locknum;
+		if (IS_CACHE(rbtdb)) {
+			isc_heap_insert(rbtdb->heaps[idx], newheader);
+			if (ZEROTTL(newheader)) {
+				ISC_LIST_APPEND(rbtdb->rdatasets[idx],
+						newheader, link);
+			} else {
+				ISC_LIST_PREPEND(rbtdb->rdatasets[idx],
+						 newheader, link);
+			}
+		} else if (RESIGN(newheader)) {
+			resign_insert(rbtdb, idx, newheader);
+			resign_delete(rbtdb, rbtversion, header);
+		}
+
+		if (topheader != NULL) {
+			/*
+			 * We have an list of rdatasets of the given type,
+			 * but they're all marked IGNORE.  We simply insert
+			 * the new rdataset at the head of the list.
+			 *
+			 * Ignored rdatasets cannot occur during loading, so
+			 * we INSIST on it.
+			 */
+			INSIST(!loading);
+			INSIST(rbtversion == NULL ||
+			       rbtversion->serial >= topheader->serial);
+			if (topheader_prev != NULL) {
+				topheader_prev->next = newheader;
+			} else {
+				rbtnode->data = newheader;
+			}
+			newheader->next = topheader->next;
+			newheader->down = topheader;
+			topheader->next = newheader;
+			rbtnode->dirty = 1;
+			if (changed != NULL) {
+				changed->dirty = true;
+			}
+		} else {
+			/*
+			 * No rdatasets of the given type exist at the node.
+			 */
+			newheader->next = rbtnode->data;
+			newheader->down = NULL;
+			rbtnode->data = newheader;
+		}
+	}
+
+	if (rbtversion != NULL && !newheader_nx) {
+		update_recordsandxfrsize(true, rbtversion, newheader,
+					 nodename->length);
+	}
+
+	/*
+	 * Check if the node now contains CNAME and other data.
+	 */
+	if (rbtversion != NULL &&
+	    cname_and_other_data(rbtnode, rbtversion->serial))
+	{
+		return (DNS_R_CNAMEANDOTHER);
+	}
+
+	if (addedrdataset != NULL) {
+		bind_rdataset(rbtdb, rbtnode, newheader, now,
+			      isc_rwlocktype_write, addedrdataset);
+	}
+
+	return (ISC_R_SUCCESS);
+}
+
+static bool
+delegating_type(dns_rbtdb_t *rbtdb, dns_rbtnode_t *node,
+		rbtdb_rdatatype_t type) {
+	if (IS_CACHE(rbtdb)) {
+		if (type == dns_rdatatype_dname) {
+			return (true);
+		} else {
+			return (false);
+		}
+	} else if (type == dns_rdatatype_dname ||
+		   (type == dns_rdatatype_ns &&
+		    (node != rbtdb->origin_node || IS_STUB(rbtdb))))
+	{
+		return (true);
+	}
+	return (false);
+}
+
+static isc_result_t
+addnoqname(dns_rbtdb_t *rbtdb, rdatasetheader_t *newheader,
+	   dns_rdataset_t *rdataset) {
+	struct noqname *noqname;
+	isc_mem_t *mctx = rbtdb->common.mctx;
+	dns_name_t name;
+	dns_rdataset_t neg, negsig;
+	isc_result_t result;
+	isc_region_t r;
+
+	dns_name_init(&name, NULL);
+	dns_rdataset_init(&neg);
+	dns_rdataset_init(&negsig);
+
+	result = dns_rdataset_getnoqname(rdataset, &name, &neg, &negsig);
+	RUNTIME_CHECK(result == ISC_R_SUCCESS);
+
+	noqname = isc_mem_get(mctx, sizeof(*noqname));
+	dns_name_init(&noqname->name, NULL);
+	noqname->neg = NULL;
+	noqname->negsig = NULL;
+	noqname->type = neg.type;
+	dns_name_dup(&name, mctx, &noqname->name);
+	result = dns_rdataslab_fromrdataset(&neg, mctx, &r, 0);
+	if (result != ISC_R_SUCCESS) {
+		goto cleanup;
+	}
+	noqname->neg = r.base;
+	result = dns_rdataslab_fromrdataset(&negsig, mctx, &r, 0);
+	if (result != ISC_R_SUCCESS) {
+		goto cleanup;
+	}
+	noqname->negsig = r.base;
+	dns_rdataset_disassociate(&neg);
+	dns_rdataset_disassociate(&negsig);
+	newheader->noqname = noqname;
+	return (ISC_R_SUCCESS);
+
+cleanup:
+	dns_rdataset_disassociate(&neg);
+	dns_rdataset_disassociate(&negsig);
+	free_noqname(mctx, &noqname);
+	return (result);
+}
+
+static isc_result_t
+addclosest(dns_rbtdb_t *rbtdb, rdatasetheader_t *newheader,
+	   dns_rdataset_t *rdataset) {
+	struct noqname *closest;
+	isc_mem_t *mctx = rbtdb->common.mctx;
+	dns_name_t name;
+	dns_rdataset_t neg, negsig;
+	isc_result_t result;
+	isc_region_t r;
+
+	dns_name_init(&name, NULL);
+	dns_rdataset_init(&neg);
+	dns_rdataset_init(&negsig);
+
+	result = dns_rdataset_getclosest(rdataset, &name, &neg, &negsig);
+	RUNTIME_CHECK(result == ISC_R_SUCCESS);
+
+	closest = isc_mem_get(mctx, sizeof(*closest));
+	dns_name_init(&closest->name, NULL);
+	closest->neg = NULL;
+	closest->negsig = NULL;
+	closest->type = neg.type;
+	dns_name_dup(&name, mctx, &closest->name);
+	result = dns_rdataslab_fromrdataset(&neg, mctx, &r, 0);
+	if (result != ISC_R_SUCCESS) {
+		goto cleanup;
+	}
+	closest->neg = r.base;
+	result = dns_rdataslab_fromrdataset(&negsig, mctx, &r, 0);
+	if (result != ISC_R_SUCCESS) {
+		goto cleanup;
+	}
+	closest->negsig = r.base;
+	dns_rdataset_disassociate(&neg);
+	dns_rdataset_disassociate(&negsig);
+	newheader->closest = closest;
+	return (ISC_R_SUCCESS);
+
+cleanup:
+	dns_rdataset_disassociate(&neg);
+	dns_rdataset_disassociate(&negsig);
+	free_noqname(mctx, &closest);
+	return (result);
+}
+
+static dns_dbmethods_t zone_methods;
+
+static size_t
+rdataset_size(rdatasetheader_t *header) {
+	if (!NONEXISTENT(header)) {
+		return (dns_rdataslab_size((unsigned char *)header,
+					   sizeof(*header)));
+	}
+
+	return (sizeof(*header));
+}
+
+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) {
+	dns_rbtdb_t *rbtdb = (dns_rbtdb_t *)db;
+	dns_rbtnode_t *rbtnode = (dns_rbtnode_t *)node;
+	rbtdb_version_t *rbtversion = version;
+	isc_region_t region;
+	rdatasetheader_t *newheader;
+	rdatasetheader_t *header;
+	isc_result_t result;
+	bool delegating;
+	bool newnsec;
+	bool tree_locked = false;
+	bool cache_is_overmem = false;
+	dns_fixedname_t fixed;
+	dns_name_t *name;
+
+	REQUIRE(VALID_RBTDB(rbtdb));
+	INSIST(rbtversion == NULL || rbtversion->rbtdb == rbtdb);
+
+	if (rbtdb->common.methods == &zone_methods) {
+		/*
+		 * SOA records are only allowed at top of zone.
+		 */
+		if (rdataset->type == dns_rdatatype_soa &&
+		    node != rbtdb->origin_node)
+		{
+			return (DNS_R_NOTZONETOP);
+		}
+		RWLOCK(&rbtdb->tree_lock, isc_rwlocktype_read);
+		REQUIRE(((rbtnode->nsec == DNS_RBT_NSEC_NSEC3 &&
+			  (rdataset->type == dns_rdatatype_nsec3 ||
+			   rdataset->covers == dns_rdatatype_nsec3)) ||
+			 (rbtnode->nsec != DNS_RBT_NSEC_NSEC3 &&
+			  rdataset->type != dns_rdatatype_nsec3 &&
+			  rdataset->covers != dns_rdatatype_nsec3)));
+		RWUNLOCK(&rbtdb->tree_lock, isc_rwlocktype_read);
+	}
+
+	if (rbtversion == NULL) {
+		if (now == 0) {
+			isc_stdtime_get(&now);
+		}
+	} else {
+		now = 0;
+	}
+
+	result = dns_rdataslab_fromrdataset(rdataset, rbtdb->common.mctx,
+					    &region, sizeof(rdatasetheader_t));
+	if (result != ISC_R_SUCCESS) {
+		return (result);
+	}
+
+	name = dns_fixedname_initname(&fixed);
+	nodefullname(db, node, name);
+	dns_rdataset_getownercase(rdataset, name);
+
+	newheader = (rdatasetheader_t *)region.base;
+	init_rdataset(rbtdb, newheader);
+	setownercase(newheader, name);
+	set_ttl(rbtdb, newheader, rdataset->ttl + now);
+	newheader->type = RBTDB_RDATATYPE_VALUE(rdataset->type,
+						rdataset->covers);
+	atomic_init(&newheader->attributes, 0);
+	if (rdataset->ttl == 0U) {
+		RDATASET_ATTR_SET(newheader, RDATASET_ATTR_ZEROTTL);
+	}
+	newheader->noqname = NULL;
+	newheader->closest = NULL;
+	atomic_init(&newheader->count,
+		    atomic_fetch_add_relaxed(&init_count, 1));
+	newheader->trust = rdataset->trust;
+	newheader->last_used = now;
+	newheader->node = rbtnode;
+	if (rbtversion != NULL) {
+		newheader->serial = rbtversion->serial;
+		now = 0;
+
+		if ((rdataset->attributes & DNS_RDATASETATTR_RESIGN) != 0) {
+			RDATASET_ATTR_SET(newheader, RDATASET_ATTR_RESIGN);
+			newheader->resign =
+				(isc_stdtime_t)(dns_time64_from32(
+							rdataset->resign) >>
+						1);
+			newheader->resign_lsb = rdataset->resign & 0x1;
+		} else {
+			newheader->resign = 0;
+			newheader->resign_lsb = 0;
+		}
+	} else {
+		newheader->serial = 1;
+		newheader->resign = 0;
+		newheader->resign_lsb = 0;
+		if ((rdataset->attributes & DNS_RDATASETATTR_PREFETCH) != 0) {
+			RDATASET_ATTR_SET(newheader, RDATASET_ATTR_PREFETCH);
+		}
+		if ((rdataset->attributes & DNS_RDATASETATTR_NEGATIVE) != 0) {
+			RDATASET_ATTR_SET(newheader, RDATASET_ATTR_NEGATIVE);
+		}
+		if ((rdataset->attributes & DNS_RDATASETATTR_NXDOMAIN) != 0) {
+			RDATASET_ATTR_SET(newheader, RDATASET_ATTR_NXDOMAIN);
+		}
+		if ((rdataset->attributes & DNS_RDATASETATTR_OPTOUT) != 0) {
+			RDATASET_ATTR_SET(newheader, RDATASET_ATTR_OPTOUT);
+		}
+		if ((rdataset->attributes & DNS_RDATASETATTR_NOQNAME) != 0) {
+			result = addnoqname(rbtdb, newheader, rdataset);
+			if (result != ISC_R_SUCCESS) {
+				free_rdataset(rbtdb, rbtdb->common.mctx,
+					      newheader);
+				return (result);
+			}
+		}
+		if ((rdataset->attributes & DNS_RDATASETATTR_CLOSEST) != 0) {
+			result = addclosest(rbtdb, newheader, rdataset);
+			if (result != ISC_R_SUCCESS) {
+				free_rdataset(rbtdb, rbtdb->common.mctx,
+					      newheader);
+				return (result);
+			}
+		}
+	}
+
+	/*
+	 * If we're adding a delegation type (e.g. NS or DNAME for a zone,
+	 * just DNAME for the cache), then we need to set the callback bit
+	 * on the node.
+	 */
+	if (delegating_type(rbtdb, rbtnode, rdataset->type)) {
+		delegating = true;
+	} else {
+		delegating = false;
+	}
+
+	/*
+	 * Add to the auxiliary NSEC tree if we're adding an NSEC record.
+	 */
+	RWLOCK(&rbtdb->tree_lock, isc_rwlocktype_read);
+	if (rbtnode->nsec != DNS_RBT_NSEC_HAS_NSEC &&
+	    rdataset->type == dns_rdatatype_nsec)
+	{
+		newnsec = true;
+	} else {
+		newnsec = false;
+	}
+	RWUNLOCK(&rbtdb->tree_lock, isc_rwlocktype_read);
+
+	/*
+	 * If we're adding a delegation type, adding to the auxiliary NSEC
+	 * tree, or the DB is a cache in an overmem state, hold an
+	 * exclusive lock on the tree.  In the latter case the lock does
+	 * not necessarily have to be acquired but it will help purge
+	 * ancient entries more effectively.
+	 */
+	if (IS_CACHE(rbtdb) && isc_mem_isovermem(rbtdb->common.mctx)) {
+		cache_is_overmem = true;
+	}
+	if (delegating || newnsec || cache_is_overmem) {
+		tree_locked = true;
+		RWLOCK(&rbtdb->tree_lock, isc_rwlocktype_write);
+	}
+
+	if (cache_is_overmem) {
+		overmem_purge(rbtdb, rbtnode->locknum, rdataset_size(newheader),
+			      tree_locked);
+	}
+
+	NODE_LOCK(&rbtdb->node_locks[rbtnode->locknum].lock,
+		  isc_rwlocktype_write);
+
+	if (rbtdb->rrsetstats != NULL) {
+		RDATASET_ATTR_SET(newheader, RDATASET_ATTR_STATCOUNT);
+		update_rrsetstats(rbtdb, newheader->type,
+				  atomic_load_acquire(&newheader->attributes),
+				  true);
+	}
+
+	if (IS_CACHE(rbtdb)) {
+		if (tree_locked) {
+			cleanup_dead_nodes(rbtdb, rbtnode->locknum);
+		}
+
+		header = isc_heap_element(rbtdb->heaps[rbtnode->locknum], 1);
+		if (header != NULL) {
+			dns_ttl_t rdh_ttl = header->rdh_ttl;
+
+			/* Only account for stale TTL if cache is not overmem */
+			if (!cache_is_overmem) {
+				rdh_ttl += STALE_TTL(header, rbtdb);
+			}
+
+			if (rdh_ttl < now - RBTDB_VIRTUAL) {
+				expire_header(rbtdb, header, tree_locked,
+					      expire_ttl);
+			}
+		}
+
+		/*
+		 * If we've been holding a write lock on the tree just for
+		 * cleaning, we can release it now.  However, we still need the
+		 * node lock.
+		 */
+		if (tree_locked && !delegating && !newnsec) {
+			RWUNLOCK(&rbtdb->tree_lock, isc_rwlocktype_write);
+			tree_locked = false;
+		}
+	}
+
+	result = ISC_R_SUCCESS;
+	if (newnsec) {
+		dns_rbtnode_t *nsecnode;
+
+		nsecnode = NULL;
+		result = dns_rbt_addnode(rbtdb->nsec, name, &nsecnode);
+		if (result == ISC_R_SUCCESS) {
+			nsecnode->nsec = DNS_RBT_NSEC_NSEC;
+			rbtnode->nsec = DNS_RBT_NSEC_HAS_NSEC;
+		} else if (result == ISC_R_EXISTS) {
+			rbtnode->nsec = DNS_RBT_NSEC_HAS_NSEC;
+			result = ISC_R_SUCCESS;
+		}
+	}
+
+	if (result == ISC_R_SUCCESS) {
+		result = add32(rbtdb, rbtnode, name, rbtversion, newheader,
+			       options, false, addedrdataset, now);
+	}
+	if (result == ISC_R_SUCCESS && delegating) {
+		rbtnode->find_callback = 1;
+	}
+
+	NODE_UNLOCK(&rbtdb->node_locks[rbtnode->locknum].lock,
+		    isc_rwlocktype_write);
+
+	if (tree_locked) {
+		RWUNLOCK(&rbtdb->tree_lock, isc_rwlocktype_write);
+	}
+
+	/*
+	 * Update the zone's secure status.  If version is non-NULL
+	 * this is deferred until closeversion() is called.
+	 */
+	if (result == ISC_R_SUCCESS && version == NULL && !IS_CACHE(rbtdb)) {
+		iszonesecure(db, version, rbtdb->origin_node);
+	}
+
+	return (result);
+}
+
+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) {
+	dns_rbtdb_t *rbtdb = (dns_rbtdb_t *)db;
+	dns_rbtnode_t *rbtnode = (dns_rbtnode_t *)node;
+	rbtdb_version_t *rbtversion = version;
+	dns_fixedname_t fname;
+	dns_name_t *nodename = dns_fixedname_initname(&fname);
+	rdatasetheader_t *topheader, *topheader_prev, *header, *newheader;
+	unsigned char *subresult;
+	isc_region_t region;
+	isc_result_t result;
+	rbtdb_changed_t *changed;
+
+	REQUIRE(VALID_RBTDB(rbtdb));
+	REQUIRE(rbtversion != NULL && rbtversion->rbtdb == rbtdb);
+
+	if (rbtdb->common.methods == &zone_methods) {
+		RWLOCK(&rbtdb->tree_lock, isc_rwlocktype_read);
+		REQUIRE(((rbtnode->nsec == DNS_RBT_NSEC_NSEC3 &&
+			  (rdataset->type == dns_rdatatype_nsec3 ||
+			   rdataset->covers == dns_rdatatype_nsec3)) ||
+			 (rbtnode->nsec != DNS_RBT_NSEC_NSEC3 &&
+			  rdataset->type != dns_rdatatype_nsec3 &&
+			  rdataset->covers != dns_rdatatype_nsec3)));
+		RWUNLOCK(&rbtdb->tree_lock, isc_rwlocktype_read);
+	}
+
+	nodefullname(db, node, nodename);
+
+	result = dns_rdataslab_fromrdataset(rdataset, rbtdb->common.mctx,
+					    &region, sizeof(rdatasetheader_t));
+	if (result != ISC_R_SUCCESS) {
+		return (result);
+	}
+	newheader = (rdatasetheader_t *)region.base;
+	init_rdataset(rbtdb, newheader);
+	set_ttl(rbtdb, newheader, rdataset->ttl);
+	newheader->type = RBTDB_RDATATYPE_VALUE(rdataset->type,
+						rdataset->covers);
+	atomic_init(&newheader->attributes, 0);
+	newheader->serial = rbtversion->serial;
+	newheader->trust = 0;
+	newheader->noqname = NULL;
+	newheader->closest = NULL;
+	atomic_init(&newheader->count,
+		    atomic_fetch_add_relaxed(&init_count, 1));
+	newheader->last_used = 0;
+	newheader->node = rbtnode;
+	if ((rdataset->attributes & DNS_RDATASETATTR_RESIGN) != 0) {
+		RDATASET_ATTR_SET(newheader, RDATASET_ATTR_RESIGN);
+		newheader->resign =
+			(isc_stdtime_t)(dns_time64_from32(rdataset->resign) >>
+					1);
+		newheader->resign_lsb = rdataset->resign & 0x1;
+	} else {
+		newheader->resign = 0;
+		newheader->resign_lsb = 0;
+	}
+
+	NODE_LOCK(&rbtdb->node_locks[rbtnode->locknum].lock,
+		  isc_rwlocktype_write);
+
+	changed = add_changed(rbtdb, rbtversion, rbtnode);
+	if (changed == NULL) {
+		free_rdataset(rbtdb, rbtdb->common.mctx, newheader);
+		NODE_UNLOCK(&rbtdb->node_locks[rbtnode->locknum].lock,
+			    isc_rwlocktype_write);
+		return (ISC_R_NOMEMORY);
+	}
+
+	topheader_prev = NULL;
+	for (topheader = rbtnode->data; topheader != NULL;
+	     topheader = topheader->next)
+	{
+		if (topheader->type == newheader->type) {
+			break;
+		}
+		topheader_prev = topheader;
+	}
+	/*
+	 * If header isn't NULL, we've found the right type.  There may be
+	 * IGNORE rdatasets between the top of the chain and the first real
+	 * data.  We skip over them.
+	 */
+	header = topheader;
+	while (header != NULL && IGNORE(header)) {
+		header = header->down;
+	}
+	if (header != NULL && EXISTS(header)) {
+		unsigned int flags = 0;
+		subresult = NULL;
+		result = ISC_R_SUCCESS;
+		if ((options & DNS_DBSUB_EXACT) != 0) {
+			flags |= DNS_RDATASLAB_EXACT;
+			if (newheader->rdh_ttl != header->rdh_ttl) {
+				result = DNS_R_NOTEXACT;
+			}
+		}
+		if (result == ISC_R_SUCCESS) {
+			result = dns_rdataslab_subtract(
+				(unsigned char *)header,
+				(unsigned char *)newheader,
+				(unsigned int)(sizeof(*newheader)),
+				rbtdb->common.mctx, rbtdb->common.rdclass,
+				(dns_rdatatype_t)header->type, flags,
+				&subresult);
+		}
+		if (result == ISC_R_SUCCESS) {
+			free_rdataset(rbtdb, rbtdb->common.mctx, newheader);
+			newheader = (rdatasetheader_t *)subresult;
+			init_rdataset(rbtdb, newheader);
+			update_newheader(newheader, header);
+			if (RESIGN(header)) {
+				RDATASET_ATTR_SET(newheader,
+						  RDATASET_ATTR_RESIGN);
+				newheader->resign = header->resign;
+				newheader->resign_lsb = header->resign_lsb;
+				resign_insert(rbtdb, rbtnode->locknum,
+					      newheader);
+			}
+			/*
+			 * We have to set the serial since the rdataslab
+			 * subtraction routine copies the reserved portion of
+			 * header, not newheader.
+			 */
+			newheader->serial = rbtversion->serial;
+			/*
+			 * XXXJT: dns_rdataslab_subtract() copied the pointers
+			 * to additional info.  We need to clear these fields
+			 * to avoid having duplicated references.
+			 */
+			update_recordsandxfrsize(true, rbtversion, newheader,
+						 nodename->length);
+		} else if (result == DNS_R_NXRRSET) {
+			/*
+			 * This subtraction would remove all of the rdata;
+			 * add a nonexistent header instead.
+			 */
+			free_rdataset(rbtdb, rbtdb->common.mctx, newheader);
+			newheader = new_rdataset(rbtdb, rbtdb->common.mctx);
+			if (newheader == NULL) {
+				result = ISC_R_NOMEMORY;
+				goto unlock;
+			}
+			init_rdataset(rbtdb, newheader);
+			set_ttl(rbtdb, newheader, 0);
+			newheader->type = topheader->type;
+			atomic_init(&newheader->attributes,
+				    RDATASET_ATTR_NONEXISTENT);
+			newheader->trust = 0;
+			newheader->serial = rbtversion->serial;
+			newheader->noqname = NULL;
+			newheader->closest = NULL;
+			atomic_init(&newheader->count, 0);
+			newheader->node = rbtnode;
+			newheader->resign = 0;
+			newheader->resign_lsb = 0;
+			newheader->last_used = 0;
+		} else {
+			free_rdataset(rbtdb, rbtdb->common.mctx, newheader);
+			goto unlock;
+		}
+
+		/*
+		 * If we're here, we want to link newheader in front of
+		 * topheader.
+		 */
+		INSIST(rbtversion->serial >= topheader->serial);
+		update_recordsandxfrsize(false, rbtversion, header,
+					 nodename->length);
+		if (topheader_prev != NULL) {
+			topheader_prev->next = newheader;
+		} else {
+			rbtnode->data = newheader;
+		}
+		newheader->next = topheader->next;
+		newheader->down = topheader;
+		topheader->next = newheader;
+		rbtnode->dirty = 1;
+		changed->dirty = true;
+		resign_delete(rbtdb, rbtversion, header);
+	} else {
+		/*
+		 * The rdataset doesn't exist, so we don't need to do anything
+		 * to satisfy the deletion request.
+		 */
+		free_rdataset(rbtdb, rbtdb->common.mctx, newheader);
+		if ((options & DNS_DBSUB_EXACT) != 0) {
+			result = DNS_R_NOTEXACT;
+		} else {
+			result = DNS_R_UNCHANGED;
+		}
+	}
+
+	if (result == ISC_R_SUCCESS && newrdataset != NULL) {
+		bind_rdataset(rbtdb, rbtnode, newheader, 0,
+			      isc_rwlocktype_write, newrdataset);
+	}
+
+	if (result == DNS_R_NXRRSET && newrdataset != NULL &&
+	    (options & DNS_DBSUB_WANTOLD) != 0)
+	{
+		bind_rdataset(rbtdb, rbtnode, header, 0, isc_rwlocktype_write,
+			      newrdataset);
+	}
+
+unlock:
+	NODE_UNLOCK(&rbtdb->node_locks[rbtnode->locknum].lock,
+		    isc_rwlocktype_write);
+
+	/*
+	 * Update the zone's secure status.  If version is non-NULL
+	 * this is deferred until closeversion() is called.
+	 */
+	if (result == ISC_R_SUCCESS && version == NULL && !IS_CACHE(rbtdb)) {
+		RBTDB_LOCK(&rbtdb->lock, isc_rwlocktype_read);
+		version = rbtdb->current_version;
+		RBTDB_UNLOCK(&rbtdb->lock, isc_rwlocktype_read);
+		iszonesecure(db, version, rbtdb->origin_node);
+	}
+
+	return (result);
+}
+
+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) {
+	dns_rbtdb_t *rbtdb = (dns_rbtdb_t *)db;
+	dns_rbtnode_t *rbtnode = (dns_rbtnode_t *)node;
+	rbtdb_version_t *rbtversion = version;
+	dns_fixedname_t fname;
+	dns_name_t *nodename = dns_fixedname_initname(&fname);
+	isc_result_t result;
+	rdatasetheader_t *newheader;
+
+	REQUIRE(VALID_RBTDB(rbtdb));
+	INSIST(rbtversion == NULL || rbtversion->rbtdb == rbtdb);
+
+	if (type == dns_rdatatype_any) {
+		return (ISC_R_NOTIMPLEMENTED);
+	}
+	if (type == dns_rdatatype_rrsig && covers == 0) {
+		return (ISC_R_NOTIMPLEMENTED);
+	}
+
+	newheader = new_rdataset(rbtdb, rbtdb->common.mctx);
+	if (newheader == NULL) {
+		return (ISC_R_NOMEMORY);
+	}
+	init_rdataset(rbtdb, newheader);
+	set_ttl(rbtdb, newheader, 0);
+	newheader->type = RBTDB_RDATATYPE_VALUE(type, covers);
+	atomic_init(&newheader->attributes, RDATASET_ATTR_NONEXISTENT);
+	newheader->trust = 0;
+	newheader->noqname = NULL;
+	newheader->closest = NULL;
+	if (rbtversion != NULL) {
+		newheader->serial = rbtversion->serial;
+	} else {
+		newheader->serial = 0;
+	}
+	atomic_init(&newheader->count, 0);
+	newheader->last_used = 0;
+	newheader->node = rbtnode;
+
+	nodefullname(db, node, nodename);
+
+	NODE_LOCK(&rbtdb->node_locks[rbtnode->locknum].lock,
+		  isc_rwlocktype_write);
+	result = add32(rbtdb, rbtnode, nodename, rbtversion, newheader,
+		       DNS_DBADD_FORCE, false, NULL, 0);
+	NODE_UNLOCK(&rbtdb->node_locks[rbtnode->locknum].lock,
+		    isc_rwlocktype_write);
+
+	/*
+	 * Update the zone's secure status.  If version is non-NULL
+	 * this is deferred until closeversion() is called.
+	 */
+	if (result == ISC_R_SUCCESS && version == NULL && !IS_CACHE(rbtdb)) {
+		RBTDB_LOCK(&rbtdb->lock, isc_rwlocktype_read);
+		version = rbtdb->current_version;
+		RBTDB_UNLOCK(&rbtdb->lock, isc_rwlocktype_read);
+		iszonesecure(db, version, rbtdb->origin_node);
+	}
+
+	return (result);
+}
+
+/*
+ * load a non-NSEC3 node in the main tree and optionally to the auxiliary NSEC
+ */
+static isc_result_t
+loadnode(dns_rbtdb_t *rbtdb, const dns_name_t *name, dns_rbtnode_t **nodep,
+	 bool hasnsec) {
+	isc_result_t noderesult, nsecresult, tmpresult;
+	dns_rbtnode_t *nsecnode = NULL, *node = NULL;
+
+	noderesult = dns_rbt_addnode(rbtdb->tree, name, &node);
+	if (!hasnsec) {
+		goto done;
+	}
+	if (noderesult == ISC_R_EXISTS) {
+		/*
+		 * Add a node to the auxiliary NSEC tree for an old node
+		 * just now getting an NSEC record.
+		 */
+		if (node->nsec == DNS_RBT_NSEC_HAS_NSEC) {
+			goto done;
+		}
+	} else if (noderesult != ISC_R_SUCCESS) {
+		goto done;
+	}
+
+	/*
+	 * Build the auxiliary tree for NSECs as we go.
+	 * This tree speeds searches for closest NSECs that would otherwise
+	 * need to examine many irrelevant nodes in large TLDs.
+	 *
+	 * Add nodes to the auxiliary tree after corresponding nodes have
+	 * been added to the main tree.
+	 */
+	nsecresult = dns_rbt_addnode(rbtdb->nsec, name, &nsecnode);
+	if (nsecresult == ISC_R_SUCCESS) {
+		nsecnode->nsec = DNS_RBT_NSEC_NSEC;
+		node->nsec = DNS_RBT_NSEC_HAS_NSEC;
+		goto done;
+	}
+
+	if (nsecresult == ISC_R_EXISTS) {
+#if 1 /* 0 */
+		isc_log_write(dns_lctx, DNS_LOGCATEGORY_DATABASE,
+			      DNS_LOGMODULE_CACHE, ISC_LOG_WARNING,
+			      "addnode: NSEC node already exists");
+#endif /* if 1 */
+		node->nsec = DNS_RBT_NSEC_HAS_NSEC;
+		goto done;
+	}
+
+	if (noderesult == ISC_R_SUCCESS) {
+		/*
+		 * Remove the node we just added above.
+		 */
+		tmpresult = dns_rbt_deletenode(rbtdb->tree, node, false);
+		if (tmpresult != ISC_R_SUCCESS) {
+			isc_log_write(dns_lctx, DNS_LOGCATEGORY_DATABASE,
+				      DNS_LOGMODULE_CACHE, ISC_LOG_WARNING,
+				      "loading_addrdataset: "
+				      "dns_rbt_deletenode: %s after "
+				      "dns_rbt_addnode(NSEC): %s",
+				      isc_result_totext(tmpresult),
+				      isc_result_totext(noderesult));
+		}
+	}
+
+	/*
+	 * Set the error condition to be returned.
+	 */
+	noderesult = nsecresult;
+
+done:
+	if (noderesult == ISC_R_SUCCESS || noderesult == ISC_R_EXISTS) {
+		*nodep = node;
+	}
+
+	return (noderesult);
+}
+
+static isc_result_t
+loading_addrdataset(void *arg, const dns_name_t *name,
+		    dns_rdataset_t *rdataset) {
+	rbtdb_load_t *loadctx = arg;
+	dns_rbtdb_t *rbtdb = loadctx->rbtdb;
+	dns_rbtnode_t *node;
+	isc_result_t result;
+	isc_region_t region;
+	rdatasetheader_t *newheader;
+
+	REQUIRE(rdataset->rdclass == rbtdb->common.rdclass);
+
+	/*
+	 * SOA records are only allowed at top of zone.
+	 */
+	if (rdataset->type == dns_rdatatype_soa && !IS_CACHE(rbtdb) &&
+	    !dns_name_equal(name, &rbtdb->common.origin))
+	{
+		return (DNS_R_NOTZONETOP);
+	}
+
+	if (rdataset->type != dns_rdatatype_nsec3 &&
+	    rdataset->covers != dns_rdatatype_nsec3)
+	{
+		add_empty_wildcards(rbtdb, name, false);
+	}
+
+	if (dns_name_iswildcard(name)) {
+		/*
+		 * NS record owners cannot legally be wild cards.
+		 */
+		if (rdataset->type == dns_rdatatype_ns) {
+			return (DNS_R_INVALIDNS);
+		}
+		/*
+		 * NSEC3 record owners cannot legally be wild cards.
+		 */
+		if (rdataset->type == dns_rdatatype_nsec3) {
+			return (DNS_R_INVALIDNSEC3);
+		}
+		result = add_wildcard_magic(rbtdb, name, false);
+		if (result != ISC_R_SUCCESS) {
+			return (result);
+		}
+	}
+
+	node = NULL;
+	if (rdataset->type == dns_rdatatype_nsec3 ||
+	    rdataset->covers == dns_rdatatype_nsec3)
+	{
+		result = dns_rbt_addnode(rbtdb->nsec3, name, &node);
+		if (result == ISC_R_SUCCESS) {
+			node->nsec = DNS_RBT_NSEC_NSEC3;
+		}
+	} else if (rdataset->type == dns_rdatatype_nsec) {
+		result = loadnode(rbtdb, name, &node, true);
+	} else {
+		result = loadnode(rbtdb, name, &node, false);
+	}
+	if (result != ISC_R_SUCCESS && result != ISC_R_EXISTS) {
+		return (result);
+	}
+	if (result == ISC_R_SUCCESS) {
+		node->locknum = node->hashval % rbtdb->node_lock_count;
+	}
+
+	result = dns_rdataslab_fromrdataset(rdataset, rbtdb->common.mctx,
+					    &region, sizeof(rdatasetheader_t));
+	if (result != ISC_R_SUCCESS) {
+		return (result);
+	}
+	newheader = (rdatasetheader_t *)region.base;
+	init_rdataset(rbtdb, newheader);
+	set_ttl(rbtdb, newheader, rdataset->ttl + loadctx->now); /* XXX overflow
+								  * check */
+	newheader->type = RBTDB_RDATATYPE_VALUE(rdataset->type,
+						rdataset->covers);
+	atomic_init(&newheader->attributes, 0);
+	newheader->trust = rdataset->trust;
+	newheader->serial = 1;
+	newheader->noqname = NULL;
+	newheader->closest = NULL;
+	atomic_init(&newheader->count,
+		    atomic_fetch_add_relaxed(&init_count, 1));
+	newheader->last_used = 0;
+	newheader->node = node;
+	setownercase(newheader, name);
+
+	if ((rdataset->attributes & DNS_RDATASETATTR_RESIGN) != 0) {
+		RDATASET_ATTR_SET(newheader, RDATASET_ATTR_RESIGN);
+		newheader->resign =
+			(isc_stdtime_t)(dns_time64_from32(rdataset->resign) >>
+					1);
+		newheader->resign_lsb = rdataset->resign & 0x1;
+	} else {
+		newheader->resign = 0;
+		newheader->resign_lsb = 0;
+	}
+
+	NODE_LOCK(&rbtdb->node_locks[node->locknum].lock, isc_rwlocktype_write);
+	result = add32(rbtdb, node, name, rbtdb->current_version, newheader,
+		       DNS_DBADD_MERGE, true, NULL, 0);
+	NODE_UNLOCK(&rbtdb->node_locks[node->locknum].lock,
+		    isc_rwlocktype_write);
+
+	if (result == ISC_R_SUCCESS &&
+	    delegating_type(rbtdb, node, rdataset->type))
+	{
+		node->find_callback = 1;
+	} else if (result == DNS_R_UNCHANGED) {
+		result = ISC_R_SUCCESS;
+	}
+
+	return (result);
+}
+
+static isc_result_t
+beginload(dns_db_t *db, dns_rdatacallbacks_t *callbacks) {
+	rbtdb_load_t *loadctx;
+	dns_rbtdb_t *rbtdb;
+	rbtdb = (dns_rbtdb_t *)db;
+
+	REQUIRE(DNS_CALLBACK_VALID(callbacks));
+	REQUIRE(VALID_RBTDB(rbtdb));
+
+	loadctx = isc_mem_get(rbtdb->common.mctx, sizeof(*loadctx));
+
+	loadctx->rbtdb = rbtdb;
+	if (IS_CACHE(rbtdb)) {
+		isc_stdtime_get(&loadctx->now);
+	} else {
+		loadctx->now = 0;
+	}
+
+	RBTDB_LOCK(&rbtdb->lock, isc_rwlocktype_write);
+
+	REQUIRE((rbtdb->attributes &
+		 (RBTDB_ATTR_LOADED | RBTDB_ATTR_LOADING)) == 0);
+	rbtdb->attributes |= RBTDB_ATTR_LOADING;
+
+	RBTDB_UNLOCK(&rbtdb->lock, isc_rwlocktype_write);
+
+	callbacks->add = loading_addrdataset;
+	callbacks->add_private = loadctx;
+
+	return (ISC_R_SUCCESS);
+}
+
+static isc_result_t
+endload(dns_db_t *db, dns_rdatacallbacks_t *callbacks) {
+	rbtdb_load_t *loadctx;
+	dns_rbtdb_t *rbtdb = (dns_rbtdb_t *)db;
+
+	REQUIRE(VALID_RBTDB(rbtdb));
+	REQUIRE(DNS_CALLBACK_VALID(callbacks));
+	loadctx = callbacks->add_private;
+	REQUIRE(loadctx != NULL);
+	REQUIRE(loadctx->rbtdb == rbtdb);
+
+	RBTDB_LOCK(&rbtdb->lock, isc_rwlocktype_write);
+
+	REQUIRE((rbtdb->attributes & RBTDB_ATTR_LOADING) != 0);
+	REQUIRE((rbtdb->attributes & RBTDB_ATTR_LOADED) == 0);
+
+	rbtdb->attributes &= ~RBTDB_ATTR_LOADING;
+	rbtdb->attributes |= RBTDB_ATTR_LOADED;
+
+	/*
+	 * If there's a KEY rdataset at the zone origin containing a
+	 * zone key, we consider the zone secure.
+	 */
+	if (!IS_CACHE(rbtdb) && rbtdb->origin_node != NULL) {
+		dns_dbversion_t *version = rbtdb->current_version;
+		RBTDB_UNLOCK(&rbtdb->lock, isc_rwlocktype_write);
+		iszonesecure(db, version, rbtdb->origin_node);
+	} else {
+		RBTDB_UNLOCK(&rbtdb->lock, isc_rwlocktype_write);
+	}
+
+	callbacks->add = NULL;
+	callbacks->add_private = NULL;
+
+	isc_mem_put(rbtdb->common.mctx, loadctx, sizeof(*loadctx));
+
+	return (ISC_R_SUCCESS);
+}
+
+static isc_result_t
+dump(dns_db_t *db, dns_dbversion_t *version, const char *filename,
+     dns_masterformat_t masterformat) {
+	dns_rbtdb_t *rbtdb;
+	rbtdb_version_t *rbtversion = version;
+
+	rbtdb = (dns_rbtdb_t *)db;
+
+	REQUIRE(VALID_RBTDB(rbtdb));
+	INSIST(rbtversion == NULL || rbtversion->rbtdb == rbtdb);
+
+	return (dns_master_dump(rbtdb->common.mctx, db, version,
+				&dns_master_style_default, filename,
+				masterformat, NULL));
+}
+
+static void
+delete_callback(void *data, void *arg) {
+	dns_rbtdb_t *rbtdb = arg;
+	rdatasetheader_t *current, *next;
+	unsigned int locknum;
+
+	current = data;
+	locknum = current->node->locknum;
+	NODE_LOCK(&rbtdb->node_locks[locknum].lock, isc_rwlocktype_write);
+	while (current != NULL) {
+		next = current->next;
+		free_rdataset(rbtdb, rbtdb->common.mctx, current);
+		current = next;
+	}
+	NODE_UNLOCK(&rbtdb->node_locks[locknum].lock, isc_rwlocktype_write);
+}
+
+static bool
+issecure(dns_db_t *db) {
+	dns_rbtdb_t *rbtdb;
+	bool secure;
+
+	rbtdb = (dns_rbtdb_t *)db;
+
+	REQUIRE(VALID_RBTDB(rbtdb));
+
+	RBTDB_LOCK(&rbtdb->lock, isc_rwlocktype_read);
+	secure = (rbtdb->current_version->secure == dns_db_secure);
+	RBTDB_UNLOCK(&rbtdb->lock, isc_rwlocktype_read);
+
+	return (secure);
+}
+
+static bool
+isdnssec(dns_db_t *db) {
+	dns_rbtdb_t *rbtdb;
+	bool dnssec;
+
+	rbtdb = (dns_rbtdb_t *)db;
+
+	REQUIRE(VALID_RBTDB(rbtdb));
+
+	RBTDB_LOCK(&rbtdb->lock, isc_rwlocktype_read);
+	dnssec = (rbtdb->current_version->secure != dns_db_insecure);
+	RBTDB_UNLOCK(&rbtdb->lock, isc_rwlocktype_read);
+
+	return (dnssec);
+}
+
+static unsigned int
+nodecount(dns_db_t *db, dns_dbtree_t tree) {
+	dns_rbtdb_t *rbtdb;
+	unsigned int count;
+
+	rbtdb = (dns_rbtdb_t *)db;
+
+	REQUIRE(VALID_RBTDB(rbtdb));
+
+	RWLOCK(&rbtdb->tree_lock, isc_rwlocktype_read);
+	switch (tree) {
+	case dns_dbtree_main:
+		count = dns_rbt_nodecount(rbtdb->tree);
+		break;
+	case dns_dbtree_nsec:
+		count = dns_rbt_nodecount(rbtdb->nsec);
+		break;
+	case dns_dbtree_nsec3:
+		count = dns_rbt_nodecount(rbtdb->nsec3);
+		break;
+	default:
+		UNREACHABLE();
+	}
+	RWUNLOCK(&rbtdb->tree_lock, isc_rwlocktype_read);
+
+	return (count);
+}
+
+static size_t
+hashsize(dns_db_t *db) {
+	dns_rbtdb_t *rbtdb;
+	size_t size;
+
+	rbtdb = (dns_rbtdb_t *)db;
+
+	REQUIRE(VALID_RBTDB(rbtdb));
+
+	RWLOCK(&rbtdb->tree_lock, isc_rwlocktype_read);
+	size = dns_rbt_hashsize(rbtdb->tree);
+	RWUNLOCK(&rbtdb->tree_lock, isc_rwlocktype_read);
+
+	return (size);
+}
+
+static void
+settask(dns_db_t *db, isc_task_t *task) {
+	dns_rbtdb_t *rbtdb;
+
+	rbtdb = (dns_rbtdb_t *)db;
+
+	REQUIRE(VALID_RBTDB(rbtdb));
+
+	RBTDB_LOCK(&rbtdb->lock, isc_rwlocktype_write);
+	if (rbtdb->task != NULL) {
+		isc_task_detach(&rbtdb->task);
+	}
+	if (task != NULL) {
+		isc_task_attach(task, &rbtdb->task);
+	}
+	RBTDB_UNLOCK(&rbtdb->lock, isc_rwlocktype_write);
+}
+
+static bool
+ispersistent(dns_db_t *db) {
+	UNUSED(db);
+	return (false);
+}
+
+static isc_result_t
+getoriginnode(dns_db_t *db, dns_dbnode_t **nodep) {
+	dns_rbtdb_t *rbtdb = (dns_rbtdb_t *)db;
+	dns_rbtnode_t *onode;
+	isc_result_t result = ISC_R_SUCCESS;
+
+	REQUIRE(VALID_RBTDB(rbtdb));
+	REQUIRE(nodep != NULL && *nodep == NULL);
+
+	/* Note that the access to origin_node doesn't require a DB lock */
+	onode = (dns_rbtnode_t *)rbtdb->origin_node;
+	if (onode != NULL) {
+		new_reference(rbtdb, onode, isc_rwlocktype_none);
+		*nodep = rbtdb->origin_node;
+	} else {
+		INSIST(IS_CACHE(rbtdb));
+		result = ISC_R_NOTFOUND;
+	}
+
+	return (result);
+}
+
+static isc_result_t
+getnsec3parameters(dns_db_t *db, dns_dbversion_t *version, dns_hash_t *hash,
+		   uint8_t *flags, uint16_t *iterations, unsigned char *salt,
+		   size_t *salt_length) {
+	dns_rbtdb_t *rbtdb;
+	isc_result_t result = ISC_R_NOTFOUND;
+	rbtdb_version_t *rbtversion = version;
+
+	rbtdb = (dns_rbtdb_t *)db;
+
+	REQUIRE(VALID_RBTDB(rbtdb));
+	INSIST(rbtversion == NULL || rbtversion->rbtdb == rbtdb);
+
+	RBTDB_LOCK(&rbtdb->lock, isc_rwlocktype_read);
+	if (rbtversion == NULL) {
+		rbtversion = rbtdb->current_version;
+	}
+
+	if (rbtversion->havensec3) {
+		if (hash != NULL) {
+			*hash = rbtversion->hash;
+		}
+		if (salt != NULL && salt_length != NULL) {
+			REQUIRE(*salt_length >= rbtversion->salt_length);
+			memmove(salt, rbtversion->salt,
+				rbtversion->salt_length);
+		}
+		if (salt_length != NULL) {
+			*salt_length = rbtversion->salt_length;
+		}
+		if (iterations != NULL) {
+			*iterations = rbtversion->iterations;
+		}
+		if (flags != NULL) {
+			*flags = rbtversion->flags;
+		}
+		result = ISC_R_SUCCESS;
+	}
+	RBTDB_UNLOCK(&rbtdb->lock, isc_rwlocktype_read);
+
+	return (result);
+}
+
+static isc_result_t
+getsize(dns_db_t *db, dns_dbversion_t *version, uint64_t *records,
+	uint64_t *xfrsize) {
+	dns_rbtdb_t *rbtdb;
+	isc_result_t result = ISC_R_SUCCESS;
+	rbtdb_version_t *rbtversion = version;
+
+	rbtdb = (dns_rbtdb_t *)db;
+
+	REQUIRE(VALID_RBTDB(rbtdb));
+	INSIST(rbtversion == NULL || rbtversion->rbtdb == rbtdb);
+
+	RBTDB_LOCK(&rbtdb->lock, isc_rwlocktype_read);
+	if (rbtversion == NULL) {
+		rbtversion = rbtdb->current_version;
+	}
+
+	RWLOCK(&rbtversion->rwlock, isc_rwlocktype_read);
+	if (records != NULL) {
+		*records = rbtversion->records;
+	}
+
+	if (xfrsize != NULL) {
+		*xfrsize = rbtversion->xfrsize;
+	}
+	RWUNLOCK(&rbtversion->rwlock, isc_rwlocktype_read);
+	RBTDB_UNLOCK(&rbtdb->lock, isc_rwlocktype_read);
+
+	return (result);
+}
+
+static isc_result_t
+setsigningtime(dns_db_t *db, dns_rdataset_t *rdataset, isc_stdtime_t resign) {
+	dns_rbtdb_t *rbtdb = (dns_rbtdb_t *)db;
+	rdatasetheader_t *header, oldheader;
+
+	REQUIRE(VALID_RBTDB(rbtdb));
+	REQUIRE(!IS_CACHE(rbtdb));
+	REQUIRE(rdataset != NULL);
+
+	header = rdataset->private3;
+	header--;
+
+	NODE_LOCK(&rbtdb->node_locks[header->node->locknum].lock,
+		  isc_rwlocktype_write);
+
+	oldheader = *header;
+	/*
+	 * Only break the heap invariant (by adjusting resign and resign_lsb)
+	 * if we are going to be restoring it by calling isc_heap_increased
+	 * or isc_heap_decreased.
+	 */
+	if (resign != 0) {
+		header->resign = (isc_stdtime_t)(dns_time64_from32(resign) >>
+						 1);
+		header->resign_lsb = resign & 0x1;
+	}
+	if (header->heap_index != 0) {
+		INSIST(RESIGN(header));
+		if (resign == 0) {
+			isc_heap_delete(rbtdb->heaps[header->node->locknum],
+					header->heap_index);
+			header->heap_index = 0;
+		} else if (resign_sooner(header, &oldheader)) {
+			isc_heap_increased(rbtdb->heaps[header->node->locknum],
+					   header->heap_index);
+		} else if (resign_sooner(&oldheader, header)) {
+			isc_heap_decreased(rbtdb->heaps[header->node->locknum],
+					   header->heap_index);
+		}
+	} else if (resign != 0) {
+		RDATASET_ATTR_SET(header, RDATASET_ATTR_RESIGN);
+		resign_insert(rbtdb, header->node->locknum, header);
+	}
+	NODE_UNLOCK(&rbtdb->node_locks[header->node->locknum].lock,
+		    isc_rwlocktype_write);
+	return (ISC_R_SUCCESS);
+}
+
+static isc_result_t
+getsigningtime(dns_db_t *db, dns_rdataset_t *rdataset, dns_name_t *foundname) {
+	dns_rbtdb_t *rbtdb = (dns_rbtdb_t *)db;
+	rdatasetheader_t *header = NULL, *this;
+	unsigned int i;
+	isc_result_t result = ISC_R_NOTFOUND;
+	unsigned int locknum = 0;
+
+	REQUIRE(VALID_RBTDB(rbtdb));
+
+	RWLOCK(&rbtdb->tree_lock, isc_rwlocktype_read);
+
+	for (i = 0; i < rbtdb->node_lock_count; i++) {
+		NODE_LOCK(&rbtdb->node_locks[i].lock, isc_rwlocktype_read);
+
+		/*
+		 * Find for the earliest signing time among all of the
+		 * heaps, each of which is covered by a different bucket
+		 * lock.
+		 */
+		this = isc_heap_element(rbtdb->heaps[i], 1);
+		if (this == NULL) {
+			/* Nothing found; unlock and try the next heap. */
+			NODE_UNLOCK(&rbtdb->node_locks[i].lock,
+				    isc_rwlocktype_read);
+			continue;
+		}
+
+		if (header == NULL) {
+			/*
+			 * Found a signing time: retain the bucket lock and
+			 * preserve the lock number so we can unlock it
+			 * later.
+			 */
+			header = this;
+			locknum = i;
+		} else if (resign_sooner(this, header)) {
+			/*
+			 * Found an earlier signing time; release the
+			 * previous bucket lock and retain this one instead.
+			 */
+			NODE_UNLOCK(&rbtdb->node_locks[locknum].lock,
+				    isc_rwlocktype_read);
+			header = this;
+			locknum = i;
+		} else {
+			/*
+			 * Earliest signing time in this heap isn't
+			 * an improvement; unlock and try the next heap.
+			 */
+			NODE_UNLOCK(&rbtdb->node_locks[i].lock,
+				    isc_rwlocktype_read);
+		}
+	}
+
+	if (header != NULL) {
+		/*
+		 * Found something; pass back the answer and unlock
+		 * the bucket.
+		 */
+		bind_rdataset(rbtdb, header->node, header, 0,
+			      isc_rwlocktype_read, rdataset);
+
+		if (foundname != NULL) {
+			dns_rbt_fullnamefromnode(header->node, foundname);
+		}
+
+		NODE_UNLOCK(&rbtdb->node_locks[locknum].lock,
+			    isc_rwlocktype_read);
+
+		result = ISC_R_SUCCESS;
+	}
+
+	RWUNLOCK(&rbtdb->tree_lock, isc_rwlocktype_read);
+
+	return (result);
+}
+
+static void
+resigned(dns_db_t *db, dns_rdataset_t *rdataset, dns_dbversion_t *version) {
+	rbtdb_version_t *rbtversion = (rbtdb_version_t *)version;
+	dns_rbtdb_t *rbtdb = (dns_rbtdb_t *)db;
+	dns_rbtnode_t *node;
+	rdatasetheader_t *header;
+
+	REQUIRE(VALID_RBTDB(rbtdb));
+	REQUIRE(rdataset != NULL);
+	REQUIRE(rdataset->methods == &rdataset_methods);
+	REQUIRE(rbtdb->future_version == rbtversion);
+	REQUIRE(rbtversion != NULL);
+	REQUIRE(rbtversion->writer);
+	REQUIRE(rbtversion->rbtdb == rbtdb);
+
+	node = rdataset->private2;
+	INSIST(node != NULL);
+	header = rdataset->private3;
+	INSIST(header != NULL);
+	header--;
+
+	if (header->heap_index == 0) {
+		return;
+	}
+
+	RWLOCK(&rbtdb->tree_lock, isc_rwlocktype_write);
+	NODE_LOCK(&rbtdb->node_locks[node->locknum].lock, isc_rwlocktype_write);
+	/*
+	 * Delete from heap and save to re-signed list so that it can
+	 * be restored if we backout of this change.
+	 */
+	resign_delete(rbtdb, rbtversion, header);
+	NODE_UNLOCK(&rbtdb->node_locks[node->locknum].lock,
+		    isc_rwlocktype_write);
+	RWUNLOCK(&rbtdb->tree_lock, isc_rwlocktype_write);
+}
+
+static isc_result_t
+setcachestats(dns_db_t *db, isc_stats_t *stats) {
+	dns_rbtdb_t *rbtdb = (dns_rbtdb_t *)db;
+
+	REQUIRE(VALID_RBTDB(rbtdb));
+	REQUIRE(IS_CACHE(rbtdb)); /* current restriction */
+	REQUIRE(stats != NULL);
+
+	isc_stats_attach(stats, &rbtdb->cachestats);
+	return (ISC_R_SUCCESS);
+}
+
+static isc_result_t
+setgluecachestats(dns_db_t *db, isc_stats_t *stats) {
+	dns_rbtdb_t *rbtdb = (dns_rbtdb_t *)db;
+
+	REQUIRE(VALID_RBTDB(rbtdb));
+	REQUIRE(!IS_CACHE(rbtdb) && !IS_STUB(rbtdb));
+	REQUIRE(stats != NULL);
+
+	isc_stats_attach(stats, &rbtdb->gluecachestats);
+	return (ISC_R_SUCCESS);
+}
+
+static dns_stats_t *
+getrrsetstats(dns_db_t *db) {
+	dns_rbtdb_t *rbtdb = (dns_rbtdb_t *)db;
+
+	REQUIRE(VALID_RBTDB(rbtdb));
+	REQUIRE(IS_CACHE(rbtdb)); /* current restriction */
+
+	return (rbtdb->rrsetstats);
+}
+
+static isc_result_t
+nodefullname(dns_db_t *db, dns_dbnode_t *node, dns_name_t *name) {
+	dns_rbtdb_t *rbtdb = (dns_rbtdb_t *)db;
+	dns_rbtnode_t *rbtnode = (dns_rbtnode_t *)node;
+	isc_result_t result;
+
+	REQUIRE(VALID_RBTDB(rbtdb));
+	REQUIRE(node != NULL);
+	REQUIRE(name != NULL);
+
+	RWLOCK(&rbtdb->tree_lock, isc_rwlocktype_read);
+	result = dns_rbt_fullnamefromnode(rbtnode, name);
+	RWUNLOCK(&rbtdb->tree_lock, isc_rwlocktype_read);
+
+	return (result);
+}
+
+static isc_result_t
+setservestalettl(dns_db_t *db, dns_ttl_t ttl) {
+	dns_rbtdb_t *rbtdb = (dns_rbtdb_t *)db;
+
+	REQUIRE(VALID_RBTDB(rbtdb));
+	REQUIRE(IS_CACHE(rbtdb));
+
+	/* currently no bounds checking.  0 means disable. */
+	rbtdb->serve_stale_ttl = ttl;
+	return (ISC_R_SUCCESS);
+}
+
+static isc_result_t
+getservestalettl(dns_db_t *db, dns_ttl_t *ttl) {
+	dns_rbtdb_t *rbtdb = (dns_rbtdb_t *)db;
+
+	REQUIRE(VALID_RBTDB(rbtdb));
+	REQUIRE(IS_CACHE(rbtdb));
+
+	*ttl = rbtdb->serve_stale_ttl;
+	return (ISC_R_SUCCESS);
+}
+
+static isc_result_t
+setservestalerefresh(dns_db_t *db, uint32_t interval) {
+	dns_rbtdb_t *rbtdb = (dns_rbtdb_t *)db;
+
+	REQUIRE(VALID_RBTDB(rbtdb));
+	REQUIRE(IS_CACHE(rbtdb));
+
+	/* currently no bounds checking.  0 means disable. */
+	rbtdb->serve_stale_refresh = interval;
+	return (ISC_R_SUCCESS);
+}
+
+static isc_result_t
+getservestalerefresh(dns_db_t *db, uint32_t *interval) {
+	dns_rbtdb_t *rbtdb = (dns_rbtdb_t *)db;
+
+	REQUIRE(VALID_RBTDB(rbtdb));
+	REQUIRE(IS_CACHE(rbtdb));
+
+	*interval = rbtdb->serve_stale_refresh;
+	return (ISC_R_SUCCESS);
+}
+
+static dns_dbmethods_t zone_methods = { attach,
+					detach,
+					beginload,
+					endload,
+					dump,
+					currentversion,
+					newversion,
+					attachversion,
+					closeversion,
+					findnode,
+					zone_find,
+					zone_findzonecut,
+					attachnode,
+					detachnode,
+					expirenode,
+					printnode,
+					createiterator,
+					zone_findrdataset,
+					allrdatasets,
+					addrdataset,
+					subtractrdataset,
+					deleterdataset,
+					issecure,
+					nodecount,
+					ispersistent,
+					overmem,
+					settask,
+					getoriginnode,
+					NULL, /* transfernode */
+					getnsec3parameters,
+					findnsec3node,
+					setsigningtime,
+					getsigningtime,
+					resigned,
+					isdnssec,
+					NULL, /* getrrsetstats */
+					NULL, /* rpz_attach */
+					NULL, /* rpz_ready */
+					NULL, /* findnodeext */
+					NULL, /* findext */
+					NULL, /* setcachestats */
+					hashsize,
+					nodefullname,
+					getsize,
+					NULL, /* setservestalettl */
+					NULL, /* getservestalettl */
+					NULL, /* setservestalerefresh */
+					NULL, /* getservestalerefresh */
+					setgluecachestats };
+
+static dns_dbmethods_t cache_methods = { attach,
+					 detach,
+					 beginload,
+					 endload,
+					 dump,
+					 currentversion,
+					 newversion,
+					 attachversion,
+					 closeversion,
+					 findnode,
+					 cache_find,
+					 cache_findzonecut,
+					 attachnode,
+					 detachnode,
+					 expirenode,
+					 printnode,
+					 createiterator,
+					 cache_findrdataset,
+					 allrdatasets,
+					 addrdataset,
+					 subtractrdataset,
+					 deleterdataset,
+					 issecure,
+					 nodecount,
+					 ispersistent,
+					 overmem,
+					 settask,
+					 getoriginnode,
+					 NULL, /* transfernode */
+					 NULL, /* getnsec3parameters */
+					 NULL, /* findnsec3node */
+					 NULL, /* setsigningtime */
+					 NULL, /* getsigningtime */
+					 NULL, /* resigned */
+					 isdnssec,
+					 getrrsetstats,
+					 NULL, /* rpz_attach */
+					 NULL, /* rpz_ready */
+					 NULL, /* findnodeext */
+					 NULL, /* findext */
+					 setcachestats,
+					 hashsize,
+					 nodefullname,
+					 NULL, /* getsize */
+					 setservestalettl,
+					 getservestalettl,
+					 setservestalerefresh,
+					 getservestalerefresh,
+					 NULL };
+
+isc_result_t
+dns_rbtdb_create(isc_mem_t *mctx, const dns_name_t *origin, dns_dbtype_t type,
+		 dns_rdataclass_t rdclass, unsigned int argc, char *argv[],
+		 void *driverarg, dns_db_t **dbp) {
+	dns_rbtdb_t *rbtdb;
+	isc_result_t result;
+	int i;
+	dns_name_t name;
+	bool (*sooner)(void *, void *);
+	isc_mem_t *hmctx = mctx;
+
+	/* Keep the compiler happy. */
+	UNUSED(driverarg);
+
+	rbtdb = isc_mem_get(mctx, sizeof(*rbtdb));
+
+	/*
+	 * If argv[0] exists, it points to a memory context to use for heap
+	 */
+	if (argc != 0) {
+		hmctx = (isc_mem_t *)argv[0];
+	}
+
+	memset(rbtdb, '\0', sizeof(*rbtdb));
+	dns_name_init(&rbtdb->common.origin, NULL);
+	rbtdb->common.attributes = 0;
+	if (type == dns_dbtype_cache) {
+		rbtdb->common.methods = &cache_methods;
+		rbtdb->common.attributes |= DNS_DBATTR_CACHE;
+	} else if (type == dns_dbtype_stub) {
+		rbtdb->common.methods = &zone_methods;
+		rbtdb->common.attributes |= DNS_DBATTR_STUB;
+	} else {
+		rbtdb->common.methods = &zone_methods;
+	}
+	rbtdb->common.rdclass = rdclass;
+	rbtdb->common.mctx = NULL;
+
+	ISC_LIST_INIT(rbtdb->common.update_listeners);
+
+	RBTDB_INITLOCK(&rbtdb->lock);
+
+	isc_rwlock_init(&rbtdb->tree_lock, 0, 0);
+
+	/*
+	 * Initialize node_lock_count in a generic way to support future
+	 * extension which allows the user to specify this value on creation.
+	 * Note that when specified for a cache DB it must be larger than 1
+	 * as commented with the definition of DEFAULT_CACHE_NODE_LOCK_COUNT.
+	 */
+	if (rbtdb->node_lock_count == 0) {
+		if (IS_CACHE(rbtdb)) {
+			rbtdb->node_lock_count = DEFAULT_CACHE_NODE_LOCK_COUNT;
+		} else {
+			rbtdb->node_lock_count = DEFAULT_NODE_LOCK_COUNT;
+		}
+	} else if (rbtdb->node_lock_count < 2 && IS_CACHE(rbtdb)) {
+		result = ISC_R_RANGE;
+		goto cleanup_tree_lock;
+	}
+	INSIST(rbtdb->node_lock_count < (1 << DNS_RBT_LOCKLENGTH));
+	rbtdb->node_locks = isc_mem_get(mctx, rbtdb->node_lock_count *
+						      sizeof(rbtdb_nodelock_t));
+
+	rbtdb->cachestats = NULL;
+	rbtdb->gluecachestats = NULL;
+
+	rbtdb->rrsetstats = NULL;
+	if (IS_CACHE(rbtdb)) {
+		result = dns_rdatasetstats_create(mctx, &rbtdb->rrsetstats);
+		if (result != ISC_R_SUCCESS) {
+			goto cleanup_node_locks;
+		}
+		rbtdb->rdatasets = isc_mem_get(
+			mctx,
+			rbtdb->node_lock_count * sizeof(rdatasetheaderlist_t));
+		for (i = 0; i < (int)rbtdb->node_lock_count; i++) {
+			ISC_LIST_INIT(rbtdb->rdatasets[i]);
+		}
+	} else {
+		rbtdb->rdatasets = NULL;
+	}
+
+	/*
+	 * Create the heaps.
+	 */
+	rbtdb->heaps = isc_mem_get(hmctx, rbtdb->node_lock_count *
+						  sizeof(isc_heap_t *));
+	for (i = 0; i < (int)rbtdb->node_lock_count; i++) {
+		rbtdb->heaps[i] = NULL;
+	}
+	sooner = IS_CACHE(rbtdb) ? ttl_sooner : resign_sooner;
+	for (i = 0; i < (int)rbtdb->node_lock_count; i++) {
+		isc_heap_create(hmctx, sooner, set_index, 0, &rbtdb->heaps[i]);
+	}
+
+	/*
+	 * Create deadnode lists.
+	 */
+	rbtdb->deadnodes = isc_mem_get(mctx, rbtdb->node_lock_count *
+						     sizeof(rbtnodelist_t));
+	for (i = 0; i < (int)rbtdb->node_lock_count; i++) {
+		ISC_LIST_INIT(rbtdb->deadnodes[i]);
+	}
+
+	rbtdb->active = rbtdb->node_lock_count;
+
+	for (i = 0; i < (int)(rbtdb->node_lock_count); i++) {
+		NODE_INITLOCK(&rbtdb->node_locks[i].lock);
+		isc_refcount_init(&rbtdb->node_locks[i].references, 0);
+		rbtdb->node_locks[i].exiting = false;
+	}
+
+	/*
+	 * Attach to the mctx.  The database will persist so long as there
+	 * are references to it, and attaching to the mctx ensures that our
+	 * mctx won't disappear out from under us.
+	 */
+	isc_mem_attach(mctx, &rbtdb->common.mctx);
+	isc_mem_attach(hmctx, &rbtdb->hmctx);
+
+	/*
+	 * Make a copy of the origin name.
+	 */
+	result = dns_name_dupwithoffsets(origin, mctx, &rbtdb->common.origin);
+	if (result != ISC_R_SUCCESS) {
+		free_rbtdb(rbtdb, false, NULL);
+		return (result);
+	}
+
+	/*
+	 * Make the Red-Black Trees.
+	 */
+	result = dns_rbt_create(mctx, delete_callback, rbtdb, &rbtdb->tree);
+	if (result != ISC_R_SUCCESS) {
+		free_rbtdb(rbtdb, false, NULL);
+		return (result);
+	}
+
+	result = dns_rbt_create(mctx, delete_callback, rbtdb, &rbtdb->nsec);
+	if (result != ISC_R_SUCCESS) {
+		free_rbtdb(rbtdb, false, NULL);
+		return (result);
+	}
+
+	result = dns_rbt_create(mctx, delete_callback, rbtdb, &rbtdb->nsec3);
+	if (result != ISC_R_SUCCESS) {
+		free_rbtdb(rbtdb, false, NULL);
+		return (result);
+	}
+
+	/*
+	 * In order to set the node callback bit correctly in zone databases,
+	 * we need to know if the node has the origin name of the zone.
+	 * In loading_addrdataset() we could simply compare the new name
+	 * to the origin name, but this is expensive.  Also, we don't know the
+	 * node name in addrdataset(), so we need another way of knowing the
+	 * zone's top.
+	 *
+	 * We now explicitly create a node for the zone's origin, and then
+	 * we simply remember the node's address.  This is safe, because
+	 * the top-of-zone node can never be deleted, nor can its address
+	 * change.
+	 */
+	if (!IS_CACHE(rbtdb)) {
+		rbtdb->origin_node = NULL;
+		result = dns_rbt_addnode(rbtdb->tree, &rbtdb->common.origin,
+					 &rbtdb->origin_node);
+		if (result != ISC_R_SUCCESS) {
+			INSIST(result != ISC_R_EXISTS);
+			free_rbtdb(rbtdb, false, NULL);
+			return (result);
+		}
+		INSIST(rbtdb->origin_node != NULL);
+		rbtdb->origin_node->nsec = DNS_RBT_NSEC_NORMAL;
+		/*
+		 * We need to give the origin node the right locknum.
+		 */
+		dns_name_init(&name, NULL);
+		dns_rbt_namefromnode(rbtdb->origin_node, &name);
+		rbtdb->origin_node->locknum = rbtdb->origin_node->hashval %
+					      rbtdb->node_lock_count;
+		/*
+		 * Add an apex node to the NSEC3 tree so that NSEC3 searches
+		 * return partial matches when there is only a single NSEC3
+		 * record in the tree.
+		 */
+		rbtdb->nsec3_origin_node = NULL;
+		result = dns_rbt_addnode(rbtdb->nsec3, &rbtdb->common.origin,
+					 &rbtdb->nsec3_origin_node);
+		if (result != ISC_R_SUCCESS) {
+			INSIST(result != ISC_R_EXISTS);
+			free_rbtdb(rbtdb, false, NULL);
+			return (result);
+		}
+		rbtdb->nsec3_origin_node->nsec = DNS_RBT_NSEC_NSEC3;
+		/*
+		 * We need to give the nsec3 origin node the right locknum.
+		 */
+		dns_name_init(&name, NULL);
+		dns_rbt_namefromnode(rbtdb->nsec3_origin_node, &name);
+		rbtdb->nsec3_origin_node->locknum =
+			rbtdb->nsec3_origin_node->hashval %
+			rbtdb->node_lock_count;
+	}
+
+	/*
+	 * Misc. Initialization.
+	 */
+	isc_refcount_init(&rbtdb->references, 1);
+	rbtdb->attributes = 0;
+	rbtdb->task = NULL;
+	rbtdb->serve_stale_ttl = 0;
+
+	/*
+	 * Version Initialization.
+	 */
+	rbtdb->current_serial = 1;
+	rbtdb->least_serial = 1;
+	rbtdb->next_serial = 2;
+	rbtdb->current_version = allocate_version(mctx, 1, 1, false);
+	rbtdb->current_version->rbtdb = rbtdb;
+	rbtdb->current_version->secure = dns_db_insecure;
+	rbtdb->current_version->havensec3 = false;
+	rbtdb->current_version->flags = 0;
+	rbtdb->current_version->iterations = 0;
+	rbtdb->current_version->hash = 0;
+	rbtdb->current_version->salt_length = 0;
+	memset(rbtdb->current_version->salt, 0,
+	       sizeof(rbtdb->current_version->salt));
+	isc_rwlock_init(&rbtdb->current_version->rwlock, 0, 0);
+	rbtdb->current_version->records = 0;
+	rbtdb->current_version->xfrsize = 0;
+	rbtdb->future_version = NULL;
+	ISC_LIST_INIT(rbtdb->open_versions);
+	/*
+	 * Keep the current version in the open list so that list operation
+	 * won't happen in normal lookup operations.
+	 */
+	PREPEND(rbtdb->open_versions, rbtdb->current_version, link);
+
+	rbtdb->common.magic = DNS_DB_MAGIC;
+	rbtdb->common.impmagic = RBTDB_MAGIC;
+
+	*dbp = (dns_db_t *)rbtdb;
+
+	return (ISC_R_SUCCESS);
+
+cleanup_node_locks:
+	isc_mem_put(mctx, rbtdb->node_locks,
+		    rbtdb->node_lock_count * sizeof(rbtdb_nodelock_t));
+
+cleanup_tree_lock:
+	isc_rwlock_destroy(&rbtdb->tree_lock);
+	RBTDB_DESTROYLOCK(&rbtdb->lock);
+	isc_mem_put(mctx, rbtdb, sizeof(*rbtdb));
+	return (result);
+}
+
+/*
+ * Slabbed Rdataset Methods
+ */
+
+static void
+rdataset_disassociate(dns_rdataset_t *rdataset) {
+	dns_db_t *db = rdataset->private1;
+	dns_dbnode_t *node = rdataset->private2;
+
+	detachnode(db, &node);
+}
+
+static isc_result_t
+rdataset_first(dns_rdataset_t *rdataset) {
+	unsigned char *raw = rdataset->private3; /* RDATASLAB */
+	unsigned int count;
+
+	count = raw[0] * 256 + raw[1];
+	if (count == 0) {
+		rdataset->private5 = NULL;
+		return (ISC_R_NOMORE);
+	}
+
+	if ((rdataset->attributes & DNS_RDATASETATTR_LOADORDER) == 0) {
+		raw += DNS_RDATASET_COUNT;
+	}
+
+	raw += DNS_RDATASET_LENGTH;
+
+	/*
+	 * The privateuint4 field is the number of rdata beyond the
+	 * cursor position, so we decrement the total count by one
+	 * before storing it.
+	 *
+	 * If DNS_RDATASETATTR_LOADORDER is not set 'raw' points to the
+	 * first record.  If DNS_RDATASETATTR_LOADORDER is set 'raw' points
+	 * to the first entry in the offset table.
+	 */
+	count--;
+	rdataset->privateuint4 = count;
+	rdataset->private5 = raw;
+
+	return (ISC_R_SUCCESS);
+}
+
+static isc_result_t
+rdataset_next(dns_rdataset_t *rdataset) {
+	unsigned int count;
+	unsigned int length;
+	unsigned char *raw; /* RDATASLAB */
+
+	count = rdataset->privateuint4;
+	if (count == 0) {
+		return (ISC_R_NOMORE);
+	}
+	count--;
+	rdataset->privateuint4 = count;
+
+	/*
+	 * Skip forward one record (length + 4) or one offset (4).
+	 */
+	raw = rdataset->private5;
+#if DNS_RDATASET_FIXED
+	if ((rdataset->attributes & DNS_RDATASETATTR_LOADORDER) == 0)
+#endif /* DNS_RDATASET_FIXED */
+	{
+		length = raw[0] * 256 + raw[1];
+		raw += length;
+	}
+
+	rdataset->private5 = raw + DNS_RDATASET_ORDER + DNS_RDATASET_LENGTH;
+
+	return (ISC_R_SUCCESS);
+}
+
+static void
+rdataset_current(dns_rdataset_t *rdataset, dns_rdata_t *rdata) {
+	unsigned char *raw = rdataset->private5; /* RDATASLAB */
+	unsigned int length;
+	isc_region_t r;
+	unsigned int flags = 0;
+
+	REQUIRE(raw != NULL);
+
+	/*
+	 * Find the start of the record if not already in private5
+	 * then skip the length and order fields.
+	 */
+#if DNS_RDATASET_FIXED
+	if ((rdataset->attributes & DNS_RDATASETATTR_LOADORDER) != 0) {
+		unsigned int offset;
+		offset = ((unsigned int)raw[0] << 24) +
+			 ((unsigned int)raw[1] << 16) +
+			 ((unsigned int)raw[2] << 8) + (unsigned int)raw[3];
+		raw = rdataset->private3;
+		raw += offset;
+	}
+#endif /* if DNS_RDATASET_FIXED */
+
+	length = raw[0] * 256 + raw[1];
+
+	raw += DNS_RDATASET_ORDER + DNS_RDATASET_LENGTH;
+
+	if (rdataset->type == dns_rdatatype_rrsig) {
+		if (*raw & DNS_RDATASLAB_OFFLINE) {
+			flags |= DNS_RDATA_OFFLINE;
+		}
+		length--;
+		raw++;
+	}
+	r.length = length;
+	r.base = raw;
+	dns_rdata_fromregion(rdata, rdataset->rdclass, rdataset->type, &r);
+	rdata->flags |= flags;
+}
+
+static void
+rdataset_clone(dns_rdataset_t *source, dns_rdataset_t *target) {
+	dns_db_t *db = source->private1;
+	dns_dbnode_t *node = source->private2;
+	dns_dbnode_t *cloned_node = NULL;
+
+	attachnode(db, node, &cloned_node);
+	INSIST(!ISC_LINK_LINKED(target, link));
+	*target = *source;
+	ISC_LINK_INIT(target, link);
+
+	/*
+	 * Reset iterator state.
+	 */
+	target->privateuint4 = 0;
+	target->private5 = NULL;
+}
+
+static unsigned int
+rdataset_count(dns_rdataset_t *rdataset) {
+	unsigned char *raw = rdataset->private3; /* RDATASLAB */
+	unsigned int count;
+
+	count = raw[0] * 256 + raw[1];
+
+	return (count);
+}
+
+static isc_result_t
+rdataset_getnoqname(dns_rdataset_t *rdataset, dns_name_t *name,
+		    dns_rdataset_t *nsec, dns_rdataset_t *nsecsig) {
+	dns_db_t *db = rdataset->private1;
+	dns_dbnode_t *node = rdataset->private2;
+	dns_dbnode_t *cloned_node;
+	const struct noqname *noqname = rdataset->private6;
+
+	cloned_node = NULL;
+	attachnode(db, node, &cloned_node);
+	nsec->methods = &slab_methods;
+	nsec->rdclass = db->rdclass;
+	nsec->type = noqname->type;
+	nsec->covers = 0;
+	nsec->ttl = rdataset->ttl;
+	nsec->trust = rdataset->trust;
+	nsec->private1 = rdataset->private1;
+	nsec->private2 = rdataset->private2;
+	nsec->private3 = noqname->neg;
+	nsec->privateuint4 = 0;
+	nsec->private5 = NULL;
+	nsec->private6 = NULL;
+	nsec->private7 = NULL;
+
+	cloned_node = NULL;
+	attachnode(db, node, &cloned_node);
+	nsecsig->methods = &slab_methods;
+	nsecsig->rdclass = db->rdclass;
+	nsecsig->type = dns_rdatatype_rrsig;
+	nsecsig->covers = noqname->type;
+	nsecsig->ttl = rdataset->ttl;
+	nsecsig->trust = rdataset->trust;
+	nsecsig->private1 = rdataset->private1;
+	nsecsig->private2 = rdataset->private2;
+	nsecsig->private3 = noqname->negsig;
+	nsecsig->privateuint4 = 0;
+	nsecsig->private5 = NULL;
+	nsec->private6 = NULL;
+	nsec->private7 = NULL;
+
+	dns_name_clone(&noqname->name, name);
+
+	return (ISC_R_SUCCESS);
+}
+
+static isc_result_t
+rdataset_getclosest(dns_rdataset_t *rdataset, dns_name_t *name,
+		    dns_rdataset_t *nsec, dns_rdataset_t *nsecsig) {
+	dns_db_t *db = rdataset->private1;
+	dns_dbnode_t *node = rdataset->private2;
+	dns_dbnode_t *cloned_node;
+	const struct noqname *closest = rdataset->private7;
+
+	cloned_node = NULL;
+	attachnode(db, node, &cloned_node);
+	nsec->methods = &slab_methods;
+	nsec->rdclass = db->rdclass;
+	nsec->type = closest->type;
+	nsec->covers = 0;
+	nsec->ttl = rdataset->ttl;
+	nsec->trust = rdataset->trust;
+	nsec->private1 = rdataset->private1;
+	nsec->private2 = rdataset->private2;
+	nsec->private3 = closest->neg;
+	nsec->privateuint4 = 0;
+	nsec->private5 = NULL;
+	nsec->private6 = NULL;
+	nsec->private7 = NULL;
+
+	cloned_node = NULL;
+	attachnode(db, node, &cloned_node);
+	nsecsig->methods = &slab_methods;
+	nsecsig->rdclass = db->rdclass;
+	nsecsig->type = dns_rdatatype_rrsig;
+	nsecsig->covers = closest->type;
+	nsecsig->ttl = rdataset->ttl;
+	nsecsig->trust = rdataset->trust;
+	nsecsig->private1 = rdataset->private1;
+	nsecsig->private2 = rdataset->private2;
+	nsecsig->private3 = closest->negsig;
+	nsecsig->privateuint4 = 0;
+	nsecsig->private5 = NULL;
+	nsec->private6 = NULL;
+	nsec->private7 = NULL;
+
+	dns_name_clone(&closest->name, name);
+
+	return (ISC_R_SUCCESS);
+}
+
+static void
+rdataset_settrust(dns_rdataset_t *rdataset, dns_trust_t trust) {
+	dns_rbtdb_t *rbtdb = rdataset->private1;
+	dns_rbtnode_t *rbtnode = rdataset->private2;
+	rdatasetheader_t *header = rdataset->private3;
+
+	header--;
+	NODE_LOCK(&rbtdb->node_locks[rbtnode->locknum].lock,
+		  isc_rwlocktype_write);
+	header->trust = rdataset->trust = trust;
+	NODE_UNLOCK(&rbtdb->node_locks[rbtnode->locknum].lock,
+		    isc_rwlocktype_write);
+}
+
+static void
+rdataset_expire(dns_rdataset_t *rdataset) {
+	dns_rbtdb_t *rbtdb = rdataset->private1;
+	dns_rbtnode_t *rbtnode = rdataset->private2;
+	rdatasetheader_t *header = rdataset->private3;
+
+	header--;
+	NODE_LOCK(&rbtdb->node_locks[rbtnode->locknum].lock,
+		  isc_rwlocktype_write);
+	expire_header(rbtdb, header, false, expire_flush);
+	NODE_UNLOCK(&rbtdb->node_locks[rbtnode->locknum].lock,
+		    isc_rwlocktype_write);
+}
+
+static void
+rdataset_clearprefetch(dns_rdataset_t *rdataset) {
+	dns_rbtdb_t *rbtdb = rdataset->private1;
+	dns_rbtnode_t *rbtnode = rdataset->private2;
+	rdatasetheader_t *header = rdataset->private3;
+
+	header--;
+	NODE_LOCK(&rbtdb->node_locks[rbtnode->locknum].lock,
+		  isc_rwlocktype_write);
+	RDATASET_ATTR_CLR(header, RDATASET_ATTR_PREFETCH);
+	NODE_UNLOCK(&rbtdb->node_locks[rbtnode->locknum].lock,
+		    isc_rwlocktype_write);
+}
+
+/*
+ * Rdataset Iterator Methods
+ */
+
+static void
+rdatasetiter_destroy(dns_rdatasetiter_t **iteratorp) {
+	rbtdb_rdatasetiter_t *rbtiterator;
+
+	rbtiterator = (rbtdb_rdatasetiter_t *)(*iteratorp);
+
+	if (rbtiterator->common.version != NULL) {
+		closeversion(rbtiterator->common.db,
+			     &rbtiterator->common.version, false);
+	}
+	detachnode(rbtiterator->common.db, &rbtiterator->common.node);
+	isc_mem_put(rbtiterator->common.db->mctx, rbtiterator,
+		    sizeof(*rbtiterator));
+
+	*iteratorp = NULL;
+}
+
+static bool
+iterator_active(dns_rbtdb_t *rbtdb, rbtdb_rdatasetiter_t *rbtiterator,
+		rdatasetheader_t *header) {
+	dns_ttl_t stale_ttl = header->rdh_ttl + STALE_TTL(header, rbtdb);
+
+	/*
+	 * Is this a "this rdataset doesn't exist" record?
+	 */
+	if (NONEXISTENT(header)) {
+		return (false);
+	}
+
+	/*
+	 * If this is a zone or this header still active then return it.
+	 */
+	if (!IS_CACHE(rbtdb) || ACTIVE(header, rbtiterator->common.now)) {
+		return (true);
+	}
+
+	/*
+	 * If we are not returning stale records or the rdataset is
+	 * too old don't return it.
+	 */
+	if (!STALEOK(rbtiterator) || (rbtiterator->common.now > stale_ttl)) {
+		return (false);
+	}
+	return (true);
+}
+
+static isc_result_t
+rdatasetiter_first(dns_rdatasetiter_t *iterator) {
+	rbtdb_rdatasetiter_t *rbtiterator = (rbtdb_rdatasetiter_t *)iterator;
+	dns_rbtdb_t *rbtdb = (dns_rbtdb_t *)(rbtiterator->common.db);
+	dns_rbtnode_t *rbtnode = rbtiterator->common.node;
+	rbtdb_version_t *rbtversion = rbtiterator->common.version;
+	rdatasetheader_t *header, *top_next;
+	rbtdb_serial_t serial = IS_CACHE(rbtdb) ? 1 : rbtversion->serial;
+
+	NODE_LOCK(&rbtdb->node_locks[rbtnode->locknum].lock,
+		  isc_rwlocktype_read);
+
+	for (header = rbtnode->data; header != NULL; header = top_next) {
+		top_next = header->next;
+		do {
+			if (EXPIREDOK(rbtiterator)) {
+				if (!NONEXISTENT(header)) {
+					break;
+				}
+				header = header->down;
+			} else if (header->serial <= serial && !IGNORE(header))
+			{
+				if (!iterator_active(rbtdb, rbtiterator,
+						     header))
+				{
+					header = NULL;
+				}
+				break;
+			} else {
+				header = header->down;
+			}
+		} while (header != NULL);
+		if (header != NULL) {
+			break;
+		}
+	}
+
+	NODE_UNLOCK(&rbtdb->node_locks[rbtnode->locknum].lock,
+		    isc_rwlocktype_read);
+
+	rbtiterator->current = header;
+
+	if (header == NULL) {
+		return (ISC_R_NOMORE);
+	}
+
+	return (ISC_R_SUCCESS);
+}
+
+static isc_result_t
+rdatasetiter_next(dns_rdatasetiter_t *iterator) {
+	rbtdb_rdatasetiter_t *rbtiterator = (rbtdb_rdatasetiter_t *)iterator;
+	dns_rbtdb_t *rbtdb = (dns_rbtdb_t *)(rbtiterator->common.db);
+	dns_rbtnode_t *rbtnode = rbtiterator->common.node;
+	rbtdb_version_t *rbtversion = rbtiterator->common.version;
+	rdatasetheader_t *header, *top_next;
+	rbtdb_serial_t serial = IS_CACHE(rbtdb) ? 1 : rbtversion->serial;
+	rbtdb_rdatatype_t type, negtype;
+	dns_rdatatype_t rdtype, covers;
+	bool expiredok = EXPIREDOK(rbtiterator);
+
+	header = rbtiterator->current;
+	if (header == NULL) {
+		return (ISC_R_NOMORE);
+	}
+
+	NODE_LOCK(&rbtdb->node_locks[rbtnode->locknum].lock,
+		  isc_rwlocktype_read);
+
+	type = header->type;
+	rdtype = RBTDB_RDATATYPE_BASE(header->type);
+	if (NEGATIVE(header)) {
+		covers = RBTDB_RDATATYPE_EXT(header->type);
+		negtype = RBTDB_RDATATYPE_VALUE(covers, 0);
+	} else {
+		negtype = RBTDB_RDATATYPE_VALUE(0, rdtype);
+	}
+
+	/*
+	 * Find the start of the header chain for the next type
+	 * by walking back up the list.
+	 */
+	top_next = header->next;
+	while (top_next != NULL &&
+	       (top_next->type == type || top_next->type == negtype))
+	{
+		top_next = top_next->next;
+	}
+	if (expiredok) {
+		/*
+		 * Keep walking down the list if possible or
+		 * start the next type.
+		 */
+		header = header->down != NULL ? header->down : top_next;
+	} else {
+		header = top_next;
+	}
+	for (; header != NULL; header = top_next) {
+		top_next = header->next;
+		do {
+			if (expiredok) {
+				if (!NONEXISTENT(header)) {
+					break;
+				}
+				header = header->down;
+			} else if (header->serial <= serial && !IGNORE(header))
+			{
+				if (!iterator_active(rbtdb, rbtiterator,
+						     header))
+				{
+					header = NULL;
+				}
+				break;
+			} else {
+				header = header->down;
+			}
+		} while (header != NULL);
+		if (header != NULL) {
+			break;
+		}
+		/*
+		 * Find the start of the header chain for the next type
+		 * by walking back up the list.
+		 */
+		while (top_next != NULL &&
+		       (top_next->type == type || top_next->type == negtype))
+		{
+			top_next = top_next->next;
+		}
+	}
+
+	NODE_UNLOCK(&rbtdb->node_locks[rbtnode->locknum].lock,
+		    isc_rwlocktype_read);
+
+	rbtiterator->current = header;
+
+	if (header == NULL) {
+		return (ISC_R_NOMORE);
+	}
+
+	return (ISC_R_SUCCESS);
+}
+
+static void
+rdatasetiter_current(dns_rdatasetiter_t *iterator, dns_rdataset_t *rdataset) {
+	rbtdb_rdatasetiter_t *rbtiterator = (rbtdb_rdatasetiter_t *)iterator;
+	dns_rbtdb_t *rbtdb = (dns_rbtdb_t *)(rbtiterator->common.db);
+	dns_rbtnode_t *rbtnode = rbtiterator->common.node;
+	rdatasetheader_t *header;
+
+	header = rbtiterator->current;
+	REQUIRE(header != NULL);
+
+	NODE_LOCK(&rbtdb->node_locks[rbtnode->locknum].lock,
+		  isc_rwlocktype_read);
+
+	bind_rdataset(rbtdb, rbtnode, header, rbtiterator->common.now,
+		      isc_rwlocktype_read, rdataset);
+
+	NODE_UNLOCK(&rbtdb->node_locks[rbtnode->locknum].lock,
+		    isc_rwlocktype_read);
+}
+
+/*
+ * Database Iterator Methods
+ */
+
+static void
+reference_iter_node(rbtdb_dbiterator_t *rbtdbiter) {
+	dns_rbtdb_t *rbtdb = (dns_rbtdb_t *)rbtdbiter->common.db;
+	dns_rbtnode_t *node = rbtdbiter->node;
+
+	if (node == NULL) {
+		return;
+	}
+
+	INSIST(rbtdbiter->tree_locked != isc_rwlocktype_none);
+	reactivate_node(rbtdb, node, rbtdbiter->tree_locked);
+}
+
+static void
+dereference_iter_node(rbtdb_dbiterator_t *rbtdbiter) {
+	dns_rbtdb_t *rbtdb = (dns_rbtdb_t *)rbtdbiter->common.db;
+	dns_rbtnode_t *node = rbtdbiter->node;
+	nodelock_t *lock;
+
+	if (node == NULL) {
+		return;
+	}
+
+	lock = &rbtdb->node_locks[node->locknum].lock;
+	NODE_LOCK(lock, isc_rwlocktype_read);
+	decrement_reference(rbtdb, node, 0, isc_rwlocktype_read,
+			    rbtdbiter->tree_locked, false);
+	NODE_UNLOCK(lock, isc_rwlocktype_read);
+
+	rbtdbiter->node = NULL;
+}
+
+static void
+flush_deletions(rbtdb_dbiterator_t *rbtdbiter) {
+	dns_rbtnode_t *node;
+	dns_rbtdb_t *rbtdb = (dns_rbtdb_t *)rbtdbiter->common.db;
+	bool was_read_locked = false;
+	nodelock_t *lock;
+	int i;
+
+	if (rbtdbiter->delcnt != 0) {
+		/*
+		 * Note that "%d node of %d in tree" can report things like
+		 * "flush_deletions: 59 nodes of 41 in tree".  This means
+		 * That some nodes appear on the deletions list more than
+		 * once.  Only the last occurrence will actually be deleted.
+		 */
+		isc_log_write(dns_lctx, DNS_LOGCATEGORY_DATABASE,
+			      DNS_LOGMODULE_CACHE, ISC_LOG_DEBUG(1),
+			      "flush_deletions: %d nodes of %d in tree",
+			      rbtdbiter->delcnt,
+			      dns_rbt_nodecount(rbtdb->tree));
+
+		if (rbtdbiter->tree_locked == isc_rwlocktype_read) {
+			RWUNLOCK(&rbtdb->tree_lock, isc_rwlocktype_read);
+			was_read_locked = true;
+		}
+		RWLOCK(&rbtdb->tree_lock, isc_rwlocktype_write);
+		rbtdbiter->tree_locked = isc_rwlocktype_write;
+
+		for (i = 0; i < rbtdbiter->delcnt; i++) {
+			node = rbtdbiter->deletions[i];
+			lock = &rbtdb->node_locks[node->locknum].lock;
+
+			NODE_LOCK(lock, isc_rwlocktype_read);
+			decrement_reference(rbtdb, node, 0, isc_rwlocktype_read,
+					    rbtdbiter->tree_locked, false);
+			NODE_UNLOCK(lock, isc_rwlocktype_read);
+		}
+
+		rbtdbiter->delcnt = 0;
+
+		RWUNLOCK(&rbtdb->tree_lock, isc_rwlocktype_write);
+		if (was_read_locked) {
+			RWLOCK(&rbtdb->tree_lock, isc_rwlocktype_read);
+			rbtdbiter->tree_locked = isc_rwlocktype_read;
+		} else {
+			rbtdbiter->tree_locked = isc_rwlocktype_none;
+		}
+	}
+}
+
+static void
+resume_iteration(rbtdb_dbiterator_t *rbtdbiter) {
+	dns_rbtdb_t *rbtdb = (dns_rbtdb_t *)rbtdbiter->common.db;
+
+	REQUIRE(rbtdbiter->paused);
+	REQUIRE(rbtdbiter->tree_locked == isc_rwlocktype_none);
+
+	RWLOCK(&rbtdb->tree_lock, isc_rwlocktype_read);
+	rbtdbiter->tree_locked = isc_rwlocktype_read;
+
+	rbtdbiter->paused = false;
+}
+
+static void
+dbiterator_destroy(dns_dbiterator_t **iteratorp) {
+	rbtdb_dbiterator_t *rbtdbiter = (rbtdb_dbiterator_t *)(*iteratorp);
+	dns_rbtdb_t *rbtdb = (dns_rbtdb_t *)rbtdbiter->common.db;
+	dns_db_t *db = NULL;
+
+	if (rbtdbiter->tree_locked == isc_rwlocktype_read) {
+		RWUNLOCK(&rbtdb->tree_lock, isc_rwlocktype_read);
+		rbtdbiter->tree_locked = isc_rwlocktype_none;
+	} else {
+		INSIST(rbtdbiter->tree_locked == isc_rwlocktype_none);
+	}
+
+	dereference_iter_node(rbtdbiter);
+
+	flush_deletions(rbtdbiter);
+
+	dns_db_attach(rbtdbiter->common.db, &db);
+	dns_db_detach(&rbtdbiter->common.db);
+
+	dns_rbtnodechain_reset(&rbtdbiter->chain);
+	dns_rbtnodechain_reset(&rbtdbiter->nsec3chain);
+	isc_mem_put(db->mctx, rbtdbiter, sizeof(*rbtdbiter));
+	dns_db_detach(&db);
+
+	*iteratorp = NULL;
+}
+
+static isc_result_t
+dbiterator_first(dns_dbiterator_t *iterator) {
+	isc_result_t result;
+	rbtdb_dbiterator_t *rbtdbiter = (rbtdb_dbiterator_t *)iterator;
+	dns_rbtdb_t *rbtdb = (dns_rbtdb_t *)iterator->db;
+	dns_name_t *name, *origin;
+
+	if (rbtdbiter->result != ISC_R_SUCCESS &&
+	    rbtdbiter->result != ISC_R_NOTFOUND &&
+	    rbtdbiter->result != DNS_R_PARTIALMATCH &&
+	    rbtdbiter->result != ISC_R_NOMORE)
+	{
+		return (rbtdbiter->result);
+	}
+
+	if (rbtdbiter->paused) {
+		resume_iteration(rbtdbiter);
+	}
+
+	dereference_iter_node(rbtdbiter);
+
+	name = dns_fixedname_name(&rbtdbiter->name);
+	origin = dns_fixedname_name(&rbtdbiter->origin);
+	dns_rbtnodechain_reset(&rbtdbiter->chain);
+	dns_rbtnodechain_reset(&rbtdbiter->nsec3chain);
+
+	if (rbtdbiter->nsec3only) {
+		rbtdbiter->current = &rbtdbiter->nsec3chain;
+		result = dns_rbtnodechain_first(rbtdbiter->current,
+						rbtdb->nsec3, name, origin);
+	} else {
+		rbtdbiter->current = &rbtdbiter->chain;
+		result = dns_rbtnodechain_first(rbtdbiter->current, rbtdb->tree,
+						name, origin);
+		if (!rbtdbiter->nonsec3 && result == ISC_R_NOTFOUND) {
+			rbtdbiter->current = &rbtdbiter->nsec3chain;
+			result = dns_rbtnodechain_first(
+				rbtdbiter->current, rbtdb->nsec3, name, origin);
+		}
+	}
+	if (result == ISC_R_SUCCESS || result == DNS_R_NEWORIGIN) {
+		result = dns_rbtnodechain_current(rbtdbiter->current, NULL,
+						  NULL, &rbtdbiter->node);
+		if (result == ISC_R_SUCCESS) {
+			rbtdbiter->new_origin = true;
+			reference_iter_node(rbtdbiter);
+		}
+	} else {
+		INSIST(result == ISC_R_NOTFOUND);
+		result = ISC_R_NOMORE; /* The tree is empty. */
+	}
+
+	rbtdbiter->result = result;
+
+	if (result != ISC_R_SUCCESS) {
+		ENSURE(!rbtdbiter->paused);
+	}
+
+	return (result);
+}
+
+static isc_result_t
+dbiterator_last(dns_dbiterator_t *iterator) {
+	isc_result_t result;
+	rbtdb_dbiterator_t *rbtdbiter = (rbtdb_dbiterator_t *)iterator;
+	dns_rbtdb_t *rbtdb = (dns_rbtdb_t *)iterator->db;
+	dns_name_t *name, *origin;
+
+	if (rbtdbiter->result != ISC_R_SUCCESS &&
+	    rbtdbiter->result != ISC_R_NOTFOUND &&
+	    rbtdbiter->result != DNS_R_PARTIALMATCH &&
+	    rbtdbiter->result != ISC_R_NOMORE)
+	{
+		return (rbtdbiter->result);
+	}
+
+	if (rbtdbiter->paused) {
+		resume_iteration(rbtdbiter);
+	}
+
+	dereference_iter_node(rbtdbiter);
+
+	name = dns_fixedname_name(&rbtdbiter->name);
+	origin = dns_fixedname_name(&rbtdbiter->origin);
+	dns_rbtnodechain_reset(&rbtdbiter->chain);
+	dns_rbtnodechain_reset(&rbtdbiter->nsec3chain);
+
+	result = ISC_R_NOTFOUND;
+	if (rbtdbiter->nsec3only && !rbtdbiter->nonsec3) {
+		rbtdbiter->current = &rbtdbiter->nsec3chain;
+		result = dns_rbtnodechain_last(rbtdbiter->current, rbtdb->nsec3,
+					       name, origin);
+	}
+	if (!rbtdbiter->nsec3only && result == ISC_R_NOTFOUND) {
+		rbtdbiter->current = &rbtdbiter->chain;
+		result = dns_rbtnodechain_last(rbtdbiter->current, rbtdb->tree,
+					       name, origin);
+	}
+	if (result == ISC_R_SUCCESS || result == DNS_R_NEWORIGIN) {
+		result = dns_rbtnodechain_current(rbtdbiter->current, NULL,
+						  NULL, &rbtdbiter->node);
+		if (result == ISC_R_SUCCESS) {
+			rbtdbiter->new_origin = true;
+			reference_iter_node(rbtdbiter);
+		}
+	} else {
+		INSIST(result == ISC_R_NOTFOUND);
+		result = ISC_R_NOMORE; /* The tree is empty. */
+	}
+
+	rbtdbiter->result = result;
+
+	return (result);
+}
+
+static isc_result_t
+dbiterator_seek(dns_dbiterator_t *iterator, const dns_name_t *name) {
+	isc_result_t result, tresult;
+	rbtdb_dbiterator_t *rbtdbiter = (rbtdb_dbiterator_t *)iterator;
+	dns_rbtdb_t *rbtdb = (dns_rbtdb_t *)iterator->db;
+	dns_name_t *iname, *origin;
+
+	if (rbtdbiter->result != ISC_R_SUCCESS &&
+	    rbtdbiter->result != ISC_R_NOTFOUND &&
+	    rbtdbiter->result != DNS_R_PARTIALMATCH &&
+	    rbtdbiter->result != ISC_R_NOMORE)
+	{
+		return (rbtdbiter->result);
+	}
+
+	if (rbtdbiter->paused) {
+		resume_iteration(rbtdbiter);
+	}
+
+	dereference_iter_node(rbtdbiter);
+
+	iname = dns_fixedname_name(&rbtdbiter->name);
+	origin = dns_fixedname_name(&rbtdbiter->origin);
+	dns_rbtnodechain_reset(&rbtdbiter->chain);
+	dns_rbtnodechain_reset(&rbtdbiter->nsec3chain);
+
+	if (rbtdbiter->nsec3only) {
+		rbtdbiter->current = &rbtdbiter->nsec3chain;
+		result = dns_rbt_findnode(rbtdb->nsec3, name, NULL,
+					  &rbtdbiter->node, rbtdbiter->current,
+					  DNS_RBTFIND_EMPTYDATA, NULL, NULL);
+	} else if (rbtdbiter->nonsec3) {
+		rbtdbiter->current = &rbtdbiter->chain;
+		result = dns_rbt_findnode(rbtdb->tree, name, NULL,
+					  &rbtdbiter->node, rbtdbiter->current,
+					  DNS_RBTFIND_EMPTYDATA, NULL, NULL);
+	} else {
+		/*
+		 * Stay on main chain if not found on either chain.
+		 */
+		rbtdbiter->current = &rbtdbiter->chain;
+		result = dns_rbt_findnode(rbtdb->tree, name, NULL,
+					  &rbtdbiter->node, rbtdbiter->current,
+					  DNS_RBTFIND_EMPTYDATA, NULL, NULL);
+		if (result == DNS_R_PARTIALMATCH) {
+			dns_rbtnode_t *node = NULL;
+			tresult = dns_rbt_findnode(
+				rbtdb->nsec3, name, NULL, &node,
+				&rbtdbiter->nsec3chain, DNS_RBTFIND_EMPTYDATA,
+				NULL, NULL);
+			if (tresult == ISC_R_SUCCESS) {
+				rbtdbiter->node = node;
+				rbtdbiter->current = &rbtdbiter->nsec3chain;
+				result = tresult;
+			}
+		}
+	}
+
+	if (result == ISC_R_SUCCESS || result == DNS_R_PARTIALMATCH) {
+		tresult = dns_rbtnodechain_current(rbtdbiter->current, iname,
+						   origin, NULL);
+		if (tresult == ISC_R_SUCCESS) {
+			rbtdbiter->new_origin = true;
+			reference_iter_node(rbtdbiter);
+		} else {
+			result = tresult;
+			rbtdbiter->node = NULL;
+		}
+	} else {
+		rbtdbiter->node = NULL;
+	}
+
+	rbtdbiter->result = (result == DNS_R_PARTIALMATCH) ? ISC_R_SUCCESS
+							   : result;
+
+	return (result);
+}
+
+static isc_result_t
+dbiterator_prev(dns_dbiterator_t *iterator) {
+	isc_result_t result;
+	rbtdb_dbiterator_t *rbtdbiter = (rbtdb_dbiterator_t *)iterator;
+	dns_name_t *name, *origin;
+	dns_rbtdb_t *rbtdb = (dns_rbtdb_t *)iterator->db;
+
+	REQUIRE(rbtdbiter->node != NULL);
+
+	if (rbtdbiter->result != ISC_R_SUCCESS) {
+		return (rbtdbiter->result);
+	}
+
+	if (rbtdbiter->paused) {
+		resume_iteration(rbtdbiter);
+	}
+
+	name = dns_fixedname_name(&rbtdbiter->name);
+	origin = dns_fixedname_name(&rbtdbiter->origin);
+	result = dns_rbtnodechain_prev(rbtdbiter->current, name, origin);
+	if (result == ISC_R_NOMORE && !rbtdbiter->nsec3only &&
+	    !rbtdbiter->nonsec3 && &rbtdbiter->nsec3chain == rbtdbiter->current)
+	{
+		rbtdbiter->current = &rbtdbiter->chain;
+		dns_rbtnodechain_reset(rbtdbiter->current);
+		result = dns_rbtnodechain_last(rbtdbiter->current, rbtdb->tree,
+					       name, origin);
+		if (result == ISC_R_NOTFOUND) {
+			result = ISC_R_NOMORE;
+		}
+	}
+
+	dereference_iter_node(rbtdbiter);
+
+	if (result == DNS_R_NEWORIGIN || result == ISC_R_SUCCESS) {
+		rbtdbiter->new_origin = (result == DNS_R_NEWORIGIN);
+		result = dns_rbtnodechain_current(rbtdbiter->current, NULL,
+						  NULL, &rbtdbiter->node);
+	}
+
+	if (result == ISC_R_SUCCESS) {
+		reference_iter_node(rbtdbiter);
+	}
+
+	rbtdbiter->result = result;
+
+	return (result);
+}
+
+static isc_result_t
+dbiterator_next(dns_dbiterator_t *iterator) {
+	isc_result_t result;
+	rbtdb_dbiterator_t *rbtdbiter = (rbtdb_dbiterator_t *)iterator;
+	dns_name_t *name, *origin;
+	dns_rbtdb_t *rbtdb = (dns_rbtdb_t *)iterator->db;
+
+	REQUIRE(rbtdbiter->node != NULL);
+
+	if (rbtdbiter->result != ISC_R_SUCCESS) {
+		return (rbtdbiter->result);
+	}
+
+	if (rbtdbiter->paused) {
+		resume_iteration(rbtdbiter);
+	}
+
+	name = dns_fixedname_name(&rbtdbiter->name);
+	origin = dns_fixedname_name(&rbtdbiter->origin);
+	result = dns_rbtnodechain_next(rbtdbiter->current, name, origin);
+	if (result == ISC_R_NOMORE && !rbtdbiter->nsec3only &&
+	    !rbtdbiter->nonsec3 && &rbtdbiter->chain == rbtdbiter->current)
+	{
+		rbtdbiter->current = &rbtdbiter->nsec3chain;
+		dns_rbtnodechain_reset(rbtdbiter->current);
+		result = dns_rbtnodechain_first(rbtdbiter->current,
+						rbtdb->nsec3, name, origin);
+		if (result == ISC_R_NOTFOUND) {
+			result = ISC_R_NOMORE;
+		}
+	}
+
+	dereference_iter_node(rbtdbiter);
+
+	if (result == DNS_R_NEWORIGIN || result == ISC_R_SUCCESS) {
+		rbtdbiter->new_origin = (result == DNS_R_NEWORIGIN);
+		result = dns_rbtnodechain_current(rbtdbiter->current, NULL,
+						  NULL, &rbtdbiter->node);
+	}
+	if (result == ISC_R_SUCCESS) {
+		reference_iter_node(rbtdbiter);
+	}
+
+	rbtdbiter->result = result;
+
+	return (result);
+}
+
+static isc_result_t
+dbiterator_current(dns_dbiterator_t *iterator, dns_dbnode_t **nodep,
+		   dns_name_t *name) {
+	dns_rbtdb_t *rbtdb = (dns_rbtdb_t *)iterator->db;
+	rbtdb_dbiterator_t *rbtdbiter = (rbtdb_dbiterator_t *)iterator;
+	dns_rbtnode_t *node = rbtdbiter->node;
+	isc_result_t result;
+	dns_name_t *nodename = dns_fixedname_name(&rbtdbiter->name);
+	dns_name_t *origin = dns_fixedname_name(&rbtdbiter->origin);
+
+	REQUIRE(rbtdbiter->result == ISC_R_SUCCESS);
+	REQUIRE(rbtdbiter->node != NULL);
+
+	if (rbtdbiter->paused) {
+		resume_iteration(rbtdbiter);
+	}
+
+	if (name != NULL) {
+		if (rbtdbiter->common.relative_names) {
+			origin = NULL;
+		}
+		result = dns_name_concatenate(nodename, origin, name, NULL);
+		if (result != ISC_R_SUCCESS) {
+			return (result);
+		}
+		if (rbtdbiter->common.relative_names && rbtdbiter->new_origin) {
+			result = DNS_R_NEWORIGIN;
+		}
+	} else {
+		result = ISC_R_SUCCESS;
+	}
+
+	new_reference(rbtdb, node, isc_rwlocktype_none);
+
+	*nodep = rbtdbiter->node;
+
+	if (iterator->cleaning && result == ISC_R_SUCCESS) {
+		isc_result_t expire_result;
+
+		/*
+		 * If the deletion array is full, flush it before trying
+		 * to expire the current node.  The current node can't
+		 * fully deleted while the iteration cursor is still on it.
+		 */
+		if (rbtdbiter->delcnt == DELETION_BATCH_MAX) {
+			flush_deletions(rbtdbiter);
+		}
+
+		expire_result = expirenode(iterator->db, *nodep, 0);
+
+		/*
+		 * expirenode() currently always returns success.
+		 */
+		if (expire_result == ISC_R_SUCCESS && node->down == NULL) {
+			rbtdbiter->deletions[rbtdbiter->delcnt++] = node;
+			isc_refcount_increment(&node->references);
+		}
+	}
+
+	return (result);
+}
+
+static isc_result_t
+dbiterator_pause(dns_dbiterator_t *iterator) {
+	dns_rbtdb_t *rbtdb = (dns_rbtdb_t *)iterator->db;
+	rbtdb_dbiterator_t *rbtdbiter = (rbtdb_dbiterator_t *)iterator;
+
+	if (rbtdbiter->result != ISC_R_SUCCESS &&
+	    rbtdbiter->result != ISC_R_NOTFOUND &&
+	    rbtdbiter->result != DNS_R_PARTIALMATCH &&
+	    rbtdbiter->result != ISC_R_NOMORE)
+	{
+		return (rbtdbiter->result);
+	}
+
+	if (rbtdbiter->paused) {
+		return (ISC_R_SUCCESS);
+	}
+
+	rbtdbiter->paused = true;
+
+	if (rbtdbiter->tree_locked != isc_rwlocktype_none) {
+		INSIST(rbtdbiter->tree_locked == isc_rwlocktype_read);
+		RWUNLOCK(&rbtdb->tree_lock, isc_rwlocktype_read);
+		rbtdbiter->tree_locked = isc_rwlocktype_none;
+	}
+
+	flush_deletions(rbtdbiter);
+
+	return (ISC_R_SUCCESS);
+}
+
+static isc_result_t
+dbiterator_origin(dns_dbiterator_t *iterator, dns_name_t *name) {
+	rbtdb_dbiterator_t *rbtdbiter = (rbtdb_dbiterator_t *)iterator;
+	dns_name_t *origin = dns_fixedname_name(&rbtdbiter->origin);
+
+	if (rbtdbiter->result != ISC_R_SUCCESS) {
+		return (rbtdbiter->result);
+	}
+
+	dns_name_copy(origin, name);
+	return (ISC_R_SUCCESS);
+}
+
+static void
+setownercase(rdatasetheader_t *header, const dns_name_t *name) {
+	unsigned int i;
+	bool fully_lower;
+
+	/*
+	 * We do not need to worry about label lengths as they are all
+	 * less than or equal to 63.
+	 */
+	memset(header->upper, 0, sizeof(header->upper));
+	fully_lower = true;
+	for (i = 0; i < name->length; i++) {
+		if (isupper(name->ndata[i])) {
+			header->upper[i / 8] |= 1 << (i % 8);
+			fully_lower = false;
+		}
+	}
+	RDATASET_ATTR_SET(header, RDATASET_ATTR_CASESET);
+	if (fully_lower) {
+		RDATASET_ATTR_SET(header, RDATASET_ATTR_CASEFULLYLOWER);
+	}
+}
+
+static void
+rdataset_setownercase(dns_rdataset_t *rdataset, const dns_name_t *name) {
+	dns_rbtdb_t *rbtdb = rdataset->private1;
+	dns_rbtnode_t *rbtnode = rdataset->private2;
+	unsigned char *raw = rdataset->private3; /* RDATASLAB */
+	rdatasetheader_t *header;
+
+	header = (struct rdatasetheader *)(raw - sizeof(*header));
+
+	NODE_LOCK(&rbtdb->node_locks[rbtnode->locknum].lock,
+		  isc_rwlocktype_write);
+	setownercase(header, name);
+	NODE_UNLOCK(&rbtdb->node_locks[rbtnode->locknum].lock,
+		    isc_rwlocktype_write);
+}
+
+static void
+rdataset_getownercase(const dns_rdataset_t *rdataset, dns_name_t *name) {
+	dns_rbtdb_t *rbtdb = rdataset->private1;
+	dns_rbtnode_t *rbtnode = rdataset->private2;
+	unsigned char *raw = rdataset->private3; /* RDATASLAB */
+	rdatasetheader_t *header = NULL;
+	uint8_t mask = (1 << 7);
+	uint8_t bits = 0;
+
+	header = (struct rdatasetheader *)(raw - sizeof(*header));
+
+	NODE_LOCK(&rbtdb->node_locks[rbtnode->locknum].lock,
+		  isc_rwlocktype_read);
+
+	if (!CASESET(header)) {
+		goto unlock;
+	}
+
+	if (CASEFULLYLOWER(header)) {
+		for (size_t i = 0; i < name->length; i++) {
+			name->ndata[i] = tolower(name->ndata[i]);
+		}
+	} else {
+		for (size_t i = 0; i < name->length; i++) {
+			if (mask == (1 << 7)) {
+				bits = header->upper[i / 8];
+				mask = 1;
+			} else {
+				mask <<= 1;
+			}
+
+			name->ndata[i] = ((bits & mask) != 0)
+						 ? toupper(name->ndata[i])
+						 : tolower(name->ndata[i]);
+		}
+	}
+
+unlock:
+	NODE_UNLOCK(&rbtdb->node_locks[rbtnode->locknum].lock,
+		    isc_rwlocktype_read);
+}
+
+struct rbtdb_glue {
+	struct rbtdb_glue *next;
+	dns_fixedname_t fixedname;
+	dns_rdataset_t rdataset_a;
+	dns_rdataset_t sigrdataset_a;
+	dns_rdataset_t rdataset_aaaa;
+	dns_rdataset_t sigrdataset_aaaa;
+};
+
+typedef struct {
+	rbtdb_glue_t *glue_list;
+	dns_rbtdb_t *rbtdb;
+	rbtdb_version_t *rbtversion;
+} rbtdb_glue_additionaldata_ctx_t;
+
+static void
+free_gluelist(rbtdb_glue_t *glue_list, dns_rbtdb_t *rbtdb) {
+	rbtdb_glue_t *cur, *cur_next;
+
+	if (glue_list == (void *)-1) {
+		return;
+	}
+
+	cur = glue_list;
+	while (cur != NULL) {
+		cur_next = cur->next;
+
+		if (dns_rdataset_isassociated(&cur->rdataset_a)) {
+			dns_rdataset_disassociate(&cur->rdataset_a);
+		}
+		if (dns_rdataset_isassociated(&cur->sigrdataset_a)) {
+			dns_rdataset_disassociate(&cur->sigrdataset_a);
+		}
+
+		if (dns_rdataset_isassociated(&cur->rdataset_aaaa)) {
+			dns_rdataset_disassociate(&cur->rdataset_aaaa);
+		}
+		if (dns_rdataset_isassociated(&cur->sigrdataset_aaaa)) {
+			dns_rdataset_disassociate(&cur->sigrdataset_aaaa);
+		}
+
+		dns_rdataset_invalidate(&cur->rdataset_a);
+		dns_rdataset_invalidate(&cur->sigrdataset_a);
+		dns_rdataset_invalidate(&cur->rdataset_aaaa);
+		dns_rdataset_invalidate(&cur->sigrdataset_aaaa);
+
+		isc_mem_put(rbtdb->common.mctx, cur, sizeof(*cur));
+		cur = cur_next;
+	}
+}
+
+static void
+free_gluetable(rbtdb_version_t *version) {
+	dns_rbtdb_t *rbtdb;
+	size_t size, i;
+
+	RWLOCK(&version->glue_rwlock, isc_rwlocktype_write);
+
+	rbtdb = version->rbtdb;
+
+	for (i = 0; i < HASHSIZE(version->glue_table_bits); i++) {
+		rbtdb_glue_table_node_t *cur, *cur_next;
+
+		cur = version->glue_table[i];
+		while (cur != NULL) {
+			cur_next = cur->next;
+			/* isc_refcount_decrement(&cur->node->references); */
+			cur->node = NULL;
+			free_gluelist(cur->glue_list, rbtdb);
+			cur->glue_list = NULL;
+			isc_mem_put(rbtdb->common.mctx, cur, sizeof(*cur));
+			cur = cur_next;
+		}
+		version->glue_table[i] = NULL;
+	}
+
+	size = HASHSIZE(version->glue_table_bits) *
+	       sizeof(*version->glue_table);
+	isc_mem_put(rbtdb->common.mctx, version->glue_table, size);
+
+	RWUNLOCK(&version->glue_rwlock, isc_rwlocktype_write);
+}
+
+static uint32_t
+rehash_bits(rbtdb_version_t *version, size_t newcount) {
+	uint32_t oldbits = version->glue_table_bits;
+	uint32_t newbits = oldbits;
+
+	while (newcount >= HASHSIZE(newbits) &&
+	       newbits <= RBTDB_GLUE_TABLE_MAX_BITS)
+	{
+		newbits += 1;
+	}
+
+	return (newbits);
+}
+
+/*%
+ * Write lock (version->glue_rwlock) must be held.
+ */
+static void
+rehash_gluetable(rbtdb_version_t *version) {
+	uint32_t oldbits, newbits;
+	size_t newsize, oldcount, i;
+	rbtdb_glue_table_node_t **oldtable;
+
+	oldbits = version->glue_table_bits;
+	oldcount = HASHSIZE(oldbits);
+	oldtable = version->glue_table;
+
+	newbits = rehash_bits(version, version->glue_table_nodecount);
+	newsize = HASHSIZE(newbits) * sizeof(version->glue_table[0]);
+
+	version->glue_table = isc_mem_get(version->rbtdb->common.mctx, newsize);
+	version->glue_table_bits = newbits;
+	memset(version->glue_table, 0, newsize);
+
+	for (i = 0; i < oldcount; i++) {
+		rbtdb_glue_table_node_t *gluenode;
+		rbtdb_glue_table_node_t *nextgluenode;
+		for (gluenode = oldtable[i]; gluenode != NULL;
+		     gluenode = nextgluenode)
+		{
+			uint32_t hash = isc_hash32(
+				&gluenode->node, sizeof(gluenode->node), true);
+			uint32_t idx = hash_32(hash, newbits);
+			nextgluenode = gluenode->next;
+			gluenode->next = version->glue_table[idx];
+			version->glue_table[idx] = gluenode;
+		}
+	}
+
+	isc_mem_put(version->rbtdb->common.mctx, oldtable,
+		    oldcount * sizeof(*version->glue_table));
+
+	isc_log_write(dns_lctx, DNS_LOGCATEGORY_DATABASE, DNS_LOGMODULE_ZONE,
+		      ISC_LOG_DEBUG(3),
+		      "rehash_gluetable(): "
+		      "resized glue table from %zu to "
+		      "%zu",
+		      oldcount, newsize / sizeof(version->glue_table[0]));
+}
+
+static void
+maybe_rehash_gluetable(rbtdb_version_t *version) {
+	size_t overcommit = HASHSIZE(version->glue_table_bits) *
+			    RBTDB_GLUE_TABLE_OVERCOMMIT;
+	if (version->glue_table_nodecount < overcommit) {
+		return;
+	}
+
+	rehash_gluetable(version);
+}
+
+static isc_result_t
+glue_nsdname_cb(void *arg, const dns_name_t *name, dns_rdatatype_t qtype,
+		dns_rdataset_t *unused) {
+	rbtdb_glue_additionaldata_ctx_t *ctx;
+	isc_result_t result;
+	dns_fixedname_t fixedname_a;
+	dns_name_t *name_a = NULL;
+	dns_rdataset_t rdataset_a, sigrdataset_a;
+	dns_rbtnode_t *node_a = NULL;
+	dns_fixedname_t fixedname_aaaa;
+	dns_name_t *name_aaaa = NULL;
+	dns_rdataset_t rdataset_aaaa, sigrdataset_aaaa;
+	dns_rbtnode_t *node_aaaa = NULL;
+	rbtdb_glue_t *glue = NULL;
+	dns_name_t *gluename = NULL;
+
+	UNUSED(unused);
+
+	/*
+	 * NS records want addresses in additional records.
+	 */
+	INSIST(qtype == dns_rdatatype_a);
+
+	ctx = (rbtdb_glue_additionaldata_ctx_t *)arg;
+
+	name_a = dns_fixedname_initname(&fixedname_a);
+	dns_rdataset_init(&rdataset_a);
+	dns_rdataset_init(&sigrdataset_a);
+
+	name_aaaa = dns_fixedname_initname(&fixedname_aaaa);
+	dns_rdataset_init(&rdataset_aaaa);
+	dns_rdataset_init(&sigrdataset_aaaa);
+
+	result = zone_find((dns_db_t *)ctx->rbtdb, name, ctx->rbtversion,
+			   dns_rdatatype_a, DNS_DBFIND_GLUEOK, 0,
+			   (dns_dbnode_t **)&node_a, name_a, &rdataset_a,
+			   &sigrdataset_a);
+	if (result == DNS_R_GLUE) {
+		glue = isc_mem_get(ctx->rbtdb->common.mctx, sizeof(*glue));
+
+		gluename = dns_fixedname_initname(&glue->fixedname);
+		dns_name_copy(name_a, gluename);
+
+		dns_rdataset_init(&glue->rdataset_a);
+		dns_rdataset_init(&glue->sigrdataset_a);
+		dns_rdataset_init(&glue->rdataset_aaaa);
+		dns_rdataset_init(&glue->sigrdataset_aaaa);
+
+		dns_rdataset_clone(&rdataset_a, &glue->rdataset_a);
+		if (dns_rdataset_isassociated(&sigrdataset_a)) {
+			dns_rdataset_clone(&sigrdataset_a,
+					   &glue->sigrdataset_a);
+		}
+	}
+
+	result = zone_find((dns_db_t *)ctx->rbtdb, name, ctx->rbtversion,
+			   dns_rdatatype_aaaa, DNS_DBFIND_GLUEOK, 0,
+			   (dns_dbnode_t **)&node_aaaa, name_aaaa,
+			   &rdataset_aaaa, &sigrdataset_aaaa);
+	if (result == DNS_R_GLUE) {
+		if (glue == NULL) {
+			glue = isc_mem_get(ctx->rbtdb->common.mctx,
+					   sizeof(*glue));
+
+			gluename = dns_fixedname_initname(&glue->fixedname);
+			dns_name_copy(name_aaaa, gluename);
+
+			dns_rdataset_init(&glue->rdataset_a);
+			dns_rdataset_init(&glue->sigrdataset_a);
+			dns_rdataset_init(&glue->rdataset_aaaa);
+			dns_rdataset_init(&glue->sigrdataset_aaaa);
+		} else {
+			INSIST(node_a == node_aaaa);
+			INSIST(dns_name_equal(name_a, name_aaaa));
+		}
+
+		dns_rdataset_clone(&rdataset_aaaa, &glue->rdataset_aaaa);
+		if (dns_rdataset_isassociated(&sigrdataset_aaaa)) {
+			dns_rdataset_clone(&sigrdataset_aaaa,
+					   &glue->sigrdataset_aaaa);
+		}
+	}
+
+	if (glue != NULL) {
+		glue->next = ctx->glue_list;
+		ctx->glue_list = glue;
+	}
+
+	result = ISC_R_SUCCESS;
+
+	if (dns_rdataset_isassociated(&rdataset_a)) {
+		rdataset_disassociate(&rdataset_a);
+	}
+	if (dns_rdataset_isassociated(&sigrdataset_a)) {
+		rdataset_disassociate(&sigrdataset_a);
+	}
+
+	if (dns_rdataset_isassociated(&rdataset_aaaa)) {
+		rdataset_disassociate(&rdataset_aaaa);
+	}
+	if (dns_rdataset_isassociated(&sigrdataset_aaaa)) {
+		rdataset_disassociate(&sigrdataset_aaaa);
+	}
+
+	if (node_a != NULL) {
+		detachnode((dns_db_t *)ctx->rbtdb, (dns_dbnode_t *)&node_a);
+	}
+	if (node_aaaa != NULL) {
+		detachnode((dns_db_t *)ctx->rbtdb, (dns_dbnode_t *)&node_aaaa);
+	}
+
+	return (result);
+}
+
+static isc_result_t
+rdataset_addglue(dns_rdataset_t *rdataset, dns_dbversion_t *version,
+		 dns_message_t *msg) {
+	dns_rbtdb_t *rbtdb = rdataset->private1;
+	dns_rbtnode_t *node = rdataset->private2;
+	rbtdb_version_t *rbtversion = version;
+	uint32_t idx;
+	rbtdb_glue_table_node_t *cur;
+	bool found = false;
+	bool restarted = false;
+	rbtdb_glue_t *ge;
+	rbtdb_glue_additionaldata_ctx_t ctx;
+	isc_result_t result;
+	uint64_t hash;
+
+	REQUIRE(rdataset->type == dns_rdatatype_ns);
+	REQUIRE(rbtdb == rbtversion->rbtdb);
+	REQUIRE(!IS_CACHE(rbtdb) && !IS_STUB(rbtdb));
+
+	/*
+	 * The glue table cache that forms a part of the DB version
+	 * structure is not explicitly bounded and there's no cache
+	 * cleaning. The zone data size itself is an implicit bound.
+	 *
+	 * The key into the glue hashtable is the node pointer. This is
+	 * because the glue hashtable is a property of the DB version,
+	 * and the glue is keyed for the ownername/NS tuple. We don't
+	 * bother with using an expensive dns_name_t comparison here as
+	 * the node pointer is a fixed value that won't change for a DB
+	 * version and can be compared directly.
+	 */
+	hash = isc_hash_function(&node, sizeof(node), true);
+
+restart:
+	/*
+	 * First, check if we have the additional entries already cached
+	 * in the glue table.
+	 */
+	RWLOCK(&rbtversion->glue_rwlock, isc_rwlocktype_read);
+
+	idx = hash_32(hash, rbtversion->glue_table_bits);
+
+	for (cur = rbtversion->glue_table[idx]; cur != NULL; cur = cur->next) {
+		if (cur->node == node) {
+			break;
+		}
+	}
+
+	if (cur == NULL) {
+		goto no_glue;
+	}
+	/*
+	 * We found a cached result. Add it to the message and
+	 * return.
+	 */
+	found = true;
+	ge = cur->glue_list;
+
+	/*
+	 * (void *) -1 is a special value that means no glue is
+	 * present in the zone.
+	 */
+	if (ge == (void *)-1) {
+		if (!restarted && (rbtdb->gluecachestats != NULL)) {
+			isc_stats_increment(
+				rbtdb->gluecachestats,
+				dns_gluecachestatscounter_hits_absent);
+		}
+		goto no_glue;
+	} else {
+		if (!restarted && (rbtdb->gluecachestats != NULL)) {
+			isc_stats_increment(
+				rbtdb->gluecachestats,
+				dns_gluecachestatscounter_hits_present);
+		}
+	}
+
+	for (; ge != NULL; ge = ge->next) {
+		dns_name_t *name = NULL;
+		dns_rdataset_t *rdataset_a = NULL;
+		dns_rdataset_t *sigrdataset_a = NULL;
+		dns_rdataset_t *rdataset_aaaa = NULL;
+		dns_rdataset_t *sigrdataset_aaaa = NULL;
+		dns_name_t *gluename = dns_fixedname_name(&ge->fixedname);
+
+		result = dns_message_gettempname(msg, &name);
+		if (result != ISC_R_SUCCESS) {
+			goto no_glue;
+		}
+
+		dns_name_copy(gluename, name);
+
+		if (dns_rdataset_isassociated(&ge->rdataset_a)) {
+			result = dns_message_gettemprdataset(msg, &rdataset_a);
+			if (result != ISC_R_SUCCESS) {
+				dns_message_puttempname(msg, &name);
+				goto no_glue;
+			}
+		}
+
+		if (dns_rdataset_isassociated(&ge->sigrdataset_a)) {
+			result = dns_message_gettemprdataset(msg,
+							     &sigrdataset_a);
+			if (result != ISC_R_SUCCESS) {
+				if (rdataset_a != NULL) {
+					dns_message_puttemprdataset(
+						msg, &rdataset_a);
+				}
+				dns_message_puttempname(msg, &name);
+				goto no_glue;
+			}
+		}
+
+		if (dns_rdataset_isassociated(&ge->rdataset_aaaa)) {
+			result = dns_message_gettemprdataset(msg,
+							     &rdataset_aaaa);
+			if (result != ISC_R_SUCCESS) {
+				dns_message_puttempname(msg, &name);
+				if (rdataset_a != NULL) {
+					dns_message_puttemprdataset(
+						msg, &rdataset_a);
+				}
+				if (sigrdataset_a != NULL) {
+					dns_message_puttemprdataset(
+						msg, &sigrdataset_a);
+				}
+				goto no_glue;
+			}
+		}
+
+		if (dns_rdataset_isassociated(&ge->sigrdataset_aaaa)) {
+			result = dns_message_gettemprdataset(msg,
+							     &sigrdataset_aaaa);
+			if (result != ISC_R_SUCCESS) {
+				dns_message_puttempname(msg, &name);
+				if (rdataset_a != NULL) {
+					dns_message_puttemprdataset(
+						msg, &rdataset_a);
+				}
+				if (sigrdataset_a != NULL) {
+					dns_message_puttemprdataset(
+						msg, &sigrdataset_a);
+				}
+				if (rdataset_aaaa != NULL) {
+					dns_message_puttemprdataset(
+						msg, &rdataset_aaaa);
+				}
+				goto no_glue;
+			}
+		}
+
+		if (rdataset_a != NULL) {
+			dns_rdataset_clone(&ge->rdataset_a, rdataset_a);
+			ISC_LIST_APPEND(name->list, rdataset_a, link);
+		}
+
+		if (sigrdataset_a != NULL) {
+			dns_rdataset_clone(&ge->sigrdataset_a, sigrdataset_a);
+			ISC_LIST_APPEND(name->list, sigrdataset_a, link);
+		}
+
+		if (rdataset_aaaa != NULL) {
+			dns_rdataset_clone(&ge->rdataset_aaaa, rdataset_aaaa);
+			ISC_LIST_APPEND(name->list, rdataset_aaaa, link);
+		}
+		if (sigrdataset_aaaa != NULL) {
+			dns_rdataset_clone(&ge->sigrdataset_aaaa,
+					   sigrdataset_aaaa);
+			ISC_LIST_APPEND(name->list, sigrdataset_aaaa, link);
+		}
+
+		dns_message_addname(msg, name, DNS_SECTION_ADDITIONAL);
+	}
+
+no_glue:
+	RWUNLOCK(&rbtversion->glue_rwlock, isc_rwlocktype_read);
+
+	if (found) {
+		return (ISC_R_SUCCESS);
+	}
+
+	if (restarted) {
+		return (ISC_R_FAILURE);
+	}
+
+	/*
+	 * No cached glue was found in the table. Cache it and restart
+	 * this function.
+	 *
+	 * Due to the gap between the read lock and the write lock, it's
+	 * possible that we may cache a duplicate glue table entry, but
+	 * we don't care.
+	 */
+
+	ctx.glue_list = NULL;
+	ctx.rbtdb = rbtdb;
+	ctx.rbtversion = rbtversion;
+
+	RWLOCK(&rbtversion->glue_rwlock, isc_rwlocktype_write);
+
+	maybe_rehash_gluetable(rbtversion);
+	idx = hash_32(hash, rbtversion->glue_table_bits);
+
+	(void)dns_rdataset_additionaldata(rdataset, dns_rootname,
+					  glue_nsdname_cb, &ctx);
+
+	cur = isc_mem_get(rbtdb->common.mctx, sizeof(*cur));
+
+	/*
+	 * XXXMUKS: it looks like the dns_dbversion is not destroyed
+	 * when named is terminated by a keyboard break. This doesn't
+	 * cleanup the node reference and keeps the process dangling.
+	 */
+	/* isc_refcount_increment0(&node->references); */
+	cur->node = node;
+
+	if (ctx.glue_list == NULL) {
+		/*
+		 * No glue was found. Cache it so.
+		 */
+		cur->glue_list = (void *)-1;
+		if (rbtdb->gluecachestats != NULL) {
+			isc_stats_increment(
+				rbtdb->gluecachestats,
+				dns_gluecachestatscounter_inserts_absent);
+		}
+	} else {
+		cur->glue_list = ctx.glue_list;
+		if (rbtdb->gluecachestats != NULL) {
+			isc_stats_increment(
+				rbtdb->gluecachestats,
+				dns_gluecachestatscounter_inserts_present);
+		}
+	}
+
+	cur->next = rbtversion->glue_table[idx];
+	rbtversion->glue_table[idx] = cur;
+	rbtversion->glue_table_nodecount++;
+
+	RWUNLOCK(&rbtversion->glue_rwlock, isc_rwlocktype_write);
+
+	restarted = true;
+	goto restart;
+
+	/* UNREACHABLE */
+}
+
+/*%
+ * Routines for LRU-based cache management.
+ */
+
+/*%
+ * See if a given cache entry that is being reused needs to be updated
+ * in the LRU-list.  From the LRU management point of view, this function is
+ * expected to return true for almost all cases.  When used with threads,
+ * however, this may cause a non-negligible performance penalty because a
+ * writer lock will have to be acquired before updating the list.
+ * If DNS_RBTDB_LIMITLRUUPDATE is defined to be non 0 at compilation time, this
+ * function returns true if the entry has not been updated for some period of
+ * time.  We differentiate the NS or glue address case and the others since
+ * experiments have shown that the former tends to be accessed relatively
+ * infrequently and the cost of cache miss is higher (e.g., a missing NS records
+ * may cause external queries at a higher level zone, involving more
+ * transactions).
+ *
+ * Caller must hold the node (read or write) lock.
+ */
+static bool
+need_headerupdate(rdatasetheader_t *header, isc_stdtime_t now) {
+	if (RDATASET_ATTR_GET(header, (RDATASET_ATTR_NONEXISTENT |
+				       RDATASET_ATTR_ANCIENT |
+				       RDATASET_ATTR_ZEROTTL)) != 0)
+	{
+		return (false);
+	}
+
+#if DNS_RBTDB_LIMITLRUUPDATE
+	if (header->type == dns_rdatatype_ns ||
+	    (header->trust == dns_trust_glue &&
+	     (header->type == dns_rdatatype_a ||
+	      header->type == dns_rdatatype_aaaa)))
+	{
+		/*
+		 * Glue records are updated if at least DNS_RBTDB_LRUUPDATE_GLUE
+		 * seconds have passed since the previous update time.
+		 */
+		return (header->last_used + DNS_RBTDB_LRUUPDATE_GLUE <= now);
+	}
+
+	/*
+	 * Other records are updated if DNS_RBTDB_LRUUPDATE_REGULAR seconds
+	 * have passed.
+	 */
+	return (header->last_used + DNS_RBTDB_LRUUPDATE_REGULAR <= now);
+#else
+	UNUSED(now);
+
+	return (true);
+#endif /* if DNS_RBTDB_LIMITLRUUPDATE */
+}
+
+/*%
+ * Update the timestamp of a given cache entry and move it to the head
+ * of the corresponding LRU list.
+ *
+ * Caller must hold the node (write) lock.
+ *
+ * Note that the we do NOT touch the heap here, as the TTL has not changed.
+ */
+static void
+update_header(dns_rbtdb_t *rbtdb, rdatasetheader_t *header, isc_stdtime_t now) {
+	INSIST(IS_CACHE(rbtdb));
+
+	/* To be checked: can we really assume this? XXXMLG */
+	INSIST(ISC_LINK_LINKED(header, link));
+
+	ISC_LIST_UNLINK(rbtdb->rdatasets[header->node->locknum], header, link);
+	header->last_used = now;
+	ISC_LIST_PREPEND(rbtdb->rdatasets[header->node->locknum], header, link);
+}
+
+static size_t
+expire_lru_headers(dns_rbtdb_t *rbtdb, unsigned int locknum, size_t purgesize,
+		   bool tree_locked) {
+	rdatasetheader_t *header, *header_prev;
+	size_t purged = 0;
+
+	for (header = ISC_LIST_TAIL(rbtdb->rdatasets[locknum]);
+	     header != NULL && purged <= purgesize; header = header_prev)
+	{
+		header_prev = ISC_LIST_PREV(header, link);
+		/*
+		 * Unlink the entry at this point to avoid checking it
+		 * again even if it's currently used someone else and
+		 * cannot be purged at this moment.  This entry won't be
+		 * referenced any more (so unlinking is safe) since the
+		 * TTL was reset to 0.
+		 */
+		ISC_LIST_UNLINK(rbtdb->rdatasets[locknum], header, link);
+		size_t header_size = rdataset_size(header);
+		expire_header(rbtdb, header, tree_locked, expire_lru);
+		purged += header_size;
+	}
+
+	return (purged);
+}
+
+/*%
+ * Purge some stale (i.e. unused for some period - LRU based cleaning) cache
+ * entries under the overmem condition.  To recover from this condition quickly,
+ * we cleanup entries up to the size of newly added rdata (passed as purgesize).
+ *
+ * This process is triggered while adding a new entry, and we specifically avoid
+ * purging entries in the same LRU bucket as the one to which the new entry will
+ * belong.  Otherwise, we might purge entries of the same name of different RR
+ * types while adding RRsets from a single response (consider the case where
+ * we're adding A and AAAA glue records of the same NS name).
+ */
+static void
+overmem_purge(dns_rbtdb_t *rbtdb, unsigned int locknum_start, size_t purgesize,
+	      bool tree_locked) {
+	unsigned int locknum;
+	size_t purged = 0;
+
+	for (locknum = (locknum_start + 1) % rbtdb->node_lock_count;
+	     locknum != locknum_start && purged <= purgesize;
+	     locknum = (locknum + 1) % rbtdb->node_lock_count)
+	{
+		NODE_LOCK(&rbtdb->node_locks[locknum].lock,
+			  isc_rwlocktype_write);
+
+		purged += expire_lru_headers(rbtdb, locknum, purgesize - purged,
+					     tree_locked);
+
+		NODE_UNLOCK(&rbtdb->node_locks[locknum].lock,
+			    isc_rwlocktype_write);
+	}
+}
+
+static void
+expire_header(dns_rbtdb_t *rbtdb, rdatasetheader_t *header, bool tree_locked,
+	      expire_t reason) {
+	set_ttl(rbtdb, header, 0);
+	mark_header_ancient(rbtdb, header);
+
+	/*
+	 * Caller must hold the node (write) lock.
+	 */
+
+	if (isc_refcount_current(&header->node->references) == 0) {
+		/*
+		 * If no one else is using the node, we can clean it up now.
+		 * We first need to gain a new reference to the node to meet a
+		 * requirement of decrement_reference().
+		 */
+		new_reference(rbtdb, header->node, isc_rwlocktype_write);
+		decrement_reference(rbtdb, header->node, 0,
+				    isc_rwlocktype_write,
+				    tree_locked ? isc_rwlocktype_write
+						: isc_rwlocktype_none,
+				    false);
+
+		if (rbtdb->cachestats == NULL) {
+			return;
+		}
+
+		switch (reason) {
+		case expire_ttl:
+			isc_stats_increment(rbtdb->cachestats,
+					    dns_cachestatscounter_deletettl);
+			break;
+		case expire_lru:
+			isc_stats_increment(rbtdb->cachestats,
+					    dns_cachestatscounter_deletelru);
+			break;
+		default:
+			break;
+		}
+	}
+}