Adding upstream version 1:9.11.5.P4+dfsg.upstream/1%9.11.5.P4+dfsgupstream

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

1 files changed, 1714 insertions, 0 deletions

diff --git a/bin/named/xfrout.c b/bin/named/xfrout.c
new file mode 100644
index 0000000..2da7e70
--- /dev/null
+++ b/bin/named/xfrout.c
@@ -0,0 +1,1714 @@
+/*
+ * Copyright (C) Internet Systems Consortium, Inc. ("ISC")
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/.
+ *
+ * See the COPYRIGHT file distributed with this work for additional
+ * information regarding copyright ownership.
+ */
+
+/* $Id$ */
+
+#include <config.h>
+
+#include <inttypes.h>
+#include <stdbool.h>
+
+#include <isc/formatcheck.h>
+#include <isc/mem.h>
+#include <isc/timer.h>
+#include <isc/print.h>
+#include <isc/stats.h>
+#include <isc/util.h>
+
+#include <dns/db.h>
+#include <dns/dbiterator.h>
+#include <dns/dlz.h>
+#include <dns/fixedname.h>
+#include <dns/journal.h>
+#include <dns/message.h>
+#include <dns/peer.h>
+#include <dns/rdataclass.h>
+#include <dns/rdatalist.h>
+#include <dns/rdataset.h>
+#include <dns/rdatasetiter.h>
+#include <dns/result.h>
+#include <dns/rriterator.h>
+#include <dns/soa.h>
+#include <dns/stats.h>
+#include <dns/timer.h>
+#include <dns/tsig.h>
+#include <dns/view.h>
+#include <dns/zone.h>
+#include <dns/zt.h>
+
+#include <named/client.h>
+#include <named/log.h>
+#include <named/server.h>
+#include <named/xfrout.h>
+
+/*! \file
+ * \brief
+ * Outgoing AXFR and IXFR.
+ */
+
+/*
+ * TODO:
+ *  - IXFR over UDP
+ */
+
+#define XFROUT_COMMON_LOGARGS \
+	ns_g_lctx, DNS_LOGCATEGORY_XFER_OUT, NS_LOGMODULE_XFER_OUT
+
+#define XFROUT_PROTOCOL_LOGARGS \
+	XFROUT_COMMON_LOGARGS, ISC_LOG_INFO
+
+#define XFROUT_DEBUG_LOGARGS(n) \
+	XFROUT_COMMON_LOGARGS, ISC_LOG_DEBUG(n)
+
+#define XFROUT_RR_LOGARGS \
+	XFROUT_COMMON_LOGARGS, XFROUT_RR_LOGLEVEL
+
+#define XFROUT_RR_LOGLEVEL	ISC_LOG_DEBUG(8)
+
+/*%
+ * Fail unconditionally and log as a client error.
+ * The test against ISC_R_SUCCESS is there to keep the Solaris compiler
+ * from complaining about "end-of-loop code not reached".
+ */
+#define FAILC(code, msg) \
+	do {							\
+		result = (code);				\
+		ns_client_log(client, DNS_LOGCATEGORY_XFER_OUT, \
+			   NS_LOGMODULE_XFER_OUT, ISC_LOG_INFO, \
+			   "bad zone transfer request: %s (%s)", \
+			   msg, isc_result_totext(code));	\
+		if (result != ISC_R_SUCCESS) goto failure;	\
+	} while (0)
+
+#define FAILQ(code, msg, question, rdclass) \
+	do {							\
+		char _buf1[DNS_NAME_FORMATSIZE];		\
+		char _buf2[DNS_RDATACLASS_FORMATSIZE]; 		\
+		result = (code);				\
+		dns_name_format(question, _buf1, sizeof(_buf1));  \
+		dns_rdataclass_format(rdclass, _buf2, sizeof(_buf2)); \
+		ns_client_log(client, DNS_LOGCATEGORY_XFER_OUT, \
+			   NS_LOGMODULE_XFER_OUT, ISC_LOG_INFO, \
+			   "bad zone transfer request: '%s/%s': %s (%s)", \
+			   _buf1, _buf2, msg, isc_result_totext(code));	\
+		if (result != ISC_R_SUCCESS) goto failure;	\
+	} while (0)
+
+#define CHECK(op) \
+	do { result = (op); 					\
+		if (result != ISC_R_SUCCESS) goto failure; 	\
+	} while (0)
+
+/**************************************************************************/
+
+static inline void
+inc_stats(dns_zone_t *zone, isc_statscounter_t counter) {
+	isc_stats_increment(ns_g_server->nsstats, counter);
+	if (zone != NULL) {
+		isc_stats_t *zonestats = dns_zone_getrequeststats(zone);
+		if (zonestats != NULL)
+			isc_stats_increment(zonestats, counter);
+	}
+}
+
+/**************************************************************************/
+
+/*% Log an RR (for debugging) */
+
+static void
+log_rr(dns_name_t *name, dns_rdata_t *rdata, uint32_t ttl) {
+	isc_result_t result;
+	isc_buffer_t buf;
+	char mem[2000];
+	dns_rdatalist_t rdl;
+	dns_rdataset_t rds;
+	dns_rdata_t rd = DNS_RDATA_INIT;
+
+	dns_rdatalist_init(&rdl);
+	rdl.type = rdata->type;
+	rdl.rdclass = rdata->rdclass;
+	rdl.ttl = ttl;
+	if (rdata->type == dns_rdatatype_sig ||
+	    rdata->type == dns_rdatatype_rrsig)
+		rdl.covers = dns_rdata_covers(rdata);
+	else
+		rdl.covers = dns_rdatatype_none;
+	dns_rdataset_init(&rds);
+	dns_rdata_init(&rd);
+	dns_rdata_clone(rdata, &rd);
+	ISC_LIST_APPEND(rdl.rdata, &rd, link);
+	RUNTIME_CHECK(dns_rdatalist_tordataset(&rdl, &rds) == ISC_R_SUCCESS);
+
+	isc_buffer_init(&buf, mem, sizeof(mem));
+	result = dns_rdataset_totext(&rds, name,
+				     false, false, &buf);
+
+	/*
+	 * We could use xfrout_log(), but that would produce
+	 * very long lines with a repetitive prefix.
+	 */
+	if (result == ISC_R_SUCCESS) {
+		/*
+		 * Get rid of final newline.
+		 */
+		INSIST(buf.used >= 1 &&
+		       ((char *) buf.base)[buf.used - 1] == '\n');
+		buf.used--;
+
+		isc_log_write(XFROUT_RR_LOGARGS, "%.*s",
+			      (int)isc_buffer_usedlength(&buf),
+			      (char *)isc_buffer_base(&buf));
+	} else {
+		isc_log_write(XFROUT_RR_LOGARGS, "<RR too large to print>");
+	}
+}
+
+/**************************************************************************/
+/*
+ * An 'rrstream_t' is a polymorphic iterator that returns
+ * a stream of resource records.  There are multiple implementations,
+ * e.g. for generating AXFR and IXFR records streams.
+ */
+
+typedef struct rrstream_methods rrstream_methods_t;
+
+typedef struct rrstream {
+	isc_mem_t 		*mctx;
+	rrstream_methods_t	*methods;
+} rrstream_t;
+
+struct rrstream_methods {
+	isc_result_t 		(*first)(rrstream_t *);
+	isc_result_t 		(*next)(rrstream_t *);
+	void			(*current)(rrstream_t *,
+					   dns_name_t **,
+					   uint32_t *,
+					   dns_rdata_t **);
+	void	 		(*pause)(rrstream_t *);
+	void 			(*destroy)(rrstream_t **);
+};
+
+static void
+rrstream_noop_pause(rrstream_t *rs) {
+	UNUSED(rs);
+}
+
+/**************************************************************************/
+/*
+ * An 'ixfr_rrstream_t' is an 'rrstream_t' that returns
+ * an IXFR-like RR stream from a journal file.
+ *
+ * The SOA at the beginning of each sequence of additions
+ * or deletions are included in the stream, but the extra
+ * SOAs at the beginning and end of the entire transfer are
+ * not included.
+ */
+
+typedef struct ixfr_rrstream {
+	rrstream_t		common;
+	dns_journal_t 		*journal;
+} ixfr_rrstream_t;
+
+/* Forward declarations. */
+static void
+ixfr_rrstream_destroy(rrstream_t **sp);
+
+static rrstream_methods_t ixfr_rrstream_methods;
+
+/*
+ * Returns: anything dns_journal_open() or dns_journal_iter_init()
+ * may return.
+ */
+
+static isc_result_t
+ixfr_rrstream_create(isc_mem_t *mctx,
+		     const char *journal_filename,
+		     uint32_t begin_serial,
+		     uint32_t end_serial,
+		     rrstream_t **sp)
+{
+	ixfr_rrstream_t *s;
+	isc_result_t result;
+
+	INSIST(sp != NULL && *sp == NULL);
+
+	s = isc_mem_get(mctx, sizeof(*s));
+	if (s == NULL)
+		return (ISC_R_NOMEMORY);
+	s->common.mctx = NULL;
+	isc_mem_attach(mctx, &s->common.mctx);
+	s->common.methods = &ixfr_rrstream_methods;
+	s->journal = NULL;
+
+	CHECK(dns_journal_open(mctx, journal_filename,
+			       DNS_JOURNAL_READ, &s->journal));
+	CHECK(dns_journal_iter_init(s->journal, begin_serial, end_serial));
+
+	*sp = (rrstream_t *) s;
+	return (ISC_R_SUCCESS);
+
+ failure:
+	ixfr_rrstream_destroy((rrstream_t **) (void *)&s);
+	return (result);
+}
+
+static isc_result_t
+ixfr_rrstream_first(rrstream_t *rs) {
+	ixfr_rrstream_t *s = (ixfr_rrstream_t *) rs;
+	return (dns_journal_first_rr(s->journal));
+}
+
+static isc_result_t
+ixfr_rrstream_next(rrstream_t *rs) {
+	ixfr_rrstream_t *s = (ixfr_rrstream_t *) rs;
+	return (dns_journal_next_rr(s->journal));
+}
+
+static void
+ixfr_rrstream_current(rrstream_t *rs,
+		       dns_name_t **name, uint32_t *ttl,
+		       dns_rdata_t **rdata)
+{
+	ixfr_rrstream_t *s = (ixfr_rrstream_t *) rs;
+	dns_journal_current_rr(s->journal, name, ttl, rdata);
+}
+
+static void
+ixfr_rrstream_destroy(rrstream_t **rsp) {
+	ixfr_rrstream_t *s = (ixfr_rrstream_t *) *rsp;
+	if (s->journal != 0)
+		dns_journal_destroy(&s->journal);
+	isc_mem_putanddetach(&s->common.mctx, s, sizeof(*s));
+}
+
+static rrstream_methods_t ixfr_rrstream_methods = {
+	ixfr_rrstream_first,
+	ixfr_rrstream_next,
+	ixfr_rrstream_current,
+	rrstream_noop_pause,
+	ixfr_rrstream_destroy
+};
+
+/**************************************************************************/
+/*
+ * An 'axfr_rrstream_t' is an 'rrstream_t' that returns
+ * an AXFR-like RR stream from a database.
+ *
+ * The SOAs at the beginning and end of the transfer are
+ * not included in the stream.
+ */
+
+typedef struct axfr_rrstream {
+	rrstream_t		common;
+	dns_rriterator_t	it;
+	bool		it_valid;
+} axfr_rrstream_t;
+
+/*
+ * Forward declarations.
+ */
+static void
+axfr_rrstream_destroy(rrstream_t **rsp);
+
+static rrstream_methods_t axfr_rrstream_methods;
+
+static isc_result_t
+axfr_rrstream_create(isc_mem_t *mctx, dns_db_t *db, dns_dbversion_t *ver,
+		     rrstream_t **sp)
+{
+	axfr_rrstream_t *s;
+	isc_result_t result;
+
+	INSIST(sp != NULL && *sp == NULL);
+
+	s = isc_mem_get(mctx, sizeof(*s));
+	if (s == NULL)
+		return (ISC_R_NOMEMORY);
+	s->common.mctx = NULL;
+	isc_mem_attach(mctx, &s->common.mctx);
+	s->common.methods = &axfr_rrstream_methods;
+	s->it_valid = false;
+
+	CHECK(dns_rriterator_init(&s->it, db, ver, 0));
+	s->it_valid = true;
+
+	*sp = (rrstream_t *) s;
+	return (ISC_R_SUCCESS);
+
+ failure:
+	axfr_rrstream_destroy((rrstream_t **) (void *)&s);
+	return (result);
+}
+
+static isc_result_t
+axfr_rrstream_first(rrstream_t *rs) {
+	axfr_rrstream_t *s = (axfr_rrstream_t *) rs;
+	isc_result_t result;
+	result = dns_rriterator_first(&s->it);
+	if (result != ISC_R_SUCCESS)
+		return (result);
+	/* Skip SOA records. */
+	for (;;) {
+		dns_name_t *name_dummy = NULL;
+		uint32_t ttl_dummy;
+		dns_rdata_t *rdata = NULL;
+		dns_rriterator_current(&s->it, &name_dummy,
+				       &ttl_dummy, NULL, &rdata);
+		if (rdata->type != dns_rdatatype_soa)
+			break;
+		result = dns_rriterator_next(&s->it);
+		if (result != ISC_R_SUCCESS)
+			break;
+	}
+	return (result);
+}
+
+static isc_result_t
+axfr_rrstream_next(rrstream_t *rs) {
+	axfr_rrstream_t *s = (axfr_rrstream_t *) rs;
+	isc_result_t result;
+
+	/* Skip SOA records. */
+	for (;;) {
+		dns_name_t *name_dummy = NULL;
+		uint32_t ttl_dummy;
+		dns_rdata_t *rdata = NULL;
+		result = dns_rriterator_next(&s->it);
+		if (result != ISC_R_SUCCESS)
+			break;
+		dns_rriterator_current(&s->it, &name_dummy,
+				       &ttl_dummy, NULL, &rdata);
+		if (rdata->type != dns_rdatatype_soa)
+			break;
+	}
+	return (result);
+}
+
+static void
+axfr_rrstream_current(rrstream_t *rs, dns_name_t **name, uint32_t *ttl,
+		      dns_rdata_t **rdata)
+{
+	axfr_rrstream_t *s = (axfr_rrstream_t *) rs;
+	dns_rriterator_current(&s->it, name, ttl, NULL, rdata);
+}
+
+static void
+axfr_rrstream_pause(rrstream_t *rs) {
+	axfr_rrstream_t *s = (axfr_rrstream_t *) rs;
+	dns_rriterator_pause(&s->it);
+}
+
+static void
+axfr_rrstream_destroy(rrstream_t **rsp) {
+	axfr_rrstream_t *s = (axfr_rrstream_t *) *rsp;
+	if (s->it_valid)
+		dns_rriterator_destroy(&s->it);
+	isc_mem_putanddetach(&s->common.mctx, s, sizeof(*s));
+}
+
+static rrstream_methods_t axfr_rrstream_methods = {
+	axfr_rrstream_first,
+	axfr_rrstream_next,
+	axfr_rrstream_current,
+	axfr_rrstream_pause,
+	axfr_rrstream_destroy
+};
+
+/**************************************************************************/
+/*
+ * An 'soa_rrstream_t' is a degenerate 'rrstream_t' that returns
+ * a single SOA record.
+ */
+
+typedef struct soa_rrstream {
+	rrstream_t		common;
+	dns_difftuple_t 	*soa_tuple;
+} soa_rrstream_t;
+
+/*
+ * Forward declarations.
+ */
+static void
+soa_rrstream_destroy(rrstream_t **rsp);
+
+static rrstream_methods_t soa_rrstream_methods;
+
+static isc_result_t
+soa_rrstream_create(isc_mem_t *mctx, dns_db_t *db, dns_dbversion_t *ver,
+		    rrstream_t **sp)
+{
+	soa_rrstream_t *s;
+	isc_result_t result;
+
+	INSIST(sp != NULL && *sp == NULL);
+
+	s = isc_mem_get(mctx, sizeof(*s));
+	if (s == NULL)
+		return (ISC_R_NOMEMORY);
+	s->common.mctx = NULL;
+	isc_mem_attach(mctx, &s->common.mctx);
+	s->common.methods = &soa_rrstream_methods;
+	s->soa_tuple = NULL;
+
+	CHECK(dns_db_createsoatuple(db, ver, mctx, DNS_DIFFOP_EXISTS,
+				    &s->soa_tuple));
+
+	*sp = (rrstream_t *) s;
+	return (ISC_R_SUCCESS);
+
+ failure:
+	soa_rrstream_destroy((rrstream_t **) (void *)&s);
+	return (result);
+}
+
+static isc_result_t
+soa_rrstream_first(rrstream_t *rs) {
+	UNUSED(rs);
+	return (ISC_R_SUCCESS);
+}
+
+static isc_result_t
+soa_rrstream_next(rrstream_t *rs) {
+	UNUSED(rs);
+	return (ISC_R_NOMORE);
+}
+
+static void
+soa_rrstream_current(rrstream_t *rs, dns_name_t **name, uint32_t *ttl,
+		     dns_rdata_t **rdata)
+{
+	soa_rrstream_t *s = (soa_rrstream_t *) rs;
+	*name = &s->soa_tuple->name;
+	*ttl = s->soa_tuple->ttl;
+	*rdata = &s->soa_tuple->rdata;
+}
+
+static void
+soa_rrstream_destroy(rrstream_t **rsp) {
+	soa_rrstream_t *s = (soa_rrstream_t *) *rsp;
+	if (s->soa_tuple != NULL)
+		dns_difftuple_free(&s->soa_tuple);
+	isc_mem_putanddetach(&s->common.mctx, s, sizeof(*s));
+}
+
+static rrstream_methods_t soa_rrstream_methods = {
+	soa_rrstream_first,
+	soa_rrstream_next,
+	soa_rrstream_current,
+	rrstream_noop_pause,
+	soa_rrstream_destroy
+};
+
+/**************************************************************************/
+/*
+ * A 'compound_rrstream_t' objects owns a soa_rrstream
+ * and another rrstream, the "data stream".  It returns
+ * a concatenated stream consisting of the soa_rrstream, then
+ * the data stream, then the soa_rrstream again.
+ *
+ * The component streams are owned by the compound_rrstream_t
+ * and are destroyed with it.
+ */
+
+typedef struct compound_rrstream {
+	rrstream_t		common;
+	rrstream_t		*components[3];
+	int			state;
+	isc_result_t		result;
+} compound_rrstream_t;
+
+/*
+ * Forward declarations.
+ */
+static void
+compound_rrstream_destroy(rrstream_t **rsp);
+
+static isc_result_t
+compound_rrstream_next(rrstream_t *rs);
+
+static rrstream_methods_t compound_rrstream_methods;
+
+/*
+ * Requires:
+ *	soa_stream != NULL && *soa_stream != NULL
+ *	data_stream != NULL && *data_stream != NULL
+ *	sp != NULL && *sp == NULL
+ *
+ * Ensures:
+ *	*soa_stream == NULL
+ *	*data_stream == NULL
+ *	*sp points to a valid compound_rrstream_t
+ *	The soa and data streams will be destroyed
+ *	when the compound_rrstream_t is destroyed.
+ */
+static isc_result_t
+compound_rrstream_create(isc_mem_t *mctx, rrstream_t **soa_stream,
+			 rrstream_t **data_stream, rrstream_t **sp)
+{
+	compound_rrstream_t *s;
+
+	INSIST(sp != NULL && *sp == NULL);
+
+	s = isc_mem_get(mctx, sizeof(*s));
+	if (s == NULL)
+		return (ISC_R_NOMEMORY);
+	s->common.mctx = NULL;
+	isc_mem_attach(mctx, &s->common.mctx);
+	s->common.methods = &compound_rrstream_methods;
+	s->components[0] = *soa_stream;
+	s->components[1] = *data_stream;
+	s->components[2] = *soa_stream;
+	s->state = -1;
+	s->result = ISC_R_FAILURE;
+
+	*soa_stream = NULL;
+	*data_stream = NULL;
+	*sp = (rrstream_t *) s;
+	return (ISC_R_SUCCESS);
+}
+
+static isc_result_t
+compound_rrstream_first(rrstream_t *rs) {
+	compound_rrstream_t *s = (compound_rrstream_t *) rs;
+	s->state = 0;
+	do {
+		rrstream_t *curstream = s->components[s->state];
+		s->result = curstream->methods->first(curstream);
+	} while (s->result == ISC_R_NOMORE && s->state < 2);
+	return (s->result);
+}
+
+static isc_result_t
+compound_rrstream_next(rrstream_t *rs) {
+	compound_rrstream_t *s = (compound_rrstream_t *) rs;
+	rrstream_t *curstream = s->components[s->state];
+	s->result = curstream->methods->next(curstream);
+	while (s->result == ISC_R_NOMORE) {
+		/*
+		 * Make sure locks held by the current stream
+		 * are released before we switch streams.
+		 */
+		curstream->methods->pause(curstream);
+		if (s->state == 2)
+			return (ISC_R_NOMORE);
+		s->state++;
+		curstream = s->components[s->state];
+		s->result = curstream->methods->first(curstream);
+	}
+	return (s->result);
+}
+
+static void
+compound_rrstream_current(rrstream_t *rs, dns_name_t **name, uint32_t *ttl,
+			  dns_rdata_t **rdata)
+{
+	compound_rrstream_t *s = (compound_rrstream_t *) rs;
+	rrstream_t *curstream;
+	INSIST(0 <= s->state && s->state < 3);
+	INSIST(s->result == ISC_R_SUCCESS);
+	curstream = s->components[s->state];
+	curstream->methods->current(curstream, name, ttl, rdata);
+}
+
+static void
+compound_rrstream_pause(rrstream_t *rs)
+{
+	compound_rrstream_t *s = (compound_rrstream_t *) rs;
+	rrstream_t *curstream;
+	INSIST(0 <= s->state && s->state < 3);
+	curstream = s->components[s->state];
+	curstream->methods->pause(curstream);
+}
+
+static void
+compound_rrstream_destroy(rrstream_t **rsp) {
+	compound_rrstream_t *s = (compound_rrstream_t *) *rsp;
+	s->components[0]->methods->destroy(&s->components[0]);
+	s->components[1]->methods->destroy(&s->components[1]);
+	s->components[2] = NULL; /* Copy of components[0]. */
+	isc_mem_putanddetach(&s->common.mctx, s, sizeof(*s));
+}
+
+static rrstream_methods_t compound_rrstream_methods = {
+	compound_rrstream_first,
+	compound_rrstream_next,
+	compound_rrstream_current,
+	compound_rrstream_pause,
+	compound_rrstream_destroy
+};
+
+/**************************************************************************/
+/*
+ * An 'xfrout_ctx_t' contains the state of an outgoing AXFR or IXFR
+ * in progress.
+ */
+
+typedef struct {
+	isc_mem_t 		*mctx;
+	ns_client_t		*client;
+	unsigned int 		id;		/* ID of request */
+	dns_name_t		*qname;		/* Question name of request */
+	dns_rdatatype_t		qtype;		/* dns_rdatatype_{a,i}xfr */
+	dns_rdataclass_t	qclass;
+	dns_zone_t 		*zone;		/* (necessary for stats) */
+	dns_db_t 		*db;
+	dns_dbversion_t 	*ver;
+	isc_quota_t		*quota;
+	rrstream_t 		*stream;	/* The XFR RR stream */
+	bool		end_of_stream;	/* EOS has been reached */
+	isc_buffer_t 		buf;		/* Buffer for message owner
+						   names and rdatas */
+	isc_buffer_t 		txlenbuf;	/* Transmit length buffer */
+	isc_buffer_t		txbuf;		/* Transmit message buffer */
+	void 			*txmem;
+	unsigned int 		txmemlen;
+	unsigned int		nmsg;		/* Number of messages sent */
+	dns_tsigkey_t		*tsigkey;	/* Key used to create TSIG */
+	isc_buffer_t		*lasttsig;	/* the last TSIG */
+	bool		verified_tsig;	/* verified request MAC */
+	bool		many_answers;
+	int			sends;		/* Send in progress */
+	bool		shuttingdown;
+	const char		*mnemonic;	/* Style of transfer */
+} xfrout_ctx_t;
+
+static isc_result_t
+xfrout_ctx_create(isc_mem_t *mctx, ns_client_t *client,
+		  unsigned int id, dns_name_t *qname, dns_rdatatype_t qtype,
+		  dns_rdataclass_t qclass, dns_zone_t *zone,
+		  dns_db_t *db, dns_dbversion_t *ver, isc_quota_t *quota,
+		  rrstream_t *stream, dns_tsigkey_t *tsigkey,
+		  isc_buffer_t *lasttsig,
+		  bool verified_tsig,
+		  unsigned int maxtime,
+		  unsigned int idletime,
+		  bool many_answers,
+		  xfrout_ctx_t **xfrp);
+
+static void
+sendstream(xfrout_ctx_t *xfr);
+
+static void
+xfrout_senddone(isc_task_t *task, isc_event_t *event);
+
+static void
+xfrout_fail(xfrout_ctx_t *xfr, isc_result_t result, const char *msg);
+
+static void
+xfrout_maybe_destroy(xfrout_ctx_t *xfr);
+
+static void
+xfrout_ctx_destroy(xfrout_ctx_t **xfrp);
+
+static void
+xfrout_client_shutdown(void *arg, isc_result_t result);
+
+static void
+xfrout_log1(ns_client_t *client, dns_name_t *zonename,
+	    dns_rdataclass_t rdclass, int level,
+	    const char *fmt, ...) ISC_FORMAT_PRINTF(5, 6);
+
+static void
+xfrout_log(xfrout_ctx_t *xfr, int level, const char *fmt, ...)
+	   ISC_FORMAT_PRINTF(3, 4);
+
+/**************************************************************************/
+
+void
+ns_xfr_start(ns_client_t *client, dns_rdatatype_t reqtype) {
+	isc_result_t result;
+	dns_name_t *question_name;
+	dns_rdataset_t *question_rdataset;
+	dns_zone_t *zone = NULL, *raw = NULL, *mayberaw;
+	dns_db_t *db = NULL;
+	dns_dbversion_t *ver = NULL;
+	dns_rdataclass_t question_class;
+	rrstream_t *soa_stream = NULL;
+	rrstream_t *data_stream = NULL;
+	rrstream_t *stream = NULL;
+	dns_difftuple_t *current_soa_tuple = NULL;
+	dns_name_t *soa_name;
+	dns_rdataset_t *soa_rdataset;
+	dns_rdata_t soa_rdata = DNS_RDATA_INIT;
+	bool have_soa = false;
+	const char *mnemonic = NULL;
+	isc_mem_t *mctx = client->mctx;
+	dns_message_t *request = client->message;
+	xfrout_ctx_t *xfr = NULL;
+	isc_quota_t *quota = NULL;
+	dns_transfer_format_t format = client->view->transfer_format;
+	isc_netaddr_t na;
+	dns_peer_t *peer = NULL;
+	isc_buffer_t *tsigbuf = NULL;
+	char *journalfile;
+	char msg[NS_CLIENT_ACLMSGSIZE("zone transfer")];
+	char keyname[DNS_NAME_FORMATSIZE];
+	bool is_poll = false;
+	bool is_dlz = false;
+	bool is_ixfr = false;
+	uint32_t begin_serial = 0, current_serial;
+
+	switch (reqtype) {
+	case dns_rdatatype_axfr:
+		mnemonic = "AXFR";
+		break;
+	case dns_rdatatype_ixfr:
+		mnemonic = "IXFR";
+		break;
+	default:
+		INSIST(0);
+		break;
+	}
+
+	ns_client_log(client,
+		      DNS_LOGCATEGORY_XFER_OUT, NS_LOGMODULE_XFER_OUT,
+		      ISC_LOG_DEBUG(6), "%s request", mnemonic);
+	/*
+	 * Apply quota.
+	 */
+	result = isc_quota_attach(&ns_g_server->xfroutquota, &quota);
+	if (result != ISC_R_SUCCESS) {
+		isc_log_write(XFROUT_COMMON_LOGARGS, ISC_LOG_WARNING,
+			      "%s request denied: %s", mnemonic,
+			      isc_result_totext(result));
+		goto failure;
+	}
+
+	/*
+	 * Interpret the question section.
+	 */
+	result = dns_message_firstname(request, DNS_SECTION_QUESTION);
+	INSIST(result == ISC_R_SUCCESS);
+
+	/*
+	 * The question section must contain exactly one question, and
+	 * it must be for AXFR/IXFR as appropriate.
+	 */
+	question_name = NULL;
+	dns_message_currentname(request, DNS_SECTION_QUESTION, &question_name);
+	question_rdataset = ISC_LIST_HEAD(question_name->list);
+	question_class = question_rdataset->rdclass;
+	INSIST(question_rdataset->type == reqtype);
+	if (ISC_LIST_NEXT(question_rdataset, link) != NULL)
+		FAILC(DNS_R_FORMERR, "multiple questions");
+	result = dns_message_nextname(request, DNS_SECTION_QUESTION);
+	if (result != ISC_R_NOMORE)
+		FAILC(DNS_R_FORMERR, "multiple questions");
+
+	result = dns_zt_find(client->view->zonetable, question_name, 0, NULL,
+			     &zone);
+
+	if (result != ISC_R_SUCCESS || dns_zone_gettype(zone) == dns_zone_dlz) {
+		/*
+		 * The normal zone table does not have a match, or this is
+		 * marked in the zone table as a DLZ zone. Check the DLZ
+		 * databases for a match.
+		 */
+		if (! ISC_LIST_EMPTY(client->view->dlz_searched)) {
+			result = dns_dlzallowzonexfr(client->view,
+						     question_name,
+						     &client->peeraddr,
+						     &db);
+
+			if (result == ISC_R_NOPERM) {
+				char _buf1[DNS_NAME_FORMATSIZE];
+				char _buf2[DNS_RDATACLASS_FORMATSIZE];
+
+				result = DNS_R_REFUSED;
+				dns_name_format(question_name, _buf1,
+						sizeof(_buf1));
+				dns_rdataclass_format(question_class,
+						      _buf2, sizeof(_buf2));
+				ns_client_log(client, DNS_LOGCATEGORY_SECURITY,
+					      NS_LOGMODULE_XFER_OUT,
+					      ISC_LOG_ERROR,
+					      "zone transfer '%s/%s' denied",
+					      _buf1, _buf2);
+				goto failure;
+			}
+			if (result != ISC_R_SUCCESS)
+				FAILQ(DNS_R_NOTAUTH, "non-authoritative zone",
+				      question_name, question_class);
+			is_dlz = true;
+		} else {
+			/*
+			 * not DLZ and not in normal zone table, we are
+			 * not authoritative
+			 */
+			FAILQ(DNS_R_NOTAUTH, "non-authoritative zone",
+			      question_name, question_class);
+		}
+	} else {
+		/* zone table has a match */
+		switch(dns_zone_gettype(zone)) {
+			/* Master and slave zones are OK for transfer. */
+			case dns_zone_master:
+			case dns_zone_slave:
+			case dns_zone_dlz:
+				break;
+			default:
+				FAILQ(DNS_R_NOTAUTH, "non-authoritative zone",
+				      question_name, question_class);
+			}
+		CHECK(dns_zone_getdb(zone, &db));
+		dns_db_currentversion(db, &ver);
+	}
+
+	xfrout_log1(client, question_name, question_class, ISC_LOG_DEBUG(6),
+		    "%s question section OK", mnemonic);
+
+	/*
+	 * Check the authority section.  Look for a SOA record with
+	 * the same name and class as the question.
+	 */
+	for (result = dns_message_firstname(request, DNS_SECTION_AUTHORITY);
+	     result == ISC_R_SUCCESS;
+	     result = dns_message_nextname(request, DNS_SECTION_AUTHORITY))
+	{
+		soa_name = NULL;
+		dns_message_currentname(request, DNS_SECTION_AUTHORITY,
+					&soa_name);
+
+		/*
+		 * Ignore data whose owner name is not the zone apex.
+		 */
+		if (! dns_name_equal(soa_name, question_name))
+			continue;
+
+		for (soa_rdataset = ISC_LIST_HEAD(soa_name->list);
+		     soa_rdataset != NULL;
+		     soa_rdataset = ISC_LIST_NEXT(soa_rdataset, link))
+		{
+			/*
+			 * Ignore non-SOA data.
+			 */
+			if (soa_rdataset->type != dns_rdatatype_soa)
+				continue;
+			if (soa_rdataset->rdclass != question_class)
+				continue;
+
+			CHECK(dns_rdataset_first(soa_rdataset));
+			dns_rdataset_current(soa_rdataset, &soa_rdata);
+			result = dns_rdataset_next(soa_rdataset);
+			if (result == ISC_R_SUCCESS)
+				FAILC(DNS_R_FORMERR,
+				      "IXFR authority section "
+				      "has multiple SOAs");
+			have_soa = true;
+			goto got_soa;
+		}
+	}
+ got_soa:
+	if (result != ISC_R_NOMORE)
+		CHECK(result);
+
+	xfrout_log1(client, question_name, question_class, ISC_LOG_DEBUG(6),
+		    "%s authority section OK", mnemonic);
+
+	/*
+	 * If not a DLZ zone, decide whether to allow this transfer.
+	 */
+	if (!is_dlz) {
+		ns_client_aclmsg("zone transfer", question_name, reqtype,
+				 client->view->rdclass, msg, sizeof(msg));
+		CHECK(ns_client_checkacl(client, NULL, msg,
+					 dns_zone_getxfracl(zone),
+					 true, ISC_LOG_ERROR));
+	}
+
+	/*
+	 * AXFR over UDP is not possible.
+	 */
+	if (reqtype == dns_rdatatype_axfr &&
+	    (client->attributes & NS_CLIENTATTR_TCP) == 0)
+		FAILC(DNS_R_FORMERR, "attempted AXFR over UDP");
+
+	/*
+	 * Look up the requesting server in the peer table.
+	 */
+	isc_netaddr_fromsockaddr(&na, &client->peeraddr);
+	(void)dns_peerlist_peerbyaddr(client->view->peers, &na, &peer);
+
+	/*
+	 * Decide on the transfer format (one-answer or many-answers).
+	 */
+	if (peer != NULL)
+		(void)dns_peer_gettransferformat(peer, &format);
+
+	/*
+	 * Get a dynamically allocated copy of the current SOA.
+	 */
+	if (is_dlz)
+		dns_db_currentversion(db, &ver);
+
+	CHECK(dns_db_createsoatuple(db, ver, mctx, DNS_DIFFOP_EXISTS,
+				    &current_soa_tuple));
+
+	current_serial = dns_soa_getserial(&current_soa_tuple->rdata);
+	if (reqtype == dns_rdatatype_ixfr) {
+		bool provide_ixfr;
+
+		/*
+		 * Outgoing IXFR may have been disabled for this peer
+		 * or globally.
+		 */
+		provide_ixfr = client->view->provideixfr;
+		if (peer != NULL)
+			(void) dns_peer_getprovideixfr(peer, &provide_ixfr);
+		if (provide_ixfr == false)
+			goto axfr_fallback;
+
+		if (! have_soa)
+			FAILC(DNS_R_FORMERR,
+			      "IXFR request missing SOA");
+
+		begin_serial = dns_soa_getserial(&soa_rdata);
+
+		/*
+		 * RFC1995 says "If an IXFR query with the same or
+		 * newer version number than that of the server
+		 * is received, it is replied to with a single SOA
+		 * record of the server's current version, just as
+		 * in AXFR".  The claim about AXFR is incorrect,
+		 * but other than that, we do as the RFC says.
+		 *
+		 * Sending a single SOA record is also how we refuse
+		 * IXFR over UDP (currently, we always do).
+		 */
+		if (DNS_SERIAL_GE(begin_serial, current_serial) ||
+		    (client->attributes & NS_CLIENTATTR_TCP) == 0)
+		{
+			CHECK(soa_rrstream_create(mctx, db, ver, &stream));
+			is_poll = true;
+			goto have_stream;
+		}
+		journalfile = is_dlz ? NULL : dns_zone_getjournal(zone);
+		if (journalfile != NULL)
+			result = ixfr_rrstream_create(mctx,
+						      journalfile,
+						      begin_serial,
+						      current_serial,
+						      &data_stream);
+		else
+			result = ISC_R_NOTFOUND;
+		if (result == ISC_R_NOTFOUND ||
+		    result == ISC_R_RANGE) {
+			xfrout_log1(client, question_name, question_class,
+				    ISC_LOG_DEBUG(4),
+				    "IXFR version not in journal, "
+				    "falling back to AXFR");
+			mnemonic = "AXFR-style IXFR";
+			goto axfr_fallback;
+		}
+		CHECK(result);
+		is_ixfr = true;
+	} else {
+	axfr_fallback:
+		CHECK(axfr_rrstream_create(mctx, db, ver, &data_stream));
+	}
+
+	/*
+	 * Bracket the data stream with SOAs.
+	 */
+	CHECK(soa_rrstream_create(mctx, db, ver, &soa_stream));
+	CHECK(compound_rrstream_create(mctx, &soa_stream, &data_stream,
+				       &stream));
+	soa_stream = NULL;
+	data_stream = NULL;
+
+ have_stream:
+	CHECK(dns_message_getquerytsig(request, mctx, &tsigbuf));
+	/*
+	 * Create the xfrout context object.  This transfers the ownership
+	 * of "stream", "db", "ver", and "quota" to the xfrout context object.
+	 */
+
+
+
+	if (is_dlz)
+		CHECK(xfrout_ctx_create(mctx, client, request->id,
+					question_name, reqtype, question_class,
+					zone, db, ver, quota, stream,
+					dns_message_gettsigkey(request),
+					tsigbuf,
+					request->verified_sig,
+					3600,
+					3600,
+					(format == dns_many_answers) ?
+					true : false,
+					&xfr));
+	else
+		CHECK(xfrout_ctx_create(mctx, client, request->id,
+					question_name, reqtype, question_class,
+					zone, db, ver, quota, stream,
+					dns_message_gettsigkey(request),
+					tsigbuf,
+					request->verified_sig,
+					dns_zone_getmaxxfrout(zone),
+					dns_zone_getidleout(zone),
+					(format == dns_many_answers) ?
+					true : false,
+					&xfr));
+
+	xfr->mnemonic = mnemonic;
+	stream = NULL;
+	quota = NULL;
+
+	CHECK(xfr->stream->methods->first(xfr->stream));
+
+	if (xfr->tsigkey != NULL)
+		dns_name_format(&xfr->tsigkey->name, keyname, sizeof(keyname));
+	else
+		keyname[0] = '\0';
+	if (is_poll)
+		xfrout_log1(client, question_name, question_class,
+			    ISC_LOG_DEBUG(1), "IXFR poll up to date%s%s",
+			    (xfr->tsigkey != NULL) ? ": TSIG " : "", keyname);
+	else if (is_ixfr)
+		xfrout_log1(client, question_name, question_class,
+			    ISC_LOG_INFO, "%s started%s%s (serial %u -> %u)",
+			    mnemonic, (xfr->tsigkey != NULL) ? ": TSIG " : "",
+			    keyname, begin_serial, current_serial);
+	else
+		xfrout_log1(client, question_name, question_class,
+			    ISC_LOG_INFO, "%s started%s%s (serial %u)",
+			    mnemonic, (xfr->tsigkey != NULL) ? ": TSIG " : "",
+			    keyname, current_serial);
+
+
+	if (zone != NULL) {
+		dns_zone_getraw(zone, &raw);
+		mayberaw = (raw != NULL) ? raw : zone;
+		if ((client->attributes & NS_CLIENTATTR_WANTEXPIRE) != 0 &&
+		    dns_zone_gettype(mayberaw) == dns_zone_slave) {
+			isc_time_t expiretime;
+			uint32_t secs;
+			dns_zone_getexpiretime(zone, &expiretime);
+			secs = isc_time_seconds(&expiretime);
+			if (secs >= client->now && result == ISC_R_SUCCESS) {
+				client->attributes |= NS_CLIENTATTR_HAVEEXPIRE;
+				client->expire = secs - client->now;
+			}
+		}
+		if (raw != NULL)
+			dns_zone_detach(&raw);
+	}
+
+	/*
+	 * Hand the context over to sendstream().  Set xfr to NULL;
+	 * sendstream() is responsible for either passing the
+	 * context on to a later event handler or destroying it.
+	 */
+	sendstream(xfr);
+	xfr = NULL;
+
+	result = ISC_R_SUCCESS;
+
+ failure:
+	if (result == DNS_R_REFUSED)
+		inc_stats(zone, dns_nsstatscounter_xfrrej);
+	if (quota != NULL)
+		isc_quota_detach(&quota);
+	if (current_soa_tuple != NULL)
+		dns_difftuple_free(&current_soa_tuple);
+	if (stream != NULL)
+		stream->methods->destroy(&stream);
+	if (soa_stream != NULL)
+		soa_stream->methods->destroy(&soa_stream);
+	if (data_stream != NULL)
+		data_stream->methods->destroy(&data_stream);
+	if (ver != NULL)
+		dns_db_closeversion(db, &ver, false);
+	if (db != NULL)
+		dns_db_detach(&db);
+	if (zone != NULL)
+		dns_zone_detach(&zone);
+	/* XXX kludge */
+	if (xfr != NULL) {
+		xfrout_fail(xfr, result, "setting up zone transfer");
+	} else if (result != ISC_R_SUCCESS) {
+		ns_client_log(client, DNS_LOGCATEGORY_XFER_OUT,
+			      NS_LOGMODULE_XFER_OUT,
+			      ISC_LOG_DEBUG(3), "zone transfer setup failed");
+		ns_client_error(client, result);
+	}
+}
+
+static isc_result_t
+xfrout_ctx_create(isc_mem_t *mctx, ns_client_t *client, unsigned int id,
+		  dns_name_t *qname, dns_rdatatype_t qtype,
+		  dns_rdataclass_t qclass, dns_zone_t *zone,
+		  dns_db_t *db, dns_dbversion_t *ver, isc_quota_t *quota,
+		  rrstream_t *stream, dns_tsigkey_t *tsigkey,
+		  isc_buffer_t *lasttsig, bool verified_tsig,
+		  unsigned int maxtime, unsigned int idletime,
+		  bool many_answers, xfrout_ctx_t **xfrp)
+{
+	xfrout_ctx_t *xfr;
+	isc_result_t result;
+	unsigned int len;
+	void *mem;
+
+	INSIST(xfrp != NULL && *xfrp == NULL);
+	xfr = isc_mem_get(mctx, sizeof(*xfr));
+	if (xfr == NULL)
+		return (ISC_R_NOMEMORY);
+	xfr->mctx = NULL;
+	isc_mem_attach(mctx, &xfr->mctx);
+	xfr->client = NULL;
+	ns_client_attach(client, &xfr->client);
+	xfr->id = id;
+	xfr->qname = qname;
+	xfr->qtype = qtype;
+	xfr->qclass = qclass;
+	xfr->zone = NULL;
+	xfr->db = NULL;
+	xfr->ver = NULL;
+	if (zone != NULL)	/* zone will be NULL if it's DLZ */
+		dns_zone_attach(zone, &xfr->zone);
+	dns_db_attach(db, &xfr->db);
+	dns_db_attachversion(db, ver, &xfr->ver);
+	xfr->end_of_stream = false;
+	xfr->tsigkey = tsigkey;
+	xfr->lasttsig = lasttsig;
+	xfr->verified_tsig = verified_tsig;
+	xfr->nmsg = 0;
+	xfr->many_answers = many_answers;
+	xfr->sends = 0;
+	xfr->shuttingdown = false;
+	xfr->mnemonic = NULL;
+	xfr->buf.base = NULL;
+	xfr->buf.length = 0;
+	xfr->txmem = NULL;
+	xfr->txmemlen = 0;
+	xfr->stream = NULL;
+	xfr->quota = NULL;
+
+	/*
+	 * Allocate a temporary buffer for the uncompressed response
+	 * message data.  The size should be no more than 65535 bytes
+	 * so that the compressed data will fit in a TCP message,
+	 * and no less than 65535 bytes so that an almost maximum-sized
+	 * RR will fit.  Note that although 65535-byte RRs are allowed
+	 * in principle, they cannot be zone-transferred (at least not
+	 * if uncompressible), because the message and RR headers would
+	 * push the size of the TCP message over the 65536 byte limit.
+	 */
+	len = 65535;
+	mem = isc_mem_get(mctx, len);
+	if (mem == NULL) {
+		result = ISC_R_NOMEMORY;
+		goto failure;
+	}
+	isc_buffer_init(&xfr->buf, mem, len);
+
+	/*
+	 * Allocate another temporary buffer for the compressed
+	 * response message and its TCP length prefix.
+	 */
+	len = 2 + 65535;
+	mem = isc_mem_get(mctx, len);
+	if (mem == NULL) {
+		result = ISC_R_NOMEMORY;
+		goto failure;
+	}
+	isc_buffer_init(&xfr->txlenbuf, mem, 2);
+	isc_buffer_init(&xfr->txbuf, (char *) mem + 2, len - 2);
+	xfr->txmem = mem;
+	xfr->txmemlen = len;
+
+	CHECK(dns_timer_setidle(xfr->client->timer,
+				maxtime, idletime, false));
+
+	/*
+	 * Register a shutdown callback with the client, so that we
+	 * can stop the transfer immediately when the client task
+	 * gets a shutdown event.
+	 */
+	xfr->client->shutdown = xfrout_client_shutdown;
+	xfr->client->shutdown_arg = xfr;
+	/*
+	 * These MUST be after the last "goto failure;" / CHECK to
+	 * prevent a double free by the caller.
+	 */
+	xfr->quota = quota;
+	xfr->stream = stream;
+
+	*xfrp = xfr;
+	return (ISC_R_SUCCESS);
+
+failure:
+	xfrout_ctx_destroy(&xfr);
+	return (result);
+}
+
+
+/*
+ * Arrange to send as much as we can of "stream" without blocking.
+ *
+ * Requires:
+ *	The stream iterator is initialized and points at an RR,
+ *      or possibly at the end of the stream (that is, the
+ *      _first method of the iterator has been called).
+ */
+static void
+sendstream(xfrout_ctx_t *xfr) {
+	dns_message_t *tcpmsg = NULL;
+	dns_message_t *msg = NULL; /* Client message if UDP, tcpmsg if TCP */
+	isc_result_t result;
+	isc_region_t used;
+	isc_region_t region;
+	dns_rdataset_t *qrdataset;
+	dns_name_t *msgname = NULL;
+	dns_rdata_t *msgrdata = NULL;
+	dns_rdatalist_t *msgrdl = NULL;
+	dns_rdataset_t *msgrds = NULL;
+	dns_compress_t cctx;
+	bool cleanup_cctx = false;
+	bool is_tcp;
+
+	int n_rrs;
+
+	isc_buffer_clear(&xfr->buf);
+	isc_buffer_clear(&xfr->txlenbuf);
+	isc_buffer_clear(&xfr->txbuf);
+
+	is_tcp = (xfr->client->attributes & NS_CLIENTATTR_TCP);
+	if (!is_tcp) {
+		/*
+		 * In the UDP case, we put the response data directly into
+		 * the client message.
+		 */
+		msg = xfr->client->message;
+		CHECK(dns_message_reply(msg, true));
+	} else {
+		/*
+		 * TCP. Build a response dns_message_t, temporarily storing
+		 * the raw, uncompressed owner names and RR data contiguously
+		 * in xfr->buf.  We know that if the uncompressed data fits
+		 * in xfr->buf, the compressed data will surely fit in a TCP
+		 * message.
+		 */
+
+		CHECK(dns_message_create(xfr->mctx,
+					 DNS_MESSAGE_INTENTRENDER, &tcpmsg));
+		msg = tcpmsg;
+
+		msg->id = xfr->id;
+		msg->rcode = dns_rcode_noerror;
+		msg->flags = DNS_MESSAGEFLAG_QR | DNS_MESSAGEFLAG_AA;
+		if ((xfr->client->attributes & NS_CLIENTATTR_RA) != 0)
+			msg->flags |= DNS_MESSAGEFLAG_RA;
+		CHECK(dns_message_settsigkey(msg, xfr->tsigkey));
+		CHECK(dns_message_setquerytsig(msg, xfr->lasttsig));
+		if (xfr->lasttsig != NULL)
+			isc_buffer_free(&xfr->lasttsig);
+		msg->verified_sig = xfr->verified_tsig;
+
+		/*
+		 * Add a EDNS option to the message?
+		 */
+		if ((xfr->client->attributes & NS_CLIENTATTR_WANTOPT) != 0) {
+			dns_rdataset_t *opt = NULL;
+
+			CHECK(ns_client_addopt(xfr->client, msg, &opt));
+			CHECK(dns_message_setopt(msg, opt));
+			/*
+			 * Add to first message only.
+			 */
+			xfr->client->attributes &= ~NS_CLIENTATTR_WANTNSID;
+			xfr->client->attributes &= ~NS_CLIENTATTR_HAVEEXPIRE;
+		}
+
+		/*
+		 * Account for reserved space.
+		 */
+		if (xfr->tsigkey != NULL)
+			INSIST(msg->reserved != 0U);
+		isc_buffer_add(&xfr->buf, msg->reserved);
+
+		/*
+		 * Include a question section in the first message only.
+		 * BIND 8.2.1 will not recognize an IXFR if it does not
+		 * have a question section.
+		 */
+		if (xfr->nmsg == 0) {
+			dns_name_t *qname = NULL;
+			isc_region_t r;
+
+			/*
+			 * Reserve space for the 12-byte message header
+			 * and 4 bytes of question.
+			 */
+			isc_buffer_add(&xfr->buf, 12 + 4);
+
+			qrdataset = NULL;
+			result = dns_message_gettemprdataset(msg, &qrdataset);
+			if (result != ISC_R_SUCCESS)
+				goto failure;
+			dns_rdataset_makequestion(qrdataset,
+					xfr->client->message->rdclass,
+					xfr->qtype);
+
+			result = dns_message_gettempname(msg, &qname);
+			if (result != ISC_R_SUCCESS)
+				goto failure;
+			dns_name_init(qname, NULL);
+			isc_buffer_availableregion(&xfr->buf, &r);
+			INSIST(r.length >= xfr->qname->length);
+			r.length = xfr->qname->length;
+			isc_buffer_putmem(&xfr->buf, xfr->qname->ndata,
+					  xfr->qname->length);
+			dns_name_fromregion(qname, &r);
+			ISC_LIST_INIT(qname->list);
+			ISC_LIST_APPEND(qname->list, qrdataset, link);
+
+			dns_message_addname(msg, qname, DNS_SECTION_QUESTION);
+		} else {
+			/*
+			 * Reserve space for the 12-byte message header
+			 */
+			isc_buffer_add(&xfr->buf, 12);
+			msg->tcp_continuation = 1;
+		}
+	}
+
+	/*
+	 * Try to fit in as many RRs as possible, unless "one-answer"
+	 * format has been requested.
+	 */
+	for (n_rrs = 0; ; n_rrs++) {
+		dns_name_t *name = NULL;
+		uint32_t ttl;
+		dns_rdata_t *rdata = NULL;
+
+		unsigned int size;
+		isc_region_t r;
+
+		msgname = NULL;
+		msgrdata = NULL;
+		msgrdl = NULL;
+		msgrds = NULL;
+
+		xfr->stream->methods->current(xfr->stream,
+					      &name, &ttl, &rdata);
+		size = name->length + 10 + rdata->length;
+		isc_buffer_availableregion(&xfr->buf, &r);
+		if (size >= r.length) {
+			/*
+			 * RR would not fit.  If there are other RRs in the
+			 * buffer, send them now and leave this RR to the
+			 * next message.  If this RR overflows the buffer
+			 * all by itself, fail.
+			 *
+			 * In theory some RRs might fit in a TCP message
+			 * when compressed even if they do not fit when
+			 * uncompressed, but surely we don't want
+			 * to send such monstrosities to an unsuspecting
+			 * slave.
+			 */
+			if (n_rrs == 0) {
+				xfrout_log(xfr, ISC_LOG_WARNING,
+					   "RR too large for zone transfer "
+					   "(%d bytes)", size);
+				/* XXX DNS_R_RRTOOLARGE? */
+				result = ISC_R_NOSPACE;
+				goto failure;
+			}
+			break;
+		}
+
+		if (isc_log_wouldlog(ns_g_lctx, XFROUT_RR_LOGLEVEL))
+			log_rr(name, rdata, ttl); /* XXX */
+
+		result = dns_message_gettempname(msg, &msgname);
+		if (result != ISC_R_SUCCESS)
+			goto failure;
+		dns_name_init(msgname, NULL);
+		isc_buffer_availableregion(&xfr->buf, &r);
+		INSIST(r.length >= name->length);
+		r.length = name->length;
+		isc_buffer_putmem(&xfr->buf, name->ndata, name->length);
+		dns_name_fromregion(msgname, &r);
+
+		/* Reserve space for RR header. */
+		isc_buffer_add(&xfr->buf, 10);
+
+		result = dns_message_gettemprdata(msg, &msgrdata);
+		if (result != ISC_R_SUCCESS)
+			goto failure;
+		isc_buffer_availableregion(&xfr->buf, &r);
+		r.length = rdata->length;
+		isc_buffer_putmem(&xfr->buf, rdata->data, rdata->length);
+		dns_rdata_init(msgrdata);
+		dns_rdata_fromregion(msgrdata,
+				     rdata->rdclass, rdata->type, &r);
+
+		result = dns_message_gettemprdatalist(msg, &msgrdl);
+		if (result != ISC_R_SUCCESS)
+			goto failure;
+		msgrdl->type = rdata->type;
+		msgrdl->rdclass = rdata->rdclass;
+		msgrdl->ttl = ttl;
+		if (rdata->type == dns_rdatatype_sig ||
+		    rdata->type == dns_rdatatype_rrsig)
+			msgrdl->covers = dns_rdata_covers(rdata);
+		else
+			msgrdl->covers = dns_rdatatype_none;
+		ISC_LIST_APPEND(msgrdl->rdata, msgrdata, link);
+
+		result = dns_message_gettemprdataset(msg, &msgrds);
+		if (result != ISC_R_SUCCESS)
+			goto failure;
+		result = dns_rdatalist_tordataset(msgrdl, msgrds);
+		INSIST(result == ISC_R_SUCCESS);
+
+		ISC_LIST_APPEND(msgname->list, msgrds, link);
+
+		dns_message_addname(msg, msgname, DNS_SECTION_ANSWER);
+		msgname = NULL;
+
+		result = xfr->stream->methods->next(xfr->stream);
+		if (result == ISC_R_NOMORE) {
+			xfr->end_of_stream = true;
+			break;
+		}
+		CHECK(result);
+
+		if (! xfr->many_answers)
+			break;
+		/*
+		 * At this stage, at least 1 RR has been rendered into
+		 * the message. Check if we want to clamp this message
+		 * here (TCP only).
+		 */
+		if ((isc_buffer_usedlength(&xfr->buf) >=
+		     ns_g_server->transfer_tcp_message_size) && is_tcp)
+			break;
+	}
+
+	if (is_tcp) {
+		CHECK(dns_compress_init(&cctx, -1, xfr->mctx));
+		dns_compress_setsensitive(&cctx, true);
+		cleanup_cctx = true;
+		CHECK(dns_message_renderbegin(msg, &cctx, &xfr->txbuf));
+		CHECK(dns_message_rendersection(msg, DNS_SECTION_QUESTION, 0));
+		CHECK(dns_message_rendersection(msg, DNS_SECTION_ANSWER, 0));
+		CHECK(dns_message_renderend(msg));
+		dns_compress_invalidate(&cctx);
+		cleanup_cctx = false;
+
+		isc_buffer_usedregion(&xfr->txbuf, &used);
+		isc_buffer_putuint16(&xfr->txlenbuf,
+				     (uint16_t)used.length);
+		region.base = xfr->txlenbuf.base;
+		region.length = 2 + used.length;
+		xfrout_log(xfr, ISC_LOG_DEBUG(8),
+			   "sending TCP message of %d bytes",
+			   used.length);
+		CHECK(isc_socket_send(xfr->client->tcpsocket, /* XXX */
+				      &region, xfr->client->task,
+				      xfrout_senddone,
+				      xfr));
+		xfr->sends++;
+	} else {
+		xfrout_log(xfr, ISC_LOG_DEBUG(8), "sending IXFR UDP response");
+		ns_client_send(xfr->client);
+		xfr->stream->methods->pause(xfr->stream);
+		xfrout_ctx_destroy(&xfr);
+		return;
+	}
+
+	/* Advance lasttsig to be the last TSIG generated */
+	CHECK(dns_message_getquerytsig(msg, xfr->mctx, &xfr->lasttsig));
+
+	xfr->nmsg++;
+
+ failure:
+	if (msgname != NULL) {
+		if (msgrds != NULL) {
+			if (dns_rdataset_isassociated(msgrds))
+				dns_rdataset_disassociate(msgrds);
+			dns_message_puttemprdataset(msg, &msgrds);
+		}
+		if (msgrdl != NULL) {
+			ISC_LIST_UNLINK(msgrdl->rdata, msgrdata, link);
+			dns_message_puttemprdatalist(msg, &msgrdl);
+		}
+		if (msgrdata != NULL)
+			dns_message_puttemprdata(msg, &msgrdata);
+		dns_message_puttempname(msg, &msgname);
+	}
+
+	if (tcpmsg != NULL)
+		dns_message_destroy(&tcpmsg);
+
+	if (cleanup_cctx)
+		dns_compress_invalidate(&cctx);
+	/*
+	 * Make sure to release any locks held by database
+	 * iterators before returning from the event handler.
+	 */
+	xfr->stream->methods->pause(xfr->stream);
+
+	if (result == ISC_R_SUCCESS)
+		return;
+
+	xfrout_fail(xfr, result, "sending zone data");
+}
+
+static void
+xfrout_ctx_destroy(xfrout_ctx_t **xfrp) {
+	xfrout_ctx_t *xfr = *xfrp;
+	ns_client_t *client = NULL;
+
+	INSIST(xfr->sends == 0);
+
+	xfr->client->shutdown = NULL;
+	xfr->client->shutdown_arg = NULL;
+
+	if (xfr->stream != NULL)
+		xfr->stream->methods->destroy(&xfr->stream);
+	if (xfr->buf.base != NULL)
+		isc_mem_put(xfr->mctx, xfr->buf.base, xfr->buf.length);
+	if (xfr->txmem != NULL)
+		isc_mem_put(xfr->mctx, xfr->txmem, xfr->txmemlen);
+	if (xfr->lasttsig != NULL)
+		isc_buffer_free(&xfr->lasttsig);
+	if (xfr->quota != NULL)
+		isc_quota_detach(&xfr->quota);
+	if (xfr->ver != NULL)
+		dns_db_closeversion(xfr->db, &xfr->ver, false);
+	if (xfr->zone != NULL)
+		dns_zone_detach(&xfr->zone);
+	if (xfr->db != NULL)
+		dns_db_detach(&xfr->db);
+
+	/*
+	 * We want to detch the client after we have released the memory
+	 * context as ns_client_detach checks the memory reference count.
+	 */
+	ns_client_attach(xfr->client, &client);
+	ns_client_detach(&xfr->client);
+	isc_mem_putanddetach(&xfr->mctx, xfr, sizeof(*xfr));
+	ns_client_detach(&client);
+
+	*xfrp = NULL;
+}
+
+static void
+xfrout_senddone(isc_task_t *task, isc_event_t *event) {
+	isc_socketevent_t *sev = (isc_socketevent_t *)event;
+	xfrout_ctx_t *xfr = (xfrout_ctx_t *)event->ev_arg;
+	isc_result_t evresult = sev->result;
+
+	UNUSED(task);
+
+	INSIST(event->ev_type == ISC_SOCKEVENT_SENDDONE);
+
+	isc_event_free(&event);
+	xfr->sends--;
+	INSIST(xfr->sends == 0);
+
+	(void)isc_timer_touch(xfr->client->timer);
+	if (xfr->shuttingdown == true) {
+		xfrout_maybe_destroy(xfr);
+	} else if (evresult != ISC_R_SUCCESS) {
+		xfrout_fail(xfr, evresult, "send");
+	} else if (xfr->end_of_stream == false) {
+		sendstream(xfr);
+	} else {
+		/* End of zone transfer stream. */
+		inc_stats(xfr->zone, dns_nsstatscounter_xfrdone);
+		xfrout_log(xfr, ISC_LOG_INFO, "%s ended", xfr->mnemonic);
+		ns_client_next(xfr->client, ISC_R_SUCCESS);
+		xfrout_ctx_destroy(&xfr);
+	}
+}
+
+static void
+xfrout_fail(xfrout_ctx_t *xfr, isc_result_t result, const char *msg) {
+	xfr->shuttingdown = true;
+	xfrout_log(xfr, ISC_LOG_ERROR, "%s: %s",
+		   msg, isc_result_totext(result));
+	xfrout_maybe_destroy(xfr);
+}
+
+static void
+xfrout_maybe_destroy(xfrout_ctx_t *xfr) {
+	INSIST(xfr->shuttingdown == true);
+	if (xfr->sends > 0) {
+		/*
+		 * If we are currently sending, cancel it and wait for
+		 * cancel event before destroying the context.
+		 */
+		isc_socket_cancel(xfr->client->tcpsocket, xfr->client->task,
+				  ISC_SOCKCANCEL_SEND);
+	} else {
+		ns_client_next(xfr->client, ISC_R_CANCELED);
+		xfrout_ctx_destroy(&xfr);
+	}
+}
+
+static void
+xfrout_client_shutdown(void *arg, isc_result_t result) {
+	xfrout_ctx_t *xfr = (xfrout_ctx_t *) arg;
+	xfrout_fail(xfr, result, "aborted");
+}
+
+/*
+ * Log outgoing zone transfer messages in a format like
+ * <client>: transfer of <zone>: <message>
+ */
+
+static void
+xfrout_logv(ns_client_t *client, dns_name_t *zonename,
+	    dns_rdataclass_t rdclass, int level, const char *fmt, va_list ap)
+     ISC_FORMAT_PRINTF(5, 0);
+
+static void
+xfrout_logv(ns_client_t *client, dns_name_t *zonename,
+	    dns_rdataclass_t rdclass, int level, const char *fmt, va_list ap)
+{
+	char msgbuf[2048];
+	char namebuf[DNS_NAME_FORMATSIZE];
+	char classbuf[DNS_RDATACLASS_FORMATSIZE];
+
+	dns_name_format(zonename, namebuf, sizeof(namebuf));
+	dns_rdataclass_format(rdclass, classbuf, sizeof(classbuf));
+	vsnprintf(msgbuf, sizeof(msgbuf), fmt, ap);
+	ns_client_log(client, DNS_LOGCATEGORY_XFER_OUT,
+		      NS_LOGMODULE_XFER_OUT, level,
+		      "transfer of '%s/%s': %s", namebuf, classbuf, msgbuf);
+}
+
+/*
+ * Logging function for use when a xfrout_ctx_t has not yet been created.
+ */
+static void
+xfrout_log1(ns_client_t *client, dns_name_t *zonename,
+	    dns_rdataclass_t rdclass, int level, const char *fmt, ...) {
+	va_list ap;
+	va_start(ap, fmt);
+	xfrout_logv(client, zonename, rdclass, level, fmt, ap);
+	va_end(ap);
+}
+
+/*
+ * Logging function for use when there is a xfrout_ctx_t.
+ */
+static void
+xfrout_log(xfrout_ctx_t *xfr, int level, const char *fmt, ...) {
+	va_list ap;
+	va_start(ap, fmt);
+	xfrout_logv(xfr->client, xfr->qname, xfr->qclass, level, fmt, ap);
+	va_end(ap);
+}