etc/services - sync with NetBSD-8

[minix.git] / external / bsd / bind / dist / bin / named / xfrout.c

/*      $NetBSD: xfrout.c,v 1.9 2015/07/08 17:28:55 christos Exp $      */

/*
 * Copyright (C) 2004-2015  Internet Systems Consortium, Inc. ("ISC")
 * Copyright (C) 1999-2003  Internet Software Consortium.
 *
 * Permission to use, copy, modify, and/or distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES WITH
 * REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
 * AND FITNESS.  IN NO EVENT SHALL ISC BE LIABLE FOR ANY SPECIAL, DIRECT,
 * INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
 * LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE
 * OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
 * PERFORMANCE OF THIS SOFTWARE.
 */

/* Id */

#include <config.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>

#include "pfilter.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 (/*CONSTCOND*/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 (/*CONSTCOND*/0)

#define CHECK(op) \
        do { result = (op);                                     \
                if (result != ISC_R_SUCCESS) goto failure;      \
        } while (/*CONSTCOND*/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, isc_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;

        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;
        ISC_LIST_INIT(rdl.rdata);
        ISC_LINK_INIT(&rdl, link);
        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,
                                     ISC_FALSE, ISC_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 **,
                                           isc_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,
                     isc_uint32_t begin_serial,
                     isc_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, isc_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;
        isc_boolean_t           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 = ISC_FALSE;

        CHECK(dns_rriterator_init(&s->it, db, ver, 0));
        s->it_valid = ISC_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;
                isc_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;
                isc_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, isc_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, isc_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, isc_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 */
        isc_boolean_t           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 */
        isc_boolean_t           many_answers;
        int                     sends;          /* Send in progress */
        isc_boolean_t           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,
                  unsigned int maxtime,
                  unsigned int idletime,
                  isc_boolean_t 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;
        isc_boolean_t have_soa = ISC_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];
        isc_boolean_t is_poll = ISC_FALSE;
        isc_boolean_t is_dlz = ISC_FALSE;
        isc_boolean_t is_ixfr = ISC_FALSE;
        isc_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) {
                /*
                 * Normal zone table does not have a match.
                 * Try the DLZ database
                 */
                // Temporary: only searching the first DLZ database
                if (! ISC_LIST_EMPTY(client->view->dlz_searched)) {
                        result = dns_dlzallowzonexfr(client->view,
                                                     question_name,
                                                     &client->peeraddr,
                                                     &db);

                        pfilter_notify(result, client, "zonexfr");
                        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 = ISC_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 = ISC_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),
                                         ISC_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) {
                isc_boolean_t 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 == ISC_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 = ISC_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 = ISC_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,
                                        3600,
                                        3600,
                                        (format == dns_many_answers) ?
                                        ISC_TRUE : ISC_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,
                                        dns_zone_getmaxxfrout(zone),
                                        dns_zone_getidleout(zone),
                                        (format == dns_many_answers) ?
                                        ISC_TRUE : ISC_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;
                        isc_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, ISC_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, unsigned int maxtime,
                  unsigned int idletime, isc_boolean_t 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 = ISC_FALSE;
        xfr->tsigkey = tsigkey;
        xfr->lasttsig = lasttsig;
        xfr->txmem = NULL;
        xfr->txmemlen = 0;
        xfr->nmsg = 0;
        xfr->many_answers = many_answers,
        xfr->sends = 0;
        xfr->shuttingdown = ISC_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, ISC_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;
        isc_boolean_t cleanup_cctx = ISC_FALSE;

        int n_rrs;

        isc_buffer_clear(&xfr->buf);
        isc_buffer_clear(&xfr->txlenbuf);
        isc_buffer_clear(&xfr->txbuf);

        if ((xfr->client->attributes & NS_CLIENTATTR_TCP) == 0) {
                /*
                 * In the UDP case, we put the response data directly into
                 * the client message.
                 */
                msg = xfr->client->message;
                CHECK(dns_message_reply(msg, ISC_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);

                /*
                 * 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;
                isc_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_LINK_INIT(msgrdl, link);
                ISC_LIST_INIT(msgrdl->rdata);
                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 = ISC_TRUE;
                        break;
                }
                CHECK(result);

                if (! xfr->many_answers)
                        break;
        }

        if ((xfr->client->attributes & NS_CLIENTATTR_TCP) != 0) {
                CHECK(dns_compress_init(&cctx, -1, xfr->mctx));
                dns_compress_setsensitive(&cctx, ISC_TRUE);
                cleanup_cctx = ISC_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 = ISC_FALSE;

                isc_buffer_usedregion(&xfr->txbuf, &used);
                isc_buffer_putuint16(&xfr->txlenbuf,
                                     (isc_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, ISC_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 == ISC_TRUE) {
                xfrout_maybe_destroy(xfr);
        } else if (evresult != ISC_R_SUCCESS) {
                xfrout_fail(xfr, evresult, "send");
        } else if (xfr->end_of_stream == ISC_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 = ISC_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 == ISC_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);
}