bin/named/xfrout.c

	xfrout.c revision 8907d8fa04fdaa65baf0bc6b01230b2ebde93106
/*
 * Copyright (C) 2004-2007  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: xfrout.c,v 1.127 2008/04/03 05:55:51 marka Exp $ */

#include <config.h>

#include <isc/formatcheck.h>
#include <isc/mem.h>
#include <isc/timer.h>
#include <isc/print.h>
#include <isc/util.h>

#include <dns/db.h>
#include <dns/dbiterator.h>
#ifdef DLZ
#include <dns/dlz.h>
#endif
#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/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)

/**************************************************************************/
/*%
 * A db_rr_iterator_t is an iterator that iterates over an entire database,
 * returning one RR at a time, in some arbitrary order.
 */

typedef struct db_rr_iterator db_rr_iterator_t;

/*% db_rr_iterator structure */
struct db_rr_iterator {
    isc_result_t        result;
    dns_db_t        *db;
        dns_dbiterator_t    *dbit;
    dns_dbversion_t     *ver;
    isc_stdtime_t       now;
    dns_dbnode_t        *node;
    dns_fixedname_t     fixedname;
        dns_rdatasetiter_t  *rdatasetit;
    dns_rdataset_t      rdataset;
    dns_rdata_t     rdata;
};

static isc_result_t
db_rr_iterator_init(db_rr_iterator_t *it, dns_db_t *db, dns_dbversion_t *ver,
            isc_stdtime_t now);

static isc_result_t
db_rr_iterator_first(db_rr_iterator_t *it);

static isc_result_t
db_rr_iterator_next(db_rr_iterator_t *it);

static void
db_rr_iterator_current(db_rr_iterator_t *it, dns_name_t **name,
               isc_uint32_t *ttl, dns_rdata_t **rdata);

static void
db_rr_iterator_destroy(db_rr_iterator_t *it);

static inline void
inc_stats(dns_zone_t *zone, dns_statscounter_t counter) {
    dns_generalstats_increment(ns_g_server->nsstats, counter);
    if (zone != NULL) {
        dns_stats_t *zonestats = dns_zone_getrequeststats(zone);
        if (zonestats != NULL)
            dns_generalstats_increment(zonestats, counter);
    }
}

static isc_result_t
db_rr_iterator_init(db_rr_iterator_t *it, dns_db_t *db, dns_dbversion_t *ver,
            isc_stdtime_t now)
{
    isc_result_t result;
    it->db = db;
    it->dbit = NULL;
    it->ver = ver;
    it->now = now;
    it->node = NULL;
    result = dns_db_createiterator(it->db, ISC_FALSE, &it->dbit);
    if (result != ISC_R_SUCCESS)
        return (result);
    it->rdatasetit = NULL;
    dns_rdata_init(&it->rdata);
    dns_rdataset_init(&it->rdataset);
    dns_fixedname_init(&it->fixedname);
    INSIST(! dns_rdataset_isassociated(&it->rdataset));
    it->result = ISC_R_SUCCESS;
    return (it->result);
}

static isc_result_t
db_rr_iterator_first(db_rr_iterator_t *it) {
    it->result = dns_dbiterator_first(it->dbit);
    /*
     * The top node may be empty when out of zone glue exists.
     * Walk the tree to find the first node with data.
     */
    while (it->result == ISC_R_SUCCESS) {
        it->result = dns_dbiterator_current(it->dbit, &it->node,
                    dns_fixedname_name(&it->fixedname));
        if (it->result != ISC_R_SUCCESS)
            return (it->result);

        it->result = dns_db_allrdatasets(it->db, it->node,
                         it->ver, it->now,
                         &it->rdatasetit);
        if (it->result != ISC_R_SUCCESS)
            return (it->result);

        it->result = dns_rdatasetiter_first(it->rdatasetit);
        if (it->result != ISC_R_SUCCESS) {
            /*
             * This node is empty. Try next node.
             */
            dns_rdatasetiter_destroy(&it->rdatasetit);
            dns_db_detachnode(it->db, &it->node);
            it->result = dns_dbiterator_next(it->dbit);
            continue;
        }
        dns_rdatasetiter_current(it->rdatasetit, &it->rdataset);
        it->rdataset.attributes |= DNS_RDATASETATTR_LOADORDER;
        it->result = dns_rdataset_first(&it->rdataset);
        return (it->result);
    }
    return (it->result);
}


static isc_result_t
db_rr_iterator_next(db_rr_iterator_t *it) {
    if (it->result != ISC_R_SUCCESS)
        return (it->result);

    INSIST(it->dbit != NULL);
    INSIST(it->node != NULL);
    INSIST(it->rdatasetit != NULL);

    it->result = dns_rdataset_next(&it->rdataset);
    if (it->result == ISC_R_NOMORE) {
        dns_rdataset_disassociate(&it->rdataset);
        it->result = dns_rdatasetiter_next(it->rdatasetit);
        /*
         * The while loop body is executed more than once
         * only when an empty dbnode needs to be skipped.
         */
        while (it->result == ISC_R_NOMORE) {
            dns_rdatasetiter_destroy(&it->rdatasetit);
            dns_db_detachnode(it->db, &it->node);
            it->result = dns_dbiterator_next(it->dbit);
            if (it->result == ISC_R_NOMORE) {
                /* We are at the end of the entire database. */
                return (it->result);
            }
            if (it->result != ISC_R_SUCCESS)
                return (it->result);
            it->result = dns_dbiterator_current(it->dbit,
                    &it->node,
                    dns_fixedname_name(&it->fixedname));
            if (it->result != ISC_R_SUCCESS)
                return (it->result);
            it->result = dns_db_allrdatasets(it->db, it->node,
                     it->ver, it->now,
                     &it->rdatasetit);
            if (it->result != ISC_R_SUCCESS)
                return (it->result);
            it->result = dns_rdatasetiter_first(it->rdatasetit);
        }
        if (it->result != ISC_R_SUCCESS)
            return (it->result);
        dns_rdatasetiter_current(it->rdatasetit, &it->rdataset);
        it->rdataset.attributes |= DNS_RDATASETATTR_LOADORDER;
        it->result = dns_rdataset_first(&it->rdataset);
        if (it->result != ISC_R_SUCCESS)
            return (it->result);
    }
    return (it->result);
}

static void
db_rr_iterator_pause(db_rr_iterator_t *it) {
    RUNTIME_CHECK(dns_dbiterator_pause(it->dbit) == ISC_R_SUCCESS);
}

static void
db_rr_iterator_destroy(db_rr_iterator_t *it) {
    if (dns_rdataset_isassociated(&it->rdataset))
        dns_rdataset_disassociate(&it->rdataset);
    if (it->rdatasetit != NULL)
        dns_rdatasetiter_destroy(&it->rdatasetit);
    if (it->node != NULL)
        dns_db_detachnode(it->db, &it->node);
    dns_dbiterator_destroy(&it->dbit);
}

static void
db_rr_iterator_current(db_rr_iterator_t *it, dns_name_t **name,
              isc_uint32_t *ttl, dns_rdata_t **rdata)
{
    REQUIRE(name != NULL && *name == NULL);
    REQUIRE(it->result == ISC_R_SUCCESS);
    *name = dns_fixedname_name(&it->fixedname);
    *ttl = it->rdataset.ttl;
    dns_rdata_reset(&it->rdata);
    dns_rdataset_current(&it->rdataset, &it->rdata);
    *rdata = &it->rdata;
}

/**************************************************************************/

/*% 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;
    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 = mctx;
    s->common.methods = &ixfr_rrstream_methods;
    s->journal = NULL;

    CHECK(dns_journal_open(mctx, journal_filename,
                   ISC_FALSE, &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_put(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;
    db_rr_iterator_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 = mctx;
    s->common.methods = &axfr_rrstream_methods;
    s->it_valid = ISC_FALSE;

    CHECK(db_rr_iterator_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 = db_rr_iterator_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;
        db_rr_iterator_current(&s->it, &name_dummy,
                      &ttl_dummy, &rdata);
        if (rdata->type != dns_rdatatype_soa)
            break;
        result = db_rr_iterator_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 = db_rr_iterator_next(&s->it);
        if (result != ISC_R_SUCCESS)
            break;
        db_rr_iterator_current(&s->it, &name_dummy,
                      &ttl_dummy, &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;
    db_rr_iterator_current(&s->it, name, ttl, rdata);
}

static void
axfr_rrstream_pause(rrstream_t *rs) {
    axfr_rrstream_t *s = (axfr_rrstream_t *) rs;
    db_rr_iterator_pause(&s->it);
}

static void
axfr_rrstream_destroy(rrstream_t **rsp) {
    axfr_rrstream_t *s = (axfr_rrstream_t *) *rsp;
    if (s->it_valid)
        db_rr_iterator_destroy(&s->it);
    isc_mem_put(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 = 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_put(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 = 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_put(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;
    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;
#ifdef DLZ
    isc_boolean_t is_dlz = ISC_FALSE;
#endif

    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)
#ifdef DLZ
    {
        /*
         * Normal zone table does not have a match.  Try the DLZ database
         */
            if (client->view->dlzdatabase != NULL) {
            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)
#endif
            FAILQ(DNS_R_NOTAUTH, "non-authoritative zone",
                  question_name, question_class);
#ifdef DLZ
            is_dlz = ISC_TRUE;
            /*
             * DLZ only support full zone transfer, not incremental
             */
            if (reqtype != dns_rdatatype_axfr) {
                mnemonic = "AXFR-style IXFR";
                reqtype = dns_rdatatype_axfr;
            }

        } 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 */
#endif
        switch(dns_zone_gettype(zone)) {
            case dns_zone_master:
            case dns_zone_slave:
                break;  /* Master and slave zones are OK for transfer. */
            default:
                FAILQ(DNS_R_NOTAUTH, "non-authoritative zone", question_name, question_class);
            }
        CHECK(dns_zone_getdb(zone, &db));
        dns_db_currentversion(db, &ver);
#ifdef DLZ
    }
#endif

    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);

    /*
     * Decide whether to allow this transfer.
     */
#ifdef DLZ
    /*
     * if not a DLZ zone decide whether to allow this transfer.
     */
    if (!is_dlz) {
#endif
        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));
#ifdef DLZ
    }
#endif

    /*
     * 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.
     */
#ifdef DLZ
    if (is_dlz)
        dns_db_currentversion(db, &ver);
#endif
    CHECK(dns_db_createsoatuple(db, ver, mctx, DNS_DIFFOP_EXISTS,
                    &current_soa_tuple));

    if (reqtype == dns_rdatatype_ixfr) {
        isc_uint32_t begin_serial, current_serial;
        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);
        current_serial = dns_soa_getserial(&current_soa_tuple->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 = 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);
    } else {
    axfr_fallback:
        CHECK(axfr_rrstream_create(mctx, db, ver,
                       &data_stream));
    }

    /*
     * Bracket the 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.
     */


#ifdef DLZ
    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
#endif
        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
        xfrout_log1(client, question_name, question_class,
                ISC_LOG_INFO, "%s started%s%s", mnemonic,
                (xfr->tsigkey != NULL) ? ": TSIG " : "", keyname);

    /*
     * 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 = 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;
    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 possiby 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);

        /*
         * 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_init(qrdataset);
            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
            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;
        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;
        dns_rdataset_init(msgrds);
        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;

    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);

    ns_client_detach(&xfr->client);

    isc_mem_put(xfr->mctx, xfr, sizeof(*xfr));

    *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);
}