Add BIND 9.2.4rc7.

[dragonfly.git] / contrib / bind-9.2.4rc7 / lib / dns / journal.c

/*
 * Copyright (C) 2004  Internet Systems Consortium, Inc. ("ISC")
 * Copyright (C) 1999-2001  Internet Software Consortium.
 *
 * Permission to use, copy, modify, and distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND 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: journal.c,v 1.77.2.2 2004/03/09 06:11:02 marka Exp $ */

#include <config.h>

#include <stdlib.h>

#include <isc/file.h>
#include <isc/mem.h>
#include <isc/stdio.h>
#include <isc/string.h>
#include <isc/util.h>

#include <dns/compress.h>
#include <dns/db.h>
#include <dns/dbiterator.h>
#include <dns/diff.h>
#include <dns/fixedname.h>
#include <dns/journal.h>
#include <dns/log.h>
#include <dns/rdataset.h>
#include <dns/rdatasetiter.h>
#include <dns/result.h>
#include <dns/soa.h>

/*
 * When true, accept IXFR difference sequences where the
 * SOA serial number does not change (BIND 8 sends such
 * sequences).
 */
static isc_boolean_t bind8_compat = ISC_TRUE; /* XXX config */

/**************************************************************************/
/*
 * Miscellaneous utilities.
 */

#define JOURNAL_COMMON_LOGARGS \
        dns_lctx, DNS_LOGCATEGORY_GENERAL, DNS_LOGMODULE_JOURNAL

#define JOURNAL_DEBUG_LOGARGS(n) \
        JOURNAL_COMMON_LOGARGS, ISC_LOG_DEBUG(n)

/*
 * It would be non-sensical (or at least obtuse) to use FAIL() with an
 * ISC_R_SUCCESS code, but the test is there to keep the Solaris compiler
 * from complaining about "end-of-loop code not reached".
 */
#define FAIL(code) \
        do { result = (code);                                   \
                if (result != ISC_R_SUCCESS) goto failure;      \
        } while (0)

#define CHECK(op) \
        do { result = (op);                                     \
                if (result != ISC_R_SUCCESS) goto failure;      \
        } while (0)

static inline isc_uint32_t
decode_uint32(unsigned char *p) {
        return ((p[0] << 24) +
                (p[1] << 16) +
                (p[2] <<  8) +
                (p[3] <<  0));
}

static inline void
encode_uint32(isc_uint32_t val, unsigned char *p) {
        p[0] = (isc_uint8_t)(val >> 24);
        p[1] = (isc_uint8_t)(val >> 16);
        p[2] = (isc_uint8_t)(val >>  8);
        p[3] = (isc_uint8_t)(val >>  0);
}

isc_result_t
dns_db_createsoatuple(dns_db_t *db, dns_dbversion_t *ver, isc_mem_t *mctx,
                      dns_diffop_t op, dns_difftuple_t **tp)
{
        isc_result_t result;
        dns_dbnode_t *node;
        dns_rdataset_t rdataset;
        dns_rdata_t rdata = DNS_RDATA_INIT;
        dns_name_t *zonename;

        zonename = dns_db_origin(db);

        node = NULL;
        result = dns_db_findnode(db, zonename, ISC_FALSE, &node);
        if (result != ISC_R_SUCCESS)
                goto nonode;

        dns_rdataset_init(&rdataset);
        result = dns_db_findrdataset(db, node, ver, dns_rdatatype_soa, 0,
                                     (isc_stdtime_t)0, &rdataset, NULL);
        if (result != ISC_R_SUCCESS)
                goto freenode;

        result = dns_rdataset_first(&rdataset);
        if (result != ISC_R_SUCCESS)
                goto freenode;

        dns_rdataset_current(&rdataset, &rdata);

        result = dns_difftuple_create(mctx, op, zonename, rdataset.ttl,
                                      &rdata, tp);

        dns_rdataset_disassociate(&rdataset);
        dns_db_detachnode(db, &node);
        return (ISC_R_SUCCESS);

 freenode:
        dns_db_detachnode(db, &node);
 nonode:
        UNEXPECTED_ERROR(__FILE__, __LINE__, "missing SOA");
        return (result);
}

/**************************************************************************/
/*
 * Journalling.
 */

/*
 * A journal file consists of
 *
 *   - A fixed-size header of type journal_rawheader_t.
 *
 *   - The index.  This is an unordered array of index entries
 *     of type journal_rawpos_t giving the locations
 *     of some arbitrary subset of the journal's addressable
 *     transactions.  The index entries are used as hints to
 *     speed up the process of locating a transaction with a given
 *     serial number.  Unused index entries have an "offset"
 *     field of zero.  The size of the index can vary between
 *     journal files, but does not change during the lifetime
 *     of a file.  The size can be zero.
 *
 *   - The journal data.  This  consists of one or more transactions.
 *     Each transaction begins with a transaction header of type
 *     journal_rawxhdr_t.  The transaction header is followed by a
 *     sequence of RRs, similar in structure to an IXFR difference
 *     sequence (RFC1995).  That is, the pre-transaction SOA,
 *     zero or more other deleted RRs, the post-transaction SOA,
 *     and zero or more other added RRs.  Unlike in IXFR, each RR
 *     is prefixed with a 32-bit length.
 *
 *     The journal data part grows as new transactions are
 *     appended to the file.  Only those transactions
 *     whose serial number is current-(2^31-1) to current
 *     are considered "addressable" and may be pointed
 *     to from the header or index.  They may be preceded
 *     by old transactions that are no longer addressable,
 *     and they may be followed by transactions that were
 *     appended to the journal but never committed by updating
 *     the "end" position in the header.  The latter will
 *     be overwritten when new transactions are added.
 */

/*
 * On-disk representation of a "pointer" to a journal entry.
 * These are used in the journal header to locate the beginning
 * and end of the journal, and in the journal index to locate
 * other transactions.
 */
typedef struct {
        unsigned char   serial[4];  /* SOA serial before update. */
        /*
         * XXXRTH  Should offset be 8 bytes?
         * XXXDCL ... probably, since isc_offset_t is 8 bytes on many OSs.
         * XXXAG  ... but we will not be able to seek >2G anyway on many
         *            platforms as long as we are using fseek() rather
         *            than lseek().
         */
        unsigned char   offset[4];  /* Offset from beginning of file. */
} journal_rawpos_t;

/*
 * The on-disk representation of the journal header.
 * All numbers are stored in big-endian order.
 */

/*
 * The header is of a fixed size, with some spare room for future
 * extensions.
 */
#define JOURNAL_HEADER_SIZE 64 /* Bytes. */

typedef union {
        struct {
                /* File format version ID. */
                unsigned char           format[16];
                /* Position of the first addressable transaction */
                journal_rawpos_t        begin;
                /* Position of the next (yet nonexistent) transaction. */
                journal_rawpos_t        end;
                /* Number of index entries following the header. */
                unsigned char           index_size[4];
        } h;
        /* Pad the header to a fixed size. */
        unsigned char pad[JOURNAL_HEADER_SIZE];
} journal_rawheader_t;

/*
 * The on-disk representation of the transaction header.
 * There is one of these at the beginning of each transaction.
 */
typedef struct {
        unsigned char   size[4];        /* In bytes, excluding header. */
        unsigned char   serial0[4];     /* SOA serial before update. */
        unsigned char   serial1[4];     /* SOA serial after update. */
} journal_rawxhdr_t;

/*
 * The on-disk representation of the RR header.
 * There is one of these at the beginning of each RR.
 */
typedef struct {
        unsigned char   size[4];        /* In bytes, excluding header. */
} journal_rawrrhdr_t;

/*
 * The in-core representation of the journal header.
 */
typedef struct {
        isc_uint32_t    serial;
        isc_offset_t    offset;
} journal_pos_t;

#define POS_VALID(pos)          ((pos).offset != 0)
#define POS_INVALIDATE(pos)     ((pos).offset = 0, (pos).serial = 0)

typedef struct {
        unsigned char   format[16];
        journal_pos_t   begin;
        journal_pos_t   end;
        isc_uint32_t    index_size;
} journal_header_t;

/*
 * The in-core representation of the transaction header.
 */

typedef struct {
        isc_uint32_t    size;
        isc_uint32_t    serial0;
        isc_uint32_t    serial1;
} journal_xhdr_t;

/*
 * The in-core representation of the RR header.
 */
typedef struct {
        isc_uint32_t    size;
} journal_rrhdr_t;


/*
 * Initial contents to store in the header of a newly created
 * journal file.
 *
 * The header starts with the magic string ";BIND LOG V9\n"
 * to identify the file as a BIND 9 journal file.  An ASCII
 * identification string is used rather than a binary magic
 * number to be consistent with BIND 8 (BIND 8 journal files
 * are ASCII text files).
 */

static journal_header_t
initial_journal_header = { ";BIND LOG V9\n", { 0, 0 }, { 0, 0 }, 0 };

#define JOURNAL_EMPTY(h) ((h)->begin.offset == (h)->end.offset)

typedef enum {
        JOURNAL_STATE_INVALID,
        JOURNAL_STATE_READ,
        JOURNAL_STATE_WRITE,
        JOURNAL_STATE_TRANSACTION
} journal_state_t;

struct dns_journal {
        unsigned int            magic;          /* JOUR */
        isc_mem_t               *mctx;          /* Memory context */
        journal_state_t         state;
        const char              *filename;      /* Journal file name */
        FILE *                  fp;             /* File handle */
        isc_offset_t            offset;         /* Current file offset */
        journal_header_t        header;         /* In-core journal header */
        unsigned char           *rawindex;      /* In-core buffer for journal
                                                   index in on-disk format */
        journal_pos_t           *index;         /* In-core journal index */

        /* Current transaction state (when writing). */
        struct {
                unsigned int    n_soa;          /* Number of SOAs seen */
                journal_pos_t   pos[2];         /* Begin/end position */
        } x;

        /* Iteration state (when reading). */
        struct {
                /* These define the part of the journal we iterate over. */
                journal_pos_t bpos;             /* Position before first, */
                journal_pos_t epos;             /* and after last
                                                   transaction */
                /* The rest is iterator state. */
                isc_uint32_t current_serial;    /* Current SOA serial */
                isc_buffer_t source;            /* Data from disk */
                isc_buffer_t target;            /* Data from _fromwire check */
                dns_decompress_t dctx;          /* Dummy decompression ctx */
                dns_name_t name;                /* Current domain name */
                dns_rdata_t rdata;              /* Current rdata */
                isc_uint32_t ttl;               /* Current TTL */
                unsigned int xsize;             /* Size of transaction data */
                unsigned int xpos;              /* Current position in it */
                isc_result_t result;            /* Result of last call */
        } it;
};

#define DNS_JOURNAL_MAGIC       ISC_MAGIC('J', 'O', 'U', 'R')
#define DNS_JOURNAL_VALID(t)    ISC_MAGIC_VALID(t, DNS_JOURNAL_MAGIC)

static void
journal_pos_decode(journal_rawpos_t *raw, journal_pos_t *cooked) {
        cooked->serial = decode_uint32(raw->serial);
        cooked->offset = decode_uint32(raw->offset);
}

static void
journal_pos_encode(journal_rawpos_t *raw, journal_pos_t *cooked) {
        encode_uint32(cooked->serial, raw->serial);
        encode_uint32(cooked->offset, raw->offset);
}

static void
journal_header_decode(journal_rawheader_t *raw, journal_header_t *cooked) {
        INSIST(sizeof(cooked->format) == sizeof(raw->h.format));
        memcpy(cooked->format, raw->h.format, sizeof(cooked->format));
        journal_pos_decode(&raw->h.begin, &cooked->begin);
        journal_pos_decode(&raw->h.end, &cooked->end);
        cooked->index_size = decode_uint32(raw->h.index_size);
}

static void
journal_header_encode(journal_header_t *cooked, journal_rawheader_t *raw) {
        INSIST(sizeof(cooked->format) == sizeof(raw->h.format));
        memset(raw->pad, 0, sizeof(raw->pad));
        memcpy(raw->h.format, cooked->format, sizeof(raw->h.format));
        journal_pos_encode(&raw->h.begin, &cooked->begin);
        journal_pos_encode(&raw->h.end, &cooked->end);
        encode_uint32(cooked->index_size, raw->h.index_size);
}

/*
 * Journal file I/O subroutines, with error checking and reporting.
 */
static isc_result_t
journal_seek(dns_journal_t *j, isc_uint32_t offset) {
        isc_result_t result;
        result = isc_stdio_seek(j->fp, (long)offset, SEEK_SET);
        if (result != ISC_R_SUCCESS) {
                isc_log_write(JOURNAL_COMMON_LOGARGS, ISC_LOG_ERROR,
                              "%s: seek: %s", j->filename,
                              isc_result_totext(result));
                return (ISC_R_UNEXPECTED);
        }
        j->offset = offset;
        return (ISC_R_SUCCESS);
}

static isc_result_t
journal_read(dns_journal_t *j, void *mem, size_t nbytes) {
        isc_result_t result;

        result = isc_stdio_read(mem, 1, nbytes, j->fp, NULL);
        if (result != ISC_R_SUCCESS) {
                if (result == ISC_R_EOF)
                        return (ISC_R_NOMORE);
                isc_log_write(JOURNAL_COMMON_LOGARGS, ISC_LOG_ERROR,
                              "%s: read: %s",
                              j->filename, isc_result_totext(result));
                return (ISC_R_UNEXPECTED);
        }
        j->offset += nbytes;
        return (ISC_R_SUCCESS);
}

static isc_result_t
journal_write(dns_journal_t *j, void *mem, size_t nbytes) {
        isc_result_t result;

        result = isc_stdio_write(mem, 1, nbytes, j->fp, NULL);
        if (result != ISC_R_SUCCESS) {
                isc_log_write(JOURNAL_COMMON_LOGARGS, ISC_LOG_ERROR,
                              "%s: write: %s",
                              j->filename, isc_result_totext(result));
                return (ISC_R_UNEXPECTED);
        }
        j->offset += nbytes;
        return (ISC_R_SUCCESS);
}

static isc_result_t
journal_fsync(dns_journal_t *j) {
        isc_result_t result;
        result = isc_stdio_flush(j->fp);
        if (result != ISC_R_SUCCESS) {
                isc_log_write(JOURNAL_COMMON_LOGARGS, ISC_LOG_ERROR,
                              "%s: flush: %s",
                              j->filename, isc_result_totext(result));
                return (ISC_R_UNEXPECTED);
        }
        result = isc_stdio_sync(j->fp);
        if (result != ISC_R_SUCCESS) {
                isc_log_write(JOURNAL_COMMON_LOGARGS, ISC_LOG_ERROR,
                              "%s: fsync: %s",
                              j->filename, isc_result_totext(result));
                return (ISC_R_UNEXPECTED);
        }
        return (ISC_R_SUCCESS);
}

/*
 * Read/write a transaction header at the current file position.
 */

static isc_result_t
journal_read_xhdr(dns_journal_t *j, journal_xhdr_t *xhdr) {
        journal_rawxhdr_t raw;
        isc_result_t result;
        result = journal_read(j, &raw, sizeof(raw));
        if (result != ISC_R_SUCCESS)
                return (result);
        xhdr->size = decode_uint32(raw.size);
        xhdr->serial0 = decode_uint32(raw.serial0);
        xhdr->serial1 = decode_uint32(raw.serial1);
        return (ISC_R_SUCCESS);
}

static isc_result_t
journal_write_xhdr(dns_journal_t *j, isc_uint32_t size,
                   isc_uint32_t serial0, isc_uint32_t serial1)
{
        journal_rawxhdr_t raw;
        encode_uint32(size, raw.size);
        encode_uint32(serial0, raw.serial0);
        encode_uint32(serial1, raw.serial1);
        return (journal_write(j, &raw, sizeof(raw)));
}


/*
 * Read an RR header at the current file position.
 */

static isc_result_t
journal_read_rrhdr(dns_journal_t *j, journal_rrhdr_t *rrhdr) {
        journal_rawrrhdr_t raw;
        isc_result_t result;
        result = journal_read(j, &raw, sizeof(raw));
        if (result != ISC_R_SUCCESS)
                return (result);
        rrhdr->size = decode_uint32(raw.size);
        return (ISC_R_SUCCESS);
}

static isc_result_t
journal_file_create(isc_mem_t *mctx, const char *filename) {
        FILE *fp = NULL;
        isc_result_t result;
        journal_header_t header;
        journal_rawheader_t rawheader;
        int index_size = 56; /* XXX configurable */
        int size;
        void *mem; /* Memory for temporary index image. */

        INSIST(sizeof(journal_rawheader_t) == JOURNAL_HEADER_SIZE);

        result = isc_stdio_open(filename, "wb", &fp);
        if (result != ISC_R_SUCCESS) {
                isc_log_write(JOURNAL_COMMON_LOGARGS, ISC_LOG_ERROR,
                              "%s: create: %s",
                              filename, isc_result_totext(result));
                return (ISC_R_UNEXPECTED);
        }

        header = initial_journal_header;
        header.index_size = index_size;
        journal_header_encode(&header, &rawheader);

        size = sizeof(journal_rawheader_t) +
                index_size * sizeof(journal_rawpos_t);

        mem = isc_mem_get(mctx, size);
        if (mem == NULL) {
                (void)isc_stdio_close(fp);
                (void)isc_file_remove(filename);
                return (ISC_R_NOMEMORY);
        }
        memset(mem, 0, size);
        memcpy(mem, &rawheader, sizeof(rawheader));

        result = isc_stdio_write(mem, 1, (size_t) size, fp, NULL);
        if (result != ISC_R_SUCCESS) {
                isc_log_write(JOURNAL_COMMON_LOGARGS, ISC_LOG_ERROR,
                                 "%s: write: %s",
                                 filename, isc_result_totext(result));
                (void)isc_stdio_close(fp);
                (void)isc_file_remove(filename);
                isc_mem_put(mctx, mem, size);
                return (ISC_R_UNEXPECTED);
        }
        isc_mem_put(mctx, mem, size);

        result = isc_stdio_close(fp);
        if (result != ISC_R_SUCCESS) {
                isc_log_write(JOURNAL_COMMON_LOGARGS, ISC_LOG_ERROR,
                                 "%s: close: %s",
                                 filename, isc_result_totext(result));
                (void)isc_file_remove(filename);
                return (ISC_R_UNEXPECTED);
        }

        return (ISC_R_SUCCESS);
}


isc_result_t
dns_journal_open(isc_mem_t *mctx, const char *filename, isc_boolean_t write,
                 dns_journal_t **journalp) {
        FILE *fp = NULL;
        isc_result_t result;
        journal_rawheader_t rawheader;
        dns_journal_t *j;

        INSIST(journalp != NULL && *journalp == NULL);
        j = isc_mem_get(mctx, sizeof(*j));
        if (j == NULL)
                return (ISC_R_NOMEMORY);

        j->mctx = mctx;
        j->state = JOURNAL_STATE_INVALID;
        j->fp = NULL;
        j->filename = filename;
        j->index = NULL;
        j->rawindex = NULL;

        result = isc_stdio_open(j->filename, write ? "rb+" : "rb", &fp);

        if (result == ISC_R_FILENOTFOUND) {
                if (write) {
                        isc_log_write(JOURNAL_COMMON_LOGARGS,
                                      ISC_LOG_INFO,
                                      "journal file %s does not exist, "
                                      "creating it",
                                      j->filename);
                        CHECK(journal_file_create(mctx, filename));
                        /*
                         * Retry.
                         */
                        result = isc_stdio_open(j->filename, "rb+", &fp);
                } else {
                        FAIL(ISC_R_NOTFOUND);
                }
        }
        if (result != ISC_R_SUCCESS) {
                isc_log_write(JOURNAL_COMMON_LOGARGS, ISC_LOG_ERROR,
                              "%s: open: %s",
                              j->filename, isc_result_totext(result));
                FAIL(ISC_R_UNEXPECTED);
        }

        j->fp = fp;

        /*
         * Set magic early so that seek/read can succeed.
         */
        j->magic = DNS_JOURNAL_MAGIC;

        CHECK(journal_seek(j, 0));
        CHECK(journal_read(j, &rawheader, sizeof(rawheader)));

        if (memcmp(rawheader.h.format, initial_journal_header.format,
                   sizeof(initial_journal_header.format)) != 0) {
                isc_log_write(JOURNAL_COMMON_LOGARGS, ISC_LOG_ERROR,
                                 "%s: journal format not recognized",
                                 j->filename);
                FAIL(ISC_R_UNEXPECTED);
        }
        journal_header_decode(&rawheader, &j->header);

        /*
         * If there is an index, read the raw index into a dynamically
         * allocated buffer and then convert it into a cooked index.
         */
        if (j->header.index_size != 0) {
                unsigned int i;
                unsigned int rawbytes;
                unsigned char *p;

                rawbytes = j->header.index_size * sizeof(journal_rawpos_t);
                j->rawindex = isc_mem_get(mctx, rawbytes);
                if (j->rawindex == NULL)
                        FAIL(ISC_R_NOMEMORY);

                CHECK(journal_read(j, j->rawindex, rawbytes));

                j->index = isc_mem_get(mctx, j->header.index_size *
                                       sizeof(journal_pos_t));
                if (j->index == NULL)
                        FAIL(ISC_R_NOMEMORY);

                p = j->rawindex;
                for (i = 0; i < j->header.index_size; i++) {
                        j->index[i].serial = decode_uint32(p);
                        p += 4;
                        j->index[i].offset = decode_uint32(p);
                        p += 4;
                }
                INSIST(p == j->rawindex + rawbytes);
        }
        j->offset = -1; /* Invalid, must seek explicitly. */

        /*
         * Initialize the iterator.
         */
        dns_name_init(&j->it.name, NULL);
        dns_rdata_init(&j->it.rdata);

        /*
         * Set up empty initial buffers for uncheched and checked
         * wire format RR data.  They will be reallocated
         * later.
         */
        isc_buffer_init(&j->it.source, NULL, 0);
        isc_buffer_init(&j->it.target, NULL, 0);
        dns_decompress_init(&j->it.dctx, -1, DNS_DECOMPRESS_NONE);

        j->state =
                write ? JOURNAL_STATE_WRITE : JOURNAL_STATE_READ;

        *journalp = j;
        return (ISC_R_SUCCESS);

 failure:
        j->magic = 0;
        if (j->index != NULL) {
                isc_mem_put(j->mctx, j->index, j->header.index_size *
                            sizeof(journal_rawpos_t));
                j->index = NULL;
        }
        if (j->fp != NULL)
                (void)isc_stdio_close(j->fp);
        isc_mem_put(j->mctx, j, sizeof(*j));
        return (result);
}

/*
 * A comparison function defining the sorting order for
 * entries in the IXFR-style journal file.
 *
 * The IXFR format requires that deletions are sorted before
 * additions, and within either one, SOA records are sorted
 * before others.
 *
 * Also sort the non-SOA records by type as a courtesy to the
 * server receiving the IXFR - it may help reduce the amount of
 * rdataset merging it has to do.
 */
static int
ixfr_order(const void *av, const void *bv) {
        dns_difftuple_t const * const *ap = av;
        dns_difftuple_t const * const *bp = bv;
        dns_difftuple_t const *a = *ap;
        dns_difftuple_t const *b = *bp;
        int r;

        r = (b->op == DNS_DIFFOP_DEL) - (a->op == DNS_DIFFOP_DEL);
        if (r != 0)
                return (r);

        r = (b->rdata.type == dns_rdatatype_soa) -
                (a->rdata.type == dns_rdatatype_soa);
        if (r != 0)
                return (r);

        r = (a->rdata.type - b->rdata.type);
        return (r);
}

/*
 * Advance '*pos' to the next journal transaction.
 *
 * Requires:
 *      *pos refers to a valid journal transaction.
 *
 * Ensures:
 *      When ISC_R_SUCCESS is returned,
 *      *pos refers to the next journal transaction.
 *
 * Returns one of:
 *
 *    ISC_R_SUCCESS
 *    ISC_R_NOMORE      *pos pointed at the last transaction
 *    Other results due to file errors are possible.
 */
static isc_result_t
journal_next(dns_journal_t *j, journal_pos_t *pos) {
        isc_result_t result;
        journal_xhdr_t xhdr;
        REQUIRE(DNS_JOURNAL_VALID(j));

        result = journal_seek(j, pos->offset);
        if (result != ISC_R_SUCCESS)
                return (result);

        /*
         * Read the header of the current transaction.
         * This will return ISC_R_NOMORE if we are at EOF.
         */
        result = journal_read_xhdr(j, &xhdr);
        if (result != ISC_R_SUCCESS)
                return (result);

        /*
         * Check serial number consistency.
         */
        if (xhdr.serial0 != pos->serial) {
                isc_log_write(JOURNAL_COMMON_LOGARGS, ISC_LOG_ERROR,
                              "%s: journal file corrupt: "
                              "expected serial %u, got %u",
                              j->filename, pos->serial, xhdr.serial0);
                return (ISC_R_UNEXPECTED);
        }

        /*
         * Check for offset wraparound.
         */
        if ((isc_offset_t)(pos->offset + sizeof(journal_rawxhdr_t) + xhdr.size)
            < pos->offset) {
                isc_log_write(JOURNAL_COMMON_LOGARGS, ISC_LOG_ERROR,
                              "%s: offset too large", j->filename);
                return (ISC_R_UNEXPECTED);
        }

        pos->offset += sizeof(journal_rawxhdr_t) + xhdr.size;
        pos->serial = xhdr.serial1;
        return (ISC_R_SUCCESS);
}

/*
 * If the index of the journal 'j' contains an entry "better"
 * than '*best_guess', replace '*best_guess' with it.
 *
 * "Better" means having a serial number closer to 'serial'
 * but not greater than 'serial'.
 */
static void
index_find(dns_journal_t *j, isc_uint32_t serial, journal_pos_t *best_guess) {
        unsigned int i;
        if (j->index == NULL)
                return;
        for (i = 0; i < j->header.index_size; i++) {
                if (POS_VALID(j->index[i]) &&
                    DNS_SERIAL_GE(serial, j->index[i].serial) &&
                    DNS_SERIAL_GT(j->index[i].serial, best_guess->serial))
                        *best_guess = j->index[i];
        }
}

/*
 * Add a new index entry.  If there is no room, make room by removing
 * the odd-numbered entries and compacting the others into the first
 * half of the index.  This decimates old index entries exponentially
 * over time, so that the index always contains a much larger fraction
 * of recent serial numbers than of old ones.  This is deliberate -
 * most index searches are for outgoing IXFR, and IXFR tends to request
 * recent versions more often than old ones.
 */
static void
index_add(dns_journal_t *j, journal_pos_t *pos) {
        unsigned int i;
        if (j->index == NULL)
                return;
        /*
         * Search for a vacant position.
         */
        for (i = 0; i < j->header.index_size; i++) {
                if (! POS_VALID(j->index[i]))
                        break;
        }
        if (i == j->header.index_size) {
                unsigned int k = 0;
                /*
                 * Found no vacant position.  Make some room.
                 */
                for (i = 0; i < j->header.index_size; i += 2) {
                        j->index[k++] = j->index[i];
                }
                i = k; /* 'i' identifies the first vacant position. */
                while (k < j->header.index_size) {
                        POS_INVALIDATE(j->index[k]);
                        k++;
                }
        }
        INSIST(i < j->header.index_size);
        INSIST(! POS_VALID(j->index[i]));

        /*
         * Store the new index entry.
         */
        j->index[i] = *pos;
}

/*
 * Invalidate any existing index entries that could become
 * ambiguous when a new transaction with number 'serial' is added.
 */
static void
index_invalidate(dns_journal_t *j, isc_uint32_t serial) {
        unsigned int i;
        if (j->index == NULL)
                return;
        for (i = 0; i < j->header.index_size; i++) {
                if (! DNS_SERIAL_GT(serial, j->index[i].serial))
                        POS_INVALIDATE(j->index[i]);
        }
}

/*
 * Try to find a transaction with initial serial number 'serial'
 * in the journal 'j'.
 *
 * If found, store its position at '*pos' and return ISC_R_SUCCESS.
 *
 * If 'serial' is current (= the ending serial number of the
 * last transaction in the journal), set '*pos' to
 * the position immediately following the last transaction and
 * return ISC_R_SUCCESS.
 *
 * If 'serial' is within the range of addressable serial numbers
 * covered by the journal but that particular serial number is missing
 * (from the journal, not just from the index), return ISC_R_NOTFOUND.
 *
 * If 'serial' is outside the range of addressable serial numbers
 * covered by the journal, return ISC_R_RANGE.
 *
 */
static isc_result_t
journal_find(dns_journal_t *j, isc_uint32_t serial, journal_pos_t *pos) {
        isc_result_t result;
        journal_pos_t current_pos;
        REQUIRE(DNS_JOURNAL_VALID(j));

        if (DNS_SERIAL_GT(j->header.begin.serial, serial))
                return (ISC_R_RANGE);
        if (DNS_SERIAL_GT(serial, j->header.end.serial))
                return (ISC_R_RANGE);
        if (serial == j->header.end.serial) {
                *pos = j->header.end;
                return (ISC_R_SUCCESS);
        }

        current_pos = j->header.begin;
        index_find(j, serial, &current_pos);

        while (current_pos.serial != serial) {
                if (DNS_SERIAL_GT(current_pos.serial, serial))
                        return (ISC_R_NOTFOUND);
                result = journal_next(j, &current_pos);
                if (result != ISC_R_SUCCESS)
                        return (result);
        }
        *pos = current_pos;
        return (ISC_R_SUCCESS);
}

isc_result_t
dns_journal_begin_transaction(dns_journal_t *j) {
        isc_uint32_t offset;
        isc_result_t result;
        journal_rawxhdr_t hdr;

        REQUIRE(DNS_JOURNAL_VALID(j));
        REQUIRE(j->state == JOURNAL_STATE_WRITE);

        /*
         * Find the file offset where the new transaction should
         * be written, and seek there.
         */
        if (JOURNAL_EMPTY(&j->header)) {
                offset = sizeof(journal_rawheader_t) +
                        j->header.index_size * sizeof(journal_rawpos_t);
        } else {
                offset = j->header.end.offset;
        }
        j->x.pos[0].offset = offset;
        j->x.pos[1].offset = offset; /* Initial value, will be incremented. */
        j->x.n_soa = 0;

        CHECK(journal_seek(j, offset));

        /*
         * Write a dummy transaction header of all zeroes to reserve
         * space.  It will be filled in when the transaction is
         * finished.
         */
        memset(&hdr, 0, sizeof(hdr));
        CHECK(journal_write(j, &hdr, sizeof(hdr)));
        j->x.pos[1].offset = j->offset;

        j->state = JOURNAL_STATE_TRANSACTION;
        result = ISC_R_SUCCESS;
 failure:
        return (result);
}

isc_result_t
dns_journal_writediff(dns_journal_t *j, dns_diff_t *diff) {
        dns_difftuple_t *t;
        isc_buffer_t buffer;
        void *mem = NULL;
        unsigned int size;
        isc_result_t result;
        isc_region_t used;

        REQUIRE(DNS_DIFF_VALID(diff));
        REQUIRE(j->state == JOURNAL_STATE_TRANSACTION);

        isc_log_write(JOURNAL_DEBUG_LOGARGS(3), "writing to journal");
        dns_diff_print(diff, NULL);

        /*
         * Pass 1: determine the buffer size needed, and
         * keep track of SOA serial numbers.
         */
        size = 0;
        for (t = ISC_LIST_HEAD(diff->tuples); t != NULL;
             t = ISC_LIST_NEXT(t, link))
        {
                if (t->rdata.type == dns_rdatatype_soa) {
                        if (j->x.n_soa < 2)
                                j->x.pos[j->x.n_soa].serial =
                                        dns_soa_getserial(&t->rdata);
                        j->x.n_soa++;
                }
                size += sizeof(journal_rawrrhdr_t);
                size += t->name.length; /* XXX should have access macro? */
                size += 10;
                size += t->rdata.length;
        }

        mem = isc_mem_get(j->mctx, size);
        if (mem == NULL)
                return (ISC_R_NOMEMORY);

        isc_buffer_init(&buffer, mem, size);

        /*
         * Pass 2.  Write RRs to buffer.
         */
        for (t = ISC_LIST_HEAD(diff->tuples); t != NULL;
             t = ISC_LIST_NEXT(t, link))
        {
                /*
                 * Write the RR header.
                 */
                isc_buffer_putuint32(&buffer, t->name.length + 10 +
                                     t->rdata.length);
                /*
                 * Write the owner name, RR header, and RR data.
                 */
                isc_buffer_putmem(&buffer, t->name.ndata, t->name.length);
                isc_buffer_putuint16(&buffer, t->rdata.type);
                isc_buffer_putuint16(&buffer, t->rdata.rdclass);
                isc_buffer_putuint32(&buffer, t->ttl);
                INSIST(t->rdata.length < 65536);
                isc_buffer_putuint16(&buffer, (isc_uint16_t)t->rdata.length);
                INSIST(isc_buffer_availablelength(&buffer) >= t->rdata.length);
                isc_buffer_putmem(&buffer, t->rdata.data, t->rdata.length);
        }

        isc_buffer_usedregion(&buffer, &used);
        INSIST(used.length == size);

        j->x.pos[1].offset += used.length;

        /*
         * Write the buffer contents to the journal file.
         */
        CHECK(journal_write(j, used.base, used.length));

        result = ISC_R_SUCCESS;

 failure:
        if (mem != NULL)
                isc_mem_put(j->mctx, mem, size);
        return (result);

}

isc_result_t
dns_journal_commit(dns_journal_t *j) {
        isc_result_t result;
        journal_rawheader_t rawheader;

        REQUIRE(DNS_JOURNAL_VALID(j));
        REQUIRE(j->state == JOURNAL_STATE_TRANSACTION);

        /*
         * Perform some basic consistency checks.
         */
        if (j->x.n_soa != 2) {
                isc_log_write(JOURNAL_COMMON_LOGARGS, ISC_LOG_ERROR,
                              "malformed transaction: %d SOAs",
                              j->x.n_soa);
                return (ISC_R_UNEXPECTED);
        }
        if (! (DNS_SERIAL_GT(j->x.pos[1].serial, j->x.pos[0].serial) ||
               (bind8_compat &&
                j->x.pos[1].serial == j->x.pos[0].serial)))
        {
                isc_log_write(JOURNAL_COMMON_LOGARGS, ISC_LOG_ERROR,
                              "malformed transaction: serial number "
                              "would decrease");
                return (ISC_R_UNEXPECTED);
        }
        if (! JOURNAL_EMPTY(&j->header)) {
                if (j->x.pos[0].serial != j->header.end.serial) {
                        isc_log_write(JOURNAL_COMMON_LOGARGS, ISC_LOG_ERROR,
                                         "malformed transaction: "
                                         "%s last serial %u != "
                                         "transaction first serial %u",
                                         j->filename,
                                         j->header.end.serial,
                                         j->x.pos[0].serial);
                        return (ISC_R_UNEXPECTED);
                }
        }

        /*
         * Some old journal entries may become non-addressable
         * when we increment the current serial number.  Purge them
         * by stepping header.begin forward to the first addressable
         * transaction.  Also purge them from the index.
         */
        if (! JOURNAL_EMPTY(&j->header)) {
                while (! DNS_SERIAL_GT(j->x.pos[1].serial,
                                       j->header.begin.serial)) {
                        CHECK(journal_next(j, &j->header.begin));
                }
                index_invalidate(j, j->x.pos[1].serial);
        }
#ifdef notyet
        if (DNS_SERIAL_GT(last_dumped_serial, j->x.pos[1].serial)) {
                force_dump(...);
        }
#endif

        /*
         * Commit the transaction data to stable storage.
         */
        CHECK(journal_fsync(j));

        /*
         * Update the transaction header.
         */
        CHECK(journal_seek(j, j->x.pos[0].offset));
        CHECK(journal_write_xhdr(j, (j->x.pos[1].offset - j->x.pos[0].offset) -
                                 sizeof(journal_rawxhdr_t),
                                 j->x.pos[0].serial, j->x.pos[1].serial));

        /*
         * Update the journal header.
         */
        if (JOURNAL_EMPTY(&j->header)) {
                j->header.begin = j->x.pos[0];
        }
        j->header.end = j->x.pos[1];
        journal_header_encode(&j->header, &rawheader);
        CHECK(journal_seek(j, 0));
        CHECK(journal_write(j, &rawheader, sizeof(rawheader)));

        /*
         * Update the index.
         */
        index_add(j, &j->x.pos[0]);

        /*
         * Convert the index into on-disk format and write
         * it to disk.
         */
        if (j->header.index_size != 0) {
                unsigned int i;
                unsigned char *p;
                unsigned int rawbytes;

                rawbytes = j->header.index_size * sizeof(journal_rawpos_t);

                p = j->rawindex;
                for (i = 0; i < j->header.index_size; i++) {
                        encode_uint32(j->index[i].serial, p);
                        p += 4;
                        encode_uint32(j->index[i].offset, p);
                        p += 4;
                }
                INSIST(p == j->rawindex + rawbytes);

                CHECK(journal_write(j, j->rawindex, rawbytes));
        }

        /*
         * Commit the header to stable storage.
         */
        CHECK(journal_fsync(j));

        /*
         * We no longer have a transaction open.
         */
        j->state = JOURNAL_STATE_WRITE;

        result = ISC_R_SUCCESS;

 failure:
        return (result);
}

isc_result_t
dns_journal_write_transaction(dns_journal_t *j, dns_diff_t *diff) {
        isc_result_t result;
        CHECK(dns_diff_sort(diff, ixfr_order));
        CHECK(dns_journal_begin_transaction(j));
        CHECK(dns_journal_writediff(j, diff));
        CHECK(dns_journal_commit(j));
        result = ISC_R_SUCCESS;
 failure:
        return (result);
}

void
dns_journal_destroy(dns_journal_t **journalp) {
        dns_journal_t *j = *journalp;
        REQUIRE(DNS_JOURNAL_VALID(j));

        j->it.result = ISC_R_FAILURE;
        dns_name_invalidate(&j->it.name);
        dns_decompress_invalidate(&j->it.dctx);
        if (j->rawindex != NULL)
                isc_mem_put(j->mctx, j->rawindex, j->header.index_size *
                            sizeof(journal_rawpos_t));
        if (j->index != NULL)
                isc_mem_put(j->mctx, j->index, j->header.index_size *
                            sizeof(journal_pos_t));
        if (j->it.target.base != NULL)
                isc_mem_put(j->mctx, j->it.target.base, j->it.target.length);
        if (j->it.source.base != NULL)
                isc_mem_put(j->mctx, j->it.source.base, j->it.source.length);

        if (j->fp != NULL)
                (void)isc_stdio_close(j->fp);
        j->magic = 0;
        isc_mem_put(j->mctx, j, sizeof(*j));
        *journalp = NULL;
}

/*
 * Roll the open journal 'j' into the database 'db'.
 * A new database version will be created.
 */

/* XXX Share code with incoming IXFR? */

static isc_result_t
roll_forward(dns_journal_t *j, dns_db_t *db) {
        isc_buffer_t source;            /* Transaction data from disk */
        isc_buffer_t target;            /* Ditto after _fromwire check */
        isc_uint32_t db_serial;         /* Database SOA serial */
        isc_uint32_t end_serial;        /* Last journal SOA serial */
        isc_result_t result;
        dns_dbversion_t *ver = NULL;
        journal_pos_t pos;
        dns_diff_t diff;
        unsigned int n_soa = 0;
        unsigned int n_put = 0;

        REQUIRE(DNS_JOURNAL_VALID(j));
        REQUIRE(DNS_DB_VALID(db));

        dns_diff_init(j->mctx, &diff);

        /*
         * Set up empty initial buffers for uncheched and checked
         * wire format transaction data.  They will be reallocated
         * later.
         */
        isc_buffer_init(&source, NULL, 0);
        isc_buffer_init(&target, NULL, 0);

        /*
         * Create the new database version.
         */
        CHECK(dns_db_newversion(db, &ver));

        /*
         * Get the current database SOA serial number.
         */
        CHECK(dns_db_getsoaserial(db, ver, &db_serial));

        /*
         * Locate a journal entry for the current database serial.
         */
        CHECK(journal_find(j, db_serial, &pos));
        /*
         * XXX do more drastic things, like marking zone stale,
         * if this fails?
         */
        /*
         * XXXRTH  The zone code should probably mark the zone as bad and
         *         scream loudly into the log if this is a dynamic update
         *         log reply that failed.
         */

        end_serial = dns_journal_last_serial(j);
        if (db_serial == end_serial)
                CHECK(DNS_R_UPTODATE);

        CHECK(dns_journal_iter_init(j, db_serial, end_serial));

        for (result = dns_journal_first_rr(j);
             result == ISC_R_SUCCESS;
             result = dns_journal_next_rr(j))
        {
                dns_name_t *name;
                isc_uint32_t ttl;
                dns_rdata_t *rdata;
                dns_difftuple_t *tuple = NULL;

                name = NULL;
                rdata = NULL;
                dns_journal_current_rr(j, &name, &ttl, &rdata);

                if (rdata->type == dns_rdatatype_soa)
                        n_soa++;

                if (n_soa == 3)
                        n_soa = 1;
                if (n_soa == 0) {
                        isc_log_write(JOURNAL_COMMON_LOGARGS, ISC_LOG_ERROR,
                                         "%s: journal file corrupt: missing "
                                         "initial SOA", j->filename);
                        FAIL(ISC_R_UNEXPECTED);
                }
                CHECK(dns_difftuple_create(diff.mctx, n_soa == 1 ?
                                           DNS_DIFFOP_DEL : DNS_DIFFOP_ADD,
                                           name, ttl, rdata, &tuple));
                dns_diff_append(&diff, &tuple);

                if (++n_put > 100)  {
                        isc_log_write(JOURNAL_DEBUG_LOGARGS(3),
                                      "applying diff to database");
                        dns_diff_print(&diff, NULL);
                        CHECK(dns_diff_apply(&diff, db, ver));
                        dns_diff_clear(&diff);
                        n_put = 0;
                }
        }
        if (result == ISC_R_NOMORE)
                result = ISC_R_SUCCESS;
        CHECK(result);

        if (n_put != 0) {
                isc_log_write(JOURNAL_DEBUG_LOGARGS(3),
                              "applying final diff to database");
                dns_diff_print(&diff, NULL);
                CHECK(dns_diff_apply(&diff, db, ver));
                dns_diff_clear(&diff);
        }

 failure:
        if (ver != NULL)
                dns_db_closeversion(db, &ver, result == ISC_R_SUCCESS ?
                                    ISC_TRUE : ISC_FALSE);

        if (source.base != NULL)
                isc_mem_put(j->mctx, source.base, source.length);
        if (target.base != NULL)
                isc_mem_put(j->mctx, target.base, target.length);

        dns_diff_clear(&diff);

        return (result);
}

isc_result_t
dns_journal_rollforward(isc_mem_t *mctx, dns_db_t *db, const char *filename) {
        dns_journal_t *j;
        isc_result_t result;

        REQUIRE(DNS_DB_VALID(db));
        REQUIRE(filename != NULL);

        j = NULL;
        result = dns_journal_open(mctx, filename, ISC_FALSE, &j);
        if (result == ISC_R_NOTFOUND) {
                isc_log_write(JOURNAL_DEBUG_LOGARGS(3),
                              "no journal file, but that's OK");
                return (DNS_R_NOJOURNAL);
        }
        if (result != ISC_R_SUCCESS)
                return (result);
        if (JOURNAL_EMPTY(&j->header))
                result = DNS_R_UPTODATE;
        else
                result = roll_forward(j, db);

        dns_journal_destroy(&j);

        return (result);
}

isc_result_t
dns_journal_print(isc_mem_t *mctx, const char *filename, FILE *file) {
        dns_journal_t *j;
        isc_buffer_t source;            /* Transaction data from disk */
        isc_buffer_t target;            /* Ditto after _fromwire check */
        isc_uint32_t start_serial;              /* Database SOA serial */
        isc_uint32_t end_serial;        /* Last journal SOA serial */
        isc_result_t result;
        dns_diff_t diff;
        unsigned int n_soa = 0;
        unsigned int n_put = 0;

        REQUIRE(filename != NULL);

        j = NULL;
        result = dns_journal_open(mctx, filename, ISC_FALSE, &j);
        if (result == ISC_R_NOTFOUND) {
                isc_log_write(JOURNAL_DEBUG_LOGARGS(3), "no journal file");
                return (DNS_R_NOJOURNAL);
        }

        if (result != ISC_R_SUCCESS) {
                isc_log_write(JOURNAL_COMMON_LOGARGS, ISC_LOG_ERROR,
                              "journal open failure");
                return (result);
        }

        dns_diff_init(j->mctx, &diff);

        /*
         * Set up empty initial buffers for uncheched and checked
         * wire format transaction data.  They will be reallocated
         * later.
         */
        isc_buffer_init(&source, NULL, 0);
        isc_buffer_init(&target, NULL, 0);

        start_serial = dns_journal_first_serial(j);
        end_serial = dns_journal_last_serial(j);

        CHECK(dns_journal_iter_init(j, start_serial, end_serial));

        for (result = dns_journal_first_rr(j);
             result == ISC_R_SUCCESS;
             result = dns_journal_next_rr(j))
        {
                dns_name_t *name;
                isc_uint32_t ttl;
                dns_rdata_t *rdata;
                dns_difftuple_t *tuple = NULL;

                name = NULL;
                rdata = NULL;
                dns_journal_current_rr(j, &name, &ttl, &rdata);

                if (rdata->type == dns_rdatatype_soa)
                        n_soa++;

                if (n_soa == 3)
                        n_soa = 1;
                if (n_soa == 0) {
                isc_log_write(JOURNAL_COMMON_LOGARGS, ISC_LOG_ERROR,
                                         "%s: journal file corrupt: missing "
                                         "initial SOA", j->filename);
                        FAIL(ISC_R_UNEXPECTED);
                }
                CHECK(dns_difftuple_create(diff.mctx, n_soa == 1 ?
                                           DNS_DIFFOP_DEL : DNS_DIFFOP_ADD,
                                           name, ttl, rdata, &tuple));
                dns_diff_append(&diff, &tuple);

                if (++n_put > 100)  {
                        result = dns_diff_print(&diff, file);
                        dns_diff_clear(&diff);
                        n_put = 0;
                        if (result != ISC_R_SUCCESS)
                                break;
                }
        }
        if (result == ISC_R_NOMORE)
                result = ISC_R_SUCCESS;
        CHECK(result);

        if (n_put != 0) {
                result = dns_diff_print(&diff, file);
                dns_diff_clear(&diff);
        }
        goto cleanup;

 failure:
        isc_log_write(JOURNAL_COMMON_LOGARGS, ISC_LOG_ERROR,
                      "%s: cannot print: journal file corrupt", j->filename);

 cleanup:
        if (source.base != NULL)
                isc_mem_put(j->mctx, source.base, source.length);
        if (target.base != NULL)
                isc_mem_put(j->mctx, target.base, target.length);

        dns_diff_clear(&diff);
        dns_journal_destroy(&j);

        return (result);
}

/**************************************************************************/
/*
 * Miscellaneous accessors.
 */
isc_uint32_t dns_journal_first_serial(dns_journal_t *j) {
        return (j->header.begin.serial);
}

isc_uint32_t dns_journal_last_serial(dns_journal_t *j) {
        return (j->header.end.serial);
}

/**************************************************************************/
/*
 * Iteration support.
 *
 * When serving an outgoing IXFR, we transmit a part the journal starting
 * at the serial number in the IXFR request and ending at the serial
 * number that is current when the IXFR request arrives.  The ending
 * serial number is not necessarily at the end of the journal:
 * the journal may grow while the IXFR is in progress, but we stop
 * when we reach the serial number that was current when the IXFR started.
 */

static isc_result_t read_one_rr(dns_journal_t *j);

/*
 * Make sure the buffer 'b' is has at least 'size' bytes
 * allocated, and clear it.
 *
 * Requires:
 *      Either b->base is NULL, or it points to b->length bytes of memory
 *      previously allocated by isc_mem_get().
 */

static isc_result_t
size_buffer(isc_mem_t *mctx, isc_buffer_t *b, unsigned size) {
        if (b->length < size) {
                void *mem = isc_mem_get(mctx, size);
                if (mem == NULL)
                        return (ISC_R_NOMEMORY);
                if (b->base != NULL)
                        isc_mem_put(mctx, b->base, b->length);
                b->base = mem;
                b->length = size;
        }
        isc_buffer_clear(b);
        return (ISC_R_SUCCESS);
}

isc_result_t
dns_journal_iter_init(dns_journal_t *j,
                      isc_uint32_t begin_serial, isc_uint32_t end_serial)
{
        isc_result_t result;

        CHECK(journal_find(j, begin_serial, &j->it.bpos));
        INSIST(j->it.bpos.serial == begin_serial);

        CHECK(journal_find(j, end_serial, &j->it.epos));
        INSIST(j->it.epos.serial == end_serial);

        result = ISC_R_SUCCESS;
 failure:
        j->it.result = result;
        return (j->it.result);
}


isc_result_t
dns_journal_first_rr(dns_journal_t *j) {
        isc_result_t result;

        /*
         * Seek to the beginning of the first transaction we are
         * interested in.
         */
        CHECK(journal_seek(j, j->it.bpos.offset));
        j->it.current_serial = j->it.bpos.serial;

        j->it.xsize = 0;  /* We have no transaction data yet... */
        j->it.xpos = 0;   /* ...and haven't used any of it. */

        return (read_one_rr(j));

 failure:
        return (result);
}

static isc_result_t
read_one_rr(dns_journal_t *j) {
        isc_result_t result;

        dns_rdatatype_t rdtype;
        dns_rdataclass_t rdclass;
        unsigned int rdlen;
        isc_uint32_t ttl;
        journal_xhdr_t xhdr;
        journal_rrhdr_t rrhdr;

        INSIST(j->offset <= j->it.epos.offset);
        if (j->offset == j->it.epos.offset)
                return (ISC_R_NOMORE);
        if (j->it.xpos == j->it.xsize) {
                /*
                 * We are at a transaction boundary.
                 * Read another transaction header.
                 */
                CHECK(journal_read_xhdr(j, &xhdr));
                if (xhdr.size == 0) {
                        isc_log_write(JOURNAL_COMMON_LOGARGS, ISC_LOG_ERROR,
                                      "journal corrupt: empty transaction");
                        FAIL(ISC_R_UNEXPECTED);
                }
                if (xhdr.serial0 != j->it.current_serial) {
                        isc_log_write(JOURNAL_COMMON_LOGARGS, ISC_LOG_ERROR,
                                         "%s: journal file corrupt: "
                                         "expected serial %u, got %u",
                                         j->filename,
                                         j->it.current_serial, xhdr.serial0);
                        FAIL(ISC_R_UNEXPECTED);
                }
                j->it.xsize = xhdr.size;
                j->it.xpos = 0;
        }
        /*
         * Read an RR.
         */
        result = journal_read_rrhdr(j, &rrhdr);
        /*
         * Perform a sanity check on the journal RR size.
         * The smallest possible RR has a 1-byte owner name
         * and a 10-byte header.  The largest possible
         * RR has 65535 bytes of data, a header, and a maximum-
         * size owner name, well below 70 k total.
         */
        if (rrhdr.size < 1+10 || rrhdr.size > 70000) {
                isc_log_write(JOURNAL_COMMON_LOGARGS, ISC_LOG_ERROR,
                                 "%s: journal corrupt: impossible RR size "
                                 "(%d bytes)", j->filename, rrhdr.size);
                FAIL(ISC_R_UNEXPECTED);
        }

        CHECK(size_buffer(j->mctx, &j->it.source, rrhdr.size));
        CHECK(journal_read(j, j->it.source.base, rrhdr.size));
        isc_buffer_add(&j->it.source, rrhdr.size);

        /*
         * The target buffer is made the same size
         * as the source buffer, with the assumption that when
         * no compression in present, the output of dns_*_fromwire()
         * is no larger than the input.
         */
        CHECK(size_buffer(j->mctx, &j->it.target, rrhdr.size));

        /*
         * Parse the owner name.  We don't know where it
         * ends yet, so we make the entire "remaining"
         * part of the buffer "active".
         */
        isc_buffer_setactive(&j->it.source,
                             j->it.source.used - j->it.source.current);
        CHECK(dns_name_fromwire(&j->it.name, &j->it.source,
                                &j->it.dctx, ISC_FALSE, &j->it.target));

        /*
         * Check that the RR header is there, and parse it.
         */
        if (isc_buffer_remaininglength(&j->it.source) < 10)
                FAIL(DNS_R_FORMERR);

        rdtype = isc_buffer_getuint16(&j->it.source);
        rdclass = isc_buffer_getuint16(&j->it.source);
        ttl = isc_buffer_getuint32(&j->it.source);
        rdlen = isc_buffer_getuint16(&j->it.source);

        /*
         * Parse the rdata.
         */
        isc_buffer_setactive(&j->it.source, rdlen);
        dns_rdata_reset(&j->it.rdata);
        CHECK(dns_rdata_fromwire(&j->it.rdata, rdclass,
                                 rdtype, &j->it.source, &j->it.dctx,
                                 ISC_FALSE, &j->it.target));
        j->it.ttl = ttl;

        j->it.xpos += sizeof(journal_rawrrhdr_t) + rrhdr.size;
        if (rdtype == dns_rdatatype_soa) {
                /* XXX could do additional consistency checks here */
                j->it.current_serial = dns_soa_getserial(&j->it.rdata);
        }

        result = ISC_R_SUCCESS;

 failure:
        j->it.result = result;
        return (result);
}

isc_result_t
dns_journal_next_rr(dns_journal_t *j) {
        j->it.result = read_one_rr(j);
        return (j->it.result);
}

void
dns_journal_current_rr(dns_journal_t *j, dns_name_t **name, isc_uint32_t *ttl,
                   dns_rdata_t **rdata)
{
        REQUIRE(j->it.result == ISC_R_SUCCESS);
        *name = &j->it.name;
        *ttl = j->it.ttl;
        *rdata = &j->it.rdata;
}

/**************************************************************************/
/*
 * Generating diffs from databases
 */

/*
 * Construct a diff containing all the RRs at the current name of the
 * database iterator 'dbit' in database 'db', version 'ver'.
 * Set '*name' to the current name, and append the diff to 'diff'.
 * All new tuples will have the operation 'op'.
 *
 * Requires: 'name' must have buffer large enough to hold the name.
 * Typically, a dns_fixedname_t would be used.
 */
static isc_result_t
get_name_diff(dns_db_t *db, dns_dbversion_t *ver, isc_stdtime_t now,
              dns_dbiterator_t *dbit, dns_name_t *name, dns_diffop_t op,
              dns_diff_t *diff)
{
        isc_result_t result;
        dns_dbnode_t *node = NULL;
        dns_rdatasetiter_t *rdsiter = NULL;
        dns_difftuple_t *tuple = NULL;

        result = dns_dbiterator_current(dbit, &node, name);
        if (result != ISC_R_SUCCESS)
                return (result);

        result = dns_db_allrdatasets(db, node, ver, now, &rdsiter);
        if (result != ISC_R_SUCCESS)
                goto cleanup_node;

        for (result = dns_rdatasetiter_first(rdsiter);
             result == ISC_R_SUCCESS;
             result = dns_rdatasetiter_next(rdsiter))
        {
                dns_rdataset_t rdataset;

                dns_rdataset_init(&rdataset);
                dns_rdatasetiter_current(rdsiter, &rdataset);

                for (result = dns_rdataset_first(&rdataset);
                     result == ISC_R_SUCCESS;
                     result = dns_rdataset_next(&rdataset))
                {
                        dns_rdata_t rdata = DNS_RDATA_INIT;
                        dns_rdataset_current(&rdataset, &rdata);
                        result = dns_difftuple_create(diff->mctx, op, name,
                                                      rdataset.ttl, &rdata,
                                                      &tuple);
                        if (result != ISC_R_SUCCESS) {
                                dns_rdataset_disassociate(&rdataset);
                                goto cleanup_iterator;
                        }
                        dns_diff_append(diff, &tuple);
                }
                dns_rdataset_disassociate(&rdataset);
                if (result != ISC_R_NOMORE)
                        goto cleanup_iterator;
        }
        if (result != ISC_R_NOMORE)
                goto cleanup_iterator;

        result = ISC_R_SUCCESS;

 cleanup_iterator:
        dns_rdatasetiter_destroy(&rdsiter);

 cleanup_node:
        dns_db_detachnode(db, &node);

        return (result);
}

/*
 * Comparison function for use by dns_diff_subtract when sorting
 * the diffs to be subtracted.  The sort keys are the rdata type
 * and the rdata itself.  The owner name is ignored, because
 * it is known to be the same for all tuples.
 */
static int
rdata_order(const void *av, const void *bv) {
        dns_difftuple_t const * const *ap = av;
        dns_difftuple_t const * const *bp = bv;
        dns_difftuple_t const *a = *ap;
        dns_difftuple_t const *b = *bp;
        int r;
        r = (b->rdata.type - a->rdata.type);
        if (r != 0)
                return (r);
        r = dns_rdata_compare(&a->rdata, &b->rdata);
        return (r);
}

static isc_result_t
dns_diff_subtract(dns_diff_t diff[2], dns_diff_t *r) {
        isc_result_t result;
        dns_difftuple_t *p[2];
        int i, t;
        CHECK(dns_diff_sort(&diff[0], rdata_order));
        CHECK(dns_diff_sort(&diff[1], rdata_order));

        for (;;) {
                p[0] = ISC_LIST_HEAD(diff[0].tuples);
                p[1] = ISC_LIST_HEAD(diff[1].tuples);
                if (p[0] == NULL && p[1] == NULL)
                        break;

                for (i = 0; i < 2; i++)
                        if (p[!i] == NULL) {
                                ISC_LIST_UNLINK(diff[i].tuples, p[i], link);
                                ISC_LIST_APPEND(r->tuples, p[i], link);
                                goto next;
                        }
                t = rdata_order(&p[0], &p[1]);
                if (t < 0) {
                        ISC_LIST_UNLINK(diff[0].tuples, p[0], link);
                        ISC_LIST_APPEND(r->tuples, p[0], link);
                        goto next;
                }
                if (t > 0) {
                        ISC_LIST_UNLINK(diff[1].tuples, p[1], link);
                        ISC_LIST_APPEND(r->tuples, p[1], link);
                        goto next;
                }
                INSIST(t == 0);
                /*
                 * Identical RRs in both databases; skip them both.
                 */
                for (i = 0; i < 2; i++) {
                        ISC_LIST_UNLINK(diff[i].tuples, p[i], link);
                        dns_difftuple_free(&p[i]);
                }
        next: ;
        }
        result = ISC_R_SUCCESS;
 failure:
        return (result);
}

/*
 * Compare the databases 'dba' and 'dbb' and generate a journal
 * entry containing the changes to make 'dba' from 'dbb' (note
 * the order).  This journal entry will consist of a single,
 * possibly very large transaction.
 */

isc_result_t
dns_db_diff(isc_mem_t *mctx,
            dns_db_t *dba, dns_dbversion_t *dbvera,
            dns_db_t *dbb, dns_dbversion_t *dbverb,
            const char *journal_filename)
{
        dns_db_t *db[2];
        dns_dbversion_t *ver[2];
        dns_dbiterator_t *dbit[2] = { NULL, NULL };
        isc_boolean_t have[2] = { ISC_FALSE, ISC_FALSE };
        dns_fixedname_t fixname[2];
        isc_result_t result, itresult[2];
        dns_diff_t diff[2], resultdiff;
        int i, t;
        dns_journal_t *journal = NULL;

        db[0] = dba, db[1] = dbb;
        ver[0] = dbvera, ver[1] = dbverb;

        dns_diff_init(mctx, &diff[0]);
        dns_diff_init(mctx, &diff[1]);
        dns_diff_init(mctx, &resultdiff);

        dns_fixedname_init(&fixname[0]);
        dns_fixedname_init(&fixname[1]);

        CHECK(dns_journal_open(mctx, journal_filename, ISC_TRUE, &journal));

        CHECK(dns_db_createiterator(db[0], ISC_FALSE, &dbit[0]));
        CHECK(dns_db_createiterator(db[1], ISC_FALSE, &dbit[1]));

        itresult[0] = dns_dbiterator_first(dbit[0]);
        itresult[1] = dns_dbiterator_first(dbit[1]);

        for (;;) {
                for (i = 0; i < 2; i++) {
                        if (! have[i] && itresult[i] == ISC_R_SUCCESS) {
                                CHECK(get_name_diff(db[i], ver[i], 0, dbit[i],
                                            dns_fixedname_name(&fixname[i]),
                                            i == 0 ?
                                            DNS_DIFFOP_ADD :
                                            DNS_DIFFOP_DEL,
                                            &diff[i]));
                                itresult[i] = dns_dbiterator_next(dbit[i]);
                                have[i] = ISC_TRUE;
                        }
                }

                if (! have[0] && ! have[1]) {
                        INSIST(ISC_LIST_EMPTY(diff[0].tuples));
                        INSIST(ISC_LIST_EMPTY(diff[1].tuples));
                        break;
                }

                for (i = 0; i < 2; i++) {
                        if (! have[!i]) {
                                ISC_LIST_APPENDLIST(resultdiff.tuples,
                                                    diff[i].tuples, link);
                                INSIST(ISC_LIST_EMPTY(diff[i].tuples));
                                have[i] = ISC_FALSE;
                                goto next;
                        }
                }

                t = dns_name_compare(dns_fixedname_name(&fixname[0]),
                                     dns_fixedname_name(&fixname[1]));
                if (t < 0) {
                        ISC_LIST_APPENDLIST(resultdiff.tuples,
                                            diff[0].tuples, link);
                        INSIST(ISC_LIST_EMPTY(diff[0].tuples));
                        have[0] = ISC_FALSE;
                        continue;
                }
                if (t > 0) {
                        ISC_LIST_APPENDLIST(resultdiff.tuples,
                                            diff[1].tuples, link);
                        INSIST(ISC_LIST_EMPTY(diff[1].tuples));
                        have[1] = ISC_FALSE;
                        continue;
                }
                INSIST(t == 0);
                CHECK(dns_diff_subtract(diff, &resultdiff));
                INSIST(ISC_LIST_EMPTY(diff[0].tuples));
                INSIST(ISC_LIST_EMPTY(diff[1].tuples));
                have[0] = have[1] = ISC_FALSE;
        next: ;
        }
        if (itresult[0] != ISC_R_NOMORE)
                FAIL(itresult[0]);
        if (itresult[1] != ISC_R_NOMORE)
                FAIL(itresult[1]);

        if (ISC_LIST_EMPTY(resultdiff.tuples)) {
                isc_log_write(JOURNAL_DEBUG_LOGARGS(3), "no changes");
        } else {
                CHECK(dns_journal_write_transaction(journal, &resultdiff));
        }
        INSIST(ISC_LIST_EMPTY(diff[0].tuples));
        INSIST(ISC_LIST_EMPTY(diff[1].tuples));
        dns_diff_clear(&resultdiff);

 failure:
        dns_dbiterator_destroy(&dbit[0]);
        dns_dbiterator_destroy(&dbit[1]);
        dns_journal_destroy(&journal);
        return (result);
}