lib/dns/compress.c

	compress.c revision 89b117b7560a7efae552539bf4a56e4b62fbac38
/*
 * Copyright (C) 1999, 2000  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 INTERNET SOFTWARE CONSORTIUM DISCLAIMS
 * ALL WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL INTERNET SOFTWARE
 * CONSORTIUM 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: compress.c,v 1.28 2000/04/27 21:46:31 halley Exp $ */

#define DNS_NAME_USEINLINE 1

#include <config.h>
#include <string.h>

#include <isc/types.h>
#include <isc/assertions.h>
#include <isc/buffer.h>

#include <dns/compress.h>
#include <dns/fixedname.h>
#include <dns/rbt.h>

#define CCTX_MAGIC  0x43435458U /* CCTX */
#define VALID_CCTX(x)   ((x) != NULL && (x)->magic == CCTX_MAGIC)

#define DCTX_MAGIC  0x44435458U /* DCTX */
#define VALID_DCTX(x)   ((x) != NULL && (x)->magic == DCTX_MAGIC)

static void
free_offset(void *offset, void *mctx);

static isc_boolean_t
compress_find(dns_rbt_t *root, dns_name_t *name, dns_name_t *prefix,
          dns_name_t *suffix, isc_uint16_t *offset,
          isc_buffer_t *workspace);

static void
compress_add(dns_rbt_t *root, dns_name_t *prefix, dns_name_t *suffix,
         isc_uint16_t offset, isc_boolean_t global16, isc_mem_t *mctx);

/***
 ***    Compression
 ***/

isc_result_t
dns_compress_init(dns_compress_t *cctx, int edns, isc_mem_t *mctx) {
    isc_result_t result;

    REQUIRE(cctx != NULL);
    REQUIRE(mctx != NULL);

    cctx->allowed = 0;
    cctx->rdata = 0;
    cctx->global16 = (edns >= 1) ? ISC_TRUE : ISC_FALSE;
    cctx->edns = edns;
    cctx->global = NULL;
    result = dns_rbt_create(mctx, free_offset, mctx, &cctx->global);
    if (result != ISC_R_SUCCESS)
        return (result);
    cctx->mctx = mctx;
    cctx->magic = CCTX_MAGIC;
    return (ISC_R_SUCCESS);
}

void
dns_compress_invalidate(dns_compress_t *cctx) {

    REQUIRE(VALID_CCTX(cctx));

    cctx->magic = 0;
    if (cctx->global != NULL)
        dns_rbt_destroy(&cctx->global);
    cctx->allowed = 0;
    cctx->rdata = 0;
    cctx->global16 = ISC_FALSE;
    cctx->edns = -1;
}

void
dns_compress_setmethods(dns_compress_t *cctx, unsigned int allowed) {
    REQUIRE(VALID_CCTX(cctx));

    if (cctx->edns >= 1 && (allowed & DNS_COMPRESS_GLOBAL14) != 0)
        allowed |= DNS_COMPRESS_GLOBAL16;
    cctx->allowed = allowed;
}

unsigned int
dns_compress_getmethods(dns_compress_t *cctx) {
    REQUIRE(VALID_CCTX(cctx));
    return (cctx->allowed);
}

int
dns_compress_getedns(dns_compress_t *cctx) {
    REQUIRE(VALID_CCTX(cctx));
    return (cctx->edns);
}

isc_boolean_t
dns_compress_findglobal(dns_compress_t *cctx, dns_name_t *name,
            dns_name_t *prefix, dns_name_t *suffix,
            isc_uint16_t *offset, isc_buffer_t *workspace)
{
    REQUIRE(VALID_CCTX(cctx));
    REQUIRE(dns_name_isabsolute(name) == ISC_TRUE);
    REQUIRE(offset != NULL);

    return (compress_find(cctx->global, name, prefix, suffix, offset,
                  workspace));
}

void
dns_compress_add(dns_compress_t *cctx, dns_name_t *prefix,
         dns_name_t *suffix, isc_uint16_t offset)
{
    REQUIRE(VALID_CCTX(cctx));

    compress_add(cctx->global, prefix, suffix, offset,
             cctx->global16, cctx->mctx);
}

void
dns_compress_rollback(dns_compress_t *cctx, isc_uint16_t offset) {
    dns_rbtnode_t *node;
    dns_fixedname_t foundfixed;
    dns_fixedname_t fullfixed;
    dns_fixedname_t originfixed;
    dns_name_t *foundname;
    dns_name_t *fullname;
    dns_name_t *origin;
    dns_rbtnodechain_t chain;
    isc_result_t result;

    REQUIRE(VALID_CCTX(cctx));

    /*
     * Initalise things.
     */
    dns_fixedname_init(&foundfixed);
    foundname = dns_fixedname_name(&foundfixed);
    dns_fixedname_init(&fullfixed);
    fullname = dns_fixedname_name(&fullfixed);
    dns_fixedname_init(&originfixed);
    origin = dns_fixedname_name(&originfixed);
    dns_rbtnodechain_init(&chain, cctx->mctx);

 again:
    result = dns_rbtnodechain_first(&chain, cctx->global, foundname,
                    origin);

    while (result == DNS_R_NEWORIGIN || result == ISC_R_SUCCESS) {
        result = dns_rbtnodechain_current(&chain, foundname,
                          origin, &node);

        if (result != ISC_R_SUCCESS)
            break;

        if (node->data != NULL &&
            (*(isc_uint16_t*)node->data >= offset)) {
            result = dns_name_concatenate(foundname,
                    dns_name_isabsolute(foundname) ?
                              NULL : origin,
                              fullname, NULL);

            if (result != ISC_R_SUCCESS)
                break;

            result = dns_rbt_deletename(cctx->global, fullname,
                            ISC_FALSE);
            if (result != ISC_R_SUCCESS)
                break;
            /*
             * If the delete is successful the chain is broken.
             */
            dns_rbtnodechain_reset(&chain);
            goto again;
        }

        result = dns_rbtnodechain_next(&chain, foundname, origin);
    }
    dns_rbtnodechain_invalidate(&chain);
}

/***
 ***    Decompression
 ***/

void
dns_decompress_init(dns_decompress_t *dctx, int edns, isc_boolean_t strict) {

    REQUIRE(dctx != NULL);
    REQUIRE(edns >= -1 && edns <= 255);

    dctx->allowed = DNS_COMPRESS_NONE;
    dctx->edns = edns;
    dctx->strict = strict;
    dctx->rdata = 0;
    dctx->magic = DCTX_MAGIC;
}

void
dns_decompress_invalidate(dns_decompress_t *dctx) {

    REQUIRE(VALID_DCTX(dctx));

    dctx->magic = 0;
}

void
dns_decompress_setmethods(dns_decompress_t *dctx, unsigned int allowed) {

    REQUIRE(VALID_DCTX(dctx));

    dctx->allowed = allowed;
}

unsigned int
dns_decompress_getmethods(dns_decompress_t *dctx) {

    REQUIRE(VALID_DCTX(dctx));

    return (dctx->allowed);
}

int
dns_decompress_edns(dns_decompress_t *dctx) {

    REQUIRE(VALID_DCTX(dctx));

    return (dctx->edns);
}

isc_boolean_t
dns_decompress_strict(dns_decompress_t *dctx) {

    REQUIRE(VALID_DCTX(dctx));

    return (dctx->strict);
}

/***
 ***    Private
 ***/

static void
free_offset(void *offset, void *mctx) {
    REQUIRE(offset != NULL);
    REQUIRE(mctx != NULL);
    isc_mem_put(mctx, offset, sizeof(isc_uint16_t));
}

/*
 *  Add the labels in prefix to RBT.
 */
static void
compress_add(dns_rbt_t *root, dns_name_t *prefix, dns_name_t *suffix,
         isc_uint16_t offset, isc_boolean_t global16, isc_mem_t *mctx)
{

    dns_name_t name;
    dns_name_t full;
    dns_label_t label;
    unsigned int count;
    unsigned int start;
    unsigned int n;
    isc_uint16_t *data;
    isc_result_t result;
    unsigned char buffer[255];
    isc_buffer_t target;
    dns_offsets_t offsets;

    count = dns_name_countlabels(prefix);
    if (dns_name_isabsolute(prefix))
        count--;
    start = 0;
    dns_name_init(&full, offsets);
    dns_name_init(&name, NULL);
    isc_buffer_init(&target, buffer, sizeof(buffer));
    result = dns_name_concatenate(prefix, suffix, &full, &target);
    if (result != ISC_R_SUCCESS)
        return;
    n = dns_name_countlabels(&full);
    while (count > 0) {
        if (offset >= 16384 && !global16)
            break;
        dns_name_getlabelsequence(&full, start, n, &name);
        data = isc_mem_get(mctx, sizeof *data);
        if (data == NULL)
            return;
        *data = offset;
        result = dns_rbt_addname(root, &name, data);
        if (result != ISC_R_SUCCESS) {
            isc_mem_put(mctx, data, sizeof *data);
            return;
        }
        dns_name_getlabel(&name, 0, &label);
        offset += label.length;
        start++;
        n--;
        count--;
    }
}

/*
 *  Find the longest match of name in root.
 *  If match is found return ISC_TRUE. prefix, suffix and offset
 *  are updated.
 *  If no match is found return ISC_FALSE.
 */

static isc_boolean_t
compress_find(dns_rbt_t *root, dns_name_t *name, dns_name_t *prefix,
          dns_name_t *suffix, isc_uint16_t *offset,
          isc_buffer_t *workspace)
{
    dns_fixedname_t found;
    dns_name_t *foundname;
    dns_name_t tmpprefix;
    dns_name_t tmpsuffix;
    isc_result_t result;
    isc_uint16_t *data = NULL;
    dns_label_t foundlabel;
    dns_label_t namelabel;
    unsigned int foundlabels;
    unsigned int namelabels;
    unsigned int foundbits;
    unsigned int namebits;
    unsigned int bits;
    unsigned int prefixlen;
    unsigned int j;
    unsigned char buf[2 + 256/8];   /* size of biggest bit label */
    dns_bitlabel_t bit;
    isc_region_t region;

    dns_fixedname_init(&found);
    foundname = dns_fixedname_name(&found);
    /*
     * Getting rid of the offsets table for foundname improves
     * perfomance, since the offsets table is not needed and maintaining
     * it has costs.
     */
    foundname->offsets = NULL;
    result = dns_rbt_findname(root, name, 0, foundname, (void *)&data);
    if (result != ISC_R_SUCCESS && result != DNS_R_PARTIALMATCH)
        return (ISC_FALSE);
    if (data == NULL)       /* root label */
        return (ISC_FALSE);
    /*
     * Do we have to do bit string processing?
     */
    dns_name_getlabel(foundname, 0, &foundlabel);
    foundlabels = dns_name_countlabels(foundname);
    INSIST(foundlabels > 1);    /* root labels are not added to tree */
    namelabels = dns_name_countlabels(name);
    if (dns_label_type(&foundlabel) == dns_labeltype_bitstring) {
        dns_name_getlabel(name, namelabels - foundlabels, &namelabel);
        INSIST(dns_label_type(&namelabel) == dns_labeltype_bitstring);
        foundbits = dns_label_countbits(&foundlabel);
        namebits = dns_label_countbits(&namelabel);
    } else
        namebits = foundbits = 0;

    if (namebits == foundbits) {
        INSIST(namelabels >= foundlabels);
        prefixlen = namelabels - foundlabels;
        if (prefixlen == 0) {
            prefix->length = 0;
            prefix->labels = 0;
        } else
            dns_name_getlabelsequence(name, 0, prefixlen, prefix);
        result = dns_name_concatenate(NULL, foundname, suffix,
                         workspace);
        if (result != ISC_R_SUCCESS)
            return (ISC_FALSE);
        *offset = *data;
        return (ISC_TRUE);
    }
    /*
     * At this stage we have a bit string label to split in two.
     * There is potentially a prefix before this label and definitly
     * a suffix after it (if only the root).
     */
    INSIST(result == DNS_R_PARTIALMATCH);
    result = dns_name_concatenate(NULL, foundname, suffix, workspace);
    if (result != ISC_R_SUCCESS)
        return (ISC_FALSE);
    prefixlen = namelabels - foundlabels;
    dns_name_init(&tmpprefix, NULL);
    dns_name_init(&tmpsuffix, NULL);
    if (prefixlen != 0) {
        dns_name_getlabelsequence(name, 0, prefixlen, &tmpprefix);
    }
    INSIST(namebits > foundbits);
    bits = namebits - foundbits;
    j = 0;
    memset(buf, 0, sizeof buf);
    INSIST((bits / 8 + 1) < sizeof buf);
    /*
     * Copy least significant bits.
     */
    while (j < bits) {
        bit = dns_label_getbit(&namelabel, foundbits + j);
        if (bit)
            buf[2 + j / 8] |= (1 << (7 - (j % 8)));
        j++;
    }
    buf[0] = DNS_LABELTYPE_BITSTRING;
    buf[1] = j;
    region.base = buf;
    region.length = 2 + (j + 7) / 8;
    dns_name_fromregion(&tmpsuffix, &region);
    result = dns_name_concatenate(&tmpprefix, &tmpsuffix, prefix,
                      workspace);
    if (result != ISC_R_SUCCESS)
        return (ISC_FALSE);
    *offset = *data;
    return (ISC_TRUE);
}