lib/dns/compress.c

	compress.c revision 499b34cea04a46823d003d4c0520c8b03e8513cb
/*
 * 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 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 1.43 2001/01/09 21:50:42 bwelling Exp $ */

#define DNS_NAME_USEINLINE 1

#include <config.h>

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

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

#define CCTX_MAGIC  0x43435458U /* CCTX */
#define VALID_CCTX(x)   ISC_MAGIC_VALID(x, CCTX_MAGIC)

#define DCTX_MAGIC  0x44435458U /* DCTX */
#define VALID_DCTX(x)   ISC_MAGIC_VALID(x, DCTX_MAGIC)

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

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

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

    cctx->allowed = 0;
    cctx->edns = edns;
    for (i = 0; i < DNS_COMPRESS_TABLESIZE; i++)
        cctx->table[i] = NULL;
    cctx->mctx = mctx;
    cctx->count = 0;
    cctx->magic = CCTX_MAGIC;
    return (ISC_R_SUCCESS);
}

void
dns_compress_invalidate(dns_compress_t *cctx) {
    dns_compressnode_t *node;
    unsigned int i;

    REQUIRE(VALID_CCTX(cctx));

    cctx->magic = 0;
    if (cctx->table != NULL) {
        for (i = 0; i < DNS_COMPRESS_TABLESIZE; i++) {
            while (cctx->table[i] != NULL) {
                node = cctx->table[i];
                cctx->table[i] = cctx->table[i]->next;
                if (node->count < DNS_COMPRESS_INITIALNODES)
                    continue;
                isc_mem_put(cctx->mctx, node, sizeof(*node));
            }
        }
    }
    cctx->allowed = 0;
    cctx->edns = -1;
}

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

    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);
}

/*
 * Find the longest match of name in the table.
 * If match is found return ISC_TRUE. prefix, suffix and offset are updated.
 * If no match is found return ISC_FALSE.
 */
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)
{
    dns_name_t tname, nname;
    dns_compressnode_t *node = NULL;
    unsigned int labels, hash, n;

    REQUIRE(VALID_CCTX(cctx));
    REQUIRE(dns_name_isabsolute(name) == ISC_TRUE);
    REQUIRE(offset != NULL);

    labels = dns_name_countlabels(name);
    INSIST(labels > 0);

    dns_name_init(&tname, NULL);
    dns_name_init(&nname, NULL);

    for (n = 0; n < labels - 1; n++) {
        dns_name_getlabelsequence(name, n, labels - n, &tname);
        hash = dns_name_hash(&tname, ISC_FALSE) %
               DNS_COMPRESS_TABLESIZE;
        for (node = cctx->table[hash]; node != NULL; node = node->next)
        {
            dns_name_fromregion(&nname, &node->r);
            if (dns_name_equal(&nname, &tname))
                break;
        }
        if (node != NULL)
            break;
    }

    /*
     * If node == NULL, we found no match at all.
     */
    if (node == NULL)
        return (ISC_FALSE);

    dns_name_clone(&tname, suffix);
    dns_name_getlabelsequence(name, 0, n, prefix);
    *offset = node->offset;
    return (ISC_TRUE);
}

void
dns_compress_add(dns_compress_t *cctx, dns_name_t *name, dns_name_t *prefix,
         isc_uint16_t offset)
{
    dns_name_t tname, nname;
    dns_label_t label;
    unsigned int start;
    unsigned int n;
    unsigned int count;
    unsigned int hash;
    dns_compressnode_t *node;

    REQUIRE(VALID_CCTX(cctx));
    REQUIRE(dns_name_isabsolute(name));

    dns_name_init(&tname, NULL);
    dns_name_init(&nname, NULL);

    n = dns_name_countlabels(name);
    count = dns_name_countlabels(prefix);
    if (dns_name_isabsolute(prefix))
        count--;
    start = 0;
    while (count > 0) {
        if (offset >= 0x4000)
            break;
        dns_name_getlabelsequence(name, start, n, &tname);
        hash = dns_name_hash(&tname, ISC_FALSE) %
               DNS_COMPRESS_TABLESIZE;
        /*
         * Look for the name in the hash bucket.  If it's there,
         * we're done.
         */
        for (node = cctx->table[hash]; node != NULL; node = node->next)
        {
            dns_name_fromregion(&nname, &node->r);
            if (dns_name_equal(&nname, &tname))
                return;
        }
        /*
         * It's not there.  Create a new node and add it.
         */
        if (cctx->count < DNS_COMPRESS_INITIALNODES)
            node = &cctx->initialnodes[cctx->count];
        else {
            node = isc_mem_get(cctx->mctx,
                       sizeof(dns_compressnode_t));
            if (node == NULL)
                return;
        }
        node->count = cctx->count++;
        node->offset = offset;
        dns_name_toregion(&tname, &node->r);
        node->next = cctx->table[hash];
        cctx->table[hash] = node;
        dns_name_getlabel(&tname, 0, &label);
        offset += label.length;
        start++;
        n--;
        count--;
    }
}

void
dns_compress_rollback(dns_compress_t *cctx, isc_uint16_t offset) {
    unsigned int i;
    dns_compressnode_t *node;

    REQUIRE(VALID_CCTX(cctx));

    for (i = 0; i < DNS_COMPRESS_TABLESIZE; i++) {
        node = cctx->table[i];
        /*
         * This relies on nodes with greater offsets being
         * closer to the beginning of the list, and the
         * items with the greatest offsets being at the end
         * of the initialnodes[] array.
         */
        while (node != NULL && node->offset >= offset) {
            cctx->table[i] = node->next;
            if (node->count >= DNS_COMPRESS_INITIALNODES)
                isc_mem_put(cctx->mctx, node, sizeof(*node));
            cctx->count--;
            node = cctx->table[i];
        }
    }
}

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

void
dns_decompress_init(dns_decompress_t *dctx, int edns,
            dns_decompresstype_t type) {

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

    dctx->allowed = DNS_COMPRESS_NONE;
    dctx->edns = edns;
    dctx->type = type;
    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));

    switch (dctx->type) {
    case DNS_DECOMPRESS_ANY:
        dctx->allowed = DNS_COMPRESS_ALL;
        break;
    case DNS_DECOMPRESS_NONE:
        dctx->allowed = DNS_COMPRESS_NONE;
        break;
    case DNS_DECOMPRESS_STRICT:
        dctx->allowed = allowed;
        break;
    }
}

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);
}

dns_decompresstype_t
dns_decompress_type(dns_decompress_t *dctx) {

    REQUIRE(VALID_DCTX(dctx));

    return (dctx->type);
}