lib/dns/compress.c

	compress.c revision 0c27b3fe77ac1d5094ba3521e8142d9e7973133f
/*
 * Copyright (C) 1999-2001, 2004-2007, 2015, 2016  Internet Systems Consortium, Inc. ("ISC")
 *
 * This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/.
 */

/*! \file */

#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  ISC_MAGIC('C', 'C', 'T', 'X')
#define VALID_CCTX(x)   ISC_MAGIC_VALID(x, CCTX_MAGIC)

#define DCTX_MAGIC  ISC_MAGIC('D', 'C', 'T', 'X')
#define VALID_DCTX(x)   ISC_MAGIC_VALID(x, DCTX_MAGIC)

#define TABLE_READY                         \
    do {                                \
        unsigned int i;                     \
                                    \
        if ((cctx->allowed & DNS_COMPRESS_READY) == 0) {    \
            cctx->allowed |= DNS_COMPRESS_READY;        \
            for (i = 0; i < DNS_COMPRESS_TABLESIZE; i++)    \
                cctx->table[i] = NULL;          \
        }                           \
    } while (0)

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

isc_result_t
dns_compress_init(dns_compress_t *cctx, int edns, isc_mem_t *mctx) {
    REQUIRE(cctx != NULL);
    REQUIRE(mctx != NULL);  /* See: rdataset.c:towiresorted(). */

    cctx->edns = edns;
    cctx->mctx = mctx;
    cctx->count = 0;
    cctx->allowed = DNS_COMPRESS_ENABLED;
    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));

    if ((cctx->allowed & DNS_COMPRESS_READY) != 0) {
        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->offset & 0x8000) != 0)
                    isc_mem_put(cctx->mctx, node->r.base,
                            node->r.length);
                if (node->count < DNS_COMPRESS_INITIALNODES)
                    continue;
                isc_mem_put(cctx->mctx, node, sizeof(*node));
            }
        }
    }
    cctx->magic = 0;
    cctx->allowed = 0;
    cctx->edns = -1;
}

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

    cctx->allowed &= ~DNS_COMPRESS_ALL;
    cctx->allowed |= (allowed & DNS_COMPRESS_ALL);
}

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

void
dns_compress_disable(dns_compress_t *cctx) {
    REQUIRE(VALID_CCTX(cctx));
    cctx->allowed &= ~DNS_COMPRESS_ENABLED;
}

void
dns_compress_setsensitive(dns_compress_t *cctx, isc_boolean_t sensitive) {
    REQUIRE(VALID_CCTX(cctx));

    if (sensitive)
        cctx->allowed |= DNS_COMPRESS_CASESENSITIVE;
    else
        cctx->allowed &= ~DNS_COMPRESS_CASESENSITIVE;
}

isc_boolean_t
dns_compress_getsensitive(dns_compress_t *cctx) {
    REQUIRE(VALID_CCTX(cctx));

    return (ISC_TF((cctx->allowed & DNS_COMPRESS_CASESENSITIVE) != 0));
}

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

#define NODENAME(node, name) \
do { \
    (name)->length = (node)->r.length; \
    (name)->labels = (node)->labels; \
    (name)->ndata = (node)->r.base; \
    (name)->attributes = DNS_NAMEATTR_ABSOLUTE; \
} while (0)

/*
 * 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, const dns_name_t *name,
            dns_name_t *prefix, 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);

    if ((cctx->allowed & DNS_COMPRESS_ENABLED) == 0)
        return (ISC_FALSE);

    TABLE_READY;

    if (cctx->count == 0)
        return (ISC_FALSE);

    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)
        {
            NODENAME(node, &nname);
            if ((cctx->allowed & DNS_COMPRESS_CASESENSITIVE) != 0) {
                if (dns_name_caseequal(&nname, &tname))
                    break;
            } else {
                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);

    if (n == 0)
        dns_name_reset(prefix);
    else
        dns_name_getlabelsequence(name, 0, n, prefix);

    *offset = (node->offset & 0x7fff);
    return (ISC_TRUE);
}

static inline unsigned int
name_length(const dns_name_t *name) {
    isc_region_t r;
    dns_name_toregion(name, &r);
    return (r.length);
}

void
dns_compress_add(dns_compress_t *cctx, const dns_name_t *name,
         const dns_name_t *prefix, isc_uint16_t offset)
{
    dns_name_t tname, xname;
    unsigned int start;
    unsigned int n;
    unsigned int count;
    unsigned int hash;
    dns_compressnode_t *node;
    unsigned int length;
    unsigned int tlength;
    isc_uint16_t toffset;
    unsigned char *tmp;
    isc_region_t r;

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

    if ((cctx->allowed & DNS_COMPRESS_ENABLED) == 0)
        return;

    TABLE_READY;

    if (offset >= 0x4000)
        return;
    dns_name_init(&tname, NULL);
    dns_name_init(&xname, NULL);

    n = dns_name_countlabels(name);
    count = dns_name_countlabels(prefix);
    if (dns_name_isabsolute(prefix))
        count--;
    if (count == 0)
        return;
    start = 0;
    dns_name_toregion(name, &r);
    length = r.length;
    tmp = isc_mem_get(cctx->mctx, length);
    if (tmp == NULL)
        return;
    /*
     * Copy name data to 'tmp' and make 'r' use 'tmp'.
     */
    memmove(tmp, r.base, r.length);
    r.base = tmp;
    dns_name_fromregion(&xname, &r);

    while (count > 0) {
        dns_name_getlabelsequence(&xname, start, n, &tname);
        hash = dns_name_hash(&tname, ISC_FALSE) %
               DNS_COMPRESS_TABLESIZE;
        tlength = name_length(&tname);
        toffset = (isc_uint16_t)(offset + (length - tlength));
        if (toffset >= 0x4000)
            break;
        /*
         * 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)
                break;
        }
        node->count = cctx->count++;
        /*
         * 'node->r.base' becomes 'tmp' when start == 0.
         * Record this by setting 0x8000 so it can be freed later.
         */
        if (start == 0)
            toffset |= 0x8000;
        node->offset = toffset;
        dns_name_toregion(&tname, &node->r);
        node->labels = (isc_uint8_t)dns_name_countlabels(&tname);
        node->next = cctx->table[hash];
        cctx->table[hash] = node;
        start++;
        n--;
        count--;
    }

    if (start == 0)
        isc_mem_put(cctx->mctx, tmp, length);
}

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

    REQUIRE(VALID_CCTX(cctx));

    if ((cctx->allowed & DNS_COMPRESS_ENABLED) == 0)
        return;

    if ((cctx->allowed & DNS_COMPRESS_READY) == 0)
        return;

    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 & 0x7fff) >= offset) {
            cctx->table[i] = node->next;
            if ((node->offset & 0x8000) != 0)
                isc_mem_put(cctx->mctx, node->r.base,
                        node->r.length);
            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);
}