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155 lines
4.0 KiB
C
155 lines
4.0 KiB
C
/* Copyright (c) 2014, Vsevolod Stakhov
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions are met:
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* * Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* * Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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*
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* THIS SOFTWARE IS PROVIDED ''AS IS'' AND ANY
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* EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
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* WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
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* DISCLAIMED. IN NO EVENT SHALL AUTHOR BE LIABLE FOR ANY
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* DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
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* (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
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* LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
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* ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
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* SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*/
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#include "compression.h"
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#include "logger.h"
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static struct rdns_compression_entry *
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rdns_can_compress (const char *pos, struct rdns_compression_entry *comp)
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{
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struct rdns_compression_entry *res;
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HASH_FIND_STR (comp, pos, res);
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return res;
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}
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static unsigned int
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rdns_calculate_label_len (const char *pos, const char *end)
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{
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const char *p = pos;
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unsigned int res = 0;
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while (p != end) {
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if (*p == '.') {
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break;
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}
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res ++;
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p ++;
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}
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return res;
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}
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static void
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rdns_add_compressed (const char *pos, const char *end,
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struct rdns_compression_entry **comp, int offset)
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{
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struct rdns_compression_entry *new;
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assert (offset >= 0);
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new = malloc (sizeof (*new));
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if (new != NULL) {
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new->label = pos;
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new->offset = offset;
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HASH_ADD_KEYPTR (hh, *comp, pos, (end - pos), new);
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}
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}
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void
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rnds_compression_free (struct rdns_compression_entry *comp)
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{
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struct rdns_compression_entry *cur, *tmp;
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if (comp) {
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free (comp->hh.tbl->buckets);
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free (comp->hh.tbl);
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HASH_ITER (hh, comp, cur, tmp) {
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free (cur);
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}
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}
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}
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bool
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rdns_write_name_compressed (struct rdns_request *req,
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const char *name, unsigned int namelen,
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struct rdns_compression_entry **comp)
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{
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uint8_t *target = req->packet + req->pos;
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const char *pos = name, *end = name + namelen;
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unsigned int remain = req->packet_len - req->pos - 5, label_len;
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struct rdns_compression_entry *head = NULL, *test;
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struct rdns_resolver *resolver = req->resolver;
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uint16_t pointer;
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if (comp != NULL) {
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head = *comp;
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}
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while (pos < end && remain > 0) {
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if (head != NULL) {
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test = rdns_can_compress (pos, head);
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if (test != NULL) {
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if (remain < 2) {
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rdns_info ("no buffer remain for constructing query");
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return false;
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}
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pointer = htons ((uint16_t)test->offset) | DNS_COMPRESSION_BITS;
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memcpy (target, &pointer, sizeof (pointer));
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req->pos += 2;
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return true;
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}
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}
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label_len = rdns_calculate_label_len (pos, end);
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if (label_len == 0) {
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/* We have empty label it is allowed only if pos == end - 1 */
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if (pos == end - 1) {
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break;
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}
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else {
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rdns_err ("double dots in the name requested");
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return false;
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}
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}
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else if (label_len > DNS_D_MAXLABEL) {
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rdns_err ("too large label: %d", (int)label_len);
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return false;
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}
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if (label_len + 1 > remain) {
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rdns_info ("no buffer remain for constructing query, strip %d to %d",
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(int)label_len, (int)remain);
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label_len = remain - 1;
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}
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if (comp != NULL) {
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rdns_add_compressed (pos, end, comp, target - req->packet);
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}
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/* Write label as is */
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*target++ = (uint8_t)label_len;
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memcpy (target, pos, label_len);
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target += label_len;
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pos += label_len + 1;
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}
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/* Termination label */
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*target++ = '\0';
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req->pos = target - req->packet;
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return true;
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}
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