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