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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"
- #include "contrib/mumhash/mum.h"
-
- #define rdns_compression_hash(n) (mum_hash(n.suffix, n.suffix_len, 0xdeadbeef))
- #define rdns_compression_equal(n1, n2) ((n1).suffix_len == (n2).suffix_len && \
- (memcmp((n1).suffix, (n2).suffix, (n1).suffix_len) == 0))
- __KHASH_IMPL(rdns_compression_hash, kh_inline, struct rdns_compression_name, char, 0, rdns_compression_hash,
- rdns_compression_equal);
-
- static struct rdns_compression_name *
- rdns_can_compress (const char *pos, unsigned int len, khash_t(rdns_compression_hash) *comp)
- {
- struct rdns_compression_name check;
- khiter_t k;
-
- if (comp == NULL) {
- return NULL;
- }
-
- check.suffix_len = len;
- check.suffix = pos;
- k = kh_get(rdns_compression_hash, comp, check);
-
- if (k != kh_end(comp)) {
- return &kh_key(comp, k);
- }
-
- return NULL;
- }
-
- 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,
- khash_t(rdns_compression_hash) *comp,
- int offset)
- {
- struct rdns_compression_name new_name;
- int r;
-
- if (comp != NULL) {
-
- assert (offset >= 0);
- new_name.suffix_len = end - pos;
- new_name.suffix = pos;
- new_name.offset = offset;
-
- kh_put(rdns_compression_hash, comp, new_name, &r);
- }
- }
-
- void
- rdns_compression_free (khash_t(rdns_compression_hash) *comp)
- {
- if (comp != NULL) {
- kh_destroy(rdns_compression_hash, comp);
- }
- }
-
- bool
- rdns_write_name_compressed (struct rdns_request *req,
- const char *name, unsigned int namelen,
- khash_t(rdns_compression_hash) **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_resolver *resolver = req->resolver;
- uint16_t pointer;
-
- if (comp != NULL && *comp == NULL) {
- *comp = kh_init(rdns_compression_hash);
- }
-
- while (pos < end && remain > 0) {
- if (comp) {
- struct rdns_compression_name *test = rdns_can_compress(pos, end - pos, *comp);
- if (test != NULL) {
- /* Can compress name */
- 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) {
- 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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