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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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