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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;
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;
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) {
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);
}
else if (comp == NULL) {
return false;
}
while (pos < end && remain > 0) {
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;
}
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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