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Diffstat (limited to '')
| -rw-r--r-- | contrib/librdns/compression.c | 168 |
1 files changed, 168 insertions, 0 deletions
diff --git a/contrib/librdns/compression.c b/contrib/librdns/compression.c new file mode 100644 index 0000000..895178e --- /dev/null +++ b/contrib/librdns/compression.c @@ -0,0 +1,168 @@ +/* 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; +} |