1 |
/* |
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vpn_dns.C -- handle the dns tunnel part of the protocol. |
3 |
Copyright (C) 2003-2005 Marc Lehmann <gvpe@schmorp.de> |
4 |
|
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This file is part of GVPE. |
6 |
|
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GVPE is free software; you can redistribute it and/or modify |
8 |
it under the terms of the GNU General Public License as published by |
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the Free Software Foundation; either version 2 of the License, or |
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(at your option) any later version. |
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|
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This program is distributed in the hope that it will be useful, |
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but WITHOUT ANY WARRANTY; without even the implied warranty of |
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
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GNU General Public License for more details. |
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|
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You should have received a copy of the GNU General Public License |
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along with gvpe; if not, write to the Free Software |
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Foundation, Inc. 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA |
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*/ |
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|
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#include "config.h" |
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|
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#if ENABLE_DNS |
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|
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// dns processing is EXTREMELY ugly. For obvious(?) reasons. |
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// it's a hack, use only in emergency situations please. |
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|
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#include <cstring> |
30 |
|
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#include <sys/types.h> |
32 |
#include <sys/socket.h> |
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#include <sys/wait.h> |
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#include <sys/uio.h> |
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#include <errno.h> |
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#include <time.h> |
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#include <unistd.h> |
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#include <fcntl.h> |
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|
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#include <map> |
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|
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#include <gmp.h> |
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|
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#include "netcompat.h" |
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|
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#include "vpn.h" |
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|
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#define MIN_POLL_INTERVAL .02 // how often to poll minimally when the server has data |
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#define MAX_POLL_INTERVAL 6. // how often to poll minimally when the server has no data |
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#define ACTIVITY_INTERVAL 5. |
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|
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#define INITIAL_TIMEOUT 1. // retry timeouts |
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#define INITIAL_SYN_TIMEOUT 2. // retry timeout for initial syn |
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|
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#define MIN_SEND_INTERVAL 0.01 // wait at least this time between sending requests |
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#define MAX_SEND_INTERVAL 0.5 // optimistic? |
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|
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#define MAX_OUTSTANDING 40 // max. outstanding requests |
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#define MAX_WINDOW 100 // max. for MAX_OUTSTANDING |
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#define MAX_BACKLOG (100*1024) // size of gvpe protocol backlog (bytes), must be > MAXSIZE |
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|
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#define MAX_DOMAIN_SIZE 220 // 255 is legal limit, but bind doesn't compress well |
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// 240 leaves about 4 bytes of server reply data |
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// every two request bytes less give room for one reply byte |
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|
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#define SEQNO_MASK 0xffff |
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#define SEQNO_EQ(a,b) ( 0 == ( ((a) ^ (b)) & SEQNO_MASK) ) |
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|
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#define MAX_LBL_SIZE 63 |
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#define MAX_PKT_SIZE 512 |
71 |
|
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#define RR_TYPE_A 1 |
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#define RR_TYPE_NULL 10 |
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#define RR_TYPE_TXT 16 |
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#define RR_TYPE_ANY 255 |
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|
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#define RR_CLASS_IN 1 |
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|
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#define CMD_IP_1 207 |
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#define CMD_IP_2 46 |
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#define CMD_IP_3 236 |
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#define CMD_IP_RST 29 |
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#define CMD_IP_SYN 113 |
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#define CMD_IP_REJ 32 |
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|
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// works for cmaps up to 255 (not 256!) |
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struct charmap |
88 |
{ |
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enum { INVALID = (u8)255 }; |
90 |
|
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char encode [256]; // index => char |
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u8 decode [256]; // char => index |
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unsigned int size; |
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|
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charmap (const char *cmap); |
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}; |
97 |
|
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charmap::charmap (const char *cmap) |
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{ |
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char *enc = encode; |
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u8 *dec = decode; |
102 |
|
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memset (enc, (char) 0, 256); |
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memset (dec, (char)INVALID, 256); |
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|
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for (size = 0; cmap [size]; size++) |
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{ |
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enc [size] = cmap [size]; |
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dec [(u8)enc [size]] = size; |
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} |
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|
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assert (size < 256); |
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} |
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|
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#define MAX_DEC_LEN 500 |
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#define MAX_ENC_LEN (MAX_DEC_LEN * 2) |
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#define MAX_LIMBS ((MAX_DEC_LEN * 8 + GMP_NUMB_BITS - 1) / GMP_NUMB_BITS) |
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|
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// ugly. minimum base is 16(!) |
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struct basecoder |
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{ |
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charmap cmap; |
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unsigned int enc_len [MAX_DEC_LEN]; |
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unsigned int dec_len [MAX_ENC_LEN]; |
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|
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unsigned int encode_len (unsigned int len); |
127 |
unsigned int decode_len (unsigned int len); |
128 |
|
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unsigned int encode (char *dst, u8 *src, unsigned int len); |
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unsigned int decode (u8 *dst, char *src, unsigned int len); |
131 |
|
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basecoder (const char *cmap); |
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}; |
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|
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basecoder::basecoder (const char *cmap) |
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: cmap (cmap) |
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{ |
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for (unsigned int len = 0; len < MAX_DEC_LEN; ++len) |
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{ |
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u8 src [MAX_DEC_LEN]; |
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u8 dst [MAX_ENC_LEN]; |
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|
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memset (src, 255, len); |
144 |
|
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mp_limb_t m [MAX_LIMBS]; |
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mp_size_t n; |
147 |
|
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n = mpn_set_str (m, src, len, 256); |
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n = mpn_get_str (dst, this->cmap.size, m, n); |
150 |
|
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for (int i = 0; !dst [i]; ++i) |
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n--; |
153 |
|
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enc_len [len] = n; |
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dec_len [n] = len; |
156 |
} |
157 |
} |
158 |
|
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unsigned int basecoder::encode_len (unsigned int len) |
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{ |
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return enc_len [len]; |
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} |
163 |
|
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unsigned int basecoder::decode_len (unsigned int len) |
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{ |
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while (len && !dec_len [len]) |
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--len; |
168 |
|
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return dec_len [len]; |
170 |
} |
171 |
|
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unsigned int basecoder::encode (char *dst, u8 *src, unsigned int len) |
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{ |
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if (!len || len > MAX_DEC_LEN) |
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return 0; |
176 |
|
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int elen = encode_len (len); |
178 |
|
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mp_limb_t m [MAX_LIMBS]; |
180 |
mp_size_t n; |
181 |
|
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u8 dst_ [MAX_ENC_LEN]; |
183 |
|
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n = mpn_set_str (m, src, len, 256); |
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n = mpn_get_str (dst_, cmap.size, m, n); |
186 |
|
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int plen = elen; // for padding |
188 |
|
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while (n < plen) |
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{ |
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*dst++ = cmap.encode [0]; |
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plen--; |
193 |
} |
194 |
|
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for (unsigned int i = n - plen; i < n; ++i) |
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*dst++ = cmap.encode [dst_ [i]]; |
197 |
|
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return elen; |
199 |
} |
200 |
|
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unsigned int basecoder::decode (u8 *dst, char *src, unsigned int len) |
202 |
{ |
203 |
if (!len || len > MAX_ENC_LEN) |
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return 0; |
205 |
|
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u8 src_ [MAX_ENC_LEN]; |
207 |
unsigned int elen = 0; |
208 |
|
209 |
while (len--) |
210 |
{ |
211 |
u8 val = cmap.decode [(u8)*src++]; |
212 |
|
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if (val != charmap::INVALID) |
214 |
src_ [elen++] = val; |
215 |
} |
216 |
|
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int dlen = decode_len (elen); |
218 |
|
219 |
mp_limb_t m [MAX_LIMBS]; |
220 |
mp_size_t n; |
221 |
|
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u8 dst_ [MAX_DEC_LEN]; |
223 |
|
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n = mpn_set_str (m, src_, elen, cmap.size); |
225 |
n = mpn_get_str (dst_, 256, m, n); |
226 |
|
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if (n < dlen) |
228 |
{ |
229 |
memset (dst, 0, dlen - n); |
230 |
memcpy (dst + dlen - n, dst_, n); |
231 |
} |
232 |
else |
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memcpy (dst, dst_ + n - dlen, dlen); |
234 |
|
235 |
return dlen; |
236 |
} |
237 |
|
238 |
#if 0 |
239 |
struct test { test (); } test; |
240 |
|
241 |
test::test () |
242 |
{ |
243 |
basecoder cdc ("0123456789abcdefghijklmnopqrstuvwxyz"); |
244 |
|
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u8 in[] = "0123456789abcdefghijklmnopqrstuvwxyz"; |
246 |
static char enc[200]; |
247 |
static u8 dec[200]; |
248 |
|
249 |
for (int i = 1; i < 20; i++) |
250 |
{ |
251 |
int elen = cdc.encode (enc, in, i); |
252 |
int dlen = cdc.decode (dec, enc, elen); |
253 |
|
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printf ("%d>%d>%d (%s>%s)\n", i, elen, dlen, enc, dec); |
255 |
} |
256 |
abort (); |
257 |
} |
258 |
#endif |
259 |
|
260 |
//static basecoder cdc64 ("_dDpPhHzZrR06QqMmjJkKBb34TtSsvVlL81xXaAeEFf92WwGgYyoO57UucCNniI-"); |
261 |
//static basecoder cdc63 ("_dDpPhHzZrR06QqMmjJkKBb34TtSsvVlL81xXaAeEFf92WwGgYyoO57UucCNniI"); |
262 |
static basecoder cdc62 ("dDpPhHzZrR06QqMmjJkKBb34TtSsvVlL81xXaAeEFf92WwGgYyoO57UucCNniI"); |
263 |
//static basecoder cdc36 ("dphzr06qmjkb34tsvl81xaef92wgyo57ucni"); // unused as of yet |
264 |
static basecoder cdc26 ("dPhZrQmJkBtSvLxAeFwGyO"); |
265 |
|
266 |
///////////////////////////////////////////////////////////////////////////// |
267 |
|
268 |
#define HDRSIZE 6 |
269 |
|
270 |
inline void encode_header (char *data, int clientid, int seqno) |
271 |
{ |
272 |
u8 hdr[3] = { clientid, seqno >> 8, seqno }; |
273 |
|
274 |
assert (clientid < 256); |
275 |
|
276 |
cdc26.encode (data, hdr, 3); |
277 |
} |
278 |
|
279 |
inline void decode_header (char *data, int &clientid, int &seqno) |
280 |
{ |
281 |
u8 hdr[3]; |
282 |
|
283 |
cdc26.decode (hdr, data, HDRSIZE); |
284 |
|
285 |
clientid = hdr[0]; |
286 |
seqno = (hdr[1] << 8) | hdr[2]; |
287 |
} |
288 |
|
289 |
///////////////////////////////////////////////////////////////////////////// |
290 |
|
291 |
struct byte_stream |
292 |
{ |
293 |
u8 *data; |
294 |
int maxsize; |
295 |
int fill; |
296 |
|
297 |
byte_stream (int maxsize); |
298 |
~byte_stream (); |
299 |
|
300 |
bool empty () { return !fill; } |
301 |
int size () { return fill; } |
302 |
|
303 |
bool put (u8 *data, unsigned int datalen); |
304 |
bool put (vpn_packet *pkt); |
305 |
vpn_packet *get (); |
306 |
|
307 |
u8 *begin () { return data; } |
308 |
void remove (int count); |
309 |
}; |
310 |
|
311 |
byte_stream::byte_stream (int maxsize) |
312 |
: maxsize (maxsize), fill (0) |
313 |
{ |
314 |
data = new u8 [maxsize]; |
315 |
} |
316 |
|
317 |
byte_stream::~byte_stream () |
318 |
{ |
319 |
delete data; |
320 |
} |
321 |
|
322 |
void byte_stream::remove (int count) |
323 |
{ |
324 |
if (count > fill) |
325 |
abort (); |
326 |
|
327 |
memmove (data, data + count, fill -= count); |
328 |
} |
329 |
|
330 |
bool byte_stream::put (u8 *data, unsigned int datalen) |
331 |
{ |
332 |
if (maxsize - fill < datalen) |
333 |
return false; |
334 |
|
335 |
memcpy (this->data + fill, data, datalen); fill += datalen; |
336 |
|
337 |
return true; |
338 |
} |
339 |
|
340 |
bool byte_stream::put (vpn_packet *pkt) |
341 |
{ |
342 |
if (maxsize - fill < pkt->len + 2) |
343 |
return false; |
344 |
|
345 |
data [fill++] = pkt->len >> 8; |
346 |
data [fill++] = pkt->len; |
347 |
|
348 |
memcpy (data + fill, pkt->at (0), pkt->len); fill += pkt->len; |
349 |
|
350 |
return true; |
351 |
} |
352 |
|
353 |
vpn_packet *byte_stream::get () |
354 |
{ |
355 |
unsigned int len = (data [0] << 8) | data [1]; |
356 |
|
357 |
if (len > MAXSIZE && fill >= 2) |
358 |
abort (); // TODO handle this gracefully, connection reset |
359 |
|
360 |
if (fill < len + 2) |
361 |
return 0; |
362 |
|
363 |
vpn_packet *pkt = new vpn_packet; |
364 |
|
365 |
pkt->len = len; |
366 |
memcpy (pkt->at (0), data + 2, len); |
367 |
remove (len + 2); |
368 |
|
369 |
return pkt; |
370 |
} |
371 |
|
372 |
///////////////////////////////////////////////////////////////////////////// |
373 |
|
374 |
#define FLAG_QUERY ( 0 << 15) |
375 |
#define FLAG_RESPONSE ( 1 << 15) |
376 |
#define FLAG_OP_MASK (15 << 11) |
377 |
#define FLAG_OP_QUERY ( 0 << 11) |
378 |
#define FLAG_AA ( 1 << 10) |
379 |
#define FLAG_TC ( 1 << 9) |
380 |
#define FLAG_RD ( 1 << 8) |
381 |
#define FLAG_RA ( 1 << 7) |
382 |
#define FLAG_AUTH ( 1 << 5) |
383 |
#define FLAG_RCODE_MASK (15 << 0) |
384 |
#define FLAG_RCODE_OK ( 0 << 0) |
385 |
#define FLAG_RCODE_FORMERR ( 1 << 0) |
386 |
#define FLAG_RCODE_SERVFAIL ( 2 << 0) |
387 |
#define FLAG_RCODE_NXDOMAIN ( 3 << 0) |
388 |
#define FLAG_RCODE_REFUSED ( 5 << 0) |
389 |
|
390 |
#define DEFAULT_CLIENT_FLAGS (FLAG_QUERY | FLAG_OP_QUERY | FLAG_RD) |
391 |
#define DEFAULT_SERVER_FLAGS (FLAG_RESPONSE | FLAG_OP_QUERY | FLAG_AA | FLAG_RD | FLAG_RA) |
392 |
|
393 |
struct dns_cfg |
394 |
{ |
395 |
static int next_uid; |
396 |
|
397 |
u8 id1, id2, id3, id4; |
398 |
u8 version; |
399 |
u8 rrtype; |
400 |
u8 flags; |
401 |
u8 def_ttl; |
402 |
u8 rcv_cdc; |
403 |
u8 snd_cdc; |
404 |
u16 max_size; |
405 |
u16 client; |
406 |
u16 uid; // to make request unique |
407 |
|
408 |
u8 reserved[8]; |
409 |
|
410 |
void reset (int clientid); |
411 |
bool valid (); |
412 |
}; |
413 |
|
414 |
int dns_cfg::next_uid; |
415 |
|
416 |
void dns_cfg::reset (int clientid) |
417 |
{ |
418 |
id1 = 'G'; |
419 |
id2 = 'V'; |
420 |
id3 = 'P'; |
421 |
id4 = 'E'; |
422 |
|
423 |
version = 1; |
424 |
|
425 |
rrtype = RR_TYPE_TXT; |
426 |
flags = 0; |
427 |
def_ttl = 0; |
428 |
rcv_cdc = 0; |
429 |
snd_cdc = 62; |
430 |
max_size = ntohs (MAX_PKT_SIZE); |
431 |
client = ntohs (clientid); |
432 |
uid = next_uid++; |
433 |
|
434 |
memset (reserved, 0, 8); |
435 |
} |
436 |
|
437 |
bool dns_cfg::valid () |
438 |
{ |
439 |
return id1 == 'G' |
440 |
&& id2 == 'V' |
441 |
&& id3 == 'P' |
442 |
&& id4 == 'E' |
443 |
&& version == 1 |
444 |
&& flags == 0 |
445 |
&& rcv_cdc == 0 |
446 |
&& snd_cdc == 62 |
447 |
&& max_size == ntohs (MAX_PKT_SIZE); |
448 |
} |
449 |
|
450 |
struct dns_packet : net_packet |
451 |
{ |
452 |
u16 id; |
453 |
u16 flags; // QR:1 Opcode:4 AA:1 TC:1 RD:1 RA:1 Z:3 RCODE:4 |
454 |
u16 qdcount, ancount, nscount, arcount; |
455 |
|
456 |
u8 data[MAXSIZE - 6 * 2]; |
457 |
|
458 |
int decode_label (char *data, int size, int &offs); |
459 |
}; |
460 |
|
461 |
int dns_packet::decode_label (char *data, int size, int &offs) |
462 |
{ |
463 |
char *orig = data; |
464 |
|
465 |
memset (data, 0, size); |
466 |
|
467 |
while (offs < size - 1) |
468 |
{ |
469 |
u8 len = (*this)[offs++]; |
470 |
|
471 |
if (!len) |
472 |
break; |
473 |
else if (len < 64) |
474 |
{ |
475 |
if (size < len + 1 || offs + len >= MAXSIZE - 1) |
476 |
break; |
477 |
|
478 |
memcpy (data, &((*this)[offs]), len); |
479 |
|
480 |
data += len; size -= len; offs += len; |
481 |
*data++ = '.'; size--; |
482 |
} |
483 |
else |
484 |
{ |
485 |
int offs2 = ((len & 63) << 8) + (*this)[offs++]; |
486 |
|
487 |
data += decode_label (data, size, offs2); |
488 |
break; |
489 |
} |
490 |
} |
491 |
|
492 |
return data - orig; |
493 |
} |
494 |
|
495 |
///////////////////////////////////////////////////////////////////////////// |
496 |
|
497 |
struct dns_snd |
498 |
{ |
499 |
dns_packet *pkt; |
500 |
tstamp timeout, sent; |
501 |
int retry; |
502 |
struct dns_connection *dns; |
503 |
int seqno; |
504 |
|
505 |
void gen_stream_req (int seqno, byte_stream &stream); |
506 |
void gen_syn_req (const dns_cfg &cfg); |
507 |
|
508 |
dns_snd (dns_connection *dns); |
509 |
~dns_snd (); |
510 |
}; |
511 |
|
512 |
static u16 dns_id = 12098; // TODO: should be per-vpn |
513 |
|
514 |
static u16 next_id () |
515 |
{ |
516 |
// the simplest lsfr with periodicity 65535 i could find |
517 |
dns_id = (dns_id << 1) |
518 |
| (((dns_id >> 1) |
519 |
^ (dns_id >> 2) |
520 |
^ (dns_id >> 4) |
521 |
^ (dns_id >> 15)) & 1); |
522 |
|
523 |
return dns_id; |
524 |
} |
525 |
|
526 |
dns_snd::dns_snd (dns_connection *dns) |
527 |
: dns (dns) |
528 |
{ |
529 |
timeout = 0; |
530 |
retry = 0; |
531 |
seqno = 0; |
532 |
sent = NOW; |
533 |
|
534 |
pkt = new dns_packet; |
535 |
|
536 |
pkt->id = next_id (); |
537 |
} |
538 |
|
539 |
dns_snd::~dns_snd () |
540 |
{ |
541 |
delete pkt; |
542 |
} |
543 |
|
544 |
static void append_domain (dns_packet &pkt, int &offs, const char *domain) |
545 |
{ |
546 |
// add tunnel domain |
547 |
for (;;) |
548 |
{ |
549 |
const char *end = strchr (domain, '.'); |
550 |
|
551 |
if (!end) |
552 |
end = domain + strlen (domain); |
553 |
|
554 |
int len = end - domain; |
555 |
|
556 |
pkt [offs++] = len; |
557 |
memcpy (pkt.at (offs), domain, len); |
558 |
offs += len; |
559 |
|
560 |
if (!*end) |
561 |
break; |
562 |
|
563 |
domain = end + 1; |
564 |
} |
565 |
} |
566 |
|
567 |
void dns_snd::gen_stream_req (int seqno, byte_stream &stream) |
568 |
{ |
569 |
this->seqno = seqno; |
570 |
|
571 |
timeout = NOW + INITIAL_TIMEOUT; |
572 |
|
573 |
pkt->flags = htons (DEFAULT_CLIENT_FLAGS); |
574 |
pkt->qdcount = htons (1); |
575 |
|
576 |
int offs = 6*2; |
577 |
int dlen = MAX_DOMAIN_SIZE - (strlen (THISNODE->domain) + 2); |
578 |
// MAX_DOMAIN_SIZE is technically 255, but bind doesn't compress responses well, |
579 |
// so we need to have space for 2*MAX_DOMAIN_SIZE + header + extra |
580 |
|
581 |
char enc[256], *encp = enc; |
582 |
encode_header (enc, THISNODE->id, seqno); |
583 |
|
584 |
int datalen = cdc62.decode_len (dlen - (dlen + MAX_LBL_SIZE - 1) / MAX_LBL_SIZE - HDRSIZE); |
585 |
|
586 |
if (datalen > stream.size ()) |
587 |
datalen = stream.size (); |
588 |
|
589 |
int enclen = cdc62.encode (enc + HDRSIZE, stream.begin (), datalen) + HDRSIZE; |
590 |
stream.remove (datalen); |
591 |
|
592 |
while (enclen) |
593 |
{ |
594 |
int lbllen = enclen < MAX_LBL_SIZE ? enclen : MAX_LBL_SIZE; |
595 |
|
596 |
(*pkt)[offs++] = lbllen; |
597 |
memcpy (pkt->at (offs), encp, lbllen); |
598 |
|
599 |
offs += lbllen; |
600 |
encp += lbllen; |
601 |
|
602 |
enclen -= lbllen; |
603 |
} |
604 |
|
605 |
append_domain (*pkt, offs, THISNODE->domain); |
606 |
|
607 |
(*pkt)[offs++] = 0; |
608 |
(*pkt)[offs++] = RR_TYPE_ANY >> 8; (*pkt)[offs++] = RR_TYPE_ANY; |
609 |
(*pkt)[offs++] = RR_CLASS_IN >> 8; (*pkt)[offs++] = RR_CLASS_IN; |
610 |
|
611 |
pkt->len = offs; |
612 |
} |
613 |
|
614 |
void dns_snd::gen_syn_req (const dns_cfg &cfg) |
615 |
{ |
616 |
timeout = NOW + INITIAL_SYN_TIMEOUT; |
617 |
|
618 |
pkt->flags = htons (DEFAULT_CLIENT_FLAGS); |
619 |
pkt->qdcount = htons (1); |
620 |
|
621 |
int offs = 6*2; |
622 |
|
623 |
int elen = cdc26.encode ((char *)pkt->at (offs + 1), (u8 *)&cfg, sizeof (dns_cfg)); |
624 |
|
625 |
assert (elen <= MAX_LBL_SIZE); |
626 |
|
627 |
(*pkt)[offs] = elen; |
628 |
offs += elen + 1; |
629 |
append_domain (*pkt, offs, THISNODE->domain); |
630 |
|
631 |
(*pkt)[offs++] = 0; |
632 |
(*pkt)[offs++] = RR_TYPE_A >> 8; (*pkt)[offs++] = RR_TYPE_A; |
633 |
(*pkt)[offs++] = RR_CLASS_IN >> 8; (*pkt)[offs++] = RR_CLASS_IN; |
634 |
|
635 |
pkt->len = offs; |
636 |
} |
637 |
|
638 |
struct dns_rcv |
639 |
{ |
640 |
int seqno; |
641 |
dns_packet *pkt; // reply packet |
642 |
u8 data [MAXSIZE]; // actually part of the reply packet... |
643 |
int datalen; |
644 |
|
645 |
dns_rcv (int seqno, u8 *data, int datalen); |
646 |
~dns_rcv (); |
647 |
}; |
648 |
|
649 |
dns_rcv::dns_rcv (int seqno, u8 *data, int datalen) |
650 |
: seqno (seqno), pkt (new dns_packet), datalen (datalen) |
651 |
{ |
652 |
memcpy (this->data, data, datalen); |
653 |
} |
654 |
|
655 |
dns_rcv::~dns_rcv () |
656 |
{ |
657 |
delete pkt; |
658 |
} |
659 |
|
660 |
///////////////////////////////////////////////////////////////////////////// |
661 |
|
662 |
struct dns_connection |
663 |
{ |
664 |
connection *c; |
665 |
struct vpn *vpn; |
666 |
|
667 |
dns_cfg cfg; |
668 |
|
669 |
bool established; |
670 |
|
671 |
tstamp last_received; |
672 |
tstamp last_sent; |
673 |
double poll_interval, send_interval; |
674 |
|
675 |
vector<dns_rcv *> rcvpq; |
676 |
|
677 |
byte_stream rcvdq; int rcvseq; |
678 |
byte_stream snddq; int sndseq; |
679 |
|
680 |
void time_cb (time_watcher &w); time_watcher tw; |
681 |
void receive_rep (dns_rcv *r); |
682 |
|
683 |
dns_connection (connection *c); |
684 |
~dns_connection (); |
685 |
}; |
686 |
|
687 |
dns_connection::dns_connection (connection *c) |
688 |
: c (c) |
689 |
, rcvdq (MAX_BACKLOG * 2) |
690 |
, snddq (MAX_BACKLOG * 2) |
691 |
, tw (this, &dns_connection::time_cb) |
692 |
{ |
693 |
vpn = c->vpn; |
694 |
|
695 |
established = false; |
696 |
|
697 |
rcvseq = sndseq = 0; |
698 |
|
699 |
last_sent = last_received = 0; |
700 |
poll_interval = MIN_POLL_INTERVAL; |
701 |
send_interval = 0.2; // starting rate |
702 |
} |
703 |
|
704 |
dns_connection::~dns_connection () |
705 |
{ |
706 |
for (vector<dns_rcv *>::iterator i = rcvpq.begin (); |
707 |
i != rcvpq.end (); |
708 |
++i) |
709 |
delete *i; |
710 |
} |
711 |
|
712 |
void dns_connection::receive_rep (dns_rcv *r) |
713 |
{ |
714 |
if (r->datalen) |
715 |
{ |
716 |
last_received = NOW; |
717 |
tw.trigger (); |
718 |
|
719 |
poll_interval = send_interval; |
720 |
} |
721 |
else |
722 |
{ |
723 |
poll_interval *= 1.1; |
724 |
if (poll_interval > MAX_POLL_INTERVAL) |
725 |
poll_interval = MAX_POLL_INTERVAL; |
726 |
} |
727 |
|
728 |
rcvpq.push_back (r); |
729 |
|
730 |
redo: |
731 |
|
732 |
// find next packet |
733 |
for (vector<dns_rcv *>::iterator i = rcvpq.end (); i-- != rcvpq.begin (); ) |
734 |
if (SEQNO_EQ (rcvseq, (*i)->seqno)) |
735 |
{ |
736 |
// enter the packet into our input stream |
737 |
r = *i; |
738 |
|
739 |
// remove the oldest packet, look forward, as it's oldest first |
740 |
for (vector<dns_rcv *>::iterator j = rcvpq.begin (); j != rcvpq.end (); ++j) |
741 |
if (SEQNO_EQ ((*j)->seqno, rcvseq - MAX_WINDOW)) |
742 |
{ |
743 |
delete *j; |
744 |
rcvpq.erase (j); |
745 |
break; |
746 |
} |
747 |
|
748 |
rcvseq = (rcvseq + 1) & SEQNO_MASK; |
749 |
|
750 |
if (!rcvdq.put (r->data, r->datalen)) |
751 |
abort (); // MUST never overflow, can be caused by data corruption, TODO |
752 |
|
753 |
while (vpn_packet *pkt = rcvdq.get ()) |
754 |
{ |
755 |
sockinfo si; |
756 |
si.host = 0; si.port = 0; si.prot = PROT_DNSv4; |
757 |
|
758 |
vpn->recv_vpn_packet (pkt, si); |
759 |
|
760 |
delete pkt; |
761 |
} |
762 |
|
763 |
// check for further packets |
764 |
goto redo; |
765 |
} |
766 |
} |
767 |
|
768 |
void |
769 |
vpn::dnsv4_server (dns_packet &pkt) |
770 |
{ |
771 |
u16 flags = ntohs (pkt.flags); |
772 |
|
773 |
int offs = 6 * 2; // skip header |
774 |
|
775 |
pkt.flags = htons (DEFAULT_SERVER_FLAGS | FLAG_RCODE_FORMERR); |
776 |
|
777 |
if (0 == (flags & (FLAG_RESPONSE | FLAG_OP_MASK)) |
778 |
&& pkt.qdcount == htons (1)) |
779 |
{ |
780 |
char qname[MAXSIZE]; |
781 |
int qlen = pkt.decode_label ((char *)qname, MAXSIZE - offs, offs); |
782 |
|
783 |
u16 qtype = pkt [offs++] << 8; qtype |= pkt [offs++]; |
784 |
u16 qclass = pkt [offs++] << 8; qclass |= pkt [offs++]; |
785 |
|
786 |
pkt.qdcount = htons (1); |
787 |
pkt.ancount = 0; |
788 |
pkt.nscount = 0; // should be self, as other nameservers reply like this |
789 |
pkt.arcount = 0; // a record for self, as other nameservers reply like this |
790 |
|
791 |
pkt.flags = htons (DEFAULT_SERVER_FLAGS | FLAG_RCODE_SERVFAIL); |
792 |
|
793 |
int dlen = strlen (THISNODE->domain); |
794 |
|
795 |
if (qclass == RR_CLASS_IN |
796 |
&& qlen > dlen + 1 |
797 |
&& !memcmp (qname + qlen - dlen - 1, THISNODE->domain, dlen)) |
798 |
{ |
799 |
// now generate reply |
800 |
pkt.ancount = htons (1); // one answer RR |
801 |
pkt.flags = htons (DEFAULT_SERVER_FLAGS | FLAG_RCODE_OK); |
802 |
|
803 |
if ((qtype == RR_TYPE_ANY |
804 |
|| qtype == RR_TYPE_TXT |
805 |
|| qtype == RR_TYPE_NULL) |
806 |
&& qlen > dlen + 1 + HDRSIZE) |
807 |
{ |
808 |
// correct class, domain: parse |
809 |
int client, seqno; |
810 |
decode_header (qname, client, seqno); |
811 |
|
812 |
u8 data[MAXSIZE]; |
813 |
int datalen = cdc62.decode (data, qname + HDRSIZE, qlen - (dlen + 1 + HDRSIZE)); |
814 |
|
815 |
if (0 < client && client <= conns.size ()) |
816 |
{ |
817 |
connection *c = conns [client - 1]; |
818 |
dns_connection *dns = c->dns; |
819 |
dns_rcv *rcv; |
820 |
|
821 |
if (dns) |
822 |
{ |
823 |
for (vector<dns_rcv *>::iterator i = dns->rcvpq.end (); i-- != dns->rcvpq.begin (); ) |
824 |
if (SEQNO_EQ ((*i)->seqno, seqno)) |
825 |
{ |
826 |
// already seen that request: simply reply with the cached reply |
827 |
dns_rcv *r = *i; |
828 |
|
829 |
slog (L_DEBUG, "DUPLICATE %d\n", htons (r->pkt->id)); |
830 |
|
831 |
memcpy (pkt.at (0), r->pkt->at (0), offs = r->pkt->len); |
832 |
pkt.id = r->pkt->id; |
833 |
goto duplicate_request; |
834 |
} |
835 |
|
836 |
// new packet, queue |
837 |
rcv = new dns_rcv (seqno, data, datalen); |
838 |
dns->receive_rep (rcv); |
839 |
} |
840 |
|
841 |
pkt [offs++] = 0xc0; pkt [offs++] = 6 * 2; // refer to name in query section |
842 |
|
843 |
int rtype = dns ? dns->cfg.rrtype : RR_TYPE_A; |
844 |
pkt [offs++] = rtype >> 8; pkt [offs++] = rtype; // type |
845 |
pkt [offs++] = RR_CLASS_IN >> 8; pkt [offs++] = RR_CLASS_IN; // class |
846 |
pkt [offs++] = 0; pkt [offs++] = 0; |
847 |
pkt [offs++] = 0; pkt [offs++] = dns ? dns->cfg.def_ttl : 0; // TTL |
848 |
|
849 |
int rdlen_offs = offs += 2; |
850 |
|
851 |
int dlen = (dns ? ntohs (dns->cfg.max_size) : MAX_PKT_SIZE) - offs; |
852 |
// bind doesn't compress well, so reduce further by one label length |
853 |
dlen -= qlen; |
854 |
|
855 |
if (dns) |
856 |
{ |
857 |
while (dlen > 1 && !dns->snddq.empty ()) |
858 |
{ |
859 |
int txtlen = dlen <= 255 ? dlen - 1 : 255; |
860 |
|
861 |
if (txtlen > dns->snddq.size ()) |
862 |
txtlen = dns->snddq.size (); |
863 |
|
864 |
pkt[offs++] = txtlen; |
865 |
memcpy (pkt.at (offs), dns->snddq.begin (), txtlen); |
866 |
offs += txtlen; |
867 |
dns->snddq.remove (txtlen); |
868 |
|
869 |
dlen -= txtlen + 1; |
870 |
} |
871 |
|
872 |
// avoid empty TXT rdata |
873 |
if (offs == rdlen_offs) |
874 |
pkt[offs++] = 0; |
875 |
|
876 |
slog (L_NOISE, "snddq %d", dns->snddq.size ()); |
877 |
} |
878 |
else |
879 |
{ |
880 |
// send RST |
881 |
pkt [offs++] = CMD_IP_1; pkt [offs++] = CMD_IP_2; pkt [offs++] = CMD_IP_3; |
882 |
pkt [offs++] = CMD_IP_RST; |
883 |
} |
884 |
|
885 |
int rdlen = offs - rdlen_offs; |
886 |
|
887 |
pkt [rdlen_offs - 2] = rdlen >> 8; |
888 |
pkt [rdlen_offs - 1] = rdlen; |
889 |
|
890 |
if (dns) |
891 |
{ |
892 |
// now update dns_rcv copy |
893 |
rcv->pkt->len = offs; |
894 |
memcpy (rcv->pkt->at (0), pkt.at (0), offs); |
895 |
} |
896 |
|
897 |
duplicate_request: ; |
898 |
} |
899 |
else |
900 |
pkt.flags = htons (DEFAULT_SERVER_FLAGS | FLAG_RCODE_FORMERR); |
901 |
} |
902 |
else if (qtype == RR_TYPE_A |
903 |
&& qlen > dlen + 1 + cdc26.encode_len (sizeof (dns_cfg))) |
904 |
{ |
905 |
dns_cfg cfg; |
906 |
cdc26.decode ((u8 *)&cfg, qname, cdc26.encode_len (sizeof (dns_cfg))); |
907 |
int client = ntohs (cfg.client); |
908 |
|
909 |
pkt [offs++] = 0xc0; pkt [offs++] = 6 * 2; // refer to name in query section |
910 |
|
911 |
pkt [offs++] = RR_TYPE_A >> 8; pkt [offs++] = RR_TYPE_A; // type |
912 |
pkt [offs++] = RR_CLASS_IN >> 8; pkt [offs++] = RR_CLASS_IN; // class |
913 |
pkt [offs++] = 0; pkt [offs++] = 0; |
914 |
pkt [offs++] = 0; pkt [offs++] = cfg.def_ttl; // TTL |
915 |
pkt [offs++] = 0; pkt [offs++] = 4; // rdlength |
916 |
|
917 |
slog (L_INFO, _("DNS tunnel: client %d tries to connect"), client); |
918 |
|
919 |
pkt [offs++] = CMD_IP_1; pkt [offs++] = CMD_IP_2; pkt [offs++] = CMD_IP_3; |
920 |
pkt [offs++] = CMD_IP_REJ; |
921 |
|
922 |
if (0 < client && client <= conns.size ()) |
923 |
{ |
924 |
connection *c = conns [client - 1]; |
925 |
|
926 |
if (cfg.valid ()) |
927 |
{ |
928 |
pkt [offs - 1] = CMD_IP_SYN; |
929 |
|
930 |
delete c->dns; |
931 |
c->dns = new dns_connection (c); |
932 |
c->dns->cfg = cfg; |
933 |
} |
934 |
} |
935 |
} |
936 |
} |
937 |
|
938 |
pkt.len = offs; |
939 |
} |
940 |
} |
941 |
|
942 |
void |
943 |
vpn::dnsv4_client (dns_packet &pkt) |
944 |
{ |
945 |
u16 flags = ntohs (pkt.flags); |
946 |
int offs = 6 * 2; // skip header |
947 |
|
948 |
pkt.qdcount = ntohs (pkt.qdcount); |
949 |
pkt.ancount = ntohs (pkt.ancount); |
950 |
|
951 |
// go through our request list and find the corresponding request |
952 |
for (vector<dns_snd *>::iterator i = dns_sndpq.begin (); |
953 |
i != dns_sndpq.end (); |
954 |
++i) |
955 |
if ((*i)->pkt->id == pkt.id) |
956 |
{ |
957 |
dns_connection *dns = (*i)->dns; |
958 |
connection *c = dns->c; |
959 |
int seqno = (*i)->seqno; |
960 |
u8 data[MAXSIZE], *datap = data; |
961 |
|
962 |
if ((*i)->retry) |
963 |
{ |
964 |
dns->send_interval *= 1.001; |
965 |
if (dns->send_interval > MAX_SEND_INTERVAL) |
966 |
dns->send_interval = MAX_SEND_INTERVAL; |
967 |
} |
968 |
else |
969 |
{ |
970 |
#if 1 |
971 |
dns->send_interval *= 0.9999; |
972 |
#endif |
973 |
if (dns->send_interval < MIN_SEND_INTERVAL) |
974 |
dns->send_interval = MIN_SEND_INTERVAL; |
975 |
|
976 |
// the latency surely puts an upper bound on |
977 |
// the minimum send interval |
978 |
double latency = NOW - (*i)->sent; |
979 |
|
980 |
if (dns->send_interval > latency) |
981 |
dns->send_interval = latency; |
982 |
} |
983 |
|
984 |
delete *i; |
985 |
dns_sndpq.erase (i); |
986 |
|
987 |
if (flags & FLAG_RESPONSE && !(flags & FLAG_OP_MASK)) |
988 |
{ |
989 |
char qname[MAXSIZE]; |
990 |
|
991 |
while (pkt.qdcount-- && offs < MAXSIZE - 4) |
992 |
{ |
993 |
int qlen = pkt.decode_label ((char *)qname, MAXSIZE - offs, offs); |
994 |
offs += 4; // skip qtype, qclass |
995 |
} |
996 |
|
997 |
while (pkt.ancount-- && offs < MAXSIZE - 10 && datap) |
998 |
{ |
999 |
int qlen = pkt.decode_label ((char *)qname, MAXSIZE - offs, offs); |
1000 |
|
1001 |
u16 qtype = pkt [offs++] << 8; qtype |= pkt [offs++]; |
1002 |
u16 qclass = pkt [offs++] << 8; qclass |= pkt [offs++]; |
1003 |
u32 ttl = pkt [offs++] << 24; |
1004 |
ttl |= pkt [offs++] << 16; |
1005 |
ttl |= pkt [offs++] << 8; |
1006 |
ttl |= pkt [offs++]; |
1007 |
u16 rdlen = pkt [offs++] << 8; rdlen |= pkt [offs++]; |
1008 |
|
1009 |
if (qtype == RR_TYPE_NULL || qtype == RR_TYPE_TXT) |
1010 |
{ |
1011 |
if (rdlen <= MAXSIZE - offs) |
1012 |
{ |
1013 |
// decode bytes, finally |
1014 |
|
1015 |
while (rdlen) |
1016 |
{ |
1017 |
int txtlen = pkt [offs++]; |
1018 |
|
1019 |
assert (txtlen + offs < MAXSIZE - 1); |
1020 |
|
1021 |
memcpy (datap, pkt.at (offs), txtlen); |
1022 |
datap += txtlen; offs += txtlen; |
1023 |
|
1024 |
rdlen -= txtlen + 1; |
1025 |
} |
1026 |
} |
1027 |
} |
1028 |
else if (qtype == RR_TYPE_A) |
1029 |
{ |
1030 |
u8 ip [4]; |
1031 |
|
1032 |
ip [0] = pkt [offs++]; |
1033 |
ip [1] = pkt [offs++]; |
1034 |
ip [2] = pkt [offs++]; |
1035 |
ip [3] = pkt [offs++]; |
1036 |
|
1037 |
if (ip [0] == CMD_IP_1 |
1038 |
&& ip [1] == CMD_IP_2 |
1039 |
&& ip [2] == CMD_IP_3) |
1040 |
{ |
1041 |
slog (L_TRACE, _("got tunnel meta command %02x"), ip [3]); |
1042 |
|
1043 |
if (ip [3] == CMD_IP_RST) |
1044 |
{ |
1045 |
slog (L_DEBUG, _("got tunnel RST request")); |
1046 |
|
1047 |
delete dns; c->dns = 0; |
1048 |
|
1049 |
return; |
1050 |
} |
1051 |
else if (ip [3] == CMD_IP_SYN) |
1052 |
{ |
1053 |
slog (L_DEBUG, _("got tunnel SYN reply, server likes us.")); |
1054 |
dns->established = true; |
1055 |
} |
1056 |
else if (ip [3] == CMD_IP_REJ) |
1057 |
{ |
1058 |
slog (L_DEBUG, _("got tunnel REJ reply, server does not like us, aborting.")); |
1059 |
abort (); |
1060 |
} |
1061 |
else |
1062 |
slog (L_INFO, _("got unknown meta command %02x"), ip [3]); |
1063 |
} |
1064 |
else |
1065 |
slog (L_INFO, _("got spurious a record %d.%d.%d.%d"), |
1066 |
ip [0], ip [1], ip [2], ip [3]); |
1067 |
|
1068 |
return; |
1069 |
} |
1070 |
|
1071 |
int client, rseqno; |
1072 |
decode_header (qname, client, rseqno); |
1073 |
|
1074 |
if (client != THISNODE->id) |
1075 |
{ |
1076 |
slog (L_INFO, _("got dns tunnel response with wrong clientid, ignoring")); |
1077 |
datap = 0; |
1078 |
} |
1079 |
else if (rseqno != seqno) |
1080 |
{ |
1081 |
slog (L_DEBUG, _("got dns tunnel response with wrong seqno, badly caching nameserver?")); |
1082 |
datap = 0; |
1083 |
} |
1084 |
} |
1085 |
} |
1086 |
|
1087 |
// todo: pkt now used |
1088 |
if (datap) |
1089 |
dns->receive_rep (new dns_rcv (seqno, data, datap - data)); |
1090 |
|
1091 |
break; |
1092 |
} |
1093 |
} |
1094 |
|
1095 |
void |
1096 |
vpn::dnsv4_ev (io_watcher &w, short revents) |
1097 |
{ |
1098 |
if (revents & EVENT_READ) |
1099 |
{ |
1100 |
dns_packet *pkt = new dns_packet; |
1101 |
struct sockaddr_in sa; |
1102 |
socklen_t sa_len = sizeof (sa); |
1103 |
|
1104 |
pkt->len = recvfrom (w.fd, pkt->at (0), MAXSIZE, 0, (sockaddr *)&sa, &sa_len); |
1105 |
|
1106 |
if (pkt->len > 0) |
1107 |
{ |
1108 |
if (THISNODE->dns_port) |
1109 |
{ |
1110 |
dnsv4_server (*pkt); |
1111 |
sendto (w.fd, pkt->at (0), pkt->len, 0, (sockaddr *)&sa, sa_len); |
1112 |
} |
1113 |
else |
1114 |
dnsv4_client (*pkt); |
1115 |
|
1116 |
delete pkt; |
1117 |
} |
1118 |
} |
1119 |
} |
1120 |
|
1121 |
bool |
1122 |
connection::send_dnsv4_packet (vpn_packet *pkt, const sockinfo &si, int tos) |
1123 |
{ |
1124 |
if (!dns) |
1125 |
dns = new dns_connection (this); |
1126 |
|
1127 |
if (!dns->snddq.put (pkt)) |
1128 |
return false; |
1129 |
|
1130 |
dns->tw.trigger (); |
1131 |
|
1132 |
return true; |
1133 |
} |
1134 |
|
1135 |
void |
1136 |
connection::dnsv4_reset_connection () |
1137 |
{ |
1138 |
//delete dns; dns = 0; //TODO |
1139 |
} |
1140 |
|
1141 |
#define NEXT(w) do { if (next > (w)) next = w; } while (0) |
1142 |
|
1143 |
void |
1144 |
dns_connection::time_cb (time_watcher &w) |
1145 |
{ |
1146 |
// servers have to be polled |
1147 |
if (THISNODE->dns_port) |
1148 |
return; |
1149 |
|
1150 |
// check for timeouts and (re)transmit |
1151 |
tstamp next = NOW + poll_interval; |
1152 |
dns_snd *send = 0; |
1153 |
|
1154 |
for (vector<dns_snd *>::iterator i = vpn->dns_sndpq.begin (); |
1155 |
i != vpn->dns_sndpq.end (); |
1156 |
++i) |
1157 |
{ |
1158 |
dns_snd *r = *i; |
1159 |
|
1160 |
if (r->timeout <= NOW) |
1161 |
{ |
1162 |
if (!send) |
1163 |
{ |
1164 |
send = r; |
1165 |
|
1166 |
r->retry++; |
1167 |
r->timeout = NOW + r->retry; |
1168 |
} |
1169 |
} |
1170 |
else |
1171 |
NEXT (r->timeout); |
1172 |
} |
1173 |
|
1174 |
if (last_sent + send_interval <= NOW) |
1175 |
{ |
1176 |
if (!send) |
1177 |
{ |
1178 |
// generate a new packet, if wise |
1179 |
|
1180 |
if (!established) |
1181 |
{ |
1182 |
if (vpn->dns_sndpq.empty ()) |
1183 |
{ |
1184 |
send = new dns_snd (this); |
1185 |
|
1186 |
cfg.reset (THISNODE->id); |
1187 |
send->gen_syn_req (cfg); |
1188 |
} |
1189 |
} |
1190 |
else if (vpn->dns_sndpq.size () < MAX_OUTSTANDING) |
1191 |
{ |
1192 |
send = new dns_snd (this); |
1193 |
send->gen_stream_req (sndseq, snddq); |
1194 |
|
1195 |
sndseq = (sndseq + 1) & SEQNO_MASK; |
1196 |
} |
1197 |
|
1198 |
if (send) |
1199 |
vpn->dns_sndpq.push_back (send); |
1200 |
} |
1201 |
|
1202 |
if (send) |
1203 |
{ |
1204 |
last_sent = NOW; |
1205 |
sendto (vpn->dnsv4_fd, |
1206 |
send->pkt->at (0), send->pkt->len, 0, |
1207 |
vpn->dns_forwarder.sav4 (), vpn->dns_forwarder.salenv4 ()); |
1208 |
} |
1209 |
} |
1210 |
else |
1211 |
NEXT (last_sent + send_interval); |
1212 |
|
1213 |
slog (L_NOISE, "pi %f si %f N %f (%d:%d)", |
1214 |
poll_interval, send_interval, next - NOW, |
1215 |
vpn->dns_sndpq.size (), snddq.size ()); |
1216 |
|
1217 |
// TODO: no idea when this happens, but when next < NOW, we have a problem |
1218 |
if (next < NOW + 0.0001) |
1219 |
next = NOW + 0.1; |
1220 |
|
1221 |
w.start (next); |
1222 |
} |
1223 |
|
1224 |
#endif |
1225 |
|