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Comparing gvpe/src/vpn_dns.C (file contents):
Revision 1.7 by pcg, Thu Mar 3 16:54:34 2005 UTC vs.
Revision 1.52 by root, Sun Mar 6 21:01:37 2011 UTC

1/* 1/*
2 vpn_dns.C -- handle the dns tunnel part of the protocol. 2 vpn_dns.C -- handle the dns tunnel part of the protocol.
3 Copyright (C) 2003-2005 Marc Lehmann <gvpe@schmorp.de> 3 Copyright (C) 2003-2011 Marc Lehmann <gvpe@schmorp.de>
4 4
5 This file is part of GVPE. 5 This file is part of GVPE.
6 6
7 GVPE is free software; you can redistribute it and/or modify 7 GVPE is free software; you can redistribute it and/or modify it
8 it under the terms of the GNU General Public License as published by 8 under the terms of the GNU General Public License as published by the
9 the Free Software Foundation; either version 2 of the License, or 9 Free Software Foundation; either version 3 of the License, or (at your
10 (at your option) any later version. 10 option) any later version.
11 11
12 This program is distributed in the hope that it will be useful, 12 This program is distributed in the hope that it will be useful, but
13 but WITHOUT ANY WARRANTY; without even the implied warranty of 13 WITHOUT ANY WARRANTY; without even the implied warranty of
14 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 14 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General
15 GNU General Public License for more details. 15 Public License for more details.
16 16
17 You should have received a copy of the GNU General Public License 17 You should have received a copy of the GNU General Public License along
18 along with gvpe; if not, write to the Free Software 18 with this program; if not, see <http://www.gnu.org/licenses/>.
19 Foundation, Inc. 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA 19
20 Additional permission under GNU GPL version 3 section 7
21
22 If you modify this Program, or any covered work, by linking or
23 combining it with the OpenSSL project's OpenSSL library (or a modified
24 version of that library), containing parts covered by the terms of the
25 OpenSSL or SSLeay licenses, the licensors of this Program grant you
26 additional permission to convey the resulting work. Corresponding
27 Source for a non-source form of such a combination shall include the
28 source code for the parts of OpenSSL used as well as that of the
29 covered work.
20*/ 30*/
31
32// TODO: EDNS0 option to increase dns mtu?
33// TODO: re-write dns packet parsing/creation using a safe mem-buffer
34// to ensure no buffer overflows or similar problems.
21 35
22#include "config.h" 36#include "config.h"
23 37
24#if ENABLE_DNS 38#if ENABLE_DNS
25 39
26// dns processing is EXTREMELY ugly. For obvious(?) reasons. 40// dns processing is EXTREMELY ugly. For obvious(?) reasons.
27// it's a hack, use only in emergency situations please. 41// it's a hack, use only in emergency situations please.
28 42
29#include <cstring> 43#include <cstring>
44#include <cassert>
30 45
31#include <sys/types.h> 46#include <sys/types.h>
32#include <sys/socket.h> 47#include <sys/socket.h>
33#include <sys/wait.h> 48#include <sys/wait.h>
34#include <sys/uio.h> 49#include <sys/uio.h>
… …
37#include <unistd.h> 52#include <unistd.h>
38#include <fcntl.h> 53#include <fcntl.h>
39 54
40#include <map> 55#include <map>
41 56
57#include <cstdio> /* bug in libgmp: gmp.h relies on cstdio being included */
58#include <gmp.h>
59
42#include "netcompat.h" 60#include "netcompat.h"
43 61
44#include "vpn.h" 62#include "vpn.h"
45 63
46#define MIN_RETRY 1. 64#define MIN_POLL_INTERVAL 0.025 // poll at most this often when no data received
47#define MAX_RETRY 60. 65#define MAX_POLL_INTERVAL 1. // how often to poll minimally when the server has no data
48 66
49#define MAX_OUTSTANDING 40 // max. outstanding requests 67#define INITIAL_TIMEOUT 0.1 // retry timeouts
68#define INITIAL_SYN_TIMEOUT 2. // retry timeout for initial syn
69
70#define MAX_SEND_INTERVAL 5. // optimistic?
71
50#define MAX_WINDOW 100 // max. for MAX_OUTSTANDING 72#define MAX_WINDOW 1000 // max. for MAX_OUTSTANDING, and backlog
51#define MAX_RATE 1000 // requests/s
52#define MAX_BACKLOG (10*1024) // size of protocol backlog, must be > MAXSIZE 73#define MAX_BACKLOG (64*1024) // size of gvpe protocol backlog (bytes), must be > MAXSIZE
53 74
54#define MAX_DOMAIN_SIZE 220 // 255 is legal limit, but bind doesn't compress well 75#define MAX_DOMAIN_SIZE 240 // 255 is legal limit, but bind doesn't compress well
55// 240 leaves about 4 bytes of server reply data 76// 240 leaves about 4 bytes of server reply data
56// every two request byte sless give room for one reply byte 77// every request byte less give room for two reply bytes
57 78
58// seqno has 12 bits, but the lower bit is always left as zero
59// as bind caches ttl=0 records and we have to generate
60// sequence numbers that always differ case-insensitively
61#define SEQNO_MASK 0x07ff 79#define SEQNO_MASK 0x3fff
62 80#define SEQNO_EQ(a,b) ( 0 == ( ((a) ^ (b)) & SEQNO_MASK) )
63/*
64
65protocol, in shorthand :)
66
67client -> server <req> ANY?
68server -> client <req> TXT <rep>
69
70<req> is dns64-encoded <client-id:12><recv-seqno:10>[<send-seqno:10><data>]
71<rep> is dns64-encoded <0:12><recv-seqno:10>[<send-seqno:10><data>]
72
73if <client-id> is zero, the connection will be configured:
74
75<0:12><0:4>client-id:12><default-ttl:8><max-size:16><flags:16>
76
77*/
78 81
79#define MAX_LBL_SIZE 63 82#define MAX_LBL_SIZE 63
80#define MAX_PKT_SIZE 512 83#define MAX_PKT_SIZE 512
81 84
85#define RR_TYPE_A 1
86#define RR_TYPE_NULL 10
82#define RR_TYPE_TXT 16 87#define RR_TYPE_TXT 16
88#define RR_TYPE_AAAA 28
83#define RR_TYPE_ANY 255 89#define RR_TYPE_ANY 255
90
84#define RR_CLASS_IN 1 91#define RR_CLASS_IN 1
85 92
86// the "_" is not valid but widely accepted (all octets should be supported, but let's be conservative) 93#define CMD_IP_1 207
87struct dns64 94#define CMD_IP_2 46
88{ 95#define CMD_IP_3 236
89 static const char encode_chars[64 + 1];
90 static s8 decode_chars[256];
91 96
92 static int encode_len (int bytes) { return (bytes * 8 + 5) / 6; } 97#define CMD_IP_RST 29 // some error, reset and retry
93 static int decode_len (int bytes) { return (bytes * 6) / 8; } 98#define CMD_IP_REJ 32 // do not want you
99#define CMD_IP_SYN 113 // connection established
100#define CMD_IP_CSE 213 // connection established, but likely case mismatch
101
102static bool
103is_uc (char c)
104{
105 return 'A' <= c && c <= 'Z';
106}
107
108static bool
109is_lc (char c)
110{
111 return 'a' <= c && c <= 'z';
112}
113
114// works for cmaps up to 255 (not 256!)
115struct charmap
116{
117 enum { INVALID = (u8)255 };
118
119 char encode [256]; // index => char
120 u8 decode [256]; // char => index
121 unsigned int size;
122
123 charmap (const char *cmap);
124};
125
126charmap::charmap (const char *cmap)
127{
128 char *enc = encode;
129 u8 *dec = decode;
130
131 memset (enc, (char) 0, 256);
132 memset (dec, (char)INVALID, 256);
133
134 for (size = 0; cmap [size]; size++)
135 {
136 char c = cmap [size];
137
138 enc [size] = c;
139 dec [(u8)c] = size;
140
141 // allow lowercase/uppercase aliases if possible
142 if (is_uc (c) && dec [c + ('a' - 'A')] == INVALID) dec [c + ('a' - 'A')] = size;
143 if (is_lc (c) && dec [c - ('a' - 'A')] == INVALID) dec [c - ('a' - 'A')] = size;
144 }
145
146 assert (size < 256);
147}
148
149#define MAX_DEC_LEN 500
150#define MAX_ENC_LEN (MAX_DEC_LEN * 2)
151#define MAX_LIMBS ((MAX_DEC_LEN * 8 + GMP_NUMB_BITS - 1) / GMP_NUMB_BITS)
152
153// ugly. minimum base is 16(!)
154struct basecoder
155{
156 charmap cmap;
157 unsigned int enc_len [MAX_DEC_LEN];
158 unsigned int dec_len [MAX_ENC_LEN];
159
160 unsigned int encode_len (unsigned int len) const;
161 unsigned int decode_len (unsigned int len) const;
162
94 static int encode (char *dst, u8 *src, int len); 163 unsigned int encode (char *dst, u8 *src, unsigned int len) const;
95 static int decode (u8 *dst, char *src, int len); 164 unsigned int decode (u8 *dst, char *src, unsigned int len) const;
96 165
97 dns64 (); 166 basecoder (const char *cmap);
98} dns64; 167};
99 168
100// the following sequence has been crafted to 169basecoder::basecoder (const char *cmap)
101// a) look somewhat random 170: cmap (cmap)
102// b) the even (and odd) indices never share the same character as upper/lowercase
103const char dns64::encode_chars[64 + 1] = "_-dDpPhHzZrR06QqMmjJkKBb34TtSsvVlL81xXaAeEFf92WwGgYyoO57UucCNniI";
104s8 dns64::decode_chars[256];
105
106dns64::dns64 ()
107{ 171{
108 for (int i = 0; i < 64; i++) 172 for (unsigned int len = 0; len < MAX_DEC_LEN; ++len)
109 decode_chars [encode_chars [i]] = i + 1; 173 {
110} 174 u8 src [MAX_DEC_LEN];
175 u8 dst [MAX_ENC_LEN];
111 176
112int dns64::encode (char *dst, u8 *src, int len) 177 memset (src, 255, len);
178
179 mp_limb_t m [MAX_LIMBS];
180 mp_size_t n;
181
182 n = mpn_set_str (m, src, len, 256);
183 n = mpn_get_str (dst, this->cmap.size, m, n);
184
185 for (int i = 0; !dst [i]; ++i)
186 n--;
187
188 enc_len [len] = n;
189 dec_len [n] = len;
190 }
191}
192
193unsigned int
194basecoder::encode_len (unsigned int len) const
113{ 195{
114 // slow, but easy to debug 196 return enc_len [len];
115 char *beg = dst; 197}
116 unsigned int accum, bits = 0; 198
199unsigned int
200basecoder::decode_len (unsigned int len) const
201{
202 while (len && !dec_len [len])
203 --len;
204
205 return dec_len [len];
206}
207
208unsigned int
209basecoder::encode (char *dst, u8 *src, unsigned int len) const
210{
211 if (!len || len > MAX_DEC_LEN)
212 return 0;
213
214 int elen = encode_len (len);
215
216 mp_limb_t m [MAX_LIMBS];
217 mp_size_t n;
218
219 u8 dst_ [MAX_ENC_LEN];
220
221 n = mpn_set_str (m, src, len, 256);
222 n = mpn_get_str (dst_, cmap.size, m, n);
223
224 int plen = elen; // for padding
225
226 while (n < plen)
227 {
228 *dst++ = cmap.encode [0];
229 plen--;
230 }
231
232 for (unsigned int i = n - plen; i < n; ++i)
233 *dst++ = cmap.encode [dst_ [i]];
234
235 return elen;
236}
237
238unsigned int
239basecoder::decode (u8 *dst, char *src, unsigned int len) const
240{
241 if (!len || len > MAX_ENC_LEN)
242 return 0;
243
244 u8 src_ [MAX_ENC_LEN];
245 unsigned int elen = 0;
117 246
118 while (len--) 247 while (len--)
119 { 248 {
120 accum <<= 8; 249 u8 val = cmap.decode [(u8)*src++];
121 accum |= *src++;
122 bits += 8;
123 250
124 while (bits >= 6) 251 if (val != charmap::INVALID)
125 { 252 src_ [elen++] = val;
126 *dst++ = encode_chars [(accum >> (bits - 6)) & 63]; 253 }
127 bits -= 6; 254
128 } 255 int dlen = decode_len (elen);
256
257 mp_limb_t m [MAX_LIMBS];
258 mp_size_t n;
259
260 u8 dst_ [MAX_DEC_LEN];
261
262 n = mpn_set_str (m, src_, elen, cmap.size);
263 n = mpn_get_str (dst_, 256, m, n);
264
265 if (n < dlen)
129 } 266 {
267 memset (dst, 0, dlen - n);
268 memcpy (dst + dlen - n, dst_, n);
269 }
270 else
271 memcpy (dst, dst_ + n - dlen, dlen);
130 272
131 if (bits) 273 return dlen;
132 *dst++ = encode_chars [(accum << (6 - bits)) & 63];
133
134 return dst - beg;
135} 274}
136 275
137int dns64::decode (u8 *dst, char *src, int len) 276#if 0
138{ 277struct test { test (); } test;
139 // slow, but easy to debug
140 u8 *beg = dst;
141 unsigned int accum, bits = 0;
142 278
143 while (len--) 279test::test ()
280{
281 basecoder cdc ("0123456789abcdefghijklmnopqrstuvwxyz");
282
283 u8 in[] = "0123456789abcdefghijklmnopqrstuvwxyz";
284 static char enc[200];
285 static u8 dec[200];
286
287 for (int i = 1; i < 20; i++)
144 { 288 {
145 s8 chr = decode_chars [(u8)*src++]; 289 int elen = cdc.encode (enc, in, i);
290 int dlen = cdc.decode (dec, enc, elen);
146 291
147 if (!chr) 292 printf ("%d>%d>%d (%s>%s)\n", i, elen, dlen, enc, dec);
148 continue;
149
150 accum <<= 6;
151 accum |= chr - 1;
152 bits += 6;
153
154 while (bits >= 8)
155 {
156 *dst++ = accum >> (bits - 8);
157 bits -= 8;
158 }
159 } 293 }
294 abort ();
295}
296#endif
160 297
161 return dst - beg; 298static basecoder cdc62 ("dDpPhHzZrR06QqMmjJkKBb34TtSsvVlL81xXaAeEFf92WwGgYyoO57UucCNniI"); // a-zA-Z0-9
299static basecoder cdc36 ("dPhZr06QmJkB34tSvL81xAeF92wGyO57uCnI"); // a-z0-9 for case-changers
300static basecoder cdc26 ("dPhZrQmJkBtSvLxAeFwGyOuCnI"); // a-z
301
302/////////////////////////////////////////////////////////////////////////////
303
304#define HDRSIZE 5
305
306inline void
307encode_header (char *data, int clientid, int seqno, int retry = 0)
308{
309 assert (clientid < 256);
310
311 seqno &= SEQNO_MASK;
312
313 u8 hdr[3] = {
314 seqno,
315 (seqno >> 8) | (retry << 6),
316 clientid,
317 };
318
319 cdc36.encode (data, hdr, 3);
320}
321
322inline void
323decode_header (char *data, int &clientid, int &seqno)
324{
325 u8 hdr[3];
326
327 cdc36.decode (hdr, data, HDRSIZE);
328
329 clientid = hdr[2];
330 seqno = ((hdr[1] << 8) | hdr[0]) & SEQNO_MASK;
162} 331}
163 332
164///////////////////////////////////////////////////////////////////////////// 333/////////////////////////////////////////////////////////////////////////////
165 334
166struct byte_stream 335struct byte_stream
… …
192byte_stream::~byte_stream () 361byte_stream::~byte_stream ()
193{ 362{
194 delete data; 363 delete data;
195} 364}
196 365
366void
197void byte_stream::remove (int count) 367byte_stream::remove (int count)
198{ 368{
199 if (count > fill) 369 if (count > fill)
200 abort (); 370 assert (count <= fill);
201 371
202 memmove (data, data + count, fill -= count); 372 memmove (data, data + count, fill -= count);
203} 373}
204 374
375bool
205bool byte_stream::put (u8 *data, unsigned int datalen) 376byte_stream::put (u8 *data, unsigned int datalen)
206{ 377{
207 if (maxsize - fill < datalen) 378 if (maxsize - fill < datalen)
208 return false; 379 return false;
209 380
210 memcpy (this->data + fill, data, datalen); fill += datalen; 381 memcpy (this->data + fill, data, datalen); fill += datalen;
211 382
212 return true; 383 return true;
213} 384}
214 385
386bool
215bool byte_stream::put (vpn_packet *pkt) 387byte_stream::put (vpn_packet *pkt)
216{ 388{
217 if (maxsize - fill < pkt->len + 2) 389 if (maxsize - fill < pkt->len + 2)
218 return false; 390 return false;
219 391
220 data [fill++] = pkt->len >> 8; 392 data [fill++] = pkt->len >> 8;
221 data [fill++] = pkt->len; 393 data [fill++] = pkt->len;
222 394
223 memcpy (data + fill, &((*pkt)[0]), pkt->len); fill += pkt->len; 395 memcpy (data + fill, pkt->at (0), pkt->len); fill += pkt->len;
224 396
225 return true; 397 return true;
226} 398}
227 399
228vpn_packet *byte_stream::get () 400vpn_packet *byte_stream::get ()
229{ 401{
402 unsigned int len;
403
404 for (;;)
405 {
230 int len = (data [0] << 8) | data [1]; 406 len = (data [0] << 8) | data [1];
231 407
232 if (len > MAXSIZE && fill >= 2) 408 if (len <= MAXSIZE || fill < 2)
233 abort (); // TODO handle this gracefully, connection reset 409 break;
234 410
411 // TODO: handle this better than skipping, e.g. by reset
412 slog (L_DEBUG, _("DNS: corrupted packet stream skipping a byte..."));
413 remove (1);
414 }
415
235 if (fill < len + 2) 416 if (fill < len + 2)
236 return 0; 417 return 0;
237 418
238 vpn_packet *pkt = new vpn_packet; 419 vpn_packet *pkt = new vpn_packet;
239 420
240 pkt->len = len; 421 pkt->len = len;
241 memcpy (&((*pkt)[0]), data + 2, len); 422 memcpy (pkt->at (0), data + 2, len);
242 remove (len + 2); 423 remove (len + 2);
243 424
244 return pkt; 425 return pkt;
245} 426}
246 427
247///////////////////////////////////////////////////////////////////////////// 428/////////////////////////////////////////////////////////////////////////////
248 429
249#define FLAG_QUERY ( 0 << 15) 430#define FLAG_QUERY ( 0 << 15)
250#define FLAG_RESPONSE ( 1 << 15) 431#define FLAG_RESPONSE ( 1 << 15)
251#define FLAG_OP_MASK (15 << 14) 432#define FLAG_OP_MASK (15 << 11)
252#define FLAG_OP_QUERY ( 0 << 11) 433#define FLAG_OP_QUERY ( 0 << 11)
253#define FLAG_AA ( 1 << 10) 434#define FLAG_AA ( 1 << 10)
254#define FLAG_TC ( 1 << 9) 435#define FLAG_TC ( 1 << 9)
255#define FLAG_RD ( 1 << 8) 436#define FLAG_RD ( 1 << 8)
256#define FLAG_RA ( 1 << 7) 437#define FLAG_RA ( 1 << 7)
… …
263#define FLAG_RCODE_REFUSED ( 5 << 0) 444#define FLAG_RCODE_REFUSED ( 5 << 0)
264 445
265#define DEFAULT_CLIENT_FLAGS (FLAG_QUERY | FLAG_OP_QUERY | FLAG_RD) 446#define DEFAULT_CLIENT_FLAGS (FLAG_QUERY | FLAG_OP_QUERY | FLAG_RD)
266#define DEFAULT_SERVER_FLAGS (FLAG_RESPONSE | FLAG_OP_QUERY | FLAG_AA | FLAG_RD | FLAG_RA) 447#define DEFAULT_SERVER_FLAGS (FLAG_RESPONSE | FLAG_OP_QUERY | FLAG_AA | FLAG_RD | FLAG_RA)
267 448
449struct dns_cfg
450{
451 static int next_uid;
452
453 u8 chksum;
454 u8 rrtype;
455 u16 uid; // to make request unique
456
457 u8 version;
458 u8 flags;
459 u16 max_size;
460
461 u8 id1, id2, id3, id4;
462
463 u16 client;
464 u8 def_ttl;
465 u8 r0;
466
467 u8 syn_cdc; // cdc en/decoder for syn (A?) requests
468 u8 hdr_cdc; // cdc en/decoder for regular request headers
469 u8 req_cdc; // cdc en/decoder for regular (ANY?) request data
470 u8 rep_cdc; // cdc en/decoder for regular (TXT) replies, 0 == 8 bit encoding
471
472 u8 r1, r2, r3, r4;
473
474 void reset (int clientid);
475 bool valid ();
476 u8 get_chksum ();
477};
478
479int dns_cfg::next_uid;
480
481void
482dns_cfg::reset (int clientid)
483{
484 // this ID must result in some mixed-case characters in cdc26-encoding
485 id1 = 'G';
486 id2 = 'V';
487 id3 = 'P';
488 id4 = 'E';
489
490 version = 2;
491
492 rrtype = RR_TYPE_TXT;
493 flags = 0;
494 def_ttl = 0;
495 syn_cdc = 26;
496 hdr_cdc = 36;
497 req_cdc = conf.dns_case_preserving ? 62 : 36;
498 rep_cdc = 0;
499 max_size = htons (MAX_PKT_SIZE);
500 client = htons (clientid);
501 uid = ++next_uid;
502
503 r0 = r1 = r2 = r3 = r4 = 0;
504
505 chksum = get_chksum ();
506}
507
508// simple but not trivial chksum
509u8
510dns_cfg::get_chksum ()
511{
512 unsigned int sum = 0xff00; // only 16 bits required
513
514 u8 old_chksum = chksum;
515 chksum = 0;
516
517 for (unsigned int i = 0; i < sizeof (*this); ++i)
518 sum += ((u8 *)this)[i] * (i + 1);
519
520 chksum = old_chksum;
521
522 return sum + (sum >> 8);
523}
524
525bool
526dns_cfg::valid ()
527{
528 // although the protocol itself allows for some configurability,
529 // only the following encoding/decoding settings are implemented.
530 return id1 == 'G'
531 && id2 == 'V'
532 && id3 == 'P'
533 && id4 == 'E'
534 && version == 2
535 && syn_cdc == 26
536 && hdr_cdc == 36
537 && (req_cdc == 36 || req_cdc == 62)
538 && rep_cdc == 0
539 && chksum == get_chksum ();
540}
541
268struct dns_packet : net_packet 542struct dns_packet : net_packet
269{ 543{
270 u16 id; 544 u16 id;
271 u16 flags; // QR:1 Opcode:4 AA:1 TC:1 RD:1 RA:1 Z:3 RCODE:4 545 u16 flags; // QR:1 Opcode:4 AA:1 TC:1 RD:1 RA:1 Z:3 RCODE:4
272 u16 qdcount, ancount, nscount, arcount; 546 u16 qdcount, ancount, nscount, arcount;
273 547
274 u8 data[MAXSIZE - 6 * 2]; 548 u8 data [MAXSIZE - 6 * 2];
275 549
276 int decode_label (char *data, int size, int &offs); 550 int decode_label (char *data, int size, int &offs);
277}; 551};
278 552
553int
279int dns_packet::decode_label (char *data, int size, int &offs) 554dns_packet::decode_label (char *data, int size, int &offs)
280{ 555{
281 char *orig = data; 556 char *orig = data;
282 557
283 memset (data, 0, size); 558 memset (data, 0, size);
284 559
… …
310 return data - orig; 585 return data - orig;
311} 586}
312 587
313///////////////////////////////////////////////////////////////////////////// 588/////////////////////////////////////////////////////////////////////////////
314 589
315struct dns_req 590static
591u16 next_id ()
316{ 592{
317 dns_packet *pkt;
318 tstamp next;
319 int retry;
320 connection *conn;
321 int seqno;
322
323 dns_req (connection *c);
324 void gen_stream_req (int seqno, byte_stream *stream);
325};
326
327static u16 dns_id = 12098; // TODO: should be per-vpn 593 static u16 dns_id = 0; // TODO: should be per-vpn
328 594
329static u16 next_id () 595 if (!dns_id)
330{ 596 dns_id = time (0);
597
331 // the simplest lsfr with periodicity 65535 i could find 598 // the simplest lsfr with periodicity 65535 i could find
332 dns_id = (dns_id << 1) 599 dns_id = (dns_id << 1)
333 | (((dns_id >> 1) 600 | (((dns_id >> 1)
334 ^ (dns_id >> 2) 601 ^ (dns_id >> 2)
335 ^ (dns_id >> 4) 602 ^ (dns_id >> 4)
336 ^ (dns_id >> 15)) & 1); 603 ^ (dns_id >> 15)) & 1);
337 604
338 return dns_id; 605 return dns_id;
339} 606}
340 607
341dns_req::dns_req (connection *c) 608struct dns_rcv;
342: conn (c) 609struct dns_snd;
610
611struct dns_connection
343{ 612{
344 next = 0; 613 connection *c;
614 struct vpn *vpn;
615
616 dns_cfg cfg;
617
618 bool established;
619 const basecoder *cdc;
620
621 tstamp last_received;
622 tstamp last_sent;
623 double min_latency;
624 double poll_interval, send_interval;
625
626 vector<dns_rcv *> rcvpq;
627
628 byte_stream rcvdq; int rcvseq; int repseq;
629 byte_stream snddq; int sndseq;
630
631 inline void time_cb (ev::timer &w, int revents); ev::timer tw;
632 void receive_rep (dns_rcv *r);
633
634 void reset (); // quite like tcp RST
635 void set_cfg (); // to be called after any cfg changes
636
637 dns_connection (connection *c);
638 ~dns_connection ();
639};
640
641struct dns_snd
642{
643 dns_packet *pkt;
644 tstamp timeout, sent;
645 int retry;
646 struct dns_connection *dns;
647 int seqno;
648 bool stdhdr;
649
650 void gen_stream_req (int seqno, byte_stream &stream);
651 void gen_syn_req ();
652
653 dns_snd (dns_connection *dns);
654 ~dns_snd ();
655};
656
657dns_snd::dns_snd (dns_connection *dns)
658: dns (dns)
659{
660 timeout = 0;
345 retry = 0; 661 retry = 0;
662 seqno = 0;
663 sent = ev_now ();
664 stdhdr = false;
346 665
347 pkt = new dns_packet; 666 pkt = new dns_packet;
348 667
349 pkt->id = next_id (); 668 pkt->id = next_id ();
350} 669}
351 670
671dns_snd::~dns_snd ()
672{
673 delete pkt;
674}
675
676static void
677append_domain (dns_packet &pkt, int &offs, const char *domain)
678{
679 // add tunnel domain
680 for (;;)
681 {
682 const char *end = strchr (domain, '.');
683
684 if (!end)
685 end = domain + strlen (domain);
686
687 int len = end - domain;
688
689 pkt [offs++] = len;
690 memcpy (pkt.at (offs), domain, len);
691 offs += len;
692
693 if (!*end)
694 break;
695
696 domain = end + 1;
697 }
698}
699
700void
352void dns_req::gen_stream_req (int seqno, byte_stream *stream) 701dns_snd::gen_stream_req (int seqno, byte_stream &stream)
353{ 702{
703 stdhdr = true;
354 this->seqno = seqno; 704 this->seqno = seqno;
705
706 timeout = ev_now () + INITIAL_TIMEOUT;
355 707
356 pkt->flags = htons (DEFAULT_CLIENT_FLAGS); 708 pkt->flags = htons (DEFAULT_CLIENT_FLAGS);
357 pkt->qdcount = htons (1); 709 pkt->qdcount = htons (1);
358 710
359 int offs = 6*2; 711 int offs = 6*2;
360 int dlen = MAX_DOMAIN_SIZE - strlen (THISNODE->domain) - 2; 712 int dlen = MAX_DOMAIN_SIZE - (strlen (dns->c->conf->domain) + 2);
361 // MAX_DOMAIN_SIZE is technically 255, but bind doesn't compress responses well, 713 // MAX_DOMAIN_SIZE is technically 255, but bind doesn't compress responses well,
362 // so we need to have space for 2*MAX_DOMAIN_SIZE + header + extra 714 // so we need to have space for 2*MAX_DOMAIN_SIZE + header + extra
363 715
364 u8 data[256]; //TODO
365
366 data[0] = THISNODE->id; //TODO
367 data[1] = seqno >> 7; //TODO
368 data[2] = seqno << 1; //TODO
369
370 int datalen = dns64::decode_len (dlen - (dlen + MAX_LBL_SIZE - 1) / MAX_LBL_SIZE) - 3;
371
372 if (datalen > stream->size ())
373 datalen = stream->size ();
374
375 char enc[256], *encp = enc; 716 char enc[256], *encp = enc;
376 717 encode_header (enc, THISNODE->id, seqno);
377 memcpy (data + 3, stream->begin (), datalen); 718
378 int enclen = dns64::encode (enc, data, datalen + 3); 719 int datalen = dns->cdc->decode_len (dlen - (dlen + MAX_LBL_SIZE - 1) / MAX_LBL_SIZE - HDRSIZE);
720
721 if (datalen > stream.size ())
722 datalen = stream.size ();
723
724 int enclen = dns->cdc->encode (enc + HDRSIZE, stream.begin (), datalen) + HDRSIZE;
379 stream->remove (datalen); 725 stream.remove (datalen);
380 726
381 while (enclen) 727 while (enclen)
382 { 728 {
383 int lbllen = enclen < MAX_LBL_SIZE ? enclen : MAX_LBL_SIZE; 729 int lbllen = enclen < MAX_LBL_SIZE ? enclen : MAX_LBL_SIZE;
384 730
… …
389 encp += lbllen; 735 encp += lbllen;
390 736
391 enclen -= lbllen; 737 enclen -= lbllen;
392 } 738 }
393 739
394 const char *suffix = THISNODE->domain; 740 append_domain (*pkt, offs, dns->c->conf->domain);
395
396 // add tunnel domain
397 for (;;)
398 {
399 const char *end = strchr (suffix, '.');
400
401 if (!end)
402 end = suffix + strlen (suffix);
403
404 int len = end - suffix;
405
406 (*pkt)[offs++] = len;
407 memcpy (&((*pkt)[offs]), suffix, len);
408 offs += len;
409
410 if (!*end)
411 break;
412
413 suffix = end + 1;
414 }
415 741
416 (*pkt)[offs++] = 0; 742 (*pkt)[offs++] = 0;
417 (*pkt)[offs++] = RR_TYPE_ANY >> 8; (*pkt)[offs++] = RR_TYPE_ANY; 743 (*pkt)[offs++] = RR_TYPE_ANY >> 8; (*pkt)[offs++] = RR_TYPE_ANY;
744 (*pkt)[offs++] = RR_CLASS_IN >> 8; (*pkt)[offs++] = RR_CLASS_IN;
745
746 pkt->len = offs;
747}
748
749void
750dns_snd::gen_syn_req ()
751{
752 timeout = ev_now () + INITIAL_SYN_TIMEOUT;
753
754 pkt->flags = htons (DEFAULT_CLIENT_FLAGS);
755 pkt->qdcount = htons (1);
756
757 int offs = 6 * 2;
758
759 int elen = cdc26.encode ((char *)pkt->at (offs + 1), (u8 *)&dns->cfg, sizeof (dns_cfg));
760
761 assert (elen <= MAX_LBL_SIZE);
762
763 (*pkt)[offs] = elen;
764 offs += elen + 1;
765 append_domain (*pkt, offs, dns->c->conf->domain);
766
767 (*pkt)[offs++] = 0;
768 (*pkt)[offs++] = RR_TYPE_A >> 8; (*pkt)[offs++] = RR_TYPE_A;
418 (*pkt)[offs++] = RR_CLASS_IN >> 8; (*pkt)[offs++] = RR_CLASS_IN; 769 (*pkt)[offs++] = RR_CLASS_IN >> 8; (*pkt)[offs++] = RR_CLASS_IN;
419 770
420 pkt->len = offs; 771 pkt->len = offs;
421} 772}
422 773
… …
441{ 792{
442 delete pkt; 793 delete pkt;
443} 794}
444 795
445///////////////////////////////////////////////////////////////////////////// 796/////////////////////////////////////////////////////////////////////////////
446 797
447struct dns_cfg 798dns_connection::dns_connection (connection *c)
799: c (c)
800, rcvdq (MAX_BACKLOG * 2)
801, snddq (MAX_BACKLOG)
448{ 802{
449 u8 id1, id2, id3; 803 tw.set<dns_connection, &dns_connection::time_cb> (this);
450 u8 def_ttl;
451 u8 unused1;
452 u16 max_size;
453 u8 flags1, flags2;
454};
455 804
805 vpn = c->vpn;
806
807 reset ();
808}
809
810dns_connection::~dns_connection ()
811{
812 reset ();
813}
814
815void
816dns_connection::reset ()
817{
818 while (!rcvpq.empty ())
819 {
820 delete rcvpq.back ();
821 rcvpq.pop_back ();
822 }
823
824 for (int i = vpn->dns_sndpq.size (); i--; )
825 if (vpn->dns_sndpq [i]->dns == this)
826 {
827 vpn->dns_sndpq [i] = vpn->dns_sndpq.back ();
828 vpn->dns_sndpq.pop_back ();
829 }
830
831 established = false;
832
833 rcvseq = repseq = sndseq = 0;
834
835 last_sent = 0;
836 poll_interval = 0.5; // starting here
837 send_interval = 0.5; // starting rate
838 min_latency = INITIAL_TIMEOUT;
839}
840
841void
842dns_connection::set_cfg ()
843{
844 cdc = cfg.req_cdc == 36 ? &cdc36 : &cdc62;
845}
846
847void
456void connection::dnsv4_receive_rep (struct dns_rcv *r) 848dns_connection::receive_rep (dns_rcv *r)
457{ 849{
850 if (r->datalen)
851 poll_interval = max (poll_interval * (1. / 1.2), MIN_POLL_INTERVAL);
852 else
853 poll_interval = min (poll_interval * 1.1, MAX_POLL_INTERVAL);
854
458 dns_rcvpq.push_back (r); 855 rcvpq.push_back (r);
459 856
460 redo: 857 redo:
461 858
859 // find next packet
462 for (vector<dns_rcv *>::iterator i = dns_rcvpq.begin (); 860 for (vector<dns_rcv *>::iterator i = rcvpq.end (); i-- != rcvpq.begin (); )
463 i != dns_rcvpq.end ();
464 ++i)
465 if (dns_rcvseq == (*i)->seqno) 861 if (SEQNO_EQ (rcvseq, (*i)->seqno))
466 { 862 {
863 //printf ("seqno eq %x %x\n", rcvseq, (*i)->seqno);//D
864 // enter the packet into our input stream
467 dns_rcv *r = *i; 865 r = *i;
468 866
867 // remove the oldest packet, look forward, as it's oldest first
868 for (vector<dns_rcv *>::iterator j = rcvpq.begin (); j != rcvpq.end (); ++j)
869 if (SEQNO_EQ ((*j)->seqno, rcvseq - MAX_WINDOW))
870 {
871 //printf ("seqno RR %x %x\n", (*j)->seqno, rcvseq - MAX_WINDOW);//D
872 delete *j;
873 rcvpq.erase (j);
874 break;
875 }
876
469 dns_rcvseq = (dns_rcvseq + 1) & SEQNO_MASK; 877 rcvseq = (rcvseq + 1) & SEQNO_MASK;
470 878
471 if (!dns_snddq && !dns_rcvdq) 879 if (!rcvdq.put (r->data, r->datalen))
472 { 880 {
473 dns_rcvdq = new byte_stream (MAX_BACKLOG * 2); 881 // MUST never overflow, can be caused by data corruption, TODO
474 dns_snddq = new byte_stream (MAX_BACKLOG); 882 slog (L_CRIT, "DNS: !rcvdq.put (r->data, r->datalen)");
475 883 reset ();
476 dns_si.set (::conf.dns_forw_host, ::conf.dns_forw_port, PROT_DNSv4); 884 return;
477 } 885 }
478 886
479 if (!dns_rcvdq->put (r->data, r->datalen))
480 abort (); // MUST never overflow, can be caused by data corruption, TODO
481
482 while (vpn_packet *pkt = dns_rcvdq->get ()) 887 while (vpn_packet *pkt = rcvdq.get ())
483 { 888 {
484 sockinfo si; 889 sockinfo si;
485 si.host = 0; si.port = 0; si.prot = PROT_DNSv4; 890 si.host = htonl (c->conf->id); si.port = 0; si.prot = PROT_DNSv4;
486 891
487 vpn->recv_vpn_packet (pkt, si); 892 vpn->recv_vpn_packet (pkt, si);
893 delete pkt;
488 } 894 }
489 } 895
490 else if ((u32)(*i)->seqno - (u32)dns_rcvseq + MAX_WINDOW > MAX_WINDOW * 2) 896 // check for further packets
491 {
492 //D
493 //abort();
494 printf ("%d erasing %d (%d)\n", THISNODE->id, (u32)(*i)->seqno, dns_rcvseq);
495 dns_rcvpq.erase (i);
496 goto redo; 897 goto redo;
497 } 898 }
498} 899}
499 900
500dns_packet * 901void
501vpn::dnsv4_server (dns_packet *pkt) 902vpn::dnsv4_server (dns_packet &pkt)
502{ 903{
503 u16 flags = ntohs (pkt->flags); 904 u16 flags = ntohs (pkt.flags);
504 905
505 //memcpy (&((*rep)[0]), &((*pkt)[0]), pkt->len);
506 int offs = 6 * 2; // skip header 906 int offs = 6 * 2; // skip header
507 907
508 pkt->flags = htons (DEFAULT_SERVER_FLAGS | FLAG_RCODE_FORMERR); 908 pkt.flags = htons (DEFAULT_SERVER_FLAGS | FLAG_RCODE_FORMERR);
509 909
510 if (!(flags & (FLAG_RESPONSE | FLAG_OP_MASK | FLAG_TC)) 910 if (0 == (flags & (FLAG_RESPONSE | FLAG_OP_MASK))
511 && pkt->qdcount == htons (1)) 911 && pkt.qdcount == htons (1))
512 { 912 {
513 char qname[MAXSIZE]; 913 char qname [MAXSIZE];
514 int qlen = pkt->decode_label ((char *)qname, MAXSIZE - offs, offs); 914 int qlen = pkt.decode_label ((char *)qname, MAXSIZE - offs, offs);
515 915
516 u16 qtype = (*pkt) [offs++] << 8; qtype |= (*pkt) [offs++]; 916 u16 qtype = pkt [offs++] << 8; qtype |= pkt [offs++];
517 u16 qclass = (*pkt) [offs++] << 8; qclass |= (*pkt) [offs++]; 917 u16 qclass = pkt [offs++] << 8; qclass |= pkt [offs++];
518 918
519 pkt->qdcount = htons (1); 919 pkt.qdcount = htons (1);
520 pkt->ancount = 0; 920 pkt.ancount = 0;
521 pkt->nscount = 0; // should be self, as other nameservers reply like this 921 pkt.nscount = 0; // should be self, as other nameservers reply like this
522 pkt->arcount = 0; // a record for self, as other nameservers reply like this 922 pkt.arcount = 0; // a record for self, as other nameservers reply like this
523 923
524 pkt->flags = htons (DEFAULT_SERVER_FLAGS | FLAG_RCODE_NXDOMAIN); 924 pkt.flags = htons (DEFAULT_SERVER_FLAGS | FLAG_RCODE_SERVFAIL);
525 925
526 int dlen = strlen (THISNODE->domain); 926 int dlen = strlen (THISNODE->domain);
527 927
528 if (qclass == RR_CLASS_IN 928 if (qclass == RR_CLASS_IN
529 && (qtype == RR_TYPE_ANY || qtype == RR_TYPE_TXT)
530 && qlen > dlen + 1 929 && qlen > dlen + 1
531 && !memcmp (qname + qlen - dlen - 1, THISNODE->domain, dlen)) 930 && !memcmp (qname + qlen - (dlen + 1), THISNODE->domain, dlen))
532 { 931 {
533 // correct class, domain: parse 932 // now generate reply
534 u8 data[MAXSIZE]; 933 pkt.ancount = htons (1); // one answer RR
535 int datalen = dns64::decode (data, qname, qlen - dlen - 1); 934 pkt.flags = htons (DEFAULT_SERVER_FLAGS | FLAG_RCODE_OK);
536 935
537 int client = data[0]; 936 if ((qtype == RR_TYPE_ANY
538 int seqno = ((data[1] << 7) | (data[2] >> 1)) & SEQNO_MASK; 937 || qtype == RR_TYPE_TXT
539 938 || qtype == RR_TYPE_NULL)
540 if (0 < client && client <= conns.size ()) 939 && qlen > dlen + 1 + HDRSIZE)
541 { 940 {
941 // correct class, domain: parse
942 int client, seqno;
943 decode_header (qname, client, seqno);
944
945 if (0 < client && client <= conns.size ())
946 {
542 connection *c = conns [client - 1]; 947 connection *c = conns [client - 1];
948 dns_connection *dns = c->dns;
949 dns_rcv *rcv;
543 950
544 redo: 951 if (dns)
545
546 for (vector<dns_rcv *>::iterator i = c->dns_rcvpq.begin ();
547 i != c->dns_rcvpq.end ();
548 ++i) 952 {
953 u8 data[MAXSIZE];
954 int datalen = dns->cdc->decode (data, qname + HDRSIZE, qlen - (dlen + 1 + HDRSIZE));
955
956 for (vector<dns_rcv *>::iterator i = dns->rcvpq.end (); i-- != dns->rcvpq.begin (); )
549 if ((*i)->seqno == seqno) 957 if (SEQNO_EQ ((*i)->seqno, seqno))
958 {
959 // already seen that request: simply reply with the cached reply
960 dns_rcv *r = *i;
961
962 slog (L_DEBUG, "DNS: duplicate packet received ID %d, SEQ %d", htons (r->pkt->id), seqno);
963
964 // refresh header & id, as the retry count could have changed
965 memcpy (r->pkt->at (6 * 2 + 1), pkt.at (6 * 2 + 1), HDRSIZE);
966 r->pkt->id = pkt.id;
967
968 memcpy (pkt.at (0), r->pkt->at (0), offs = r->pkt->len);
969
970 goto duplicate_request;
971 }
972
973 // new packet, queue
974 rcv = new dns_rcv (seqno, data, datalen);
975 dns->receive_rep (rcv);
976 }
977
550 { 978 {
551 // already seen that request: simply reply with the cached reply 979 pkt [offs++] = 0xc0; pkt [offs++] = 6 * 2; // refer to name in query section
552 dns_rcv *r = *i;
553 980
554 printf ("DUPLICATE %d\n", htons (r->pkt->id));//D 981 int rtype = dns ? dns->cfg.rrtype : RR_TYPE_A;
982 pkt [offs++] = rtype >> 8; pkt [offs++] = rtype; // type
983 pkt [offs++] = RR_CLASS_IN >> 8; pkt [offs++] = RR_CLASS_IN; // class
984 pkt [offs++] = 0; pkt [offs++] = 0;
985 pkt [offs++] = 0; pkt [offs++] = dns ? dns->cfg.def_ttl : 0; // TTL
555 986
987 int rdlen_offs = offs += 2;
988
989 if (dns)
990 {
991 int dlen = ntohs (dns->cfg.max_size) - offs;
992
993 // bind doesn't compress well, so reduce further by one label length
994 dlen -= qlen;
995
996 // only put data into in-order sequence packets, if
997 // we receive out-of-order packets we generate empty
998 // replies
999 //printf ("%d - %d & %x (=%d) < %d\n", seqno, dns->repseq, SEQNO_MASK, (seqno - dns->repseq) & SEQNO_MASK, MAX_WINDOW);//D
1000 if (((seqno - dns->repseq) & SEQNO_MASK) <= MAX_WINDOW)
1001 {
1002 dns->repseq = seqno;
1003
1004 while (dlen > 1 && !dns->snddq.empty ())
1005 {
1006 int txtlen = dlen <= 255 ? dlen - 1 : 255;
1007
1008 if (txtlen > dns->snddq.size ())
1009 txtlen = dns->snddq.size ();
1010
1011 pkt[offs++] = txtlen;
1012 memcpy (pkt.at (offs), dns->snddq.begin (), txtlen);
1013 offs += txtlen;
1014 dns->snddq.remove (txtlen);
1015
1016 dlen -= txtlen + 1;
1017 }
1018 }
1019
1020 // avoid completely empty TXT rdata
1021 if (offs == rdlen_offs)
1022 pkt[offs++] = 0;
1023
1024 slog (L_NOISE, "DNS: snddq %d", dns->snddq.size ());
1025 }
1026 else
1027 {
1028 // send RST
1029 pkt [offs++] = CMD_IP_1; pkt [offs++] = CMD_IP_2; pkt [offs++] = CMD_IP_3;
1030 pkt [offs++] = CMD_IP_RST;
1031 }
1032
1033 int rdlen = offs - rdlen_offs;
1034
1035 pkt [rdlen_offs - 2] = rdlen >> 8;
1036 pkt [rdlen_offs - 1] = rdlen;
1037
1038 if (dns)
1039 {
1040 // now update dns_rcv copy
556 offs = r->pkt->len; 1041 rcv->pkt->len = offs;
557 memcpy (pkt->at (0), r->pkt->at (0), offs); 1042 memcpy (rcv->pkt->at (0), pkt.at (0), offs);
558 goto duplicate_request; 1043 }
559 } 1044 }
560 1045
561 // new packet, queue 1046 duplicate_request: ;
562 dns_rcv *rcv = new dns_rcv (seqno, data + 3, datalen - 3); 1047 }
563 c->dnsv4_receive_rep (rcv); 1048 else
564
565 // now generate reply
566 pkt->ancount = htons (1); // one answer RR
567 pkt->flags = htons (DEFAULT_SERVER_FLAGS | FLAG_RCODE_OK); 1049 pkt.flags = htons (DEFAULT_SERVER_FLAGS | FLAG_RCODE_FORMERR);
1050 }
1051 else if (qtype == RR_TYPE_A
1052 && qlen > dlen + 1 + cdc26.encode_len (sizeof (dns_cfg)))
1053 {
1054 dns_cfg cfg;
1055 cdc26.decode ((u8 *)&cfg, qname, cdc26.encode_len (sizeof (dns_cfg)));
1056 int client = ntohs (cfg.client);
568 1057
569 (*pkt) [offs++] = 0xc0;
570 (*pkt) [offs++] = 6 * 2; // same as in query section 1058 pkt [offs++] = 0xc0; pkt [offs++] = 6 * 2; // refer to name in query section
571 1059
572 (*pkt) [offs++] = RR_TYPE_TXT >> 8; (*pkt) [offs++] = RR_TYPE_TXT; 1060 pkt [offs++] = RR_TYPE_A >> 8; pkt [offs++] = RR_TYPE_A; // type
573 (*pkt) [offs++] = RR_CLASS_IN >> 8; (*pkt) [offs++] = RR_CLASS_IN; 1061 pkt [offs++] = RR_CLASS_IN >> 8; pkt [offs++] = RR_CLASS_IN; // class
574
575 (*pkt) [offs++] = 0; (*pkt) [offs++] = 0; 1062 pkt [offs++] = 0; pkt [offs++] = 0;
576 (*pkt) [offs++] = 0; (*pkt) [offs++] = 0; // TTL 1063 pkt [offs++] = 0; pkt [offs++] = cfg.def_ttl; // TTL
1064 pkt [offs++] = 0; pkt [offs++] = 4; // rdlength
577 1065
578 int dlen = MAX_PKT_SIZE - offs - 2; 1066 pkt [offs++] = CMD_IP_1; pkt [offs++] = CMD_IP_2; pkt [offs++] = CMD_IP_3;
1067 pkt [offs++] = CMD_IP_REJ;
579 1068
580 // bind doesn't compress well, so reduce further by one label length 1069 if (0 < client && client <= conns.size ())
581 dlen -= qlen;
582
583 int rdlen_offs = offs += 2;
584
585 while (c->dns_snddq
586 && !c->dns_snddq->empty ()
587 && dlen > 1)
588 { 1070 {
589 int txtlen = dlen <= 255 ? dlen - 1 : 255; 1071 connection *c = conns [client - 1];
590 1072
591 if (txtlen > c->dns_snddq->size ()) 1073 if (cfg.valid ())
1074 {
1075 slog (L_INFO, _("DNS: client %d connects (version %d, req_cdc %d)"), client, cfg.version, cfg.req_cdc);
1076
1077 // check for any encoding mismatches - hints at a case problem
1078 char qname2 [MAX_ENC_LEN];
1079 cdc26.encode (qname2, (u8 *)&cfg, sizeof (dns_cfg));
1080
1081 delete c->dns;
1082
1083 pkt [offs - 1] = memcmp (qname, qname2, cdc26.encode_len (sizeof (dns_cfg)))
1084 ? CMD_IP_CSE : CMD_IP_SYN;
1085
1086 c->dns = new dns_connection (c);
1087 c->dns->cfg = cfg;
592 txtlen = c->dns_snddq->size (); 1088 c->dns->set_cfg ();
593 1089 }
594 (*pkt)[offs++] = txtlen;
595 memcpy (pkt->at (offs), c->dns_snddq->begin (), txtlen);
596 offs += txtlen;
597 c->dns_snddq->remove (txtlen);
598
599 dlen -= txtlen + 1;
600 } 1090 }
601
602 // avoid empty TXT rdata
603 if (offs == rdlen_offs)
604 (*pkt)[offs++] = 0;
605
606 int rdlen = offs - rdlen_offs;
607
608 (*pkt) [rdlen_offs - 2] = rdlen >> 8;
609 (*pkt) [rdlen_offs - 1] = rdlen;
610
611 // now update dns_rcv copy
612 rcv->pkt->len = offs;
613 memcpy (rcv->pkt->at (0), pkt->at (0), offs);
614
615 duplicate_request: ;
616 } 1091 }
617 else
618 pkt->flags = htons (DEFAULT_SERVER_FLAGS | FLAG_RCODE_FORMERR);
619 } 1092 }
620 1093
621 pkt->len = offs; 1094 pkt.len = offs;
622 } 1095 }
623
624 return pkt;
625} 1096}
626 1097
627void 1098void
628vpn::dnsv4_client (dns_packet *pkt) 1099vpn::dnsv4_client (dns_packet &pkt)
629{ 1100{
630 u16 flags = ntohs (pkt->flags); 1101 u16 flags = ntohs (pkt.flags);
631 int offs = 6 * 2; // skip header 1102 int offs = 6 * 2; // skip header
632 1103
633 pkt->qdcount = ntohs (pkt->qdcount); 1104 pkt.qdcount = ntohs (pkt.qdcount);
634 pkt->ancount = ntohs (pkt->ancount); 1105 pkt.ancount = ntohs (pkt.ancount);
635 1106
636 // go through our request list and find the corresponding request 1107 // go through our request list and find the corresponding request
637 for (vector<dns_req *>::iterator i = dns_sndpq.begin (); 1108 for (vector<dns_snd *>::iterator i = dns_sndpq.begin ();
638 i != dns_sndpq.end (); 1109 i != dns_sndpq.end ();
639 ++i) 1110 ++i)
640 if ((*i)->pkt->id == pkt->id) 1111 if ((*i)->pkt->id == pkt.id)
641 { 1112 {
1113 dns_connection *dns = (*i)->dns;
642 connection *c = (*i)->conn; 1114 connection *c = dns->c;
643 int seqno = (*i)->seqno; 1115 int seqno = (*i)->seqno;
644 u8 data[MAXSIZE], *datap = data; 1116 u8 data[MAXSIZE], *datap = data;
1117 //printf ("rcv pkt %x\n", seqno);//D
1118
1119 if ((*i)->retry)
1120 {
1121 dns->send_interval *= 1.01;
1122 if (dns->send_interval > MAX_SEND_INTERVAL)
1123 dns->send_interval = MAX_SEND_INTERVAL;
1124 }
1125 else
1126 {
1127#if 0
1128 dns->send_interval *= 0.999;
1129#endif
1130 // the latency surely puts an upper bound on
1131 // the minimum send interval
1132 double latency = ev_now () - (*i)->sent;
1133
1134 if (latency < dns->min_latency)
1135 dns->min_latency = latency;
1136
1137 if (dns->send_interval > dns->min_latency * conf.dns_overlap_factor)
1138 dns->send_interval = dns->min_latency * conf.dns_overlap_factor;
1139
1140 if (dns->send_interval < conf.dns_send_interval)
1141 dns->send_interval = conf.dns_send_interval;
1142 }
645 1143
646 delete *i; 1144 delete *i;
647 dns_sndpq.erase (i); 1145 dns_sndpq.erase (i);
648 1146
649 if (flags & (FLAG_RESPONSE | FLAG_OP_MASK | FLAG_TC)) 1147 if (flags & FLAG_RESPONSE && !(flags & FLAG_OP_MASK))
650 { 1148 {
651 char qname[MAXSIZE]; 1149 char qname[MAXSIZE];
652 1150
653 while (pkt->qdcount-- && offs < MAXSIZE - 4) 1151 while (pkt.qdcount-- && offs < MAXSIZE - 4)
654 { 1152 {
655 int qlen = pkt->decode_label ((char *)qname, MAXSIZE - offs, offs); 1153 int qlen = pkt.decode_label ((char *)qname, MAXSIZE - offs, offs);
656 offs += 4; // skip qtype, qclass 1154 offs += 4; // skip qtype, qclass
657 } 1155 }
658 1156
659 while (pkt->ancount-- && offs < MAXSIZE - 10) 1157 while (pkt.ancount-- && offs < MAXSIZE - 10 && datap)
660 { 1158 {
661 pkt->decode_label ((char *)qname, MAXSIZE - offs, offs); 1159 int qlen = pkt.decode_label ((char *)qname, MAXSIZE - offs, offs);
662 1160
663 u16 qtype = (*pkt) [offs++] << 8; qtype |= (*pkt) [offs++]; 1161 u16 qtype = pkt [offs++] << 8; qtype |= pkt [offs++];
664 u16 qclass = (*pkt) [offs++] << 8; qclass |= (*pkt) [offs++]; 1162 u16 qclass = pkt [offs++] << 8; qclass |= pkt [offs++];
665 u32 ttl = (*pkt) [offs++] << 24; 1163 u32 ttl = pkt [offs++] << 24;
666 ttl |= (*pkt) [offs++] << 16; 1164 ttl |= pkt [offs++] << 16;
667 ttl |= (*pkt) [offs++] << 8; 1165 ttl |= pkt [offs++] << 8;
668 ttl |= (*pkt) [offs++]; 1166 ttl |= pkt [offs++];
669
670 u16 rdlen = (*pkt) [offs++] << 8; rdlen |= (*pkt) [offs++]; 1167 u16 rdlen = pkt [offs++] << 8; rdlen |= pkt [offs++];
671 1168
672 if (rdlen <= MAXSIZE - offs) 1169 if (qtype == RR_TYPE_NULL || qtype == RR_TYPE_TXT || qtype == dns->cfg.rrtype)
673 { 1170 {
674 // decode bytes, finally 1171 if (rdlen <= MAXSIZE - offs)
675
676 while (rdlen)
677 { 1172 {
1173 // decode bytes, finally
1174
1175 while (rdlen)
1176 {
678 int txtlen = (*pkt) [offs++]; 1177 int txtlen = pkt [offs++];
679 1178
680 assert (txtlen + offs < MAXSIZE - 1); 1179 assert (txtlen + offs < MAXSIZE - 1);
681 1180
682 memcpy (datap, pkt->at (offs), txtlen); 1181 memcpy (datap, pkt.at (offs), txtlen);
683 datap += txtlen; offs += txtlen; 1182 datap += txtlen; offs += txtlen;
684 1183
685 rdlen -= txtlen + 1; 1184 rdlen -= txtlen + 1;
1185 }
686 } 1186 }
687
688 } 1187 }
1188 else if (qtype == RR_TYPE_A)
1189 {
1190 u8 ip [4];
689 1191
1192 ip [0] = pkt [offs++];
1193 ip [1] = pkt [offs++];
1194 ip [2] = pkt [offs++];
1195 ip [3] = pkt [offs++];
1196
1197 if (ip [0] == CMD_IP_1
1198 && ip [1] == CMD_IP_2
1199 && ip [2] == CMD_IP_3)
1200 {
1201 slog (L_TRACE, _("DNS: got tunnel meta command %02x"), ip [3]);
1202
1203 if (ip [3] == CMD_IP_RST)
1204 {
1205 slog (L_DEBUG, _("DNS: got tunnel RST request."));
1206
1207 dns->reset ();
1208 return;
1209 }
1210 else if (ip [3] == CMD_IP_SYN)
1211 {
1212 slog (L_DEBUG, _("DNS: got tunnel SYN reply, server likes us."));
1213 dns->established = true;
1214 }
1215 else if (ip [3] == CMD_IP_CSE)
1216 {
1217 if (conf.dns_case_preserving)
1218 {
1219 slog (L_INFO, _("DNS: got tunnel CSE reply, globally downgrading to case-insensitive protocol."));
1220 conf.dns_case_preserving = false;
1221 dns->reset ();
1222 return;
1223 }
1224 else
1225 {
1226 slog (L_DEBUG, _("DNS: got tunnel CSE reply, server likes us."));
1227 dns->established = true;
1228 }
1229 }
1230 else if (ip [3] == CMD_IP_REJ)
1231 {
1232 slog (L_ERR, _("DNS: got tunnel REJ reply, server does not like us."));
1233 dns->tw.start (60.);
1234 }
1235 else
1236 {
1237 slog (L_INFO, _("DNS: got unknown meta command %02x"), ip [3]);
1238 dns->tw.start (60.);
1239 }
1240 }
1241 else
1242 slog (L_INFO, _("DNS: got spurious a record %d.%d.%d.%d"),
1243 ip [0], ip [1], ip [2], ip [3]);
1244
1245 return;
1246 }
1247
1248 int client, rseqno;
1249 decode_header (qname, client, rseqno);
1250
1251 if (client != THISNODE->id)
1252 {
1253 slog (L_INFO, _("DNS: got dns tunnel response with wrong clientid, ignoring"));
1254 datap = 0;
1255 }
1256 else if (rseqno != seqno)
1257 {
1258 slog (L_DEBUG, _("DNS: got dns tunnel response with wrong seqno, badly caching nameserver?"));
1259 datap = 0;
1260 }
690 } 1261 }
691 } 1262 }
692 1263
693 // todo: pkt now used 1264 // todo: pkt now used
1265 if (datap)
694 c->dnsv4_receive_rep (new dns_rcv (seqno, data, datap - data)); 1266 dns->receive_rep (new dns_rcv (seqno, data, datap - data));
695 1267
696 break; 1268 break;
697 } 1269 }
698
699 delete pkt;
700} 1270}
701 1271
702void 1272void
703vpn::dnsv4_ev (io_watcher &w, short revents) 1273vpn::dnsv4_ev (ev::io &w, int revents)
704{ 1274{
705 if (revents & EVENT_READ) 1275 if (revents & EV_READ)
706 { 1276 {
707 dns_packet *pkt = new dns_packet; 1277 dns_packet *pkt = new dns_packet;
708 struct sockaddr_in sa; 1278 struct sockaddr_in sa;
709 socklen_t sa_len = sizeof (sa); 1279 socklen_t sa_len = sizeof (sa);
710 1280
711 pkt->len = recvfrom (w.fd, &((*pkt)[0]), MAXSIZE, 0, (sockaddr *)&sa, &sa_len); 1281 pkt->len = recvfrom (w.fd, pkt->at (0), MAXSIZE, 0, (sockaddr *)&sa, &sa_len);
712 1282
713 if (pkt->len > 0) 1283 if (pkt->len > 0)
714 { 1284 {
715 if (pkt->flags & htons (FLAG_TC)) 1285 if (ntohs (pkt->flags) & FLAG_RESPONSE)
1286 dnsv4_client (*pkt);
1287 else
716 { 1288 {
717 slog (L_WARN, _("DNS request/response truncated, check protocol settings.")); 1289 dnsv4_server (*pkt);
718 //TODO connection reset 1290 sendto (w.fd, pkt->at (0), pkt->len, 0, (sockaddr *)&sa, sa_len);
719 } 1291 }
720 1292
721 if (THISNODE->dns_port) 1293 delete pkt;
722 {
723 pkt = dnsv4_server (pkt);
724 sendto (w.fd, &((*pkt)[0]), pkt->len, 0, (sockaddr *)&sa, sa_len);
725 }
726 else
727 dnsv4_client (pkt);
728 } 1294 }
729 } 1295 }
730} 1296}
731 1297
732bool 1298bool
733connection::send_dnsv4_packet (vpn_packet *pkt, const sockinfo &si, int tos) 1299vpn::send_dnsv4_packet (vpn_packet *pkt, const sockinfo &si, int tos)
734{ 1300{
735 // never initialized 1301 int client = ntohl (si.host);
736 if (!dns_snddq && !dns_rcvdq)
737 {
738 dns_rcvdq = new byte_stream (MAX_BACKLOG * 2);
739 dns_snddq = new byte_stream (MAX_BACKLOG);
740 1302
741 //dns_rcvseq = dns_sndseq = 0; 1303 assert (0 < client && client <= conns.size ());
742 1304
743 dns_si.set (::conf.dns_forw_host, ::conf.dns_forw_port, PROT_DNSv4); 1305 connection *c = conns [client - 1];
744 } 1306
1307 if (!c->dns)
1308 c->dns = new dns_connection (c);
745 1309
746 if (!dns_snddq->put (pkt)) 1310 if (c->dns->snddq.put (pkt))
747 return false; 1311 {
1312 min_it (c->dns->poll_interval, 0.25);
1313 c->dns->tw ();
1314 }
748 1315
749 // start timer if neccessary 1316 // always return true even if the buffer overflows
750 if (!THISNODE->dns_port && !dnsv4_tw.active)
751 dnsv4_cb (dnsv4_tw);
752
753 return true; 1317 return true;
754} 1318}
755 1319
756void 1320void
757connection::dnsv4_cb (time_watcher &w) 1321dns_connection::time_cb (ev::timer &w, int revents)
758{ 1322{
1323 // servers have to be polled
1324 if (THISNODE->dns_port)
1325 return;
1326
759 // check for timeouts and (re)transmit 1327 // check for timeouts and (re)transmit
760 tstamp next = NOW + 60; 1328 tstamp next = 86400 * 365;
761 dns_req *send = 0; 1329 dns_snd *send = 0;
762 1330
763 for (vector<dns_req *>::iterator i = vpn->dns_sndpq.begin (); 1331 for (vector<dns_snd *>::iterator i = vpn->dns_sndpq.begin ();
764 i != vpn->dns_sndpq.end (); 1332 i != vpn->dns_sndpq.end ();
765 ++i) 1333 ++i)
766 { 1334 {
767 dns_req *r = *i; 1335 dns_snd *r = *i;
768 1336
769 if (r->next <= NOW) 1337 if (r->timeout <= ev_now ())
770 { 1338 {
771 if (!send) 1339 if (!send)
772 { 1340 {
773 send = r; 1341 send = r;
774 1342
775 if (r->retry)//D
776 printf ("req %d, retry %d\n", r->pkt->id, r->retry);
777 r->retry++; 1343 r->retry++;
778 r->next = NOW + r->retry; 1344 r->timeout = ev_now () + r->retry * min_latency * conf.dns_timeout_factor;
1345 //printf ("RETRY %x (%d, %f)\n", r->seqno, r->retry, r->timeout - ev_now ());//D
1346
1347 // the following code changes the query section a bit, forcing
1348 // the forwarder to generate a new request
1349 if (r->stdhdr)
1350 encode_header ((char *)r->pkt->at (6 * 2 + 1), THISNODE->id, r->seqno, r->retry);
779 } 1351 }
780 } 1352 }
781 1353 else
782 if (r->next < next) 1354 min_it (next, r->timeout - ev_now ());
783 next = r->next;
784 } 1355 }
785 1356
786 if (!send 1357 if (!send)
787 && vpn->dns_sndpq.size () < MAX_OUTSTANDING)
788 { 1358 {
1359 // generate a new packet, if wise
1360
1361 if (!established)
1362 {
1363 if (vpn->dns_sndpq.empty ())
1364 {
789 send = new dns_req (this); 1365 send = new dns_snd (this);
1366
1367 cfg.reset (THISNODE->id);
1368 set_cfg ();
1369 send->gen_syn_req ();
1370 }
1371 }
1372 else if (vpn->dns_sndpq.size () < conf.dns_max_outstanding
1373 && !SEQNO_EQ (rcvseq, sndseq - (MAX_WINDOW - 1)))
1374 {
1375 if (last_sent + send_interval <= ev_now ())
1376 {
1377 //printf ("sending data request etc.\n"); //D
1378 if (!snddq.empty ())
1379 min_it (next, send_interval);
1380
1381 send = new dns_snd (this);
790 send->gen_stream_req (dns_sndseq, dns_snddq); 1382 send->gen_stream_req (sndseq, snddq);
1383 send->timeout = ev_now () + min_latency * conf.dns_timeout_factor;
1384 //printf ("SEND %x (%f)\n", send->seqno, send->timeout - ev_now (), min_latency, conf.dns_timeout_factor);//D
1385
1386 sndseq = (sndseq + 1) & SEQNO_MASK;
1387 }
1388 else
1389 min_it (next, last_sent + send_interval - ev_now ());
1390 }
1391
1392 if (send)
791 vpn->dns_sndpq.push_back (send); 1393 vpn->dns_sndpq.push_back (send);
792
793 dns_sndseq = (dns_sndseq + 1) & SEQNO_MASK;
794 } 1394 }
795
796 tstamp min_next = NOW + (1. / (tstamp)MAX_RATE);
797 1395
798 if (send) 1396 if (send)
799 { 1397 {
800 dns_packet *pkt = send->pkt; 1398 last_sent = ev_now ();
801 1399 sendto (vpn->dnsv4_fd,
802 next = min_next; 1400 send->pkt->at (0), send->pkt->len, 0,
803 1401 vpn->dns_forwarder.sav4 (), vpn->dns_forwarder.salenv4 ());
804 sendto (vpn->dnsv4_fd, &((*pkt)[0]), pkt->len, 0, dns_si.sav4 (), dns_si.salenv4 ());
805 } 1402 }
806 else if (next < min_next) 1403
807 next = min_next; 1404 min_it (next, last_sent + max (poll_interval, send_interval) - ev_now ());
1405
1406 slog (L_NOISE, "DNS: pi %f si %f N %f (%d:%d %d)",
1407 poll_interval, send_interval, next - ev_now (),
1408 vpn->dns_sndpq.size (), snddq.size (),
1409 rcvpq.size ());
808 1410
809 w.start (next); 1411 w.start (next);
810} 1412}
811 1413
812#endif 1414#endif

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