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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 1.51 by root, Sun Mar 6 19:40:28 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 0.1 // 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 2. // 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 = last_received = 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 {
852 last_received = ev_now ();
853 tw ();
854
855 poll_interval = send_interval;
856 }
857 else
858 {
859 poll_interval *= 1.5;
860
861 if (poll_interval > MAX_POLL_INTERVAL)
862 poll_interval = MAX_POLL_INTERVAL;
863 }
864
458 dns_rcvpq.push_back (r); 865 rcvpq.push_back (r);
459 866
460 redo: 867 redo:
461 868
869 // find next packet
462 for (vector<dns_rcv *>::iterator i = dns_rcvpq.begin (); 870 for (vector<dns_rcv *>::iterator i = rcvpq.end (); i-- != rcvpq.begin (); )
463 i != dns_rcvpq.end ();
464 ++i)
465 if (dns_rcvseq == (*i)->seqno) 871 if (SEQNO_EQ (rcvseq, (*i)->seqno))
466 { 872 {
873 //printf ("seqno eq %x %x\n", rcvseq, (*i)->seqno);//D
874 // enter the packet into our input stream
467 dns_rcv *r = *i; 875 r = *i;
468 876
877 // remove the oldest packet, look forward, as it's oldest first
878 for (vector<dns_rcv *>::iterator j = rcvpq.begin (); j != rcvpq.end (); ++j)
879 if (SEQNO_EQ ((*j)->seqno, rcvseq - MAX_WINDOW))
880 {
881 //printf ("seqno RR %x %x\n", (*j)->seqno, rcvseq - MAX_WINDOW);//D
882 delete *j;
883 rcvpq.erase (j);
884 break;
885 }
886
469 dns_rcvseq = (dns_rcvseq + 1) & SEQNO_MASK; 887 rcvseq = (rcvseq + 1) & SEQNO_MASK;
470 888
471 if (!dns_snddq && !dns_rcvdq) 889 if (!rcvdq.put (r->data, r->datalen))
472 { 890 {
473 dns_rcvdq = new byte_stream (MAX_BACKLOG * 2); 891 // MUST never overflow, can be caused by data corruption, TODO
474 dns_snddq = new byte_stream (MAX_BACKLOG); 892 slog (L_CRIT, "DNS: !rcvdq.put (r->data, r->datalen)");
475 893 reset ();
476 dns_si.set (::conf.dns_forw_host, ::conf.dns_forw_port, PROT_DNSv4); 894 return;
477 } 895 }
478 896
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 ()) 897 while (vpn_packet *pkt = rcvdq.get ())
483 { 898 {
484 sockinfo si; 899 sockinfo si;
485 si.host = 0; si.port = 0; si.prot = PROT_DNSv4; 900 si.host = htonl (c->conf->id); si.port = 0; si.prot = PROT_DNSv4;
486 901
487 vpn->recv_vpn_packet (pkt, si); 902 vpn->recv_vpn_packet (pkt, si);
903 delete pkt;
488 } 904 }
489 } 905
490 else if ((u32)(*i)->seqno - (u32)dns_rcvseq + MAX_WINDOW > MAX_WINDOW * 2) 906 // 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; 907 goto redo;
497 } 908 }
498} 909}
499 910
500dns_packet * 911void
501vpn::dnsv4_server (dns_packet *pkt) 912vpn::dnsv4_server (dns_packet &pkt)
502{ 913{
503 u16 flags = ntohs (pkt->flags); 914 u16 flags = ntohs (pkt.flags);
504 915
505 //memcpy (&((*rep)[0]), &((*pkt)[0]), pkt->len);
506 int offs = 6 * 2; // skip header 916 int offs = 6 * 2; // skip header
507 917
508 pkt->flags = htons (DEFAULT_SERVER_FLAGS | FLAG_RCODE_FORMERR); 918 pkt.flags = htons (DEFAULT_SERVER_FLAGS | FLAG_RCODE_FORMERR);
509 919
510 if (!(flags & (FLAG_RESPONSE | FLAG_OP_MASK | FLAG_TC)) 920 if (0 == (flags & (FLAG_RESPONSE | FLAG_OP_MASK))
511 && pkt->qdcount == htons (1)) 921 && pkt.qdcount == htons (1))
512 { 922 {
513 char qname[MAXSIZE]; 923 char qname [MAXSIZE];
514 int qlen = pkt->decode_label ((char *)qname, MAXSIZE - offs, offs); 924 int qlen = pkt.decode_label ((char *)qname, MAXSIZE - offs, offs);
515 925
516 u16 qtype = (*pkt) [offs++] << 8; qtype |= (*pkt) [offs++]; 926 u16 qtype = pkt [offs++] << 8; qtype |= pkt [offs++];
517 u16 qclass = (*pkt) [offs++] << 8; qclass |= (*pkt) [offs++]; 927 u16 qclass = pkt [offs++] << 8; qclass |= pkt [offs++];
518 928
519 pkt->qdcount = htons (1); 929 pkt.qdcount = htons (1);
520 pkt->ancount = 0; 930 pkt.ancount = 0;
521 pkt->nscount = 0; // should be self, as other nameservers reply like this 931 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 932 pkt.arcount = 0; // a record for self, as other nameservers reply like this
523 933
524 pkt->flags = htons (DEFAULT_SERVER_FLAGS | FLAG_RCODE_NXDOMAIN); 934 pkt.flags = htons (DEFAULT_SERVER_FLAGS | FLAG_RCODE_SERVFAIL);
525 935
526 int dlen = strlen (THISNODE->domain); 936 int dlen = strlen (THISNODE->domain);
527 937
528 if (qclass == RR_CLASS_IN 938 if (qclass == RR_CLASS_IN
529 && (qtype == RR_TYPE_ANY || qtype == RR_TYPE_TXT)
530 && qlen > dlen + 1 939 && qlen > dlen + 1
531 && !memcmp (qname + qlen - dlen - 1, THISNODE->domain, dlen)) 940 && !memcmp (qname + qlen - (dlen + 1), THISNODE->domain, dlen))
532 { 941 {
533 // correct class, domain: parse 942 // now generate reply
534 u8 data[MAXSIZE]; 943 pkt.ancount = htons (1); // one answer RR
535 int datalen = dns64::decode (data, qname, qlen - dlen - 1); 944 pkt.flags = htons (DEFAULT_SERVER_FLAGS | FLAG_RCODE_OK);
536 945
537 int client = data[0]; 946 if ((qtype == RR_TYPE_ANY
538 int seqno = ((data[1] << 7) | (data[2] >> 1)) & SEQNO_MASK; 947 || qtype == RR_TYPE_TXT
539 948 || qtype == RR_TYPE_NULL)
540 if (0 < client && client <= conns.size ()) 949 && qlen > dlen + 1 + HDRSIZE)
541 { 950 {
951 // correct class, domain: parse
952 int client, seqno;
953 decode_header (qname, client, seqno);
954
955 if (0 < client && client <= conns.size ())
956 {
542 connection *c = conns [client - 1]; 957 connection *c = conns [client - 1];
958 dns_connection *dns = c->dns;
959 dns_rcv *rcv;
543 960
544 redo: 961 if (dns)
545
546 for (vector<dns_rcv *>::iterator i = c->dns_rcvpq.begin ();
547 i != c->dns_rcvpq.end ();
548 ++i) 962 {
963 u8 data[MAXSIZE];
964 int datalen = dns->cdc->decode (data, qname + HDRSIZE, qlen - (dlen + 1 + HDRSIZE));
965
966 for (vector<dns_rcv *>::iterator i = dns->rcvpq.end (); i-- != dns->rcvpq.begin (); )
549 if ((*i)->seqno == seqno) 967 if (SEQNO_EQ ((*i)->seqno, seqno))
968 {
969 // already seen that request: simply reply with the cached reply
970 dns_rcv *r = *i;
971
972 slog (L_DEBUG, "DNS: duplicate packet received ID %d, SEQ %d", htons (r->pkt->id), seqno);
973
974 // refresh header & id, as the retry count could have changed
975 memcpy (r->pkt->at (6 * 2 + 1), pkt.at (6 * 2 + 1), HDRSIZE);
976 r->pkt->id = pkt.id;
977
978 memcpy (pkt.at (0), r->pkt->at (0), offs = r->pkt->len);
979
980 goto duplicate_request;
981 }
982
983 // new packet, queue
984 rcv = new dns_rcv (seqno, data, datalen);
985 dns->receive_rep (rcv);
986 }
987
550 { 988 {
551 // already seen that request: simply reply with the cached reply 989 pkt [offs++] = 0xc0; pkt [offs++] = 6 * 2; // refer to name in query section
552 dns_rcv *r = *i;
553 990
554 printf ("DUPLICATE %d\n", htons (r->pkt->id));//D 991 int rtype = dns ? dns->cfg.rrtype : RR_TYPE_A;
992 pkt [offs++] = rtype >> 8; pkt [offs++] = rtype; // type
993 pkt [offs++] = RR_CLASS_IN >> 8; pkt [offs++] = RR_CLASS_IN; // class
994 pkt [offs++] = 0; pkt [offs++] = 0;
995 pkt [offs++] = 0; pkt [offs++] = dns ? dns->cfg.def_ttl : 0; // TTL
555 996
997 int rdlen_offs = offs += 2;
998
999 if (dns)
1000 {
1001 int dlen = ntohs (dns->cfg.max_size) - offs;
1002
1003 // bind doesn't compress well, so reduce further by one label length
1004 dlen -= qlen;
1005
1006 // only put data into in-order sequence packets, if
1007 // we receive out-of-order packets we generate empty
1008 // replies
1009 //printf ("%d - %d & %x (=%d) < %d\n", seqno, dns->repseq, SEQNO_MASK, (seqno - dns->repseq) & SEQNO_MASK, MAX_WINDOW);//D
1010 if (((seqno - dns->repseq) & SEQNO_MASK) <= MAX_WINDOW)
1011 {
1012 dns->repseq = seqno;
1013
1014 while (dlen > 1 && !dns->snddq.empty ())
1015 {
1016 int txtlen = dlen <= 255 ? dlen - 1 : 255;
1017
1018 if (txtlen > dns->snddq.size ())
1019 txtlen = dns->snddq.size ();
1020
1021 pkt[offs++] = txtlen;
1022 memcpy (pkt.at (offs), dns->snddq.begin (), txtlen);
1023 offs += txtlen;
1024 dns->snddq.remove (txtlen);
1025
1026 dlen -= txtlen + 1;
1027 }
1028 }
1029
1030 // avoid completely empty TXT rdata
1031 if (offs == rdlen_offs)
1032 pkt[offs++] = 0;
1033
1034 slog (L_NOISE, "DNS: snddq %d", dns->snddq.size ());
1035 }
1036 else
1037 {
1038 // send RST
1039 pkt [offs++] = CMD_IP_1; pkt [offs++] = CMD_IP_2; pkt [offs++] = CMD_IP_3;
1040 pkt [offs++] = CMD_IP_RST;
1041 }
1042
1043 int rdlen = offs - rdlen_offs;
1044
1045 pkt [rdlen_offs - 2] = rdlen >> 8;
1046 pkt [rdlen_offs - 1] = rdlen;
1047
1048 if (dns)
1049 {
1050 // now update dns_rcv copy
556 offs = r->pkt->len; 1051 rcv->pkt->len = offs;
557 memcpy (pkt->at (0), r->pkt->at (0), offs); 1052 memcpy (rcv->pkt->at (0), pkt.at (0), offs);
558 goto duplicate_request; 1053 }
559 } 1054 }
560 1055
561 // new packet, queue 1056 duplicate_request: ;
562 dns_rcv *rcv = new dns_rcv (seqno, data + 3, datalen - 3); 1057 }
563 c->dnsv4_receive_rep (rcv); 1058 else
564
565 // now generate reply
566 pkt->ancount = htons (1); // one answer RR
567 pkt->flags = htons (DEFAULT_SERVER_FLAGS | FLAG_RCODE_OK); 1059 pkt.flags = htons (DEFAULT_SERVER_FLAGS | FLAG_RCODE_FORMERR);
1060 }
1061 else if (qtype == RR_TYPE_A
1062 && qlen > dlen + 1 + cdc26.encode_len (sizeof (dns_cfg)))
1063 {
1064 dns_cfg cfg;
1065 cdc26.decode ((u8 *)&cfg, qname, cdc26.encode_len (sizeof (dns_cfg)));
1066 int client = ntohs (cfg.client);
568 1067
569 (*pkt) [offs++] = 0xc0;
570 (*pkt) [offs++] = 6 * 2; // same as in query section 1068 pkt [offs++] = 0xc0; pkt [offs++] = 6 * 2; // refer to name in query section
571 1069
572 (*pkt) [offs++] = RR_TYPE_TXT >> 8; (*pkt) [offs++] = RR_TYPE_TXT; 1070 pkt [offs++] = RR_TYPE_A >> 8; pkt [offs++] = RR_TYPE_A; // type
573 (*pkt) [offs++] = RR_CLASS_IN >> 8; (*pkt) [offs++] = RR_CLASS_IN; 1071 pkt [offs++] = RR_CLASS_IN >> 8; pkt [offs++] = RR_CLASS_IN; // class
574
575 (*pkt) [offs++] = 0; (*pkt) [offs++] = 0; 1072 pkt [offs++] = 0; pkt [offs++] = 0;
576 (*pkt) [offs++] = 0; (*pkt) [offs++] = 0; // TTL 1073 pkt [offs++] = 0; pkt [offs++] = cfg.def_ttl; // TTL
1074 pkt [offs++] = 0; pkt [offs++] = 4; // rdlength
577 1075
578 int dlen = MAX_PKT_SIZE - offs - 2; 1076 pkt [offs++] = CMD_IP_1; pkt [offs++] = CMD_IP_2; pkt [offs++] = CMD_IP_3;
1077 pkt [offs++] = CMD_IP_REJ;
579 1078
580 // bind doesn't compress well, so reduce further by one label length 1079 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 { 1080 {
589 int txtlen = dlen <= 255 ? dlen - 1 : 255; 1081 connection *c = conns [client - 1];
590 1082
591 if (txtlen > c->dns_snddq->size ()) 1083 if (cfg.valid ())
1084 {
1085 slog (L_INFO, _("DNS: client %d connects (version %d, req_cdc %d)"), client, cfg.version, cfg.req_cdc);
1086
1087 // check for any encoding mismatches - hints at a case problem
1088 char qname2 [MAX_ENC_LEN];
1089 cdc26.encode (qname2, (u8 *)&cfg, sizeof (dns_cfg));
1090
1091 delete c->dns;
1092
1093 pkt [offs - 1] = memcmp (qname, qname2, cdc26.encode_len (sizeof (dns_cfg)))
1094 ? CMD_IP_CSE : CMD_IP_SYN;
1095
1096 c->dns = new dns_connection (c);
1097 c->dns->cfg = cfg;
592 txtlen = c->dns_snddq->size (); 1098 c->dns->set_cfg ();
593 1099 }
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 } 1100 }
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 } 1101 }
617 else
618 pkt->flags = htons (DEFAULT_SERVER_FLAGS | FLAG_RCODE_FORMERR);
619 } 1102 }
620 1103
621 pkt->len = offs; 1104 pkt.len = offs;
622 } 1105 }
623
624 return pkt;
625} 1106}
626 1107
627void 1108void
628vpn::dnsv4_client (dns_packet *pkt) 1109vpn::dnsv4_client (dns_packet &pkt)
629{ 1110{
630 u16 flags = ntohs (pkt->flags); 1111 u16 flags = ntohs (pkt.flags);
631 int offs = 6 * 2; // skip header 1112 int offs = 6 * 2; // skip header
632 1113
633 pkt->qdcount = ntohs (pkt->qdcount); 1114 pkt.qdcount = ntohs (pkt.qdcount);
634 pkt->ancount = ntohs (pkt->ancount); 1115 pkt.ancount = ntohs (pkt.ancount);
635 1116
636 // go through our request list and find the corresponding request 1117 // go through our request list and find the corresponding request
637 for (vector<dns_req *>::iterator i = dns_sndpq.begin (); 1118 for (vector<dns_snd *>::iterator i = dns_sndpq.begin ();
638 i != dns_sndpq.end (); 1119 i != dns_sndpq.end ();
639 ++i) 1120 ++i)
640 if ((*i)->pkt->id == pkt->id) 1121 if ((*i)->pkt->id == pkt.id)
641 { 1122 {
1123 dns_connection *dns = (*i)->dns;
642 connection *c = (*i)->conn; 1124 connection *c = dns->c;
643 int seqno = (*i)->seqno; 1125 int seqno = (*i)->seqno;
644 u8 data[MAXSIZE], *datap = data; 1126 u8 data[MAXSIZE], *datap = data;
1127 //printf ("rcv pkt %x\n", seqno);//D
1128 bool back_off = (*i)->retry;
1129
1130 if (back_off)
1131 {
1132 dns->send_interval *= 1.01;
1133 if (dns->send_interval > MAX_SEND_INTERVAL)
1134 dns->send_interval = MAX_SEND_INTERVAL;
1135 }
1136 else
1137 {
1138#if 0
1139 dns->send_interval *= 0.999;
1140#endif
1141 // the latency surely puts an upper bound on
1142 // the minimum send interval
1143 double latency = ev_now () - (*i)->sent;
1144
1145 if (latency < dns->min_latency)
1146 dns->min_latency = latency;
1147
1148 if (dns->send_interval > dns->min_latency * conf.dns_overlap_factor)
1149 dns->send_interval = dns->min_latency * conf.dns_overlap_factor;
1150
1151 if (dns->send_interval < conf.dns_send_interval)
1152 dns->send_interval = conf.dns_send_interval;
1153 }
645 1154
646 delete *i; 1155 delete *i;
647 dns_sndpq.erase (i); 1156 dns_sndpq.erase (i);
648 1157
649 if (flags & (FLAG_RESPONSE | FLAG_OP_MASK | FLAG_TC)) 1158 if (flags & FLAG_RESPONSE && !(flags & FLAG_OP_MASK))
650 { 1159 {
651 char qname[MAXSIZE]; 1160 char qname[MAXSIZE];
652 1161
653 while (pkt->qdcount-- && offs < MAXSIZE - 4) 1162 while (pkt.qdcount-- && offs < MAXSIZE - 4)
654 { 1163 {
655 int qlen = pkt->decode_label ((char *)qname, MAXSIZE - offs, offs); 1164 int qlen = pkt.decode_label ((char *)qname, MAXSIZE - offs, offs);
656 offs += 4; // skip qtype, qclass 1165 offs += 4; // skip qtype, qclass
657 } 1166 }
658 1167
659 while (pkt->ancount-- && offs < MAXSIZE - 10) 1168 while (pkt.ancount-- && offs < MAXSIZE - 10 && datap)
660 { 1169 {
661 pkt->decode_label ((char *)qname, MAXSIZE - offs, offs); 1170 int qlen = pkt.decode_label ((char *)qname, MAXSIZE - offs, offs);
662 1171
663 u16 qtype = (*pkt) [offs++] << 8; qtype |= (*pkt) [offs++]; 1172 u16 qtype = pkt [offs++] << 8; qtype |= pkt [offs++];
664 u16 qclass = (*pkt) [offs++] << 8; qclass |= (*pkt) [offs++]; 1173 u16 qclass = pkt [offs++] << 8; qclass |= pkt [offs++];
665 u32 ttl = (*pkt) [offs++] << 24; 1174 u32 ttl = pkt [offs++] << 24;
666 ttl |= (*pkt) [offs++] << 16; 1175 ttl |= pkt [offs++] << 16;
667 ttl |= (*pkt) [offs++] << 8; 1176 ttl |= pkt [offs++] << 8;
668 ttl |= (*pkt) [offs++]; 1177 ttl |= pkt [offs++];
669
670 u16 rdlen = (*pkt) [offs++] << 8; rdlen |= (*pkt) [offs++]; 1178 u16 rdlen = pkt [offs++] << 8; rdlen |= pkt [offs++];
671 1179
672 if (rdlen <= MAXSIZE - offs) 1180 if (qtype == RR_TYPE_NULL || qtype == RR_TYPE_TXT || qtype == dns->cfg.rrtype)
673 { 1181 {
674 // decode bytes, finally 1182 if (rdlen <= MAXSIZE - offs)
675
676 while (rdlen)
677 { 1183 {
1184 // decode bytes, finally
1185
1186 while (rdlen)
1187 {
678 int txtlen = (*pkt) [offs++]; 1188 int txtlen = pkt [offs++];
679 1189
680 assert (txtlen + offs < MAXSIZE - 1); 1190 assert (txtlen + offs < MAXSIZE - 1);
681 1191
682 memcpy (datap, pkt->at (offs), txtlen); 1192 memcpy (datap, pkt.at (offs), txtlen);
683 datap += txtlen; offs += txtlen; 1193 datap += txtlen; offs += txtlen;
684 1194
685 rdlen -= txtlen + 1; 1195 rdlen -= txtlen + 1;
1196 }
686 } 1197 }
687
688 } 1198 }
1199 else if (qtype == RR_TYPE_A)
1200 {
1201 u8 ip [4];
689 1202
1203 ip [0] = pkt [offs++];
1204 ip [1] = pkt [offs++];
1205 ip [2] = pkt [offs++];
1206 ip [3] = pkt [offs++];
1207
1208 if (ip [0] == CMD_IP_1
1209 && ip [1] == CMD_IP_2
1210 && ip [2] == CMD_IP_3)
1211 {
1212 slog (L_TRACE, _("DNS: got tunnel meta command %02x"), ip [3]);
1213
1214 if (ip [3] == CMD_IP_RST)
1215 {
1216 slog (L_DEBUG, _("DNS: got tunnel RST request."));
1217
1218 dns->reset ();
1219 return;
1220 }
1221 else if (ip [3] == CMD_IP_SYN)
1222 {
1223 slog (L_DEBUG, _("DNS: got tunnel SYN reply, server likes us."));
1224 dns->established = true;
1225 }
1226 else if (ip [3] == CMD_IP_CSE)
1227 {
1228 if (conf.dns_case_preserving)
1229 {
1230 slog (L_INFO, _("DNS: got tunnel CSE reply, globally downgrading to case-insensitive protocol."));
1231 conf.dns_case_preserving = false;
1232 dns->reset ();
1233 return;
1234 }
1235 else
1236 {
1237 slog (L_DEBUG, _("DNS: got tunnel CSE reply, server likes us."));
1238 dns->established = true;
1239 }
1240 }
1241 else if (ip [3] == CMD_IP_REJ)
1242 {
1243 slog (L_ERR, _("DNS: got tunnel REJ reply, server does not like us."));
1244 dns->tw.start (60.);
1245 }
1246 else
1247 {
1248 slog (L_INFO, _("DNS: got unknown meta command %02x"), ip [3]);
1249 dns->tw.start (60.);
1250 }
1251 }
1252 else
1253 slog (L_INFO, _("DNS: got spurious a record %d.%d.%d.%d"),
1254 ip [0], ip [1], ip [2], ip [3]);
1255
1256 return;
1257 }
1258
1259 int client, rseqno;
1260 decode_header (qname, client, rseqno);
1261
1262 if (client != THISNODE->id)
1263 {
1264 slog (L_INFO, _("DNS: got dns tunnel response with wrong clientid, ignoring"));
1265 datap = 0;
1266 }
1267 else if (rseqno != seqno)
1268 {
1269 slog (L_DEBUG, _("DNS: got dns tunnel response with wrong seqno, badly caching nameserver?"));
1270 datap = 0;
1271 }
690 } 1272 }
691 } 1273 }
692 1274
693 // todo: pkt now used 1275 // todo: pkt now used
1276 if (datap)
694 c->dnsv4_receive_rep (new dns_rcv (seqno, data, datap - data)); 1277 dns->receive_rep (new dns_rcv (seqno, data, datap - data));
1278 else if (dns_sndpq.empty ()) // no data received, and nothing to send - idle
1279 {
1280 dns->send_interval *= 1.1;
1281
1282 if (dns->send_interval < MIN_POLL_INTERVAL)
1283 dns->send_interval = MIN_POLL_INTERVAL;
1284
1285 if (dns->send_interval > MAX_POLL_INTERVAL && !back_off)
1286 dns->send_interval = MAX_POLL_INTERVAL;
1287 }
695 1288
696 break; 1289 break;
697 } 1290 }
698
699 delete pkt;
700} 1291}
701 1292
702void 1293void
703vpn::dnsv4_ev (io_watcher &w, short revents) 1294vpn::dnsv4_ev (ev::io &w, int revents)
704{ 1295{
705 if (revents & EVENT_READ) 1296 if (revents & EV_READ)
706 { 1297 {
707 dns_packet *pkt = new dns_packet; 1298 dns_packet *pkt = new dns_packet;
708 struct sockaddr_in sa; 1299 struct sockaddr_in sa;
709 socklen_t sa_len = sizeof (sa); 1300 socklen_t sa_len = sizeof (sa);
710 1301
711 pkt->len = recvfrom (w.fd, &((*pkt)[0]), MAXSIZE, 0, (sockaddr *)&sa, &sa_len); 1302 pkt->len = recvfrom (w.fd, pkt->at (0), MAXSIZE, 0, (sockaddr *)&sa, &sa_len);
712 1303
713 if (pkt->len > 0) 1304 if (pkt->len > 0)
714 { 1305 {
715 if (pkt->flags & htons (FLAG_TC)) 1306 if (ntohs (pkt->flags) & FLAG_RESPONSE)
1307 dnsv4_client (*pkt);
1308 else
716 { 1309 {
717 slog (L_WARN, _("DNS request/response truncated, check protocol settings.")); 1310 dnsv4_server (*pkt);
718 //TODO connection reset 1311 sendto (w.fd, pkt->at (0), pkt->len, 0, (sockaddr *)&sa, sa_len);
719 } 1312 }
720 1313
721 if (THISNODE->dns_port) 1314 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 } 1315 }
729 } 1316 }
730} 1317}
731 1318
732bool 1319bool
733connection::send_dnsv4_packet (vpn_packet *pkt, const sockinfo &si, int tos) 1320vpn::send_dnsv4_packet (vpn_packet *pkt, const sockinfo &si, int tos)
734{ 1321{
735 // never initialized 1322 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 1323
741 //dns_rcvseq = dns_sndseq = 0; 1324 assert (0 < client && client <= conns.size ());
742 1325
743 dns_si.set (::conf.dns_forw_host, ::conf.dns_forw_port, PROT_DNSv4); 1326 connection *c = conns [client - 1];
744 } 1327
1328 if (!c->dns)
1329 c->dns = new dns_connection (c);
745 1330
746 if (!dns_snddq->put (pkt)) 1331 if (c->dns->snddq.put (pkt))
747 return false; 1332 c->dns->tw ();
748 1333
749 // start timer if neccessary 1334 // 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; 1335 return true;
754} 1336}
755 1337
1338#define NEXT(w) do { if (next > (w)) next = w; } while (0)
1339
756void 1340void
757connection::dnsv4_cb (time_watcher &w) 1341dns_connection::time_cb (ev::timer &w, int revents)
758{ 1342{
1343 // servers have to be polled
1344 if (THISNODE->dns_port)
1345 return;
1346
759 // check for timeouts and (re)transmit 1347 // check for timeouts and (re)transmit
760 tstamp next = NOW + 60; 1348 tstamp next = ev::now () + poll_interval;
761 dns_req *send = 0; 1349 dns_snd *send = 0;
762 1350
763 for (vector<dns_req *>::iterator i = vpn->dns_sndpq.begin (); 1351 for (vector<dns_snd *>::iterator i = vpn->dns_sndpq.begin ();
764 i != vpn->dns_sndpq.end (); 1352 i != vpn->dns_sndpq.end ();
765 ++i) 1353 ++i)
766 { 1354 {
767 dns_req *r = *i; 1355 dns_snd *r = *i;
768 1356
769 if (r->next <= NOW) 1357 if (r->timeout <= ev_now ())
770 { 1358 {
771 if (!send) 1359 if (!send)
772 { 1360 {
773 send = r; 1361 send = r;
774 1362
775 if (r->retry)//D
776 printf ("req %d, retry %d\n", r->pkt->id, r->retry);
777 r->retry++; 1363 r->retry++;
778 r->next = NOW + r->retry; 1364 r->timeout = ev_now () + (r->retry * min_latency * conf.dns_timeout_factor);
1365 //printf ("RETRY %x (%d, %f)\n", r->seqno, r->retry, r->timeout - ev_now ());//D
1366
1367 // the following code changes the query section a bit, forcing
1368 // the forwarder to generate a new request
1369 if (r->stdhdr)
1370 encode_header ((char *)r->pkt->at (6 * 2 + 1), THISNODE->id, r->seqno, r->retry);
779 } 1371 }
780 } 1372 }
781 1373 else
782 if (r->next < next) 1374 NEXT (r->timeout);
783 next = r->next;
784 } 1375 }
785 1376
786 if (!send 1377 if (!send)
787 && vpn->dns_sndpq.size () < MAX_OUTSTANDING)
788 { 1378 {
1379 // generate a new packet, if wise
1380
1381 if (!established)
1382 {
1383 if (vpn->dns_sndpq.empty ())
1384 {
789 send = new dns_req (this); 1385 send = new dns_snd (this);
1386
1387 cfg.reset (THISNODE->id);
1388 set_cfg ();
1389 send->gen_syn_req ();
1390 }
1391 }
1392 else if (vpn->dns_sndpq.size () < conf.dns_max_outstanding
1393 && !SEQNO_EQ (rcvseq, sndseq - (MAX_WINDOW - 1)))
1394 {
1395 if (last_sent + send_interval <= ev_now ())
1396 {
1397 //printf ("sending data request etc.\n"); //D
1398 if (!snddq.empty () || last_received + 1. > ev_now ())
1399 {
1400 poll_interval = send_interval;
1401 NEXT (ev_now () + send_interval);
1402 }
1403
1404 send = new dns_snd (this);
790 send->gen_stream_req (dns_sndseq, dns_snddq); 1405 send->gen_stream_req (sndseq, snddq);
1406 send->timeout = ev_now () + min_latency * conf.dns_timeout_factor;
1407 //printf ("SEND %x (%f)\n", send->seqno, send->timeout - ev_now (), min_latency, conf.dns_timeout_factor);//D
1408
1409 sndseq = (sndseq + 1) & SEQNO_MASK;
1410 }
1411 else
1412 NEXT (last_sent + send_interval);
1413 }
1414
1415 if (send)
791 vpn->dns_sndpq.push_back (send); 1416 vpn->dns_sndpq.push_back (send);
792
793 dns_sndseq = (dns_sndseq + 1) & SEQNO_MASK;
794 } 1417 }
795
796 tstamp min_next = NOW + (1. / (tstamp)MAX_RATE);
797 1418
798 if (send) 1419 if (send)
799 { 1420 {
800 dns_packet *pkt = send->pkt; 1421 last_sent = ev_now ();
801 1422 sendto (vpn->dnsv4_fd,
802 next = min_next; 1423 send->pkt->at (0), send->pkt->len, 0,
803 1424 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 } 1425 }
806 else if (next < min_next)
807 next = min_next;
808 1426
809 w.start (next); 1427 slog (L_NOISE, "DNS: pi %f si %f N %f (%d:%d %d)",
1428 poll_interval, send_interval, next - ev_now (),
1429 vpn->dns_sndpq.size (), snddq.size (),
1430 rcvpq.size ());
1431
1432 // TODO: no idea when this happens, but when next < ev_now (), we have a problem
1433 // doesn't seem to happen anymore
1434 if (next < ev_now () + 0.001)
1435 next = ev_now () + 0.1;
1436
1437 w.start (next - ev_now ());
810} 1438}
811 1439
812#endif 1440#endif
813 1441

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