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Comparing gvpe/src/vpn_dns.C (file contents):
Revision 1.6 by pcg, Thu Mar 3 08:38:32 2005 UTC vs.
Revision 1.57 by root, Thu Oct 6 03:03:09 2022 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) 2003-2004 Marc Lehmann <pcg@goof.com> 3 Copyright (C) 2003-2011 Marc Lehmann <gvpe@schmorp.de>
4 4
5 This file is part of GVPE.
6
5 This program is free software; you can redistribute it and/or modify 7 GVPE is free software; you can redistribute it and/or modify it
6 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
7 the Free Software Foundation; either version 2 of the License, or 9 Free Software Foundation; either version 3 of the License, or (at your
8 (at your option) any later version. 10 option) any later version.
9 11
10 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
11 but WITHOUT ANY WARRANTY; without even the implied warranty of 13 WITHOUT ANY WARRANTY; without even the implied warranty of
12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 14 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General
13 GNU General Public License for more details. 15 Public License for more details.
14 16
15 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
16 along with this program; if not, write to the Free Software 18 with this program; if not, see <http://www.gnu.org/licenses/>.
17 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.
18*/ 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.
19 35
20#include "config.h" 36#include "config.h"
21 37
22#if ENABLE_DNS 38#if ENABLE_DNS
23 39
24// dns processing is EXTREMELY ugly. For obvious(?) reasons. 40// dns processing is EXTREMELY ugly. For obvious(?) reasons.
25// it's a hack, use only in emergency situations please. 41// it's a hack, use only in emergency situations please.
26 42
27#include <cstring> 43#include <cstring>
44#include <cassert>
28 45
29#include <sys/types.h> 46#include <sys/types.h>
30#include <sys/socket.h> 47#include <sys/socket.h>
31#include <sys/wait.h> 48#include <sys/wait.h>
32#include <sys/uio.h> 49#include <sys/uio.h>
… …
35#include <unistd.h> 52#include <unistd.h>
36#include <fcntl.h> 53#include <fcntl.h>
37 54
38#include <map> 55#include <map>
39 56
57#include <cstdio> /* bug in libgmp: gmp.h relies on cstdio being included */
58#include <gmp.h>
59
40#include "netcompat.h" 60#include "netcompat.h"
41 61
42#include "vpn.h" 62#include "vpn.h"
43 63
44#define MIN_RETRY 1. 64#define MIN_POLL_INTERVAL 0.025 // poll at most this often when no data received
45#define MAX_RETRY 60. 65#define MAX_POLL_INTERVAL 1. // how often to poll minimally when the server has no data
46 66
47#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
48#define MAX_WINDOW 100 // max. for MAX_OUTSTANDING 72#define MAX_WINDOW 1000 // max. for MAX_OUTSTANDING, and backlog
49#define MAX_RATE 1000 // requests/s
50#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
51 74
52#define MAX_DOMAIN_SIZE 220 // 255 is legal limit, but bind doesn't compress well 75#define MAX_DOMAIN_SIZE 235 // 255 is legal limit, but bind doesn't compress well
53// 240 leaves about 4 bytes of server reply data 76// 240 leaves about 4 bytes of server reply data
54// every two request byte sless give room for one reply byte 77// every request byte less give room for two reply bytes
55 78
56// seqno has 12 bits, but the lower bit is always left as zero
57// as bind caches ttl=0 records and we have to generate
58// sequence numbers that always differ case-insensitively
59#define SEQNO_MASK 0x07ff 79#define SEQNO_MASK 0x3fff
60 80#define SEQNO_EQ(a,b) ( 0 == ( ((a) ^ (b)) & SEQNO_MASK) )
61/*
62
63protocol, in shorthand :)
64
65client -> server <req> ANY?
66server -> client <req> TXT <rep>
67
68<req> is dns64-encoded <client-id:12><recv-seqno:10>[<send-seqno:10><data>]
69<rep> is dns64-encoded <0:12><recv-seqno:10>[<send-seqno:10><data>]
70
71if <client-id> is zero, the connection will be configured:
72
73<0:12><0:4>client-id:12><default-ttl:8><max-size:16><flags:16>
74
75*/
76 81
77#define MAX_LBL_SIZE 63 82#define MAX_LBL_SIZE 63
78#define MAX_PKT_SIZE 512 83#define MAX_PKT_SIZE 512
79 84
85#define RR_TYPE_A 1
86#define RR_TYPE_NULL 10
80#define RR_TYPE_TXT 16 87#define RR_TYPE_TXT 16
88#define RR_TYPE_AAAA 28
81#define RR_TYPE_ANY 255 89#define RR_TYPE_ANY 255
90
82#define RR_CLASS_IN 1 91#define RR_CLASS_IN 1
83 92
84// the "_" is not valid but widely accepted (all octets should be supported, but let's be conservative) 93#define CMD_IP_1 207
85struct dns64 94#define CMD_IP_2 46
86{ 95#define CMD_IP_3 236
87 static const char encode_chars[64 + 1];
88 static s8 decode_chars[256];
89 96
90 static int encode_len (int bytes) { return (bytes * 8 + 5) / 6; } 97#define CMD_IP_RST 29 // some error, reset and retry
91 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 + 1)
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
92 static int encode (char *dst, u8 *src, int len); 163 unsigned int encode (char *dst, u8 *src, unsigned int len) const;
93 static int decode (u8 *dst, char *src, int len); 164 unsigned int decode (u8 *dst, char *src, unsigned int len) const;
94 165
95 dns64 (); 166 basecoder (const char *cmap);
96} dns64; 167};
97 168
98// the following sequence has been crafted to 169basecoder::basecoder (const char *cmap)
99// a) look somewhat random 170: cmap (cmap)
100// b) the even (and odd) indices never share the same character as upper/lowercase
101const char dns64::encode_chars[64 + 1] = "_-dDpPhHzZrR06QqMmjJkKBb34TtSsvVlL81xXaAeEFf92WwGgYyoO57UucCNniI";
102s8 dns64::decode_chars[256];
103
104dns64::dns64 ()
105{ 171{
106 for (int i = 0; i < 64; i++) 172 int decn = -1;
107 decode_chars [encode_chars [i]] = i + 1;
108}
109 173
110int dns64::encode (char *dst, u8 *src, int len) 174 for (unsigned int len = 0; len < MAX_DEC_LEN; ++len)
175 {
176 u8 src [MAX_DEC_LEN];
177 u8 dst [MAX_ENC_LEN];
178
179 memset (src, 255, len);
180
181 mp_limb_t m [MAX_LIMBS];
182 mp_size_t n;
183
184 n = mpn_set_str (m, src, len, 256);
185 n = mpn_get_str (dst, this->cmap.size, m, n);
186
187 for (int i = 0; n && !dst [i]; ++i, --n)
188 ;
189
190 enc_len [len] = n;
191 while (decn < n)
192 dec_len [++decn] = len;
193 }
194}
195
196unsigned int
197basecoder::encode_len (unsigned int len) const
111{ 198{
112 // slow, but easy to debug 199 return enc_len [len];
113 char *beg = dst; 200}
114 unsigned int accum, bits = 0; 201
202unsigned int
203basecoder::decode_len (unsigned int len) const
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;
115 246
116 while (len--) 247 while (len--)
117 { 248 {
118 accum <<= 8; 249 u8 val = cmap.decode [(u8)*src++];
119 accum |= *src++;
120 bits += 8;
121 250
122 while (bits >= 6) 251 if (val != charmap::INVALID)
123 { 252 src_ [elen++] = val;
124 *dst++ = encode_chars [(accum >> (bits - 6)) & 63]; 253 }
125 bits -= 6; 254
126 } 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)
127 } 266 {
267 memset (dst, 0, dlen - n);
268 memcpy (dst + dlen - n, dst_, n);
269 }
270 else
271 memcpy (dst, dst_ + n - dlen, dlen);
128 272
129 if (bits) 273 return dlen;
130 *dst++ = encode_chars [(accum << (6 - bits)) & 63];
131
132 return dst - beg;
133} 274}
134 275
135int dns64::decode (u8 *dst, char *src, int len) 276#if 0
136{ 277struct test { test (); } test;
137 // slow, but easy to debug
138 u8 *beg = dst;
139 unsigned int accum, bits = 0;
140 278
141 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++)
142 { 288 {
143 s8 chr = decode_chars [(u8)*src++]; 289 int elen = cdc.encode (enc, in, i);
290 int dlen = cdc.decode (dec, enc, elen);
144 291
145 if (!chr) 292 printf ("%d>%d>%d (%s>%s)\n", i, elen, dlen, enc, dec);
146 continue;
147
148 accum <<= 6;
149 accum |= chr - 1;
150 bits += 6;
151
152 while (bits >= 8)
153 {
154 *dst++ = accum >> (bits - 8);
155 bits -= 8;
156 }
157 } 293 }
294 abort ();
295}
296#endif
158 297
159 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 u8 (seqno),
315 u8 ((seqno >> 8) | (retry << 6)),
316 u8 (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;
160} 331}
161 332
162///////////////////////////////////////////////////////////////////////////// 333/////////////////////////////////////////////////////////////////////////////
163 334
164struct byte_stream 335struct byte_stream
… …
190byte_stream::~byte_stream () 361byte_stream::~byte_stream ()
191{ 362{
192 delete data; 363 delete data;
193} 364}
194 365
366void
195void byte_stream::remove (int count) 367byte_stream::remove (int count)
196{ 368{
197 if (count > fill) 369 assert (count <= fill);
198 abort ();
199 370
200 memmove (data, data + count, fill -= count); 371 memmove (data, data + count, fill -= count);
201} 372}
202 373
374bool
203bool byte_stream::put (u8 *data, unsigned int datalen) 375byte_stream::put (u8 *data, unsigned int datalen)
204{ 376{
205 if (maxsize - fill < datalen) 377 if (maxsize - fill < datalen)
206 return false; 378 return false;
207 379
208 memcpy (this->data + fill, data, datalen); fill += datalen; 380 memcpy (this->data + fill, data, datalen); fill += datalen;
209 381
210 return true; 382 return true;
211} 383}
212 384
385bool
213bool byte_stream::put (vpn_packet *pkt) 386byte_stream::put (vpn_packet *pkt)
214{ 387{
215 if (maxsize - fill < pkt->len + 2) 388 if (maxsize - fill < pkt->len + 2)
216 return false; 389 return false;
217 390
218 data [fill++] = pkt->len >> 8; 391 data [fill++] = pkt->len >> 8;
219 data [fill++] = pkt->len; 392 data [fill++] = pkt->len;
220 393
221 memcpy (data + fill, &((*pkt)[0]), pkt->len); fill += pkt->len; 394 memcpy (data + fill, pkt->at (0), pkt->len); fill += pkt->len;
222 395
223 return true; 396 return true;
224} 397}
225 398
399vpn_packet *
226vpn_packet *byte_stream::get () 400byte_stream::get ()
227{ 401{
402 unsigned int len;
403
404 for (;;)
405 {
406 if (fill < 2)
407 return 0;
408
228 int len = (data [0] << 8) | data [1]; 409 len = (data [0] << 8) | data [1];
229 410
230 if (len > MAXSIZE && fill >= 2) 411 if (len <= MAXSIZE)
231 abort (); // TODO handle this gracefully, connection reset 412 break;
232 413
414 // TODO: handle this better than skipping, e.g. by reset
415 slog (L_DEBUG, _("DNS: corrupted packet (%02x %02x > %d) stream skipping a byte..."), data [0], data [1], MAXSIZE);
416 remove (1);
417 }
418
233 if (fill < len + 2) 419 if (fill < len + 2)
234 return 0; 420 return 0;
235 421
236 vpn_packet *pkt = new vpn_packet; 422 vpn_packet *pkt = new vpn_packet;
237 423
238 pkt->len = len; 424 pkt->len = len;
239 memcpy (&((*pkt)[0]), data + 2, len); 425 memcpy (pkt->at (0), data + 2, len);
240 remove (len + 2); 426 remove (len + 2);
241 427
242 return pkt; 428 return pkt;
243} 429}
244 430
245///////////////////////////////////////////////////////////////////////////// 431/////////////////////////////////////////////////////////////////////////////
246 432
247#define FLAG_QUERY ( 0 << 15) 433#define FLAG_QUERY ( 0 << 15)
248#define FLAG_RESPONSE ( 1 << 15) 434#define FLAG_RESPONSE ( 1 << 15)
249#define FLAG_OP_MASK (15 << 14) 435#define FLAG_OP_MASK (15 << 11)
250#define FLAG_OP_QUERY ( 0 << 11) 436#define FLAG_OP_QUERY ( 0 << 11)
251#define FLAG_AA ( 1 << 10) 437#define FLAG_AA ( 1 << 10)
252#define FLAG_TC ( 1 << 9) 438#define FLAG_TC ( 1 << 9)
253#define FLAG_RD ( 1 << 8) 439#define FLAG_RD ( 1 << 8)
254#define FLAG_RA ( 1 << 7) 440#define FLAG_RA ( 1 << 7)
… …
261#define FLAG_RCODE_REFUSED ( 5 << 0) 447#define FLAG_RCODE_REFUSED ( 5 << 0)
262 448
263#define DEFAULT_CLIENT_FLAGS (FLAG_QUERY | FLAG_OP_QUERY | FLAG_RD) 449#define DEFAULT_CLIENT_FLAGS (FLAG_QUERY | FLAG_OP_QUERY | FLAG_RD)
264#define DEFAULT_SERVER_FLAGS (FLAG_RESPONSE | FLAG_OP_QUERY | FLAG_AA | FLAG_RD | FLAG_RA) 450#define DEFAULT_SERVER_FLAGS (FLAG_RESPONSE | FLAG_OP_QUERY | FLAG_AA | FLAG_RD | FLAG_RA)
265 451
452struct dns_cfg
453{
454 static int next_uid;
455
456 u8 chksum;
457 u8 rrtype;
458 u16 uid; // to make request unique
459
460 u8 version;
461 u8 flags;
462 u16 max_size;
463
464 u8 id1, id2, id3, id4;
465
466 u16 client;
467 u8 def_ttl;
468 u8 r0;
469
470 u8 syn_cdc; // cdc en/decoder for syn (A?) requests
471 u8 hdr_cdc; // cdc en/decoder for regular request headers
472 u8 req_cdc; // cdc en/decoder for regular (ANY?) request data
473 u8 rep_cdc; // cdc en/decoder for regular (TXT) replies, 0 == 8 bit encoding
474
475 u8 r1, r2, r3, r4;
476
477 void reset (int clientid);
478 bool valid ();
479 u8 get_chksum ();
480};
481
482int dns_cfg::next_uid;
483
484void
485dns_cfg::reset (int clientid)
486{
487 // this ID must result in some mixed-case characters in cdc26-encoding
488 id1 = 'G';
489 id2 = 'V';
490 id3 = 'P';
491 id4 = 'E';
492
493 version = 2;
494
495 rrtype = RR_TYPE_TXT;
496 flags = 0;
497 def_ttl = 0;
498 syn_cdc = 26;
499 hdr_cdc = 36;
500 req_cdc = conf.dns_case_preserving ? 62 : 36;
501 rep_cdc = 0;
502 max_size = htons (MAX_PKT_SIZE);
503 client = htons (clientid);
504 uid = ++next_uid;
505
506 r0 = r1 = r2 = r3 = r4 = 0;
507
508 chksum = get_chksum ();
509}
510
511// simple but not trivial chksum
512u8
513dns_cfg::get_chksum ()
514{
515 unsigned int sum = 0xff00; // only 16 bits required
516
517 u8 old_chksum = chksum;
518 chksum = 0;
519
520 for (unsigned int i = 0; i < sizeof (*this); ++i)
521 sum += ((u8 *)this)[i] * (i + 1);
522
523 chksum = old_chksum;
524
525 return sum + (sum >> 8);
526}
527
528bool
529dns_cfg::valid ()
530{
531 // although the protocol itself allows for some configurability,
532 // only the following encoding/decoding settings are implemented.
533 return id1 == 'G'
534 && id2 == 'V'
535 && id3 == 'P'
536 && id4 == 'E'
537 && version == 2
538 && syn_cdc == 26
539 && hdr_cdc == 36
540 && (req_cdc == 36 || req_cdc == 62)
541 && rep_cdc == 0
542 && chksum == get_chksum ();
543}
544
266struct dns_packet : net_packet 545struct dns_packet : net_packet
267{ 546{
268 u16 id; 547 u16 id;
269 u16 flags; // QR:1 Opcode:4 AA:1 TC:1 RD:1 RA:1 Z:3 RCODE:4 548 u16 flags; // QR:1 Opcode:4 AA:1 TC:1 RD:1 RA:1 Z:3 RCODE:4
270 u16 qdcount, ancount, nscount, arcount; 549 u16 qdcount, ancount, nscount, arcount;
271 550
272 u8 data[MAXSIZE - 6 * 2]; 551 u8 data [MAXSIZE - 6 * 2];
273 552
274 int decode_label (char *data, int size, int &offs); 553 int decode_label (char *data, int size, int &offs);
275}; 554};
276 555
556int
277int dns_packet::decode_label (char *data, int size, int &offs) 557dns_packet::decode_label (char *data, int size, int &offs)
278{ 558{
279 char *orig = data; 559 char *orig = data;
280 560
281 memset (data, 0, size); 561 memset (data, 0, size);
282 562
… …
308 return data - orig; 588 return data - orig;
309} 589}
310 590
311///////////////////////////////////////////////////////////////////////////// 591/////////////////////////////////////////////////////////////////////////////
312 592
313struct dns_req 593static
594u16 next_id ()
314{ 595{
315 dns_packet *pkt;
316 tstamp next;
317 int retry;
318 connection *conn;
319 int seqno;
320
321 dns_req (connection *c);
322 void gen_stream_req (int seqno, byte_stream *stream);
323};
324
325static u16 dns_id = 12098; // TODO: should be per-vpn 596 static u16 dns_id = 0; // TODO: should be per-vpn
326 597
327static u16 next_id () 598#if 1
328{ 599 if (!dns_id)
600 dns_id = time (0);
601
329 // the simplest lsfr with periodicity 65535 i could find 602 // the simplest lsfr with periodicity 65535 i could find
330 dns_id = (dns_id << 1) 603 dns_id = (dns_id << 1)
331 | (((dns_id >> 1) 604 | (((dns_id >> 1)
332 ^ (dns_id >> 2) 605 ^ (dns_id >> 2)
333 ^ (dns_id >> 4) 606 ^ (dns_id >> 4)
334 ^ (dns_id >> 15)) & 1); 607 ^ (dns_id >> 15)) & 1);
335 608
336 return dns_id; 609 return dns_id;
337} 610#else
611 dns_id++;//D
338 612
339dns_req::dns_req (connection *c) 613 return htons (dns_id);
340: conn (c) 614#endif
615}
616
617struct dns_rcv;
618struct dns_snd;
619
620struct dns_connection
341{ 621{
342 next = 0; 622 connection *c;
623 struct vpn *vpn;
624
625 dns_cfg cfg;
626
627 bool established;
628 const basecoder *cdc;
629
630 tstamp last_received;
631 tstamp last_sent;
632 double min_latency;
633 double poll_interval, send_interval;
634
635 vector<dns_rcv *> rcvpq;
636
637 byte_stream rcvdq; int rcvseq; int repseq;
638 byte_stream snddq; int sndseq;
639
640 inline void time_cb (ev::timer &w, int revents); ev::timer tw;
641 void receive_rep (dns_rcv *r);
642
643 void reset (); // quite like tcp RST
644 void set_cfg (); // to be called after any cfg changes
645
646 dns_connection (connection *c);
647 ~dns_connection ();
648};
649
650struct dns_snd
651{
652 dns_packet *pkt;
653 tstamp timeout, sent;
654 int retry;
655 struct dns_connection *dns;
656 int seqno;
657 bool stdhdr;
658
659 void gen_stream_req (int seqno, byte_stream &stream);
660 void gen_syn_req ();
661
662 dns_snd (dns_connection *dns);
663 ~dns_snd ();
664};
665
666dns_snd::dns_snd (dns_connection *dns)
667: dns (dns)
668{
669 timeout = 0;
343 retry = 0; 670 retry = 0;
671 seqno = 0;
672 sent = ev_now ();
673 stdhdr = false;
344 674
345 pkt = new dns_packet; 675 pkt = new dns_packet;
346 676
347 pkt->id = next_id (); 677 pkt->id = next_id ();
348} 678}
349 679
680dns_snd::~dns_snd ()
681{
682 delete pkt;
683}
684
685static void
686append_domain (dns_packet &pkt, int &offs, const char *domain)
687{
688 // add tunnel domain
689 for (;;)
690 {
691 const char *end = strchr (domain, '.');
692
693 if (!end)
694 end = domain + strlen (domain);
695
696 int len = end - domain;
697
698 pkt [offs++] = len;
699 memcpy (pkt.at (offs), domain, len);
700 offs += len;
701
702 if (!*end)
703 break;
704
705 domain = end + 1;
706 }
707}
708
709void
350void dns_req::gen_stream_req (int seqno, byte_stream *stream) 710dns_snd::gen_stream_req (int seqno, byte_stream &stream)
351{ 711{
712 stdhdr = true;
352 this->seqno = seqno; 713 this->seqno = seqno;
714
715 timeout = ev_now () + INITIAL_TIMEOUT;
353 716
354 pkt->flags = htons (DEFAULT_CLIENT_FLAGS); 717 pkt->flags = htons (DEFAULT_CLIENT_FLAGS);
355 pkt->qdcount = htons (1); 718 pkt->qdcount = htons (1);
356 719
357 int offs = 6*2; 720 int offs = 6*2;
358 int dlen = MAX_DOMAIN_SIZE - strlen (THISNODE->domain) - 2; 721 int dlen = MAX_DOMAIN_SIZE - (strlen (dns->c->conf->domain) + 2);
359 // MAX_DOMAIN_SIZE is technically 255, but bind doesn't compress responses well, 722 // MAX_DOMAIN_SIZE is technically 255, but bind doesn't compress responses well,
360 // so we need to have space for 2*MAX_DOMAIN_SIZE + header + extra 723 // so we need to have space for 2*MAX_DOMAIN_SIZE + header + extra
361 724
362 u8 data[256]; //TODO
363
364 data[0] = THISNODE->id; //TODO
365 data[1] = seqno >> 7; //TODO
366 data[2] = seqno << 1; //TODO
367
368 int datalen = dns64::decode_len (dlen - (dlen + MAX_LBL_SIZE - 1) / MAX_LBL_SIZE) - 3;
369
370 if (datalen > stream->size ())
371 datalen = stream->size ();
372
373 char enc[256], *encp = enc; 725 char enc[256], *encp = enc;
374 726 encode_header (enc, THISNODE->id, seqno);
375 memcpy (data + 3, stream->begin (), datalen); 727
376 int enclen = dns64::encode (enc, data, datalen + 3); 728 int datalen = dns->cdc->decode_len (dlen - (dlen + MAX_LBL_SIZE - 1) / MAX_LBL_SIZE - HDRSIZE);
729
730 if (datalen > stream.size ())
731 datalen = stream.size ();
732
733 int enclen = dns->cdc->encode (enc + HDRSIZE, stream.begin (), datalen) + HDRSIZE;
377 stream->remove (datalen); 734 stream.remove (datalen);
378 735
379 while (enclen) 736 while (enclen)
380 { 737 {
381 int lbllen = enclen < MAX_LBL_SIZE ? enclen : MAX_LBL_SIZE; 738 int lbllen = enclen < MAX_LBL_SIZE ? enclen : MAX_LBL_SIZE;
382 739
… …
387 encp += lbllen; 744 encp += lbllen;
388 745
389 enclen -= lbllen; 746 enclen -= lbllen;
390 } 747 }
391 748
392 const char *suffix = THISNODE->domain; 749 append_domain (*pkt, offs, dns->c->conf->domain);
393
394 // add tunnel domain
395 for (;;)
396 {
397 const char *end = strchr (suffix, '.');
398
399 if (!end)
400 end = suffix + strlen (suffix);
401
402 int len = end - suffix;
403
404 (*pkt)[offs++] = len;
405 memcpy (&((*pkt)[offs]), suffix, len);
406 offs += len;
407
408 if (!*end)
409 break;
410
411 suffix = end + 1;
412 }
413 750
414 (*pkt)[offs++] = 0; 751 (*pkt)[offs++] = 0;
415 (*pkt)[offs++] = RR_TYPE_ANY >> 8; (*pkt)[offs++] = RR_TYPE_ANY; 752 (*pkt)[offs++] = RR_TYPE_ANY >> 8; (*pkt)[offs++] = RR_TYPE_ANY;
753 (*pkt)[offs++] = RR_CLASS_IN >> 8; (*pkt)[offs++] = RR_CLASS_IN;
754
755 pkt->len = offs;
756}
757
758void
759dns_snd::gen_syn_req ()
760{
761 timeout = ev_now () + INITIAL_SYN_TIMEOUT;
762
763 pkt->flags = htons (DEFAULT_CLIENT_FLAGS);
764 pkt->qdcount = htons (1);
765
766 int offs = 6 * 2;
767
768 int elen = cdc26.encode ((char *)pkt->at (offs + 1), (u8 *)&dns->cfg, sizeof (dns_cfg));
769
770 assert (elen <= MAX_LBL_SIZE);
771
772 (*pkt)[offs] = elen;
773 offs += elen + 1;
774 append_domain (*pkt, offs, dns->c->conf->domain);
775
776 (*pkt)[offs++] = 0;
777 (*pkt)[offs++] = RR_TYPE_A >> 8; (*pkt)[offs++] = RR_TYPE_A;
416 (*pkt)[offs++] = RR_CLASS_IN >> 8; (*pkt)[offs++] = RR_CLASS_IN; 778 (*pkt)[offs++] = RR_CLASS_IN >> 8; (*pkt)[offs++] = RR_CLASS_IN;
417 779
418 pkt->len = offs; 780 pkt->len = offs;
419} 781}
420 782
… …
439{ 801{
440 delete pkt; 802 delete pkt;
441} 803}
442 804
443///////////////////////////////////////////////////////////////////////////// 805/////////////////////////////////////////////////////////////////////////////
444 806
445struct dns_cfg 807dns_connection::dns_connection (connection *c)
808: c (c)
809, rcvdq (MAX_BACKLOG * 2)
810, snddq (MAX_BACKLOG)
446{ 811{
447 u8 id1, id2, id3; 812 tw.set<dns_connection, &dns_connection::time_cb> (this);
448 u8 def_ttl;
449 u8 unused1;
450 u16 max_size;
451 u8 flags1, flags2;
452};
453 813
814 vpn = c->vpn;
815
816 reset ();
817}
818
819dns_connection::~dns_connection ()
820{
821 reset ();
822}
823
824void
825dns_connection::reset ()
826{
827 while (!rcvpq.empty ())
828 {
829 delete rcvpq.back ();
830 rcvpq.pop_back ();
831 }
832
833 for (int i = vpn->dns_sndpq.size (); i--; )
834 if (vpn->dns_sndpq [i]->dns == this)
835 {
836 vpn->dns_sndpq [i] = vpn->dns_sndpq.back ();
837 vpn->dns_sndpq.pop_back ();
838 }
839
840 established = false;
841
842 rcvseq = repseq = sndseq = 0;
843
844 last_sent = 0;
845 poll_interval = 0.5; // starting here
846 send_interval = 0.5; // starting rate
847 min_latency = INITIAL_TIMEOUT;
848}
849
850void
851dns_connection::set_cfg ()
852{
853 cdc = cfg.req_cdc == 36 ? &cdc36 : &cdc62;
854}
855
856void
454void connection::dnsv4_receive_rep (struct dns_rcv *r) 857dns_connection::receive_rep (dns_rcv *r)
455{ 858{
859 if (r->datalen)
860 poll_interval = max (poll_interval * (1. / 1.2), MIN_POLL_INTERVAL);
861 else
862 poll_interval = min (poll_interval * 1.1, MAX_POLL_INTERVAL);
863
456 dns_rcvpq.push_back (r); 864 rcvpq.push_back (r);
457 865
458 redo: 866 redo:
459 867
868 // find next packet
460 for (vector<dns_rcv *>::iterator i = dns_rcvpq.begin (); 869 for (vector<dns_rcv *>::iterator i = rcvpq.end (); i-- != rcvpq.begin (); )
461 i != dns_rcvpq.end ();
462 ++i)
463 if (dns_rcvseq == (*i)->seqno) 870 if (SEQNO_EQ (rcvseq, (*i)->seqno))
464 { 871 {
872 //printf ("seqno eq %x %x\n", rcvseq, (*i)->seqno);//D
873 // enter the packet into our input stream
465 dns_rcv *r = *i; 874 r = *i;
466 875
876 // remove the oldest packet, look forward, as it's oldest first
877 for (vector<dns_rcv *>::iterator j = rcvpq.begin (); j != rcvpq.end (); ++j)
878 if (SEQNO_EQ ((*j)->seqno, rcvseq - MAX_WINDOW))
879 {
880 //printf ("seqno RR %x %x\n", (*j)->seqno, rcvseq - MAX_WINDOW);//D
881 delete *j;
882 rcvpq.erase (j);
883 break;
884 }
885
467 dns_rcvseq = (dns_rcvseq + 1) & SEQNO_MASK; 886 rcvseq = (rcvseq + 1) & SEQNO_MASK;
468 887
469 if (!dns_snddq && !dns_rcvdq) 888 if (!rcvdq.put (r->data, r->datalen))
470 { 889 {
471 dns_rcvdq = new byte_stream (MAX_BACKLOG * 2); 890 // MUST never overflow, can be caused by data corruption, TODO
472 dns_snddq = new byte_stream (MAX_BACKLOG); 891 slog (L_CRIT, "DNS: !rcvdq.put (r->data, r->datalen)");
473 892 reset ();
474 dns_si.set (::conf.dns_forw_host, ::conf.dns_forw_port, PROT_DNSv4); 893 return;
475 } 894 }
476 895
477 if (!dns_rcvdq->put (r->data, r->datalen))
478 abort (); // MUST never overflow, can be caused by data corruption, TODO
479
480 while (vpn_packet *pkt = dns_rcvdq->get ()) 896 while (vpn_packet *pkt = rcvdq.get ())
481 { 897 {
482 sockinfo si; 898 sockinfo si;
483 si.host = 0; si.port = 0; si.prot = PROT_DNSv4; 899 si.host = htonl (c->conf->id); si.port = 0; si.prot = PROT_DNSv4;
484 900
485 vpn->recv_vpn_packet (pkt, si); 901 vpn->recv_vpn_packet (pkt, si);
902 delete pkt;
486 } 903 }
487 } 904
488 else if ((u32)(*i)->seqno - (u32)dns_rcvseq + MAX_WINDOW > MAX_WINDOW * 2) 905 // check for further packets
489 {
490 //D
491 //abort();
492 printf ("%d erasing %d (%d)\n", THISNODE->id, (u32)(*i)->seqno, dns_rcvseq);
493 dns_rcvpq.erase (i);
494 goto redo; 906 goto redo;
495 } 907 }
496} 908}
497 909
498dns_packet * 910void
499vpn::dnsv4_server (dns_packet *pkt) 911vpn::dnsv4_server (dns_packet &pkt)
500{ 912{
501 u16 flags = ntohs (pkt->flags); 913 u16 flags = ntohs (pkt.flags);
502 914
503 //memcpy (&((*rep)[0]), &((*pkt)[0]), pkt->len);
504 int offs = 6 * 2; // skip header 915 int offs = 6 * 2; // skip header
505 916
506 pkt->flags = htons (DEFAULT_SERVER_FLAGS | FLAG_RCODE_FORMERR); 917 pkt.flags = htons (DEFAULT_SERVER_FLAGS | FLAG_RCODE_FORMERR);
507 918
508 if (!(flags & (FLAG_RESPONSE | FLAG_OP_MASK | FLAG_TC)) 919 if (0 == (flags & (FLAG_RESPONSE | FLAG_OP_MASK))
509 && pkt->qdcount == htons (1)) 920 && pkt.qdcount == htons (1))
510 { 921 {
511 char qname[MAXSIZE]; 922 char qname [MAXSIZE];
512 int qlen = pkt->decode_label ((char *)qname, MAXSIZE - offs, offs); 923 int qlen = pkt.decode_label ((char *)qname, MAXSIZE - offs, offs);
513 924
514 u16 qtype = (*pkt) [offs++] << 8; qtype |= (*pkt) [offs++]; 925 u16 qtype = pkt [offs++] << 8; qtype |= pkt [offs++];
515 u16 qclass = (*pkt) [offs++] << 8; qclass |= (*pkt) [offs++]; 926 u16 qclass = pkt [offs++] << 8; qclass |= pkt [offs++];
516 927
517 pkt->qdcount = htons (1); 928 pkt.qdcount = htons (1);
518 pkt->ancount = 0; 929 pkt.ancount = 0;
519 pkt->nscount = 0; // should be self, as other nameservers reply like this 930 pkt.nscount = 0; // should be self, as other nameservers reply like this
520 pkt->arcount = 0; // a record for self, as other nameservers reply like this 931 pkt.arcount = 0; // a record for self, as other nameservers reply like this
521 932
522 pkt->flags = htons (DEFAULT_SERVER_FLAGS | FLAG_RCODE_NXDOMAIN); 933 pkt.flags = htons (DEFAULT_SERVER_FLAGS | FLAG_RCODE_SERVFAIL);
523 934
524 int dlen = strlen (THISNODE->domain); 935 int dlen = strlen (THISNODE->domain);
525 936
526 if (qclass == RR_CLASS_IN 937 if (qclass == RR_CLASS_IN
527 && (qtype == RR_TYPE_ANY || qtype == RR_TYPE_TXT)
528 && qlen > dlen + 1 938 && qlen > dlen + 1
529 && !memcmp (qname + qlen - dlen - 1, THISNODE->domain, dlen)) 939 && !memcmp (qname + qlen - (dlen + 1), THISNODE->domain, dlen))
530 { 940 {
531 // correct class, domain: parse 941 // now generate reply
532 u8 data[MAXSIZE]; 942 pkt.ancount = htons (1); // one answer RR
533 int datalen = dns64::decode (data, qname, qlen - dlen - 1); 943 pkt.flags = htons (DEFAULT_SERVER_FLAGS | FLAG_RCODE_OK);
534 944
535 int client = data[0]; 945 if ((qtype == RR_TYPE_ANY
536 int seqno = ((data[1] << 7) | (data[2] >> 1)) & SEQNO_MASK; 946 || qtype == RR_TYPE_TXT
537 947 || qtype == RR_TYPE_NULL)
538 if (0 < client && client <= conns.size ()) 948 && qlen > dlen + 1 + HDRSIZE)
539 { 949 {
950 // correct class, domain: parse
951 int client, seqno;
952 decode_header (qname, client, seqno);
953
954 if (0 < client && client <= conns.size ())
955 {
540 connection *c = conns [client - 1]; 956 connection *c = conns [client - 1];
957 dns_connection *dns = c->dns;
958 dns_rcv *rcv;
541 959
542 redo: 960 if (dns)
543
544 for (vector<dns_rcv *>::iterator i = c->dns_rcvpq.begin ();
545 i != c->dns_rcvpq.end ();
546 ++i) 961 {
962 u8 data[MAXSIZE];
963 int datalen = dns->cdc->decode (data, qname + HDRSIZE, qlen - (dlen + 1 + HDRSIZE));
964
965 for (vector<dns_rcv *>::iterator i = dns->rcvpq.end (); i-- != dns->rcvpq.begin (); )
547 if ((*i)->seqno == seqno) 966 if (SEQNO_EQ ((*i)->seqno, seqno))
967 {
968 // already seen that request: simply reply with the cached reply
969 dns_rcv *r = *i;
970
971 slog (L_DEBUG, "DNS: duplicate packet received ID %d, SEQ %d", htons (r->pkt->id), seqno);
972
973 // refresh header & id, as the retry count could have changed
974 memcpy (r->pkt->at (6 * 2 + 1), pkt.at (6 * 2 + 1), HDRSIZE);
975 r->pkt->id = pkt.id;
976
977 memcpy (pkt.at (0), r->pkt->at (0), offs = r->pkt->len);
978
979 goto duplicate_request;
980 }
981
982 // new packet, queue
983 rcv = new dns_rcv (seqno, data, datalen);
984 dns->receive_rep (rcv);
985 }
986
548 { 987 {
549 // already seen that request: simply reply with the cached reply 988 pkt [offs++] = 0xc0; pkt [offs++] = 6 * 2; // refer to name in query section
550 dns_rcv *r = *i;
551 989
552 printf ("DUPLICATE %d\n", htons (r->pkt->id));//D 990 int rtype = dns ? dns->cfg.rrtype : RR_TYPE_A;
991 pkt [offs++] = rtype >> 8; pkt [offs++] = rtype; // type
992 pkt [offs++] = RR_CLASS_IN >> 8; pkt [offs++] = RR_CLASS_IN; // class
993 pkt [offs++] = 0; pkt [offs++] = 0;
994 pkt [offs++] = 0; pkt [offs++] = dns ? dns->cfg.def_ttl : 0; // TTL
553 995
996 int rdlen_offs = offs += 2;
997
998 if (dns)
999 {
1000 int dlen = ntohs (dns->cfg.max_size) - offs;
1001
1002 // bind doesn't compress well, so reduce further by one label length
1003 dlen -= qlen;
1004
1005 // only put data into in-order sequence packets, if
1006 // we receive out-of-order packets we generate empty
1007 // replies
1008 //printf ("%d - %d & %x (=%d) < %d\n", seqno, dns->repseq, SEQNO_MASK, (seqno - dns->repseq) & SEQNO_MASK, MAX_WINDOW);//D
1009 if (((seqno - dns->repseq) & SEQNO_MASK) <= MAX_WINDOW)
1010 {
1011 dns->repseq = seqno;
1012
1013 while (dlen > 1 && !dns->snddq.empty ())
1014 {
1015 int txtlen = dlen <= 255 ? dlen - 1 : 255;
1016
1017 if (txtlen > dns->snddq.size ())
1018 txtlen = dns->snddq.size ();
1019
1020 pkt[offs++] = txtlen;
1021 memcpy (pkt.at (offs), dns->snddq.begin (), txtlen);
1022 offs += txtlen;
1023 dns->snddq.remove (txtlen);
1024
1025 dlen -= txtlen + 1;
1026 }
1027 }
1028
1029 // avoid completely empty TXT rdata
1030 if (offs == rdlen_offs)
1031 pkt[offs++] = 0;
1032
1033 slog (L_NOISE, "DNS: snddq %d", dns->snddq.size ());
1034 }
1035 else
1036 {
1037 // send RST
1038 pkt [offs++] = CMD_IP_1; pkt [offs++] = CMD_IP_2; pkt [offs++] = CMD_IP_3;
1039 pkt [offs++] = CMD_IP_RST;
1040 }
1041
1042 int rdlen = offs - rdlen_offs;
1043
1044 pkt [rdlen_offs - 2] = rdlen >> 8;
1045 pkt [rdlen_offs - 1] = rdlen;
1046
1047 if (dns)
1048 {
1049 // now update dns_rcv copy
554 offs = r->pkt->len; 1050 rcv->pkt->len = offs;
555 memcpy (pkt->at (0), r->pkt->at (0), offs); 1051 memcpy (rcv->pkt->at (0), pkt.at (0), offs);
556 goto duplicate_request; 1052 }
557 } 1053 }
558 1054
559 // new packet, queue 1055 duplicate_request: ;
560 dns_rcv *rcv = new dns_rcv (seqno, data + 3, datalen - 3); 1056 }
561 c->dnsv4_receive_rep (rcv); 1057 else
562
563 // now generate reply
564 pkt->ancount = htons (1); // one answer RR
565 pkt->flags = htons (DEFAULT_SERVER_FLAGS | FLAG_RCODE_OK); 1058 pkt.flags = htons (DEFAULT_SERVER_FLAGS | FLAG_RCODE_FORMERR);
1059 }
1060 else if (qtype == RR_TYPE_A
1061 && qlen > dlen + 1 + cdc26.encode_len (sizeof (dns_cfg)))
1062 {
1063 dns_cfg cfg;
1064 cdc26.decode ((u8 *)&cfg, qname, cdc26.encode_len (sizeof (dns_cfg)));
1065 int client = ntohs (cfg.client);
566 1066
567 (*pkt) [offs++] = 0xc0;
568 (*pkt) [offs++] = 6 * 2; // same as in query section 1067 pkt [offs++] = 0xc0; pkt [offs++] = 6 * 2; // refer to name in query section
569 1068
570 (*pkt) [offs++] = RR_TYPE_TXT >> 8; (*pkt) [offs++] = RR_TYPE_TXT; 1069 pkt [offs++] = RR_TYPE_A >> 8; pkt [offs++] = RR_TYPE_A; // type
571 (*pkt) [offs++] = RR_CLASS_IN >> 8; (*pkt) [offs++] = RR_CLASS_IN; 1070 pkt [offs++] = RR_CLASS_IN >> 8; pkt [offs++] = RR_CLASS_IN; // class
572
573 (*pkt) [offs++] = 0; (*pkt) [offs++] = 0; 1071 pkt [offs++] = 0; pkt [offs++] = 0;
574 (*pkt) [offs++] = 0; (*pkt) [offs++] = 0; // TTL 1072 pkt [offs++] = 0; pkt [offs++] = cfg.def_ttl; // TTL
1073 pkt [offs++] = 0; pkt [offs++] = 4; // rdlength
575 1074
576 int dlen = MAX_PKT_SIZE - offs - 2; 1075 pkt [offs++] = CMD_IP_1; pkt [offs++] = CMD_IP_2; pkt [offs++] = CMD_IP_3;
1076 pkt [offs++] = CMD_IP_REJ;
577 1077
578 // bind doesn't compress well, so reduce further by one label length 1078 if (0 < client && client <= conns.size ())
579 dlen -= qlen;
580
581 int rdlen_offs = offs += 2;
582
583 while (c->dns_snddq
584 && !c->dns_snddq->empty ()
585 && dlen > 1)
586 { 1079 {
587 int txtlen = dlen <= 255 ? dlen - 1 : 255; 1080 connection *c = conns [client - 1];
588 1081
589 if (txtlen > c->dns_snddq->size ()) 1082 if (cfg.valid ())
1083 {
1084 slog (L_INFO, _("DNS: client %d connects (version %d, req_cdc %d)"), client, cfg.version, cfg.req_cdc);
1085
1086 // check for any encoding mismatches - hints at a case problem
1087 char qname2 [MAX_ENC_LEN];
1088 cdc26.encode (qname2, (u8 *)&cfg, sizeof (dns_cfg));
1089
1090 delete c->dns;
1091
1092 pkt [offs - 1] = memcmp (qname, qname2, cdc26.encode_len (sizeof (dns_cfg)))
1093 ? CMD_IP_CSE : CMD_IP_SYN;
1094
1095 c->dns = new dns_connection (c);
1096 c->dns->cfg = cfg;
590 txtlen = c->dns_snddq->size (); 1097 c->dns->set_cfg ();
591 1098 }
592 (*pkt)[offs++] = txtlen;
593 memcpy (pkt->at (offs), c->dns_snddq->begin (), txtlen);
594 offs += txtlen;
595 c->dns_snddq->remove (txtlen);
596
597 dlen -= txtlen + 1;
598 } 1099 }
599
600 // avoid empty TXT rdata
601 if (offs == rdlen_offs)
602 (*pkt)[offs++] = 0;
603
604 int rdlen = offs - rdlen_offs;
605
606 (*pkt) [rdlen_offs - 2] = rdlen >> 8;
607 (*pkt) [rdlen_offs - 1] = rdlen;
608
609 // now update dns_rcv copy
610 rcv->pkt->len = offs;
611 memcpy (rcv->pkt->at (0), pkt->at (0), offs);
612
613 duplicate_request: ;
614 } 1100 }
615 else
616 pkt->flags = htons (DEFAULT_SERVER_FLAGS | FLAG_RCODE_FORMERR);
617 } 1101 }
618 1102
619 pkt->len = offs; 1103 pkt.len = offs;
620 } 1104 }
621
622 return pkt;
623} 1105}
624 1106
625void 1107void
626vpn::dnsv4_client (dns_packet *pkt) 1108vpn::dnsv4_client (dns_packet &pkt)
627{ 1109{
628 u16 flags = ntohs (pkt->flags); 1110 u16 flags = ntohs (pkt.flags);
629 int offs = 6 * 2; // skip header 1111 int offs = 6 * 2; // skip header
630 1112
631 pkt->qdcount = ntohs (pkt->qdcount); 1113 pkt.qdcount = ntohs (pkt.qdcount);
632 pkt->ancount = ntohs (pkt->ancount); 1114 pkt.ancount = ntohs (pkt.ancount);
633 1115
634 // go through our request list and find the corresponding request 1116 // go through our request list and find the corresponding request
635 for (vector<dns_req *>::iterator i = dns_sndpq.begin (); 1117 for (vector<dns_snd *>::iterator i = dns_sndpq.begin ();
636 i != dns_sndpq.end (); 1118 i != dns_sndpq.end ();
637 ++i) 1119 ++i)
638 if ((*i)->pkt->id == pkt->id) 1120 if ((*i)->pkt->id == pkt.id)
639 { 1121 {
1122 dns_connection *dns = (*i)->dns;
640 connection *c = (*i)->conn; 1123 connection *c = dns->c;
641 int seqno = (*i)->seqno; 1124 int seqno = (*i)->seqno;
642 u8 data[MAXSIZE], *datap = data; 1125 u8 data[MAXSIZE], *datap = data;
1126 //printf ("rcv pkt %x\n", seqno);//D
1127
1128 if ((*i)->retry)
1129 {
1130 dns->send_interval *= 1.01;
1131 if (dns->send_interval > MAX_SEND_INTERVAL)
1132 dns->send_interval = MAX_SEND_INTERVAL;
1133 }
1134 else
1135 {
1136#if 0
1137 dns->send_interval *= 0.999;
1138#endif
1139 // the latency surely puts an upper bound on
1140 // the minimum send interval
1141 double latency = ev_now () - (*i)->sent;
1142
1143 if (latency < dns->min_latency)
1144 dns->min_latency = latency;
1145
1146 if (dns->send_interval > dns->min_latency * conf.dns_overlap_factor)
1147 dns->send_interval = dns->min_latency * conf.dns_overlap_factor;
1148
1149 if (dns->send_interval < conf.dns_send_interval)
1150 dns->send_interval = conf.dns_send_interval;
1151 }
643 1152
644 delete *i; 1153 delete *i;
645 dns_sndpq.erase (i); 1154 dns_sndpq.erase (i);
646 1155
647 if (flags & (FLAG_RESPONSE | FLAG_OP_MASK | FLAG_TC)) 1156 if (flags & FLAG_RESPONSE && !(flags & FLAG_OP_MASK))
648 { 1157 {
649 char qname[MAXSIZE]; 1158 char qname[MAXSIZE];
650 1159
651 while (pkt->qdcount-- && offs < MAXSIZE - 4) 1160 while (pkt.qdcount-- && offs < MAXSIZE - 4)
652 { 1161 {
653 int qlen = pkt->decode_label ((char *)qname, MAXSIZE - offs, offs); 1162 int qlen = pkt.decode_label ((char *)qname, MAXSIZE - offs, offs);
654 offs += 4; // skip qtype, qclass 1163 offs += 4; // skip qtype, qclass
655 } 1164 }
656 1165
657 while (pkt->ancount-- && offs < MAXSIZE - 10) 1166 while (pkt.ancount-- && offs < MAXSIZE - 10 && datap)
658 { 1167 {
659 pkt->decode_label ((char *)qname, MAXSIZE - offs, offs); 1168 int qlen = pkt.decode_label ((char *)qname, MAXSIZE - offs, offs);
660 1169
661 u16 qtype = (*pkt) [offs++] << 8; qtype |= (*pkt) [offs++]; 1170 u16 qtype = pkt [offs++] << 8; qtype |= pkt [offs++];
662 u16 qclass = (*pkt) [offs++] << 8; qclass |= (*pkt) [offs++]; 1171 u16 qclass = pkt [offs++] << 8; qclass |= pkt [offs++];
663 u32 ttl = (*pkt) [offs++] << 24; 1172 u32 ttl = pkt [offs++] << 24;
664 ttl |= (*pkt) [offs++] << 16; 1173 ttl |= pkt [offs++] << 16;
665 ttl |= (*pkt) [offs++] << 8; 1174 ttl |= pkt [offs++] << 8;
666 ttl |= (*pkt) [offs++]; 1175 ttl |= pkt [offs++];
667
668 u16 rdlen = (*pkt) [offs++] << 8; rdlen |= (*pkt) [offs++]; 1176 u16 rdlen = pkt [offs++] << 8; rdlen |= pkt [offs++];
669 1177
670 if (rdlen <= MAXSIZE - offs) 1178 if (qtype == RR_TYPE_NULL || qtype == RR_TYPE_TXT || qtype == dns->cfg.rrtype)
671 { 1179 {
672 // decode bytes, finally 1180 if (rdlen <= MAXSIZE - offs)
673
674 while (rdlen)
675 { 1181 {
1182 // decode bytes, finally
1183
1184 while (rdlen)
1185 {
676 int txtlen = (*pkt) [offs++]; 1186 int txtlen = pkt [offs++];
677 1187
678 assert (txtlen + offs < MAXSIZE - 1); 1188 assert (txtlen + offs < MAXSIZE - 1);
679 1189
680 memcpy (datap, pkt->at (offs), txtlen); 1190 memcpy (datap, pkt.at (offs), txtlen);
681 datap += txtlen; offs += txtlen; 1191 datap += txtlen; offs += txtlen;
682 1192
683 rdlen -= txtlen + 1; 1193 rdlen -= txtlen + 1;
1194 }
684 } 1195 }
685
686 } 1196 }
1197 else if (qtype == RR_TYPE_A)
1198 {
1199 u8 ip [4];
687 1200
1201 ip [0] = pkt [offs++];
1202 ip [1] = pkt [offs++];
1203 ip [2] = pkt [offs++];
1204 ip [3] = pkt [offs++];
1205
1206 if (ip [0] == CMD_IP_1
1207 && ip [1] == CMD_IP_2
1208 && ip [2] == CMD_IP_3)
1209 {
1210 slog (L_TRACE, _("DNS: got tunnel meta command %02x"), ip [3]);
1211
1212 if (ip [3] == CMD_IP_RST)
1213 {
1214 slog (L_DEBUG, _("DNS: got tunnel RST request."));
1215
1216 dns->reset ();
1217 return;
1218 }
1219 else if (ip [3] == CMD_IP_SYN)
1220 {
1221 slog (L_DEBUG, _("DNS: got tunnel SYN reply, server likes us."));
1222 dns->established = true;
1223 }
1224 else if (ip [3] == CMD_IP_CSE)
1225 {
1226 if (conf.dns_case_preserving)
1227 {
1228 slog (L_INFO, _("DNS: got tunnel CSE reply, globally downgrading to case-insensitive protocol."));
1229 conf.dns_case_preserving = false;
1230 dns->reset ();
1231 return;
1232 }
1233 else
1234 {
1235 slog (L_DEBUG, _("DNS: got tunnel CSE reply, server likes us."));
1236 dns->established = true;
1237 }
1238 }
1239 else if (ip [3] == CMD_IP_REJ)
1240 {
1241 slog (L_ERR, _("DNS: got tunnel REJ reply, server does not like us."));
1242 dns->tw.start (60.);
1243 }
1244 else
1245 {
1246 slog (L_INFO, _("DNS: got unknown meta command %02x"), ip [3]);
1247 dns->tw.start (60.);
1248 }
1249 }
1250 else
1251 slog (L_INFO, _("DNS: got spurious a record %d.%d.%d.%d"),
1252 ip [0], ip [1], ip [2], ip [3]);
1253
1254 return;
1255 }
1256
1257 int client, rseqno;
1258 decode_header (qname, client, rseqno);
1259
1260 if (client != THISNODE->id)
1261 {
1262 slog (L_INFO, _("DNS: got dns tunnel response with wrong clientid, ignoring"));
1263 datap = 0;
1264 }
1265 else if (rseqno != seqno)
1266 {
1267 slog (L_DEBUG, _("DNS: got dns tunnel response with wrong seqno, badly caching nameserver?"));
1268 datap = 0;
1269 }
688 } 1270 }
689 } 1271 }
690 1272
691 // todo: pkt now used 1273 // todo: pkt now used
1274 if (datap)
692 c->dnsv4_receive_rep (new dns_rcv (seqno, data, datap - data)); 1275 dns->receive_rep (new dns_rcv (seqno, data, datap - data));
693 1276
694 break; 1277 break;
695 } 1278 }
696
697 delete pkt;
698} 1279}
699 1280
700void 1281void
701vpn::dnsv4_ev (io_watcher &w, short revents) 1282vpn::dnsv4_ev (ev::io &w, int revents)
702{ 1283{
703 if (revents & EVENT_READ) 1284 if (revents & EV_READ)
704 { 1285 {
705 dns_packet *pkt = new dns_packet; 1286 dns_packet *pkt = new dns_packet;
706 struct sockaddr_in sa; 1287 struct sockaddr_in sa;
707 socklen_t sa_len = sizeof (sa); 1288 socklen_t sa_len = sizeof (sa);
708 1289
709 pkt->len = recvfrom (w.fd, &((*pkt)[0]), MAXSIZE, 0, (sockaddr *)&sa, &sa_len); 1290 pkt->len = recvfrom (w.fd, pkt->at (0), MAXSIZE, 0, (sockaddr *)&sa, &sa_len);
710 1291
711 if (pkt->len > 0) 1292 if (pkt->len > 0)
712 { 1293 {
713 if (pkt->flags & htons (FLAG_TC)) 1294 if (ntohs (pkt->flags) & FLAG_RESPONSE)
1295 dnsv4_client (*pkt);
1296 else
714 { 1297 {
715 slog (L_WARN, _("DNS request/response truncated, check protocol settings.")); 1298 dnsv4_server (*pkt);
716 //TODO connection reset 1299 sendto (w.fd, pkt->at (0), pkt->len, 0, (sockaddr *)&sa, sa_len);
717 } 1300 }
718 1301
719 if (THISNODE->dns_port) 1302 delete pkt;
720 {
721 pkt = dnsv4_server (pkt);
722 sendto (w.fd, &((*pkt)[0]), pkt->len, 0, (sockaddr *)&sa, sa_len);
723 }
724 else
725 dnsv4_client (pkt);
726 } 1303 }
727 } 1304 }
728} 1305}
729 1306
730bool 1307bool
731connection::send_dnsv4_packet (vpn_packet *pkt, const sockinfo &si, int tos) 1308vpn::send_dnsv4_packet (vpn_packet *pkt, const sockinfo &si, int tos)
732{ 1309{
733 // never initialized 1310 int client = ntohl (si.host);
734 if (!dns_snddq && !dns_rcvdq)
735 {
736 dns_rcvdq = new byte_stream (MAX_BACKLOG * 2);
737 dns_snddq = new byte_stream (MAX_BACKLOG);
738 1311
739 //dns_rcvseq = dns_sndseq = 0; 1312 assert (0 < client && client <= conns.size ());
740 1313
741 dns_si.set (::conf.dns_forw_host, ::conf.dns_forw_port, PROT_DNSv4); 1314 connection *c = conns [client - 1];
742 } 1315
1316 if (!c->dns)
1317 c->dns = new dns_connection (c);
743 1318
744 if (!dns_snddq->put (pkt)) 1319 if (c->dns->snddq.put (pkt))
745 return false; 1320 {
1321 min_it (c->dns->poll_interval, 0.25);
1322 c->dns->tw ();
1323 }
746 1324
747 // start timer if neccessary 1325 // always return true even if the buffer overflows
748 if (!THISNODE->dns_port && !dnsv4_tw.active)
749 dnsv4_cb (dnsv4_tw);
750
751 return true; 1326 return true;
752} 1327}
753 1328
754void 1329void
755connection::dnsv4_cb (time_watcher &w) 1330dns_connection::time_cb (ev::timer &w, int revents)
756{ 1331{
1332 // servers have to be polled
1333 if (THISNODE->dns_port)
1334 return;
1335
757 // check for timeouts and (re)transmit 1336 // check for timeouts and (re)transmit
758 tstamp next = NOW + 60; 1337 tstamp next = 86400 * 365;
759 dns_req *send = 0; 1338 dns_snd *send = 0;
760 1339
761 for (vector<dns_req *>::iterator i = vpn->dns_sndpq.begin (); 1340 for (vector<dns_snd *>::iterator i = vpn->dns_sndpq.begin ();
762 i != vpn->dns_sndpq.end (); 1341 i != vpn->dns_sndpq.end ();
763 ++i) 1342 ++i)
764 { 1343 {
765 dns_req *r = *i; 1344 dns_snd *r = *i;
766 1345
767 if (r->next <= NOW) 1346 if (r->timeout <= ev_now ())
768 { 1347 {
769 if (!send) 1348 if (!send)
770 { 1349 {
771 send = r; 1350 send = r;
772 1351
773 if (r->retry)//D
774 printf ("req %d, retry %d\n", r->pkt->id, r->retry);
775 r->retry++; 1352 r->retry++;
776 r->next = NOW + r->retry; 1353 r->timeout = ev_now () + r->retry * min_latency * conf.dns_timeout_factor;
1354 //printf ("RETRY %x (%d, %f)\n", r->seqno, r->retry, r->timeout - ev_now ());//D
1355
1356 // the following code changes the query section a bit, forcing
1357 // the forwarder to generate a new request
1358 if (r->stdhdr)
1359 encode_header ((char *)r->pkt->at (6 * 2 + 1), THISNODE->id, r->seqno, r->retry);
777 } 1360 }
778 } 1361 }
779 1362 else
780 if (r->next < next) 1363 min_it (next, r->timeout - ev_now ());
781 next = r->next;
782 } 1364 }
783 1365
784 if (!send 1366 if (!send)
785 && vpn->dns_sndpq.size () < MAX_OUTSTANDING)
786 { 1367 {
1368 // generate a new packet, if wise
1369
1370 if (!established)
1371 {
1372 if (vpn->dns_sndpq.empty ())
1373 {
787 send = new dns_req (this); 1374 send = new dns_snd (this);
1375
1376 cfg.reset (THISNODE->id);
1377 set_cfg ();
1378 send->gen_syn_req ();
1379 }
1380 }
1381 else if (vpn->dns_sndpq.size () < conf.dns_max_outstanding
1382 && !SEQNO_EQ (rcvseq, sndseq - (MAX_WINDOW - 1)))
1383 {
1384 if (last_sent + send_interval <= ev_now ())
1385 {
1386 //printf ("sending data request etc.\n"); //D
1387 if (!snddq.empty ())
1388 min_it (next, send_interval);
1389
1390 send = new dns_snd (this);
788 send->gen_stream_req (dns_sndseq, dns_snddq); 1391 send->gen_stream_req (sndseq, snddq);
1392 send->timeout = ev_now () + min_latency * conf.dns_timeout_factor;
1393 //printf ("SEND %x (%f)\n", send->seqno, send->timeout - ev_now (), min_latency, conf.dns_timeout_factor);//D
1394
1395 sndseq = (sndseq + 1) & SEQNO_MASK;
1396 }
1397 else
1398 min_it (next, last_sent + send_interval - ev_now ());
1399 }
1400
1401 if (send)
789 vpn->dns_sndpq.push_back (send); 1402 vpn->dns_sndpq.push_back (send);
790
791 dns_sndseq = (dns_sndseq + 1) & SEQNO_MASK;
792 } 1403 }
793
794 tstamp min_next = NOW + (1. / (tstamp)MAX_RATE);
795 1404
796 if (send) 1405 if (send)
797 { 1406 {
798 dns_packet *pkt = send->pkt; 1407 last_sent = ev_now ();
799 1408 sendto (vpn->dnsv4_fd,
800 next = min_next; 1409 send->pkt->at (0), send->pkt->len, 0,
801 1410 vpn->dns_forwarder.sav4 (), vpn->dns_forwarder.salenv4 ());
802 sendto (vpn->dnsv4_fd, &((*pkt)[0]), pkt->len, 0, dns_si.sav4 (), dns_si.salenv4 ());
803 } 1411 }
804 else if (next < min_next) 1412
805 next = min_next; 1413 min_it (next, last_sent + max (poll_interval, send_interval) - ev_now ());
1414
1415 slog (L_NOISE, "DNS: pi %f si %f N %f (%d:%d %d)",
1416 poll_interval, send_interval, next - ev_now (),
1417 vpn->dns_sndpq.size (), snddq.size (),
1418 rcvpq.size ());
806 1419
807 w.start (next); 1420 w.start (next);
808} 1421}
809 1422
810#endif 1423#endif

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