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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 1.54 by root, Tue Oct 18 11:07:28 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 0.025 // poll at most this often when no data received
47#define MAX_RETRY 60. 65#define MAX_POLL_INTERVAL 1. // how often to poll minimally when the server has no data
48 66
49#define MAX_OUTSTANDING 40 // max. outstanding requests 67#define INITIAL_TIMEOUT 0.1 // retry timeouts
68#define INITIAL_SYN_TIMEOUT 2. // retry timeout for initial syn
69
70#define MAX_SEND_INTERVAL 5. // optimistic?
71
50#define MAX_WINDOW 100 // max. for MAX_OUTSTANDING 72#define MAX_WINDOW 1000 // max. for MAX_OUTSTANDING, and backlog
51#define MAX_RATE 1000 // requests/s
52#define MAX_BACKLOG (10*1024) // size of protocol backlog, must be > MAXSIZE 73#define MAX_BACKLOG (64*1024) // size of gvpe protocol backlog (bytes), must be > MAXSIZE
53 74
54#define MAX_DOMAIN_SIZE 220 // 255 is legal limit, but bind doesn't compress well 75#define MAX_DOMAIN_SIZE 235 // 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 if (fill < 2)
403 return 0;
404
405 unsigned int len;
406
407 for (;;)
408 {
230 int len = (data [0] << 8) | data [1]; 409 len = (data [0] << 8) | data [1];
231 410
232 if (len > MAXSIZE && fill >= 2) 411 if (len <= MAXSIZE)
233 abort (); // TODO handle this gracefully, connection reset 412 break;
234 413
414 // TODO: handle this better than skipping, e.g. by reset
415 slog (L_DEBUG, _("DNS: corrupted packet (%02x %02x) stream skipping a byte..."), data [0], data [1]);
416 remove (1);
417 }
418
235 if (fill < len + 2) 419 if (fill < len + 2)
236 return 0; 420 return 0;
237 421
238 vpn_packet *pkt = new vpn_packet; 422 vpn_packet *pkt = new vpn_packet;
239 423
240 pkt->len = len; 424 pkt->len = len;
241 memcpy (&((*pkt)[0]), data + 2, len); 425 memcpy (pkt->at (0), data + 2, len);
242 remove (len + 2); 426 remove (len + 2);
243 427
244 return pkt; 428 return pkt;
245} 429}
246 430
247///////////////////////////////////////////////////////////////////////////// 431/////////////////////////////////////////////////////////////////////////////
248 432
249#define FLAG_QUERY ( 0 << 15) 433#define FLAG_QUERY ( 0 << 15)
250#define FLAG_RESPONSE ( 1 << 15) 434#define FLAG_RESPONSE ( 1 << 15)
251#define FLAG_OP_MASK (15 << 14) 435#define FLAG_OP_MASK (15 << 11)
252#define FLAG_OP_QUERY ( 0 << 11) 436#define FLAG_OP_QUERY ( 0 << 11)
253#define FLAG_AA ( 1 << 10) 437#define FLAG_AA ( 1 << 10)
254#define FLAG_TC ( 1 << 9) 438#define FLAG_TC ( 1 << 9)
255#define FLAG_RD ( 1 << 8) 439#define FLAG_RD ( 1 << 8)
256#define FLAG_RA ( 1 << 7) 440#define FLAG_RA ( 1 << 7)
… …
263#define FLAG_RCODE_REFUSED ( 5 << 0) 447#define FLAG_RCODE_REFUSED ( 5 << 0)
264 448
265#define DEFAULT_CLIENT_FLAGS (FLAG_QUERY | FLAG_OP_QUERY | FLAG_RD) 449#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) 450#define DEFAULT_SERVER_FLAGS (FLAG_RESPONSE | FLAG_OP_QUERY | FLAG_AA | FLAG_RD | FLAG_RA)
267 451
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
268struct dns_packet : net_packet 545struct dns_packet : net_packet
269{ 546{
270 u16 id; 547 u16 id;
271 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
272 u16 qdcount, ancount, nscount, arcount; 549 u16 qdcount, ancount, nscount, arcount;
273 550
274 u8 data[MAXSIZE - 6 * 2]; 551 u8 data [MAXSIZE - 6 * 2];
275 552
276 int decode_label (char *data, int size, int &offs); 553 int decode_label (char *data, int size, int &offs);
277}; 554};
278 555
556int
279int dns_packet::decode_label (char *data, int size, int &offs) 557dns_packet::decode_label (char *data, int size, int &offs)
280{ 558{
281 char *orig = data; 559 char *orig = data;
282 560
283 memset (data, 0, size); 561 memset (data, 0, size);
284 562
… …
310 return data - orig; 588 return data - orig;
311} 589}
312 590
313///////////////////////////////////////////////////////////////////////////// 591/////////////////////////////////////////////////////////////////////////////
314 592
315struct dns_req 593static
594u16 next_id ()
316{ 595{
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 596 static u16 dns_id = 0; // TODO: should be per-vpn
328 597
329static u16 next_id () 598#if 1
330{ 599 if (!dns_id)
600 dns_id = time (0);
601
331 // the simplest lsfr with periodicity 65535 i could find 602 // the simplest lsfr with periodicity 65535 i could find
332 dns_id = (dns_id << 1) 603 dns_id = (dns_id << 1)
333 | (((dns_id >> 1) 604 | (((dns_id >> 1)
334 ^ (dns_id >> 2) 605 ^ (dns_id >> 2)
335 ^ (dns_id >> 4) 606 ^ (dns_id >> 4)
336 ^ (dns_id >> 15)) & 1); 607 ^ (dns_id >> 15)) & 1);
337 608
338 return dns_id; 609 return dns_id;
339} 610#else
611 dns_id++;//D
340 612
341dns_req::dns_req (connection *c) 613 return htons (dns_id);
342: conn (c) 614#endif
615}
616
617struct dns_rcv;
618struct dns_snd;
619
620struct dns_connection
343{ 621{
344 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;
345 retry = 0; 670 retry = 0;
671 seqno = 0;
672 sent = ev_now ();
673 stdhdr = false;
346 674
347 pkt = new dns_packet; 675 pkt = new dns_packet;
348 676
349 pkt->id = next_id (); 677 pkt->id = next_id ();
350} 678}
351 679
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
352void dns_req::gen_stream_req (int seqno, byte_stream *stream) 710dns_snd::gen_stream_req (int seqno, byte_stream &stream)
353{ 711{
712 stdhdr = true;
354 this->seqno = seqno; 713 this->seqno = seqno;
714
715 timeout = ev_now () + INITIAL_TIMEOUT;
355 716
356 pkt->flags = htons (DEFAULT_CLIENT_FLAGS); 717 pkt->flags = htons (DEFAULT_CLIENT_FLAGS);
357 pkt->qdcount = htons (1); 718 pkt->qdcount = htons (1);
358 719
359 int offs = 6*2; 720 int offs = 6*2;
360 int dlen = MAX_DOMAIN_SIZE - strlen (THISNODE->domain) - 2; 721 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, 722 // 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 723 // so we need to have space for 2*MAX_DOMAIN_SIZE + header + extra
363 724
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; 725 char enc[256], *encp = enc;
376 726 encode_header (enc, THISNODE->id, seqno);
377 memcpy (data + 3, stream->begin (), datalen); 727
378 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;
379 stream->remove (datalen); 734 stream.remove (datalen);
380 735
381 while (enclen) 736 while (enclen)
382 { 737 {
383 int lbllen = enclen < MAX_LBL_SIZE ? enclen : MAX_LBL_SIZE; 738 int lbllen = enclen < MAX_LBL_SIZE ? enclen : MAX_LBL_SIZE;
384 739
… …
389 encp += lbllen; 744 encp += lbllen;
390 745
391 enclen -= lbllen; 746 enclen -= lbllen;
392 } 747 }
393 748
394 const char *suffix = THISNODE->domain; 749 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 }
415 750
416 (*pkt)[offs++] = 0; 751 (*pkt)[offs++] = 0;
417 (*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;
418 (*pkt)[offs++] = RR_CLASS_IN >> 8; (*pkt)[offs++] = RR_CLASS_IN; 778 (*pkt)[offs++] = RR_CLASS_IN >> 8; (*pkt)[offs++] = RR_CLASS_IN;
419 779
420 pkt->len = offs; 780 pkt->len = offs;
421} 781}
422 782
… …
441{ 801{
442 delete pkt; 802 delete pkt;
443} 803}
444 804
445///////////////////////////////////////////////////////////////////////////// 805/////////////////////////////////////////////////////////////////////////////
446 806
447struct dns_cfg 807dns_connection::dns_connection (connection *c)
808: c (c)
809, rcvdq (MAX_BACKLOG * 2)
810, snddq (MAX_BACKLOG)
448{ 811{
449 u8 id1, id2, id3; 812 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};
455 813
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
456void connection::dnsv4_receive_rep (struct dns_rcv *r) 857dns_connection::receive_rep (dns_rcv *r)
457{ 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
458 dns_rcvpq.push_back (r); 864 rcvpq.push_back (r);
459 865
460 redo: 866 redo:
461 867
868 // find next packet
462 for (vector<dns_rcv *>::iterator i = dns_rcvpq.begin (); 869 for (vector<dns_rcv *>::iterator i = rcvpq.end (); i-- != rcvpq.begin (); )
463 i != dns_rcvpq.end ();
464 ++i)
465 if (dns_rcvseq == (*i)->seqno) 870 if (SEQNO_EQ (rcvseq, (*i)->seqno))
466 { 871 {
872 //printf ("seqno eq %x %x\n", rcvseq, (*i)->seqno);//D
873 // enter the packet into our input stream
467 dns_rcv *r = *i; 874 r = *i;
468 875
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
469 dns_rcvseq = (dns_rcvseq + 1) & SEQNO_MASK; 886 rcvseq = (rcvseq + 1) & SEQNO_MASK;
470 887
471 if (!dns_snddq && !dns_rcvdq) 888 if (!rcvdq.put (r->data, r->datalen))
472 { 889 {
473 dns_rcvdq = new byte_stream (MAX_BACKLOG * 2); 890 // MUST never overflow, can be caused by data corruption, TODO
474 dns_snddq = new byte_stream (MAX_BACKLOG); 891 slog (L_CRIT, "DNS: !rcvdq.put (r->data, r->datalen)");
475 892 reset ();
476 dns_si.set (::conf.dns_forw_host, ::conf.dns_forw_port, PROT_DNSv4); 893 return;
477 } 894 }
478 895
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 ()) 896 while (vpn_packet *pkt = rcvdq.get ())
483 { 897 {
484 sockinfo si; 898 sockinfo si;
485 si.host = 0; si.port = 0; si.prot = PROT_DNSv4; 899 si.host = htonl (c->conf->id); si.port = 0; si.prot = PROT_DNSv4;
486 900
487 vpn->recv_vpn_packet (pkt, si); 901 vpn->recv_vpn_packet (pkt, si);
902 delete pkt;
488 } 903 }
489 } 904
490 else if ((u32)(*i)->seqno - (u32)dns_rcvseq + MAX_WINDOW > MAX_WINDOW * 2) 905 // 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; 906 goto redo;
497 } 907 }
498} 908}
499 909
500dns_packet * 910void
501vpn::dnsv4_server (dns_packet *pkt) 911vpn::dnsv4_server (dns_packet &pkt)
502{ 912{
503 u16 flags = ntohs (pkt->flags); 913 u16 flags = ntohs (pkt.flags);
504 914
505 //memcpy (&((*rep)[0]), &((*pkt)[0]), pkt->len);
506 int offs = 6 * 2; // skip header 915 int offs = 6 * 2; // skip header
507 916
508 pkt->flags = htons (DEFAULT_SERVER_FLAGS | FLAG_RCODE_FORMERR); 917 pkt.flags = htons (DEFAULT_SERVER_FLAGS | FLAG_RCODE_FORMERR);
509 918
510 if (!(flags & (FLAG_RESPONSE | FLAG_OP_MASK | FLAG_TC)) 919 if (0 == (flags & (FLAG_RESPONSE | FLAG_OP_MASK))
511 && pkt->qdcount == htons (1)) 920 && pkt.qdcount == htons (1))
512 { 921 {
513 char qname[MAXSIZE]; 922 char qname [MAXSIZE];
514 int qlen = pkt->decode_label ((char *)qname, MAXSIZE - offs, offs); 923 int qlen = pkt.decode_label ((char *)qname, MAXSIZE - offs, offs);
515 924
516 u16 qtype = (*pkt) [offs++] << 8; qtype |= (*pkt) [offs++]; 925 u16 qtype = pkt [offs++] << 8; qtype |= pkt [offs++];
517 u16 qclass = (*pkt) [offs++] << 8; qclass |= (*pkt) [offs++]; 926 u16 qclass = pkt [offs++] << 8; qclass |= pkt [offs++];
518 927
519 pkt->qdcount = htons (1); 928 pkt.qdcount = htons (1);
520 pkt->ancount = 0; 929 pkt.ancount = 0;
521 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
522 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
523 932
524 pkt->flags = htons (DEFAULT_SERVER_FLAGS | FLAG_RCODE_NXDOMAIN); 933 pkt.flags = htons (DEFAULT_SERVER_FLAGS | FLAG_RCODE_SERVFAIL);
525 934
526 int dlen = strlen (THISNODE->domain); 935 int dlen = strlen (THISNODE->domain);
527 936
528 if (qclass == RR_CLASS_IN 937 if (qclass == RR_CLASS_IN
529 && (qtype == RR_TYPE_ANY || qtype == RR_TYPE_TXT)
530 && qlen > dlen + 1 938 && qlen > dlen + 1
531 && !memcmp (qname + qlen - dlen - 1, THISNODE->domain, dlen)) 939 && !memcmp (qname + qlen - (dlen + 1), THISNODE->domain, dlen))
532 { 940 {
533 // correct class, domain: parse 941 // now generate reply
534 u8 data[MAXSIZE]; 942 pkt.ancount = htons (1); // one answer RR
535 int datalen = dns64::decode (data, qname, qlen - dlen - 1); 943 pkt.flags = htons (DEFAULT_SERVER_FLAGS | FLAG_RCODE_OK);
536 944
537 int client = data[0]; 945 if ((qtype == RR_TYPE_ANY
538 int seqno = ((data[1] << 7) | (data[2] >> 1)) & SEQNO_MASK; 946 || qtype == RR_TYPE_TXT
539 947 || qtype == RR_TYPE_NULL)
540 if (0 < client && client <= conns.size ()) 948 && qlen > dlen + 1 + HDRSIZE)
541 { 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 {
542 connection *c = conns [client - 1]; 956 connection *c = conns [client - 1];
957 dns_connection *dns = c->dns;
958 dns_rcv *rcv;
543 959
544 redo: 960 if (dns)
545
546 for (vector<dns_rcv *>::iterator i = c->dns_rcvpq.begin ();
547 i != c->dns_rcvpq.end ();
548 ++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 (); )
549 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
550 { 987 {
551 // already seen that request: simply reply with the cached reply 988 pkt [offs++] = 0xc0; pkt [offs++] = 6 * 2; // refer to name in query section
552 dns_rcv *r = *i;
553 989
554 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
555 995
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
556 offs = r->pkt->len; 1050 rcv->pkt->len = offs;
557 memcpy (pkt->at (0), r->pkt->at (0), offs); 1051 memcpy (rcv->pkt->at (0), pkt.at (0), offs);
558 goto duplicate_request; 1052 }
559 } 1053 }
560 1054
561 // new packet, queue 1055 duplicate_request: ;
562 dns_rcv *rcv = new dns_rcv (seqno, data + 3, datalen - 3); 1056 }
563 c->dnsv4_receive_rep (rcv); 1057 else
564
565 // now generate reply
566 pkt->ancount = htons (1); // one answer RR
567 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);
568 1066
569 (*pkt) [offs++] = 0xc0;
570 (*pkt) [offs++] = 6 * 2; // same as in query section 1067 pkt [offs++] = 0xc0; pkt [offs++] = 6 * 2; // refer to name in query section
571 1068
572 (*pkt) [offs++] = RR_TYPE_TXT >> 8; (*pkt) [offs++] = RR_TYPE_TXT; 1069 pkt [offs++] = RR_TYPE_A >> 8; pkt [offs++] = RR_TYPE_A; // type
573 (*pkt) [offs++] = RR_CLASS_IN >> 8; (*pkt) [offs++] = RR_CLASS_IN; 1070 pkt [offs++] = RR_CLASS_IN >> 8; pkt [offs++] = RR_CLASS_IN; // class
574
575 (*pkt) [offs++] = 0; (*pkt) [offs++] = 0; 1071 pkt [offs++] = 0; pkt [offs++] = 0;
576 (*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
577 1074
578 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;
579 1077
580 // bind doesn't compress well, so reduce further by one label length 1078 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 { 1079 {
589 int txtlen = dlen <= 255 ? dlen - 1 : 255; 1080 connection *c = conns [client - 1];
590 1081
591 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;
592 txtlen = c->dns_snddq->size (); 1097 c->dns->set_cfg ();
593 1098 }
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 } 1099 }
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 } 1100 }
617 else
618 pkt->flags = htons (DEFAULT_SERVER_FLAGS | FLAG_RCODE_FORMERR);
619 } 1101 }
620 1102
621 pkt->len = offs; 1103 pkt.len = offs;
622 } 1104 }
623
624 return pkt;
625} 1105}
626 1106
627void 1107void
628vpn::dnsv4_client (dns_packet *pkt) 1108vpn::dnsv4_client (dns_packet &pkt)
629{ 1109{
630 u16 flags = ntohs (pkt->flags); 1110 u16 flags = ntohs (pkt.flags);
631 int offs = 6 * 2; // skip header 1111 int offs = 6 * 2; // skip header
632 1112
633 pkt->qdcount = ntohs (pkt->qdcount); 1113 pkt.qdcount = ntohs (pkt.qdcount);
634 pkt->ancount = ntohs (pkt->ancount); 1114 pkt.ancount = ntohs (pkt.ancount);
635 1115
636 // go through our request list and find the corresponding request 1116 // go through our request list and find the corresponding request
637 for (vector<dns_req *>::iterator i = dns_sndpq.begin (); 1117 for (vector<dns_snd *>::iterator i = dns_sndpq.begin ();
638 i != dns_sndpq.end (); 1118 i != dns_sndpq.end ();
639 ++i) 1119 ++i)
640 if ((*i)->pkt->id == pkt->id) 1120 if ((*i)->pkt->id == pkt.id)
641 { 1121 {
1122 dns_connection *dns = (*i)->dns;
642 connection *c = (*i)->conn; 1123 connection *c = dns->c;
643 int seqno = (*i)->seqno; 1124 int seqno = (*i)->seqno;
644 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 }
645 1152
646 delete *i; 1153 delete *i;
647 dns_sndpq.erase (i); 1154 dns_sndpq.erase (i);
648 1155
649 if (flags & (FLAG_RESPONSE | FLAG_OP_MASK | FLAG_TC)) 1156 if (flags & FLAG_RESPONSE && !(flags & FLAG_OP_MASK))
650 { 1157 {
651 char qname[MAXSIZE]; 1158 char qname[MAXSIZE];
652 1159
653 while (pkt->qdcount-- && offs < MAXSIZE - 4) 1160 while (pkt.qdcount-- && offs < MAXSIZE - 4)
654 { 1161 {
655 int qlen = pkt->decode_label ((char *)qname, MAXSIZE - offs, offs); 1162 int qlen = pkt.decode_label ((char *)qname, MAXSIZE - offs, offs);
656 offs += 4; // skip qtype, qclass 1163 offs += 4; // skip qtype, qclass
657 } 1164 }
658 1165
659 while (pkt->ancount-- && offs < MAXSIZE - 10) 1166 while (pkt.ancount-- && offs < MAXSIZE - 10 && datap)
660 { 1167 {
661 pkt->decode_label ((char *)qname, MAXSIZE - offs, offs); 1168 int qlen = pkt.decode_label ((char *)qname, MAXSIZE - offs, offs);
662 1169
663 u16 qtype = (*pkt) [offs++] << 8; qtype |= (*pkt) [offs++]; 1170 u16 qtype = pkt [offs++] << 8; qtype |= pkt [offs++];
664 u16 qclass = (*pkt) [offs++] << 8; qclass |= (*pkt) [offs++]; 1171 u16 qclass = pkt [offs++] << 8; qclass |= pkt [offs++];
665 u32 ttl = (*pkt) [offs++] << 24; 1172 u32 ttl = pkt [offs++] << 24;
666 ttl |= (*pkt) [offs++] << 16; 1173 ttl |= pkt [offs++] << 16;
667 ttl |= (*pkt) [offs++] << 8; 1174 ttl |= pkt [offs++] << 8;
668 ttl |= (*pkt) [offs++]; 1175 ttl |= pkt [offs++];
669
670 u16 rdlen = (*pkt) [offs++] << 8; rdlen |= (*pkt) [offs++]; 1176 u16 rdlen = pkt [offs++] << 8; rdlen |= pkt [offs++];
671 1177
672 if (rdlen <= MAXSIZE - offs) 1178 if (qtype == RR_TYPE_NULL || qtype == RR_TYPE_TXT || qtype == dns->cfg.rrtype)
673 { 1179 {
674 // decode bytes, finally 1180 if (rdlen <= MAXSIZE - offs)
675
676 while (rdlen)
677 { 1181 {
1182 // decode bytes, finally
1183
1184 while (rdlen)
1185 {
678 int txtlen = (*pkt) [offs++]; 1186 int txtlen = pkt [offs++];
679 1187
680 assert (txtlen + offs < MAXSIZE - 1); 1188 assert (txtlen + offs < MAXSIZE - 1);
681 1189
682 memcpy (datap, pkt->at (offs), txtlen); 1190 memcpy (datap, pkt.at (offs), txtlen);
683 datap += txtlen; offs += txtlen; 1191 datap += txtlen; offs += txtlen;
684 1192
685 rdlen -= txtlen + 1; 1193 rdlen -= txtlen + 1;
1194 }
686 } 1195 }
687
688 } 1196 }
1197 else if (qtype == RR_TYPE_A)
1198 {
1199 u8 ip [4];
689 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 }
690 } 1270 }
691 } 1271 }
692 1272
693 // todo: pkt now used 1273 // todo: pkt now used
1274 if (datap)
694 c->dnsv4_receive_rep (new dns_rcv (seqno, data, datap - data)); 1275 dns->receive_rep (new dns_rcv (seqno, data, datap - data));
695 1276
696 break; 1277 break;
697 } 1278 }
698
699 delete pkt;
700} 1279}
701 1280
702void 1281void
703vpn::dnsv4_ev (io_watcher &w, short revents) 1282vpn::dnsv4_ev (ev::io &w, int revents)
704{ 1283{
705 if (revents & EVENT_READ) 1284 if (revents & EV_READ)
706 { 1285 {
707 dns_packet *pkt = new dns_packet; 1286 dns_packet *pkt = new dns_packet;
708 struct sockaddr_in sa; 1287 struct sockaddr_in sa;
709 socklen_t sa_len = sizeof (sa); 1288 socklen_t sa_len = sizeof (sa);
710 1289
711 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);
712 1291
713 if (pkt->len > 0) 1292 if (pkt->len > 0)
714 { 1293 {
715 if (pkt->flags & htons (FLAG_TC)) 1294 if (ntohs (pkt->flags) & FLAG_RESPONSE)
1295 dnsv4_client (*pkt);
1296 else
716 { 1297 {
717 slog (L_WARN, _("DNS request/response truncated, check protocol settings.")); 1298 dnsv4_server (*pkt);
718 //TODO connection reset 1299 sendto (w.fd, pkt->at (0), pkt->len, 0, (sockaddr *)&sa, sa_len);
719 } 1300 }
720 1301
721 if (THISNODE->dns_port) 1302 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 } 1303 }
729 } 1304 }
730} 1305}
731 1306
732bool 1307bool
733connection::send_dnsv4_packet (vpn_packet *pkt, const sockinfo &si, int tos) 1308vpn::send_dnsv4_packet (vpn_packet *pkt, const sockinfo &si, int tos)
734{ 1309{
735 // never initialized 1310 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 1311
741 //dns_rcvseq = dns_sndseq = 0; 1312 assert (0 < client && client <= conns.size ());
742 1313
743 dns_si.set (::conf.dns_forw_host, ::conf.dns_forw_port, PROT_DNSv4); 1314 connection *c = conns [client - 1];
744 } 1315
1316 if (!c->dns)
1317 c->dns = new dns_connection (c);
745 1318
746 if (!dns_snddq->put (pkt)) 1319 if (c->dns->snddq.put (pkt))
747 return false; 1320 {
1321 min_it (c->dns->poll_interval, 0.25);
1322 c->dns->tw ();
1323 }
748 1324
749 // start timer if neccessary 1325 // 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; 1326 return true;
754} 1327}
755 1328
756void 1329void
757connection::dnsv4_cb (time_watcher &w) 1330dns_connection::time_cb (ev::timer &w, int revents)
758{ 1331{
1332 // servers have to be polled
1333 if (THISNODE->dns_port)
1334 return;
1335
759 // check for timeouts and (re)transmit 1336 // check for timeouts and (re)transmit
760 tstamp next = NOW + 60; 1337 tstamp next = 86400 * 365;
761 dns_req *send = 0; 1338 dns_snd *send = 0;
762 1339
763 for (vector<dns_req *>::iterator i = vpn->dns_sndpq.begin (); 1340 for (vector<dns_snd *>::iterator i = vpn->dns_sndpq.begin ();
764 i != vpn->dns_sndpq.end (); 1341 i != vpn->dns_sndpq.end ();
765 ++i) 1342 ++i)
766 { 1343 {
767 dns_req *r = *i; 1344 dns_snd *r = *i;
768 1345
769 if (r->next <= NOW) 1346 if (r->timeout <= ev_now ())
770 { 1347 {
771 if (!send) 1348 if (!send)
772 { 1349 {
773 send = r; 1350 send = r;
774 1351
775 if (r->retry)//D
776 printf ("req %d, retry %d\n", r->pkt->id, r->retry);
777 r->retry++; 1352 r->retry++;
778 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);
779 } 1360 }
780 } 1361 }
781 1362 else
782 if (r->next < next) 1363 min_it (next, r->timeout - ev_now ());
783 next = r->next;
784 } 1364 }
785 1365
786 if (!send 1366 if (!send)
787 && vpn->dns_sndpq.size () < MAX_OUTSTANDING)
788 { 1367 {
1368 // generate a new packet, if wise
1369
1370 if (!established)
1371 {
1372 if (vpn->dns_sndpq.empty ())
1373 {
789 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);
790 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)
791 vpn->dns_sndpq.push_back (send); 1402 vpn->dns_sndpq.push_back (send);
792
793 dns_sndseq = (dns_sndseq + 1) & SEQNO_MASK;
794 } 1403 }
795
796 tstamp min_next = NOW + (1. / (tstamp)MAX_RATE);
797 1404
798 if (send) 1405 if (send)
799 { 1406 {
800 dns_packet *pkt = send->pkt; 1407 last_sent = ev_now ();
801 1408 sendto (vpn->dnsv4_fd,
802 next = min_next; 1409 send->pkt->at (0), send->pkt->len, 0,
803 1410 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 } 1411 }
806 else if (next < min_next) 1412
807 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 ());
808 1419
809 w.start (next); 1420 w.start (next);
810} 1421}
811 1422
812#endif 1423#endif

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