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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 1.53 by root, Tue Oct 18 10:54:17 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 unsigned int len;
403
404 for (;;)
405 {
230 int len = (data [0] << 8) | data [1]; 406 len = (data [0] << 8) | data [1];
231 407
232 if (len > MAXSIZE && fill >= 2) 408 if (len <= MAXSIZE || fill < 2)
233 abort (); // TODO handle this gracefully, connection reset 409 break;
234 410
411 // TODO: handle this better than skipping, e.g. by reset
412 slog (L_DEBUG, _("DNS: corrupted packet stream skipping a byte..."));
413 remove (1);
414 }
415
235 if (fill < len + 2) 416 if (fill < len + 2)
236 return 0; 417 return 0;
237 418
238 vpn_packet *pkt = new vpn_packet; 419 vpn_packet *pkt = new vpn_packet;
239 420
240 pkt->len = len; 421 pkt->len = len;
241 memcpy (&((*pkt)[0]), data + 2, len); 422 memcpy (pkt->at (0), data + 2, len);
242 remove (len + 2); 423 remove (len + 2);
243 424
244 return pkt; 425 return pkt;
245} 426}
246 427
247///////////////////////////////////////////////////////////////////////////// 428/////////////////////////////////////////////////////////////////////////////
248 429
249#define FLAG_QUERY ( 0 << 15) 430#define FLAG_QUERY ( 0 << 15)
250#define FLAG_RESPONSE ( 1 << 15) 431#define FLAG_RESPONSE ( 1 << 15)
251#define FLAG_OP_MASK (15 << 14) 432#define FLAG_OP_MASK (15 << 11)
252#define FLAG_OP_QUERY ( 0 << 11) 433#define FLAG_OP_QUERY ( 0 << 11)
253#define FLAG_AA ( 1 << 10) 434#define FLAG_AA ( 1 << 10)
254#define FLAG_TC ( 1 << 9) 435#define FLAG_TC ( 1 << 9)
255#define FLAG_RD ( 1 << 8) 436#define FLAG_RD ( 1 << 8)
256#define FLAG_RA ( 1 << 7) 437#define FLAG_RA ( 1 << 7)
… …
263#define FLAG_RCODE_REFUSED ( 5 << 0) 444#define FLAG_RCODE_REFUSED ( 5 << 0)
264 445
265#define DEFAULT_CLIENT_FLAGS (FLAG_QUERY | FLAG_OP_QUERY | FLAG_RD) 446#define DEFAULT_CLIENT_FLAGS (FLAG_QUERY | FLAG_OP_QUERY | FLAG_RD)
266#define DEFAULT_SERVER_FLAGS (FLAG_RESPONSE | FLAG_OP_QUERY | FLAG_AA | FLAG_RD | FLAG_RA) 447#define DEFAULT_SERVER_FLAGS (FLAG_RESPONSE | FLAG_OP_QUERY | FLAG_AA | FLAG_RD | FLAG_RA)
267 448
449struct dns_cfg
450{
451 static int next_uid;
452
453 u8 chksum;
454 u8 rrtype;
455 u16 uid; // to make request unique
456
457 u8 version;
458 u8 flags;
459 u16 max_size;
460
461 u8 id1, id2, id3, id4;
462
463 u16 client;
464 u8 def_ttl;
465 u8 r0;
466
467 u8 syn_cdc; // cdc en/decoder for syn (A?) requests
468 u8 hdr_cdc; // cdc en/decoder for regular request headers
469 u8 req_cdc; // cdc en/decoder for regular (ANY?) request data
470 u8 rep_cdc; // cdc en/decoder for regular (TXT) replies, 0 == 8 bit encoding
471
472 u8 r1, r2, r3, r4;
473
474 void reset (int clientid);
475 bool valid ();
476 u8 get_chksum ();
477};
478
479int dns_cfg::next_uid;
480
481void
482dns_cfg::reset (int clientid)
483{
484 // this ID must result in some mixed-case characters in cdc26-encoding
485 id1 = 'G';
486 id2 = 'V';
487 id3 = 'P';
488 id4 = 'E';
489
490 version = 2;
491
492 rrtype = RR_TYPE_TXT;
493 flags = 0;
494 def_ttl = 0;
495 syn_cdc = 26;
496 hdr_cdc = 36;
497 req_cdc = conf.dns_case_preserving ? 62 : 36;
498 rep_cdc = 0;
499 max_size = htons (MAX_PKT_SIZE);
500 client = htons (clientid);
501 uid = ++next_uid;
502
503 r0 = r1 = r2 = r3 = r4 = 0;
504
505 chksum = get_chksum ();
506}
507
508// simple but not trivial chksum
509u8
510dns_cfg::get_chksum ()
511{
512 unsigned int sum = 0xff00; // only 16 bits required
513
514 u8 old_chksum = chksum;
515 chksum = 0;
516
517 for (unsigned int i = 0; i < sizeof (*this); ++i)
518 sum += ((u8 *)this)[i] * (i + 1);
519
520 chksum = old_chksum;
521
522 return sum + (sum >> 8);
523}
524
525bool
526dns_cfg::valid ()
527{
528 // although the protocol itself allows for some configurability,
529 // only the following encoding/decoding settings are implemented.
530 return id1 == 'G'
531 && id2 == 'V'
532 && id3 == 'P'
533 && id4 == 'E'
534 && version == 2
535 && syn_cdc == 26
536 && hdr_cdc == 36
537 && (req_cdc == 36 || req_cdc == 62)
538 && rep_cdc == 0
539 && chksum == get_chksum ();
540}
541
268struct dns_packet : net_packet 542struct dns_packet : net_packet
269{ 543{
270 u16 id; 544 u16 id;
271 u16 flags; // QR:1 Opcode:4 AA:1 TC:1 RD:1 RA:1 Z:3 RCODE:4 545 u16 flags; // QR:1 Opcode:4 AA:1 TC:1 RD:1 RA:1 Z:3 RCODE:4
272 u16 qdcount, ancount, nscount, arcount; 546 u16 qdcount, ancount, nscount, arcount;
273 547
274 u8 data[MAXSIZE - 6 * 2]; 548 u8 data [MAXSIZE - 6 * 2];
275 549
276 int decode_label (char *data, int size, int &offs); 550 int decode_label (char *data, int size, int &offs);
277}; 551};
278 552
553int
279int dns_packet::decode_label (char *data, int size, int &offs) 554dns_packet::decode_label (char *data, int size, int &offs)
280{ 555{
281 char *orig = data; 556 char *orig = data;
282 557
283 memset (data, 0, size); 558 memset (data, 0, size);
284 559
… …
310 return data - orig; 585 return data - orig;
311} 586}
312 587
313///////////////////////////////////////////////////////////////////////////// 588/////////////////////////////////////////////////////////////////////////////
314 589
315struct dns_req 590static
591u16 next_id ()
316{ 592{
317 dns_packet *pkt;
318 tstamp next;
319 int retry;
320 connection *conn;
321 int seqno;
322
323 dns_req (connection *c);
324 void gen_stream_req (int seqno, byte_stream *stream);
325};
326
327static u16 dns_id = 12098; // TODO: should be per-vpn 593 static u16 dns_id = 0; // TODO: should be per-vpn
328 594
329static u16 next_id () 595#if 1
330{ 596 if (!dns_id)
597 dns_id = time (0);
598
331 // the simplest lsfr with periodicity 65535 i could find 599 // the simplest lsfr with periodicity 65535 i could find
332 dns_id = (dns_id << 1) 600 dns_id = (dns_id << 1)
333 | (((dns_id >> 1) 601 | (((dns_id >> 1)
334 ^ (dns_id >> 2) 602 ^ (dns_id >> 2)
335 ^ (dns_id >> 4) 603 ^ (dns_id >> 4)
336 ^ (dns_id >> 15)) & 1); 604 ^ (dns_id >> 15)) & 1);
337 605
338 return dns_id; 606 return dns_id;
339} 607#else
608 dns_id++;//D
340 609
341dns_req::dns_req (connection *c) 610 return htons (dns_id);
342: conn (c) 611#endif
612}
613
614struct dns_rcv;
615struct dns_snd;
616
617struct dns_connection
343{ 618{
344 next = 0; 619 connection *c;
620 struct vpn *vpn;
621
622 dns_cfg cfg;
623
624 bool established;
625 const basecoder *cdc;
626
627 tstamp last_received;
628 tstamp last_sent;
629 double min_latency;
630 double poll_interval, send_interval;
631
632 vector<dns_rcv *> rcvpq;
633
634 byte_stream rcvdq; int rcvseq; int repseq;
635 byte_stream snddq; int sndseq;
636
637 inline void time_cb (ev::timer &w, int revents); ev::timer tw;
638 void receive_rep (dns_rcv *r);
639
640 void reset (); // quite like tcp RST
641 void set_cfg (); // to be called after any cfg changes
642
643 dns_connection (connection *c);
644 ~dns_connection ();
645};
646
647struct dns_snd
648{
649 dns_packet *pkt;
650 tstamp timeout, sent;
651 int retry;
652 struct dns_connection *dns;
653 int seqno;
654 bool stdhdr;
655
656 void gen_stream_req (int seqno, byte_stream &stream);
657 void gen_syn_req ();
658
659 dns_snd (dns_connection *dns);
660 ~dns_snd ();
661};
662
663dns_snd::dns_snd (dns_connection *dns)
664: dns (dns)
665{
666 timeout = 0;
345 retry = 0; 667 retry = 0;
668 seqno = 0;
669 sent = ev_now ();
670 stdhdr = false;
346 671
347 pkt = new dns_packet; 672 pkt = new dns_packet;
348 673
349 pkt->id = next_id (); 674 pkt->id = next_id ();
350} 675}
351 676
677dns_snd::~dns_snd ()
678{
679 delete pkt;
680}
681
682static void
683append_domain (dns_packet &pkt, int &offs, const char *domain)
684{
685 // add tunnel domain
686 for (;;)
687 {
688 const char *end = strchr (domain, '.');
689
690 if (!end)
691 end = domain + strlen (domain);
692
693 int len = end - domain;
694
695 pkt [offs++] = len;
696 memcpy (pkt.at (offs), domain, len);
697 offs += len;
698
699 if (!*end)
700 break;
701
702 domain = end + 1;
703 }
704}
705
706void
352void dns_req::gen_stream_req (int seqno, byte_stream *stream) 707dns_snd::gen_stream_req (int seqno, byte_stream &stream)
353{ 708{
709 stdhdr = true;
354 this->seqno = seqno; 710 this->seqno = seqno;
711
712 timeout = ev_now () + INITIAL_TIMEOUT;
355 713
356 pkt->flags = htons (DEFAULT_CLIENT_FLAGS); 714 pkt->flags = htons (DEFAULT_CLIENT_FLAGS);
357 pkt->qdcount = htons (1); 715 pkt->qdcount = htons (1);
358 716
359 int offs = 6*2; 717 int offs = 6*2;
360 int dlen = MAX_DOMAIN_SIZE - strlen (THISNODE->domain) - 2; 718 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, 719 // 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 720 // so we need to have space for 2*MAX_DOMAIN_SIZE + header + extra
363 721
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; 722 char enc[256], *encp = enc;
376 723 encode_header (enc, THISNODE->id, seqno);
377 memcpy (data + 3, stream->begin (), datalen); 724
378 int enclen = dns64::encode (enc, data, datalen + 3); 725 int datalen = dns->cdc->decode_len (dlen - (dlen + MAX_LBL_SIZE - 1) / MAX_LBL_SIZE - HDRSIZE);
726
727 if (datalen > stream.size ())
728 datalen = stream.size ();
729
730 int enclen = dns->cdc->encode (enc + HDRSIZE, stream.begin (), datalen) + HDRSIZE;
379 stream->remove (datalen); 731 stream.remove (datalen);
380 732
381 while (enclen) 733 while (enclen)
382 { 734 {
383 int lbllen = enclen < MAX_LBL_SIZE ? enclen : MAX_LBL_SIZE; 735 int lbllen = enclen < MAX_LBL_SIZE ? enclen : MAX_LBL_SIZE;
384 736
… …
389 encp += lbllen; 741 encp += lbllen;
390 742
391 enclen -= lbllen; 743 enclen -= lbllen;
392 } 744 }
393 745
394 const char *suffix = THISNODE->domain; 746 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 }
415 747
416 (*pkt)[offs++] = 0; 748 (*pkt)[offs++] = 0;
417 (*pkt)[offs++] = RR_TYPE_ANY >> 8; (*pkt)[offs++] = RR_TYPE_ANY; 749 (*pkt)[offs++] = RR_TYPE_ANY >> 8; (*pkt)[offs++] = RR_TYPE_ANY;
750 (*pkt)[offs++] = RR_CLASS_IN >> 8; (*pkt)[offs++] = RR_CLASS_IN;
751
752 pkt->len = offs;
753}
754
755void
756dns_snd::gen_syn_req ()
757{
758 timeout = ev_now () + INITIAL_SYN_TIMEOUT;
759
760 pkt->flags = htons (DEFAULT_CLIENT_FLAGS);
761 pkt->qdcount = htons (1);
762
763 int offs = 6 * 2;
764
765 int elen = cdc26.encode ((char *)pkt->at (offs + 1), (u8 *)&dns->cfg, sizeof (dns_cfg));
766
767 assert (elen <= MAX_LBL_SIZE);
768
769 (*pkt)[offs] = elen;
770 offs += elen + 1;
771 append_domain (*pkt, offs, dns->c->conf->domain);
772
773 (*pkt)[offs++] = 0;
774 (*pkt)[offs++] = RR_TYPE_A >> 8; (*pkt)[offs++] = RR_TYPE_A;
418 (*pkt)[offs++] = RR_CLASS_IN >> 8; (*pkt)[offs++] = RR_CLASS_IN; 775 (*pkt)[offs++] = RR_CLASS_IN >> 8; (*pkt)[offs++] = RR_CLASS_IN;
419 776
420 pkt->len = offs; 777 pkt->len = offs;
421} 778}
422 779
… …
441{ 798{
442 delete pkt; 799 delete pkt;
443} 800}
444 801
445///////////////////////////////////////////////////////////////////////////// 802/////////////////////////////////////////////////////////////////////////////
446 803
447struct dns_cfg 804dns_connection::dns_connection (connection *c)
805: c (c)
806, rcvdq (MAX_BACKLOG * 2)
807, snddq (MAX_BACKLOG)
448{ 808{
449 u8 id1, id2, id3; 809 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};
455 810
811 vpn = c->vpn;
812
813 reset ();
814}
815
816dns_connection::~dns_connection ()
817{
818 reset ();
819}
820
821void
822dns_connection::reset ()
823{
824 while (!rcvpq.empty ())
825 {
826 delete rcvpq.back ();
827 rcvpq.pop_back ();
828 }
829
830 for (int i = vpn->dns_sndpq.size (); i--; )
831 if (vpn->dns_sndpq [i]->dns == this)
832 {
833 vpn->dns_sndpq [i] = vpn->dns_sndpq.back ();
834 vpn->dns_sndpq.pop_back ();
835 }
836
837 established = false;
838
839 rcvseq = repseq = sndseq = 0;
840
841 last_sent = 0;
842 poll_interval = 0.5; // starting here
843 send_interval = 0.5; // starting rate
844 min_latency = INITIAL_TIMEOUT;
845}
846
847void
848dns_connection::set_cfg ()
849{
850 cdc = cfg.req_cdc == 36 ? &cdc36 : &cdc62;
851}
852
853void
456void connection::dnsv4_receive_rep (struct dns_rcv *r) 854dns_connection::receive_rep (dns_rcv *r)
457{ 855{
856 if (r->datalen)
857 poll_interval = max (poll_interval * (1. / 1.2), MIN_POLL_INTERVAL);
858 else
859 poll_interval = min (poll_interval * 1.1, MAX_POLL_INTERVAL);
860
458 dns_rcvpq.push_back (r); 861 rcvpq.push_back (r);
459 862
460 redo: 863 redo:
461 864
865 // find next packet
462 for (vector<dns_rcv *>::iterator i = dns_rcvpq.begin (); 866 for (vector<dns_rcv *>::iterator i = rcvpq.end (); i-- != rcvpq.begin (); )
463 i != dns_rcvpq.end ();
464 ++i)
465 if (dns_rcvseq == (*i)->seqno) 867 if (SEQNO_EQ (rcvseq, (*i)->seqno))
466 { 868 {
869 //printf ("seqno eq %x %x\n", rcvseq, (*i)->seqno);//D
870 // enter the packet into our input stream
467 dns_rcv *r = *i; 871 r = *i;
468 872
873 // remove the oldest packet, look forward, as it's oldest first
874 for (vector<dns_rcv *>::iterator j = rcvpq.begin (); j != rcvpq.end (); ++j)
875 if (SEQNO_EQ ((*j)->seqno, rcvseq - MAX_WINDOW))
876 {
877 //printf ("seqno RR %x %x\n", (*j)->seqno, rcvseq - MAX_WINDOW);//D
878 delete *j;
879 rcvpq.erase (j);
880 break;
881 }
882
469 dns_rcvseq = (dns_rcvseq + 1) & SEQNO_MASK; 883 rcvseq = (rcvseq + 1) & SEQNO_MASK;
470 884
471 if (!dns_snddq && !dns_rcvdq) 885 if (!rcvdq.put (r->data, r->datalen))
472 { 886 {
473 dns_rcvdq = new byte_stream (MAX_BACKLOG * 2); 887 // MUST never overflow, can be caused by data corruption, TODO
474 dns_snddq = new byte_stream (MAX_BACKLOG); 888 slog (L_CRIT, "DNS: !rcvdq.put (r->data, r->datalen)");
475 889 reset ();
476 dns_si.set (::conf.dns_forw_host, ::conf.dns_forw_port, PROT_DNSv4); 890 return;
477 } 891 }
478 892
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 ()) 893 while (vpn_packet *pkt = rcvdq.get ())
483 { 894 {
484 sockinfo si; 895 sockinfo si;
485 si.host = 0; si.port = 0; si.prot = PROT_DNSv4; 896 si.host = htonl (c->conf->id); si.port = 0; si.prot = PROT_DNSv4;
486 897
487 vpn->recv_vpn_packet (pkt, si); 898 vpn->recv_vpn_packet (pkt, si);
899 delete pkt;
488 } 900 }
489 } 901
490 else if ((u32)(*i)->seqno - (u32)dns_rcvseq + MAX_WINDOW > MAX_WINDOW * 2) 902 // 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; 903 goto redo;
497 } 904 }
498} 905}
499 906
500dns_packet * 907void
501vpn::dnsv4_server (dns_packet *pkt) 908vpn::dnsv4_server (dns_packet &pkt)
502{ 909{
503 u16 flags = ntohs (pkt->flags); 910 u16 flags = ntohs (pkt.flags);
504 911
505 //memcpy (&((*rep)[0]), &((*pkt)[0]), pkt->len);
506 int offs = 6 * 2; // skip header 912 int offs = 6 * 2; // skip header
507 913
508 pkt->flags = htons (DEFAULT_SERVER_FLAGS | FLAG_RCODE_FORMERR); 914 pkt.flags = htons (DEFAULT_SERVER_FLAGS | FLAG_RCODE_FORMERR);
509 915
510 if (!(flags & (FLAG_RESPONSE | FLAG_OP_MASK | FLAG_TC)) 916 if (0 == (flags & (FLAG_RESPONSE | FLAG_OP_MASK))
511 && pkt->qdcount == htons (1)) 917 && pkt.qdcount == htons (1))
512 { 918 {
513 char qname[MAXSIZE]; 919 char qname [MAXSIZE];
514 int qlen = pkt->decode_label ((char *)qname, MAXSIZE - offs, offs); 920 int qlen = pkt.decode_label ((char *)qname, MAXSIZE - offs, offs);
515 921
516 u16 qtype = (*pkt) [offs++] << 8; qtype |= (*pkt) [offs++]; 922 u16 qtype = pkt [offs++] << 8; qtype |= pkt [offs++];
517 u16 qclass = (*pkt) [offs++] << 8; qclass |= (*pkt) [offs++]; 923 u16 qclass = pkt [offs++] << 8; qclass |= pkt [offs++];
518 924
519 pkt->qdcount = htons (1); 925 pkt.qdcount = htons (1);
520 pkt->ancount = 0; 926 pkt.ancount = 0;
521 pkt->nscount = 0; // should be self, as other nameservers reply like this 927 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 928 pkt.arcount = 0; // a record for self, as other nameservers reply like this
523 929
524 pkt->flags = htons (DEFAULT_SERVER_FLAGS | FLAG_RCODE_NXDOMAIN); 930 pkt.flags = htons (DEFAULT_SERVER_FLAGS | FLAG_RCODE_SERVFAIL);
525 931
526 int dlen = strlen (THISNODE->domain); 932 int dlen = strlen (THISNODE->domain);
527 933
528 if (qclass == RR_CLASS_IN 934 if (qclass == RR_CLASS_IN
529 && (qtype == RR_TYPE_ANY || qtype == RR_TYPE_TXT)
530 && qlen > dlen + 1 935 && qlen > dlen + 1
531 && !memcmp (qname + qlen - dlen - 1, THISNODE->domain, dlen)) 936 && !memcmp (qname + qlen - (dlen + 1), THISNODE->domain, dlen))
532 { 937 {
533 // correct class, domain: parse 938 // now generate reply
534 u8 data[MAXSIZE]; 939 pkt.ancount = htons (1); // one answer RR
535 int datalen = dns64::decode (data, qname, qlen - dlen - 1); 940 pkt.flags = htons (DEFAULT_SERVER_FLAGS | FLAG_RCODE_OK);
536 941
537 int client = data[0]; 942 if ((qtype == RR_TYPE_ANY
538 int seqno = ((data[1] << 7) | (data[2] >> 1)) & SEQNO_MASK; 943 || qtype == RR_TYPE_TXT
539 944 || qtype == RR_TYPE_NULL)
540 if (0 < client && client <= conns.size ()) 945 && qlen > dlen + 1 + HDRSIZE)
541 { 946 {
947 // correct class, domain: parse
948 int client, seqno;
949 decode_header (qname, client, seqno);
950
951 if (0 < client && client <= conns.size ())
952 {
542 connection *c = conns [client - 1]; 953 connection *c = conns [client - 1];
954 dns_connection *dns = c->dns;
955 dns_rcv *rcv;
543 956
544 redo: 957 if (dns)
545
546 for (vector<dns_rcv *>::iterator i = c->dns_rcvpq.begin ();
547 i != c->dns_rcvpq.end ();
548 ++i) 958 {
959 u8 data[MAXSIZE];
960 int datalen = dns->cdc->decode (data, qname + HDRSIZE, qlen - (dlen + 1 + HDRSIZE));
961
962 for (vector<dns_rcv *>::iterator i = dns->rcvpq.end (); i-- != dns->rcvpq.begin (); )
549 if ((*i)->seqno == seqno) 963 if (SEQNO_EQ ((*i)->seqno, seqno))
964 {
965 // already seen that request: simply reply with the cached reply
966 dns_rcv *r = *i;
967
968 slog (L_DEBUG, "DNS: duplicate packet received ID %d, SEQ %d", htons (r->pkt->id), seqno);
969
970 // refresh header & id, as the retry count could have changed
971 memcpy (r->pkt->at (6 * 2 + 1), pkt.at (6 * 2 + 1), HDRSIZE);
972 r->pkt->id = pkt.id;
973
974 memcpy (pkt.at (0), r->pkt->at (0), offs = r->pkt->len);
975
976 goto duplicate_request;
977 }
978
979 // new packet, queue
980 rcv = new dns_rcv (seqno, data, datalen);
981 dns->receive_rep (rcv);
982 }
983
550 { 984 {
551 // already seen that request: simply reply with the cached reply 985 pkt [offs++] = 0xc0; pkt [offs++] = 6 * 2; // refer to name in query section
552 dns_rcv *r = *i;
553 986
554 printf ("DUPLICATE %d\n", htons (r->pkt->id));//D 987 int rtype = dns ? dns->cfg.rrtype : RR_TYPE_A;
988 pkt [offs++] = rtype >> 8; pkt [offs++] = rtype; // type
989 pkt [offs++] = RR_CLASS_IN >> 8; pkt [offs++] = RR_CLASS_IN; // class
990 pkt [offs++] = 0; pkt [offs++] = 0;
991 pkt [offs++] = 0; pkt [offs++] = dns ? dns->cfg.def_ttl : 0; // TTL
555 992
993 int rdlen_offs = offs += 2;
994
995 if (dns)
996 {
997 int dlen = ntohs (dns->cfg.max_size) - offs;
998
999 // bind doesn't compress well, so reduce further by one label length
1000 dlen -= qlen;
1001
1002 // only put data into in-order sequence packets, if
1003 // we receive out-of-order packets we generate empty
1004 // replies
1005 //printf ("%d - %d & %x (=%d) < %d\n", seqno, dns->repseq, SEQNO_MASK, (seqno - dns->repseq) & SEQNO_MASK, MAX_WINDOW);//D
1006 if (((seqno - dns->repseq) & SEQNO_MASK) <= MAX_WINDOW)
1007 {
1008 dns->repseq = seqno;
1009
1010 while (dlen > 1 && !dns->snddq.empty ())
1011 {
1012 int txtlen = dlen <= 255 ? dlen - 1 : 255;
1013
1014 if (txtlen > dns->snddq.size ())
1015 txtlen = dns->snddq.size ();
1016
1017 pkt[offs++] = txtlen;
1018 memcpy (pkt.at (offs), dns->snddq.begin (), txtlen);
1019 offs += txtlen;
1020 dns->snddq.remove (txtlen);
1021
1022 dlen -= txtlen + 1;
1023 }
1024 }
1025
1026 // avoid completely empty TXT rdata
1027 if (offs == rdlen_offs)
1028 pkt[offs++] = 0;
1029
1030 slog (L_NOISE, "DNS: snddq %d", dns->snddq.size ());
1031 }
1032 else
1033 {
1034 // send RST
1035 pkt [offs++] = CMD_IP_1; pkt [offs++] = CMD_IP_2; pkt [offs++] = CMD_IP_3;
1036 pkt [offs++] = CMD_IP_RST;
1037 }
1038
1039 int rdlen = offs - rdlen_offs;
1040
1041 pkt [rdlen_offs - 2] = rdlen >> 8;
1042 pkt [rdlen_offs - 1] = rdlen;
1043
1044 if (dns)
1045 {
1046 // now update dns_rcv copy
556 offs = r->pkt->len; 1047 rcv->pkt->len = offs;
557 memcpy (pkt->at (0), r->pkt->at (0), offs); 1048 memcpy (rcv->pkt->at (0), pkt.at (0), offs);
558 goto duplicate_request; 1049 }
559 } 1050 }
560 1051
561 // new packet, queue 1052 duplicate_request: ;
562 dns_rcv *rcv = new dns_rcv (seqno, data + 3, datalen - 3); 1053 }
563 c->dnsv4_receive_rep (rcv); 1054 else
564
565 // now generate reply
566 pkt->ancount = htons (1); // one answer RR
567 pkt->flags = htons (DEFAULT_SERVER_FLAGS | FLAG_RCODE_OK); 1055 pkt.flags = htons (DEFAULT_SERVER_FLAGS | FLAG_RCODE_FORMERR);
1056 }
1057 else if (qtype == RR_TYPE_A
1058 && qlen > dlen + 1 + cdc26.encode_len (sizeof (dns_cfg)))
1059 {
1060 dns_cfg cfg;
1061 cdc26.decode ((u8 *)&cfg, qname, cdc26.encode_len (sizeof (dns_cfg)));
1062 int client = ntohs (cfg.client);
568 1063
569 (*pkt) [offs++] = 0xc0;
570 (*pkt) [offs++] = 6 * 2; // same as in query section 1064 pkt [offs++] = 0xc0; pkt [offs++] = 6 * 2; // refer to name in query section
571 1065
572 (*pkt) [offs++] = RR_TYPE_TXT >> 8; (*pkt) [offs++] = RR_TYPE_TXT; 1066 pkt [offs++] = RR_TYPE_A >> 8; pkt [offs++] = RR_TYPE_A; // type
573 (*pkt) [offs++] = RR_CLASS_IN >> 8; (*pkt) [offs++] = RR_CLASS_IN; 1067 pkt [offs++] = RR_CLASS_IN >> 8; pkt [offs++] = RR_CLASS_IN; // class
574
575 (*pkt) [offs++] = 0; (*pkt) [offs++] = 0; 1068 pkt [offs++] = 0; pkt [offs++] = 0;
576 (*pkt) [offs++] = 0; (*pkt) [offs++] = 0; // TTL 1069 pkt [offs++] = 0; pkt [offs++] = cfg.def_ttl; // TTL
1070 pkt [offs++] = 0; pkt [offs++] = 4; // rdlength
577 1071
578 int dlen = MAX_PKT_SIZE - offs - 2; 1072 pkt [offs++] = CMD_IP_1; pkt [offs++] = CMD_IP_2; pkt [offs++] = CMD_IP_3;
1073 pkt [offs++] = CMD_IP_REJ;
579 1074
580 // bind doesn't compress well, so reduce further by one label length 1075 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 { 1076 {
589 int txtlen = dlen <= 255 ? dlen - 1 : 255; 1077 connection *c = conns [client - 1];
590 1078
591 if (txtlen > c->dns_snddq->size ()) 1079 if (cfg.valid ())
1080 {
1081 slog (L_INFO, _("DNS: client %d connects (version %d, req_cdc %d)"), client, cfg.version, cfg.req_cdc);
1082
1083 // check for any encoding mismatches - hints at a case problem
1084 char qname2 [MAX_ENC_LEN];
1085 cdc26.encode (qname2, (u8 *)&cfg, sizeof (dns_cfg));
1086
1087 delete c->dns;
1088
1089 pkt [offs - 1] = memcmp (qname, qname2, cdc26.encode_len (sizeof (dns_cfg)))
1090 ? CMD_IP_CSE : CMD_IP_SYN;
1091
1092 c->dns = new dns_connection (c);
1093 c->dns->cfg = cfg;
592 txtlen = c->dns_snddq->size (); 1094 c->dns->set_cfg ();
593 1095 }
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 } 1096 }
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 } 1097 }
617 else
618 pkt->flags = htons (DEFAULT_SERVER_FLAGS | FLAG_RCODE_FORMERR);
619 } 1098 }
620 1099
621 pkt->len = offs; 1100 pkt.len = offs;
622 } 1101 }
623
624 return pkt;
625} 1102}
626 1103
627void 1104void
628vpn::dnsv4_client (dns_packet *pkt) 1105vpn::dnsv4_client (dns_packet &pkt)
629{ 1106{
630 u16 flags = ntohs (pkt->flags); 1107 u16 flags = ntohs (pkt.flags);
631 int offs = 6 * 2; // skip header 1108 int offs = 6 * 2; // skip header
632 1109
633 pkt->qdcount = ntohs (pkt->qdcount); 1110 pkt.qdcount = ntohs (pkt.qdcount);
634 pkt->ancount = ntohs (pkt->ancount); 1111 pkt.ancount = ntohs (pkt.ancount);
635 1112
636 // go through our request list and find the corresponding request 1113 // go through our request list and find the corresponding request
637 for (vector<dns_req *>::iterator i = dns_sndpq.begin (); 1114 for (vector<dns_snd *>::iterator i = dns_sndpq.begin ();
638 i != dns_sndpq.end (); 1115 i != dns_sndpq.end ();
639 ++i) 1116 ++i)
640 if ((*i)->pkt->id == pkt->id) 1117 if ((*i)->pkt->id == pkt.id)
641 { 1118 {
1119 dns_connection *dns = (*i)->dns;
642 connection *c = (*i)->conn; 1120 connection *c = dns->c;
643 int seqno = (*i)->seqno; 1121 int seqno = (*i)->seqno;
644 u8 data[MAXSIZE], *datap = data; 1122 u8 data[MAXSIZE], *datap = data;
1123 //printf ("rcv pkt %x\n", seqno);//D
1124
1125 if ((*i)->retry)
1126 {
1127 dns->send_interval *= 1.01;
1128 if (dns->send_interval > MAX_SEND_INTERVAL)
1129 dns->send_interval = MAX_SEND_INTERVAL;
1130 }
1131 else
1132 {
1133#if 0
1134 dns->send_interval *= 0.999;
1135#endif
1136 // the latency surely puts an upper bound on
1137 // the minimum send interval
1138 double latency = ev_now () - (*i)->sent;
1139
1140 if (latency < dns->min_latency)
1141 dns->min_latency = latency;
1142
1143 if (dns->send_interval > dns->min_latency * conf.dns_overlap_factor)
1144 dns->send_interval = dns->min_latency * conf.dns_overlap_factor;
1145
1146 if (dns->send_interval < conf.dns_send_interval)
1147 dns->send_interval = conf.dns_send_interval;
1148 }
645 1149
646 delete *i; 1150 delete *i;
647 dns_sndpq.erase (i); 1151 dns_sndpq.erase (i);
648 1152
649 if (flags & (FLAG_RESPONSE | FLAG_OP_MASK | FLAG_TC)) 1153 if (flags & FLAG_RESPONSE && !(flags & FLAG_OP_MASK))
650 { 1154 {
651 char qname[MAXSIZE]; 1155 char qname[MAXSIZE];
652 1156
653 while (pkt->qdcount-- && offs < MAXSIZE - 4) 1157 while (pkt.qdcount-- && offs < MAXSIZE - 4)
654 { 1158 {
655 int qlen = pkt->decode_label ((char *)qname, MAXSIZE - offs, offs); 1159 int qlen = pkt.decode_label ((char *)qname, MAXSIZE - offs, offs);
656 offs += 4; // skip qtype, qclass 1160 offs += 4; // skip qtype, qclass
657 } 1161 }
658 1162
659 while (pkt->ancount-- && offs < MAXSIZE - 10) 1163 while (pkt.ancount-- && offs < MAXSIZE - 10 && datap)
660 { 1164 {
661 pkt->decode_label ((char *)qname, MAXSIZE - offs, offs); 1165 int qlen = pkt.decode_label ((char *)qname, MAXSIZE - offs, offs);
662 1166
663 u16 qtype = (*pkt) [offs++] << 8; qtype |= (*pkt) [offs++]; 1167 u16 qtype = pkt [offs++] << 8; qtype |= pkt [offs++];
664 u16 qclass = (*pkt) [offs++] << 8; qclass |= (*pkt) [offs++]; 1168 u16 qclass = pkt [offs++] << 8; qclass |= pkt [offs++];
665 u32 ttl = (*pkt) [offs++] << 24; 1169 u32 ttl = pkt [offs++] << 24;
666 ttl |= (*pkt) [offs++] << 16; 1170 ttl |= pkt [offs++] << 16;
667 ttl |= (*pkt) [offs++] << 8; 1171 ttl |= pkt [offs++] << 8;
668 ttl |= (*pkt) [offs++]; 1172 ttl |= pkt [offs++];
669
670 u16 rdlen = (*pkt) [offs++] << 8; rdlen |= (*pkt) [offs++]; 1173 u16 rdlen = pkt [offs++] << 8; rdlen |= pkt [offs++];
671 1174
672 if (rdlen <= MAXSIZE - offs) 1175 if (qtype == RR_TYPE_NULL || qtype == RR_TYPE_TXT || qtype == dns->cfg.rrtype)
673 { 1176 {
674 // decode bytes, finally 1177 if (rdlen <= MAXSIZE - offs)
675
676 while (rdlen)
677 { 1178 {
1179 // decode bytes, finally
1180
1181 while (rdlen)
1182 {
678 int txtlen = (*pkt) [offs++]; 1183 int txtlen = pkt [offs++];
679 1184
680 assert (txtlen + offs < MAXSIZE - 1); 1185 assert (txtlen + offs < MAXSIZE - 1);
681 1186
682 memcpy (datap, pkt->at (offs), txtlen); 1187 memcpy (datap, pkt.at (offs), txtlen);
683 datap += txtlen; offs += txtlen; 1188 datap += txtlen; offs += txtlen;
684 1189
685 rdlen -= txtlen + 1; 1190 rdlen -= txtlen + 1;
1191 }
686 } 1192 }
687
688 } 1193 }
1194 else if (qtype == RR_TYPE_A)
1195 {
1196 u8 ip [4];
689 1197
1198 ip [0] = pkt [offs++];
1199 ip [1] = pkt [offs++];
1200 ip [2] = pkt [offs++];
1201 ip [3] = pkt [offs++];
1202
1203 if (ip [0] == CMD_IP_1
1204 && ip [1] == CMD_IP_2
1205 && ip [2] == CMD_IP_3)
1206 {
1207 slog (L_TRACE, _("DNS: got tunnel meta command %02x"), ip [3]);
1208
1209 if (ip [3] == CMD_IP_RST)
1210 {
1211 slog (L_DEBUG, _("DNS: got tunnel RST request."));
1212
1213 dns->reset ();
1214 return;
1215 }
1216 else if (ip [3] == CMD_IP_SYN)
1217 {
1218 slog (L_DEBUG, _("DNS: got tunnel SYN reply, server likes us."));
1219 dns->established = true;
1220 }
1221 else if (ip [3] == CMD_IP_CSE)
1222 {
1223 if (conf.dns_case_preserving)
1224 {
1225 slog (L_INFO, _("DNS: got tunnel CSE reply, globally downgrading to case-insensitive protocol."));
1226 conf.dns_case_preserving = false;
1227 dns->reset ();
1228 return;
1229 }
1230 else
1231 {
1232 slog (L_DEBUG, _("DNS: got tunnel CSE reply, server likes us."));
1233 dns->established = true;
1234 }
1235 }
1236 else if (ip [3] == CMD_IP_REJ)
1237 {
1238 slog (L_ERR, _("DNS: got tunnel REJ reply, server does not like us."));
1239 dns->tw.start (60.);
1240 }
1241 else
1242 {
1243 slog (L_INFO, _("DNS: got unknown meta command %02x"), ip [3]);
1244 dns->tw.start (60.);
1245 }
1246 }
1247 else
1248 slog (L_INFO, _("DNS: got spurious a record %d.%d.%d.%d"),
1249 ip [0], ip [1], ip [2], ip [3]);
1250
1251 return;
1252 }
1253
1254 int client, rseqno;
1255 decode_header (qname, client, rseqno);
1256
1257 if (client != THISNODE->id)
1258 {
1259 slog (L_INFO, _("DNS: got dns tunnel response with wrong clientid, ignoring"));
1260 datap = 0;
1261 }
1262 else if (rseqno != seqno)
1263 {
1264 slog (L_DEBUG, _("DNS: got dns tunnel response with wrong seqno, badly caching nameserver?"));
1265 datap = 0;
1266 }
690 } 1267 }
691 } 1268 }
692 1269
693 // todo: pkt now used 1270 // todo: pkt now used
1271 if (datap)
694 c->dnsv4_receive_rep (new dns_rcv (seqno, data, datap - data)); 1272 dns->receive_rep (new dns_rcv (seqno, data, datap - data));
695 1273
696 break; 1274 break;
697 } 1275 }
698
699 delete pkt;
700} 1276}
701 1277
702void 1278void
703vpn::dnsv4_ev (io_watcher &w, short revents) 1279vpn::dnsv4_ev (ev::io &w, int revents)
704{ 1280{
705 if (revents & EVENT_READ) 1281 if (revents & EV_READ)
706 { 1282 {
707 dns_packet *pkt = new dns_packet; 1283 dns_packet *pkt = new dns_packet;
708 struct sockaddr_in sa; 1284 struct sockaddr_in sa;
709 socklen_t sa_len = sizeof (sa); 1285 socklen_t sa_len = sizeof (sa);
710 1286
711 pkt->len = recvfrom (w.fd, &((*pkt)[0]), MAXSIZE, 0, (sockaddr *)&sa, &sa_len); 1287 pkt->len = recvfrom (w.fd, pkt->at (0), MAXSIZE, 0, (sockaddr *)&sa, &sa_len);
712 1288
713 if (pkt->len > 0) 1289 if (pkt->len > 0)
714 { 1290 {
715 if (pkt->flags & htons (FLAG_TC)) 1291 if (ntohs (pkt->flags) & FLAG_RESPONSE)
1292 dnsv4_client (*pkt);
1293 else
716 { 1294 {
717 slog (L_WARN, _("DNS request/response truncated, check protocol settings.")); 1295 dnsv4_server (*pkt);
718 //TODO connection reset 1296 sendto (w.fd, pkt->at (0), pkt->len, 0, (sockaddr *)&sa, sa_len);
719 } 1297 }
720 1298
721 if (THISNODE->dns_port) 1299 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 } 1300 }
729 } 1301 }
730} 1302}
731 1303
732bool 1304bool
733connection::send_dnsv4_packet (vpn_packet *pkt, const sockinfo &si, int tos) 1305vpn::send_dnsv4_packet (vpn_packet *pkt, const sockinfo &si, int tos)
734{ 1306{
735 // never initialized 1307 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 1308
741 //dns_rcvseq = dns_sndseq = 0; 1309 assert (0 < client && client <= conns.size ());
742 1310
743 dns_si.set (::conf.dns_forw_host, ::conf.dns_forw_port, PROT_DNSv4); 1311 connection *c = conns [client - 1];
744 } 1312
1313 if (!c->dns)
1314 c->dns = new dns_connection (c);
745 1315
746 if (!dns_snddq->put (pkt)) 1316 if (c->dns->snddq.put (pkt))
747 return false; 1317 {
1318 min_it (c->dns->poll_interval, 0.25);
1319 c->dns->tw ();
1320 }
748 1321
749 // start timer if neccessary 1322 // 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; 1323 return true;
754} 1324}
755 1325
756void 1326void
757connection::dnsv4_cb (time_watcher &w) 1327dns_connection::time_cb (ev::timer &w, int revents)
758{ 1328{
1329 // servers have to be polled
1330 if (THISNODE->dns_port)
1331 return;
1332
759 // check for timeouts and (re)transmit 1333 // check for timeouts and (re)transmit
760 tstamp next = NOW + 60; 1334 tstamp next = 86400 * 365;
761 dns_req *send = 0; 1335 dns_snd *send = 0;
762 1336
763 for (vector<dns_req *>::iterator i = vpn->dns_sndpq.begin (); 1337 for (vector<dns_snd *>::iterator i = vpn->dns_sndpq.begin ();
764 i != vpn->dns_sndpq.end (); 1338 i != vpn->dns_sndpq.end ();
765 ++i) 1339 ++i)
766 { 1340 {
767 dns_req *r = *i; 1341 dns_snd *r = *i;
768 1342
769 if (r->next <= NOW) 1343 if (r->timeout <= ev_now ())
770 { 1344 {
771 if (!send) 1345 if (!send)
772 { 1346 {
773 send = r; 1347 send = r;
774 1348
775 if (r->retry)//D
776 printf ("req %d, retry %d\n", r->pkt->id, r->retry);
777 r->retry++; 1349 r->retry++;
778 r->next = NOW + r->retry; 1350 r->timeout = ev_now () + r->retry * min_latency * conf.dns_timeout_factor;
1351 //printf ("RETRY %x (%d, %f)\n", r->seqno, r->retry, r->timeout - ev_now ());//D
1352
1353 // the following code changes the query section a bit, forcing
1354 // the forwarder to generate a new request
1355 if (r->stdhdr)
1356 encode_header ((char *)r->pkt->at (6 * 2 + 1), THISNODE->id, r->seqno, r->retry);
779 } 1357 }
780 } 1358 }
781 1359 else
782 if (r->next < next) 1360 min_it (next, r->timeout - ev_now ());
783 next = r->next;
784 } 1361 }
785 1362
786 if (!send 1363 if (!send)
787 && vpn->dns_sndpq.size () < MAX_OUTSTANDING)
788 { 1364 {
1365 // generate a new packet, if wise
1366
1367 if (!established)
1368 {
1369 if (vpn->dns_sndpq.empty ())
1370 {
789 send = new dns_req (this); 1371 send = new dns_snd (this);
1372
1373 cfg.reset (THISNODE->id);
1374 set_cfg ();
1375 send->gen_syn_req ();
1376 }
1377 }
1378 else if (vpn->dns_sndpq.size () < conf.dns_max_outstanding
1379 && !SEQNO_EQ (rcvseq, sndseq - (MAX_WINDOW - 1)))
1380 {
1381 if (last_sent + send_interval <= ev_now ())
1382 {
1383 //printf ("sending data request etc.\n"); //D
1384 if (!snddq.empty ())
1385 min_it (next, send_interval);
1386
1387 send = new dns_snd (this);
790 send->gen_stream_req (dns_sndseq, dns_snddq); 1388 send->gen_stream_req (sndseq, snddq);
1389 send->timeout = ev_now () + min_latency * conf.dns_timeout_factor;
1390 //printf ("SEND %x (%f)\n", send->seqno, send->timeout - ev_now (), min_latency, conf.dns_timeout_factor);//D
1391
1392 sndseq = (sndseq + 1) & SEQNO_MASK;
1393 }
1394 else
1395 min_it (next, last_sent + send_interval - ev_now ());
1396 }
1397
1398 if (send)
791 vpn->dns_sndpq.push_back (send); 1399 vpn->dns_sndpq.push_back (send);
792
793 dns_sndseq = (dns_sndseq + 1) & SEQNO_MASK;
794 } 1400 }
795
796 tstamp min_next = NOW + (1. / (tstamp)MAX_RATE);
797 1401
798 if (send) 1402 if (send)
799 { 1403 {
800 dns_packet *pkt = send->pkt; 1404 last_sent = ev_now ();
801 1405 sendto (vpn->dnsv4_fd,
802 next = min_next; 1406 send->pkt->at (0), send->pkt->len, 0,
803 1407 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 } 1408 }
806 else if (next < min_next) 1409
807 next = min_next; 1410 min_it (next, last_sent + max (poll_interval, send_interval) - ev_now ());
1411
1412 slog (L_NOISE, "DNS: pi %f si %f N %f (%d:%d %d)",
1413 poll_interval, send_interval, next - ev_now (),
1414 vpn->dns_sndpq.size (), snddq.size (),
1415 rcvpq.size ());
808 1416
809 w.start (next); 1417 w.start (next);
810} 1418}
811 1419
812#endif 1420#endif

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