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Comparing gvpe/src/vpn_dns.C (file contents):
Revision 1.3 by pcg, Tue Mar 1 06:27:20 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) 2003-2004 Marc Lehmann <pcg@goof.com> 3 Copyright (C) 2003-2011 Marc Lehmann <gvpe@schmorp.de>
4 4
5 This file is part of GVPE.
6
5 This program is free software; you can redistribute it and/or modify 7 GVPE is free software; you can redistribute it and/or modify it
6 it under the terms of the GNU General Public License as published by 8 under the terms of the GNU General Public License as published by the
7 the Free Software Foundation; either version 2 of the License, or 9 Free Software Foundation; either version 3 of the License, or (at your
8 (at your option) any later version. 10 option) any later version.
9 11
10 This program is distributed in the hope that it will be useful, 12 This program is distributed in the hope that it will be useful, but
11 but WITHOUT ANY WARRANTY; without even the implied warranty of 13 WITHOUT ANY WARRANTY; without even the implied warranty of
12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 14 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General
13 GNU General Public License for more details. 15 Public License for more details.
14 16
15 You should have received a copy of the GNU General Public License 17 You should have received a copy of the GNU General Public License along
16 along with this program; if not, write to the Free Software 18 with this program; if not, see <http://www.gnu.org/licenses/>.
17 Foundation, Inc. 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA 19
20 Additional permission under GNU GPL version 3 section 7
21
22 If you modify this Program, or any covered work, by linking or
23 combining it with the OpenSSL project's OpenSSL library (or a modified
24 version of that library), containing parts covered by the terms of the
25 OpenSSL or SSLeay licenses, the licensors of this Program grant you
26 additional permission to convey the resulting work. Corresponding
27 Source for a non-source form of such a combination shall include the
28 source code for the parts of OpenSSL used as well as that of the
29 covered work.
18*/ 30*/
31
32// TODO: EDNS0 option to increase dns mtu?
33// TODO: re-write dns packet parsing/creation using a safe mem-buffer
34// to ensure no buffer overflows or similar problems.
19 35
20#include "config.h" 36#include "config.h"
21 37
22#if ENABLE_DNS 38#if ENABLE_DNS
23 39
24// dns processing is EXTREMELY ugly. For obvious(?) reasons. 40// dns processing is EXTREMELY ugly. For obvious(?) reasons.
25// it's a hack, use only in emergency situations please. 41// it's a hack, use only in emergency situations please.
26 42
27#include <cstring> 43#include <cstring>
44#include <cassert>
28 45
29#include <sys/types.h> 46#include <sys/types.h>
30#include <sys/socket.h> 47#include <sys/socket.h>
31#include <sys/wait.h> 48#include <sys/wait.h>
32#include <sys/uio.h> 49#include <sys/uio.h>
35#include <unistd.h> 52#include <unistd.h>
36#include <fcntl.h> 53#include <fcntl.h>
37 54
38#include <map> 55#include <map>
39 56
57#include <cstdio> /* bug in libgmp: gmp.h relies on cstdio being included */
58#include <gmp.h>
59
40#include "netcompat.h" 60#include "netcompat.h"
41 61
42#include "vpn.h" 62#include "vpn.h"
43 63
44#define MIN_RETRY 1. 64#define MIN_POLL_INTERVAL 0.025 // poll at most this often when no data received
45#define MAX_RETRY 60. 65#define MAX_POLL_INTERVAL 1. // how often to poll minimally when the server has no data
46 66
47#define MAX_OUTSTANDING 10 // max. outstanding requests 67#define INITIAL_TIMEOUT 0.1 // retry timeouts
68#define INITIAL_SYN_TIMEOUT 2. // retry timeout for initial syn
48 69
49/* 70#define MAX_SEND_INTERVAL 5. // optimistic?
50 71
51protocol, in shorthand :) 72#define MAX_WINDOW 1000 // max. for MAX_OUTSTANDING, and backlog
73#define MAX_BACKLOG (64*1024) // size of gvpe protocol backlog (bytes), must be > MAXSIZE
52 74
53client -> server <req> ANY? 75#define MAX_DOMAIN_SIZE 235 // 255 is legal limit, but bind doesn't compress well
54server -> client <req> TXT <rep> 76// 240 leaves about 4 bytes of server reply data
77// every request byte less give room for two reply bytes
55 78
56<req> is dns64-encoded <client-id:12><recv-seqno:10>[<send-seqno:10><data>] 79#define SEQNO_MASK 0x3fff
57<rep> is dns64-encoded <0:12><recv-seqno:10>[<send-seqno:10><data>] 80#define SEQNO_EQ(a,b) ( 0 == ( ((a) ^ (b)) & SEQNO_MASK) )
58
59if <client-id> is zero, the connection will be configured:
60
61<0:12><0:4>client-id:12><default-ttl:8><max-size:16><flags:16>
62
63*/
64 81
65#define MAX_LBL_SIZE 63 82#define MAX_LBL_SIZE 63
66#define MAX_PKT_SIZE 512 83#define MAX_PKT_SIZE 512
67 84
85#define RR_TYPE_A 1
86#define RR_TYPE_NULL 10
68#define RR_TYPE_TXT 16 87#define RR_TYPE_TXT 16
88#define RR_TYPE_AAAA 28
69#define RR_TYPE_ANY 255 89#define RR_TYPE_ANY 255
90
70#define RR_CLASS_IN 1 91#define RR_CLASS_IN 1
71 92
72// the "_" is not valid but widely accepted (all octets should be supported, but let's be conservative) 93#define CMD_IP_1 207
73struct dns64 94#define CMD_IP_2 46
74{ 95#define CMD_IP_3 236
75 static const char encode_chars[64 + 1];
76 static s8 decode_chars[256];
77 96
78 static int encode_len (int bytes) { return (bytes * 8 + 5) / 6; } 97#define CMD_IP_RST 29 // some error, reset and retry
79 static int decode_len (int bytes) { return (bytes * 6) / 8; } 98#define CMD_IP_REJ 32 // do not want you
80 static void encode (char *dst, u8 *src, int len); 99#define CMD_IP_SYN 113 // connection established
81 static void decode (u8 *dst, char *src, int len); 100#define CMD_IP_CSE 213 // connection established, but likely case mismatch
82 101
83 dns64 (); 102static bool
84} dns64; 103is_uc (char c)
85
86const char dns64::encode_chars[64 + 1] = "0123456789-abcdefghijklmnopqrstuvwxyz_ABCDEFGHIJKLMNOPQRSTUVWXYZ";
87s8 dns64::decode_chars[256];
88
89dns64::dns64 ()
90{ 104{
91 for (int i = 0; i < 64; i++) 105 return 'A' <= c && c <= 'Z';
92 decode_chars [encode_chars [i]] = i + 1;
93} 106}
94 107
95void dns64::encode (char *dst, u8 *src, int len) 108static bool
109is_lc (char c)
96{ 110{
97 // slow, but easy to debug 111 return 'a' <= c && c <= 'z';
98 unsigned int accum, bits = 0; 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
163 unsigned int encode (char *dst, u8 *src, unsigned int len) const;
164 unsigned int decode (u8 *dst, char *src, unsigned int len) const;
165
166 basecoder (const char *cmap);
167};
168
169basecoder::basecoder (const char *cmap)
170: cmap (cmap)
171{
172 for (unsigned int len = 0; len < MAX_DEC_LEN; ++len)
173 {
174 u8 src [MAX_DEC_LEN];
175 u8 dst [MAX_ENC_LEN];
176
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
195{
196 return enc_len [len];
197}
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;
99 246
100 while (len--) 247 while (len--)
101 { 248 {
102 accum <<= 8; 249 u8 val = cmap.decode [(u8)*src++];
103 accum |= *src++;
104 bits += 8;
105 250
106 while (bits >= 6) 251 if (val != charmap::INVALID)
107 { 252 src_ [elen++] = val;
108 *dst++ = encode_chars [(accum >> (bits - 6)) & 63]; 253 }
109 bits -= 6; 254
110 } 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)
111 } 266 {
267 memset (dst, 0, dlen - n);
268 memcpy (dst + dlen - n, dst_, n);
269 }
270 else
271 memcpy (dst, dst_ + n - dlen, dlen);
112 272
113 if (bits) 273 return dlen;
114 *dst++ = encode_chars [(accum << (6 - bits)) & 63];
115} 274}
116 275
117void dns64::decode (u8 *dst, char *src, int len) 276#if 0
118{ 277struct test { test (); } test;
119 // slow, but easy to debug
120 unsigned int accum, bits = 0;
121 278
122 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++)
123 { 288 {
124 s8 chr = decode_chars [(u8)*src++]; 289 int elen = cdc.encode (enc, in, i);
290 int dlen = cdc.decode (dec, enc, elen);
125 291
292 printf ("%d>%d>%d (%s>%s)\n", i, elen, dlen, enc, dec);
293 }
294 abort ();
295}
296#endif
126 297
127 if (!chr) 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;
331}
332
333/////////////////////////////////////////////////////////////////////////////
334
335struct byte_stream
336{
337 u8 *data;
338 int maxsize;
339 int fill;
340
341 byte_stream (int maxsize);
342 ~byte_stream ();
343
344 bool empty () { return !fill; }
345 int size () { return fill; }
346
347 bool put (u8 *data, unsigned int datalen);
348 bool put (vpn_packet *pkt);
349 vpn_packet *get ();
350
351 u8 *begin () { return data; }
352 void remove (int count);
353};
354
355byte_stream::byte_stream (int maxsize)
356: maxsize (maxsize), fill (0)
357{
358 data = new u8 [maxsize];
359}
360
361byte_stream::~byte_stream ()
362{
363 delete data;
364}
365
366void
367byte_stream::remove (int count)
368{
369 if (count > fill)
370 assert (count <= fill);
371
372 memmove (data, data + count, fill -= count);
373}
374
375bool
376byte_stream::put (u8 *data, unsigned int datalen)
377{
378 if (maxsize - fill < datalen)
379 return false;
380
381 memcpy (this->data + fill, data, datalen); fill += datalen;
382
383 return true;
384}
385
386bool
387byte_stream::put (vpn_packet *pkt)
388{
389 if (maxsize - fill < pkt->len + 2)
390 return false;
391
392 data [fill++] = pkt->len >> 8;
393 data [fill++] = pkt->len;
394
395 memcpy (data + fill, pkt->at (0), pkt->len); fill += pkt->len;
396
397 return true;
398}
399
400vpn_packet *byte_stream::get ()
401{
402 unsigned int len;
403
404 for (;;)
405 {
406 len = (data [0] << 8) | data [1];
407
408 if (len <= MAXSIZE || fill < 2)
128 break; 409 break;
129 410
130 accum <<= 6; 411 // TODO: handle this better than skipping, e.g. by reset
131 accum |= chr - 1; 412 slog (L_DEBUG, _("DNS: corrupted packet stream skipping a byte..."));
132 bits += 6; 413 remove (1);
133 414 }
134 while (bits >= 8)
135 { 415
136 *dst++ = accum >> (bits - 8); 416 if (fill < len + 2)
137 bits -= 8; 417 return 0;
138 } 418
139 } 419 vpn_packet *pkt = new vpn_packet;
420
421 pkt->len = len;
422 memcpy (pkt->at (0), data + 2, len);
423 remove (len + 2);
424
425 return pkt;
140} 426}
141 427
142///////////////////////////////////////////////////////////////////////////// 428/////////////////////////////////////////////////////////////////////////////
143 429
144#define FLAG_QUERY ( 0 << 15) 430#define FLAG_QUERY ( 0 << 15)
145#define FLAG_RESPONSE ( 1 << 15) 431#define FLAG_RESPONSE ( 1 << 15)
146#define FLAG_OP_MASK (15 << 14) 432#define FLAG_OP_MASK (15 << 11)
147#define FLAG_OP_QUERY ( 0 << 11) 433#define FLAG_OP_QUERY ( 0 << 11)
148#define FLAG_AA ( 1 << 10) 434#define FLAG_AA ( 1 << 10)
149#define FLAG_TC ( 1 << 9) 435#define FLAG_TC ( 1 << 9)
150#define FLAG_RD ( 1 << 8) 436#define FLAG_RD ( 1 << 8)
151#define FLAG_RA ( 1 << 7) 437#define FLAG_RA ( 1 << 7)
438#define FLAG_AUTH ( 1 << 5)
152#define FLAG_RCODE_MASK (15 << 0) 439#define FLAG_RCODE_MASK (15 << 0)
153#define FLAG_RCODE_OK ( 0 << 0) 440#define FLAG_RCODE_OK ( 0 << 0)
154#define FLAG_RCODE_FORMERR ( 1 << 0) 441#define FLAG_RCODE_FORMERR ( 1 << 0)
155#define FLAG_RCODE_SERVFAIL ( 2 << 0) 442#define FLAG_RCODE_SERVFAIL ( 2 << 0)
156#define FLAG_RCODE_NXDOMAIN ( 3 << 0) 443#define FLAG_RCODE_NXDOMAIN ( 3 << 0)
157#define FLAG_RCODE_REFUSED ( 5 << 0) 444#define FLAG_RCODE_REFUSED ( 5 << 0)
158 445
159#define DEFAULT_CLIENT_FLAGS (FLAG_QUERY | FLAG_OP_QUERY | FLAG_RD) 446#define DEFAULT_CLIENT_FLAGS (FLAG_QUERY | FLAG_OP_QUERY | FLAG_RD)
160#define DEFAULT_SERVER_FLAGS (FLAG_RESPONSE | FLAG_OP_QUERY | FLAG_AA | FLAG_RD) 447#define DEFAULT_SERVER_FLAGS (FLAG_RESPONSE | FLAG_OP_QUERY | FLAG_AA | FLAG_RD | FLAG_RA)
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}
161 541
162struct dns_packet : net_packet 542struct dns_packet : net_packet
163{ 543{
164 u16 id; 544 u16 id;
165 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
166 u16 qdcount, ancount, nscount, arcount; 546 u16 qdcount, ancount, nscount, arcount;
167 547
168 u8 data[MAXSIZE - 6 * 2]; 548 u8 data [MAXSIZE - 6 * 2];
169 549
170 int decode_label (char *data, int size, int &offs); 550 int decode_label (char *data, int size, int &offs);
171}; 551};
172 552
553int
173int dns_packet::decode_label (char *data, int size, int &offs) 554dns_packet::decode_label (char *data, int size, int &offs)
174{ 555{
175 char *orig = data; 556 char *orig = data;
176 557
177 memset (data, 0, size); 558 memset (data, 0, size);
178 559
204 return data - orig; 585 return data - orig;
205} 586}
206 587
207///////////////////////////////////////////////////////////////////////////// 588/////////////////////////////////////////////////////////////////////////////
208 589
590static
591u16 next_id ()
592{
593 static u16 dns_id = 0; // TODO: should be per-vpn
594
595#if 1
596 if (!dns_id)
597 dns_id = time (0);
598
599 // the simplest lsfr with periodicity 65535 i could find
600 dns_id = (dns_id << 1)
601 | (((dns_id >> 1)
602 ^ (dns_id >> 2)
603 ^ (dns_id >> 4)
604 ^ (dns_id >> 15)) & 1);
605
606 return dns_id;
607#else
608 dns_id++;//D
609
610 return htons (dns_id);
611#endif
612}
613
209struct dns_req 614struct dns_rcv;
615struct dns_snd;
616
617struct dns_connection
618{
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
210{ 648{
211 dns_packet *pkt; 649 dns_packet *pkt;
212 tstamp next; 650 tstamp timeout, sent;
213 int retry; 651 int retry;
652 struct dns_connection *dns;
653 int seqno;
654 bool stdhdr;
214 655
215 dns_req (connection *c, vpn_packet *p, int &offs); 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 ();
216}; 661};
217 662
663dns_snd::dns_snd (dns_connection *dns)
664: dns (dns)
665{
666 timeout = 0;
667 retry = 0;
668 seqno = 0;
669 sent = ev_now ();
670 stdhdr = false;
671
672 pkt = new dns_packet;
673
674 pkt->id = next_id ();
675}
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
707dns_snd::gen_stream_req (int seqno, byte_stream &stream)
708{
709 stdhdr = true;
710 this->seqno = seqno;
711
712 timeout = ev_now () + INITIAL_TIMEOUT;
713
714 pkt->flags = htons (DEFAULT_CLIENT_FLAGS);
715 pkt->qdcount = htons (1);
716
717 int offs = 6*2;
718 int dlen = MAX_DOMAIN_SIZE - (strlen (dns->c->conf->domain) + 2);
719 // MAX_DOMAIN_SIZE is technically 255, but bind doesn't compress responses well,
720 // so we need to have space for 2*MAX_DOMAIN_SIZE + header + extra
721
722 char enc[256], *encp = enc;
723 encode_header (enc, THISNODE->id, seqno);
724
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;
731 stream.remove (datalen);
732
733 while (enclen)
734 {
735 int lbllen = enclen < MAX_LBL_SIZE ? enclen : MAX_LBL_SIZE;
736
737 (*pkt)[offs++] = lbllen;
738 memcpy (pkt->at (offs), encp, lbllen);
739
740 offs += lbllen;
741 encp += lbllen;
742
743 enclen -= lbllen;
744 }
745
746 append_domain (*pkt, offs, dns->c->conf->domain);
747
748 (*pkt)[offs++] = 0;
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;
775 (*pkt)[offs++] = RR_CLASS_IN >> 8; (*pkt)[offs++] = RR_CLASS_IN;
776
777 pkt->len = offs;
778}
779
218struct dns_rep 780struct dns_rcv
219{ 781{
782 int seqno;
783 dns_packet *pkt; // reply packet
784 u8 data [MAXSIZE]; // actually part of the reply packet...
785 int datalen;
786
787 dns_rcv (int seqno, u8 *data, int datalen);
788 ~dns_rcv ();
220}; 789};
221 790
222static u16 dns_id; // TODO: should be per-vpn 791dns_rcv::dns_rcv (int seqno, u8 *data, int datalen)
223 792: seqno (seqno), pkt (new dns_packet), datalen (datalen)
224dns_req::dns_req (connection *c, vpn_packet *p, int &offs)
225{ 793{
226 next = 0; 794 memcpy (this->data, data, datalen);
227 retry = 0; 795}
228 796
229 pkt = new dns_packet; 797dns_rcv::~dns_rcv ()
230 798{
231 pkt->id = dns_id++; 799 delete pkt;
232 pkt->flags = DEFAULT_CLIENT_FLAGS;
233 pkt->qdcount = htons (1 * 0);
234 pkt->ancount = 0;
235 pkt->nscount = 0;
236 pkt->arcount = 0;
237
238 offs += 10000;
239
240 c->dns_sndq.push_back (this);
241} 800}
242 801
243///////////////////////////////////////////////////////////////////////////// 802/////////////////////////////////////////////////////////////////////////////
244 803
245struct dns_cfg 804dns_connection::dns_connection (connection *c)
805: c (c)
806, rcvdq (MAX_BACKLOG * 2)
807, snddq (MAX_BACKLOG)
246{ 808{
247 u8 id1, id2, id3; 809 tw.set<dns_connection, &dns_connection::time_cb> (this);
248 u8 def_ttl;
249 u8 unused1;
250 u16 max_size;
251 u8 flags1, flags2;
252};
253 810
254// reply to client-poll 811 vpn = c->vpn;
255void dnsv4_poll (dns_packet *pkt, int &offs)
256{
257 int dlen = MAX_PKT_SIZE - offs - 2;
258 812
259 (*pkt) [offs++] = 0; 813 reset ();
260 (*pkt) [offs++] = 5; 814}
261 memcpy (&((*pkt)[offs]), "\01H\02\xff\x00", 5);
262 offs += 5;
263 815
264 pkt->ancount = htons (1); 816dns_connection::~dns_connection ()
265 pkt->flags = htons (DEFAULT_SERVER_FLAGS | FLAG_RCODE_OK); 817{
266 818 reset ();
267 printf ("we have room for %d bytes\n", dlen);
268} 819}
269 820
270void 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
854dns_connection::receive_rep (dns_rcv *r)
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
861 rcvpq.push_back (r);
862
863 redo:
864
865 // find next packet
866 for (vector<dns_rcv *>::iterator i = rcvpq.end (); i-- != rcvpq.begin (); )
867 if (SEQNO_EQ (rcvseq, (*i)->seqno))
868 {
869 //printf ("seqno eq %x %x\n", rcvseq, (*i)->seqno);//D
870 // enter the packet into our input stream
871 r = *i;
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
883 rcvseq = (rcvseq + 1) & SEQNO_MASK;
884
885 if (!rcvdq.put (r->data, r->datalen))
886 {
887 // MUST never overflow, can be caused by data corruption, TODO
888 slog (L_CRIT, "DNS: !rcvdq.put (r->data, r->datalen)");
889 reset ();
890 return;
891 }
892
893 while (vpn_packet *pkt = rcvdq.get ())
894 {
895 sockinfo si;
896 si.host = htonl (c->conf->id); si.port = 0; si.prot = PROT_DNSv4;
897
898 vpn->recv_vpn_packet (pkt, si);
899 delete pkt;
900 }
901
902 // check for further packets
903 goto redo;
904 }
905}
906
907void
908vpn::dnsv4_server (dns_packet &pkt)
909{
910 u16 flags = ntohs (pkt.flags);
911
912 int offs = 6 * 2; // skip header
913
914 pkt.flags = htons (DEFAULT_SERVER_FLAGS | FLAG_RCODE_FORMERR);
915
916 if (0 == (flags & (FLAG_RESPONSE | FLAG_OP_MASK))
917 && pkt.qdcount == htons (1))
918 {
919 char qname [MAXSIZE];
920 int qlen = pkt.decode_label ((char *)qname, MAXSIZE - offs, offs);
921
922 u16 qtype = pkt [offs++] << 8; qtype |= pkt [offs++];
923 u16 qclass = pkt [offs++] << 8; qclass |= pkt [offs++];
924
925 pkt.qdcount = htons (1);
926 pkt.ancount = 0;
927 pkt.nscount = 0; // should be self, as other nameservers reply like this
928 pkt.arcount = 0; // a record for self, as other nameservers reply like this
929
930 pkt.flags = htons (DEFAULT_SERVER_FLAGS | FLAG_RCODE_SERVFAIL);
931
932 int dlen = strlen (THISNODE->domain);
933
934 if (qclass == RR_CLASS_IN
935 && qlen > dlen + 1
936 && !memcmp (qname + qlen - (dlen + 1), THISNODE->domain, dlen))
937 {
938 // now generate reply
939 pkt.ancount = htons (1); // one answer RR
940 pkt.flags = htons (DEFAULT_SERVER_FLAGS | FLAG_RCODE_OK);
941
942 if ((qtype == RR_TYPE_ANY
943 || qtype == RR_TYPE_TXT
944 || qtype == RR_TYPE_NULL)
945 && qlen > dlen + 1 + HDRSIZE)
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 {
953 connection *c = conns [client - 1];
954 dns_connection *dns = c->dns;
955 dns_rcv *rcv;
956
957 if (dns)
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 (); )
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
984 {
985 pkt [offs++] = 0xc0; pkt [offs++] = 6 * 2; // refer to name in query section
986
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
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
1047 rcv->pkt->len = offs;
1048 memcpy (rcv->pkt->at (0), pkt.at (0), offs);
1049 }
1050 }
1051
1052 duplicate_request: ;
1053 }
1054 else
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);
1063
1064 pkt [offs++] = 0xc0; pkt [offs++] = 6 * 2; // refer to name in query section
1065
1066 pkt [offs++] = RR_TYPE_A >> 8; pkt [offs++] = RR_TYPE_A; // type
1067 pkt [offs++] = RR_CLASS_IN >> 8; pkt [offs++] = RR_CLASS_IN; // class
1068 pkt [offs++] = 0; pkt [offs++] = 0;
1069 pkt [offs++] = 0; pkt [offs++] = cfg.def_ttl; // TTL
1070 pkt [offs++] = 0; pkt [offs++] = 4; // rdlength
1071
1072 pkt [offs++] = CMD_IP_1; pkt [offs++] = CMD_IP_2; pkt [offs++] = CMD_IP_3;
1073 pkt [offs++] = CMD_IP_REJ;
1074
1075 if (0 < client && client <= conns.size ())
1076 {
1077 connection *c = conns [client - 1];
1078
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;
1094 c->dns->set_cfg ();
1095 }
1096 }
1097 }
1098 }
1099
1100 pkt.len = offs;
1101 }
1102}
1103
1104void
1105vpn::dnsv4_client (dns_packet &pkt)
1106{
1107 u16 flags = ntohs (pkt.flags);
1108 int offs = 6 * 2; // skip header
1109
1110 pkt.qdcount = ntohs (pkt.qdcount);
1111 pkt.ancount = ntohs (pkt.ancount);
1112
1113 // go through our request list and find the corresponding request
1114 for (vector<dns_snd *>::iterator i = dns_sndpq.begin ();
1115 i != dns_sndpq.end ();
1116 ++i)
1117 if ((*i)->pkt->id == pkt.id)
1118 {
1119 dns_connection *dns = (*i)->dns;
1120 connection *c = dns->c;
1121 int seqno = (*i)->seqno;
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 }
1149
1150 delete *i;
1151 dns_sndpq.erase (i);
1152
1153 if (flags & FLAG_RESPONSE && !(flags & FLAG_OP_MASK))
1154 {
1155 char qname[MAXSIZE];
1156
1157 while (pkt.qdcount-- && offs < MAXSIZE - 4)
1158 {
1159 int qlen = pkt.decode_label ((char *)qname, MAXSIZE - offs, offs);
1160 offs += 4; // skip qtype, qclass
1161 }
1162
1163 while (pkt.ancount-- && offs < MAXSIZE - 10 && datap)
1164 {
1165 int qlen = pkt.decode_label ((char *)qname, MAXSIZE - offs, offs);
1166
1167 u16 qtype = pkt [offs++] << 8; qtype |= pkt [offs++];
1168 u16 qclass = pkt [offs++] << 8; qclass |= pkt [offs++];
1169 u32 ttl = pkt [offs++] << 24;
1170 ttl |= pkt [offs++] << 16;
1171 ttl |= pkt [offs++] << 8;
1172 ttl |= pkt [offs++];
1173 u16 rdlen = pkt [offs++] << 8; rdlen |= pkt [offs++];
1174
1175 if (qtype == RR_TYPE_NULL || qtype == RR_TYPE_TXT || qtype == dns->cfg.rrtype)
1176 {
1177 if (rdlen <= MAXSIZE - offs)
1178 {
1179 // decode bytes, finally
1180
1181 while (rdlen)
1182 {
1183 int txtlen = pkt [offs++];
1184
1185 assert (txtlen + offs < MAXSIZE - 1);
1186
1187 memcpy (datap, pkt.at (offs), txtlen);
1188 datap += txtlen; offs += txtlen;
1189
1190 rdlen -= txtlen + 1;
1191 }
1192 }
1193 }
1194 else if (qtype == RR_TYPE_A)
1195 {
1196 u8 ip [4];
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 }
1267 }
1268 }
1269
1270 // todo: pkt now used
1271 if (datap)
1272 dns->receive_rep (new dns_rcv (seqno, data, datap - data));
1273
1274 break;
1275 }
1276}
1277
1278void
271vpn::dnsv4_ev (io_watcher &w, short revents) 1279vpn::dnsv4_ev (ev::io &w, int revents)
272{ 1280{
273 if (revents & EVENT_READ) 1281 if (revents & EV_READ)
274 { 1282 {
275 dns_packet *pkt = new dns_packet; 1283 dns_packet *pkt = new dns_packet;
276 struct sockaddr_in sa; 1284 struct sockaddr_in sa;
277 socklen_t sa_len = sizeof (sa); 1285 socklen_t sa_len = sizeof (sa);
278 1286
279 int 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);
280 pkt->len = len;
281 1288
282 u16 flags = ntohs (pkt->flags); 1289 if (pkt->len > 0)
283
284 if (THISNODE->dns_port)
285 { 1290 {
286 // server 1291 if (ntohs (pkt->flags) & FLAG_RESPONSE)
287 pkt->flags = htons (DEFAULT_SERVER_FLAGS | FLAG_RCODE_FORMERR); 1292 dnsv4_client (*pkt);
288 1293 else
289 int offs = 6 * 2; // skip header
290
291 if (!(flags & (FLAG_RESPONSE | FLAG_OP_MASK | FLAG_TC))
292 && pkt->qdcount == htons (1))
293 { 1294 {
294 char qname[MAXSIZE]; 1295 dnsv4_server (*pkt);
295 int qlen = pkt->decode_label ((char *)qname, MAXSIZE, offs); 1296 sendto (w.fd, pkt->at (0), pkt->len, 0, (sockaddr *)&sa, sa_len);
296
297 printf ("rcvd packet len %d, id%04x flags%04x q%04x a%04x n%04x a%04x <%s>\n", len,
298 pkt->id, flags, pkt->qdcount, pkt->ancount, pkt->nscount, pkt->arcount, qname);//D
299
300 u16 qtype = (*pkt) [offs++] << 8; qtype |= (*pkt) [offs++];
301 u16 qclass = (*pkt) [offs++] << 8; qclass |= (*pkt) [offs++];
302
303 pkt->qdcount = htons (1);
304 pkt->ancount = 0;
305 pkt->nscount = 0; // should be self, as other nameservers reply like this
306 pkt->arcount = 0; // a record for self, as other nameservers reply like this
307
308 pkt->flags = htons (DEFAULT_SERVER_FLAGS | FLAG_RCODE_NXDOMAIN);
309
310 int dlen = strlen (THISNODE->domain);
311
312 if (qclass == RR_CLASS_IN
313 && (qtype == RR_TYPE_ANY || qtype == RR_TYPE_TXT)
314 && qlen > dlen + 1
315 && !memcmp (qname + qlen - dlen - 1, THISNODE->domain, dlen))
316 {
317 // correct class, now generate reply
318 pkt->ancount = htons (1); // one answer RR
319
320 (*pkt) [offs++] = 0xc0;
321 (*pkt) [offs++] = 6 * 2; // same as in query section
322
323 (*pkt) [offs++] = RR_TYPE_TXT >> 8; (*pkt) [offs++] = RR_TYPE_TXT;
324 (*pkt) [offs++] = RR_CLASS_IN >> 8; (*pkt) [offs++] = RR_CLASS_IN;
325
326 (*pkt) [offs++] = 0; (*pkt) [offs++] = 0;
327 (*pkt) [offs++] = 0; (*pkt) [offs++] = 0; // TTL
328
329 dnsv4_poll (pkt, offs);
330 printf ("correct class\n");
331 }
332 } 1297 }
333 1298
334 sendto (w.fd, &((*pkt)[0]), offs, 0, (sockaddr *)&sa, sa_len); 1299 delete pkt;
1300 }
1301 }
1302}
1303
1304bool
1305vpn::send_dnsv4_packet (vpn_packet *pkt, const sockinfo &si, int tos)
1306{
1307 int client = ntohl (si.host);
1308
1309 assert (0 < client && client <= conns.size ());
1310
1311 connection *c = conns [client - 1];
1312
1313 if (!c->dns)
1314 c->dns = new dns_connection (c);
1315
1316 if (c->dns->snddq.put (pkt))
1317 {
1318 min_it (c->dns->poll_interval, 0.25);
1319 c->dns->tw ();
1320 }
1321
1322 // always return true even if the buffer overflows
1323 return true;
1324}
1325
1326void
1327dns_connection::time_cb (ev::timer &w, int revents)
1328{
1329 // servers have to be polled
1330 if (THISNODE->dns_port)
1331 return;
1332
1333 // check for timeouts and (re)transmit
1334 tstamp next = 86400 * 365;
1335 dns_snd *send = 0;
1336
1337 for (vector<dns_snd *>::iterator i = vpn->dns_sndpq.begin ();
1338 i != vpn->dns_sndpq.end ();
1339 ++i)
1340 {
1341 dns_snd *r = *i;
1342
1343 if (r->timeout <= ev_now ())
1344 {
1345 if (!send)
1346 {
1347 send = r;
1348
1349 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);
1357 }
335 } 1358 }
336 else 1359 else
1360 min_it (next, r->timeout - ev_now ());
1361 }
1362
1363 if (!send)
1364 {
1365 // generate a new packet, if wise
1366
1367 if (!established)
337 { 1368 {
338 // client 1369 if (vpn->dns_sndpq.empty ())
1370 {
1371 send = new dns_snd (this);
1372
1373 cfg.reset (THISNODE->id);
1374 set_cfg ();
1375 send->gen_syn_req ();
1376 }
339 } 1377 }
340 } 1378 else if (vpn->dns_sndpq.size () < conf.dns_max_outstanding
341} 1379 && !SEQNO_EQ (rcvseq, sndseq - (MAX_WINDOW - 1)))
342
343bool
344connection::send_dnsv4_packet (vpn_packet *pkt, const sockinfo &si, int tos)
345{
346 if (dns_sndq.size () >= MAX_OUTSTANDING)
347 return false;
348
349 // split vpn packet into dns packets, add to sndq
350 for (int offs = 0; offs < pkt->len; )
351 new dns_req (this, pkt, offs);
352
353 // force transmit
354 dnsv4_cb (dnsv4_tw);
355
356 return true;
357}
358
359void
360connection::dnsv4_cb (time_watcher &w)
361{
362 // check for timeouts and (re)transmit
363 tstamp next = NOW + 60;
364
365 slog (L_NOISE, _("dnsv4, %d packets in send queue\n"), dns_sndq.size ());
366
367 if (dns_sndq.empty ())
368 {
369 next = NOW + 1;
370 // push poll packet
371 }
372
373 for (vector<dns_req *>::iterator i = dns_sndq.begin ();
374 i != dns_sndq.end ();
375 ++i)
376 {
377 dns_req *r = *i;
378
379 if (r->next <= NOW)
380 { 1380 {
381 slog (L_NOISE, _("dnsv4, send req %d\n"), r->pkt->id); 1381 if (last_sent + send_interval <= ev_now ())
382 r->retry++; 1382 {
383 r->next = NOW + r->retry; 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);
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 ());
384 } 1396 }
385 1397
386 if (r->next < next) 1398 if (send)
387 next = r->next; 1399 vpn->dns_sndpq.push_back (send);
1400 }
1401
1402 if (send)
388 } 1403 {
1404 last_sent = ev_now ();
1405 sendto (vpn->dnsv4_fd,
1406 send->pkt->at (0), send->pkt->len, 0,
1407 vpn->dns_forwarder.sav4 (), vpn->dns_forwarder.salenv4 ());
1408 }
389 1409
390 printf ("%f next\n", 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 ());
1416
391 w.start (next); 1417 w.start (next);
392} 1418}
393 1419
394#endif 1420#endif
395 1421

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