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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 1.51 by root, Sun Mar 6 19:40:28 2011 UTC

1/* 1/*
2 vpn_dns.C -- handle the dns tunnel part of the protocol. 2 vpn_dns.C -- handle the dns tunnel part of the protocol.
3 Copyright (C) 2003-2004 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 0.1 // 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 2. // 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 240 // 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 (!dns_id)
596 dns_id = time (0);
597
598 // the simplest lsfr with periodicity 65535 i could find
599 dns_id = (dns_id << 1)
600 | (((dns_id >> 1)
601 ^ (dns_id >> 2)
602 ^ (dns_id >> 4)
603 ^ (dns_id >> 15)) & 1);
604
605 return dns_id;
606}
607
209struct dns_req 608struct dns_rcv;
609struct dns_snd;
610
611struct dns_connection
612{
613 connection *c;
614 struct vpn *vpn;
615
616 dns_cfg cfg;
617
618 bool established;
619 const basecoder *cdc;
620
621 tstamp last_received;
622 tstamp last_sent;
623 double min_latency;
624 double poll_interval, send_interval;
625
626 vector<dns_rcv *> rcvpq;
627
628 byte_stream rcvdq; int rcvseq; int repseq;
629 byte_stream snddq; int sndseq;
630
631 inline void time_cb (ev::timer &w, int revents); ev::timer tw;
632 void receive_rep (dns_rcv *r);
633
634 void reset (); // quite like tcp RST
635 void set_cfg (); // to be called after any cfg changes
636
637 dns_connection (connection *c);
638 ~dns_connection ();
639};
640
641struct dns_snd
210{ 642{
211 dns_packet *pkt; 643 dns_packet *pkt;
212 tstamp next; 644 tstamp timeout, sent;
213 int retry; 645 int retry;
646 struct dns_connection *dns;
647 int seqno;
648 bool stdhdr;
214 649
215 dns_req (connection *c, vpn_packet *p, int &offs); 650 void gen_stream_req (int seqno, byte_stream &stream);
651 void gen_syn_req ();
652
653 dns_snd (dns_connection *dns);
654 ~dns_snd ();
216}; 655};
217 656
657dns_snd::dns_snd (dns_connection *dns)
658: dns (dns)
659{
660 timeout = 0;
661 retry = 0;
662 seqno = 0;
663 sent = ev_now ();
664 stdhdr = false;
665
666 pkt = new dns_packet;
667
668 pkt->id = next_id ();
669}
670
671dns_snd::~dns_snd ()
672{
673 delete pkt;
674}
675
676static void
677append_domain (dns_packet &pkt, int &offs, const char *domain)
678{
679 // add tunnel domain
680 for (;;)
681 {
682 const char *end = strchr (domain, '.');
683
684 if (!end)
685 end = domain + strlen (domain);
686
687 int len = end - domain;
688
689 pkt [offs++] = len;
690 memcpy (pkt.at (offs), domain, len);
691 offs += len;
692
693 if (!*end)
694 break;
695
696 domain = end + 1;
697 }
698}
699
700void
701dns_snd::gen_stream_req (int seqno, byte_stream &stream)
702{
703 stdhdr = true;
704 this->seqno = seqno;
705
706 timeout = ev_now () + INITIAL_TIMEOUT;
707
708 pkt->flags = htons (DEFAULT_CLIENT_FLAGS);
709 pkt->qdcount = htons (1);
710
711 int offs = 6*2;
712 int dlen = MAX_DOMAIN_SIZE - (strlen (dns->c->conf->domain) + 2);
713 // MAX_DOMAIN_SIZE is technically 255, but bind doesn't compress responses well,
714 // so we need to have space for 2*MAX_DOMAIN_SIZE + header + extra
715
716 char enc[256], *encp = enc;
717 encode_header (enc, THISNODE->id, seqno);
718
719 int datalen = dns->cdc->decode_len (dlen - (dlen + MAX_LBL_SIZE - 1) / MAX_LBL_SIZE - HDRSIZE);
720
721 if (datalen > stream.size ())
722 datalen = stream.size ();
723
724 int enclen = dns->cdc->encode (enc + HDRSIZE, stream.begin (), datalen) + HDRSIZE;
725 stream.remove (datalen);
726
727 while (enclen)
728 {
729 int lbllen = enclen < MAX_LBL_SIZE ? enclen : MAX_LBL_SIZE;
730
731 (*pkt)[offs++] = lbllen;
732 memcpy (pkt->at (offs), encp, lbllen);
733
734 offs += lbllen;
735 encp += lbllen;
736
737 enclen -= lbllen;
738 }
739
740 append_domain (*pkt, offs, dns->c->conf->domain);
741
742 (*pkt)[offs++] = 0;
743 (*pkt)[offs++] = RR_TYPE_ANY >> 8; (*pkt)[offs++] = RR_TYPE_ANY;
744 (*pkt)[offs++] = RR_CLASS_IN >> 8; (*pkt)[offs++] = RR_CLASS_IN;
745
746 pkt->len = offs;
747}
748
749void
750dns_snd::gen_syn_req ()
751{
752 timeout = ev_now () + INITIAL_SYN_TIMEOUT;
753
754 pkt->flags = htons (DEFAULT_CLIENT_FLAGS);
755 pkt->qdcount = htons (1);
756
757 int offs = 6 * 2;
758
759 int elen = cdc26.encode ((char *)pkt->at (offs + 1), (u8 *)&dns->cfg, sizeof (dns_cfg));
760
761 assert (elen <= MAX_LBL_SIZE);
762
763 (*pkt)[offs] = elen;
764 offs += elen + 1;
765 append_domain (*pkt, offs, dns->c->conf->domain);
766
767 (*pkt)[offs++] = 0;
768 (*pkt)[offs++] = RR_TYPE_A >> 8; (*pkt)[offs++] = RR_TYPE_A;
769 (*pkt)[offs++] = RR_CLASS_IN >> 8; (*pkt)[offs++] = RR_CLASS_IN;
770
771 pkt->len = offs;
772}
773
218struct dns_rep 774struct dns_rcv
219{ 775{
776 int seqno;
777 dns_packet *pkt; // reply packet
778 u8 data [MAXSIZE]; // actually part of the reply packet...
779 int datalen;
780
781 dns_rcv (int seqno, u8 *data, int datalen);
782 ~dns_rcv ();
220}; 783};
221 784
222static u16 dns_id; // TODO: should be per-vpn 785dns_rcv::dns_rcv (int seqno, u8 *data, int datalen)
223 786: seqno (seqno), pkt (new dns_packet), datalen (datalen)
224dns_req::dns_req (connection *c, vpn_packet *p, int &offs)
225{ 787{
226 next = 0; 788 memcpy (this->data, data, datalen);
227 retry = 0; 789}
228 790
229 pkt = new dns_packet; 791dns_rcv::~dns_rcv ()
230 792{
231 pkt->id = dns_id++; 793 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} 794}
242 795
243///////////////////////////////////////////////////////////////////////////// 796/////////////////////////////////////////////////////////////////////////////
244 797
245struct dns_cfg 798dns_connection::dns_connection (connection *c)
799: c (c)
800, rcvdq (MAX_BACKLOG * 2)
801, snddq (MAX_BACKLOG)
246{ 802{
247 u8 id1, id2, id3; 803 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};
253 804
254// reply to client-poll 805 vpn = c->vpn;
255void dnsv4_poll (dns_packet *pkt, int &offs)
256{
257 int dlen = MAX_PKT_SIZE - offs - 2;
258 806
259 (*pkt) [offs++] = 0; 807 reset ();
260 (*pkt) [offs++] = 5; 808}
261 memcpy (&((*pkt)[offs]), "\01H\02\xff\x00", 5);
262 offs += 5;
263 809
264 pkt->ancount = htons (1); 810dns_connection::~dns_connection ()
265 pkt->flags = htons (DEFAULT_SERVER_FLAGS | FLAG_RCODE_OK); 811{
266 812 reset ();
267 printf ("we have room for %d bytes\n", dlen);
268} 813}
269 814
270void 815void
816dns_connection::reset ()
817{
818 while (!rcvpq.empty ())
819 {
820 delete rcvpq.back ();
821 rcvpq.pop_back ();
822 }
823
824 for (int i = vpn->dns_sndpq.size (); i--; )
825 if (vpn->dns_sndpq [i]->dns == this)
826 {
827 vpn->dns_sndpq [i] = vpn->dns_sndpq.back ();
828 vpn->dns_sndpq.pop_back ();
829 }
830
831 established = false;
832
833 rcvseq = repseq = sndseq = 0;
834
835 last_sent = last_received = 0;
836 poll_interval = 0.5; // starting here
837 send_interval = 0.5; // starting rate
838 min_latency = INITIAL_TIMEOUT;
839}
840
841void
842dns_connection::set_cfg ()
843{
844 cdc = cfg.req_cdc == 36 ? &cdc36 : &cdc62;
845}
846
847void
848dns_connection::receive_rep (dns_rcv *r)
849{
850 if (r->datalen)
851 {
852 last_received = ev_now ();
853 tw ();
854
855 poll_interval = send_interval;
856 }
857 else
858 {
859 poll_interval *= 1.5;
860
861 if (poll_interval > MAX_POLL_INTERVAL)
862 poll_interval = MAX_POLL_INTERVAL;
863 }
864
865 rcvpq.push_back (r);
866
867 redo:
868
869 // find next packet
870 for (vector<dns_rcv *>::iterator i = rcvpq.end (); i-- != rcvpq.begin (); )
871 if (SEQNO_EQ (rcvseq, (*i)->seqno))
872 {
873 //printf ("seqno eq %x %x\n", rcvseq, (*i)->seqno);//D
874 // enter the packet into our input stream
875 r = *i;
876
877 // remove the oldest packet, look forward, as it's oldest first
878 for (vector<dns_rcv *>::iterator j = rcvpq.begin (); j != rcvpq.end (); ++j)
879 if (SEQNO_EQ ((*j)->seqno, rcvseq - MAX_WINDOW))
880 {
881 //printf ("seqno RR %x %x\n", (*j)->seqno, rcvseq - MAX_WINDOW);//D
882 delete *j;
883 rcvpq.erase (j);
884 break;
885 }
886
887 rcvseq = (rcvseq + 1) & SEQNO_MASK;
888
889 if (!rcvdq.put (r->data, r->datalen))
890 {
891 // MUST never overflow, can be caused by data corruption, TODO
892 slog (L_CRIT, "DNS: !rcvdq.put (r->data, r->datalen)");
893 reset ();
894 return;
895 }
896
897 while (vpn_packet *pkt = rcvdq.get ())
898 {
899 sockinfo si;
900 si.host = htonl (c->conf->id); si.port = 0; si.prot = PROT_DNSv4;
901
902 vpn->recv_vpn_packet (pkt, si);
903 delete pkt;
904 }
905
906 // check for further packets
907 goto redo;
908 }
909}
910
911void
912vpn::dnsv4_server (dns_packet &pkt)
913{
914 u16 flags = ntohs (pkt.flags);
915
916 int offs = 6 * 2; // skip header
917
918 pkt.flags = htons (DEFAULT_SERVER_FLAGS | FLAG_RCODE_FORMERR);
919
920 if (0 == (flags & (FLAG_RESPONSE | FLAG_OP_MASK))
921 && pkt.qdcount == htons (1))
922 {
923 char qname [MAXSIZE];
924 int qlen = pkt.decode_label ((char *)qname, MAXSIZE - offs, offs);
925
926 u16 qtype = pkt [offs++] << 8; qtype |= pkt [offs++];
927 u16 qclass = pkt [offs++] << 8; qclass |= pkt [offs++];
928
929 pkt.qdcount = htons (1);
930 pkt.ancount = 0;
931 pkt.nscount = 0; // should be self, as other nameservers reply like this
932 pkt.arcount = 0; // a record for self, as other nameservers reply like this
933
934 pkt.flags = htons (DEFAULT_SERVER_FLAGS | FLAG_RCODE_SERVFAIL);
935
936 int dlen = strlen (THISNODE->domain);
937
938 if (qclass == RR_CLASS_IN
939 && qlen > dlen + 1
940 && !memcmp (qname + qlen - (dlen + 1), THISNODE->domain, dlen))
941 {
942 // now generate reply
943 pkt.ancount = htons (1); // one answer RR
944 pkt.flags = htons (DEFAULT_SERVER_FLAGS | FLAG_RCODE_OK);
945
946 if ((qtype == RR_TYPE_ANY
947 || qtype == RR_TYPE_TXT
948 || qtype == RR_TYPE_NULL)
949 && qlen > dlen + 1 + HDRSIZE)
950 {
951 // correct class, domain: parse
952 int client, seqno;
953 decode_header (qname, client, seqno);
954
955 if (0 < client && client <= conns.size ())
956 {
957 connection *c = conns [client - 1];
958 dns_connection *dns = c->dns;
959 dns_rcv *rcv;
960
961 if (dns)
962 {
963 u8 data[MAXSIZE];
964 int datalen = dns->cdc->decode (data, qname + HDRSIZE, qlen - (dlen + 1 + HDRSIZE));
965
966 for (vector<dns_rcv *>::iterator i = dns->rcvpq.end (); i-- != dns->rcvpq.begin (); )
967 if (SEQNO_EQ ((*i)->seqno, seqno))
968 {
969 // already seen that request: simply reply with the cached reply
970 dns_rcv *r = *i;
971
972 slog (L_DEBUG, "DNS: duplicate packet received ID %d, SEQ %d", htons (r->pkt->id), seqno);
973
974 // refresh header & id, as the retry count could have changed
975 memcpy (r->pkt->at (6 * 2 + 1), pkt.at (6 * 2 + 1), HDRSIZE);
976 r->pkt->id = pkt.id;
977
978 memcpy (pkt.at (0), r->pkt->at (0), offs = r->pkt->len);
979
980 goto duplicate_request;
981 }
982
983 // new packet, queue
984 rcv = new dns_rcv (seqno, data, datalen);
985 dns->receive_rep (rcv);
986 }
987
988 {
989 pkt [offs++] = 0xc0; pkt [offs++] = 6 * 2; // refer to name in query section
990
991 int rtype = dns ? dns->cfg.rrtype : RR_TYPE_A;
992 pkt [offs++] = rtype >> 8; pkt [offs++] = rtype; // type
993 pkt [offs++] = RR_CLASS_IN >> 8; pkt [offs++] = RR_CLASS_IN; // class
994 pkt [offs++] = 0; pkt [offs++] = 0;
995 pkt [offs++] = 0; pkt [offs++] = dns ? dns->cfg.def_ttl : 0; // TTL
996
997 int rdlen_offs = offs += 2;
998
999 if (dns)
1000 {
1001 int dlen = ntohs (dns->cfg.max_size) - offs;
1002
1003 // bind doesn't compress well, so reduce further by one label length
1004 dlen -= qlen;
1005
1006 // only put data into in-order sequence packets, if
1007 // we receive out-of-order packets we generate empty
1008 // replies
1009 //printf ("%d - %d & %x (=%d) < %d\n", seqno, dns->repseq, SEQNO_MASK, (seqno - dns->repseq) & SEQNO_MASK, MAX_WINDOW);//D
1010 if (((seqno - dns->repseq) & SEQNO_MASK) <= MAX_WINDOW)
1011 {
1012 dns->repseq = seqno;
1013
1014 while (dlen > 1 && !dns->snddq.empty ())
1015 {
1016 int txtlen = dlen <= 255 ? dlen - 1 : 255;
1017
1018 if (txtlen > dns->snddq.size ())
1019 txtlen = dns->snddq.size ();
1020
1021 pkt[offs++] = txtlen;
1022 memcpy (pkt.at (offs), dns->snddq.begin (), txtlen);
1023 offs += txtlen;
1024 dns->snddq.remove (txtlen);
1025
1026 dlen -= txtlen + 1;
1027 }
1028 }
1029
1030 // avoid completely empty TXT rdata
1031 if (offs == rdlen_offs)
1032 pkt[offs++] = 0;
1033
1034 slog (L_NOISE, "DNS: snddq %d", dns->snddq.size ());
1035 }
1036 else
1037 {
1038 // send RST
1039 pkt [offs++] = CMD_IP_1; pkt [offs++] = CMD_IP_2; pkt [offs++] = CMD_IP_3;
1040 pkt [offs++] = CMD_IP_RST;
1041 }
1042
1043 int rdlen = offs - rdlen_offs;
1044
1045 pkt [rdlen_offs - 2] = rdlen >> 8;
1046 pkt [rdlen_offs - 1] = rdlen;
1047
1048 if (dns)
1049 {
1050 // now update dns_rcv copy
1051 rcv->pkt->len = offs;
1052 memcpy (rcv->pkt->at (0), pkt.at (0), offs);
1053 }
1054 }
1055
1056 duplicate_request: ;
1057 }
1058 else
1059 pkt.flags = htons (DEFAULT_SERVER_FLAGS | FLAG_RCODE_FORMERR);
1060 }
1061 else if (qtype == RR_TYPE_A
1062 && qlen > dlen + 1 + cdc26.encode_len (sizeof (dns_cfg)))
1063 {
1064 dns_cfg cfg;
1065 cdc26.decode ((u8 *)&cfg, qname, cdc26.encode_len (sizeof (dns_cfg)));
1066 int client = ntohs (cfg.client);
1067
1068 pkt [offs++] = 0xc0; pkt [offs++] = 6 * 2; // refer to name in query section
1069
1070 pkt [offs++] = RR_TYPE_A >> 8; pkt [offs++] = RR_TYPE_A; // type
1071 pkt [offs++] = RR_CLASS_IN >> 8; pkt [offs++] = RR_CLASS_IN; // class
1072 pkt [offs++] = 0; pkt [offs++] = 0;
1073 pkt [offs++] = 0; pkt [offs++] = cfg.def_ttl; // TTL
1074 pkt [offs++] = 0; pkt [offs++] = 4; // rdlength
1075
1076 pkt [offs++] = CMD_IP_1; pkt [offs++] = CMD_IP_2; pkt [offs++] = CMD_IP_3;
1077 pkt [offs++] = CMD_IP_REJ;
1078
1079 if (0 < client && client <= conns.size ())
1080 {
1081 connection *c = conns [client - 1];
1082
1083 if (cfg.valid ())
1084 {
1085 slog (L_INFO, _("DNS: client %d connects (version %d, req_cdc %d)"), client, cfg.version, cfg.req_cdc);
1086
1087 // check for any encoding mismatches - hints at a case problem
1088 char qname2 [MAX_ENC_LEN];
1089 cdc26.encode (qname2, (u8 *)&cfg, sizeof (dns_cfg));
1090
1091 delete c->dns;
1092
1093 pkt [offs - 1] = memcmp (qname, qname2, cdc26.encode_len (sizeof (dns_cfg)))
1094 ? CMD_IP_CSE : CMD_IP_SYN;
1095
1096 c->dns = new dns_connection (c);
1097 c->dns->cfg = cfg;
1098 c->dns->set_cfg ();
1099 }
1100 }
1101 }
1102 }
1103
1104 pkt.len = offs;
1105 }
1106}
1107
1108void
1109vpn::dnsv4_client (dns_packet &pkt)
1110{
1111 u16 flags = ntohs (pkt.flags);
1112 int offs = 6 * 2; // skip header
1113
1114 pkt.qdcount = ntohs (pkt.qdcount);
1115 pkt.ancount = ntohs (pkt.ancount);
1116
1117 // go through our request list and find the corresponding request
1118 for (vector<dns_snd *>::iterator i = dns_sndpq.begin ();
1119 i != dns_sndpq.end ();
1120 ++i)
1121 if ((*i)->pkt->id == pkt.id)
1122 {
1123 dns_connection *dns = (*i)->dns;
1124 connection *c = dns->c;
1125 int seqno = (*i)->seqno;
1126 u8 data[MAXSIZE], *datap = data;
1127 //printf ("rcv pkt %x\n", seqno);//D
1128 bool back_off = (*i)->retry;
1129
1130 if (back_off)
1131 {
1132 dns->send_interval *= 1.01;
1133 if (dns->send_interval > MAX_SEND_INTERVAL)
1134 dns->send_interval = MAX_SEND_INTERVAL;
1135 }
1136 else
1137 {
1138#if 0
1139 dns->send_interval *= 0.999;
1140#endif
1141 // the latency surely puts an upper bound on
1142 // the minimum send interval
1143 double latency = ev_now () - (*i)->sent;
1144
1145 if (latency < dns->min_latency)
1146 dns->min_latency = latency;
1147
1148 if (dns->send_interval > dns->min_latency * conf.dns_overlap_factor)
1149 dns->send_interval = dns->min_latency * conf.dns_overlap_factor;
1150
1151 if (dns->send_interval < conf.dns_send_interval)
1152 dns->send_interval = conf.dns_send_interval;
1153 }
1154
1155 delete *i;
1156 dns_sndpq.erase (i);
1157
1158 if (flags & FLAG_RESPONSE && !(flags & FLAG_OP_MASK))
1159 {
1160 char qname[MAXSIZE];
1161
1162 while (pkt.qdcount-- && offs < MAXSIZE - 4)
1163 {
1164 int qlen = pkt.decode_label ((char *)qname, MAXSIZE - offs, offs);
1165 offs += 4; // skip qtype, qclass
1166 }
1167
1168 while (pkt.ancount-- && offs < MAXSIZE - 10 && datap)
1169 {
1170 int qlen = pkt.decode_label ((char *)qname, MAXSIZE - offs, offs);
1171
1172 u16 qtype = pkt [offs++] << 8; qtype |= pkt [offs++];
1173 u16 qclass = pkt [offs++] << 8; qclass |= pkt [offs++];
1174 u32 ttl = pkt [offs++] << 24;
1175 ttl |= pkt [offs++] << 16;
1176 ttl |= pkt [offs++] << 8;
1177 ttl |= pkt [offs++];
1178 u16 rdlen = pkt [offs++] << 8; rdlen |= pkt [offs++];
1179
1180 if (qtype == RR_TYPE_NULL || qtype == RR_TYPE_TXT || qtype == dns->cfg.rrtype)
1181 {
1182 if (rdlen <= MAXSIZE - offs)
1183 {
1184 // decode bytes, finally
1185
1186 while (rdlen)
1187 {
1188 int txtlen = pkt [offs++];
1189
1190 assert (txtlen + offs < MAXSIZE - 1);
1191
1192 memcpy (datap, pkt.at (offs), txtlen);
1193 datap += txtlen; offs += txtlen;
1194
1195 rdlen -= txtlen + 1;
1196 }
1197 }
1198 }
1199 else if (qtype == RR_TYPE_A)
1200 {
1201 u8 ip [4];
1202
1203 ip [0] = pkt [offs++];
1204 ip [1] = pkt [offs++];
1205 ip [2] = pkt [offs++];
1206 ip [3] = pkt [offs++];
1207
1208 if (ip [0] == CMD_IP_1
1209 && ip [1] == CMD_IP_2
1210 && ip [2] == CMD_IP_3)
1211 {
1212 slog (L_TRACE, _("DNS: got tunnel meta command %02x"), ip [3]);
1213
1214 if (ip [3] == CMD_IP_RST)
1215 {
1216 slog (L_DEBUG, _("DNS: got tunnel RST request."));
1217
1218 dns->reset ();
1219 return;
1220 }
1221 else if (ip [3] == CMD_IP_SYN)
1222 {
1223 slog (L_DEBUG, _("DNS: got tunnel SYN reply, server likes us."));
1224 dns->established = true;
1225 }
1226 else if (ip [3] == CMD_IP_CSE)
1227 {
1228 if (conf.dns_case_preserving)
1229 {
1230 slog (L_INFO, _("DNS: got tunnel CSE reply, globally downgrading to case-insensitive protocol."));
1231 conf.dns_case_preserving = false;
1232 dns->reset ();
1233 return;
1234 }
1235 else
1236 {
1237 slog (L_DEBUG, _("DNS: got tunnel CSE reply, server likes us."));
1238 dns->established = true;
1239 }
1240 }
1241 else if (ip [3] == CMD_IP_REJ)
1242 {
1243 slog (L_ERR, _("DNS: got tunnel REJ reply, server does not like us."));
1244 dns->tw.start (60.);
1245 }
1246 else
1247 {
1248 slog (L_INFO, _("DNS: got unknown meta command %02x"), ip [3]);
1249 dns->tw.start (60.);
1250 }
1251 }
1252 else
1253 slog (L_INFO, _("DNS: got spurious a record %d.%d.%d.%d"),
1254 ip [0], ip [1], ip [2], ip [3]);
1255
1256 return;
1257 }
1258
1259 int client, rseqno;
1260 decode_header (qname, client, rseqno);
1261
1262 if (client != THISNODE->id)
1263 {
1264 slog (L_INFO, _("DNS: got dns tunnel response with wrong clientid, ignoring"));
1265 datap = 0;
1266 }
1267 else if (rseqno != seqno)
1268 {
1269 slog (L_DEBUG, _("DNS: got dns tunnel response with wrong seqno, badly caching nameserver?"));
1270 datap = 0;
1271 }
1272 }
1273 }
1274
1275 // todo: pkt now used
1276 if (datap)
1277 dns->receive_rep (new dns_rcv (seqno, data, datap - data));
1278 else if (dns_sndpq.empty ()) // no data received, and nothing to send - idle
1279 {
1280 dns->send_interval *= 1.1;
1281
1282 if (dns->send_interval < MIN_POLL_INTERVAL)
1283 dns->send_interval = MIN_POLL_INTERVAL;
1284
1285 if (dns->send_interval > MAX_POLL_INTERVAL && !back_off)
1286 dns->send_interval = MAX_POLL_INTERVAL;
1287 }
1288
1289 break;
1290 }
1291}
1292
1293void
271vpn::dnsv4_ev (io_watcher &w, short revents) 1294vpn::dnsv4_ev (ev::io &w, int revents)
272{ 1295{
273 if (revents & EVENT_READ) 1296 if (revents & EV_READ)
274 { 1297 {
275 dns_packet *pkt = new dns_packet; 1298 dns_packet *pkt = new dns_packet;
276 struct sockaddr_in sa; 1299 struct sockaddr_in sa;
277 socklen_t sa_len = sizeof (sa); 1300 socklen_t sa_len = sizeof (sa);
278 1301
279 int len = recvfrom (w.fd, &((*pkt)[0]), MAXSIZE, 0, (sockaddr *)&sa, &sa_len); 1302 pkt->len = recvfrom (w.fd, pkt->at (0), MAXSIZE, 0, (sockaddr *)&sa, &sa_len);
280 pkt->len = len;
281 1303
282 u16 flags = ntohs (pkt->flags); 1304 if (pkt->len > 0)
283
284 if (THISNODE->dns_port)
285 { 1305 {
286 // server 1306 if (ntohs (pkt->flags) & FLAG_RESPONSE)
287 pkt->flags = htons (DEFAULT_SERVER_FLAGS | FLAG_RCODE_FORMERR); 1307 dnsv4_client (*pkt);
288 1308 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 { 1309 {
294 char qname[MAXSIZE]; 1310 dnsv4_server (*pkt);
295 int qlen = pkt->decode_label ((char *)qname, MAXSIZE, offs); 1311 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 } 1312 }
333 1313
334 sendto (w.fd, &((*pkt)[0]), offs, 0, (sockaddr *)&sa, sa_len); 1314 delete pkt;
1315 }
1316 }
1317}
1318
1319bool
1320vpn::send_dnsv4_packet (vpn_packet *pkt, const sockinfo &si, int tos)
1321{
1322 int client = ntohl (si.host);
1323
1324 assert (0 < client && client <= conns.size ());
1325
1326 connection *c = conns [client - 1];
1327
1328 if (!c->dns)
1329 c->dns = new dns_connection (c);
1330
1331 if (c->dns->snddq.put (pkt))
1332 c->dns->tw ();
1333
1334 // always return true even if the buffer overflows
1335 return true;
1336}
1337
1338#define NEXT(w) do { if (next > (w)) next = w; } while (0)
1339
1340void
1341dns_connection::time_cb (ev::timer &w, int revents)
1342{
1343 // servers have to be polled
1344 if (THISNODE->dns_port)
1345 return;
1346
1347 // check for timeouts and (re)transmit
1348 tstamp next = ev::now () + poll_interval;
1349 dns_snd *send = 0;
1350
1351 for (vector<dns_snd *>::iterator i = vpn->dns_sndpq.begin ();
1352 i != vpn->dns_sndpq.end ();
1353 ++i)
1354 {
1355 dns_snd *r = *i;
1356
1357 if (r->timeout <= ev_now ())
1358 {
1359 if (!send)
1360 {
1361 send = r;
1362
1363 r->retry++;
1364 r->timeout = ev_now () + (r->retry * min_latency * conf.dns_timeout_factor);
1365 //printf ("RETRY %x (%d, %f)\n", r->seqno, r->retry, r->timeout - ev_now ());//D
1366
1367 // the following code changes the query section a bit, forcing
1368 // the forwarder to generate a new request
1369 if (r->stdhdr)
1370 encode_header ((char *)r->pkt->at (6 * 2 + 1), THISNODE->id, r->seqno, r->retry);
1371 }
335 } 1372 }
336 else 1373 else
1374 NEXT (r->timeout);
1375 }
1376
1377 if (!send)
1378 {
1379 // generate a new packet, if wise
1380
1381 if (!established)
337 { 1382 {
338 // client 1383 if (vpn->dns_sndpq.empty ())
1384 {
1385 send = new dns_snd (this);
1386
1387 cfg.reset (THISNODE->id);
1388 set_cfg ();
1389 send->gen_syn_req ();
1390 }
339 } 1391 }
340 } 1392 else if (vpn->dns_sndpq.size () < conf.dns_max_outstanding
341} 1393 && !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 { 1394 {
381 slog (L_NOISE, _("dnsv4, send req %d\n"), r->pkt->id); 1395 if (last_sent + send_interval <= ev_now ())
382 r->retry++; 1396 {
383 r->next = NOW + r->retry; 1397 //printf ("sending data request etc.\n"); //D
1398 if (!snddq.empty () || last_received + 1. > ev_now ())
1399 {
1400 poll_interval = send_interval;
1401 NEXT (ev_now () + send_interval);
1402 }
1403
1404 send = new dns_snd (this);
1405 send->gen_stream_req (sndseq, snddq);
1406 send->timeout = ev_now () + min_latency * conf.dns_timeout_factor;
1407 //printf ("SEND %x (%f)\n", send->seqno, send->timeout - ev_now (), min_latency, conf.dns_timeout_factor);//D
1408
1409 sndseq = (sndseq + 1) & SEQNO_MASK;
1410 }
1411 else
1412 NEXT (last_sent + send_interval);
384 } 1413 }
385 1414
386 if (r->next < next) 1415 if (send)
387 next = r->next; 1416 vpn->dns_sndpq.push_back (send);
1417 }
1418
1419 if (send)
388 } 1420 {
1421 last_sent = ev_now ();
1422 sendto (vpn->dnsv4_fd,
1423 send->pkt->at (0), send->pkt->len, 0,
1424 vpn->dns_forwarder.sav4 (), vpn->dns_forwarder.salenv4 ());
1425 }
389 1426
390 printf ("%f next\n", next); 1427 slog (L_NOISE, "DNS: pi %f si %f N %f (%d:%d %d)",
391 w.start (next); 1428 poll_interval, send_interval, next - ev_now (),
1429 vpn->dns_sndpq.size (), snddq.size (),
1430 rcvpq.size ());
1431
1432 // TODO: no idea when this happens, but when next < ev_now (), we have a problem
1433 // doesn't seem to happen anymore
1434 if (next < ev_now () + 0.001)
1435 next = ev_now () + 0.1;
1436
1437 w.start (next - ev_now ());
392} 1438}
393 1439
394#endif 1440#endif
395 1441

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