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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 1.47 by pcg, Thu Aug 7 17:54:27 2008 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) 2003-2008 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 MAX_POLL_INTERVAL 5. // how often to poll minimally when the server has no data
45	#define MAX_RETRY 60.	65	#define ACTIVITY_INTERVAL 5.
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
51	protocol, 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
53	client -> server <req> ANY?	75	#define MAX_DOMAIN_SIZE 240 // 255 is legal limit, but bind doesn't compress well
54	server -> 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
59	if <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
69	#define RR_TYPE_ANY 255	88	#define RR_TYPE_ANY 255
		89
70	#define RR_CLASS_IN 1	90	#define RR_CLASS_IN 1
71		91
72	// the "_" is not valid but widely accepted (all octets should be supported, but let's be conservative)	92	#define CMD_IP_1 207
73	struct dns64	93	#define CMD_IP_2 46
74	{	94	#define CMD_IP_3 236
75	static const char encode_chars[64 + 1];	95	#define CMD_IP_RST 29
76	static s8 decode_chars[256];	96	#define CMD_IP_SYN 113
		97	#define CMD_IP_REJ 32
77		98
78	static int encode_len (int bytes) { return (bytes * 8 + 5) / 6; }	99	// works for cmaps up to 255 (not 256!)
79	static int decode_len (int bytes) { return (bytes * 6) / 8; }	100	struct charmap
		101	{
		102	enum { INVALID = (u8)255 };
		103
		104	char encode [256]; // index => char
		105	u8 decode [256]; // char => index
		106	unsigned int size;
		107
		108	charmap (const char *cmap);
		109	};
		110
		111	charmap::charmap (const char *cmap)
		112	{
		113	char *enc = encode;
		114	u8 *dec = decode;
		115
		116	memset (enc, (char) 0, 256);
		117	memset (dec, (char)INVALID, 256);
		118
		119	for (size = 0; cmap [size]; size++)
		120	{
		121	enc [size] = cmap [size];
		122	dec [(u8)enc [size]] = size;
		123	}
		124
		125	assert (size < 256);
		126	}
		127
		128	#define MAX_DEC_LEN 500
		129	#define MAX_ENC_LEN (MAX_DEC_LEN * 2)
		130	#define MAX_LIMBS ((MAX_DEC_LEN * 8 + GMP_NUMB_BITS - 1) / GMP_NUMB_BITS)
		131
		132	// ugly. minimum base is 16(!)
		133	struct basecoder
		134	{
		135	charmap cmap;
		136	unsigned int enc_len [MAX_DEC_LEN];
		137	unsigned int dec_len [MAX_ENC_LEN];
		138
		139	unsigned int encode_len (unsigned int len);
		140	unsigned int decode_len (unsigned int len);
		141
80	static void encode (char *dst, u8 *src, int len);	142	unsigned int encode (char *dst, u8 *src, unsigned int len);
81	static void decode (u8 *dst, char *src, int len);	143	unsigned int decode (u8 *dst, char *src, unsigned int len);
82		144
83	dns64 ();	145	basecoder (const char *cmap);
84	} dns64;	146	};
85		147
86	const char dns64::encode_chars[64 + 1] = "0123456789-abcdefghijklmnopqrstuvwxyz_ABCDEFGHIJKLMNOPQRSTUVWXYZ";	148	basecoder::basecoder (const char *cmap)
87	s8 dns64::decode_chars[256];	149	: cmap (cmap)
88
89	dns64::dns64 ()
90	{	150	{
91	for (int i = 0; i < 64; i++)	151	for (unsigned int len = 0; len < MAX_DEC_LEN; ++len)
92	decode_chars [encode_chars [i]] = i + 1;	152	{
93	}	153	u8 src [MAX_DEC_LEN];
		154	u8 dst [MAX_ENC_LEN];
94		155
95	void dns64::encode (char *dst, u8 *src, int len)	156	memset (src, 255, len);
		157
		158	mp_limb_t m [MAX_LIMBS];
		159	mp_size_t n;
		160
		161	n = mpn_set_str (m, src, len, 256);
		162	n = mpn_get_str (dst, this->cmap.size, m, n);
		163
		164	for (int i = 0; !dst [i]; ++i)
		165	n--;
		166
		167	enc_len [len] = n;
		168	dec_len [n] = len;
		169	}
		170	}
		171
		172	unsigned int basecoder::encode_len (unsigned int len)
96	{	173	{
97	// slow, but easy to debug	174	return enc_len [len];
98	unsigned int accum, bits = 0;	175	}
		176
		177	unsigned int basecoder::decode_len (unsigned int len)
		178	{
		179	while (len && !dec_len [len])
		180	--len;
		181
		182	return dec_len [len];
		183	}
		184
		185	unsigned int basecoder::encode (char *dst, u8 *src, unsigned int len)
		186	{
		187	if (!len || len > MAX_DEC_LEN)
		188	return 0;
		189
		190	int elen = encode_len (len);
		191
		192	mp_limb_t m [MAX_LIMBS];
		193	mp_size_t n;
		194
		195	u8 dst_ [MAX_ENC_LEN];
		196
		197	n = mpn_set_str (m, src, len, 256);
		198	n = mpn_get_str (dst_, cmap.size, m, n);
		199
		200	int plen = elen; // for padding
		201
		202	while (n < plen)
		203	{
		204	*dst++ = cmap.encode [0];
		205	plen--;
		206	}
		207
		208	for (unsigned int i = n - plen; i < n; ++i)
		209	*dst++ = cmap.encode [dst_ [i]];
		210
		211	return elen;
		212	}
		213
		214	unsigned int basecoder::decode (u8 *dst, char *src, unsigned int len)
		215	{
		216	if (!len || len > MAX_ENC_LEN)
		217	return 0;
		218
		219	u8 src_ [MAX_ENC_LEN];
		220	unsigned int elen = 0;
99		221
100	while (len--)	222	while (len--)
101	{	223	{
102	accum <<= 8;	224	u8 val = cmap.decode [(u8)*src++];
103	accum |= *src++;
104	bits += 8;
105		225
106	while (bits >= 6)	226	if (val != charmap::INVALID)
107	{	227	src_ [elen++] = val;
108	*dst++ = encode_chars [(accum >> (bits - 6)) & 63];	228	}
109	bits -= 6;	229
110	}	230	int dlen = decode_len (elen);
		231
		232	mp_limb_t m [MAX_LIMBS];
		233	mp_size_t n;
		234
		235	u8 dst_ [MAX_DEC_LEN];
		236
		237	n = mpn_set_str (m, src_, elen, cmap.size);
		238	n = mpn_get_str (dst_, 256, m, n);
		239
		240	if (n < dlen)
111	}	241	{
		242	memset (dst, 0, dlen - n);
		243	memcpy (dst + dlen - n, dst_, n);
		244	}
		245	else
		246	memcpy (dst, dst_ + n - dlen, dlen);
112		247
113	if (bits)	248	return dlen;
114	*dst++ = encode_chars [(accum << (6 - bits)) & 63];
115	}	249	}
116		250
117	void dns64::decode (u8 *dst, char *src, int len)	251	#if 0
118	{	252	struct test { test (); } test;
119	// slow, but easy to debug
120	unsigned int accum, bits = 0;
121		253
122	while (len--)	254	test::test ()
		255	{
		256	basecoder cdc ("0123456789abcdefghijklmnopqrstuvwxyz");
		257
		258	u8 in[] = "0123456789abcdefghijklmnopqrstuvwxyz";
		259	static char enc[200];
		260	static u8 dec[200];
		261
		262	for (int i = 1; i < 20; i++)
123	{	263	{
124	s8 chr = decode_chars [(u8)*src++];	264	int elen = cdc.encode (enc, in, i);
		265	int dlen = cdc.decode (dec, enc, elen);
125		266
		267	printf ("%d>%d>%d (%s>%s)\n", i, elen, dlen, enc, dec);
		268	}
		269	abort ();
		270	}
		271	#endif
126		272
127	if (!chr)	273	//static basecoder cdc64 ("_dDpPhHzZrR06QqMmjJkKBb34TtSsvVlL81xXaAeEFf92WwGgYyoO57UucCNniI-");
		274	//static basecoder cdc63 ("_dDpPhHzZrR06QqMmjJkKBb34TtSsvVlL81xXaAeEFf92WwGgYyoO57UucCNniI");
		275	static basecoder cdc62 ("dDpPhHzZrR06QqMmjJkKBb34TtSsvVlL81xXaAeEFf92WwGgYyoO57UucCNniI");
		276	//static basecoder cdc36 ("dphzr06qmjkb34tsvl81xaef92wgyo57ucni"); // unused as of yet
		277	static basecoder cdc26 ("dPhZrQmJkBtSvLxAeFwGyO");
		278
		279	/////////////////////////////////////////////////////////////////////////////
		280
		281	#define HDRSIZE 6
		282
		283	inline void encode_header (char *data, int clientid, int seqno, int retry = 0)
		284	{
		285	seqno &= SEQNO_MASK;
		286
		287	u8 hdr[3] = {
		288	clientid,
		289	(seqno >> 8) | (retry << 6),
		290	seqno,
		291	};
		292
		293	assert (clientid < 256);
		294
		295	cdc26.encode (data, hdr, 3);
		296	}
		297
		298	inline void decode_header (char *data, int &clientid, int &seqno)
		299	{
		300	u8 hdr[3];
		301
		302	cdc26.decode (hdr, data, HDRSIZE);
		303
		304	clientid = hdr[0];
		305	seqno = ((hdr[1] << 8) | hdr[2]) & SEQNO_MASK;
		306	}
		307
		308	/////////////////////////////////////////////////////////////////////////////
		309
		310	struct byte_stream
		311	{
		312	u8 *data;
		313	int maxsize;
		314	int fill;
		315
		316	byte_stream (int maxsize);
		317	~byte_stream ();
		318
		319	bool empty () { return !fill; }
		320	int size () { return fill; }
		321
		322	bool put (u8 *data, unsigned int datalen);
		323	bool put (vpn_packet *pkt);
		324	vpn_packet *get ();
		325
		326	u8 *begin () { return data; }
		327	void remove (int count);
		328	};
		329
		330	byte_stream::byte_stream (int maxsize)
		331	: maxsize (maxsize), fill (0)
		332	{
		333	data = new u8 [maxsize];
		334	}
		335
		336	byte_stream::~byte_stream ()
		337	{
		338	delete data;
		339	}
		340
		341	void byte_stream::remove (int count)
		342	{
		343	if (count > fill)
		344	assert (count <= fill);
		345
		346	memmove (data, data + count, fill -= count);
		347	}
		348
		349	bool byte_stream::put (u8 *data, unsigned int datalen)
		350	{
		351	if (maxsize - fill < datalen)
		352	return false;
		353
		354	memcpy (this->data + fill, data, datalen); fill += datalen;
		355
		356	return true;
		357	}
		358
		359	bool byte_stream::put (vpn_packet *pkt)
		360	{
		361	if (maxsize - fill < pkt->len + 2)
		362	return false;
		363
		364	data [fill++] = pkt->len >> 8;
		365	data [fill++] = pkt->len;
		366
		367	memcpy (data + fill, pkt->at (0), pkt->len); fill += pkt->len;
		368
		369	return true;
		370	}
		371
		372	vpn_packet *byte_stream::get ()
		373	{
		374	unsigned int len;
		375
		376	for (;;)
		377	{
		378	len = (data [0] << 8) | data [1];
		379
		380	if (len <= MAXSIZE || fill < 2)
128	break;	381	break;
129		382
130	accum <<= 6;	383	// TODO: handle this better than skipping, e.g. by reset
131	accum |= chr - 1;	384	slog (L_DEBUG, _("DNS: corrupted packet stream skipping a byte..."));
132	bits += 6;	385	remove (1);
133		386	}
134	while (bits >= 8)
135	{	387
136	*dst++ = accum >> (bits - 8);	388	if (fill < len + 2)
137	bits -= 8;	389	return 0;
138	}	390
139	}	391	vpn_packet *pkt = new vpn_packet;
		392
		393	pkt->len = len;
		394	memcpy (pkt->at (0), data + 2, len);
		395	remove (len + 2);
		396
		397	return pkt;
140	}	398	}
141		399
142	/////////////////////////////////////////////////////////////////////////////	400	/////////////////////////////////////////////////////////////////////////////
143		401
144	#define FLAG_QUERY ( 0 << 15)	402	#define FLAG_QUERY ( 0 << 15)
145	#define FLAG_RESPONSE ( 1 << 15)	403	#define FLAG_RESPONSE ( 1 << 15)
146	#define FLAG_OP_MASK (15 << 14)	404	#define FLAG_OP_MASK (15 << 11)
147	#define FLAG_OP_QUERY ( 0 << 11)	405	#define FLAG_OP_QUERY ( 0 << 11)
148	#define FLAG_AA ( 1 << 10)	406	#define FLAG_AA ( 1 << 10)
149	#define FLAG_TC ( 1 << 9)	407	#define FLAG_TC ( 1 << 9)
150	#define FLAG_RD ( 1 << 8)	408	#define FLAG_RD ( 1 << 8)
151	#define FLAG_RA ( 1 << 7)	409	#define FLAG_RA ( 1 << 7)
		410	#define FLAG_AUTH ( 1 << 5)
152	#define FLAG_RCODE_MASK (15 << 0)	411	#define FLAG_RCODE_MASK (15 << 0)
153	#define FLAG_RCODE_OK ( 0 << 0)	412	#define FLAG_RCODE_OK ( 0 << 0)
154	#define FLAG_RCODE_FORMERR ( 1 << 0)	413	#define FLAG_RCODE_FORMERR ( 1 << 0)
155	#define FLAG_RCODE_SERVFAIL ( 2 << 0)	414	#define FLAG_RCODE_SERVFAIL ( 2 << 0)
156	#define FLAG_RCODE_NXDOMAIN ( 3 << 0)	415	#define FLAG_RCODE_NXDOMAIN ( 3 << 0)
157	#define FLAG_RCODE_REFUSED ( 5 << 0)	416	#define FLAG_RCODE_REFUSED ( 5 << 0)
158		417
159	#define DEFAULT_CLIENT_FLAGS (FLAG_QUERY | FLAG_OP_QUERY | FLAG_RD)	418	#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)	419	#define DEFAULT_SERVER_FLAGS (FLAG_RESPONSE | FLAG_OP_QUERY | FLAG_AA | FLAG_RD | FLAG_RA)
		420
		421	struct dns_cfg
		422	{
		423	static int next_uid;
		424
		425	u8 id1, id2, id3, id4;
		426
		427	u8 version;
		428	u8 flags;
		429	u8 rrtype;
		430	u8 def_ttl;
		431
		432	u16 client;
		433	u16 uid; // to make request unique
		434
		435	u16 max_size;
		436	u8 seq_cdc;
		437	u8 req_cdc;
		438
		439	u8 rep_cdc;
		440	u8 delay; // time in 0.01s units that the server may delay replying packets
		441	u8 r3, r4;
		442
		443	u8 r5, r6, r7, r8;
		444
		445	void reset (int clientid);
		446	bool valid ();
		447	};
		448
		449	int dns_cfg::next_uid;
		450
		451	void dns_cfg::reset (int clientid)
		452	{
		453	id1 = 'G';
		454	id2 = 'V';
		455	id3 = 'P';
		456	id4 = 'E';
		457
		458	version = 1;
		459
		460	rrtype = RR_TYPE_TXT;
		461	flags = 0;
		462	def_ttl = 0;
		463	seq_cdc = 26;
		464	req_cdc = 62;
		465	rep_cdc = 0;
		466	max_size = htons (MAX_PKT_SIZE);
		467	client = htons (clientid);
		468	uid = next_uid++;
		469	delay = 0;
		470
		471	r3 = r4 = 0;
		472	r4 = r5 = r6 = r7 = 0;
		473	}
		474
		475	bool dns_cfg::valid ()
		476	{
		477	// although the protocol itself allows for some configurability,
		478	// only the following encoding/decoding settings are implemented.
		479	return id1 == 'G'
		480	&& id2 == 'V'
		481	&& id3 == 'P'
		482	&& id4 == 'E'
		483	&& seq_cdc == 26
		484	&& req_cdc == 62
		485	&& rep_cdc == 0
		486	&& version == 1;
		487	}
161		488
162	struct dns_packet : net_packet	489	struct dns_packet : net_packet
163	{	490	{
164	u16 id;	491	u16 id;
165	u16 flags; // QR:1 Opcode:4 AA:1 TC:1 RD:1 RA:1 Z:3 RCODE:4	492	u16 flags; // QR:1 Opcode:4 AA:1 TC:1 RD:1 RA:1 Z:3 RCODE:4
166	u16 qdcount, ancount, nscount, arcount;	493	u16 qdcount, ancount, nscount, arcount;
167		494
168	u8 data[MAXSIZE - 6 * 2];	495	u8 data [MAXSIZE - 6 * 2];
169		496
170	int decode_label (char *data, int size, int &offs);	497	int decode_label (char *data, int size, int &offs);
171	};	498	};
172		499
173	int dns_packet::decode_label (char *data, int size, int &offs)	500	int dns_packet::decode_label (char *data, int size, int &offs)
…		…
204	return data - orig;	531	return data - orig;
205	}	532	}
206		533
207	/////////////////////////////////////////////////////////////////////////////	534	/////////////////////////////////////////////////////////////////////////////
208		535
		536	static u16 dns_id = 0; // TODO: should be per-vpn
		537
		538	static u16 next_id ()
		539	{
		540	if (!dns_id)
		541	dns_id = time (0);
		542
		543	// the simplest lsfr with periodicity 65535 i could find
		544	dns_id = (dns_id << 1)
		545	| (((dns_id >> 1)
		546	^ (dns_id >> 2)
		547	^ (dns_id >> 4)
		548	^ (dns_id >> 15)) & 1);
		549
		550	return dns_id;
		551	}
		552
209	struct dns_req	553	struct dns_rcv;
		554	struct dns_snd;
		555
		556	struct dns_connection
		557	{
		558	connection *c;
		559	struct vpn *vpn;
		560
		561	dns_cfg cfg;
		562
		563	bool established;
		564
		565	tstamp last_received;
		566	tstamp last_sent;
		567	double min_latency;
		568	double poll_interval, send_interval;
		569
		570	vector<dns_rcv *> rcvpq;
		571
		572	byte_stream rcvdq; int rcvseq; int repseq;
		573	byte_stream snddq; int sndseq;
		574
		575	inline void time_cb (ev::timer &w, int revents); ev::timer tw;
		576	void receive_rep (dns_rcv *r);
		577
		578	dns_connection (connection *c);
		579	~dns_connection ();
		580	};
		581
		582	struct dns_snd
210	{	583	{
211	dns_packet *pkt;	584	dns_packet *pkt;
212	tstamp next;	585	tstamp timeout, sent;
213	int retry;	586	int retry;
		587	struct dns_connection *dns;
		588	int seqno;
		589	bool stdhdr;
214		590
215	dns_req (connection *c, vpn_packet *p, int &offs);	591	void gen_stream_req (int seqno, byte_stream &stream);
		592	void gen_syn_req ();
		593
		594	dns_snd (dns_connection *dns);
		595	~dns_snd ();
216	};	596	};
217		597
		598	dns_snd::dns_snd (dns_connection *dns)
		599	: dns (dns)
		600	{
		601	timeout = 0;
		602	retry = 0;
		603	seqno = 0;
		604	sent = ev_now ();
		605	stdhdr = false;
		606
		607	pkt = new dns_packet;
		608
		609	pkt->id = next_id ();
		610	}
		611
		612	dns_snd::~dns_snd ()
		613	{
		614	delete pkt;
		615	}
		616
		617	static void append_domain (dns_packet &pkt, int &offs, const char *domain)
		618	{
		619	// add tunnel domain
		620	for (;;)
		621	{
		622	const char *end = strchr (domain, '.');
		623
		624	if (!end)
		625	end = domain + strlen (domain);
		626
		627	int len = end - domain;
		628
		629	pkt [offs++] = len;
		630	memcpy (pkt.at (offs), domain, len);
		631	offs += len;
		632
		633	if (!*end)
		634	break;
		635
		636	domain = end + 1;
		637	}
		638	}
		639
		640	void dns_snd::gen_stream_req (int seqno, byte_stream &stream)
		641	{
		642	stdhdr = true;
		643	this->seqno = seqno;
		644
		645	timeout = ev_now () + INITIAL_TIMEOUT;
		646
		647	pkt->flags = htons (DEFAULT_CLIENT_FLAGS);
		648	pkt->qdcount = htons (1);
		649
		650	int offs = 6*2;
		651	int dlen = MAX_DOMAIN_SIZE - (strlen (dns->c->conf->domain) + 2);
		652	// MAX_DOMAIN_SIZE is technically 255, but bind doesn't compress responses well,
		653	// so we need to have space for 2*MAX_DOMAIN_SIZE + header + extra
		654
		655	char enc[256], *encp = enc;
		656	encode_header (enc, THISNODE->id, seqno);
		657
		658	int datalen = cdc62.decode_len (dlen - (dlen + MAX_LBL_SIZE - 1) / MAX_LBL_SIZE - HDRSIZE);
		659
		660	if (datalen > stream.size ())
		661	datalen = stream.size ();
		662
		663	int enclen = cdc62.encode (enc + HDRSIZE, stream.begin (), datalen) + HDRSIZE;
		664	stream.remove (datalen);
		665
		666	while (enclen)
		667	{
		668	int lbllen = enclen < MAX_LBL_SIZE ? enclen : MAX_LBL_SIZE;
		669
		670	(*pkt)[offs++] = lbllen;
		671	memcpy (pkt->at (offs), encp, lbllen);
		672
		673	offs += lbllen;
		674	encp += lbllen;
		675
		676	enclen -= lbllen;
		677	}
		678
		679	append_domain (*pkt, offs, dns->c->conf->domain);
		680
		681	(*pkt)[offs++] = 0;
		682	(*pkt)[offs++] = RR_TYPE_ANY >> 8; (*pkt)[offs++] = RR_TYPE_ANY;
		683	(*pkt)[offs++] = RR_CLASS_IN >> 8; (*pkt)[offs++] = RR_CLASS_IN;
		684
		685	pkt->len = offs;
		686	}
		687
		688	void dns_snd::gen_syn_req ()
		689	{
		690	timeout = ev_now () + INITIAL_SYN_TIMEOUT;
		691
		692	pkt->flags = htons (DEFAULT_CLIENT_FLAGS);
		693	pkt->qdcount = htons (1);
		694
		695	int offs = 6 * 2;
		696
		697	int elen = cdc26.encode ((char *)pkt->at (offs + 1), (u8 *)&dns->cfg, sizeof (dns_cfg));
		698
		699	assert (elen <= MAX_LBL_SIZE);
		700
		701	(*pkt)[offs] = elen;
		702	offs += elen + 1;
		703	append_domain (*pkt, offs, dns->c->conf->domain);
		704
		705	(*pkt)[offs++] = 0;
		706	(*pkt)[offs++] = RR_TYPE_A >> 8; (*pkt)[offs++] = RR_TYPE_A;
		707	(*pkt)[offs++] = RR_CLASS_IN >> 8; (*pkt)[offs++] = RR_CLASS_IN;
		708
		709	pkt->len = offs;
		710	}
		711
218	struct dns_rep	712	struct dns_rcv
219	{	713	{
		714	int seqno;
		715	dns_packet *pkt; // reply packet
		716	u8 data [MAXSIZE]; // actually part of the reply packet...
		717	int datalen;
		718
		719	dns_rcv (int seqno, u8 *data, int datalen);
		720	~dns_rcv ();
220	};	721	};
221		722
222	static u16 dns_id; // TODO: should be per-vpn	723	dns_rcv::dns_rcv (int seqno, u8 *data, int datalen)
223		724	: seqno (seqno), pkt (new dns_packet), datalen (datalen)
224	dns_req::dns_req (connection *c, vpn_packet *p, int &offs)
225	{	725	{
226	next = 0;	726	memcpy (this->data, data, datalen);
227	retry = 0;	727	}
228		728
229	pkt = new dns_packet;	729	dns_rcv::~dns_rcv ()
230		730	{
231	pkt->id = dns_id++;	731	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	}	732	}
242		733
243	/////////////////////////////////////////////////////////////////////////////	734	/////////////////////////////////////////////////////////////////////////////
244		735
245	struct dns_cfg	736	dns_connection::dns_connection (connection *c)
		737	: c (c)
		738	, rcvdq (MAX_BACKLOG * 2)
		739	, snddq (MAX_BACKLOG)
246	{	740	{
247	u8 id1, id2, id3;	741	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		742
254	// reply to client-poll	743	vpn = c->vpn;
255	void dnsv4_poll (dns_packet *pkt, int &offs)
256	{
257	int dlen = MAX_PKT_SIZE - offs - 2;
258		744
259	(*pkt) [offs++] = 0;	745	established = false;
260	(*pkt) [offs++] = 5;
261	memcpy (&((*pkt)[offs]), "\01H\02\xff\x00", 5);
262	offs += 5;
263		746
264	pkt->ancount = htons (1);	747	rcvseq = repseq = sndseq = 0;
265	pkt->flags = htons (DEFAULT_SERVER_FLAGS | FLAG_RCODE_OK);
266		748
267	printf ("we have room for %d bytes\n", dlen);	749	last_sent = last_received = 0;
		750	poll_interval = 0.5; // starting here
		751	send_interval = 0.5; // starting rate
		752	min_latency = INITIAL_TIMEOUT;
		753	}
		754
		755	dns_connection::~dns_connection ()
		756	{
		757	for (vector<dns_rcv *>::iterator i = rcvpq.begin ();
		758	i != rcvpq.end ();
		759	++i)
		760	delete *i;
		761	}
		762
		763	void dns_connection::receive_rep (dns_rcv *r)
		764	{
		765	if (r->datalen)
		766	{
		767	last_received = ev_now ();
		768	tw ();
		769
		770	poll_interval = send_interval;
		771	}
		772	else
		773	{
		774	poll_interval *= 1.5;
		775
		776	if (poll_interval > MAX_POLL_INTERVAL)
		777	poll_interval = MAX_POLL_INTERVAL;
		778	}
		779
		780	rcvpq.push_back (r);
		781
		782	redo:
		783
		784	// find next packet
		785	for (vector<dns_rcv *>::iterator i = rcvpq.end (); i-- != rcvpq.begin (); )
		786	if (SEQNO_EQ (rcvseq, (*i)->seqno))
		787	{
		788	//printf ("seqno eq %x %x\n", rcvseq, (*i)->seqno);//D
		789	// enter the packet into our input stream
		790	r = *i;
		791
		792	// remove the oldest packet, look forward, as it's oldest first
		793	for (vector<dns_rcv *>::iterator j = rcvpq.begin (); j != rcvpq.end (); ++j)
		794	if (SEQNO_EQ ((*j)->seqno, rcvseq - MAX_WINDOW))
		795	{
		796	//printf ("seqno RR %x %x\n", (*j)->seqno, rcvseq - MAX_WINDOW);//D
		797	delete *j;
		798	rcvpq.erase (j);
		799	break;
		800	}
		801
		802	rcvseq = (rcvseq + 1) & SEQNO_MASK;
		803
		804	if (!rcvdq.put (r->data, r->datalen))
		805	{
		806	slog (L_ERR, "DNS: !rcvdq.put (r->data, r->datalen)");
		807	abort (); // MUST never overflow, can be caused by data corruption, TODO
		808	}
		809
		810	while (vpn_packet *pkt = rcvdq.get ())
		811	{
		812	sockinfo si;
		813	si.host = htonl (c->conf->id); si.port = 0; si.prot = PROT_DNSv4;
		814
		815	vpn->recv_vpn_packet (pkt, si);
		816
		817	delete pkt;
		818	}
		819
		820	// check for further packets
		821	goto redo;
		822	}
268	}	823	}
269		824
270	void	825	void
		826	vpn::dnsv4_server (dns_packet &pkt)
		827	{
		828	u16 flags = ntohs (pkt.flags);
		829
		830	int offs = 6 * 2; // skip header
		831
		832	pkt.flags = htons (DEFAULT_SERVER_FLAGS | FLAG_RCODE_FORMERR);
		833
		834	if (0 == (flags & (FLAG_RESPONSE | FLAG_OP_MASK))
		835	&& pkt.qdcount == htons (1))
		836	{
		837	char qname [MAXSIZE];
		838	int qlen = pkt.decode_label ((char *)qname, MAXSIZE - offs, offs);
		839
		840	u16 qtype = pkt [offs++] << 8; qtype |= pkt [offs++];
		841	u16 qclass = pkt [offs++] << 8; qclass |= pkt [offs++];
		842
		843	pkt.qdcount = htons (1);
		844	pkt.ancount = 0;
		845	pkt.nscount = 0; // should be self, as other nameservers reply like this
		846	pkt.arcount = 0; // a record for self, as other nameservers reply like this
		847
		848	pkt.flags = htons (DEFAULT_SERVER_FLAGS | FLAG_RCODE_SERVFAIL);
		849
		850	int dlen = strlen (THISNODE->domain);
		851
		852	if (qclass == RR_CLASS_IN
		853	&& qlen > dlen + 1
		854	&& !memcmp (qname + qlen - (dlen + 1), THISNODE->domain, dlen))
		855	{
		856	// now generate reply
		857	pkt.ancount = htons (1); // one answer RR
		858	pkt.flags = htons (DEFAULT_SERVER_FLAGS | FLAG_RCODE_OK);
		859
		860	if ((qtype == RR_TYPE_ANY
		861	|| qtype == RR_TYPE_TXT
		862	|| qtype == RR_TYPE_NULL)
		863	&& qlen > dlen + 1 + HDRSIZE)
		864	{
		865	// correct class, domain: parse
		866	int client, seqno;
		867	decode_header (qname, client, seqno);
		868
		869	u8 data[MAXSIZE];
		870	int datalen = cdc62.decode (data, qname + HDRSIZE, qlen - (dlen + 1 + HDRSIZE));
		871
		872	if (0 < client && client <= conns.size ())
		873	{
		874	connection *c = conns [client - 1];
		875	dns_connection *dns = c->dns;
		876	dns_rcv *rcv;
		877
		878	if (dns)
		879	{
		880	for (vector<dns_rcv *>::iterator i = dns->rcvpq.end (); i-- != dns->rcvpq.begin (); )
		881	if (SEQNO_EQ ((*i)->seqno, seqno))
		882	{
		883	// already seen that request: simply reply with the cached reply
		884	dns_rcv *r = *i;
		885
		886	slog (L_DEBUG, "DNS: duplicate packet received ID %d, SEQ %d", htons (r->pkt->id), seqno);
		887
		888	// refresh header & id, as the retry count could have changed
		889	memcpy (r->pkt->at (6 * 2 + 1), pkt.at (6 * 2 + 1), HDRSIZE);
		890	r->pkt->id = pkt.id;
		891
		892	memcpy (pkt.at (0), r->pkt->at (0), offs = r->pkt->len);
		893
		894	goto duplicate_request;
		895	}
		896
		897	// new packet, queue
		898	rcv = new dns_rcv (seqno, data, datalen);
		899	dns->receive_rep (rcv);
		900	}
		901
		902	{
		903	pkt [offs++] = 0xc0; pkt [offs++] = 6 * 2; // refer to name in query section
		904
		905	int rtype = dns ? dns->cfg.rrtype : RR_TYPE_A;
		906	pkt [offs++] = rtype >> 8; pkt [offs++] = rtype; // type
		907	pkt [offs++] = RR_CLASS_IN >> 8; pkt [offs++] = RR_CLASS_IN; // class
		908	pkt [offs++] = 0; pkt [offs++] = 0;
		909	pkt [offs++] = 0; pkt [offs++] = dns ? dns->cfg.def_ttl : 0; // TTL
		910
		911	int rdlen_offs = offs += 2;
		912
		913	if (dns)
		914	{
		915	int dlen = ntohs (dns->cfg.max_size) - offs;
		916
		917	// bind doesn't compress well, so reduce further by one label length
		918	dlen -= qlen;
		919
		920	// only put data into in-order sequence packets, if
		921	// we receive out-of-order packets we generate empty
		922	// replies
		923	//printf ("%d - %d & %x (=%d) < %d\n", seqno, dns->repseq, SEQNO_MASK, (seqno - dns->repseq) & SEQNO_MASK, MAX_WINDOW);//D
		924	if (((seqno - dns->repseq) & SEQNO_MASK) <= MAX_WINDOW)
		925	{
		926	dns->repseq = seqno;
		927
		928	while (dlen > 1 && !dns->snddq.empty ())
		929	{
		930	int txtlen = dlen <= 255 ? dlen - 1 : 255;
		931
		932	if (txtlen > dns->snddq.size ())
		933	txtlen = dns->snddq.size ();
		934
		935	pkt[offs++] = txtlen;
		936	memcpy (pkt.at (offs), dns->snddq.begin (), txtlen);
		937	offs += txtlen;
		938	dns->snddq.remove (txtlen);
		939
		940	dlen -= txtlen + 1;
		941	}
		942	}
		943
		944	// avoid completely empty TXT rdata
		945	if (offs == rdlen_offs)
		946	pkt[offs++] = 0;
		947
		948	slog (L_NOISE, "DNS: snddq %d", dns->snddq.size ());
		949	}
		950	else
		951	{
		952	// send RST
		953	pkt [offs++] = CMD_IP_1; pkt [offs++] = CMD_IP_2; pkt [offs++] = CMD_IP_3;
		954	pkt [offs++] = CMD_IP_RST;
		955	}
		956
		957	int rdlen = offs - rdlen_offs;
		958
		959	pkt [rdlen_offs - 2] = rdlen >> 8;
		960	pkt [rdlen_offs - 1] = rdlen;
		961
		962	if (dns)
		963	{
		964	// now update dns_rcv copy
		965	rcv->pkt->len = offs;
		966	memcpy (rcv->pkt->at (0), pkt.at (0), offs);
		967	}
		968	}
		969
		970	duplicate_request: ;
		971	}
		972	else
		973	pkt.flags = htons (DEFAULT_SERVER_FLAGS | FLAG_RCODE_FORMERR);
		974	}
		975	else if (qtype == RR_TYPE_A
		976	&& qlen > dlen + 1 + cdc26.encode_len (sizeof (dns_cfg)))
		977	{
		978	dns_cfg cfg;
		979	cdc26.decode ((u8 *)&cfg, qname, cdc26.encode_len (sizeof (dns_cfg)));
		980	int client = ntohs (cfg.client);
		981
		982	pkt [offs++] = 0xc0; pkt [offs++] = 6 * 2; // refer to name in query section
		983
		984	pkt [offs++] = RR_TYPE_A >> 8; pkt [offs++] = RR_TYPE_A; // type
		985	pkt [offs++] = RR_CLASS_IN >> 8; pkt [offs++] = RR_CLASS_IN; // class
		986	pkt [offs++] = 0; pkt [offs++] = 0;
		987	pkt [offs++] = 0; pkt [offs++] = cfg.def_ttl; // TTL
		988	pkt [offs++] = 0; pkt [offs++] = 4; // rdlength
		989
		990	slog (L_INFO, _("DNS: client %d connects"), client);
		991
		992	pkt [offs++] = CMD_IP_1; pkt [offs++] = CMD_IP_2; pkt [offs++] = CMD_IP_3;
		993	pkt [offs++] = CMD_IP_REJ;
		994
		995	if (0 < client && client <= conns.size ())
		996	{
		997	connection *c = conns [client - 1];
		998
		999	if (cfg.valid ())
		1000	{
		1001	pkt [offs - 1] = CMD_IP_SYN;
		1002
		1003	delete c->dns;
		1004	c->dns = new dns_connection (c);
		1005	c->dns->cfg = cfg;
		1006	}
		1007	}
		1008	}
		1009	}
		1010
		1011	pkt.len = offs;
		1012	}
		1013	}
		1014
		1015	void
		1016	vpn::dnsv4_client (dns_packet &pkt)
		1017	{
		1018	u16 flags = ntohs (pkt.flags);
		1019	int offs = 6 * 2; // skip header
		1020
		1021	pkt.qdcount = ntohs (pkt.qdcount);
		1022	pkt.ancount = ntohs (pkt.ancount);
		1023
		1024	// go through our request list and find the corresponding request
		1025	for (vector<dns_snd *>::iterator i = dns_sndpq.begin ();
		1026	i != dns_sndpq.end ();
		1027	++i)
		1028	if ((*i)->pkt->id == pkt.id)
		1029	{
		1030	dns_connection *dns = (*i)->dns;
		1031	connection *c = dns->c;
		1032	int seqno = (*i)->seqno;
		1033	u8 data[MAXSIZE], *datap = data;
		1034	//printf ("rcv pkt %x\n", seqno);//D
		1035
		1036	if ((*i)->retry)
		1037	{
		1038	dns->send_interval *= 1.01;
		1039	if (dns->send_interval > MAX_SEND_INTERVAL)
		1040	dns->send_interval = MAX_SEND_INTERVAL;
		1041	}
		1042	else
		1043	{
		1044	#if 0
		1045	dns->send_interval *= 0.999;
		1046	#endif
		1047	// the latency surely puts an upper bound on
		1048	// the minimum send interval
		1049	double latency = ev_now () - (*i)->sent;
		1050
		1051	if (latency < dns->min_latency)
		1052	dns->min_latency = latency;
		1053
		1054	if (dns->send_interval > dns->min_latency * conf.dns_overlap_factor)
		1055	dns->send_interval = dns->min_latency * conf.dns_overlap_factor;
		1056
		1057	if (dns->send_interval < conf.dns_send_interval)
		1058	dns->send_interval = conf.dns_send_interval;
		1059	}
		1060
		1061	delete *i;
		1062	dns_sndpq.erase (i);
		1063
		1064	if (flags & FLAG_RESPONSE && !(flags & FLAG_OP_MASK))
		1065	{
		1066	char qname[MAXSIZE];
		1067
		1068	while (pkt.qdcount-- && offs < MAXSIZE - 4)
		1069	{
		1070	int qlen = pkt.decode_label ((char *)qname, MAXSIZE - offs, offs);
		1071	offs += 4; // skip qtype, qclass
		1072	}
		1073
		1074	while (pkt.ancount-- && offs < MAXSIZE - 10 && datap)
		1075	{
		1076	int qlen = pkt.decode_label ((char *)qname, MAXSIZE - offs, offs);
		1077
		1078	u16 qtype = pkt [offs++] << 8; qtype |= pkt [offs++];
		1079	u16 qclass = pkt [offs++] << 8; qclass |= pkt [offs++];
		1080	u32 ttl = pkt [offs++] << 24;
		1081	ttl |= pkt [offs++] << 16;
		1082	ttl |= pkt [offs++] << 8;
		1083	ttl |= pkt [offs++];
		1084	u16 rdlen = pkt [offs++] << 8; rdlen |= pkt [offs++];
		1085
		1086	if (qtype == RR_TYPE_NULL || qtype == RR_TYPE_TXT)
		1087	{
		1088	if (rdlen <= MAXSIZE - offs)
		1089	{
		1090	// decode bytes, finally
		1091
		1092	while (rdlen)
		1093	{
		1094	int txtlen = pkt [offs++];
		1095
		1096	assert (txtlen + offs < MAXSIZE - 1);
		1097
		1098	memcpy (datap, pkt.at (offs), txtlen);
		1099	datap += txtlen; offs += txtlen;
		1100
		1101	rdlen -= txtlen + 1;
		1102	}
		1103	}
		1104	}
		1105	else if (qtype == RR_TYPE_A)
		1106	{
		1107	u8 ip [4];
		1108
		1109	ip [0] = pkt [offs++];
		1110	ip [1] = pkt [offs++];
		1111	ip [2] = pkt [offs++];
		1112	ip [3] = pkt [offs++];
		1113
		1114	if (ip [0] == CMD_IP_1
		1115	&& ip [1] == CMD_IP_2
		1116	&& ip [2] == CMD_IP_3)
		1117	{
		1118	slog (L_TRACE, _("DNS: got tunnel meta command %02x"), ip [3]);
		1119
		1120	if (ip [3] == CMD_IP_RST)
		1121	{
		1122	slog (L_DEBUG, _("DNS: got tunnel RST request"));
		1123
		1124	delete dns; c->dns = 0;
		1125
		1126	return;
		1127	}
		1128	else if (ip [3] == CMD_IP_SYN)
		1129	{
		1130	slog (L_DEBUG, _("DNS: got tunnel SYN reply, server likes us."));
		1131	dns->established = true;
		1132	}
		1133	else if (ip [3] == CMD_IP_REJ)
		1134	{
		1135	slog (L_DEBUG, _("DNS: got tunnel REJ reply, server does not like us, aborting."));
		1136	abort ();
		1137	}
		1138	else
		1139	slog (L_INFO, _("DNS: got unknown meta command %02x"), ip [3]);
		1140	}
		1141	else
		1142	slog (L_INFO, _("DNS: got spurious a record %d.%d.%d.%d"),
		1143	ip [0], ip [1], ip [2], ip [3]);
		1144
		1145	return;
		1146	}
		1147
		1148	int client, rseqno;
		1149	decode_header (qname, client, rseqno);
		1150
		1151	if (client != THISNODE->id)
		1152	{
		1153	slog (L_INFO, _("DNS: got dns tunnel response with wrong clientid, ignoring"));
		1154	datap = 0;
		1155	}
		1156	else if (rseqno != seqno)
		1157	{
		1158	slog (L_DEBUG, _("DNS: got dns tunnel response with wrong seqno, badly caching nameserver?"));
		1159	datap = 0;
		1160	}
		1161	}
		1162	}
		1163
		1164	// todo: pkt now used
		1165	if (datap)
		1166	dns->receive_rep (new dns_rcv (seqno, data, datap - data));
		1167
		1168	break;
		1169	}
		1170	}
		1171
		1172	void
271	vpn::dnsv4_ev (io_watcher &w, short revents)	1173	vpn::dnsv4_ev (ev::io &w, int revents)
272	{	1174	{
273	if (revents & EVENT_READ)	1175	if (revents & EV_READ)
274	{	1176	{
275	dns_packet *pkt = new dns_packet;	1177	dns_packet *pkt = new dns_packet;
276	struct sockaddr_in sa;	1178	struct sockaddr_in sa;
277	socklen_t sa_len = sizeof (sa);	1179	socklen_t sa_len = sizeof (sa);
278		1180
279	int len = recvfrom (w.fd, &((*pkt)[0]), MAXSIZE, 0, (sockaddr *)&sa, &sa_len);	1181	pkt->len = recvfrom (w.fd, pkt->at (0), MAXSIZE, 0, (sockaddr *)&sa, &sa_len);
280	pkt->len = len;
281		1182
282	u16 flags = ntohs (pkt->flags);	1183	if (pkt->len > 0)
283
284	if (THISNODE->dns_port)
285	{	1184	{
286	// server	1185	if (ntohs (pkt->flags) & FLAG_RESPONSE)
287	pkt->flags = htons (DEFAULT_SERVER_FLAGS | FLAG_RCODE_FORMERR);	1186	dnsv4_client (*pkt);
288		1187	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	{	1188	{
294	char qname[MAXSIZE];	1189	dnsv4_server (*pkt);
295	int qlen = pkt->decode_label ((char *)qname, MAXSIZE, offs);	1190	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	}	1191	}
333		1192
334	sendto (w.fd, &((*pkt)[0]), offs, 0, (sockaddr *)&sa, sa_len);	1193	delete pkt;
		1194	}
		1195	}
		1196	}
		1197
		1198	bool
		1199	vpn::send_dnsv4_packet (vpn_packet *pkt, const sockinfo &si, int tos)
		1200	{
		1201	int client = ntohl (si.host);
		1202
		1203	assert (0 < client && client <= conns.size ());
		1204
		1205	connection *c = conns [client - 1];
		1206
		1207	if (!c->dns)
		1208	c->dns = new dns_connection (c);
		1209
		1210	if (c->dns->snddq.put (pkt))
		1211	c->dns->tw ();
		1212
		1213	// always return true even if the buffer overflows
		1214	return true;
		1215	}
		1216
		1217	void
		1218	connection::dnsv4_reset_connection ()
		1219	{
		1220	//delete dns; dns = 0; //TODO
		1221	}
		1222
		1223	#define NEXT(w) do { if (next > (w)) next = w; } while (0)
		1224
		1225	void
		1226	dns_connection::time_cb (ev::timer &w, int revents)
		1227	{
		1228	// servers have to be polled
		1229	if (THISNODE->dns_port)
		1230	return;
		1231
		1232	// check for timeouts and (re)transmit
		1233	tstamp next = ev::now () + poll_interval;
		1234	dns_snd *send = 0;
		1235
		1236	for (vector<dns_snd *>::iterator i = vpn->dns_sndpq.begin ();
		1237	i != vpn->dns_sndpq.end ();
		1238	++i)
		1239	{
		1240	dns_snd *r = *i;
		1241
		1242	if (r->timeout <= ev_now ())
		1243	{
		1244	if (!send)
		1245	{
		1246	send = r;
		1247
		1248	r->retry++;
		1249	r->timeout = ev_now () + (r->retry * min_latency * conf.dns_timeout_factor);
		1250	//printf ("RETRY %x (%d, %f)\n", r->seqno, r->retry, r->timeout - ev_now ());//D
		1251
		1252	// the following code changes the query section a bit, forcing
		1253	// the forwarder to generate a new request
		1254	if (r->stdhdr)
		1255	encode_header ((char *)r->pkt->at (6 * 2 + 1), THISNODE->id, r->seqno, r->retry);
		1256	}
335	}	1257	}
336	else	1258	else
		1259	NEXT (r->timeout);
		1260	}
		1261
		1262	if (!send)
		1263	{
		1264	// generate a new packet, if wise
		1265
		1266	if (!established)
337	{	1267	{
338	// client	1268	if (vpn->dns_sndpq.empty ())
		1269	{
		1270	send = new dns_snd (this);
		1271
		1272	cfg.reset (THISNODE->id);
		1273	send->gen_syn_req ();
		1274	}
339	}	1275	}
340	}	1276	else if (vpn->dns_sndpq.size () < conf.dns_max_outstanding
341	}	1277	&& !SEQNO_EQ (rcvseq, sndseq - (MAX_WINDOW - 1)))
342
343	bool
344	connection::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
359	void
360	connection::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	{	1278	{
381	slog (L_NOISE, _("dnsv4, send req %d\n"), r->pkt->id);	1279	if (last_sent + send_interval <= ev_now ())
382	r->retry++;	1280	{
383	r->next = NOW + r->retry;	1281	//printf ("sending data request etc.\n"); //D
		1282	if (!snddq.empty () || last_received + 1. > ev_now ())
		1283	{
		1284	poll_interval = send_interval;
		1285	NEXT (ev_now () + send_interval);
		1286	}
		1287
		1288	send = new dns_snd (this);
		1289	send->gen_stream_req (sndseq, snddq);
		1290	send->timeout = ev_now () + min_latency * conf.dns_timeout_factor;
		1291	//printf ("SEND %x (%f)\n", send->seqno, send->timeout - ev_now (), min_latency, conf.dns_timeout_factor);//D
		1292
		1293	sndseq = (sndseq + 1) & SEQNO_MASK;
		1294	}
		1295	else
		1296	NEXT (last_sent + send_interval);
384	}	1297	}
385		1298
386	if (r->next < next)	1299	if (send)
387	next = r->next;	1300	vpn->dns_sndpq.push_back (send);
		1301	}
		1302
		1303	if (send)
388	}	1304	{
		1305	last_sent = ev_now ();
		1306	sendto (vpn->dnsv4_fd,
		1307	send->pkt->at (0), send->pkt->len, 0,
		1308	vpn->dns_forwarder.sav4 (), vpn->dns_forwarder.salenv4 ());
		1309	}
389		1310
390	printf ("%f next\n", next);	1311	slog (L_NOISE, "DNS: pi %f si %f N %f (%d:%d %d)",
391	w.start (next);	1312	poll_interval, send_interval, next - ev_now (),
		1313	vpn->dns_sndpq.size (), snddq.size (),
		1314	rcvpq.size ());
		1315
		1316	// TODO: no idea when this happens, but when next < ev_now (), we have a problem
		1317	// doesn't seem to happen anymore
		1318	if (next < ev_now () + 0.001)
		1319	next = ev_now () + 0.1;
		1320
		1321	w.start (next - ev_now ());
392	}	1322	}
393		1323
394	#endif	1324	#endif
395		1325

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