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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 1.31 by pcg, Tue Mar 15 11:43:38 2005 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) 2003-2005 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
6	it under the terms of the GNU General Public License as published by	8	it under the terms of the GNU General Public License as published by
7	the Free Software Foundation; either version 2 of the License, or	9	the Free Software Foundation; either version 2 of the License, or
8	(at your option) any later version.	10	(at your 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,
11	but WITHOUT ANY WARRANTY; without even the implied warranty of	13	but 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
13	GNU General Public License for more details.	15	GNU General 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
16	along with this program; if not, write to the Free Software	18	along with gvpe; if not, write to the Free Software
17	Foundation, Inc. 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA	19	Foundation, Inc. 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
18	*/	20	*/
19		21
20	#include "config.h"	22	#include "config.h"
21		23
…		…
23		25
24	// dns processing is EXTREMELY ugly. For obvious(?) reasons.	26	// dns processing is EXTREMELY ugly. For obvious(?) reasons.
25	// it's a hack, use only in emergency situations please.	27	// it's a hack, use only in emergency situations please.
26		28
27	#include <cstring>	29	#include <cstring>
		30	#include <cassert>
28		31
29	#include <sys/types.h>	32	#include <sys/types.h>
30	#include <sys/socket.h>	33	#include <sys/socket.h>
31	#include <sys/wait.h>	34	#include <sys/wait.h>
32	#include <sys/uio.h>	35	#include <sys/uio.h>
…		…
35	#include <unistd.h>	38	#include <unistd.h>
36	#include <fcntl.h>	39	#include <fcntl.h>
37		40
38	#include <map>	41	#include <map>
39		42
		43	#include <gmp.h>
		44
40	#include "netcompat.h"	45	#include "netcompat.h"
41		46
42	#include "vpn.h"	47	#include "vpn.h"
43		48
44	#define MIN_RETRY 1.	49	#define MAX_POLL_INTERVAL 5. // how often to poll minimally when the server has no data
45	#define MAX_RETRY 60.	50	#define ACTIVITY_INTERVAL 5.
46		51
		52	#define TIMEOUT_FACTOR 2.
		53
		54	#define INITIAL_TIMEOUT 0.1 // retry timeouts
		55	#define INITIAL_SYN_TIMEOUT 10. // retry timeout for initial syn
		56
		57	#define MIN_SEND_INTERVAL 0.001 // wait at least this time between sending requests
		58	#define MAX_SEND_INTERVAL 2. // optimistic?
		59
		60	#define LATENCY_FACTOR 0.5 // RTT * LATENCY_FACTOR == sending rate
47	#define MAX_OUTSTANDING 10 // max. outstanding requests	61	#define MAX_OUTSTANDING 100 // max. outstanding requests
		62	#define MAX_WINDOW 1000 // max. for MAX_OUTSTANDING, and backlog
		63	#define MAX_BACKLOG (32*1024) // size of gvpe protocol backlog (bytes), must be > MAXSIZE
48		64
49	/*	65	#define MAX_DOMAIN_SIZE 240 // 255 is legal limit, but bind doesn't compress well
		66	// 240 leaves about 4 bytes of server reply data
		67	// every two request bytes less give room for one reply byte
50		68
51	protocol, in shorthand :)	69	#define SEQNO_MASK 0x0fff
52		70	#define SEQNO_EQ(a,b) ( 0 == ( ((a) ^ (b)) & SEQNO_MASK) )
53	client -> server <req> ANY?
54	server -> client <req> TXT <rep>
55
56	<req> is dns64-encoded <client-id:12><recv-seqno:10>[<send-seqno:10><data>]
57	<rep> is dns64-encoded <0:12><recv-seqno:10>[<send-seqno:10><data>]
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		71
65	#define MAX_LBL_SIZE 63	72	#define MAX_LBL_SIZE 63
66	#define MAX_PKT_SIZE 512	73	#define MAX_PKT_SIZE 512
67		74
		75	#define RR_TYPE_A 1
		76	#define RR_TYPE_NULL 10
68	#define RR_TYPE_TXT 16	77	#define RR_TYPE_TXT 16
69	#define RR_TYPE_ANY 255	78	#define RR_TYPE_ANY 255
		79
70	#define RR_CLASS_IN 1	80	#define RR_CLASS_IN 1
71		81
72	// the "_" is not valid but widely accepted (all octets should be supported, but let's be conservative)	82	#define CMD_IP_1 207
73	struct dns64	83	#define CMD_IP_2 46
74	{	84	#define CMD_IP_3 236
75	static const char encode_chars[64 + 1];	85	#define CMD_IP_RST 29
76	static s8 decode_chars[256];	86	#define CMD_IP_SYN 113
		87	#define CMD_IP_REJ 32
77		88
78	static int encode_len (int bytes) { return (bytes * 8 + 5) / 6; }	89	// works for cmaps up to 255 (not 256!)
79	static int decode_len (int bytes) { return (bytes * 6) / 8; }	90	struct charmap
		91	{
		92	enum { INVALID = (u8)255 };
		93
		94	char encode [256]; // index => char
		95	u8 decode [256]; // char => index
		96	unsigned int size;
		97
		98	charmap (const char *cmap);
		99	};
		100
		101	charmap::charmap (const char *cmap)
		102	{
		103	char *enc = encode;
		104	u8 *dec = decode;
		105
		106	memset (enc, (char) 0, 256);
		107	memset (dec, (char)INVALID, 256);
		108
		109	for (size = 0; cmap [size]; size++)
		110	{
		111	enc [size] = cmap [size];
		112	dec [(u8)enc [size]] = size;
		113	}
		114
		115	assert (size < 256);
		116	}
		117
		118	#define MAX_DEC_LEN 500
		119	#define MAX_ENC_LEN (MAX_DEC_LEN * 2)
		120	#define MAX_LIMBS ((MAX_DEC_LEN * 8 + GMP_NUMB_BITS - 1) / GMP_NUMB_BITS)
		121
		122	// ugly. minimum base is 16(!)
		123	struct basecoder
		124	{
		125	charmap cmap;
		126	unsigned int enc_len [MAX_DEC_LEN];
		127	unsigned int dec_len [MAX_ENC_LEN];
		128
		129	unsigned int encode_len (unsigned int len);
		130	unsigned int decode_len (unsigned int len);
		131
80	static void encode (char *dst, u8 *src, int len);	132	unsigned int encode (char *dst, u8 *src, unsigned int len);
81	static void decode (u8 *dst, char *src, int len);	133	unsigned int decode (u8 *dst, char *src, unsigned int len);
82		134
83	dns64 ();	135	basecoder (const char *cmap);
84	} dns64;	136	};
85		137
86	const char dns64::encode_chars[64 + 1] = "0123456789-abcdefghijklmnopqrstuvwxyz_ABCDEFGHIJKLMNOPQRSTUVWXYZ";	138	basecoder::basecoder (const char *cmap)
87	s8 dns64::decode_chars[256];	139	: cmap (cmap)
88
89	dns64::dns64 ()
90	{	140	{
91	for (int i = 0; i < 64; i++)	141	for (unsigned int len = 0; len < MAX_DEC_LEN; ++len)
92	decode_chars [encode_chars [i]] = i + 1;	142	{
93	}	143	u8 src [MAX_DEC_LEN];
		144	u8 dst [MAX_ENC_LEN];
94		145
95	void dns64::encode (char *dst, u8 *src, int len)	146	memset (src, 255, len);
		147
		148	mp_limb_t m [MAX_LIMBS];
		149	mp_size_t n;
		150
		151	n = mpn_set_str (m, src, len, 256);
		152	n = mpn_get_str (dst, this->cmap.size, m, n);
		153
		154	for (int i = 0; !dst [i]; ++i)
		155	n--;
		156
		157	enc_len [len] = n;
		158	dec_len [n] = len;
		159	}
		160	}
		161
		162	unsigned int basecoder::encode_len (unsigned int len)
96	{	163	{
97	// slow, but easy to debug	164	return enc_len [len];
98	unsigned int accum, bits = 0;	165	}
		166
		167	unsigned int basecoder::decode_len (unsigned int len)
		168	{
		169	while (len && !dec_len [len])
		170	--len;
		171
		172	return dec_len [len];
		173	}
		174
		175	unsigned int basecoder::encode (char *dst, u8 *src, unsigned int len)
		176	{
		177	if (!len || len > MAX_DEC_LEN)
		178	return 0;
		179
		180	int elen = encode_len (len);
		181
		182	mp_limb_t m [MAX_LIMBS];
		183	mp_size_t n;
		184
		185	u8 dst_ [MAX_ENC_LEN];
		186
		187	n = mpn_set_str (m, src, len, 256);
		188	n = mpn_get_str (dst_, cmap.size, m, n);
		189
		190	int plen = elen; // for padding
		191
		192	while (n < plen)
		193	{
		194	*dst++ = cmap.encode [0];
		195	plen--;
		196	}
		197
		198	for (unsigned int i = n - plen; i < n; ++i)
		199	*dst++ = cmap.encode [dst_ [i]];
		200
		201	return elen;
		202	}
		203
		204	unsigned int basecoder::decode (u8 *dst, char *src, unsigned int len)
		205	{
		206	if (!len || len > MAX_ENC_LEN)
		207	return 0;
		208
		209	u8 src_ [MAX_ENC_LEN];
		210	unsigned int elen = 0;
99		211
100	while (len--)	212	while (len--)
101	{	213	{
102	accum <<= 8;	214	u8 val = cmap.decode [(u8)*src++];
103	accum |= *src++;
104	bits += 8;
105		215
106	while (bits >= 6)	216	if (val != charmap::INVALID)
107	{	217	src_ [elen++] = val;
108	*dst++ = encode_chars [(accum >> (bits - 6)) & 63];	218	}
109	bits -= 6;	219
110	}	220	int dlen = decode_len (elen);
		221
		222	mp_limb_t m [MAX_LIMBS];
		223	mp_size_t n;
		224
		225	u8 dst_ [MAX_DEC_LEN];
		226
		227	n = mpn_set_str (m, src_, elen, cmap.size);
		228	n = mpn_get_str (dst_, 256, m, n);
		229
		230	if (n < dlen)
111	}	231	{
		232	memset (dst, 0, dlen - n);
		233	memcpy (dst + dlen - n, dst_, n);
		234	}
		235	else
		236	memcpy (dst, dst_ + n - dlen, dlen);
112		237
113	if (bits)	238	return dlen;
114	*dst++ = encode_chars [(accum << (6 - bits)) & 63];
115	}	239	}
116		240
117	void dns64::decode (u8 *dst, char *src, int len)	241	#if 0
118	{	242	struct test { test (); } test;
119	// slow, but easy to debug
120	unsigned int accum, bits = 0;
121		243
122	while (len--)	244	test::test ()
		245	{
		246	basecoder cdc ("0123456789abcdefghijklmnopqrstuvwxyz");
		247
		248	u8 in[] = "0123456789abcdefghijklmnopqrstuvwxyz";
		249	static char enc[200];
		250	static u8 dec[200];
		251
		252	for (int i = 1; i < 20; i++)
123	{	253	{
124	s8 chr = decode_chars [(u8)*src++];	254	int elen = cdc.encode (enc, in, i);
		255	int dlen = cdc.decode (dec, enc, elen);
125		256
		257	printf ("%d>%d>%d (%s>%s)\n", i, elen, dlen, enc, dec);
		258	}
		259	abort ();
		260	}
		261	#endif
126		262
127	if (!chr)	263	//static basecoder cdc64 ("_dDpPhHzZrR06QqMmjJkKBb34TtSsvVlL81xXaAeEFf92WwGgYyoO57UucCNniI-");
		264	//static basecoder cdc63 ("_dDpPhHzZrR06QqMmjJkKBb34TtSsvVlL81xXaAeEFf92WwGgYyoO57UucCNniI");
		265	static basecoder cdc62 ("dDpPhHzZrR06QqMmjJkKBb34TtSsvVlL81xXaAeEFf92WwGgYyoO57UucCNniI");
		266	//static basecoder cdc36 ("dphzr06qmjkb34tsvl81xaef92wgyo57ucni"); // unused as of yet
		267	static basecoder cdc26 ("dPhZrQmJkBtSvLxAeFwGyO");
		268
		269	/////////////////////////////////////////////////////////////////////////////
		270
		271	#define HDRSIZE 6
		272
		273	inline void encode_header (char *data, int clientid, int seqno, int retry = 0)
		274	{
		275	seqno &= SEQNO_MASK;
		276
		277	u8 hdr[3] = {
		278	clientid,
		279	(seqno >> 8) | (retry << 6),
		280	seqno,
		281	};
		282
		283	assert (clientid < 256);
		284
		285	cdc26.encode (data, hdr, 3);
		286	}
		287
		288	inline void decode_header (char *data, int &clientid, int &seqno)
		289	{
		290	u8 hdr[3];
		291
		292	cdc26.decode (hdr, data, HDRSIZE);
		293
		294	clientid = hdr[0];
		295	seqno = ((hdr[1] << 8) | hdr[2]) & SEQNO_MASK;
		296	}
		297
		298	/////////////////////////////////////////////////////////////////////////////
		299
		300	struct byte_stream
		301	{
		302	u8 *data;
		303	int maxsize;
		304	int fill;
		305
		306	byte_stream (int maxsize);
		307	~byte_stream ();
		308
		309	bool empty () { return !fill; }
		310	int size () { return fill; }
		311
		312	bool put (u8 *data, unsigned int datalen);
		313	bool put (vpn_packet *pkt);
		314	vpn_packet *get ();
		315
		316	u8 *begin () { return data; }
		317	void remove (int count);
		318	};
		319
		320	byte_stream::byte_stream (int maxsize)
		321	: maxsize (maxsize), fill (0)
		322	{
		323	data = new u8 [maxsize];
		324	}
		325
		326	byte_stream::~byte_stream ()
		327	{
		328	delete data;
		329	}
		330
		331	void byte_stream::remove (int count)
		332	{
		333	if (count > fill)
		334	assert (count <= fill);
		335
		336	memmove (data, data + count, fill -= count);
		337	}
		338
		339	bool byte_stream::put (u8 *data, unsigned int datalen)
		340	{
		341	if (maxsize - fill < datalen)
		342	return false;
		343
		344	memcpy (this->data + fill, data, datalen); fill += datalen;
		345
		346	return true;
		347	}
		348
		349	bool byte_stream::put (vpn_packet *pkt)
		350	{
		351	if (maxsize - fill < pkt->len + 2)
		352	return false;
		353
		354	data [fill++] = pkt->len >> 8;
		355	data [fill++] = pkt->len;
		356
		357	memcpy (data + fill, pkt->at (0), pkt->len); fill += pkt->len;
		358
		359	return true;
		360	}
		361
		362	vpn_packet *byte_stream::get ()
		363	{
		364	unsigned int len;
		365
		366	for (;;)
		367	{
		368	len = (data [0] << 8) | data [1];
		369
		370	if (len <= MAXSIZE || fill < 2)
128	break;	371	break;
129		372
130	accum <<= 6;	373	// TODO: handle this better than skipping, e.g. by reset
131	accum |= chr - 1;	374	slog (L_DEBUG, _("DNS: corrupted packet stream skipping a byte..."));
132	bits += 6;	375	remove (1);
133		376	}
134	while (bits >= 8)
135	{	377
136	*dst++ = accum >> (bits - 8);	378	if (fill < len + 2)
137	bits -= 8;	379	return 0;
138	}	380
139	}	381	vpn_packet *pkt = new vpn_packet;
		382
		383	pkt->len = len;
		384	memcpy (pkt->at (0), data + 2, len);
		385	remove (len + 2);
		386
		387	return pkt;
140	}	388	}
141		389
142	/////////////////////////////////////////////////////////////////////////////	390	/////////////////////////////////////////////////////////////////////////////
143		391
144	#define FLAG_QUERY ( 0 << 15)	392	#define FLAG_QUERY ( 0 << 15)
145	#define FLAG_RESPONSE ( 1 << 15)	393	#define FLAG_RESPONSE ( 1 << 15)
146	#define FLAG_OP_MASK (15 << 14)	394	#define FLAG_OP_MASK (15 << 11)
147	#define FLAG_OP_QUERY ( 0 << 11)	395	#define FLAG_OP_QUERY ( 0 << 11)
148	#define FLAG_AA ( 1 << 10)	396	#define FLAG_AA ( 1 << 10)
149	#define FLAG_TC ( 1 << 9)	397	#define FLAG_TC ( 1 << 9)
150	#define FLAG_RD ( 1 << 8)	398	#define FLAG_RD ( 1 << 8)
151	#define FLAG_RA ( 1 << 7)	399	#define FLAG_RA ( 1 << 7)
		400	#define FLAG_AUTH ( 1 << 5)
152	#define FLAG_RCODE_MASK (15 << 0)	401	#define FLAG_RCODE_MASK (15 << 0)
153	#define FLAG_RCODE_OK ( 0 << 0)	402	#define FLAG_RCODE_OK ( 0 << 0)
154	#define FLAG_RCODE_FORMERR ( 1 << 0)	403	#define FLAG_RCODE_FORMERR ( 1 << 0)
155	#define FLAG_RCODE_SERVFAIL ( 2 << 0)	404	#define FLAG_RCODE_SERVFAIL ( 2 << 0)
156	#define FLAG_RCODE_NXDOMAIN ( 3 << 0)	405	#define FLAG_RCODE_NXDOMAIN ( 3 << 0)
157	#define FLAG_RCODE_REFUSED ( 5 << 0)	406	#define FLAG_RCODE_REFUSED ( 5 << 0)
158		407
159	#define DEFAULT_CLIENT_FLAGS (FLAG_QUERY | FLAG_OP_QUERY | FLAG_RD)	408	#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)	409	#define DEFAULT_SERVER_FLAGS (FLAG_RESPONSE | FLAG_OP_QUERY | FLAG_AA | FLAG_RD | FLAG_RA)
		410
		411	struct dns_cfg
		412	{
		413	static int next_uid;
		414
		415	u8 id1, id2, id3, id4;
		416
		417	u8 version;
		418	u8 flags;
		419	u8 rrtype;
		420	u8 def_ttl;
		421
		422	u16 client;
		423	u16 uid; // to make request unique
		424
		425	u16 max_size;
		426	u8 seq_cdc;
		427	u8 req_cdc;
		428
		429	u8 rep_cdc;
		430	u8 delay; // time in 0.01s units that the server may delay replying packets
		431	u8 r3, r4;
		432
		433	u8 r5, r6, r7, r8;
		434
		435	void reset (int clientid);
		436	bool valid ();
		437	};
		438
		439	int dns_cfg::next_uid;
		440
		441	void dns_cfg::reset (int clientid)
		442	{
		443	id1 = 'G';
		444	id2 = 'V';
		445	id3 = 'P';
		446	id4 = 'E';
		447
		448	version = 1;
		449
		450	rrtype = RR_TYPE_TXT;
		451	flags = 0;
		452	def_ttl = 0;
		453	seq_cdc = 26;
		454	req_cdc = 62;
		455	rep_cdc = 0;
		456	max_size = htons (MAX_PKT_SIZE);
		457	client = htons (clientid);
		458	uid = next_uid++;
		459	delay = 0;
		460
		461	r3 = r4 = 0;
		462	r4 = r5 = r6 = r7 = 0;
		463	}
		464
		465	bool dns_cfg::valid ()
		466	{
		467	return id1 == 'G'
		468	&& id2 == 'V'
		469	&& id3 == 'P'
		470	&& id4 == 'E'
		471	&& seq_cdc == 26
		472	&& req_cdc == 62
		473	&& rep_cdc == 0
		474	&& version == 1;
		475	}
161		476
162	struct dns_packet : net_packet	477	struct dns_packet : net_packet
163	{	478	{
164	u16 id;	479	u16 id;
165	u16 flags; // QR:1 Opcode:4 AA:1 TC:1 RD:1 RA:1 Z:3 RCODE:4	480	u16 flags; // QR:1 Opcode:4 AA:1 TC:1 RD:1 RA:1 Z:3 RCODE:4
166	u16 qdcount, ancount, nscount, arcount;	481	u16 qdcount, ancount, nscount, arcount;
167		482
168	u8 data[MAXSIZE - 6 * 2];	483	u8 data [MAXSIZE - 6 * 2];
169		484
170	int decode_label (char *data, int size, int &offs);	485	int decode_label (char *data, int size, int &offs);
171	};	486	};
172		487
173	int dns_packet::decode_label (char *data, int size, int &offs)	488	int dns_packet::decode_label (char *data, int size, int &offs)
…		…
204	return data - orig;	519	return data - orig;
205	}	520	}
206		521
207	/////////////////////////////////////////////////////////////////////////////	522	/////////////////////////////////////////////////////////////////////////////
208		523
		524	static u16 dns_id = 0; // TODO: should be per-vpn
		525
		526	static u16 next_id ()
		527	{
		528	if (!dns_id)
		529	dns_id = time (0);
		530
		531	// the simplest lsfr with periodicity 65535 i could find
		532	dns_id = (dns_id << 1)
		533	| (((dns_id >> 1)
		534	^ (dns_id >> 2)
		535	^ (dns_id >> 4)
		536	^ (dns_id >> 15)) & 1);
		537
		538	return dns_id;
		539	}
		540
209	struct dns_req	541	struct dns_rcv;
		542	struct dns_snd;
		543
		544	struct dns_connection
		545	{
		546	connection *c;
		547	struct vpn *vpn;
		548
		549	dns_cfg cfg;
		550
		551	bool established;
		552
		553	tstamp last_received;
		554	tstamp last_sent;
		555	double min_latency;
		556	double poll_interval, send_interval;
		557
		558	vector<dns_rcv *> rcvpq;
		559
		560	byte_stream rcvdq; int rcvseq; int repseq;
		561	byte_stream snddq; int sndseq;
		562
		563	void time_cb (time_watcher &w); time_watcher tw;
		564	void receive_rep (dns_rcv *r);
		565
		566	dns_connection (connection *c);
		567	~dns_connection ();
		568	};
		569
		570	struct dns_snd
210	{	571	{
211	dns_packet *pkt;	572	dns_packet *pkt;
212	tstamp next;	573	tstamp timeout, sent;
213	int retry;	574	int retry;
		575	struct dns_connection *dns;
		576	int seqno;
		577	bool stdhdr;
214		578
215	dns_req (connection *c, vpn_packet *p, int &offs);	579	void gen_stream_req (int seqno, byte_stream &stream);
		580	void gen_syn_req ();
		581
		582	dns_snd (dns_connection *dns);
		583	~dns_snd ();
216	};	584	};
217		585
		586	dns_snd::dns_snd (dns_connection *dns)
		587	: dns (dns)
		588	{
		589	timeout = 0;
		590	retry = 0;
		591	seqno = 0;
		592	sent = NOW;
		593	stdhdr = false;
		594
		595	pkt = new dns_packet;
		596
		597	pkt->id = next_id ();
		598	}
		599
		600	dns_snd::~dns_snd ()
		601	{
		602	delete pkt;
		603	}
		604
		605	static void append_domain (dns_packet &pkt, int &offs, const char *domain)
		606	{
		607	// add tunnel domain
		608	for (;;)
		609	{
		610	const char *end = strchr (domain, '.');
		611
		612	if (!end)
		613	end = domain + strlen (domain);
		614
		615	int len = end - domain;
		616
		617	pkt [offs++] = len;
		618	memcpy (pkt.at (offs), domain, len);
		619	offs += len;
		620
		621	if (!*end)
		622	break;
		623
		624	domain = end + 1;
		625	}
		626	}
		627
		628	void dns_snd::gen_stream_req (int seqno, byte_stream &stream)
		629	{
		630	stdhdr = true;
		631	this->seqno = seqno;
		632
		633	timeout = NOW + INITIAL_TIMEOUT;
		634
		635	pkt->flags = htons (DEFAULT_CLIENT_FLAGS);
		636	pkt->qdcount = htons (1);
		637
		638	int offs = 6*2;
		639	int dlen = MAX_DOMAIN_SIZE - (strlen (dns->c->conf->domain) + 2);
		640	// MAX_DOMAIN_SIZE is technically 255, but bind doesn't compress responses well,
		641	// so we need to have space for 2*MAX_DOMAIN_SIZE + header + extra
		642
		643	char enc[256], *encp = enc;
		644	encode_header (enc, THISNODE->id, seqno);
		645
		646	int datalen = cdc62.decode_len (dlen - (dlen + MAX_LBL_SIZE - 1) / MAX_LBL_SIZE - HDRSIZE);
		647
		648	if (datalen > stream.size ())
		649	datalen = stream.size ();
		650
		651	int enclen = cdc62.encode (enc + HDRSIZE, stream.begin (), datalen) + HDRSIZE;
		652	stream.remove (datalen);
		653
		654	while (enclen)
		655	{
		656	int lbllen = enclen < MAX_LBL_SIZE ? enclen : MAX_LBL_SIZE;
		657
		658	(*pkt)[offs++] = lbllen;
		659	memcpy (pkt->at (offs), encp, lbllen);
		660
		661	offs += lbllen;
		662	encp += lbllen;
		663
		664	enclen -= lbllen;
		665	}
		666
		667	append_domain (*pkt, offs, dns->c->conf->domain);
		668
		669	(*pkt)[offs++] = 0;
		670	(*pkt)[offs++] = RR_TYPE_ANY >> 8; (*pkt)[offs++] = RR_TYPE_ANY;
		671	(*pkt)[offs++] = RR_CLASS_IN >> 8; (*pkt)[offs++] = RR_CLASS_IN;
		672
		673	pkt->len = offs;
		674	}
		675
		676	void dns_snd::gen_syn_req ()
		677	{
		678	timeout = NOW + INITIAL_SYN_TIMEOUT;
		679
		680	pkt->flags = htons (DEFAULT_CLIENT_FLAGS);
		681	pkt->qdcount = htons (1);
		682
		683	int offs = 6 * 2;
		684
		685	int elen = cdc26.encode ((char *)pkt->at (offs + 1), (u8 *)&dns->cfg, sizeof (dns_cfg));
		686
		687	assert (elen <= MAX_LBL_SIZE);
		688
		689	(*pkt)[offs] = elen;
		690	offs += elen + 1;
		691	append_domain (*pkt, offs, dns->c->conf->domain);
		692
		693	(*pkt)[offs++] = 0;
		694	(*pkt)[offs++] = RR_TYPE_A >> 8; (*pkt)[offs++] = RR_TYPE_A;
		695	(*pkt)[offs++] = RR_CLASS_IN >> 8; (*pkt)[offs++] = RR_CLASS_IN;
		696
		697	pkt->len = offs;
		698	}
		699
218	struct dns_rep	700	struct dns_rcv
219	{	701	{
		702	int seqno;
		703	dns_packet *pkt; // reply packet
		704	u8 data [MAXSIZE]; // actually part of the reply packet...
		705	int datalen;
		706
		707	dns_rcv (int seqno, u8 *data, int datalen);
		708	~dns_rcv ();
220	};	709	};
221		710
222	static u16 dns_id; // TODO: should be per-vpn	711	dns_rcv::dns_rcv (int seqno, u8 *data, int datalen)
223		712	: seqno (seqno), pkt (new dns_packet), datalen (datalen)
224	dns_req::dns_req (connection *c, vpn_packet *p, int &offs)
225	{	713	{
226	next = 0;	714	memcpy (this->data, data, datalen);
227	retry = 0;	715	}
228		716
229	pkt = new dns_packet;	717	dns_rcv::~dns_rcv ()
230		718	{
231	pkt->id = dns_id++;	719	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	}	720	}
242		721
243	/////////////////////////////////////////////////////////////////////////////	722	/////////////////////////////////////////////////////////////////////////////
244		723
245	struct dns_cfg	724	dns_connection::dns_connection (connection *c)
		725	: c (c)
		726	, rcvdq (MAX_BACKLOG * 2)
		727	, snddq (MAX_BACKLOG)
		728	, tw (this, &dns_connection::time_cb)
246	{	729	{
247	u8 id1, id2, id3;	730	vpn = c->vpn;
248	u8 def_ttl;
249	u8 unused1;
250	u16 max_size;
251	u8 flags1, flags2;
252	};
253		731
254	// reply to client-poll	732	established = false;
255	void dnsv4_poll (dns_packet *pkt, int &offs)
256	{
257	int dlen = MAX_PKT_SIZE - offs - 2;
258		733
259	(*pkt) [offs++] = 0;	734	rcvseq = repseq = sndseq = 0;
260	(*pkt) [offs++] = 5;
261	memcpy (&((*pkt)[offs]), "\01H\02\xff\x00", 5);
262	offs += 5;
263		735
264	pkt->ancount = htons (1);	736	last_sent = last_received = 0;
		737	poll_interval = 0.5; // starting here
		738	send_interval = 0.5; // starting rate
		739	min_latency = INITIAL_TIMEOUT;
		740	}
		741
		742	dns_connection::~dns_connection ()
		743	{
		744	for (vector<dns_rcv *>::iterator i = rcvpq.begin ();
		745	i != rcvpq.end ();
		746	++i)
		747	delete *i;
		748	}
		749
		750	void dns_connection::receive_rep (dns_rcv *r)
		751	{
		752	if (r->datalen)
		753	{
		754	last_received = NOW;
		755	tw.trigger ();
		756
		757	poll_interval = send_interval;
		758	}
		759	else
		760	{
		761	poll_interval *= 1.5;
		762
		763	if (poll_interval > MAX_POLL_INTERVAL)
		764	poll_interval = MAX_POLL_INTERVAL;
		765	}
		766
		767	rcvpq.push_back (r);
		768
		769	redo:
		770
		771	// find next packet
		772	for (vector<dns_rcv *>::iterator i = rcvpq.end (); i-- != rcvpq.begin (); )
		773	if (SEQNO_EQ (rcvseq, (*i)->seqno))
		774	{
		775	// enter the packet into our input stream
		776	r = *i;
		777
		778	// remove the oldest packet, look forward, as it's oldest first
		779	for (vector<dns_rcv *>::iterator j = rcvpq.begin (); j != rcvpq.end (); ++j)
		780	if (SEQNO_EQ ((*j)->seqno, rcvseq - MAX_WINDOW))
		781	{
		782	delete *j;
		783	rcvpq.erase (j);
		784	break;
		785	}
		786
		787	rcvseq = (rcvseq + 1) & SEQNO_MASK;
		788
		789	if (!rcvdq.put (r->data, r->datalen))
		790	{
		791	slog (L_ERR, "DNS: !rcvdq.put (r->data, r->datalen)");
		792	abort (); // MUST never overflow, can be caused by data corruption, TODO
		793	}
		794
		795	while (vpn_packet *pkt = rcvdq.get ())
		796	{
		797	sockinfo si;
		798	si.host = 0x01010101; si.port = htons (c->conf->id); si.prot = PROT_DNSv4;
		799
		800	vpn->recv_vpn_packet (pkt, si);
		801
		802	delete pkt;
		803	}
		804
		805	// check for further packets
		806	goto redo;
		807	}
		808	}
		809
		810	void
		811	vpn::dnsv4_server (dns_packet &pkt)
		812	{
		813	u16 flags = ntohs (pkt.flags);
		814
		815	int offs = 6 * 2; // skip header
		816
265	pkt->flags = htons (DEFAULT_SERVER_FLAGS | FLAG_RCODE_OK);	817	pkt.flags = htons (DEFAULT_SERVER_FLAGS | FLAG_RCODE_FORMERR);
266		818
267	printf ("we have room for %d bytes\n", dlen);	819	if (0 == (flags & (FLAG_RESPONSE | FLAG_OP_MASK))
		820	&& pkt.qdcount == htons (1))
		821	{
		822	char qname [MAXSIZE];
		823	int qlen = pkt.decode_label ((char *)qname, MAXSIZE - offs, offs);
		824
		825	u16 qtype = pkt [offs++] << 8; qtype |= pkt [offs++];
		826	u16 qclass = pkt [offs++] << 8; qclass |= pkt [offs++];
		827
		828	pkt.qdcount = htons (1);
		829	pkt.ancount = 0;
		830	pkt.nscount = 0; // should be self, as other nameservers reply like this
		831	pkt.arcount = 0; // a record for self, as other nameservers reply like this
		832
		833	pkt.flags = htons (DEFAULT_SERVER_FLAGS | FLAG_RCODE_SERVFAIL);
		834
		835	int dlen = strlen (THISNODE->domain);
		836
		837	if (qclass == RR_CLASS_IN
		838	&& qlen > dlen + 1
		839	&& !memcmp (qname + qlen - (dlen + 1), THISNODE->domain, dlen))
		840	{
		841	// now generate reply
		842	pkt.ancount = htons (1); // one answer RR
		843	pkt.flags = htons (DEFAULT_SERVER_FLAGS | FLAG_RCODE_OK);
		844
		845	if ((qtype == RR_TYPE_ANY
		846	|| qtype == RR_TYPE_TXT
		847	|| qtype == RR_TYPE_NULL)
		848	&& qlen > dlen + 1 + HDRSIZE)
		849	{
		850	// correct class, domain: parse
		851	int client, seqno;
		852	decode_header (qname, client, seqno);
		853
		854	u8 data[MAXSIZE];
		855	int datalen = cdc62.decode (data, qname + HDRSIZE, qlen - (dlen + 1 + HDRSIZE));
		856
		857	if (0 < client && client <= conns.size ())
		858	{
		859	connection *c = conns [client - 1];
		860	dns_connection *dns = c->dns;
		861	dns_rcv *rcv;
		862
		863	if (dns)
		864	{
		865	for (vector<dns_rcv *>::iterator i = dns->rcvpq.end (); i-- != dns->rcvpq.begin (); )
		866	if (SEQNO_EQ ((*i)->seqno, seqno))
		867	{
		868	// already seen that request: simply reply with the cached reply
		869	dns_rcv *r = *i;
		870
		871	slog (L_DEBUG, "DNS: duplicate packet received ID %d, SEQ %d", htons (r->pkt->id), seqno);
		872
		873	// refresh header & id, as the retry count could have changed
		874	memcpy (r->pkt->at (6 * 2 + 1), pkt.at (6 * 2 + 1), HDRSIZE);
		875	r->pkt->id = pkt.id;
		876
		877	memcpy (pkt.at (0), r->pkt->at (0), offs = r->pkt->len);
		878
		879	goto duplicate_request;
		880	}
		881
		882	// new packet, queue
		883	rcv = new dns_rcv (seqno, data, datalen);
		884	dns->receive_rep (rcv);
		885	}
		886
		887	{
		888	pkt [offs++] = 0xc0; pkt [offs++] = 6 * 2; // refer to name in query section
		889
		890	int rtype = dns ? dns->cfg.rrtype : RR_TYPE_A;
		891	pkt [offs++] = rtype >> 8; pkt [offs++] = rtype; // type
		892	pkt [offs++] = RR_CLASS_IN >> 8; pkt [offs++] = RR_CLASS_IN; // class
		893	pkt [offs++] = 0; pkt [offs++] = 0;
		894	pkt [offs++] = 0; pkt [offs++] = dns ? dns->cfg.def_ttl : 0; // TTL
		895
		896	int rdlen_offs = offs += 2;
		897
		898	if (dns)
		899	{
		900	int dlen = ntohs (dns->cfg.max_size) - offs;
		901
		902	// bind doesn't compress well, so reduce further by one label length
		903	dlen -= qlen;
		904
		905	// only put data into in-order sequence packets, if
		906	// we receive out-of-order packets we generate empty
		907	// replies
		908	//printf ("%d - %d & %x (=%d) < %d\n", seqno, dns->repseq, SEQNO_MASK, (seqno - dns->repseq) & SEQNO_MASK, MAX_WINDOW);//D
		909	if (((seqno - dns->repseq) & SEQNO_MASK) <= MAX_WINDOW)
		910	{
		911	dns->repseq = seqno;
		912
		913	while (dlen > 1 && !dns->snddq.empty ())
		914	{
		915	int txtlen = dlen <= 255 ? dlen - 1 : 255;
		916
		917	if (txtlen > dns->snddq.size ())
		918	txtlen = dns->snddq.size ();
		919
		920	pkt[offs++] = txtlen;
		921	memcpy (pkt.at (offs), dns->snddq.begin (), txtlen);
		922	offs += txtlen;
		923	dns->snddq.remove (txtlen);
		924
		925	dlen -= txtlen + 1;
		926	}
		927	}
		928
		929	// avoid completely empty TXT rdata
		930	if (offs == rdlen_offs)
		931	pkt[offs++] = 0;
		932
		933	slog (L_NOISE, "DNS: snddq %d", dns->snddq.size ());
		934	}
		935	else
		936	{
		937	// send RST
		938	pkt [offs++] = CMD_IP_1; pkt [offs++] = CMD_IP_2; pkt [offs++] = CMD_IP_3;
		939	pkt [offs++] = CMD_IP_RST;
		940	}
		941
		942	int rdlen = offs - rdlen_offs;
		943
		944	pkt [rdlen_offs - 2] = rdlen >> 8;
		945	pkt [rdlen_offs - 1] = rdlen;
		946
		947	if (dns)
		948	{
		949	// now update dns_rcv copy
		950	rcv->pkt->len = offs;
		951	memcpy (rcv->pkt->at (0), pkt.at (0), offs);
		952	}
		953	}
		954
		955	duplicate_request: ;
		956	}
		957	else
		958	pkt.flags = htons (DEFAULT_SERVER_FLAGS | FLAG_RCODE_FORMERR);
		959	}
		960	else if (qtype == RR_TYPE_A
		961	&& qlen > dlen + 1 + cdc26.encode_len (sizeof (dns_cfg)))
		962	{
		963	dns_cfg cfg;
		964	cdc26.decode ((u8 *)&cfg, qname, cdc26.encode_len (sizeof (dns_cfg)));
		965	int client = ntohs (cfg.client);
		966
		967	pkt [offs++] = 0xc0; pkt [offs++] = 6 * 2; // refer to name in query section
		968
		969	pkt [offs++] = RR_TYPE_A >> 8; pkt [offs++] = RR_TYPE_A; // type
		970	pkt [offs++] = RR_CLASS_IN >> 8; pkt [offs++] = RR_CLASS_IN; // class
		971	pkt [offs++] = 0; pkt [offs++] = 0;
		972	pkt [offs++] = 0; pkt [offs++] = cfg.def_ttl; // TTL
		973	pkt [offs++] = 0; pkt [offs++] = 4; // rdlength
		974
		975	slog (L_INFO, _("DNS: client %d connects"), client);
		976
		977	pkt [offs++] = CMD_IP_1; pkt [offs++] = CMD_IP_2; pkt [offs++] = CMD_IP_3;
		978	pkt [offs++] = CMD_IP_REJ;
		979
		980	if (0 < client && client <= conns.size ())
		981	{
		982	connection *c = conns [client - 1];
		983
		984	if (cfg.valid ())
		985	{
		986	pkt [offs - 1] = CMD_IP_SYN;
		987
		988	delete c->dns;
		989	c->dns = new dns_connection (c);
		990	c->dns->cfg = cfg;
		991	}
		992	}
		993	}
		994	}
		995
		996	pkt.len = offs;
		997	}
		998	}
		999
		1000	void
		1001	vpn::dnsv4_client (dns_packet &pkt)
		1002	{
		1003	u16 flags = ntohs (pkt.flags);
		1004	int offs = 6 * 2; // skip header
		1005
		1006	pkt.qdcount = ntohs (pkt.qdcount);
		1007	pkt.ancount = ntohs (pkt.ancount);
		1008
		1009	// go through our request list and find the corresponding request
		1010	for (vector<dns_snd *>::iterator i = dns_sndpq.begin ();
		1011	i != dns_sndpq.end ();
		1012	++i)
		1013	if ((*i)->pkt->id == pkt.id)
		1014	{
		1015	dns_connection *dns = (*i)->dns;
		1016	connection *c = dns->c;
		1017	int seqno = (*i)->seqno;
		1018	u8 data[MAXSIZE], *datap = data;
		1019
		1020	if ((*i)->retry)
		1021	{
		1022	dns->send_interval *= 1.01;
		1023	if (dns->send_interval > MAX_SEND_INTERVAL)
		1024	dns->send_interval = MAX_SEND_INTERVAL;
		1025	}
		1026	else
		1027	{
		1028	#if 0
		1029	dns->send_interval *= 0.999;
		1030	#endif
		1031	// the latency surely puts an upper bound on
		1032	// the minimum send interval
		1033	double latency = NOW - (*i)->sent;
		1034
		1035	if (latency < dns->min_latency)
		1036	dns->min_latency = latency;
		1037
		1038	if (dns->send_interval > dns->min_latency * LATENCY_FACTOR)
		1039	dns->send_interval = dns->min_latency * LATENCY_FACTOR;
		1040
		1041	if (dns->send_interval < MIN_SEND_INTERVAL)
		1042	dns->send_interval = MIN_SEND_INTERVAL;
		1043	}
		1044
		1045	delete *i;
		1046	dns_sndpq.erase (i);
		1047
		1048	if (flags & FLAG_RESPONSE && !(flags & FLAG_OP_MASK))
		1049	{
		1050	char qname[MAXSIZE];
		1051
		1052	while (pkt.qdcount-- && offs < MAXSIZE - 4)
		1053	{
		1054	int qlen = pkt.decode_label ((char *)qname, MAXSIZE - offs, offs);
		1055	offs += 4; // skip qtype, qclass
		1056	}
		1057
		1058	while (pkt.ancount-- && offs < MAXSIZE - 10 && datap)
		1059	{
		1060	int qlen = pkt.decode_label ((char *)qname, MAXSIZE - offs, offs);
		1061
		1062	u16 qtype = pkt [offs++] << 8; qtype |= pkt [offs++];
		1063	u16 qclass = pkt [offs++] << 8; qclass |= pkt [offs++];
		1064	u32 ttl = pkt [offs++] << 24;
		1065	ttl |= pkt [offs++] << 16;
		1066	ttl |= pkt [offs++] << 8;
		1067	ttl |= pkt [offs++];
		1068	u16 rdlen = pkt [offs++] << 8; rdlen |= pkt [offs++];
		1069
		1070	if (qtype == RR_TYPE_NULL || qtype == RR_TYPE_TXT)
		1071	{
		1072	if (rdlen <= MAXSIZE - offs)
		1073	{
		1074	// decode bytes, finally
		1075
		1076	while (rdlen)
		1077	{
		1078	int txtlen = pkt [offs++];
		1079
		1080	assert (txtlen + offs < MAXSIZE - 1);
		1081
		1082	memcpy (datap, pkt.at (offs), txtlen);
		1083	datap += txtlen; offs += txtlen;
		1084
		1085	rdlen -= txtlen + 1;
		1086	}
		1087	}
		1088	}
		1089	else if (qtype == RR_TYPE_A)
		1090	{
		1091	u8 ip [4];
		1092
		1093	ip [0] = pkt [offs++];
		1094	ip [1] = pkt [offs++];
		1095	ip [2] = pkt [offs++];
		1096	ip [3] = pkt [offs++];
		1097
		1098	if (ip [0] == CMD_IP_1
		1099	&& ip [1] == CMD_IP_2
		1100	&& ip [2] == CMD_IP_3)
		1101	{
		1102	slog (L_TRACE, _("DNS: got tunnel meta command %02x"), ip [3]);
		1103
		1104	if (ip [3] == CMD_IP_RST)
		1105	{
		1106	slog (L_DEBUG, _("DNS: got tunnel RST request"));
		1107
		1108	delete dns; c->dns = 0;
		1109
		1110	return;
		1111	}
		1112	else if (ip [3] == CMD_IP_SYN)
		1113	{
		1114	slog (L_DEBUG, _("DNS: got tunnel SYN reply, server likes us."));
		1115	dns->established = true;
		1116	}
		1117	else if (ip [3] == CMD_IP_REJ)
		1118	{
		1119	slog (L_DEBUG, _("DNS: got tunnel REJ reply, server does not like us, aborting."));
		1120	abort ();
		1121	}
		1122	else
		1123	slog (L_INFO, _("DNS: got unknown meta command %02x"), ip [3]);
		1124	}
		1125	else
		1126	slog (L_INFO, _("DNS: got spurious a record %d.%d.%d.%d"),
		1127	ip [0], ip [1], ip [2], ip [3]);
		1128
		1129	return;
		1130	}
		1131
		1132	int client, rseqno;
		1133	decode_header (qname, client, rseqno);
		1134
		1135	if (client != THISNODE->id)
		1136	{
		1137	slog (L_INFO, _("DNS: got dns tunnel response with wrong clientid, ignoring"));
		1138	datap = 0;
		1139	}
		1140	else if (rseqno != seqno)
		1141	{
		1142	slog (L_DEBUG, _("DNS: got dns tunnel response with wrong seqno, badly caching nameserver?"));
		1143	datap = 0;
		1144	}
		1145	}
		1146	}
		1147
		1148	// todo: pkt now used
		1149	if (datap)
		1150	dns->receive_rep (new dns_rcv (seqno, data, datap - data));
		1151
		1152	break;
		1153	}
268	}	1154	}
269		1155
270	void	1156	void
271	vpn::dnsv4_ev (io_watcher &w, short revents)	1157	vpn::dnsv4_ev (io_watcher &w, short revents)
272	{	1158	{
…		…
274	{	1160	{
275	dns_packet *pkt = new dns_packet;	1161	dns_packet *pkt = new dns_packet;
276	struct sockaddr_in sa;	1162	struct sockaddr_in sa;
277	socklen_t sa_len = sizeof (sa);	1163	socklen_t sa_len = sizeof (sa);
278		1164
279	int len = recvfrom (w.fd, &((*pkt)[0]), MAXSIZE, 0, (sockaddr *)&sa, &sa_len);	1165	pkt->len = recvfrom (w.fd, pkt->at (0), MAXSIZE, 0, (sockaddr *)&sa, &sa_len);
280	pkt->len = len;
281		1166
282	u16 flags = ntohs (pkt->flags);	1167	if (pkt->len > 0)
283
284	if (THISNODE->dns_port)
285	{	1168	{
286	// server	1169	if (ntohs (pkt->flags) & FLAG_RESPONSE)
287	pkt->flags = htons (DEFAULT_SERVER_FLAGS | FLAG_RCODE_FORMERR);	1170	dnsv4_client (*pkt);
288		1171	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	{	1172	{
294	char qname[MAXSIZE];	1173	dnsv4_server (*pkt);
295	int qlen = pkt->decode_label ((char *)qname, MAXSIZE, offs);	1174	sendto (w.fd, pkt->at (0), pkt->len, 0, (sockaddr *)&sa, sa_len);
		1175	}
296		1176
297	printf ("rcvd packet len %d, id%04x flags%04x q%04x a%04x n%04x a%04x <%s>\n", len,	1177	delete pkt;
298	pkt->id, flags, pkt->qdcount, pkt->ancount, pkt->nscount, pkt->arcount, qname);//D	1178	}
		1179	}
		1180	}
299		1181
300	u16 qtype = (*pkt) [offs++] << 8; qtype |= (*pkt) [offs++];	1182	bool
301	u16 qclass = (*pkt) [offs++] << 8; qclass |= (*pkt) [offs++];	1183	vpn::send_dnsv4_packet (vpn_packet *pkt, const sockinfo &si, int tos)
		1184	{
		1185	int client = ntohs (si.port);
302		1186
303	pkt->qdcount = htons (1);	1187	assert (0 < client && client <= conns.size ());
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		1188
308	pkt->flags = htons (DEFAULT_SERVER_FLAGS | FLAG_RCODE_NXDOMAIN);	1189	connection *c = conns [client - 1];
309		1190
310	int dlen = strlen (THISNODE->domain);	1191	if (!c->dns)
		1192	c->dns = new dns_connection (c);
		1193
		1194	if (c->dns->snddq.put (pkt))
		1195	c->dns->tw.trigger ();
311		1196
312	if (qclass == RR_CLASS_IN	1197	// always return true even if the buffer overflows
313	&& (qtype == RR_TYPE_ANY || qtype == RR_TYPE_TXT)	1198	return true;
314	&& qlen > dlen + 1	1199	}
315	&& !memcmp (qname + qlen - dlen - 1, THISNODE->domain, dlen))	1200
		1201	void
		1202	connection::dnsv4_reset_connection ()
		1203	{
		1204	//delete dns; dns = 0; //TODO
		1205	}
		1206
		1207	#define NEXT(w) do { if (next > (w)) next = w; } while (0)
		1208
		1209	void
		1210	dns_connection::time_cb (time_watcher &w)
		1211	{
		1212	// servers have to be polled
		1213	if (THISNODE->dns_port)
		1214	return;
		1215
		1216	// check for timeouts and (re)transmit
		1217	tstamp next = NOW + poll_interval;
		1218	dns_snd *send = 0;
		1219
		1220	for (vector<dns_snd *>::iterator i = vpn->dns_sndpq.begin ();
		1221	i != vpn->dns_sndpq.end ();
		1222	++i)
		1223	{
		1224	dns_snd *r = *i;
		1225
		1226	if (r->timeout <= NOW)
		1227	{
		1228	if (!send)
		1229	{
		1230	send = r;
		1231
		1232	r->retry++;
		1233	r->timeout = NOW + (r->retry * min_latency * TIMEOUT_FACTOR);
		1234
		1235	// the following code changes the query section a bit, forcing
		1236	// the forwarder to generate a new request
		1237	if (r->stdhdr)
316	{	1238	{
317	// correct class, now generate reply	1239	//printf ("reencoded header for ID %d retry %d:%d:%d (%p)\n", htons (r->pkt->id), THISNODE->id, r->seqno, r->retry);
318	pkt->ancount = htons (1); // one answer RR	1240	//encode_header ((char *)r->pkt->at (6 * 2 + 1), THISNODE->id, r->seqno, r->retry);
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	}	1241	}
332	}	1242	}
333
334	sendto (w.fd, &((*pkt)[0]), offs, 0, (sockaddr *)&sa, sa_len);
335	}	1243	}
336	else	1244	else
		1245	NEXT (r->timeout);
		1246	}
		1247
		1248	if (!send)
		1249	{
		1250	// generate a new packet, if wise
		1251
		1252	if (!established)
337	{	1253	{
338	// client	1254	if (vpn->dns_sndpq.empty ())
		1255	{
		1256	send = new dns_snd (this);
		1257
		1258	cfg.reset (THISNODE->id);
		1259	send->gen_syn_req ();
		1260	}
339	}	1261	}
340	}
341	}
342
343	bool
344	connection::send_dnsv4_packet (vpn_packet *pkt, const sockinfo &si, int tos)
345	{
346	if (dns_sndq.size () >= MAX_OUTSTANDING)	1262	else if (vpn->dns_sndpq.size () < MAX_OUTSTANDING
347	return false;	1263	&& !SEQNO_EQ (rcvseq, sndseq - (MAX_WINDOW - 1)))
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	{	1264	{
381	slog (L_NOISE, _("dnsv4, send req %d\n"), r->pkt->id);	1265	if (last_sent + send_interval <= NOW)
382	r->retry++;	1266	{
383	r->next = NOW + r->retry;	1267	//printf ("sending data request etc.\n"); //D
		1268	if (!snddq.empty () || last_received + 1. > NOW)
		1269	{
		1270	poll_interval = send_interval;
		1271	NEXT (NOW + send_interval);
		1272	}
		1273
		1274	send = new dns_snd (this);
		1275	send->gen_stream_req (sndseq, snddq);
		1276	send->timeout = NOW + min_latency * TIMEOUT_FACTOR;
		1277
		1278	sndseq = (sndseq + 1) & SEQNO_MASK;
		1279	}
		1280	else
		1281	NEXT (last_sent + send_interval);
384	}	1282	}
385		1283
386	if (r->next < next)	1284	if (send)
387	next = r->next;	1285	vpn->dns_sndpq.push_back (send);
		1286	}
		1287
		1288	if (send)
388	}	1289	{
		1290	last_sent = NOW;
		1291	if (rand () & 15 != 0)//D
		1292	sendto (vpn->dnsv4_fd,
		1293	send->pkt->at (0), send->pkt->len, 0,
		1294	vpn->dns_forwarder.sav4 (), vpn->dns_forwarder.salenv4 ());
		1295	}
389		1296
390	printf ("%f next\n", next);	1297	slog (L_NOISE, "DNS: pi %f si %f N %f (%d:%d %d)",
		1298	poll_interval, send_interval, next - NOW,
		1299	vpn->dns_sndpq.size (), snddq.size (),
		1300	rcvpq.size ());
		1301
		1302	// TODO: no idea when this happens, but when next < NOW, we have a problem
		1303	if (next < NOW + 0.001)
		1304	next = NOW + 0.1;
		1305
391	w.start (next);	1306	w.start (next);
392	}	1307	}
393		1308
394	#endif	1309	#endif
395		1310

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