--- gvpe/src/vpn_dns.C 2004/04/02 14:42:45 1.1 +++ gvpe/src/vpn_dns.C 2005/03/14 17:40:01 1.30 @@ -1,8 +1,10 @@ /* vpn_dns.C -- handle the dns tunnel part of the protocol. - Copyright (C) 2003-2004 Marc Lehmann + Copyright (C) 2003-2005 Marc Lehmann - This program is free software; you can redistribute it and/or modify + This file is part of GVPE. + + GVPE is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 2 of the License, or (at your option) any later version. @@ -13,7 +15,7 @@ GNU General Public License for more details. You should have received a copy of the GNU General Public License - along with this program; if not, write to the Free Software + along with gvpe; if not, write to the Free Software Foundation, Inc. 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA */ @@ -25,6 +27,7 @@ // it's a hack, use only in emergency situations please. #include +#include #include #include @@ -37,48 +40,1265 @@ #include +#include + #include "netcompat.h" #include "vpn.h" -#if ENABLE_HTTP_PROXY -# include "conf.h" +#define MAX_POLL_INTERVAL 5. // how often to poll minimally when the server has no data +#define ACTIVITY_INTERVAL 5. + +#define INITIAL_TIMEOUT 0.1 // retry timeouts +#define INITIAL_SYN_TIMEOUT 10. // retry timeout for initial syn + +#define MIN_SEND_INTERVAL 0.001 // wait at least this time between sending requests +#define MAX_SEND_INTERVAL 2. // optimistic? + +#define LATENCY_FACTOR 0.5 // RTT * LATENCY_FACTOR == sending rate +#define MAX_OUTSTANDING 2 // max. outstanding requests +#define MAX_WINDOW 1000 // max. for MAX_OUTSTANDING, and backlog +#define MAX_BACKLOG (100*1024) // size of gvpe protocol backlog (bytes), must be > MAXSIZE + +#define MAX_DOMAIN_SIZE 240 // 255 is legal limit, but bind doesn't compress well +// 240 leaves about 4 bytes of server reply data +// every two request bytes less give room for one reply byte + +#define SEQNO_MASK 0x3fff +#define SEQNO_EQ(a,b) ( 0 == ( ((a) ^ (b)) & SEQNO_MASK) ) + +#define MAX_LBL_SIZE 63 +#define MAX_PKT_SIZE 512 + +#define RR_TYPE_A 1 +#define RR_TYPE_NULL 10 +#define RR_TYPE_TXT 16 +#define RR_TYPE_ANY 255 + +#define RR_CLASS_IN 1 + +#define CMD_IP_1 207 +#define CMD_IP_2 46 +#define CMD_IP_3 236 +#define CMD_IP_RST 29 +#define CMD_IP_SYN 113 +#define CMD_IP_REJ 32 + +// works for cmaps up to 255 (not 256!) +struct charmap +{ + enum { INVALID = (u8)255 }; + + char encode [256]; // index => char + u8 decode [256]; // char => index + unsigned int size; + + charmap (const char *cmap); +}; + +charmap::charmap (const char *cmap) +{ + char *enc = encode; + u8 *dec = decode; + + memset (enc, (char) 0, 256); + memset (dec, (char)INVALID, 256); + + for (size = 0; cmap [size]; size++) + { + enc [size] = cmap [size]; + dec [(u8)enc [size]] = size; + } + + assert (size < 256); +} + +#define MAX_DEC_LEN 500 +#define MAX_ENC_LEN (MAX_DEC_LEN * 2) +#define MAX_LIMBS ((MAX_DEC_LEN * 8 + GMP_NUMB_BITS - 1) / GMP_NUMB_BITS) + +// ugly. minimum base is 16(!) +struct basecoder +{ + charmap cmap; + unsigned int enc_len [MAX_DEC_LEN]; + unsigned int dec_len [MAX_ENC_LEN]; + + unsigned int encode_len (unsigned int len); + unsigned int decode_len (unsigned int len); + + unsigned int encode (char *dst, u8 *src, unsigned int len); + unsigned int decode (u8 *dst, char *src, unsigned int len); + + basecoder (const char *cmap); +}; + +basecoder::basecoder (const char *cmap) +: cmap (cmap) +{ + for (unsigned int len = 0; len < MAX_DEC_LEN; ++len) + { + u8 src [MAX_DEC_LEN]; + u8 dst [MAX_ENC_LEN]; + + memset (src, 255, len); + + mp_limb_t m [MAX_LIMBS]; + mp_size_t n; + + n = mpn_set_str (m, src, len, 256); + n = mpn_get_str (dst, this->cmap.size, m, n); + + for (int i = 0; !dst [i]; ++i) + n--; + + enc_len [len] = n; + dec_len [n] = len; + } +} + +unsigned int basecoder::encode_len (unsigned int len) +{ + return enc_len [len]; +} + +unsigned int basecoder::decode_len (unsigned int len) +{ + while (len && !dec_len [len]) + --len; + + return dec_len [len]; +} + +unsigned int basecoder::encode (char *dst, u8 *src, unsigned int len) +{ + if (!len || len > MAX_DEC_LEN) + return 0; + + int elen = encode_len (len); + + mp_limb_t m [MAX_LIMBS]; + mp_size_t n; + + u8 dst_ [MAX_ENC_LEN]; + + n = mpn_set_str (m, src, len, 256); + n = mpn_get_str (dst_, cmap.size, m, n); + + int plen = elen; // for padding + + while (n < plen) + { + *dst++ = cmap.encode [0]; + plen--; + } + + for (unsigned int i = n - plen; i < n; ++i) + *dst++ = cmap.encode [dst_ [i]]; + + return elen; +} + +unsigned int basecoder::decode (u8 *dst, char *src, unsigned int len) +{ + if (!len || len > MAX_ENC_LEN) + return 0; + + u8 src_ [MAX_ENC_LEN]; + unsigned int elen = 0; + + while (len--) + { + u8 val = cmap.decode [(u8)*src++]; + + if (val != charmap::INVALID) + src_ [elen++] = val; + } + + int dlen = decode_len (elen); + + mp_limb_t m [MAX_LIMBS]; + mp_size_t n; + + u8 dst_ [MAX_DEC_LEN]; + + n = mpn_set_str (m, src_, elen, cmap.size); + n = mpn_get_str (dst_, 256, m, n); + + if (n < dlen) + { + memset (dst, 0, dlen - n); + memcpy (dst + dlen - n, dst_, n); + } + else + memcpy (dst, dst_ + n - dlen, dlen); + + return dlen; +} + +#if 0 +struct test { test (); } test; + +test::test () +{ + basecoder cdc ("0123456789abcdefghijklmnopqrstuvwxyz"); + + u8 in[] = "0123456789abcdefghijklmnopqrstuvwxyz"; + static char enc[200]; + static u8 dec[200]; + + for (int i = 1; i < 20; i++) + { + int elen = cdc.encode (enc, in, i); + int dlen = cdc.decode (dec, enc, elen); + + printf ("%d>%d>%d (%s>%s)\n", i, elen, dlen, enc, dec); + } + abort (); +} #endif -#define MIN_RETRY 1. -#define MAX_RETRY 60. +//static basecoder cdc64 ("_dDpPhHzZrR06QqMmjJkKBb34TtSsvVlL81xXaAeEFf92WwGgYyoO57UucCNniI-"); +//static basecoder cdc63 ("_dDpPhHzZrR06QqMmjJkKBb34TtSsvVlL81xXaAeEFf92WwGgYyoO57UucCNniI"); +static basecoder cdc62 ("dDpPhHzZrR06QqMmjJkKBb34TtSsvVlL81xXaAeEFf92WwGgYyoO57UucCNniI"); +//static basecoder cdc36 ("dphzr06qmjkb34tsvl81xaef92wgyo57ucni"); // unused as of yet +static basecoder cdc26 ("dPhZrQmJkBtSvLxAeFwGyO"); -#define SERVER conf.dns_port +///////////////////////////////////////////////////////////////////////////// -/* +#define HDRSIZE 6 + +inline void encode_header (char *data, int clientid, int seqno, int retry = 0) +{ + seqno &= SEQNO_MASK; -protocol, in shorthand :) + u8 hdr[3] = { + clientid, + (seqno >> 8) | (retry << 6), + seqno, + }; - ANY? poll for more data - => TXT - TXT? send more data - => TXT + assert (clientid < 256); -sequence numbers are 12 bit, 9 bit packet-number and 3 bit fragment id (7 -- id, actually) last fragment is sent first, however + cdc26.encode (data, hdr, 3); +} -*/ +inline void decode_header (char *data, int &clientid, int &seqno) +{ + u8 hdr[3]; + + cdc26.decode (hdr, data, HDRSIZE); + + clientid = hdr[0]; + seqno = ((hdr[1] << 8) | hdr[2]) & SEQNO_MASK; +} + +///////////////////////////////////////////////////////////////////////////// + +struct byte_stream +{ + u8 *data; + int maxsize; + int fill; + + byte_stream (int maxsize); + ~byte_stream (); + + bool empty () { return !fill; } + int size () { return fill; } + + bool put (u8 *data, unsigned int datalen); + bool put (vpn_packet *pkt); + vpn_packet *get (); + + u8 *begin () { return data; } + void remove (int count); +}; + +byte_stream::byte_stream (int maxsize) +: maxsize (maxsize), fill (0) +{ + data = new u8 [maxsize]; +} + +byte_stream::~byte_stream () +{ + delete data; +} + +void byte_stream::remove (int count) +{ + if (count > fill) + assert (count <= fill); + + memmove (data, data + count, fill -= count); +} + +bool byte_stream::put (u8 *data, unsigned int datalen) +{ + if (maxsize - fill < datalen) + return false; + + memcpy (this->data + fill, data, datalen); fill += datalen; + + return true; +} + +bool byte_stream::put (vpn_packet *pkt) +{ + if (maxsize - fill < pkt->len + 2) + return false; + + data [fill++] = pkt->len >> 8; + data [fill++] = pkt->len; + + memcpy (data + fill, pkt->at (0), pkt->len); fill += pkt->len; + + return true; +} + +vpn_packet *byte_stream::get () +{ + unsigned int len; + + for (;;) + { + len = (data [0] << 8) | data [1]; + + if (len <= MAXSIZE || fill < 2) + break; + + // TODO: handle this better than skipping, e.g. by reset + slog (L_DEBUG, _("DNS: corrupted packet stream skipping a byte...")); + remove (1); + } + + if (fill < len + 2) + return 0; + + vpn_packet *pkt = new vpn_packet; + + pkt->len = len; + memcpy (pkt->at (0), data + 2, len); + remove (len + 2); + + return pkt; +} + +///////////////////////////////////////////////////////////////////////////// + +#define FLAG_QUERY ( 0 << 15) +#define FLAG_RESPONSE ( 1 << 15) +#define FLAG_OP_MASK (15 << 11) +#define FLAG_OP_QUERY ( 0 << 11) +#define FLAG_AA ( 1 << 10) +#define FLAG_TC ( 1 << 9) +#define FLAG_RD ( 1 << 8) +#define FLAG_RA ( 1 << 7) +#define FLAG_AUTH ( 1 << 5) +#define FLAG_RCODE_MASK (15 << 0) +#define FLAG_RCODE_OK ( 0 << 0) +#define FLAG_RCODE_FORMERR ( 1 << 0) +#define FLAG_RCODE_SERVFAIL ( 2 << 0) +#define FLAG_RCODE_NXDOMAIN ( 3 << 0) +#define FLAG_RCODE_REFUSED ( 5 << 0) + +#define DEFAULT_CLIENT_FLAGS (FLAG_QUERY | FLAG_OP_QUERY | FLAG_RD) +#define DEFAULT_SERVER_FLAGS (FLAG_RESPONSE | FLAG_OP_QUERY | FLAG_AA | FLAG_RD | FLAG_RA) + +struct dns_cfg +{ + static int next_uid; + + u8 id1, id2, id3, id4; + + u8 version; + u8 flags; + u8 rrtype; + u8 def_ttl; + + u16 client; + u16 uid; // to make request unique + + u16 max_size; + u8 seq_cdc; + u8 req_cdc; + + u8 rep_cdc; + u8 delay; // time in 0.01s units that the server may delay replying packets + u8 r3, r4; + + u8 r5, r6, r7, r8; + + void reset (int clientid); + bool valid (); +}; + +int dns_cfg::next_uid; + +void dns_cfg::reset (int clientid) +{ + id1 = 'G'; + id2 = 'V'; + id3 = 'P'; + id4 = 'E'; + + version = 1; + + rrtype = RR_TYPE_TXT; + flags = 0; + def_ttl = 0; + seq_cdc = 26; + req_cdc = 62; + rep_cdc = 0; + max_size = htons (MAX_PKT_SIZE); + client = htons (clientid); + uid = next_uid++; + delay = 0; + + r3 = r4 = 0; + r4 = r5 = r6 = r7 = 0; +} + +bool dns_cfg::valid () +{ + return id1 == 'G' + && id2 == 'V' + && id3 == 'P' + && id4 == 'E' + && seq_cdc == 26 + && req_cdc == 62 + && rep_cdc == 0 + && version == 1; +} + +struct dns_packet : net_packet +{ + u16 id; + u16 flags; // QR:1 Opcode:4 AA:1 TC:1 RD:1 RA:1 Z:3 RCODE:4 + u16 qdcount, ancount, nscount, arcount; + + u8 data [MAXSIZE - 6 * 2]; + + int decode_label (char *data, int size, int &offs); +}; + +int dns_packet::decode_label (char *data, int size, int &offs) +{ + char *orig = data; + + memset (data, 0, size); + + while (offs < size - 1) + { + u8 len = (*this)[offs++]; + + if (!len) + break; + else if (len < 64) + { + if (size < len + 1 || offs + len >= MAXSIZE - 1) + break; + + memcpy (data, &((*this)[offs]), len); + + data += len; size -= len; offs += len; + *data++ = '.'; size--; + } + else + { + int offs2 = ((len & 63) << 8) + (*this)[offs++]; + + data += decode_label (data, size, offs2); + break; + } + } + + return data - orig; +} + +///////////////////////////////////////////////////////////////////////////// + +static u16 dns_id = 0; // TODO: should be per-vpn + +static u16 next_id () +{ + if (!dns_id) + dns_id = time (0); + + // the simplest lsfr with periodicity 65535 i could find + dns_id = (dns_id << 1) + | (((dns_id >> 1) + ^ (dns_id >> 2) + ^ (dns_id >> 4) + ^ (dns_id >> 15)) & 1); + + return dns_id; +} + +struct dns_rcv; +struct dns_snd; + +struct dns_connection +{ + connection *c; + struct vpn *vpn; + + dns_cfg cfg; + + bool established; + + tstamp last_received; + tstamp last_sent; + double min_latency; + double poll_interval, send_interval; + + vector rcvpq; + + byte_stream rcvdq; int rcvseq; + byte_stream snddq; int sndseq; + + void time_cb (time_watcher &w); time_watcher tw; + void receive_rep (dns_rcv *r); + + dns_connection (connection *c); + ~dns_connection (); +}; + +struct dns_snd +{ + dns_packet *pkt; + tstamp timeout, sent; + int retry; + struct dns_connection *dns; + int seqno; + bool stdhdr; + + void gen_stream_req (int seqno, byte_stream &stream); + void gen_syn_req (); + + dns_snd (dns_connection *dns); + ~dns_snd (); +}; + +dns_snd::dns_snd (dns_connection *dns) +: dns (dns) +{ + timeout = 0; + retry = 0; + seqno = 0; + sent = NOW; + stdhdr = false; + + pkt = new dns_packet; + + pkt->id = next_id (); +} + +dns_snd::~dns_snd () +{ + delete pkt; +} + +static void append_domain (dns_packet &pkt, int &offs, const char *domain) +{ + // add tunnel domain + for (;;) + { + const char *end = strchr (domain, '.'); + + if (!end) + end = domain + strlen (domain); + + int len = end - domain; + + pkt [offs++] = len; + memcpy (pkt.at (offs), domain, len); + offs += len; + + if (!*end) + break; + + domain = end + 1; + } +} + +void dns_snd::gen_stream_req (int seqno, byte_stream &stream) +{ + stdhdr = true; + this->seqno = seqno; + + timeout = NOW + INITIAL_TIMEOUT; + + pkt->flags = htons (DEFAULT_CLIENT_FLAGS); + pkt->qdcount = htons (1); + + int offs = 6*2; + int dlen = MAX_DOMAIN_SIZE - (strlen (dns->c->conf->domain) + 2); + // MAX_DOMAIN_SIZE is technically 255, but bind doesn't compress responses well, + // so we need to have space for 2*MAX_DOMAIN_SIZE + header + extra + + char enc[256], *encp = enc; + encode_header (enc, THISNODE->id, seqno); + + int datalen = cdc62.decode_len (dlen - (dlen + MAX_LBL_SIZE - 1) / MAX_LBL_SIZE - HDRSIZE); + + if (datalen > stream.size ()) + datalen = stream.size (); + + int enclen = cdc62.encode (enc + HDRSIZE, stream.begin (), datalen) + HDRSIZE; + stream.remove (datalen); + + while (enclen) + { + int lbllen = enclen < MAX_LBL_SIZE ? enclen : MAX_LBL_SIZE; + + (*pkt)[offs++] = lbllen; + memcpy (pkt->at (offs), encp, lbllen); + + offs += lbllen; + encp += lbllen; + + enclen -= lbllen; + } + + append_domain (*pkt, offs, dns->c->conf->domain); + + (*pkt)[offs++] = 0; + (*pkt)[offs++] = RR_TYPE_ANY >> 8; (*pkt)[offs++] = RR_TYPE_ANY; + (*pkt)[offs++] = RR_CLASS_IN >> 8; (*pkt)[offs++] = RR_CLASS_IN; + + pkt->len = offs; +} + +void dns_snd::gen_syn_req () +{ + timeout = NOW + INITIAL_SYN_TIMEOUT; + + pkt->flags = htons (DEFAULT_CLIENT_FLAGS); + pkt->qdcount = htons (1); + + int offs = 6 * 2; + + int elen = cdc26.encode ((char *)pkt->at (offs + 1), (u8 *)&dns->cfg, sizeof (dns_cfg)); + + assert (elen <= MAX_LBL_SIZE); + + (*pkt)[offs] = elen; + offs += elen + 1; + append_domain (*pkt, offs, dns->c->conf->domain); + + (*pkt)[offs++] = 0; + (*pkt)[offs++] = RR_TYPE_A >> 8; (*pkt)[offs++] = RR_TYPE_A; + (*pkt)[offs++] = RR_CLASS_IN >> 8; (*pkt)[offs++] = RR_CLASS_IN; + + pkt->len = offs; +} + +struct dns_rcv +{ + int seqno; + dns_packet *pkt; // reply packet + u8 data [MAXSIZE]; // actually part of the reply packet... + int datalen; + + dns_rcv (int seqno, u8 *data, int datalen); + ~dns_rcv (); +}; + +dns_rcv::dns_rcv (int seqno, u8 *data, int datalen) +: seqno (seqno), pkt (new dns_packet), datalen (datalen) +{ + memcpy (this->data, data, datalen); +} + +dns_rcv::~dns_rcv () +{ + delete pkt; +} + +///////////////////////////////////////////////////////////////////////////// + +dns_connection::dns_connection (connection *c) +: c (c) +, rcvdq (MAX_BACKLOG * 2) +, snddq (MAX_BACKLOG * 2) +, tw (this, &dns_connection::time_cb) +{ + vpn = c->vpn; + + established = false; + + rcvseq = sndseq = 0; + + last_sent = last_received = 0; + poll_interval = 0.5; // starting here + send_interval = 0.5; // starting rate + min_latency = INITIAL_TIMEOUT; +} + +dns_connection::~dns_connection () +{ + for (vector::iterator i = rcvpq.begin (); + i != rcvpq.end (); + ++i) + delete *i; +} + +void dns_connection::receive_rep (dns_rcv *r) +{ + if (r->datalen) + { + last_received = NOW; + tw.trigger (); + + poll_interval = send_interval; + } + else + { + poll_interval *= 1.5; + + if (poll_interval > MAX_POLL_INTERVAL) + poll_interval = MAX_POLL_INTERVAL; + } + + rcvpq.push_back (r); + + redo: + + // find next packet + for (vector::iterator i = rcvpq.end (); i-- != rcvpq.begin (); ) + if (SEQNO_EQ (rcvseq, (*i)->seqno)) + { + // enter the packet into our input stream + r = *i; + + // remove the oldest packet, look forward, as it's oldest first + for (vector::iterator j = rcvpq.begin (); j != rcvpq.end (); ++j) + if (SEQNO_EQ ((*j)->seqno, rcvseq - MAX_WINDOW)) + { + delete *j; + rcvpq.erase (j); + break; + } + + rcvseq = (rcvseq + 1) & SEQNO_MASK; + + if (!rcvdq.put (r->data, r->datalen)) + { + slog (L_ERR, "DNS: !rcvdq.put (r->data, r->datalen)"); + abort (); // MUST never overflow, can be caused by data corruption, TODO + } + + while (vpn_packet *pkt = rcvdq.get ()) + { + sockinfo si; + si.host = 0x01010101; si.port = htons (c->conf->id); si.prot = PROT_DNSv4; + + vpn->recv_vpn_packet (pkt, si); + + delete pkt; + } + + // check for further packets + goto redo; + } +} + +void +vpn::dnsv4_server (dns_packet &pkt) +{ + u16 flags = ntohs (pkt.flags); + + int offs = 6 * 2; // skip header + + pkt.flags = htons (DEFAULT_SERVER_FLAGS | FLAG_RCODE_FORMERR); + + if (0 == (flags & (FLAG_RESPONSE | FLAG_OP_MASK)) + && pkt.qdcount == htons (1)) + { + char qname [MAXSIZE]; + int qlen = pkt.decode_label ((char *)qname, MAXSIZE - offs, offs); + + u16 qtype = pkt [offs++] << 8; qtype |= pkt [offs++]; + u16 qclass = pkt [offs++] << 8; qclass |= pkt [offs++]; + + pkt.qdcount = htons (1); + pkt.ancount = 0; + pkt.nscount = 0; // should be self, as other nameservers reply like this + pkt.arcount = 0; // a record for self, as other nameservers reply like this + + pkt.flags = htons (DEFAULT_SERVER_FLAGS | FLAG_RCODE_SERVFAIL); + + int dlen = strlen (THISNODE->domain); + + if (qclass == RR_CLASS_IN + && qlen > dlen + 1 + && !memcmp (qname + qlen - (dlen + 1), THISNODE->domain, dlen)) + { + // now generate reply + pkt.ancount = htons (1); // one answer RR + pkt.flags = htons (DEFAULT_SERVER_FLAGS | FLAG_RCODE_OK); + + if ((qtype == RR_TYPE_ANY + || qtype == RR_TYPE_TXT + || qtype == RR_TYPE_NULL) + && qlen > dlen + 1 + HDRSIZE) + { + // correct class, domain: parse + int client, seqno; + decode_header (qname, client, seqno); + + u8 data[MAXSIZE]; + int datalen = cdc62.decode (data, qname + HDRSIZE, qlen - (dlen + 1 + HDRSIZE)); + + if (0 < client && client <= conns.size ()) + { + connection *c = conns [client - 1]; + dns_connection *dns = c->dns; + dns_rcv *rcv; + bool in_seq; + + if (dns) + { + for (vector::iterator i = dns->rcvpq.end (); i-- != dns->rcvpq.begin (); ) + if (SEQNO_EQ ((*i)->seqno, seqno)) + { + // already seen that request: simply reply with the cached reply + dns_rcv *r = *i; + + slog (L_DEBUG, "DNS: duplicate packet received ID %d, SEQ %d", htons (r->pkt->id), seqno); + + // refresh header & id, as the retry count could have changed + memcpy (r->pkt->at (6 * 2 + 1), pkt.at (6 * 2 + 1), HDRSIZE); + r->pkt->id = pkt.id; + + memcpy (pkt.at (0), r->pkt->at (0), offs = r->pkt->len); + + goto duplicate_request; + } + + in_seq = dns->rcvseq == seqno; + + // new packet, queue + rcv = new dns_rcv (seqno, data, datalen); + dns->receive_rep (rcv); + } + + { + pkt [offs++] = 0xc0; pkt [offs++] = 6 * 2; // refer to name in query section + + int rtype = dns ? dns->cfg.rrtype : RR_TYPE_A; + pkt [offs++] = rtype >> 8; pkt [offs++] = rtype; // type + pkt [offs++] = RR_CLASS_IN >> 8; pkt [offs++] = RR_CLASS_IN; // class + pkt [offs++] = 0; pkt [offs++] = 0; + pkt [offs++] = 0; pkt [offs++] = dns ? dns->cfg.def_ttl : 0; // TTL + + int rdlen_offs = offs += 2; + + if (dns) + { + int dlen = ntohs (dns->cfg.max_size) - offs; + + // bind doesn't compress well, so reduce further by one label length + dlen -= qlen; + + // only put data into in-order sequence packets, if + // we receive out-of-order packets we generate empty + // replies + while (dlen > 1 && !dns->snddq.empty () && in_seq) + { + int txtlen = dlen <= 255 ? dlen - 1 : 255; + + if (txtlen > dns->snddq.size ()) + txtlen = dns->snddq.size (); + + pkt[offs++] = txtlen; + memcpy (pkt.at (offs), dns->snddq.begin (), txtlen); + offs += txtlen; + dns->snddq.remove (txtlen); + + dlen -= txtlen + 1; + } + + // avoid empty TXT rdata + if (offs == rdlen_offs) + pkt[offs++] = 0; + + slog (L_NOISE, "DNS: snddq %d", dns->snddq.size ()); + } + else + { + // send RST + pkt [offs++] = CMD_IP_1; pkt [offs++] = CMD_IP_2; pkt [offs++] = CMD_IP_3; + pkt [offs++] = CMD_IP_RST; + } + + int rdlen = offs - rdlen_offs; + + pkt [rdlen_offs - 2] = rdlen >> 8; + pkt [rdlen_offs - 1] = rdlen; + + if (dns) + { + // now update dns_rcv copy + rcv->pkt->len = offs; + memcpy (rcv->pkt->at (0), pkt.at (0), offs); + } + } + + duplicate_request: ; + } + else + pkt.flags = htons (DEFAULT_SERVER_FLAGS | FLAG_RCODE_FORMERR); + } + else if (qtype == RR_TYPE_A + && qlen > dlen + 1 + cdc26.encode_len (sizeof (dns_cfg))) + { + dns_cfg cfg; + cdc26.decode ((u8 *)&cfg, qname, cdc26.encode_len (sizeof (dns_cfg))); + int client = ntohs (cfg.client); + + pkt [offs++] = 0xc0; pkt [offs++] = 6 * 2; // refer to name in query section + + pkt [offs++] = RR_TYPE_A >> 8; pkt [offs++] = RR_TYPE_A; // type + pkt [offs++] = RR_CLASS_IN >> 8; pkt [offs++] = RR_CLASS_IN; // class + pkt [offs++] = 0; pkt [offs++] = 0; + pkt [offs++] = 0; pkt [offs++] = cfg.def_ttl; // TTL + pkt [offs++] = 0; pkt [offs++] = 4; // rdlength + + slog (L_INFO, _("DNS: client %d connects"), client); + + pkt [offs++] = CMD_IP_1; pkt [offs++] = CMD_IP_2; pkt [offs++] = CMD_IP_3; + pkt [offs++] = CMD_IP_REJ; + + if (0 < client && client <= conns.size ()) + { + connection *c = conns [client - 1]; + + if (cfg.valid ()) + { + pkt [offs - 1] = CMD_IP_SYN; + + delete c->dns; + c->dns = new dns_connection (c); + c->dns->cfg = cfg; + } + } + } + } + + pkt.len = offs; + } +} + +void +vpn::dnsv4_client (dns_packet &pkt) +{ + u16 flags = ntohs (pkt.flags); + int offs = 6 * 2; // skip header + + pkt.qdcount = ntohs (pkt.qdcount); + pkt.ancount = ntohs (pkt.ancount); + + // go through our request list and find the corresponding request + for (vector::iterator i = dns_sndpq.begin (); + i != dns_sndpq.end (); + ++i) + if ((*i)->pkt->id == pkt.id) + { + dns_connection *dns = (*i)->dns; + connection *c = dns->c; + int seqno = (*i)->seqno; + u8 data[MAXSIZE], *datap = data; + + if ((*i)->retry) + { + dns->send_interval *= 1.01; + if (dns->send_interval > MAX_SEND_INTERVAL) + dns->send_interval = MAX_SEND_INTERVAL; + } + else + { +#if 0 + dns->send_interval *= 0.999; +#endif + // the latency surely puts an upper bound on + // the minimum send interval + double latency = NOW - (*i)->sent; + + if (latency < dns->min_latency) + dns->min_latency = latency; + + if (dns->send_interval > dns->min_latency * LATENCY_FACTOR) + dns->send_interval = dns->min_latency * LATENCY_FACTOR; + + if (dns->send_interval < MIN_SEND_INTERVAL) + dns->send_interval = MIN_SEND_INTERVAL; + } + + delete *i; + dns_sndpq.erase (i); + + if (flags & FLAG_RESPONSE && !(flags & FLAG_OP_MASK)) + { + char qname[MAXSIZE]; + + while (pkt.qdcount-- && offs < MAXSIZE - 4) + { + int qlen = pkt.decode_label ((char *)qname, MAXSIZE - offs, offs); + offs += 4; // skip qtype, qclass + } + + while (pkt.ancount-- && offs < MAXSIZE - 10 && datap) + { + int qlen = pkt.decode_label ((char *)qname, MAXSIZE - offs, offs); + + u16 qtype = pkt [offs++] << 8; qtype |= pkt [offs++]; + u16 qclass = pkt [offs++] << 8; qclass |= pkt [offs++]; + u32 ttl = pkt [offs++] << 24; + ttl |= pkt [offs++] << 16; + ttl |= pkt [offs++] << 8; + ttl |= pkt [offs++]; + u16 rdlen = pkt [offs++] << 8; rdlen |= pkt [offs++]; + + if (qtype == RR_TYPE_NULL || qtype == RR_TYPE_TXT) + { + if (rdlen <= MAXSIZE - offs) + { + // decode bytes, finally + + while (rdlen) + { + int txtlen = pkt [offs++]; + + assert (txtlen + offs < MAXSIZE - 1); + + memcpy (datap, pkt.at (offs), txtlen); + datap += txtlen; offs += txtlen; + + rdlen -= txtlen + 1; + } + } + } + else if (qtype == RR_TYPE_A) + { + u8 ip [4]; + + ip [0] = pkt [offs++]; + ip [1] = pkt [offs++]; + ip [2] = pkt [offs++]; + ip [3] = pkt [offs++]; + + if (ip [0] == CMD_IP_1 + && ip [1] == CMD_IP_2 + && ip [2] == CMD_IP_3) + { + slog (L_TRACE, _("DNS: got tunnel meta command %02x"), ip [3]); + + if (ip [3] == CMD_IP_RST) + { + slog (L_DEBUG, _("DNS: got tunnel RST request")); + + delete dns; c->dns = 0; + + return; + } + else if (ip [3] == CMD_IP_SYN) + { + slog (L_DEBUG, _("DNS: got tunnel SYN reply, server likes us.")); + dns->established = true; + } + else if (ip [3] == CMD_IP_REJ) + { + slog (L_DEBUG, _("DNS: got tunnel REJ reply, server does not like us, aborting.")); + abort (); + } + else + slog (L_INFO, _("DNS: got unknown meta command %02x"), ip [3]); + } + else + slog (L_INFO, _("DNS: got spurious a record %d.%d.%d.%d"), + ip [0], ip [1], ip [2], ip [3]); + + return; + } + + int client, rseqno; + decode_header (qname, client, rseqno); + + if (client != THISNODE->id) + { + slog (L_INFO, _("DNS: got dns tunnel response with wrong clientid, ignoring")); + datap = 0; + } + else if (rseqno != seqno) + { + slog (L_DEBUG, _("DNS: got dns tunnel response with wrong seqno, badly caching nameserver?")); + datap = 0; + } + } + } + + // todo: pkt now used + if (datap) + dns->receive_rep (new dns_rcv (seqno, data, datap - data)); + + break; + } +} void vpn::dnsv4_ev (io_watcher &w, short revents) { if (revents & EVENT_READ) { + dns_packet *pkt = new dns_packet; struct sockaddr_in sa; socklen_t sa_len = sizeof (sa); - int len; + + pkt->len = recvfrom (w.fd, pkt->at (0), MAXSIZE, 0, (sockaddr *)&sa, &sa_len); + + if (pkt->len > 0) + { + if (ntohs (pkt->flags) & FLAG_RESPONSE) + dnsv4_client (*pkt); + else + { + dnsv4_server (*pkt); + sendto (w.fd, pkt->at (0), pkt->len, 0, (sockaddr *)&sa, sa_len); + } + + delete pkt; + } } } bool vpn::send_dnsv4_packet (vpn_packet *pkt, const sockinfo &si, int tos) { - //return i->send_packet (pkt, tos); + int client = ntohs (si.port); + + assert (0 < client && client <= conns.size ()); + + connection *c = conns [client - 1]; + + if (!c->dns) + c->dns = new dns_connection (c); + + if (!c->dns->snddq.put (pkt)) + return false; + + c->dns->tw.trigger (); + + return true; +} + +void +connection::dnsv4_reset_connection () +{ + //delete dns; dns = 0; //TODO +} + +#define NEXT(w) do { if (next > (w)) next = w; } while (0) + +void +dns_connection::time_cb (time_watcher &w) +{ + // servers have to be polled + if (THISNODE->dns_port) + return; + + // check for timeouts and (re)transmit + tstamp next = NOW + poll_interval; + dns_snd *send = 0; + + for (vector::iterator i = vpn->dns_sndpq.begin (); + i != vpn->dns_sndpq.end (); + ++i) + { + dns_snd *r = *i; + + if (r->timeout <= NOW) + { + if (!send) + { + send = r; + + r->retry++; + r->timeout = NOW + (r->retry * min_latency * 8.); + + // the following code changes the query section a bit, forcing + // the forwarder to generate a new request + if (r->stdhdr) + { + //printf ("reencoded header for ID %d retry %d:%d:%d (%p)\n", htons (r->pkt->id), THISNODE->id, r->seqno, r->retry); + //encode_header ((char *)r->pkt->at (6 * 2 + 1), THISNODE->id, r->seqno, r->retry); + } + } + } + else + NEXT (r->timeout); + } + + if (!send) + { + // generate a new packet, if wise + + if (!established) + { + if (vpn->dns_sndpq.empty ()) + { + send = new dns_snd (this); + + cfg.reset (THISNODE->id); + send->gen_syn_req (); + } + } + else if (vpn->dns_sndpq.size () < MAX_OUTSTANDING + && !SEQNO_EQ (rcvseq, sndseq - (MAX_WINDOW - 1))) + { + if (last_sent + send_interval <= NOW) + { + //printf ("sending data request etc.\n"); //D + if (!snddq.empty () || last_received + 1. > NOW) + { + poll_interval = send_interval; + NEXT (NOW + send_interval); + } + + send = new dns_snd (this); + send->gen_stream_req (sndseq, snddq); + send->timeout = NOW + min_latency * 8.; + + sndseq = (sndseq + 1) & SEQNO_MASK; + } + else + NEXT (last_sent + send_interval); + } + + if (send) + vpn->dns_sndpq.push_back (send); + } + + if (send) + { + last_sent = NOW; + sendto (vpn->dnsv4_fd, + send->pkt->at (0), send->pkt->len, 0, + vpn->dns_forwarder.sav4 (), vpn->dns_forwarder.salenv4 ()); + } + + slog (L_NOISE, "DNS: pi %f si %f N %f (%d:%d %d)", + poll_interval, send_interval, next - NOW, + vpn->dns_sndpq.size (), snddq.size (), + rcvpq.size ()); + + // TODO: no idea when this happens, but when next < NOW, we have a problem + if (next < NOW + 0.001) + next = NOW + 0.1; + + w.start (next); } #endif