--- gvpe/src/vpn_dns.C 2005/03/02 05:49:31 1.4 +++ gvpe/src/vpn_dns.C 2007/11/10 05:14:22 1.42 @@ -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. @@ -13,10 +15,14 @@ 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 - Foundation, Inc. 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA + along with gvpe; if not, write to the Free Software + Foundation, Inc. 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA */ +// TODO: EDNS0 option to increase dns mtu? +// TODO: re-write dns packet parsing/creation using a safe mem-buffer +// to ensure no buffer overflows or similar problems. + #include "config.h" #if ENABLE_DNS @@ -25,6 +31,7 @@ // it's a hack, use only in emergency situations please. #include +#include #include #include @@ -37,114 +44,254 @@ #include +#include + #include "netcompat.h" #include "vpn.h" -#define MIN_RETRY 1. -#define MAX_RETRY 60. - -#define MAX_OUTSTANDING 10 // max. outstanding requests -#define MAX_WINDOW 100 // max. for MAX_OUTSTANDING -#define MAX_RATE 1 // requests/s -#define MAX_BACKLOG (10*1024) // size of protocol backlog - -/* - -protocol, in shorthand :) +#define MAX_POLL_INTERVAL 5. // how often to poll minimally when the server has no data +#define ACTIVITY_INTERVAL 5. -client -> server ANY? -server -> client TXT +#define INITIAL_TIMEOUT 0.1 // retry timeouts +#define INITIAL_SYN_TIMEOUT 2. // retry timeout for initial syn - is dns64-encoded [] - is dns64-encoded <0:12>[] +#define MAX_SEND_INTERVAL 2. // optimistic? -if is zero, the connection will be configured: +#define MAX_WINDOW 1000 // max. for MAX_OUTSTANDING, and backlog +#define MAX_BACKLOG (64*1024) // size of gvpe protocol backlog (bytes), must be > MAXSIZE -<0:12><0:4>client-id:12> +#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 request byte less give room for two reply bytes -*/ +#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_TXT 16 +#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 -// the "_" is not valid but widely accepted (all octets should be supported, but let's be conservative) -struct dns64 -{ - static const char encode_chars[64 + 1]; - static s8 decode_chars[256]; +#define RR_CLASS_IN 1 - static int encode_len (int bytes) { return (bytes * 8 + 5) / 6; } - static int decode_len (int bytes) { return (bytes * 6) / 8; } - static int encode (char *dst, u8 *src, int len); - static int decode (u8 *dst, char *src, int len); +#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 - dns64 (); -} dns64; +// works for cmaps up to 255 (not 256!) +struct charmap +{ + enum { INVALID = (u8)255 }; -const char dns64::encode_chars[64 + 1] = "0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ_-"; -s8 dns64::decode_chars[256]; + char encode [256]; // index => char + u8 decode [256]; // char => index + unsigned int size; -dns64::dns64 () + charmap (const char *cmap); +}; + +charmap::charmap (const char *cmap) { - for (int i = 0; i < 64; i++) - decode_chars [encode_chars [i]] = i + 1; + 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); } -int dns64::encode (char *dst, u8 *src, int len) +#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 { - // slow, but easy to debug - char *beg = dst; - unsigned int accum, bits = 0; + charmap cmap; + unsigned int enc_len [MAX_DEC_LEN]; + unsigned int dec_len [MAX_ENC_LEN]; - while (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) { - accum <<= 8; - accum |= *src++; - bits += 8; + u8 src [MAX_DEC_LEN]; + u8 dst [MAX_ENC_LEN]; - while (bits >= 6) - { - *dst++ = encode_chars [(accum >> (bits - 6)) & 63]; - bits -= 6; - } + 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--; } - if (bits) - *dst++ = encode_chars [(accum << (6 - bits)) & 63]; + for (unsigned int i = n - plen; i < n; ++i) + *dst++ = cmap.encode [dst_ [i]]; - return dst - beg; + return elen; } -int dns64::decode (u8 *dst, char *src, int len) +unsigned int basecoder::decode (u8 *dst, char *src, unsigned int len) { - // slow, but easy to debug - u8 *beg = dst; - unsigned int accum, bits = 0; + if (!len || len > MAX_ENC_LEN) + return 0; + + u8 src_ [MAX_ENC_LEN]; + unsigned int elen = 0; while (len--) { - s8 chr = decode_chars [(u8)*src++]; + u8 val = cmap.decode [(u8)*src++]; - if (!chr) - break; + if (val != charmap::INVALID) + src_ [elen++] = val; + } - accum <<= 6; - accum |= chr - 1; - bits += 6; + int dlen = decode_len (elen); - while (bits >= 8) - { - *dst++ = accum >> (bits - 8); - bits -= 8; - } + 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"); - return dst - beg; + 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 + +//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 HDRSIZE 6 + +inline void encode_header (char *data, int clientid, int seqno, int retry = 0) +{ + seqno &= SEQNO_MASK; + + u8 hdr[3] = { + clientid, + (seqno >> 8) | (retry << 6), + seqno, + }; + + assert (clientid < 256); + + 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; } ///////////////////////////////////////////////////////////////////////////// @@ -161,6 +308,7 @@ bool empty () { return !fill; } int size () { return fill; } + bool put (u8 *data, unsigned int datalen); bool put (vpn_packet *pkt); vpn_packet *get (); @@ -182,11 +330,21 @@ void byte_stream::remove (int count) { if (count > fill) - abort (); + 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) @@ -195,20 +353,34 @@ data [fill++] = pkt->len >> 8; data [fill++] = pkt->len; - memcpy (data + fill, &((*pkt)[0]), pkt->len); fill += pkt->len; + memcpy (data + fill, pkt->at (0), pkt->len); fill += pkt->len; return true; } vpn_packet *byte_stream::get () { - int len = (data [0] << 8) | data [1]; + 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; - memcpy (&((*pkt)[0]), data + 2, len); + + pkt->len = len; + memcpy (pkt->at (0), data + 2, len); remove (len + 2); return pkt; @@ -218,12 +390,13 @@ #define FLAG_QUERY ( 0 << 15) #define FLAG_RESPONSE ( 1 << 15) -#define FLAG_OP_MASK (15 << 14) +#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) @@ -232,7 +405,75 @@ #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) +#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 () +{ + // although the protocol itself allows for some configurability, + // only the following encoding/decoding settings are implemented. + 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 { @@ -240,7 +481,7 @@ 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]; + u8 data [MAXSIZE - 6 * 2]; int decode_label (char *data, int size, int &offs); }; @@ -281,370 +522,791 @@ ///////////////////////////////////////////////////////////////////////////// -struct dns_req +static u16 dns_id = 0; // TODO: should be per-vpn + +static u16 next_id () { - dns_packet *pkt; - tstamp next; - int retry; - connection *conn; + if (!dns_id) + dns_id = time (0); - dns_req (connection *c, int seqno, byte_stream *stream); -}; + // 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); -struct dns_rep -{ -}; + return dns_id; +} -static u16 dns_id; // TODO: should be per-vpn +struct dns_rcv; +struct dns_snd; -dns_req::dns_req (connection *c, int seqno, byte_stream *stream) -: conn (c) +struct dns_connection { - next = 0; - retry = 0; + connection *c; + struct vpn *vpn; - pkt = new dns_packet; + dns_cfg cfg; - pkt->id = dns_id++; - pkt->flags = DEFAULT_CLIENT_FLAGS; - pkt->qdcount = htons (1); - pkt->ancount = 0; - pkt->nscount = 0; - pkt->arcount = 0; + bool established; - int offs = 6*2; - int dlen = 255 - strlen (THISNODE->domain) - 1; // here we always have room for the max. label length + tstamp last_received; + tstamp last_sent; + double min_latency; + double poll_interval, send_interval; - u8 lbl[64]; //D - char enc[65]; - int lbllen = 3; - lbl[0] = c->conf->id; //D - lbl[1] = seqno >> 8; //D - lbl[2] = seqno; //D + vector rcvpq; - while (dlen > 0) - { - int sndlen = dlen; + byte_stream rcvdq; int rcvseq; int repseq; + byte_stream snddq; int sndseq; - if (sndlen + lbllen > dns64::decode_len (MAX_LBL_SIZE)) - sndlen = dns64::decode_len (MAX_LBL_SIZE) - lbllen; + void time_cb (ev::timer &w, int revents); ev::timer tw; + void receive_rep (dns_rcv *r); - if (sndlen > stream->size ()) - sndlen = stream->size (); + dns_connection (connection *c); + ~dns_connection (); +}; - if (sndlen + lbllen == 0) - break; +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 (); - memcpy (lbl + lbllen, stream->begin (), sndlen); - stream->remove (sndlen); - lbllen += sndlen; + dns_snd (dns_connection *dns); + ~dns_snd (); +}; - dns64::encode (enc, lbl, lbllen); +dns_snd::dns_snd (dns_connection *dns) +: dns (dns) +{ + timeout = 0; + retry = 0; + seqno = 0; + sent = ev::ev_now (); + stdhdr = false; - int elen = dns64::encode_len (lbllen); - (*pkt)[offs++] = elen; - memcpy (&((*pkt)[offs]), enc, elen); - offs += elen; - dlen -= elen + 1; + pkt = new dns_packet; - lbllen = 0; - } + pkt->id = next_id (); +} - const char *suffix = THISNODE->domain; +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 (suffix, '.'); + const char *end = strchr (domain, '.'); if (!end) - end = suffix + strlen (suffix); + end = domain + strlen (domain); - int len = end - suffix; + int len = end - domain; - (*pkt)[offs++] = len; - memcpy (&((*pkt)[offs]), suffix, len); + pkt [offs++] = len; + memcpy (pkt.at (offs), domain, len); offs += len; if (!*end) break; - suffix = end + 1; + domain = end + 1; + } +} + +void dns_snd::gen_stream_req (int seqno, byte_stream &stream) +{ + stdhdr = true; + this->seqno = seqno; + + timeout = ev::ev_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; - - c->vpn->dns_sndpq.push_back (this); } -///////////////////////////////////////////////////////////////////////////// +void dns_snd::gen_syn_req () +{ + timeout = ev::ev_now () + INITIAL_SYN_TIMEOUT; -struct dns_cfg + 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 { - u8 id1, id2, id3; - u8 def_ttl; - u8 unused1; - u16 max_size; - u8 flags1, flags2; + 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_packet * -vpn::dnsv4_server (dns_packet *pkt) +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 () { - u16 flags = ntohs (pkt->flags); + delete pkt; +} - //memcpy (&((*rep)[0]), &((*pkt)[0]), pkt->len); - int offs = 6 * 2; // skip header +///////////////////////////////////////////////////////////////////////////// + +dns_connection::dns_connection (connection *c) +: c (c) +, rcvdq (MAX_BACKLOG * 2) +, snddq (MAX_BACKLOG) +, tw (this, &dns_connection::time_cb) +{ + vpn = c->vpn; + + established = false; + + rcvseq = repseq = sndseq = 0; + + last_sent = last_received = 0; + poll_interval = 0.5; // starting here + send_interval = 0.5; // starting rate + min_latency = INITIAL_TIMEOUT; +} - pkt->flags = htons (DEFAULT_SERVER_FLAGS | FLAG_RCODE_FORMERR); +dns_connection::~dns_connection () +{ + for (vector::iterator i = rcvpq.begin (); + i != rcvpq.end (); + ++i) + delete *i; +} - if (!(flags & (FLAG_RESPONSE | FLAG_OP_MASK | FLAG_TC)) - && pkt->qdcount == htons (1)) +void dns_connection::receive_rep (dns_rcv *r) +{ + if (r->datalen) { - char qname[MAXSIZE]; - int qlen = pkt->decode_label ((char *)qname, MAXSIZE - offs, offs); + last_received = ev::ev_now (); + tw (); + + poll_interval = send_interval; + } + else + { + poll_interval *= 1.5; - printf ("rcvd packet len %d, id%04x flags%04x q%04x a%04x n%04x a%04x <%s>\n", pkt->len, - pkt->id, flags, pkt->qdcount, pkt->ancount, pkt->nscount, pkt->arcount, qname);//D + if (poll_interval > MAX_POLL_INTERVAL) + poll_interval = MAX_POLL_INTERVAL; + } - u16 qtype = (*pkt) [offs++] << 8; qtype |= (*pkt) [offs++]; - u16 qclass = (*pkt) [offs++] << 8; qclass |= (*pkt) [offs++]; + rcvpq.push_back (r); - 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 + redo: - pkt->flags = htons (DEFAULT_SERVER_FLAGS | FLAG_RCODE_NXDOMAIN); + // find next packet + for (vector::iterator i = rcvpq.end (); i-- != rcvpq.begin (); ) + if (SEQNO_EQ (rcvseq, (*i)->seqno)) + { + //printf ("seqno eq %x %x\n", rcvseq, (*i)->seqno);//D + // 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)) + { + //printf ("seqno RR %x %x\n", (*j)->seqno, rcvseq - MAX_WINDOW);//D + delete *j; + rcvpq.erase (j); + break; + } - int dlen = strlen (THISNODE->domain); + rcvseq = (rcvseq + 1) & SEQNO_MASK; - if (qclass == RR_CLASS_IN - && (qtype == RR_TYPE_ANY || qtype == RR_TYPE_TXT) - && qlen > dlen + 1 - && !memcmp (qname + qlen - dlen - 1, THISNODE->domain, dlen)) - { - // correct class, domain, parse - u8 data[MAXSIZE]; - int datalen = dns64::decode (data, qname, qlen - dlen - 1); - - for (int i = 0; i < datalen; i++) - printf ("%02x ", data[i]); - printf ("\n"); + 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 = htonl (c->conf->id); si.port = 0; si.prot = PROT_DNSv4; + vpn->recv_vpn_packet (pkt, si); -#if 0 - // now generate reply - rep->ancount = htons (1); // one answer RR - rep->flags = htons (DEFAULT_SERVER_FLAGS | FLAG_RCODE_OK); - - (*rep) [offs++] = 0xc0; - (*rep) [offs++] = 6 * 2; // same as in query section + delete pkt; + } - (*rep) [offs++] = RR_TYPE_TXT >> 8; (*rep) [offs++] = RR_TYPE_TXT; - (*rep) [offs++] = RR_CLASS_IN >> 8; (*rep) [offs++] = RR_CLASS_IN; + // check for further packets + goto redo; + } +} - (*rep) [offs++] = 0; (*rep) [offs++] = 0; - (*rep) [offs++] = 0; (*rep) [offs++] = 0; // TTL +void +vpn::dnsv4_server (dns_packet &pkt) +{ + u16 flags = ntohs (pkt.flags); - int dlen = MAX_PKT_SIZE - offs - 2; + int offs = 6 * 2; // skip header - printf ("we have room for %d bytes\n", dlen); + pkt.flags = htons (DEFAULT_SERVER_FLAGS | FLAG_RCODE_FORMERR); - int rdlen_offs = offs += 2; + 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); - u8 txt[255]; - txt[0] = 0; - txt[1] = 0; + u16 qtype = pkt [offs++] << 8; qtype |= pkt [offs++]; + u16 qclass = pkt [offs++] << 8; qclass |= pkt [offs++]; - int txtlen = 2; + 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 - while (dlen > 1) - { - int sndlen = --dlen; + pkt.flags = htons (DEFAULT_SERVER_FLAGS | FLAG_RCODE_SERVFAIL); - if (sndlen + txtlen > 255) - sndlen = 255 - txtlen; + int dlen = strlen (THISNODE->domain); - sndlen = 0; + 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); - (*rep)[offs++] = sndlen + txtlen; - memcpy (&((*rep)[offs]), txt, txtlen); - offs += txtlen; + 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; + + 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; + } + + // new packet, queue + rcv = new dns_rcv (seqno, data, datalen); + dns->receive_rep (rcv); + } - //if (sndlen + txtlen > dns_snddq. - } + { + pkt [offs++] = 0xc0; pkt [offs++] = 6 * 2; // refer to name in query section - int rdlen = offs - rdlen_offs; + 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 + //printf ("%d - %d & %x (=%d) < %d\n", seqno, dns->repseq, SEQNO_MASK, (seqno - dns->repseq) & SEQNO_MASK, MAX_WINDOW);//D + if (((seqno - dns->repseq) & SEQNO_MASK) <= MAX_WINDOW) + { + dns->repseq = seqno; + + while (dlen > 1 && !dns->snddq.empty ()) + { + 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 completely 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); + } + } - (*rep) [rdlen_offs - 2] = rdlen >> 8; - (*rep) [rdlen_offs - 1] = rdlen; -#endif + 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; - return pkt; + pkt.len = offs; + } } void -vpn::dnsv4_client (dns_packet *pkt) +vpn::dnsv4_client (dns_packet &pkt) { - u16 flags = ntohs (pkt->flags); + u16 flags = ntohs (pkt.flags); int offs = 6 * 2; // skip header - pkt->qdcount = ntohs (pkt->qdcount); - pkt->ancount = ntohs (pkt->ancount); + pkt.qdcount = ntohs (pkt.qdcount); + pkt.ancount = ntohs (pkt.ancount); - for (vector::iterator i = dns_sndpq.begin (); + // 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) + if ((*i)->pkt->id == pkt.id) { - connection *c = (*i)->conn; - printf ("GOT RESPONSE id %x %p\n", pkt->id, c);//D + dns_connection *dns = (*i)->dns; + connection *c = dns->c; + int seqno = (*i)->seqno; + u8 data[MAXSIZE], *datap = data; + //printf ("rcv pkt %x\n", seqno);//D + + 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 = ev::ev_now () - (*i)->sent; + + if (latency < dns->min_latency) + dns->min_latency = latency; + + if (dns->send_interval > dns->min_latency * conf.dns_overlap_factor) + dns->send_interval = dns->min_latency * conf.dns_overlap_factor; + + if (dns->send_interval < conf.dns_send_interval) + dns->send_interval = conf.dns_send_interval; + } + delete *i; dns_sndpq.erase (i); - if (flags & (FLAG_RESPONSE | FLAG_OP_MASK | FLAG_TC)) + if (flags & FLAG_RESPONSE && !(flags & FLAG_OP_MASK)) { char qname[MAXSIZE]; - while (pkt->qdcount-- && offs < MAXSIZE - 4) + while (pkt.qdcount-- && offs < MAXSIZE - 4) { - int qlen = pkt->decode_label ((char *)qname, MAXSIZE - offs, offs); + int qlen = pkt.decode_label ((char *)qname, MAXSIZE - offs, offs); offs += 4; // skip qtype, qclass } - while (pkt->ancount-- && offs < MAXSIZE - 10) + while (pkt.ancount-- && offs < MAXSIZE - 10 && datap) { - pkt->decode_label ((char *)qname, MAXSIZE - offs, offs); + 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 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]; - u16 rdlen = (*pkt) [offs++] << 8; rdlen |= (*pkt) [offs++]; + 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]); - printf ("REPLY %d:%d TTL %d RD %d\n", qtype, qclass, ttl, rdlen); + return; + } - offs += rdlen; + int client, rseqno; + decode_header (qname, client, rseqno); - if (MAXSIZE - offs < rdlen) + if (client != THISNODE->id) + { + slog (L_INFO, _("DNS: got dns tunnel response with wrong clientid, ignoring")); + datap = 0; + } + else if (rseqno != seqno) { - // decode bytes, finally + 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) +vpn::dnsv4_ev (ev::io &w, int revents) { - if (revents & EVENT_READ) + if (revents & EV_READ) { dns_packet *pkt = new dns_packet; struct sockaddr_in sa; socklen_t sa_len = sizeof (sa); - pkt->len = recvfrom (w.fd, &((*pkt)[0]), MAXSIZE, 0, (sockaddr *)&sa, &sa_len); + pkt->len = recvfrom (w.fd, pkt->at (0), MAXSIZE, 0, (sockaddr *)&sa, &sa_len); if (pkt->len > 0) - if (THISNODE->dns_port) - { - pkt = dnsv4_server (pkt); - sendto (w.fd, &((*pkt)[0]), pkt->len, 0, (sockaddr *)&sa, sa_len); - } - else - dnsv4_client (pkt); + { + 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 -connection::send_dnsv4_packet (vpn_packet *pkt, const sockinfo &si, int tos) +vpn::send_dnsv4_packet (vpn_packet *pkt, const sockinfo &si, int tos) { - // never initialized - if (!dns_snddq && !dns_rcvdq) - { - dns_rcvdq = new byte_stream (MAX_BACKLOG * 2); - dns_snddq = new byte_stream (MAX_BACKLOG); + int client = ntohl (si.host); - dns_rcvseq = dns_sndseq = 0; + assert (0 < client && client <= conns.size ()); - dns_si.set (::conf.dns_forw_host, ::conf.dns_forw_port, PROT_DNSv4); - } - - if (!dns_snddq->put (pkt)) - return false; + connection *c = conns [client - 1]; - // start timer if neccessary - if (!dnsv4_tw.active) - dnsv4_cb (dnsv4_tw); + if (!c->dns) + c->dns = new dns_connection (c); + + if (c->dns->snddq.put (pkt)) + c->dns->tw (); + // always return true even if the buffer overflows return true; } void -connection::dnsv4_cb (time_watcher &w) +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 (ev::timer &w, int revents) +{ + // servers have to be polled + if (THISNODE->dns_port) + return; + // check for timeouts and (re)transmit - tstamp next = NOW + 60; - dns_req *send = 0; + tstamp next = ev::now () + poll_interval; + dns_snd *send = 0; - slog (L_NOISE, _("dnsv4, %d packets in send queue\n"), vpn->dns_sndpq.size ()); - - for (vector::iterator i = vpn->dns_sndpq.begin (); + for (vector::iterator i = vpn->dns_sndpq.begin (); i != vpn->dns_sndpq.end (); ++i) { - dns_req *r = *i; + dns_snd *r = *i; - if (r->next <= NOW) + if (r->timeout <= ev::ev_now ()) { if (!send) { send = r; - slog (L_NOISE, _("dnsv4, send req %d\n"), r->pkt->id); r->retry++; - r->next = NOW + r->retry; + r->timeout = ev::ev_now () + (r->retry * min_latency * conf.dns_timeout_factor); + //printf ("RETRY %x (%d, %f)\n", r->seqno, r->retry, r->timeout - ev::ev_now ());//D + + // the following code changes the query section a bit, forcing + // the forwarder to generate a new request + if (r->stdhdr) + encode_header ((char *)r->pkt->at (6 * 2 + 1), THISNODE->id, r->seqno, r->retry); } } - - if (r->next < next) - next = r->next; + else + NEXT (r->timeout); } - if (!send - && vpn->dns_sndpq.size () < MAX_OUTSTANDING) - send = new dns_req (this, dns_sndseq++, dns_snddq); + if (!send) + { + // generate a new packet, if wise - tstamp min_next = NOW + (1. / (tstamp)MAX_RATE); + if (!established) + { + if (vpn->dns_sndpq.empty ()) + { + send = new dns_snd (this); - if (send) - { - dns_packet *pkt = send->pkt; + cfg.reset (THISNODE->id); + send->gen_syn_req (); + } + } + else if (vpn->dns_sndpq.size () < conf.dns_max_outstanding + && !SEQNO_EQ (rcvseq, sndseq - (MAX_WINDOW - 1))) + { + if (last_sent + send_interval <= ev::ev_now ()) + { + //printf ("sending data request etc.\n"); //D + if (!snddq.empty () || last_received + 1. > ev::ev_now ()) + { + poll_interval = send_interval; + NEXT (ev::ev_now () + send_interval); + } + + send = new dns_snd (this); + send->gen_stream_req (sndseq, snddq); + send->timeout = ev::ev_now () + min_latency * conf.dns_timeout_factor; + //printf ("SEND %x (%f)\n", send->seqno, send->timeout - ev::ev_now (), min_latency, conf.dns_timeout_factor);//D - next = min_next; + sndseq = (sndseq + 1) & SEQNO_MASK; + } + else + NEXT (last_sent + send_interval); + } - sendto (vpn->dnsv4_fd, &((*pkt)[0]), pkt->len, 0, dns_si.sav4 (), dns_si.salenv4 ()); + if (send) + vpn->dns_sndpq.push_back (send); } - else if (next < min_next) - next = min_next; - w.start (next); + if (send) + { + last_sent = ev::ev_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 - ev::ev_now (), + vpn->dns_sndpq.size (), snddq.size (), + rcvpq.size ()); + + // TODO: no idea when this happens, but when next < ev::ev_now (), we have a problem + // doesn't seem to happen anymore + if (next < ev::ev_now () + 0.001) + next = ev::ev_now () + 0.1; + + w.start (next - ev::ev_now ()); } #endif