--- gvpe/src/vpn_dns.C 2005/03/04 04:52:38 1.9 +++ gvpe/src/vpn_dns.C 2007/12/06 00:35:29 1.46 @@ -16,9 +16,13 @@ You should have received a copy of the GNU General Public License along with gvpe; if not, write to the Free Software - Foundation, Inc. 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA + 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 @@ -27,6 +31,7 @@ // it's a hack, use only in emergency situations please. #include +#include #include #include @@ -39,33 +44,47 @@ #include +#include /* bug in libgmp: gmp.h relies on cstdio being included */ #include #include "netcompat.h" #include "vpn.h" -#define MIN_RETRY 1. -#define MAX_RETRY 6. +#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 2. // retry timeout for initial syn -#define MAX_OUTSTANDING 400 // max. outstanding requests -#define MAX_WINDOW 1000 // max. for MAX_OUTSTANDING -#define MAX_RATE 100 // requests/s -#define MAX_BACKLOG (10*1024) // size of protocol backlog, must be > MAXSIZE +#define MAX_SEND_INTERVAL 2. // optimistic? -#define MAX_DOMAIN_SIZE 220 // 255 is legal limit, but bind doesn't compress well +#define MAX_WINDOW 1000 // max. for MAX_OUTSTANDING, and backlog +#define MAX_BACKLOG (64*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 byte sless give room for one reply byte +// every request byte less give room for two reply bytes -#define SEQNO_MASK 0xffff +#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 + +#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 @@ -155,7 +174,7 @@ unsigned int basecoder::encode (char *dst, u8 *src, unsigned int len) { - if (!len) + if (!len || len > MAX_DEC_LEN) return 0; int elen = encode_len (len); @@ -184,7 +203,7 @@ unsigned int basecoder::decode (u8 *dst, char *src, unsigned int len) { - if (!len) + if (!len || len > MAX_ENC_LEN) return 0; u8 src_ [MAX_ENC_LEN]; @@ -241,11 +260,7 @@ } #endif -// the following sequence has been crafted to -// a) look somewhat random -// b) the even (and odd) indices never share the same character as upper/lowercase -// the "_" is not valid but widely accepted (all octets should be supported, but let's be conservative) -// the other sequences are obviously derived +//static basecoder cdc64 ("_dDpPhHzZrR06QqMmjJkKBb34TtSsvVlL81xXaAeEFf92WwGgYyoO57UucCNniI-"); //static basecoder cdc63 ("_dDpPhHzZrR06QqMmjJkKBb34TtSsvVlL81xXaAeEFf92WwGgYyoO57UucCNniI"); static basecoder cdc62 ("dDpPhHzZrR06QqMmjJkKBb34TtSsvVlL81xXaAeEFf92WwGgYyoO57UucCNniI"); //static basecoder cdc36 ("dphzr06qmjkb34tsvl81xaef92wgyo57ucni"); // unused as of yet @@ -254,10 +269,16 @@ ///////////////////////////////////////////////////////////////////////////// #define HDRSIZE 6 - -inline void encode_header (char *data, int clientid, int seqno) + +inline void encode_header (char *data, int clientid, int seqno, int retry = 0) { - u8 hdr[3] = { clientid, seqno >> 8, seqno }; + seqno &= SEQNO_MASK; + + u8 hdr[3] = { + clientid, + (seqno >> 8) | (retry << 6), + seqno, + }; assert (clientid < 256); @@ -271,7 +292,7 @@ cdc26.decode (hdr, data, HDRSIZE); clientid = hdr[0]; - seqno = (hdr[1] << 8) | hdr[2]; + seqno = ((hdr[1] << 8) | hdr[2]) & SEQNO_MASK; } ///////////////////////////////////////////////////////////////////////////// @@ -310,7 +331,7 @@ void byte_stream::remove (int count) { if (count > fill) - abort (); + assert (count <= fill); memmove (data, data + count, fill -= count); } @@ -333,25 +354,34 @@ 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) - abort (); // TODO handle this gracefully, connection reset + 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)[0]), data + 2, len); + memcpy (pkt->at (0), data + 2, len); remove (len + 2); return pkt; @@ -378,13 +408,81 @@ #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 () +{ + // 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 { 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]; + u8 data [MAXSIZE - 6 * 2]; int decode_label (char *data, int size, int &offs); }; @@ -425,22 +523,13 @@ ///////////////////////////////////////////////////////////////////////////// -struct dns_req -{ - dns_packet *pkt; - tstamp next; - int retry; - struct dns_connection *dns; - int seqno; - - dns_req (dns_connection *dns); - void gen_stream_req (int seqno, byte_stream &stream); -}; - -static u16 dns_id = 12098; // TODO: should be per-vpn +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) @@ -451,26 +540,105 @@ return dns_id; } -dns_req::dns_req (dns_connection *dns) +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; int repseq; + byte_stream snddq; int sndseq; + + inline void time_cb (ev::timer &w, int revents); ev::timer 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) { - next = 0; + timeout = 0; retry = 0; + seqno = 0; + sent = ev_now (); + stdhdr = false; pkt = new dns_packet; pkt->id = next_id (); } -void dns_req::gen_stream_req (int seqno, byte_stream &stream) +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 = ev_now () + INITIAL_TIMEOUT; + pkt->flags = htons (DEFAULT_CLIENT_FLAGS); pkt->qdcount = htons (1); int offs = 6*2; - int dlen = MAX_DOMAIN_SIZE - (strlen (THISNODE->domain) + 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 @@ -498,30 +666,34 @@ enclen -= lbllen; } - const char *suffix = THISNODE->domain; + append_domain (*pkt, offs, dns->c->conf->domain); - // add tunnel domain - for (;;) - { - const char *end = strchr (suffix, '.'); + (*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; - if (!end) - end = suffix + strlen (suffix); + pkt->len = offs; +} + +void dns_snd::gen_syn_req () +{ + timeout = ev_now () + INITIAL_SYN_TIMEOUT; - int len = end - suffix; + pkt->flags = htons (DEFAULT_CLIENT_FLAGS); + pkt->qdcount = htons (1); - (*pkt)[offs++] = len; - memcpy (&((*pkt)[offs]), suffix, len); - offs += len; + int offs = 6 * 2; - if (!*end) - break; + int elen = cdc26.encode ((char *)pkt->at (offs + 1), (u8 *)&dns->cfg, sizeof (dns_cfg)); - suffix = end + 1; - } + 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_ANY >> 8; (*pkt)[offs++] = RR_TYPE_ANY; + (*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; @@ -551,35 +723,23 @@ ///////////////////////////////////////////////////////////////////////////// -struct dns_connection -{ - connection *c; - struct vpn *vpn; - - vector rcvpq; - - int rcvseq; - int sndseq; - - byte_stream rcvdq; - byte_stream snddq; - - void time_cb (time_watcher &w); time_watcher tw; - void receive_rep (dns_rcv *r); - - dns_connection (connection *c); - ~dns_connection (); -}; - dns_connection::dns_connection (connection *c) : c (c) , rcvdq (MAX_BACKLOG * 2) -, snddq (MAX_BACKLOG * 2) -, tw (this, &dns_connection::time_cb) +, snddq (MAX_BACKLOG) { + tw.set (this); + vpn = c->vpn; - rcvseq = sndseq = 0; + 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; } dns_connection::~dns_connection () @@ -590,17 +750,23 @@ delete *i; } -struct dns_cfg -{ - u8 id1, id2, id3; - u8 def_ttl; - u8 unused1; - u16 max_size; - u8 flags1, flags2; -}; - void dns_connection::receive_rep (dns_rcv *r) { + if (r->datalen) + { + last_received = ev_now (); + tw (); + + 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: @@ -609,6 +775,7 @@ 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; @@ -616,6 +783,7 @@ 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; @@ -624,14 +792,19 @@ rcvseq = (rcvseq + 1) & SEQNO_MASK; if (!rcvdq.put (r->data, r->datalen)) - abort (); // MUST never overflow, can be caused by data corruption, TODO + { + 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 = 0; si.port = 0; si.prot = PROT_DNSv4; + si.host = htonl (c->conf->id); si.port = 0; si.prot = PROT_DNSv4; vpn->recv_vpn_packet (pkt, si); + + delete pkt; } // check for further packets @@ -639,192 +812,327 @@ } } -dns_packet * -vpn::dnsv4_server (dns_packet *pkt) +void +vpn::dnsv4_server (dns_packet &pkt) { - u16 flags = ntohs (pkt->flags); + u16 flags = ntohs (pkt.flags); - //memcpy (&((*rep)[0]), &((*pkt)[0]), pkt->len); int offs = 6 * 2; // skip header - pkt->flags = htons (DEFAULT_SERVER_FLAGS | FLAG_RCODE_FORMERR); + pkt.flags = htons (DEFAULT_SERVER_FLAGS | FLAG_RCODE_FORMERR); - if (0 == (flags & (FLAG_RESPONSE | FLAG_OP_MASK | FLAG_TC)) - && pkt->qdcount == htons (1)) + 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); + 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++]; + 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.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_NXDOMAIN); + pkt.flags = htons (DEFAULT_SERVER_FLAGS | FLAG_RCODE_SERVFAIL); int dlen = strlen (THISNODE->domain); if (qclass == RR_CLASS_IN - && (qtype == RR_TYPE_ANY || qtype == RR_TYPE_TXT) - && qlen > dlen + 1 + HDRSIZE - && !memcmp (qname + qlen - dlen - 1, THISNODE->domain, dlen)) + && qlen > dlen + 1 + && !memcmp (qname + qlen - (dlen + 1), THISNODE->domain, dlen)) { - // 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 ()) + // 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) { - connection *c = conns [client - 1]; + // correct class, domain: parse + int client, seqno; + decode_header (qname, client, seqno); - if (!c->dns) - c->dns = new dns_connection (c); + u8 data[MAXSIZE]; + int datalen = cdc62.decode (data, qname + HDRSIZE, qlen - (dlen + 1 + HDRSIZE)); - dns_connection *dns = c->dns; + 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); + } - 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; - - printf ("DUPLICATE %d\n", htons (r->pkt->id));//D - - memcpy (pkt->at (0), r->pkt->at (0), offs = r->pkt->len); - pkt->id = r->pkt->id; - goto duplicate_request; - } + pkt [offs++] = 0xc0; pkt [offs++] = 6 * 2; // refer to name in query section - // new packet, queue - dns_rcv *rcv = new dns_rcv (seqno, data, datalen); - dns->receive_rep (rcv); + 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 - // now generate reply - pkt->ancount = htons (1); // one answer RR - pkt->flags = htons (DEFAULT_SERVER_FLAGS | FLAG_RCODE_OK); + int rdlen_offs = offs += 2; - (*pkt) [offs++] = 0xc0; - (*pkt) [offs++] = 6 * 2; // same as in query section - - (*pkt) [offs++] = RR_TYPE_TXT >> 8; (*pkt) [offs++] = RR_TYPE_TXT; - (*pkt) [offs++] = RR_CLASS_IN >> 8; (*pkt) [offs++] = RR_CLASS_IN; - - (*pkt) [offs++] = 0; (*pkt) [offs++] = 0; - (*pkt) [offs++] = 0; (*pkt) [offs++] = 0; // TTL + if (dns) + { + int dlen = ntohs (dns->cfg.max_size) - offs; - int dlen = MAX_PKT_SIZE - offs - 2; + // bind doesn't compress well, so reduce further by one label length + dlen -= qlen; - // 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; - int rdlen_offs = offs += 2; + 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; + } - while (dlen > 1 && !dns->snddq.empty ()) - { - int txtlen = dlen <= 255 ? dlen - 1 : 255; + int rdlen = offs - rdlen_offs; - if (txtlen > dns->snddq.size ()) - txtlen = dns->snddq.size (); + pkt [rdlen_offs - 2] = rdlen >> 8; + pkt [rdlen_offs - 1] = rdlen; - (*pkt)[offs++] = txtlen; - memcpy (pkt->at (offs), dns->snddq.begin (), txtlen); - offs += txtlen; - dns->snddq.remove (txtlen); + if (dns) + { + // now update dns_rcv copy + rcv->pkt->len = offs; + memcpy (rcv->pkt->at (0), pkt.at (0), offs); + } + } - dlen -= txtlen + 1; + 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 - // avoid empty TXT rdata - if (offs == rdlen_offs) - (*pkt)[offs++] = 0; + 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 - int rdlen = offs - rdlen_offs; + slog (L_INFO, _("DNS: client %d connects"), client); - (*pkt) [rdlen_offs - 2] = rdlen >> 8; - (*pkt) [rdlen_offs - 1] = rdlen; + pkt [offs++] = CMD_IP_1; pkt [offs++] = CMD_IP_2; pkt [offs++] = CMD_IP_3; + pkt [offs++] = CMD_IP_REJ; - // now update dns_rcv copy - rcv->pkt->len = offs; - memcpy (rcv->pkt->at (0), pkt->at (0), offs); + if (0 < client && client <= conns.size ()) + { + connection *c = conns [client - 1]; - duplicate_request: ; + if (cfg.valid ()) + { + pkt [offs - 1] = CMD_IP_SYN; + + delete c->dns; + c->dns = new dns_connection (c); + c->dns->cfg = cfg; + } + } } - else - pkt->flags = htons (DEFAULT_SERVER_FLAGS | FLAG_RCODE_FORMERR); } - pkt->len = offs; + pkt.len = offs; } - - return pkt; } 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); // go through our request list and find the corresponding request - for (vector::iterator i = dns_sndpq.begin (); + for (vector::iterator i = dns_sndpq.begin (); i != dns_sndpq.end (); ++i) - if ((*i)->pkt->id == pkt->id) + if ((*i)->pkt->id == pkt.id) { 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_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 && !(flags & (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 && datap) + while (pkt.ancount-- && offs < MAXSIZE - 10 && datap) { - int qlen = 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++]; - u16 rdlen = (*pkt) [offs++] << 8; rdlen |= (*pkt) [offs++]; - - if (rdlen <= MAXSIZE - offs) + if (qtype == RR_TYPE_NULL || qtype == RR_TYPE_TXT) { - // decode bytes, finally - - while (rdlen) + if (rdlen <= MAXSIZE - offs) { - int txtlen = (*pkt) [offs++]; + // decode bytes, finally + + while (rdlen) + { + int txtlen = pkt [offs++]; + + assert (txtlen + offs < MAXSIZE - 1); - 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]; - memcpy (datap, pkt->at (offs), txtlen); - datap += txtlen; offs += txtlen; + 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]); - rdlen -= txtlen + 1; + 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; @@ -832,12 +1140,12 @@ if (client != THISNODE->id) { - slog (L_INFO, _("got dns tunnel response with wrong clientid, ignoring")); + slog (L_INFO, _("DNS: got dns tunnel response with wrong clientid, ignoring")); datap = 0; } else if (rseqno != seqno) { - slog (L_DEBUG, _("got dns tunnel response with wrong seqno, badly caching nameserver?")); + slog (L_DEBUG, _("DNS: got dns tunnel response with wrong seqno, badly caching nameserver?")); datap = 0; } } @@ -849,111 +1157,158 @@ break; } - - delete pkt; } 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 (pkt->flags & htons (FLAG_TC)) + if (ntohs (pkt->flags) & FLAG_RESPONSE) + dnsv4_client (*pkt); + else { - slog (L_WARN, _("DNS request/response truncated, check protocol settings.")); - //TODO connection reset + dnsv4_server (*pkt); + sendto (w.fd, pkt->at (0), pkt->len, 0, (sockaddr *)&sa, sa_len); } - if (THISNODE->dns_port) - { - pkt = dnsv4_server (pkt); - sendto (w.fd, &((*pkt)[0]), pkt->len, 0, (sockaddr *)&sa, sa_len); - } - else - dnsv4_client (pkt); + 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) { - if (!dns) - dns = new dns_connection (this); - - if (!dns->snddq.put (pkt)) - return false; + int client = ntohl (si.host); - // start timer if neccessary - if (!THISNODE->dns_port && !dns->tw.active) - dns->tw.trigger (); + 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)) + c->dns->tw (); + // always return true even if the buffer overflows return true; } void -dns_connection::time_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; - 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_now ()) { if (!send) { send = r; - if (r->retry)//D - printf ("req %d:%d, retry %d\n", r->seqno, r->pkt->id, r->retry); r->retry++; - r->next = NOW + r->retry; + r->timeout = ev_now () + (r->retry * min_latency * conf.dns_timeout_factor); + //printf ("RETRY %x (%d, %f)\n", r->seqno, r->retry, r->timeout - 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) + if (!send) { - send = new dns_req (this); - send->gen_stream_req (sndseq, snddq); - vpn->dns_sndpq.push_back (send); + // generate a new packet, if wise - sndseq = (sndseq + 1) & SEQNO_MASK; - } + 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 () < conf.dns_max_outstanding + && !SEQNO_EQ (rcvseq, sndseq - (MAX_WINDOW - 1))) + { + if (last_sent + send_interval <= ev_now ()) + { + //printf ("sending data request etc.\n"); //D + if (!snddq.empty () || last_received + 1. > ev_now ()) + { + poll_interval = send_interval; + NEXT (ev_now () + send_interval); + } - tstamp min_next = NOW + (1. / (tstamp)MAX_RATE); + send = new dns_snd (this); + send->gen_stream_req (sndseq, snddq); + send->timeout = ev_now () + min_latency * conf.dns_timeout_factor; + //printf ("SEND %x (%f)\n", send->seqno, send->timeout - ev_now (), min_latency, conf.dns_timeout_factor);//D - if (send) - { - dns_packet *pkt = send->pkt; + sndseq = (sndseq + 1) & SEQNO_MASK; + } + else + NEXT (last_sent + send_interval); + } - next = min_next; + if (send) + vpn->dns_sndpq.push_back (send); + } - sendto (vpn->dnsv4_fd, &((*pkt)[0]), pkt->len, 0, + if (send) + { + last_sent = ev_now (); + sendto (vpn->dnsv4_fd, + send->pkt->at (0), send->pkt->len, 0, vpn->dns_forwarder.sav4 (), vpn->dns_forwarder.salenv4 ()); } - else if (next < min_next) - next = min_next; - w.start (next); + slog (L_NOISE, "DNS: pi %f si %f N %f (%d:%d %d)", + poll_interval, send_interval, next - ev_now (), + vpn->dns_sndpq.size (), snddq.size (), + rcvpq.size ()); + + // TODO: no idea when this happens, but when next < ev_now (), we have a problem + // doesn't seem to happen anymore + if (next < ev_now () + 0.001) + next = ev_now () + 0.1; + + w.start (next - ev_now ()); } #endif