2 net_packet.c -- Handles in- and outgoing VPN packets
3 Copyright (C) 1998-2005 Ivo Timmermans,
4 2000-2014 Guus Sliepen <guus@tinc-vpn.org>
5 2010 Timothy Redaelli <timothy@redaelli.eu>
6 2010 Brandon Black <blblack@gmail.com>
8 This program is free software; you can redistribute it and/or modify
9 it under the terms of the GNU General Public License as published by
10 the Free Software Foundation; either version 2 of the License, or
11 (at your option) any later version.
13 This program is distributed in the hope that it will be useful,
14 but WITHOUT ANY WARRANTY; without even the implied warranty of
15 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
16 GNU General Public License for more details.
18 You should have received a copy of the GNU General Public License along
19 with this program; if not, write to the Free Software Foundation, Inc.,
20 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
35 #include "connection.h"
52 #define MAX(a, b) ((a) > (b) ? (a) : (b))
55 /* The minimum size of a probe is 14 bytes, but since we normally use CBC mode
56 encryption, we can add a few extra random bytes without increasing the
57 resulting packet size. */
58 #define MIN_PROBE_SIZE 18
62 static char lzo_wrkmem[LZO1X_999_MEM_COMPRESS > LZO1X_1_MEM_COMPRESS ? LZO1X_999_MEM_COMPRESS : LZO1X_1_MEM_COMPRESS];
65 static void send_udppacket(node_t *, vpn_packet_t *);
67 unsigned replaywin = 16;
68 bool localdiscovery = true;
69 bool udp_discovery = true;
70 int udp_discovery_keepalive_interval = 10;
71 int udp_discovery_interval = 2;
72 int udp_discovery_timeout = 30;
74 #define MAX_SEQNO 1073741824
76 static void try_fix_mtu(node_t *n) {
80 if(n->mtuprobes == 20 || n->minmtu >= n->maxmtu) {
81 if(n->minmtu > n->maxmtu)
82 n->minmtu = n->maxmtu;
84 n->maxmtu = n->minmtu;
86 logger(DEBUG_TRAFFIC, LOG_INFO, "Fixing MTU of %s (%s) to %d after %d probes", n->name, n->hostname, n->mtu, n->mtuprobes);
91 static void udp_probe_timeout_handler(void *data) {
93 if(!n->status.udp_confirmed)
96 logger(DEBUG_TRAFFIC, LOG_INFO, "Too much time has elapsed since last UDP ping response from %s (%s), stopping UDP communication", n->name, n->hostname);
97 n->status.udp_confirmed = false;
104 static void send_udp_probe_reply(node_t *n, vpn_packet_t *packet, length_t len) {
105 if(!n->status.sptps && !n->status.validkey) {
106 logger(DEBUG_TRAFFIC, LOG_INFO, "Trying to send UDP probe reply to %s (%s) but we don't have his key yet", n->name, n->hostname);
110 /* Type 2 probe replies were introduced in protocol 17.3 */
111 if ((n->options >> 24) >= 3) {
113 uint16_t len16 = htons(len);
114 memcpy(DATA(packet) + 1, &len16, 2);
115 packet->len = MIN_PROBE_SIZE;
116 logger(DEBUG_TRAFFIC, LOG_INFO, "Sending type 2 probe reply length %u to %s (%s)", len, n->name, n->hostname);
119 /* Legacy protocol: n won't understand type 2 probe replies. */
121 logger(DEBUG_TRAFFIC, LOG_INFO, "Sending type 1 probe reply length %u to %s (%s)", len, n->name, n->hostname);
124 /* Temporarily set udp_confirmed, so that the reply is sent
125 back exactly the way it came in. */
127 bool udp_confirmed = n->status.udp_confirmed;
128 n->status.udp_confirmed = true;
129 send_udppacket(n, packet);
130 n->status.udp_confirmed = udp_confirmed;
133 static void udp_probe_h(node_t *n, vpn_packet_t *packet, length_t len) {
134 if(!DATA(packet)[0]) {
135 logger(DEBUG_TRAFFIC, LOG_INFO, "Got UDP probe request %d from %s (%s)", packet->len, n->name, n->hostname);
136 return send_udp_probe_reply(n, packet, len);
139 if (DATA(packet)[0] == 2) {
140 // It's a type 2 probe reply, use the length field inside the packet
142 memcpy(&len16, DATA(packet) + 1, 2);
146 logger(DEBUG_TRAFFIC, LOG_INFO, "Got type %d UDP probe reply %d from %s (%s)", DATA(packet)[0], len, n->name, n->hostname);
148 /* It's a valid reply: now we know bidirectional communication
149 is possible using the address and socket that the reply
151 n->status.udp_confirmed = true;
153 // Reset the UDP ping timer.
154 n->udp_ping_sent = now;
157 timeout_del(&n->udp_ping_timeout);
158 timeout_add(&n->udp_ping_timeout, &udp_probe_timeout_handler, n, &(struct timeval){udp_discovery_timeout, 0});
161 if(len > n->maxmtu) {
162 logger(DEBUG_TRAFFIC, LOG_INFO, "Increase in PMTU to %s (%s) detected, restarting PMTU discovery", n->name, n->hostname);
165 /* Set mtuprobes to 1 so that try_mtu() doesn't reset maxmtu */
168 } else if(n->mtuprobes < 0 && len == n->maxmtu) {
169 /* We got a maxmtu sized packet, confirming the PMTU is still valid. */
171 n->mtu_ping_sent = now;
174 /* If applicable, raise the minimum supported MTU */
176 if(n->minmtu < len) {
182 static length_t compress_packet(uint8_t *dest, const uint8_t *source, length_t len, int level) {
184 memcpy(dest, source, len);
186 } else if(level == 10) {
188 lzo_uint lzolen = MAXSIZE;
189 lzo1x_1_compress(source, len, dest, &lzolen, lzo_wrkmem);
194 } else if(level < 10) {
196 unsigned long destlen = MAXSIZE;
197 if(compress2(dest, &destlen, source, len, level) == Z_OK)
204 lzo_uint lzolen = MAXSIZE;
205 lzo1x_999_compress(source, len, dest, &lzolen, lzo_wrkmem);
215 static length_t uncompress_packet(uint8_t *dest, const uint8_t *source, length_t len, int level) {
217 memcpy(dest, source, len);
219 } else if(level > 9) {
221 lzo_uint lzolen = MAXSIZE;
222 if(lzo1x_decompress_safe(source, len, dest, &lzolen, NULL) == LZO_E_OK)
230 unsigned long destlen = MAXSIZE;
231 if(uncompress(dest, &destlen, source, len) == Z_OK)
243 static void receive_packet(node_t *n, vpn_packet_t *packet) {
244 logger(DEBUG_TRAFFIC, LOG_DEBUG, "Received packet of %d bytes from %s (%s)",
245 packet->len, n->name, n->hostname);
248 n->in_bytes += packet->len;
253 static bool try_mac(node_t *n, const vpn_packet_t *inpkt) {
255 return sptps_verify_datagram(&n->sptps, DATA(inpkt), inpkt->len);
257 #ifdef DISABLE_LEGACY
260 if(!n->status.validkey_in || !digest_active(n->indigest) || inpkt->len < sizeof(seqno_t) + digest_length(n->indigest))
263 return digest_verify(n->indigest, SEQNO(inpkt), inpkt->len - digest_length(n->indigest), DATA(inpkt) + inpkt->len - digest_length(n->indigest));
267 static bool receive_udppacket(node_t *n, vpn_packet_t *inpkt) {
268 vpn_packet_t pkt1, pkt2;
269 vpn_packet_t *pkt[] = { &pkt1, &pkt2, &pkt1, &pkt2 };
272 pkt1.offset = DEFAULT_PACKET_OFFSET;
273 pkt2.offset = DEFAULT_PACKET_OFFSET;
275 if(n->status.sptps) {
276 if(!n->sptps.state) {
277 if(!n->status.waitingforkey) {
278 logger(DEBUG_TRAFFIC, LOG_DEBUG, "Got packet from %s (%s) but we haven't exchanged keys yet", n->name, n->hostname);
281 logger(DEBUG_TRAFFIC, LOG_DEBUG, "Got packet from %s (%s) but he hasn't got our key yet", n->name, n->hostname);
285 inpkt->offset += 2 * sizeof(node_id_t);
286 n->status.udppacket = true;
287 bool result = sptps_receive_data(&n->sptps, DATA(inpkt), inpkt->len - 2 * sizeof(node_id_t));
288 n->status.udppacket = false;
291 logger(DEBUG_TRAFFIC, LOG_ERR, "Got bad packet from %s (%s)", n->name, n->hostname);
297 #ifdef DISABLE_LEGACY
300 if(!n->status.validkey_in) {
301 logger(DEBUG_TRAFFIC, LOG_DEBUG, "Got packet from %s (%s) but he hasn't got our key yet", n->name, n->hostname);
305 /* Check packet length */
307 if(inpkt->len < sizeof(seqno_t) + digest_length(n->indigest)) {
308 logger(DEBUG_TRAFFIC, LOG_DEBUG, "Got too short packet from %s (%s)",
309 n->name, n->hostname);
313 /* It's a legacy UDP packet, the data starts after the seqno */
315 inpkt->offset += sizeof(seqno_t);
317 /* Check the message authentication code */
319 if(digest_active(n->indigest)) {
320 inpkt->len -= digest_length(n->indigest);
321 if(!digest_verify(n->indigest, SEQNO(inpkt), inpkt->len, SEQNO(inpkt) + inpkt->len)) {
322 logger(DEBUG_TRAFFIC, LOG_DEBUG, "Got unauthenticated packet from %s (%s)", n->name, n->hostname);
326 /* Decrypt the packet */
328 if(cipher_active(n->incipher)) {
329 vpn_packet_t *outpkt = pkt[nextpkt++];
332 if(!cipher_decrypt(n->incipher, SEQNO(inpkt), inpkt->len, SEQNO(outpkt), &outlen, true)) {
333 logger(DEBUG_TRAFFIC, LOG_DEBUG, "Error decrypting packet from %s (%s)", n->name, n->hostname);
337 outpkt->len = outlen;
341 /* Check the sequence number */
344 memcpy(&seqno, SEQNO(inpkt), sizeof seqno);
345 seqno = ntohl(seqno);
346 inpkt->len -= sizeof seqno;
349 if(seqno != n->received_seqno + 1) {
350 if(seqno >= n->received_seqno + replaywin * 8) {
351 if(n->farfuture++ < replaywin >> 2) {
352 logger(DEBUG_ALWAYS, LOG_WARNING, "Packet from %s (%s) is %d seqs in the future, dropped (%u)",
353 n->name, n->hostname, seqno - n->received_seqno - 1, n->farfuture);
356 logger(DEBUG_ALWAYS, LOG_WARNING, "Lost %d packets from %s (%s)",
357 seqno - n->received_seqno - 1, n->name, n->hostname);
358 memset(n->late, 0, replaywin);
359 } else if (seqno <= n->received_seqno) {
360 if((n->received_seqno >= replaywin * 8 && seqno <= n->received_seqno - replaywin * 8) || !(n->late[(seqno / 8) % replaywin] & (1 << seqno % 8))) {
361 logger(DEBUG_ALWAYS, LOG_WARNING, "Got late or replayed packet from %s (%s), seqno %d, last received %d",
362 n->name, n->hostname, seqno, n->received_seqno);
366 for(int i = n->received_seqno + 1; i < seqno; i++)
367 n->late[(i / 8) % replaywin] |= 1 << i % 8;
372 n->late[(seqno / 8) % replaywin] &= ~(1 << seqno % 8);
375 if(seqno > n->received_seqno)
376 n->received_seqno = seqno;
380 if(n->received_seqno > MAX_SEQNO)
383 /* Decompress the packet */
385 length_t origlen = inpkt->len;
387 if(n->incompression) {
388 vpn_packet_t *outpkt = pkt[nextpkt++];
390 if((outpkt->len = uncompress_packet(DATA(outpkt), DATA(inpkt), inpkt->len, n->incompression)) < 0) {
391 logger(DEBUG_TRAFFIC, LOG_ERR, "Error while uncompressing packet from %s (%s)",
392 n->name, n->hostname);
398 origlen -= MTU/64 + 20;
401 if(inpkt->len > n->maxrecentlen)
402 n->maxrecentlen = inpkt->len;
406 if(!DATA(inpkt)[12] && !DATA(inpkt)[13])
407 udp_probe_h(n, inpkt, origlen);
409 receive_packet(n, inpkt);
414 void receive_tcppacket(connection_t *c, const char *buffer, int len) {
416 outpkt.offset = DEFAULT_PACKET_OFFSET;
418 if(len > sizeof outpkt.data - outpkt.offset)
422 if(c->options & OPTION_TCPONLY)
425 outpkt.priority = -1;
426 memcpy(DATA(&outpkt), buffer, len);
428 receive_packet(c->node, &outpkt);
431 static void send_sptps_packet(node_t *n, vpn_packet_t *origpkt) {
432 if(!n->status.validkey && !n->connection)
438 if(!(DATA(origpkt)[12] | DATA(origpkt)[13])) {
439 sptps_send_record(&n->sptps, PKT_PROBE, (char *)DATA(origpkt), origpkt->len);
443 if(routing_mode == RMODE_ROUTER)
448 if(origpkt->len < offset)
453 if(n->outcompression) {
455 int len = compress_packet(DATA(&outpkt) + offset, DATA(origpkt) + offset, origpkt->len - offset, n->outcompression);
457 logger(DEBUG_TRAFFIC, LOG_ERR, "Error while compressing packet to %s (%s)", n->name, n->hostname);
458 } else if(len < origpkt->len - offset) {
459 outpkt.len = len + offset;
461 type |= PKT_COMPRESSED;
465 /* If we have a direct metaconnection to n, and we can't use UDP, then
466 don't bother with SPTPS and just use a "plaintext" PACKET message.
467 We don't really care about end-to-end security since we're not
468 sending the message through any intermediate nodes. */
469 if(n->connection && origpkt->len > n->minmtu)
470 send_tcppacket(n->connection, origpkt);
472 sptps_send_record(&n->sptps, type, DATA(origpkt) + offset, origpkt->len - offset);
476 static void adapt_socket(const sockaddr_t *sa, int *sock) {
477 /* Make sure we have a suitable socket for the chosen address */
478 if(listen_socket[*sock].sa.sa.sa_family != sa->sa.sa_family) {
479 for(int i = 0; i < listen_sockets; i++) {
480 if(listen_socket[i].sa.sa.sa_family == sa->sa.sa_family) {
488 static void choose_udp_address(const node_t *n, const sockaddr_t **sa, int *sock) {
493 /* If the UDP address is confirmed, use it. */
494 if(n->status.udp_confirmed)
497 /* Send every third packet to n->address; that could be set
498 to the node's reflexive UDP address discovered during key
507 /* Otherwise, address are found in edges to this node.
508 So we pick a random edge and a random socket. */
511 int j = rand() % n->edge_tree->count;
512 edge_t *candidate = NULL;
514 for splay_each(edge_t, e, n->edge_tree) {
516 candidate = e->reverse;
522 *sa = &candidate->address;
523 *sock = rand() % listen_sockets;
526 adapt_socket(*sa, sock);
529 static void choose_local_address(const node_t *n, const sockaddr_t **sa, int *sock) {
532 /* Pick one of the edges from this node at random, then use its local address. */
535 int j = rand() % n->edge_tree->count;
536 edge_t *candidate = NULL;
538 for splay_each(edge_t, e, n->edge_tree) {
545 if (candidate && candidate->local_address.sa.sa_family) {
546 *sa = &candidate->local_address;
547 *sock = rand() % listen_sockets;
548 adapt_socket(*sa, sock);
552 static void send_udppacket(node_t *n, vpn_packet_t *origpkt) {
553 vpn_packet_t pkt1, pkt2;
554 vpn_packet_t *pkt[] = { &pkt1, &pkt2, &pkt1, &pkt2 };
555 vpn_packet_t *inpkt = origpkt;
557 vpn_packet_t *outpkt;
558 int origlen = origpkt->len;
560 #if defined(SOL_IP) && defined(IP_TOS)
561 static int priority = 0;
562 int origpriority = origpkt->priority;
565 pkt1.offset = DEFAULT_PACKET_OFFSET;
566 pkt2.offset = DEFAULT_PACKET_OFFSET;
568 if(!n->status.reachable) {
569 logger(DEBUG_TRAFFIC, LOG_INFO, "Trying to send UDP packet to unreachable node %s (%s)", n->name, n->hostname);
574 return send_sptps_packet(n, origpkt);
576 #ifdef DISABLE_LEGACY
579 /* Make sure we have a valid key */
581 if(!n->status.validkey) {
582 logger(DEBUG_TRAFFIC, LOG_INFO,
583 "No valid key known yet for %s (%s), forwarding via TCP",
584 n->name, n->hostname);
585 send_tcppacket(n->nexthop->connection, origpkt);
589 if(n->options & OPTION_PMTU_DISCOVERY && inpkt->len > n->minmtu && (DATA(inpkt)[12] | DATA(inpkt)[13])) {
590 logger(DEBUG_TRAFFIC, LOG_INFO,
591 "Packet for %s (%s) larger than minimum MTU, forwarding via %s",
592 n->name, n->hostname, n != n->nexthop ? n->nexthop->name : "TCP");
595 send_packet(n->nexthop, origpkt);
597 send_tcppacket(n->nexthop->connection, origpkt);
602 /* Compress the packet */
604 if(n->outcompression) {
605 outpkt = pkt[nextpkt++];
607 if((outpkt->len = compress_packet(DATA(outpkt), DATA(inpkt), inpkt->len, n->outcompression)) < 0) {
608 logger(DEBUG_TRAFFIC, LOG_ERR, "Error while compressing packet to %s (%s)",
609 n->name, n->hostname);
616 /* Add sequence number */
618 seqno_t seqno = htonl(++(n->sent_seqno));
619 memcpy(SEQNO(inpkt), &seqno, sizeof seqno);
620 inpkt->len += sizeof seqno;
622 /* Encrypt the packet */
624 if(cipher_active(n->outcipher)) {
625 outpkt = pkt[nextpkt++];
628 if(!cipher_encrypt(n->outcipher, SEQNO(inpkt), inpkt->len, SEQNO(outpkt), &outlen, true)) {
629 logger(DEBUG_TRAFFIC, LOG_ERR, "Error while encrypting packet to %s (%s)", n->name, n->hostname);
633 outpkt->len = outlen;
637 /* Add the message authentication code */
639 if(digest_active(n->outdigest)) {
640 if(!digest_create(n->outdigest, SEQNO(inpkt), inpkt->len, SEQNO(inpkt) + inpkt->len)) {
641 logger(DEBUG_TRAFFIC, LOG_ERR, "Error while encrypting packet to %s (%s)", n->name, n->hostname);
645 inpkt->len += digest_length(n->outdigest);
648 /* Send the packet */
650 const sockaddr_t *sa = NULL;
653 if(n->status.send_locally)
654 choose_local_address(n, &sa, &sock);
656 choose_udp_address(n, &sa, &sock);
658 #if defined(SOL_IP) && defined(IP_TOS)
659 if(priorityinheritance && origpriority != priority
660 && listen_socket[n->sock].sa.sa.sa_family == AF_INET) {
661 priority = origpriority;
662 logger(DEBUG_TRAFFIC, LOG_DEBUG, "Setting outgoing packet priority to %d", priority);
663 if(setsockopt(listen_socket[n->sock].udp.fd, SOL_IP, IP_TOS, &priority, sizeof(priority))) /* SO_PRIORITY doesn't seem to work */
664 logger(DEBUG_ALWAYS, LOG_ERR, "System call `%s' failed: %s", "setsockopt", sockstrerror(sockerrno));
668 if(sendto(listen_socket[sock].udp.fd, SEQNO(inpkt), inpkt->len, 0, &sa->sa, SALEN(sa->sa)) < 0 && !sockwouldblock(sockerrno)) {
669 if(sockmsgsize(sockerrno)) {
670 if(n->maxmtu >= origlen)
671 n->maxmtu = origlen - 1;
672 if(n->mtu >= origlen)
673 n->mtu = origlen - 1;
676 logger(DEBUG_TRAFFIC, LOG_WARNING, "Error sending packet to %s (%s): %s", n->name, n->hostname, sockstrerror(sockerrno));
680 origpkt->len = origlen;
684 static bool send_sptps_data_priv(node_t *to, node_t *from, int type, const void *data, size_t len) {
685 node_t *relay = (to->via != myself && (type == PKT_PROBE || (len - SPTPS_DATAGRAM_OVERHEAD) <= to->via->minmtu)) ? to->via : to->nexthop;
686 bool direct = from == myself && to == relay;
687 bool relay_supported = (relay->options >> 24) >= 4;
688 bool tcponly = (myself->options | relay->options) & OPTION_TCPONLY;
690 /* Send it via TCP if it is a handshake packet, TCPOnly is in use, this is a relay packet that the other node cannot understand, or this packet is larger than the MTU. */
692 if(type == SPTPS_HANDSHAKE || tcponly || (!direct && !relay_supported) || (type != PKT_PROBE && (len - SPTPS_DATAGRAM_OVERHEAD) > relay->minmtu)) {
693 char buf[len * 4 / 3 + 5];
694 b64encode(data, buf, len);
695 /* If no valid key is known yet, send the packets using ANS_KEY requests,
696 to ensure we get to learn the reflexive UDP address. */
697 if(from == myself && !to->status.validkey) {
698 to->incompression = myself->incompression;
699 return send_request(to->nexthop->connection, "%d %s %s %s -1 -1 -1 %d", ANS_KEY, from->name, to->name, buf, to->incompression);
701 return send_request(to->nexthop->connection, "%d %s %s %d %s", REQ_KEY, from->name, to->name, REQ_SPTPS, buf);
706 if(relay_supported) overhead += sizeof to->id + sizeof from->id;
707 char buf[len + overhead]; char* buf_ptr = buf;
708 if(relay_supported) {
710 /* Inform the recipient that this packet was sent directly. */
711 node_id_t nullid = {};
712 memcpy(buf_ptr, &nullid, sizeof nullid); buf_ptr += sizeof nullid;
714 memcpy(buf_ptr, &to->id, sizeof to->id); buf_ptr += sizeof to->id;
716 memcpy(buf_ptr, &from->id, sizeof from->id); buf_ptr += sizeof from->id;
719 /* TODO: if this copy turns out to be a performance concern, change sptps_send_record() to add some "pre-padding" to the buffer and use that instead */
720 memcpy(buf_ptr, data, len); buf_ptr += len;
722 const sockaddr_t *sa = NULL;
724 if(relay->status.send_locally)
725 choose_local_address(relay, &sa, &sock);
727 choose_udp_address(relay, &sa, &sock);
728 logger(DEBUG_TRAFFIC, LOG_INFO, "Sending packet from %s (%s) to %s (%s) via %s (%s)", from->name, from->hostname, to->name, to->hostname, relay->name, relay->hostname);
729 if(sendto(listen_socket[sock].udp.fd, buf, buf_ptr - buf, 0, &sa->sa, SALEN(sa->sa)) < 0 && !sockwouldblock(sockerrno)) {
730 if(sockmsgsize(sockerrno)) {
731 // Compensate for SPTPS overhead
732 len -= SPTPS_DATAGRAM_OVERHEAD;
733 if(relay->maxmtu >= len)
734 relay->maxmtu = len - 1;
735 if(relay->mtu >= len)
736 relay->mtu = len - 1;
739 logger(DEBUG_TRAFFIC, LOG_WARNING, "Error sending UDP SPTPS packet to %s (%s): %s", relay->name, relay->hostname, sockstrerror(sockerrno));
747 bool send_sptps_data(void *handle, uint8_t type, const void *data, size_t len) {
748 return send_sptps_data_priv(handle, myself, type, data, len);
751 bool receive_sptps_record(void *handle, uint8_t type, const void *data, uint16_t len) {
752 node_t *from = handle;
754 if(type == SPTPS_HANDSHAKE) {
755 if(!from->status.validkey) {
756 from->status.validkey = true;
757 from->status.waitingforkey = false;
758 logger(DEBUG_META, LOG_INFO, "SPTPS key exchange with %s (%s) succesful", from->name, from->hostname);
764 logger(DEBUG_ALWAYS, LOG_ERR, "Packet from %s (%s) larger than maximum supported size (%d > %d)", from->name, from->hostname, len, MTU);
769 inpkt.offset = DEFAULT_PACKET_OFFSET;
771 if(type == PKT_PROBE) {
772 if(!from->status.udppacket) {
773 logger(DEBUG_ALWAYS, LOG_ERR, "Got SPTPS PROBE packet from %s (%s) via TCP", from->name, from->hostname);
777 memcpy(DATA(&inpkt), data, len);
778 if(inpkt.len > from->maxrecentlen)
779 from->maxrecentlen = inpkt.len;
780 udp_probe_h(from, &inpkt, len);
784 if(type & ~(PKT_COMPRESSED | PKT_MAC)) {
785 logger(DEBUG_ALWAYS, LOG_ERR, "Unexpected SPTPS record type %d len %d from %s (%s)", type, len, from->name, from->hostname);
789 /* Check if we have the headers we need */
790 if(routing_mode != RMODE_ROUTER && !(type & PKT_MAC)) {
791 logger(DEBUG_TRAFFIC, LOG_ERR, "Received packet from %s (%s) without MAC header (maybe Mode is not set correctly)", from->name, from->hostname);
793 } else if(routing_mode == RMODE_ROUTER && (type & PKT_MAC)) {
794 logger(DEBUG_TRAFFIC, LOG_WARNING, "Received packet from %s (%s) with MAC header (maybe Mode is not set correctly)", from->name, from->hostname);
797 int offset = (type & PKT_MAC) ? 0 : 14;
798 if(type & PKT_COMPRESSED) {
799 length_t ulen = uncompress_packet(DATA(&inpkt) + offset, (const uint8_t *)data, len, from->incompression);
803 inpkt.len = ulen + offset;
805 if(inpkt.len > MAXSIZE)
808 memcpy(DATA(&inpkt) + offset, data, len);
809 inpkt.len = len + offset;
812 /* Generate the Ethernet packet type if necessary */
814 switch(DATA(&inpkt)[14] >> 4) {
816 DATA(&inpkt)[12] = 0x08;
817 DATA(&inpkt)[13] = 0x00;
820 DATA(&inpkt)[12] = 0x86;
821 DATA(&inpkt)[13] = 0xDD;
824 logger(DEBUG_TRAFFIC, LOG_ERR,
825 "Unknown IP version %d while reading packet from %s (%s)",
826 DATA(&inpkt)[14] >> 4, from->name, from->hostname);
831 if(from->status.udppacket && inpkt.len > from->maxrecentlen)
832 from->maxrecentlen = inpkt.len;
834 receive_packet(from, &inpkt);
838 // This function tries to get SPTPS keys, if they aren't already known.
839 // This function makes no guarantees - it is up to the caller to check the node's state to figure out if the keys are available.
840 static void try_sptps(node_t *n) {
841 if(n->status.validkey)
844 logger(DEBUG_TRAFFIC, LOG_INFO, "No valid key known yet for %s (%s)", n->name, n->hostname);
846 if(!n->status.waitingforkey)
848 else if(n->last_req_key + 10 < now.tv_sec) {
849 logger(DEBUG_ALWAYS, LOG_DEBUG, "No key from %s after 10 seconds, restarting SPTPS", n->name);
850 sptps_stop(&n->sptps);
851 n->status.waitingforkey = false;
858 static void send_udp_probe_packet(node_t *n, int len) {
860 packet.offset = DEFAULT_PACKET_OFFSET;
861 memset(DATA(&packet), 0, 14);
862 randomize(DATA(&packet) + 14, len - 14);
866 logger(DEBUG_TRAFFIC, LOG_INFO, "Sending UDP probe length %d to %s (%s)", len, n->name, n->hostname);
868 send_udppacket(n, &packet);
871 // This function tries to establish a UDP tunnel to a node so that packets can be sent.
872 // If a tunnel is already established, it makes sure it stays up.
873 // This function makes no guarantees - it is up to the caller to check the node's state to figure out if UDP is usable.
874 static void try_udp(node_t* n) {
878 /* Send gratuitous probe replies to 1.1 nodes. */
880 if((n->options >> 24) >= 3 && n->status.udp_confirmed) {
881 struct timeval ping_tx_elapsed;
882 timersub(&now, &n->udp_reply_sent, &ping_tx_elapsed);
884 if(ping_tx_elapsed.tv_sec >= udp_discovery_keepalive_interval - 1) {
885 n->udp_reply_sent = now;
886 if(n->maxrecentlen) {
888 pkt.len = n->maxrecentlen;
889 pkt.offset = DEFAULT_PACKET_OFFSET;
890 memset(DATA(&pkt), 0, 14);
891 randomize(DATA(&pkt) + 14, MIN_PROBE_SIZE - 14);
892 send_udp_probe_reply(n, &pkt, pkt.len);
900 struct timeval ping_tx_elapsed;
901 timersub(&now, &n->udp_ping_sent, &ping_tx_elapsed);
903 int interval = n->status.udp_confirmed ? udp_discovery_keepalive_interval : udp_discovery_interval;
905 if(ping_tx_elapsed.tv_sec >= interval) {
906 send_udp_probe_packet(n, MIN_PROBE_SIZE);
907 n->udp_ping_sent = now;
909 if(localdiscovery && !n->status.udp_confirmed && n->prevedge) {
910 n->status.send_locally = true;
911 send_udp_probe_packet(n, MIN_PROBE_SIZE);
912 n->status.send_locally = false;
917 static length_t choose_initial_maxmtu(node_t *n) {
922 const sockaddr_t *sa = NULL;
924 choose_udp_address(n, &sa, &sockindex);
928 sock = socket(sa->sa.sa_family, SOCK_DGRAM, IPPROTO_UDP);
930 logger(DEBUG_TRAFFIC, LOG_ERR, "Creating MTU assessment socket for %s (%s) failed: %s", n->name, n->hostname, sockstrerror(sockerrno));
934 if(connect(sock, &sa->sa, SALEN(sa->sa))) {
935 logger(DEBUG_TRAFFIC, LOG_ERR, "Connecting MTU assessment socket for %s (%s) failed: %s", n->name, n->hostname, sockstrerror(sockerrno));
941 socklen_t ip_mtu_len = sizeof ip_mtu;
942 if(getsockopt(sock, IPPROTO_IP, IP_MTU, &ip_mtu, &ip_mtu_len)) {
943 logger(DEBUG_TRAFFIC, LOG_ERR, "getsockopt(IP_MTU) on %s (%s) failed: %s", n->name, n->hostname, sockstrerror(sockerrno));
950 /* getsockopt(IP_MTU) returns the MTU of the physical interface.
951 We need to remove various overheads to get to the tinc MTU. */
952 length_t mtu = ip_mtu;
953 mtu -= (sa->sa.sa_family == AF_INET6) ? sizeof(struct ip6_hdr) : sizeof(struct ip);
955 if(n->status.sptps) {
956 mtu -= SPTPS_DATAGRAM_OVERHEAD;
957 if((n->options >> 24) >= 4)
958 mtu -= sizeof(node_id_t) + sizeof(node_id_t);
959 #ifndef DISABLE_LEGACY
961 mtu -= digest_length(n->outdigest);
963 /* Now it's tricky. We use CBC mode, so the length of the
964 encrypted payload must be a multiple of the blocksize. The
965 sequence number is also part of the encrypted payload, so we
966 must account for it after correcting for the blocksize.
967 Furthermore, the padding in the last block must be at least
970 length_t blocksize = cipher_blocksize(n->outcipher);
983 logger(DEBUG_TRAFFIC, LOG_ERR, "getsockopt(IP_MTU) on %s (%s) returned absurdly small value: %d", n->name, n->hostname, ip_mtu);
989 logger(DEBUG_TRAFFIC, LOG_INFO, "Using system-provided maximum tinc MTU for %s (%s): %hd", n->name, n->hostname, mtu);
999 /* This function tries to determines the MTU of a node.
1000 By calling this function repeatedly, n->minmtu will be progressively
1001 increased, and at some point, n->mtu will be fixed to n->minmtu. If the MTU
1002 is already fixed, this function checks if it can be increased.
1005 static void try_mtu(node_t *n) {
1006 if(!(n->options & OPTION_PMTU_DISCOVERY))
1009 if(udp_discovery && !n->status.udp_confirmed) {
1010 n->maxrecentlen = 0;
1017 /* mtuprobes == 0..19: initial discovery, send bursts with 1 second interval, mtuprobes++
1018 mtuprobes == 20: fix MTU, and go to -1
1019 mtuprobes == -1: send one maxmtu and one maxmtu+1 probe every pinginterval
1020 mtuprobes ==-2..-3: send one maxmtu probe every second
1021 mtuprobes == -4: maxmtu no longer valid, reset minmtu and maxmtu and go to 0 */
1023 struct timeval elapsed;
1024 timersub(&now, &n->mtu_ping_sent, &elapsed);
1025 if(n->mtuprobes >= 0) {
1026 if(n->mtuprobes != 0 && elapsed.tv_sec == 0 && elapsed.tv_usec < 333333)
1029 if(n->mtuprobes < -1) {
1030 if(elapsed.tv_sec < 1)
1033 if(elapsed.tv_sec < pinginterval)
1038 n->mtu_ping_sent = now;
1042 if(n->mtuprobes < -3) {
1043 /* We lost three MTU probes, restart discovery */
1044 logger(DEBUG_TRAFFIC, LOG_INFO, "Decrease in PMTU to %s (%s) detected, restarting PMTU discovery", n->name, n->hostname);
1049 if(n->mtuprobes < 0) {
1050 /* After the initial discovery, we only send one maxmtu and one
1051 maxmtu+1 probe to detect PMTU increases. */
1052 send_udp_probe_packet(n, n->maxmtu);
1053 if(n->mtuprobes == -1 && n->maxmtu + 1 < MTU)
1054 send_udp_probe_packet(n, n->maxmtu + 1);
1057 /* Before initial discovery begins, set maxmtu to the most likely value.
1058 If it's underestimated, we will correct it after initial discovery. */
1059 if(n->mtuprobes == 0)
1060 n->maxmtu = choose_initial_maxmtu(n);
1063 /* Decreasing the number of probes per cycle might make the algorithm react faster to lost packets,
1064 but it will typically increase convergence time in the no-loss case. */
1065 const length_t probes_per_cycle = 8;
1067 /* This magic value was determined using math simulations.
1068 It will result in a 1329-byte first probe, followed (if there was a reply) by a 1407-byte probe.
1069 Since 1407 is just below the range of tinc MTUs over typical networks,
1070 this fine-tuning allows tinc to cover a lot of ground very quickly.
1071 This fine-tuning is only valid for maxmtu = MTU; if maxmtu is smaller,
1072 then it's better to use a multiplier of 1. Indeed, this leads to an interesting scenario
1073 if choose_initial_maxmtu() returns the actual MTU value - it will get confirmed with one single probe. */
1074 const float multiplier = (n->maxmtu == MTU) ? 0.97 : 1;
1076 const float cycle_position = probes_per_cycle - (n->mtuprobes % probes_per_cycle) - 1;
1077 const length_t minmtu = MAX(n->minmtu, 512);
1078 const float interval = n->maxmtu - minmtu;
1080 /* The core of the discovery algorithm is this exponential.
1081 It produces very large probes early in the cycle, and then it very quickly decreases the probe size.
1082 This reflects the fact that in the most difficult cases, we don't get any feedback for probes that
1083 are too large, and therefore we need to concentrate on small offsets so that we can quickly converge
1084 on the precise MTU as we are approaching it.
1085 The last probe of the cycle is always 1 byte in size - this is to make sure we'll get at least one
1086 reply per cycle so that we can make progress. */
1087 const length_t offset = powf(interval, multiplier * cycle_position / (probes_per_cycle - 1));
1089 length_t maxmtu = n->maxmtu;
1090 send_udp_probe_packet(n, minmtu + offset);
1091 /* If maxmtu changed, it means the probe was rejected by the system because it was too large.
1092 In that case, we recalculate with the new maxmtu and try again. */
1093 if(n->mtuprobes < 0 || maxmtu == n->maxmtu)
1097 if(n->mtuprobes >= 0)
1102 /* These functions try to establish a tunnel to a node (or its relay) so that
1103 packets can be sent (e.g. exchange keys).
1104 If a tunnel is already established, it tries to improve it (e.g. by trying
1105 to establish a UDP tunnel instead of TCP). This function makes no
1106 guarantees - it is up to the caller to check the node's state to figure out
1107 if TCP and/or UDP is usable. By calling this function repeatedly, the
1108 tunnel is gradually improved until we hit the wall imposed by the underlying
1109 network environment. It is recommended to call this function every time a
1110 packet is sent (or intended to be sent) to a node, so that the tunnel keeps
1111 improving as packets flow, and then gracefully downgrades itself as it goes
1115 static void try_tx_sptps(node_t *n, bool mtu) {
1116 /* If n is a TCP-only neighbor, we'll only use "cleartext" PACKET
1117 messages anyway, so there's no need for SPTPS at all. */
1119 if(n->connection && ((myself->options | n->options) & OPTION_TCPONLY))
1122 /* Otherwise, try to do SPTPS authentication with n if necessary. */
1126 /* Do we need to statically relay packets? */
1128 node_t *via = (n->via == myself) ? n->nexthop : n->via;
1130 /* If the static relay doesn't support SPTPS, everything goes via TCP anyway. */
1132 if((via->options >> 24) < 4)
1135 /* If we do have a static relay, try everything with that one instead. */
1138 return try_tx_sptps(via, mtu);
1140 /* Otherwise, try to establish UDP connectivity. */
1146 /* If we don't have UDP connectivity (yet), we need to use a dynamic relay (nexthop)
1147 while we try to establish direct connectivity. */
1149 if(!n->status.udp_confirmed && n != n->nexthop && (n->nexthop->options >> 24) >= 4)
1150 try_tx_sptps(n->nexthop, mtu);
1153 static void try_tx_legacy(node_t *n, bool mtu) {
1154 /* Does he have our key? If not, send one. */
1156 if(!n->status.validkey_in)
1159 /* Check if we already have a key, or request one. */
1161 if(!n->status.validkey) {
1162 if(n->last_req_key + 10 <= now.tv_sec) {
1164 n->last_req_key = now.tv_sec;
1174 void try_tx(node_t *n, bool mtu) {
1176 try_tx_sptps(n, mtu);
1178 try_tx_legacy(n, mtu);
1181 void send_packet(node_t *n, vpn_packet_t *packet) {
1182 // If it's for myself, write it to the tun/tap device.
1186 memcpy(DATA(packet), mymac.x, ETH_ALEN);
1188 n->out_bytes += packet->len;
1189 devops.write(packet);
1193 logger(DEBUG_TRAFFIC, LOG_ERR, "Sending packet of %d bytes to %s (%s)", packet->len, n->name, n->hostname);
1195 // If the node is not reachable, drop it.
1197 if(!n->status.reachable) {
1198 logger(DEBUG_TRAFFIC, LOG_INFO, "Node %s (%s) is not reachable", n->name, n->hostname);
1202 // Keep track of packet statistics.
1205 n->out_bytes += packet->len;
1207 // Check if it should be sent as an SPTPS packet.
1209 if(n->status.sptps) {
1210 send_sptps_packet(n, packet);
1211 try_tx_sptps(n, true);
1215 // Determine which node to actually send it to.
1217 node_t *via = (packet->priority == -1 || n->via == myself) ? n->nexthop : n->via;
1220 logger(DEBUG_TRAFFIC, LOG_INFO, "Sending packet to %s via %s (%s)", n->name, via->name, n->via->hostname);
1222 // Try to send via UDP, unless TCP is forced.
1224 if(packet->priority == -1 || ((myself->options | via->options) & OPTION_TCPONLY)) {
1225 if(!send_tcppacket(via->connection, packet))
1226 terminate_connection(via->connection, true);
1230 send_udppacket(via, packet);
1231 try_tx_legacy(via, true);
1234 void broadcast_packet(const node_t *from, vpn_packet_t *packet) {
1235 // Always give ourself a copy of the packet.
1237 send_packet(myself, packet);
1239 // In TunnelServer mode, do not forward broadcast packets.
1240 // The MST might not be valid and create loops.
1241 if(tunnelserver || broadcast_mode == BMODE_NONE)
1244 logger(DEBUG_TRAFFIC, LOG_INFO, "Broadcasting packet of %d bytes from %s (%s)",
1245 packet->len, from->name, from->hostname);
1247 switch(broadcast_mode) {
1248 // In MST mode, broadcast packets travel via the Minimum Spanning Tree.
1249 // This guarantees all nodes receive the broadcast packet, and
1250 // usually distributes the sending of broadcast packets over all nodes.
1252 for list_each(connection_t, c, connection_list)
1253 if(c->edge && c->status.mst && c != from->nexthop->connection)
1254 send_packet(c->node, packet);
1257 // In direct mode, we send copies to each node we know of.
1258 // However, this only reaches nodes that can be reached in a single hop.
1259 // We don't have enough information to forward broadcast packets in this case.
1264 for splay_each(node_t, n, node_tree)
1265 if(n->status.reachable && n != myself && ((n->via == myself && n->nexthop == n) || n->via == n))
1266 send_packet(n, packet);
1274 /* We got a packet from some IP address, but we don't know who sent it. Try to
1275 verify the message authentication code against all active session keys.
1276 Since this is actually an expensive operation, we only do a full check once
1277 a minute, the rest of the time we only check against nodes for which we know
1278 an IP address that matches the one from the packet. */
1280 static node_t *try_harder(const sockaddr_t *from, const vpn_packet_t *pkt) {
1281 node_t *match = NULL;
1283 static time_t last_hard_try = 0;
1285 for splay_each(node_t, n, node_tree) {
1286 if(!n->status.reachable || n == myself)
1289 if((n->status.sptps && !n->sptps.instate) || !n->status.validkey_in)
1294 for splay_each(edge_t, e, n->edge_tree) {
1297 if(!sockaddrcmp_noport(from, &e->reverse->address)) {
1304 if(last_hard_try == now.tv_sec)
1309 if(!try_mac(n, pkt))
1317 last_hard_try = now.tv_sec;
1322 void handle_incoming_vpn_data(void *data, int flags) {
1323 listen_socket_t *ls = data;
1326 node_id_t nullid = {};
1327 sockaddr_t addr = {};
1328 socklen_t addrlen = sizeof addr;
1330 bool direct = false;
1333 int len = recvfrom(ls->udp.fd, DATA(&pkt), MAXSIZE, 0, &addr.sa, &addrlen);
1335 if(len <= 0 || len > MAXSIZE) {
1336 if(!sockwouldblock(sockerrno))
1337 logger(DEBUG_ALWAYS, LOG_ERR, "Receiving packet failed: %s", sockstrerror(sockerrno));
1343 sockaddrunmap(&addr); /* Some braindead IPv6 implementations do stupid things. */
1345 // Try to figure out who sent this packet.
1347 node_t *n = lookup_node_udp(&addr);
1349 if(n && !n->status.udp_confirmed)
1350 n = NULL; // Don't believe it if we don't have confirmation yet.
1353 // It might be from a 1.1 node, which might have a source ID in the packet.
1354 pkt.offset = 2 * sizeof(node_id_t);
1355 from = lookup_node_id(SRCID(&pkt));
1356 if(from && !memcmp(DSTID(&pkt), &nullid, sizeof nullid) && from->status.sptps) {
1357 if(sptps_verify_datagram(&from->sptps, DATA(&pkt), pkt.len - 2 * sizeof(node_id_t)))
1366 n = try_harder(&addr, &pkt);
1371 if(debug_level >= DEBUG_PROTOCOL) {
1372 hostname = sockaddr2hostname(&addr);
1373 logger(DEBUG_PROTOCOL, LOG_WARNING, "Received UDP packet from unknown source %s", hostname);
1379 if(n->status.sptps) {
1380 pkt.offset = 2 * sizeof(node_id_t);
1382 if(!memcmp(DSTID(&pkt), &nullid, sizeof nullid)) {
1387 from = lookup_node_id(SRCID(&pkt));
1388 to = lookup_node_id(DSTID(&pkt));
1391 logger(DEBUG_PROTOCOL, LOG_WARNING, "Received UDP packet from %s (%s) with unknown source and/or destination ID", n->name, n->hostname);
1395 /* The packet is supposed to come from the originator or its static relay
1396 (i.e. with no dynamic relays in between).
1397 If it did not, "help" the static relay by sending it UDP info.
1398 Note that we only do this if we're the destination or the static relay;
1399 otherwise every hop would initiate its own UDP info message, resulting in elevated chatter. */
1401 if(n != from->via && to->via == myself)
1402 send_udp_info(myself, from);
1404 /* If we're not the final recipient, relay the packet. */
1407 send_sptps_data_priv(to, n, 0, DATA(&pkt), pkt.len - 2 * sizeof(node_id_t));
1408 try_tx_sptps(n, true);
1417 if(!receive_udppacket(from, &pkt))
1420 n->sock = ls - listen_socket;
1421 if(direct && sockaddrcmp(&addr, &n->address))
1422 update_node_udp(n, &addr);
1424 /* If the packet went through a relay, help the sender find the appropriate MTU
1425 through the relay path. */
1428 send_mtu_info(myself, n, MTU);
1431 void handle_device_data(void *data, int flags) {
1432 vpn_packet_t packet;
1433 packet.offset = DEFAULT_PACKET_OFFSET;
1434 packet.priority = 0;
1436 if(devops.read(&packet)) {
1437 myself->in_packets++;
1438 myself->in_bytes += packet.len;
1439 route(myself, &packet);