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 = 32;
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 bool send_sptps_data(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, SPTPS_PACKET, 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 receive_sptps_record(void *handle, uint8_t type, const void *data, uint16_t len) {
748 node_t *from = handle;
750 if(type == SPTPS_HANDSHAKE) {
751 if(!from->status.validkey) {
752 from->status.validkey = true;
753 from->status.waitingforkey = false;
754 logger(DEBUG_META, LOG_INFO, "SPTPS key exchange with %s (%s) succesful", from->name, from->hostname);
760 logger(DEBUG_ALWAYS, LOG_ERR, "Packet from %s (%s) larger than maximum supported size (%d > %d)", from->name, from->hostname, len, MTU);
765 inpkt.offset = DEFAULT_PACKET_OFFSET;
767 if(type == PKT_PROBE) {
768 if(!from->status.udppacket) {
769 logger(DEBUG_ALWAYS, LOG_ERR, "Got SPTPS PROBE packet from %s (%s) via TCP", from->name, from->hostname);
773 memcpy(DATA(&inpkt), data, len);
774 if(inpkt.len > from->maxrecentlen)
775 from->maxrecentlen = inpkt.len;
776 udp_probe_h(from, &inpkt, len);
780 if(type & ~(PKT_COMPRESSED | PKT_MAC)) {
781 logger(DEBUG_ALWAYS, LOG_ERR, "Unexpected SPTPS record type %d len %d from %s (%s)", type, len, from->name, from->hostname);
785 /* Check if we have the headers we need */
786 if(routing_mode != RMODE_ROUTER && !(type & PKT_MAC)) {
787 logger(DEBUG_TRAFFIC, LOG_ERR, "Received packet from %s (%s) without MAC header (maybe Mode is not set correctly)", from->name, from->hostname);
789 } else if(routing_mode == RMODE_ROUTER && (type & PKT_MAC)) {
790 logger(DEBUG_TRAFFIC, LOG_WARNING, "Received packet from %s (%s) with MAC header (maybe Mode is not set correctly)", from->name, from->hostname);
793 int offset = (type & PKT_MAC) ? 0 : 14;
794 if(type & PKT_COMPRESSED) {
795 length_t ulen = uncompress_packet(DATA(&inpkt) + offset, (const uint8_t *)data, len, from->incompression);
799 inpkt.len = ulen + offset;
801 if(inpkt.len > MAXSIZE)
804 memcpy(DATA(&inpkt) + offset, data, len);
805 inpkt.len = len + offset;
808 /* Generate the Ethernet packet type if necessary */
810 switch(DATA(&inpkt)[14] >> 4) {
812 DATA(&inpkt)[12] = 0x08;
813 DATA(&inpkt)[13] = 0x00;
816 DATA(&inpkt)[12] = 0x86;
817 DATA(&inpkt)[13] = 0xDD;
820 logger(DEBUG_TRAFFIC, LOG_ERR,
821 "Unknown IP version %d while reading packet from %s (%s)",
822 DATA(&inpkt)[14] >> 4, from->name, from->hostname);
827 if(from->status.udppacket && inpkt.len > from->maxrecentlen)
828 from->maxrecentlen = inpkt.len;
830 receive_packet(from, &inpkt);
834 // This function tries to get SPTPS keys, if they aren't already known.
835 // 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.
836 static void try_sptps(node_t *n) {
837 if(n->status.validkey)
840 logger(DEBUG_TRAFFIC, LOG_INFO, "No valid key known yet for %s (%s)", n->name, n->hostname);
842 if(!n->status.waitingforkey)
844 else if(n->last_req_key + 10 < now.tv_sec) {
845 logger(DEBUG_ALWAYS, LOG_DEBUG, "No key from %s after 10 seconds, restarting SPTPS", n->name);
846 sptps_stop(&n->sptps);
847 n->status.waitingforkey = false;
854 static void send_udp_probe_packet(node_t *n, int len) {
856 packet.offset = DEFAULT_PACKET_OFFSET;
857 memset(DATA(&packet), 0, 14);
858 randomize(DATA(&packet) + 14, len - 14);
862 logger(DEBUG_TRAFFIC, LOG_INFO, "Sending UDP probe length %d to %s (%s)", len, n->name, n->hostname);
864 send_udppacket(n, &packet);
867 // This function tries to establish a UDP tunnel to a node so that packets can be sent.
868 // If a tunnel is already established, it makes sure it stays up.
869 // This function makes no guarantees - it is up to the caller to check the node's state to figure out if UDP is usable.
870 static void try_udp(node_t* n) {
874 /* Send gratuitous probe replies to 1.1 nodes. */
876 if((n->options >> 24) >= 3 && n->status.udp_confirmed) {
877 struct timeval ping_tx_elapsed;
878 timersub(&now, &n->udp_reply_sent, &ping_tx_elapsed);
880 if(ping_tx_elapsed.tv_sec >= udp_discovery_keepalive_interval - 1) {
881 n->udp_reply_sent = now;
882 if(n->maxrecentlen) {
884 pkt.len = n->maxrecentlen;
885 pkt.offset = DEFAULT_PACKET_OFFSET;
886 memset(DATA(&pkt), 0, 14);
887 randomize(DATA(&pkt) + 14, MIN_PROBE_SIZE - 14);
888 send_udp_probe_reply(n, &pkt, pkt.len);
896 struct timeval ping_tx_elapsed;
897 timersub(&now, &n->udp_ping_sent, &ping_tx_elapsed);
899 int interval = n->status.udp_confirmed ? udp_discovery_keepalive_interval : udp_discovery_interval;
901 if(ping_tx_elapsed.tv_sec >= interval) {
902 send_udp_probe_packet(n, MIN_PROBE_SIZE);
903 n->udp_ping_sent = now;
905 if(localdiscovery && !n->status.udp_confirmed && n->prevedge) {
906 n->status.send_locally = true;
907 send_udp_probe_packet(n, MIN_PROBE_SIZE);
908 n->status.send_locally = false;
913 static length_t choose_initial_maxmtu(node_t *n) {
918 const sockaddr_t *sa = NULL;
920 choose_udp_address(n, &sa, &sockindex);
924 sock = socket(sa->sa.sa_family, SOCK_DGRAM, IPPROTO_UDP);
926 logger(DEBUG_TRAFFIC, LOG_ERR, "Creating MTU assessment socket for %s (%s) failed: %s", n->name, n->hostname, sockstrerror(sockerrno));
930 if(connect(sock, &sa->sa, SALEN(sa->sa))) {
931 logger(DEBUG_TRAFFIC, LOG_ERR, "Connecting MTU assessment socket for %s (%s) failed: %s", n->name, n->hostname, sockstrerror(sockerrno));
937 socklen_t ip_mtu_len = sizeof ip_mtu;
938 if(getsockopt(sock, IPPROTO_IP, IP_MTU, &ip_mtu, &ip_mtu_len)) {
939 logger(DEBUG_TRAFFIC, LOG_ERR, "getsockopt(IP_MTU) on %s (%s) failed: %s", n->name, n->hostname, sockstrerror(sockerrno));
946 /* getsockopt(IP_MTU) returns the MTU of the physical interface.
947 We need to remove various overheads to get to the tinc MTU. */
948 length_t mtu = ip_mtu;
949 mtu -= (sa->sa.sa_family == AF_INET6) ? sizeof(struct ip6_hdr) : sizeof(struct ip);
951 if(n->status.sptps) {
952 mtu -= SPTPS_DATAGRAM_OVERHEAD;
953 if((n->options >> 24) >= 4)
954 mtu -= sizeof(node_id_t) + sizeof(node_id_t);
955 #ifndef DISABLE_LEGACY
957 mtu -= digest_length(n->outdigest);
959 /* Now it's tricky. We use CBC mode, so the length of the
960 encrypted payload must be a multiple of the blocksize. The
961 sequence number is also part of the encrypted payload, so we
962 must account for it after correcting for the blocksize.
963 Furthermore, the padding in the last block must be at least
966 length_t blocksize = cipher_blocksize(n->outcipher);
979 logger(DEBUG_TRAFFIC, LOG_ERR, "getsockopt(IP_MTU) on %s (%s) returned absurdly small value: %d", n->name, n->hostname, ip_mtu);
985 logger(DEBUG_TRAFFIC, LOG_INFO, "Using system-provided maximum tinc MTU for %s (%s): %hd", n->name, n->hostname, mtu);
995 /* This function tries to determines the MTU of a node.
996 By calling this function repeatedly, n->minmtu will be progressively
997 increased, and at some point, n->mtu will be fixed to n->minmtu. If the MTU
998 is already fixed, this function checks if it can be increased.
1001 static void try_mtu(node_t *n) {
1002 if(!(n->options & OPTION_PMTU_DISCOVERY))
1005 if(udp_discovery && !n->status.udp_confirmed) {
1006 n->maxrecentlen = 0;
1013 /* mtuprobes == 0..19: initial discovery, send bursts with 1 second interval, mtuprobes++
1014 mtuprobes == 20: fix MTU, and go to -1
1015 mtuprobes == -1: send one maxmtu and one maxmtu+1 probe every pinginterval
1016 mtuprobes ==-2..-3: send one maxmtu probe every second
1017 mtuprobes == -4: maxmtu no longer valid, reset minmtu and maxmtu and go to 0 */
1019 struct timeval elapsed;
1020 timersub(&now, &n->mtu_ping_sent, &elapsed);
1021 if(n->mtuprobes >= 0) {
1022 if(n->mtuprobes != 0 && elapsed.tv_sec == 0 && elapsed.tv_usec < 333333)
1025 if(n->mtuprobes < -1) {
1026 if(elapsed.tv_sec < 1)
1029 if(elapsed.tv_sec < pinginterval)
1034 n->mtu_ping_sent = now;
1038 if(n->mtuprobes < -3) {
1039 /* We lost three MTU probes, restart discovery */
1040 logger(DEBUG_TRAFFIC, LOG_INFO, "Decrease in PMTU to %s (%s) detected, restarting PMTU discovery", n->name, n->hostname);
1045 if(n->mtuprobes < 0) {
1046 /* After the initial discovery, we only send one maxmtu and one
1047 maxmtu+1 probe to detect PMTU increases. */
1048 send_udp_probe_packet(n, n->maxmtu);
1049 if(n->mtuprobes == -1 && n->maxmtu + 1 < MTU)
1050 send_udp_probe_packet(n, n->maxmtu + 1);
1053 /* Before initial discovery begins, set maxmtu to the most likely value.
1054 If it's underestimated, we will correct it after initial discovery. */
1055 if(n->mtuprobes == 0)
1056 n->maxmtu = choose_initial_maxmtu(n);
1059 /* Decreasing the number of probes per cycle might make the algorithm react faster to lost packets,
1060 but it will typically increase convergence time in the no-loss case. */
1061 const length_t probes_per_cycle = 8;
1063 /* This magic value was determined using math simulations.
1064 It will result in a 1329-byte first probe, followed (if there was a reply) by a 1407-byte probe.
1065 Since 1407 is just below the range of tinc MTUs over typical networks,
1066 this fine-tuning allows tinc to cover a lot of ground very quickly.
1067 This fine-tuning is only valid for maxmtu = MTU; if maxmtu is smaller,
1068 then it's better to use a multiplier of 1. Indeed, this leads to an interesting scenario
1069 if choose_initial_maxmtu() returns the actual MTU value - it will get confirmed with one single probe. */
1070 const float multiplier = (n->maxmtu == MTU) ? 0.97 : 1;
1072 const float cycle_position = probes_per_cycle - (n->mtuprobes % probes_per_cycle) - 1;
1073 const length_t minmtu = MAX(n->minmtu, 512);
1074 const float interval = n->maxmtu - minmtu;
1076 /* The core of the discovery algorithm is this exponential.
1077 It produces very large probes early in the cycle, and then it very quickly decreases the probe size.
1078 This reflects the fact that in the most difficult cases, we don't get any feedback for probes that
1079 are too large, and therefore we need to concentrate on small offsets so that we can quickly converge
1080 on the precise MTU as we are approaching it.
1081 The last probe of the cycle is always 1 byte in size - this is to make sure we'll get at least one
1082 reply per cycle so that we can make progress. */
1083 const length_t offset = powf(interval, multiplier * cycle_position / (probes_per_cycle - 1));
1085 length_t maxmtu = n->maxmtu;
1086 send_udp_probe_packet(n, minmtu + offset);
1087 /* If maxmtu changed, it means the probe was rejected by the system because it was too large.
1088 In that case, we recalculate with the new maxmtu and try again. */
1089 if(n->mtuprobes < 0 || maxmtu == n->maxmtu)
1093 if(n->mtuprobes >= 0)
1098 /* These functions try to establish a tunnel to a node (or its relay) so that
1099 packets can be sent (e.g. exchange keys).
1100 If a tunnel is already established, it tries to improve it (e.g. by trying
1101 to establish a UDP tunnel instead of TCP). This function makes no
1102 guarantees - it is up to the caller to check the node's state to figure out
1103 if TCP and/or UDP is usable. By calling this function repeatedly, the
1104 tunnel is gradually improved until we hit the wall imposed by the underlying
1105 network environment. It is recommended to call this function every time a
1106 packet is sent (or intended to be sent) to a node, so that the tunnel keeps
1107 improving as packets flow, and then gracefully downgrades itself as it goes
1111 static void try_tx_sptps(node_t *n, bool mtu) {
1112 /* If n is a TCP-only neighbor, we'll only use "cleartext" PACKET
1113 messages anyway, so there's no need for SPTPS at all. */
1115 if(n->connection && ((myself->options | n->options) & OPTION_TCPONLY))
1118 /* Otherwise, try to do SPTPS authentication with n if necessary. */
1122 /* Do we need to statically relay packets? */
1124 node_t *via = (n->via == myself) ? n->nexthop : n->via;
1126 /* If the static relay doesn't support SPTPS, everything goes via TCP anyway. */
1128 if((via->options >> 24) < 4)
1131 /* If we do have a static relay, try everything with that one instead. */
1134 return try_tx_sptps(via, mtu);
1136 /* Otherwise, try to establish UDP connectivity. */
1142 /* If we don't have UDP connectivity (yet), we need to use a dynamic relay (nexthop)
1143 while we try to establish direct connectivity. */
1145 if(!n->status.udp_confirmed && n != n->nexthop && (n->nexthop->options >> 24) >= 4)
1146 try_tx_sptps(n->nexthop, mtu);
1149 static void try_tx_legacy(node_t *n, bool mtu) {
1150 /* Does he have our key? If not, send one. */
1152 if(!n->status.validkey_in)
1155 /* Check if we already have a key, or request one. */
1157 if(!n->status.validkey) {
1158 if(n->last_req_key + 10 <= now.tv_sec) {
1160 n->last_req_key = now.tv_sec;
1170 void try_tx(node_t *n, bool mtu) {
1172 try_tx_sptps(n, mtu);
1174 try_tx_legacy(n, mtu);
1177 void send_packet(node_t *n, vpn_packet_t *packet) {
1178 // If it's for myself, write it to the tun/tap device.
1182 memcpy(DATA(packet), mymac.x, ETH_ALEN);
1184 n->out_bytes += packet->len;
1185 devops.write(packet);
1189 logger(DEBUG_TRAFFIC, LOG_ERR, "Sending packet of %d bytes to %s (%s)", packet->len, n->name, n->hostname);
1191 // If the node is not reachable, drop it.
1193 if(!n->status.reachable) {
1194 logger(DEBUG_TRAFFIC, LOG_INFO, "Node %s (%s) is not reachable", n->name, n->hostname);
1198 // Keep track of packet statistics.
1201 n->out_bytes += packet->len;
1203 // Check if it should be sent as an SPTPS packet.
1205 if(n->status.sptps) {
1206 send_sptps_packet(n, packet);
1207 try_tx_sptps(n, true);
1211 // Determine which node to actually send it to.
1213 node_t *via = (packet->priority == -1 || n->via == myself) ? n->nexthop : n->via;
1216 logger(DEBUG_TRAFFIC, LOG_INFO, "Sending packet to %s via %s (%s)", n->name, via->name, n->via->hostname);
1218 // Try to send via UDP, unless TCP is forced.
1220 if(packet->priority == -1 || ((myself->options | via->options) & OPTION_TCPONLY)) {
1221 if(!send_tcppacket(via->connection, packet))
1222 terminate_connection(via->connection, true);
1226 send_udppacket(via, packet);
1227 try_tx_legacy(via, true);
1230 void broadcast_packet(const node_t *from, vpn_packet_t *packet) {
1231 // Always give ourself a copy of the packet.
1233 send_packet(myself, packet);
1235 // In TunnelServer mode, do not forward broadcast packets.
1236 // The MST might not be valid and create loops.
1237 if(tunnelserver || broadcast_mode == BMODE_NONE)
1240 logger(DEBUG_TRAFFIC, LOG_INFO, "Broadcasting packet of %d bytes from %s (%s)",
1241 packet->len, from->name, from->hostname);
1243 switch(broadcast_mode) {
1244 // In MST mode, broadcast packets travel via the Minimum Spanning Tree.
1245 // This guarantees all nodes receive the broadcast packet, and
1246 // usually distributes the sending of broadcast packets over all nodes.
1248 for list_each(connection_t, c, connection_list)
1249 if(c->edge && c->status.mst && c != from->nexthop->connection)
1250 send_packet(c->node, packet);
1253 // In direct mode, we send copies to each node we know of.
1254 // However, this only reaches nodes that can be reached in a single hop.
1255 // We don't have enough information to forward broadcast packets in this case.
1260 for splay_each(node_t, n, node_tree)
1261 if(n->status.reachable && n != myself && ((n->via == myself && n->nexthop == n) || n->via == n))
1262 send_packet(n, packet);
1270 /* We got a packet from some IP address, but we don't know who sent it. Try to
1271 verify the message authentication code against all active session keys.
1272 Since this is actually an expensive operation, we only do a full check once
1273 a minute, the rest of the time we only check against nodes for which we know
1274 an IP address that matches the one from the packet. */
1276 static node_t *try_harder(const sockaddr_t *from, const vpn_packet_t *pkt) {
1277 node_t *match = NULL;
1279 static time_t last_hard_try = 0;
1281 for splay_each(node_t, n, node_tree) {
1282 if(!n->status.reachable || n == myself)
1285 if((n->status.sptps && !n->sptps.instate) || !n->status.validkey_in)
1290 for splay_each(edge_t, e, n->edge_tree) {
1293 if(!sockaddrcmp_noport(from, &e->reverse->address)) {
1300 if(last_hard_try == now.tv_sec)
1305 if(!try_mac(n, pkt))
1313 last_hard_try = now.tv_sec;
1318 void handle_incoming_vpn_data(void *data, int flags) {
1319 listen_socket_t *ls = data;
1322 node_id_t nullid = {};
1323 sockaddr_t addr = {};
1324 socklen_t addrlen = sizeof addr;
1326 bool direct = false;
1329 int len = recvfrom(ls->udp.fd, DATA(&pkt), MAXSIZE, 0, &addr.sa, &addrlen);
1331 if(len <= 0 || len > MAXSIZE) {
1332 if(!sockwouldblock(sockerrno))
1333 logger(DEBUG_ALWAYS, LOG_ERR, "Receiving packet failed: %s", sockstrerror(sockerrno));
1339 sockaddrunmap(&addr); /* Some braindead IPv6 implementations do stupid things. */
1341 // Try to figure out who sent this packet.
1343 node_t *n = lookup_node_udp(&addr);
1345 if(n && !n->status.udp_confirmed)
1346 n = NULL; // Don't believe it if we don't have confirmation yet.
1349 // It might be from a 1.1 node, which might have a source ID in the packet.
1350 pkt.offset = 2 * sizeof(node_id_t);
1351 from = lookup_node_id(SRCID(&pkt));
1352 if(from && !memcmp(DSTID(&pkt), &nullid, sizeof nullid) && from->status.sptps) {
1353 if(sptps_verify_datagram(&from->sptps, DATA(&pkt), pkt.len - 2 * sizeof(node_id_t)))
1362 n = try_harder(&addr, &pkt);
1367 if(debug_level >= DEBUG_PROTOCOL) {
1368 hostname = sockaddr2hostname(&addr);
1369 logger(DEBUG_PROTOCOL, LOG_WARNING, "Received UDP packet from unknown source %s", hostname);
1375 if(n->status.sptps) {
1376 pkt.offset = 2 * sizeof(node_id_t);
1378 if(!memcmp(DSTID(&pkt), &nullid, sizeof nullid)) {
1383 from = lookup_node_id(SRCID(&pkt));
1384 to = lookup_node_id(DSTID(&pkt));
1387 logger(DEBUG_PROTOCOL, LOG_WARNING, "Received UDP packet from %s (%s) with unknown source and/or destination ID", n->name, n->hostname);
1391 /* The packet is supposed to come from the originator or its static relay
1392 (i.e. with no dynamic relays in between).
1393 If it did not, "help" the static relay by sending it UDP info.
1394 Note that we only do this if we're the destination or the static relay;
1395 otherwise every hop would initiate its own UDP info message, resulting in elevated chatter. */
1397 if(n != from->via && to->via == myself)
1398 send_udp_info(myself, from);
1400 /* If we're not the final recipient, relay the packet. */
1403 send_sptps_data(to, from, 0, DATA(&pkt), pkt.len - 2 * sizeof(node_id_t));
1404 try_tx_sptps(to, true);
1413 if(!receive_udppacket(from, &pkt))
1416 n->sock = ls - listen_socket;
1417 if(direct && sockaddrcmp(&addr, &n->address))
1418 update_node_udp(n, &addr);
1420 /* If the packet went through a relay, help the sender find the appropriate MTU
1421 through the relay path. */
1424 send_mtu_info(myself, n, MTU);
1427 void handle_device_data(void *data, int flags) {
1428 vpn_packet_t packet;
1429 packet.offset = DEFAULT_PACKET_OFFSET;
1430 packet.priority = 0;
1432 if(devops.read(&packet)) {
1433 myself->in_packets++;
1434 myself->in_bytes += packet.len;
1435 route(myself, &packet);