2 net_packet.c -- Handles in- and outgoing VPN packets
3 Copyright (C) 2014-2017 Guus Sliepen <guus@meshlink.io>
5 This program is free software; you can redistribute it and/or modify
6 it under the terms of the GNU General Public License as published by
7 the Free Software Foundation; either version 2 of the License, or
8 (at your option) any later version.
10 This program is distributed in the hope that it will be useful,
11 but WITHOUT ANY WARRANTY; without even the implied warranty of
12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
13 GNU General Public License for more details.
15 You should have received a copy of the GNU General Public License along
16 with this program; if not, write to the Free Software Foundation, Inc.,
17 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
23 #include "connection.h"
27 #include "meshlink_internal.h"
37 static void send_udppacket(meshlink_handle_t *mesh, node_t *, vpn_packet_t *);
39 #define MAX_SEQNO 1073741824
41 /* mtuprobes == 1..30: initial discovery, send bursts with 1 second interval
42 mtuprobes == 31: sleep pinginterval seconds
43 mtuprobes == 32: send 1 burst, sleep pingtimeout second
44 mtuprobes == 33: no response from other side, restart PMTU discovery process
46 Probes are sent in batches of at least three, with random sizes between the
47 lower and upper boundaries for the MTU thus far discovered.
49 After the initial discovery, a fourth packet is added to each batch with a
50 size larger than the currently known PMTU, to test if the PMTU has increased.
52 In case local discovery is enabled, another packet is added to each batch,
53 which will be broadcast to the local network.
57 static void send_mtu_probe_handler(event_loop_t *loop, void *data) {
58 meshlink_handle_t *mesh = loop->data;
64 if(!n->status.reachable || !n->status.validkey) {
65 logger(mesh, MESHLINK_INFO, "Trying to send MTU probe to unreachable or rekeying node %s", n->name);
70 if(n->mtuprobes > 32) {
73 timeout = mesh->dev_class_traits[n->devclass].pinginterval;
77 logger(mesh, MESHLINK_INFO, "%s did not respond to UDP ping, restarting PMTU discovery", n->name);
78 n->status.udp_confirmed = false;
83 update_node_pmtu(mesh, n);
86 if(n->mtuprobes >= 10 && n->mtuprobes < 32 && !n->minmtu) {
87 logger(mesh, MESHLINK_INFO, "No response to MTU probes from %s", n->name);
91 if(n->mtuprobes == 30 || (n->mtuprobes < 30 && n->minmtu >= n->maxmtu)) {
92 if(n->minmtu > n->maxmtu) {
93 n->minmtu = n->maxmtu;
94 update_node_pmtu(mesh, n);
96 n->maxmtu = n->minmtu;
100 logger(mesh, MESHLINK_INFO, "Fixing MTU of %s to %d after %d probes", n->name, n->mtu, n->mtuprobes);
104 if(n->mtuprobes == 31) {
105 if(!n->minmtu && n->status.want_udp) {
106 /* Send a dummy ANS_KEY to try to update the reflexive UDP address */
107 send_request(mesh, n->nexthop->connection, NULL, "%d %s %s . -1 -1 -1 0", ANS_KEY, mesh->self->name, n->name);
108 n->status.want_udp = false;
111 timeout = mesh->dev_class_traits[n->devclass].pinginterval;
113 } else if(n->mtuprobes == 32) {
114 timeout = mesh->dev_class_traits[n->devclass].pingtimeout;
117 for(int i = 0; i < 5; i++) {
121 if(n->mtuprobes < 30 || n->maxmtu + 8 >= MTU) {
126 } else if(n->maxmtu <= n->minmtu) {
129 len = n->minmtu + 1 + prng(mesh, n->maxmtu - n->minmtu);
138 memset(packet.data, 0, 14);
139 randomize(packet.data + 14, len - 14);
141 n->status.broadcast = i >= 4 && n->mtuprobes <= 10 && n->prevedge;
143 logger(mesh, MESHLINK_DEBUG, "Sending MTU probe length %d to %s", len, n->name);
145 send_udppacket(mesh, n, &packet);
148 n->status.broadcast = false;
151 timeout_set(&mesh->loop, &n->mtutimeout, &(struct timespec) {
152 timeout, prng(mesh, TIMER_FUDGE)
156 void send_mtu_probe(meshlink_handle_t *mesh, node_t *n) {
157 timeout_add(&mesh->loop, &n->mtutimeout, send_mtu_probe_handler, n, &(struct timespec) {
160 send_mtu_probe_handler(&mesh->loop, n);
163 static void mtu_probe_h(meshlink_handle_t *mesh, node_t *n, vpn_packet_t *packet, uint16_t len) {
165 logger(mesh, MESHLINK_WARNING, "Got too short MTU probe length %d from %s", packet->len, n->name);
169 logger(mesh, MESHLINK_DEBUG, "Got MTU probe length %d from %s", packet->len, n->name);
171 if(!packet->data[0]) {
172 /* It's a probe request, send back a reply */
176 /* Temporarily set udp_confirmed, so that the reply is sent
177 back exactly the way it came in. */
179 bool udp_confirmed = n->status.udp_confirmed;
180 n->status.udp_confirmed = true;
181 send_udppacket(mesh, n, packet);
182 n->status.udp_confirmed = udp_confirmed;
184 /* It's a valid reply: now we know bidirectional communication
185 is possible using the address and socket that the reply
188 if(!n->status.udp_confirmed) {
189 char *address, *port;
190 sockaddr2str(&n->address, &address, &port);
191 send_request(mesh, n->nexthop->connection, NULL, "%d %s %s . -1 -1 -1 0 %s %s", ANS_KEY, n->name, n->name, address, port);
194 n->status.udp_confirmed = true;
197 /* If we haven't established the PMTU yet, restart the discovery process. */
199 if(n->mtuprobes > 30) {
200 if(len == n->maxmtu + 8) {
201 logger(mesh, MESHLINK_INFO, "Increase in PMTU to %s detected, restarting PMTU discovery", n->name);
214 /* If applicable, raise the minimum supported MTU */
216 if(len > n->maxmtu) {
220 if(n->minmtu < len) {
222 update_node_pmtu(mesh, n);
229 static void receive_packet(meshlink_handle_t *mesh, node_t *n, vpn_packet_t *packet) {
230 logger(mesh, MESHLINK_DEBUG, "Received packet of %d bytes from %s", packet->len, n->name);
232 if(n->status.blacklisted) {
233 logger(mesh, MESHLINK_WARNING, "Dropping packet from blacklisted node %s", n->name);
236 n->in_bytes += packet->len;
238 route(mesh, n, packet);
242 static bool try_mac(meshlink_handle_t *mesh, node_t *n, const vpn_packet_t *inpkt) {
244 return sptps_verify_datagram(&n->sptps, inpkt->data, inpkt->len);
247 static void receive_udppacket(meshlink_handle_t *mesh, node_t *n, vpn_packet_t *inpkt) {
248 if(!n->sptps.state) {
249 if(!n->status.waitingforkey) {
250 logger(mesh, MESHLINK_DEBUG, "Got packet from %s but we haven't exchanged keys yet", n->name);
251 send_req_key(mesh, n);
253 logger(mesh, MESHLINK_DEBUG, "Got packet from %s but he hasn't got our key yet", n->name);
259 if(!sptps_receive_data(&n->sptps, inpkt->data, inpkt->len)) {
260 logger(mesh, MESHLINK_ERROR, "Could not process SPTPS data from %s: %s", n->name, strerror(errno));
264 static void send_sptps_packet(meshlink_handle_t *mesh, node_t *n, vpn_packet_t *origpkt) {
265 if(!n->status.validkey) {
266 logger(mesh, MESHLINK_INFO, "No valid key known yet for %s", n->name);
268 if(!n->status.waitingforkey) {
269 send_req_key(mesh, n);
270 } else if(n->last_req_key + 10 < mesh->loop.now.tv_sec) {
271 logger(mesh, MESHLINK_DEBUG, "No key from %s after 10 seconds, restarting SPTPS", n->name);
272 sptps_stop(&n->sptps);
273 n->status.waitingforkey = false;
274 send_req_key(mesh, n);
282 // If it's a probe, send it immediately without trying to compress it.
284 sptps_send_record(&n->sptps, PKT_PROBE, origpkt->data, origpkt->len);
288 sptps_send_record(&n->sptps, type, origpkt->data, origpkt->len);
292 static void choose_udp_address(meshlink_handle_t *mesh, const node_t *n, const sockaddr_t **sa, int *sock) {
297 /* If the UDP address is confirmed, use it. */
298 if(n->status.udp_confirmed) {
302 /* Send every third packet to n->address; that could be set
303 to the node's reflexive UDP address discovered during key
306 if(++mesh->udp_choice >= 3) {
307 mesh->udp_choice = 0;
311 /* If we have learned an address via Catta, try this once every batch */
312 if(mesh->udp_choice == 1 && n->catta_address.sa.sa_family != AF_UNSPEC) {
313 *sa = &n->catta_address;
317 /* Otherwise, address are found in edges to this node.
318 So we pick a random edge and a random socket. */
321 int j = prng(mesh, n->edge_tree->count);
322 edge_t *candidate = NULL;
324 for splay_each(edge_t, e, n->edge_tree) {
326 candidate = e->reverse;
332 *sa = &candidate->address;
333 *sock = prng(mesh, mesh->listen_sockets);
337 /* Make sure we have a suitable socket for the chosen address */
338 if(mesh->listen_socket[*sock].sa.sa.sa_family != (*sa)->sa.sa_family) {
339 for(int i = 0; i < mesh->listen_sockets; i++) {
340 if(mesh->listen_socket[i].sa.sa.sa_family == (*sa)->sa.sa_family) {
348 static void choose_broadcast_address(meshlink_handle_t *mesh, const node_t *n, const sockaddr_t **sa, int *sock) {
349 *sock = prng(mesh, mesh->listen_sockets);
350 sockaddr_t *broadcast_sa = &mesh->listen_socket[*sock].broadcast_sa;
352 if(broadcast_sa->sa.sa_family == AF_INET6) {
353 broadcast_sa->in6.sin6_port = n->prevedge->address.in.sin_port;
355 broadcast_sa->in.sin_port = n->prevedge->address.in.sin_port;
361 static void send_udppacket(meshlink_handle_t *mesh, node_t *n, vpn_packet_t *origpkt) {
362 if(!n->status.reachable) {
363 logger(mesh, MESHLINK_INFO, "Trying to send UDP packet to unreachable node %s", n->name);
367 send_sptps_packet(mesh, n, origpkt);
370 bool send_sptps_data(void *handle, uint8_t type, const void *data, size_t len) {
376 meshlink_handle_t *mesh = to->mesh;
378 /* Send it via TCP if it is a handshake packet, TCPOnly is in use, or this packet is larger than the MTU. */
380 if(type >= SPTPS_HANDSHAKE || (type != PKT_PROBE && (len - 21) > to->minmtu)) {
381 char buf[len * 4 / 3 + 5];
382 b64encode(data, buf, len);
384 /* If no valid key is known yet, send the packets using ANS_KEY requests,
385 to ensure we get to learn the reflexive UDP address. */
386 if(!to->status.validkey) {
387 return send_request(mesh, to->nexthop->connection, NULL, "%d %s %s %s -1 -1 -1 %d", ANS_KEY, mesh->self->name, to->name, buf, 0);
389 return send_request(mesh, to->nexthop->connection, NULL, "%d %s %s %d %s", REQ_KEY, mesh->self->name, to->name, REQ_SPTPS, buf);
393 /* Otherwise, send the packet via UDP */
395 const sockaddr_t *sa;
398 if(to->status.broadcast) {
399 choose_broadcast_address(mesh, to, &sa, &sock);
401 choose_udp_address(mesh, to, &sa, &sock);
404 if(sendto(mesh->listen_socket[sock].udp.fd, data, len, 0, &sa->sa, SALEN(sa->sa)) < 0 && !sockwouldblock(sockerrno)) {
405 if(sockmsgsize(sockerrno)) {
406 if(to->maxmtu >= len) {
407 to->maxmtu = len - 1;
414 logger(mesh, MESHLINK_WARNING, "Error sending UDP SPTPS packet to %s: %s", to->name, sockstrerror(sockerrno));
422 bool receive_sptps_record(void *handle, uint8_t type, const void *data, uint16_t len) {
424 assert(!data || len);
426 node_t *from = handle;
427 meshlink_handle_t *mesh = from->mesh;
429 if(type == SPTPS_HANDSHAKE) {
430 if(!from->status.validkey) {
431 logger(mesh, MESHLINK_INFO, "SPTPS key exchange with %s successful", from->name);
432 from->status.validkey = true;
433 from->status.waitingforkey = false;
436 utcp_reset_timers(from->utcp);
444 logger(mesh, MESHLINK_ERROR, "Packet from %s larger than maximum supported size (%d > %d)", from->name, len, MAXSIZE);
450 if(type == PKT_PROBE) {
453 memcpy(inpkt.data, data, len);
454 mtu_probe_h(mesh, from, &inpkt, len);
460 if(type & ~(PKT_COMPRESSED)) {
461 logger(mesh, MESHLINK_ERROR, "Unexpected SPTPS record type %d len %d from %s", type, len, from->name);
465 if(type & PKT_COMPRESSED) {
466 logger(mesh, MESHLINK_ERROR, "Error while decompressing packet from %s", from->name);
470 memcpy(inpkt.data, data, len); // TODO: get rid of memcpy
473 receive_packet(mesh, from, &inpkt);
478 send a packet to the given vpn ip.
480 void send_packet(meshlink_handle_t *mesh, node_t *n, vpn_packet_t *packet) {
481 if(n == mesh->self) {
483 n->out_bytes += packet->len;
484 // TODO: send to application
488 logger(mesh, MESHLINK_DEBUG, "Sending packet of %d bytes to %s", packet->len, n->name);
490 if(!n->status.reachable) {
491 logger(mesh, MESHLINK_WARNING, "Node %s is not reachable", n->name);
496 n->out_bytes += packet->len;
497 n->status.want_udp = true;
499 send_sptps_packet(mesh, n, packet);
503 static node_t *try_harder(meshlink_handle_t *mesh, const sockaddr_t *from, const vpn_packet_t *pkt) {
507 for splay_each(edge_t, e, mesh->edges) {
508 if(!e->to->status.reachable || e->to == mesh->self) {
512 if(sockaddrcmp_noport(from, &e->address)) {
513 if(mesh->last_hard_try == mesh->loop.now.tv_sec) {
520 if(!try_mac(mesh, e->to, pkt)) {
529 mesh->last_hard_try = mesh->loop.now.tv_sec;
535 void handle_incoming_vpn_data(event_loop_t *loop, void *data, int flags) {
537 meshlink_handle_t *mesh = loop->data;
538 listen_socket_t *ls = data;
542 socklen_t fromlen = sizeof(from);
546 memset(&from, 0, sizeof(from));
548 len = recvfrom(ls->udp.fd, pkt.data, MAXSIZE, 0, &from.sa, &fromlen);
550 if(len <= 0 || len > MAXSIZE) {
551 if(!sockwouldblock(sockerrno)) {
552 logger(mesh, MESHLINK_ERROR, "Receiving packet failed: %s", sockstrerror(sockerrno));
560 sockaddrunmap(&from); /* Some braindead IPv6 implementations do stupid things. */
562 n = lookup_node_udp(mesh, &from);
565 n = try_harder(mesh, &from, &pkt);
568 update_node_udp(mesh, n, &from);
569 } else if(mesh->log_level <= MESHLINK_WARNING) {
570 hostname = sockaddr2hostname(&from);
571 logger(mesh, MESHLINK_WARNING, "Received UDP packet from unknown source %s", hostname);
579 if(n->status.blacklisted) {
580 logger(mesh, MESHLINK_WARNING, "Dropping packet from blacklisted node %s", n->name);
584 n->sock = ls - mesh->listen_socket;
586 receive_udppacket(mesh, n, &pkt);