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 timeval) {
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 timeval) {
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 sptps_receive_data(&n->sptps, inpkt->data, inpkt->len);
262 static void send_sptps_packet(meshlink_handle_t *mesh, node_t *n, vpn_packet_t *origpkt) {
263 if(!n->status.validkey) {
264 logger(mesh, MESHLINK_INFO, "No valid key known yet for %s", n->name);
266 if(!n->status.waitingforkey) {
267 send_req_key(mesh, n);
268 } else if(n->last_req_key + 10 < mesh->loop.now.tv_sec) {
269 logger(mesh, MESHLINK_DEBUG, "No key from %s after 10 seconds, restarting SPTPS", n->name);
270 sptps_stop(&n->sptps);
271 n->status.waitingforkey = false;
272 send_req_key(mesh, n);
280 // If it's a probe, send it immediately without trying to compress it.
282 sptps_send_record(&n->sptps, PKT_PROBE, origpkt->data, origpkt->len);
286 sptps_send_record(&n->sptps, type, origpkt->data, origpkt->len);
290 static void choose_udp_address(meshlink_handle_t *mesh, const node_t *n, const sockaddr_t **sa, int *sock) {
295 /* If the UDP address is confirmed, use it. */
296 if(n->status.udp_confirmed) {
300 /* Send every third packet to n->address; that could be set
301 to the node's reflexive UDP address discovered during key
304 if(++mesh->udp_choice >= 3) {
305 mesh->udp_choice = 0;
309 /* Otherwise, address are found in edges to this node.
310 So we pick a random edge and a random socket. */
313 int j = prng(mesh, n->edge_tree->count);
314 edge_t *candidate = NULL;
316 for splay_each(edge_t, e, n->edge_tree) {
318 candidate = e->reverse;
324 *sa = &candidate->address;
325 *sock = prng(mesh, mesh->listen_sockets);
328 /* Make sure we have a suitable socket for the chosen address */
329 if(mesh->listen_socket[*sock].sa.sa.sa_family != (*sa)->sa.sa_family) {
330 for(int i = 0; i < mesh->listen_sockets; i++) {
331 if(mesh->listen_socket[i].sa.sa.sa_family == (*sa)->sa.sa_family) {
339 static void choose_broadcast_address(meshlink_handle_t *mesh, const node_t *n, const sockaddr_t **sa, int *sock) {
340 *sock = prng(mesh, mesh->listen_sockets);
341 sockaddr_t *broadcast_sa = &mesh->listen_socket[*sock].broadcast_sa;
343 if(broadcast_sa->sa.sa_family == AF_INET6) {
344 broadcast_sa->in6.sin6_port = n->prevedge->address.in.sin_port;
346 broadcast_sa->in.sin_port = n->prevedge->address.in.sin_port;
352 static void send_udppacket(meshlink_handle_t *mesh, node_t *n, vpn_packet_t *origpkt) {
353 if(!n->status.reachable) {
354 logger(mesh, MESHLINK_INFO, "Trying to send UDP packet to unreachable node %s", n->name);
358 send_sptps_packet(mesh, n, origpkt);
361 bool send_sptps_data(void *handle, uint8_t type, const void *data, size_t len) {
367 meshlink_handle_t *mesh = to->mesh;
369 /* Send it via TCP if it is a handshake packet, TCPOnly is in use, or this packet is larger than the MTU. */
371 if(type >= SPTPS_HANDSHAKE || (type != PKT_PROBE && len > to->minmtu)) {
372 char buf[len * 4 / 3 + 5];
373 b64encode(data, buf, len);
375 /* If no valid key is known yet, send the packets using ANS_KEY requests,
376 to ensure we get to learn the reflexive UDP address. */
377 if(!to->status.validkey) {
378 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);
380 return send_request(mesh, to->nexthop->connection, NULL, "%d %s %s %d %s", REQ_KEY, mesh->self->name, to->name, REQ_SPTPS, buf);
384 /* Otherwise, send the packet via UDP */
386 const sockaddr_t *sa;
389 if(to->status.broadcast) {
390 choose_broadcast_address(mesh, to, &sa, &sock);
392 choose_udp_address(mesh, to, &sa, &sock);
395 if(sendto(mesh->listen_socket[sock].udp.fd, data, len, 0, &sa->sa, SALEN(sa->sa)) < 0 && !sockwouldblock(sockerrno)) {
396 if(sockmsgsize(sockerrno)) {
397 if(to->maxmtu >= len) {
398 to->maxmtu = len - 1;
405 logger(mesh, MESHLINK_WARNING, "Error sending UDP SPTPS packet to %s: %s", to->name, sockstrerror(sockerrno));
413 bool receive_sptps_record(void *handle, uint8_t type, const void *data, uint16_t len) {
415 assert(!data || len);
417 node_t *from = handle;
418 meshlink_handle_t *mesh = from->mesh;
420 if(type == SPTPS_HANDSHAKE) {
421 if(!from->status.validkey) {
422 logger(mesh, MESHLINK_INFO, "SPTPS key exchange with %s successful", from->name);
423 from->status.validkey = true;
424 from->status.waitingforkey = false;
427 utcp_reset_timers(from->utcp);
435 logger(mesh, MESHLINK_ERROR, "Packet from %s larger than maximum supported size (%d > %d)", from->name, len, MTU);
441 if(type == PKT_PROBE) {
444 memcpy(inpkt.data, data, len);
445 mtu_probe_h(mesh, from, &inpkt, len);
451 if(type & ~(PKT_COMPRESSED)) {
452 logger(mesh, MESHLINK_ERROR, "Unexpected SPTPS record type %d len %d from %s", type, len, from->name);
456 if(type & PKT_COMPRESSED) {
457 logger(mesh, MESHLINK_ERROR, "Error while decompressing packet from %s", from->name);
461 memcpy(inpkt.data, data, len); // TODO: get rid of memcpy
464 receive_packet(mesh, from, &inpkt);
469 send a packet to the given vpn ip.
471 void send_packet(meshlink_handle_t *mesh, node_t *n, vpn_packet_t *packet) {
472 if(n == mesh->self) {
474 n->out_bytes += packet->len;
475 // TODO: send to application
479 logger(mesh, MESHLINK_DEBUG, "Sending packet of %d bytes to %s", packet->len, n->name);
481 if(!n->status.reachable) {
482 logger(mesh, MESHLINK_WARNING, "Node %s is not reachable", n->name);
487 n->out_bytes += packet->len;
488 n->status.want_udp = true;
490 send_sptps_packet(mesh, n, packet);
494 static node_t *try_harder(meshlink_handle_t *mesh, const sockaddr_t *from, const vpn_packet_t *pkt) {
498 for splay_each(edge_t, e, mesh->edges) {
499 if(!e->to->status.reachable || e->to == mesh->self) {
503 if(sockaddrcmp_noport(from, &e->address)) {
504 if(mesh->last_hard_try == mesh->loop.now.tv_sec) {
511 if(!try_mac(mesh, e->to, pkt)) {
520 mesh->last_hard_try = mesh->loop.now.tv_sec;
526 void handle_incoming_vpn_data(event_loop_t *loop, void *data, int flags) {
528 meshlink_handle_t *mesh = loop->data;
529 listen_socket_t *ls = data;
533 socklen_t fromlen = sizeof(from);
537 memset(&from, 0, sizeof(from));
539 len = recvfrom(ls->udp.fd, pkt.data, MAXSIZE, 0, &from.sa, &fromlen);
541 if(len <= 0 || len > MAXSIZE) {
542 if(!sockwouldblock(sockerrno)) {
543 logger(mesh, MESHLINK_ERROR, "Receiving packet failed: %s", sockstrerror(sockerrno));
551 sockaddrunmap(&from); /* Some braindead IPv6 implementations do stupid things. */
553 n = lookup_node_udp(mesh, &from);
556 n = try_harder(mesh, &from, &pkt);
559 update_node_udp(mesh, n, &from);
560 } else if(mesh->log_level >= MESHLINK_WARNING) {
561 hostname = sockaddr2hostname(&from);
562 logger(mesh, MESHLINK_WARNING, "Received UDP packet from unknown source %s", hostname);
570 if(n->status.blacklisted) {
571 logger(mesh, MESHLINK_WARNING, "Dropping packet from blacklisted node %s", n->name);
575 n->sock = ls - mesh->listen_socket;
577 receive_udppacket(mesh, n, &pkt);