2 net_packet.c -- Handles in- and outgoing VPN packets
3 Copyright (C) 2014 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.
27 #include "connection.h"
31 #include "meshlink_internal.h"
41 static void send_udppacket(meshlink_handle_t *mesh, node_t *, vpn_packet_t *);
43 #define MAX_SEQNO 1073741824
45 /* mtuprobes == 1..30: initial discovery, send bursts with 1 second interval
46 mtuprobes == 31: sleep pinginterval seconds
47 mtuprobes == 32: send 1 burst, sleep pingtimeout second
48 mtuprobes == 33: no response from other side, restart PMTU discovery process
50 Probes are sent in batches of at least three, with random sizes between the
51 lower and upper boundaries for the MTU thus far discovered.
53 After the initial discovery, a fourth packet is added to each batch with a
54 size larger than the currently known PMTU, to test if the PMTU has increased.
56 In case local discovery is enabled, another packet is added to each batch,
57 which will be broadcast to the local network.
61 static void send_mtu_probe_handler(event_loop_t *loop, void *data) {
62 meshlink_handle_t *mesh = loop->data;
68 if(!n->status.reachable || !n->status.validkey) {
69 logger(mesh, MESHLINK_INFO, "Trying to send MTU probe to unreachable or rekeying node %s", n->name);
74 if(n->mtuprobes > 32) {
77 timeout = mesh->pinginterval;
81 logger(mesh, MESHLINK_INFO, "%s did not respond to UDP ping, restarting PMTU discovery", n->name);
82 n->status.udp_confirmed = false;
88 if(n->mtuprobes >= 10 && n->mtuprobes < 32 && !n->minmtu) {
89 logger(mesh, MESHLINK_INFO, "No response to MTU probes from %s", n->name);
93 if(n->mtuprobes == 30 || (n->mtuprobes < 30 && n->minmtu >= n->maxmtu)) {
94 if(n->minmtu > n->maxmtu)
95 n->minmtu = n->maxmtu;
97 n->maxmtu = n->minmtu;
99 logger(mesh, MESHLINK_INFO, "Fixing MTU of %s to %d after %d probes", n->name, n->mtu, n->mtuprobes);
103 if(n->mtuprobes == 31) {
104 timeout = mesh->pinginterval;
106 } else if(n->mtuprobes == 32)
107 timeout = mesh->pingtimeout;
109 for(int i = 0; i < 4 + mesh->localdiscovery; i++) {
113 if(n->mtuprobes < 30 || n->maxmtu + 8 >= MTU)
116 } else if(n->maxmtu <= n->minmtu)
119 len = n->minmtu + 1 + rand() % (n->maxmtu - n->minmtu);
126 memset(packet.data, 0, 14);
127 randomize(packet.data + 14, len - 14);
129 n->status.broadcast = i >= 4 && n->mtuprobes <= 10 && n->prevedge;
131 logger(mesh, MESHLINK_DEBUG, "Sending MTU probe length %d to %s", len, n->name);
133 send_udppacket(mesh, n, &packet);
136 n->status.broadcast = false;
139 timeout_set(&mesh->loop, &n->mtutimeout, &(struct timeval) {
140 timeout, rand() % 100000
144 void send_mtu_probe(meshlink_handle_t *mesh, node_t *n) {
145 timeout_add(&mesh->loop, &n->mtutimeout, send_mtu_probe_handler, n, &(struct timeval) {
148 send_mtu_probe_handler(&mesh->loop, n);
151 static void mtu_probe_h(meshlink_handle_t *mesh, node_t *n, vpn_packet_t *packet, uint16_t len) {
152 logger(mesh, MESHLINK_DEBUG, "Got MTU probe length %d from %s", packet->len, n->name);
154 if(!packet->data[0]) {
155 /* It's a probe request, send back a reply */
159 /* Temporarily set udp_confirmed, so that the reply is sent
160 back exactly the way it came in. */
162 bool udp_confirmed = n->status.udp_confirmed;
163 n->status.udp_confirmed = true;
164 send_udppacket(mesh, n, packet);
165 n->status.udp_confirmed = udp_confirmed;
167 /* It's a valid reply: now we know bidirectional communication
168 is possible using the address and socket that the reply
171 n->status.udp_confirmed = true;
173 /* If we haven't established the PMTU yet, restart the discovery process. */
175 if(n->mtuprobes > 30) {
176 if(len == n->maxmtu + 8) {
177 logger(mesh, MESHLINK_INFO, "Increase in PMTU to %s detected, restarting PMTU discovery", n->name);
189 /* If applicable, raise the minimum supported MTU */
198 static uint16_t compress_packet(uint8_t *dest, const uint8_t *source, uint16_t len, int level) {
202 static uint16_t uncompress_packet(uint8_t *dest, const uint8_t *source, uint16_t len, int level) {
208 static void receive_packet(meshlink_handle_t *mesh, node_t *n, vpn_packet_t *packet) {
209 logger(mesh, MESHLINK_DEBUG, "Received packet of %d bytes from %s", packet->len, n->name);
211 if(n->status.blacklisted)
212 logger(mesh, MESHLINK_WARNING, "Dropping packet from blacklisted node %s", n->name);
215 n->in_bytes += packet->len;
217 route(mesh, n, packet);
221 static bool try_mac(meshlink_handle_t *mesh, node_t *n, const vpn_packet_t *inpkt) {
222 return sptps_verify_datagram(&n->sptps, inpkt->data, inpkt->len);
225 static void receive_udppacket(meshlink_handle_t *mesh, node_t *n, vpn_packet_t *inpkt) {
226 if(!n->sptps.state) {
227 if(!n->status.waitingforkey) {
228 logger(mesh, MESHLINK_DEBUG, "Got packet from %s but we haven't exchanged keys yet", n->name);
229 send_req_key(mesh, n);
231 logger(mesh, MESHLINK_DEBUG, "Got packet from %s but he hasn't got our key yet", n->name);
234 sptps_receive_data(&n->sptps, inpkt->data, inpkt->len);
237 void receive_tcppacket(meshlink_handle_t *mesh, connection_t *c, const char *buffer, int len) {
240 if(len > sizeof(outpkt).data)
245 memcpy(outpkt.data, buffer, len);
247 receive_packet(mesh, c->node, &outpkt);
250 static void send_sptps_packet(meshlink_handle_t *mesh, node_t *n, vpn_packet_t *origpkt) {
251 if(!n->status.validkey) {
252 logger(mesh, MESHLINK_INFO, "No valid key known yet for %s", n->name);
253 if(!n->status.waitingforkey)
254 send_req_key(mesh, n);
255 else if(n->last_req_key + 10 < mesh->loop.now.tv_sec) {
256 logger(mesh, MESHLINK_DEBUG, "No key from %s after 10 seconds, restarting SPTPS", n->name);
257 sptps_stop(&n->sptps);
258 n->status.waitingforkey = false;
259 send_req_key(mesh, n);
266 // If it's a probe, send it immediately without trying to compress it.
268 sptps_send_record(&n->sptps, PKT_PROBE, origpkt->data, origpkt->len);
274 if(n->outcompression) {
275 int len = compress_packet(outpkt.data, origpkt->data, origpkt->len, n->outcompression);
277 logger(mesh, MESHLINK_ERROR, "Error while compressing packet to %s", n->name);
278 else if(len < origpkt->len) {
281 type |= PKT_COMPRESSED;
285 sptps_send_record(&n->sptps, type, origpkt->data, origpkt->len);
289 static void choose_udp_address(meshlink_handle_t *mesh, const node_t *n, const sockaddr_t **sa, int *sock) {
294 /* If the UDP address is confirmed, use it. */
295 if(n->status.udp_confirmed)
298 /* Send every third packet to n->address; that could be set
299 to the node's reflexive UDP address discovered during key
308 /* Otherwise, address are found in edges to this node.
309 So we pick a random edge and a random socket. */
312 int j = rand() % n->edge_tree->count;
313 edge_t *candidate = NULL;
315 for splay_each(edge_t, e, n->edge_tree) {
317 candidate = e->reverse;
323 *sa = &candidate->address;
324 *sock = rand() % mesh->listen_sockets;
327 /* Make sure we have a suitable socket for the chosen address */
328 if(mesh->listen_socket[*sock].sa.sa.sa_family != (*sa)->sa.sa_family) {
329 for(int i = 0; i < mesh->listen_sockets; i++) {
330 if(mesh->listen_socket[i].sa.sa.sa_family == (*sa)->sa.sa_family) {
338 static void choose_broadcast_address(meshlink_handle_t *mesh, const node_t *n, const sockaddr_t **sa, int *sock) {
339 static sockaddr_t broadcast_ipv4 = {
341 .sin_family = AF_INET,
342 .sin_addr.s_addr = -1,
346 static sockaddr_t broadcast_ipv6 = {
348 .sin6_family = AF_INET6,
349 .sin6_addr.s6_addr[0x0] = 0xff,
350 .sin6_addr.s6_addr[0x1] = 0x02,
351 .sin6_addr.s6_addr[0xf] = 0x01,
355 *sock = rand() % mesh->listen_sockets;
357 if(mesh->listen_socket[*sock].sa.sa.sa_family == AF_INET6) {
358 if(mesh->localdiscovery_address.sa.sa_family == AF_INET6) {
359 mesh->localdiscovery_address.in6.sin6_port = n->prevedge->address.in.sin_port;
360 *sa = &mesh->localdiscovery_address;
362 broadcast_ipv6.in6.sin6_port = n->prevedge->address.in.sin_port;
363 broadcast_ipv6.in6.sin6_scope_id = mesh->listen_socket[*sock].sa.in6.sin6_scope_id;
364 *sa = &broadcast_ipv6;
367 if(mesh->localdiscovery_address.sa.sa_family == AF_INET) {
368 mesh->localdiscovery_address.in.sin_port = n->prevedge->address.in.sin_port;
369 *sa = &mesh->localdiscovery_address;
371 broadcast_ipv4.in.sin_port = n->prevedge->address.in.sin_port;
372 *sa = &broadcast_ipv4;
377 static void send_udppacket(meshlink_handle_t *mesh, node_t *n, vpn_packet_t *origpkt) {
378 if(!n->status.reachable) {
379 logger(mesh, MESHLINK_INFO, "Trying to send UDP packet to unreachable node %s", n->name);
383 return send_sptps_packet(mesh, n, origpkt);
386 bool send_sptps_data(void *handle, uint8_t type, const void *data, size_t len) {
388 meshlink_handle_t *mesh = to->mesh;
390 /* Send it via TCP if it is a handshake packet, TCPOnly is in use, or this packet is larger than the MTU. */
392 if(type >= SPTPS_HANDSHAKE || ((mesh->self->options | to->options) & OPTION_TCPONLY) || (type != PKT_PROBE && len > to->minmtu)) {
393 char buf[len * 4 / 3 + 5];
394 b64encode(data, buf, len);
395 /* If no valid key is known yet, send the packets using ANS_KEY requests,
396 to ensure we get to learn the reflexive UDP address. */
397 if(!to->status.validkey) {
398 to->incompression = mesh->self->incompression;
399 return send_request(mesh, to->nexthop->connection, "%d %s %s %s -1 -1 -1 %d", ANS_KEY, mesh->self->name, to->name, buf, to->incompression);
401 return send_request(mesh, to->nexthop->connection, "%d %s %s %d %s", REQ_KEY, mesh->self->name, to->name, REQ_SPTPS, buf);
404 /* Otherwise, send the packet via UDP */
406 const sockaddr_t *sa;
409 if(to->status.broadcast)
410 choose_broadcast_address(mesh, to, &sa, &sock);
412 choose_udp_address(mesh, to, &sa, &sock);
414 if(sendto(mesh->listen_socket[sock].udp.fd, data, len, 0, &sa->sa, SALEN(sa->sa)) < 0 && !sockwouldblock(sockerrno)) {
415 if(sockmsgsize(sockerrno)) {
416 if(to->maxmtu >= len)
417 to->maxmtu = len - 1;
421 logger(mesh, MESHLINK_WARNING, "Error sending UDP SPTPS packet to %s: %s", to->name, sockstrerror(sockerrno));
429 bool receive_sptps_record(void *handle, uint8_t type, const void *data, uint16_t len) {
430 node_t *from = handle;
431 meshlink_handle_t *mesh = from->mesh;
433 if(type == SPTPS_HANDSHAKE) {
434 if(!from->status.validkey) {
435 logger(mesh, MESHLINK_INFO, "SPTPS key exchange with %s succesful", from->name);
436 from->status.validkey = true;
437 from->status.waitingforkey = false;
439 utcp_reset_timers(from->utcp);
445 logger(mesh, MESHLINK_ERROR, "Packet from %s larger than maximum supported size (%d > %d)", from->name, len, MTU);
451 if(type == PKT_PROBE) {
454 memcpy(inpkt.data, data, len);
455 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 uint16_t ulen = uncompress_packet(inpkt.data, (const uint8_t *)data, len, from->incompression);
471 if(inpkt.len > MAXSIZE)
474 memcpy(inpkt.data, data, len);
478 receive_packet(mesh, from, &inpkt);
483 send a packet to the given vpn ip.
485 void send_packet(meshlink_handle_t *mesh, node_t *n, vpn_packet_t *packet) {
486 if(n == mesh->self) {
488 n->out_bytes += packet->len;
489 // TODO: send to application
493 logger(mesh, MESHLINK_DEBUG, "Sending packet of %d bytes to %s", packet->len, n->name);
495 if(!n->status.reachable) {
496 logger(mesh, MESHLINK_WARNING, "Node %s is not reachable", n->name);
501 n->out_bytes += packet->len;
503 send_sptps_packet(mesh, n, packet);
507 /* Broadcast a packet using the minimum spanning tree */
509 void broadcast_packet(meshlink_handle_t *mesh, const node_t *from, vpn_packet_t *packet) {
510 // Always give ourself a copy of the packet.
511 if(from != mesh->self)
512 send_packet(mesh, mesh->self, packet);
514 logger(mesh, MESHLINK_INFO, "Broadcasting packet of %d bytes from %s", packet->len, from->name);
516 for list_each(connection_t, c, mesh->connections)
517 if(c->status.active && c->status.mst && c != from->nexthop->connection)
518 send_packet(mesh, c->node, packet);
521 static node_t *try_harder(meshlink_handle_t *mesh, const sockaddr_t *from, const vpn_packet_t *pkt) {
524 static time_t last_hard_try = 0;
526 for splay_each(edge_t, e, mesh->edges) {
527 if(!e->to->status.reachable || e->to == mesh->self)
530 if(sockaddrcmp_noport(from, &e->address)) {
531 if(last_hard_try == mesh->loop.now.tv_sec)
536 if(!try_mac(mesh, e->to, pkt))
544 last_hard_try = mesh->loop.now.tv_sec;
546 last_hard_try = mesh->loop.now.tv_sec;
550 void handle_incoming_vpn_data(event_loop_t *loop, void *data, int flags) {
551 meshlink_handle_t *mesh = loop->data;
552 listen_socket_t *ls = data;
555 sockaddr_t from = {{0}};
556 socklen_t fromlen = sizeof(from);
560 len = recvfrom(ls->udp.fd, pkt.data, MAXSIZE, 0, &from.sa, &fromlen);
562 if(len <= 0 || len > MAXSIZE) {
563 if(!sockwouldblock(sockerrno))
564 logger(mesh, MESHLINK_ERROR, "Receiving packet failed: %s", sockstrerror(sockerrno));
570 sockaddrunmap(&from); /* Some braindead IPv6 implementations do stupid things. */
572 n = lookup_node_udp(mesh, &from);
575 n = try_harder(mesh, &from, &pkt);
577 update_node_udp(mesh, n, &from);
578 else if(mesh->log_level >= MESHLINK_WARNING) {
579 hostname = sockaddr2hostname(&from);
580 logger(mesh, MESHLINK_WARNING, "Received UDP packet from unknown source %s", hostname);
587 if(n->status.blacklisted) {
588 logger(mesh, MESHLINK_WARNING, "Dropping packet from blacklisted node %s", n->name);
591 n->sock = ls - mesh->listen_socket;
593 receive_udppacket(mesh, n, &pkt);