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;
84 if(n->mtuprobes >= 10 && n->mtuprobes < 32 && !n->minmtu) {
85 logger(mesh, MESHLINK_INFO, "No response to MTU probes from %s", n->name);
89 if(n->mtuprobes == 30 || (n->mtuprobes < 30 && n->minmtu >= n->maxmtu)) {
90 if(n->minmtu > n->maxmtu) {
91 n->minmtu = n->maxmtu;
93 n->maxmtu = n->minmtu;
97 logger(mesh, MESHLINK_INFO, "Fixing MTU of %s to %d after %d probes", n->name, n->mtu, n->mtuprobes);
101 if(n->mtuprobes == 31) {
102 timeout = mesh->dev_class_traits[n->devclass].pinginterval;
104 } else if(n->mtuprobes == 32) {
105 timeout = mesh->dev_class_traits[n->devclass].pingtimeout;
108 for(int i = 0; i < 5; i++) {
112 if(n->mtuprobes < 30 || n->maxmtu + 8 >= MTU) {
117 } else if(n->maxmtu <= n->minmtu) {
120 len = n->minmtu + 1 + rand() % (n->maxmtu - n->minmtu);
129 memset(packet.data, 0, 14);
130 randomize(packet.data + 14, len - 14);
132 n->status.broadcast = i >= 4 && n->mtuprobes <= 10 && n->prevedge;
134 logger(mesh, MESHLINK_DEBUG, "Sending MTU probe length %d to %s", len, n->name);
136 send_udppacket(mesh, n, &packet);
139 n->status.broadcast = false;
142 timeout_set(&mesh->loop, &n->mtutimeout, &(struct timeval) {
143 timeout, rand() % 100000
147 void send_mtu_probe(meshlink_handle_t *mesh, node_t *n) {
148 timeout_add(&mesh->loop, &n->mtutimeout, send_mtu_probe_handler, n, &(struct timeval) {
151 send_mtu_probe_handler(&mesh->loop, n);
154 static void mtu_probe_h(meshlink_handle_t *mesh, node_t *n, vpn_packet_t *packet, uint16_t len) {
155 logger(mesh, MESHLINK_DEBUG, "Got MTU probe length %d from %s", packet->len, n->name);
157 if(!packet->data[0]) {
158 /* It's a probe request, send back a reply */
162 /* Temporarily set udp_confirmed, so that the reply is sent
163 back exactly the way it came in. */
165 bool udp_confirmed = n->status.udp_confirmed;
166 n->status.udp_confirmed = true;
167 send_udppacket(mesh, n, packet);
168 n->status.udp_confirmed = udp_confirmed;
170 /* It's a valid reply: now we know bidirectional communication
171 is possible using the address and socket that the reply
174 n->status.udp_confirmed = true;
176 /* If we haven't established the PMTU yet, restart the discovery process. */
178 if(n->mtuprobes > 30) {
179 if(len == n->maxmtu + 8) {
180 logger(mesh, MESHLINK_INFO, "Increase in PMTU to %s detected, restarting PMTU discovery", n->name);
193 /* If applicable, raise the minimum supported MTU */
195 if(len > n->maxmtu) {
199 if(n->minmtu < len) {
207 static void receive_packet(meshlink_handle_t *mesh, node_t *n, vpn_packet_t *packet) {
208 logger(mesh, MESHLINK_DEBUG, "Received packet of %d bytes from %s", packet->len, n->name);
210 if(n->status.blacklisted) {
211 logger(mesh, MESHLINK_WARNING, "Dropping packet from blacklisted node %s", n->name);
214 n->in_bytes += packet->len;
216 route(mesh, n, packet);
220 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);
237 sptps_receive_data(&n->sptps, inpkt->data, inpkt->len);
240 static void send_sptps_packet(meshlink_handle_t *mesh, node_t *n, vpn_packet_t *origpkt) {
241 if(!n->status.validkey) {
242 logger(mesh, MESHLINK_INFO, "No valid key known yet for %s", n->name);
244 if(!n->status.waitingforkey) {
245 send_req_key(mesh, n);
246 } else if(n->last_req_key + 10 < mesh->loop.now.tv_sec) {
247 logger(mesh, MESHLINK_DEBUG, "No key from %s after 10 seconds, restarting SPTPS", n->name);
248 sptps_stop(&n->sptps);
249 n->status.waitingforkey = false;
250 send_req_key(mesh, n);
258 // If it's a probe, send it immediately without trying to compress it.
260 sptps_send_record(&n->sptps, PKT_PROBE, origpkt->data, origpkt->len);
264 sptps_send_record(&n->sptps, type, origpkt->data, origpkt->len);
268 static void choose_udp_address(meshlink_handle_t *mesh, const node_t *n, const sockaddr_t **sa, int *sock) {
273 /* If the UDP address is confirmed, use it. */
274 if(n->status.udp_confirmed) {
278 /* Send every third packet to n->address; that could be set
279 to the node's reflexive UDP address discovered during key
282 if(++mesh->udp_choice >= 3) {
283 mesh->udp_choice = 0;
287 /* Otherwise, address are found in edges to this node.
288 So we pick a random edge and a random socket. */
291 int j = rand() % n->edge_tree->count;
292 edge_t *candidate = NULL;
294 for splay_each(edge_t, e, n->edge_tree) {
296 candidate = e->reverse;
302 *sa = &candidate->address;
303 *sock = rand() % mesh->listen_sockets;
306 /* Make sure we have a suitable socket for the chosen address */
307 if(mesh->listen_socket[*sock].sa.sa.sa_family != (*sa)->sa.sa_family) {
308 for(int i = 0; i < mesh->listen_sockets; i++) {
309 if(mesh->listen_socket[i].sa.sa.sa_family == (*sa)->sa.sa_family) {
317 static void choose_broadcast_address(meshlink_handle_t *mesh, const node_t *n, const sockaddr_t **sa, int *sock) {
318 static sockaddr_t broadcast_ipv4 = {
320 .sin_family = AF_INET,
321 .sin_addr.s_addr = -1,
325 static sockaddr_t broadcast_ipv6 = {
327 .sin6_family = AF_INET6,
328 .sin6_addr.s6_addr[0x0] = 0xff,
329 .sin6_addr.s6_addr[0x1] = 0x02,
330 .sin6_addr.s6_addr[0xf] = 0x01,
334 *sock = rand() % mesh->listen_sockets;
336 if(mesh->listen_socket[*sock].sa.sa.sa_family == AF_INET6) {
337 broadcast_ipv6.in6.sin6_port = n->prevedge->address.in.sin_port;
338 broadcast_ipv6.in6.sin6_scope_id = mesh->listen_socket[*sock].sa.in6.sin6_scope_id;
339 *sa = &broadcast_ipv6;
341 broadcast_ipv4.in.sin_port = n->prevedge->address.in.sin_port;
342 *sa = &broadcast_ipv4;
346 static void send_udppacket(meshlink_handle_t *mesh, node_t *n, vpn_packet_t *origpkt) {
347 if(!n->status.reachable) {
348 logger(mesh, MESHLINK_INFO, "Trying to send UDP packet to unreachable node %s", n->name);
352 send_sptps_packet(mesh, n, origpkt);
355 bool send_sptps_data(void *handle, uint8_t type, const void *data, size_t len) {
357 meshlink_handle_t *mesh = to->mesh;
359 /* Send it via TCP if it is a handshake packet, TCPOnly is in use, or this packet is larger than the MTU. */
361 if(type >= SPTPS_HANDSHAKE || (type != PKT_PROBE && len > to->minmtu)) {
362 char buf[len * 4 / 3 + 5];
363 b64encode(data, buf, len);
365 /* If no valid key is known yet, send the packets using ANS_KEY requests,
366 to ensure we get to learn the reflexive UDP address. */
367 if(!to->status.validkey) {
368 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);
370 return send_request(mesh, to->nexthop->connection, NULL, "%d %s %s %d %s", REQ_KEY, mesh->self->name, to->name, REQ_SPTPS, buf);
374 /* Otherwise, send the packet via UDP */
376 const sockaddr_t *sa;
379 if(to->status.broadcast) {
380 choose_broadcast_address(mesh, to, &sa, &sock);
382 choose_udp_address(mesh, to, &sa, &sock);
385 if(sendto(mesh->listen_socket[sock].udp.fd, data, len, 0, &sa->sa, SALEN(sa->sa)) < 0 && !sockwouldblock(sockerrno)) {
386 if(sockmsgsize(sockerrno)) {
387 if(to->maxmtu >= len) {
388 to->maxmtu = len - 1;
395 logger(mesh, MESHLINK_WARNING, "Error sending UDP SPTPS packet to %s: %s", to->name, sockstrerror(sockerrno));
403 bool receive_sptps_record(void *handle, uint8_t type, const void *data, uint16_t len) {
404 node_t *from = handle;
405 meshlink_handle_t *mesh = from->mesh;
407 if(type == SPTPS_HANDSHAKE) {
408 if(!from->status.validkey) {
409 logger(mesh, MESHLINK_INFO, "SPTPS key exchange with %s successful", from->name);
410 from->status.validkey = true;
411 from->status.waitingforkey = false;
414 utcp_reset_timers(from->utcp);
422 logger(mesh, MESHLINK_ERROR, "Packet from %s larger than maximum supported size (%d > %d)", from->name, len, MTU);
428 if(type == PKT_PROBE) {
431 memcpy(inpkt.data, data, len);
432 mtu_probe_h(mesh, from, &inpkt, len);
438 if(type & ~(PKT_COMPRESSED)) {
439 logger(mesh, MESHLINK_ERROR, "Unexpected SPTPS record type %d len %d from %s", type, len, from->name);
443 if(type & PKT_COMPRESSED) {
444 logger(mesh, MESHLINK_ERROR, "Error while decompressing packet from %s", from->name);
448 memcpy(inpkt.data, data, len); // TODO: get rid of memcpy
451 receive_packet(mesh, from, &inpkt);
456 send a packet to the given vpn ip.
458 void send_packet(meshlink_handle_t *mesh, node_t *n, vpn_packet_t *packet) {
459 if(n == mesh->self) {
461 n->out_bytes += packet->len;
462 // TODO: send to application
466 logger(mesh, MESHLINK_DEBUG, "Sending packet of %d bytes to %s", packet->len, n->name);
468 if(!n->status.reachable) {
469 logger(mesh, MESHLINK_WARNING, "Node %s is not reachable", n->name);
474 n->out_bytes += packet->len;
476 send_sptps_packet(mesh, n, packet);
480 /* Broadcast a packet using the minimum spanning tree */
482 void broadcast_packet(meshlink_handle_t *mesh, const node_t *from, vpn_packet_t *packet) {
483 // Always give ourself a copy of the packet.
484 if(from != mesh->self) {
485 send_packet(mesh, mesh->self, packet);
488 logger(mesh, MESHLINK_INFO, "Broadcasting packet of %d bytes from %s", packet->len, from->name);
490 for list_each(connection_t, c, mesh->connections)
491 if(c->status.active && c->status.mst && c != from->nexthop->connection) {
492 send_packet(mesh, c->node, packet);
496 static node_t *try_harder(meshlink_handle_t *mesh, const sockaddr_t *from, const vpn_packet_t *pkt) {
500 for splay_each(edge_t, e, mesh->edges) {
501 if(!e->to->status.reachable || e->to == mesh->self) {
505 if(sockaddrcmp_noport(from, &e->address)) {
506 if(mesh->last_hard_try == mesh->loop.now.tv_sec) {
513 if(!try_mac(mesh, e->to, pkt)) {
522 mesh->last_hard_try = mesh->loop.now.tv_sec;
528 void handle_incoming_vpn_data(event_loop_t *loop, void *data, int flags) {
530 meshlink_handle_t *mesh = loop->data;
531 listen_socket_t *ls = data;
535 socklen_t fromlen = sizeof(from);
539 memset(&from, 0, sizeof(from));
541 len = recvfrom(ls->udp.fd, pkt.data, MAXSIZE, 0, &from.sa, &fromlen);
543 if(len <= 0 || len > MAXSIZE) {
544 if(!sockwouldblock(sockerrno)) {
545 logger(mesh, MESHLINK_ERROR, "Receiving packet failed: %s", sockstrerror(sockerrno));
553 sockaddrunmap(&from); /* Some braindead IPv6 implementations do stupid things. */
555 n = lookup_node_udp(mesh, &from);
558 n = try_harder(mesh, &from, &pkt);
561 update_node_udp(mesh, n, &from);
562 } else if(mesh->log_level >= MESHLINK_WARNING) {
563 hostname = sockaddr2hostname(&from);
564 logger(mesh, MESHLINK_WARNING, "Received UDP packet from unknown source %s", hostname);
572 if(n->status.blacklisted) {
573 logger(mesh, MESHLINK_WARNING, "Dropping packet from blacklisted node %s", n->name);
577 n->sock = ls - mesh->listen_socket;
579 receive_udppacket(mesh, n, &pkt);