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 && n->nexthop && n->nexthop->connection) {
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);
192 if(n->nexthop && n->nexthop->connection) {
193 send_request(mesh, n->nexthop->connection, NULL, "%d %s %s . -1 -1 -1 0 %s %s", ANS_KEY, n->name, n->name, address, port);
195 logger(mesh, MESHLINK_WARNING, "Cannot send reflexive address to %s via %s", n->name, n->nexthop ? n->nexthop->name : n->name);
200 n->status.udp_confirmed = true;
203 /* If we haven't established the PMTU yet, restart the discovery process. */
205 if(n->mtuprobes > 30) {
206 if(len == n->maxmtu + 8) {
207 logger(mesh, MESHLINK_INFO, "Increase in PMTU to %s detected, restarting PMTU discovery", n->name);
220 /* If applicable, raise the minimum supported MTU */
222 if(len > n->maxmtu) {
226 if(n->minmtu < len) {
228 update_node_pmtu(mesh, n);
235 static void receive_packet(meshlink_handle_t *mesh, node_t *n, vpn_packet_t *packet) {
236 logger(mesh, MESHLINK_DEBUG, "Received packet of %d bytes from %s", packet->len, n->name);
238 if(n->status.blacklisted) {
239 logger(mesh, MESHLINK_WARNING, "Dropping packet from blacklisted node %s", n->name);
242 n->in_bytes += packet->len;
244 route(mesh, n, packet);
248 static bool try_mac(meshlink_handle_t *mesh, node_t *n, const vpn_packet_t *inpkt) {
250 return sptps_verify_datagram(&n->sptps, inpkt->data, inpkt->len);
253 static void receive_udppacket(meshlink_handle_t *mesh, node_t *n, vpn_packet_t *inpkt) {
254 if(!n->status.reachable) {
255 logger(mesh, MESHLINK_ERROR, "Got SPTPS data from unreachable node %s", n->name);
259 if(!n->sptps.state) {
260 if(!n->status.waitingforkey) {
261 logger(mesh, MESHLINK_DEBUG, "Got packet from %s but we haven't exchanged keys yet", n->name);
262 send_req_key(mesh, n);
264 logger(mesh, MESHLINK_DEBUG, "Got packet from %s but he hasn't got our key yet", n->name);
270 if(!sptps_receive_data(&n->sptps, inpkt->data, inpkt->len)) {
271 logger(mesh, MESHLINK_ERROR, "Could not process SPTPS data from %s: %s", n->name, strerror(errno));
275 static void send_sptps_packet(meshlink_handle_t *mesh, node_t *n, vpn_packet_t *origpkt) {
276 if(!n->status.reachable) {
277 logger(mesh, MESHLINK_ERROR, "Trying to send SPTPS data to unreachable node %s", n->name);
281 if(!n->status.validkey) {
282 logger(mesh, MESHLINK_INFO, "No valid key known yet for %s", n->name);
284 if(!n->status.waitingforkey) {
285 send_req_key(mesh, n);
286 } else if(n->last_req_key + 10 < mesh->loop.now.tv_sec) {
287 logger(mesh, MESHLINK_DEBUG, "No key from %s after 10 seconds, restarting SPTPS", n->name);
288 sptps_stop(&n->sptps);
289 n->status.waitingforkey = false;
290 send_req_key(mesh, n);
298 // If it's a probe, send it immediately without trying to compress it.
300 sptps_send_record(&n->sptps, PKT_PROBE, origpkt->data, origpkt->len);
304 sptps_send_record(&n->sptps, type, origpkt->data, origpkt->len);
308 static void choose_udp_address(meshlink_handle_t *mesh, const node_t *n, const sockaddr_t **sa, int *sock, sockaddr_t *sa_buf) {
313 /* If the UDP address is confirmed, use it. */
314 if(n->status.udp_confirmed) {
318 /* Send every third packet to n->address; that could be set
319 to the node's reflexive UDP address discovered during key
322 if(++mesh->udp_choice >= 3) {
323 mesh->udp_choice = 0;
327 /* If we have learned an address via Catta, try this once every batch */
328 if(mesh->udp_choice == 1 && n->catta_address.sa.sa_family != AF_UNSPEC) {
329 *sa = &n->catta_address;
333 /* Else, if we have a canonical address, try this once every batch */
334 if(mesh->udp_choice == 1 && n->canonical_address) {
335 char *host = xstrdup(n->canonical_address);
336 char *port = strchr(host, ' ');
340 *sa_buf = str2sockaddr_random(mesh, host, port);
349 /* Otherwise, address are found in edges to this node.
350 So we pick a random edge and a random socket. */
352 edge_t *candidate = NULL;
356 int j = prng(mesh, n->edge_tree->count);
358 for splay_each(edge_t, e, n->edge_tree) {
360 candidate = e->reverse;
367 *sa = &candidate->address;
368 *sock = prng(mesh, mesh->listen_sockets);
373 /* Make sure we have a suitable socket for the chosen address */
374 if(mesh->listen_socket[*sock].sa.sa.sa_family != (*sa)->sa.sa_family) {
375 for(int i = 0; i < mesh->listen_sockets; i++) {
376 if(mesh->listen_socket[i].sa.sa.sa_family == (*sa)->sa.sa_family) {
384 static void choose_broadcast_address(meshlink_handle_t *mesh, const node_t *n, const sockaddr_t **sa, int *sock) {
385 *sock = prng(mesh, mesh->listen_sockets);
386 sockaddr_t *broadcast_sa = &mesh->listen_socket[*sock].broadcast_sa;
388 if(broadcast_sa->sa.sa_family == AF_INET6) {
389 broadcast_sa->in6.sin6_port = n->prevedge->address.in.sin_port;
391 broadcast_sa->in.sin_port = n->prevedge->address.in.sin_port;
397 static void send_udppacket(meshlink_handle_t *mesh, node_t *n, vpn_packet_t *origpkt) {
398 if(!n->status.reachable) {
399 logger(mesh, MESHLINK_INFO, "Trying to send UDP packet to unreachable node %s", n->name);
403 send_sptps_packet(mesh, n, origpkt);
406 bool send_sptps_data(void *handle, uint8_t type, const void *data, size_t len) {
412 meshlink_handle_t *mesh = to->mesh;
414 if(!to->status.reachable) {
415 logger(mesh, MESHLINK_ERROR, "Trying to send SPTPS data to unreachable node %s", to->name);
419 /* Send it via TCP if it is a handshake packet, TCPOnly is in use, or this packet is larger than the MTU. */
421 if(type >= SPTPS_HANDSHAKE || (type != PKT_PROBE && (len - 21) > to->minmtu)) {
422 char buf[len * 4 / 3 + 5];
423 b64encode(data, buf, len);
425 if(!to->nexthop || !to->nexthop->connection) {
426 logger(mesh, MESHLINK_WARNING, "Unable to forward SPTPS packet to %s via %s", to->name, to->nexthop ? to->nexthop->name : to->name);
430 /* If no valid key is known yet, send the packets using ANS_KEY requests,
431 to ensure we get to learn the reflexive UDP address. */
432 if(!to->status.validkey) {
433 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);
435 return send_request(mesh, to->nexthop->connection, NULL, "%d %s %s %d %s", REQ_KEY, mesh->self->name, to->name, REQ_SPTPS, buf);
439 /* Otherwise, send the packet via UDP */
442 const sockaddr_t *sa;
445 if(to->status.broadcast) {
446 choose_broadcast_address(mesh, to, &sa, &sock);
448 choose_udp_address(mesh, to, &sa, &sock, &sa_buf);
451 if(sendto(mesh->listen_socket[sock].udp.fd, data, len, 0, &sa->sa, SALEN(sa->sa)) < 0 && !sockwouldblock(sockerrno)) {
452 if(sockmsgsize(sockerrno)) {
453 if(to->maxmtu >= len) {
454 to->maxmtu = len - 1;
461 logger(mesh, MESHLINK_WARNING, "Error sending UDP SPTPS packet to %s: %s", to->name, sockstrerror(sockerrno));
469 bool receive_sptps_record(void *handle, uint8_t type, const void *data, uint16_t len) {
471 assert(!data || len);
473 node_t *from = handle;
474 meshlink_handle_t *mesh = from->mesh;
476 if(type == SPTPS_HANDSHAKE) {
477 if(!from->status.validkey) {
478 logger(mesh, MESHLINK_INFO, "SPTPS key exchange with %s successful", from->name);
479 from->status.validkey = true;
480 from->status.waitingforkey = false;
483 utcp_reset_timers(from->utcp);
491 logger(mesh, MESHLINK_ERROR, "Packet from %s larger than maximum supported size (%d > %d)", from->name, len, MAXSIZE);
497 if(type == PKT_PROBE) {
500 memcpy(inpkt.data, data, len);
501 mtu_probe_h(mesh, from, &inpkt, len);
507 if(type & ~(PKT_COMPRESSED)) {
508 logger(mesh, MESHLINK_ERROR, "Unexpected SPTPS record type %d len %d from %s", type, len, from->name);
512 if(type & PKT_COMPRESSED) {
513 logger(mesh, MESHLINK_ERROR, "Error while decompressing packet from %s", from->name);
517 memcpy(inpkt.data, data, len); // TODO: get rid of memcpy
520 receive_packet(mesh, from, &inpkt);
525 send a packet to the given vpn ip.
527 void send_packet(meshlink_handle_t *mesh, node_t *n, vpn_packet_t *packet) {
528 if(n == mesh->self) {
530 n->out_bytes += packet->len;
531 // TODO: send to application
535 logger(mesh, MESHLINK_DEBUG, "Sending packet of %d bytes to %s", packet->len, n->name);
537 if(!n->status.reachable) {
538 logger(mesh, MESHLINK_WARNING, "Node %s is not reachable", n->name);
543 n->out_bytes += packet->len;
544 n->status.want_udp = true;
546 send_sptps_packet(mesh, n, packet);
550 static node_t *try_harder(meshlink_handle_t *mesh, const sockaddr_t *from, const vpn_packet_t *pkt) {
554 for splay_each(edge_t, e, mesh->edges) {
555 if(!e->to->status.reachable || e->to == mesh->self) {
559 if(sockaddrcmp_noport(from, &e->address)) {
560 if(mesh->last_hard_try == mesh->loop.now.tv_sec) {
567 if(!try_mac(mesh, e->to, pkt)) {
576 mesh->last_hard_try = mesh->loop.now.tv_sec;
582 void handle_incoming_vpn_data(event_loop_t *loop, void *data, int flags) {
584 meshlink_handle_t *mesh = loop->data;
585 listen_socket_t *ls = data;
589 socklen_t fromlen = sizeof(from);
593 memset(&from, 0, sizeof(from));
595 len = recvfrom(ls->udp.fd, pkt.data, MAXSIZE, 0, &from.sa, &fromlen);
597 if(len <= 0 || len > MAXSIZE) {
598 if(!sockwouldblock(sockerrno)) {
599 logger(mesh, MESHLINK_ERROR, "Receiving packet failed: %s", sockstrerror(sockerrno));
607 sockaddrunmap(&from); /* Some braindead IPv6 implementations do stupid things. */
609 n = lookup_node_udp(mesh, &from);
612 n = try_harder(mesh, &from, &pkt);
615 update_node_udp(mesh, n, &from);
616 } else if(mesh->log_level <= MESHLINK_WARNING) {
617 hostname = sockaddr2hostname(&from);
618 logger(mesh, MESHLINK_WARNING, "Received UDP packet from unknown source %s", hostname);
626 if(n->status.blacklisted) {
627 logger(mesh, MESHLINK_WARNING, "Dropping packet from blacklisted node %s", n->name);
631 n->sock = ls - mesh->listen_socket;
633 receive_udppacket(mesh, n, &pkt);