git.meshlink.io Git - meshlink/blob - src/net_packet.c

   1 /*
   2     net_packet.c -- Handles in- and outgoing VPN packets
   3     Copyright (C) 2014-2017 Guus Sliepen <guus@meshlink.io>
   4
   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.
   9
  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.
  14
  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.
  18 */
  19
  20 #include "system.h"
  21
  22 #include "conf.h"
  23 #include "connection.h"
  24 #include "crypto.h"
  25 #include "graph.h"
  26 #include "logger.h"
  27 #include "meshlink_internal.h"
  28 #include "net.h"
  29 #include "netutl.h"
  30 #include "protocol.h"
  31 #include "route.h"
  32 #include "utils.h"
  33 #include "xalloc.h"
  34
  35 int keylifetime = 0;
  36
  37 static void send_udppacket(meshlink_handle_t *mesh, node_t *, vpn_packet_t *);
  38
  39 #define MAX_SEQNO 1073741824
  40
  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
  45
  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.
  48
  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.
  51
  52    In case local discovery is enabled, another packet is added to each batch,
  53    which will be broadcast to the local network.
  54
  55 */
  56
  57 static void send_mtu_probe_handler(event_loop_t *loop, void *data) {
  58         meshlink_handle_t *mesh = loop->data;
  59         node_t *n = data;
  60         int timeout = 1;
  61
  62         n->mtuprobes++;
  63
  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);
  66                 n->mtuprobes = 0;
  67                 return;
  68         }
  69
  70         if(n->mtuprobes > 32) {
  71                 if(!n->minmtu) {
  72                         n->mtuprobes = 31;
  73                         timeout = mesh->dev_class_traits[n->devclass].pinginterval;
  74                         goto end;
  75                 }
  76
  77                 logger(mesh, MESHLINK_INFO, "%s did not respond to UDP ping, restarting PMTU discovery", n->name);
  78                 n->status.udp_confirmed = false;
  79                 n->mtuprobes = 1;
  80                 n->minmtu = 0;
  81                 n->maxmtu = MTU;
  82         }
  83
  84         if(n->mtuprobes >= 10 && n->mtuprobes < 32 && !n->minmtu) {
  85                 logger(mesh, MESHLINK_INFO, "No response to MTU probes from %s", n->name);
  86                 n->mtuprobes = 31;
  87         }
  88
  89         if(n->mtuprobes == 30 || (n->mtuprobes < 30 && n->minmtu >= n->maxmtu)) {
  90                 if(n->minmtu > n->maxmtu) {
  91                         n->minmtu = n->maxmtu;
  92                 } else {
  93                         n->maxmtu = n->minmtu;
  94                 }
  95
  96                 n->mtu = n->minmtu;
  97                 logger(mesh, MESHLINK_INFO, "Fixing MTU of %s to %d after %d probes", n->name, n->mtu, n->mtuprobes);
  98                 n->mtuprobes = 31;
  99         }
 100
 101         if(n->mtuprobes == 31) {
 102                 timeout = mesh->dev_class_traits[n->devclass].pinginterval;
 103                 goto end;
 104         } else if(n->mtuprobes == 32) {
 105                 timeout = mesh->dev_class_traits[n->devclass].pingtimeout;
 106         }
 107
 108         for(int i = 0; i < 5; i++) {
 109                 int len;
 110
 111                 if(i == 0) {
 112                         if(n->mtuprobes < 30 || n->maxmtu + 8 >= MTU) {
 113                                 continue;
 114                         }
 115
 116                         len = n->maxmtu + 8;
 117                 } else if(n->maxmtu <= n->minmtu) {
 118                         len = n->maxmtu;
 119                 } else {
 120                         len = n->minmtu + 1 + rand() % (n->maxmtu - n->minmtu);
 121                 }
 122
 123                 if(len < 64) {
 124                         len = 64;
 125                 }
 126
 127                 vpn_packet_t packet;
 128                 packet.probe = true;
 129                 memset(packet.data, 0, 14);
 130                 randomize(packet.data + 14, len - 14);
 131                 packet.len = len;
 132                 n->status.broadcast = i >= 4 && n->mtuprobes <= 10 && n->prevedge;
 133
 134                 logger(mesh, MESHLINK_DEBUG, "Sending MTU probe length %d to %s", len, n->name);
 135
 136                 send_udppacket(mesh, n, &packet);
 137         }
 138
 139         n->status.broadcast = false;
 140
 141 end:
 142         timeout_set(&mesh->loop, &n->mtutimeout, &(struct timeval) {
 143                 timeout, rand() % 100000
 144         });
 145 }
 146
 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) {
 149                 1, 0
 150         });
 151         send_mtu_probe_handler(&mesh->loop, n);
 152 }
 153
 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);
 156
 157         if(!packet->data[0]) {
 158                 /* It's a probe request, send back a reply */
 159
 160                 packet->data[0] = 1;
 161
 162                 /* Temporarily set udp_confirmed, so that the reply is sent
 163                    back exactly the way it came in. */
 164
 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;
 169         } else {
 170                 /* It's a valid reply: now we know bidirectional communication
 171                    is possible using the address and socket that the reply
 172                    packet used. */
 173
 174                 n->status.udp_confirmed = true;
 175
 176                 /* If we haven't established the PMTU yet, restart the discovery process. */
 177
 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);
 181                                 n->maxmtu = MTU;
 182                                 n->mtuprobes = 10;
 183                                 return;
 184                         }
 185
 186                         if(n->minmtu) {
 187                                 n->mtuprobes = 30;
 188                         } else {
 189                                 n->mtuprobes = 1;
 190                         }
 191                 }
 192
 193                 /* If applicable, raise the minimum supported MTU */
 194
 195                 if(len > n->maxmtu) {
 196                         len = n->maxmtu;
 197                 }
 198
 199                 if(n->minmtu < len) {
 200                         n->minmtu = len;
 201                 }
 202         }
 203 }
 204
 205 /* VPN packet I/O */
 206
 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);
 209
 210         if(n->status.blacklisted) {
 211                 logger(mesh, MESHLINK_WARNING, "Dropping packet from blacklisted node %s", n->name);
 212         } else {
 213                 n->in_packets++;
 214                 n->in_bytes += packet->len;
 215
 216                 route(mesh, n, packet);
 217         }
 218 }
 219
 220 static bool try_mac(meshlink_handle_t *mesh, node_t *n, const vpn_packet_t *inpkt) {
 221         (void)mesh;
 222         return sptps_verify_datagram(&n->sptps, inpkt->data, inpkt->len);
 223 }
 224
 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);
 230                 } else {
 231                         logger(mesh, MESHLINK_DEBUG, "Got packet from %s but he hasn't got our key yet", n->name);
 232                 }
 233
 234                 return;
 235         }
 236
 237         sptps_receive_data(&n->sptps, inpkt->data, inpkt->len);
 238 }
 239
 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);
 243
 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);
 251                 }
 252
 253                 return;
 254         }
 255
 256         uint8_t type = 0;
 257
 258         // If it's a probe, send it immediately without trying to compress it.
 259         if(origpkt->probe) {
 260                 sptps_send_record(&n->sptps, PKT_PROBE, origpkt->data, origpkt->len);
 261                 return;
 262         }
 263
 264         sptps_send_record(&n->sptps, type, origpkt->data, origpkt->len);
 265         return;
 266 }
 267
 268 static void choose_udp_address(meshlink_handle_t *mesh, const node_t *n, const sockaddr_t **sa, int *sock) {
 269         /* Latest guess */
 270         *sa = &n->address;
 271         *sock = n->sock;
 272
 273         /* If the UDP address is confirmed, use it. */
 274         if(n->status.udp_confirmed) {
 275                 return;
 276         }
 277
 278         /* Send every third packet to n->address; that could be set
 279            to the node's reflexive UDP address discovered during key
 280            exchange. */
 281
 282         if(++mesh->udp_choice >= 3) {
 283                 mesh->udp_choice = 0;
 284                 return;
 285         }
 286
 287         /* Otherwise, address are found in edges to this node.
 288            So we pick a random edge and a random socket. */
 289
 290         int i = 0;
 291         int j = rand() % n->edge_tree->count;
 292         edge_t *candidate = NULL;
 293
 294         for splay_each(edge_t, e, n->edge_tree) {
 295                 if(i++ == j) {
 296                         candidate = e->reverse;
 297                         break;
 298                 }
 299         }
 300
 301         if(candidate) {
 302                 *sa = &candidate->address;
 303                 *sock = rand() % mesh->listen_sockets;
 304         }
 305
 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) {
 310                                 *sock = i;
 311                                 break;
 312                         }
 313                 }
 314         }
 315 }
 316
 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 = {
 319                 .in = {
 320                         .sin_family = AF_INET,
 321                         .sin_addr.s_addr = -1,
 322                 }
 323         };
 324
 325         static sockaddr_t broadcast_ipv6 = {
 326                 .in6 = {
 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,
 331                 }
 332         };
 333
 334         *sock = rand() % mesh->listen_sockets;
 335
 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;
 340         } else {
 341                 broadcast_ipv4.in.sin_port = n->prevedge->address.in.sin_port;
 342                 *sa = &broadcast_ipv4;
 343         }
 344 }
 345
 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);
 349                 return;
 350         }
 351
 352         send_sptps_packet(mesh, n, origpkt);
 353 }
 354
 355 bool send_sptps_data(void *handle, uint8_t type, const void *data, size_t len) {
 356         node_t *to = handle;
 357         meshlink_handle_t *mesh = to->mesh;
 358
 359         /* Send it via TCP if it is a handshake packet, TCPOnly is in use, or this packet is larger than the MTU. */
 360
 361         if(type >= SPTPS_HANDSHAKE || (type != PKT_PROBE && len > to->minmtu)) {
 362                 char buf[len * 4 / 3 + 5];
 363                 b64encode(data, buf, len);
 364
 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);
 369                 } else {
 370                         return send_request(mesh, to->nexthop->connection, NULL, "%d %s %s %d %s", REQ_KEY, mesh->self->name, to->name, REQ_SPTPS, buf);
 371                 }
 372         }
 373
 374         /* Otherwise, send the packet via UDP */
 375
 376         const sockaddr_t *sa;
 377         int sock;
 378
 379         if(to->status.broadcast) {
 380                 choose_broadcast_address(mesh, to, &sa, &sock);
 381         } else {
 382                 choose_udp_address(mesh, to, &sa, &sock);
 383         }
 384
 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;
 389                         }
 390
 391                         if(to->mtu >= len) {
 392                                 to->mtu = len - 1;
 393                         }
 394                 } else {
 395                         logger(mesh, MESHLINK_WARNING, "Error sending UDP SPTPS packet to %s: %s", to->name, sockstrerror(sockerrno));
 396                         return false;
 397                 }
 398         }
 399
 400         return true;
 401 }
 402
 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;
 406
 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;
 412
 413                         if(from->utcp) {
 414                                 utcp_reset_timers(from->utcp);
 415                         }
 416                 }
 417
 418                 return true;
 419         }
 420
 421         if(len > MTU) {
 422                 logger(mesh, MESHLINK_ERROR, "Packet from %s larger than maximum supported size (%d > %d)", from->name, len, MTU);
 423                 return false;
 424         }
 425
 426         vpn_packet_t inpkt;
 427
 428         if(type == PKT_PROBE) {
 429                 inpkt.len = len;
 430                 inpkt.probe = true;
 431                 memcpy(inpkt.data, data, len);
 432                 mtu_probe_h(mesh, from, &inpkt, len);
 433                 return true;
 434         } else {
 435                 inpkt.probe = false;
 436         }
 437
 438         if(type & ~(PKT_COMPRESSED)) {
 439                 logger(mesh, MESHLINK_ERROR, "Unexpected SPTPS record type %d len %d from %s", type, len, from->name);
 440                 return false;
 441         }
 442
 443         if(type & PKT_COMPRESSED) {
 444                 logger(mesh, MESHLINK_ERROR, "Error while decompressing packet from %s", from->name);
 445                 return false;
 446         }
 447
 448         memcpy(inpkt.data, data, len); // TODO: get rid of memcpy
 449         inpkt.len = len;
 450
 451         receive_packet(mesh, from, &inpkt);
 452         return true;
 453 }
 454
 455 /*
 456   send a packet to the given vpn ip.
 457 */
 458 void send_packet(meshlink_handle_t *mesh, node_t *n, vpn_packet_t *packet) {
 459         if(n == mesh->self) {
 460                 n->out_packets++;
 461                 n->out_bytes += packet->len;
 462                 // TODO: send to application
 463                 return;
 464         }
 465
 466         logger(mesh, MESHLINK_DEBUG, "Sending packet of %d bytes to %s", packet->len, n->name);
 467
 468         if(!n->status.reachable) {
 469                 logger(mesh, MESHLINK_WARNING, "Node %s is not reachable", n->name);
 470                 return;
 471         }
 472
 473         n->out_packets++;
 474         n->out_bytes += packet->len;
 475
 476         send_sptps_packet(mesh, n, packet);
 477         return;
 478 }
 479
 480 /* Broadcast a packet using the minimum spanning tree */
 481
 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);
 486         }
 487
 488         logger(mesh, MESHLINK_INFO, "Broadcasting packet of %d bytes from %s", packet->len, from->name);
 489
 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);
 493                 }
 494 }
 495
 496 static node_t *try_harder(meshlink_handle_t *mesh, const sockaddr_t *from, const vpn_packet_t *pkt) {
 497         node_t *n = NULL;
 498         bool hard = false;
 499
 500         for splay_each(edge_t, e, mesh->edges) {
 501                 if(!e->to->status.reachable || e->to == mesh->self) {
 502                         continue;
 503                 }
 504
 505                 if(sockaddrcmp_noport(from, &e->address)) {
 506                         if(mesh->last_hard_try == mesh->loop.now.tv_sec) {
 507                                 continue;
 508                         }
 509
 510                         hard = true;
 511                 }
 512
 513                 if(!try_mac(mesh, e->to, pkt)) {
 514                         continue;
 515                 }
 516
 517                 n = e->to;
 518                 break;
 519         }
 520
 521         if(hard) {
 522                 mesh->last_hard_try = mesh->loop.now.tv_sec;
 523         }
 524
 525         return n;
 526 }
 527
 528 void handle_incoming_vpn_data(event_loop_t *loop, void *data, int flags) {
 529         (void)flags;
 530         meshlink_handle_t *mesh = loop->data;
 531         listen_socket_t *ls = data;
 532         vpn_packet_t pkt;
 533         char *hostname;
 534         sockaddr_t from;
 535         socklen_t fromlen = sizeof(from);
 536         node_t *n;
 537         int len;
 538
 539         memset(&from, 0, sizeof(from));
 540
 541         len = recvfrom(ls->udp.fd, pkt.data, MAXSIZE, 0, &from.sa, &fromlen);
 542
 543         if(len <= 0 || len > MAXSIZE) {
 544                 if(!sockwouldblock(sockerrno)) {
 545                         logger(mesh, MESHLINK_ERROR, "Receiving packet failed: %s", sockstrerror(sockerrno));
 546                 }
 547
 548                 return;
 549         }
 550
 551         pkt.len = len;
 552
 553         sockaddrunmap(&from); /* Some braindead IPv6 implementations do stupid things. */
 554
 555         n = lookup_node_udp(mesh, &from);
 556
 557         if(!n) {
 558                 n = try_harder(mesh, &from, &pkt);
 559
 560                 if(n) {
 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);
 565                         free(hostname);
 566                         return;
 567                 } else {
 568                         return;
 569                 }
 570         }
 571
 572         if(n->status.blacklisted) {
 573                 logger(mesh, MESHLINK_WARNING, "Dropping packet from blacklisted node %s", n->name);
 574                 return;
 575         }
 576
 577         n->sock = ls - mesh->listen_socket;
 578
 579         receive_udppacket(mesh, n, &pkt);
 580 }