tinc-vpn.org Git - tinc/blob - src/net_packet.c

   1 /*
   2     net_packet.c -- Handles in- and outgoing VPN packets
   3     Copyright (C) 1998-2005 Ivo Timmermans,
   4                   2000-2009 Guus Sliepen <guus@tinc-vpn.org>
   5
   6     This program is free software; you can redistribute it and/or modify
   7     it under the terms of the GNU General Public License as published by
   8     the Free Software Foundation; either version 2 of the License, or
   9     (at your option) any later version.
  10
  11     This program is distributed in the hope that it will be useful,
  12     but WITHOUT ANY WARRANTY; without even the implied warranty of
  13     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14     GNU General Public License for more details.
  15
  16     You should have received a copy of the GNU General Public License along
  17     with this program; if not, write to the Free Software Foundation, Inc.,
  18     51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  19 */
  20
  21 #include "system.h"
  22
  23 #include <zlib.h>
  24 #include LZO1X_H
  25
  26 #include "splay_tree.h"
  27 #include "cipher.h"
  28 #include "conf.h"
  29 #include "connection.h"
  30 #include "crypto.h"
  31 #include "digest.h"
  32 #include "device.h"
  33 #include "ethernet.h"
  34 #include "graph.h"
  35 #include "list.h"
  36 #include "logger.h"
  37 #include "net.h"
  38 #include "netutl.h"
  39 #include "protocol.h"
  40 #include "process.h"
  41 #include "route.h"
  42 #include "utils.h"
  43 #include "xalloc.h"
  44
  45 int keylifetime = 0;
  46 int keyexpires = 0;
  47 static char lzo_wrkmem[LZO1X_999_MEM_COMPRESS > LZO1X_1_MEM_COMPRESS ? LZO1X_999_MEM_COMPRESS : LZO1X_1_MEM_COMPRESS];
  48
  49 static void send_udppacket(node_t *, vpn_packet_t *);
  50
  51 #define MAX_SEQNO 1073741824
  52
  53 // mtuprobes == 1..30: initial discovery, send bursts with 1 second interval
  54 // mtuprobes ==    31: sleep pinginterval seconds
  55 // mtuprobes ==    32: send 1 burst, sleep pingtimeout second
  56 // mtuprobes ==    33: no response from other side, restart PMTU discovery process
  57
  58 static void send_mtu_probe_handler(int fd, short events, void *data) {
  59         node_t *n = data;
  60         vpn_packet_t packet;
  61         int len, i;
  62         int timeout = 1;
  63
  64         n->mtuprobes++;
  65
  66         if(!n->status.reachable || !n->status.validkey) {
  67                 ifdebug(TRAFFIC) logger(LOG_INFO, "Trying to send MTU probe to unreachable or rekeying node %s (%s)", n->name, n->hostname);
  68                 n->mtuprobes = 0;
  69                 return;
  70         }
  71
  72         if(n->mtuprobes > 32) {
  73                 ifdebug(TRAFFIC) logger(LOG_INFO, "%s (%s) did not respond to UDP ping, restarting PMTU discovery", n->name, n->hostname);
  74                 n->mtuprobes = 1;
  75                 n->minmtu = 0;
  76                 n->maxmtu = MTU;
  77         }
  78
  79         if(n->mtuprobes >= 10 && !n->minmtu) {
  80                 ifdebug(TRAFFIC) logger(LOG_INFO, "No response to MTU probes from %s (%s)", n->name, n->hostname);
  81                 n->mtuprobes = 0;
  82                 return;
  83         }
  84
  85         if(n->mtuprobes == 30 || (n->mtuprobes < 30 && n->minmtu >= n->maxmtu)) {
  86                 if(n->minmtu > n->maxmtu)
  87                         n->minmtu = n->maxmtu;
  88                 else
  89                         n->maxmtu = n->minmtu;
  90                 n->mtu = n->minmtu;
  91                 ifdebug(TRAFFIC) logger(LOG_INFO, "Fixing MTU of %s (%s) to %d after %d probes", n->name, n->hostname, n->mtu, n->mtuprobes);
  92                 n->mtuprobes = 31;
  93         }
  94
  95         if(n->mtuprobes == 31) {
  96                 timeout = pinginterval;
  97                 goto end;
  98         } else if(n->mtuprobes == 32) {
  99                 timeout = pingtimeout;
 100         }
 101
 102         for(i = 0; i < 3; i++) {
 103                 if(n->maxmtu <= n->minmtu)
 104                         len = n->maxmtu;
 105                 else
 106                         len = n->minmtu + 1 + rand() % (n->maxmtu - n->minmtu);
 107
 108                 if(len < 64)
 109                         len = 64;
 110
 111                 memset(packet.data, 0, 14);
 112                 randomize(packet.data + 14, len - 14);
 113                 packet.len = len;
 114                 packet.priority = 0;
 115
 116                 ifdebug(TRAFFIC) logger(LOG_INFO, "Sending MTU probe length %d to %s (%s)", len, n->name, n->hostname);
 117
 118                 send_udppacket(n, &packet);
 119         }
 120
 121 end:
 122         event_add(&n->mtuevent, &(struct timeval){timeout, 0});
 123 }
 124
 125 void send_mtu_probe(node_t *n) {
 126         if(!timeout_initialized(&n->mtuevent))
 127                 timeout_set(&n->mtuevent, send_mtu_probe_handler, n);
 128         send_mtu_probe_handler(0, 0, n);
 129 }
 130
 131 void mtu_probe_h(node_t *n, vpn_packet_t *packet, length_t len) {
 132         ifdebug(TRAFFIC) logger(LOG_INFO, "Got MTU probe length %d from %s (%s)", packet->len, n->name, n->hostname);
 133
 134         if(!packet->data[0]) {
 135                 packet->data[0] = 1;
 136                 send_udppacket(n, packet);
 137         } else {
 138                 if(len > n->maxmtu)
 139                         len = n->maxmtu;
 140                 if(n->minmtu < len)
 141                         n->minmtu = len;
 142                 if(n->mtuprobes > 30)
 143                         n->mtuprobes = 30;
 144         }
 145 }
 146
 147 static length_t compress_packet(uint8_t *dest, const uint8_t *source, length_t len, int level) {
 148         if(level == 10) {
 149                 lzo_uint lzolen = MAXSIZE;
 150                 lzo1x_1_compress(source, len, dest, &lzolen, lzo_wrkmem);
 151                 return lzolen;
 152         } else if(level < 10) {
 153                 unsigned long destlen = MAXSIZE;
 154                 if(compress2(dest, &destlen, source, len, level) == Z_OK)
 155                         return destlen;
 156                 else
 157                         return -1;
 158         } else {
 159                 lzo_uint lzolen = MAXSIZE;
 160                 lzo1x_999_compress(source, len, dest, &lzolen, lzo_wrkmem);
 161                 return lzolen;
 162         }
 163
 164         return -1;
 165 }
 166
 167 static length_t uncompress_packet(uint8_t *dest, const uint8_t *source, length_t len, int level) {
 168         if(level > 9) {
 169                 lzo_uint lzolen = MAXSIZE;
 170                 if(lzo1x_decompress_safe(source, len, dest, &lzolen, NULL) == LZO_E_OK)
 171                         return lzolen;
 172                 else
 173                         return -1;
 174         } else {
 175                 unsigned long destlen = MAXSIZE;
 176                 if(uncompress(dest, &destlen, source, len) == Z_OK)
 177                         return destlen;
 178                 else
 179                         return -1;
 180         }
 181
 182         return -1;
 183 }
 184
 185 /* VPN packet I/O */
 186
 187 static void receive_packet(node_t *n, vpn_packet_t *packet) {
 188         ifdebug(TRAFFIC) logger(LOG_DEBUG, "Received packet of %d bytes from %s (%s)",
 189                            packet->len, n->name, n->hostname);
 190
 191         route(n, packet);
 192 }
 193
 194 static bool try_mac(node_t *n, const vpn_packet_t *inpkt) {
 195         if(!digest_active(&n->indigest) || inpkt->len < sizeof inpkt->seqno + digest_length(&n->indigest))
 196                 return false;
 197
 198         return digest_verify(&n->indigest, &inpkt->seqno, inpkt->len, (const char *)&inpkt->seqno + inpkt->len);
 199 }
 200
 201 static void receive_udppacket(node_t *n, vpn_packet_t *inpkt) {
 202         vpn_packet_t pkt1, pkt2;
 203         vpn_packet_t *pkt[] = { &pkt1, &pkt2, &pkt1, &pkt2 };
 204         int nextpkt = 0;
 205         vpn_packet_t *outpkt = pkt[0];
 206         size_t outlen;
 207         int i;
 208
 209         if(!cipher_active(&n->incipher)) {
 210                 ifdebug(TRAFFIC) logger(LOG_DEBUG, "Got packet from %s (%s) but he hasn't got our key yet",
 211                                         n->name, n->hostname);
 212                 return;
 213         }
 214
 215         /* Check packet length */
 216
 217         if(inpkt->len < sizeof inpkt->seqno + digest_length(&n->indigest)) {
 218                 ifdebug(TRAFFIC) logger(LOG_DEBUG, "Got too short packet from %s (%s)",
 219                                         n->name, n->hostname);
 220                 return;
 221         }
 222
 223         /* Check the message authentication code */
 224
 225         if(digest_active(&n->indigest) && !digest_verify(&n->indigest, &inpkt->seqno, inpkt->len, (const char *)&inpkt->seqno + inpkt->len)) {
 226                 ifdebug(TRAFFIC) logger(LOG_DEBUG, "Got unauthenticated packet from %s (%s)", n->name, n->hostname);
 227                 return;
 228         }
 229
 230         /* Decrypt the packet */
 231
 232         if(cipher_active(&n->incipher)) {
 233                 outpkt = pkt[nextpkt++];
 234                 outlen = MAXSIZE;
 235
 236                 if(!cipher_decrypt(&n->incipher, &inpkt->seqno, inpkt->len, &outpkt->seqno, &outlen, true)) {
 237                         ifdebug(TRAFFIC) logger(LOG_DEBUG, "Error decrypting packet from %s (%s)", n->name, n->hostname);
 238                         return;
 239                 }
 240
 241                 outpkt->len = outlen;
 242                 inpkt = outpkt;
 243         }
 244
 245         /* Check the sequence number */
 246
 247         inpkt->len -= sizeof inpkt->seqno;
 248         inpkt->seqno = ntohl(inpkt->seqno);
 249
 250         if(inpkt->seqno != n->received_seqno + 1) {
 251                 if(inpkt->seqno >= n->received_seqno + sizeof n->late * 8) {
 252                         logger(LOG_WARNING, "Lost %d packets from %s (%s)",
 253                                            inpkt->seqno - n->received_seqno - 1, n->name, n->hostname);
 254
 255                         memset(n->late, 0, sizeof n->late);
 256                 } else if (inpkt->seqno <= n->received_seqno) {
 257                         if((n->received_seqno >= sizeof n->late * 8 && inpkt->seqno <= n->received_seqno - sizeof n->late * 8) || !(n->late[(inpkt->seqno / 8) % sizeof n->late] & (1 << inpkt->seqno % 8))) {
 258                                 logger(LOG_WARNING, "Got late or replayed packet from %s (%s), seqno %d, last received %d",
 259                                            n->name, n->hostname, inpkt->seqno, n->received_seqno);
 260                                 return;
 261                         }
 262                 } else {
 263                         for(i = n->received_seqno + 1; i < inpkt->seqno; i++)
 264                                 n->late[(i / 8) % sizeof n->late] |= 1 << i % 8;
 265                 }
 266         }
 267
 268         n->late[(inpkt->seqno / 8) % sizeof n->late] &= ~(1 << inpkt->seqno % 8);
 269
 270         if(inpkt->seqno > n->received_seqno)
 271                 n->received_seqno = inpkt->seqno;
 272
 273         if(n->received_seqno > MAX_SEQNO)
 274                 regenerate_key();
 275
 276         /* Decompress the packet */
 277
 278         length_t origlen = inpkt->len;
 279
 280         if(n->incompression) {
 281                 outpkt = pkt[nextpkt++];
 282
 283                 if((outpkt->len = uncompress_packet(outpkt->data, inpkt->data, inpkt->len, n->incompression)) < 0) {
 284                         ifdebug(TRAFFIC) logger(LOG_ERR, "Error while uncompressing packet from %s (%s)",
 285                                                  n->name, n->hostname);
 286                         return;
 287                 }
 288
 289                 inpkt = outpkt;
 290
 291                 origlen -= MTU/64 + 20;
 292         }
 293
 294         inpkt->priority = 0;
 295
 296         if(!inpkt->data[12] && !inpkt->data[13])
 297                 mtu_probe_h(n, inpkt, origlen);
 298         else
 299                 receive_packet(n, inpkt);
 300 }
 301
 302 void receive_tcppacket(connection_t *c, char *buffer, int len) {
 303         vpn_packet_t outpkt;
 304
 305         outpkt.len = len;
 306         if(c->options & OPTION_TCPONLY)
 307                 outpkt.priority = 0;
 308         else
 309                 outpkt.priority = -1;
 310         memcpy(outpkt.data, buffer, len);
 311
 312         receive_packet(c->node, &outpkt);
 313 }
 314
 315 static void send_udppacket(node_t *n, vpn_packet_t *origpkt) {
 316         vpn_packet_t pkt1, pkt2;
 317         vpn_packet_t *pkt[] = { &pkt1, &pkt2, &pkt1, &pkt2 };
 318         vpn_packet_t *inpkt = origpkt;
 319         int nextpkt = 0;
 320         vpn_packet_t *outpkt;
 321         int origlen;
 322         size_t outlen;
 323         static int priority = 0;
 324         int origpriority;
 325         int sock;
 326
 327         if(!n->status.reachable) {
 328                 ifdebug(TRAFFIC) logger(LOG_INFO, "Trying to send UDP packet to unreachable node %s (%s)", n->name, n->hostname);
 329                 return;
 330         }
 331
 332         /* Make sure we have a valid key */
 333
 334         if(!n->status.validkey) {
 335                 ifdebug(TRAFFIC) logger(LOG_INFO,
 336                                    "No valid key known yet for %s (%s), forwarding via TCP",
 337                                    n->name, n->hostname);
 338
 339                 if(!n->status.waitingforkey)
 340                         send_req_key(n);
 341
 342                 n->status.waitingforkey = true;
 343
 344                 send_tcppacket(n->nexthop->connection, origpkt);
 345
 346                 return;
 347         }
 348
 349         if(n->options & OPTION_PMTU_DISCOVERY && inpkt->len > n->minmtu && (inpkt->data[12] | inpkt->data[13])) {
 350                 ifdebug(TRAFFIC) logger(LOG_INFO,
 351                                 "Packet for %s (%s) larger than minimum MTU, forwarding via %s",
 352                                 n->name, n->hostname, n != n->nexthop ? n->nexthop->name : "TCP");
 353
 354                 if(n != n->nexthop)
 355                         send_packet(n->nexthop, origpkt);
 356                 else
 357                         send_tcppacket(n->nexthop->connection, origpkt);
 358
 359                 return;
 360         }
 361
 362         origlen = inpkt->len;
 363         origpriority = inpkt->priority;
 364
 365         /* Compress the packet */
 366
 367         if(n->outcompression) {
 368                 outpkt = pkt[nextpkt++];
 369
 370                 if((outpkt->len = compress_packet(outpkt->data, inpkt->data, inpkt->len, n->outcompression)) < 0) {
 371                         ifdebug(TRAFFIC) logger(LOG_ERR, "Error while compressing packet to %s (%s)",
 372                                    n->name, n->hostname);
 373                         return;
 374                 }
 375
 376                 inpkt = outpkt;
 377         }
 378
 379         /* Add sequence number */
 380
 381         inpkt->seqno = htonl(++(n->sent_seqno));
 382         inpkt->len += sizeof inpkt->seqno;
 383
 384         /* Encrypt the packet */
 385
 386         if(cipher_active(&n->outcipher)) {
 387                 outpkt = pkt[nextpkt++];
 388                 outlen = MAXSIZE;
 389
 390                 if(!cipher_encrypt(&n->outcipher, &inpkt->seqno, inpkt->len, &outpkt->seqno, &outlen, true)) {
 391                         ifdebug(TRAFFIC) logger(LOG_ERR, "Error while encrypting packet to %s (%s)", n->name, n->hostname);
 392                         goto end;
 393                 }
 394
 395                 outpkt->len = outlen;
 396                 inpkt = outpkt;
 397         }
 398
 399         /* Add the message authentication code */
 400
 401         if(digest_active(&n->outdigest)) {
 402                 digest_create(&n->outdigest, &inpkt->seqno, inpkt->len, (char *)&inpkt->seqno + inpkt->len);
 403                 inpkt->len += digest_length(&n->outdigest);
 404         }
 405
 406         /* Determine which socket we have to use */
 407
 408         for(sock = 0; sock < listen_sockets; sock++)
 409                 if(n->address.sa.sa_family == listen_socket[sock].sa.sa.sa_family)
 410                         break;
 411
 412         if(sock >= listen_sockets)
 413                 sock = 0;                               /* If none is available, just use the first and hope for the best. */
 414
 415         /* Send the packet */
 416
 417 #if defined(SOL_IP) && defined(IP_TOS)
 418         if(priorityinheritance && origpriority != priority
 419            && listen_socket[sock].sa.sa.sa_family == AF_INET) {
 420                 priority = origpriority;
 421                 ifdebug(TRAFFIC) logger(LOG_DEBUG, "Setting outgoing packet priority to %d", priority);
 422                 if(setsockopt(listen_socket[sock].udp, SOL_IP, IP_TOS, &priority, sizeof priority))     /* SO_PRIORITY doesn't seem to work */
 423                         logger(LOG_ERR, "System call `%s' failed: %s", "setsockopt", strerror(errno));
 424         }
 425 #endif
 426
 427         if(sendto(listen_socket[sock].udp, (char *) &inpkt->seqno, inpkt->len, 0, &(n->address.sa), SALEN(n->address.sa)) < 0 && !sockwouldblock(sockerrno)) {
 428                 if(sockmsgsize(sockerrno)) {
 429                         if(n->maxmtu >= origlen)
 430                                 n->maxmtu = origlen - 1;
 431                         if(n->mtu >= origlen)
 432                                 n->mtu = origlen - 1;
 433                 } else
 434                         logger(LOG_ERR, "Error sending packet to %s (%s): %s", n->name, n->hostname, sockstrerror(sockerrno));
 435         }
 436
 437 end:
 438         origpkt->len = origlen;
 439 }
 440
 441 /*
 442   send a packet to the given vpn ip.
 443 */
 444 void send_packet(const node_t *n, vpn_packet_t *packet) {
 445         node_t *via;
 446
 447         if(n == myself) {
 448                 if(overwrite_mac)
 449                          memcpy(packet->data, mymac.x, ETH_ALEN);
 450                 write_packet(packet);
 451                 return;
 452         }
 453
 454         ifdebug(TRAFFIC) logger(LOG_ERR, "Sending packet of %d bytes to %s (%s)",
 455                            packet->len, n->name, n->hostname);
 456
 457         if(!n->status.reachable) {
 458                 ifdebug(TRAFFIC) logger(LOG_INFO, "Node %s (%s) is not reachable",
 459                                    n->name, n->hostname);
 460                 return;
 461         }
 462
 463         via = (packet->priority == -1 || n->via == myself) ? n->nexthop : n->via;
 464
 465         if(via != n)
 466                 ifdebug(TRAFFIC) logger(LOG_INFO, "Sending packet to %s via %s (%s)",
 467                            n->name, via->name, n->via->hostname);
 468
 469         if(packet->priority == -1 || ((myself->options | via->options) & OPTION_TCPONLY)) {
 470                 if(!send_tcppacket(via->connection, packet))
 471                         terminate_connection(via->connection, true);
 472         } else
 473                 send_udppacket(via, packet);
 474 }
 475
 476 /* Broadcast a packet using the minimum spanning tree */
 477
 478 void broadcast_packet(const node_t *from, vpn_packet_t *packet) {
 479         splay_node_t *node;
 480         connection_t *c;
 481
 482         ifdebug(TRAFFIC) logger(LOG_INFO, "Broadcasting packet of %d bytes from %s (%s)",
 483                            packet->len, from->name, from->hostname);
 484
 485         if(from != myself) {
 486                 send_packet(myself, packet);
 487
 488                 // In TunnelServer mode, do not forward broadcast packets.
 489                 // The MST might not be valid and create loops.
 490                 if(tunnelserver)
 491                         return;
 492         }
 493
 494         for(node = connection_tree->head; node; node = node->next) {
 495                 c = node->data;
 496
 497                 if(c->status.active && c->status.mst && c != from->nexthop->connection)
 498                         send_packet(c->node, packet);
 499         }
 500 }
 501
 502 static node_t *try_harder(const sockaddr_t *from, const vpn_packet_t *pkt) {
 503         splay_node_t *node;
 504         edge_t *e;
 505         node_t *n = NULL;
 506         static time_t last_hard_try = 0;
 507         time_t now = time(NULL);
 508
 509         for(node = edge_weight_tree->head; node; node = node->next) {
 510                 e = node->data;
 511
 512                 if(sockaddrcmp_noport(from, &e->address)) {
 513                         if(last_hard_try == now)
 514                                 continue;
 515                         last_hard_try = now;
 516                 }
 517
 518                 if(!n)
 519                         n = e->to;
 520
 521                 if(!try_mac(e->to, pkt))
 522                         continue;
 523
 524                 n = e->to;
 525                 break;
 526         }
 527
 528         return n;
 529 }
 530
 531 void handle_incoming_vpn_data(int sock, short events, void *data) {
 532         vpn_packet_t pkt;
 533         char *hostname;
 534         sockaddr_t from;
 535         socklen_t fromlen = sizeof from;
 536         node_t *n;
 537
 538         pkt.len = recvfrom(sock, (char *) &pkt.seqno, MAXSIZE, 0, &from.sa, &fromlen);
 539
 540         if(pkt.len < 0) {
 541                 if(!sockwouldblock(sockerrno))
 542                         logger(LOG_ERR, "Receiving packet failed: %s", sockstrerror(sockerrno));
 543                 return;
 544         }
 545
 546         sockaddrunmap(&from);           /* Some braindead IPv6 implementations do stupid things. */
 547
 548         n = lookup_node_udp(&from);
 549
 550         if(!n) {
 551                 n = try_harder(&from, &pkt);
 552                 if(n)
 553                         update_node_udp(n, &from);
 554                 else ifdebug(PROTOCOL) {
 555                         hostname = sockaddr2hostname(&from);
 556                         logger(LOG_WARNING, "Received UDP packet from unknown source %s", hostname);
 557                         free(hostname);
 558                         return;
 559                 }
 560                 else
 561                         return;
 562         }
 563
 564         receive_udppacket(n, &pkt);
 565 }
 566
 567 void handle_device_data(int sock, short events, void *data) {
 568         vpn_packet_t packet;
 569
 570         if(read_packet(&packet))
 571                 route(myself, &packet);
 572 }