www.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 - n->indigest.maclength, (const char *)&inpkt->seqno + inpkt->len - n->indigest.maclength);
 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)) {
 226                 inpkt->len -= n->indigest.maclength;
 227                 if(!digest_verify(&n->indigest, &inpkt->seqno, inpkt->len, (const char *)&inpkt->seqno + inpkt->len)) {
 228                         ifdebug(TRAFFIC) logger(LOG_DEBUG, "Got unauthenticated packet from %s (%s)", n->name, n->hostname);
 229                         return;
 230                 }
 231         }
 232         /* Decrypt the packet */
 233
 234         if(cipher_active(&n->incipher)) {
 235                 outpkt = pkt[nextpkt++];
 236                 outlen = MAXSIZE;
 237
 238                 if(!cipher_decrypt(&n->incipher, &inpkt->seqno, inpkt->len, &outpkt->seqno, &outlen, true)) {
 239                         ifdebug(TRAFFIC) logger(LOG_DEBUG, "Error decrypting packet from %s (%s)", n->name, n->hostname);
 240                         return;
 241                 }
 242
 243                 outpkt->len = outlen;
 244                 inpkt = outpkt;
 245         }
 246
 247         /* Check the sequence number */
 248
 249         inpkt->len -= sizeof inpkt->seqno;
 250         inpkt->seqno = ntohl(inpkt->seqno);
 251
 252         if(inpkt->seqno != n->received_seqno + 1) {
 253                 if(inpkt->seqno >= n->received_seqno + sizeof n->late * 8) {
 254                         logger(LOG_WARNING, "Lost %d packets from %s (%s)",
 255                                            inpkt->seqno - n->received_seqno - 1, n->name, n->hostname);
 256
 257                         memset(n->late, 0, sizeof n->late);
 258                 } else if (inpkt->seqno <= n->received_seqno) {
 259                         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))) {
 260                                 logger(LOG_WARNING, "Got late or replayed packet from %s (%s), seqno %d, last received %d",
 261                                            n->name, n->hostname, inpkt->seqno, n->received_seqno);
 262                                 return;
 263                         }
 264                 } else {
 265                         for(i = n->received_seqno + 1; i < inpkt->seqno; i++)
 266                                 n->late[(i / 8) % sizeof n->late] |= 1 << i % 8;
 267                 }
 268         }
 269
 270         n->late[(inpkt->seqno / 8) % sizeof n->late] &= ~(1 << inpkt->seqno % 8);
 271
 272         if(inpkt->seqno > n->received_seqno)
 273                 n->received_seqno = inpkt->seqno;
 274
 275         if(n->received_seqno > MAX_SEQNO)
 276                 regenerate_key();
 277
 278         /* Decompress the packet */
 279
 280         length_t origlen = inpkt->len;
 281
 282         if(n->incompression) {
 283                 outpkt = pkt[nextpkt++];
 284
 285                 if((outpkt->len = uncompress_packet(outpkt->data, inpkt->data, inpkt->len, n->incompression)) < 0) {
 286                         ifdebug(TRAFFIC) logger(LOG_ERR, "Error while uncompressing packet from %s (%s)",
 287                                                  n->name, n->hostname);
 288                         return;
 289                 }
 290
 291                 inpkt = outpkt;
 292
 293                 origlen -= MTU/64 + 20;
 294         }
 295
 296         inpkt->priority = 0;
 297
 298         if(!inpkt->data[12] && !inpkt->data[13])
 299                 mtu_probe_h(n, inpkt, origlen);
 300         else
 301                 receive_packet(n, inpkt);
 302 }
 303
 304 void receive_tcppacket(connection_t *c, char *buffer, int len) {
 305         vpn_packet_t outpkt;
 306
 307         outpkt.len = len;
 308         if(c->options & OPTION_TCPONLY)
 309                 outpkt.priority = 0;
 310         else
 311                 outpkt.priority = -1;
 312         memcpy(outpkt.data, buffer, len);
 313
 314         receive_packet(c->node, &outpkt);
 315 }
 316
 317 static void send_udppacket(node_t *n, vpn_packet_t *origpkt) {
 318         vpn_packet_t pkt1, pkt2;
 319         vpn_packet_t *pkt[] = { &pkt1, &pkt2, &pkt1, &pkt2 };
 320         vpn_packet_t *inpkt = origpkt;
 321         int nextpkt = 0;
 322         vpn_packet_t *outpkt;
 323         int origlen;
 324         size_t outlen;
 325         static int priority = 0;
 326         int origpriority;
 327         int sock;
 328
 329         if(!n->status.reachable) {
 330                 ifdebug(TRAFFIC) logger(LOG_INFO, "Trying to send UDP packet to unreachable node %s (%s)", n->name, n->hostname);
 331                 return;
 332         }
 333
 334         /* Make sure we have a valid key */
 335
 336         if(!n->status.validkey) {
 337                 ifdebug(TRAFFIC) logger(LOG_INFO,
 338                                    "No valid key known yet for %s (%s), forwarding via TCP",
 339                                    n->name, n->hostname);
 340
 341                 if(!n->status.waitingforkey)
 342                         send_req_key(n);
 343
 344                 n->status.waitingforkey = true;
 345
 346                 send_tcppacket(n->nexthop->connection, origpkt);
 347
 348                 return;
 349         }
 350
 351         if(n->options & OPTION_PMTU_DISCOVERY && inpkt->len > n->minmtu && (inpkt->data[12] | inpkt->data[13])) {
 352                 ifdebug(TRAFFIC) logger(LOG_INFO,
 353                                 "Packet for %s (%s) larger than minimum MTU, forwarding via %s",
 354                                 n->name, n->hostname, n != n->nexthop ? n->nexthop->name : "TCP");
 355
 356                 if(n != n->nexthop)
 357                         send_packet(n->nexthop, origpkt);
 358                 else
 359                         send_tcppacket(n->nexthop->connection, origpkt);
 360
 361                 return;
 362         }
 363
 364         origlen = inpkt->len;
 365         origpriority = inpkt->priority;
 366
 367         /* Compress the packet */
 368
 369         if(n->outcompression) {
 370                 outpkt = pkt[nextpkt++];
 371
 372                 if((outpkt->len = compress_packet(outpkt->data, inpkt->data, inpkt->len, n->outcompression)) < 0) {
 373                         ifdebug(TRAFFIC) logger(LOG_ERR, "Error while compressing packet to %s (%s)",
 374                                    n->name, n->hostname);
 375                         return;
 376                 }
 377
 378                 inpkt = outpkt;
 379         }
 380
 381         /* Add sequence number */
 382
 383         inpkt->seqno = htonl(++(n->sent_seqno));
 384         inpkt->len += sizeof inpkt->seqno;
 385
 386         /* Encrypt the packet */
 387
 388         if(cipher_active(&n->outcipher)) {
 389                 outpkt = pkt[nextpkt++];
 390                 outlen = MAXSIZE;
 391
 392                 if(!cipher_encrypt(&n->outcipher, &inpkt->seqno, inpkt->len, &outpkt->seqno, &outlen, true)) {
 393                         ifdebug(TRAFFIC) logger(LOG_ERR, "Error while encrypting packet to %s (%s)", n->name, n->hostname);
 394                         goto end;
 395                 }
 396
 397                 outpkt->len = outlen;
 398                 inpkt = outpkt;
 399         }
 400
 401         /* Add the message authentication code */
 402
 403         if(digest_active(&n->outdigest)) {
 404                 digest_create(&n->outdigest, &inpkt->seqno, inpkt->len, (char *)&inpkt->seqno + inpkt->len);
 405                 inpkt->len += digest_length(&n->outdigest);
 406         }
 407
 408         /* Determine which socket we have to use */
 409
 410         for(sock = 0; sock < listen_sockets; sock++)
 411                 if(n->address.sa.sa_family == listen_socket[sock].sa.sa.sa_family)
 412                         break;
 413
 414         if(sock >= listen_sockets)
 415                 sock = 0;                               /* If none is available, just use the first and hope for the best. */
 416
 417         /* Send the packet */
 418
 419 #if defined(SOL_IP) && defined(IP_TOS)
 420         if(priorityinheritance && origpriority != priority
 421            && listen_socket[sock].sa.sa.sa_family == AF_INET) {
 422                 priority = origpriority;
 423                 ifdebug(TRAFFIC) logger(LOG_DEBUG, "Setting outgoing packet priority to %d", priority);
 424                 if(setsockopt(listen_socket[sock].udp, SOL_IP, IP_TOS, &priority, sizeof priority))     /* SO_PRIORITY doesn't seem to work */
 425                         logger(LOG_ERR, "System call `%s' failed: %s", "setsockopt", strerror(errno));
 426         }
 427 #endif
 428
 429         if(sendto(listen_socket[sock].udp, (char *) &inpkt->seqno, inpkt->len, 0, &(n->address.sa), SALEN(n->address.sa)) < 0 && !sockwouldblock(sockerrno)) {
 430                 if(sockmsgsize(sockerrno)) {
 431                         if(n->maxmtu >= origlen)
 432                                 n->maxmtu = origlen - 1;
 433                         if(n->mtu >= origlen)
 434                                 n->mtu = origlen - 1;
 435                 } else
 436                         logger(LOG_ERR, "Error sending packet to %s (%s): %s", n->name, n->hostname, sockstrerror(sockerrno));
 437         }
 438
 439 end:
 440         origpkt->len = origlen;
 441 }
 442
 443 /*
 444   send a packet to the given vpn ip.
 445 */
 446 void send_packet(const node_t *n, vpn_packet_t *packet) {
 447         node_t *via;
 448
 449         if(n == myself) {
 450                 if(overwrite_mac)
 451                          memcpy(packet->data, mymac.x, ETH_ALEN);
 452                 write_packet(packet);
 453                 return;
 454         }
 455
 456         ifdebug(TRAFFIC) logger(LOG_ERR, "Sending packet of %d bytes to %s (%s)",
 457                            packet->len, n->name, n->hostname);
 458
 459         if(!n->status.reachable) {
 460                 ifdebug(TRAFFIC) logger(LOG_INFO, "Node %s (%s) is not reachable",
 461                                    n->name, n->hostname);
 462                 return;
 463         }
 464
 465         via = (packet->priority == -1 || n->via == myself) ? n->nexthop : n->via;
 466
 467         if(via != n)
 468                 ifdebug(TRAFFIC) logger(LOG_INFO, "Sending packet to %s via %s (%s)",
 469                            n->name, via->name, n->via->hostname);
 470
 471         if(packet->priority == -1 || ((myself->options | via->options) & OPTION_TCPONLY)) {
 472                 if(!send_tcppacket(via->connection, packet))
 473                         terminate_connection(via->connection, true);
 474         } else
 475                 send_udppacket(via, packet);
 476 }
 477
 478 /* Broadcast a packet using the minimum spanning tree */
 479
 480 void broadcast_packet(const node_t *from, vpn_packet_t *packet) {
 481         splay_node_t *node;
 482         connection_t *c;
 483
 484         ifdebug(TRAFFIC) logger(LOG_INFO, "Broadcasting packet of %d bytes from %s (%s)",
 485                            packet->len, from->name, from->hostname);
 486
 487         if(from != myself) {
 488                 send_packet(myself, packet);
 489
 490                 // In TunnelServer mode, do not forward broadcast packets.
 491                 // The MST might not be valid and create loops.
 492                 if(tunnelserver)
 493                         return;
 494         }
 495
 496         for(node = connection_tree->head; node; node = node->next) {
 497                 c = node->data;
 498
 499                 if(c->status.active && c->status.mst && c != from->nexthop->connection)
 500                         send_packet(c->node, packet);
 501         }
 502 }
 503
 504 static node_t *try_harder(const sockaddr_t *from, const vpn_packet_t *pkt) {
 505         splay_node_t *node;
 506         node_t *n, *found = NULL;
 507         static time_t last_hard_try = 0;
 508         time_t now = time(NULL);
 509
 510         if(last_hard_try == now)
 511                 return NULL;
 512         else
 513                 last_hard_try = now;
 514
 515         for(node = node_tree->head; node; node = node->next) {
 516                 n = node->data;
 517
 518                 if(n == myself || !n->status.reachable || !digest_active(&n->indigest))
 519                         continue;
 520
 521                 if(try_mac(n, pkt)) {
 522                         found = n;
 523                         break;
 524                 }
 525         }
 526
 527         return found;
 528 }
 529
 530 void handle_incoming_vpn_data(int sock, short events, void *data) {
 531         vpn_packet_t pkt;
 532         char *hostname;
 533         sockaddr_t from;
 534         socklen_t fromlen = sizeof from;
 535         node_t *n;
 536         int len;
 537
 538         len = recvfrom(sock, (char *) &pkt.seqno, MAXSIZE, 0, &from.sa, &fromlen);
 539
 540         if(len <= 0 || len > MAXSIZE) {
 541                 if(!sockwouldblock(sockerrno))
 542                         logger(LOG_ERR, "Receiving packet failed: %s", sockstrerror(sockerrno));
 543                 return;
 544         }
 545
 546         pkt.len = len;
 547
 548         sockaddrunmap(&from);           /* Some braindead IPv6 implementations do stupid things. */
 549
 550         n = lookup_node_udp(&from);
 551
 552         if(!n) {
 553                 n = try_harder(&from, &pkt);
 554                 if(n)
 555                         update_node_udp(n, &from);
 556                 else ifdebug(PROTOCOL) {
 557                         hostname = sockaddr2hostname(&from);
 558                         logger(LOG_WARNING, "Received UDP packet from unknown source %s", hostname);
 559                         free(hostname);
 560                         return;
 561                 }
 562                 else
 563                         return;
 564         }
 565
 566         receive_udppacket(n, &pkt);
 567 }
 568
 569 void handle_device_data(int sock, short events, void *data) {
 570         vpn_packet_t packet;
 571
 572         if(read_packet(&packet))
 573                 route(myself, &packet);
 574 }