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