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

   1 /*
   2     route.c -- routing
   3     Copyright (C) 2000-2005 Ivo Timmermans,
   4                   2000-2006 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
  17     along with this program; if not, write to the Free Software
  18     Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  19
  20     $Id$
  21 */
  22
  23 #include "system.h"
  24
  25 #include "avl_tree.h"
  26 #include "connection.h"
  27 #include "ethernet.h"
  28 #include "ipv4.h"
  29 #include "ipv6.h"
  30 #include "logger.h"
  31 #include "net.h"
  32 #include "protocol.h"
  33 #include "route.h"
  34 #include "subnet.h"
  35 #include "utils.h"
  36
  37 rmode_t routing_mode = RMODE_ROUTER;
  38 bool priorityinheritance = false;
  39 int macexpire = 600;
  40 bool overwrite_mac = false;
  41 mac_t mymac = {{0xFE, 0xFD, 0, 0, 0, 0}};
  42
  43 /* Sizes of various headers */
  44
  45 static const size_t ether_size = sizeof(struct ether_header);
  46 static const size_t arp_size = sizeof(struct ether_arp);
  47 static const size_t ip_size = sizeof(struct ip);
  48 static const size_t icmp_size = sizeof(struct icmp) - sizeof(struct ip);
  49 static const size_t ip6_size = sizeof(struct ip6_hdr);
  50 static const size_t icmp6_size = sizeof(struct icmp6_hdr);
  51 static const size_t ns_size = sizeof(struct nd_neighbor_solicit);
  52 static const size_t opt_size = sizeof(struct nd_opt_hdr);
  53
  54 static struct event age_subnets_event;
  55
  56 /* RFC 1071 */
  57
  58 static uint16_t inet_checksum(void *data, int len, uint16_t prevsum)
  59 {
  60         uint16_t *p = data;
  61         uint32_t checksum = prevsum ^ 0xFFFF;
  62
  63         while(len >= 2) {
  64                 checksum += *p++;
  65                 len -= 2;
  66         }
  67
  68         if(len)
  69                 checksum += *(uint8_t *)p;
  70
  71         while(checksum >> 16)
  72                 checksum = (checksum & 0xFFFF) + (checksum >> 16);
  73
  74         return ~checksum;
  75 }
  76
  77 static bool ratelimit(int frequency) {
  78         static time_t lasttime = 0;
  79         static int count = 0;
  80
  81         if(lasttime == now) {
  82                 if(++count > frequency)
  83                         return true;
  84         } else {
  85                 lasttime = now;
  86                 count = 0;
  87         }
  88
  89         return false;
  90 }
  91
  92 static bool checklength(node_t *source, vpn_packet_t *packet, length_t length) {
  93         if(packet->len < length) {
  94                 ifdebug(TRAFFIC) logger(LOG_WARNING, _("Got too short packet from %s (%s)"), source->name, source->hostname);
  95                 return false;
  96         } else
  97                 return true;
  98 }
  99
 100 static void age_subnets(int fd, short events, void *data)
 101 {
 102         subnet_t *s;
 103         connection_t *c;
 104         avl_node_t *node, *next, *node2;
 105         bool left = false;
 106
 107         cp();
 108
 109         for(node = myself->subnet_tree->head; node; node = next) {
 110                 next = node->next;
 111                 s = node->data;
 112                 if(s->expires && s->expires < now) {
 113                         ifdebug(TRAFFIC) {
 114                                 char netstr[MAXNETSTR];
 115                                 if(net2str(netstr, sizeof netstr, s))
 116                                         logger(LOG_INFO, _("Subnet %s expired"), netstr);
 117                         }
 118
 119                         for(node2 = connection_tree->head; node2; node2 = node2->next) {
 120                                 c = node2->data;
 121                                 if(c->status.active)
 122                                         send_del_subnet(c, s);
 123                         }
 124
 125                         subnet_del(myself, s);
 126                 } else {
 127                         if(s->expires)
 128                                 left = true;
 129                 }
 130         }
 131
 132         if(left)
 133                 event_add(&age_subnets_event, &(struct timeval){10, 0});
 134 }
 135
 136 static void learn_mac(mac_t *address)
 137 {
 138         subnet_t *subnet;
 139         avl_node_t *node;
 140         connection_t *c;
 141
 142         cp();
 143
 144         subnet = lookup_subnet_mac(address);
 145
 146         /* If we don't know this MAC address yet, store it */
 147
 148         if(!subnet) {
 149                 ifdebug(TRAFFIC) logger(LOG_INFO, _("Learned new MAC address %hx:%hx:%hx:%hx:%hx:%hx"),
 150                                    address->x[0], address->x[1], address->x[2], address->x[3],
 151                                    address->x[4], address->x[5]);
 152
 153                 subnet = new_subnet();
 154                 subnet->type = SUBNET_MAC;
 155                 subnet->expires = now + macexpire;
 156                 subnet->net.mac.address = *address;
 157                 subnet_add(myself, subnet);
 158
 159                 /* And tell all other tinc daemons it's our MAC */
 160
 161                 for(node = connection_tree->head; node; node = node->next) {
 162                         c = node->data;
 163                         if(c->status.active)
 164                                 send_add_subnet(c, subnet);
 165                 }
 166
 167                 if(!timeout_initialized(&age_subnets_event))
 168                         timeout_set(&age_subnets_event, age_subnets, NULL);
 169                 event_add(&age_subnets_event, &(struct timeval){10, 0});
 170         }
 171
 172         if(subnet->expires)
 173                 subnet->expires = now + macexpire;
 174 }
 175
 176 static void route_mac(node_t *source, vpn_packet_t *packet)
 177 {
 178         subnet_t *subnet;
 179         mac_t dest;
 180
 181         cp();
 182
 183
 184         /* Learn source address */
 185
 186         if(source == myself) {
 187                 mac_t src;
 188                 memcpy(&src, &packet->data[6], sizeof src);
 189                 learn_mac(&src);
 190         }
 191
 192         /* Lookup destination address */
 193
 194         memcpy(&dest, &packet->data[0], sizeof dest);
 195         subnet = lookup_subnet_mac(&dest);
 196
 197         if(!subnet) {
 198                 broadcast_packet(source, packet);
 199                 return;
 200         }
 201
 202         if(subnet->owner == source) {
 203                 ifdebug(TRAFFIC) logger(LOG_WARNING, _("Packet looping back to %s (%s)!"), source->name, source->hostname);
 204                 return;
 205         }
 206
 207         send_packet(subnet->owner, packet);
 208 }
 209
 210 /* RFC 792 */
 211
 212 static void route_ipv4_unreachable(node_t *source, vpn_packet_t *packet, uint8_t type, uint8_t code)
 213 {
 214         struct ip ip = {0};
 215         struct icmp icmp = {0};
 216
 217         struct in_addr ip_src;
 218         struct in_addr ip_dst;
 219         uint32_t oldlen;
 220
 221         if(ratelimit(3))
 222                 return;
 223
 224         cp();
 225
 226         /* Copy headers from packet into properly aligned structs on the stack */
 227
 228         memcpy(&ip, packet->data + ether_size, ip_size);
 229
 230         /* Remember original source and destination */
 231
 232         ip_src = ip.ip_src;
 233         ip_dst = ip.ip_dst;
 234
 235         oldlen = packet->len - ether_size;
 236
 237         if(type == ICMP_DEST_UNREACH && code == ICMP_FRAG_NEEDED)
 238                 icmp.icmp_nextmtu = htons(packet->len - ether_size);
 239
 240         if(oldlen >= IP_MSS - ip_size - icmp_size)
 241                 oldlen = IP_MSS - ip_size - icmp_size;
 242
 243         /* Copy first part of original contents to ICMP message */
 244
 245         memmove(packet->data + ether_size + ip_size + icmp_size, packet->data + ether_size, oldlen);
 246
 247         /* Fill in IPv4 header */
 248
 249         ip.ip_v = 4;
 250         ip.ip_hl = ip_size / 4;
 251         ip.ip_tos = 0;
 252         ip.ip_len = htons(ip_size + icmp_size + oldlen);
 253         ip.ip_id = 0;
 254         ip.ip_off = 0;
 255         ip.ip_ttl = 255;
 256         ip.ip_p = IPPROTO_ICMP;
 257         ip.ip_sum = 0;
 258         ip.ip_src = ip_dst;
 259         ip.ip_dst = ip_src;
 260
 261         ip.ip_sum = inet_checksum(&ip, ip_size, ~0);
 262
 263         /* Fill in ICMP header */
 264
 265         icmp.icmp_type = type;
 266         icmp.icmp_code = code;
 267         icmp.icmp_cksum = 0;
 268
 269         icmp.icmp_cksum = inet_checksum(&icmp, icmp_size, ~0);
 270         icmp.icmp_cksum = inet_checksum(packet->data + ether_size + ip_size + icmp_size, oldlen, icmp.icmp_cksum);
 271
 272         /* Copy structs on stack back to packet */
 273
 274         memcpy(packet->data + ether_size, &ip, ip_size);
 275         memcpy(packet->data + ether_size + ip_size, &icmp, icmp_size);
 276
 277         packet->len = ether_size + ip_size + icmp_size + oldlen;
 278
 279         send_packet(source, packet);
 280 }
 281
 282 /* RFC 791 */
 283
 284 static void fragment_ipv4_packet(node_t *dest, vpn_packet_t *packet) {
 285         struct ip ip;
 286         vpn_packet_t fragment;
 287         int len, maxlen, todo;
 288         uint8_t *offset;
 289         uint16_t ip_off, origf;
 290
 291         cp();
 292
 293         memcpy(&ip, packet->data + ether_size, ip_size);
 294         fragment.priority = packet->priority;
 295
 296         if(ip.ip_hl != ip_size / 4)
 297                 return;
 298
 299         todo = ntohs(ip.ip_len) - ip_size;
 300
 301         if(ether_size + ip_size + todo != packet->len) {
 302                 ifdebug(TRAFFIC) logger(LOG_WARNING, _("Length of packet (%d) doesn't match length in IPv4 header (%zd)"), packet->len, ether_size + ip_size + todo);
 303                 return;
 304         }
 305
 306         ifdebug(TRAFFIC) logger(LOG_INFO, _("Fragmenting packet of %d bytes to %s (%s)"), packet->len, dest->name, dest->hostname);
 307
 308         offset = packet->data + ether_size + ip_size;
 309         maxlen = (dest->mtu - ether_size - ip_size) & ~0x7;
 310         ip_off = ntohs(ip.ip_off);
 311         origf = ip_off & ~IP_OFFMASK;
 312         ip_off &= IP_OFFMASK;
 313
 314         while(todo) {
 315                 len = todo > maxlen ? maxlen : todo;
 316                 memcpy(fragment.data + ether_size + ip_size, offset, len);
 317                 todo -= len;
 318                 offset += len;
 319
 320                 ip.ip_len = htons(ip_size + len);
 321                 ip.ip_off = htons(ip_off | origf | (todo ? IP_MF : 0));
 322                 ip.ip_sum = 0;
 323                 ip.ip_sum = inet_checksum(&ip, ip_size, ~0);
 324                 memcpy(fragment.data, packet->data, ether_size);
 325                 memcpy(fragment.data + ether_size, &ip, ip_size);
 326                 fragment.len = ether_size + ip_size + len;
 327
 328                 send_packet(dest, &fragment);
 329
 330                 ip_off += len / 8;
 331         }
 332 }
 333
 334 static void route_ipv4_unicast(node_t *source, vpn_packet_t *packet)
 335 {
 336         subnet_t *subnet;
 337         node_t *via;
 338         ipv4_t dest;
 339
 340         cp();
 341
 342         memcpy(&dest, &packet->data[30], sizeof dest);
 343         subnet = lookup_subnet_ipv4(&dest);
 344
 345         if(!subnet) {
 346                 ifdebug(TRAFFIC) logger(LOG_WARNING, _("Cannot route packet from %s (%s): unknown IPv4 destination address %d.%d.%d.%d"),
 347                                 source->name, source->hostname,
 348                                 dest.x[0],
 349                                 dest.x[1],
 350                                 dest.x[2],
 351                                 dest.x[3]);
 352
 353                 route_ipv4_unreachable(source, packet, ICMP_DEST_UNREACH, ICMP_NET_UNKNOWN);
 354                 return;
 355         }
 356
 357         if(subnet->owner == source) {
 358                 ifdebug(TRAFFIC) logger(LOG_WARNING, _("Packet looping back to %s (%s)!"), source->name, source->hostname);
 359                 return;
 360         }
 361
 362         if(!subnet->owner->status.reachable)
 363                 route_ipv4_unreachable(source, packet, ICMP_DEST_UNREACH, ICMP_NET_UNREACH);
 364
 365         if(priorityinheritance)
 366                 packet->priority = packet->data[15];
 367
 368         via = (subnet->owner->via == myself) ? subnet->owner->nexthop : subnet->owner->via;
 369
 370         if(via && packet->len > via->mtu && via != myself) {
 371                 ifdebug(TRAFFIC) logger(LOG_INFO, _("Packet for %s (%s) length %d larger than MTU %d"), subnet->owner->name, subnet->owner->hostname, packet->len, via->mtu);
 372                 if(packet->data[20] & 0x40) {
 373                         packet->len = via->mtu;
 374                         route_ipv4_unreachable(source, packet, ICMP_DEST_UNREACH, ICMP_FRAG_NEEDED);
 375                 } else {
 376                         fragment_ipv4_packet(via, packet);
 377                 }
 378
 379                 return;
 380         }
 381
 382         send_packet(subnet->owner, packet);
 383 }
 384
 385 static void route_ipv4(node_t *source, vpn_packet_t *packet)
 386 {
 387         cp();
 388
 389         if(!checklength(source, packet, ether_size + ip_size))
 390                 return;
 391
 392         route_ipv4_unicast(source, packet);
 393 }
 394
 395 /* RFC 2463 */
 396
 397 static void route_ipv6_unreachable(node_t *source, vpn_packet_t *packet, uint8_t type, uint8_t code)
 398 {
 399         struct ip6_hdr ip6;
 400         struct icmp6_hdr icmp6 = {0};
 401         uint16_t checksum;
 402
 403         struct {
 404                 struct in6_addr ip6_src;        /* source address */
 405                 struct in6_addr ip6_dst;        /* destination address */
 406                 uint32_t length;
 407                 uint32_t next;
 408         } pseudo;
 409
 410         if(ratelimit(3))
 411                 return;
 412
 413         cp();
 414
 415         /* Copy headers from packet to structs on the stack */
 416
 417         memcpy(&ip6, packet->data + ether_size, ip6_size);
 418
 419         /* Remember original source and destination */
 420
 421         pseudo.ip6_src = ip6.ip6_dst;
 422         pseudo.ip6_dst = ip6.ip6_src;
 423
 424         pseudo.length = packet->len - ether_size;
 425
 426         if(type == ICMP6_PACKET_TOO_BIG)
 427                 icmp6.icmp6_mtu = htonl(pseudo.length);
 428
 429         if(pseudo.length >= IP_MSS - ip6_size - icmp6_size)
 430                 pseudo.length = IP_MSS - ip6_size - icmp6_size;
 431
 432         /* Copy first part of original contents to ICMP message */
 433
 434         memmove(packet->data + ether_size + ip6_size + icmp6_size, packet->data + ether_size, pseudo.length);
 435
 436         /* Fill in IPv6 header */
 437
 438         ip6.ip6_flow = htonl(0x60000000UL);
 439         ip6.ip6_plen = htons(icmp6_size + pseudo.length);
 440         ip6.ip6_nxt = IPPROTO_ICMPV6;
 441         ip6.ip6_hlim = 255;
 442         ip6.ip6_src = pseudo.ip6_src;
 443         ip6.ip6_dst = pseudo.ip6_dst;
 444
 445         /* Fill in ICMP header */
 446
 447         icmp6.icmp6_type = type;
 448         icmp6.icmp6_code = code;
 449         icmp6.icmp6_cksum = 0;
 450
 451         /* Create pseudo header */
 452
 453         pseudo.length = htonl(icmp6_size + pseudo.length);
 454         pseudo.next = htonl(IPPROTO_ICMPV6);
 455
 456         /* Generate checksum */
 457
 458         checksum = inet_checksum(&pseudo, sizeof(pseudo), ~0);
 459         checksum = inet_checksum(&icmp6, icmp6_size, checksum);
 460         checksum = inet_checksum(packet->data + ether_size + ip6_size + icmp6_size, ntohl(pseudo.length) - icmp6_size, checksum);
 461
 462         icmp6.icmp6_cksum = checksum;
 463
 464         /* Copy structs on stack back to packet */
 465
 466         memcpy(packet->data + ether_size, &ip6, ip6_size);
 467         memcpy(packet->data + ether_size + ip6_size, &icmp6, icmp6_size);
 468
 469         packet->len = ether_size + ip6_size + ntohl(pseudo.length);
 470
 471         send_packet(source, packet);
 472 }
 473
 474 static void route_ipv6_unicast(node_t *source, vpn_packet_t *packet)
 475 {
 476         subnet_t *subnet;
 477         node_t *via;
 478         ipv6_t dest;
 479
 480         cp();
 481
 482         memcpy(&dest, &packet->data[38], sizeof dest);
 483         subnet = lookup_subnet_ipv6(&dest);
 484
 485         if(!subnet) {
 486                 ifdebug(TRAFFIC) logger(LOG_WARNING, _("Cannot route packet from %s (%s): unknown IPv6 destination address %hx:%hx:%hx:%hx:%hx:%hx:%hx:%hx"),
 487                                 source->name, source->hostname,
 488                                 ntohs(dest.x[0]),
 489                                 ntohs(dest.x[1]),
 490                                 ntohs(dest.x[2]),
 491                                 ntohs(dest.x[3]),
 492                                 ntohs(dest.x[4]),
 493                                 ntohs(dest.x[5]),
 494                                 ntohs(dest.x[6]),
 495                                 ntohs(dest.x[7]));
 496
 497                 route_ipv6_unreachable(source, packet, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_ADDR);
 498                 return;
 499         }
 500
 501         if(subnet->owner == source) {
 502                 ifdebug(TRAFFIC) logger(LOG_WARNING, _("Packet looping back to %s (%s)!"), source->name, source->hostname);
 503                 return;
 504         }
 505
 506         if(!subnet->owner->status.reachable)
 507                 route_ipv6_unreachable(source, packet, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_NOROUTE);
 508
 509         via = (subnet->owner->via == myself) ? subnet->owner->nexthop : subnet->owner->via;
 510
 511         if(via && packet->len > via->mtu && via != myself) {
 512                 ifdebug(TRAFFIC) logger(LOG_INFO, _("Packet for %s (%s) length %d larger than MTU %d"), subnet->owner->name, subnet->owner->hostname, packet->len, via->mtu);
 513                 packet->len = via->mtu;
 514                 route_ipv6_unreachable(source, packet, ICMP6_PACKET_TOO_BIG, 0);
 515                 return;
 516         }
 517
 518         send_packet(subnet->owner, packet);
 519 }
 520
 521 /* RFC 2461 */
 522
 523 static void route_neighborsol(node_t *source, vpn_packet_t *packet)
 524 {
 525         struct ip6_hdr ip6;
 526         struct nd_neighbor_solicit ns;
 527         struct nd_opt_hdr opt;
 528         subnet_t *subnet;
 529         uint16_t checksum;
 530
 531         struct {
 532                 struct in6_addr ip6_src;        /* source address */
 533                 struct in6_addr ip6_dst;        /* destination address */
 534                 uint32_t length;
 535                 uint32_t next;
 536         } pseudo;
 537
 538         cp();
 539
 540         if(!checklength(source, packet, ether_size + ip6_size + ns_size + opt_size + ETH_ALEN))
 541                 return;
 542
 543         if(source != myself) {
 544                 ifdebug(TRAFFIC) logger(LOG_WARNING, _("Got neighbor solicitation request from %s (%s) while in router mode!"), source->name, source->hostname);
 545                 return;
 546         }
 547
 548         /* Copy headers from packet to structs on the stack */
 549
 550         memcpy(&ip6, packet->data + ether_size, ip6_size);
 551         memcpy(&ns, packet->data + ether_size + ip6_size, ns_size);
 552         memcpy(&opt, packet->data + ether_size + ip6_size + ns_size, opt_size);
 553
 554         /* First, snatch the source address from the neighbor solicitation packet */
 555
 556         if(overwrite_mac)
 557                 memcpy(mymac.x, packet->data + ETH_ALEN, ETH_ALEN);
 558
 559         /* Check if this is a valid neighbor solicitation request */
 560
 561         if(ns.nd_ns_hdr.icmp6_type != ND_NEIGHBOR_SOLICIT ||
 562            opt.nd_opt_type != ND_OPT_SOURCE_LINKADDR) {
 563                 ifdebug(TRAFFIC) logger(LOG_WARNING, _("Cannot route packet: received unknown type neighbor solicitation request"));
 564                 return;
 565         }
 566
 567         /* Create pseudo header */
 568
 569         pseudo.ip6_src = ip6.ip6_src;
 570         pseudo.ip6_dst = ip6.ip6_dst;
 571         pseudo.length = htonl(ns_size + opt_size + ETH_ALEN);
 572         pseudo.next = htonl(IPPROTO_ICMPV6);
 573
 574         /* Generate checksum */
 575
 576         checksum = inet_checksum(&pseudo, sizeof(pseudo), ~0);
 577         checksum = inet_checksum(&ns, ns_size, checksum);
 578         checksum = inet_checksum(&opt, opt_size, checksum);
 579         checksum = inet_checksum(packet->data + ether_size + ip6_size + ns_size + opt_size, ETH_ALEN, checksum);
 580
 581         if(checksum) {
 582                 ifdebug(TRAFFIC) logger(LOG_WARNING, _("Cannot route packet: checksum error for neighbor solicitation request"));
 583                 return;
 584         }
 585
 586         /* Check if the IPv6 address exists on the VPN */
 587
 588         subnet = lookup_subnet_ipv6((ipv6_t *) &ns.nd_ns_target);
 589
 590         if(!subnet) {
 591                 ifdebug(TRAFFIC) logger(LOG_WARNING, _("Cannot route packet: neighbor solicitation request for unknown address %hx:%hx:%hx:%hx:%hx:%hx:%hx:%hx"),
 592                                    ntohs(((uint16_t *) &ns.nd_ns_target)[0]),
 593                                    ntohs(((uint16_t *) &ns.nd_ns_target)[1]),
 594                                    ntohs(((uint16_t *) &ns.nd_ns_target)[2]),
 595                                    ntohs(((uint16_t *) &ns.nd_ns_target)[3]),
 596                                    ntohs(((uint16_t *) &ns.nd_ns_target)[4]),
 597                                    ntohs(((uint16_t *) &ns.nd_ns_target)[5]),
 598                                    ntohs(((uint16_t *) &ns.nd_ns_target)[6]),
 599                                    ntohs(((uint16_t *) &ns.nd_ns_target)[7]));
 600
 601                 return;
 602         }
 603
 604         /* Check if it is for our own subnet */
 605
 606         if(subnet->owner == myself)
 607                 return;                                 /* silently ignore */
 608
 609         /* Create neighbor advertation reply */
 610
 611         memcpy(packet->data, packet->data + ETH_ALEN, ETH_ALEN);        /* copy destination address */
 612         packet->data[ETH_ALEN * 2 - 1] ^= 0xFF; /* mangle source address so it looks like it's not from us */
 613
 614         ip6.ip6_dst = ip6.ip6_src;                      /* swap destination and source protocoll address */
 615         ip6.ip6_src = ns.nd_ns_target;
 616
 617         memcpy(packet->data + ether_size + ip6_size + ns_size + opt_size, packet->data + ETH_ALEN, ETH_ALEN);   /* add fake source hard addr */
 618
 619         ns.nd_ns_cksum = 0;
 620         ns.nd_ns_type = ND_NEIGHBOR_ADVERT;
 621         ns.nd_ns_reserved = htonl(0x40000000UL);        /* Set solicited flag */
 622         opt.nd_opt_type = ND_OPT_TARGET_LINKADDR;
 623
 624         /* Create pseudo header */
 625
 626         pseudo.ip6_src = ip6.ip6_src;
 627         pseudo.ip6_dst = ip6.ip6_dst;
 628         pseudo.length = htonl(ns_size + opt_size + ETH_ALEN);
 629         pseudo.next = htonl(IPPROTO_ICMPV6);
 630
 631         /* Generate checksum */
 632
 633         checksum = inet_checksum(&pseudo, sizeof(pseudo), ~0);
 634         checksum = inet_checksum(&ns, ns_size, checksum);
 635         checksum = inet_checksum(&opt, opt_size, checksum);
 636         checksum = inet_checksum(packet->data + ether_size + ip6_size + ns_size + opt_size, ETH_ALEN, checksum);
 637
 638         ns.nd_ns_hdr.icmp6_cksum = checksum;
 639
 640         /* Copy structs on stack back to packet */
 641
 642         memcpy(packet->data + ether_size, &ip6, ip6_size);
 643         memcpy(packet->data + ether_size + ip6_size, &ns, ns_size);
 644         memcpy(packet->data + ether_size + ip6_size + ns_size, &opt, opt_size);
 645
 646         send_packet(source, packet);
 647 }
 648
 649 static void route_ipv6(node_t *source, vpn_packet_t *packet)
 650 {
 651         cp();
 652
 653         if(!checklength(source, packet, ether_size + ip6_size))
 654                 return;
 655
 656         if(packet->data[20] == IPPROTO_ICMPV6 && checklength(source, packet, ether_size + ip6_size + icmp6_size) && packet->data[54] == ND_NEIGHBOR_SOLICIT) {
 657                 route_neighborsol(source, packet);
 658                 return;
 659         }
 660
 661         route_ipv6_unicast(source, packet);
 662 }
 663
 664 /* RFC 826 */
 665
 666 static void route_arp(node_t *source, vpn_packet_t *packet)
 667 {
 668         struct ether_arp arp;
 669         subnet_t *subnet;
 670         struct in_addr addr;
 671
 672         cp();
 673
 674         if(!checklength(source, packet, ether_size + arp_size))
 675                 return;
 676
 677         if(source != myself) {
 678                 ifdebug(TRAFFIC) logger(LOG_WARNING, _("Got ARP request from %s (%s) while in router mode!"), source->name, source->hostname);
 679                 return;
 680         }
 681
 682         /* First, snatch the source address from the ARP packet */
 683
 684         if(overwrite_mac)
 685                 memcpy(mymac.x, packet->data + ETH_ALEN, ETH_ALEN);
 686
 687         /* Copy headers from packet to structs on the stack */
 688
 689         memcpy(&arp, packet->data + ether_size, arp_size);
 690
 691         /* Check if this is a valid ARP request */
 692
 693         if(ntohs(arp.arp_hrd) != ARPHRD_ETHER || ntohs(arp.arp_pro) != ETH_P_IP ||
 694            arp.arp_hln != ETH_ALEN || arp.arp_pln != sizeof(addr) || ntohs(arp.arp_op) != ARPOP_REQUEST) {
 695                 ifdebug(TRAFFIC) logger(LOG_WARNING, _("Cannot route packet: received unknown type ARP request"));
 696                 return;
 697         }
 698
 699         /* Check if the IPv4 address exists on the VPN */
 700
 701         subnet = lookup_subnet_ipv4((ipv4_t *) &arp.arp_tpa);
 702
 703         if(!subnet) {
 704                 ifdebug(TRAFFIC) logger(LOG_WARNING, _("Cannot route packet: ARP request for unknown address %d.%d.%d.%d"),
 705                                    arp.arp_tpa[0], arp.arp_tpa[1], arp.arp_tpa[2],
 706                                    arp.arp_tpa[3]);
 707                 return;
 708         }
 709
 710         /* Check if it is for our own subnet */
 711
 712         if(subnet->owner == myself)
 713                 return;                                 /* silently ignore */
 714
 715         memcpy(packet->data, packet->data + ETH_ALEN, ETH_ALEN);        /* copy destination address */
 716         packet->data[ETH_ALEN * 2 - 1] ^= 0xFF; /* mangle source address so it looks like it's not from us */
 717
 718         memcpy(&addr, arp.arp_tpa, sizeof(addr));       /* save protocol addr */
 719         memcpy(arp.arp_tpa, arp.arp_spa, sizeof(addr)); /* swap destination and source protocol address */
 720         memcpy(arp.arp_spa, &addr, sizeof(addr));       /* ... */
 721
 722         memcpy(arp.arp_tha, arp.arp_sha, ETH_ALEN);     /* set target hard/proto addr */
 723         memcpy(arp.arp_sha, packet->data + ETH_ALEN, ETH_ALEN); /* add fake source hard addr */
 724         arp.arp_op = htons(ARPOP_REPLY);
 725
 726         /* Copy structs on stack back to packet */
 727
 728         memcpy(packet->data + ether_size, &arp, arp_size);
 729
 730         send_packet(source, packet);
 731 }
 732
 733 void route(node_t *source, vpn_packet_t *packet)
 734 {
 735         cp();
 736
 737         if(!checklength(source, packet, ether_size))
 738                 return;
 739
 740         switch (routing_mode) {
 741                 case RMODE_ROUTER:
 742                         {
 743                                 uint16_t type;
 744
 745                                 type = ntohs(*((uint16_t *)(&packet->data[12])));
 746                                 switch (type) {
 747                                         case ETH_P_ARP:
 748                                                 route_arp(source, packet);
 749                                                 break;
 750
 751                                         case ETH_P_IP:
 752                                                 route_ipv4(source, packet);
 753                                                 break;
 754
 755                                         case ETH_P_IPV6:
 756                                                 route_ipv6(source, packet);
 757                                                 break;
 758
 759                                         default:
 760                                                 ifdebug(TRAFFIC) logger(LOG_WARNING, _("Cannot route packet from %s (%s): unknown type %hx"), source->name, source->hostname, type);
 761                                                 break;
 762                                 }
 763                         }
 764                         break;
 765
 766                 case RMODE_SWITCH:
 767                         route_mac(source, packet);
 768                         break;
 769
 770                 case RMODE_HUB:
 771                         broadcast_packet(source, packet);
 772                         break;
 773         }
 774 }