src/route.c

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