src/route.c

   1 /*
   2     route.c -- routing
   3     Copyright (C) 2000-2005 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 "avl_tree.h"
  24 #include "connection.h"
  25 #include "ethernet.h"
  26 #include "ipv4.h"
  27 #include "ipv6.h"
  28 #include "logger.h"
  29 #include "net.h"
  30 #include "protocol.h"
  31 #include "route.h"
  32 #include "subnet.h"
  33 #include "utils.h"
  34
  35 rmode_t routing_mode = RMODE_ROUTER;
  36 bool priorityinheritance = false;
  37 int macexpire = 600;
  38 bool overwrite_mac = false;
  39 mac_t mymac = {{0xFE, 0xFD, 0, 0, 0, 0}};
  40
  41 /* Sizes of various headers */
  42
  43 static const size_t ether_size = sizeof(struct ether_header);
  44 static const size_t arp_size = sizeof(struct ether_arp);
  45 static const size_t ip_size = sizeof(struct ip);
  46 static const size_t icmp_size = sizeof(struct icmp) - sizeof(struct ip);
  47 static const size_t ip6_size = sizeof(struct ip6_hdr);
  48 static const size_t icmp6_size = sizeof(struct icmp6_hdr);
  49 static const size_t ns_size = sizeof(struct nd_neighbor_solicit);
  50 static const size_t opt_size = sizeof(struct nd_opt_hdr);
  51
  52 /* RFC 1071 */
  53
  54 static uint16_t inet_checksum(void *data, int len, uint16_t prevsum) {
  55         uint16_t *p = data;
  56         uint32_t checksum = prevsum ^ 0xFFFF;
  57
  58         while(len >= 2) {
  59                 checksum += *p++;
  60                 len -= 2;
  61         }
  62
  63         if(len)
  64                 checksum += *(uint8_t *)p;
  65
  66         while(checksum >> 16)
  67                 checksum = (checksum & 0xFFFF) + (checksum >> 16);
  68
  69         return ~checksum;
  70 }
  71
  72 static bool ratelimit(int frequency) {
  73         static time_t lasttime = 0;
  74         static int count = 0;
  75
  76         if(lasttime == now) {
  77                 if(++count > frequency)
  78                         return true;
  79         } else {
  80                 lasttime = now;
  81                 count = 0;
  82         }
  83
  84         return false;
  85 }
  86
  87 static bool checklength(node_t *source, vpn_packet_t *packet, length_t length) {
  88         if(packet->len < length) {
  89                 ifdebug(TRAFFIC) logger(LOG_WARNING, _("Got too short packet from %s (%s)"), source->name, source->hostname);
  90                 return false;
  91         } else
  92                 return true;
  93 }
  94
  95 static void swap_mac_addresses(vpn_packet_t *packet) {
  96         mac_t tmp;
  97         memcpy(&tmp, &packet->data[0], sizeof tmp);
  98         memcpy(&packet->data[0], &packet->data[6], sizeof tmp);
  99         memcpy(&packet->data[6], &tmp, sizeof tmp);
 100 }
 101
 102 static void learn_mac(mac_t *address) {
 103         subnet_t *subnet;
 104         avl_node_t *node;
 105         connection_t *c;
 106
 107         subnet = lookup_subnet_mac(address);
 108
 109         /* If we don't know this MAC address yet, store it */
 110
 111         if(!subnet) {
 112                 ifdebug(TRAFFIC) logger(LOG_INFO, _("Learned new MAC address %hx:%hx:%hx:%hx:%hx:%hx"),
 113                                    address->x[0], address->x[1], address->x[2], address->x[3],
 114                                    address->x[4], address->x[5]);
 115
 116                 subnet = new_subnet();
 117                 subnet->type = SUBNET_MAC;
 118                 subnet->expires = now + macexpire;
 119                 subnet->net.mac.address = *address;
 120                 subnet_add(myself, subnet);
 121
 122                 /* And tell all other tinc daemons it's our MAC */
 123
 124                 for(node = connection_tree->head; node; node = node->next) {
 125                         c = node->data;
 126                         if(c->status.active)
 127                                 send_add_subnet(c, subnet);
 128                 }
 129         }
 130
 131         if(subnet->expires)
 132                 subnet->expires = now + macexpire;
 133 }
 134
 135 void age_subnets(void) {
 136         subnet_t *s;
 137         connection_t *c;
 138         avl_node_t *node, *next, *node2;
 139
 140         for(node = myself->subnet_tree->head; node; node = next) {
 141                 next = node->next;
 142                 s = node->data;
 143                 if(s->expires && s->expires < now) {
 144                         ifdebug(TRAFFIC) {
 145                                 char netstr[MAXNETSTR];
 146                                 if(net2str(netstr, sizeof netstr, s))
 147                                         logger(LOG_INFO, _("Subnet %s expired"), netstr);
 148                         }
 149
 150                         for(node2 = connection_tree->head; node2; node2 = node2->next) {
 151                                 c = node2->data;
 152                                 if(c->status.active)
 153                                         send_del_subnet(c, s);
 154                         }
 155
 156                         subnet_del(myself, s);
 157                 }
 158         }
 159 }
 160
 161 /* RFC 792 */
 162
 163 static void route_ipv4_unreachable(node_t *source, vpn_packet_t *packet, uint8_t type, uint8_t code) {
 164         struct ip ip = {0};
 165         struct icmp icmp = {0};
 166
 167         struct in_addr ip_src;
 168         struct in_addr ip_dst;
 169         uint32_t oldlen;
 170
 171         if(ratelimit(3))
 172                 return;
 173
 174         /* Swap Ethernet source and destination addresses */
 175
 176         swap_mac_addresses(packet);
 177
 178         /* Copy headers from packet into properly aligned structs on the stack */
 179
 180         memcpy(&ip, packet->data + ether_size, ip_size);
 181
 182         /* Remember original source and destination */
 183
 184         ip_src = ip.ip_src;
 185         ip_dst = ip.ip_dst;
 186
 187         oldlen = packet->len - ether_size;
 188
 189         if(type == ICMP_DEST_UNREACH && code == ICMP_FRAG_NEEDED)
 190                 icmp.icmp_nextmtu = htons(packet->len - ether_size);
 191
 192         if(oldlen >= IP_MSS - ip_size - icmp_size)
 193                 oldlen = IP_MSS - ip_size - icmp_size;
 194
 195         /* Copy first part of original contents to ICMP message */
 196
 197         memmove(packet->data + ether_size + ip_size + icmp_size, packet->data + ether_size, oldlen);
 198
 199         /* Fill in IPv4 header */
 200
 201         ip.ip_v = 4;
 202         ip.ip_hl = ip_size / 4;
 203         ip.ip_tos = 0;
 204         ip.ip_len = htons(ip_size + icmp_size + oldlen);
 205         ip.ip_id = 0;
 206         ip.ip_off = 0;
 207         ip.ip_ttl = 255;
 208         ip.ip_p = IPPROTO_ICMP;
 209         ip.ip_sum = 0;
 210         ip.ip_src = ip_dst;
 211         ip.ip_dst = ip_src;
 212
 213         ip.ip_sum = inet_checksum(&ip, ip_size, ~0);
 214
 215         /* Fill in ICMP header */
 216
 217         icmp.icmp_type = type;
 218         icmp.icmp_code = code;
 219         icmp.icmp_cksum = 0;
 220
 221         icmp.icmp_cksum = inet_checksum(&icmp, icmp_size, ~0);
 222         icmp.icmp_cksum = inet_checksum(packet->data + ether_size + ip_size + icmp_size, oldlen, icmp.icmp_cksum);
 223
 224         /* Copy structs on stack back to packet */
 225
 226         memcpy(packet->data + ether_size, &ip, ip_size);
 227         memcpy(packet->data + ether_size + ip_size, &icmp, icmp_size);
 228
 229         packet->len = ether_size + ip_size + icmp_size + oldlen;
 230
 231         send_packet(source, packet);
 232 }
 233
 234 /* RFC 791 */
 235
 236 static void fragment_ipv4_packet(node_t *dest, vpn_packet_t *packet) {
 237         struct ip ip;
 238         vpn_packet_t fragment;
 239         int len, maxlen, todo;
 240         uint8_t *offset;
 241         uint16_t ip_off, origf;
 242
 243         memcpy(&ip, packet->data + ether_size, ip_size);
 244         fragment.priority = packet->priority;
 245
 246         if(ip.ip_hl != ip_size / 4)
 247                 return;
 248
 249         todo = ntohs(ip.ip_len) - ip_size;
 250
 251         if(ether_size + ip_size + todo != packet->len) {
 252                 ifdebug(TRAFFIC) logger(LOG_WARNING, _("Length of packet (%d) doesn't match length in IPv4 header (%zd)"), packet->len, ether_size + ip_size + todo);
 253                 return;
 254         }
 255
 256         ifdebug(TRAFFIC) logger(LOG_INFO, _("Fragmenting packet of %d bytes to %s (%s)"), packet->len, dest->name, dest->hostname);
 257
 258         offset = packet->data + ether_size + ip_size;
 259         maxlen = (dest->mtu - ether_size - ip_size) & ~0x7;
 260         ip_off = ntohs(ip.ip_off);
 261         origf = ip_off & ~IP_OFFMASK;
 262         ip_off &= IP_OFFMASK;
 263
 264         while(todo) {
 265                 len = todo > maxlen ? maxlen : todo;
 266                 memcpy(fragment.data + ether_size + ip_size, offset, len);
 267                 todo -= len;
 268                 offset += len;
 269
 270                 ip.ip_len = htons(ip_size + len);
 271                 ip.ip_off = htons(ip_off | origf | (todo ? IP_MF : 0));
 272                 ip.ip_sum = 0;
 273                 ip.ip_sum = inet_checksum(&ip, ip_size, ~0);
 274                 memcpy(fragment.data, packet->data, ether_size);
 275                 memcpy(fragment.data + ether_size, &ip, ip_size);
 276                 fragment.len = ether_size + ip_size + len;
 277
 278                 send_packet(dest, &fragment);
 279
 280                 ip_off += len / 8;
 281         }
 282 }
 283
 284 static void route_ipv4_unicast(node_t *source, vpn_packet_t *packet) {
 285         subnet_t *subnet;
 286         node_t *via;
 287         ipv4_t dest;
 288
 289         memcpy(&dest, &packet->data[30], sizeof dest);
 290         subnet = lookup_subnet_ipv4(&dest);
 291
 292         if(!subnet) {
 293                 ifdebug(TRAFFIC) logger(LOG_WARNING, _("Cannot route packet from %s (%s): unknown IPv4 destination address %d.%d.%d.%d"),
 294                                 source->name, source->hostname,
 295                                 dest.x[0],
 296                                 dest.x[1],
 297                                 dest.x[2],
 298                                 dest.x[3]);
 299
 300                 route_ipv4_unreachable(source, packet, ICMP_DEST_UNREACH, ICMP_NET_UNKNOWN);
 301                 return;
 302         }
 303
 304         if(subnet->owner == source) {
 305                 ifdebug(TRAFFIC) logger(LOG_WARNING, _("Packet looping back to %s (%s)!"), source->name, source->hostname);
 306                 return;
 307         }
 308
 309         if(!subnet->owner->status.reachable)
 310                 route_ipv4_unreachable(source, packet, ICMP_DEST_UNREACH, ICMP_NET_UNREACH);
 311
 312         if(priorityinheritance)
 313                 packet->priority = packet->data[15];
 314
 315         via = (subnet->owner->via == myself) ? subnet->owner->nexthop : subnet->owner->via;
 316
 317         if(via && packet->len > via->mtu && via != myself) {
 318                 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);
 319                 if(packet->data[20] & 0x40) {
 320                         packet->len = via->mtu;
 321                         route_ipv4_unreachable(source, packet, ICMP_DEST_UNREACH, ICMP_FRAG_NEEDED);
 322                 } else {
 323                         fragment_ipv4_packet(via, packet);
 324                 }
 325
 326                 return;
 327         }
 328
 329         send_packet(subnet->owner, packet);
 330 }
 331
 332 static void route_ipv4(node_t *source, vpn_packet_t *packet) {
 333         if(!checklength(source, packet, ether_size + ip_size))
 334                 return;
 335
 336         if(((packet->data[30] & 0xf0) == 0xe0) || (
 337                         packet->data[30] == 255 &&
 338                         packet->data[31] == 255 &&
 339                         packet->data[32] == 255 &&
 340                         packet->data[33] == 255))
 341                 broadcast_packet(source, packet);
 342         else
 343                 route_ipv4_unicast(source, packet);
 344 }
 345
 346 /* RFC 2463 */
 347
 348 static void route_ipv6_unreachable(node_t *source, vpn_packet_t *packet, uint8_t type, uint8_t code) {
 349         struct ip6_hdr ip6;
 350         struct icmp6_hdr icmp6 = {0};
 351         uint16_t checksum;
 352
 353         struct {
 354                 struct in6_addr ip6_src;        /* source address */
 355                 struct in6_addr ip6_dst;        /* destination address */
 356                 uint32_t length;
 357                 uint32_t next;
 358         } pseudo;
 359
 360         if(ratelimit(3))
 361                 return;
 362
 363         /* Swap Ethernet source and destination addresses */
 364
 365         swap_mac_addresses(packet);
 366
 367         /* Copy headers from packet to structs on the stack */
 368
 369         memcpy(&ip6, packet->data + ether_size, ip6_size);
 370
 371         /* Remember original source and destination */
 372
 373         pseudo.ip6_src = ip6.ip6_dst;
 374         pseudo.ip6_dst = ip6.ip6_src;
 375
 376         pseudo.length = packet->len - ether_size;
 377
 378         if(type == ICMP6_PACKET_TOO_BIG)
 379                 icmp6.icmp6_mtu = htonl(pseudo.length);
 380
 381         if(pseudo.length >= IP_MSS - ip6_size - icmp6_size)
 382                 pseudo.length = IP_MSS - ip6_size - icmp6_size;
 383
 384         /* Copy first part of original contents to ICMP message */
 385
 386         memmove(packet->data + ether_size + ip6_size + icmp6_size, packet->data + ether_size, pseudo.length);
 387
 388         /* Fill in IPv6 header */
 389
 390         ip6.ip6_flow = htonl(0x60000000UL);
 391         ip6.ip6_plen = htons(icmp6_size + pseudo.length);
 392         ip6.ip6_nxt = IPPROTO_ICMPV6;
 393         ip6.ip6_hlim = 255;
 394         ip6.ip6_src = pseudo.ip6_src;
 395         ip6.ip6_dst = pseudo.ip6_dst;
 396
 397         /* Fill in ICMP header */
 398
 399         icmp6.icmp6_type = type;
 400         icmp6.icmp6_code = code;
 401         icmp6.icmp6_cksum = 0;
 402
 403         /* Create pseudo header */
 404
 405         pseudo.length = htonl(icmp6_size + pseudo.length);
 406         pseudo.next = htonl(IPPROTO_ICMPV6);
 407
 408         /* Generate checksum */
 409
 410         checksum = inet_checksum(&pseudo, sizeof(pseudo), ~0);
 411         checksum = inet_checksum(&icmp6, icmp6_size, checksum);
 412         checksum = inet_checksum(packet->data + ether_size + ip6_size + icmp6_size, ntohl(pseudo.length) - icmp6_size, checksum);
 413
 414         icmp6.icmp6_cksum = checksum;
 415
 416         /* Copy structs on stack back to packet */
 417
 418         memcpy(packet->data + ether_size, &ip6, ip6_size);
 419         memcpy(packet->data + ether_size + ip6_size, &icmp6, icmp6_size);
 420
 421         packet->len = ether_size + ip6_size + ntohl(pseudo.length);
 422
 423         send_packet(source, packet);
 424 }
 425
 426 static void route_ipv6_unicast(node_t *source, vpn_packet_t *packet) {
 427         subnet_t *subnet;
 428         node_t *via;
 429         ipv6_t dest;
 430
 431         memcpy(&dest, &packet->data[38], sizeof dest);
 432         subnet = lookup_subnet_ipv6(&dest);
 433
 434         if(!subnet) {
 435                 ifdebug(TRAFFIC) logger(LOG_WARNING, _("Cannot route packet from %s (%s): unknown IPv6 destination address %hx:%hx:%hx:%hx:%hx:%hx:%hx:%hx"),
 436                                 source->name, source->hostname,
 437                                 ntohs(dest.x[0]),
 438                                 ntohs(dest.x[1]),
 439                                 ntohs(dest.x[2]),
 440                                 ntohs(dest.x[3]),
 441                                 ntohs(dest.x[4]),
 442                                 ntohs(dest.x[5]),
 443                                 ntohs(dest.x[6]),
 444                                 ntohs(dest.x[7]));
 445
 446                 route_ipv6_unreachable(source, packet, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_ADDR);
 447                 return;
 448         }
 449
 450         if(subnet->owner == source) {
 451                 ifdebug(TRAFFIC) logger(LOG_WARNING, _("Packet looping back to %s (%s)!"), source->name, source->hostname);
 452                 return;
 453         }
 454
 455         if(!subnet->owner->status.reachable)
 456                 route_ipv6_unreachable(source, packet, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_NOROUTE);
 457
 458         via = (subnet->owner->via == myself) ? subnet->owner->nexthop : subnet->owner->via;
 459
 460         if(via && packet->len > via->mtu && via != myself) {
 461                 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);
 462                 packet->len = via->mtu;
 463                 route_ipv6_unreachable(source, packet, ICMP6_PACKET_TOO_BIG, 0);
 464                 return;
 465         }
 466
 467         send_packet(subnet->owner, packet);
 468 }
 469
 470 /* RFC 2461 */
 471
 472 static void route_neighborsol(node_t *source, vpn_packet_t *packet) {
 473         struct ip6_hdr ip6;
 474         struct nd_neighbor_solicit ns;
 475         struct nd_opt_hdr opt;
 476         subnet_t *subnet;
 477         uint16_t checksum;
 478         bool has_opt;
 479
 480         struct {
 481                 struct in6_addr ip6_src;        /* source address */
 482                 struct in6_addr ip6_dst;        /* destination address */
 483                 uint32_t length;
 484                 uint32_t next;
 485         } pseudo;
 486
 487         if(!checklength(source, packet, ether_size + ip6_size + ns_size))
 488                 return;
 489
 490         has_opt = packet->len >= ether_size + ip6_size + ns_size + opt_size + ETH_ALEN;
 491
 492         if(source != myself) {
 493                 ifdebug(TRAFFIC) logger(LOG_WARNING, _("Got neighbor solicitation request from %s (%s) while in router mode!"), source->name, source->hostname);
 494                 return;
 495         }
 496
 497         /* Copy headers from packet to structs on the stack */
 498
 499         memcpy(&ip6, packet->data + ether_size, ip6_size);
 500         memcpy(&ns, packet->data + ether_size + ip6_size, ns_size);
 501         if(has_opt)
 502                 memcpy(&opt, packet->data + ether_size + ip6_size + ns_size, opt_size);
 503
 504         /* First, snatch the source address from the neighbor solicitation packet */
 505
 506         if(overwrite_mac)
 507                 memcpy(mymac.x, packet->data + ETH_ALEN, ETH_ALEN);
 508
 509         /* Check if this is a valid neighbor solicitation request */
 510
 511         if(ns.nd_ns_hdr.icmp6_type != ND_NEIGHBOR_SOLICIT ||
 512            (has_opt && opt.nd_opt_type != ND_OPT_SOURCE_LINKADDR)) {
 513                 ifdebug(TRAFFIC) logger(LOG_WARNING, _("Cannot route packet: received unknown type neighbor solicitation request"));
 514                 return;
 515         }
 516
 517         /* Create pseudo header */
 518
 519         pseudo.ip6_src = ip6.ip6_src;
 520         pseudo.ip6_dst = ip6.ip6_dst;
 521         if(has_opt)
 522                 pseudo.length = htonl(ns_size + opt_size + ETH_ALEN);
 523         else
 524                 pseudo.length = htonl(ns_size);
 525         pseudo.next = htonl(IPPROTO_ICMPV6);
 526
 527         /* Generate checksum */
 528
 529         checksum = inet_checksum(&pseudo, sizeof(pseudo), ~0);
 530         checksum = inet_checksum(&ns, ns_size, checksum);
 531         if(has_opt) {
 532                 checksum = inet_checksum(&opt, opt_size, checksum);
 533                 checksum = inet_checksum(packet->data + ether_size + ip6_size + ns_size + opt_size, ETH_ALEN, checksum);
 534         }
 535
 536         if(checksum) {
 537                 ifdebug(TRAFFIC) logger(LOG_WARNING, _("Cannot route packet: checksum error for neighbor solicitation request"));
 538                 return;
 539         }
 540
 541         /* Check if the IPv6 address exists on the VPN */
 542
 543         subnet = lookup_subnet_ipv6((ipv6_t *) &ns.nd_ns_target);
 544
 545         if(!subnet) {
 546                 ifdebug(TRAFFIC) logger(LOG_WARNING, _("Cannot route packet: neighbor solicitation request for unknown address %hx:%hx:%hx:%hx:%hx:%hx:%hx:%hx"),
 547                                    ntohs(((uint16_t *) &ns.nd_ns_target)[0]),
 548                                    ntohs(((uint16_t *) &ns.nd_ns_target)[1]),
 549                                    ntohs(((uint16_t *) &ns.nd_ns_target)[2]),
 550                                    ntohs(((uint16_t *) &ns.nd_ns_target)[3]),
 551                                    ntohs(((uint16_t *) &ns.nd_ns_target)[4]),
 552                                    ntohs(((uint16_t *) &ns.nd_ns_target)[5]),
 553                                    ntohs(((uint16_t *) &ns.nd_ns_target)[6]),
 554                                    ntohs(((uint16_t *) &ns.nd_ns_target)[7]));
 555
 556                 return;
 557         }
 558
 559         /* Check if it is for our own subnet */
 560
 561         if(subnet->owner == myself)
 562                 return;                                 /* silently ignore */
 563
 564         /* Create neighbor advertation reply */
 565
 566         memcpy(packet->data, packet->data + ETH_ALEN, ETH_ALEN);        /* copy destination address */
 567         packet->data[ETH_ALEN * 2 - 1] ^= 0xFF; /* mangle source address so it looks like it's not from us */
 568
 569         ip6.ip6_dst = ip6.ip6_src;                      /* swap destination and source protocoll address */
 570         ip6.ip6_src = ns.nd_ns_target;
 571
 572         if(has_opt)
 573                 memcpy(packet->data + ether_size + ip6_size + ns_size + opt_size, packet->data + ETH_ALEN, ETH_ALEN);   /* add fake source hard addr */
 574
 575         ns.nd_ns_cksum = 0;
 576         ns.nd_ns_type = ND_NEIGHBOR_ADVERT;
 577         ns.nd_ns_reserved = htonl(0x40000000UL);        /* Set solicited flag */
 578         opt.nd_opt_type = ND_OPT_TARGET_LINKADDR;
 579
 580         /* Create pseudo header */
 581
 582         pseudo.ip6_src = ip6.ip6_src;
 583         pseudo.ip6_dst = ip6.ip6_dst;
 584         if(has_opt)
 585                 pseudo.length = htonl(ns_size + opt_size + ETH_ALEN);
 586         else
 587                 pseudo.length = htonl(ns_size);
 588         pseudo.next = htonl(IPPROTO_ICMPV6);
 589
 590         /* Generate checksum */
 591
 592         checksum = inet_checksum(&pseudo, sizeof(pseudo), ~0);
 593         checksum = inet_checksum(&ns, ns_size, checksum);
 594         if(has_opt) {
 595                 checksum = inet_checksum(&opt, opt_size, checksum);
 596                 checksum = inet_checksum(packet->data + ether_size + ip6_size + ns_size + opt_size, ETH_ALEN, checksum);
 597         }
 598
 599         ns.nd_ns_hdr.icmp6_cksum = checksum;
 600
 601         /* Copy structs on stack back to packet */
 602
 603         memcpy(packet->data + ether_size, &ip6, ip6_size);
 604         memcpy(packet->data + ether_size + ip6_size, &ns, ns_size);
 605         if(has_opt)
 606                 memcpy(packet->data + ether_size + ip6_size + ns_size, &opt, opt_size);
 607
 608         send_packet(source, packet);
 609 }
 610
 611 static void route_ipv6(node_t *source, vpn_packet_t *packet) {
 612         if(!checklength(source, packet, ether_size + ip6_size))
 613                 return;
 614
 615         if(packet->data[20] == IPPROTO_ICMPV6 && checklength(source, packet, ether_size + ip6_size + icmp6_size) && packet->data[54] == ND_NEIGHBOR_SOLICIT) {
 616                 route_neighborsol(source, packet);
 617                 return;
 618         }
 619
 620         if(packet->data[38] == 255)
 621                 broadcast_packet(source, packet);
 622         else
 623                 route_ipv6_unicast(source, packet);
 624 }
 625
 626 /* RFC 826 */
 627
 628 static void route_arp(node_t *source, vpn_packet_t *packet) {
 629         struct ether_arp arp;
 630         subnet_t *subnet;
 631         struct in_addr addr;
 632
 633         if(!checklength(source, packet, ether_size + arp_size))
 634                 return;
 635
 636         if(source != myself) {
 637                 ifdebug(TRAFFIC) logger(LOG_WARNING, _("Got ARP request from %s (%s) while in router mode!"), source->name, source->hostname);
 638                 return;
 639         }
 640
 641         /* First, snatch the source address from the ARP packet */
 642
 643         if(overwrite_mac)
 644                 memcpy(mymac.x, packet->data + ETH_ALEN, ETH_ALEN);
 645
 646         /* Copy headers from packet to structs on the stack */
 647
 648         memcpy(&arp, packet->data + ether_size, arp_size);
 649
 650         /* Check if this is a valid ARP request */
 651
 652         if(ntohs(arp.arp_hrd) != ARPHRD_ETHER || ntohs(arp.arp_pro) != ETH_P_IP ||
 653            arp.arp_hln != ETH_ALEN || arp.arp_pln != sizeof(addr) || ntohs(arp.arp_op) != ARPOP_REQUEST) {
 654                 ifdebug(TRAFFIC) logger(LOG_WARNING, _("Cannot route packet: received unknown type ARP request"));
 655                 return;
 656         }
 657
 658         /* Check if the IPv4 address exists on the VPN */
 659
 660         subnet = lookup_subnet_ipv4((ipv4_t *) &arp.arp_tpa);
 661
 662         if(!subnet) {
 663                 ifdebug(TRAFFIC) logger(LOG_WARNING, _("Cannot route packet: ARP request for unknown address %d.%d.%d.%d"),
 664                                    arp.arp_tpa[0], arp.arp_tpa[1], arp.arp_tpa[2],
 665                                    arp.arp_tpa[3]);
 666                 return;
 667         }
 668
 669         /* Check if it is for our own subnet */
 670
 671         if(subnet->owner == myself)
 672                 return;                                 /* silently ignore */
 673
 674         memcpy(packet->data, packet->data + ETH_ALEN, ETH_ALEN);        /* copy destination address */
 675         packet->data[ETH_ALEN * 2 - 1] ^= 0xFF; /* mangle source address so it looks like it's not from us */
 676
 677         memcpy(&addr, arp.arp_tpa, sizeof(addr));       /* save protocol addr */
 678         memcpy(arp.arp_tpa, arp.arp_spa, sizeof(addr)); /* swap destination and source protocol address */
 679         memcpy(arp.arp_spa, &addr, sizeof(addr));       /* ... */
 680
 681         memcpy(arp.arp_tha, arp.arp_sha, ETH_ALEN);     /* set target hard/proto addr */
 682         memcpy(arp.arp_sha, packet->data + ETH_ALEN, ETH_ALEN); /* add fake source hard addr */
 683         arp.arp_op = htons(ARPOP_REPLY);
 684
 685         /* Copy structs on stack back to packet */
 686
 687         memcpy(packet->data + ether_size, &arp, arp_size);
 688
 689         send_packet(source, packet);
 690 }
 691
 692 static void route_mac(node_t *source, vpn_packet_t *packet) {
 693         subnet_t *subnet;
 694         mac_t dest;
 695
 696         /* Learn source address */
 697
 698         if(source == myself) {
 699                 mac_t src;
 700                 memcpy(&src, &packet->data[6], sizeof src);
 701                 learn_mac(&src);
 702         }
 703
 704         /* Lookup destination address */
 705
 706         memcpy(&dest, &packet->data[0], sizeof dest);
 707         subnet = lookup_subnet_mac(&dest);
 708
 709         if(!subnet) {
 710                 broadcast_packet(source, packet);
 711                 return;
 712         }
 713
 714         if(subnet->owner == source) {
 715                 ifdebug(TRAFFIC) logger(LOG_WARNING, _("Packet looping back to %s (%s)!"), source->name, source->hostname);
 716                 return;
 717         }
 718
 719         // Handle packets larger than PMTU
 720
 721         node_t *via = (subnet->owner->via == myself) ? subnet->owner->nexthop : subnet->owner->via;
 722
 723         if(via && packet->len > via->mtu && via != myself) {
 724                 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);
 725                 uint16_t type = packet->data[12] << 8 | packet->data[13];
 726                 if(type == ETH_P_IP) {
 727                         if(packet->data[20] & 0x40) {
 728                                 packet->len = via->mtu;
 729                                 route_ipv4_unreachable(source, packet, ICMP_DEST_UNREACH, ICMP_FRAG_NEEDED);
 730                         } else {
 731                                 fragment_ipv4_packet(via, packet);
 732                         }
 733                         return;
 734                 } else if(type == ETH_P_IPV6) {
 735                         packet->len = via->mtu;
 736                         route_ipv6_unreachable(source, packet, ICMP6_PACKET_TOO_BIG, 0);
 737                         return;
 738                 }
 739         }
 740
 741         send_packet(subnet->owner, packet);
 742 }
 743
 744 void route(node_t *source, vpn_packet_t *packet) {
 745         if(!checklength(source, packet, ether_size))
 746                 return;
 747
 748         switch (routing_mode) {
 749                 case RMODE_ROUTER:
 750                         {
 751                                 uint16_t type = packet->data[12] << 8 | packet->data[13];
 752
 753                                 switch (type) {
 754                                         case ETH_P_ARP:
 755                                                 route_arp(source, packet);
 756                                                 break;
 757
 758                                         case ETH_P_IP:
 759                                                 route_ipv4(source, packet);
 760                                                 break;
 761
 762                                         case ETH_P_IPV6:
 763                                                 route_ipv6(source, packet);
 764                                                 break;
 765
 766                                         default:
 767                                                 ifdebug(TRAFFIC) logger(LOG_WARNING, _("Cannot route packet from %s (%s): unknown type %hx"), source->name, source->hostname, type);
 768                                                 break;
 769                                 }
 770                         }
 771                         break;
 772
 773                 case RMODE_SWITCH:
 774                         route_mac(source, packet);
 775                         break;
 776
 777                 case RMODE_HUB:
 778                         broadcast_packet(source, packet);
 779                         break;
 780         }
 781 }