www.tinc-vpn.org Git - tinc/blob - 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->weight = 10;
 121                 subnet_add(myself, subnet);
 122
 123                 /* And tell all other tinc daemons it's our MAC */
 124
 125                 for(node = connection_tree->head; node; node = node->next) {
 126                         c = node->data;
 127                         if(c->status.active)
 128                                 send_add_subnet(c, subnet);
 129                 }
 130         }
 131
 132         if(subnet->expires)
 133                 subnet->expires = now + macexpire;
 134 }
 135
 136 void age_subnets(void) {
 137         subnet_t *s;
 138         connection_t *c;
 139         avl_node_t *node, *next, *node2;
 140
 141         for(node = myself->subnet_tree->head; node; node = next) {
 142                 next = node->next;
 143                 s = node->data;
 144                 if(s->expires && s->expires < now) {
 145                         ifdebug(TRAFFIC) {
 146                                 char netstr[MAXNETSTR];
 147                                 if(net2str(netstr, sizeof netstr, s))
 148                                         logger(LOG_INFO, "Subnet %s expired", netstr);
 149                         }
 150
 151                         for(node2 = connection_tree->head; node2; node2 = node2->next) {
 152                                 c = node2->data;
 153                                 if(c->status.active)
 154                                         send_del_subnet(c, s);
 155                         }
 156
 157                         subnet_del(myself, s);
 158                 }
 159         }
 160 }
 161
 162 /* RFC 792 */
 163
 164 static void route_ipv4_unreachable(node_t *source, vpn_packet_t *packet, uint8_t type, uint8_t code) {
 165         struct ip ip = {0};
 166         struct icmp icmp = {0};
 167
 168         struct in_addr ip_src;
 169         struct in_addr ip_dst;
 170         uint32_t oldlen;
 171
 172         if(ratelimit(3))
 173                 return;
 174
 175         /* Swap Ethernet source and destination addresses */
 176
 177         swap_mac_addresses(packet);
 178
 179         /* Copy headers from packet into properly aligned structs on the stack */
 180
 181         memcpy(&ip, packet->data + ether_size, ip_size);
 182
 183         /* Remember original source and destination */
 184
 185         ip_src = ip.ip_src;
 186         ip_dst = ip.ip_dst;
 187
 188         oldlen = packet->len - ether_size;
 189
 190         if(type == ICMP_DEST_UNREACH && code == ICMP_FRAG_NEEDED)
 191                 icmp.icmp_nextmtu = htons(packet->len - ether_size);
 192
 193         if(oldlen >= IP_MSS - ip_size - icmp_size)
 194                 oldlen = IP_MSS - ip_size - icmp_size;
 195
 196         /* Copy first part of original contents to ICMP message */
 197
 198         memmove(packet->data + ether_size + ip_size + icmp_size, packet->data + ether_size, oldlen);
 199
 200         /* Fill in IPv4 header */
 201
 202         ip.ip_v = 4;
 203         ip.ip_hl = ip_size / 4;
 204         ip.ip_tos = 0;
 205         ip.ip_len = htons(ip_size + icmp_size + oldlen);
 206         ip.ip_id = 0;
 207         ip.ip_off = 0;
 208         ip.ip_ttl = 255;
 209         ip.ip_p = IPPROTO_ICMP;
 210         ip.ip_sum = 0;
 211         ip.ip_src = ip_dst;
 212         ip.ip_dst = ip_src;
 213
 214         ip.ip_sum = inet_checksum(&ip, ip_size, ~0);
 215
 216         /* Fill in ICMP header */
 217
 218         icmp.icmp_type = type;
 219         icmp.icmp_code = code;
 220         icmp.icmp_cksum = 0;
 221
 222         icmp.icmp_cksum = inet_checksum(&icmp, icmp_size, ~0);
 223         icmp.icmp_cksum = inet_checksum(packet->data + ether_size + ip_size + icmp_size, oldlen, icmp.icmp_cksum);
 224
 225         /* Copy structs on stack back to packet */
 226
 227         memcpy(packet->data + ether_size, &ip, ip_size);
 228         memcpy(packet->data + ether_size + ip_size, &icmp, icmp_size);
 229
 230         packet->len = ether_size + ip_size + icmp_size + oldlen;
 231
 232         send_packet(source, packet);
 233 }
 234
 235 /* RFC 791 */
 236
 237 static void fragment_ipv4_packet(node_t *dest, vpn_packet_t *packet) {
 238         struct ip ip;
 239         vpn_packet_t fragment;
 240         int len, maxlen, todo;
 241         uint8_t *offset;
 242         uint16_t ip_off, origf;
 243
 244         memcpy(&ip, packet->data + ether_size, ip_size);
 245         fragment.priority = packet->priority;
 246
 247         if(ip.ip_hl != ip_size / 4)
 248                 return;
 249
 250         todo = ntohs(ip.ip_len) - ip_size;
 251
 252         if(ether_size + ip_size + todo != packet->len) {
 253                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Length of packet (%d) doesn't match length in IPv4 header (%zd)", packet->len, ether_size + ip_size + todo);
 254                 return;
 255         }
 256
 257         ifdebug(TRAFFIC) logger(LOG_INFO, "Fragmenting packet of %d bytes to %s (%s)", packet->len, dest->name, dest->hostname);
 258
 259         offset = packet->data + ether_size + ip_size;
 260         maxlen = (dest->mtu - ether_size - ip_size) & ~0x7;
 261         ip_off = ntohs(ip.ip_off);
 262         origf = ip_off & ~IP_OFFMASK;
 263         ip_off &= IP_OFFMASK;
 264
 265         while(todo) {
 266                 len = todo > maxlen ? maxlen : todo;
 267                 memcpy(fragment.data + ether_size + ip_size, offset, len);
 268                 todo -= len;
 269                 offset += len;
 270
 271                 ip.ip_len = htons(ip_size + len);
 272                 ip.ip_off = htons(ip_off | origf | (todo ? IP_MF : 0));
 273                 ip.ip_sum = 0;
 274                 ip.ip_sum = inet_checksum(&ip, ip_size, ~0);
 275                 memcpy(fragment.data, packet->data, ether_size);
 276                 memcpy(fragment.data + ether_size, &ip, ip_size);
 277                 fragment.len = ether_size + ip_size + len;
 278
 279                 send_packet(dest, &fragment);
 280
 281                 ip_off += len / 8;
 282         }
 283 }
 284
 285 static void route_ipv4_unicast(node_t *source, vpn_packet_t *packet) {
 286         subnet_t *subnet;
 287         node_t *via;
 288         ipv4_t dest;
 289
 290         memcpy(&dest, &packet->data[30], sizeof dest);
 291         subnet = lookup_subnet_ipv4(&dest);
 292
 293         if(!subnet) {
 294                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Cannot route packet from %s (%s): unknown IPv4 destination address %d.%d.%d.%d",
 295                                 source->name, source->hostname,
 296                                 dest.x[0],
 297                                 dest.x[1],
 298                                 dest.x[2],
 299                                 dest.x[3]);
 300
 301                 route_ipv4_unreachable(source, packet, ICMP_DEST_UNREACH, ICMP_NET_UNKNOWN);
 302                 return;
 303         }
 304
 305         if(subnet->owner == source) {
 306                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Packet looping back to %s (%s)!", source->name, source->hostname);
 307                 return;
 308         }
 309
 310         if(!subnet->owner->status.reachable)
 311                 route_ipv4_unreachable(source, packet, ICMP_DEST_UNREACH, ICMP_NET_UNREACH);
 312
 313         if(priorityinheritance)
 314                 packet->priority = packet->data[15];
 315
 316         via = (subnet->owner->via == myself) ? subnet->owner->nexthop : subnet->owner->via;
 317
 318         if(via && packet->len > via->mtu && via != myself) {
 319                 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);
 320                 if(packet->data[20] & 0x40) {
 321                         packet->len = via->mtu;
 322                         route_ipv4_unreachable(source, packet, ICMP_DEST_UNREACH, ICMP_FRAG_NEEDED);
 323                 } else {
 324                         fragment_ipv4_packet(via, packet);
 325                 }
 326
 327                 return;
 328         }
 329
 330         send_packet(subnet->owner, packet);
 331 }
 332
 333 static void route_ipv4(node_t *source, vpn_packet_t *packet) {
 334         if(!checklength(source, packet, ether_size + ip_size))
 335                 return;
 336
 337         if(((packet->data[30] & 0xf0) == 0xe0) || (
 338                         packet->data[30] == 255 &&
 339                         packet->data[31] == 255 &&
 340                         packet->data[32] == 255 &&
 341                         packet->data[33] == 255))
 342                 broadcast_packet(source, packet);
 343         else
 344                 route_ipv4_unicast(source, packet);
 345 }
 346
 347 /* RFC 2463 */
 348
 349 static void route_ipv6_unreachable(node_t *source, vpn_packet_t *packet, uint8_t type, uint8_t code) {
 350         struct ip6_hdr ip6;
 351         struct icmp6_hdr icmp6 = {0};
 352         uint16_t checksum;
 353
 354         struct {
 355                 struct in6_addr ip6_src;        /* source address */
 356                 struct in6_addr ip6_dst;        /* destination address */
 357                 uint32_t length;
 358                 uint32_t next;
 359         } pseudo;
 360
 361         if(ratelimit(3))
 362                 return;
 363
 364         /* Swap Ethernet source and destination addresses */
 365
 366         swap_mac_addresses(packet);
 367
 368         /* Copy headers from packet to structs on the stack */
 369
 370         memcpy(&ip6, packet->data + ether_size, ip6_size);
 371
 372         /* Remember original source and destination */
 373
 374         pseudo.ip6_src = ip6.ip6_dst;
 375         pseudo.ip6_dst = ip6.ip6_src;
 376
 377         pseudo.length = packet->len - ether_size;
 378
 379         if(type == ICMP6_PACKET_TOO_BIG)
 380                 icmp6.icmp6_mtu = htonl(pseudo.length);
 381
 382         if(pseudo.length >= IP_MSS - ip6_size - icmp6_size)
 383                 pseudo.length = IP_MSS - ip6_size - icmp6_size;
 384
 385         /* Copy first part of original contents to ICMP message */
 386
 387         memmove(packet->data + ether_size + ip6_size + icmp6_size, packet->data + ether_size, pseudo.length);
 388
 389         /* Fill in IPv6 header */
 390
 391         ip6.ip6_flow = htonl(0x60000000UL);
 392         ip6.ip6_plen = htons(icmp6_size + pseudo.length);
 393         ip6.ip6_nxt = IPPROTO_ICMPV6;
 394         ip6.ip6_hlim = 255;
 395         ip6.ip6_src = pseudo.ip6_src;
 396         ip6.ip6_dst = pseudo.ip6_dst;
 397
 398         /* Fill in ICMP header */
 399
 400         icmp6.icmp6_type = type;
 401         icmp6.icmp6_code = code;
 402         icmp6.icmp6_cksum = 0;
 403
 404         /* Create pseudo header */
 405
 406         pseudo.length = htonl(icmp6_size + pseudo.length);
 407         pseudo.next = htonl(IPPROTO_ICMPV6);
 408
 409         /* Generate checksum */
 410
 411         checksum = inet_checksum(&pseudo, sizeof(pseudo), ~0);
 412         checksum = inet_checksum(&icmp6, icmp6_size, checksum);
 413         checksum = inet_checksum(packet->data + ether_size + ip6_size + icmp6_size, ntohl(pseudo.length) - icmp6_size, checksum);
 414
 415         icmp6.icmp6_cksum = checksum;
 416
 417         /* Copy structs on stack back to packet */
 418
 419         memcpy(packet->data + ether_size, &ip6, ip6_size);
 420         memcpy(packet->data + ether_size + ip6_size, &icmp6, icmp6_size);
 421
 422         packet->len = ether_size + ip6_size + ntohl(pseudo.length);
 423
 424         send_packet(source, packet);
 425 }
 426
 427 static void route_ipv6_unicast(node_t *source, vpn_packet_t *packet) {
 428         subnet_t *subnet;
 429         node_t *via;
 430         ipv6_t dest;
 431
 432         memcpy(&dest, &packet->data[38], sizeof dest);
 433         subnet = lookup_subnet_ipv6(&dest);
 434
 435         if(!subnet) {
 436                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Cannot route packet from %s (%s): unknown IPv6 destination address %hx:%hx:%hx:%hx:%hx:%hx:%hx:%hx",
 437                                 source->name, source->hostname,
 438                                 ntohs(dest.x[0]),
 439                                 ntohs(dest.x[1]),
 440                                 ntohs(dest.x[2]),
 441                                 ntohs(dest.x[3]),
 442                                 ntohs(dest.x[4]),
 443                                 ntohs(dest.x[5]),
 444                                 ntohs(dest.x[6]),
 445                                 ntohs(dest.x[7]));
 446
 447                 route_ipv6_unreachable(source, packet, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_ADDR);
 448                 return;
 449         }
 450
 451         if(subnet->owner == source) {
 452                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Packet looping back to %s (%s)!", source->name, source->hostname);
 453                 return;
 454         }
 455
 456         if(!subnet->owner->status.reachable)
 457                 route_ipv6_unreachable(source, packet, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_NOROUTE);
 458
 459         via = (subnet->owner->via == myself) ? subnet->owner->nexthop : subnet->owner->via;
 460
 461         if(via && packet->len > via->mtu && via != myself) {
 462                 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);
 463                 packet->len = via->mtu;
 464                 route_ipv6_unreachable(source, packet, ICMP6_PACKET_TOO_BIG, 0);
 465                 return;
 466         }
 467
 468         send_packet(subnet->owner, packet);
 469 }
 470
 471 /* RFC 2461 */
 472
 473 static void route_neighborsol(node_t *source, vpn_packet_t *packet) {
 474         struct ip6_hdr ip6;
 475         struct nd_neighbor_solicit ns;
 476         struct nd_opt_hdr opt;
 477         subnet_t *subnet;
 478         uint16_t checksum;
 479         bool has_opt;
 480
 481         struct {
 482                 struct in6_addr ip6_src;        /* source address */
 483                 struct in6_addr ip6_dst;        /* destination address */
 484                 uint32_t length;
 485                 uint32_t next;
 486         } pseudo;
 487
 488         if(!checklength(source, packet, ether_size + ip6_size + ns_size))
 489                 return;
 490
 491         has_opt = packet->len >= ether_size + ip6_size + ns_size + opt_size + ETH_ALEN;
 492
 493         if(source != myself) {
 494                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Got neighbor solicitation request from %s (%s) while in router mode!", source->name, source->hostname);
 495                 return;
 496         }
 497
 498         /* Copy headers from packet to structs on the stack */
 499
 500         memcpy(&ip6, packet->data + ether_size, ip6_size);
 501         memcpy(&ns, packet->data + ether_size + ip6_size, ns_size);
 502         if(has_opt)
 503                 memcpy(&opt, packet->data + ether_size + ip6_size + ns_size, opt_size);
 504
 505         /* First, snatch the source address from the neighbor solicitation packet */
 506
 507         if(overwrite_mac)
 508                 memcpy(mymac.x, packet->data + ETH_ALEN, ETH_ALEN);
 509
 510         /* Check if this is a valid neighbor solicitation request */
 511
 512         if(ns.nd_ns_hdr.icmp6_type != ND_NEIGHBOR_SOLICIT ||
 513            (has_opt && opt.nd_opt_type != ND_OPT_SOURCE_LINKADDR)) {
 514                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Cannot route packet: received unknown type neighbor solicitation request");
 515                 return;
 516         }
 517
 518         /* Create pseudo header */
 519
 520         pseudo.ip6_src = ip6.ip6_src;
 521         pseudo.ip6_dst = ip6.ip6_dst;
 522         if(has_opt)
 523                 pseudo.length = htonl(ns_size + opt_size + ETH_ALEN);
 524         else
 525                 pseudo.length = htonl(ns_size);
 526         pseudo.next = htonl(IPPROTO_ICMPV6);
 527
 528         /* Generate checksum */
 529
 530         checksum = inet_checksum(&pseudo, sizeof(pseudo), ~0);
 531         checksum = inet_checksum(&ns, ns_size, checksum);
 532         if(has_opt) {
 533                 checksum = inet_checksum(&opt, opt_size, checksum);
 534                 checksum = inet_checksum(packet->data + ether_size + ip6_size + ns_size + opt_size, ETH_ALEN, checksum);
 535         }
 536
 537         if(checksum) {
 538                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Cannot route packet: checksum error for neighbor solicitation request");
 539                 return;
 540         }
 541
 542         /* Check if the IPv6 address exists on the VPN */
 543
 544         subnet = lookup_subnet_ipv6((ipv6_t *) &ns.nd_ns_target);
 545
 546         if(!subnet) {
 547                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Cannot route packet: neighbor solicitation request for unknown address %hx:%hx:%hx:%hx:%hx:%hx:%hx:%hx",
 548                                    ntohs(((uint16_t *) &ns.nd_ns_target)[0]),
 549                                    ntohs(((uint16_t *) &ns.nd_ns_target)[1]),
 550                                    ntohs(((uint16_t *) &ns.nd_ns_target)[2]),
 551                                    ntohs(((uint16_t *) &ns.nd_ns_target)[3]),
 552                                    ntohs(((uint16_t *) &ns.nd_ns_target)[4]),
 553                                    ntohs(((uint16_t *) &ns.nd_ns_target)[5]),
 554                                    ntohs(((uint16_t *) &ns.nd_ns_target)[6]),
 555                                    ntohs(((uint16_t *) &ns.nd_ns_target)[7]));
 556
 557                 return;
 558         }
 559
 560         /* Check if it is for our own subnet */
 561
 562         if(subnet->owner == myself)
 563                 return;                                 /* silently ignore */
 564
 565         /* Create neighbor advertation reply */
 566
 567         memcpy(packet->data, packet->data + ETH_ALEN, ETH_ALEN);        /* copy destination address */
 568         packet->data[ETH_ALEN * 2 - 1] ^= 0xFF; /* mangle source address so it looks like it's not from us */
 569
 570         ip6.ip6_dst = ip6.ip6_src;                      /* swap destination and source protocoll address */
 571         ip6.ip6_src = ns.nd_ns_target;
 572
 573         if(has_opt)
 574                 memcpy(packet->data + ether_size + ip6_size + ns_size + opt_size, packet->data + ETH_ALEN, ETH_ALEN);   /* add fake source hard addr */
 575
 576         ns.nd_ns_cksum = 0;
 577         ns.nd_ns_type = ND_NEIGHBOR_ADVERT;
 578         ns.nd_ns_reserved = htonl(0x40000000UL);        /* Set solicited flag */
 579         opt.nd_opt_type = ND_OPT_TARGET_LINKADDR;
 580
 581         /* Create pseudo header */
 582
 583         pseudo.ip6_src = ip6.ip6_src;
 584         pseudo.ip6_dst = ip6.ip6_dst;
 585         if(has_opt)
 586                 pseudo.length = htonl(ns_size + opt_size + ETH_ALEN);
 587         else
 588                 pseudo.length = htonl(ns_size);
 589         pseudo.next = htonl(IPPROTO_ICMPV6);
 590
 591         /* Generate checksum */
 592
 593         checksum = inet_checksum(&pseudo, sizeof(pseudo), ~0);
 594         checksum = inet_checksum(&ns, ns_size, checksum);
 595         if(has_opt) {
 596                 checksum = inet_checksum(&opt, opt_size, checksum);
 597                 checksum = inet_checksum(packet->data + ether_size + ip6_size + ns_size + opt_size, ETH_ALEN, checksum);
 598         }
 599
 600         ns.nd_ns_hdr.icmp6_cksum = checksum;
 601
 602         /* Copy structs on stack back to packet */
 603
 604         memcpy(packet->data + ether_size, &ip6, ip6_size);
 605         memcpy(packet->data + ether_size + ip6_size, &ns, ns_size);
 606         if(has_opt)
 607                 memcpy(packet->data + ether_size + ip6_size + ns_size, &opt, opt_size);
 608
 609         send_packet(source, packet);
 610 }
 611
 612 static void route_ipv6(node_t *source, vpn_packet_t *packet) {
 613         if(!checklength(source, packet, ether_size + ip6_size))
 614                 return;
 615
 616         if(packet->data[20] == IPPROTO_ICMPV6 && checklength(source, packet, ether_size + ip6_size + icmp6_size) && packet->data[54] == ND_NEIGHBOR_SOLICIT) {
 617                 route_neighborsol(source, packet);
 618                 return;
 619         }
 620
 621         if(packet->data[38] == 255)
 622                 broadcast_packet(source, packet);
 623         else
 624                 route_ipv6_unicast(source, packet);
 625 }
 626
 627 /* RFC 826 */
 628
 629 static void route_arp(node_t *source, vpn_packet_t *packet) {
 630         struct ether_arp arp;
 631         subnet_t *subnet;
 632         struct in_addr addr;
 633
 634         if(!checklength(source, packet, ether_size + arp_size))
 635                 return;
 636
 637         if(source != myself) {
 638                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Got ARP request from %s (%s) while in router mode!", source->name, source->hostname);
 639                 return;
 640         }
 641
 642         /* First, snatch the source address from the ARP packet */
 643
 644         if(overwrite_mac)
 645                 memcpy(mymac.x, packet->data + ETH_ALEN, ETH_ALEN);
 646
 647         /* Copy headers from packet to structs on the stack */
 648
 649         memcpy(&arp, packet->data + ether_size, arp_size);
 650
 651         /* Check if this is a valid ARP request */
 652
 653         if(ntohs(arp.arp_hrd) != ARPHRD_ETHER || ntohs(arp.arp_pro) != ETH_P_IP ||
 654            arp.arp_hln != ETH_ALEN || arp.arp_pln != sizeof(addr) || ntohs(arp.arp_op) != ARPOP_REQUEST) {
 655                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Cannot route packet: received unknown type ARP request");
 656                 return;
 657         }
 658
 659         /* Check if the IPv4 address exists on the VPN */
 660
 661         subnet = lookup_subnet_ipv4((ipv4_t *) &arp.arp_tpa);
 662
 663         if(!subnet) {
 664                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Cannot route packet: ARP request for unknown address %d.%d.%d.%d",
 665                                    arp.arp_tpa[0], arp.arp_tpa[1], arp.arp_tpa[2],
 666                                    arp.arp_tpa[3]);
 667                 return;
 668         }
 669
 670         /* Check if it is for our own subnet */
 671
 672         if(subnet->owner == myself)
 673                 return;                                 /* silently ignore */
 674
 675         memcpy(packet->data, packet->data + ETH_ALEN, ETH_ALEN);        /* copy destination address */
 676         packet->data[ETH_ALEN * 2 - 1] ^= 0xFF; /* mangle source address so it looks like it's not from us */
 677
 678         memcpy(&addr, arp.arp_tpa, sizeof(addr));       /* save protocol addr */
 679         memcpy(arp.arp_tpa, arp.arp_spa, sizeof(addr)); /* swap destination and source protocol address */
 680         memcpy(arp.arp_spa, &addr, sizeof(addr));       /* ... */
 681
 682         memcpy(arp.arp_tha, arp.arp_sha, ETH_ALEN);     /* set target hard/proto addr */
 683         memcpy(arp.arp_sha, packet->data + ETH_ALEN, ETH_ALEN); /* add fake source hard addr */
 684         arp.arp_op = htons(ARPOP_REPLY);
 685
 686         /* Copy structs on stack back to packet */
 687
 688         memcpy(packet->data + ether_size, &arp, arp_size);
 689
 690         send_packet(source, packet);
 691 }
 692
 693 static void route_mac(node_t *source, vpn_packet_t *packet) {
 694         subnet_t *subnet;
 695         mac_t dest;
 696
 697         /* Learn source address */
 698
 699         if(source == myself) {
 700                 mac_t src;
 701                 memcpy(&src, &packet->data[6], sizeof src);
 702                 learn_mac(&src);
 703         }
 704
 705         /* Lookup destination address */
 706
 707         memcpy(&dest, &packet->data[0], sizeof dest);
 708         subnet = lookup_subnet_mac(&dest);
 709
 710         if(!subnet) {
 711                 broadcast_packet(source, packet);
 712                 return;
 713         }
 714
 715         if(subnet->owner == source) {
 716                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Packet looping back to %s (%s)!", source->name, source->hostname);
 717                 return;
 718         }
 719
 720         // Handle packets larger than PMTU
 721
 722         node_t *via = (subnet->owner->via == myself) ? subnet->owner->nexthop : subnet->owner->via;
 723
 724         if(via && packet->len > via->mtu && via != myself) {
 725                 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);
 726                 uint16_t type = packet->data[12] << 8 | packet->data[13];
 727                 if(type == ETH_P_IP) {
 728                         if(packet->data[20] & 0x40) {
 729                                 packet->len = via->mtu;
 730                                 route_ipv4_unreachable(source, packet, ICMP_DEST_UNREACH, ICMP_FRAG_NEEDED);
 731                         } else {
 732                                 fragment_ipv4_packet(via, packet);
 733                         }
 734                         return;
 735                 } else if(type == ETH_P_IPV6) {
 736                         packet->len = via->mtu;
 737                         route_ipv6_unreachable(source, packet, ICMP6_PACKET_TOO_BIG, 0);
 738                         return;
 739                 }
 740         }
 741
 742         send_packet(subnet->owner, packet);
 743 }
 744
 745 void route(node_t *source, vpn_packet_t *packet) {
 746         if(!checklength(source, packet, ether_size))
 747                 return;
 748
 749         switch (routing_mode) {
 750                 case RMODE_ROUTER:
 751                         {
 752                                 uint16_t type = packet->data[12] << 8 | packet->data[13];
 753
 754                                 switch (type) {
 755                                         case ETH_P_ARP:
 756                                                 route_arp(source, packet);
 757                                                 break;
 758
 759                                         case ETH_P_IP:
 760                                                 route_ipv4(source, packet);
 761                                                 break;
 762
 763                                         case ETH_P_IPV6:
 764                                                 route_ipv6(source, packet);
 765                                                 break;
 766
 767                                         default:
 768                                                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Cannot route packet from %s (%s): unknown type %hx", source->name, source->hostname, type);
 769                                                 break;
 770                                 }
 771                         }
 772                         break;
 773
 774                 case RMODE_SWITCH:
 775                         route_mac(source, packet);
 776                         break;
 777
 778                 case RMODE_HUB:
 779                         broadcast_packet(source, packet);
 780                         break;
 781         }
 782 }