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 #define max(a, b) ((a) > (b) ? (a) : (b))
  52
  53 /* RFC 1071 */
  54
  55 static uint16_t inet_checksum(void *data, int len, uint16_t prevsum) {
  56         uint16_t *p = data;
  57         uint32_t checksum = prevsum ^ 0xFFFF;
  58
  59         while(len >= 2) {
  60                 checksum += *p++;
  61                 len -= 2;
  62         }
  63
  64         if(len)
  65                 checksum += *(uint8_t *)p;
  66
  67         while(checksum >> 16)
  68                 checksum = (checksum & 0xFFFF) + (checksum >> 16);
  69
  70         return ~checksum;
  71 }
  72
  73 static bool ratelimit(int frequency) {
  74         static time_t lasttime = 0;
  75         static int count = 0;
  76
  77         if(lasttime == now) {
  78                 if(++count > frequency)
  79                         return true;
  80         } else {
  81                 lasttime = now;
  82                 count = 0;
  83         }
  84
  85         return false;
  86 }
  87
  88 static bool checklength(node_t *source, vpn_packet_t *packet, length_t length) {
  89         if(packet->len < length) {
  90                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Got too short packet from %s (%s)", source->name, source->hostname);
  91                 return false;
  92         } else
  93                 return true;
  94 }
  95
  96 void clamp_mss(node_t *source, node_t *via, vpn_packet_t *packet) {
  97         int i;
  98         int len = ((packet->data[46] >> 4) - 5) * 4;
  99
 100         for(int i = 0; i < len;) {
 101                 if(packet->data[54 + i] == 0)
 102                         break;
 103
 104                 if(packet->data[54 + i] == 1) {
 105                         i++;
 106                         continue;
 107                 }
 108
 109                 if(i > len - 2 || i > len - packet->data[55 + i])
 110                         break;
 111
 112                 if(packet->data[54 + i] != 2) {
 113                         if(packet->data[55 + i] < 2)
 114                                 break;
 115                         i += packet->data[55 + i];
 116                         continue;
 117                 }
 118
 119                 if(packet->data[55] != 4)
 120                         break;
 121
 122                 uint16_t oldmss = packet->data[56 + i] << 8 | packet->data[57 + i];
 123                 uint16_t newmss = via->mtu - 54;
 124                 uint16_t csum = packet->data[50] << 8 | packet->data[51];
 125
 126                 if(oldmss <= newmss)
 127                         break;
 128
 129                 ifdebug(TRAFFIC) logger(LOG_INFO, "Clamping MSS of packet from %s to %s to %d", source->name, via->name, newmss);
 130
 131                 packet->data[56 + i] = newmss >> 8;
 132                 packet->data[57 + i] = newmss & 0xff;
 133                 csum ^= 0xffff;
 134                 csum -= oldmss;
 135                 csum += newmss;
 136                 csum ^= 0xffff;
 137                 packet->data[50] = csum >> 8;
 138                 packet->data[51] = csum & 0xff;
 139                 break;
 140         }
 141 }
 142
 143 static void swap_mac_addresses(vpn_packet_t *packet) {
 144         mac_t tmp;
 145         memcpy(&tmp, &packet->data[0], sizeof tmp);
 146         memcpy(&packet->data[0], &packet->data[6], sizeof tmp);
 147         memcpy(&packet->data[6], &tmp, sizeof tmp);
 148 }
 149
 150 static void learn_mac(mac_t *address) {
 151         subnet_t *subnet;
 152         avl_node_t *node;
 153         connection_t *c;
 154
 155         subnet = lookup_subnet_mac(myself, address);
 156
 157         /* If we don't know this MAC address yet, store it */
 158
 159         if(!subnet) {
 160                 ifdebug(TRAFFIC) logger(LOG_INFO, "Learned new MAC address %hx:%hx:%hx:%hx:%hx:%hx",
 161                                    address->x[0], address->x[1], address->x[2], address->x[3],
 162                                    address->x[4], address->x[5]);
 163
 164                 subnet = new_subnet();
 165                 subnet->type = SUBNET_MAC;
 166                 subnet->expires = now + macexpire;
 167                 subnet->net.mac.address = *address;
 168                 subnet->weight = 10;
 169                 subnet_add(myself, subnet);
 170
 171                 /* And tell all other tinc daemons it's our MAC */
 172
 173                 for(node = connection_tree->head; node; node = node->next) {
 174                         c = node->data;
 175                         if(c->status.active)
 176                                 send_add_subnet(c, subnet);
 177                 }
 178         }
 179
 180         if(subnet->expires)
 181                 subnet->expires = now + macexpire;
 182 }
 183
 184 void age_subnets(void) {
 185         subnet_t *s;
 186         connection_t *c;
 187         avl_node_t *node, *next, *node2;
 188
 189         for(node = myself->subnet_tree->head; node; node = next) {
 190                 next = node->next;
 191                 s = node->data;
 192                 if(s->expires && s->expires < now) {
 193                         ifdebug(TRAFFIC) {
 194                                 char netstr[MAXNETSTR];
 195                                 if(net2str(netstr, sizeof netstr, s))
 196                                         logger(LOG_INFO, "Subnet %s expired", netstr);
 197                         }
 198
 199                         for(node2 = connection_tree->head; node2; node2 = node2->next) {
 200                                 c = node2->data;
 201                                 if(c->status.active)
 202                                         send_del_subnet(c, s);
 203                         }
 204
 205                         subnet_del(myself, s);
 206                 }
 207         }
 208 }
 209
 210 /* RFC 792 */
 211
 212 static void route_ipv4_unreachable(node_t *source, vpn_packet_t *packet, uint8_t type, uint8_t code) {
 213         struct ip ip = {0};
 214         struct icmp icmp = {0};
 215
 216         struct in_addr ip_src;
 217         struct in_addr ip_dst;
 218         uint32_t oldlen;
 219
 220         if(ratelimit(3))
 221                 return;
 222
 223         /* Swap Ethernet source and destination addresses */
 224
 225         swap_mac_addresses(packet);
 226
 227         /* Copy headers from packet into properly aligned structs on the stack */
 228
 229         memcpy(&ip, packet->data + ether_size, ip_size);
 230
 231         /* Remember original source and destination */
 232
 233         ip_src = ip.ip_src;
 234         ip_dst = ip.ip_dst;
 235
 236         oldlen = packet->len - ether_size;
 237
 238         if(type == ICMP_DEST_UNREACH && code == ICMP_FRAG_NEEDED)
 239                 icmp.icmp_nextmtu = htons(packet->len - ether_size);
 240
 241         if(oldlen >= IP_MSS - ip_size - icmp_size)
 242                 oldlen = IP_MSS - ip_size - icmp_size;
 243
 244         /* Copy first part of original contents to ICMP message */
 245
 246         memmove(packet->data + ether_size + ip_size + icmp_size, packet->data + ether_size, oldlen);
 247
 248         /* Fill in IPv4 header */
 249
 250         ip.ip_v = 4;
 251         ip.ip_hl = ip_size / 4;
 252         ip.ip_tos = 0;
 253         ip.ip_len = htons(ip_size + icmp_size + oldlen);
 254         ip.ip_id = 0;
 255         ip.ip_off = 0;
 256         ip.ip_ttl = 255;
 257         ip.ip_p = IPPROTO_ICMP;
 258         ip.ip_sum = 0;
 259         ip.ip_src = ip_dst;
 260         ip.ip_dst = ip_src;
 261
 262         ip.ip_sum = inet_checksum(&ip, ip_size, ~0);
 263
 264         /* Fill in ICMP header */
 265
 266         icmp.icmp_type = type;
 267         icmp.icmp_code = code;
 268         icmp.icmp_cksum = 0;
 269
 270         icmp.icmp_cksum = inet_checksum(&icmp, icmp_size, ~0);
 271         icmp.icmp_cksum = inet_checksum(packet->data + ether_size + ip_size + icmp_size, oldlen, icmp.icmp_cksum);
 272
 273         /* Copy structs on stack back to packet */
 274
 275         memcpy(packet->data + ether_size, &ip, ip_size);
 276         memcpy(packet->data + ether_size + ip_size, &icmp, icmp_size);
 277
 278         packet->len = ether_size + ip_size + icmp_size + oldlen;
 279
 280         send_packet(source, packet);
 281 }
 282
 283 /* RFC 791 */
 284
 285 static void fragment_ipv4_packet(node_t *dest, vpn_packet_t *packet) {
 286         struct ip ip;
 287         vpn_packet_t fragment;
 288         int len, maxlen, todo;
 289         uint8_t *offset;
 290         uint16_t ip_off, origf;
 291
 292         memcpy(&ip, packet->data + ether_size, ip_size);
 293         fragment.priority = packet->priority;
 294
 295         if(ip.ip_hl != ip_size / 4)
 296                 return;
 297
 298         todo = ntohs(ip.ip_len) - ip_size;
 299
 300         if(ether_size + ip_size + todo != packet->len) {
 301                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Length of packet (%d) doesn't match length in IPv4 header (%zd)", packet->len, ether_size + ip_size + todo);
 302                 return;
 303         }
 304
 305         ifdebug(TRAFFIC) logger(LOG_INFO, "Fragmenting packet of %d bytes to %s (%s)", packet->len, dest->name, dest->hostname);
 306
 307         offset = packet->data + ether_size + ip_size;
 308         maxlen = (dest->mtu - ether_size - ip_size) & ~0x7;
 309         ip_off = ntohs(ip.ip_off);
 310         origf = ip_off & ~IP_OFFMASK;
 311         ip_off &= IP_OFFMASK;
 312
 313         while(todo) {
 314                 len = todo > maxlen ? maxlen : todo;
 315                 memcpy(fragment.data + ether_size + ip_size, offset, len);
 316                 todo -= len;
 317                 offset += len;
 318
 319                 ip.ip_len = htons(ip_size + len);
 320                 ip.ip_off = htons(ip_off | origf | (todo ? IP_MF : 0));
 321                 ip.ip_sum = 0;
 322                 ip.ip_sum = inet_checksum(&ip, ip_size, ~0);
 323                 memcpy(fragment.data, packet->data, ether_size);
 324                 memcpy(fragment.data + ether_size, &ip, ip_size);
 325                 fragment.len = ether_size + ip_size + len;
 326
 327                 send_packet(dest, &fragment);
 328
 329                 ip_off += len / 8;
 330         }
 331 }
 332
 333 static void route_ipv4_unicast(node_t *source, vpn_packet_t *packet) {
 334         subnet_t *subnet;
 335         node_t *via;
 336         ipv4_t dest;
 337
 338         memcpy(&dest, &packet->data[30], sizeof dest);
 339         subnet = lookup_subnet_ipv4(&dest);
 340
 341         if(!subnet) {
 342                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Cannot route packet from %s (%s): unknown IPv4 destination address %d.%d.%d.%d",
 343                                 source->name, source->hostname,
 344                                 dest.x[0],
 345                                 dest.x[1],
 346                                 dest.x[2],
 347                                 dest.x[3]);
 348
 349                 route_ipv4_unreachable(source, packet, ICMP_DEST_UNREACH, ICMP_NET_UNKNOWN);
 350                 return;
 351         }
 352
 353         if(subnet->owner == source) {
 354                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Packet looping back to %s (%s)!", source->name, source->hostname);
 355                 return;
 356         }
 357
 358         if(!subnet->owner->status.reachable)
 359                 route_ipv4_unreachable(source, packet, ICMP_DEST_UNREACH, ICMP_NET_UNREACH);
 360
 361         if(priorityinheritance)
 362                 packet->priority = packet->data[15];
 363
 364         via = (subnet->owner->via == myself) ? subnet->owner->nexthop : subnet->owner->via;
 365
 366         if(via && packet->len > max(via->mtu, 590) && via != myself) {
 367                 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);
 368                 if(packet->data[20] & 0x40) {
 369                         packet->len = max(via->mtu, 590);
 370                         route_ipv4_unreachable(source, packet, ICMP_DEST_UNREACH, ICMP_FRAG_NEEDED);
 371                 } else {
 372                         fragment_ipv4_packet(via, packet);
 373                 }
 374
 375                 return;
 376         }
 377
 378         if(via && via != myself && packet->data[23] == 6 && packet->len >= 58 && (packet->data[46] >> 4) > 5)
 379                 clamp_mss(source, via, packet);
 380
 381         send_packet(subnet->owner, packet);
 382 }
 383
 384 static void route_ipv4(node_t *source, vpn_packet_t *packet) {
 385         if(!checklength(source, packet, ether_size + ip_size))
 386                 return;
 387
 388         if(((packet->data[30] & 0xf0) == 0xe0) || (
 389                         packet->data[30] == 255 &&
 390                         packet->data[31] == 255 &&
 391                         packet->data[32] == 255 &&
 392                         packet->data[33] == 255))
 393                 broadcast_packet(source, packet);
 394         else
 395                 route_ipv4_unicast(source, packet);
 396 }
 397
 398 /* RFC 2463 */
 399
 400 static void route_ipv6_unreachable(node_t *source, vpn_packet_t *packet, uint8_t type, uint8_t code) {
 401         struct ip6_hdr ip6;
 402         struct icmp6_hdr icmp6 = {0};
 403         uint16_t checksum;
 404
 405         struct {
 406                 struct in6_addr ip6_src;        /* source address */
 407                 struct in6_addr ip6_dst;        /* destination address */
 408                 uint32_t length;
 409                 uint32_t next;
 410         } pseudo;
 411
 412         if(ratelimit(3))
 413                 return;
 414
 415         /* Swap Ethernet source and destination addresses */
 416
 417         swap_mac_addresses(packet);
 418
 419         /* Copy headers from packet to structs on the stack */
 420
 421         memcpy(&ip6, packet->data + ether_size, ip6_size);
 422
 423         /* Remember original source and destination */
 424
 425         pseudo.ip6_src = ip6.ip6_dst;
 426         pseudo.ip6_dst = ip6.ip6_src;
 427
 428         pseudo.length = packet->len - ether_size;
 429
 430         if(type == ICMP6_PACKET_TOO_BIG)
 431                 icmp6.icmp6_mtu = htonl(pseudo.length);
 432
 433         if(pseudo.length >= IP_MSS - ip6_size - icmp6_size)
 434                 pseudo.length = IP_MSS - ip6_size - icmp6_size;
 435
 436         /* Copy first part of original contents to ICMP message */
 437
 438         memmove(packet->data + ether_size + ip6_size + icmp6_size, packet->data + ether_size, pseudo.length);
 439
 440         /* Fill in IPv6 header */
 441
 442         ip6.ip6_flow = htonl(0x60000000UL);
 443         ip6.ip6_plen = htons(icmp6_size + pseudo.length);
 444         ip6.ip6_nxt = IPPROTO_ICMPV6;
 445         ip6.ip6_hlim = 255;
 446         ip6.ip6_src = pseudo.ip6_src;
 447         ip6.ip6_dst = pseudo.ip6_dst;
 448
 449         /* Fill in ICMP header */
 450
 451         icmp6.icmp6_type = type;
 452         icmp6.icmp6_code = code;
 453         icmp6.icmp6_cksum = 0;
 454
 455         /* Create pseudo header */
 456
 457         pseudo.length = htonl(icmp6_size + pseudo.length);
 458         pseudo.next = htonl(IPPROTO_ICMPV6);
 459
 460         /* Generate checksum */
 461
 462         checksum = inet_checksum(&pseudo, sizeof(pseudo), ~0);
 463         checksum = inet_checksum(&icmp6, icmp6_size, checksum);
 464         checksum = inet_checksum(packet->data + ether_size + ip6_size + icmp6_size, ntohl(pseudo.length) - icmp6_size, checksum);
 465
 466         icmp6.icmp6_cksum = checksum;
 467
 468         /* Copy structs on stack back to packet */
 469
 470         memcpy(packet->data + ether_size, &ip6, ip6_size);
 471         memcpy(packet->data + ether_size + ip6_size, &icmp6, icmp6_size);
 472
 473         packet->len = ether_size + ip6_size + ntohl(pseudo.length);
 474
 475         send_packet(source, packet);
 476 }
 477
 478 static void route_ipv6_unicast(node_t *source, vpn_packet_t *packet) {
 479         subnet_t *subnet;
 480         node_t *via;
 481         ipv6_t dest;
 482
 483         memcpy(&dest, &packet->data[38], sizeof dest);
 484         subnet = lookup_subnet_ipv6(&dest);
 485
 486         if(!subnet) {
 487                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Cannot route packet from %s (%s): unknown IPv6 destination address %hx:%hx:%hx:%hx:%hx:%hx:%hx:%hx",
 488                                 source->name, source->hostname,
 489                                 ntohs(dest.x[0]),
 490                                 ntohs(dest.x[1]),
 491                                 ntohs(dest.x[2]),
 492                                 ntohs(dest.x[3]),
 493                                 ntohs(dest.x[4]),
 494                                 ntohs(dest.x[5]),
 495                                 ntohs(dest.x[6]),
 496                                 ntohs(dest.x[7]));
 497
 498                 route_ipv6_unreachable(source, packet, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_ADDR);
 499                 return;
 500         }
 501
 502         if(subnet->owner == source) {
 503                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Packet looping back to %s (%s)!", source->name, source->hostname);
 504                 return;
 505         }
 506
 507         if(!subnet->owner->status.reachable)
 508                 route_ipv6_unreachable(source, packet, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_NOROUTE);
 509
 510         via = (subnet->owner->via == myself) ? subnet->owner->nexthop : subnet->owner->via;
 511
 512         if(via && packet->len > max(via->mtu, 1294) && via != myself) {
 513                 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);
 514                 packet->len = max(via->mtu, 1294);
 515                 route_ipv6_unreachable(source, packet, ICMP6_PACKET_TOO_BIG, 0);
 516                 return;
 517         }
 518
 519         send_packet(subnet->owner, packet);
 520 }
 521
 522 /* RFC 2461 */
 523
 524 static void route_neighborsol(node_t *source, vpn_packet_t *packet) {
 525         struct ip6_hdr ip6;
 526         struct nd_neighbor_solicit ns;
 527         struct nd_opt_hdr opt;
 528         subnet_t *subnet;
 529         uint16_t checksum;
 530         bool has_opt;
 531
 532         struct {
 533                 struct in6_addr ip6_src;        /* source address */
 534                 struct in6_addr ip6_dst;        /* destination address */
 535                 uint32_t length;
 536                 uint32_t next;
 537         } pseudo;
 538
 539         if(!checklength(source, packet, ether_size + ip6_size + ns_size))
 540                 return;
 541
 542         has_opt = packet->len >= ether_size + ip6_size + ns_size + opt_size + ETH_ALEN;
 543
 544         if(source != myself) {
 545                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Got neighbor solicitation request from %s (%s) while in router mode!", source->name, source->hostname);
 546                 return;
 547         }
 548
 549         /* Copy headers from packet to structs on the stack */
 550
 551         memcpy(&ip6, packet->data + ether_size, ip6_size);
 552         memcpy(&ns, packet->data + ether_size + ip6_size, ns_size);
 553         if(has_opt)
 554                 memcpy(&opt, packet->data + ether_size + ip6_size + ns_size, opt_size);
 555
 556         /* First, snatch the source address from the neighbor solicitation packet */
 557
 558         if(overwrite_mac)
 559                 memcpy(mymac.x, packet->data + ETH_ALEN, ETH_ALEN);
 560
 561         /* Check if this is a valid neighbor solicitation request */
 562
 563         if(ns.nd_ns_hdr.icmp6_type != ND_NEIGHBOR_SOLICIT ||
 564            (has_opt && opt.nd_opt_type != ND_OPT_SOURCE_LINKADDR)) {
 565                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Cannot route packet: received unknown type neighbor solicitation request");
 566                 return;
 567         }
 568
 569         /* Create pseudo header */
 570
 571         pseudo.ip6_src = ip6.ip6_src;
 572         pseudo.ip6_dst = ip6.ip6_dst;
 573         if(has_opt)
 574                 pseudo.length = htonl(ns_size + opt_size + ETH_ALEN);
 575         else
 576                 pseudo.length = htonl(ns_size);
 577         pseudo.next = htonl(IPPROTO_ICMPV6);
 578
 579         /* Generate checksum */
 580
 581         checksum = inet_checksum(&pseudo, sizeof(pseudo), ~0);
 582         checksum = inet_checksum(&ns, ns_size, checksum);
 583         if(has_opt) {
 584                 checksum = inet_checksum(&opt, opt_size, checksum);
 585                 checksum = inet_checksum(packet->data + ether_size + ip6_size + ns_size + opt_size, ETH_ALEN, checksum);
 586         }
 587
 588         if(checksum) {
 589                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Cannot route packet: checksum error for neighbor solicitation request");
 590                 return;
 591         }
 592
 593         /* Check if the IPv6 address exists on the VPN */
 594
 595         subnet = lookup_subnet_ipv6((ipv6_t *) &ns.nd_ns_target);
 596
 597         if(!subnet) {
 598                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Cannot route packet: neighbor solicitation request for unknown address %hx:%hx:%hx:%hx:%hx:%hx:%hx:%hx",
 599                                    ntohs(((uint16_t *) &ns.nd_ns_target)[0]),
 600                                    ntohs(((uint16_t *) &ns.nd_ns_target)[1]),
 601                                    ntohs(((uint16_t *) &ns.nd_ns_target)[2]),
 602                                    ntohs(((uint16_t *) &ns.nd_ns_target)[3]),
 603                                    ntohs(((uint16_t *) &ns.nd_ns_target)[4]),
 604                                    ntohs(((uint16_t *) &ns.nd_ns_target)[5]),
 605                                    ntohs(((uint16_t *) &ns.nd_ns_target)[6]),
 606                                    ntohs(((uint16_t *) &ns.nd_ns_target)[7]));
 607
 608                 return;
 609         }
 610
 611         /* Check if it is for our own subnet */
 612
 613         if(subnet->owner == myself)
 614                 return;                                 /* silently ignore */
 615
 616         /* Create neighbor advertation reply */
 617
 618         memcpy(packet->data, packet->data + ETH_ALEN, ETH_ALEN);        /* copy destination address */
 619         packet->data[ETH_ALEN * 2 - 1] ^= 0xFF; /* mangle source address so it looks like it's not from us */
 620
 621         ip6.ip6_dst = ip6.ip6_src;                      /* swap destination and source protocoll address */
 622         ip6.ip6_src = ns.nd_ns_target;
 623
 624         if(has_opt)
 625                 memcpy(packet->data + ether_size + ip6_size + ns_size + opt_size, packet->data + ETH_ALEN, ETH_ALEN);   /* add fake source hard addr */
 626
 627         ns.nd_ns_cksum = 0;
 628         ns.nd_ns_type = ND_NEIGHBOR_ADVERT;
 629         ns.nd_ns_reserved = htonl(0x40000000UL);        /* Set solicited flag */
 630         opt.nd_opt_type = ND_OPT_TARGET_LINKADDR;
 631
 632         /* Create pseudo header */
 633
 634         pseudo.ip6_src = ip6.ip6_src;
 635         pseudo.ip6_dst = ip6.ip6_dst;
 636         if(has_opt)
 637                 pseudo.length = htonl(ns_size + opt_size + ETH_ALEN);
 638         else
 639                 pseudo.length = htonl(ns_size);
 640         pseudo.next = htonl(IPPROTO_ICMPV6);
 641
 642         /* Generate checksum */
 643
 644         checksum = inet_checksum(&pseudo, sizeof(pseudo), ~0);
 645         checksum = inet_checksum(&ns, ns_size, checksum);
 646         if(has_opt) {
 647                 checksum = inet_checksum(&opt, opt_size, checksum);
 648                 checksum = inet_checksum(packet->data + ether_size + ip6_size + ns_size + opt_size, ETH_ALEN, checksum);
 649         }
 650
 651         ns.nd_ns_hdr.icmp6_cksum = checksum;
 652
 653         /* Copy structs on stack back to packet */
 654
 655         memcpy(packet->data + ether_size, &ip6, ip6_size);
 656         memcpy(packet->data + ether_size + ip6_size, &ns, ns_size);
 657         if(has_opt)
 658                 memcpy(packet->data + ether_size + ip6_size + ns_size, &opt, opt_size);
 659
 660         send_packet(source, packet);
 661 }
 662
 663 static void route_ipv6(node_t *source, vpn_packet_t *packet) {
 664         if(!checklength(source, packet, ether_size + ip6_size))
 665                 return;
 666
 667         if(packet->data[20] == IPPROTO_ICMPV6 && checklength(source, packet, ether_size + ip6_size + icmp6_size) && packet->data[54] == ND_NEIGHBOR_SOLICIT) {
 668                 route_neighborsol(source, packet);
 669                 return;
 670         }
 671
 672         if(packet->data[38] == 255)
 673                 broadcast_packet(source, packet);
 674         else
 675                 route_ipv6_unicast(source, packet);
 676 }
 677
 678 /* RFC 826 */
 679
 680 static void route_arp(node_t *source, vpn_packet_t *packet) {
 681         struct ether_arp arp;
 682         subnet_t *subnet;
 683         struct in_addr addr;
 684
 685         if(!checklength(source, packet, ether_size + arp_size))
 686                 return;
 687
 688         if(source != myself) {
 689                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Got ARP request from %s (%s) while in router mode!", source->name, source->hostname);
 690                 return;
 691         }
 692
 693         /* First, snatch the source address from the ARP packet */
 694
 695         if(overwrite_mac)
 696                 memcpy(mymac.x, packet->data + ETH_ALEN, ETH_ALEN);
 697
 698         /* Copy headers from packet to structs on the stack */
 699
 700         memcpy(&arp, packet->data + ether_size, arp_size);
 701
 702         /* Check if this is a valid ARP request */
 703
 704         if(ntohs(arp.arp_hrd) != ARPHRD_ETHER || ntohs(arp.arp_pro) != ETH_P_IP ||
 705            arp.arp_hln != ETH_ALEN || arp.arp_pln != sizeof(addr) || ntohs(arp.arp_op) != ARPOP_REQUEST) {
 706                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Cannot route packet: received unknown type ARP request");
 707                 return;
 708         }
 709
 710         /* Check if the IPv4 address exists on the VPN */
 711
 712         subnet = lookup_subnet_ipv4((ipv4_t *) &arp.arp_tpa);
 713
 714         if(!subnet) {
 715                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Cannot route packet: ARP request for unknown address %d.%d.%d.%d",
 716                                    arp.arp_tpa[0], arp.arp_tpa[1], arp.arp_tpa[2],
 717                                    arp.arp_tpa[3]);
 718                 return;
 719         }
 720
 721         /* Check if it is for our own subnet */
 722
 723         if(subnet->owner == myself)
 724                 return;                                 /* silently ignore */
 725
 726         memcpy(packet->data, packet->data + ETH_ALEN, ETH_ALEN);        /* copy destination address */
 727         packet->data[ETH_ALEN * 2 - 1] ^= 0xFF; /* mangle source address so it looks like it's not from us */
 728
 729         memcpy(&addr, arp.arp_tpa, sizeof(addr));       /* save protocol addr */
 730         memcpy(arp.arp_tpa, arp.arp_spa, sizeof(addr)); /* swap destination and source protocol address */
 731         memcpy(arp.arp_spa, &addr, sizeof(addr));       /* ... */
 732
 733         memcpy(arp.arp_tha, arp.arp_sha, ETH_ALEN);     /* set target hard/proto addr */
 734         memcpy(arp.arp_sha, packet->data + ETH_ALEN, ETH_ALEN); /* add fake source hard addr */
 735         arp.arp_op = htons(ARPOP_REPLY);
 736
 737         /* Copy structs on stack back to packet */
 738
 739         memcpy(packet->data + ether_size, &arp, arp_size);
 740
 741         send_packet(source, packet);
 742 }
 743
 744 static void route_mac(node_t *source, vpn_packet_t *packet) {
 745         subnet_t *subnet;
 746         mac_t dest;
 747
 748         /* Learn source address */
 749
 750         if(source == myself) {
 751                 mac_t src;
 752                 memcpy(&src, &packet->data[6], sizeof src);
 753                 learn_mac(&src);
 754         }
 755
 756         /* Lookup destination address */
 757
 758         memcpy(&dest, &packet->data[0], sizeof dest);
 759         subnet = lookup_subnet_mac(NULL, &dest);
 760
 761         if(!subnet) {
 762                 broadcast_packet(source, packet);
 763                 return;
 764         }
 765
 766         if(subnet->owner == source) {
 767                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Packet looping back to %s (%s)!", source->name, source->hostname);
 768                 return;
 769         }
 770
 771         // Handle packets larger than PMTU
 772
 773         node_t *via = (subnet->owner->via == myself) ? subnet->owner->nexthop : subnet->owner->via;
 774
 775         if(via && packet->len > via->mtu && via != myself) {
 776                 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);
 777                 uint16_t type = packet->data[12] << 8 | packet->data[13];
 778                 if(type == ETH_P_IP && packet->len > 590) {
 779                         if(packet->data[20] & 0x40) {
 780                                 packet->len = via->mtu;
 781                                 route_ipv4_unreachable(source, packet, ICMP_DEST_UNREACH, ICMP_FRAG_NEEDED);
 782                         } else {
 783                                 fragment_ipv4_packet(via, packet);
 784                         }
 785                         return;
 786                 } else if(type == ETH_P_IPV6 && packet->len > 1294) {
 787                         packet->len = via->mtu;
 788                         route_ipv6_unreachable(source, packet, ICMP6_PACKET_TOO_BIG, 0);
 789                         return;
 790                 }
 791         }
 792
 793         if(via && via != myself && (packet->data[12] << 8 | packet->data[13]) == ETH_P_IP && packet->len >= 58 && packet->data[23] == 6 && (packet->data[46] >> 4) > 5)
 794                 clamp_mss(source, via, packet);
 795
 796         send_packet(subnet->owner, packet);
 797 }
 798
 799 void route(node_t *source, vpn_packet_t *packet) {
 800         if(!checklength(source, packet, ether_size))
 801                 return;
 802
 803         switch (routing_mode) {
 804                 case RMODE_ROUTER:
 805                         {
 806                                 uint16_t type = packet->data[12] << 8 | packet->data[13];
 807
 808                                 switch (type) {
 809                                         case ETH_P_ARP:
 810                                                 route_arp(source, packet);
 811                                                 break;
 812
 813                                         case ETH_P_IP:
 814                                                 route_ipv4(source, packet);
 815                                                 break;
 816
 817                                         case ETH_P_IPV6:
 818                                                 route_ipv6(source, packet);
 819                                                 break;
 820
 821                                         default:
 822                                                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Cannot route packet from %s (%s): unknown type %hx", source->name, source->hostname, type);
 823                                                 break;
 824                                 }
 825                         }
 826                         break;
 827
 828                 case RMODE_SWITCH:
 829                         route_mac(source, packet);
 830                         break;
 831
 832                 case RMODE_HUB:
 833                         broadcast_packet(source, packet);
 834                         break;
 835         }
 836 }