src/route.c

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