tinc-vpn.org Git - tinc/blob - src/route.c

   1 /*
   2     route.c -- routing
   3     Copyright (C) 2000-2004 Ivo Timmermans <ivo@tinc-vpn.org>,
   4                   2000-2004 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 #ifdef HAVE_NET_ETHERNET_H
  26 #include <net/ethernet.h>
  27 #endif
  28 #ifdef HAVE_NET_IF_ARP_H
  29 #include <net/if_arp.h>
  30 #endif
  31 #ifdef HAVE_NETINET_IP_ICMP_H
  32 #include <netinet/ip_icmp.h>
  33 #endif
  34 #ifdef HAVE_NETINET_ICMP6_H
  35 #include <netinet/icmp6.h>
  36 #endif
  37 #ifdef HAVE_NETINET_IF_ETHER_H
  38 #include <netinet/if_ether.h>
  39 #endif
  40
  41 #include "avl_tree.h"
  42 #include "connection.h"
  43 #include "ethernet.h"
  44 #include "ipv4.h"
  45 #include "ipv6.h"
  46 #include "logger.h"
  47 #include "net.h"
  48 #include "protocol.h"
  49 #include "route.h"
  50 #include "subnet.h"
  51 #include "utils.h"
  52
  53 rmode_t routing_mode = RMODE_ROUTER;
  54 bool priorityinheritance = false;
  55 int macexpire = 600;
  56 bool overwrite_mac = false;
  57 mac_t mymac = {{0xFE, 0xFD, 0, 0, 0, 0}};
  58
  59 /* Sizes of various headers */
  60
  61 static const size_t ether_size = sizeof(struct ether_header);
  62 static const size_t arp_size = sizeof(struct ether_arp);
  63 static const size_t ip_size = sizeof(struct ip);
  64 static const size_t icmp_size = sizeof(struct icmp) - sizeof(struct ip);
  65 static const size_t ip6_size = sizeof(struct ip6_hdr);
  66 static const size_t icmp6_size = sizeof(struct icmp6_hdr);
  67 static const size_t ns_size = sizeof(struct nd_neighbor_solicit);
  68 static const size_t opt_size = sizeof(struct nd_opt_hdr);
  69
  70 /* RFC 1071 */
  71
  72 static __inline__ uint16_t inet_checksum(void *data, int len, uint16_t prevsum)
  73 {
  74         uint16_t *p = data;
  75         uint32_t checksum = prevsum ^ 0xFFFF;
  76
  77         while(len >= 2) {
  78                 checksum += *p++;
  79                 len -= 2;
  80         }
  81
  82         if(len)
  83                 checksum += *(uint8_t *)p;
  84
  85         while(checksum >> 16)
  86                 checksum = (checksum & 0xFFFF) + (checksum >> 16);
  87
  88         return ~checksum;
  89 }
  90
  91 static __inline__ bool ratelimit(int frequency) {
  92         static time_t lasttime = 0;
  93         static int count = 0;
  94
  95         if(lasttime == now) {
  96                 if(++count > frequency)
  97                         return true;
  98         } else {
  99                 lasttime = now;
 100                 count = 0;
 101         }
 102
 103         return false;
 104 }
 105
 106 static __inline__ bool checklength(node_t *source, vpn_packet_t *packet, length_t length) {
 107         if(packet->len < length) {
 108                 ifdebug(TRAFFIC) logger(LOG_WARNING, _("Got too short packet from %s (%s)"), source->name, source->hostname);
 109                 return false;
 110         } else
 111                 return true;
 112 }
 113
 114 static __inline__ void learn_mac(mac_t *address)
 115 {
 116         subnet_t *subnet;
 117         avl_node_t *node;
 118         connection_t *c;
 119
 120         cp();
 121
 122         subnet = lookup_subnet_mac(address);
 123
 124         /* If we don't know this MAC address yet, store it */
 125
 126         if(!subnet) {
 127                 ifdebug(TRAFFIC) logger(LOG_INFO, _("Learned new MAC address %hx:%hx:%hx:%hx:%hx:%hx"),
 128                                    address->x[0], address->x[1], address->x[2], address->x[3],
 129                                    address->x[4], address->x[5]);
 130
 131                 subnet = new_subnet();
 132                 subnet->type = SUBNET_MAC;
 133                 subnet->expires = now + macexpire;
 134                 subnet->net.mac.address = *address;
 135                 subnet_add(myself, subnet);
 136
 137                 /* And tell all other tinc daemons it's our MAC */
 138
 139                 for(node = connection_tree->head; node; node = node->next) {
 140                         c = node->data;
 141                         if(c->status.active)
 142                                 send_add_subnet(c, subnet);
 143                 }
 144         }
 145
 146         if(subnet->expires)
 147                 subnet->expires = now + macexpire;
 148 }
 149
 150 void age_subnets(void)
 151 {
 152         subnet_t *s;
 153         connection_t *c;
 154         avl_node_t *node, *next, *node2;
 155
 156         cp();
 157
 158         for(node = myself->subnet_tree->head; node; node = next) {
 159                 next = node->next;
 160                 s = node->data;
 161                 if(s->expires && s->expires < now) {
 162                         ifdebug(TRAFFIC) {
 163                                 char netstr[MAXNETSTR];
 164                                 if(net2str(netstr, sizeof netstr, s))
 165                                         logger(LOG_INFO, _("Subnet %s expired"), netstr);
 166                         }
 167
 168                         for(node2 = connection_tree->head; node2; node2 = node2->next) {
 169                                 c = node2->data;
 170                                 if(c->status.active)
 171                                         send_del_subnet(c, s);
 172                         }
 173
 174                         subnet_del(myself, s);
 175                 }
 176         }
 177 }
 178
 179 static __inline__ void route_mac(node_t *source, vpn_packet_t *packet)
 180 {
 181         subnet_t *subnet;
 182
 183         cp();
 184
 185         /* Learn source address */
 186
 187         if(source == myself)
 188                 learn_mac((mac_t *)(&packet->data[6]));
 189
 190         /* Lookup destination address */
 191
 192         subnet = lookup_subnet_mac((mac_t *)(&packet->data[0]));
 193
 194         if(!subnet) {
 195                 broadcast_packet(source, packet);
 196                 return;
 197         }
 198
 199         if(subnet->owner == source) {
 200                 ifdebug(TRAFFIC) logger(LOG_WARNING, _("Packet looping back to %s (%s)!"), source->name, source->hostname);
 201                 return;
 202         }
 203
 204         send_packet(subnet->owner, packet);
 205 }
 206
 207 /* RFC 792 */
 208
 209 static void route_ipv4_unreachable(node_t *source, vpn_packet_t *packet, uint8_t type, uint8_t code)
 210 {
 211         struct ip ip = {0};
 212         struct icmp icmp = {0};
 213
 214         struct in_addr ip_src;
 215         struct in_addr ip_dst;
 216         uint32_t oldlen;
 217
 218         if(ratelimit(3))
 219                 return;
 220
 221         cp();
 222
 223         /* Copy headers from packet into properly aligned structs on the stack */
 224
 225         memcpy(&ip, packet->data + ether_size, ip_size);
 226
 227         /* Remember original source and destination */
 228
 229         ip_src = ip.ip_src;
 230         ip_dst = ip.ip_dst;
 231
 232         oldlen = packet->len - ether_size;
 233
 234         if(type == ICMP_DEST_UNREACH && code == ICMP_FRAG_NEEDED)
 235                 icmp.icmp_nextmtu = htons(packet->len - ether_size);
 236
 237         if(oldlen >= IP_MSS - ip_size - icmp_size)
 238                 oldlen = IP_MSS - ip_size - icmp_size;
 239
 240         /* Copy first part of original contents to ICMP message */
 241
 242         memmove(packet->data + ether_size + ip_size + icmp_size, packet->data + ether_size, oldlen);
 243
 244         /* Fill in IPv4 header */
 245
 246         ip.ip_v = 4;
 247         ip.ip_hl = ip_size / 4;
 248         ip.ip_tos = 0;
 249         ip.ip_len = htons(ip_size + icmp_size + oldlen);
 250         ip.ip_id = 0;
 251         ip.ip_off = 0;
 252         ip.ip_ttl = 255;
 253         ip.ip_p = IPPROTO_ICMP;
 254         ip.ip_sum = 0;
 255         ip.ip_src = ip_dst;
 256         ip.ip_dst = ip_src;
 257
 258         ip.ip_sum = inet_checksum(&ip, ip_size, ~0);
 259
 260         /* Fill in ICMP header */
 261
 262         icmp.icmp_type = type;
 263         icmp.icmp_code = code;
 264         icmp.icmp_cksum = 0;
 265
 266         icmp.icmp_cksum = inet_checksum(&icmp, icmp_size, ~0);
 267         icmp.icmp_cksum = inet_checksum(packet->data + ether_size + ip_size + icmp_size, oldlen, icmp.icmp_cksum);
 268
 269         /* Copy structs on stack back to packet */
 270
 271         memcpy(packet->data + ether_size, &ip, ip_size);
 272         memcpy(packet->data + ether_size + ip_size, &icmp, icmp_size);
 273
 274         packet->len = ether_size + ip_size + icmp_size + oldlen;
 275
 276         send_packet(source, packet);
 277 }
 278
 279 /* RFC 791 */
 280
 281 static __inline__ void fragment_ipv4_packet(node_t *dest, vpn_packet_t *packet) {
 282         struct ip ip;
 283         vpn_packet_t fragment;
 284         int len, maxlen, todo;
 285         uint8_t *offset;
 286         uint16_t ip_off, origf;
 287
 288         cp();
 289
 290         memcpy(&ip, packet->data + ether_size, ip_size);
 291         fragment.priority = packet->priority;
 292
 293         if(ip.ip_hl != ip_size / 4)
 294                 return;
 295
 296         todo = ntohs(ip.ip_len) - ip_size;
 297
 298         if(ether_size + ip_size + todo != packet->len) {
 299                 ifdebug(TRAFFIC) logger(LOG_WARNING, _("Length of packet (%d) doesn't match length in IPv4 header (%d)"), packet->len, ether_size + ip_size + todo);
 300                 return;
 301         }
 302
 303         ifdebug(TRAFFIC) logger(LOG_INFO, _("Fragmenting packet of %d bytes to %s (%s)"), packet->len, dest->name, dest->hostname);
 304
 305         offset = packet->data + ether_size + ip_size;
 306         maxlen = (dest->mtu - ether_size - ip_size) & ~0x7;
 307         ip_off = ntohs(ip.ip_off);
 308         origf = ip_off & ~IP_OFFMASK;
 309         ip_off &= IP_OFFMASK;
 310
 311         while(todo) {
 312                 len = todo > maxlen ? maxlen : todo;
 313                 memcpy(fragment.data + ether_size + ip_size, offset, len);
 314                 todo -= len;
 315                 offset += len;
 316
 317                 ip.ip_len = htons(ip_size + len);
 318                 ip.ip_off = htons(ip_off | origf | (todo ? IP_MF : 0));
 319                 ip.ip_sum = 0;
 320                 ip.ip_sum = inet_checksum(&ip, ip_size, ~0);
 321                 memcpy(fragment.data, packet->data, ether_size);
 322                 memcpy(fragment.data + ether_size, &ip, ip_size);
 323                 fragment.len = ether_size + ip_size + len;
 324
 325                 send_packet(dest, &fragment);
 326
 327                 ip_off += len / 8;
 328         }
 329 }
 330
 331 static __inline__ void route_ipv4_unicast(node_t *source, vpn_packet_t *packet)
 332 {
 333         subnet_t *subnet;
 334         node_t *via;
 335
 336         cp();
 337
 338         subnet = lookup_subnet_ipv4((ipv4_t *) &packet->data[30]);
 339
 340         if(!subnet) {
 341                 ifdebug(TRAFFIC) logger(LOG_WARNING, _("Cannot route packet from %s (%s): unknown IPv4 destination address %d.%d.%d.%d"),
 342                                 source->name, source->hostname,
 343                                 packet->data[30],
 344                                 packet->data[31],
 345                                 packet->data[32],
 346                                 packet->data[33]);
 347
 348                 route_ipv4_unreachable(source, packet, ICMP_DEST_UNREACH, ICMP_NET_UNKNOWN);
 349                 return;
 350         }
 351
 352         if(subnet->owner == source) {
 353                 ifdebug(TRAFFIC) logger(LOG_WARNING, _("Packet looping back to %s (%s)!"), source->name, source->hostname);
 354                 return;
 355         }
 356
 357         if(!subnet->owner->status.reachable)
 358                 route_ipv4_unreachable(source, packet, ICMP_DEST_UNREACH, ICMP_NET_UNREACH);
 359
 360         if(priorityinheritance)
 361                 packet->priority = packet->data[15];
 362
 363         via = (subnet->owner->via == myself) ? subnet->owner->nexthop : subnet->owner->via;
 364
 365         if(packet->len > via->mtu && via != myself) {
 366                 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);
 367                 if(packet->data[20] & 0x40) {
 368                         packet->len = via->mtu;
 369                         route_ipv4_unreachable(source, packet, ICMP_DEST_UNREACH, ICMP_FRAG_NEEDED);
 370                 } else {
 371                         fragment_ipv4_packet(via, packet);
 372                 }
 373
 374                 return;
 375         }
 376
 377         send_packet(subnet->owner, packet);
 378 }
 379
 380 static __inline__ void route_ipv4(node_t *source, vpn_packet_t *packet)
 381 {
 382         cp();
 383
 384         if(!checklength(source, packet, ether_size + ip_size))
 385                 return;
 386
 387         route_ipv4_unicast(source, packet);
 388 }
 389
 390 /* RFC 2463 */
 391
 392 static void route_ipv6_unreachable(node_t *source, vpn_packet_t *packet, uint8_t type, uint8_t code)
 393 {
 394         struct ip6_hdr ip6;
 395         struct icmp6_hdr icmp6 = {0};
 396         uint16_t checksum;
 397
 398         struct {
 399                 struct in6_addr ip6_src;        /* source address */
 400                 struct in6_addr ip6_dst;        /* destination address */
 401                 uint32_t length;
 402                 uint32_t next;
 403         } pseudo;
 404
 405         if(ratelimit(3))
 406                 return;
 407
 408         cp();
 409
 410         /* Copy headers from packet to structs on the stack */
 411
 412         memcpy(&ip6, packet->data + ether_size, ip6_size);
 413
 414         /* Remember original source and destination */
 415
 416         pseudo.ip6_src = ip6.ip6_dst;
 417         pseudo.ip6_dst = ip6.ip6_src;
 418
 419         pseudo.length = packet->len - ether_size;
 420
 421         if(type == ICMP6_PACKET_TOO_BIG)
 422                 icmp6.icmp6_mtu = htonl(pseudo.length);
 423
 424         if(pseudo.length >= IP_MSS - ip6_size - icmp6_size)
 425                 pseudo.length = IP_MSS - ip6_size - icmp6_size;
 426
 427         /* Copy first part of original contents to ICMP message */
 428
 429         memmove(packet->data + ether_size + ip6_size + icmp6_size, packet->data + ether_size, pseudo.length);
 430
 431         /* Fill in IPv6 header */
 432
 433         ip6.ip6_flow = htonl(0x60000000UL);
 434         ip6.ip6_plen = htons(icmp6_size + pseudo.length);
 435         ip6.ip6_nxt = IPPROTO_ICMPV6;
 436         ip6.ip6_hlim = 255;
 437         ip6.ip6_src = pseudo.ip6_src;
 438         ip6.ip6_dst = pseudo.ip6_dst;
 439
 440         /* Fill in ICMP header */
 441
 442         icmp6.icmp6_type = type;
 443         icmp6.icmp6_code = code;
 444         icmp6.icmp6_cksum = 0;
 445
 446         /* Create pseudo header */
 447
 448         pseudo.length = htonl(icmp6_size + pseudo.length);
 449         pseudo.next = htonl(IPPROTO_ICMPV6);
 450
 451         /* Generate checksum */
 452
 453         checksum = inet_checksum(&pseudo, sizeof(pseudo), ~0);
 454         checksum = inet_checksum(&icmp6, icmp6_size, checksum);
 455         checksum = inet_checksum(packet->data + ether_size + ip6_size + icmp6_size, ntohl(pseudo.length) - icmp6_size, checksum);
 456
 457         icmp6.icmp6_cksum = checksum;
 458
 459         /* Copy structs on stack back to packet */
 460
 461         memcpy(packet->data + ether_size, &ip6, ip6_size);
 462         memcpy(packet->data + ether_size + ip6_size, &icmp6, icmp6_size);
 463
 464         packet->len = ether_size + ip6_size + ntohl(pseudo.length);
 465
 466         send_packet(source, packet);
 467 }
 468
 469 static __inline__ void route_ipv6_unicast(node_t *source, vpn_packet_t *packet)
 470 {
 471         subnet_t *subnet;
 472         node_t *via;
 473
 474         cp();
 475
 476         subnet = lookup_subnet_ipv6((ipv6_t *) &packet->data[38]);
 477
 478         if(!subnet) {
 479                 ifdebug(TRAFFIC) logger(LOG_WARNING, _("Cannot route packet from %s (%s): unknown IPv6 destination address %hx:%hx:%hx:%hx:%hx:%hx:%hx:%hx"),
 480                                 source->name, source->hostname,
 481                                 ntohs(*(uint16_t *) &packet->data[38]),
 482                                 ntohs(*(uint16_t *) &packet->data[40]),
 483                                 ntohs(*(uint16_t *) &packet->data[42]),
 484                                 ntohs(*(uint16_t *) &packet->data[44]),
 485                                 ntohs(*(uint16_t *) &packet->data[46]),
 486                                 ntohs(*(uint16_t *) &packet->data[48]),
 487                                 ntohs(*(uint16_t *) &packet->data[50]),
 488                                 ntohs(*(uint16_t *) &packet->data[52]));
 489
 490                 route_ipv6_unreachable(source, packet, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_ADDR);
 491                 return;
 492         }
 493
 494         if(subnet->owner == source) {
 495                 ifdebug(TRAFFIC) logger(LOG_WARNING, _("Packet looping back to %s (%s)!"), source->name, source->hostname);
 496                 return;
 497         }
 498
 499         if(!subnet->owner->status.reachable)
 500                 route_ipv6_unreachable(source, packet, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_NOROUTE);
 501
 502         via = (subnet->owner->via == myself) ? subnet->owner->nexthop : subnet->owner->via;
 503
 504         if(packet->len > via->mtu && via != myself) {
 505                 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);
 506                 packet->len = via->mtu;
 507                 route_ipv6_unreachable(source, packet, ICMP6_PACKET_TOO_BIG, 0);
 508                 return;
 509         }
 510
 511         send_packet(subnet->owner, packet);
 512 }
 513
 514 /* RFC 2461 */
 515
 516 static void route_neighborsol(node_t *source, vpn_packet_t *packet)
 517 {
 518         struct ip6_hdr ip6;
 519         struct nd_neighbor_solicit ns;
 520         struct nd_opt_hdr opt;
 521         subnet_t *subnet;
 522         uint16_t checksum;
 523
 524         struct {
 525                 struct in6_addr ip6_src;        /* source address */
 526                 struct in6_addr ip6_dst;        /* destination address */
 527                 uint32_t length;
 528                 uint32_t next;
 529         } pseudo;
 530
 531         cp();
 532
 533         if(!checklength(source, packet, ether_size + ip6_size + ns_size + opt_size + ETH_ALEN))
 534                 return;
 535
 536         if(source != myself) {
 537                 ifdebug(TRAFFIC) logger(LOG_WARNING, _("Got neighbor solicitation request from %s (%s) while in router mode!"), source->name, source->hostname);
 538                 return;
 539         }
 540
 541         /* Copy headers from packet to structs on the stack */
 542
 543         memcpy(&ip6, packet->data + ether_size, ip6_size);
 544         memcpy(&ns, packet->data + ether_size + ip6_size, ns_size);
 545         memcpy(&opt, packet->data + ether_size + ip6_size + ns_size, opt_size);
 546
 547         /* First, snatch the source address from the neighbor solicitation packet */
 548
 549         if(overwrite_mac)
 550                 memcpy(mymac.x, packet->data + ETH_ALEN, ETH_ALEN);
 551
 552         /* Check if this is a valid neighbor solicitation request */
 553
 554         if(ns.nd_ns_hdr.icmp6_type != ND_NEIGHBOR_SOLICIT ||
 555            opt.nd_opt_type != ND_OPT_SOURCE_LINKADDR) {
 556                 ifdebug(TRAFFIC) logger(LOG_WARNING, _("Cannot route packet: received unknown type neighbor solicitation request"));
 557                 return;
 558         }
 559
 560         /* Create pseudo header */
 561
 562         pseudo.ip6_src = ip6.ip6_src;
 563         pseudo.ip6_dst = ip6.ip6_dst;
 564         pseudo.length = htonl(ns_size + opt_size + ETH_ALEN);
 565         pseudo.next = htonl(IPPROTO_ICMPV6);
 566
 567         /* Generate checksum */
 568
 569         checksum = inet_checksum(&pseudo, sizeof(pseudo), ~0);
 570         checksum = inet_checksum(&ns, ns_size, checksum);
 571         checksum = inet_checksum(&opt, opt_size, checksum);
 572         checksum = inet_checksum(packet->data + ether_size + ip6_size + ns_size + opt_size, ETH_ALEN, checksum);
 573
 574         if(checksum) {
 575                 ifdebug(TRAFFIC) logger(LOG_WARNING, _("Cannot route packet: checksum error for neighbor solicitation request"));
 576                 return;
 577         }
 578
 579         /* Check if the IPv6 address exists on the VPN */
 580
 581         subnet = lookup_subnet_ipv6((ipv6_t *) &ns.nd_ns_target);
 582
 583         if(!subnet) {
 584                 ifdebug(TRAFFIC) logger(LOG_WARNING, _("Cannot route packet: neighbor solicitation request for unknown address %hx:%hx:%hx:%hx:%hx:%hx:%hx:%hx"),
 585                                    ntohs(((uint16_t *) &ns.nd_ns_target)[0]),
 586                                    ntohs(((uint16_t *) &ns.nd_ns_target)[1]),
 587                                    ntohs(((uint16_t *) &ns.nd_ns_target)[2]),
 588                                    ntohs(((uint16_t *) &ns.nd_ns_target)[3]),
 589                                    ntohs(((uint16_t *) &ns.nd_ns_target)[4]),
 590                                    ntohs(((uint16_t *) &ns.nd_ns_target)[5]),
 591                                    ntohs(((uint16_t *) &ns.nd_ns_target)[6]),
 592                                    ntohs(((uint16_t *) &ns.nd_ns_target)[7]));
 593
 594                 return;
 595         }
 596
 597         /* Check if it is for our own subnet */
 598
 599         if(subnet->owner == myself)
 600                 return;                                 /* silently ignore */
 601
 602         /* Create neighbor advertation reply */
 603
 604         memcpy(packet->data, packet->data + ETH_ALEN, ETH_ALEN);        /* copy destination address */
 605         packet->data[ETH_ALEN * 2 - 1] ^= 0xFF; /* mangle source address so it looks like it's not from us */
 606
 607         ip6.ip6_dst = ip6.ip6_src;                      /* swap destination and source protocoll address */
 608         ip6.ip6_src = ns.nd_ns_target;
 609
 610         memcpy(packet->data + ether_size + ip6_size + ns_size + opt_size, packet->data + ETH_ALEN, ETH_ALEN);   /* add fake source hard addr */
 611
 612         ns.nd_ns_cksum = 0;
 613         ns.nd_ns_type = ND_NEIGHBOR_ADVERT;
 614         ns.nd_ns_reserved = htonl(0x40000000UL);        /* Set solicited flag */
 615         opt.nd_opt_type = ND_OPT_TARGET_LINKADDR;
 616
 617         /* Create pseudo header */
 618
 619         pseudo.ip6_src = ip6.ip6_src;
 620         pseudo.ip6_dst = ip6.ip6_dst;
 621         pseudo.length = htonl(ns_size + opt_size + ETH_ALEN);
 622         pseudo.next = htonl(IPPROTO_ICMPV6);
 623
 624         /* Generate checksum */
 625
 626         checksum = inet_checksum(&pseudo, sizeof(pseudo), ~0);
 627         checksum = inet_checksum(&ns, ns_size, checksum);
 628         checksum = inet_checksum(&opt, opt_size, checksum);
 629         checksum = inet_checksum(packet->data + ether_size + ip6_size + ns_size + opt_size, ETH_ALEN, checksum);
 630
 631         ns.nd_ns_hdr.icmp6_cksum = checksum;
 632
 633         /* Copy structs on stack back to packet */
 634
 635         memcpy(packet->data + ether_size, &ip6, ip6_size);
 636         memcpy(packet->data + ether_size + ip6_size, &ns, ns_size);
 637         memcpy(packet->data + ether_size + ip6_size + ns_size, &opt, opt_size);
 638
 639         send_packet(source, packet);
 640 }
 641
 642 static __inline__ void route_ipv6(node_t *source, vpn_packet_t *packet)
 643 {
 644         cp();
 645
 646         if(!checklength(source, packet, ether_size + ip6_size))
 647                 return;
 648
 649         if(packet->data[20] == IPPROTO_ICMPV6 && checklength(source, packet, ether_size + ip6_size + icmp6_size) && packet->data[54] == ND_NEIGHBOR_SOLICIT) {
 650                 route_neighborsol(source, packet);
 651                 return;
 652         }
 653
 654         route_ipv6_unicast(source, packet);
 655 }
 656
 657 /* RFC 826 */
 658
 659 static void route_arp(node_t *source, vpn_packet_t *packet)
 660 {
 661         struct ether_arp arp;
 662         subnet_t *subnet;
 663         struct in_addr addr;
 664
 665         cp();
 666
 667         if(!checklength(source, packet, ether_size + arp_size))
 668                 return;
 669
 670         if(source != myself) {
 671                 ifdebug(TRAFFIC) logger(LOG_WARNING, _("Got ARP request from %s (%s) while in router mode!"), source->name, source->hostname);
 672                 return;
 673         }
 674
 675         /* First, snatch the source address from the ARP packet */
 676
 677         if(overwrite_mac)
 678                 memcpy(mymac.x, packet->data + ETH_ALEN, ETH_ALEN);
 679
 680         /* Copy headers from packet to structs on the stack */
 681
 682         memcpy(&arp, packet->data + ether_size, arp_size);
 683
 684         /* Check if this is a valid ARP request */
 685
 686         if(ntohs(arp.arp_hrd) != ARPHRD_ETHER || ntohs(arp.arp_pro) != ETH_P_IP ||
 687            arp.arp_hln != ETH_ALEN || arp.arp_pln != sizeof(addr) || ntohs(arp.arp_op) != ARPOP_REQUEST) {
 688                 ifdebug(TRAFFIC) logger(LOG_WARNING, _("Cannot route packet: received unknown type ARP request"));
 689                 return;
 690         }
 691
 692         /* Check if the IPv4 address exists on the VPN */
 693
 694         subnet = lookup_subnet_ipv4((ipv4_t *) &arp.arp_tpa);
 695
 696         if(!subnet) {
 697                 ifdebug(TRAFFIC) logger(LOG_WARNING, _("Cannot route packet: ARP request for unknown address %d.%d.%d.%d"),
 698                                    arp.arp_tpa[0], arp.arp_tpa[1], arp.arp_tpa[2],
 699                                    arp.arp_tpa[3]);
 700                 return;
 701         }
 702
 703         /* Check if it is for our own subnet */
 704
 705         if(subnet->owner == myself)
 706                 return;                                 /* silently ignore */
 707
 708         memcpy(packet->data, packet->data + ETH_ALEN, ETH_ALEN);        /* copy destination address */
 709         packet->data[ETH_ALEN * 2 - 1] ^= 0xFF; /* mangle source address so it looks like it's not from us */
 710
 711         memcpy(&addr, arp.arp_tpa, sizeof(addr));       /* save protocol addr */
 712         memcpy(arp.arp_tpa, arp.arp_spa, sizeof(addr)); /* swap destination and source protocol address */
 713         memcpy(arp.arp_spa, &addr, sizeof(addr));       /* ... */
 714
 715         memcpy(arp.arp_tha, arp.arp_sha, ETH_ALEN);     /* set target hard/proto addr */
 716         memcpy(arp.arp_sha, packet->data + ETH_ALEN, ETH_ALEN); /* add fake source hard addr */
 717         arp.arp_op = htons(ARPOP_REPLY);
 718
 719         /* Copy structs on stack back to packet */
 720
 721         memcpy(packet->data + ether_size, &arp, arp_size);
 722
 723         send_packet(source, packet);
 724 }
 725
 726 void route(node_t *source, vpn_packet_t *packet)
 727 {
 728         cp();
 729
 730         if(!checklength(source, packet, ether_size))
 731                 return;
 732
 733         switch (routing_mode) {
 734                 case RMODE_ROUTER:
 735                         {
 736                                 uint16_t type;
 737
 738                                 type = ntohs(*((uint16_t *)(&packet->data[12])));
 739                                 switch (type) {
 740                                         case ETH_P_ARP:
 741                                                 route_arp(source, packet);
 742                                                 break;
 743
 744                                         case ETH_P_IP:
 745                                                 route_ipv4(source, packet);
 746                                                 break;
 747
 748                                         case ETH_P_IPV6:
 749                                                 route_ipv6(source, packet);
 750                                                 break;
 751
 752                                         default:
 753                                                 ifdebug(TRAFFIC) logger(LOG_WARNING, _("Cannot route packet from %s (%s): unknown type %hx"), source->name, source->hostname, type);
 754                                                 break;
 755                                 }
 756                         }
 757                         break;
 758
 759                 case RMODE_SWITCH:
 760                         route_mac(source, packet);
 761                         break;
 762
 763                 case RMODE_HUB:
 764                         broadcast_packet(source, packet);
 765                         break;
 766         }
 767 }