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

   1 /*
   2     route.c -- routing
   3     Copyright (C) 2000-2003 Ivo Timmermans <ivo@o2w.nl>,
   4                   2000-2003 Guus Sliepen <guus@sliepen.eu.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: route.c,v 1.1.2.74 2003/12/22 11:04:17 guus Exp $
  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
 335         cp();
 336
 337         subnet = lookup_subnet_ipv4((ipv4_t *) &packet->data[30]);
 338
 339         if(!subnet) {
 340                 ifdebug(TRAFFIC) logger(LOG_WARNING, _("Cannot route packet from %s (%s): unknown IPv4 destination address %d.%d.%d.%d"),
 341                                 source->name, source->hostname,
 342                                 packet->data[30],
 343                                 packet->data[31],
 344                                 packet->data[32],
 345                                 packet->data[33]);
 346
 347                 route_ipv4_unreachable(source, packet, ICMP_DEST_UNREACH, ICMP_NET_UNKNOWN);
 348                 return;
 349         }
 350
 351         if(subnet->owner == source) {
 352                 ifdebug(TRAFFIC) logger(LOG_WARNING, _("Packet looping back to %s (%s)!"), source->name, source->hostname);
 353                 return;
 354         }
 355
 356         if(!subnet->owner->status.reachable)
 357                 route_ipv4_unreachable(source, packet, ICMP_DEST_UNREACH, ICMP_NET_UNREACH);
 358
 359         if(priorityinheritance)
 360                 packet->priority = packet->data[15];
 361
 362         if(subnet->owner->options & OPTION_PMTU_DISCOVERY && packet->len > subnet->owner->mtu && subnet->owner != myself) {
 363                 ifdebug(TRAFFIC) logger(LOG_INFO, _("Packet for %s (%s) length %d larger than MTU %d"), subnet->owner->name, subnet->owner->hostname, packet->len, subnet->owner->mtu);
 364                 if(packet->data[20] & 0x40) {
 365                         packet->len = subnet->owner->mtu;
 366                         route_ipv4_unreachable(source, packet, ICMP_DEST_UNREACH, ICMP_FRAG_NEEDED);
 367                 } else {
 368                         fragment_ipv4_packet(subnet->owner, packet);
 369                 }
 370
 371                 return;
 372         }
 373
 374         send_packet(subnet->owner, packet);
 375 }
 376
 377 static __inline__ void route_ipv4(node_t *source, vpn_packet_t *packet)
 378 {
 379         cp();
 380
 381         if(!checklength(source, packet, ether_size + ip_size))
 382                 return;
 383
 384         route_ipv4_unicast(source, packet);
 385 }
 386
 387 /* RFC 2463 */
 388
 389 static void route_ipv6_unreachable(node_t *source, vpn_packet_t *packet, uint8_t type, uint8_t code)
 390 {
 391         struct ip6_hdr ip6;
 392         struct icmp6_hdr icmp6 = {0};
 393         uint16_t checksum;
 394
 395         struct {
 396                 struct in6_addr ip6_src;        /* source address */
 397                 struct in6_addr ip6_dst;        /* destination address */
 398                 uint32_t length;
 399                 uint32_t next;
 400         } pseudo;
 401
 402         if(ratelimit(3))
 403                 return;
 404
 405         cp();
 406
 407         /* Copy headers from packet to structs on the stack */
 408
 409         memcpy(&ip6, packet->data + ether_size, ip6_size);
 410
 411         /* Remember original source and destination */
 412
 413         pseudo.ip6_src = ip6.ip6_dst;
 414         pseudo.ip6_dst = ip6.ip6_src;
 415
 416         pseudo.length = packet->len - ether_size;
 417
 418         if(type == ICMP6_PACKET_TOO_BIG)
 419                 icmp6.icmp6_mtu = htonl(pseudo.length);
 420
 421         if(pseudo.length >= IP_MSS - ip6_size - icmp6_size)
 422                 pseudo.length = IP_MSS - ip6_size - icmp6_size;
 423
 424         /* Copy first part of original contents to ICMP message */
 425
 426         memmove(packet->data + ether_size + ip6_size + icmp6_size, packet->data + ether_size, pseudo.length);
 427
 428         /* Fill in IPv6 header */
 429
 430         ip6.ip6_flow = htonl(0x60000000UL);
 431         ip6.ip6_plen = htons(icmp6_size + pseudo.length);
 432         ip6.ip6_nxt = IPPROTO_ICMPV6;
 433         ip6.ip6_hlim = 255;
 434         ip6.ip6_src = pseudo.ip6_src;
 435         ip6.ip6_dst = pseudo.ip6_dst;
 436
 437         /* Fill in ICMP header */
 438
 439         icmp6.icmp6_type = type;
 440         icmp6.icmp6_code = code;
 441         icmp6.icmp6_cksum = 0;
 442
 443         /* Create pseudo header */
 444
 445         pseudo.length = htonl(icmp6_size + pseudo.length);
 446         pseudo.next = htonl(IPPROTO_ICMPV6);
 447
 448         /* Generate checksum */
 449
 450         checksum = inet_checksum(&pseudo, sizeof(pseudo), ~0);
 451         checksum = inet_checksum(&icmp6, icmp6_size, checksum);
 452         checksum = inet_checksum(packet->data + ether_size + ip6_size + icmp6_size, ntohl(pseudo.length) - icmp6_size, checksum);
 453
 454         icmp6.icmp6_cksum = checksum;
 455
 456         /* Copy structs on stack back to packet */
 457
 458         memcpy(packet->data + ether_size, &ip6, ip6_size);
 459         memcpy(packet->data + ether_size + ip6_size, &icmp6, icmp6_size);
 460
 461         packet->len = ether_size + ip6_size + ntohl(pseudo.length);
 462
 463         send_packet(source, packet);
 464 }
 465
 466 static __inline__ void route_ipv6_unicast(node_t *source, vpn_packet_t *packet)
 467 {
 468         subnet_t *subnet;
 469
 470         cp();
 471
 472         subnet = lookup_subnet_ipv6((ipv6_t *) &packet->data[38]);
 473
 474         if(!subnet) {
 475                 ifdebug(TRAFFIC) logger(LOG_WARNING, _("Cannot route packet from %s (%s): unknown IPv6 destination address %hx:%hx:%hx:%hx:%hx:%hx:%hx:%hx"),
 476                                 source->name, source->hostname,
 477                                 ntohs(*(uint16_t *) &packet->data[38]),
 478                                 ntohs(*(uint16_t *) &packet->data[40]),
 479                                 ntohs(*(uint16_t *) &packet->data[42]),
 480                                 ntohs(*(uint16_t *) &packet->data[44]),
 481                                 ntohs(*(uint16_t *) &packet->data[46]),
 482                                 ntohs(*(uint16_t *) &packet->data[48]),
 483                                 ntohs(*(uint16_t *) &packet->data[50]),
 484                                 ntohs(*(uint16_t *) &packet->data[52]));
 485
 486                 route_ipv6_unreachable(source, packet, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_ADDR);
 487                 return;
 488         }
 489
 490         if(subnet->owner == source) {
 491                 ifdebug(TRAFFIC) logger(LOG_WARNING, _("Packet looping back to %s (%s)!"), source->name, source->hostname);
 492                 return;
 493         }
 494
 495         if(!subnet->owner->status.reachable)
 496                 route_ipv6_unreachable(source, packet, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_NOROUTE);
 497
 498         if(subnet->owner->options & OPTION_PMTU_DISCOVERY && packet->len > subnet->owner->mtu && subnet->owner != 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, subnet->owner->mtu);
 500                 packet->len = subnet->owner->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 __inline__ 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 }