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
  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 "splay_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 static struct event age_subnets_event;
  55
  56 /* RFC 1071 */
  57
  58 static uint16_t inet_checksum(void *data, int len, uint16_t prevsum)
  59 {
  60         uint16_t *p = data;
  61         uint32_t checksum = prevsum ^ 0xFFFF;
  62
  63         while(len >= 2) {
  64                 checksum += *p++;
  65                 len -= 2;
  66         }
  67
  68         if(len)
  69                 checksum += *(uint8_t *)p;
  70
  71         while(checksum >> 16)
  72                 checksum = (checksum & 0xFFFF) + (checksum >> 16);
  73
  74         return ~checksum;
  75 }
  76
  77 static bool ratelimit(int frequency) {
  78         static time_t lasttime = 0;
  79         static int count = 0;
  80         time_t now = time(NULL);
  81
  82         if(lasttime == now) {
  83                 if(++count > frequency)
  84                         return true;
  85         } else {
  86                 lasttime = now;
  87                 count = 0;
  88         }
  89
  90         return false;
  91 }
  92
  93 static bool checklength(node_t *source, vpn_packet_t *packet, length_t length) {
  94         if(packet->len < length) {
  95                 ifdebug(TRAFFIC) logger(LOG_WARNING, _("Got too short packet from %s (%s)"), source->name, source->hostname);
  96                 return false;
  97         } else
  98                 return true;
  99 }
 100
 101 static void swap_mac_addresses(vpn_packet_t *packet) {
 102         mac_t tmp;
 103         memcpy(&tmp, &packet->data[0], sizeof tmp);
 104         memcpy(&packet->data[0], &packet->data[6], sizeof tmp);
 105         memcpy(&packet->data[6], &tmp, sizeof tmp);
 106 }
 107
 108 static void age_subnets(int fd, short events, void *data)
 109 {
 110         subnet_t *s;
 111         connection_t *c;
 112         splay_node_t *node, *next, *node2;
 113         bool left = false;
 114         time_t now = time(NULL);
 115
 116         cp();
 117
 118         for(node = myself->subnet_tree->head; node; node = next) {
 119                 next = node->next;
 120                 s = node->data;
 121                 if(s->expires && s->expires < now) {
 122                         ifdebug(TRAFFIC) {
 123                                 char netstr[MAXNETSTR];
 124                                 if(net2str(netstr, sizeof netstr, s))
 125                                         logger(LOG_INFO, _("Subnet %s expired"), netstr);
 126                         }
 127
 128                         for(node2 = connection_tree->head; node2; node2 = node2->next) {
 129                                 c = node2->data;
 130                                 if(c->status.active)
 131                                         send_del_subnet(c, s);
 132                         }
 133
 134                         subnet_del(myself, s);
 135                 } else {
 136                         if(s->expires)
 137                                 left = true;
 138                 }
 139         }
 140
 141         if(left)
 142                 event_add(&age_subnets_event, &(struct timeval){10, 0});
 143 }
 144
 145 static void learn_mac(mac_t *address)
 146 {
 147         subnet_t *subnet;
 148         splay_node_t *node;
 149         connection_t *c;
 150
 151         cp();
 152
 153         subnet = lookup_subnet_mac(address);
 154
 155         /* If we don't know this MAC address yet, store it */
 156
 157         if(!subnet) {
 158                 ifdebug(TRAFFIC) logger(LOG_INFO, _("Learned new MAC address %hx:%hx:%hx:%hx:%hx:%hx"),
 159                                    address->x[0], address->x[1], address->x[2], address->x[3],
 160                                    address->x[4], address->x[5]);
 161
 162                 subnet = new_subnet();
 163                 subnet->type = SUBNET_MAC;
 164                 subnet->expires = time(NULL) + macexpire;
 165                 subnet->net.mac.address = *address;
 166                 subnet_add(myself, subnet);
 167
 168                 /* And tell all other tinc daemons it's our MAC */
 169
 170                 for(node = connection_tree->head; node; node = node->next) {
 171                         c = node->data;
 172                         if(c->status.active)
 173                                 send_add_subnet(c, subnet);
 174                 }
 175
 176                 if(!timeout_initialized(&age_subnets_event))
 177                         timeout_set(&age_subnets_event, age_subnets, NULL);
 178                 event_add(&age_subnets_event, &(struct timeval){10, 0});
 179         } else {
 180                 if(subnet->expires)
 181                         subnet->expires = time(NULL) + macexpire;
 182         }
 183 }
 184
 185 /* RFC 792 */
 186
 187 static void route_ipv4_unreachable(node_t *source, vpn_packet_t *packet, uint8_t type, uint8_t code)
 188 {
 189         struct ip ip = {0};
 190         struct icmp icmp = {0};
 191
 192         struct in_addr ip_src;
 193         struct in_addr ip_dst;
 194         uint32_t oldlen;
 195
 196         if(ratelimit(3))
 197                 return;
 198
 199         cp();
 200
 201         /* Swap Ethernet source and destination addresses */
 202
 203         swap_mac_addresses(packet);
 204
 205         /* Copy headers from packet into properly aligned structs on the stack */
 206
 207         memcpy(&ip, packet->data + ether_size, ip_size);
 208
 209         /* Remember original source and destination */
 210
 211         ip_src = ip.ip_src;
 212         ip_dst = ip.ip_dst;
 213
 214         oldlen = packet->len - ether_size;
 215
 216         if(type == ICMP_DEST_UNREACH && code == ICMP_FRAG_NEEDED)
 217                 icmp.icmp_nextmtu = htons(packet->len - ether_size);
 218
 219         if(oldlen >= IP_MSS - ip_size - icmp_size)
 220                 oldlen = IP_MSS - ip_size - icmp_size;
 221
 222         /* Copy first part of original contents to ICMP message */
 223
 224         memmove(packet->data + ether_size + ip_size + icmp_size, packet->data + ether_size, oldlen);
 225
 226         /* Fill in IPv4 header */
 227
 228         ip.ip_v = 4;
 229         ip.ip_hl = ip_size / 4;
 230         ip.ip_tos = 0;
 231         ip.ip_len = htons(ip_size + icmp_size + oldlen);
 232         ip.ip_id = 0;
 233         ip.ip_off = 0;
 234         ip.ip_ttl = 255;
 235         ip.ip_p = IPPROTO_ICMP;
 236         ip.ip_sum = 0;
 237         ip.ip_src = ip_dst;
 238         ip.ip_dst = ip_src;
 239
 240         ip.ip_sum = inet_checksum(&ip, ip_size, ~0);
 241
 242         /* Fill in ICMP header */
 243
 244         icmp.icmp_type = type;
 245         icmp.icmp_code = code;
 246         icmp.icmp_cksum = 0;
 247
 248         icmp.icmp_cksum = inet_checksum(&icmp, icmp_size, ~0);
 249         icmp.icmp_cksum = inet_checksum(packet->data + ether_size + ip_size + icmp_size, oldlen, icmp.icmp_cksum);
 250
 251         /* Copy structs on stack back to packet */
 252
 253         memcpy(packet->data + ether_size, &ip, ip_size);
 254         memcpy(packet->data + ether_size + ip_size, &icmp, icmp_size);
 255
 256         packet->len = ether_size + ip_size + icmp_size + oldlen;
 257
 258         send_packet(source, packet);
 259 }
 260
 261 /* RFC 791 */
 262
 263 static void fragment_ipv4_packet(node_t *dest, vpn_packet_t *packet) {
 264         struct ip ip;
 265         vpn_packet_t fragment;
 266         int len, maxlen, todo;
 267         uint8_t *offset;
 268         uint16_t ip_off, origf;
 269
 270         cp();
 271
 272         memcpy(&ip, packet->data + ether_size, ip_size);
 273         fragment.priority = packet->priority;
 274
 275         if(ip.ip_hl != ip_size / 4)
 276                 return;
 277
 278         todo = ntohs(ip.ip_len) - ip_size;
 279
 280         if(ether_size + ip_size + todo != packet->len) {
 281                 ifdebug(TRAFFIC) logger(LOG_WARNING, _("Length of packet (%d) doesn't match length in IPv4 header (%zd)"), packet->len, ether_size + ip_size + todo);
 282                 return;
 283         }
 284
 285         ifdebug(TRAFFIC) logger(LOG_INFO, _("Fragmenting packet of %d bytes to %s (%s)"), packet->len, dest->name, dest->hostname);
 286
 287         offset = packet->data + ether_size + ip_size;
 288         maxlen = (dest->mtu - ether_size - ip_size) & ~0x7;
 289         ip_off = ntohs(ip.ip_off);
 290         origf = ip_off & ~IP_OFFMASK;
 291         ip_off &= IP_OFFMASK;
 292
 293         while(todo) {
 294                 len = todo > maxlen ? maxlen : todo;
 295                 memcpy(fragment.data + ether_size + ip_size, offset, len);
 296                 todo -= len;
 297                 offset += len;
 298
 299                 ip.ip_len = htons(ip_size + len);
 300                 ip.ip_off = htons(ip_off | origf | (todo ? IP_MF : 0));
 301                 ip.ip_sum = 0;
 302                 ip.ip_sum = inet_checksum(&ip, ip_size, ~0);
 303                 memcpy(fragment.data, packet->data, ether_size);
 304                 memcpy(fragment.data + ether_size, &ip, ip_size);
 305                 fragment.len = ether_size + ip_size + len;
 306
 307                 send_packet(dest, &fragment);
 308
 309                 ip_off += len / 8;
 310         }
 311 }
 312
 313 static void route_ipv4_unicast(node_t *source, vpn_packet_t *packet)
 314 {
 315         subnet_t *subnet;
 316         node_t *via;
 317         ipv4_t dest;
 318
 319         cp();
 320
 321         memcpy(&dest, &packet->data[30], sizeof dest);
 322         subnet = lookup_subnet_ipv4(&dest);
 323
 324         if(!subnet) {
 325                 ifdebug(TRAFFIC) logger(LOG_WARNING, _("Cannot route packet from %s (%s): unknown IPv4 destination address %d.%d.%d.%d"),
 326                                 source->name, source->hostname,
 327                                 dest.x[0],
 328                                 dest.x[1],
 329                                 dest.x[2],
 330                                 dest.x[3]);
 331
 332                 route_ipv4_unreachable(source, packet, ICMP_DEST_UNREACH, ICMP_NET_UNKNOWN);
 333                 return;
 334         }
 335
 336         if(subnet->owner == source) {
 337                 ifdebug(TRAFFIC) logger(LOG_WARNING, _("Packet looping back to %s (%s)!"), source->name, source->hostname);
 338                 return;
 339         }
 340
 341         if(!subnet->owner->status.reachable)
 342                 route_ipv4_unreachable(source, packet, ICMP_DEST_UNREACH, ICMP_NET_UNREACH);
 343
 344         if(priorityinheritance)
 345                 packet->priority = packet->data[15];
 346
 347         via = (subnet->owner->via == myself) ? subnet->owner->nexthop : subnet->owner->via;
 348
 349         if(via && packet->len > via->mtu && via != myself) {
 350                 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);
 351                 if(packet->data[20] & 0x40) {
 352                         packet->len = via->mtu;
 353                         route_ipv4_unreachable(source, packet, ICMP_DEST_UNREACH, ICMP_FRAG_NEEDED);
 354                 } else {
 355                         fragment_ipv4_packet(via, packet);
 356                 }
 357
 358                 return;
 359         }
 360
 361         send_packet(subnet->owner, packet);
 362 }
 363
 364 static void route_ipv4(node_t *source, vpn_packet_t *packet)
 365 {
 366         cp();
 367
 368         if(!checklength(source, packet, ether_size + ip_size))
 369                 return;
 370
 371         if(((packet->data[30] & 0xf0) == 0xe0) || (
 372                         packet->data[30] == 255 &&
 373                         packet->data[31] == 255 &&
 374                         packet->data[32] == 255 &&
 375                         packet->data[33] == 255))
 376                 broadcast_packet(source, packet);
 377         else
 378                 route_ipv4_unicast(source, packet);
 379 }
 380
 381 /* RFC 2463 */
 382
 383 static void route_ipv6_unreachable(node_t *source, vpn_packet_t *packet, uint8_t type, uint8_t code)
 384 {
 385         struct ip6_hdr ip6;
 386         struct icmp6_hdr icmp6 = {0};
 387         uint16_t checksum;
 388
 389         struct {
 390                 struct in6_addr ip6_src;        /* source address */
 391                 struct in6_addr ip6_dst;        /* destination address */
 392                 uint32_t length;
 393                 uint32_t next;
 394         } pseudo;
 395
 396         if(ratelimit(3))
 397                 return;
 398
 399         cp();
 400
 401         /* Swap Ethernet source and destination addresses */
 402
 403         swap_mac_addresses(packet);
 404
 405         /* Copy headers from packet to structs on the stack */
 406
 407         memcpy(&ip6, packet->data + ether_size, ip6_size);
 408
 409         /* Remember original source and destination */
 410
 411         pseudo.ip6_src = ip6.ip6_dst;
 412         pseudo.ip6_dst = ip6.ip6_src;
 413
 414         pseudo.length = packet->len - ether_size;
 415
 416         if(type == ICMP6_PACKET_TOO_BIG)
 417                 icmp6.icmp6_mtu = htonl(pseudo.length);
 418
 419         if(pseudo.length >= IP_MSS - ip6_size - icmp6_size)
 420                 pseudo.length = IP_MSS - ip6_size - icmp6_size;
 421
 422         /* Copy first part of original contents to ICMP message */
 423
 424         memmove(packet->data + ether_size + ip6_size + icmp6_size, packet->data + ether_size, pseudo.length);
 425
 426         /* Fill in IPv6 header */
 427
 428         ip6.ip6_flow = htonl(0x60000000UL);
 429         ip6.ip6_plen = htons(icmp6_size + pseudo.length);
 430         ip6.ip6_nxt = IPPROTO_ICMPV6;
 431         ip6.ip6_hlim = 255;
 432         ip6.ip6_src = pseudo.ip6_src;
 433         ip6.ip6_dst = pseudo.ip6_dst;
 434
 435         /* Fill in ICMP header */
 436
 437         icmp6.icmp6_type = type;
 438         icmp6.icmp6_code = code;
 439         icmp6.icmp6_cksum = 0;
 440
 441         /* Create pseudo header */
 442
 443         pseudo.length = htonl(icmp6_size + pseudo.length);
 444         pseudo.next = htonl(IPPROTO_ICMPV6);
 445
 446         /* Generate checksum */
 447
 448         checksum = inet_checksum(&pseudo, sizeof pseudo, ~0);
 449         checksum = inet_checksum(&icmp6, icmp6_size, checksum);
 450         checksum = inet_checksum(packet->data + ether_size + ip6_size + icmp6_size, ntohl(pseudo.length) - icmp6_size, checksum);
 451
 452         icmp6.icmp6_cksum = checksum;
 453
 454         /* Copy structs on stack back to packet */
 455
 456         memcpy(packet->data + ether_size, &ip6, ip6_size);
 457         memcpy(packet->data + ether_size + ip6_size, &icmp6, icmp6_size);
 458
 459         packet->len = ether_size + ip6_size + ntohl(pseudo.length);
 460
 461         send_packet(source, packet);
 462 }
 463
 464 static void route_ipv6_unicast(node_t *source, vpn_packet_t *packet)
 465 {
 466         subnet_t *subnet;
 467         node_t *via;
 468         ipv6_t dest;
 469
 470         cp();
 471
 472         memcpy(&dest, &packet->data[38], sizeof dest);
 473         subnet = lookup_subnet_ipv6(&dest);
 474
 475         if(!subnet) {
 476                 ifdebug(TRAFFIC) logger(LOG_WARNING, _("Cannot route packet from %s (%s): unknown IPv6 destination address %hx:%hx:%hx:%hx:%hx:%hx:%hx:%hx"),
 477                                 source->name, source->hostname,
 478                                 ntohs(dest.x[0]),
 479                                 ntohs(dest.x[1]),
 480                                 ntohs(dest.x[2]),
 481                                 ntohs(dest.x[3]),
 482                                 ntohs(dest.x[4]),
 483                                 ntohs(dest.x[5]),
 484                                 ntohs(dest.x[6]),
 485                                 ntohs(dest.x[7]));
 486
 487                 route_ipv6_unreachable(source, packet, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_ADDR);
 488                 return;
 489         }
 490
 491         if(subnet->owner == source) {
 492                 ifdebug(TRAFFIC) logger(LOG_WARNING, _("Packet looping back to %s (%s)!"), source->name, source->hostname);
 493                 return;
 494         }
 495
 496         if(!subnet->owner->status.reachable)
 497                 route_ipv6_unreachable(source, packet, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_NOROUTE);
 498
 499         via = (subnet->owner->via == myself) ? subnet->owner->nexthop : subnet->owner->via;
 500
 501         if(via && packet->len > via->mtu && via != myself) {
 502                 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);
 503                 packet->len = via->mtu;
 504                 route_ipv6_unreachable(source, packet, ICMP6_PACKET_TOO_BIG, 0);
 505                 return;
 506         }
 507
 508         send_packet(subnet->owner, packet);
 509 }
 510
 511 /* RFC 2461 */
 512
 513 static void route_neighborsol(node_t *source, vpn_packet_t *packet)
 514 {
 515         struct ip6_hdr ip6;
 516         struct nd_neighbor_solicit ns;
 517         struct nd_opt_hdr opt;
 518         subnet_t *subnet;
 519         uint16_t checksum;
 520         bool has_opt;
 521
 522         struct {
 523                 struct in6_addr ip6_src;        /* source address */
 524                 struct in6_addr ip6_dst;        /* destination address */
 525                 uint32_t length;
 526                 uint32_t next;
 527         } pseudo;
 528
 529         cp();
 530
 531         if(!checklength(source, packet, ether_size + ip6_size + ns_size))
 532                 return;
 533
 534         has_opt = packet->len >= ether_size + ip6_size + ns_size + opt_size + ETH_ALEN;
 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         if(has_opt)
 546                 memcpy(&opt, packet->data + ether_size + ip6_size + ns_size, opt_size);
 547
 548         /* First, snatch the source address from the neighbor solicitation packet */
 549
 550         if(overwrite_mac)
 551                 memcpy(mymac.x, packet->data + ETH_ALEN, ETH_ALEN);
 552
 553         /* Check if this is a valid neighbor solicitation request */
 554
 555         if(ns.nd_ns_hdr.icmp6_type != ND_NEIGHBOR_SOLICIT ||
 556            (has_opt && opt.nd_opt_type != ND_OPT_SOURCE_LINKADDR)) {
 557                 ifdebug(TRAFFIC) logger(LOG_WARNING, _("Cannot route packet: received unknown type neighbor solicitation request"));
 558                 return;
 559         }
 560
 561         /* Create pseudo header */
 562
 563         pseudo.ip6_src = ip6.ip6_src;
 564         pseudo.ip6_dst = ip6.ip6_dst;
 565         if(has_opt)
 566                 pseudo.length = htonl(ns_size + opt_size + ETH_ALEN);
 567         else
 568                 pseudo.length = htonl(ns_size);
 569         pseudo.next = htonl(IPPROTO_ICMPV6);
 570
 571         /* Generate checksum */
 572
 573         checksum = inet_checksum(&pseudo, sizeof pseudo, ~0);
 574         checksum = inet_checksum(&ns, ns_size, checksum);
 575         if(has_opt) {
 576                 checksum = inet_checksum(&opt, opt_size, checksum);
 577                 checksum = inet_checksum(packet->data + ether_size + ip6_size + ns_size + opt_size, ETH_ALEN, checksum);
 578         }
 579
 580         if(checksum) {
 581                 ifdebug(TRAFFIC) logger(LOG_WARNING, _("Cannot route packet: checksum error for neighbor solicitation request"));
 582                 return;
 583         }
 584
 585         /* Check if the IPv6 address exists on the VPN */
 586
 587         subnet = lookup_subnet_ipv6((ipv6_t *) &ns.nd_ns_target);
 588
 589         if(!subnet) {
 590                 ifdebug(TRAFFIC) logger(LOG_WARNING, _("Cannot route packet: neighbor solicitation request for unknown address %hx:%hx:%hx:%hx:%hx:%hx:%hx:%hx"),
 591                                    ntohs(((uint16_t *) &ns.nd_ns_target)[0]),
 592                                    ntohs(((uint16_t *) &ns.nd_ns_target)[1]),
 593                                    ntohs(((uint16_t *) &ns.nd_ns_target)[2]),
 594                                    ntohs(((uint16_t *) &ns.nd_ns_target)[3]),
 595                                    ntohs(((uint16_t *) &ns.nd_ns_target)[4]),
 596                                    ntohs(((uint16_t *) &ns.nd_ns_target)[5]),
 597                                    ntohs(((uint16_t *) &ns.nd_ns_target)[6]),
 598                                    ntohs(((uint16_t *) &ns.nd_ns_target)[7]));
 599
 600                 return;
 601         }
 602
 603         /* Check if it is for our own subnet */
 604
 605         if(subnet->owner == myself)
 606                 return;                                 /* silently ignore */
 607
 608         /* Create neighbor advertation reply */
 609
 610         memcpy(packet->data, packet->data + ETH_ALEN, ETH_ALEN);        /* copy destination address */
 611         packet->data[ETH_ALEN * 2 - 1] ^= 0xFF; /* mangle source address so it looks like it's not from us */
 612
 613         ip6.ip6_dst = ip6.ip6_src;                      /* swap destination and source protocoll address */
 614         ip6.ip6_src = ns.nd_ns_target;
 615
 616         if(has_opt)
 617                 memcpy(packet->data + ether_size + ip6_size + ns_size + opt_size, packet->data + ETH_ALEN, ETH_ALEN);   /* add fake source hard addr */
 618
 619         ns.nd_ns_cksum = 0;
 620         ns.nd_ns_type = ND_NEIGHBOR_ADVERT;
 621         ns.nd_ns_reserved = htonl(0x40000000UL);        /* Set solicited flag */
 622         opt.nd_opt_type = ND_OPT_TARGET_LINKADDR;
 623
 624         /* Create pseudo header */
 625
 626         pseudo.ip6_src = ip6.ip6_src;
 627         pseudo.ip6_dst = ip6.ip6_dst;
 628         if(has_opt)
 629                 pseudo.length = htonl(ns_size + opt_size + ETH_ALEN);
 630         else
 631                 pseudo.length = htonl(ns_size);
 632         pseudo.next = htonl(IPPROTO_ICMPV6);
 633
 634         /* Generate checksum */
 635
 636         checksum = inet_checksum(&pseudo, sizeof pseudo, ~0);
 637         checksum = inet_checksum(&ns, ns_size, checksum);
 638         if(has_opt) {
 639                 checksum = inet_checksum(&opt, opt_size, checksum);
 640                 checksum = inet_checksum(packet->data + ether_size + ip6_size + ns_size + opt_size, ETH_ALEN, checksum);
 641         }
 642
 643         ns.nd_ns_hdr.icmp6_cksum = checksum;
 644
 645         /* Copy structs on stack back to packet */
 646
 647         memcpy(packet->data + ether_size, &ip6, ip6_size);
 648         memcpy(packet->data + ether_size + ip6_size, &ns, ns_size);
 649         if(has_opt)
 650                 memcpy(packet->data + ether_size + ip6_size + ns_size, &opt, opt_size);
 651
 652         send_packet(source, packet);
 653 }
 654
 655 static void route_ipv6(node_t *source, vpn_packet_t *packet)
 656 {
 657         cp();
 658
 659         if(!checklength(source, packet, ether_size + ip6_size))
 660                 return;
 661
 662         if(packet->data[20] == IPPROTO_ICMPV6 && checklength(source, packet, ether_size + ip6_size + icmp6_size) && packet->data[54] == ND_NEIGHBOR_SOLICIT) {
 663                 route_neighborsol(source, packet);
 664                 return;
 665         }
 666
 667         if(packet->data[38] == 255)
 668                 broadcast_packet(source, packet);
 669         else
 670                 route_ipv6_unicast(source, packet);
 671 }
 672
 673 /* RFC 826 */
 674
 675 static void route_arp(node_t *source, vpn_packet_t *packet)
 676 {
 677         struct ether_arp arp;
 678         subnet_t *subnet;
 679         struct in_addr addr;
 680
 681         cp();
 682
 683         if(!checklength(source, packet, ether_size + arp_size))
 684                 return;
 685
 686         if(source != myself) {
 687                 ifdebug(TRAFFIC) logger(LOG_WARNING, _("Got ARP request from %s (%s) while in router mode!"), source->name, source->hostname);
 688                 return;
 689         }
 690
 691         /* First, snatch the source address from the ARP packet */
 692
 693         if(overwrite_mac)
 694                 memcpy(mymac.x, packet->data + ETH_ALEN, ETH_ALEN);
 695
 696         /* Copy headers from packet to structs on the stack */
 697
 698         memcpy(&arp, packet->data + ether_size, arp_size);
 699
 700         /* Check if this is a valid ARP request */
 701
 702         if(ntohs(arp.arp_hrd) != ARPHRD_ETHER || ntohs(arp.arp_pro) != ETH_P_IP ||
 703            arp.arp_hln != ETH_ALEN || arp.arp_pln != sizeof addr || ntohs(arp.arp_op) != ARPOP_REQUEST) {
 704                 ifdebug(TRAFFIC) logger(LOG_WARNING, _("Cannot route packet: received unknown type ARP request"));
 705                 return;
 706         }
 707
 708         /* Check if the IPv4 address exists on the VPN */
 709
 710         subnet = lookup_subnet_ipv4((ipv4_t *) &arp.arp_tpa);
 711
 712         if(!subnet) {
 713                 ifdebug(TRAFFIC) logger(LOG_WARNING, _("Cannot route packet: ARP request for unknown address %d.%d.%d.%d"),
 714                                    arp.arp_tpa[0], arp.arp_tpa[1], arp.arp_tpa[2],
 715                                    arp.arp_tpa[3]);
 716                 return;
 717         }
 718
 719         /* Check if it is for our own subnet */
 720
 721         if(subnet->owner == myself)
 722                 return;                                 /* silently ignore */
 723
 724         memcpy(packet->data, packet->data + ETH_ALEN, ETH_ALEN);        /* copy destination address */
 725         packet->data[ETH_ALEN * 2 - 1] ^= 0xFF; /* mangle source address so it looks like it's not from us */
 726
 727         memcpy(&addr, arp.arp_tpa, sizeof addr);        /* save protocol addr */
 728         memcpy(arp.arp_tpa, arp.arp_spa, sizeof addr);  /* swap destination and source protocol address */
 729         memcpy(arp.arp_spa, &addr, sizeof addr);        /* ... */
 730
 731         memcpy(arp.arp_tha, arp.arp_sha, ETH_ALEN);     /* set target hard/proto addr */
 732         memcpy(arp.arp_sha, packet->data + ETH_ALEN, ETH_ALEN); /* add fake source hard addr */
 733         arp.arp_op = htons(ARPOP_REPLY);
 734
 735         /* Copy structs on stack back to packet */
 736
 737         memcpy(packet->data + ether_size, &arp, arp_size);
 738
 739         send_packet(source, packet);
 740 }
 741
 742 static void route_mac(node_t *source, vpn_packet_t *packet)
 743 {
 744         subnet_t *subnet;
 745         mac_t dest;
 746
 747         cp();
 748
 749
 750         /* Learn source address */
 751
 752         if(source == myself) {
 753                 mac_t src;
 754                 memcpy(&src, &packet->data[6], sizeof src);
 755                 learn_mac(&src);
 756         }
 757
 758         /* Lookup destination address */
 759
 760         memcpy(&dest, &packet->data[0], sizeof dest);
 761         subnet = lookup_subnet_mac(&dest);
 762
 763         if(!subnet) {
 764                 broadcast_packet(source, packet);
 765                 return;
 766         }
 767
 768         if(subnet->owner == source) {
 769                 ifdebug(TRAFFIC) logger(LOG_WARNING, _("Packet looping back to %s (%s)!"), source->name, source->hostname);
 770                 return;
 771         }
 772
 773         // Handle packets larger than PMTU
 774
 775         node_t *via = (subnet->owner->via == myself) ? subnet->owner->nexthop : subnet->owner->via;
 776
 777         if(via && packet->len > via->mtu && via != myself) {
 778                 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);
 779                 uint16_t type = packet->data[12] << 8 | packet->data[13];
 780                 if(type == ETH_P_IP) {
 781                         if(packet->data[20] & 0x40) {
 782                                 packet->len = via->mtu;
 783                                 route_ipv4_unreachable(source, packet, ICMP_DEST_UNREACH, ICMP_FRAG_NEEDED);
 784                         } else {
 785                                 fragment_ipv4_packet(via, packet);
 786                         }
 787                         return;
 788                 } else if(type == ETH_P_IPV6) {
 789                         packet->len = via->mtu;
 790                         route_ipv6_unreachable(source, packet, ICMP6_PACKET_TOO_BIG, 0);
 791                         return;
 792                 }
 793         }
 794
 795         send_packet(subnet->owner, packet);
 796 }
 797
 798
 799 void route(node_t *source, vpn_packet_t *packet)
 800 {
 801         cp();
 802
 803         if(!checklength(source, packet, ether_size))
 804                 return;
 805
 806         switch (routing_mode) {
 807                 case RMODE_ROUTER:
 808                         {
 809                                 uint16_t type = packet->data[12] << 8 | packet->data[13];
 810
 811                                 switch (type) {
 812                                         case ETH_P_ARP:
 813                                                 route_arp(source, packet);
 814                                                 break;
 815
 816                                         case ETH_P_IP:
 817                                                 route_ipv4(source, packet);
 818                                                 break;
 819
 820                                         case ETH_P_IPV6:
 821                                                 route_ipv6(source, packet);
 822                                                 break;
 823
 824                                         default:
 825                                                 ifdebug(TRAFFIC) logger(LOG_WARNING, _("Cannot route packet from %s (%s): unknown type %hx"), source->name, source->hostname, type);
 826                                                 break;
 827                                 }
 828                         }
 829                         break;
 830
 831                 case RMODE_SWITCH:
 832                         route_mac(source, packet);
 833                         break;
 834
 835                 case RMODE_HUB:
 836                         broadcast_packet(source, packet);
 837                         break;
 838         }
 839 }