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

   1 /*
   2     route.c -- routing
   3     Copyright (C) 2000-2005 Ivo Timmermans,
   4                   2000-2010 Guus Sliepen <guus@tinc-vpn.org>
   5
   6     This program is free software; you can redistribute it and/or modify
   7     it under the terms of the GNU General Public License as published by
   8     the Free Software Foundation; either version 2 of the License, or
   9     (at your option) any later version.
  10
  11     This program is distributed in the hope that it will be useful,
  12     but WITHOUT ANY WARRANTY; without even the implied warranty of
  13     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14     GNU General Public License for more details.
  15
  16     You should have received a copy of the GNU General Public License along
  17     with this program; if not, write to the Free Software Foundation, Inc.,
  18     51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  19 */
  20
  21 #include "system.h"
  22
  23 #include "avl_tree.h"
  24 #include "connection.h"
  25 #include "ethernet.h"
  26 #include "ipv4.h"
  27 #include "ipv6.h"
  28 #include "logger.h"
  29 #include "net.h"
  30 #include "protocol.h"
  31 #include "route.h"
  32 #include "subnet.h"
  33 #include "utils.h"
  34
  35 rmode_t routing_mode = RMODE_ROUTER;
  36 bool priorityinheritance = false;
  37 int macexpire = 600;
  38 bool overwrite_mac = false;
  39 mac_t mymac = {{0xFE, 0xFD, 0, 0, 0, 0}};
  40
  41 /* Sizes of various headers */
  42
  43 static const size_t ether_size = sizeof(struct ether_header);
  44 static const size_t arp_size = sizeof(struct ether_arp);
  45 static const size_t ip_size = sizeof(struct ip);
  46 static const size_t icmp_size = sizeof(struct icmp) - sizeof(struct ip);
  47 static const size_t ip6_size = sizeof(struct ip6_hdr);
  48 static const size_t icmp6_size = sizeof(struct icmp6_hdr);
  49 static const size_t ns_size = sizeof(struct nd_neighbor_solicit);
  50 static const size_t opt_size = sizeof(struct nd_opt_hdr);
  51 #define max(a, b) ((a) > (b) ? (a) : (b))
  52
  53 /* RFC 1071 */
  54
  55 static uint16_t inet_checksum(void *data, int len, uint16_t prevsum) {
  56         uint16_t *p = data;
  57         uint32_t checksum = prevsum ^ 0xFFFF;
  58
  59         while(len >= 2) {
  60                 checksum += *p++;
  61                 len -= 2;
  62         }
  63
  64         if(len)
  65                 checksum += *(uint8_t *)p;
  66
  67         while(checksum >> 16)
  68                 checksum = (checksum & 0xFFFF) + (checksum >> 16);
  69
  70         return ~checksum;
  71 }
  72
  73 static bool ratelimit(int frequency) {
  74         static time_t lasttime = 0;
  75         static int count = 0;
  76
  77         if(lasttime == now) {
  78                 if(++count > frequency)
  79                         return true;
  80         } else {
  81                 lasttime = now;
  82                 count = 0;
  83         }
  84
  85         return false;
  86 }
  87
  88 static bool checklength(node_t *source, vpn_packet_t *packet, length_t length) {
  89         if(packet->len < length) {
  90                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Got too short packet from %s (%s)", source->name, source->hostname);
  91                 return false;
  92         } else
  93                 return true;
  94 }
  95
  96 static void clamp_mss(const node_t *source, const node_t *via, vpn_packet_t *packet) {
  97         if(!via || via == myself || !(via->options & OPTION_CLAMP_MSS))
  98                 return;
  99
 100         /* Find TCP header */
 101         int start = 0;
 102         uint16_t type = packet->data[12] << 8 | packet->data[13];
 103
 104         if(type == ETH_P_IP && packet->data[23] == 6)
 105                 start = 14 + (packet->data[14] & 0xf) * 4;
 106         else if(type == ETH_P_IPV6 && packet->data[20] == 6)
 107                 start = 14 + 40;
 108
 109         if(!start || packet->len <= start + 20)
 110                 return;
 111
 112         /* Use data offset field to calculate length of options field */
 113         int len = ((packet->data[start + 12] >> 4) - 5) * 4;
 114
 115         if(packet->len < start + 20 + len)
 116                 return;
 117
 118         /* Search for MSS option header */
 119         for(int i = 0; i < len;) {
 120                 if(packet->data[start + 20 + i] == 0)
 121                         break;
 122
 123                 if(packet->data[start + 20 + i] == 1) {
 124                         i++;
 125                         continue;
 126                 }
 127
 128                 if(i > len - 2 || i > len - packet->data[start + 21 + i])
 129                         break;
 130
 131                 if(packet->data[start + 20 + i] != 2) {
 132                         if(packet->data[start + 21 + i] < 2)
 133                                 break;
 134                         i += packet->data[start + 21 + i];
 135                         continue;
 136                 }
 137
 138                 if(packet->data[start + 21] != 4)
 139                         break;
 140
 141                 /* Found it */
 142                 uint16_t oldmss = packet->data[start + 22 + i] << 8 | packet->data[start + 23 + i];
 143                 uint16_t newmss = via->mtu - start - 20;
 144                 uint16_t csum = packet->data[start + 16] << 8 | packet->data[start + 17];
 145
 146                 if(oldmss <= newmss)
 147                         break;
 148
 149                 ifdebug(TRAFFIC) logger(LOG_INFO, "Clamping MSS of packet from %s to %s to %d", source->name, via->name, newmss);
 150
 151                 /* Update the MSS value and the checksum */
 152                 packet->data[start + 22 + i] = newmss >> 8;
 153                 packet->data[start + 23 + i] = newmss & 0xff;
 154                 csum ^= 0xffff;
 155                 csum -= oldmss;
 156                 csum += newmss;
 157                 csum ^= 0xffff;
 158                 packet->data[start + 16] = csum >> 8;
 159                 packet->data[start + 17] = csum & 0xff;
 160                 break;
 161         }
 162 }
 163
 164 static void swap_mac_addresses(vpn_packet_t *packet) {
 165         mac_t tmp;
 166         memcpy(&tmp, &packet->data[0], sizeof tmp);
 167         memcpy(&packet->data[0], &packet->data[6], sizeof tmp);
 168         memcpy(&packet->data[6], &tmp, sizeof tmp);
 169 }
 170
 171 static void learn_mac(mac_t *address) {
 172         subnet_t *subnet;
 173         avl_node_t *node;
 174         connection_t *c;
 175
 176         subnet = lookup_subnet_mac(myself, address);
 177
 178         /* If we don't know this MAC address yet, store it */
 179
 180         if(!subnet) {
 181                 ifdebug(TRAFFIC) logger(LOG_INFO, "Learned new MAC address %hx:%hx:%hx:%hx:%hx:%hx",
 182                                    address->x[0], address->x[1], address->x[2], address->x[3],
 183                                    address->x[4], address->x[5]);
 184
 185                 subnet = new_subnet();
 186                 subnet->type = SUBNET_MAC;
 187                 subnet->expires = now + macexpire;
 188                 subnet->net.mac.address = *address;
 189                 subnet->weight = 10;
 190                 subnet_add(myself, subnet);
 191                 subnet_update(myself, subnet, true);
 192
 193                 /* And tell all other tinc daemons it's our MAC */
 194
 195                 for(node = connection_tree->head; node; node = node->next) {
 196                         c = node->data;
 197                         if(c->status.active)
 198                                 send_add_subnet(c, subnet);
 199                 }
 200         }
 201
 202         if(subnet->expires)
 203                 subnet->expires = now + macexpire;
 204 }
 205
 206 void age_subnets(void) {
 207         subnet_t *s;
 208         connection_t *c;
 209         avl_node_t *node, *next, *node2;
 210
 211         for(node = myself->subnet_tree->head; node; node = next) {
 212                 next = node->next;
 213                 s = node->data;
 214                 if(s->expires && s->expires < now) {
 215                         ifdebug(TRAFFIC) {
 216                                 char netstr[MAXNETSTR];
 217                                 if(net2str(netstr, sizeof netstr, s))
 218                                         logger(LOG_INFO, "Subnet %s expired", netstr);
 219                         }
 220
 221                         for(node2 = connection_tree->head; node2; node2 = node2->next) {
 222                                 c = node2->data;
 223                                 if(c->status.active)
 224                                         send_del_subnet(c, s);
 225                         }
 226
 227                         subnet_update(myself, s, false);
 228                         subnet_del(myself, s);
 229                 }
 230         }
 231 }
 232
 233 /* RFC 792 */
 234
 235 static void route_ipv4_unreachable(node_t *source, vpn_packet_t *packet, uint8_t type, uint8_t code) {
 236         struct ip ip = {0};
 237         struct icmp icmp = {0};
 238
 239         struct in_addr ip_src;
 240         struct in_addr ip_dst;
 241         uint32_t oldlen;
 242
 243         if(ratelimit(3))
 244                 return;
 245
 246         /* Swap Ethernet source and destination addresses */
 247
 248         swap_mac_addresses(packet);
 249
 250         /* Copy headers from packet into properly aligned structs on the stack */
 251
 252         memcpy(&ip, packet->data + ether_size, ip_size);
 253
 254         /* Remember original source and destination */
 255
 256         ip_src = ip.ip_src;
 257         ip_dst = ip.ip_dst;
 258
 259         oldlen = packet->len - ether_size;
 260
 261         if(type == ICMP_DEST_UNREACH && code == ICMP_FRAG_NEEDED)
 262                 icmp.icmp_nextmtu = htons(packet->len - ether_size);
 263
 264         if(oldlen >= IP_MSS - ip_size - icmp_size)
 265                 oldlen = IP_MSS - ip_size - icmp_size;
 266
 267         /* Copy first part of original contents to ICMP message */
 268
 269         memmove(packet->data + ether_size + ip_size + icmp_size, packet->data + ether_size, oldlen);
 270
 271         /* Fill in IPv4 header */
 272
 273         ip.ip_v = 4;
 274         ip.ip_hl = ip_size / 4;
 275         ip.ip_tos = 0;
 276         ip.ip_len = htons(ip_size + icmp_size + oldlen);
 277         ip.ip_id = 0;
 278         ip.ip_off = 0;
 279         ip.ip_ttl = 255;
 280         ip.ip_p = IPPROTO_ICMP;
 281         ip.ip_sum = 0;
 282         ip.ip_src = ip_dst;
 283         ip.ip_dst = ip_src;
 284
 285         ip.ip_sum = inet_checksum(&ip, ip_size, ~0);
 286
 287         /* Fill in ICMP header */
 288
 289         icmp.icmp_type = type;
 290         icmp.icmp_code = code;
 291         icmp.icmp_cksum = 0;
 292
 293         icmp.icmp_cksum = inet_checksum(&icmp, icmp_size, ~0);
 294         icmp.icmp_cksum = inet_checksum(packet->data + ether_size + ip_size + icmp_size, oldlen, icmp.icmp_cksum);
 295
 296         /* Copy structs on stack back to packet */
 297
 298         memcpy(packet->data + ether_size, &ip, ip_size);
 299         memcpy(packet->data + ether_size + ip_size, &icmp, icmp_size);
 300
 301         packet->len = ether_size + ip_size + icmp_size + oldlen;
 302
 303         send_packet(source, packet);
 304 }
 305
 306 /* RFC 791 */
 307
 308 static void fragment_ipv4_packet(node_t *dest, vpn_packet_t *packet) {
 309         struct ip ip;
 310         vpn_packet_t fragment;
 311         int len, maxlen, todo;
 312         uint8_t *offset;
 313         uint16_t ip_off, origf;
 314
 315         memcpy(&ip, packet->data + ether_size, ip_size);
 316         fragment.priority = packet->priority;
 317
 318         if(ip.ip_hl != ip_size / 4)
 319                 return;
 320
 321         todo = ntohs(ip.ip_len) - ip_size;
 322
 323         if(ether_size + ip_size + todo != packet->len) {
 324                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Length of packet (%d) doesn't match length in IPv4 header (%zd)", packet->len, ether_size + ip_size + todo);
 325                 return;
 326         }
 327
 328         ifdebug(TRAFFIC) logger(LOG_INFO, "Fragmenting packet of %d bytes to %s (%s)", packet->len, dest->name, dest->hostname);
 329
 330         offset = packet->data + ether_size + ip_size;
 331         maxlen = (dest->mtu - ether_size - ip_size) & ~0x7;
 332         ip_off = ntohs(ip.ip_off);
 333         origf = ip_off & ~IP_OFFMASK;
 334         ip_off &= IP_OFFMASK;
 335
 336         while(todo) {
 337                 len = todo > maxlen ? maxlen : todo;
 338                 memcpy(fragment.data + ether_size + ip_size, offset, len);
 339                 todo -= len;
 340                 offset += len;
 341
 342                 ip.ip_len = htons(ip_size + len);
 343                 ip.ip_off = htons(ip_off | origf | (todo ? IP_MF : 0));
 344                 ip.ip_sum = 0;
 345                 ip.ip_sum = inet_checksum(&ip, ip_size, ~0);
 346                 memcpy(fragment.data, packet->data, ether_size);
 347                 memcpy(fragment.data + ether_size, &ip, ip_size);
 348                 fragment.len = ether_size + ip_size + len;
 349
 350                 send_packet(dest, &fragment);
 351
 352                 ip_off += len / 8;
 353         }
 354 }
 355
 356 static void route_ipv4_unicast(node_t *source, vpn_packet_t *packet) {
 357         subnet_t *subnet;
 358         node_t *via;
 359         ipv4_t dest;
 360
 361         memcpy(&dest, &packet->data[30], sizeof dest);
 362         subnet = lookup_subnet_ipv4(&dest);
 363
 364         if(!subnet) {
 365                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Cannot route packet from %s (%s): unknown IPv4 destination address %d.%d.%d.%d",
 366                                 source->name, source->hostname,
 367                                 dest.x[0],
 368                                 dest.x[1],
 369                                 dest.x[2],
 370                                 dest.x[3]);
 371
 372                 route_ipv4_unreachable(source, packet, ICMP_DEST_UNREACH, ICMP_NET_UNKNOWN);
 373                 return;
 374         }
 375
 376         if(subnet->owner == source) {
 377                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Packet looping back to %s (%s)!", source->name, source->hostname);
 378                 return;
 379         }
 380
 381         if(!subnet->owner->status.reachable)
 382                 route_ipv4_unreachable(source, packet, ICMP_DEST_UNREACH, ICMP_NET_UNREACH);
 383
 384         if(priorityinheritance)
 385                 packet->priority = packet->data[15];
 386
 387         via = (subnet->owner->via == myself) ? subnet->owner->nexthop : subnet->owner->via;
 388
 389         if(via && packet->len > max(via->mtu, 590) && via != myself) {
 390                 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);
 391                 if(packet->data[20] & 0x40) {
 392                         packet->len = max(via->mtu, 590);
 393                         route_ipv4_unreachable(source, packet, ICMP_DEST_UNREACH, ICMP_FRAG_NEEDED);
 394                 } else {
 395                         fragment_ipv4_packet(via, packet);
 396                 }
 397
 398                 return;
 399         }
 400
 401         clamp_mss(source, via, packet);
 402
 403         send_packet(subnet->owner, packet);
 404 }
 405
 406 static void route_ipv4(node_t *source, vpn_packet_t *packet) {
 407         if(!checklength(source, packet, ether_size + ip_size))
 408                 return;
 409
 410         if(((packet->data[30] & 0xf0) == 0xe0) || (
 411                         packet->data[30] == 255 &&
 412                         packet->data[31] == 255 &&
 413                         packet->data[32] == 255 &&
 414                         packet->data[33] == 255))
 415                 broadcast_packet(source, packet);
 416         else
 417                 route_ipv4_unicast(source, packet);
 418 }
 419
 420 /* RFC 2463 */
 421
 422 static void route_ipv6_unreachable(node_t *source, vpn_packet_t *packet, uint8_t type, uint8_t code) {
 423         struct ip6_hdr ip6;
 424         struct icmp6_hdr icmp6 = {0};
 425         uint16_t checksum;
 426
 427         struct {
 428                 struct in6_addr ip6_src;        /* source address */
 429                 struct in6_addr ip6_dst;        /* destination address */
 430                 uint32_t length;
 431                 uint32_t next;
 432         } pseudo;
 433
 434         if(ratelimit(3))
 435                 return;
 436
 437         /* Swap Ethernet source and destination addresses */
 438
 439         swap_mac_addresses(packet);
 440
 441         /* Copy headers from packet to structs on the stack */
 442
 443         memcpy(&ip6, packet->data + ether_size, ip6_size);
 444
 445         /* Remember original source and destination */
 446
 447         pseudo.ip6_src = ip6.ip6_dst;
 448         pseudo.ip6_dst = ip6.ip6_src;
 449
 450         pseudo.length = packet->len - ether_size;
 451
 452         if(type == ICMP6_PACKET_TOO_BIG)
 453                 icmp6.icmp6_mtu = htonl(pseudo.length);
 454
 455         if(pseudo.length >= IP_MSS - ip6_size - icmp6_size)
 456                 pseudo.length = IP_MSS - ip6_size - icmp6_size;
 457
 458         /* Copy first part of original contents to ICMP message */
 459
 460         memmove(packet->data + ether_size + ip6_size + icmp6_size, packet->data + ether_size, pseudo.length);
 461
 462         /* Fill in IPv6 header */
 463
 464         ip6.ip6_flow = htonl(0x60000000UL);
 465         ip6.ip6_plen = htons(icmp6_size + pseudo.length);
 466         ip6.ip6_nxt = IPPROTO_ICMPV6;
 467         ip6.ip6_hlim = 255;
 468         ip6.ip6_src = pseudo.ip6_src;
 469         ip6.ip6_dst = pseudo.ip6_dst;
 470
 471         /* Fill in ICMP header */
 472
 473         icmp6.icmp6_type = type;
 474         icmp6.icmp6_code = code;
 475         icmp6.icmp6_cksum = 0;
 476
 477         /* Create pseudo header */
 478
 479         pseudo.length = htonl(icmp6_size + pseudo.length);
 480         pseudo.next = htonl(IPPROTO_ICMPV6);
 481
 482         /* Generate checksum */
 483
 484         checksum = inet_checksum(&pseudo, sizeof(pseudo), ~0);
 485         checksum = inet_checksum(&icmp6, icmp6_size, checksum);
 486         checksum = inet_checksum(packet->data + ether_size + ip6_size + icmp6_size, ntohl(pseudo.length) - icmp6_size, checksum);
 487
 488         icmp6.icmp6_cksum = checksum;
 489
 490         /* Copy structs on stack back to packet */
 491
 492         memcpy(packet->data + ether_size, &ip6, ip6_size);
 493         memcpy(packet->data + ether_size + ip6_size, &icmp6, icmp6_size);
 494
 495         packet->len = ether_size + ip6_size + ntohl(pseudo.length);
 496
 497         send_packet(source, packet);
 498 }
 499
 500 static void route_ipv6_unicast(node_t *source, vpn_packet_t *packet) {
 501         subnet_t *subnet;
 502         node_t *via;
 503         ipv6_t dest;
 504
 505         memcpy(&dest, &packet->data[38], sizeof dest);
 506         subnet = lookup_subnet_ipv6(&dest);
 507
 508         if(!subnet) {
 509                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Cannot route packet from %s (%s): unknown IPv6 destination address %hx:%hx:%hx:%hx:%hx:%hx:%hx:%hx",
 510                                 source->name, source->hostname,
 511                                 ntohs(dest.x[0]),
 512                                 ntohs(dest.x[1]),
 513                                 ntohs(dest.x[2]),
 514                                 ntohs(dest.x[3]),
 515                                 ntohs(dest.x[4]),
 516                                 ntohs(dest.x[5]),
 517                                 ntohs(dest.x[6]),
 518                                 ntohs(dest.x[7]));
 519
 520                 route_ipv6_unreachable(source, packet, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_ADDR);
 521                 return;
 522         }
 523
 524         if(subnet->owner == source) {
 525                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Packet looping back to %s (%s)!", source->name, source->hostname);
 526                 return;
 527         }
 528
 529         if(!subnet->owner->status.reachable)
 530                 route_ipv6_unreachable(source, packet, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_NOROUTE);
 531
 532         via = (subnet->owner->via == myself) ? subnet->owner->nexthop : subnet->owner->via;
 533
 534         if(via && packet->len > max(via->mtu, 1294) && via != myself) {
 535                 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);
 536                 packet->len = max(via->mtu, 1294);
 537                 route_ipv6_unreachable(source, packet, ICMP6_PACKET_TOO_BIG, 0);
 538                 return;
 539         }
 540
 541         clamp_mss(source, via, packet);
 542
 543         send_packet(subnet->owner, packet);
 544 }
 545
 546 /* RFC 2461 */
 547
 548 static void route_neighborsol(node_t *source, vpn_packet_t *packet) {
 549         struct ip6_hdr ip6;
 550         struct nd_neighbor_solicit ns;
 551         struct nd_opt_hdr opt;
 552         subnet_t *subnet;
 553         uint16_t checksum;
 554         bool has_opt;
 555
 556         struct {
 557                 struct in6_addr ip6_src;        /* source address */
 558                 struct in6_addr ip6_dst;        /* destination address */
 559                 uint32_t length;
 560                 uint32_t next;
 561         } pseudo;
 562
 563         if(!checklength(source, packet, ether_size + ip6_size + ns_size))
 564                 return;
 565
 566         has_opt = packet->len >= ether_size + ip6_size + ns_size + opt_size + ETH_ALEN;
 567
 568         if(source != myself) {
 569                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Got neighbor solicitation request from %s (%s) while in router mode!", source->name, source->hostname);
 570                 return;
 571         }
 572
 573         /* Copy headers from packet to structs on the stack */
 574
 575         memcpy(&ip6, packet->data + ether_size, ip6_size);
 576         memcpy(&ns, packet->data + ether_size + ip6_size, ns_size);
 577         if(has_opt)
 578                 memcpy(&opt, packet->data + ether_size + ip6_size + ns_size, opt_size);
 579
 580         /* First, snatch the source address from the neighbor solicitation packet */
 581
 582         if(overwrite_mac)
 583                 memcpy(mymac.x, packet->data + ETH_ALEN, ETH_ALEN);
 584
 585         /* Check if this is a valid neighbor solicitation request */
 586
 587         if(ns.nd_ns_hdr.icmp6_type != ND_NEIGHBOR_SOLICIT ||
 588            (has_opt && opt.nd_opt_type != ND_OPT_SOURCE_LINKADDR)) {
 589                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Cannot route packet: received unknown type neighbor solicitation request");
 590                 return;
 591         }
 592
 593         /* Create pseudo header */
 594
 595         pseudo.ip6_src = ip6.ip6_src;
 596         pseudo.ip6_dst = ip6.ip6_dst;
 597         if(has_opt)
 598                 pseudo.length = htonl(ns_size + opt_size + ETH_ALEN);
 599         else
 600                 pseudo.length = htonl(ns_size);
 601         pseudo.next = htonl(IPPROTO_ICMPV6);
 602
 603         /* Generate checksum */
 604
 605         checksum = inet_checksum(&pseudo, sizeof(pseudo), ~0);
 606         checksum = inet_checksum(&ns, ns_size, checksum);
 607         if(has_opt) {
 608                 checksum = inet_checksum(&opt, opt_size, checksum);
 609                 checksum = inet_checksum(packet->data + ether_size + ip6_size + ns_size + opt_size, ETH_ALEN, checksum);
 610         }
 611
 612         if(checksum) {
 613                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Cannot route packet: checksum error for neighbor solicitation request");
 614                 return;
 615         }
 616
 617         /* Check if the IPv6 address exists on the VPN */
 618
 619         subnet = lookup_subnet_ipv6((ipv6_t *) &ns.nd_ns_target);
 620
 621         if(!subnet) {
 622                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Cannot route packet: neighbor solicitation request for unknown address %hx:%hx:%hx:%hx:%hx:%hx:%hx:%hx",
 623                                    ntohs(((uint16_t *) &ns.nd_ns_target)[0]),
 624                                    ntohs(((uint16_t *) &ns.nd_ns_target)[1]),
 625                                    ntohs(((uint16_t *) &ns.nd_ns_target)[2]),
 626                                    ntohs(((uint16_t *) &ns.nd_ns_target)[3]),
 627                                    ntohs(((uint16_t *) &ns.nd_ns_target)[4]),
 628                                    ntohs(((uint16_t *) &ns.nd_ns_target)[5]),
 629                                    ntohs(((uint16_t *) &ns.nd_ns_target)[6]),
 630                                    ntohs(((uint16_t *) &ns.nd_ns_target)[7]));
 631
 632                 return;
 633         }
 634
 635         /* Check if it is for our own subnet */
 636
 637         if(subnet->owner == myself)
 638                 return;                                 /* silently ignore */
 639
 640         /* Create neighbor advertation reply */
 641
 642         memcpy(packet->data, packet->data + ETH_ALEN, ETH_ALEN);        /* copy destination address */
 643         packet->data[ETH_ALEN * 2 - 1] ^= 0xFF; /* mangle source address so it looks like it's not from us */
 644
 645         ip6.ip6_dst = ip6.ip6_src;                      /* swap destination and source protocoll address */
 646         ip6.ip6_src = ns.nd_ns_target;
 647
 648         if(has_opt)
 649                 memcpy(packet->data + ether_size + ip6_size + ns_size + opt_size, packet->data + ETH_ALEN, ETH_ALEN);   /* add fake source hard addr */
 650
 651         ns.nd_ns_cksum = 0;
 652         ns.nd_ns_type = ND_NEIGHBOR_ADVERT;
 653         ns.nd_ns_reserved = htonl(0x40000000UL);        /* Set solicited flag */
 654         opt.nd_opt_type = ND_OPT_TARGET_LINKADDR;
 655
 656         /* Create pseudo header */
 657
 658         pseudo.ip6_src = ip6.ip6_src;
 659         pseudo.ip6_dst = ip6.ip6_dst;
 660         if(has_opt)
 661                 pseudo.length = htonl(ns_size + opt_size + ETH_ALEN);
 662         else
 663                 pseudo.length = htonl(ns_size);
 664         pseudo.next = htonl(IPPROTO_ICMPV6);
 665
 666         /* Generate checksum */
 667
 668         checksum = inet_checksum(&pseudo, sizeof(pseudo), ~0);
 669         checksum = inet_checksum(&ns, ns_size, checksum);
 670         if(has_opt) {
 671                 checksum = inet_checksum(&opt, opt_size, checksum);
 672                 checksum = inet_checksum(packet->data + ether_size + ip6_size + ns_size + opt_size, ETH_ALEN, checksum);
 673         }
 674
 675         ns.nd_ns_hdr.icmp6_cksum = checksum;
 676
 677         /* Copy structs on stack back to packet */
 678
 679         memcpy(packet->data + ether_size, &ip6, ip6_size);
 680         memcpy(packet->data + ether_size + ip6_size, &ns, ns_size);
 681         if(has_opt)
 682                 memcpy(packet->data + ether_size + ip6_size + ns_size, &opt, opt_size);
 683
 684         send_packet(source, packet);
 685 }
 686
 687 static void route_ipv6(node_t *source, vpn_packet_t *packet) {
 688         if(!checklength(source, packet, ether_size + ip6_size))
 689                 return;
 690
 691         if(packet->data[20] == IPPROTO_ICMPV6 && checklength(source, packet, ether_size + ip6_size + icmp6_size) && packet->data[54] == ND_NEIGHBOR_SOLICIT) {
 692                 route_neighborsol(source, packet);
 693                 return;
 694         }
 695
 696         if(packet->data[38] == 255)
 697                 broadcast_packet(source, packet);
 698         else
 699                 route_ipv6_unicast(source, packet);
 700 }
 701
 702 /* RFC 826 */
 703
 704 static void route_arp(node_t *source, vpn_packet_t *packet) {
 705         struct ether_arp arp;
 706         subnet_t *subnet;
 707         struct in_addr addr;
 708
 709         if(!checklength(source, packet, ether_size + arp_size))
 710                 return;
 711
 712         if(source != myself) {
 713                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Got ARP request from %s (%s) while in router mode!", source->name, source->hostname);
 714                 return;
 715         }
 716
 717         /* First, snatch the source address from the ARP packet */
 718
 719         if(overwrite_mac)
 720                 memcpy(mymac.x, packet->data + ETH_ALEN, ETH_ALEN);
 721
 722         /* Copy headers from packet to structs on the stack */
 723
 724         memcpy(&arp, packet->data + ether_size, arp_size);
 725
 726         /* Check if this is a valid ARP request */
 727
 728         if(ntohs(arp.arp_hrd) != ARPHRD_ETHER || ntohs(arp.arp_pro) != ETH_P_IP ||
 729            arp.arp_hln != ETH_ALEN || arp.arp_pln != sizeof(addr) || ntohs(arp.arp_op) != ARPOP_REQUEST) {
 730                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Cannot route packet: received unknown type ARP request");
 731                 return;
 732         }
 733
 734         /* Check if the IPv4 address exists on the VPN */
 735
 736         subnet = lookup_subnet_ipv4((ipv4_t *) &arp.arp_tpa);
 737
 738         if(!subnet) {
 739                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Cannot route packet: ARP request for unknown address %d.%d.%d.%d",
 740                                    arp.arp_tpa[0], arp.arp_tpa[1], arp.arp_tpa[2],
 741                                    arp.arp_tpa[3]);
 742                 return;
 743         }
 744
 745         /* Check if it is for our own subnet */
 746
 747         if(subnet->owner == myself)
 748                 return;                                 /* silently ignore */
 749
 750         memcpy(packet->data, packet->data + ETH_ALEN, ETH_ALEN);        /* copy destination address */
 751         packet->data[ETH_ALEN * 2 - 1] ^= 0xFF; /* mangle source address so it looks like it's not from us */
 752
 753         memcpy(&addr, arp.arp_tpa, sizeof(addr));       /* save protocol addr */
 754         memcpy(arp.arp_tpa, arp.arp_spa, sizeof(addr)); /* swap destination and source protocol address */
 755         memcpy(arp.arp_spa, &addr, sizeof(addr));       /* ... */
 756
 757         memcpy(arp.arp_tha, arp.arp_sha, ETH_ALEN);     /* set target hard/proto addr */
 758         memcpy(arp.arp_sha, packet->data + ETH_ALEN, ETH_ALEN); /* add fake source hard addr */
 759         arp.arp_op = htons(ARPOP_REPLY);
 760
 761         /* Copy structs on stack back to packet */
 762
 763         memcpy(packet->data + ether_size, &arp, arp_size);
 764
 765         send_packet(source, packet);
 766 }
 767
 768 static void route_mac(node_t *source, vpn_packet_t *packet) {
 769         subnet_t *subnet;
 770         mac_t dest;
 771
 772         /* Learn source address */
 773
 774         if(source == myself) {
 775                 mac_t src;
 776                 memcpy(&src, &packet->data[6], sizeof src);
 777                 learn_mac(&src);
 778         }
 779
 780         /* Lookup destination address */
 781
 782         memcpy(&dest, &packet->data[0], sizeof dest);
 783         subnet = lookup_subnet_mac(NULL, &dest);
 784
 785         if(!subnet) {
 786                 broadcast_packet(source, packet);
 787                 return;
 788         }
 789
 790         if(subnet->owner == source) {
 791                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Packet looping back to %s (%s)!", source->name, source->hostname);
 792                 return;
 793         }
 794
 795         // Handle packets larger than PMTU
 796
 797         node_t *via = (subnet->owner->via == myself) ? subnet->owner->nexthop : subnet->owner->via;
 798
 799         if(via && packet->len > via->mtu && via != myself) {
 800                 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);
 801                 uint16_t type = packet->data[12] << 8 | packet->data[13];
 802                 if(type == ETH_P_IP && packet->len > 590) {
 803                         if(packet->data[20] & 0x40) {
 804                                 packet->len = via->mtu;
 805                                 route_ipv4_unreachable(source, packet, ICMP_DEST_UNREACH, ICMP_FRAG_NEEDED);
 806                         } else {
 807                                 fragment_ipv4_packet(via, packet);
 808                         }
 809                         return;
 810                 } else if(type == ETH_P_IPV6 && packet->len > 1294) {
 811                         packet->len = via->mtu;
 812                         route_ipv6_unreachable(source, packet, ICMP6_PACKET_TOO_BIG, 0);
 813                         return;
 814                 }
 815         }
 816
 817         clamp_mss(source, via, packet);
 818
 819         send_packet(subnet->owner, packet);
 820 }
 821
 822 void route(node_t *source, vpn_packet_t *packet) {
 823         if(!checklength(source, packet, ether_size))
 824                 return;
 825
 826         switch (routing_mode) {
 827                 case RMODE_ROUTER:
 828                         {
 829                                 uint16_t type = packet->data[12] << 8 | packet->data[13];
 830
 831                                 switch (type) {
 832                                         case ETH_P_ARP:
 833                                                 route_arp(source, packet);
 834                                                 break;
 835
 836                                         case ETH_P_IP:
 837                                                 route_ipv4(source, packet);
 838                                                 break;
 839
 840                                         case ETH_P_IPV6:
 841                                                 route_ipv6(source, packet);
 842                                                 break;
 843
 844                                         default:
 845                                                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Cannot route packet from %s (%s): unknown type %hx", source->name, source->hostname, type);
 846                                                 break;
 847                                 }
 848                         }
 849                         break;
 850
 851                 case RMODE_SWITCH:
 852                         route_mac(source, packet);
 853                         break;
 854
 855                 case RMODE_HUB:
 856                         broadcast_packet(source, packet);
 857                         break;
 858         }
 859 }