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 "splay_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 fmode_t forwarding_mode = FMODE_INTERNAL;
  37 bool directonly = false;
  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 #define max(a, b) ((a) > (b) ? (a) : (b))
  54
  55 static struct event age_subnets_event;
  56
  57 /* RFC 1071 */
  58
  59 static uint16_t inet_checksum(void *data, int len, uint16_t prevsum) {
  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 clamp_mss(const node_t *source, const node_t *via, vpn_packet_t *packet) {
 102         if(!source || !via || !(via->options & OPTION_CLAMP_MSS))
 103                 return;
 104
 105         uint16_t mtu = source->mtu;
 106         if(via != myself && via->mtu < mtu)
 107                 mtu = via->mtu;
 108
 109         /* Find TCP header */
 110         int start = 0;
 111         uint16_t type = packet->data[12] << 8 | packet->data[13];
 112
 113         if(type == ETH_P_IP && packet->data[23] == 6)
 114                 start = 14 + (packet->data[14] & 0xf) * 4;
 115         else if(type == ETH_P_IPV6 && packet->data[20] == 6)
 116                 start = 14 + 40;
 117
 118         if(!start || packet->len <= start + 20)
 119                 return;
 120
 121         /* Use data offset field to calculate length of options field */
 122         int len = ((packet->data[start + 12] >> 4) - 5) * 4;
 123
 124         if(packet->len < start + 20 + len)
 125                 return;
 126
 127         /* Search for MSS option header */
 128         for(int i = 0; i < len;) {
 129                 if(packet->data[start + 20 + i] == 0)
 130                         break;
 131
 132                 if(packet->data[start + 20 + i] == 1) {
 133                         i++;
 134                         continue;
 135                 }
 136
 137                 if(i > len - 2 || i > len - packet->data[start + 21 + i])
 138                         break;
 139
 140                 if(packet->data[start + 20 + i] != 2) {
 141                         if(packet->data[start + 21 + i] < 2)
 142                                 break;
 143                         i += packet->data[start + 21 + i];
 144                         continue;
 145                 }
 146
 147                 if(packet->data[start + 21] != 4)
 148                         break;
 149
 150                 /* Found it */
 151                 uint16_t oldmss = packet->data[start + 22 + i] << 8 | packet->data[start + 23 + i];
 152                 uint16_t newmss = mtu - start - 20;
 153                 uint16_t csum = packet->data[start + 16] << 8 | packet->data[start + 17];
 154
 155                 if(oldmss <= newmss)
 156                         break;
 157
 158                 ifdebug(TRAFFIC) logger(LOG_INFO, "Clamping MSS of packet from %s to %s to %d", source->name, via->name, newmss);
 159
 160                 /* Update the MSS value and the checksum */
 161                 packet->data[start + 22 + i] = newmss >> 8;
 162                 packet->data[start + 23 + i] = newmss & 0xff;
 163                 csum ^= 0xffff;
 164                 csum -= oldmss;
 165                 csum += newmss;
 166                 csum ^= 0xffff;
 167                 packet->data[start + 16] = csum >> 8;
 168                 packet->data[start + 17] = csum & 0xff;
 169                 break;
 170         }
 171 }
 172
 173 static void swap_mac_addresses(vpn_packet_t *packet) {
 174         mac_t tmp;
 175         memcpy(&tmp, &packet->data[0], sizeof tmp);
 176         memcpy(&packet->data[0], &packet->data[6], sizeof tmp);
 177         memcpy(&packet->data[6], &tmp, sizeof tmp);
 178 }
 179
 180 static void age_subnets(int fd, short events, void *data) {
 181         subnet_t *s;
 182         connection_t *c;
 183         splay_node_t *node, *next, *node2;
 184         bool left = false;
 185         time_t now = time(NULL);
 186
 187         for(node = myself->subnet_tree->head; node; node = next) {
 188                 next = node->next;
 189                 s = node->data;
 190                 if(s->expires && s->expires < now) {
 191                         ifdebug(TRAFFIC) {
 192                                 char netstr[MAXNETSTR];
 193                                 if(net2str(netstr, sizeof netstr, s))
 194                                         logger(LOG_INFO, "Subnet %s expired", netstr);
 195                         }
 196
 197                         for(node2 = connection_tree->head; node2; node2 = node2->next) {
 198                                 c = node2->data;
 199                                 if(c->status.active)
 200                                         send_del_subnet(c, s);
 201                         }
 202
 203                         subnet_del(myself, s);
 204                 } else {
 205                         if(s->expires)
 206                                 left = true;
 207                 }
 208         }
 209
 210         if(left)
 211                 event_add(&age_subnets_event, &(struct timeval){10, 0});
 212 }
 213
 214 static void learn_mac(mac_t *address) {
 215         subnet_t *subnet;
 216         splay_node_t *node;
 217         connection_t *c;
 218
 219         subnet = lookup_subnet_mac(myself, address);
 220
 221         /* If we don't know this MAC address yet, store it */
 222
 223         if(!subnet) {
 224                 ifdebug(TRAFFIC) logger(LOG_INFO, "Learned new MAC address %hx:%hx:%hx:%hx:%hx:%hx",
 225                                    address->x[0], address->x[1], address->x[2], address->x[3],
 226                                    address->x[4], address->x[5]);
 227
 228                 subnet = new_subnet();
 229                 subnet->type = SUBNET_MAC;
 230                 subnet->expires = time(NULL) + macexpire;
 231                 subnet->net.mac.address = *address;
 232                 subnet->weight = 10;
 233                 subnet_add(myself, subnet);
 234                 subnet_update(myself, subnet, true);
 235
 236                 /* And tell all other tinc daemons it's our MAC */
 237
 238                 for(node = connection_tree->head; node; node = node->next) {
 239                         c = node->data;
 240                         if(c->status.active)
 241                                 send_add_subnet(c, subnet);
 242                 }
 243
 244                 if(!timeout_initialized(&age_subnets_event))
 245                         timeout_set(&age_subnets_event, age_subnets, NULL);
 246                 event_add(&age_subnets_event, &(struct timeval){10, 0});
 247         } else {
 248                 if(subnet->expires)
 249                         subnet->expires = time(NULL) + macexpire;
 250         }
 251 }
 252
 253 /* RFC 792 */
 254
 255 static void route_ipv4_unreachable(node_t *source, vpn_packet_t *packet, uint8_t type, uint8_t code) {
 256         struct ip ip = {0};
 257         struct icmp icmp = {0};
 258
 259         struct in_addr ip_src;
 260         struct in_addr ip_dst;
 261         uint32_t oldlen;
 262
 263         if(ratelimit(3))
 264                 return;
 265
 266         /* Swap Ethernet source and destination addresses */
 267
 268         swap_mac_addresses(packet);
 269
 270         /* Copy headers from packet into properly aligned structs on the stack */
 271
 272         memcpy(&ip, packet->data + ether_size, ip_size);
 273
 274         /* Remember original source and destination */
 275
 276         ip_src = ip.ip_src;
 277         ip_dst = ip.ip_dst;
 278
 279         oldlen = packet->len - ether_size;
 280
 281         if(type == ICMP_DEST_UNREACH && code == ICMP_FRAG_NEEDED)
 282                 icmp.icmp_nextmtu = htons(packet->len - ether_size);
 283
 284         if(oldlen >= IP_MSS - ip_size - icmp_size)
 285                 oldlen = IP_MSS - ip_size - icmp_size;
 286
 287         /* Copy first part of original contents to ICMP message */
 288
 289         memmove(packet->data + ether_size + ip_size + icmp_size, packet->data + ether_size, oldlen);
 290
 291         /* Fill in IPv4 header */
 292
 293         ip.ip_v = 4;
 294         ip.ip_hl = ip_size / 4;
 295         ip.ip_tos = 0;
 296         ip.ip_len = htons(ip_size + icmp_size + oldlen);
 297         ip.ip_id = 0;
 298         ip.ip_off = 0;
 299         ip.ip_ttl = 255;
 300         ip.ip_p = IPPROTO_ICMP;
 301         ip.ip_sum = 0;
 302         ip.ip_src = ip_dst;
 303         ip.ip_dst = ip_src;
 304
 305         ip.ip_sum = inet_checksum(&ip, ip_size, ~0);
 306
 307         /* Fill in ICMP header */
 308
 309         icmp.icmp_type = type;
 310         icmp.icmp_code = code;
 311         icmp.icmp_cksum = 0;
 312
 313         icmp.icmp_cksum = inet_checksum(&icmp, icmp_size, ~0);
 314         icmp.icmp_cksum = inet_checksum(packet->data + ether_size + ip_size + icmp_size, oldlen, icmp.icmp_cksum);
 315
 316         /* Copy structs on stack back to packet */
 317
 318         memcpy(packet->data + ether_size, &ip, ip_size);
 319         memcpy(packet->data + ether_size + ip_size, &icmp, icmp_size);
 320
 321         packet->len = ether_size + ip_size + icmp_size + oldlen;
 322
 323         send_packet(source, packet);
 324 }
 325
 326 /* RFC 791 */
 327
 328 static void fragment_ipv4_packet(node_t *dest, vpn_packet_t *packet) {
 329         struct ip ip;
 330         vpn_packet_t fragment;
 331         int len, maxlen, todo;
 332         uint8_t *offset;
 333         uint16_t ip_off, origf;
 334
 335         memcpy(&ip, packet->data + ether_size, ip_size);
 336         fragment.priority = packet->priority;
 337
 338         if(ip.ip_hl != ip_size / 4)
 339                 return;
 340
 341         todo = ntohs(ip.ip_len) - ip_size;
 342
 343         if(ether_size + ip_size + todo != packet->len) {
 344                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Length of packet (%d) doesn't match length in IPv4 header (%zd)", packet->len, ether_size + ip_size + todo);
 345                 return;
 346         }
 347
 348         ifdebug(TRAFFIC) logger(LOG_INFO, "Fragmenting packet of %d bytes to %s (%s)", packet->len, dest->name, dest->hostname);
 349
 350         offset = packet->data + ether_size + ip_size;
 351         maxlen = (dest->mtu - ether_size - ip_size) & ~0x7;
 352         ip_off = ntohs(ip.ip_off);
 353         origf = ip_off & ~IP_OFFMASK;
 354         ip_off &= IP_OFFMASK;
 355
 356         while(todo) {
 357                 len = todo > maxlen ? maxlen : todo;
 358                 memcpy(fragment.data + ether_size + ip_size, offset, len);
 359                 todo -= len;
 360                 offset += len;
 361
 362                 ip.ip_len = htons(ip_size + len);
 363                 ip.ip_off = htons(ip_off | origf | (todo ? IP_MF : 0));
 364                 ip.ip_sum = 0;
 365                 ip.ip_sum = inet_checksum(&ip, ip_size, ~0);
 366                 memcpy(fragment.data, packet->data, ether_size);
 367                 memcpy(fragment.data + ether_size, &ip, ip_size);
 368                 fragment.len = ether_size + ip_size + len;
 369
 370                 send_packet(dest, &fragment);
 371
 372                 ip_off += len / 8;
 373         }
 374 }
 375
 376 static void route_ipv4_unicast(node_t *source, vpn_packet_t *packet) {
 377         subnet_t *subnet;
 378         node_t *via;
 379         ipv4_t dest;
 380
 381         memcpy(&dest, &packet->data[30], sizeof dest);
 382         subnet = lookup_subnet_ipv4(&dest);
 383
 384         if(!subnet) {
 385                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Cannot route packet from %s (%s): unknown IPv4 destination address %d.%d.%d.%d",
 386                                 source->name, source->hostname,
 387                                 dest.x[0],
 388                                 dest.x[1],
 389                                 dest.x[2],
 390                                 dest.x[3]);
 391
 392                 route_ipv4_unreachable(source, packet, ICMP_DEST_UNREACH, ICMP_NET_UNKNOWN);
 393                 return;
 394         }
 395
 396         if(subnet->owner == source) {
 397                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Packet looping back to %s (%s)!", source->name, source->hostname);
 398                 return;
 399         }
 400
 401         if(!subnet->owner->status.reachable)
 402                 return route_ipv4_unreachable(source, packet, ICMP_DEST_UNREACH, ICMP_NET_UNREACH);
 403
 404         if(forwarding_mode == FMODE_OFF && source != myself && subnet->owner != myself)
 405                 return route_ipv4_unreachable(source, packet, ICMP_DEST_UNREACH, ICMP_NET_ANO);
 406
 407         if(priorityinheritance)
 408                 packet->priority = packet->data[15];
 409
 410         via = (subnet->owner->via == myself) ? subnet->owner->nexthop : subnet->owner->via;
 411
 412         if(directonly && subnet->owner != via)
 413                 return route_ipv4_unreachable(source, packet, ICMP_DEST_UNREACH, ICMP_NET_ANO);
 414
 415         if(via && packet->len > max(via->mtu, 590) && via != myself) {
 416                 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);
 417                 if(packet->data[20] & 0x40) {
 418                         packet->len = max(via->mtu, 590);
 419                         route_ipv4_unreachable(source, packet, ICMP_DEST_UNREACH, ICMP_FRAG_NEEDED);
 420                 } else {
 421                         fragment_ipv4_packet(via, packet);
 422                 }
 423
 424                 return;
 425         }
 426
 427         clamp_mss(source, via, packet);
 428
 429         send_packet(subnet->owner, packet);
 430 }
 431
 432 static void route_ipv4(node_t *source, vpn_packet_t *packet) {
 433         if(!checklength(source, packet, ether_size + ip_size))
 434                 return;
 435
 436         if(((packet->data[30] & 0xf0) == 0xe0) || (
 437                         packet->data[30] == 255 &&
 438                         packet->data[31] == 255 &&
 439                         packet->data[32] == 255 &&
 440                         packet->data[33] == 255))
 441                 broadcast_packet(source, packet);
 442         else
 443                 route_ipv4_unicast(source, packet);
 444 }
 445
 446 /* RFC 2463 */
 447
 448 static void route_ipv6_unreachable(node_t *source, vpn_packet_t *packet, uint8_t type, uint8_t code) {
 449         struct ip6_hdr ip6;
 450         struct icmp6_hdr icmp6 = {0};
 451         uint16_t checksum;
 452
 453         struct {
 454                 struct in6_addr ip6_src;        /* source address */
 455                 struct in6_addr ip6_dst;        /* destination address */
 456                 uint32_t length;
 457                 uint32_t next;
 458         } pseudo;
 459
 460         if(ratelimit(3))
 461                 return;
 462
 463         /* Swap Ethernet source and destination addresses */
 464
 465         swap_mac_addresses(packet);
 466
 467         /* Copy headers from packet to structs on the stack */
 468
 469         memcpy(&ip6, packet->data + ether_size, ip6_size);
 470
 471         /* Remember original source and destination */
 472
 473         pseudo.ip6_src = ip6.ip6_dst;
 474         pseudo.ip6_dst = ip6.ip6_src;
 475
 476         pseudo.length = packet->len - ether_size;
 477
 478         if(type == ICMP6_PACKET_TOO_BIG)
 479                 icmp6.icmp6_mtu = htonl(pseudo.length);
 480
 481         if(pseudo.length >= IP_MSS - ip6_size - icmp6_size)
 482                 pseudo.length = IP_MSS - ip6_size - icmp6_size;
 483
 484         /* Copy first part of original contents to ICMP message */
 485
 486         memmove(packet->data + ether_size + ip6_size + icmp6_size, packet->data + ether_size, pseudo.length);
 487
 488         /* Fill in IPv6 header */
 489
 490         ip6.ip6_flow = htonl(0x60000000UL);
 491         ip6.ip6_plen = htons(icmp6_size + pseudo.length);
 492         ip6.ip6_nxt = IPPROTO_ICMPV6;
 493         ip6.ip6_hlim = 255;
 494         ip6.ip6_src = pseudo.ip6_src;
 495         ip6.ip6_dst = pseudo.ip6_dst;
 496
 497         /* Fill in ICMP header */
 498
 499         icmp6.icmp6_type = type;
 500         icmp6.icmp6_code = code;
 501         icmp6.icmp6_cksum = 0;
 502
 503         /* Create pseudo header */
 504
 505         pseudo.length = htonl(icmp6_size + pseudo.length);
 506         pseudo.next = htonl(IPPROTO_ICMPV6);
 507
 508         /* Generate checksum */
 509
 510         checksum = inet_checksum(&pseudo, sizeof pseudo, ~0);
 511         checksum = inet_checksum(&icmp6, icmp6_size, checksum);
 512         checksum = inet_checksum(packet->data + ether_size + ip6_size + icmp6_size, ntohl(pseudo.length) - icmp6_size, checksum);
 513
 514         icmp6.icmp6_cksum = checksum;
 515
 516         /* Copy structs on stack back to packet */
 517
 518         memcpy(packet->data + ether_size, &ip6, ip6_size);
 519         memcpy(packet->data + ether_size + ip6_size, &icmp6, icmp6_size);
 520
 521         packet->len = ether_size + ip6_size + ntohl(pseudo.length);
 522
 523         send_packet(source, packet);
 524 }
 525
 526 static void route_ipv6_unicast(node_t *source, vpn_packet_t *packet) {
 527         subnet_t *subnet;
 528         node_t *via;
 529         ipv6_t dest;
 530
 531         memcpy(&dest, &packet->data[38], sizeof dest);
 532         subnet = lookup_subnet_ipv6(&dest);
 533
 534         if(!subnet) {
 535                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Cannot route packet from %s (%s): unknown IPv6 destination address %hx:%hx:%hx:%hx:%hx:%hx:%hx:%hx",
 536                                 source->name, source->hostname,
 537                                 ntohs(dest.x[0]),
 538                                 ntohs(dest.x[1]),
 539                                 ntohs(dest.x[2]),
 540                                 ntohs(dest.x[3]),
 541                                 ntohs(dest.x[4]),
 542                                 ntohs(dest.x[5]),
 543                                 ntohs(dest.x[6]),
 544                                 ntohs(dest.x[7]));
 545
 546                 route_ipv6_unreachable(source, packet, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_ADDR);
 547                 return;
 548         }
 549
 550         if(subnet->owner == source) {
 551                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Packet looping back to %s (%s)!", source->name, source->hostname);
 552                 return;
 553         }
 554
 555         if(!subnet->owner->status.reachable)
 556                 return route_ipv6_unreachable(source, packet, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_NOROUTE);
 557
 558         if(forwarding_mode == FMODE_OFF && source != myself && subnet->owner != myself)
 559                 return route_ipv6_unreachable(source, packet, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_ADMIN);
 560
 561         via = (subnet->owner->via == myself) ? subnet->owner->nexthop : subnet->owner->via;
 562
 563         if(directonly && subnet->owner != via)
 564                 return route_ipv6_unreachable(source, packet, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_ADMIN);
 565
 566         if(via && packet->len > max(via->mtu, 1294) && via != myself) {
 567                 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);
 568                 packet->len = max(via->mtu, 1294);
 569                 route_ipv6_unreachable(source, packet, ICMP6_PACKET_TOO_BIG, 0);
 570                 return;
 571         }
 572
 573         clamp_mss(source, via, packet);
 574
 575         send_packet(subnet->owner, packet);
 576 }
 577
 578 /* RFC 2461 */
 579
 580 static void route_neighborsol(node_t *source, vpn_packet_t *packet) {
 581         struct ip6_hdr ip6;
 582         struct nd_neighbor_solicit ns;
 583         struct nd_opt_hdr opt;
 584         subnet_t *subnet;
 585         uint16_t checksum;
 586         bool has_opt;
 587
 588         struct {
 589                 struct in6_addr ip6_src;        /* source address */
 590                 struct in6_addr ip6_dst;        /* destination address */
 591                 uint32_t length;
 592                 uint32_t next;
 593         } pseudo;
 594
 595         if(!checklength(source, packet, ether_size + ip6_size + ns_size))
 596                 return;
 597
 598         has_opt = packet->len >= ether_size + ip6_size + ns_size + opt_size + ETH_ALEN;
 599
 600         if(source != myself) {
 601                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Got neighbor solicitation request from %s (%s) while in router mode!", source->name, source->hostname);
 602                 return;
 603         }
 604
 605         /* Copy headers from packet to structs on the stack */
 606
 607         memcpy(&ip6, packet->data + ether_size, ip6_size);
 608         memcpy(&ns, packet->data + ether_size + ip6_size, ns_size);
 609         if(has_opt)
 610                 memcpy(&opt, packet->data + ether_size + ip6_size + ns_size, opt_size);
 611
 612         /* First, snatch the source address from the neighbor solicitation packet */
 613
 614         if(overwrite_mac)
 615                 memcpy(mymac.x, packet->data + ETH_ALEN, ETH_ALEN);
 616
 617         /* Check if this is a valid neighbor solicitation request */
 618
 619         if(ns.nd_ns_hdr.icmp6_type != ND_NEIGHBOR_SOLICIT ||
 620            (has_opt && opt.nd_opt_type != ND_OPT_SOURCE_LINKADDR)) {
 621                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Cannot route packet: received unknown type neighbor solicitation request");
 622                 return;
 623         }
 624
 625         /* Create pseudo header */
 626
 627         pseudo.ip6_src = ip6.ip6_src;
 628         pseudo.ip6_dst = ip6.ip6_dst;
 629         if(has_opt)
 630                 pseudo.length = htonl(ns_size + opt_size + ETH_ALEN);
 631         else
 632                 pseudo.length = htonl(ns_size);
 633         pseudo.next = htonl(IPPROTO_ICMPV6);
 634
 635         /* Generate checksum */
 636
 637         checksum = inet_checksum(&pseudo, sizeof pseudo, ~0);
 638         checksum = inet_checksum(&ns, ns_size, checksum);
 639         if(has_opt) {
 640                 checksum = inet_checksum(&opt, opt_size, checksum);
 641                 checksum = inet_checksum(packet->data + ether_size + ip6_size + ns_size + opt_size, ETH_ALEN, checksum);
 642         }
 643
 644         if(checksum) {
 645                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Cannot route packet: checksum error for neighbor solicitation request");
 646                 return;
 647         }
 648
 649         /* Check if the IPv6 address exists on the VPN */
 650
 651         subnet = lookup_subnet_ipv6((ipv6_t *) &ns.nd_ns_target);
 652
 653         if(!subnet) {
 654                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Cannot route packet: neighbor solicitation request for unknown address %hx:%hx:%hx:%hx:%hx:%hx:%hx:%hx",
 655                                    ntohs(((uint16_t *) &ns.nd_ns_target)[0]),
 656                                    ntohs(((uint16_t *) &ns.nd_ns_target)[1]),
 657                                    ntohs(((uint16_t *) &ns.nd_ns_target)[2]),
 658                                    ntohs(((uint16_t *) &ns.nd_ns_target)[3]),
 659                                    ntohs(((uint16_t *) &ns.nd_ns_target)[4]),
 660                                    ntohs(((uint16_t *) &ns.nd_ns_target)[5]),
 661                                    ntohs(((uint16_t *) &ns.nd_ns_target)[6]),
 662                                    ntohs(((uint16_t *) &ns.nd_ns_target)[7]));
 663
 664                 return;
 665         }
 666
 667         /* Check if it is for our own subnet */
 668
 669         if(subnet->owner == myself)
 670                 return;                                 /* silently ignore */
 671
 672         /* Create neighbor advertation reply */
 673
 674         memcpy(packet->data, packet->data + ETH_ALEN, ETH_ALEN);        /* copy destination address */
 675         packet->data[ETH_ALEN * 2 - 1] ^= 0xFF; /* mangle source address so it looks like it's not from us */
 676
 677         ip6.ip6_dst = ip6.ip6_src;                      /* swap destination and source protocoll address */
 678         ip6.ip6_src = ns.nd_ns_target;
 679
 680         if(has_opt)
 681                 memcpy(packet->data + ether_size + ip6_size + ns_size + opt_size, packet->data + ETH_ALEN, ETH_ALEN);   /* add fake source hard addr */
 682
 683         ns.nd_ns_cksum = 0;
 684         ns.nd_ns_type = ND_NEIGHBOR_ADVERT;
 685         ns.nd_ns_reserved = htonl(0x40000000UL);        /* Set solicited flag */
 686         opt.nd_opt_type = ND_OPT_TARGET_LINKADDR;
 687
 688         /* Create pseudo header */
 689
 690         pseudo.ip6_src = ip6.ip6_src;
 691         pseudo.ip6_dst = ip6.ip6_dst;
 692         if(has_opt)
 693                 pseudo.length = htonl(ns_size + opt_size + ETH_ALEN);
 694         else
 695                 pseudo.length = htonl(ns_size);
 696         pseudo.next = htonl(IPPROTO_ICMPV6);
 697
 698         /* Generate checksum */
 699
 700         checksum = inet_checksum(&pseudo, sizeof pseudo, ~0);
 701         checksum = inet_checksum(&ns, ns_size, checksum);
 702         if(has_opt) {
 703                 checksum = inet_checksum(&opt, opt_size, checksum);
 704                 checksum = inet_checksum(packet->data + ether_size + ip6_size + ns_size + opt_size, ETH_ALEN, checksum);
 705         }
 706
 707         ns.nd_ns_hdr.icmp6_cksum = checksum;
 708
 709         /* Copy structs on stack back to packet */
 710
 711         memcpy(packet->data + ether_size, &ip6, ip6_size);
 712         memcpy(packet->data + ether_size + ip6_size, &ns, ns_size);
 713         if(has_opt)
 714                 memcpy(packet->data + ether_size + ip6_size + ns_size, &opt, opt_size);
 715
 716         send_packet(source, packet);
 717 }
 718
 719 static void route_ipv6(node_t *source, vpn_packet_t *packet) {
 720         if(!checklength(source, packet, ether_size + ip6_size))
 721                 return;
 722
 723         if(packet->data[20] == IPPROTO_ICMPV6 && checklength(source, packet, ether_size + ip6_size + icmp6_size) && packet->data[54] == ND_NEIGHBOR_SOLICIT) {
 724                 route_neighborsol(source, packet);
 725                 return;
 726         }
 727
 728         if(packet->data[38] == 255)
 729                 broadcast_packet(source, packet);
 730         else
 731                 route_ipv6_unicast(source, packet);
 732 }
 733
 734 /* RFC 826 */
 735
 736 static void route_arp(node_t *source, vpn_packet_t *packet) {
 737         struct ether_arp arp;
 738         subnet_t *subnet;
 739         struct in_addr addr;
 740
 741         if(!checklength(source, packet, ether_size + arp_size))
 742                 return;
 743
 744         if(source != myself) {
 745                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Got ARP request from %s (%s) while in router mode!", source->name, source->hostname);
 746                 return;
 747         }
 748
 749         /* First, snatch the source address from the ARP packet */
 750
 751         if(overwrite_mac)
 752                 memcpy(mymac.x, packet->data + ETH_ALEN, ETH_ALEN);
 753
 754         /* Copy headers from packet to structs on the stack */
 755
 756         memcpy(&arp, packet->data + ether_size, arp_size);
 757
 758         /* Check if this is a valid ARP request */
 759
 760         if(ntohs(arp.arp_hrd) != ARPHRD_ETHER || ntohs(arp.arp_pro) != ETH_P_IP ||
 761            arp.arp_hln != ETH_ALEN || arp.arp_pln != sizeof addr || ntohs(arp.arp_op) != ARPOP_REQUEST) {
 762                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Cannot route packet: received unknown type ARP request");
 763                 return;
 764         }
 765
 766         /* Check if the IPv4 address exists on the VPN */
 767
 768         subnet = lookup_subnet_ipv4((ipv4_t *) &arp.arp_tpa);
 769
 770         if(!subnet) {
 771                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Cannot route packet: ARP request for unknown address %d.%d.%d.%d",
 772                                    arp.arp_tpa[0], arp.arp_tpa[1], arp.arp_tpa[2],
 773                                    arp.arp_tpa[3]);
 774                 return;
 775         }
 776
 777         /* Check if it is for our own subnet */
 778
 779         if(subnet->owner == myself)
 780                 return;                                 /* silently ignore */
 781
 782         memcpy(packet->data, packet->data + ETH_ALEN, ETH_ALEN);        /* copy destination address */
 783         packet->data[ETH_ALEN * 2 - 1] ^= 0xFF; /* mangle source address so it looks like it's not from us */
 784
 785         memcpy(&addr, arp.arp_tpa, sizeof addr);        /* save protocol addr */
 786         memcpy(arp.arp_tpa, arp.arp_spa, sizeof addr);  /* swap destination and source protocol address */
 787         memcpy(arp.arp_spa, &addr, sizeof addr);        /* ... */
 788
 789         memcpy(arp.arp_tha, arp.arp_sha, ETH_ALEN);     /* set target hard/proto addr */
 790         memcpy(arp.arp_sha, packet->data + ETH_ALEN, ETH_ALEN); /* add fake source hard addr */
 791         arp.arp_op = htons(ARPOP_REPLY);
 792
 793         /* Copy structs on stack back to packet */
 794
 795         memcpy(packet->data + ether_size, &arp, arp_size);
 796
 797         send_packet(source, packet);
 798 }
 799
 800 static void route_mac(node_t *source, vpn_packet_t *packet) {
 801         subnet_t *subnet;
 802         mac_t dest;
 803
 804         /* Learn source address */
 805
 806         if(source == myself) {
 807                 mac_t src;
 808                 memcpy(&src, &packet->data[6], sizeof src);
 809                 learn_mac(&src);
 810         }
 811
 812         /* Lookup destination address */
 813
 814         memcpy(&dest, &packet->data[0], sizeof dest);
 815         subnet = lookup_subnet_mac(NULL, &dest);
 816
 817         if(!subnet) {
 818                 broadcast_packet(source, packet);
 819                 return;
 820         }
 821
 822         if(subnet->owner == source) {
 823                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Packet looping back to %s (%s)!", source->name, source->hostname);
 824                 return;
 825         }
 826
 827         if(forwarding_mode == FMODE_OFF && source != myself && subnet->owner != myself)
 828                 return;
 829
 830         // Handle packets larger than PMTU
 831
 832         node_t *via = (subnet->owner->via == myself) ? subnet->owner->nexthop : subnet->owner->via;
 833
 834         if(directonly && subnet->owner != via)
 835                 return;
 836
 837         if(via && packet->len > via->mtu && via != myself) {
 838                 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);
 839                 uint16_t type = packet->data[12] << 8 | packet->data[13];
 840                 if(type == ETH_P_IP && packet->len > 590) {
 841                         if(packet->data[20] & 0x40) {
 842                                 packet->len = via->mtu;
 843                                 route_ipv4_unreachable(source, packet, ICMP_DEST_UNREACH, ICMP_FRAG_NEEDED);
 844                         } else {
 845                                 fragment_ipv4_packet(via, packet);
 846                         }
 847                         return;
 848                 } else if(type == ETH_P_IPV6 && packet->len > 1294) {
 849                         packet->len = via->mtu;
 850                         route_ipv6_unreachable(source, packet, ICMP6_PACKET_TOO_BIG, 0);
 851                         return;
 852                 }
 853         }
 854
 855         clamp_mss(source, via, packet);
 856
 857         send_packet(subnet->owner, packet);
 858 }
 859
 860 void route(node_t *source, vpn_packet_t *packet) {
 861         if(forwarding_mode == FMODE_KERNEL && source != myself) {
 862                 send_packet(myself, packet);
 863                 return;
 864         }
 865
 866         if(!checklength(source, packet, ether_size))
 867                 return;
 868
 869         switch (routing_mode) {
 870                 case RMODE_ROUTER:
 871                         {
 872                                 uint16_t type = packet->data[12] << 8 | packet->data[13];
 873
 874                                 switch (type) {
 875                                         case ETH_P_ARP:
 876                                                 route_arp(source, packet);
 877                                                 break;
 878
 879                                         case ETH_P_IP:
 880                                                 route_ipv4(source, packet);
 881                                                 break;
 882
 883                                         case ETH_P_IPV6:
 884                                                 route_ipv6(source, packet);
 885                                                 break;
 886
 887                                         default:
 888                                                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Cannot route packet from %s (%s): unknown type %hx", source->name, source->hostname, type);
 889                                                 break;
 890                                 }
 891                         }
 892                         break;
 893
 894                 case RMODE_SWITCH:
 895                         route_mac(source, packet);
 896                         break;
 897
 898                 case RMODE_HUB:
 899                         broadcast_packet(source, packet);
 900                         break;
 901         }
 902 }