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(!source || !via || !(via->options & OPTION_CLAMP_MSS))
  98                 return;
  99
 100         uint16_t mtu = source->mtu;
 101         if(via != myself && via->mtu < mtu)
 102                 mtu = via->mtu;
 103
 104         /* Find TCP header */
 105         int start = 0;
 106         uint16_t type = packet->data[12] << 8 | packet->data[13];
 107
 108         if(type == ETH_P_IP && packet->data[23] == 6)
 109                 start = 14 + (packet->data[14] & 0xf) * 4;
 110         else if(type == ETH_P_IPV6 && packet->data[20] == 6)
 111                 start = 14 + 40;
 112
 113         if(!start || packet->len <= start + 20)
 114                 return;
 115
 116         /* Use data offset field to calculate length of options field */
 117         int len = ((packet->data[start + 12] >> 4) - 5) * 4;
 118
 119         if(packet->len < start + 20 + len)
 120                 return;
 121
 122         /* Search for MSS option header */
 123         for(int i = 0; i < len;) {
 124                 if(packet->data[start + 20 + i] == 0)
 125                         break;
 126
 127                 if(packet->data[start + 20 + i] == 1) {
 128                         i++;
 129                         continue;
 130                 }
 131
 132                 if(i > len - 2 || i > len - packet->data[start + 21 + i])
 133                         break;
 134
 135                 if(packet->data[start + 20 + i] != 2) {
 136                         if(packet->data[start + 21 + i] < 2)
 137                                 break;
 138                         i += packet->data[start + 21 + i];
 139                         continue;
 140                 }
 141
 142                 if(packet->data[start + 21] != 4)
 143                         break;
 144
 145                 /* Found it */
 146                 uint16_t oldmss = packet->data[start + 22 + i] << 8 | packet->data[start + 23 + i];
 147                 uint16_t newmss = mtu - start - 20;
 148                 uint16_t csum = packet->data[start + 16] << 8 | packet->data[start + 17];
 149
 150                 if(oldmss <= newmss)
 151                         break;
 152
 153                 ifdebug(TRAFFIC) logger(LOG_INFO, "Clamping MSS of packet from %s to %s to %d", source->name, via->name, newmss);
 154
 155                 /* Update the MSS value and the checksum */
 156                 packet->data[start + 22 + i] = newmss >> 8;
 157                 packet->data[start + 23 + i] = newmss & 0xff;
 158                 csum ^= 0xffff;
 159                 csum -= oldmss;
 160                 csum += newmss;
 161                 csum ^= 0xffff;
 162                 packet->data[start + 16] = csum >> 8;
 163                 packet->data[start + 17] = csum & 0xff;
 164                 break;
 165         }
 166 }
 167
 168 static void swap_mac_addresses(vpn_packet_t *packet) {
 169         mac_t tmp;
 170         memcpy(&tmp, &packet->data[0], sizeof tmp);
 171         memcpy(&packet->data[0], &packet->data[6], sizeof tmp);
 172         memcpy(&packet->data[6], &tmp, sizeof tmp);
 173 }
 174
 175 static void learn_mac(mac_t *address) {
 176         subnet_t *subnet;
 177         avl_node_t *node;
 178         connection_t *c;
 179
 180         subnet = lookup_subnet_mac(myself, address);
 181
 182         /* If we don't know this MAC address yet, store it */
 183
 184         if(!subnet) {
 185                 ifdebug(TRAFFIC) logger(LOG_INFO, "Learned new MAC address %hx:%hx:%hx:%hx:%hx:%hx",
 186                                    address->x[0], address->x[1], address->x[2], address->x[3],
 187                                    address->x[4], address->x[5]);
 188
 189                 subnet = new_subnet();
 190                 subnet->type = SUBNET_MAC;
 191                 subnet->expires = now + macexpire;
 192                 subnet->net.mac.address = *address;
 193                 subnet->weight = 10;
 194                 subnet_add(myself, subnet);
 195                 subnet_update(myself, subnet, true);
 196
 197                 /* And tell all other tinc daemons it's our MAC */
 198
 199                 for(node = connection_tree->head; node; node = node->next) {
 200                         c = node->data;
 201                         if(c->status.active)
 202                                 send_add_subnet(c, subnet);
 203                 }
 204         }
 205
 206         if(subnet->expires)
 207                 subnet->expires = now + macexpire;
 208 }
 209
 210 void age_subnets(void) {
 211         subnet_t *s;
 212         connection_t *c;
 213         avl_node_t *node, *next, *node2;
 214
 215         for(node = myself->subnet_tree->head; node; node = next) {
 216                 next = node->next;
 217                 s = node->data;
 218                 if(s->expires && s->expires < now) {
 219                         ifdebug(TRAFFIC) {
 220                                 char netstr[MAXNETSTR];
 221                                 if(net2str(netstr, sizeof netstr, s))
 222                                         logger(LOG_INFO, "Subnet %s expired", netstr);
 223                         }
 224
 225                         for(node2 = connection_tree->head; node2; node2 = node2->next) {
 226                                 c = node2->data;
 227                                 if(c->status.active)
 228                                         send_del_subnet(c, s);
 229                         }
 230
 231                         subnet_update(myself, s, false);
 232                         subnet_del(myself, s);
 233                 }
 234         }
 235 }
 236
 237 /* RFC 792 */
 238
 239 static void route_ipv4_unreachable(node_t *source, vpn_packet_t *packet, uint8_t type, uint8_t code) {
 240         struct ip ip = {0};
 241         struct icmp icmp = {0};
 242
 243         struct in_addr ip_src;
 244         struct in_addr ip_dst;
 245         uint32_t oldlen;
 246
 247         if(ratelimit(3))
 248                 return;
 249
 250         /* Swap Ethernet source and destination addresses */
 251
 252         swap_mac_addresses(packet);
 253
 254         /* Copy headers from packet into properly aligned structs on the stack */
 255
 256         memcpy(&ip, packet->data + ether_size, ip_size);
 257
 258         /* Remember original source and destination */
 259
 260         ip_src = ip.ip_src;
 261         ip_dst = ip.ip_dst;
 262
 263         oldlen = packet->len - ether_size;
 264
 265         if(type == ICMP_DEST_UNREACH && code == ICMP_FRAG_NEEDED)
 266                 icmp.icmp_nextmtu = htons(packet->len - ether_size);
 267
 268         if(oldlen >= IP_MSS - ip_size - icmp_size)
 269                 oldlen = IP_MSS - ip_size - icmp_size;
 270
 271         /* Copy first part of original contents to ICMP message */
 272
 273         memmove(packet->data + ether_size + ip_size + icmp_size, packet->data + ether_size, oldlen);
 274
 275         /* Fill in IPv4 header */
 276
 277         ip.ip_v = 4;
 278         ip.ip_hl = ip_size / 4;
 279         ip.ip_tos = 0;
 280         ip.ip_len = htons(ip_size + icmp_size + oldlen);
 281         ip.ip_id = 0;
 282         ip.ip_off = 0;
 283         ip.ip_ttl = 255;
 284         ip.ip_p = IPPROTO_ICMP;
 285         ip.ip_sum = 0;
 286         ip.ip_src = ip_dst;
 287         ip.ip_dst = ip_src;
 288
 289         ip.ip_sum = inet_checksum(&ip, ip_size, ~0);
 290
 291         /* Fill in ICMP header */
 292
 293         icmp.icmp_type = type;
 294         icmp.icmp_code = code;
 295         icmp.icmp_cksum = 0;
 296
 297         icmp.icmp_cksum = inet_checksum(&icmp, icmp_size, ~0);
 298         icmp.icmp_cksum = inet_checksum(packet->data + ether_size + ip_size + icmp_size, oldlen, icmp.icmp_cksum);
 299
 300         /* Copy structs on stack back to packet */
 301
 302         memcpy(packet->data + ether_size, &ip, ip_size);
 303         memcpy(packet->data + ether_size + ip_size, &icmp, icmp_size);
 304
 305         packet->len = ether_size + ip_size + icmp_size + oldlen;
 306
 307         send_packet(source, packet);
 308 }
 309
 310 /* RFC 791 */
 311
 312 static void fragment_ipv4_packet(node_t *dest, vpn_packet_t *packet) {
 313         struct ip ip;
 314         vpn_packet_t fragment;
 315         int len, maxlen, todo;
 316         uint8_t *offset;
 317         uint16_t ip_off, origf;
 318
 319         memcpy(&ip, packet->data + ether_size, ip_size);
 320         fragment.priority = packet->priority;
 321
 322         if(ip.ip_hl != ip_size / 4)
 323                 return;
 324
 325         todo = ntohs(ip.ip_len) - ip_size;
 326
 327         if(ether_size + ip_size + todo != packet->len) {
 328                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Length of packet (%d) doesn't match length in IPv4 header (%zd)", packet->len, ether_size + ip_size + todo);
 329                 return;
 330         }
 331
 332         ifdebug(TRAFFIC) logger(LOG_INFO, "Fragmenting packet of %d bytes to %s (%s)", packet->len, dest->name, dest->hostname);
 333
 334         offset = packet->data + ether_size + ip_size;
 335         maxlen = (dest->mtu - ether_size - ip_size) & ~0x7;
 336         ip_off = ntohs(ip.ip_off);
 337         origf = ip_off & ~IP_OFFMASK;
 338         ip_off &= IP_OFFMASK;
 339
 340         while(todo) {
 341                 len = todo > maxlen ? maxlen : todo;
 342                 memcpy(fragment.data + ether_size + ip_size, offset, len);
 343                 todo -= len;
 344                 offset += len;
 345
 346                 ip.ip_len = htons(ip_size + len);
 347                 ip.ip_off = htons(ip_off | origf | (todo ? IP_MF : 0));
 348                 ip.ip_sum = 0;
 349                 ip.ip_sum = inet_checksum(&ip, ip_size, ~0);
 350                 memcpy(fragment.data, packet->data, ether_size);
 351                 memcpy(fragment.data + ether_size, &ip, ip_size);
 352                 fragment.len = ether_size + ip_size + len;
 353
 354                 send_packet(dest, &fragment);
 355
 356                 ip_off += len / 8;
 357         }
 358 }
 359
 360 static void route_ipv4_unicast(node_t *source, vpn_packet_t *packet) {
 361         subnet_t *subnet;
 362         node_t *via;
 363         ipv4_t dest;
 364
 365         memcpy(&dest, &packet->data[30], sizeof dest);
 366         subnet = lookup_subnet_ipv4(&dest);
 367
 368         if(!subnet) {
 369                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Cannot route packet from %s (%s): unknown IPv4 destination address %d.%d.%d.%d",
 370                                 source->name, source->hostname,
 371                                 dest.x[0],
 372                                 dest.x[1],
 373                                 dest.x[2],
 374                                 dest.x[3]);
 375
 376                 route_ipv4_unreachable(source, packet, ICMP_DEST_UNREACH, ICMP_NET_UNKNOWN);
 377                 return;
 378         }
 379
 380         if(subnet->owner == source) {
 381                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Packet looping back to %s (%s)!", source->name, source->hostname);
 382                 return;
 383         }
 384
 385         if(!subnet->owner->status.reachable)
 386                 route_ipv4_unreachable(source, packet, ICMP_DEST_UNREACH, ICMP_NET_UNREACH);
 387
 388         if(priorityinheritance)
 389                 packet->priority = packet->data[15];
 390
 391         via = (subnet->owner->via == myself) ? subnet->owner->nexthop : subnet->owner->via;
 392
 393         if(via && packet->len > max(via->mtu, 590) && via != myself) {
 394                 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);
 395                 if(packet->data[20] & 0x40) {
 396                         packet->len = max(via->mtu, 590);
 397                         route_ipv4_unreachable(source, packet, ICMP_DEST_UNREACH, ICMP_FRAG_NEEDED);
 398                 } else {
 399                         fragment_ipv4_packet(via, packet);
 400                 }
 401
 402                 return;
 403         }
 404
 405         clamp_mss(source, via, packet);
 406
 407         send_packet(subnet->owner, packet);
 408 }
 409
 410 static void route_ipv4(node_t *source, vpn_packet_t *packet) {
 411         if(!checklength(source, packet, ether_size + ip_size))
 412                 return;
 413
 414         if(((packet->data[30] & 0xf0) == 0xe0) || (
 415                         packet->data[30] == 255 &&
 416                         packet->data[31] == 255 &&
 417                         packet->data[32] == 255 &&
 418                         packet->data[33] == 255))
 419                 broadcast_packet(source, packet);
 420         else
 421                 route_ipv4_unicast(source, packet);
 422 }
 423
 424 /* RFC 2463 */
 425
 426 static void route_ipv6_unreachable(node_t *source, vpn_packet_t *packet, uint8_t type, uint8_t code) {
 427         struct ip6_hdr ip6;
 428         struct icmp6_hdr icmp6 = {0};
 429         uint16_t checksum;
 430
 431         struct {
 432                 struct in6_addr ip6_src;        /* source address */
 433                 struct in6_addr ip6_dst;        /* destination address */
 434                 uint32_t length;
 435                 uint32_t next;
 436         } pseudo;
 437
 438         if(ratelimit(3))
 439                 return;
 440
 441         /* Swap Ethernet source and destination addresses */
 442
 443         swap_mac_addresses(packet);
 444
 445         /* Copy headers from packet to structs on the stack */
 446
 447         memcpy(&ip6, packet->data + ether_size, ip6_size);
 448
 449         /* Remember original source and destination */
 450
 451         pseudo.ip6_src = ip6.ip6_dst;
 452         pseudo.ip6_dst = ip6.ip6_src;
 453
 454         pseudo.length = packet->len - ether_size;
 455
 456         if(type == ICMP6_PACKET_TOO_BIG)
 457                 icmp6.icmp6_mtu = htonl(pseudo.length);
 458
 459         if(pseudo.length >= IP_MSS - ip6_size - icmp6_size)
 460                 pseudo.length = IP_MSS - ip6_size - icmp6_size;
 461
 462         /* Copy first part of original contents to ICMP message */
 463
 464         memmove(packet->data + ether_size + ip6_size + icmp6_size, packet->data + ether_size, pseudo.length);
 465
 466         /* Fill in IPv6 header */
 467
 468         ip6.ip6_flow = htonl(0x60000000UL);
 469         ip6.ip6_plen = htons(icmp6_size + pseudo.length);
 470         ip6.ip6_nxt = IPPROTO_ICMPV6;
 471         ip6.ip6_hlim = 255;
 472         ip6.ip6_src = pseudo.ip6_src;
 473         ip6.ip6_dst = pseudo.ip6_dst;
 474
 475         /* Fill in ICMP header */
 476
 477         icmp6.icmp6_type = type;
 478         icmp6.icmp6_code = code;
 479         icmp6.icmp6_cksum = 0;
 480
 481         /* Create pseudo header */
 482
 483         pseudo.length = htonl(icmp6_size + pseudo.length);
 484         pseudo.next = htonl(IPPROTO_ICMPV6);
 485
 486         /* Generate checksum */
 487
 488         checksum = inet_checksum(&pseudo, sizeof(pseudo), ~0);
 489         checksum = inet_checksum(&icmp6, icmp6_size, checksum);
 490         checksum = inet_checksum(packet->data + ether_size + ip6_size + icmp6_size, ntohl(pseudo.length) - icmp6_size, checksum);
 491
 492         icmp6.icmp6_cksum = checksum;
 493
 494         /* Copy structs on stack back to packet */
 495
 496         memcpy(packet->data + ether_size, &ip6, ip6_size);
 497         memcpy(packet->data + ether_size + ip6_size, &icmp6, icmp6_size);
 498
 499         packet->len = ether_size + ip6_size + ntohl(pseudo.length);
 500
 501         send_packet(source, packet);
 502 }
 503
 504 static void route_ipv6_unicast(node_t *source, vpn_packet_t *packet) {
 505         subnet_t *subnet;
 506         node_t *via;
 507         ipv6_t dest;
 508
 509         memcpy(&dest, &packet->data[38], sizeof dest);
 510         subnet = lookup_subnet_ipv6(&dest);
 511
 512         if(!subnet) {
 513                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Cannot route packet from %s (%s): unknown IPv6 destination address %hx:%hx:%hx:%hx:%hx:%hx:%hx:%hx",
 514                                 source->name, source->hostname,
 515                                 ntohs(dest.x[0]),
 516                                 ntohs(dest.x[1]),
 517                                 ntohs(dest.x[2]),
 518                                 ntohs(dest.x[3]),
 519                                 ntohs(dest.x[4]),
 520                                 ntohs(dest.x[5]),
 521                                 ntohs(dest.x[6]),
 522                                 ntohs(dest.x[7]));
 523
 524                 route_ipv6_unreachable(source, packet, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_ADDR);
 525                 return;
 526         }
 527
 528         if(subnet->owner == source) {
 529                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Packet looping back to %s (%s)!", source->name, source->hostname);
 530                 return;
 531         }
 532
 533         if(!subnet->owner->status.reachable)
 534                 route_ipv6_unreachable(source, packet, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_NOROUTE);
 535
 536         via = (subnet->owner->via == myself) ? subnet->owner->nexthop : subnet->owner->via;
 537
 538         if(via && packet->len > max(via->mtu, 1294) && via != myself) {
 539                 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);
 540                 packet->len = max(via->mtu, 1294);
 541                 route_ipv6_unreachable(source, packet, ICMP6_PACKET_TOO_BIG, 0);
 542                 return;
 543         }
 544
 545         clamp_mss(source, via, packet);
 546
 547         send_packet(subnet->owner, packet);
 548 }
 549
 550 /* RFC 2461 */
 551
 552 static void route_neighborsol(node_t *source, vpn_packet_t *packet) {
 553         struct ip6_hdr ip6;
 554         struct nd_neighbor_solicit ns;
 555         struct nd_opt_hdr opt;
 556         subnet_t *subnet;
 557         uint16_t checksum;
 558         bool has_opt;
 559
 560         struct {
 561                 struct in6_addr ip6_src;        /* source address */
 562                 struct in6_addr ip6_dst;        /* destination address */
 563                 uint32_t length;
 564                 uint32_t next;
 565         } pseudo;
 566
 567         if(!checklength(source, packet, ether_size + ip6_size + ns_size))
 568                 return;
 569
 570         has_opt = packet->len >= ether_size + ip6_size + ns_size + opt_size + ETH_ALEN;
 571
 572         if(source != myself) {
 573                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Got neighbor solicitation request from %s (%s) while in router mode!", source->name, source->hostname);
 574                 return;
 575         }
 576
 577         /* Copy headers from packet to structs on the stack */
 578
 579         memcpy(&ip6, packet->data + ether_size, ip6_size);
 580         memcpy(&ns, packet->data + ether_size + ip6_size, ns_size);
 581         if(has_opt)
 582                 memcpy(&opt, packet->data + ether_size + ip6_size + ns_size, opt_size);
 583
 584         /* First, snatch the source address from the neighbor solicitation packet */
 585
 586         if(overwrite_mac)
 587                 memcpy(mymac.x, packet->data + ETH_ALEN, ETH_ALEN);
 588
 589         /* Check if this is a valid neighbor solicitation request */
 590
 591         if(ns.nd_ns_hdr.icmp6_type != ND_NEIGHBOR_SOLICIT ||
 592            (has_opt && opt.nd_opt_type != ND_OPT_SOURCE_LINKADDR)) {
 593                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Cannot route packet: received unknown type neighbor solicitation request");
 594                 return;
 595         }
 596
 597         /* Create pseudo header */
 598
 599         pseudo.ip6_src = ip6.ip6_src;
 600         pseudo.ip6_dst = ip6.ip6_dst;
 601         if(has_opt)
 602                 pseudo.length = htonl(ns_size + opt_size + ETH_ALEN);
 603         else
 604                 pseudo.length = htonl(ns_size);
 605         pseudo.next = htonl(IPPROTO_ICMPV6);
 606
 607         /* Generate checksum */
 608
 609         checksum = inet_checksum(&pseudo, sizeof(pseudo), ~0);
 610         checksum = inet_checksum(&ns, ns_size, checksum);
 611         if(has_opt) {
 612                 checksum = inet_checksum(&opt, opt_size, checksum);
 613                 checksum = inet_checksum(packet->data + ether_size + ip6_size + ns_size + opt_size, ETH_ALEN, checksum);
 614         }
 615
 616         if(checksum) {
 617                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Cannot route packet: checksum error for neighbor solicitation request");
 618                 return;
 619         }
 620
 621         /* Check if the IPv6 address exists on the VPN */
 622
 623         subnet = lookup_subnet_ipv6((ipv6_t *) &ns.nd_ns_target);
 624
 625         if(!subnet) {
 626                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Cannot route packet: neighbor solicitation request for unknown address %hx:%hx:%hx:%hx:%hx:%hx:%hx:%hx",
 627                                    ntohs(((uint16_t *) &ns.nd_ns_target)[0]),
 628                                    ntohs(((uint16_t *) &ns.nd_ns_target)[1]),
 629                                    ntohs(((uint16_t *) &ns.nd_ns_target)[2]),
 630                                    ntohs(((uint16_t *) &ns.nd_ns_target)[3]),
 631                                    ntohs(((uint16_t *) &ns.nd_ns_target)[4]),
 632                                    ntohs(((uint16_t *) &ns.nd_ns_target)[5]),
 633                                    ntohs(((uint16_t *) &ns.nd_ns_target)[6]),
 634                                    ntohs(((uint16_t *) &ns.nd_ns_target)[7]));
 635
 636                 return;
 637         }
 638
 639         /* Check if it is for our own subnet */
 640
 641         if(subnet->owner == myself)
 642                 return;                                 /* silently ignore */
 643
 644         /* Create neighbor advertation reply */
 645
 646         memcpy(packet->data, packet->data + ETH_ALEN, ETH_ALEN);        /* copy destination address */
 647         packet->data[ETH_ALEN * 2 - 1] ^= 0xFF; /* mangle source address so it looks like it's not from us */
 648
 649         ip6.ip6_dst = ip6.ip6_src;                      /* swap destination and source protocoll address */
 650         ip6.ip6_src = ns.nd_ns_target;
 651
 652         if(has_opt)
 653                 memcpy(packet->data + ether_size + ip6_size + ns_size + opt_size, packet->data + ETH_ALEN, ETH_ALEN);   /* add fake source hard addr */
 654
 655         ns.nd_ns_cksum = 0;
 656         ns.nd_ns_type = ND_NEIGHBOR_ADVERT;
 657         ns.nd_ns_reserved = htonl(0x40000000UL);        /* Set solicited flag */
 658         opt.nd_opt_type = ND_OPT_TARGET_LINKADDR;
 659
 660         /* Create pseudo header */
 661
 662         pseudo.ip6_src = ip6.ip6_src;
 663         pseudo.ip6_dst = ip6.ip6_dst;
 664         if(has_opt)
 665                 pseudo.length = htonl(ns_size + opt_size + ETH_ALEN);
 666         else
 667                 pseudo.length = htonl(ns_size);
 668         pseudo.next = htonl(IPPROTO_ICMPV6);
 669
 670         /* Generate checksum */
 671
 672         checksum = inet_checksum(&pseudo, sizeof(pseudo), ~0);
 673         checksum = inet_checksum(&ns, ns_size, checksum);
 674         if(has_opt) {
 675                 checksum = inet_checksum(&opt, opt_size, checksum);
 676                 checksum = inet_checksum(packet->data + ether_size + ip6_size + ns_size + opt_size, ETH_ALEN, checksum);
 677         }
 678
 679         ns.nd_ns_hdr.icmp6_cksum = checksum;
 680
 681         /* Copy structs on stack back to packet */
 682
 683         memcpy(packet->data + ether_size, &ip6, ip6_size);
 684         memcpy(packet->data + ether_size + ip6_size, &ns, ns_size);
 685         if(has_opt)
 686                 memcpy(packet->data + ether_size + ip6_size + ns_size, &opt, opt_size);
 687
 688         send_packet(source, packet);
 689 }
 690
 691 static void route_ipv6(node_t *source, vpn_packet_t *packet) {
 692         if(!checklength(source, packet, ether_size + ip6_size))
 693                 return;
 694
 695         if(packet->data[20] == IPPROTO_ICMPV6 && checklength(source, packet, ether_size + ip6_size + icmp6_size) && packet->data[54] == ND_NEIGHBOR_SOLICIT) {
 696                 route_neighborsol(source, packet);
 697                 return;
 698         }
 699
 700         if(packet->data[38] == 255)
 701                 broadcast_packet(source, packet);
 702         else
 703                 route_ipv6_unicast(source, packet);
 704 }
 705
 706 /* RFC 826 */
 707
 708 static void route_arp(node_t *source, vpn_packet_t *packet) {
 709         struct ether_arp arp;
 710         subnet_t *subnet;
 711         struct in_addr addr;
 712
 713         if(!checklength(source, packet, ether_size + arp_size))
 714                 return;
 715
 716         if(source != myself) {
 717                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Got ARP request from %s (%s) while in router mode!", source->name, source->hostname);
 718                 return;
 719         }
 720
 721         /* First, snatch the source address from the ARP packet */
 722
 723         if(overwrite_mac)
 724                 memcpy(mymac.x, packet->data + ETH_ALEN, ETH_ALEN);
 725
 726         /* Copy headers from packet to structs on the stack */
 727
 728         memcpy(&arp, packet->data + ether_size, arp_size);
 729
 730         /* Check if this is a valid ARP request */
 731
 732         if(ntohs(arp.arp_hrd) != ARPHRD_ETHER || ntohs(arp.arp_pro) != ETH_P_IP ||
 733            arp.arp_hln != ETH_ALEN || arp.arp_pln != sizeof(addr) || ntohs(arp.arp_op) != ARPOP_REQUEST) {
 734                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Cannot route packet: received unknown type ARP request");
 735                 return;
 736         }
 737
 738         /* Check if the IPv4 address exists on the VPN */
 739
 740         subnet = lookup_subnet_ipv4((ipv4_t *) &arp.arp_tpa);
 741
 742         if(!subnet) {
 743                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Cannot route packet: ARP request for unknown address %d.%d.%d.%d",
 744                                    arp.arp_tpa[0], arp.arp_tpa[1], arp.arp_tpa[2],
 745                                    arp.arp_tpa[3]);
 746                 return;
 747         }
 748
 749         /* Check if it is for our own subnet */
 750
 751         if(subnet->owner == myself)
 752                 return;                                 /* silently ignore */
 753
 754         memcpy(packet->data, packet->data + ETH_ALEN, ETH_ALEN);        /* copy destination address */
 755         packet->data[ETH_ALEN * 2 - 1] ^= 0xFF; /* mangle source address so it looks like it's not from us */
 756
 757         memcpy(&addr, arp.arp_tpa, sizeof(addr));       /* save protocol addr */
 758         memcpy(arp.arp_tpa, arp.arp_spa, sizeof(addr)); /* swap destination and source protocol address */
 759         memcpy(arp.arp_spa, &addr, sizeof(addr));       /* ... */
 760
 761         memcpy(arp.arp_tha, arp.arp_sha, ETH_ALEN);     /* set target hard/proto addr */
 762         memcpy(arp.arp_sha, packet->data + ETH_ALEN, ETH_ALEN); /* add fake source hard addr */
 763         arp.arp_op = htons(ARPOP_REPLY);
 764
 765         /* Copy structs on stack back to packet */
 766
 767         memcpy(packet->data + ether_size, &arp, arp_size);
 768
 769         send_packet(source, packet);
 770 }
 771
 772 static void route_mac(node_t *source, vpn_packet_t *packet) {
 773         subnet_t *subnet;
 774         mac_t dest;
 775
 776         /* Learn source address */
 777
 778         if(source == myself) {
 779                 mac_t src;
 780                 memcpy(&src, &packet->data[6], sizeof src);
 781                 learn_mac(&src);
 782         }
 783
 784         /* Lookup destination address */
 785
 786         memcpy(&dest, &packet->data[0], sizeof dest);
 787         subnet = lookup_subnet_mac(NULL, &dest);
 788
 789         if(!subnet) {
 790                 broadcast_packet(source, packet);
 791                 return;
 792         }
 793
 794         if(subnet->owner == source) {
 795                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Packet looping back to %s (%s)!", source->name, source->hostname);
 796                 return;
 797         }
 798
 799         // Handle packets larger than PMTU
 800
 801         node_t *via = (subnet->owner->via == myself) ? subnet->owner->nexthop : subnet->owner->via;
 802
 803         if(via && packet->len > via->mtu && via != myself) {
 804                 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);
 805                 uint16_t type = packet->data[12] << 8 | packet->data[13];
 806                 if(type == ETH_P_IP && packet->len > 590) {
 807                         if(packet->data[20] & 0x40) {
 808                                 packet->len = via->mtu;
 809                                 route_ipv4_unreachable(source, packet, ICMP_DEST_UNREACH, ICMP_FRAG_NEEDED);
 810                         } else {
 811                                 fragment_ipv4_packet(via, packet);
 812                         }
 813                         return;
 814                 } else if(type == ETH_P_IPV6 && packet->len > 1294) {
 815                         packet->len = via->mtu;
 816                         route_ipv6_unreachable(source, packet, ICMP6_PACKET_TOO_BIG, 0);
 817                         return;
 818                 }
 819         }
 820
 821         clamp_mss(source, via, packet);
 822
 823         send_packet(subnet->owner, packet);
 824 }
 825
 826 void route(node_t *source, vpn_packet_t *packet) {
 827         if(!checklength(source, packet, ether_size))
 828                 return;
 829
 830         switch (routing_mode) {
 831                 case RMODE_ROUTER:
 832                         {
 833                                 uint16_t type = packet->data[12] << 8 | packet->data[13];
 834
 835                                 switch (type) {
 836                                         case ETH_P_ARP:
 837                                                 route_arp(source, packet);
 838                                                 break;
 839
 840                                         case ETH_P_IP:
 841                                                 route_ipv4(source, packet);
 842                                                 break;
 843
 844                                         case ETH_P_IPV6:
 845                                                 route_ipv6(source, packet);
 846                                                 break;
 847
 848                                         default:
 849                                                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Cannot route packet from %s (%s): unknown type %hx", source->name, source->hostname, type);
 850                                                 break;
 851                                 }
 852                         }
 853                         break;
 854
 855                 case RMODE_SWITCH:
 856                         route_mac(source, packet);
 857                         break;
 858
 859                 case RMODE_HUB:
 860                         broadcast_packet(source, packet);
 861                         break;
 862         }
 863 }