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 fmode_t forwarding_mode = FMODE_INTERNAL;
  37 bool priorityinheritance = false;
  38 int macexpire = 600;
  39 bool overwrite_mac = false;
  40 mac_t mymac = {{0xFE, 0xFD, 0, 0, 0, 0}};
  41
  42 /* Sizes of various headers */
  43
  44 static const size_t ether_size = sizeof(struct ether_header);
  45 static const size_t arp_size = sizeof(struct ether_arp);
  46 static const size_t ip_size = sizeof(struct ip);
  47 static const size_t icmp_size = sizeof(struct icmp) - sizeof(struct ip);
  48 static const size_t ip6_size = sizeof(struct ip6_hdr);
  49 static const size_t icmp6_size = sizeof(struct icmp6_hdr);
  50 static const size_t ns_size = sizeof(struct nd_neighbor_solicit);
  51 static const size_t opt_size = sizeof(struct nd_opt_hdr);
  52 #define max(a, b) ((a) > (b) ? (a) : (b))
  53
  54 /* RFC 1071 */
  55
  56 static uint16_t inet_checksum(void *data, int len, uint16_t prevsum) {
  57         uint16_t *p = data;
  58         uint32_t checksum = prevsum ^ 0xFFFF;
  59
  60         while(len >= 2) {
  61                 checksum += *p++;
  62                 len -= 2;
  63         }
  64
  65         if(len)
  66                 checksum += *(uint8_t *)p;
  67
  68         while(checksum >> 16)
  69                 checksum = (checksum & 0xFFFF) + (checksum >> 16);
  70
  71         return ~checksum;
  72 }
  73
  74 static bool ratelimit(int frequency) {
  75         static time_t lasttime = 0;
  76         static int count = 0;
  77
  78         if(lasttime == now) {
  79                 if(++count > frequency)
  80                         return true;
  81         } else {
  82                 lasttime = now;
  83                 count = 0;
  84         }
  85
  86         return false;
  87 }
  88
  89 static bool checklength(node_t *source, vpn_packet_t *packet, length_t length) {
  90         if(packet->len < length) {
  91                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Got too short packet from %s (%s)", source->name, source->hostname);
  92                 return false;
  93         } else
  94                 return true;
  95 }
  96
  97 static void clamp_mss(const node_t *source, const node_t *via, vpn_packet_t *packet) {
  98         if(!source || !via || !(via->options & OPTION_CLAMP_MSS))
  99                 return;
 100
 101         uint16_t mtu = source->mtu;
 102         if(via != myself && via->mtu < mtu)
 103                 mtu = via->mtu;
 104
 105         /* Find TCP header */
 106         int start = 0;
 107         uint16_t type = packet->data[12] << 8 | packet->data[13];
 108
 109         if(type == ETH_P_IP && packet->data[23] == 6)
 110                 start = 14 + (packet->data[14] & 0xf) * 4;
 111         else if(type == ETH_P_IPV6 && packet->data[20] == 6)
 112                 start = 14 + 40;
 113
 114         if(!start || packet->len <= start + 20)
 115                 return;
 116
 117         /* Use data offset field to calculate length of options field */
 118         int len = ((packet->data[start + 12] >> 4) - 5) * 4;
 119
 120         if(packet->len < start + 20 + len)
 121                 return;
 122
 123         /* Search for MSS option header */
 124         for(int i = 0; i < len;) {
 125                 if(packet->data[start + 20 + i] == 0)
 126                         break;
 127
 128                 if(packet->data[start + 20 + i] == 1) {
 129                         i++;
 130                         continue;
 131                 }
 132
 133                 if(i > len - 2 || i > len - packet->data[start + 21 + i])
 134                         break;
 135
 136                 if(packet->data[start + 20 + i] != 2) {
 137                         if(packet->data[start + 21 + i] < 2)
 138                                 break;
 139                         i += packet->data[start + 21 + i];
 140                         continue;
 141                 }
 142
 143                 if(packet->data[start + 21] != 4)
 144                         break;
 145
 146                 /* Found it */
 147                 uint16_t oldmss = packet->data[start + 22 + i] << 8 | packet->data[start + 23 + i];
 148                 uint16_t newmss = mtu - start - 20;
 149                 uint16_t csum = packet->data[start + 16] << 8 | packet->data[start + 17];
 150
 151                 if(oldmss <= newmss)
 152                         break;
 153
 154                 ifdebug(TRAFFIC) logger(LOG_INFO, "Clamping MSS of packet from %s to %s to %d", source->name, via->name, newmss);
 155
 156                 /* Update the MSS value and the checksum */
 157                 packet->data[start + 22 + i] = newmss >> 8;
 158                 packet->data[start + 23 + i] = newmss & 0xff;
 159                 csum ^= 0xffff;
 160                 csum -= oldmss;
 161                 csum += newmss;
 162                 csum ^= 0xffff;
 163                 packet->data[start + 16] = csum >> 8;
 164                 packet->data[start + 17] = csum & 0xff;
 165                 break;
 166         }
 167 }
 168
 169 static void swap_mac_addresses(vpn_packet_t *packet) {
 170         mac_t tmp;
 171         memcpy(&tmp, &packet->data[0], sizeof tmp);
 172         memcpy(&packet->data[0], &packet->data[6], sizeof tmp);
 173         memcpy(&packet->data[6], &tmp, sizeof tmp);
 174 }
 175
 176 static void learn_mac(mac_t *address) {
 177         subnet_t *subnet;
 178         avl_node_t *node;
 179         connection_t *c;
 180
 181         subnet = lookup_subnet_mac(myself, address);
 182
 183         /* If we don't know this MAC address yet, store it */
 184
 185         if(!subnet) {
 186                 ifdebug(TRAFFIC) logger(LOG_INFO, "Learned new MAC address %hx:%hx:%hx:%hx:%hx:%hx",
 187                                    address->x[0], address->x[1], address->x[2], address->x[3],
 188                                    address->x[4], address->x[5]);
 189
 190                 subnet = new_subnet();
 191                 subnet->type = SUBNET_MAC;
 192                 subnet->expires = now + macexpire;
 193                 subnet->net.mac.address = *address;
 194                 subnet->weight = 10;
 195                 subnet_add(myself, subnet);
 196                 subnet_update(myself, subnet, true);
 197
 198                 /* And tell all other tinc daemons it's our MAC */
 199
 200                 for(node = connection_tree->head; node; node = node->next) {
 201                         c = node->data;
 202                         if(c->status.active)
 203                                 send_add_subnet(c, subnet);
 204                 }
 205         }
 206
 207         if(subnet->expires)
 208                 subnet->expires = now + macexpire;
 209 }
 210
 211 void age_subnets(void) {
 212         subnet_t *s;
 213         connection_t *c;
 214         avl_node_t *node, *next, *node2;
 215
 216         for(node = myself->subnet_tree->head; node; node = next) {
 217                 next = node->next;
 218                 s = node->data;
 219                 if(s->expires && s->expires < now) {
 220                         ifdebug(TRAFFIC) {
 221                                 char netstr[MAXNETSTR];
 222                                 if(net2str(netstr, sizeof netstr, s))
 223                                         logger(LOG_INFO, "Subnet %s expired", netstr);
 224                         }
 225
 226                         for(node2 = connection_tree->head; node2; node2 = node2->next) {
 227                                 c = node2->data;
 228                                 if(c->status.active)
 229                                         send_del_subnet(c, s);
 230                         }
 231
 232                         subnet_update(myself, s, false);
 233                         subnet_del(myself, s);
 234                 }
 235         }
 236 }
 237
 238 /* RFC 792 */
 239
 240 static void route_ipv4_unreachable(node_t *source, vpn_packet_t *packet, uint8_t type, uint8_t code) {
 241         struct ip ip = {0};
 242         struct icmp icmp = {0};
 243
 244         struct in_addr ip_src;
 245         struct in_addr ip_dst;
 246         uint32_t oldlen;
 247
 248         if(ratelimit(3))
 249                 return;
 250
 251         /* Swap Ethernet source and destination addresses */
 252
 253         swap_mac_addresses(packet);
 254
 255         /* Copy headers from packet into properly aligned structs on the stack */
 256
 257         memcpy(&ip, packet->data + ether_size, ip_size);
 258
 259         /* Remember original source and destination */
 260
 261         ip_src = ip.ip_src;
 262         ip_dst = ip.ip_dst;
 263
 264         oldlen = packet->len - ether_size;
 265
 266         if(type == ICMP_DEST_UNREACH && code == ICMP_FRAG_NEEDED)
 267                 icmp.icmp_nextmtu = htons(packet->len - ether_size);
 268
 269         if(oldlen >= IP_MSS - ip_size - icmp_size)
 270                 oldlen = IP_MSS - ip_size - icmp_size;
 271
 272         /* Copy first part of original contents to ICMP message */
 273
 274         memmove(packet->data + ether_size + ip_size + icmp_size, packet->data + ether_size, oldlen);
 275
 276         /* Fill in IPv4 header */
 277
 278         ip.ip_v = 4;
 279         ip.ip_hl = ip_size / 4;
 280         ip.ip_tos = 0;
 281         ip.ip_len = htons(ip_size + icmp_size + oldlen);
 282         ip.ip_id = 0;
 283         ip.ip_off = 0;
 284         ip.ip_ttl = 255;
 285         ip.ip_p = IPPROTO_ICMP;
 286         ip.ip_sum = 0;
 287         ip.ip_src = ip_dst;
 288         ip.ip_dst = ip_src;
 289
 290         ip.ip_sum = inet_checksum(&ip, ip_size, ~0);
 291
 292         /* Fill in ICMP header */
 293
 294         icmp.icmp_type = type;
 295         icmp.icmp_code = code;
 296         icmp.icmp_cksum = 0;
 297
 298         icmp.icmp_cksum = inet_checksum(&icmp, icmp_size, ~0);
 299         icmp.icmp_cksum = inet_checksum(packet->data + ether_size + ip_size + icmp_size, oldlen, icmp.icmp_cksum);
 300
 301         /* Copy structs on stack back to packet */
 302
 303         memcpy(packet->data + ether_size, &ip, ip_size);
 304         memcpy(packet->data + ether_size + ip_size, &icmp, icmp_size);
 305
 306         packet->len = ether_size + ip_size + icmp_size + oldlen;
 307
 308         send_packet(source, packet);
 309 }
 310
 311 /* RFC 791 */
 312
 313 static void fragment_ipv4_packet(node_t *dest, vpn_packet_t *packet) {
 314         struct ip ip;
 315         vpn_packet_t fragment;
 316         int len, maxlen, todo;
 317         uint8_t *offset;
 318         uint16_t ip_off, origf;
 319
 320         memcpy(&ip, packet->data + ether_size, ip_size);
 321         fragment.priority = packet->priority;
 322
 323         if(ip.ip_hl != ip_size / 4)
 324                 return;
 325
 326         todo = ntohs(ip.ip_len) - ip_size;
 327
 328         if(ether_size + ip_size + todo != packet->len) {
 329                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Length of packet (%d) doesn't match length in IPv4 header (%zd)", packet->len, ether_size + ip_size + todo);
 330                 return;
 331         }
 332
 333         ifdebug(TRAFFIC) logger(LOG_INFO, "Fragmenting packet of %d bytes to %s (%s)", packet->len, dest->name, dest->hostname);
 334
 335         offset = packet->data + ether_size + ip_size;
 336         maxlen = (dest->mtu - ether_size - ip_size) & ~0x7;
 337         ip_off = ntohs(ip.ip_off);
 338         origf = ip_off & ~IP_OFFMASK;
 339         ip_off &= IP_OFFMASK;
 340
 341         while(todo) {
 342                 len = todo > maxlen ? maxlen : todo;
 343                 memcpy(fragment.data + ether_size + ip_size, offset, len);
 344                 todo -= len;
 345                 offset += len;
 346
 347                 ip.ip_len = htons(ip_size + len);
 348                 ip.ip_off = htons(ip_off | origf | (todo ? IP_MF : 0));
 349                 ip.ip_sum = 0;
 350                 ip.ip_sum = inet_checksum(&ip, ip_size, ~0);
 351                 memcpy(fragment.data, packet->data, ether_size);
 352                 memcpy(fragment.data + ether_size, &ip, ip_size);
 353                 fragment.len = ether_size + ip_size + len;
 354
 355                 send_packet(dest, &fragment);
 356
 357                 ip_off += len / 8;
 358         }
 359 }
 360
 361 static void route_ipv4_unicast(node_t *source, vpn_packet_t *packet) {
 362         subnet_t *subnet;
 363         node_t *via;
 364         ipv4_t dest;
 365
 366         memcpy(&dest, &packet->data[30], sizeof dest);
 367         subnet = lookup_subnet_ipv4(&dest);
 368
 369         if(!subnet) {
 370                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Cannot route packet from %s (%s): unknown IPv4 destination address %d.%d.%d.%d",
 371                                 source->name, source->hostname,
 372                                 dest.x[0],
 373                                 dest.x[1],
 374                                 dest.x[2],
 375                                 dest.x[3]);
 376
 377                 route_ipv4_unreachable(source, packet, ICMP_DEST_UNREACH, ICMP_NET_UNKNOWN);
 378                 return;
 379         }
 380
 381         if(subnet->owner == source) {
 382                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Packet looping back to %s (%s)!", source->name, source->hostname);
 383                 return;
 384         }
 385
 386         if(!subnet->owner->status.reachable)
 387                 return route_ipv4_unreachable(source, packet, ICMP_DEST_UNREACH, ICMP_NET_UNREACH);
 388
 389         if(forwarding_mode == FMODE_OFF && source != myself && subnet->owner != myself)
 390                 return route_ipv4_unreachable(source, packet, ICMP_DEST_UNREACH, ICMP_NET_ANO);
 391
 392         if(priorityinheritance)
 393                 packet->priority = packet->data[15];
 394
 395         via = (subnet->owner->via == myself) ? subnet->owner->nexthop : subnet->owner->via;
 396
 397         if(via && packet->len > max(via->mtu, 590) && via != myself) {
 398                 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);
 399                 if(packet->data[20] & 0x40) {
 400                         packet->len = max(via->mtu, 590);
 401                         route_ipv4_unreachable(source, packet, ICMP_DEST_UNREACH, ICMP_FRAG_NEEDED);
 402                 } else {
 403                         fragment_ipv4_packet(via, packet);
 404                 }
 405
 406                 return;
 407         }
 408
 409         clamp_mss(source, via, packet);
 410
 411         send_packet(subnet->owner, packet);
 412 }
 413
 414 static void route_ipv4(node_t *source, vpn_packet_t *packet) {
 415         if(!checklength(source, packet, ether_size + ip_size))
 416                 return;
 417
 418         if(((packet->data[30] & 0xf0) == 0xe0) || (
 419                         packet->data[30] == 255 &&
 420                         packet->data[31] == 255 &&
 421                         packet->data[32] == 255 &&
 422                         packet->data[33] == 255))
 423                 broadcast_packet(source, packet);
 424         else
 425                 route_ipv4_unicast(source, packet);
 426 }
 427
 428 /* RFC 2463 */
 429
 430 static void route_ipv6_unreachable(node_t *source, vpn_packet_t *packet, uint8_t type, uint8_t code) {
 431         struct ip6_hdr ip6;
 432         struct icmp6_hdr icmp6 = {0};
 433         uint16_t checksum;
 434
 435         struct {
 436                 struct in6_addr ip6_src;        /* source address */
 437                 struct in6_addr ip6_dst;        /* destination address */
 438                 uint32_t length;
 439                 uint32_t next;
 440         } pseudo;
 441
 442         if(ratelimit(3))
 443                 return;
 444
 445         /* Swap Ethernet source and destination addresses */
 446
 447         swap_mac_addresses(packet);
 448
 449         /* Copy headers from packet to structs on the stack */
 450
 451         memcpy(&ip6, packet->data + ether_size, ip6_size);
 452
 453         /* Remember original source and destination */
 454
 455         pseudo.ip6_src = ip6.ip6_dst;
 456         pseudo.ip6_dst = ip6.ip6_src;
 457
 458         pseudo.length = packet->len - ether_size;
 459
 460         if(type == ICMP6_PACKET_TOO_BIG)
 461                 icmp6.icmp6_mtu = htonl(pseudo.length);
 462
 463         if(pseudo.length >= IP_MSS - ip6_size - icmp6_size)
 464                 pseudo.length = IP_MSS - ip6_size - icmp6_size;
 465
 466         /* Copy first part of original contents to ICMP message */
 467
 468         memmove(packet->data + ether_size + ip6_size + icmp6_size, packet->data + ether_size, pseudo.length);
 469
 470         /* Fill in IPv6 header */
 471
 472         ip6.ip6_flow = htonl(0x60000000UL);
 473         ip6.ip6_plen = htons(icmp6_size + pseudo.length);
 474         ip6.ip6_nxt = IPPROTO_ICMPV6;
 475         ip6.ip6_hlim = 255;
 476         ip6.ip6_src = pseudo.ip6_src;
 477         ip6.ip6_dst = pseudo.ip6_dst;
 478
 479         /* Fill in ICMP header */
 480
 481         icmp6.icmp6_type = type;
 482         icmp6.icmp6_code = code;
 483         icmp6.icmp6_cksum = 0;
 484
 485         /* Create pseudo header */
 486
 487         pseudo.length = htonl(icmp6_size + pseudo.length);
 488         pseudo.next = htonl(IPPROTO_ICMPV6);
 489
 490         /* Generate checksum */
 491
 492         checksum = inet_checksum(&pseudo, sizeof(pseudo), ~0);
 493         checksum = inet_checksum(&icmp6, icmp6_size, checksum);
 494         checksum = inet_checksum(packet->data + ether_size + ip6_size + icmp6_size, ntohl(pseudo.length) - icmp6_size, checksum);
 495
 496         icmp6.icmp6_cksum = checksum;
 497
 498         /* Copy structs on stack back to packet */
 499
 500         memcpy(packet->data + ether_size, &ip6, ip6_size);
 501         memcpy(packet->data + ether_size + ip6_size, &icmp6, icmp6_size);
 502
 503         packet->len = ether_size + ip6_size + ntohl(pseudo.length);
 504
 505         send_packet(source, packet);
 506 }
 507
 508 static void route_ipv6_unicast(node_t *source, vpn_packet_t *packet) {
 509         subnet_t *subnet;
 510         node_t *via;
 511         ipv6_t dest;
 512
 513         memcpy(&dest, &packet->data[38], sizeof dest);
 514         subnet = lookup_subnet_ipv6(&dest);
 515
 516         if(!subnet) {
 517                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Cannot route packet from %s (%s): unknown IPv6 destination address %hx:%hx:%hx:%hx:%hx:%hx:%hx:%hx",
 518                                 source->name, source->hostname,
 519                                 ntohs(dest.x[0]),
 520                                 ntohs(dest.x[1]),
 521                                 ntohs(dest.x[2]),
 522                                 ntohs(dest.x[3]),
 523                                 ntohs(dest.x[4]),
 524                                 ntohs(dest.x[5]),
 525                                 ntohs(dest.x[6]),
 526                                 ntohs(dest.x[7]));
 527
 528                 route_ipv6_unreachable(source, packet, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_ADDR);
 529                 return;
 530         }
 531
 532         if(subnet->owner == source) {
 533                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Packet looping back to %s (%s)!", source->name, source->hostname);
 534                 return;
 535         }
 536
 537         if(!subnet->owner->status.reachable)
 538                 return route_ipv6_unreachable(source, packet, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_NOROUTE);
 539
 540         if(forwarding_mode == FMODE_OFF && source != myself && subnet->owner != myself)
 541                 return route_ipv6_unreachable(source, packet, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_ADMIN);
 542
 543         via = (subnet->owner->via == myself) ? subnet->owner->nexthop : subnet->owner->via;
 544
 545         if(via && packet->len > max(via->mtu, 1294) && via != myself) {
 546                 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);
 547                 packet->len = max(via->mtu, 1294);
 548                 route_ipv6_unreachable(source, packet, ICMP6_PACKET_TOO_BIG, 0);
 549                 return;
 550         }
 551
 552         clamp_mss(source, via, packet);
 553
 554         send_packet(subnet->owner, packet);
 555 }
 556
 557 /* RFC 2461 */
 558
 559 static void route_neighborsol(node_t *source, vpn_packet_t *packet) {
 560         struct ip6_hdr ip6;
 561         struct nd_neighbor_solicit ns;
 562         struct nd_opt_hdr opt;
 563         subnet_t *subnet;
 564         uint16_t checksum;
 565         bool has_opt;
 566
 567         struct {
 568                 struct in6_addr ip6_src;        /* source address */
 569                 struct in6_addr ip6_dst;        /* destination address */
 570                 uint32_t length;
 571                 uint32_t next;
 572         } pseudo;
 573
 574         if(!checklength(source, packet, ether_size + ip6_size + ns_size))
 575                 return;
 576
 577         has_opt = packet->len >= ether_size + ip6_size + ns_size + opt_size + ETH_ALEN;
 578
 579         if(source != myself) {
 580                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Got neighbor solicitation request from %s (%s) while in router mode!", source->name, source->hostname);
 581                 return;
 582         }
 583
 584         /* Copy headers from packet to structs on the stack */
 585
 586         memcpy(&ip6, packet->data + ether_size, ip6_size);
 587         memcpy(&ns, packet->data + ether_size + ip6_size, ns_size);
 588         if(has_opt)
 589                 memcpy(&opt, packet->data + ether_size + ip6_size + ns_size, opt_size);
 590
 591         /* First, snatch the source address from the neighbor solicitation packet */
 592
 593         if(overwrite_mac)
 594                 memcpy(mymac.x, packet->data + ETH_ALEN, ETH_ALEN);
 595
 596         /* Check if this is a valid neighbor solicitation request */
 597
 598         if(ns.nd_ns_hdr.icmp6_type != ND_NEIGHBOR_SOLICIT ||
 599            (has_opt && opt.nd_opt_type != ND_OPT_SOURCE_LINKADDR)) {
 600                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Cannot route packet: received unknown type neighbor solicitation request");
 601                 return;
 602         }
 603
 604         /* Create pseudo header */
 605
 606         pseudo.ip6_src = ip6.ip6_src;
 607         pseudo.ip6_dst = ip6.ip6_dst;
 608         if(has_opt)
 609                 pseudo.length = htonl(ns_size + opt_size + ETH_ALEN);
 610         else
 611                 pseudo.length = htonl(ns_size);
 612         pseudo.next = htonl(IPPROTO_ICMPV6);
 613
 614         /* Generate checksum */
 615
 616         checksum = inet_checksum(&pseudo, sizeof(pseudo), ~0);
 617         checksum = inet_checksum(&ns, ns_size, checksum);
 618         if(has_opt) {
 619                 checksum = inet_checksum(&opt, opt_size, checksum);
 620                 checksum = inet_checksum(packet->data + ether_size + ip6_size + ns_size + opt_size, ETH_ALEN, checksum);
 621         }
 622
 623         if(checksum) {
 624                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Cannot route packet: checksum error for neighbor solicitation request");
 625                 return;
 626         }
 627
 628         /* Check if the IPv6 address exists on the VPN */
 629
 630         subnet = lookup_subnet_ipv6((ipv6_t *) &ns.nd_ns_target);
 631
 632         if(!subnet) {
 633                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Cannot route packet: neighbor solicitation request for unknown address %hx:%hx:%hx:%hx:%hx:%hx:%hx:%hx",
 634                                    ntohs(((uint16_t *) &ns.nd_ns_target)[0]),
 635                                    ntohs(((uint16_t *) &ns.nd_ns_target)[1]),
 636                                    ntohs(((uint16_t *) &ns.nd_ns_target)[2]),
 637                                    ntohs(((uint16_t *) &ns.nd_ns_target)[3]),
 638                                    ntohs(((uint16_t *) &ns.nd_ns_target)[4]),
 639                                    ntohs(((uint16_t *) &ns.nd_ns_target)[5]),
 640                                    ntohs(((uint16_t *) &ns.nd_ns_target)[6]),
 641                                    ntohs(((uint16_t *) &ns.nd_ns_target)[7]));
 642
 643                 return;
 644         }
 645
 646         /* Check if it is for our own subnet */
 647
 648         if(subnet->owner == myself)
 649                 return;                                 /* silently ignore */
 650
 651         /* Create neighbor advertation reply */
 652
 653         memcpy(packet->data, packet->data + ETH_ALEN, ETH_ALEN);        /* copy destination address */
 654         packet->data[ETH_ALEN * 2 - 1] ^= 0xFF; /* mangle source address so it looks like it's not from us */
 655
 656         ip6.ip6_dst = ip6.ip6_src;                      /* swap destination and source protocoll address */
 657         ip6.ip6_src = ns.nd_ns_target;
 658
 659         if(has_opt)
 660                 memcpy(packet->data + ether_size + ip6_size + ns_size + opt_size, packet->data + ETH_ALEN, ETH_ALEN);   /* add fake source hard addr */
 661
 662         ns.nd_ns_cksum = 0;
 663         ns.nd_ns_type = ND_NEIGHBOR_ADVERT;
 664         ns.nd_ns_reserved = htonl(0x40000000UL);        /* Set solicited flag */
 665         opt.nd_opt_type = ND_OPT_TARGET_LINKADDR;
 666
 667         /* Create pseudo header */
 668
 669         pseudo.ip6_src = ip6.ip6_src;
 670         pseudo.ip6_dst = ip6.ip6_dst;
 671         if(has_opt)
 672                 pseudo.length = htonl(ns_size + opt_size + ETH_ALEN);
 673         else
 674                 pseudo.length = htonl(ns_size);
 675         pseudo.next = htonl(IPPROTO_ICMPV6);
 676
 677         /* Generate checksum */
 678
 679         checksum = inet_checksum(&pseudo, sizeof(pseudo), ~0);
 680         checksum = inet_checksum(&ns, ns_size, checksum);
 681         if(has_opt) {
 682                 checksum = inet_checksum(&opt, opt_size, checksum);
 683                 checksum = inet_checksum(packet->data + ether_size + ip6_size + ns_size + opt_size, ETH_ALEN, checksum);
 684         }
 685
 686         ns.nd_ns_hdr.icmp6_cksum = checksum;
 687
 688         /* Copy structs on stack back to packet */
 689
 690         memcpy(packet->data + ether_size, &ip6, ip6_size);
 691         memcpy(packet->data + ether_size + ip6_size, &ns, ns_size);
 692         if(has_opt)
 693                 memcpy(packet->data + ether_size + ip6_size + ns_size, &opt, opt_size);
 694
 695         send_packet(source, packet);
 696 }
 697
 698 static void route_ipv6(node_t *source, vpn_packet_t *packet) {
 699         if(!checklength(source, packet, ether_size + ip6_size))
 700                 return;
 701
 702         if(packet->data[20] == IPPROTO_ICMPV6 && checklength(source, packet, ether_size + ip6_size + icmp6_size) && packet->data[54] == ND_NEIGHBOR_SOLICIT) {
 703                 route_neighborsol(source, packet);
 704                 return;
 705         }
 706
 707         if(packet->data[38] == 255)
 708                 broadcast_packet(source, packet);
 709         else
 710                 route_ipv6_unicast(source, packet);
 711 }
 712
 713 /* RFC 826 */
 714
 715 static void route_arp(node_t *source, vpn_packet_t *packet) {
 716         struct ether_arp arp;
 717         subnet_t *subnet;
 718         struct in_addr addr;
 719
 720         if(!checklength(source, packet, ether_size + arp_size))
 721                 return;
 722
 723         if(source != myself) {
 724                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Got ARP request from %s (%s) while in router mode!", source->name, source->hostname);
 725                 return;
 726         }
 727
 728         /* First, snatch the source address from the ARP packet */
 729
 730         if(overwrite_mac)
 731                 memcpy(mymac.x, packet->data + ETH_ALEN, ETH_ALEN);
 732
 733         /* Copy headers from packet to structs on the stack */
 734
 735         memcpy(&arp, packet->data + ether_size, arp_size);
 736
 737         /* Check if this is a valid ARP request */
 738
 739         if(ntohs(arp.arp_hrd) != ARPHRD_ETHER || ntohs(arp.arp_pro) != ETH_P_IP ||
 740            arp.arp_hln != ETH_ALEN || arp.arp_pln != sizeof(addr) || ntohs(arp.arp_op) != ARPOP_REQUEST) {
 741                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Cannot route packet: received unknown type ARP request");
 742                 return;
 743         }
 744
 745         /* Check if the IPv4 address exists on the VPN */
 746
 747         subnet = lookup_subnet_ipv4((ipv4_t *) &arp.arp_tpa);
 748
 749         if(!subnet) {
 750                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Cannot route packet: ARP request for unknown address %d.%d.%d.%d",
 751                                    arp.arp_tpa[0], arp.arp_tpa[1], arp.arp_tpa[2],
 752                                    arp.arp_tpa[3]);
 753                 return;
 754         }
 755
 756         /* Check if it is for our own subnet */
 757
 758         if(subnet->owner == myself)
 759                 return;                                 /* silently ignore */
 760
 761         memcpy(packet->data, packet->data + ETH_ALEN, ETH_ALEN);        /* copy destination address */
 762         packet->data[ETH_ALEN * 2 - 1] ^= 0xFF; /* mangle source address so it looks like it's not from us */
 763
 764         memcpy(&addr, arp.arp_tpa, sizeof(addr));       /* save protocol addr */
 765         memcpy(arp.arp_tpa, arp.arp_spa, sizeof(addr)); /* swap destination and source protocol address */
 766         memcpy(arp.arp_spa, &addr, sizeof(addr));       /* ... */
 767
 768         memcpy(arp.arp_tha, arp.arp_sha, ETH_ALEN);     /* set target hard/proto addr */
 769         memcpy(arp.arp_sha, packet->data + ETH_ALEN, ETH_ALEN); /* add fake source hard addr */
 770         arp.arp_op = htons(ARPOP_REPLY);
 771
 772         /* Copy structs on stack back to packet */
 773
 774         memcpy(packet->data + ether_size, &arp, arp_size);
 775
 776         send_packet(source, packet);
 777 }
 778
 779 static void route_mac(node_t *source, vpn_packet_t *packet) {
 780         subnet_t *subnet;
 781         mac_t dest;
 782
 783         /* Learn source address */
 784
 785         if(source == myself) {
 786                 mac_t src;
 787                 memcpy(&src, &packet->data[6], sizeof src);
 788                 learn_mac(&src);
 789         }
 790
 791         /* Lookup destination address */
 792
 793         memcpy(&dest, &packet->data[0], sizeof dest);
 794         subnet = lookup_subnet_mac(NULL, &dest);
 795
 796         if(!subnet) {
 797                 broadcast_packet(source, packet);
 798                 return;
 799         }
 800
 801         if(subnet->owner == source) {
 802                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Packet looping back to %s (%s)!", source->name, source->hostname);
 803                 return;
 804         }
 805
 806         if(forwarding_mode == FMODE_OFF && source != myself && subnet->owner != myself)
 807                 return;
 808
 809         // Handle packets larger than PMTU
 810
 811         node_t *via = (subnet->owner->via == myself) ? subnet->owner->nexthop : subnet->owner->via;
 812
 813         if(via && packet->len > via->mtu && via != myself) {
 814                 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);
 815                 uint16_t type = packet->data[12] << 8 | packet->data[13];
 816                 if(type == ETH_P_IP && packet->len > 590) {
 817                         if(packet->data[20] & 0x40) {
 818                                 packet->len = via->mtu;
 819                                 route_ipv4_unreachable(source, packet, ICMP_DEST_UNREACH, ICMP_FRAG_NEEDED);
 820                         } else {
 821                                 fragment_ipv4_packet(via, packet);
 822                         }
 823                         return;
 824                 } else if(type == ETH_P_IPV6 && packet->len > 1294) {
 825                         packet->len = via->mtu;
 826                         route_ipv6_unreachable(source, packet, ICMP6_PACKET_TOO_BIG, 0);
 827                         return;
 828                 }
 829         }
 830
 831         clamp_mss(source, via, packet);
 832
 833         send_packet(subnet->owner, packet);
 834 }
 835
 836 void route(node_t *source, vpn_packet_t *packet) {
 837         if(forwarding_mode == FMODE_KERNEL) {
 838                 send_packet(myself, packet);
 839                 return;
 840         }
 841
 842         if(!checklength(source, packet, ether_size))
 843                 return;
 844
 845         switch (routing_mode) {
 846                 case RMODE_ROUTER:
 847                         {
 848                                 uint16_t type = packet->data[12] << 8 | packet->data[13];
 849
 850                                 switch (type) {
 851                                         case ETH_P_ARP:
 852                                                 route_arp(source, packet);
 853                                                 break;
 854
 855                                         case ETH_P_IP:
 856                                                 route_ipv4(source, packet);
 857                                                 break;
 858
 859                                         case ETH_P_IPV6:
 860                                                 route_ipv6(source, packet);
 861                                                 break;
 862
 863                                         default:
 864                                                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Cannot route packet from %s (%s): unknown type %hx", source->name, source->hostname, type);
 865                                                 break;
 866                                 }
 867                         }
 868                         break;
 869
 870                 case RMODE_SWITCH:
 871                         route_mac(source, packet);
 872                         break;
 873
 874                 case RMODE_HUB:
 875                         broadcast_packet(source, packet);
 876                         break;
 877         }
 878 }