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 "control_common.h"
  26 #include "ethernet.h"
  27 #include "ipv4.h"
  28 #include "ipv6.h"
  29 #include "logger.h"
  30 #include "meta.h"
  31 #include "net.h"
  32 #include "protocol.h"
  33 #include "route.h"
  34 #include "subnet.h"
  35 #include "utils.h"
  36
  37 rmode_t routing_mode = RMODE_ROUTER;
  38 fmode_t forwarding_mode = FMODE_INTERNAL;
  39 bool decrement_ttl = true;
  40 bool directonly = false;
  41 bool priorityinheritance = false;
  42 int macexpire = 600;
  43 bool overwrite_mac = false;
  44 bool broadcast = true;
  45 mac_t mymac = {{0xFE, 0xFD, 0, 0, 0, 0}};
  46 bool pcap = false;
  47
  48 /* Sizes of various headers */
  49
  50 static const size_t ether_size = sizeof(struct ether_header);
  51 static const size_t arp_size = sizeof(struct ether_arp);
  52 static const size_t ip_size = sizeof(struct ip);
  53 static const size_t icmp_size = sizeof(struct icmp) - sizeof(struct ip);
  54 static const size_t ip6_size = sizeof(struct ip6_hdr);
  55 static const size_t icmp6_size = sizeof(struct icmp6_hdr);
  56 static const size_t ns_size = sizeof(struct nd_neighbor_solicit);
  57 static const size_t opt_size = sizeof(struct nd_opt_hdr);
  58
  59 #ifndef MAX
  60 #define MAX(a, b) ((a) > (b) ? (a) : (b))
  61 #endif
  62
  63 static struct event age_subnets_event;
  64
  65 /* RFC 1071 */
  66
  67 static uint16_t inet_checksum(void *data, int len, uint16_t prevsum) {
  68         uint16_t *p = data;
  69         uint32_t checksum = prevsum ^ 0xFFFF;
  70
  71         while(len >= 2) {
  72                 checksum += *p++;
  73                 len -= 2;
  74         }
  75
  76         if(len)
  77                 checksum += *(uint8_t *)p;
  78
  79         while(checksum >> 16)
  80                 checksum = (checksum & 0xFFFF) + (checksum >> 16);
  81
  82         return ~checksum;
  83 }
  84
  85 static bool ratelimit(int frequency) {
  86         static time_t lasttime = 0;
  87         static int count = 0;
  88         time_t now = time(NULL);
  89
  90         if(lasttime == now) {
  91                 if(count >= frequency)
  92                         return true;
  93         } else {
  94                 lasttime = now;
  95                 count = 0;
  96         }
  97
  98         count++;
  99         return false;
 100 }
 101
 102 static bool checklength(node_t *source, vpn_packet_t *packet, length_t length) {
 103         if(packet->len < length) {
 104                 logger(DEBUG_TRAFFIC, LOG_WARNING, "Got too short packet from %s (%s)", source->name, source->hostname);
 105                 return false;
 106         } else
 107                 return true;
 108 }
 109
 110 static void clamp_mss(const node_t *source, const node_t *via, vpn_packet_t *packet) {
 111         if(!source || !via || !(via->options & OPTION_CLAMP_MSS))
 112                 return;
 113
 114         uint16_t mtu = source->mtu;
 115         if(via != myself && via->mtu < mtu)
 116                 mtu = via->mtu;
 117
 118         /* Find TCP header */
 119         int start = 0;
 120         uint16_t type = packet->data[12] << 8 | packet->data[13];
 121
 122         if(type == ETH_P_IP && packet->data[23] == 6)
 123                 start = 14 + (packet->data[14] & 0xf) * 4;
 124         else if(type == ETH_P_IPV6 && packet->data[20] == 6)
 125                 start = 14 + 40;
 126
 127         if(!start || packet->len <= start + 20)
 128                 return;
 129
 130         /* Use data offset field to calculate length of options field */
 131         int len = ((packet->data[start + 12] >> 4) - 5) * 4;
 132
 133         if(packet->len < start + 20 + len)
 134                 return;
 135
 136         /* Search for MSS option header */
 137         for(int i = 0; i < len;) {
 138                 if(packet->data[start + 20 + i] == 0)
 139                         break;
 140
 141                 if(packet->data[start + 20 + i] == 1) {
 142                         i++;
 143                         continue;
 144                 }
 145
 146                 if(i > len - 2 || i > len - packet->data[start + 21 + i])
 147                         break;
 148
 149                 if(packet->data[start + 20 + i] != 2) {
 150                         if(packet->data[start + 21 + i] < 2)
 151                                 break;
 152                         i += packet->data[start + 21 + i];
 153                         continue;
 154                 }
 155
 156                 if(packet->data[start + 21] != 4)
 157                         break;
 158
 159                 /* Found it */
 160                 uint16_t oldmss = packet->data[start + 22 + i] << 8 | packet->data[start + 23 + i];
 161                 uint16_t newmss = mtu - start - 20;
 162                 uint16_t csum = packet->data[start + 16] << 8 | packet->data[start + 17];
 163
 164                 if(oldmss <= newmss)
 165                         break;
 166
 167                 logger(DEBUG_TRAFFIC, LOG_INFO, "Clamping MSS of packet from %s to %s to %d", source->name, via->name, newmss);
 168
 169                 /* Update the MSS value and the checksum */
 170                 packet->data[start + 22 + i] = newmss >> 8;
 171                 packet->data[start + 23 + i] = newmss & 0xff;
 172                 csum ^= 0xffff;
 173                 csum -= oldmss;
 174                 csum += newmss;
 175                 csum ^= 0xffff;
 176                 packet->data[start + 16] = csum >> 8;
 177                 packet->data[start + 17] = csum & 0xff;
 178                 break;
 179         }
 180 }
 181
 182 static void swap_mac_addresses(vpn_packet_t *packet) {
 183         mac_t tmp;
 184         memcpy(&tmp, &packet->data[0], sizeof tmp);
 185         memcpy(&packet->data[0], &packet->data[6], sizeof tmp);
 186         memcpy(&packet->data[6], &tmp, sizeof tmp);
 187 }
 188
 189 static void age_subnets(int fd, short events, void *data) {
 190         subnet_t *s;
 191         connection_t *c;
 192         splay_node_t *node, *next, *node2;
 193         bool left = false;
 194         time_t now = time(NULL);
 195
 196         for(node = myself->subnet_tree->head; node; node = next) {
 197                 next = node->next;
 198                 s = node->data;
 199                 if(s->expires && s->expires < now) {
 200                         if(debug_level >= DEBUG_TRAFFIC) {
 201                                 char netstr[MAXNETSTR];
 202                                 if(net2str(netstr, sizeof netstr, s))
 203                                         logger(DEBUG_TRAFFIC, LOG_INFO, "Subnet %s expired", netstr);
 204                         }
 205
 206                         for(node2 = connection_tree->head; node2; node2 = node2->next) {
 207                                 c = node2->data;
 208                                 if(c->status.active)
 209                                         send_del_subnet(c, s);
 210                         }
 211
 212                         subnet_del(myself, s);
 213                 } else {
 214                         if(s->expires)
 215                                 left = true;
 216                 }
 217         }
 218
 219         if(left)
 220                 event_add(&age_subnets_event, &(struct timeval){10, 0});
 221 }
 222
 223 static void learn_mac(mac_t *address) {
 224         subnet_t *subnet;
 225         splay_node_t *node;
 226         connection_t *c;
 227
 228         subnet = lookup_subnet_mac(myself, address);
 229
 230         /* If we don't know this MAC address yet, store it */
 231
 232         if(!subnet) {
 233                 logger(DEBUG_TRAFFIC, LOG_INFO, "Learned new MAC address %hx:%hx:%hx:%hx:%hx:%hx",
 234                                    address->x[0], address->x[1], address->x[2], address->x[3],
 235                                    address->x[4], address->x[5]);
 236
 237                 subnet = new_subnet();
 238                 subnet->type = SUBNET_MAC;
 239                 subnet->expires = time(NULL) + macexpire;
 240                 subnet->net.mac.address = *address;
 241                 subnet->weight = 10;
 242                 subnet_add(myself, subnet);
 243                 subnet_update(myself, subnet, true);
 244
 245                 /* And tell all other tinc daemons it's our MAC */
 246
 247                 for(node = connection_tree->head; node; node = node->next) {
 248                         c = node->data;
 249                         if(c->status.active)
 250                                 send_add_subnet(c, subnet);
 251                 }
 252
 253                 if(!timeout_initialized(&age_subnets_event))
 254                         timeout_set(&age_subnets_event, age_subnets, NULL);
 255                 event_add(&age_subnets_event, &(struct timeval){10, 0});
 256         } else {
 257                 if(subnet->expires)
 258                         subnet->expires = time(NULL) + macexpire;
 259         }
 260 }
 261
 262 /* RFC 792 */
 263
 264 static void route_ipv4_unreachable(node_t *source, vpn_packet_t *packet, uint8_t type, uint8_t code) {
 265         struct ip ip = {0};
 266         struct icmp icmp = {0};
 267
 268         struct in_addr ip_src;
 269         struct in_addr ip_dst;
 270         uint32_t oldlen;
 271
 272         if(ratelimit(3))
 273                 return;
 274
 275         /* Swap Ethernet source and destination addresses */
 276
 277         swap_mac_addresses(packet);
 278
 279         /* Copy headers from packet into properly aligned structs on the stack */
 280
 281         memcpy(&ip, packet->data + ether_size, ip_size);
 282
 283         /* Remember original source and destination */
 284
 285         ip_src = ip.ip_src;
 286         ip_dst = ip.ip_dst;
 287
 288         oldlen = packet->len - ether_size;
 289
 290         if(type == ICMP_DEST_UNREACH && code == ICMP_FRAG_NEEDED)
 291                 icmp.icmp_nextmtu = htons(packet->len - ether_size);
 292
 293         if(oldlen >= IP_MSS - ip_size - icmp_size)
 294                 oldlen = IP_MSS - ip_size - icmp_size;
 295
 296         /* Copy first part of original contents to ICMP message */
 297
 298         memmove(packet->data + ether_size + ip_size + icmp_size, packet->data + ether_size, oldlen);
 299
 300         /* Fill in IPv4 header */
 301
 302         ip.ip_v = 4;
 303         ip.ip_hl = ip_size / 4;
 304         ip.ip_tos = 0;
 305         ip.ip_len = htons(ip_size + icmp_size + oldlen);
 306         ip.ip_id = 0;
 307         ip.ip_off = 0;
 308         ip.ip_ttl = 255;
 309         ip.ip_p = IPPROTO_ICMP;
 310         ip.ip_sum = 0;
 311         ip.ip_src = ip_dst;
 312         ip.ip_dst = ip_src;
 313
 314         ip.ip_sum = inet_checksum(&ip, ip_size, ~0);
 315
 316         /* Fill in ICMP header */
 317
 318         icmp.icmp_type = type;
 319         icmp.icmp_code = code;
 320         icmp.icmp_cksum = 0;
 321
 322         icmp.icmp_cksum = inet_checksum(&icmp, icmp_size, ~0);
 323         icmp.icmp_cksum = inet_checksum(packet->data + ether_size + ip_size + icmp_size, oldlen, icmp.icmp_cksum);
 324
 325         /* Copy structs on stack back to packet */
 326
 327         memcpy(packet->data + ether_size, &ip, ip_size);
 328         memcpy(packet->data + ether_size + ip_size, &icmp, icmp_size);
 329
 330         packet->len = ether_size + ip_size + icmp_size + oldlen;
 331
 332         send_packet(source, packet);
 333 }
 334
 335 /* RFC 791 */
 336
 337 static void fragment_ipv4_packet(node_t *dest, vpn_packet_t *packet) {
 338         struct ip ip;
 339         vpn_packet_t fragment;
 340         int len, maxlen, todo;
 341         uint8_t *offset;
 342         uint16_t ip_off, origf;
 343
 344         memcpy(&ip, packet->data + ether_size, ip_size);
 345         fragment.priority = packet->priority;
 346
 347         if(ip.ip_hl != ip_size / 4)
 348                 return;
 349
 350         todo = ntohs(ip.ip_len) - ip_size;
 351
 352         if(ether_size + ip_size + todo != packet->len) {
 353                 logger(DEBUG_TRAFFIC, LOG_WARNING, "Length of packet (%d) doesn't match length in IPv4 header (%d)", packet->len, (int)(ether_size + ip_size + todo));
 354                 return;
 355         }
 356
 357         logger(DEBUG_TRAFFIC, LOG_INFO, "Fragmenting packet of %d bytes to %s (%s)", packet->len, dest->name, dest->hostname);
 358
 359         offset = packet->data + ether_size + ip_size;
 360         maxlen = (dest->mtu - ether_size - ip_size) & ~0x7;
 361         ip_off = ntohs(ip.ip_off);
 362         origf = ip_off & ~IP_OFFMASK;
 363         ip_off &= IP_OFFMASK;
 364
 365         while(todo) {
 366                 len = todo > maxlen ? maxlen : todo;
 367                 memcpy(fragment.data + ether_size + ip_size, offset, len);
 368                 todo -= len;
 369                 offset += len;
 370
 371                 ip.ip_len = htons(ip_size + len);
 372                 ip.ip_off = htons(ip_off | origf | (todo ? IP_MF : 0));
 373                 ip.ip_sum = 0;
 374                 ip.ip_sum = inet_checksum(&ip, ip_size, ~0);
 375                 memcpy(fragment.data, packet->data, ether_size);
 376                 memcpy(fragment.data + ether_size, &ip, ip_size);
 377                 fragment.len = ether_size + ip_size + len;
 378
 379                 send_packet(dest, &fragment);
 380
 381                 ip_off += len / 8;
 382         }
 383 }
 384
 385 static void route_ipv4_unicast(node_t *source, vpn_packet_t *packet) {
 386         subnet_t *subnet;
 387         node_t *via;
 388         ipv4_t dest;
 389
 390         memcpy(&dest, &packet->data[30], sizeof dest);
 391         subnet = lookup_subnet_ipv4(&dest);
 392
 393         if(!subnet) {
 394                 logger(DEBUG_TRAFFIC, LOG_WARNING, "Cannot route packet from %s (%s): unknown IPv4 destination address %d.%d.%d.%d",
 395                                 source->name, source->hostname,
 396                                 dest.x[0],
 397                                 dest.x[1],
 398                                 dest.x[2],
 399                                 dest.x[3]);
 400
 401                 route_ipv4_unreachable(source, packet, ICMP_DEST_UNREACH, ICMP_NET_UNKNOWN);
 402                 return;
 403         }
 404
 405         if(subnet->owner == source) {
 406                 logger(DEBUG_TRAFFIC, LOG_WARNING, "Packet looping back to %s (%s)!", source->name, source->hostname);
 407                 return;
 408         }
 409
 410         if(!subnet->owner->status.reachable)
 411                 return route_ipv4_unreachable(source, packet, ICMP_DEST_UNREACH, ICMP_NET_UNREACH);
 412
 413         if(forwarding_mode == FMODE_OFF && source != myself && subnet->owner != myself)
 414                 return route_ipv4_unreachable(source, packet, ICMP_DEST_UNREACH, ICMP_NET_ANO);
 415
 416         if(priorityinheritance)
 417                 packet->priority = packet->data[15];
 418
 419         via = (subnet->owner->via == myself) ? subnet->owner->nexthop : subnet->owner->via;
 420
 421         if(via == source) {
 422                 logger(DEBUG_TRAFFIC, LOG_ERR, "Routing loop for packet from %s (%s)!", source->name, source->hostname);
 423                 return;
 424         }
 425
 426         if(directonly && subnet->owner != via)
 427                 return route_ipv4_unreachable(source, packet, ICMP_DEST_UNREACH, ICMP_NET_ANO);
 428
 429         if(via && packet->len > MAX(via->mtu, 590) && via != myself) {
 430                 logger(DEBUG_TRAFFIC, LOG_INFO, "Packet for %s (%s) length %d larger than MTU %d", subnet->owner->name, subnet->owner->hostname, packet->len, via->mtu);
 431                 if(packet->data[20] & 0x40) {
 432                         packet->len = MAX(via->mtu, 590);
 433                         route_ipv4_unreachable(source, packet, ICMP_DEST_UNREACH, ICMP_FRAG_NEEDED);
 434                 } else {
 435                         fragment_ipv4_packet(via, packet);
 436                 }
 437
 438                 return;
 439         }
 440
 441         clamp_mss(source, via, packet);
 442
 443         send_packet(subnet->owner, packet);
 444 }
 445
 446 static void route_ipv4(node_t *source, vpn_packet_t *packet) {
 447         if(!checklength(source, packet, ether_size + ip_size))
 448                 return;
 449
 450         if(broadcast && (((packet->data[30] & 0xf0) == 0xe0) || (
 451                         packet->data[30] == 255 &&
 452                         packet->data[31] == 255 &&
 453                         packet->data[32] == 255 &&
 454                         packet->data[33] == 255)))
 455                 broadcast_packet(source, packet);
 456         else
 457                 route_ipv4_unicast(source, packet);
 458 }
 459
 460 /* RFC 2463 */
 461
 462 static void route_ipv6_unreachable(node_t *source, vpn_packet_t *packet, uint8_t type, uint8_t code) {
 463         struct ip6_hdr ip6;
 464         struct icmp6_hdr icmp6 = {0};
 465         uint16_t checksum;
 466
 467         struct {
 468                 struct in6_addr ip6_src;        /* source address */
 469                 struct in6_addr ip6_dst;        /* destination address */
 470                 uint32_t length;
 471                 uint32_t next;
 472         } pseudo;
 473
 474         if(ratelimit(3))
 475                 return;
 476
 477         /* Swap Ethernet source and destination addresses */
 478
 479         swap_mac_addresses(packet);
 480
 481         /* Copy headers from packet to structs on the stack */
 482
 483         memcpy(&ip6, packet->data + ether_size, ip6_size);
 484
 485         /* Remember original source and destination */
 486
 487         pseudo.ip6_src = ip6.ip6_dst;
 488         pseudo.ip6_dst = ip6.ip6_src;
 489
 490         pseudo.length = packet->len - ether_size;
 491
 492         if(type == ICMP6_PACKET_TOO_BIG)
 493                 icmp6.icmp6_mtu = htonl(pseudo.length);
 494
 495         if(pseudo.length >= IP_MSS - ip6_size - icmp6_size)
 496                 pseudo.length = IP_MSS - ip6_size - icmp6_size;
 497
 498         /* Copy first part of original contents to ICMP message */
 499
 500         memmove(packet->data + ether_size + ip6_size + icmp6_size, packet->data + ether_size, pseudo.length);
 501
 502         /* Fill in IPv6 header */
 503
 504         ip6.ip6_flow = htonl(0x60000000UL);
 505         ip6.ip6_plen = htons(icmp6_size + pseudo.length);
 506         ip6.ip6_nxt = IPPROTO_ICMPV6;
 507         ip6.ip6_hlim = 255;
 508         ip6.ip6_src = pseudo.ip6_src;
 509         ip6.ip6_dst = pseudo.ip6_dst;
 510
 511         /* Fill in ICMP header */
 512
 513         icmp6.icmp6_type = type;
 514         icmp6.icmp6_code = code;
 515         icmp6.icmp6_cksum = 0;
 516
 517         /* Create pseudo header */
 518
 519         pseudo.length = htonl(icmp6_size + pseudo.length);
 520         pseudo.next = htonl(IPPROTO_ICMPV6);
 521
 522         /* Generate checksum */
 523
 524         checksum = inet_checksum(&pseudo, sizeof pseudo, ~0);
 525         checksum = inet_checksum(&icmp6, icmp6_size, checksum);
 526         checksum = inet_checksum(packet->data + ether_size + ip6_size + icmp6_size, ntohl(pseudo.length) - icmp6_size, checksum);
 527
 528         icmp6.icmp6_cksum = checksum;
 529
 530         /* Copy structs on stack back to packet */
 531
 532         memcpy(packet->data + ether_size, &ip6, ip6_size);
 533         memcpy(packet->data + ether_size + ip6_size, &icmp6, icmp6_size);
 534
 535         packet->len = ether_size + ip6_size + ntohl(pseudo.length);
 536
 537         send_packet(source, packet);
 538 }
 539
 540 static void route_ipv6_unicast(node_t *source, vpn_packet_t *packet) {
 541         subnet_t *subnet;
 542         node_t *via;
 543         ipv6_t dest;
 544
 545         memcpy(&dest, &packet->data[38], sizeof dest);
 546         subnet = lookup_subnet_ipv6(&dest);
 547
 548         if(!subnet) {
 549                 logger(DEBUG_TRAFFIC, LOG_WARNING, "Cannot route packet from %s (%s): unknown IPv6 destination address %hx:%hx:%hx:%hx:%hx:%hx:%hx:%hx",
 550                                 source->name, source->hostname,
 551                                 ntohs(dest.x[0]),
 552                                 ntohs(dest.x[1]),
 553                                 ntohs(dest.x[2]),
 554                                 ntohs(dest.x[3]),
 555                                 ntohs(dest.x[4]),
 556                                 ntohs(dest.x[5]),
 557                                 ntohs(dest.x[6]),
 558                                 ntohs(dest.x[7]));
 559
 560                 route_ipv6_unreachable(source, packet, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_ADDR);
 561                 return;
 562         }
 563
 564         if(subnet->owner == source) {
 565                 logger(DEBUG_TRAFFIC, LOG_WARNING, "Packet looping back to %s (%s)!", source->name, source->hostname);
 566                 return;
 567         }
 568
 569         if(!subnet->owner->status.reachable)
 570                 return route_ipv6_unreachable(source, packet, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_NOROUTE);
 571
 572         if(forwarding_mode == FMODE_OFF && source != myself && subnet->owner != myself)
 573                 return route_ipv6_unreachable(source, packet, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_ADMIN);
 574
 575         via = (subnet->owner->via == myself) ? subnet->owner->nexthop : subnet->owner->via;
 576
 577         if(via == source) {
 578                 logger(DEBUG_TRAFFIC, LOG_ERR, "Routing loop for packet from %s (%s)!", source->name, source->hostname);
 579                 return;
 580         }
 581
 582         if(directonly && subnet->owner != via)
 583                 return route_ipv6_unreachable(source, packet, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_ADMIN);
 584
 585         if(via && packet->len > MAX(via->mtu, 1294) && via != myself) {
 586                 logger(DEBUG_TRAFFIC, LOG_INFO, "Packet for %s (%s) length %d larger than MTU %d", subnet->owner->name, subnet->owner->hostname, packet->len, via->mtu);
 587                 packet->len = MAX(via->mtu, 1294);
 588                 route_ipv6_unreachable(source, packet, ICMP6_PACKET_TOO_BIG, 0);
 589                 return;
 590         }
 591
 592         clamp_mss(source, via, packet);
 593
 594         send_packet(subnet->owner, packet);
 595 }
 596
 597 /* RFC 2461 */
 598
 599 static void route_neighborsol(node_t *source, vpn_packet_t *packet) {
 600         struct ip6_hdr ip6;
 601         struct nd_neighbor_solicit ns;
 602         struct nd_opt_hdr opt;
 603         subnet_t *subnet;
 604         uint16_t checksum;
 605         bool has_opt;
 606
 607         struct {
 608                 struct in6_addr ip6_src;        /* source address */
 609                 struct in6_addr ip6_dst;        /* destination address */
 610                 uint32_t length;
 611                 uint32_t next;
 612         } pseudo;
 613
 614         if(!checklength(source, packet, ether_size + ip6_size + ns_size))
 615                 return;
 616
 617         has_opt = packet->len >= ether_size + ip6_size + ns_size + opt_size + ETH_ALEN;
 618
 619         if(source != myself) {
 620                 logger(DEBUG_TRAFFIC, LOG_WARNING, "Got neighbor solicitation request from %s (%s) while in router mode!", source->name, source->hostname);
 621                 return;
 622         }
 623
 624         /* Copy headers from packet to structs on the stack */
 625
 626         memcpy(&ip6, packet->data + ether_size, ip6_size);
 627         memcpy(&ns, packet->data + ether_size + ip6_size, ns_size);
 628         if(has_opt)
 629                 memcpy(&opt, packet->data + ether_size + ip6_size + ns_size, opt_size);
 630
 631         /* First, snatch the source address from the neighbor solicitation packet */
 632
 633         if(overwrite_mac)
 634                 memcpy(mymac.x, packet->data + ETH_ALEN, ETH_ALEN);
 635
 636         /* Check if this is a valid neighbor solicitation request */
 637
 638         if(ns.nd_ns_hdr.icmp6_type != ND_NEIGHBOR_SOLICIT ||
 639            (has_opt && opt.nd_opt_type != ND_OPT_SOURCE_LINKADDR)) {
 640                 logger(DEBUG_TRAFFIC, LOG_WARNING, "Cannot route packet: received unknown type neighbor solicitation request");
 641                 return;
 642         }
 643
 644         /* Create pseudo header */
 645
 646         pseudo.ip6_src = ip6.ip6_src;
 647         pseudo.ip6_dst = ip6.ip6_dst;
 648         if(has_opt)
 649                 pseudo.length = htonl(ns_size + opt_size + ETH_ALEN);
 650         else
 651                 pseudo.length = htonl(ns_size);
 652         pseudo.next = htonl(IPPROTO_ICMPV6);
 653
 654         /* Generate checksum */
 655
 656         checksum = inet_checksum(&pseudo, sizeof pseudo, ~0);
 657         checksum = inet_checksum(&ns, ns_size, checksum);
 658         if(has_opt) {
 659                 checksum = inet_checksum(&opt, opt_size, checksum);
 660                 checksum = inet_checksum(packet->data + ether_size + ip6_size + ns_size + opt_size, ETH_ALEN, checksum);
 661         }
 662
 663         if(checksum) {
 664                 logger(DEBUG_TRAFFIC, LOG_WARNING, "Cannot route packet: checksum error for neighbor solicitation request");
 665                 return;
 666         }
 667
 668         /* Check if the IPv6 address exists on the VPN */
 669
 670         subnet = lookup_subnet_ipv6((ipv6_t *) &ns.nd_ns_target);
 671
 672         if(!subnet) {
 673                 logger(DEBUG_TRAFFIC, LOG_WARNING, "Cannot route packet: neighbor solicitation request for unknown address %hx:%hx:%hx:%hx:%hx:%hx:%hx:%hx",
 674                                    ntohs(((uint16_t *) &ns.nd_ns_target)[0]),
 675                                    ntohs(((uint16_t *) &ns.nd_ns_target)[1]),
 676                                    ntohs(((uint16_t *) &ns.nd_ns_target)[2]),
 677                                    ntohs(((uint16_t *) &ns.nd_ns_target)[3]),
 678                                    ntohs(((uint16_t *) &ns.nd_ns_target)[4]),
 679                                    ntohs(((uint16_t *) &ns.nd_ns_target)[5]),
 680                                    ntohs(((uint16_t *) &ns.nd_ns_target)[6]),
 681                                    ntohs(((uint16_t *) &ns.nd_ns_target)[7]));
 682
 683                 return;
 684         }
 685
 686         /* Check if it is for our own subnet */
 687
 688         if(subnet->owner == myself)
 689                 return;                                 /* silently ignore */
 690
 691         /* Create neighbor advertation reply */
 692
 693         memcpy(packet->data, packet->data + ETH_ALEN, ETH_ALEN);        /* copy destination address */
 694         packet->data[ETH_ALEN * 2 - 1] ^= 0xFF; /* mangle source address so it looks like it's not from us */
 695
 696         ip6.ip6_dst = ip6.ip6_src;                      /* swap destination and source protocoll address */
 697         ip6.ip6_src = ns.nd_ns_target;
 698
 699         if(has_opt)
 700                 memcpy(packet->data + ether_size + ip6_size + ns_size + opt_size, packet->data + ETH_ALEN, ETH_ALEN);   /* add fake source hard addr */
 701
 702         ns.nd_ns_cksum = 0;
 703         ns.nd_ns_type = ND_NEIGHBOR_ADVERT;
 704         ns.nd_ns_reserved = htonl(0x40000000UL);        /* Set solicited flag */
 705         opt.nd_opt_type = ND_OPT_TARGET_LINKADDR;
 706
 707         /* Create pseudo header */
 708
 709         pseudo.ip6_src = ip6.ip6_src;
 710         pseudo.ip6_dst = ip6.ip6_dst;
 711         if(has_opt)
 712                 pseudo.length = htonl(ns_size + opt_size + ETH_ALEN);
 713         else
 714                 pseudo.length = htonl(ns_size);
 715         pseudo.next = htonl(IPPROTO_ICMPV6);
 716
 717         /* Generate checksum */
 718
 719         checksum = inet_checksum(&pseudo, sizeof pseudo, ~0);
 720         checksum = inet_checksum(&ns, ns_size, checksum);
 721         if(has_opt) {
 722                 checksum = inet_checksum(&opt, opt_size, checksum);
 723                 checksum = inet_checksum(packet->data + ether_size + ip6_size + ns_size + opt_size, ETH_ALEN, checksum);
 724         }
 725
 726         ns.nd_ns_hdr.icmp6_cksum = checksum;
 727
 728         /* Copy structs on stack back to packet */
 729
 730         memcpy(packet->data + ether_size, &ip6, ip6_size);
 731         memcpy(packet->data + ether_size + ip6_size, &ns, ns_size);
 732         if(has_opt)
 733                 memcpy(packet->data + ether_size + ip6_size + ns_size, &opt, opt_size);
 734
 735         send_packet(source, packet);
 736 }
 737
 738 static void route_ipv6(node_t *source, vpn_packet_t *packet) {
 739         if(!checklength(source, packet, ether_size + ip6_size))
 740                 return;
 741
 742         if(packet->data[20] == IPPROTO_ICMPV6 && checklength(source, packet, ether_size + ip6_size + icmp6_size) && packet->data[54] == ND_NEIGHBOR_SOLICIT) {
 743                 route_neighborsol(source, packet);
 744                 return;
 745         }
 746
 747         if(broadcast && packet->data[38] == 255)
 748                 broadcast_packet(source, packet);
 749         else
 750                 route_ipv6_unicast(source, packet);
 751 }
 752
 753 /* RFC 826 */
 754
 755 static void route_arp(node_t *source, vpn_packet_t *packet) {
 756         struct ether_arp arp;
 757         subnet_t *subnet;
 758         struct in_addr addr;
 759
 760         if(!checklength(source, packet, ether_size + arp_size))
 761                 return;
 762
 763         if(source != myself) {
 764                 logger(DEBUG_TRAFFIC, LOG_WARNING, "Got ARP request from %s (%s) while in router mode!", source->name, source->hostname);
 765                 return;
 766         }
 767
 768         /* First, snatch the source address from the ARP packet */
 769
 770         if(overwrite_mac)
 771                 memcpy(mymac.x, packet->data + ETH_ALEN, ETH_ALEN);
 772
 773         /* Copy headers from packet to structs on the stack */
 774
 775         memcpy(&arp, packet->data + ether_size, arp_size);
 776
 777         /* Check if this is a valid ARP request */
 778
 779         if(ntohs(arp.arp_hrd) != ARPHRD_ETHER || ntohs(arp.arp_pro) != ETH_P_IP ||
 780            arp.arp_hln != ETH_ALEN || arp.arp_pln != sizeof addr || ntohs(arp.arp_op) != ARPOP_REQUEST) {
 781                 logger(DEBUG_TRAFFIC, LOG_WARNING, "Cannot route packet: received unknown type ARP request");
 782                 return;
 783         }
 784
 785         /* Check if the IPv4 address exists on the VPN */
 786
 787         subnet = lookup_subnet_ipv4((ipv4_t *) &arp.arp_tpa);
 788
 789         if(!subnet) {
 790                 logger(DEBUG_TRAFFIC, LOG_WARNING, "Cannot route packet: ARP request for unknown address %d.%d.%d.%d",
 791                                    arp.arp_tpa[0], arp.arp_tpa[1], arp.arp_tpa[2],
 792                                    arp.arp_tpa[3]);
 793                 return;
 794         }
 795
 796         /* Check if it is for our own subnet */
 797
 798         if(subnet->owner == myself)
 799                 return;                                 /* silently ignore */
 800
 801         memcpy(packet->data, packet->data + ETH_ALEN, ETH_ALEN);        /* copy destination address */
 802         packet->data[ETH_ALEN * 2 - 1] ^= 0xFF; /* mangle source address so it looks like it's not from us */
 803
 804         memcpy(&addr, arp.arp_tpa, sizeof addr);        /* save protocol addr */
 805         memcpy(arp.arp_tpa, arp.arp_spa, sizeof addr);  /* swap destination and source protocol address */
 806         memcpy(arp.arp_spa, &addr, sizeof addr);        /* ... */
 807
 808         memcpy(arp.arp_tha, arp.arp_sha, ETH_ALEN);     /* set target hard/proto addr */
 809         memcpy(arp.arp_sha, packet->data + ETH_ALEN, ETH_ALEN); /* add fake source hard addr */
 810         arp.arp_op = htons(ARPOP_REPLY);
 811
 812         /* Copy structs on stack back to packet */
 813
 814         memcpy(packet->data + ether_size, &arp, arp_size);
 815
 816         send_packet(source, packet);
 817 }
 818
 819 static void route_mac(node_t *source, vpn_packet_t *packet) {
 820         subnet_t *subnet;
 821         mac_t dest;
 822
 823         /* Learn source address */
 824
 825         if(source == myself) {
 826                 mac_t src;
 827                 memcpy(&src, &packet->data[6], sizeof src);
 828                 learn_mac(&src);
 829         }
 830
 831         /* Lookup destination address */
 832
 833         memcpy(&dest, &packet->data[0], sizeof dest);
 834         subnet = lookup_subnet_mac(NULL, &dest);
 835
 836         if(!subnet) {
 837                 if(broadcast)
 838                         broadcast_packet(source, packet);
 839                 return;
 840         }
 841
 842         if(subnet->owner == source) {
 843                 logger(DEBUG_TRAFFIC, LOG_WARNING, "Packet looping back to %s (%s)!", source->name, source->hostname);
 844                 return;
 845         }
 846
 847         if(forwarding_mode == FMODE_OFF && source != myself && subnet->owner != myself)
 848                 return;
 849
 850         // Handle packets larger than PMTU
 851
 852         node_t *via = (subnet->owner->via == myself) ? subnet->owner->nexthop : subnet->owner->via;
 853
 854         if(directonly && subnet->owner != via)
 855                 return;
 856
 857         if(via && packet->len > via->mtu && via != myself) {
 858                 logger(DEBUG_TRAFFIC, LOG_INFO, "Packet for %s (%s) length %d larger than MTU %d", subnet->owner->name, subnet->owner->hostname, packet->len, via->mtu);
 859                 uint16_t type = packet->data[12] << 8 | packet->data[13];
 860                 if(type == ETH_P_IP && packet->len > 590) {
 861                         if(packet->data[20] & 0x40) {
 862                                 packet->len = via->mtu;
 863                                 route_ipv4_unreachable(source, packet, ICMP_DEST_UNREACH, ICMP_FRAG_NEEDED);
 864                         } else {
 865                                 fragment_ipv4_packet(via, packet);
 866                         }
 867                         return;
 868                 } else if(type == ETH_P_IPV6 && packet->len > 1294) {
 869                         packet->len = via->mtu;
 870                         route_ipv6_unreachable(source, packet, ICMP6_PACKET_TOO_BIG, 0);
 871                         return;
 872                 }
 873         }
 874
 875         clamp_mss(source, via, packet);
 876
 877         send_packet(subnet->owner, packet);
 878 }
 879
 880 static void send_pcap(vpn_packet_t *packet) {
 881         pcap = false;
 882         for(splay_node_t *node = connection_tree->head; node; node = node->next) {
 883                 connection_t *c = node->data;
 884                 if(!c->status.pcap)
 885                         continue;
 886
 887                 pcap = true;
 888                 int len = packet->len;
 889                 if(c->outmaclength && c->outmaclength < len)
 890                         len = c->outmaclength;
 891
 892                 if(send_request(c, "%d %d %d", CONTROL, REQ_PCAP, len))
 893                         send_meta(c, (char *)packet->data, len);
 894         }
 895 }
 896
 897 static bool do_decrement_ttl(node_t *source, vpn_packet_t *packet) {
 898         uint16_t type = packet->data[12] << 8 | packet->data[13];
 899
 900         switch (type) {
 901                 case ETH_P_IP:
 902                         if(!checklength(source, packet, 14 + 32))
 903                                 return false;
 904
 905                         if(packet->data[22] < 1) {
 906                                 if(packet->data[25] != IPPROTO_ICMP || packet->data[46] != ICMP_TIME_EXCEEDED)
 907                                         route_ipv4_unreachable(source, packet, ICMP_TIME_EXCEEDED, ICMP_EXC_TTL);
 908                                 return false;
 909                         }
 910
 911                         uint16_t old = packet->data[22] << 8 | packet->data[23];
 912                         packet->data[22]--;
 913                         uint16_t new = packet->data[22] << 8 | packet->data[23];
 914
 915                         uint32_t checksum = packet->data[24] << 8 | packet->data[25];
 916                         checksum += old + (~new & 0xFFFF);
 917                         while(checksum >> 16)
 918                                 checksum = (checksum & 0xFFFF) + (checksum >> 16);
 919                         packet->data[24] = checksum >> 8;
 920                         packet->data[25] = checksum & 0xff;
 921
 922                         return true;
 923
 924                 case ETH_P_IPV6:
 925                         if(!checklength(source, packet, 14 + 40))
 926                                 return false;
 927
 928                         if(packet->data[21] < 1) {
 929                                 if(packet->data[20] != IPPROTO_ICMPV6 || packet->data[54] != ICMP6_TIME_EXCEEDED)
 930                                         route_ipv6_unreachable(source, packet, ICMP6_TIME_EXCEEDED, ICMP6_TIME_EXCEED_TRANSIT);
 931                                 return false;
 932                         }
 933
 934                         packet->data[21]--;
 935
 936                         return true;
 937
 938                 default:
 939                         return true;
 940         }
 941 }
 942
 943 void route(node_t *source, vpn_packet_t *packet) {
 944         if(pcap)
 945                 send_pcap(packet);
 946
 947         if(forwarding_mode == FMODE_KERNEL && source != myself) {
 948                 send_packet(myself, packet);
 949                 return;
 950         }
 951
 952         if(!checklength(source, packet, ether_size))
 953                 return;
 954
 955         if(decrement_ttl && source != myself)
 956                 if(!do_decrement_ttl(source, packet))
 957                         return;
 958
 959         switch (routing_mode) {
 960                 case RMODE_ROUTER:
 961                         {
 962                                 uint16_t type = packet->data[12] << 8 | packet->data[13];
 963
 964                                 switch (type) {
 965                                         case ETH_P_ARP:
 966                                                 route_arp(source, packet);
 967                                                 break;
 968
 969                                         case ETH_P_IP:
 970                                                 route_ipv4(source, packet);
 971                                                 break;
 972
 973                                         case ETH_P_IPV6:
 974                                                 route_ipv6(source, packet);
 975                                                 break;
 976
 977                                         default:
 978                                                 logger(DEBUG_TRAFFIC, LOG_WARNING, "Cannot route packet from %s (%s): unknown type %hx", source->name, source->hostname, type);
 979                                                 break;
 980                                 }
 981                         }
 982                         break;
 983
 984                 case RMODE_SWITCH:
 985                         route_mac(source, packet);
 986                         break;
 987
 988                 case RMODE_HUB:
 989                         broadcast_packet(source, packet);
 990                         break;
 991         }
 992 }