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