tinc-vpn.org Git - tinc/blob - src/route.c

   1 /*
   2     route.c -- routing
   3     Copyright (C) 2000-2005 Ivo Timmermans,
   4                   2000-2013 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 "connection.h"
  24 #include "control_common.h"
  25 #include "ethernet.h"
  26 #include "ipv4.h"
  27 #include "ipv6.h"
  28 #include "logger.h"
  29 #include "meta.h"
  30 #include "net.h"
  31 #include "protocol.h"
  32 #include "route.h"
  33 #include "subnet.h"
  34 #include "utils.h"
  35
  36 rmode_t routing_mode = RMODE_ROUTER;
  37 fmode_t forwarding_mode = FMODE_INTERNAL;
  38 bmode_t broadcast_mode = BMODE_MST;
  39 bool decrement_ttl = false;
  40 bool directonly = false;
  41 bool priorityinheritance = false;
  42 int macexpire = 600;
  43 bool overwrite_mac = false;
  44 mac_t mymac = {{0xFE, 0xFD, 0, 0, 0, 0}};
  45 bool pcap = false;
  46
  47 /* Sizes of various headers */
  48
  49 static const size_t ether_size = sizeof(struct ether_header);
  50 static const size_t arp_size = sizeof(struct ether_arp);
  51 static const size_t ip_size = sizeof(struct ip);
  52 static const size_t icmp_size = sizeof(struct icmp) - sizeof(struct ip);
  53 static const size_t ip6_size = sizeof(struct ip6_hdr);
  54 static const size_t icmp6_size = sizeof(struct icmp6_hdr);
  55 static const size_t ns_size = sizeof(struct nd_neighbor_solicit);
  56 static const size_t opt_size = sizeof(struct nd_opt_hdr);
  57
  58 #ifndef MAX
  59 #define MAX(a, b) ((a) > (b) ? (a) : (b))
  60 #endif
  61
  62 static timeout_t age_subnets_timeout;
  63
  64 /* RFC 1071 */
  65
  66 static uint16_t inet_checksum(void *data, int len, uint16_t prevsum) {
  67         uint16_t *p = data;
  68         uint32_t checksum = prevsum ^ 0xFFFF;
  69
  70         while(len >= 2) {
  71                 checksum += *p++;
  72                 len -= 2;
  73         }
  74
  75         if(len)
  76                 checksum += *(uint8_t *)p;
  77
  78         while(checksum >> 16)
  79                 checksum = (checksum & 0xFFFF) + (checksum >> 16);
  80
  81         return ~checksum;
  82 }
  83
  84 static bool ratelimit(int frequency) {
  85         static time_t lasttime = 0;
  86         static int count = 0;
  87
  88         if(lasttime == now.tv_sec) {
  89                 if(count >= frequency)
  90                         return true;
  91         } else {
  92                 lasttime = now.tv_sec;
  93                 count = 0;
  94         }
  95
  96         count++;
  97         return false;
  98 }
  99
 100 static bool checklength(node_t *source, vpn_packet_t *packet, length_t length) {
 101         if(packet->len < length) {
 102                 logger(DEBUG_TRAFFIC, LOG_WARNING, "Got too short packet from %s (%s)", source->name, source->hostname);
 103                 return false;
 104         } else
 105                 return true;
 106 }
 107
 108 static void clamp_mss(const node_t *source, const node_t *via, vpn_packet_t *packet) {
 109         if(!source || !via || !(via->options & OPTION_CLAMP_MSS))
 110                 return;
 111
 112         uint16_t mtu = source->mtu;
 113         if(via != myself && via->mtu < mtu)
 114                 mtu = via->mtu;
 115
 116         /* Find TCP header */
 117         int start = ether_size;
 118         uint16_t type = DATA(packet)[12] << 8 | DATA(packet)[13];
 119
 120         if(type == ETH_P_8021Q) {
 121                 start += 4;
 122                 type = DATA(packet)[16] << 8 | DATA(packet)[17];
 123         }
 124
 125         if(type == ETH_P_IP && DATA(packet)[start + 9] == 6)
 126                 start += (DATA(packet)[start] & 0xf) * 4;
 127         else if(type == ETH_P_IPV6 && DATA(packet)[start + 6] == 6)
 128                 start += 40;
 129         else
 130                 return;
 131
 132         if(packet->len <= start + 20)
 133                 return;
 134
 135         /* Use data offset field to calculate length of options field */
 136         int len = ((DATA(packet)[start + 12] >> 4) - 5) * 4;
 137
 138         if(packet->len < start + 20 + len)
 139                 return;
 140
 141         /* Search for MSS option header */
 142         for(int i = 0; i < len;) {
 143                 if(DATA(packet)[start + 20 + i] == 0)
 144                         break;
 145
 146                 if(DATA(packet)[start + 20 + i] == 1) {
 147                         i++;
 148                         continue;
 149                 }
 150
 151                 if(i > len - 2 || i > len - DATA(packet)[start + 21 + i])
 152                         break;
 153
 154                 if(DATA(packet)[start + 20 + i] != 2) {
 155                         if(DATA(packet)[start + 21 + i] < 2)
 156                                 break;
 157                         i += DATA(packet)[start + 21 + i];
 158                         continue;
 159                 }
 160
 161                 if(DATA(packet)[start + 21] != 4)
 162                         break;
 163
 164                 /* Found it */
 165                 uint16_t oldmss = DATA(packet)[start + 22 + i] << 8 | DATA(packet)[start + 23 + i];
 166                 uint16_t newmss = mtu - start - 20;
 167                 uint32_t csum = DATA(packet)[start + 16] << 8 | DATA(packet)[start + 17];
 168
 169                 if(oldmss <= newmss)
 170                         break;
 171
 172                 logger(DEBUG_TRAFFIC, LOG_INFO, "Clamping MSS of packet from %s to %s to %d", source->name, via->name, newmss);
 173
 174                 /* Update the MSS value and the checksum */
 175                 DATA(packet)[start + 22 + i] = newmss >> 8;
 176                 DATA(packet)[start + 23 + i] = newmss & 0xff;
 177                 csum ^= 0xffff;
 178                 csum += oldmss ^ 0xffff;
 179                 csum += newmss;
 180                 csum = (csum & 0xffff) + (csum >> 16);
 181                 csum += csum >> 16;
 182                 csum ^= 0xffff;
 183                 DATA(packet)[start + 16] = csum >> 8;
 184                 DATA(packet)[start + 17] = csum;
 185                 break;
 186         }
 187 }
 188
 189 static void swap_mac_addresses(vpn_packet_t *packet) {
 190         mac_t tmp;
 191         memcpy(&tmp, &DATA(packet)[0], sizeof tmp);
 192         memcpy(&DATA(packet)[0], &DATA(packet)[6], sizeof tmp);
 193         memcpy(&DATA(packet)[6], &tmp, sizeof tmp);
 194 }
 195
 196 static void age_subnets(void *data) {
 197         bool left = false;
 198
 199         for splay_each(subnet_t, s, myself->subnet_tree) {
 200                 if(s->expires && s->expires < now.tv_sec) {
 201                         if(debug_level >= DEBUG_TRAFFIC) {
 202                                 char netstr[MAXNETSTR];
 203                                 if(net2str(netstr, sizeof netstr, s))
 204                                         logger(DEBUG_TRAFFIC, LOG_INFO, "Subnet %s expired", netstr);
 205                         }
 206
 207                         for list_each(connection_t, c, connection_list)
 208                                 if(c->edge)
 209                                         send_del_subnet(c, s);
 210
 211                         subnet_del(myself, s);
 212                 } else {
 213                         if(s->expires)
 214                                 left = true;
 215                 }
 216         }
 217
 218         if(left)
 219                 timeout_set(&age_subnets_timeout, &(struct timeval){10, rand() % 100000});
 220 }
 221
 222 static void learn_mac(mac_t *address) {
 223         subnet_t *subnet = lookup_subnet_mac(myself, address);
 224
 225         /* If we don't know this MAC address yet, store it */
 226
 227         if(!subnet) {
 228                 logger(DEBUG_TRAFFIC, LOG_INFO, "Learned new MAC address %x:%x:%x:%x:%x:%x",
 229                                    address->x[0], address->x[1], address->x[2], address->x[3],
 230                                    address->x[4], address->x[5]);
 231
 232                 subnet = new_subnet();
 233                 subnet->type = SUBNET_MAC;
 234                 subnet->expires = now.tv_sec + macexpire;
 235                 subnet->net.mac.address = *address;
 236                 subnet->weight = 10;
 237                 subnet_add(myself, subnet);
 238                 subnet_update(myself, subnet, true);
 239
 240                 /* And tell all other tinc daemons it's our MAC */
 241
 242                 for list_each(connection_t, c, connection_list)
 243                         if(c->edge)
 244                                 send_add_subnet(c, subnet);
 245
 246                 timeout_add(&age_subnets_timeout, age_subnets, NULL, &(struct timeval){10, rand() % 100000});
 247         } else {
 248                 if(subnet->expires)
 249                         subnet->expires = now.tv_sec + macexpire;
 250         }
 251 }
 252
 253 /* RFC 792 */
 254
 255 static void route_ipv4_unreachable(node_t *source, vpn_packet_t *packet, length_t ether_size, uint8_t type, uint8_t code) {
 256         struct ip ip = {0};
 257         struct icmp icmp = {0};
 258
 259         struct in_addr ip_src;
 260         struct in_addr ip_dst;
 261         uint32_t oldlen;
 262
 263         if(ratelimit(3))
 264                 return;
 265
 266         /* Swap Ethernet source and destination addresses */
 267
 268         swap_mac_addresses(packet);
 269
 270         /* Copy headers from packet into properly aligned structs on the stack */
 271
 272         memcpy(&ip, DATA(packet) + ether_size, ip_size);
 273
 274         /* Remember original source and destination */
 275
 276         ip_src = ip.ip_src;
 277         ip_dst = ip.ip_dst;
 278
 279         oldlen = packet->len - ether_size;
 280
 281         if(type == ICMP_DEST_UNREACH && code == ICMP_FRAG_NEEDED)
 282                 icmp.icmp_nextmtu = htons(packet->len - ether_size);
 283
 284         if(oldlen >= IP_MSS - ip_size - icmp_size)
 285                 oldlen = IP_MSS - ip_size - icmp_size;
 286
 287         /* Copy first part of original contents to ICMP message */
 288
 289         memmove(DATA(packet) + ether_size + ip_size + icmp_size, DATA(packet) + ether_size, oldlen);
 290
 291         /* Fill in IPv4 header */
 292
 293         ip.ip_v = 4;
 294         ip.ip_hl = ip_size / 4;
 295         ip.ip_tos = 0;
 296         ip.ip_len = htons(ip_size + icmp_size + oldlen);
 297         ip.ip_id = 0;
 298         ip.ip_off = 0;
 299         ip.ip_ttl = 255;
 300         ip.ip_p = IPPROTO_ICMP;
 301         ip.ip_sum = 0;
 302         ip.ip_src = ip_dst;
 303         ip.ip_dst = ip_src;
 304
 305         ip.ip_sum = inet_checksum(&ip, ip_size, ~0);
 306
 307         /* Fill in ICMP header */
 308
 309         icmp.icmp_type = type;
 310         icmp.icmp_code = code;
 311         icmp.icmp_cksum = 0;
 312
 313         icmp.icmp_cksum = inet_checksum(&icmp, icmp_size, ~0);
 314         icmp.icmp_cksum = inet_checksum(DATA(packet) + ether_size + ip_size + icmp_size, oldlen, icmp.icmp_cksum);
 315
 316         /* Copy structs on stack back to packet */
 317
 318         memcpy(DATA(packet) + ether_size, &ip, ip_size);
 319         memcpy(DATA(packet) + ether_size + ip_size, &icmp, icmp_size);
 320
 321         packet->len = ether_size + ip_size + icmp_size + oldlen;
 322
 323         send_packet(source, packet);
 324 }
 325
 326 /* RFC 791 */
 327
 328 static void fragment_ipv4_packet(node_t *dest, vpn_packet_t *packet, length_t ether_size) {
 329         struct ip ip;
 330         vpn_packet_t fragment;
 331         int len, maxlen, todo;
 332         uint8_t *offset;
 333         uint16_t ip_off, origf;
 334
 335         memcpy(&ip, DATA(packet) + ether_size, ip_size);
 336         fragment.priority = packet->priority;
 337         fragment.offset = DEFAULT_PACKET_OFFSET;
 338
 339         if(ip.ip_hl != ip_size / 4)
 340                 return;
 341
 342         todo = ntohs(ip.ip_len) - ip_size;
 343
 344         if(ether_size + ip_size + todo != packet->len) {
 345                 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));
 346                 return;
 347         }
 348
 349         logger(DEBUG_TRAFFIC, LOG_INFO, "Fragmenting packet of %d bytes to %s (%s)", packet->len, dest->name, dest->hostname);
 350
 351         offset = DATA(packet) + ether_size + ip_size;
 352         maxlen = (dest->mtu - ether_size - ip_size) & ~0x7;
 353         ip_off = ntohs(ip.ip_off);
 354         origf = ip_off & ~IP_OFFMASK;
 355         ip_off &= IP_OFFMASK;
 356
 357         while(todo) {
 358                 len = todo > maxlen ? maxlen : todo;
 359                 memcpy(DATA(&fragment) + ether_size + ip_size, offset, len);
 360                 todo -= len;
 361                 offset += len;
 362
 363                 ip.ip_len = htons(ip_size + len);
 364                 ip.ip_off = htons(ip_off | origf | (todo ? IP_MF : 0));
 365                 ip.ip_sum = 0;
 366                 ip.ip_sum = inet_checksum(&ip, ip_size, ~0);
 367                 memcpy(DATA(&fragment), DATA(packet), ether_size);
 368                 memcpy(DATA(&fragment) + ether_size, &ip, ip_size);
 369                 fragment.len = ether_size + ip_size + len;
 370
 371                 send_packet(dest, &fragment);
 372
 373                 ip_off += len / 8;
 374         }
 375 }
 376
 377 static void route_ipv4(node_t *source, vpn_packet_t *packet) {
 378         if(!checklength(source, packet, ether_size + ip_size))
 379                 return;
 380
 381         subnet_t *subnet;
 382         node_t *via;
 383         ipv4_t dest;
 384
 385         memcpy(&dest, &DATA(packet)[30], sizeof dest);
 386         subnet = lookup_subnet_ipv4(&dest);
 387
 388         if(!subnet) {
 389                 logger(DEBUG_TRAFFIC, LOG_WARNING, "Cannot route packet from %s (%s): unknown IPv4 destination address %d.%d.%d.%d",
 390                                 source->name, source->hostname,
 391                                 dest.x[0],
 392                                 dest.x[1],
 393                                 dest.x[2],
 394                                 dest.x[3]);
 395
 396                 route_ipv4_unreachable(source, packet, ether_size, ICMP_DEST_UNREACH, ICMP_NET_UNKNOWN);
 397                 return;
 398         }
 399
 400         if (!subnet->owner) {
 401                 broadcast_packet(source, packet);
 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, ether_size, 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, ether_size, ICMP_DEST_UNREACH, ICMP_NET_ANO);
 415
 416         if(priorityinheritance)
 417                 packet->priority = DATA(packet)[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, ether_size, 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(DATA(packet)[20] & 0x40) {
 432                         packet->len = MAX(via->mtu, 590);
 433                         route_ipv4_unreachable(source, packet, ether_size, ICMP_DEST_UNREACH, ICMP_FRAG_NEEDED);
 434                 } else {
 435                         fragment_ipv4_packet(via, packet, ether_size);
 436                 }
 437
 438                 return;
 439         }
 440
 441         clamp_mss(source, via, packet);
 442
 443         send_packet(subnet->owner, packet);
 444 }
 445
 446 /* RFC 2463 */
 447
 448 static void route_ipv6_unreachable(node_t *source, vpn_packet_t *packet, length_t ether_size, uint8_t type, uint8_t code) {
 449         struct ip6_hdr ip6;
 450         struct icmp6_hdr icmp6 = {0};
 451         uint16_t checksum;
 452
 453         struct {
 454                 struct in6_addr ip6_src;        /* source address */
 455                 struct in6_addr ip6_dst;        /* destination address */
 456                 uint32_t length;
 457                 uint32_t next;
 458         } pseudo;
 459
 460         if(ratelimit(3))
 461                 return;
 462
 463         /* Swap Ethernet source and destination addresses */
 464
 465         swap_mac_addresses(packet);
 466
 467         /* Copy headers from packet to structs on the stack */
 468
 469         memcpy(&ip6, DATA(packet) + ether_size, ip6_size);
 470
 471         /* Remember original source and destination */
 472
 473         pseudo.ip6_src = ip6.ip6_dst;
 474         pseudo.ip6_dst = ip6.ip6_src;
 475
 476         pseudo.length = packet->len - ether_size;
 477
 478         if(type == ICMP6_PACKET_TOO_BIG)
 479                 icmp6.icmp6_mtu = htonl(pseudo.length);
 480
 481         if(pseudo.length >= IP_MSS - ip6_size - icmp6_size)
 482                 pseudo.length = IP_MSS - ip6_size - icmp6_size;
 483
 484         /* Copy first part of original contents to ICMP message */
 485
 486         memmove(DATA(packet) + ether_size + ip6_size + icmp6_size, DATA(packet) + ether_size, pseudo.length);
 487
 488         /* Fill in IPv6 header */
 489
 490         ip6.ip6_flow = htonl(0x60000000UL);
 491         ip6.ip6_plen = htons(icmp6_size + pseudo.length);
 492         ip6.ip6_nxt = IPPROTO_ICMPV6;
 493         ip6.ip6_hlim = 255;
 494         ip6.ip6_src = pseudo.ip6_src;
 495         ip6.ip6_dst = pseudo.ip6_dst;
 496
 497         /* Fill in ICMP header */
 498
 499         icmp6.icmp6_type = type;
 500         icmp6.icmp6_code = code;
 501         icmp6.icmp6_cksum = 0;
 502
 503         /* Create pseudo header */
 504
 505         pseudo.length = htonl(icmp6_size + pseudo.length);
 506         pseudo.next = htonl(IPPROTO_ICMPV6);
 507
 508         /* Generate checksum */
 509
 510         checksum = inet_checksum(&pseudo, sizeof pseudo, ~0);
 511         checksum = inet_checksum(&icmp6, icmp6_size, checksum);
 512         checksum = inet_checksum(DATA(packet) + ether_size + ip6_size + icmp6_size, ntohl(pseudo.length) - icmp6_size, checksum);
 513
 514         icmp6.icmp6_cksum = checksum;
 515
 516         /* Copy structs on stack back to packet */
 517
 518         memcpy(DATA(packet) + ether_size, &ip6, ip6_size);
 519         memcpy(DATA(packet) + ether_size + ip6_size, &icmp6, icmp6_size);
 520
 521         packet->len = ether_size + ip6_size + ntohl(pseudo.length);
 522
 523         send_packet(source, packet);
 524 }
 525
 526 static void route_neighborsol(node_t *source, vpn_packet_t *packet);
 527
 528 static void route_ipv6(node_t *source, vpn_packet_t *packet) {
 529         if(!checklength(source, packet, ether_size + ip6_size))
 530                 return;
 531
 532         if(DATA(packet)[20] == IPPROTO_ICMPV6 && checklength(source, packet, ether_size + ip6_size + icmp6_size) && DATA(packet)[54] == ND_NEIGHBOR_SOLICIT) {
 533                 route_neighborsol(source, packet);
 534                 return;
 535         }
 536
 537         subnet_t *subnet;
 538         node_t *via;
 539         ipv6_t dest;
 540
 541         memcpy(&dest, &DATA(packet)[38], sizeof dest);
 542         subnet = lookup_subnet_ipv6(&dest);
 543
 544         if(!subnet) {
 545                 logger(DEBUG_TRAFFIC, LOG_WARNING, "Cannot route packet from %s (%s): unknown IPv6 destination address %hx:%hx:%hx:%hx:%hx:%hx:%hx:%hx",
 546                                 source->name, source->hostname,
 547                                 ntohs(dest.x[0]),
 548                                 ntohs(dest.x[1]),
 549                                 ntohs(dest.x[2]),
 550                                 ntohs(dest.x[3]),
 551                                 ntohs(dest.x[4]),
 552                                 ntohs(dest.x[5]),
 553                                 ntohs(dest.x[6]),
 554                                 ntohs(dest.x[7]));
 555
 556                 route_ipv6_unreachable(source, packet, ether_size, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_ADDR);
 557                 return;
 558         }
 559
 560         if (!subnet->owner) {
 561                 broadcast_packet(source, packet);
 562                 return;
 563         }
 564
 565         if(subnet->owner == source) {
 566                 logger(DEBUG_TRAFFIC, LOG_WARNING, "Packet looping back to %s (%s)!", source->name, source->hostname);
 567                 return;
 568         }
 569
 570         if(!subnet->owner->status.reachable)
 571                 return route_ipv6_unreachable(source, packet, ether_size, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_NOROUTE);
 572
 573         if(forwarding_mode == FMODE_OFF && source != myself && subnet->owner != myself)
 574                 return route_ipv6_unreachable(source, packet, ether_size, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_ADMIN);
 575
 576         via = (subnet->owner->via == myself) ? subnet->owner->nexthop : subnet->owner->via;
 577
 578         if(via == source) {
 579                 logger(DEBUG_TRAFFIC, LOG_ERR, "Routing loop for packet from %s (%s)!", source->name, source->hostname);
 580                 return;
 581         }
 582
 583         if(directonly && subnet->owner != via)
 584                 return route_ipv6_unreachable(source, packet, ether_size, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_ADMIN);
 585
 586         if(via && packet->len > MAX(via->mtu, 1294) && via != myself) {
 587                 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);
 588                 packet->len = MAX(via->mtu, 1294);
 589                 route_ipv6_unreachable(source, packet, ether_size, ICMP6_PACKET_TOO_BIG, 0);
 590                 return;
 591         }
 592
 593         clamp_mss(source, via, packet);
 594
 595         send_packet(subnet->owner, packet);
 596 }
 597
 598 /* RFC 2461 */
 599
 600 static void route_neighborsol(node_t *source, vpn_packet_t *packet) {
 601         struct ip6_hdr ip6;
 602         struct nd_neighbor_solicit ns;
 603         struct nd_opt_hdr opt;
 604         subnet_t *subnet;
 605         uint16_t checksum;
 606         bool has_opt;
 607
 608         struct {
 609                 struct in6_addr ip6_src;
 610                 struct in6_addr ip6_dst;
 611                 uint32_t length;
 612                 uint32_t next;
 613         } pseudo;
 614
 615         if(!checklength(source, packet, ether_size + ip6_size + ns_size))
 616                 return;
 617
 618         has_opt = packet->len >= ether_size + ip6_size + ns_size + opt_size + ETH_ALEN;
 619
 620         if(source != myself) {
 621                 logger(DEBUG_TRAFFIC, LOG_WARNING, "Got neighbor solicitation request from %s (%s) while in router mode!", source->name, source->hostname);
 622                 return;
 623         }
 624
 625         /* Copy headers from packet to structs on the stack */
 626
 627         memcpy(&ip6, DATA(packet) + ether_size, ip6_size);
 628         memcpy(&ns, DATA(packet) + ether_size + ip6_size, ns_size);
 629         if(has_opt)
 630                 memcpy(&opt, DATA(packet) + ether_size + ip6_size + ns_size, opt_size);
 631
 632         /* First, snatch the source address from the neighbor solicitation packet */
 633
 634         if(overwrite_mac)
 635                 memcpy(mymac.x, DATA(packet) + ETH_ALEN, ETH_ALEN);
 636
 637         /* Check if this is a valid neighbor solicitation request */
 638
 639         if(ns.nd_ns_hdr.icmp6_type != ND_NEIGHBOR_SOLICIT ||
 640            (has_opt && opt.nd_opt_type != ND_OPT_SOURCE_LINKADDR)) {
 641                 logger(DEBUG_TRAFFIC, LOG_WARNING, "Cannot route packet: received unknown type neighbor solicitation request");
 642                 return;
 643         }
 644
 645         /* Create pseudo header */
 646
 647         pseudo.ip6_src = ip6.ip6_src;
 648         pseudo.ip6_dst = ip6.ip6_dst;
 649         if(has_opt)
 650                 pseudo.length = htonl(ns_size + opt_size + ETH_ALEN);
 651         else
 652                 pseudo.length = htonl(ns_size);
 653         pseudo.next = htonl(IPPROTO_ICMPV6);
 654
 655         /* Generate checksum */
 656
 657         checksum = inet_checksum(&pseudo, sizeof pseudo, ~0);
 658         checksum = inet_checksum(&ns, ns_size, checksum);
 659         if(has_opt) {
 660                 checksum = inet_checksum(&opt, opt_size, checksum);
 661                 checksum = inet_checksum(DATA(packet) + ether_size + ip6_size + ns_size + opt_size, ETH_ALEN, checksum);
 662         }
 663
 664         if(checksum) {
 665                 logger(DEBUG_TRAFFIC, LOG_WARNING, "Cannot route packet: checksum error for neighbor solicitation request");
 666                 return;
 667         }
 668
 669         /* Check if the IPv6 address exists on the VPN */
 670
 671         subnet = lookup_subnet_ipv6((ipv6_t *) &ns.nd_ns_target);
 672
 673         if(!subnet) {
 674                 logger(DEBUG_TRAFFIC, LOG_WARNING, "Cannot route packet: neighbor solicitation request for unknown address %hx:%hx:%hx:%hx:%hx:%hx:%hx:%hx",
 675                                    ntohs(((uint16_t *) &ns.nd_ns_target)[0]),
 676                                    ntohs(((uint16_t *) &ns.nd_ns_target)[1]),
 677                                    ntohs(((uint16_t *) &ns.nd_ns_target)[2]),
 678                                    ntohs(((uint16_t *) &ns.nd_ns_target)[3]),
 679                                    ntohs(((uint16_t *) &ns.nd_ns_target)[4]),
 680                                    ntohs(((uint16_t *) &ns.nd_ns_target)[5]),
 681                                    ntohs(((uint16_t *) &ns.nd_ns_target)[6]),
 682                                    ntohs(((uint16_t *) &ns.nd_ns_target)[7]));
 683
 684                 return;
 685         }
 686
 687         /* Check if it is for our own subnet */
 688
 689         if(subnet->owner == myself)
 690                 return;                                          /* silently ignore */
 691
 692         /* Create neighbor advertation reply */
 693
 694         memcpy(DATA(packet), DATA(packet) + ETH_ALEN, ETH_ALEN); /* copy destination address */
 695         DATA(packet)[ETH_ALEN * 2 - 1] ^= 0xFF;                  /* mangle source address so it looks like it's not from us */
 696
 697         ip6.ip6_dst = ip6.ip6_src;                               /* swap destination and source protocoll address */
 698         ip6.ip6_src = ns.nd_ns_target;
 699
 700         if(has_opt)
 701                 memcpy(DATA(packet) + ether_size + ip6_size + ns_size + opt_size, DATA(packet) + ETH_ALEN, ETH_ALEN);   /* add fake source hard addr */
 702
 703         ns.nd_ns_cksum = 0;
 704         ns.nd_ns_type = ND_NEIGHBOR_ADVERT;
 705         ns.nd_ns_reserved = htonl(0x40000000UL);                 /* Set solicited flag */
 706         opt.nd_opt_type = ND_OPT_TARGET_LINKADDR;
 707
 708         /* Create pseudo header */
 709
 710         pseudo.ip6_src = ip6.ip6_src;
 711         pseudo.ip6_dst = ip6.ip6_dst;
 712         if(has_opt)
 713                 pseudo.length = htonl(ns_size + opt_size + ETH_ALEN);
 714         else
 715                 pseudo.length = htonl(ns_size);
 716         pseudo.next = htonl(IPPROTO_ICMPV6);
 717
 718         /* Generate checksum */
 719
 720         checksum = inet_checksum(&pseudo, sizeof pseudo, ~0);
 721         checksum = inet_checksum(&ns, ns_size, checksum);
 722         if(has_opt) {
 723                 checksum = inet_checksum(&opt, opt_size, checksum);
 724                 checksum = inet_checksum(DATA(packet) + ether_size + ip6_size + ns_size + opt_size, ETH_ALEN, checksum);
 725         }
 726
 727         ns.nd_ns_hdr.icmp6_cksum = checksum;
 728
 729         /* Copy structs on stack back to packet */
 730
 731         memcpy(DATA(packet) + ether_size, &ip6, ip6_size);
 732         memcpy(DATA(packet) + ether_size + ip6_size, &ns, ns_size);
 733         if(has_opt)
 734                 memcpy(DATA(packet) + ether_size + ip6_size + ns_size, &opt, opt_size);
 735
 736         send_packet(source, packet);
 737 }
 738
 739 /* RFC 826 */
 740
 741 static void route_arp(node_t *source, vpn_packet_t *packet) {
 742         struct ether_arp arp;
 743         subnet_t *subnet;
 744         struct in_addr addr;
 745
 746         if(!checklength(source, packet, ether_size + arp_size))
 747                 return;
 748
 749         if(source != myself) {
 750                 logger(DEBUG_TRAFFIC, LOG_WARNING, "Got ARP request from %s (%s) while in router mode!", source->name, source->hostname);
 751                 return;
 752         }
 753
 754         /* First, snatch the source address from the ARP packet */
 755
 756         if(overwrite_mac)
 757                 memcpy(mymac.x, DATA(packet) + ETH_ALEN, ETH_ALEN);
 758
 759         /* Copy headers from packet to structs on the stack */
 760
 761         memcpy(&arp, DATA(packet) + ether_size, arp_size);
 762
 763         /* Check if this is a valid ARP request */
 764
 765         if(ntohs(arp.arp_hrd) != ARPHRD_ETHER || ntohs(arp.arp_pro) != ETH_P_IP ||
 766            arp.arp_hln != ETH_ALEN || arp.arp_pln != sizeof addr || ntohs(arp.arp_op) != ARPOP_REQUEST) {
 767                 logger(DEBUG_TRAFFIC, LOG_WARNING, "Cannot route packet: received unknown type ARP request");
 768                 return;
 769         }
 770
 771         /* Check if the IPv4 address exists on the VPN */
 772
 773         subnet = lookup_subnet_ipv4((ipv4_t *) &arp.arp_tpa);
 774
 775         if(!subnet) {
 776                 logger(DEBUG_TRAFFIC, LOG_WARNING, "Cannot route packet: ARP request for unknown address %d.%d.%d.%d",
 777                                    arp.arp_tpa[0], arp.arp_tpa[1], arp.arp_tpa[2],
 778                                    arp.arp_tpa[3]);
 779                 return;
 780         }
 781
 782         /* Check if it is for our own subnet */
 783
 784         if(subnet->owner == myself)
 785                 return;                                          /* silently ignore */
 786
 787         memcpy(&addr, arp.arp_tpa, sizeof addr);                 /* save protocol addr */
 788         memcpy(arp.arp_tpa, arp.arp_spa, sizeof addr);           /* swap destination and source protocol address */
 789         memcpy(arp.arp_spa, &addr, sizeof addr);                 /* ... */
 790
 791         memcpy(arp.arp_tha, arp.arp_sha, ETH_ALEN);              /* set target hard/proto addr */
 792         memcpy(arp.arp_sha, DATA(packet) + ETH_ALEN, ETH_ALEN);  /* set source hard/proto addr */
 793         arp.arp_sha[ETH_ALEN - 1] ^= 0xFF;                       /* for consistency with route_packet() */
 794         arp.arp_op = htons(ARPOP_REPLY);
 795
 796         /* Copy structs on stack back to packet */
 797
 798         memcpy(DATA(packet) + ether_size, &arp, arp_size);
 799
 800         send_packet(source, packet);
 801 }
 802
 803 static void route_mac(node_t *source, vpn_packet_t *packet) {
 804         subnet_t *subnet;
 805         mac_t dest;
 806
 807         /* Learn source address */
 808
 809         if(source == myself) {
 810                 mac_t src;
 811                 memcpy(&src, &DATA(packet)[6], sizeof src);
 812                 learn_mac(&src);
 813         }
 814
 815         /* Lookup destination address */
 816
 817         memcpy(&dest, &DATA(packet)[0], sizeof dest);
 818         subnet = lookup_subnet_mac(NULL, &dest);
 819
 820         if(!subnet || !subnet->owner) {
 821                 broadcast_packet(source, packet);
 822                 return;
 823         }
 824
 825         if(subnet->owner == source) {
 826                 logger(DEBUG_TRAFFIC, LOG_WARNING, "Packet looping back to %s (%s)!", source->name, source->hostname);
 827                 return;
 828         }
 829
 830         if(forwarding_mode == FMODE_OFF && source != myself && subnet->owner != myself)
 831                 return;
 832
 833         uint16_t type = DATA(packet)[12] << 8 | DATA(packet)[13];
 834
 835         if(priorityinheritance && type == ETH_P_IP && packet->len >= ether_size + ip_size)
 836                 packet->priority = DATA(packet)[15];
 837
 838         // Handle packets larger than PMTU
 839
 840         node_t *via = (subnet->owner->via == myself) ? subnet->owner->nexthop : subnet->owner->via;
 841
 842         if(directonly && subnet->owner != via)
 843                 return;
 844
 845         if(via && packet->len > via->mtu && via != myself) {
 846                 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);
 847                 length_t ethlen = 14;
 848
 849                 if(type == ETH_P_8021Q) {
 850                         type = DATA(packet)[16] << 8 | DATA(packet)[17];
 851                         ethlen += 4;
 852                 }
 853
 854                 if(type == ETH_P_IP && packet->len > 576 + ethlen) {
 855                         if(DATA(packet)[6 + ethlen] & 0x40) {
 856                                 packet->len = via->mtu;
 857                                 route_ipv4_unreachable(source, packet, ethlen, ICMP_DEST_UNREACH, ICMP_FRAG_NEEDED);
 858                         } else {
 859                                 fragment_ipv4_packet(via, packet, ethlen);
 860                         }
 861                         return;
 862                 } else if(type == ETH_P_IPV6 && packet->len > 1280 + ethlen) {
 863                         packet->len = via->mtu;
 864                         route_ipv6_unreachable(source, packet, ethlen, ICMP6_PACKET_TOO_BIG, 0);
 865                         return;
 866                 }
 867         }
 868
 869         clamp_mss(source, via, packet);
 870
 871         send_packet(subnet->owner, packet);
 872 }
 873
 874 static void send_pcap(vpn_packet_t *packet) {
 875         pcap = false;
 876
 877         for list_each(connection_t, c, connection_list) {
 878                 if(!c->status.pcap)
 879                         continue;
 880
 881                 pcap = true;
 882                 int len = packet->len;
 883                 if(c->outmaclength && c->outmaclength < len)
 884                         len = c->outmaclength;
 885
 886                 if(send_request(c, "%d %d %d", CONTROL, REQ_PCAP, len))
 887                         send_meta(c, (char *)DATA(packet), len);
 888         }
 889 }
 890
 891 static bool do_decrement_ttl(node_t *source, vpn_packet_t *packet) {
 892         uint16_t type = DATA(packet)[12] << 8 | DATA(packet)[13];
 893         length_t ethlen = ether_size;
 894
 895         if(type == ETH_P_8021Q) {
 896                 type = DATA(packet)[16] << 8 | DATA(packet)[17];
 897                 ethlen += 4;
 898         }
 899
 900         switch (type) {
 901                 case ETH_P_IP:
 902                         if(!checklength(source, packet, ethlen + ip_size))
 903                                 return false;
 904
 905                         if(DATA(packet)[ethlen + 8] <= 1) {
 906                                 if(DATA(packet)[ethlen + 11] != IPPROTO_ICMP || DATA(packet)[ethlen + 32] != ICMP_TIME_EXCEEDED)
 907                                         route_ipv4_unreachable(source, packet, ethlen, ICMP_TIME_EXCEEDED, ICMP_EXC_TTL);
 908                                 return false;
 909                         }
 910
 911                         uint16_t old = DATA(packet)[ethlen + 8] << 8 | DATA(packet)[ethlen + 9];
 912                         DATA(packet)[ethlen + 8]--;
 913                         uint16_t new = DATA(packet)[ethlen + 8] << 8 | DATA(packet)[ethlen + 9];
 914
 915                         uint32_t checksum = DATA(packet)[ethlen + 10] << 8 | DATA(packet)[ethlen + 11];
 916                         checksum += old + (~new & 0xFFFF);
 917                         while(checksum >> 16)
 918                                 checksum = (checksum & 0xFFFF) + (checksum >> 16);
 919                         DATA(packet)[ethlen + 10] = checksum >> 8;
 920                         DATA(packet)[ethlen + 11] = checksum & 0xff;
 921
 922                         return true;
 923
 924                 case ETH_P_IPV6:
 925                         if(!checklength(source, packet, ethlen + ip6_size))
 926                                 return false;
 927
 928                         if(DATA(packet)[ethlen + 7] <= 1) {
 929                                 if(DATA(packet)[ethlen + 6] != IPPROTO_ICMPV6 || DATA(packet)[ethlen + 40] != ICMP6_TIME_EXCEEDED)
 930                                         route_ipv6_unreachable(source, packet, ethlen, ICMP6_TIME_EXCEEDED, ICMP6_TIME_EXCEED_TRANSIT);
 931                                 return false;
 932                         }
 933
 934                         DATA(packet)[ethlen + 7]--;
 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         uint16_t type = DATA(packet)[12] << 8 | DATA(packet)[13];
 960
 961         switch (routing_mode) {
 962                 case RMODE_ROUTER:
 963                         switch (type) {
 964                                 case ETH_P_ARP:
 965                                         route_arp(source, packet);
 966                                         break;
 967
 968                                 case ETH_P_IP:
 969                                         route_ipv4(source, packet);
 970                                         break;
 971
 972                                 case ETH_P_IPV6:
 973                                         route_ipv6(source, packet);
 974                                         break;
 975
 976                                 default:
 977                                         logger(DEBUG_TRAFFIC, LOG_WARNING, "Cannot route packet from %s (%s): unknown type %hx", source->name, source->hostname, type);
 978                                         break;
 979                         }
 980                         break;
 981
 982                 case RMODE_SWITCH:
 983                         route_mac(source, packet);
 984                         break;
 985
 986                 case RMODE_HUB:
 987                         broadcast_packet(source, packet);
 988                         break;
 989         }
 990 }