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         /* Try to reply with an IP address assigned to the local machine */
 280
 281         if (type == ICMP_TIME_EXCEEDED && code == ICMP_EXC_TTL) {
 282                 int sockfd = socket(AF_INET, SOCK_DGRAM, 0);
 283                 if (sockfd != -1) {
 284                         struct sockaddr_in addr;
 285                         memset(&addr, 0, sizeof(addr));
 286                         addr.sin_family = AF_INET;
 287                         addr.sin_addr = ip.ip_src;
 288                         if (!connect(sockfd, (const struct sockaddr*) &addr, sizeof(addr))) {
 289                                 memset(&addr, 0, sizeof(addr));
 290                                 addr.sin_family = AF_INET;
 291                                 socklen_t addrlen = sizeof(addr);
 292                                 if (!getsockname(sockfd, (struct sockaddr*) &addr, &addrlen) && addrlen <= sizeof(addr)) {
 293                                         ip_dst = addr.sin_addr;
 294                                 }
 295                         }
 296                         close(sockfd);
 297                 }
 298         }
 299
 300         oldlen = packet->len - ether_size;
 301
 302         if(type == ICMP_DEST_UNREACH && code == ICMP_FRAG_NEEDED)
 303                 icmp.icmp_nextmtu = htons(packet->len - ether_size);
 304
 305         if(oldlen >= IP_MSS - ip_size - icmp_size)
 306                 oldlen = IP_MSS - ip_size - icmp_size;
 307
 308         /* Copy first part of original contents to ICMP message */
 309
 310         memmove(DATA(packet) + ether_size + ip_size + icmp_size, DATA(packet) + ether_size, oldlen);
 311
 312         /* Fill in IPv4 header */
 313
 314         ip.ip_v = 4;
 315         ip.ip_hl = ip_size / 4;
 316         ip.ip_tos = 0;
 317         ip.ip_len = htons(ip_size + icmp_size + oldlen);
 318         ip.ip_id = 0;
 319         ip.ip_off = 0;
 320         ip.ip_ttl = 255;
 321         ip.ip_p = IPPROTO_ICMP;
 322         ip.ip_sum = 0;
 323         ip.ip_src = ip_dst;
 324         ip.ip_dst = ip_src;
 325
 326         ip.ip_sum = inet_checksum(&ip, ip_size, ~0);
 327
 328         /* Fill in ICMP header */
 329
 330         icmp.icmp_type = type;
 331         icmp.icmp_code = code;
 332         icmp.icmp_cksum = 0;
 333
 334         icmp.icmp_cksum = inet_checksum(&icmp, icmp_size, ~0);
 335         icmp.icmp_cksum = inet_checksum(DATA(packet) + ether_size + ip_size + icmp_size, oldlen, icmp.icmp_cksum);
 336
 337         /* Copy structs on stack back to packet */
 338
 339         memcpy(DATA(packet) + ether_size, &ip, ip_size);
 340         memcpy(DATA(packet) + ether_size + ip_size, &icmp, icmp_size);
 341
 342         packet->len = ether_size + ip_size + icmp_size + oldlen;
 343
 344         send_packet(source, packet);
 345 }
 346
 347 /* RFC 791 */
 348
 349 static void fragment_ipv4_packet(node_t *dest, vpn_packet_t *packet, length_t ether_size) {
 350         struct ip ip;
 351         vpn_packet_t fragment;
 352         int len, maxlen, todo;
 353         uint8_t *offset;
 354         uint16_t ip_off, origf;
 355
 356         memcpy(&ip, DATA(packet) + ether_size, ip_size);
 357         fragment.priority = packet->priority;
 358         fragment.offset = DEFAULT_PACKET_OFFSET;
 359
 360         if(ip.ip_hl != ip_size / 4)
 361                 return;
 362
 363         todo = ntohs(ip.ip_len) - ip_size;
 364
 365         if(ether_size + ip_size + todo != packet->len) {
 366                 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));
 367                 return;
 368         }
 369
 370         logger(DEBUG_TRAFFIC, LOG_INFO, "Fragmenting packet of %d bytes to %s (%s)", packet->len, dest->name, dest->hostname);
 371
 372         offset = DATA(packet) + ether_size + ip_size;
 373         maxlen = (dest->mtu - ether_size - ip_size) & ~0x7;
 374         ip_off = ntohs(ip.ip_off);
 375         origf = ip_off & ~IP_OFFMASK;
 376         ip_off &= IP_OFFMASK;
 377
 378         while(todo) {
 379                 len = todo > maxlen ? maxlen : todo;
 380                 memcpy(DATA(&fragment) + ether_size + ip_size, offset, len);
 381                 todo -= len;
 382                 offset += len;
 383
 384                 ip.ip_len = htons(ip_size + len);
 385                 ip.ip_off = htons(ip_off | origf | (todo ? IP_MF : 0));
 386                 ip.ip_sum = 0;
 387                 ip.ip_sum = inet_checksum(&ip, ip_size, ~0);
 388                 memcpy(DATA(&fragment), DATA(packet), ether_size);
 389                 memcpy(DATA(&fragment) + ether_size, &ip, ip_size);
 390                 fragment.len = ether_size + ip_size + len;
 391
 392                 send_packet(dest, &fragment);
 393
 394                 ip_off += len / 8;
 395         }
 396 }
 397
 398 static void route_ipv4(node_t *source, vpn_packet_t *packet) {
 399         if(!checklength(source, packet, ether_size + ip_size))
 400                 return;
 401
 402         subnet_t *subnet;
 403         node_t *via;
 404         ipv4_t dest;
 405
 406         memcpy(&dest, &DATA(packet)[30], sizeof dest);
 407         subnet = lookup_subnet_ipv4(&dest);
 408
 409         if(!subnet) {
 410                 logger(DEBUG_TRAFFIC, LOG_WARNING, "Cannot route packet from %s (%s): unknown IPv4 destination address %d.%d.%d.%d",
 411                                 source->name, source->hostname,
 412                                 dest.x[0],
 413                                 dest.x[1],
 414                                 dest.x[2],
 415                                 dest.x[3]);
 416
 417                 route_ipv4_unreachable(source, packet, ether_size, ICMP_DEST_UNREACH, ICMP_NET_UNKNOWN);
 418                 return;
 419         }
 420
 421         if (!subnet->owner) {
 422                 broadcast_packet(source, packet);
 423                 return;
 424         }
 425
 426         if(subnet->owner == source) {
 427                 logger(DEBUG_TRAFFIC, LOG_WARNING, "Packet looping back to %s (%s)!", source->name, source->hostname);
 428                 return;
 429         }
 430
 431         if(!subnet->owner->status.reachable)
 432                 return route_ipv4_unreachable(source, packet, ether_size, ICMP_DEST_UNREACH, ICMP_NET_UNREACH);
 433
 434         if(forwarding_mode == FMODE_OFF && source != myself && subnet->owner != myself)
 435                 return route_ipv4_unreachable(source, packet, ether_size, ICMP_DEST_UNREACH, ICMP_NET_ANO);
 436
 437         if(priorityinheritance)
 438                 packet->priority = DATA(packet)[15];
 439
 440         via = (subnet->owner->via == myself) ? subnet->owner->nexthop : subnet->owner->via;
 441
 442         if(via == source) {
 443                 logger(DEBUG_TRAFFIC, LOG_ERR, "Routing loop for packet from %s (%s)!", source->name, source->hostname);
 444                 return;
 445         }
 446
 447         if(directonly && subnet->owner != via)
 448                 return route_ipv4_unreachable(source, packet, ether_size, ICMP_DEST_UNREACH, ICMP_NET_ANO);
 449
 450         if(via && packet->len > MAX(via->mtu, 590) && via != myself) {
 451                 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);
 452                 if(DATA(packet)[20] & 0x40) {
 453                         packet->len = MAX(via->mtu, 590);
 454                         route_ipv4_unreachable(source, packet, ether_size, ICMP_DEST_UNREACH, ICMP_FRAG_NEEDED);
 455                 } else {
 456                         fragment_ipv4_packet(via, packet, ether_size);
 457                 }
 458
 459                 return;
 460         }
 461
 462         clamp_mss(source, via, packet);
 463
 464         send_packet(subnet->owner, packet);
 465 }
 466
 467 /* RFC 2463 */
 468
 469 static void route_ipv6_unreachable(node_t *source, vpn_packet_t *packet, length_t ether_size, uint8_t type, uint8_t code) {
 470         struct ip6_hdr ip6;
 471         struct icmp6_hdr icmp6 = {0};
 472         uint16_t checksum;
 473
 474         struct {
 475                 struct in6_addr ip6_src;        /* source address */
 476                 struct in6_addr ip6_dst;        /* destination address */
 477                 uint32_t length;
 478                 uint32_t next;
 479         } pseudo;
 480
 481         if(ratelimit(3))
 482                 return;
 483
 484         /* Swap Ethernet source and destination addresses */
 485
 486         swap_mac_addresses(packet);
 487
 488         /* Copy headers from packet to structs on the stack */
 489
 490         memcpy(&ip6, DATA(packet) + ether_size, ip6_size);
 491
 492         /* Remember original source and destination */
 493
 494         pseudo.ip6_src = ip6.ip6_dst;
 495         pseudo.ip6_dst = ip6.ip6_src;
 496
 497         /* Try to reply with an IP address assigned to the local machine */
 498
 499         if (type == ICMP6_TIME_EXCEEDED && code == ICMP6_TIME_EXCEED_TRANSIT) {
 500                 int sockfd = socket(AF_INET6, SOCK_DGRAM, 0);
 501                 if (sockfd != -1) {
 502                         struct sockaddr_in6 addr;
 503                         memset(&addr, 0, sizeof(addr));
 504                         addr.sin6_family = AF_INET6;
 505                         addr.sin6_addr = ip6.ip6_src;
 506                         if (!connect(sockfd, (const struct sockaddr*) &addr, sizeof(addr))) {
 507                                 memset(&addr, 0, sizeof(addr));
 508                                 addr.sin6_family = AF_INET6;
 509                                 socklen_t addrlen = sizeof(addr);
 510                                 if (!getsockname(sockfd, (struct sockaddr*) &addr, &addrlen) && addrlen <= sizeof(addr)) {
 511                                         pseudo.ip6_src = addr.sin6_addr;
 512                                 }
 513                         }
 514                         close(sockfd);
 515                 }
 516         }
 517
 518         pseudo.length = packet->len - ether_size;
 519
 520         if(type == ICMP6_PACKET_TOO_BIG)
 521                 icmp6.icmp6_mtu = htonl(pseudo.length);
 522
 523         if(pseudo.length >= IP_MSS - ip6_size - icmp6_size)
 524                 pseudo.length = IP_MSS - ip6_size - icmp6_size;
 525
 526         /* Copy first part of original contents to ICMP message */
 527
 528         memmove(DATA(packet) + ether_size + ip6_size + icmp6_size, DATA(packet) + ether_size, pseudo.length);
 529
 530         /* Fill in IPv6 header */
 531
 532         ip6.ip6_flow = htonl(0x60000000UL);
 533         ip6.ip6_plen = htons(icmp6_size + pseudo.length);
 534         ip6.ip6_nxt = IPPROTO_ICMPV6;
 535         ip6.ip6_hlim = 255;
 536         ip6.ip6_src = pseudo.ip6_src;
 537         ip6.ip6_dst = pseudo.ip6_dst;
 538
 539         /* Fill in ICMP header */
 540
 541         icmp6.icmp6_type = type;
 542         icmp6.icmp6_code = code;
 543         icmp6.icmp6_cksum = 0;
 544
 545         /* Create pseudo header */
 546
 547         pseudo.length = htonl(icmp6_size + pseudo.length);
 548         pseudo.next = htonl(IPPROTO_ICMPV6);
 549
 550         /* Generate checksum */
 551
 552         checksum = inet_checksum(&pseudo, sizeof pseudo, ~0);
 553         checksum = inet_checksum(&icmp6, icmp6_size, checksum);
 554         checksum = inet_checksum(DATA(packet) + ether_size + ip6_size + icmp6_size, ntohl(pseudo.length) - icmp6_size, checksum);
 555
 556         icmp6.icmp6_cksum = checksum;
 557
 558         /* Copy structs on stack back to packet */
 559
 560         memcpy(DATA(packet) + ether_size, &ip6, ip6_size);
 561         memcpy(DATA(packet) + ether_size + ip6_size, &icmp6, icmp6_size);
 562
 563         packet->len = ether_size + ip6_size + ntohl(pseudo.length);
 564
 565         send_packet(source, packet);
 566 }
 567
 568 static void route_neighborsol(node_t *source, vpn_packet_t *packet);
 569
 570 static void route_ipv6(node_t *source, vpn_packet_t *packet) {
 571         if(!checklength(source, packet, ether_size + ip6_size))
 572                 return;
 573
 574         if(DATA(packet)[20] == IPPROTO_ICMPV6 && checklength(source, packet, ether_size + ip6_size + icmp6_size) && DATA(packet)[54] == ND_NEIGHBOR_SOLICIT) {
 575                 route_neighborsol(source, packet);
 576                 return;
 577         }
 578
 579         subnet_t *subnet;
 580         node_t *via;
 581         ipv6_t dest;
 582
 583         memcpy(&dest, &DATA(packet)[38], sizeof dest);
 584         subnet = lookup_subnet_ipv6(&dest);
 585
 586         if(!subnet) {
 587                 logger(DEBUG_TRAFFIC, LOG_WARNING, "Cannot route packet from %s (%s): unknown IPv6 destination address %hx:%hx:%hx:%hx:%hx:%hx:%hx:%hx",
 588                                 source->name, source->hostname,
 589                                 ntohs(dest.x[0]),
 590                                 ntohs(dest.x[1]),
 591                                 ntohs(dest.x[2]),
 592                                 ntohs(dest.x[3]),
 593                                 ntohs(dest.x[4]),
 594                                 ntohs(dest.x[5]),
 595                                 ntohs(dest.x[6]),
 596                                 ntohs(dest.x[7]));
 597
 598                 route_ipv6_unreachable(source, packet, ether_size, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_ADDR);
 599                 return;
 600         }
 601
 602         if (!subnet->owner) {
 603                 broadcast_packet(source, packet);
 604                 return;
 605         }
 606
 607         if(subnet->owner == source) {
 608                 logger(DEBUG_TRAFFIC, LOG_WARNING, "Packet looping back to %s (%s)!", source->name, source->hostname);
 609                 return;
 610         }
 611
 612         if(!subnet->owner->status.reachable)
 613                 return route_ipv6_unreachable(source, packet, ether_size, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_NOROUTE);
 614
 615         if(forwarding_mode == FMODE_OFF && source != myself && subnet->owner != myself)
 616                 return route_ipv6_unreachable(source, packet, ether_size, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_ADMIN);
 617
 618         via = (subnet->owner->via == myself) ? subnet->owner->nexthop : subnet->owner->via;
 619
 620         if(via == source) {
 621                 logger(DEBUG_TRAFFIC, LOG_ERR, "Routing loop for packet from %s (%s)!", source->name, source->hostname);
 622                 return;
 623         }
 624
 625         if(directonly && subnet->owner != via)
 626                 return route_ipv6_unreachable(source, packet, ether_size, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_ADMIN);
 627
 628         if(via && packet->len > MAX(via->mtu, 1294) && via != myself) {
 629                 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);
 630                 packet->len = MAX(via->mtu, 1294);
 631                 route_ipv6_unreachable(source, packet, ether_size, ICMP6_PACKET_TOO_BIG, 0);
 632                 return;
 633         }
 634
 635         clamp_mss(source, via, packet);
 636
 637         send_packet(subnet->owner, packet);
 638 }
 639
 640 /* RFC 2461 */
 641
 642 static void route_neighborsol(node_t *source, vpn_packet_t *packet) {
 643         struct ip6_hdr ip6;
 644         struct nd_neighbor_solicit ns;
 645         struct nd_opt_hdr opt;
 646         subnet_t *subnet;
 647         uint16_t checksum;
 648         bool has_opt;
 649
 650         struct {
 651                 struct in6_addr ip6_src;
 652                 struct in6_addr ip6_dst;
 653                 uint32_t length;
 654                 uint32_t next;
 655         } pseudo;
 656
 657         if(!checklength(source, packet, ether_size + ip6_size + ns_size))
 658                 return;
 659
 660         has_opt = packet->len >= ether_size + ip6_size + ns_size + opt_size + ETH_ALEN;
 661
 662         if(source != myself) {
 663                 logger(DEBUG_TRAFFIC, LOG_WARNING, "Got neighbor solicitation request from %s (%s) while in router mode!", source->name, source->hostname);
 664                 return;
 665         }
 666
 667         /* Copy headers from packet to structs on the stack */
 668
 669         memcpy(&ip6, DATA(packet) + ether_size, ip6_size);
 670         memcpy(&ns, DATA(packet) + ether_size + ip6_size, ns_size);
 671         if(has_opt)
 672                 memcpy(&opt, DATA(packet) + ether_size + ip6_size + ns_size, opt_size);
 673
 674         /* First, snatch the source address from the neighbor solicitation packet */
 675
 676         if(overwrite_mac)
 677                 memcpy(mymac.x, DATA(packet) + ETH_ALEN, ETH_ALEN);
 678
 679         /* Check if this is a valid neighbor solicitation request */
 680
 681         if(ns.nd_ns_hdr.icmp6_type != ND_NEIGHBOR_SOLICIT ||
 682            (has_opt && opt.nd_opt_type != ND_OPT_SOURCE_LINKADDR)) {
 683                 logger(DEBUG_TRAFFIC, LOG_WARNING, "Cannot route packet: received unknown type neighbor solicitation request");
 684                 return;
 685         }
 686
 687         /* Create pseudo header */
 688
 689         pseudo.ip6_src = ip6.ip6_src;
 690         pseudo.ip6_dst = ip6.ip6_dst;
 691         if(has_opt)
 692                 pseudo.length = htonl(ns_size + opt_size + ETH_ALEN);
 693         else
 694                 pseudo.length = htonl(ns_size);
 695         pseudo.next = htonl(IPPROTO_ICMPV6);
 696
 697         /* Generate checksum */
 698
 699         checksum = inet_checksum(&pseudo, sizeof pseudo, ~0);
 700         checksum = inet_checksum(&ns, ns_size, checksum);
 701         if(has_opt) {
 702                 checksum = inet_checksum(&opt, opt_size, checksum);
 703                 checksum = inet_checksum(DATA(packet) + ether_size + ip6_size + ns_size + opt_size, ETH_ALEN, checksum);
 704         }
 705
 706         if(checksum) {
 707                 logger(DEBUG_TRAFFIC, LOG_WARNING, "Cannot route packet: checksum error for neighbor solicitation request");
 708                 return;
 709         }
 710
 711         /* Check if the IPv6 address exists on the VPN */
 712
 713         subnet = lookup_subnet_ipv6((ipv6_t *) &ns.nd_ns_target);
 714
 715         if(!subnet) {
 716                 logger(DEBUG_TRAFFIC, LOG_WARNING, "Cannot route packet: neighbor solicitation request for unknown address %hx:%hx:%hx:%hx:%hx:%hx:%hx:%hx",
 717                                    ntohs(((uint16_t *) &ns.nd_ns_target)[0]),
 718                                    ntohs(((uint16_t *) &ns.nd_ns_target)[1]),
 719                                    ntohs(((uint16_t *) &ns.nd_ns_target)[2]),
 720                                    ntohs(((uint16_t *) &ns.nd_ns_target)[3]),
 721                                    ntohs(((uint16_t *) &ns.nd_ns_target)[4]),
 722                                    ntohs(((uint16_t *) &ns.nd_ns_target)[5]),
 723                                    ntohs(((uint16_t *) &ns.nd_ns_target)[6]),
 724                                    ntohs(((uint16_t *) &ns.nd_ns_target)[7]));
 725
 726                 return;
 727         }
 728
 729         /* Check if it is for our own subnet */
 730
 731         if(subnet->owner == myself)
 732                 return;                                          /* silently ignore */
 733
 734         /* Create neighbor advertation reply */
 735
 736         memcpy(DATA(packet), DATA(packet) + ETH_ALEN, ETH_ALEN); /* copy destination address */
 737         DATA(packet)[ETH_ALEN * 2 - 1] ^= 0xFF;                  /* mangle source address so it looks like it's not from us */
 738
 739         ip6.ip6_dst = ip6.ip6_src;                               /* swap destination and source protocoll address */
 740         ip6.ip6_src = ns.nd_ns_target;
 741
 742         if(has_opt)
 743                 memcpy(DATA(packet) + ether_size + ip6_size + ns_size + opt_size, DATA(packet) + ETH_ALEN, ETH_ALEN);   /* add fake source hard addr */
 744
 745         ns.nd_ns_cksum = 0;
 746         ns.nd_ns_type = ND_NEIGHBOR_ADVERT;
 747         ns.nd_ns_reserved = htonl(0x40000000UL);                 /* Set solicited flag */
 748         opt.nd_opt_type = ND_OPT_TARGET_LINKADDR;
 749
 750         /* Create pseudo header */
 751
 752         pseudo.ip6_src = ip6.ip6_src;
 753         pseudo.ip6_dst = ip6.ip6_dst;
 754         if(has_opt)
 755                 pseudo.length = htonl(ns_size + opt_size + ETH_ALEN);
 756         else
 757                 pseudo.length = htonl(ns_size);
 758         pseudo.next = htonl(IPPROTO_ICMPV6);
 759
 760         /* Generate checksum */
 761
 762         checksum = inet_checksum(&pseudo, sizeof pseudo, ~0);
 763         checksum = inet_checksum(&ns, ns_size, checksum);
 764         if(has_opt) {
 765                 checksum = inet_checksum(&opt, opt_size, checksum);
 766                 checksum = inet_checksum(DATA(packet) + ether_size + ip6_size + ns_size + opt_size, ETH_ALEN, checksum);
 767         }
 768
 769         ns.nd_ns_hdr.icmp6_cksum = checksum;
 770
 771         /* Copy structs on stack back to packet */
 772
 773         memcpy(DATA(packet) + ether_size, &ip6, ip6_size);
 774         memcpy(DATA(packet) + ether_size + ip6_size, &ns, ns_size);
 775         if(has_opt)
 776                 memcpy(DATA(packet) + ether_size + ip6_size + ns_size, &opt, opt_size);
 777
 778         send_packet(source, packet);
 779 }
 780
 781 /* RFC 826 */
 782
 783 static void route_arp(node_t *source, vpn_packet_t *packet) {
 784         struct ether_arp arp;
 785         subnet_t *subnet;
 786         struct in_addr addr;
 787
 788         if(!checklength(source, packet, ether_size + arp_size))
 789                 return;
 790
 791         if(source != myself) {
 792                 logger(DEBUG_TRAFFIC, LOG_WARNING, "Got ARP request from %s (%s) while in router mode!", source->name, source->hostname);
 793                 return;
 794         }
 795
 796         /* First, snatch the source address from the ARP packet */
 797
 798         if(overwrite_mac)
 799                 memcpy(mymac.x, DATA(packet) + ETH_ALEN, ETH_ALEN);
 800
 801         /* Copy headers from packet to structs on the stack */
 802
 803         memcpy(&arp, DATA(packet) + ether_size, arp_size);
 804
 805         /* Check if this is a valid ARP request */
 806
 807         if(ntohs(arp.arp_hrd) != ARPHRD_ETHER || ntohs(arp.arp_pro) != ETH_P_IP ||
 808            arp.arp_hln != ETH_ALEN || arp.arp_pln != sizeof addr || ntohs(arp.arp_op) != ARPOP_REQUEST) {
 809                 logger(DEBUG_TRAFFIC, LOG_WARNING, "Cannot route packet: received unknown type ARP request");
 810                 return;
 811         }
 812
 813         /* Check if the IPv4 address exists on the VPN */
 814
 815         subnet = lookup_subnet_ipv4((ipv4_t *) &arp.arp_tpa);
 816
 817         if(!subnet) {
 818                 logger(DEBUG_TRAFFIC, LOG_WARNING, "Cannot route packet: ARP request for unknown address %d.%d.%d.%d",
 819                                    arp.arp_tpa[0], arp.arp_tpa[1], arp.arp_tpa[2],
 820                                    arp.arp_tpa[3]);
 821                 return;
 822         }
 823
 824         /* Check if it is for our own subnet */
 825
 826         if(subnet->owner == myself)
 827                 return;                                          /* silently ignore */
 828
 829         memcpy(&addr, arp.arp_tpa, sizeof addr);                 /* save protocol addr */
 830         memcpy(arp.arp_tpa, arp.arp_spa, sizeof addr);           /* swap destination and source protocol address */
 831         memcpy(arp.arp_spa, &addr, sizeof addr);                 /* ... */
 832
 833         memcpy(arp.arp_tha, arp.arp_sha, ETH_ALEN);              /* set target hard/proto addr */
 834         memcpy(arp.arp_sha, DATA(packet) + ETH_ALEN, ETH_ALEN);  /* set source hard/proto addr */
 835         arp.arp_sha[ETH_ALEN - 1] ^= 0xFF;                       /* for consistency with route_packet() */
 836         arp.arp_op = htons(ARPOP_REPLY);
 837
 838         /* Copy structs on stack back to packet */
 839
 840         memcpy(DATA(packet) + ether_size, &arp, arp_size);
 841
 842         send_packet(source, packet);
 843 }
 844
 845 static void route_mac(node_t *source, vpn_packet_t *packet) {
 846         subnet_t *subnet;
 847         mac_t dest;
 848
 849         /* Learn source address */
 850
 851         if(source == myself) {
 852                 mac_t src;
 853                 memcpy(&src, &DATA(packet)[6], sizeof src);
 854                 learn_mac(&src);
 855         }
 856
 857         /* Lookup destination address */
 858
 859         memcpy(&dest, &DATA(packet)[0], sizeof dest);
 860         subnet = lookup_subnet_mac(NULL, &dest);
 861
 862         if(!subnet || !subnet->owner) {
 863                 broadcast_packet(source, packet);
 864                 return;
 865         }
 866
 867         if(subnet->owner == source) {
 868                 logger(DEBUG_TRAFFIC, LOG_WARNING, "Packet looping back to %s (%s)!", source->name, source->hostname);
 869                 return;
 870         }
 871
 872         if(forwarding_mode == FMODE_OFF && source != myself && subnet->owner != myself)
 873                 return;
 874
 875         uint16_t type = DATA(packet)[12] << 8 | DATA(packet)[13];
 876
 877         if(priorityinheritance && type == ETH_P_IP && packet->len >= ether_size + ip_size)
 878                 packet->priority = DATA(packet)[15];
 879
 880         // Handle packets larger than PMTU
 881
 882         node_t *via = (subnet->owner->via == myself) ? subnet->owner->nexthop : subnet->owner->via;
 883
 884         if(directonly && subnet->owner != via)
 885                 return;
 886
 887         if(via && packet->len > via->mtu && via != myself) {
 888                 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);
 889                 length_t ethlen = 14;
 890
 891                 if(type == ETH_P_8021Q) {
 892                         type = DATA(packet)[16] << 8 | DATA(packet)[17];
 893                         ethlen += 4;
 894                 }
 895
 896                 if(type == ETH_P_IP && packet->len > 576 + ethlen) {
 897                         if(DATA(packet)[6 + ethlen] & 0x40) {
 898                                 packet->len = via->mtu;
 899                                 route_ipv4_unreachable(source, packet, ethlen, ICMP_DEST_UNREACH, ICMP_FRAG_NEEDED);
 900                         } else {
 901                                 fragment_ipv4_packet(via, packet, ethlen);
 902                         }
 903                         return;
 904                 } else if(type == ETH_P_IPV6 && packet->len > 1280 + ethlen) {
 905                         packet->len = via->mtu;
 906                         route_ipv6_unreachable(source, packet, ethlen, ICMP6_PACKET_TOO_BIG, 0);
 907                         return;
 908                 }
 909         }
 910
 911         clamp_mss(source, via, packet);
 912
 913         send_packet(subnet->owner, packet);
 914 }
 915
 916 static void send_pcap(vpn_packet_t *packet) {
 917         pcap = false;
 918
 919         for list_each(connection_t, c, connection_list) {
 920                 if(!c->status.pcap)
 921                         continue;
 922
 923                 pcap = true;
 924                 int len = packet->len;
 925                 if(c->outmaclength && c->outmaclength < len)
 926                         len = c->outmaclength;
 927
 928                 if(send_request(c, "%d %d %d", CONTROL, REQ_PCAP, len))
 929                         send_meta(c, (char *)DATA(packet), len);
 930         }
 931 }
 932
 933 static bool do_decrement_ttl(node_t *source, vpn_packet_t *packet) {
 934         uint16_t type = DATA(packet)[12] << 8 | DATA(packet)[13];
 935         length_t ethlen = ether_size;
 936
 937         if(type == ETH_P_8021Q) {
 938                 type = DATA(packet)[16] << 8 | DATA(packet)[17];
 939                 ethlen += 4;
 940         }
 941
 942         switch (type) {
 943                 case ETH_P_IP:
 944                         if(!checklength(source, packet, ethlen + ip_size))
 945                                 return false;
 946
 947                         if(DATA(packet)[ethlen + 8] <= 1) {
 948                                 if(DATA(packet)[ethlen + 11] != IPPROTO_ICMP || DATA(packet)[ethlen + 32] != ICMP_TIME_EXCEEDED)
 949                                         route_ipv4_unreachable(source, packet, ethlen, ICMP_TIME_EXCEEDED, ICMP_EXC_TTL);
 950                                 return false;
 951                         }
 952
 953                         uint16_t old = DATA(packet)[ethlen + 8] << 8 | DATA(packet)[ethlen + 9];
 954                         DATA(packet)[ethlen + 8]--;
 955                         uint16_t new = DATA(packet)[ethlen + 8] << 8 | DATA(packet)[ethlen + 9];
 956
 957                         uint32_t checksum = DATA(packet)[ethlen + 10] << 8 | DATA(packet)[ethlen + 11];
 958                         checksum += old + (~new & 0xFFFF);
 959                         while(checksum >> 16)
 960                                 checksum = (checksum & 0xFFFF) + (checksum >> 16);
 961                         DATA(packet)[ethlen + 10] = checksum >> 8;
 962                         DATA(packet)[ethlen + 11] = checksum & 0xff;
 963
 964                         return true;
 965
 966                 case ETH_P_IPV6:
 967                         if(!checklength(source, packet, ethlen + ip6_size))
 968                                 return false;
 969
 970                         if(DATA(packet)[ethlen + 7] <= 1) {
 971                                 if(DATA(packet)[ethlen + 6] != IPPROTO_ICMPV6 || DATA(packet)[ethlen + 40] != ICMP6_TIME_EXCEEDED)
 972                                         route_ipv6_unreachable(source, packet, ethlen, ICMP6_TIME_EXCEEDED, ICMP6_TIME_EXCEED_TRANSIT);
 973                                 return false;
 974                         }
 975
 976                         DATA(packet)[ethlen + 7]--;
 977
 978                         return true;
 979
 980                 default:
 981                         return true;
 982         }
 983 }
 984
 985 void route(node_t *source, vpn_packet_t *packet) {
 986         if(pcap)
 987                 send_pcap(packet);
 988
 989         if(forwarding_mode == FMODE_KERNEL && source != myself) {
 990                 send_packet(myself, packet);
 991                 return;
 992         }
 993
 994         if(!checklength(source, packet, ether_size))
 995                 return;
 996
 997         if(decrement_ttl && source != myself)
 998                 if(!do_decrement_ttl(source, packet))
 999                         return;
1000
1001         uint16_t type = DATA(packet)[12] << 8 | DATA(packet)[13];
1002
1003         switch (routing_mode) {
1004                 case RMODE_ROUTER:
1005                         switch (type) {
1006                                 case ETH_P_ARP:
1007                                         route_arp(source, packet);
1008                                         break;
1009
1010                                 case ETH_P_IP:
1011                                         route_ipv4(source, packet);
1012                                         break;
1013
1014                                 case ETH_P_IPV6:
1015                                         route_ipv6(source, packet);
1016                                         break;
1017
1018                                 default:
1019                                         logger(DEBUG_TRAFFIC, LOG_WARNING, "Cannot route packet from %s (%s): unknown type %hx", source->name, source->hostname, type);
1020                                         break;
1021                         }
1022                         break;
1023
1024                 case RMODE_SWITCH:
1025                         route_mac(source, packet);
1026                         break;
1027
1028                 case RMODE_HUB:
1029                         broadcast_packet(source, packet);
1030                         break;
1031         }
1032 }