tinc-vpn.org Git - tinc/blob - 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 = packet->data[12] << 8 | packet->data[13];
 119
 120         if(type == ETH_P_8021Q) {
 121                 start += 4;
 122                 type = packet->data[16] << 8 | packet->data[17];
 123         }
 124
 125         if(type == ETH_P_IP && packet->data[start + 9] == 6)
 126                 start += (packet->data[start] & 0xf) * 4;
 127         else if(type == ETH_P_IPV6 && packet->data[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 = ((packet->data[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(packet->data[start + 20 + i] == 0)
 144                         break;
 145
 146                 if(packet->data[start + 20 + i] == 1) {
 147                         i++;
 148                         continue;
 149                 }
 150
 151                 if(i > len - 2 || i > len - packet->data[start + 21 + i])
 152                         break;
 153
 154                 if(packet->data[start + 20 + i] != 2) {
 155                         if(packet->data[start + 21 + i] < 2)
 156                                 break;
 157                         i += packet->data[start + 21 + i];
 158                         continue;
 159                 }
 160
 161                 if(packet->data[start + 21] != 4)
 162                         break;
 163
 164                 /* Found it */
 165                 uint16_t oldmss = packet->data[start + 22 + i] << 8 | packet->data[start + 23 + i];
 166                 uint16_t newmss = mtu - start - 20;
 167                 uint16_t csum = packet->data[start + 16] << 8 | packet->data[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                 packet->data[start + 22 + i] = newmss >> 8;
 176                 packet->data[start + 23 + i] = newmss & 0xff;
 177                 csum ^= 0xffff;
 178                 csum -= oldmss;
 179                 csum += newmss;
 180                 csum ^= 0xffff;
 181                 packet->data[start + 16] = csum >> 8;
 182                 packet->data[start + 17] = csum & 0xff;
 183                 break;
 184         }
 185 }
 186
 187 static void swap_mac_addresses(vpn_packet_t *packet) {
 188         mac_t tmp;
 189         memcpy(&tmp, &packet->data[0], sizeof tmp);
 190         memcpy(&packet->data[0], &packet->data[6], sizeof tmp);
 191         memcpy(&packet->data[6], &tmp, sizeof tmp);
 192 }
 193
 194 static void age_subnets(void *data) {
 195         bool left = false;
 196
 197         for splay_each(subnet_t, s, myself->subnet_tree) {
 198                 if(s->expires && s->expires < now.tv_sec) {
 199                         if(debug_level >= DEBUG_TRAFFIC) {
 200                                 char netstr[MAXNETSTR];
 201                                 if(net2str(netstr, sizeof netstr, s))
 202                                         logger(DEBUG_TRAFFIC, LOG_INFO, "Subnet %s expired", netstr);
 203                         }
 204
 205                         for list_each(connection_t, c, connection_list)
 206                                 if(c->status.active)
 207                                         send_del_subnet(c, s);
 208
 209                         subnet_del(myself, s);
 210                 } else {
 211                         if(s->expires)
 212                                 left = true;
 213                 }
 214         }
 215
 216         if(left)
 217                 timeout_set(&age_subnets_timeout, &(struct timeval){10, rand() % 100000});
 218 }
 219
 220 static void learn_mac(mac_t *address) {
 221         subnet_t *subnet = lookup_subnet_mac(myself, address);
 222
 223         /* If we don't know this MAC address yet, store it */
 224
 225         if(!subnet) {
 226                 logger(DEBUG_TRAFFIC, LOG_INFO, "Learned new MAC address %hx:%hx:%hx:%hx:%hx:%hx",
 227                                    address->x[0], address->x[1], address->x[2], address->x[3],
 228                                    address->x[4], address->x[5]);
 229
 230                 subnet = new_subnet();
 231                 subnet->type = SUBNET_MAC;
 232                 subnet->expires = now.tv_sec + macexpire;
 233                 subnet->net.mac.address = *address;
 234                 subnet->weight = 10;
 235                 subnet_add(myself, subnet);
 236                 subnet_update(myself, subnet, true);
 237
 238                 /* And tell all other tinc daemons it's our MAC */
 239
 240                 for list_each(connection_t, c, connection_list)
 241                         if(c->status.active)
 242                                 send_add_subnet(c, subnet);
 243
 244                 timeout_add(&age_subnets_timeout, age_subnets, NULL, &(struct timeval){10, rand() % 100000});
 245         } else {
 246                 if(subnet->expires)
 247                         subnet->expires = now.tv_sec + macexpire;
 248         }
 249 }
 250
 251 /* RFC 792 */
 252
 253 static void route_ipv4_unreachable(node_t *source, vpn_packet_t *packet, length_t ether_size, uint8_t type, uint8_t code) {
 254         struct ip ip = {0};
 255         struct icmp icmp = {0};
 256
 257         struct in_addr ip_src;
 258         struct in_addr ip_dst;
 259         uint32_t oldlen;
 260
 261         if(ratelimit(3))
 262                 return;
 263
 264         /* Swap Ethernet source and destination addresses */
 265
 266         swap_mac_addresses(packet);
 267
 268         /* Copy headers from packet into properly aligned structs on the stack */
 269
 270         memcpy(&ip, packet->data + ether_size, ip_size);
 271
 272         /* Remember original source and destination */
 273
 274         ip_src = ip.ip_src;
 275         ip_dst = ip.ip_dst;
 276
 277         oldlen = packet->len - ether_size;
 278
 279         if(type == ICMP_DEST_UNREACH && code == ICMP_FRAG_NEEDED)
 280                 icmp.icmp_nextmtu = htons(packet->len - ether_size);
 281
 282         if(oldlen >= IP_MSS - ip_size - icmp_size)
 283                 oldlen = IP_MSS - ip_size - icmp_size;
 284
 285         /* Copy first part of original contents to ICMP message */
 286
 287         memmove(packet->data + ether_size + ip_size + icmp_size, packet->data + ether_size, oldlen);
 288
 289         /* Fill in IPv4 header */
 290
 291         ip.ip_v = 4;
 292         ip.ip_hl = ip_size / 4;
 293         ip.ip_tos = 0;
 294         ip.ip_len = htons(ip_size + icmp_size + oldlen);
 295         ip.ip_id = 0;
 296         ip.ip_off = 0;
 297         ip.ip_ttl = 255;
 298         ip.ip_p = IPPROTO_ICMP;
 299         ip.ip_sum = 0;
 300         ip.ip_src = ip_dst;
 301         ip.ip_dst = ip_src;
 302
 303         ip.ip_sum = inet_checksum(&ip, ip_size, ~0);
 304
 305         /* Fill in ICMP header */
 306
 307         icmp.icmp_type = type;
 308         icmp.icmp_code = code;
 309         icmp.icmp_cksum = 0;
 310
 311         icmp.icmp_cksum = inet_checksum(&icmp, icmp_size, ~0);
 312         icmp.icmp_cksum = inet_checksum(packet->data + ether_size + ip_size + icmp_size, oldlen, icmp.icmp_cksum);
 313
 314         /* Copy structs on stack back to packet */
 315
 316         memcpy(packet->data + ether_size, &ip, ip_size);
 317         memcpy(packet->data + ether_size + ip_size, &icmp, icmp_size);
 318
 319         packet->len = ether_size + ip_size + icmp_size + oldlen;
 320
 321         send_packet(source, packet);
 322 }
 323
 324 /* RFC 791 */
 325
 326 static void fragment_ipv4_packet(node_t *dest, vpn_packet_t *packet, length_t ether_size) {
 327         struct ip ip;
 328         vpn_packet_t fragment;
 329         int len, maxlen, todo;
 330         uint8_t *offset;
 331         uint16_t ip_off, origf;
 332
 333         memcpy(&ip, packet->data + ether_size, ip_size);
 334         fragment.priority = packet->priority;
 335
 336         if(ip.ip_hl != ip_size / 4)
 337                 return;
 338
 339         todo = ntohs(ip.ip_len) - ip_size;
 340
 341         if(ether_size + ip_size + todo != packet->len) {
 342                 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));
 343                 return;
 344         }
 345
 346         logger(DEBUG_TRAFFIC, LOG_INFO, "Fragmenting packet of %d bytes to %s (%s)", packet->len, dest->name, dest->hostname);
 347
 348         offset = packet->data + ether_size + ip_size;
 349         maxlen = (dest->mtu - ether_size - ip_size) & ~0x7;
 350         ip_off = ntohs(ip.ip_off);
 351         origf = ip_off & ~IP_OFFMASK;
 352         ip_off &= IP_OFFMASK;
 353
 354         while(todo) {
 355                 len = todo > maxlen ? maxlen : todo;
 356                 memcpy(fragment.data + ether_size + ip_size, offset, len);
 357                 todo -= len;
 358                 offset += len;
 359
 360                 ip.ip_len = htons(ip_size + len);
 361                 ip.ip_off = htons(ip_off | origf | (todo ? IP_MF : 0));
 362                 ip.ip_sum = 0;
 363                 ip.ip_sum = inet_checksum(&ip, ip_size, ~0);
 364                 memcpy(fragment.data, packet->data, ether_size);
 365                 memcpy(fragment.data + ether_size, &ip, ip_size);
 366                 fragment.len = ether_size + ip_size + len;
 367
 368                 send_packet(dest, &fragment);
 369
 370                 ip_off += len / 8;
 371         }
 372 }
 373
 374 static void route_ipv4(node_t *source, vpn_packet_t *packet) {
 375         if(!checklength(source, packet, ether_size + ip_size))
 376                 return;
 377
 378         subnet_t *subnet;
 379         node_t *via;
 380         ipv4_t dest;
 381
 382         memcpy(&dest, &packet->data[30], sizeof dest);
 383         subnet = lookup_subnet_ipv4(&dest);
 384
 385         if(!subnet) {
 386                 logger(DEBUG_TRAFFIC, LOG_WARNING, "Cannot route packet from %s (%s): unknown IPv4 destination address %d.%d.%d.%d",
 387                                 source->name, source->hostname,
 388                                 dest.x[0],
 389                                 dest.x[1],
 390                                 dest.x[2],
 391                                 dest.x[3]);
 392
 393                 route_ipv4_unreachable(source, packet, ether_size, ICMP_DEST_UNREACH, ICMP_NET_UNKNOWN);
 394                 return;
 395         }
 396
 397         if (!subnet->owner) {
 398                 broadcast_packet(source, packet);
 399                 return;
 400         }
 401
 402         if(subnet->owner == source) {
 403                 logger(DEBUG_TRAFFIC, LOG_WARNING, "Packet looping back to %s (%s)!", source->name, source->hostname);
 404                 return;
 405         }
 406
 407         if(!subnet->owner->status.reachable)
 408                 return route_ipv4_unreachable(source, packet, ether_size, ICMP_DEST_UNREACH, ICMP_NET_UNREACH);
 409
 410         if(forwarding_mode == FMODE_OFF && source != myself && subnet->owner != myself)
 411                 return route_ipv4_unreachable(source, packet, ether_size, ICMP_DEST_UNREACH, ICMP_NET_ANO);
 412
 413         if(priorityinheritance)
 414                 packet->priority = packet->data[15];
 415
 416         via = (subnet->owner->via == myself) ? subnet->owner->nexthop : subnet->owner->via;
 417
 418         if(via == source) {
 419                 logger(DEBUG_TRAFFIC, LOG_ERR, "Routing loop for packet from %s (%s)!", source->name, source->hostname);
 420                 return;
 421         }
 422
 423         if(directonly && subnet->owner != via)
 424                 return route_ipv4_unreachable(source, packet, ether_size, ICMP_DEST_UNREACH, ICMP_NET_ANO);
 425
 426         if(via && packet->len > MAX(via->mtu, 590) && via != myself) {
 427                 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);
 428                 if(packet->data[20] & 0x40) {
 429                         packet->len = MAX(via->mtu, 590);
 430                         route_ipv4_unreachable(source, packet, ether_size, ICMP_DEST_UNREACH, ICMP_FRAG_NEEDED);
 431                 } else {
 432                         fragment_ipv4_packet(via, packet, ether_size);
 433                 }
 434
 435                 return;
 436         }
 437
 438         clamp_mss(source, via, packet);
 439
 440         send_packet(subnet->owner, packet);
 441 }
 442
 443 /* RFC 2463 */
 444
 445 static void route_ipv6_unreachable(node_t *source, vpn_packet_t *packet, length_t ether_size, uint8_t type, uint8_t code) {
 446         struct ip6_hdr ip6;
 447         struct icmp6_hdr icmp6 = {0};
 448         uint16_t checksum;
 449
 450         struct {
 451                 struct in6_addr ip6_src;        /* source address */
 452                 struct in6_addr ip6_dst;        /* destination address */
 453                 uint32_t length;
 454                 uint32_t next;
 455         } pseudo;
 456
 457         if(ratelimit(3))
 458                 return;
 459
 460         /* Swap Ethernet source and destination addresses */
 461
 462         swap_mac_addresses(packet);
 463
 464         /* Copy headers from packet to structs on the stack */
 465
 466         memcpy(&ip6, packet->data + ether_size, ip6_size);
 467
 468         /* Remember original source and destination */
 469
 470         pseudo.ip6_src = ip6.ip6_dst;
 471         pseudo.ip6_dst = ip6.ip6_src;
 472
 473         pseudo.length = packet->len - ether_size;
 474
 475         if(type == ICMP6_PACKET_TOO_BIG)
 476                 icmp6.icmp6_mtu = htonl(pseudo.length);
 477
 478         if(pseudo.length >= IP_MSS - ip6_size - icmp6_size)
 479                 pseudo.length = IP_MSS - ip6_size - icmp6_size;
 480
 481         /* Copy first part of original contents to ICMP message */
 482
 483         memmove(packet->data + ether_size + ip6_size + icmp6_size, packet->data + ether_size, pseudo.length);
 484
 485         /* Fill in IPv6 header */
 486
 487         ip6.ip6_flow = htonl(0x60000000UL);
 488         ip6.ip6_plen = htons(icmp6_size + pseudo.length);
 489         ip6.ip6_nxt = IPPROTO_ICMPV6;
 490         ip6.ip6_hlim = 255;
 491         ip6.ip6_src = pseudo.ip6_src;
 492         ip6.ip6_dst = pseudo.ip6_dst;
 493
 494         /* Fill in ICMP header */
 495
 496         icmp6.icmp6_type = type;
 497         icmp6.icmp6_code = code;
 498         icmp6.icmp6_cksum = 0;
 499
 500         /* Create pseudo header */
 501
 502         pseudo.length = htonl(icmp6_size + pseudo.length);
 503         pseudo.next = htonl(IPPROTO_ICMPV6);
 504
 505         /* Generate checksum */
 506
 507         checksum = inet_checksum(&pseudo, sizeof pseudo, ~0);
 508         checksum = inet_checksum(&icmp6, icmp6_size, checksum);
 509         checksum = inet_checksum(packet->data + ether_size + ip6_size + icmp6_size, ntohl(pseudo.length) - icmp6_size, checksum);
 510
 511         icmp6.icmp6_cksum = checksum;
 512
 513         /* Copy structs on stack back to packet */
 514
 515         memcpy(packet->data + ether_size, &ip6, ip6_size);
 516         memcpy(packet->data + ether_size + ip6_size, &icmp6, icmp6_size);
 517
 518         packet->len = ether_size + ip6_size + ntohl(pseudo.length);
 519
 520         send_packet(source, packet);
 521 }
 522
 523 static void route_neighborsol(node_t *source, vpn_packet_t *packet);
 524
 525 static void route_ipv6(node_t *source, vpn_packet_t *packet) {
 526         if(!checklength(source, packet, ether_size + ip6_size))
 527                 return;
 528
 529         if(packet->data[20] == IPPROTO_ICMPV6 && checklength(source, packet, ether_size + ip6_size + icmp6_size) && packet->data[54] == ND_NEIGHBOR_SOLICIT) {
 530                 route_neighborsol(source, packet);
 531                 return;
 532         }
 533
 534         subnet_t *subnet;
 535         node_t *via;
 536         ipv6_t dest;
 537
 538         memcpy(&dest, &packet->data[38], sizeof dest);
 539         subnet = lookup_subnet_ipv6(&dest);
 540
 541         if(!subnet) {
 542                 logger(DEBUG_TRAFFIC, LOG_WARNING, "Cannot route packet from %s (%s): unknown IPv6 destination address %hx:%hx:%hx:%hx:%hx:%hx:%hx:%hx",
 543                                 source->name, source->hostname,
 544                                 ntohs(dest.x[0]),
 545                                 ntohs(dest.x[1]),
 546                                 ntohs(dest.x[2]),
 547                                 ntohs(dest.x[3]),
 548                                 ntohs(dest.x[4]),
 549                                 ntohs(dest.x[5]),
 550                                 ntohs(dest.x[6]),
 551                                 ntohs(dest.x[7]));
 552
 553                 route_ipv6_unreachable(source, packet, ether_size, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_ADDR);
 554                 return;
 555         }
 556
 557         if (!subnet->owner) {
 558                 broadcast_packet(source, packet);
 559                 return;
 560         }
 561
 562         if(subnet->owner == source) {
 563                 logger(DEBUG_TRAFFIC, LOG_WARNING, "Packet looping back to %s (%s)!", source->name, source->hostname);
 564                 return;
 565         }
 566
 567         if(!subnet->owner->status.reachable)
 568                 return route_ipv6_unreachable(source, packet, ether_size, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_NOROUTE);
 569
 570         if(forwarding_mode == FMODE_OFF && source != myself && subnet->owner != myself)
 571                 return route_ipv6_unreachable(source, packet, ether_size, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_ADMIN);
 572
 573         via = (subnet->owner->via == myself) ? subnet->owner->nexthop : subnet->owner->via;
 574
 575         if(via == source) {
 576                 logger(DEBUG_TRAFFIC, LOG_ERR, "Routing loop for packet from %s (%s)!", source->name, source->hostname);
 577                 return;
 578         }
 579
 580         if(directonly && subnet->owner != via)
 581                 return route_ipv6_unreachable(source, packet, ether_size, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_ADMIN);
 582
 583         if(via && packet->len > MAX(via->mtu, 1294) && via != myself) {
 584                 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);
 585                 packet->len = MAX(via->mtu, 1294);
 586                 route_ipv6_unreachable(source, packet, ether_size, ICMP6_PACKET_TOO_BIG, 0);
 587                 return;
 588         }
 589
 590         clamp_mss(source, via, packet);
 591
 592         send_packet(subnet->owner, packet);
 593 }
 594
 595 /* RFC 2461 */
 596
 597 static void route_neighborsol(node_t *source, vpn_packet_t *packet) {
 598         struct ip6_hdr ip6;
 599         struct nd_neighbor_solicit ns;
 600         struct nd_opt_hdr opt;
 601         subnet_t *subnet;
 602         uint16_t checksum;
 603         bool has_opt;
 604
 605         struct {
 606                 struct in6_addr ip6_src;
 607                 struct in6_addr ip6_dst;
 608                 uint32_t length;
 609                 uint32_t next;
 610         } pseudo;
 611
 612         if(!checklength(source, packet, ether_size + ip6_size + ns_size))
 613                 return;
 614
 615         has_opt = packet->len >= ether_size + ip6_size + ns_size + opt_size + ETH_ALEN;
 616
 617         if(source != myself) {
 618                 logger(DEBUG_TRAFFIC, LOG_WARNING, "Got neighbor solicitation request from %s (%s) while in router mode!", source->name, source->hostname);
 619                 return;
 620         }
 621
 622         /* Copy headers from packet to structs on the stack */
 623
 624         memcpy(&ip6, packet->data + ether_size, ip6_size);
 625         memcpy(&ns, packet->data + ether_size + ip6_size, ns_size);
 626         if(has_opt)
 627                 memcpy(&opt, packet->data + ether_size + ip6_size + ns_size, opt_size);
 628
 629         /* First, snatch the source address from the neighbor solicitation packet */
 630
 631         if(overwrite_mac)
 632                 memcpy(mymac.x, packet->data + ETH_ALEN, ETH_ALEN);
 633
 634         /* Check if this is a valid neighbor solicitation request */
 635
 636         if(ns.nd_ns_hdr.icmp6_type != ND_NEIGHBOR_SOLICIT ||
 637            (has_opt && opt.nd_opt_type != ND_OPT_SOURCE_LINKADDR)) {
 638                 logger(DEBUG_TRAFFIC, LOG_WARNING, "Cannot route packet: received unknown type neighbor solicitation request");
 639                 return;
 640         }
 641
 642         /* Create pseudo header */
 643
 644         pseudo.ip6_src = ip6.ip6_src;
 645         pseudo.ip6_dst = ip6.ip6_dst;
 646         if(has_opt)
 647                 pseudo.length = htonl(ns_size + opt_size + ETH_ALEN);
 648         else
 649                 pseudo.length = htonl(ns_size);
 650         pseudo.next = htonl(IPPROTO_ICMPV6);
 651
 652         /* Generate checksum */
 653
 654         checksum = inet_checksum(&pseudo, sizeof pseudo, ~0);
 655         checksum = inet_checksum(&ns, ns_size, checksum);
 656         if(has_opt) {
 657                 checksum = inet_checksum(&opt, opt_size, checksum);
 658                 checksum = inet_checksum(packet->data + ether_size + ip6_size + ns_size + opt_size, ETH_ALEN, checksum);
 659         }
 660
 661         if(checksum) {
 662                 logger(DEBUG_TRAFFIC, LOG_WARNING, "Cannot route packet: checksum error for neighbor solicitation request");
 663                 return;
 664         }
 665
 666         /* Check if the IPv6 address exists on the VPN */
 667
 668         subnet = lookup_subnet_ipv6((ipv6_t *) &ns.nd_ns_target);
 669
 670         if(!subnet) {
 671                 logger(DEBUG_TRAFFIC, LOG_WARNING, "Cannot route packet: neighbor solicitation request for unknown address %hx:%hx:%hx:%hx:%hx:%hx:%hx:%hx",
 672                                    ntohs(((uint16_t *) &ns.nd_ns_target)[0]),
 673                                    ntohs(((uint16_t *) &ns.nd_ns_target)[1]),
 674                                    ntohs(((uint16_t *) &ns.nd_ns_target)[2]),
 675                                    ntohs(((uint16_t *) &ns.nd_ns_target)[3]),
 676                                    ntohs(((uint16_t *) &ns.nd_ns_target)[4]),
 677                                    ntohs(((uint16_t *) &ns.nd_ns_target)[5]),
 678                                    ntohs(((uint16_t *) &ns.nd_ns_target)[6]),
 679                                    ntohs(((uint16_t *) &ns.nd_ns_target)[7]));
 680
 681                 return;
 682         }
 683
 684         /* Check if it is for our own subnet */
 685
 686         if(subnet->owner == myself)
 687                 return;                                          /* silently ignore */
 688
 689         /* Create neighbor advertation reply */
 690
 691         memcpy(packet->data, packet->data + ETH_ALEN, ETH_ALEN); /* copy destination address */
 692         packet->data[ETH_ALEN * 2 - 1] ^= 0xFF;                  /* mangle source address so it looks like it's not from us */
 693
 694         ip6.ip6_dst = ip6.ip6_src;                               /* swap destination and source protocoll address */
 695         ip6.ip6_src = ns.nd_ns_target;
 696
 697         if(has_opt)
 698                 memcpy(packet->data + ether_size + ip6_size + ns_size + opt_size, packet->data + ETH_ALEN, ETH_ALEN);   /* add fake source hard addr */
 699
 700         ns.nd_ns_cksum = 0;
 701         ns.nd_ns_type = ND_NEIGHBOR_ADVERT;
 702         ns.nd_ns_reserved = htonl(0x40000000UL);                 /* Set solicited flag */
 703         opt.nd_opt_type = ND_OPT_TARGET_LINKADDR;
 704
 705         /* Create pseudo header */
 706
 707         pseudo.ip6_src = ip6.ip6_src;
 708         pseudo.ip6_dst = ip6.ip6_dst;
 709         if(has_opt)
 710                 pseudo.length = htonl(ns_size + opt_size + ETH_ALEN);
 711         else
 712                 pseudo.length = htonl(ns_size);
 713         pseudo.next = htonl(IPPROTO_ICMPV6);
 714
 715         /* Generate checksum */
 716
 717         checksum = inet_checksum(&pseudo, sizeof pseudo, ~0);
 718         checksum = inet_checksum(&ns, ns_size, checksum);
 719         if(has_opt) {
 720                 checksum = inet_checksum(&opt, opt_size, checksum);
 721                 checksum = inet_checksum(packet->data + ether_size + ip6_size + ns_size + opt_size, ETH_ALEN, checksum);
 722         }
 723
 724         ns.nd_ns_hdr.icmp6_cksum = checksum;
 725
 726         /* Copy structs on stack back to packet */
 727
 728         memcpy(packet->data + ether_size, &ip6, ip6_size);
 729         memcpy(packet->data + ether_size + ip6_size, &ns, ns_size);
 730         if(has_opt)
 731                 memcpy(packet->data + ether_size + ip6_size + ns_size, &opt, opt_size);
 732
 733         send_packet(source, packet);
 734 }
 735
 736 /* RFC 826 */
 737
 738 static void route_arp(node_t *source, vpn_packet_t *packet) {
 739         struct ether_arp arp;
 740         subnet_t *subnet;
 741         struct in_addr addr;
 742
 743         if(!checklength(source, packet, ether_size + arp_size))
 744                 return;
 745
 746         if(source != myself) {
 747                 logger(DEBUG_TRAFFIC, LOG_WARNING, "Got ARP request from %s (%s) while in router mode!", source->name, source->hostname);
 748                 return;
 749         }
 750
 751         /* First, snatch the source address from the ARP packet */
 752
 753         if(overwrite_mac)
 754                 memcpy(mymac.x, packet->data + ETH_ALEN, ETH_ALEN);
 755
 756         /* Copy headers from packet to structs on the stack */
 757
 758         memcpy(&arp, packet->data + ether_size, arp_size);
 759
 760         /* Check if this is a valid ARP request */
 761
 762         if(ntohs(arp.arp_hrd) != ARPHRD_ETHER || ntohs(arp.arp_pro) != ETH_P_IP ||
 763            arp.arp_hln != ETH_ALEN || arp.arp_pln != sizeof addr || ntohs(arp.arp_op) != ARPOP_REQUEST) {
 764                 logger(DEBUG_TRAFFIC, LOG_WARNING, "Cannot route packet: received unknown type ARP request");
 765                 return;
 766         }
 767
 768         /* Check if the IPv4 address exists on the VPN */
 769
 770         subnet = lookup_subnet_ipv4((ipv4_t *) &arp.arp_tpa);
 771
 772         if(!subnet) {
 773                 logger(DEBUG_TRAFFIC, LOG_WARNING, "Cannot route packet: ARP request for unknown address %d.%d.%d.%d",
 774                                    arp.arp_tpa[0], arp.arp_tpa[1], arp.arp_tpa[2],
 775                                    arp.arp_tpa[3]);
 776                 return;
 777         }
 778
 779         /* Check if it is for our own subnet */
 780
 781         if(subnet->owner == myself)
 782                 return;                                          /* silently ignore */
 783
 784         memcpy(packet->data, packet->data + ETH_ALEN, ETH_ALEN); /* copy destination address */
 785         packet->data[ETH_ALEN * 2 - 1] ^= 0xFF;                  /* mangle source address so it looks like it's not from us */
 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, packet->data + ETH_ALEN, ETH_ALEN);  /* add fake source hard addr */
 793         arp.arp_op = htons(ARPOP_REPLY);
 794
 795         /* Copy structs on stack back to packet */
 796
 797         memcpy(packet->data + ether_size, &arp, arp_size);
 798
 799         send_packet(source, packet);
 800 }
 801
 802 static void route_mac(node_t *source, vpn_packet_t *packet) {
 803         subnet_t *subnet;
 804         mac_t dest;
 805
 806         /* Learn source address */
 807
 808         if(source == myself) {
 809                 mac_t src;
 810                 memcpy(&src, &packet->data[6], sizeof src);
 811                 learn_mac(&src);
 812         }
 813
 814         /* Lookup destination address */
 815
 816         memcpy(&dest, &packet->data[0], sizeof dest);
 817         subnet = lookup_subnet_mac(NULL, &dest);
 818
 819         if(!subnet || !subnet->owner) {
 820                 broadcast_packet(source, packet);
 821                 return;
 822         }
 823
 824         if(subnet->owner == source) {
 825                 logger(DEBUG_TRAFFIC, LOG_WARNING, "Packet looping back to %s (%s)!", source->name, source->hostname);
 826                 return;
 827         }
 828
 829         if(forwarding_mode == FMODE_OFF && source != myself && subnet->owner != myself)
 830                 return;
 831
 832         uint16_t type = packet->data[12] << 8 | packet->data[13];
 833
 834         if(priorityinheritance && type == ETH_P_IP && packet->len >= ether_size + ip_size)
 835                 packet->priority = packet->data[15];
 836
 837         // Handle packets larger than PMTU
 838
 839         node_t *via = (subnet->owner->via == myself) ? subnet->owner->nexthop : subnet->owner->via;
 840
 841         if(directonly && subnet->owner != via)
 842                 return;
 843
 844         if(via && packet->len > via->mtu && via != myself) {
 845                 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);
 846                 length_t ethlen = 14;
 847
 848                 if(type == ETH_P_8021Q) {
 849                         type = packet->data[16] << 8 | packet->data[17];
 850                         ethlen += 4;
 851                 }
 852
 853                 if(type == ETH_P_IP && packet->len > 576 + ethlen) {
 854                         if(packet->data[6 + ethlen] & 0x40) {
 855                                 packet->len = via->mtu;
 856                                 route_ipv4_unreachable(source, packet, ethlen, ICMP_DEST_UNREACH, ICMP_FRAG_NEEDED);
 857                         } else {
 858                                 fragment_ipv4_packet(via, packet, ethlen);
 859                         }
 860                         return;
 861                 } else if(type == ETH_P_IPV6 && packet->len > 1280 + ethlen) {
 862                         packet->len = via->mtu;
 863                         route_ipv6_unreachable(source, packet, ethlen, ICMP6_PACKET_TOO_BIG, 0);
 864                         return;
 865                 }
 866         }
 867
 868         clamp_mss(source, via, packet);
 869
 870         send_packet(subnet->owner, packet);
 871 }
 872
 873 static void send_pcap(vpn_packet_t *packet) {
 874         pcap = false;
 875
 876         for list_each(connection_t, c, connection_list) {
 877                 if(!c->status.pcap)
 878                         continue;
 879
 880                 pcap = true;
 881                 int len = packet->len;
 882                 if(c->outmaclength && c->outmaclength < len)
 883                         len = c->outmaclength;
 884
 885                 if(send_request(c, "%d %d %d", CONTROL, REQ_PCAP, len))
 886                         send_meta(c, (char *)packet->data, len);
 887         }
 888 }
 889
 890 static bool do_decrement_ttl(node_t *source, vpn_packet_t *packet) {
 891         uint16_t type = packet->data[12] << 8 | packet->data[13];
 892         length_t ethlen = ether_size;
 893
 894         if(type == ETH_P_8021Q) {
 895                 type = packet->data[16] << 8 | packet->data[17];
 896                 ethlen += 4;
 897         }
 898
 899         switch (type) {
 900                 case ETH_P_IP:
 901                         if(!checklength(source, packet, ethlen + ip_size))
 902                                 return false;
 903
 904                         if(packet->data[ethlen + 8] < 1) {
 905                                 if(packet->data[ethlen + 11] != IPPROTO_ICMP || packet->data[ethlen + 32] != ICMP_TIME_EXCEEDED)
 906                                         route_ipv4_unreachable(source, packet, ethlen, ICMP_TIME_EXCEEDED, ICMP_EXC_TTL);
 907                                 return false;
 908                         }
 909
 910                         uint16_t old = packet->data[ethlen + 8] << 8 | packet->data[ethlen + 9];
 911                         packet->data[ethlen + 8]--;
 912                         uint16_t new = packet->data[ethlen + 8] << 8 | packet->data[ethlen + 9];
 913
 914                         uint32_t checksum = packet->data[ethlen + 10] << 8 | packet->data[ethlen + 11];
 915                         checksum += old + (~new & 0xFFFF);
 916                         while(checksum >> 16)
 917                                 checksum = (checksum & 0xFFFF) + (checksum >> 16);
 918                         packet->data[ethlen + 10] = checksum >> 8;
 919                         packet->data[ethlen + 11] = checksum & 0xff;
 920
 921                         return true;
 922
 923                 case ETH_P_IPV6:
 924                         if(!checklength(source, packet, ethlen + ip6_size))
 925                                 return false;
 926
 927                         if(packet->data[ethlen + 7] < 1) {
 928                                 if(packet->data[ethlen + 6] != IPPROTO_ICMPV6 || packet->data[ethlen + 40] != ICMP6_TIME_EXCEEDED)
 929                                         route_ipv6_unreachable(source, packet, ethlen, ICMP6_TIME_EXCEEDED, ICMP6_TIME_EXCEED_TRANSIT);
 930                                 return false;
 931                         }
 932
 933                         packet->data[ethlen + 7]--;
 934
 935                         return true;
 936
 937                 default:
 938                         return true;
 939         }
 940 }
 941
 942 void route(node_t *source, vpn_packet_t *packet) {
 943         if(pcap)
 944                 send_pcap(packet);
 945
 946         if(forwarding_mode == FMODE_KERNEL && source != myself) {
 947                 send_packet(myself, packet);
 948                 return;
 949         }
 950
 951         if(!checklength(source, packet, ether_size))
 952                 return;
 953
 954         if(decrement_ttl && source != myself)
 955                 if(!do_decrement_ttl(source, packet))
 956                         return;
 957
 958         uint16_t type = packet->data[12] << 8 | packet->data[13];
 959
 960         switch (routing_mode) {
 961                 case RMODE_ROUTER:
 962                         switch (type) {
 963                                 case ETH_P_ARP:
 964                                         route_arp(source, packet);
 965                                         break;
 966
 967                                 case ETH_P_IP:
 968                                         route_ipv4(source, packet);
 969                                         break;
 970
 971                                 case ETH_P_IPV6:
 972                                         route_ipv6(source, packet);
 973                                         break;
 974
 975                                 default:
 976                                         logger(DEBUG_TRAFFIC, LOG_WARNING, "Cannot route packet from %s (%s): unknown type %hx", source->name, source->hostname, type);
 977                                         break;
 978                         }
 979                         break;
 980
 981                 case RMODE_SWITCH:
 982                         route_mac(source, packet);
 983                         break;
 984
 985                 case RMODE_HUB:
 986                         broadcast_packet(source, packet);
 987                         break;
 988         }
 989 }