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

   1 /*
   2     route.c -- routing
   3     Copyright (C) 2000-2005 Ivo Timmermans,
   4                   2000-2012 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 struct event age_subnets_event;
  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         time_t now = time(NULL);
  88
  89         if(lasttime == now) {
  90                 if(count >= frequency)
  91                         return true;
  92         } else {
  93                 lasttime = now;
  94                 count = 0;
  95         }
  96
  97         count++;
  98         return false;
  99 }
 100
 101 static bool checklength(node_t *source, vpn_packet_t *packet, length_t length) {
 102         if(packet->len < length) {
 103                 logger(DEBUG_TRAFFIC, LOG_WARNING, "Got too short packet from %s (%s)", source->name, source->hostname);
 104                 return false;
 105         } else
 106                 return true;
 107 }
 108
 109 static void clamp_mss(const node_t *source, const node_t *via, vpn_packet_t *packet) {
 110         if(!source || !via || !(via->options & OPTION_CLAMP_MSS))
 111                 return;
 112
 113         uint16_t mtu = source->mtu;
 114         if(via != myself && via->mtu < mtu)
 115                 mtu = via->mtu;
 116
 117         /* Find TCP header */
 118         int start = ether_size;
 119         uint16_t type = packet->data[12] << 8 | packet->data[13];
 120
 121         if(type == ETH_P_8021Q) {
 122                 start += 4;
 123                 type = packet->data[16] << 8 | packet->data[17];
 124         }
 125
 126         if(type == ETH_P_IP && packet->data[start + 9] == 6)
 127                 start += (packet->data[start] & 0xf) * 4;
 128         else if(type == ETH_P_IPV6 && packet->data[start + 6] == 6)
 129                 start += 40;
 130         else
 131                 return;
 132
 133         if(packet->len <= start + 20)
 134                 return;
 135
 136         /* Use data offset field to calculate length of options field */
 137         int len = ((packet->data[start + 12] >> 4) - 5) * 4;
 138
 139         if(packet->len < start + 20 + len)
 140                 return;
 141
 142         /* Search for MSS option header */
 143         for(int i = 0; i < len;) {
 144                 if(packet->data[start + 20 + i] == 0)
 145                         break;
 146
 147                 if(packet->data[start + 20 + i] == 1) {
 148                         i++;
 149                         continue;
 150                 }
 151
 152                 if(i > len - 2 || i > len - packet->data[start + 21 + i])
 153                         break;
 154
 155                 if(packet->data[start + 20 + i] != 2) {
 156                         if(packet->data[start + 21 + i] < 2)
 157                                 break;
 158                         i += packet->data[start + 21 + i];
 159                         continue;
 160                 }
 161
 162                 if(packet->data[start + 21] != 4)
 163                         break;
 164
 165                 /* Found it */
 166                 uint16_t oldmss = packet->data[start + 22 + i] << 8 | packet->data[start + 23 + i];
 167                 uint16_t newmss = mtu - start - 20;
 168                 uint16_t csum = packet->data[start + 16] << 8 | packet->data[start + 17];
 169
 170                 if(oldmss <= newmss)
 171                         break;
 172
 173                 logger(DEBUG_TRAFFIC, LOG_INFO, "Clamping MSS of packet from %s to %s to %d", source->name, via->name, newmss);
 174
 175                 /* Update the MSS value and the checksum */
 176                 packet->data[start + 22 + i] = newmss >> 8;
 177                 packet->data[start + 23 + i] = newmss & 0xff;
 178                 csum ^= 0xffff;
 179                 csum -= oldmss;
 180                 csum += newmss;
 181                 csum ^= 0xffff;
 182                 packet->data[start + 16] = csum >> 8;
 183                 packet->data[start + 17] = csum & 0xff;
 184                 break;
 185         }
 186 }
 187
 188 static void swap_mac_addresses(vpn_packet_t *packet) {
 189         mac_t tmp;
 190         memcpy(&tmp, &packet->data[0], sizeof tmp);
 191         memcpy(&packet->data[0], &packet->data[6], sizeof tmp);
 192         memcpy(&packet->data[6], &tmp, sizeof tmp);
 193 }
 194
 195 static void age_subnets(int fd, short events, void *data) {
 196         bool left = false;
 197         time_t now = time(NULL);
 198
 199         for splay_each(subnet_t, s, myself->subnet_tree) {
 200                 if(s->expires && s->expires < now) {
 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->status.active)
 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                 event_add(&age_subnets_event, &(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 %hx:%hx:%hx:%hx:%hx:%hx",
 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 = time(NULL) + 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->status.active)
 244                                 send_add_subnet(c, subnet);
 245
 246                 if(!timeout_initialized(&age_subnets_event))
 247                         timeout_set(&age_subnets_event, age_subnets, NULL);
 248                 event_add(&age_subnets_event, &(struct timeval){10, rand() % 100000});
 249         } else {
 250                 if(subnet->expires)
 251                         subnet->expires = time(NULL) + macexpire;
 252         }
 253 }
 254
 255 /* RFC 792 */
 256
 257 static void route_ipv4_unreachable(node_t *source, vpn_packet_t *packet, length_t ether_size, uint8_t type, uint8_t code) {
 258         struct ip ip = {0};
 259         struct icmp icmp = {0};
 260
 261         struct in_addr ip_src;
 262         struct in_addr ip_dst;
 263         uint32_t oldlen;
 264
 265         if(ratelimit(3))
 266                 return;
 267
 268         /* Swap Ethernet source and destination addresses */
 269
 270         swap_mac_addresses(packet);
 271
 272         /* Copy headers from packet into properly aligned structs on the stack */
 273
 274         memcpy(&ip, packet->data + ether_size, ip_size);
 275
 276         /* Remember original source and destination */
 277
 278         ip_src = ip.ip_src;
 279         ip_dst = ip.ip_dst;
 280
 281         oldlen = packet->len - ether_size;
 282
 283         if(type == ICMP_DEST_UNREACH && code == ICMP_FRAG_NEEDED)
 284                 icmp.icmp_nextmtu = htons(packet->len - ether_size);
 285
 286         if(oldlen >= IP_MSS - ip_size - icmp_size)
 287                 oldlen = IP_MSS - ip_size - icmp_size;
 288
 289         /* Copy first part of original contents to ICMP message */
 290
 291         memmove(packet->data + ether_size + ip_size + icmp_size, packet->data + ether_size, oldlen);
 292
 293         /* Fill in IPv4 header */
 294
 295         ip.ip_v = 4;
 296         ip.ip_hl = ip_size / 4;
 297         ip.ip_tos = 0;
 298         ip.ip_len = htons(ip_size + icmp_size + oldlen);
 299         ip.ip_id = 0;
 300         ip.ip_off = 0;
 301         ip.ip_ttl = 255;
 302         ip.ip_p = IPPROTO_ICMP;
 303         ip.ip_sum = 0;
 304         ip.ip_src = ip_dst;
 305         ip.ip_dst = ip_src;
 306
 307         ip.ip_sum = inet_checksum(&ip, ip_size, ~0);
 308
 309         /* Fill in ICMP header */
 310
 311         icmp.icmp_type = type;
 312         icmp.icmp_code = code;
 313         icmp.icmp_cksum = 0;
 314
 315         icmp.icmp_cksum = inet_checksum(&icmp, icmp_size, ~0);
 316         icmp.icmp_cksum = inet_checksum(packet->data + ether_size + ip_size + icmp_size, oldlen, icmp.icmp_cksum);
 317
 318         /* Copy structs on stack back to packet */
 319
 320         memcpy(packet->data + ether_size, &ip, ip_size);
 321         memcpy(packet->data + ether_size + ip_size, &icmp, icmp_size);
 322
 323         packet->len = ether_size + ip_size + icmp_size + oldlen;
 324
 325         send_packet(source, packet);
 326 }
 327
 328 /* RFC 791 */
 329
 330 static void fragment_ipv4_packet(node_t *dest, vpn_packet_t *packet, length_t ether_size) {
 331         struct ip ip;
 332         vpn_packet_t fragment;
 333         int len, maxlen, todo;
 334         uint8_t *offset;
 335         uint16_t ip_off, origf;
 336
 337         memcpy(&ip, packet->data + ether_size, ip_size);
 338         fragment.priority = packet->priority;
 339
 340         if(ip.ip_hl != ip_size / 4)
 341                 return;
 342
 343         todo = ntohs(ip.ip_len) - ip_size;
 344
 345         if(ether_size + ip_size + todo != packet->len) {
 346                 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));
 347                 return;
 348         }
 349
 350         logger(DEBUG_TRAFFIC, LOG_INFO, "Fragmenting packet of %d bytes to %s (%s)", packet->len, dest->name, dest->hostname);
 351
 352         offset = packet->data + ether_size + ip_size;
 353         maxlen = (dest->mtu - ether_size - ip_size) & ~0x7;
 354         ip_off = ntohs(ip.ip_off);
 355         origf = ip_off & ~IP_OFFMASK;
 356         ip_off &= IP_OFFMASK;
 357
 358         while(todo) {
 359                 len = todo > maxlen ? maxlen : todo;
 360                 memcpy(fragment.data + ether_size + ip_size, offset, len);
 361                 todo -= len;
 362                 offset += len;
 363
 364                 ip.ip_len = htons(ip_size + len);
 365                 ip.ip_off = htons(ip_off | origf | (todo ? IP_MF : 0));
 366                 ip.ip_sum = 0;
 367                 ip.ip_sum = inet_checksum(&ip, ip_size, ~0);
 368                 memcpy(fragment.data, packet->data, ether_size);
 369                 memcpy(fragment.data + ether_size, &ip, ip_size);
 370                 fragment.len = ether_size + ip_size + len;
 371
 372                 send_packet(dest, &fragment);
 373
 374                 ip_off += len / 8;
 375         }
 376 }
 377
 378 static void route_ipv4_unicast(node_t *source, vpn_packet_t *packet) {
 379         subnet_t *subnet;
 380         node_t *via;
 381         ipv4_t dest;
 382
 383         memcpy(&dest, &packet->data[30], sizeof dest);
 384         subnet = lookup_subnet_ipv4(&dest);
 385
 386         if(!subnet) {
 387                 logger(DEBUG_TRAFFIC, LOG_WARNING, "Cannot route packet from %s (%s): unknown IPv4 destination address %d.%d.%d.%d",
 388                                 source->name, source->hostname,
 389                                 dest.x[0],
 390                                 dest.x[1],
 391                                 dest.x[2],
 392                                 dest.x[3]);
 393
 394                 route_ipv4_unreachable(source, packet, ether_size, ICMP_DEST_UNREACH, ICMP_NET_UNKNOWN);
 395                 return;
 396         }
 397
 398         if(subnet->owner == source) {
 399                 logger(DEBUG_TRAFFIC, LOG_WARNING, "Packet looping back to %s (%s)!", source->name, source->hostname);
 400                 return;
 401         }
 402
 403         if(!subnet->owner->status.reachable)
 404                 return route_ipv4_unreachable(source, packet, ether_size, ICMP_DEST_UNREACH, ICMP_NET_UNREACH);
 405
 406         if(forwarding_mode == FMODE_OFF && source != myself && subnet->owner != myself)
 407                 return route_ipv4_unreachable(source, packet, ether_size, ICMP_DEST_UNREACH, ICMP_NET_ANO);
 408
 409         if(priorityinheritance)
 410                 packet->priority = packet->data[15];
 411
 412         via = (subnet->owner->via == myself) ? subnet->owner->nexthop : subnet->owner->via;
 413
 414         if(via == source) {
 415                 logger(DEBUG_TRAFFIC, LOG_ERR, "Routing loop for packet from %s (%s)!", source->name, source->hostname);
 416                 return;
 417         }
 418
 419         if(directonly && subnet->owner != via)
 420                 return route_ipv4_unreachable(source, packet, ether_size, ICMP_DEST_UNREACH, ICMP_NET_ANO);
 421
 422         if(via && packet->len > MAX(via->mtu, 590) && via != myself) {
 423                 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);
 424                 if(packet->data[20] & 0x40) {
 425                         packet->len = MAX(via->mtu, 590);
 426                         route_ipv4_unreachable(source, packet, ether_size, ICMP_DEST_UNREACH, ICMP_FRAG_NEEDED);
 427                 } else {
 428                         fragment_ipv4_packet(via, packet, ether_size);
 429                 }
 430
 431                 return;
 432         }
 433
 434         clamp_mss(source, via, packet);
 435
 436         send_packet(subnet->owner, packet);
 437 }
 438
 439 static void route_ipv4(node_t *source, vpn_packet_t *packet) {
 440         if(!checklength(source, packet, ether_size + ip_size))
 441                 return;
 442
 443         if(broadcast_mode && (((packet->data[30] & 0xf0) == 0xe0) || (
 444                         packet->data[30] == 255 &&
 445                         packet->data[31] == 255 &&
 446                         packet->data[32] == 255 &&
 447                         packet->data[33] == 255)))
 448                 broadcast_packet(source, packet);
 449         else
 450                 route_ipv4_unicast(source, packet);
 451 }
 452
 453 /* RFC 2463 */
 454
 455 static void route_ipv6_unreachable(node_t *source, vpn_packet_t *packet, length_t ether_size, uint8_t type, uint8_t code) {
 456         struct ip6_hdr ip6;
 457         struct icmp6_hdr icmp6 = {0};
 458         uint16_t checksum;
 459
 460         struct {
 461                 struct in6_addr ip6_src;        /* source address */
 462                 struct in6_addr ip6_dst;        /* destination address */
 463                 uint32_t length;
 464                 uint32_t next;
 465         } pseudo;
 466
 467         if(ratelimit(3))
 468                 return;
 469
 470         /* Swap Ethernet source and destination addresses */
 471
 472         swap_mac_addresses(packet);
 473
 474         /* Copy headers from packet to structs on the stack */
 475
 476         memcpy(&ip6, packet->data + ether_size, ip6_size);
 477
 478         /* Remember original source and destination */
 479
 480         pseudo.ip6_src = ip6.ip6_dst;
 481         pseudo.ip6_dst = ip6.ip6_src;
 482
 483         pseudo.length = packet->len - ether_size;
 484
 485         if(type == ICMP6_PACKET_TOO_BIG)
 486                 icmp6.icmp6_mtu = htonl(pseudo.length);
 487
 488         if(pseudo.length >= IP_MSS - ip6_size - icmp6_size)
 489                 pseudo.length = IP_MSS - ip6_size - icmp6_size;
 490
 491         /* Copy first part of original contents to ICMP message */
 492
 493         memmove(packet->data + ether_size + ip6_size + icmp6_size, packet->data + ether_size, pseudo.length);
 494
 495         /* Fill in IPv6 header */
 496
 497         ip6.ip6_flow = htonl(0x60000000UL);
 498         ip6.ip6_plen = htons(icmp6_size + pseudo.length);
 499         ip6.ip6_nxt = IPPROTO_ICMPV6;
 500         ip6.ip6_hlim = 255;
 501         ip6.ip6_src = pseudo.ip6_src;
 502         ip6.ip6_dst = pseudo.ip6_dst;
 503
 504         /* Fill in ICMP header */
 505
 506         icmp6.icmp6_type = type;
 507         icmp6.icmp6_code = code;
 508         icmp6.icmp6_cksum = 0;
 509
 510         /* Create pseudo header */
 511
 512         pseudo.length = htonl(icmp6_size + pseudo.length);
 513         pseudo.next = htonl(IPPROTO_ICMPV6);
 514
 515         /* Generate checksum */
 516
 517         checksum = inet_checksum(&pseudo, sizeof pseudo, ~0);
 518         checksum = inet_checksum(&icmp6, icmp6_size, checksum);
 519         checksum = inet_checksum(packet->data + ether_size + ip6_size + icmp6_size, ntohl(pseudo.length) - icmp6_size, checksum);
 520
 521         icmp6.icmp6_cksum = checksum;
 522
 523         /* Copy structs on stack back to packet */
 524
 525         memcpy(packet->data + ether_size, &ip6, ip6_size);
 526         memcpy(packet->data + ether_size + ip6_size, &icmp6, icmp6_size);
 527
 528         packet->len = ether_size + ip6_size + ntohl(pseudo.length);
 529
 530         send_packet(source, packet);
 531 }
 532
 533 static void route_ipv6_unicast(node_t *source, vpn_packet_t *packet) {
 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 == source) {
 558                 logger(DEBUG_TRAFFIC, LOG_WARNING, "Packet looping back to %s (%s)!", source->name, source->hostname);
 559                 return;
 560         }
 561
 562         if(!subnet->owner->status.reachable)
 563                 return route_ipv6_unreachable(source, packet, ether_size, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_NOROUTE);
 564
 565         if(forwarding_mode == FMODE_OFF && source != myself && subnet->owner != myself)
 566                 return route_ipv6_unreachable(source, packet, ether_size, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_ADMIN);
 567
 568         via = (subnet->owner->via == myself) ? subnet->owner->nexthop : subnet->owner->via;
 569
 570         if(via == source) {
 571                 logger(DEBUG_TRAFFIC, LOG_ERR, "Routing loop for packet from %s (%s)!", source->name, source->hostname);
 572                 return;
 573         }
 574
 575         if(directonly && subnet->owner != via)
 576                 return route_ipv6_unreachable(source, packet, ether_size, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_ADMIN);
 577
 578         if(via && packet->len > MAX(via->mtu, 1294) && via != myself) {
 579                 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);
 580                 packet->len = MAX(via->mtu, 1294);
 581                 route_ipv6_unreachable(source, packet, ether_size, ICMP6_PACKET_TOO_BIG, 0);
 582                 return;
 583         }
 584
 585         clamp_mss(source, via, packet);
 586
 587         send_packet(subnet->owner, packet);
 588 }
 589
 590 /* RFC 2461 */
 591
 592 static void route_neighborsol(node_t *source, vpn_packet_t *packet) {
 593         struct ip6_hdr ip6;
 594         struct nd_neighbor_solicit ns;
 595         struct nd_opt_hdr opt;
 596         subnet_t *subnet;
 597         uint16_t checksum;
 598         bool has_opt;
 599
 600         struct {
 601                 struct in6_addr ip6_src;
 602                 struct in6_addr ip6_dst;
 603                 uint32_t length;
 604                 uint32_t next;
 605         } pseudo;
 606
 607         if(!checklength(source, packet, ether_size + ip6_size + ns_size))
 608                 return;
 609
 610         has_opt = packet->len >= ether_size + ip6_size + ns_size + opt_size + ETH_ALEN;
 611
 612         if(source != myself) {
 613                 logger(DEBUG_TRAFFIC, LOG_WARNING, "Got neighbor solicitation request from %s (%s) while in router mode!", source->name, source->hostname);
 614                 return;
 615         }
 616
 617         /* Copy headers from packet to structs on the stack */
 618
 619         memcpy(&ip6, packet->data + ether_size, ip6_size);
 620         memcpy(&ns, packet->data + ether_size + ip6_size, ns_size);
 621         if(has_opt)
 622                 memcpy(&opt, packet->data + ether_size + ip6_size + ns_size, opt_size);
 623
 624         /* First, snatch the source address from the neighbor solicitation packet */
 625
 626         if(overwrite_mac)
 627                 memcpy(mymac.x, packet->data + ETH_ALEN, ETH_ALEN);
 628
 629         /* Check if this is a valid neighbor solicitation request */
 630
 631         if(ns.nd_ns_hdr.icmp6_type != ND_NEIGHBOR_SOLICIT ||
 632            (has_opt && opt.nd_opt_type != ND_OPT_SOURCE_LINKADDR)) {
 633                 logger(DEBUG_TRAFFIC, LOG_WARNING, "Cannot route packet: received unknown type neighbor solicitation request");
 634                 return;
 635         }
 636
 637         /* Create pseudo header */
 638
 639         pseudo.ip6_src = ip6.ip6_src;
 640         pseudo.ip6_dst = ip6.ip6_dst;
 641         if(has_opt)
 642                 pseudo.length = htonl(ns_size + opt_size + ETH_ALEN);
 643         else
 644                 pseudo.length = htonl(ns_size);
 645         pseudo.next = htonl(IPPROTO_ICMPV6);
 646
 647         /* Generate checksum */
 648
 649         checksum = inet_checksum(&pseudo, sizeof pseudo, ~0);
 650         checksum = inet_checksum(&ns, ns_size, checksum);
 651         if(has_opt) {
 652                 checksum = inet_checksum(&opt, opt_size, checksum);
 653                 checksum = inet_checksum(packet->data + ether_size + ip6_size + ns_size + opt_size, ETH_ALEN, checksum);
 654         }
 655
 656         if(checksum) {
 657                 logger(DEBUG_TRAFFIC, LOG_WARNING, "Cannot route packet: checksum error for neighbor solicitation request");
 658                 return;
 659         }
 660
 661         /* Check if the IPv6 address exists on the VPN */
 662
 663         subnet = lookup_subnet_ipv6((ipv6_t *) &ns.nd_ns_target);
 664
 665         if(!subnet) {
 666                 logger(DEBUG_TRAFFIC, LOG_WARNING, "Cannot route packet: neighbor solicitation request for unknown address %hx:%hx:%hx:%hx:%hx:%hx:%hx:%hx",
 667                                    ntohs(((uint16_t *) &ns.nd_ns_target)[0]),
 668                                    ntohs(((uint16_t *) &ns.nd_ns_target)[1]),
 669                                    ntohs(((uint16_t *) &ns.nd_ns_target)[2]),
 670                                    ntohs(((uint16_t *) &ns.nd_ns_target)[3]),
 671                                    ntohs(((uint16_t *) &ns.nd_ns_target)[4]),
 672                                    ntohs(((uint16_t *) &ns.nd_ns_target)[5]),
 673                                    ntohs(((uint16_t *) &ns.nd_ns_target)[6]),
 674                                    ntohs(((uint16_t *) &ns.nd_ns_target)[7]));
 675
 676                 return;
 677         }
 678
 679         /* Check if it is for our own subnet */
 680
 681         if(subnet->owner == myself)
 682                 return;                                          /* silently ignore */
 683
 684         /* Create neighbor advertation reply */
 685
 686         memcpy(packet->data, packet->data + ETH_ALEN, ETH_ALEN); /* copy destination address */
 687         packet->data[ETH_ALEN * 2 - 1] ^= 0xFF;                  /* mangle source address so it looks like it's not from us */
 688
 689         ip6.ip6_dst = ip6.ip6_src;                               /* swap destination and source protocoll address */
 690         ip6.ip6_src = ns.nd_ns_target;
 691
 692         if(has_opt)
 693                 memcpy(packet->data + ether_size + ip6_size + ns_size + opt_size, packet->data + ETH_ALEN, ETH_ALEN);   /* add fake source hard addr */
 694
 695         ns.nd_ns_cksum = 0;
 696         ns.nd_ns_type = ND_NEIGHBOR_ADVERT;
 697         ns.nd_ns_reserved = htonl(0x40000000UL);                 /* Set solicited flag */
 698         opt.nd_opt_type = ND_OPT_TARGET_LINKADDR;
 699
 700         /* Create pseudo header */
 701
 702         pseudo.ip6_src = ip6.ip6_src;
 703         pseudo.ip6_dst = ip6.ip6_dst;
 704         if(has_opt)
 705                 pseudo.length = htonl(ns_size + opt_size + ETH_ALEN);
 706         else
 707                 pseudo.length = htonl(ns_size);
 708         pseudo.next = htonl(IPPROTO_ICMPV6);
 709
 710         /* Generate checksum */
 711
 712         checksum = inet_checksum(&pseudo, sizeof pseudo, ~0);
 713         checksum = inet_checksum(&ns, ns_size, checksum);
 714         if(has_opt) {
 715                 checksum = inet_checksum(&opt, opt_size, checksum);
 716                 checksum = inet_checksum(packet->data + ether_size + ip6_size + ns_size + opt_size, ETH_ALEN, checksum);
 717         }
 718
 719         ns.nd_ns_hdr.icmp6_cksum = checksum;
 720
 721         /* Copy structs on stack back to packet */
 722
 723         memcpy(packet->data + ether_size, &ip6, ip6_size);
 724         memcpy(packet->data + ether_size + ip6_size, &ns, ns_size);
 725         if(has_opt)
 726                 memcpy(packet->data + ether_size + ip6_size + ns_size, &opt, opt_size);
 727
 728         send_packet(source, packet);
 729 }
 730
 731 static void route_ipv6(node_t *source, vpn_packet_t *packet) {
 732         if(!checklength(source, packet, ether_size + ip6_size))
 733                 return;
 734
 735         if(packet->data[20] == IPPROTO_ICMPV6 && checklength(source, packet, ether_size + ip6_size + icmp6_size) && packet->data[54] == ND_NEIGHBOR_SOLICIT) {
 736                 route_neighborsol(source, packet);
 737                 return;
 738         }
 739
 740         if(broadcast_mode && packet->data[38] == 255)
 741                 broadcast_packet(source, packet);
 742         else
 743                 route_ipv6_unicast(source, packet);
 744 }
 745
 746 /* RFC 826 */
 747
 748 static void route_arp(node_t *source, vpn_packet_t *packet) {
 749         struct ether_arp arp;
 750         subnet_t *subnet;
 751         struct in_addr addr;
 752
 753         if(!checklength(source, packet, ether_size + arp_size))
 754                 return;
 755
 756         if(source != myself) {
 757                 logger(DEBUG_TRAFFIC, LOG_WARNING, "Got ARP request from %s (%s) while in router mode!", source->name, source->hostname);
 758                 return;
 759         }
 760
 761         /* First, snatch the source address from the ARP packet */
 762
 763         if(overwrite_mac)
 764                 memcpy(mymac.x, packet->data + ETH_ALEN, ETH_ALEN);
 765
 766         /* Copy headers from packet to structs on the stack */
 767
 768         memcpy(&arp, packet->data + ether_size, arp_size);
 769
 770         /* Check if this is a valid ARP request */
 771
 772         if(ntohs(arp.arp_hrd) != ARPHRD_ETHER || ntohs(arp.arp_pro) != ETH_P_IP ||
 773            arp.arp_hln != ETH_ALEN || arp.arp_pln != sizeof addr || ntohs(arp.arp_op) != ARPOP_REQUEST) {
 774                 logger(DEBUG_TRAFFIC, LOG_WARNING, "Cannot route packet: received unknown type ARP request");
 775                 return;
 776         }
 777
 778         /* Check if the IPv4 address exists on the VPN */
 779
 780         subnet = lookup_subnet_ipv4((ipv4_t *) &arp.arp_tpa);
 781
 782         if(!subnet) {
 783                 logger(DEBUG_TRAFFIC, LOG_WARNING, "Cannot route packet: ARP request for unknown address %d.%d.%d.%d",
 784                                    arp.arp_tpa[0], arp.arp_tpa[1], arp.arp_tpa[2],
 785                                    arp.arp_tpa[3]);
 786                 return;
 787         }
 788
 789         /* Check if it is for our own subnet */
 790
 791         if(subnet->owner == myself)
 792                 return;                                          /* silently ignore */
 793
 794         memcpy(packet->data, packet->data + ETH_ALEN, ETH_ALEN); /* copy destination address */
 795         packet->data[ETH_ALEN * 2 - 1] ^= 0xFF;                  /* mangle source address so it looks like it's not from us */
 796
 797         memcpy(&addr, arp.arp_tpa, sizeof addr);                 /* save protocol addr */
 798         memcpy(arp.arp_tpa, arp.arp_spa, sizeof addr);           /* swap destination and source protocol address */
 799         memcpy(arp.arp_spa, &addr, sizeof addr);                 /* ... */
 800
 801         memcpy(arp.arp_tha, arp.arp_sha, ETH_ALEN);              /* set target hard/proto addr */
 802         memcpy(arp.arp_sha, packet->data + ETH_ALEN, ETH_ALEN);  /* add fake source hard addr */
 803         arp.arp_op = htons(ARPOP_REPLY);
 804
 805         /* Copy structs on stack back to packet */
 806
 807         memcpy(packet->data + ether_size, &arp, arp_size);
 808
 809         send_packet(source, packet);
 810 }
 811
 812 static void route_mac(node_t *source, vpn_packet_t *packet) {
 813         subnet_t *subnet;
 814         mac_t dest;
 815
 816         /* Learn source address */
 817
 818         if(source == myself) {
 819                 mac_t src;
 820                 memcpy(&src, &packet->data[6], sizeof src);
 821                 learn_mac(&src);
 822         }
 823
 824         /* Lookup destination address */
 825
 826         memcpy(&dest, &packet->data[0], sizeof dest);
 827         subnet = lookup_subnet_mac(NULL, &dest);
 828
 829         if(!subnet) {
 830                 broadcast_packet(source, packet);
 831                 return;
 832         }
 833
 834         if(subnet->owner == source) {
 835                 logger(DEBUG_TRAFFIC, LOG_WARNING, "Packet looping back to %s (%s)!", source->name, source->hostname);
 836                 return;
 837         }
 838
 839         if(forwarding_mode == FMODE_OFF && source != myself && subnet->owner != myself)
 840                 return;
 841
 842         // Handle packets larger than PMTU
 843
 844         node_t *via = (subnet->owner->via == myself) ? subnet->owner->nexthop : subnet->owner->via;
 845
 846         if(directonly && subnet->owner != via)
 847                 return;
 848
 849         if(via && packet->len > via->mtu && via != myself) {
 850                 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);
 851                 uint16_t type = packet->data[12] << 8 | packet->data[13];
 852                 length_t ethlen = 14;
 853
 854                 if(type == ETH_P_8021Q) {
 855                         type = packet->data[16] << 8 | packet->data[17];
 856                         ethlen += 4;
 857                 }
 858
 859                 if(type == ETH_P_IP && packet->len > 576 + ethlen) {
 860                         if(packet->data[6 + ethlen] & 0x40) {
 861                                 packet->len = via->mtu;
 862                                 route_ipv4_unreachable(source, packet, ethlen, ICMP_DEST_UNREACH, ICMP_FRAG_NEEDED);
 863                         } else {
 864                                 fragment_ipv4_packet(via, packet, ethlen);
 865                         }
 866                         return;
 867                 } else if(type == ETH_P_IPV6 && packet->len > 1280 + ethlen) {
 868                         packet->len = via->mtu;
 869                         route_ipv6_unreachable(source, packet, ethlen, ICMP6_PACKET_TOO_BIG, 0);
 870                         return;
 871                 }
 872         }
 873
 874         clamp_mss(source, via, packet);
 875
 876         send_packet(subnet->owner, packet);
 877 }
 878
 879 static void send_pcap(vpn_packet_t *packet) {
 880         pcap = false;
 881
 882         for list_each(connection_t, c, connection_list) {
 883                 if(!c->status.pcap)
 884                         continue;
 885
 886                 pcap = true;
 887                 int len = packet->len;
 888                 if(c->outmaclength && c->outmaclength < len)
 889                         len = c->outmaclength;
 890
 891                 if(send_request(c, "%d %d %d", CONTROL, REQ_PCAP, len))
 892                         send_meta(c, (char *)packet->data, len);
 893         }
 894 }
 895
 896 static bool do_decrement_ttl(node_t *source, vpn_packet_t *packet) {
 897         uint16_t type = packet->data[12] << 8 | packet->data[13];
 898         length_t ethlen = ether_size;
 899
 900         if(type == ETH_P_8021Q) {
 901                 type = packet->data[16] << 8 | packet->data[17];
 902                 ethlen += 4;
 903         }
 904
 905         switch (type) {
 906                 case ETH_P_IP:
 907                         if(!checklength(source, packet, ethlen + ip_size))
 908                                 return false;
 909
 910                         if(packet->data[ethlen + 8] < 1) {
 911                                 if(packet->data[ethlen + 11] != IPPROTO_ICMP || packet->data[ethlen + 32] != ICMP_TIME_EXCEEDED)
 912                                         route_ipv4_unreachable(source, packet, ethlen, ICMP_TIME_EXCEEDED, ICMP_EXC_TTL);
 913                                 return false;
 914                         }
 915
 916                         uint16_t old = packet->data[ethlen + 8] << 8 | packet->data[ethlen + 9];
 917                         packet->data[ethlen + 8]--;
 918                         uint16_t new = packet->data[ethlen + 8] << 8 | packet->data[ethlen + 9];
 919
 920                         uint32_t checksum = packet->data[ethlen + 10] << 8 | packet->data[ethlen + 11];
 921                         checksum += old + (~new & 0xFFFF);
 922                         while(checksum >> 16)
 923                                 checksum = (checksum & 0xFFFF) + (checksum >> 16);
 924                         packet->data[ethlen + 10] = checksum >> 8;
 925                         packet->data[ethlen + 11] = checksum & 0xff;
 926
 927                         return true;
 928
 929                 case ETH_P_IPV6:
 930                         if(!checklength(source, packet, ethlen + ip6_size))
 931                                 return false;
 932
 933                         if(packet->data[ethlen + 7] < 1) {
 934                                 if(packet->data[ethlen + 6] != IPPROTO_ICMPV6 || packet->data[ethlen + 40] != ICMP6_TIME_EXCEEDED)
 935                                         route_ipv6_unreachable(source, packet, ethlen, ICMP6_TIME_EXCEEDED, ICMP6_TIME_EXCEED_TRANSIT);
 936                                 return false;
 937                         }
 938
 939                         packet->data[ethlen + 7]--;
 940
 941                         return true;
 942
 943                 default:
 944                         return true;
 945         }
 946 }
 947
 948 void route(node_t *source, vpn_packet_t *packet) {
 949         if(pcap)
 950                 send_pcap(packet);
 951
 952         if(forwarding_mode == FMODE_KERNEL && source != myself) {
 953                 send_packet(myself, packet);
 954                 return;
 955         }
 956
 957         if(!checklength(source, packet, ether_size))
 958                 return;
 959
 960         if(decrement_ttl && source != myself)
 961                 if(!do_decrement_ttl(source, packet))
 962                         return;
 963
 964         uint16_t type = packet->data[12] << 8 | packet->data[13];
 965
 966         switch (routing_mode) {
 967                 case RMODE_ROUTER:
 968                         switch (type) {
 969                                 case ETH_P_ARP:
 970                                         route_arp(source, packet);
 971                                         break;
 972
 973                                 case ETH_P_IP:
 974                                         route_ipv4(source, packet);
 975                                         break;
 976
 977                                 case ETH_P_IPV6:
 978                                         route_ipv6(source, packet);
 979                                         break;
 980
 981                                 default:
 982                                         logger(DEBUG_TRAFFIC, LOG_WARNING, "Cannot route packet from %s (%s): unknown type %hx", source->name, source->hostname, type);
 983                                         break;
 984                         }
 985                         break;
 986
 987                 case RMODE_SWITCH:
 988                         route_mac(source, packet);
 989                         break;
 990
 991                 case RMODE_HUB:
 992                         broadcast_packet(source, packet);
 993                         break;
 994         }
 995 }