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

   1 /*
   2     route.c -- routing
   3     Copyright (C) 2000-2005 Ivo Timmermans,
   4                   2000-2010 Guus Sliepen <guus@tinc-vpn.org>
   5
   6     This program is free software; you can redistribute it and/or modify
   7     it under the terms of the GNU General Public License as published by
   8     the Free Software Foundation; either version 2 of the License, or
   9     (at your option) any later version.
  10
  11     This program is distributed in the hope that it will be useful,
  12     but WITHOUT ANY WARRANTY; without even the implied warranty of
  13     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14     GNU General Public License for more details.
  15
  16     You should have received a copy of the GNU General Public License along
  17     with this program; if not, write to the Free Software Foundation, Inc.,
  18     51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  19 */
  20
  21 #include "system.h"
  22
  23 #include "splay_tree.h"
  24 #include "connection.h"
  25 #include "control_common.h"
  26 #include "ethernet.h"
  27 #include "ipv4.h"
  28 #include "ipv6.h"
  29 #include "logger.h"
  30 #include "meta.h"
  31 #include "net.h"
  32 #include "protocol.h"
  33 #include "route.h"
  34 #include "subnet.h"
  35 #include "utils.h"
  36
  37 rmode_t routing_mode = RMODE_ROUTER;
  38 fmode_t forwarding_mode = FMODE_INTERNAL;
  39 bool directonly = false;
  40 bool priorityinheritance = false;
  41 int macexpire = 600;
  42 bool overwrite_mac = false;
  43 mac_t mymac = {{0xFE, 0xFD, 0, 0, 0, 0}};
  44 bool pcap = false;
  45
  46 /* Sizes of various headers */
  47
  48 static const size_t ether_size = sizeof(struct ether_header);
  49 static const size_t arp_size = sizeof(struct ether_arp);
  50 static const size_t ip_size = sizeof(struct ip);
  51 static const size_t icmp_size = sizeof(struct icmp) - sizeof(struct ip);
  52 static const size_t ip6_size = sizeof(struct ip6_hdr);
  53 static const size_t icmp6_size = sizeof(struct icmp6_hdr);
  54 static const size_t ns_size = sizeof(struct nd_neighbor_solicit);
  55 static const size_t opt_size = sizeof(struct nd_opt_hdr);
  56
  57 #ifndef MAX
  58 #define MAX(a, b) ((a) > (b) ? (a) : (b))
  59 #endif
  60
  61 static struct event age_subnets_event;
  62
  63 /* RFC 1071 */
  64
  65 static uint16_t inet_checksum(void *data, int len, uint16_t prevsum) {
  66         uint16_t *p = data;
  67         uint32_t checksum = prevsum ^ 0xFFFF;
  68
  69         while(len >= 2) {
  70                 checksum += *p++;
  71                 len -= 2;
  72         }
  73
  74         if(len)
  75                 checksum += *(uint8_t *)p;
  76
  77         while(checksum >> 16)
  78                 checksum = (checksum & 0xFFFF) + (checksum >> 16);
  79
  80         return ~checksum;
  81 }
  82
  83 static bool ratelimit(int frequency) {
  84         static time_t lasttime = 0;
  85         static int count = 0;
  86         time_t now = time(NULL);
  87
  88         if(lasttime == now) {
  89                 if(++count > frequency)
  90                         return true;
  91         } else {
  92                 lasttime = now;
  93                 count = 0;
  94         }
  95
  96         return false;
  97 }
  98
  99 static bool checklength(node_t *source, vpn_packet_t *packet, length_t length) {
 100         if(packet->len < length) {
 101                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Got too short packet from %s (%s)", source->name, source->hostname);
 102                 return false;
 103         } else
 104                 return true;
 105 }
 106
 107 static void clamp_mss(const node_t *source, const node_t *via, vpn_packet_t *packet) {
 108         if(!source || !via || !(via->options & OPTION_CLAMP_MSS))
 109                 return;
 110
 111         uint16_t mtu = source->mtu;
 112         if(via != myself && via->mtu < mtu)
 113                 mtu = via->mtu;
 114
 115         /* Find TCP header */
 116         int start = 0;
 117         uint16_t type = packet->data[12] << 8 | packet->data[13];
 118
 119         if(type == ETH_P_IP && packet->data[23] == 6)
 120                 start = 14 + (packet->data[14] & 0xf) * 4;
 121         else if(type == ETH_P_IPV6 && packet->data[20] == 6)
 122                 start = 14 + 40;
 123
 124         if(!start || packet->len <= start + 20)
 125                 return;
 126
 127         /* Use data offset field to calculate length of options field */
 128         int len = ((packet->data[start + 12] >> 4) - 5) * 4;
 129
 130         if(packet->len < start + 20 + len)
 131                 return;
 132
 133         /* Search for MSS option header */
 134         for(int i = 0; i < len;) {
 135                 if(packet->data[start + 20 + i] == 0)
 136                         break;
 137
 138                 if(packet->data[start + 20 + i] == 1) {
 139                         i++;
 140                         continue;
 141                 }
 142
 143                 if(i > len - 2 || i > len - packet->data[start + 21 + i])
 144                         break;
 145
 146                 if(packet->data[start + 20 + i] != 2) {
 147                         if(packet->data[start + 21 + i] < 2)
 148                                 break;
 149                         i += packet->data[start + 21 + i];
 150                         continue;
 151                 }
 152
 153                 if(packet->data[start + 21] != 4)
 154                         break;
 155
 156                 /* Found it */
 157                 uint16_t oldmss = packet->data[start + 22 + i] << 8 | packet->data[start + 23 + i];
 158                 uint16_t newmss = mtu - start - 20;
 159                 uint16_t csum = packet->data[start + 16] << 8 | packet->data[start + 17];
 160
 161                 if(oldmss <= newmss)
 162                         break;
 163
 164                 ifdebug(TRAFFIC) logger(LOG_INFO, "Clamping MSS of packet from %s to %s to %d", source->name, via->name, newmss);
 165
 166                 /* Update the MSS value and the checksum */
 167                 packet->data[start + 22 + i] = newmss >> 8;
 168                 packet->data[start + 23 + i] = newmss & 0xff;
 169                 csum ^= 0xffff;
 170                 csum -= oldmss;
 171                 csum += newmss;
 172                 csum ^= 0xffff;
 173                 packet->data[start + 16] = csum >> 8;
 174                 packet->data[start + 17] = csum & 0xff;
 175                 break;
 176         }
 177 }
 178
 179 static void swap_mac_addresses(vpn_packet_t *packet) {
 180         mac_t tmp;
 181         memcpy(&tmp, &packet->data[0], sizeof tmp);
 182         memcpy(&packet->data[0], &packet->data[6], sizeof tmp);
 183         memcpy(&packet->data[6], &tmp, sizeof tmp);
 184 }
 185
 186 static void age_subnets(int fd, short events, void *data) {
 187         subnet_t *s;
 188         connection_t *c;
 189         splay_node_t *node, *next, *node2;
 190         bool left = false;
 191         time_t now = time(NULL);
 192
 193         for(node = myself->subnet_tree->head; node; node = next) {
 194                 next = node->next;
 195                 s = node->data;
 196                 if(s->expires && s->expires < now) {
 197                         ifdebug(TRAFFIC) {
 198                                 char netstr[MAXNETSTR];
 199                                 if(net2str(netstr, sizeof netstr, s))
 200                                         logger(LOG_INFO, "Subnet %s expired", netstr);
 201                         }
 202
 203                         for(node2 = connection_tree->head; node2; node2 = node2->next) {
 204                                 c = node2->data;
 205                                 if(c->status.active)
 206                                         send_del_subnet(c, s);
 207                         }
 208
 209                         subnet_del(myself, s);
 210                 } else {
 211                         if(s->expires)
 212                                 left = true;
 213                 }
 214         }
 215
 216         if(left)
 217                 event_add(&age_subnets_event, &(struct timeval){10, 0});
 218 }
 219
 220 static void learn_mac(mac_t *address) {
 221         subnet_t *subnet;
 222         splay_node_t *node;
 223         connection_t *c;
 224
 225         subnet = lookup_subnet_mac(myself, address);
 226
 227         /* If we don't know this MAC address yet, store it */
 228
 229         if(!subnet) {
 230                 ifdebug(TRAFFIC) logger(LOG_INFO, "Learned new MAC address %hx:%hx:%hx:%hx:%hx:%hx",
 231                                    address->x[0], address->x[1], address->x[2], address->x[3],
 232                                    address->x[4], address->x[5]);
 233
 234                 subnet = new_subnet();
 235                 subnet->type = SUBNET_MAC;
 236                 subnet->expires = time(NULL) + macexpire;
 237                 subnet->net.mac.address = *address;
 238                 subnet->weight = 10;
 239                 subnet_add(myself, subnet);
 240                 subnet_update(myself, subnet, true);
 241
 242                 /* And tell all other tinc daemons it's our MAC */
 243
 244                 for(node = connection_tree->head; node; node = node->next) {
 245                         c = node->data;
 246                         if(c->status.active)
 247                                 send_add_subnet(c, subnet);
 248                 }
 249
 250                 if(!timeout_initialized(&age_subnets_event))
 251                         timeout_set(&age_subnets_event, age_subnets, NULL);
 252                 event_add(&age_subnets_event, &(struct timeval){10, 0});
 253         } else {
 254                 if(subnet->expires)
 255                         subnet->expires = time(NULL) + macexpire;
 256         }
 257 }
 258
 259 /* RFC 792 */
 260
 261 static void route_ipv4_unreachable(node_t *source, vpn_packet_t *packet, uint8_t type, uint8_t code) {
 262         struct ip ip = {0};
 263         struct icmp icmp = {0};
 264
 265         struct in_addr ip_src;
 266         struct in_addr ip_dst;
 267         uint32_t oldlen;
 268
 269         if(ratelimit(3))
 270                 return;
 271
 272         /* Swap Ethernet source and destination addresses */
 273
 274         swap_mac_addresses(packet);
 275
 276         /* Copy headers from packet into properly aligned structs on the stack */
 277
 278         memcpy(&ip, packet->data + ether_size, ip_size);
 279
 280         /* Remember original source and destination */
 281
 282         ip_src = ip.ip_src;
 283         ip_dst = ip.ip_dst;
 284
 285         oldlen = packet->len - ether_size;
 286
 287         if(type == ICMP_DEST_UNREACH && code == ICMP_FRAG_NEEDED)
 288                 icmp.icmp_nextmtu = htons(packet->len - ether_size);
 289
 290         if(oldlen >= IP_MSS - ip_size - icmp_size)
 291                 oldlen = IP_MSS - ip_size - icmp_size;
 292
 293         /* Copy first part of original contents to ICMP message */
 294
 295         memmove(packet->data + ether_size + ip_size + icmp_size, packet->data + ether_size, oldlen);
 296
 297         /* Fill in IPv4 header */
 298
 299         ip.ip_v = 4;
 300         ip.ip_hl = ip_size / 4;
 301         ip.ip_tos = 0;
 302         ip.ip_len = htons(ip_size + icmp_size + oldlen);
 303         ip.ip_id = 0;
 304         ip.ip_off = 0;
 305         ip.ip_ttl = 255;
 306         ip.ip_p = IPPROTO_ICMP;
 307         ip.ip_sum = 0;
 308         ip.ip_src = ip_dst;
 309         ip.ip_dst = ip_src;
 310
 311         ip.ip_sum = inet_checksum(&ip, ip_size, ~0);
 312
 313         /* Fill in ICMP header */
 314
 315         icmp.icmp_type = type;
 316         icmp.icmp_code = code;
 317         icmp.icmp_cksum = 0;
 318
 319         icmp.icmp_cksum = inet_checksum(&icmp, icmp_size, ~0);
 320         icmp.icmp_cksum = inet_checksum(packet->data + ether_size + ip_size + icmp_size, oldlen, icmp.icmp_cksum);
 321
 322         /* Copy structs on stack back to packet */
 323
 324         memcpy(packet->data + ether_size, &ip, ip_size);
 325         memcpy(packet->data + ether_size + ip_size, &icmp, icmp_size);
 326
 327         packet->len = ether_size + ip_size + icmp_size + oldlen;
 328
 329         send_packet(source, packet);
 330 }
 331
 332 /* RFC 791 */
 333
 334 static void fragment_ipv4_packet(node_t *dest, vpn_packet_t *packet) {
 335         struct ip ip;
 336         vpn_packet_t fragment;
 337         int len, maxlen, todo;
 338         uint8_t *offset;
 339         uint16_t ip_off, origf;
 340
 341         memcpy(&ip, packet->data + ether_size, ip_size);
 342         fragment.priority = packet->priority;
 343
 344         if(ip.ip_hl != ip_size / 4)
 345                 return;
 346
 347         todo = ntohs(ip.ip_len) - ip_size;
 348
 349         if(ether_size + ip_size + todo != packet->len) {
 350                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Length of packet (%d) doesn't match length in IPv4 header (%d)", packet->len, (int)(ether_size + ip_size + todo));
 351                 return;
 352         }
 353
 354         ifdebug(TRAFFIC) logger(LOG_INFO, "Fragmenting packet of %d bytes to %s (%s)", packet->len, dest->name, dest->hostname);
 355
 356         offset = packet->data + ether_size + ip_size;
 357         maxlen = (dest->mtu - ether_size - ip_size) & ~0x7;
 358         ip_off = ntohs(ip.ip_off);
 359         origf = ip_off & ~IP_OFFMASK;
 360         ip_off &= IP_OFFMASK;
 361
 362         while(todo) {
 363                 len = todo > maxlen ? maxlen : todo;
 364                 memcpy(fragment.data + ether_size + ip_size, offset, len);
 365                 todo -= len;
 366                 offset += len;
 367
 368                 ip.ip_len = htons(ip_size + len);
 369                 ip.ip_off = htons(ip_off | origf | (todo ? IP_MF : 0));
 370                 ip.ip_sum = 0;
 371                 ip.ip_sum = inet_checksum(&ip, ip_size, ~0);
 372                 memcpy(fragment.data, packet->data, ether_size);
 373                 memcpy(fragment.data + ether_size, &ip, ip_size);
 374                 fragment.len = ether_size + ip_size + len;
 375
 376                 send_packet(dest, &fragment);
 377
 378                 ip_off += len / 8;
 379         }
 380 }
 381
 382 static void route_ipv4_unicast(node_t *source, vpn_packet_t *packet) {
 383         subnet_t *subnet;
 384         node_t *via;
 385         ipv4_t dest;
 386
 387         memcpy(&dest, &packet->data[30], sizeof dest);
 388         subnet = lookup_subnet_ipv4(&dest);
 389
 390         if(!subnet) {
 391                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Cannot route packet from %s (%s): unknown IPv4 destination address %d.%d.%d.%d",
 392                                 source->name, source->hostname,
 393                                 dest.x[0],
 394                                 dest.x[1],
 395                                 dest.x[2],
 396                                 dest.x[3]);
 397
 398                 route_ipv4_unreachable(source, packet, ICMP_DEST_UNREACH, ICMP_NET_UNKNOWN);
 399                 return;
 400         }
 401
 402         if(subnet->owner == source) {
 403                 ifdebug(TRAFFIC) logger(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, 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, 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(directonly && subnet->owner != via)
 419                 return route_ipv4_unreachable(source, packet, ICMP_DEST_UNREACH, ICMP_NET_ANO);
 420
 421         if(via && packet->len > MAX(via->mtu, 590) && via != myself) {
 422                 ifdebug(TRAFFIC) logger(LOG_INFO, "Packet for %s (%s) length %d larger than MTU %d", subnet->owner->name, subnet->owner->hostname, packet->len, via->mtu);
 423                 if(packet->data[20] & 0x40) {
 424                         packet->len = MAX(via->mtu, 590);
 425                         route_ipv4_unreachable(source, packet, ICMP_DEST_UNREACH, ICMP_FRAG_NEEDED);
 426                 } else {
 427                         fragment_ipv4_packet(via, packet);
 428                 }
 429
 430                 return;
 431         }
 432
 433         clamp_mss(source, via, packet);
 434
 435         send_packet(subnet->owner, packet);
 436 }
 437
 438 static void route_ipv4(node_t *source, vpn_packet_t *packet) {
 439         if(!checklength(source, packet, ether_size + ip_size))
 440                 return;
 441
 442         if(((packet->data[30] & 0xf0) == 0xe0) || (
 443                         packet->data[30] == 255 &&
 444                         packet->data[31] == 255 &&
 445                         packet->data[32] == 255 &&
 446                         packet->data[33] == 255))
 447                 broadcast_packet(source, packet);
 448         else
 449                 route_ipv4_unicast(source, packet);
 450 }
 451
 452 /* RFC 2463 */
 453
 454 static void route_ipv6_unreachable(node_t *source, vpn_packet_t *packet, uint8_t type, uint8_t code) {
 455         struct ip6_hdr ip6;
 456         struct icmp6_hdr icmp6 = {0};
 457         uint16_t checksum;
 458
 459         struct {
 460                 struct in6_addr ip6_src;        /* source address */
 461                 struct in6_addr ip6_dst;        /* destination address */
 462                 uint32_t length;
 463                 uint32_t next;
 464         } pseudo;
 465
 466         if(ratelimit(3))
 467                 return;
 468
 469         /* Swap Ethernet source and destination addresses */
 470
 471         swap_mac_addresses(packet);
 472
 473         /* Copy headers from packet to structs on the stack */
 474
 475         memcpy(&ip6, packet->data + ether_size, ip6_size);
 476
 477         /* Remember original source and destination */
 478
 479         pseudo.ip6_src = ip6.ip6_dst;
 480         pseudo.ip6_dst = ip6.ip6_src;
 481
 482         pseudo.length = packet->len - ether_size;
 483
 484         if(type == ICMP6_PACKET_TOO_BIG)
 485                 icmp6.icmp6_mtu = htonl(pseudo.length);
 486
 487         if(pseudo.length >= IP_MSS - ip6_size - icmp6_size)
 488                 pseudo.length = IP_MSS - ip6_size - icmp6_size;
 489
 490         /* Copy first part of original contents to ICMP message */
 491
 492         memmove(packet->data + ether_size + ip6_size + icmp6_size, packet->data + ether_size, pseudo.length);
 493
 494         /* Fill in IPv6 header */
 495
 496         ip6.ip6_flow = htonl(0x60000000UL);
 497         ip6.ip6_plen = htons(icmp6_size + pseudo.length);
 498         ip6.ip6_nxt = IPPROTO_ICMPV6;
 499         ip6.ip6_hlim = 255;
 500         ip6.ip6_src = pseudo.ip6_src;
 501         ip6.ip6_dst = pseudo.ip6_dst;
 502
 503         /* Fill in ICMP header */
 504
 505         icmp6.icmp6_type = type;
 506         icmp6.icmp6_code = code;
 507         icmp6.icmp6_cksum = 0;
 508
 509         /* Create pseudo header */
 510
 511         pseudo.length = htonl(icmp6_size + pseudo.length);
 512         pseudo.next = htonl(IPPROTO_ICMPV6);
 513
 514         /* Generate checksum */
 515
 516         checksum = inet_checksum(&pseudo, sizeof pseudo, ~0);
 517         checksum = inet_checksum(&icmp6, icmp6_size, checksum);
 518         checksum = inet_checksum(packet->data + ether_size + ip6_size + icmp6_size, ntohl(pseudo.length) - icmp6_size, checksum);
 519
 520         icmp6.icmp6_cksum = checksum;
 521
 522         /* Copy structs on stack back to packet */
 523
 524         memcpy(packet->data + ether_size, &ip6, ip6_size);
 525         memcpy(packet->data + ether_size + ip6_size, &icmp6, icmp6_size);
 526
 527         packet->len = ether_size + ip6_size + ntohl(pseudo.length);
 528
 529         send_packet(source, packet);
 530 }
 531
 532 static void route_ipv6_unicast(node_t *source, vpn_packet_t *packet) {
 533         subnet_t *subnet;
 534         node_t *via;
 535         ipv6_t dest;
 536
 537         memcpy(&dest, &packet->data[38], sizeof dest);
 538         subnet = lookup_subnet_ipv6(&dest);
 539
 540         if(!subnet) {
 541                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Cannot route packet from %s (%s): unknown IPv6 destination address %hx:%hx:%hx:%hx:%hx:%hx:%hx:%hx",
 542                                 source->name, source->hostname,
 543                                 ntohs(dest.x[0]),
 544                                 ntohs(dest.x[1]),
 545                                 ntohs(dest.x[2]),
 546                                 ntohs(dest.x[3]),
 547                                 ntohs(dest.x[4]),
 548                                 ntohs(dest.x[5]),
 549                                 ntohs(dest.x[6]),
 550                                 ntohs(dest.x[7]));
 551
 552                 route_ipv6_unreachable(source, packet, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_ADDR);
 553                 return;
 554         }
 555
 556         if(subnet->owner == source) {
 557                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Packet looping back to %s (%s)!", source->name, source->hostname);
 558                 return;
 559         }
 560
 561         if(!subnet->owner->status.reachable)
 562                 return route_ipv6_unreachable(source, packet, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_NOROUTE);
 563
 564         if(forwarding_mode == FMODE_OFF && source != myself && subnet->owner != myself)
 565                 return route_ipv6_unreachable(source, packet, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_ADMIN);
 566
 567         via = (subnet->owner->via == myself) ? subnet->owner->nexthop : subnet->owner->via;
 568
 569         if(directonly && subnet->owner != via)
 570                 return route_ipv6_unreachable(source, packet, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_ADMIN);
 571
 572         if(via && packet->len > MAX(via->mtu, 1294) && via != myself) {
 573                 ifdebug(TRAFFIC) logger(LOG_INFO, "Packet for %s (%s) length %d larger than MTU %d", subnet->owner->name, subnet->owner->hostname, packet->len, via->mtu);
 574                 packet->len = MAX(via->mtu, 1294);
 575                 route_ipv6_unreachable(source, packet, ICMP6_PACKET_TOO_BIG, 0);
 576                 return;
 577         }
 578
 579         clamp_mss(source, via, packet);
 580
 581         send_packet(subnet->owner, packet);
 582 }
 583
 584 /* RFC 2461 */
 585
 586 static void route_neighborsol(node_t *source, vpn_packet_t *packet) {
 587         struct ip6_hdr ip6;
 588         struct nd_neighbor_solicit ns;
 589         struct nd_opt_hdr opt;
 590         subnet_t *subnet;
 591         uint16_t checksum;
 592         bool has_opt;
 593
 594         struct {
 595                 struct in6_addr ip6_src;        /* source address */
 596                 struct in6_addr ip6_dst;        /* destination address */
 597                 uint32_t length;
 598                 uint32_t next;
 599         } pseudo;
 600
 601         if(!checklength(source, packet, ether_size + ip6_size + ns_size))
 602                 return;
 603
 604         has_opt = packet->len >= ether_size + ip6_size + ns_size + opt_size + ETH_ALEN;
 605
 606         if(source != myself) {
 607                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Got neighbor solicitation request from %s (%s) while in router mode!", source->name, source->hostname);
 608                 return;
 609         }
 610
 611         /* Copy headers from packet to structs on the stack */
 612
 613         memcpy(&ip6, packet->data + ether_size, ip6_size);
 614         memcpy(&ns, packet->data + ether_size + ip6_size, ns_size);
 615         if(has_opt)
 616                 memcpy(&opt, packet->data + ether_size + ip6_size + ns_size, opt_size);
 617
 618         /* First, snatch the source address from the neighbor solicitation packet */
 619
 620         if(overwrite_mac)
 621                 memcpy(mymac.x, packet->data + ETH_ALEN, ETH_ALEN);
 622
 623         /* Check if this is a valid neighbor solicitation request */
 624
 625         if(ns.nd_ns_hdr.icmp6_type != ND_NEIGHBOR_SOLICIT ||
 626            (has_opt && opt.nd_opt_type != ND_OPT_SOURCE_LINKADDR)) {
 627                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Cannot route packet: received unknown type neighbor solicitation request");
 628                 return;
 629         }
 630
 631         /* Create pseudo header */
 632
 633         pseudo.ip6_src = ip6.ip6_src;
 634         pseudo.ip6_dst = ip6.ip6_dst;
 635         if(has_opt)
 636                 pseudo.length = htonl(ns_size + opt_size + ETH_ALEN);
 637         else
 638                 pseudo.length = htonl(ns_size);
 639         pseudo.next = htonl(IPPROTO_ICMPV6);
 640
 641         /* Generate checksum */
 642
 643         checksum = inet_checksum(&pseudo, sizeof pseudo, ~0);
 644         checksum = inet_checksum(&ns, ns_size, checksum);
 645         if(has_opt) {
 646                 checksum = inet_checksum(&opt, opt_size, checksum);
 647                 checksum = inet_checksum(packet->data + ether_size + ip6_size + ns_size + opt_size, ETH_ALEN, checksum);
 648         }
 649
 650         if(checksum) {
 651                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Cannot route packet: checksum error for neighbor solicitation request");
 652                 return;
 653         }
 654
 655         /* Check if the IPv6 address exists on the VPN */
 656
 657         subnet = lookup_subnet_ipv6((ipv6_t *) &ns.nd_ns_target);
 658
 659         if(!subnet) {
 660                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Cannot route packet: neighbor solicitation request for unknown address %hx:%hx:%hx:%hx:%hx:%hx:%hx:%hx",
 661                                    ntohs(((uint16_t *) &ns.nd_ns_target)[0]),
 662                                    ntohs(((uint16_t *) &ns.nd_ns_target)[1]),
 663                                    ntohs(((uint16_t *) &ns.nd_ns_target)[2]),
 664                                    ntohs(((uint16_t *) &ns.nd_ns_target)[3]),
 665                                    ntohs(((uint16_t *) &ns.nd_ns_target)[4]),
 666                                    ntohs(((uint16_t *) &ns.nd_ns_target)[5]),
 667                                    ntohs(((uint16_t *) &ns.nd_ns_target)[6]),
 668                                    ntohs(((uint16_t *) &ns.nd_ns_target)[7]));
 669
 670                 return;
 671         }
 672
 673         /* Check if it is for our own subnet */
 674
 675         if(subnet->owner == myself)
 676                 return;                                 /* silently ignore */
 677
 678         /* Create neighbor advertation reply */
 679
 680         memcpy(packet->data, packet->data + ETH_ALEN, ETH_ALEN);        /* copy destination address */
 681         packet->data[ETH_ALEN * 2 - 1] ^= 0xFF; /* mangle source address so it looks like it's not from us */
 682
 683         ip6.ip6_dst = ip6.ip6_src;                      /* swap destination and source protocoll address */
 684         ip6.ip6_src = ns.nd_ns_target;
 685
 686         if(has_opt)
 687                 memcpy(packet->data + ether_size + ip6_size + ns_size + opt_size, packet->data + ETH_ALEN, ETH_ALEN);   /* add fake source hard addr */
 688
 689         ns.nd_ns_cksum = 0;
 690         ns.nd_ns_type = ND_NEIGHBOR_ADVERT;
 691         ns.nd_ns_reserved = htonl(0x40000000UL);        /* Set solicited flag */
 692         opt.nd_opt_type = ND_OPT_TARGET_LINKADDR;
 693
 694         /* Create pseudo header */
 695
 696         pseudo.ip6_src = ip6.ip6_src;
 697         pseudo.ip6_dst = ip6.ip6_dst;
 698         if(has_opt)
 699                 pseudo.length = htonl(ns_size + opt_size + ETH_ALEN);
 700         else
 701                 pseudo.length = htonl(ns_size);
 702         pseudo.next = htonl(IPPROTO_ICMPV6);
 703
 704         /* Generate checksum */
 705
 706         checksum = inet_checksum(&pseudo, sizeof pseudo, ~0);
 707         checksum = inet_checksum(&ns, ns_size, checksum);
 708         if(has_opt) {
 709                 checksum = inet_checksum(&opt, opt_size, checksum);
 710                 checksum = inet_checksum(packet->data + ether_size + ip6_size + ns_size + opt_size, ETH_ALEN, checksum);
 711         }
 712
 713         ns.nd_ns_hdr.icmp6_cksum = checksum;
 714
 715         /* Copy structs on stack back to packet */
 716
 717         memcpy(packet->data + ether_size, &ip6, ip6_size);
 718         memcpy(packet->data + ether_size + ip6_size, &ns, ns_size);
 719         if(has_opt)
 720                 memcpy(packet->data + ether_size + ip6_size + ns_size, &opt, opt_size);
 721
 722         send_packet(source, packet);
 723 }
 724
 725 static void route_ipv6(node_t *source, vpn_packet_t *packet) {
 726         if(!checklength(source, packet, ether_size + ip6_size))
 727                 return;
 728
 729         if(packet->data[20] == IPPROTO_ICMPV6 && checklength(source, packet, ether_size + ip6_size + icmp6_size) && packet->data[54] == ND_NEIGHBOR_SOLICIT) {
 730                 route_neighborsol(source, packet);
 731                 return;
 732         }
 733
 734         if(packet->data[38] == 255)
 735                 broadcast_packet(source, packet);
 736         else
 737                 route_ipv6_unicast(source, packet);
 738 }
 739
 740 /* RFC 826 */
 741
 742 static void route_arp(node_t *source, vpn_packet_t *packet) {
 743         struct ether_arp arp;
 744         subnet_t *subnet;
 745         struct in_addr addr;
 746
 747         if(!checklength(source, packet, ether_size + arp_size))
 748                 return;
 749
 750         if(source != myself) {
 751                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Got ARP request from %s (%s) while in router mode!", source->name, source->hostname);
 752                 return;
 753         }
 754
 755         /* First, snatch the source address from the ARP packet */
 756
 757         if(overwrite_mac)
 758                 memcpy(mymac.x, packet->data + ETH_ALEN, ETH_ALEN);
 759
 760         /* Copy headers from packet to structs on the stack */
 761
 762         memcpy(&arp, packet->data + ether_size, arp_size);
 763
 764         /* Check if this is a valid ARP request */
 765
 766         if(ntohs(arp.arp_hrd) != ARPHRD_ETHER || ntohs(arp.arp_pro) != ETH_P_IP ||
 767            arp.arp_hln != ETH_ALEN || arp.arp_pln != sizeof addr || ntohs(arp.arp_op) != ARPOP_REQUEST) {
 768                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Cannot route packet: received unknown type ARP request");
 769                 return;
 770         }
 771
 772         /* Check if the IPv4 address exists on the VPN */
 773
 774         subnet = lookup_subnet_ipv4((ipv4_t *) &arp.arp_tpa);
 775
 776         if(!subnet) {
 777                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Cannot route packet: ARP request for unknown address %d.%d.%d.%d",
 778                                    arp.arp_tpa[0], arp.arp_tpa[1], arp.arp_tpa[2],
 779                                    arp.arp_tpa[3]);
 780                 return;
 781         }
 782
 783         /* Check if it is for our own subnet */
 784
 785         if(subnet->owner == myself)
 786                 return;                                 /* silently ignore */
 787
 788         memcpy(packet->data, packet->data + ETH_ALEN, ETH_ALEN);        /* copy destination address */
 789         packet->data[ETH_ALEN * 2 - 1] ^= 0xFF; /* mangle source address so it looks like it's not from us */
 790
 791         memcpy(&addr, arp.arp_tpa, sizeof addr);        /* save protocol addr */
 792         memcpy(arp.arp_tpa, arp.arp_spa, sizeof addr);  /* swap destination and source protocol address */
 793         memcpy(arp.arp_spa, &addr, sizeof addr);        /* ... */
 794
 795         memcpy(arp.arp_tha, arp.arp_sha, ETH_ALEN);     /* set target hard/proto addr */
 796         memcpy(arp.arp_sha, packet->data + ETH_ALEN, ETH_ALEN); /* add fake source hard addr */
 797         arp.arp_op = htons(ARPOP_REPLY);
 798
 799         /* Copy structs on stack back to packet */
 800
 801         memcpy(packet->data + ether_size, &arp, arp_size);
 802
 803         send_packet(source, packet);
 804 }
 805
 806 static void route_mac(node_t *source, vpn_packet_t *packet) {
 807         subnet_t *subnet;
 808         mac_t dest;
 809
 810         /* Learn source address */
 811
 812         if(source == myself) {
 813                 mac_t src;
 814                 memcpy(&src, &packet->data[6], sizeof src);
 815                 learn_mac(&src);
 816         }
 817
 818         /* Lookup destination address */
 819
 820         memcpy(&dest, &packet->data[0], sizeof dest);
 821         subnet = lookup_subnet_mac(NULL, &dest);
 822
 823         if(!subnet) {
 824                 broadcast_packet(source, packet);
 825                 return;
 826         }
 827
 828         if(subnet->owner == source) {
 829                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Packet looping back to %s (%s)!", source->name, source->hostname);
 830                 return;
 831         }
 832
 833         if(forwarding_mode == FMODE_OFF && source != myself && subnet->owner != myself)
 834                 return;
 835
 836         // Handle packets larger than PMTU
 837
 838         node_t *via = (subnet->owner->via == myself) ? subnet->owner->nexthop : subnet->owner->via;
 839
 840         if(directonly && subnet->owner != via)
 841                 return;
 842
 843         if(via && packet->len > via->mtu && via != myself) {
 844                 ifdebug(TRAFFIC) logger(LOG_INFO, "Packet for %s (%s) length %d larger than MTU %d", subnet->owner->name, subnet->owner->hostname, packet->len, via->mtu);
 845                 uint16_t type = packet->data[12] << 8 | packet->data[13];
 846                 if(type == ETH_P_IP && packet->len > 590) {
 847                         if(packet->data[20] & 0x40) {
 848                                 packet->len = via->mtu;
 849                                 route_ipv4_unreachable(source, packet, ICMP_DEST_UNREACH, ICMP_FRAG_NEEDED);
 850                         } else {
 851                                 fragment_ipv4_packet(via, packet);
 852                         }
 853                         return;
 854                 } else if(type == ETH_P_IPV6 && packet->len > 1294) {
 855                         packet->len = via->mtu;
 856                         route_ipv6_unreachable(source, packet, ICMP6_PACKET_TOO_BIG, 0);
 857                         return;
 858                 }
 859         }
 860
 861         clamp_mss(source, via, packet);
 862
 863         send_packet(subnet->owner, packet);
 864 }
 865
 866 static void send_pcap(vpn_packet_t *packet) {
 867         pcap = false;
 868         for(splay_node_t *node = connection_tree->head; node; node = node->next) {
 869                 connection_t *c = node->data;
 870                 if(!c->status.pcap)
 871                         continue;
 872                 else
 873                         pcap = true;
 874                 if(send_request(c, "%d %d %d", CONTROL, REQ_PCAP, packet->len))
 875                         send_meta(c, (char *)packet->data, packet->len);
 876         }
 877 }
 878
 879 void route(node_t *source, vpn_packet_t *packet) {
 880         if(pcap)
 881                 send_pcap(packet);
 882
 883         if(forwarding_mode == FMODE_KERNEL && source != myself) {
 884                 send_packet(myself, packet);
 885                 return;
 886         }
 887
 888         if(!checklength(source, packet, ether_size))
 889                 return;
 890
 891         switch (routing_mode) {
 892                 case RMODE_ROUTER:
 893                         {
 894                                 uint16_t type = packet->data[12] << 8 | packet->data[13];
 895
 896                                 switch (type) {
 897                                         case ETH_P_ARP:
 898                                                 route_arp(source, packet);
 899                                                 break;
 900
 901                                         case ETH_P_IP:
 902                                                 route_ipv4(source, packet);
 903                                                 break;
 904
 905                                         case ETH_P_IPV6:
 906                                                 route_ipv6(source, packet);
 907                                                 break;
 908
 909                                         default:
 910                                                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Cannot route packet from %s (%s): unknown type %hx", source->name, source->hostname, type);
 911                                                 break;
 912                                 }
 913                         }
 914                         break;
 915
 916                 case RMODE_SWITCH:
 917                         route_mac(source, packet);
 918                         break;
 919
 920                 case RMODE_HUB:
 921                         broadcast_packet(source, packet);
 922                         break;
 923         }
 924 }