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

   1 /*
   2     route.c -- routing
   3     Copyright (C) 2000-2005 Ivo Timmermans,
   4                   2000-2009 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 "avl_tree.h"
  24 #include "connection.h"
  25 #include "ethernet.h"
  26 #include "ipv4.h"
  27 #include "ipv6.h"
  28 #include "logger.h"
  29 #include "net.h"
  30 #include "protocol.h"
  31 #include "route.h"
  32 #include "subnet.h"
  33 #include "utils.h"
  34
  35 rmode_t routing_mode = RMODE_ROUTER;
  36 bool priorityinheritance = false;
  37 int macexpire = 600;
  38 bool overwrite_mac = false;
  39 mac_t mymac = {{0xFE, 0xFD, 0, 0, 0, 0}};
  40
  41 /* Sizes of various headers */
  42
  43 static const size_t ether_size = sizeof(struct ether_header);
  44 static const size_t arp_size = sizeof(struct ether_arp);
  45 static const size_t ip_size = sizeof(struct ip);
  46 static const size_t icmp_size = sizeof(struct icmp) - sizeof(struct ip);
  47 static const size_t ip6_size = sizeof(struct ip6_hdr);
  48 static const size_t icmp6_size = sizeof(struct icmp6_hdr);
  49 static const size_t ns_size = sizeof(struct nd_neighbor_solicit);
  50 static const size_t opt_size = sizeof(struct nd_opt_hdr);
  51 #define max(a, b) ((a) > (b) ? (a) : (b))
  52
  53 /* RFC 1071 */
  54
  55 static uint16_t inet_checksum(void *data, int len, uint16_t prevsum) {
  56         uint16_t *p = data;
  57         uint32_t checksum = prevsum ^ 0xFFFF;
  58
  59         while(len >= 2) {
  60                 checksum += *p++;
  61                 len -= 2;
  62         }
  63
  64         if(len)
  65                 checksum += *(uint8_t *)p;
  66
  67         while(checksum >> 16)
  68                 checksum = (checksum & 0xFFFF) + (checksum >> 16);
  69
  70         return ~checksum;
  71 }
  72
  73 static bool ratelimit(int frequency) {
  74         static time_t lasttime = 0;
  75         static int count = 0;
  76
  77         if(lasttime == now) {
  78                 if(++count > frequency)
  79                         return true;
  80         } else {
  81                 lasttime = now;
  82                 count = 0;
  83         }
  84
  85         return false;
  86 }
  87
  88 static bool checklength(node_t *source, vpn_packet_t *packet, length_t length) {
  89         if(packet->len < length) {
  90                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Got too short packet from %s (%s)", source->name, source->hostname);
  91                 return false;
  92         } else
  93                 return true;
  94 }
  95
  96 static void swap_mac_addresses(vpn_packet_t *packet) {
  97         mac_t tmp;
  98         memcpy(&tmp, &packet->data[0], sizeof tmp);
  99         memcpy(&packet->data[0], &packet->data[6], sizeof tmp);
 100         memcpy(&packet->data[6], &tmp, sizeof tmp);
 101 }
 102
 103 static void learn_mac(mac_t *address) {
 104         subnet_t *subnet;
 105         avl_node_t *node;
 106         connection_t *c;
 107
 108         subnet = lookup_subnet_mac(myself, address);
 109
 110         /* If we don't know this MAC address yet, store it */
 111
 112         if(!subnet) {
 113                 ifdebug(TRAFFIC) logger(LOG_INFO, "Learned new MAC address %hx:%hx:%hx:%hx:%hx:%hx",
 114                                    address->x[0], address->x[1], address->x[2], address->x[3],
 115                                    address->x[4], address->x[5]);
 116
 117                 subnet = new_subnet();
 118                 subnet->type = SUBNET_MAC;
 119                 subnet->expires = now + macexpire;
 120                 subnet->net.mac.address = *address;
 121                 subnet->weight = 10;
 122                 subnet_add(myself, subnet);
 123
 124                 /* And tell all other tinc daemons it's our MAC */
 125
 126                 for(node = connection_tree->head; node; node = node->next) {
 127                         c = node->data;
 128                         if(c->status.active)
 129                                 send_add_subnet(c, subnet);
 130                 }
 131         }
 132
 133         if(subnet->expires)
 134                 subnet->expires = now + macexpire;
 135 }
 136
 137 void age_subnets(void) {
 138         subnet_t *s;
 139         connection_t *c;
 140         avl_node_t *node, *next, *node2;
 141
 142         for(node = myself->subnet_tree->head; node; node = next) {
 143                 next = node->next;
 144                 s = node->data;
 145                 if(s->expires && s->expires < now) {
 146                         ifdebug(TRAFFIC) {
 147                                 char netstr[MAXNETSTR];
 148                                 if(net2str(netstr, sizeof netstr, s))
 149                                         logger(LOG_INFO, "Subnet %s expired", netstr);
 150                         }
 151
 152                         for(node2 = connection_tree->head; node2; node2 = node2->next) {
 153                                 c = node2->data;
 154                                 if(c->status.active)
 155                                         send_del_subnet(c, s);
 156                         }
 157
 158                         subnet_del(myself, s);
 159                 }
 160         }
 161 }
 162
 163 /* RFC 792 */
 164
 165 static void route_ipv4_unreachable(node_t *source, vpn_packet_t *packet, uint8_t type, uint8_t code) {
 166         struct ip ip = {0};
 167         struct icmp icmp = {0};
 168
 169         struct in_addr ip_src;
 170         struct in_addr ip_dst;
 171         uint32_t oldlen;
 172
 173         if(ratelimit(3))
 174                 return;
 175
 176         /* Swap Ethernet source and destination addresses */
 177
 178         swap_mac_addresses(packet);
 179
 180         /* Copy headers from packet into properly aligned structs on the stack */
 181
 182         memcpy(&ip, packet->data + ether_size, ip_size);
 183
 184         /* Remember original source and destination */
 185
 186         ip_src = ip.ip_src;
 187         ip_dst = ip.ip_dst;
 188
 189         oldlen = packet->len - ether_size;
 190
 191         if(type == ICMP_DEST_UNREACH && code == ICMP_FRAG_NEEDED)
 192                 icmp.icmp_nextmtu = htons(packet->len - ether_size);
 193
 194         if(oldlen >= IP_MSS - ip_size - icmp_size)
 195                 oldlen = IP_MSS - ip_size - icmp_size;
 196
 197         /* Copy first part of original contents to ICMP message */
 198
 199         memmove(packet->data + ether_size + ip_size + icmp_size, packet->data + ether_size, oldlen);
 200
 201         /* Fill in IPv4 header */
 202
 203         ip.ip_v = 4;
 204         ip.ip_hl = ip_size / 4;
 205         ip.ip_tos = 0;
 206         ip.ip_len = htons(ip_size + icmp_size + oldlen);
 207         ip.ip_id = 0;
 208         ip.ip_off = 0;
 209         ip.ip_ttl = 255;
 210         ip.ip_p = IPPROTO_ICMP;
 211         ip.ip_sum = 0;
 212         ip.ip_src = ip_dst;
 213         ip.ip_dst = ip_src;
 214
 215         ip.ip_sum = inet_checksum(&ip, ip_size, ~0);
 216
 217         /* Fill in ICMP header */
 218
 219         icmp.icmp_type = type;
 220         icmp.icmp_code = code;
 221         icmp.icmp_cksum = 0;
 222
 223         icmp.icmp_cksum = inet_checksum(&icmp, icmp_size, ~0);
 224         icmp.icmp_cksum = inet_checksum(packet->data + ether_size + ip_size + icmp_size, oldlen, icmp.icmp_cksum);
 225
 226         /* Copy structs on stack back to packet */
 227
 228         memcpy(packet->data + ether_size, &ip, ip_size);
 229         memcpy(packet->data + ether_size + ip_size, &icmp, icmp_size);
 230
 231         packet->len = ether_size + ip_size + icmp_size + oldlen;
 232
 233         send_packet(source, packet);
 234 }
 235
 236 /* RFC 791 */
 237
 238 static void fragment_ipv4_packet(node_t *dest, vpn_packet_t *packet) {
 239         struct ip ip;
 240         vpn_packet_t fragment;
 241         int len, maxlen, todo;
 242         uint8_t *offset;
 243         uint16_t ip_off, origf;
 244
 245         memcpy(&ip, packet->data + ether_size, ip_size);
 246         fragment.priority = packet->priority;
 247
 248         if(ip.ip_hl != ip_size / 4)
 249                 return;
 250
 251         todo = ntohs(ip.ip_len) - ip_size;
 252
 253         if(ether_size + ip_size + todo != packet->len) {
 254                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Length of packet (%d) doesn't match length in IPv4 header (%zd)", packet->len, ether_size + ip_size + todo);
 255                 return;
 256         }
 257
 258         ifdebug(TRAFFIC) logger(LOG_INFO, "Fragmenting packet of %d bytes to %s (%s)", packet->len, dest->name, dest->hostname);
 259
 260         offset = packet->data + ether_size + ip_size;
 261         maxlen = (dest->mtu - ether_size - ip_size) & ~0x7;
 262         ip_off = ntohs(ip.ip_off);
 263         origf = ip_off & ~IP_OFFMASK;
 264         ip_off &= IP_OFFMASK;
 265
 266         while(todo) {
 267                 len = todo > maxlen ? maxlen : todo;
 268                 memcpy(fragment.data + ether_size + ip_size, offset, len);
 269                 todo -= len;
 270                 offset += len;
 271
 272                 ip.ip_len = htons(ip_size + len);
 273                 ip.ip_off = htons(ip_off | origf | (todo ? IP_MF : 0));
 274                 ip.ip_sum = 0;
 275                 ip.ip_sum = inet_checksum(&ip, ip_size, ~0);
 276                 memcpy(fragment.data, packet->data, ether_size);
 277                 memcpy(fragment.data + ether_size, &ip, ip_size);
 278                 fragment.len = ether_size + ip_size + len;
 279
 280                 send_packet(dest, &fragment);
 281
 282                 ip_off += len / 8;
 283         }
 284 }
 285
 286 static void route_ipv4_unicast(node_t *source, vpn_packet_t *packet) {
 287         subnet_t *subnet;
 288         node_t *via;
 289         ipv4_t dest;
 290
 291         memcpy(&dest, &packet->data[30], sizeof dest);
 292         subnet = lookup_subnet_ipv4(&dest);
 293
 294         if(!subnet) {
 295                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Cannot route packet from %s (%s): unknown IPv4 destination address %d.%d.%d.%d",
 296                                 source->name, source->hostname,
 297                                 dest.x[0],
 298                                 dest.x[1],
 299                                 dest.x[2],
 300                                 dest.x[3]);
 301
 302                 route_ipv4_unreachable(source, packet, ICMP_DEST_UNREACH, ICMP_NET_UNKNOWN);
 303                 return;
 304         }
 305
 306         if(subnet->owner == source) {
 307                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Packet looping back to %s (%s)!", source->name, source->hostname);
 308                 return;
 309         }
 310
 311         if(!subnet->owner->status.reachable)
 312                 route_ipv4_unreachable(source, packet, ICMP_DEST_UNREACH, ICMP_NET_UNREACH);
 313
 314         if(priorityinheritance)
 315                 packet->priority = packet->data[15];
 316
 317         via = (subnet->owner->via == myself) ? subnet->owner->nexthop : subnet->owner->via;
 318
 319         if(via && packet->len > max(via->mtu, 590) && via != myself) {
 320                 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);
 321                 if(packet->data[20] & 0x40) {
 322                         packet->len = max(via->mtu, 590);
 323                         route_ipv4_unreachable(source, packet, ICMP_DEST_UNREACH, ICMP_FRAG_NEEDED);
 324                 } else {
 325                         fragment_ipv4_packet(via, packet);
 326                 }
 327
 328                 return;
 329         }
 330
 331         send_packet(subnet->owner, packet);
 332 }
 333
 334 static void route_ipv4(node_t *source, vpn_packet_t *packet) {
 335         if(!checklength(source, packet, ether_size + ip_size))
 336                 return;
 337
 338         if(((packet->data[30] & 0xf0) == 0xe0) || (
 339                         packet->data[30] == 255 &&
 340                         packet->data[31] == 255 &&
 341                         packet->data[32] == 255 &&
 342                         packet->data[33] == 255))
 343                 broadcast_packet(source, packet);
 344         else
 345                 route_ipv4_unicast(source, packet);
 346 }
 347
 348 /* RFC 2463 */
 349
 350 static void route_ipv6_unreachable(node_t *source, vpn_packet_t *packet, uint8_t type, uint8_t code) {
 351         struct ip6_hdr ip6;
 352         struct icmp6_hdr icmp6 = {0};
 353         uint16_t checksum;
 354
 355         struct {
 356                 struct in6_addr ip6_src;        /* source address */
 357                 struct in6_addr ip6_dst;        /* destination address */
 358                 uint32_t length;
 359                 uint32_t next;
 360         } pseudo;
 361
 362         if(ratelimit(3))
 363                 return;
 364
 365         /* Swap Ethernet source and destination addresses */
 366
 367         swap_mac_addresses(packet);
 368
 369         /* Copy headers from packet to structs on the stack */
 370
 371         memcpy(&ip6, packet->data + ether_size, ip6_size);
 372
 373         /* Remember original source and destination */
 374
 375         pseudo.ip6_src = ip6.ip6_dst;
 376         pseudo.ip6_dst = ip6.ip6_src;
 377
 378         pseudo.length = packet->len - ether_size;
 379
 380         if(type == ICMP6_PACKET_TOO_BIG)
 381                 icmp6.icmp6_mtu = htonl(pseudo.length);
 382
 383         if(pseudo.length >= IP_MSS - ip6_size - icmp6_size)
 384                 pseudo.length = IP_MSS - ip6_size - icmp6_size;
 385
 386         /* Copy first part of original contents to ICMP message */
 387
 388         memmove(packet->data + ether_size + ip6_size + icmp6_size, packet->data + ether_size, pseudo.length);
 389
 390         /* Fill in IPv6 header */
 391
 392         ip6.ip6_flow = htonl(0x60000000UL);
 393         ip6.ip6_plen = htons(icmp6_size + pseudo.length);
 394         ip6.ip6_nxt = IPPROTO_ICMPV6;
 395         ip6.ip6_hlim = 255;
 396         ip6.ip6_src = pseudo.ip6_src;
 397         ip6.ip6_dst = pseudo.ip6_dst;
 398
 399         /* Fill in ICMP header */
 400
 401         icmp6.icmp6_type = type;
 402         icmp6.icmp6_code = code;
 403         icmp6.icmp6_cksum = 0;
 404
 405         /* Create pseudo header */
 406
 407         pseudo.length = htonl(icmp6_size + pseudo.length);
 408         pseudo.next = htonl(IPPROTO_ICMPV6);
 409
 410         /* Generate checksum */
 411
 412         checksum = inet_checksum(&pseudo, sizeof(pseudo), ~0);
 413         checksum = inet_checksum(&icmp6, icmp6_size, checksum);
 414         checksum = inet_checksum(packet->data + ether_size + ip6_size + icmp6_size, ntohl(pseudo.length) - icmp6_size, checksum);
 415
 416         icmp6.icmp6_cksum = checksum;
 417
 418         /* Copy structs on stack back to packet */
 419
 420         memcpy(packet->data + ether_size, &ip6, ip6_size);
 421         memcpy(packet->data + ether_size + ip6_size, &icmp6, icmp6_size);
 422
 423         packet->len = ether_size + ip6_size + ntohl(pseudo.length);
 424
 425         send_packet(source, packet);
 426 }
 427
 428 static void route_ipv6_unicast(node_t *source, vpn_packet_t *packet) {
 429         subnet_t *subnet;
 430         node_t *via;
 431         ipv6_t dest;
 432
 433         memcpy(&dest, &packet->data[38], sizeof dest);
 434         subnet = lookup_subnet_ipv6(&dest);
 435
 436         if(!subnet) {
 437                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Cannot route packet from %s (%s): unknown IPv6 destination address %hx:%hx:%hx:%hx:%hx:%hx:%hx:%hx",
 438                                 source->name, source->hostname,
 439                                 ntohs(dest.x[0]),
 440                                 ntohs(dest.x[1]),
 441                                 ntohs(dest.x[2]),
 442                                 ntohs(dest.x[3]),
 443                                 ntohs(dest.x[4]),
 444                                 ntohs(dest.x[5]),
 445                                 ntohs(dest.x[6]),
 446                                 ntohs(dest.x[7]));
 447
 448                 route_ipv6_unreachable(source, packet, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_ADDR);
 449                 return;
 450         }
 451
 452         if(subnet->owner == source) {
 453                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Packet looping back to %s (%s)!", source->name, source->hostname);
 454                 return;
 455         }
 456
 457         if(!subnet->owner->status.reachable)
 458                 route_ipv6_unreachable(source, packet, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_NOROUTE);
 459
 460         via = (subnet->owner->via == myself) ? subnet->owner->nexthop : subnet->owner->via;
 461
 462         if(via && packet->len > max(via->mtu, 1294) && via != myself) {
 463                 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);
 464                 packet->len = max(via->mtu, 1294);
 465                 route_ipv6_unreachable(source, packet, ICMP6_PACKET_TOO_BIG, 0);
 466                 return;
 467         }
 468
 469         send_packet(subnet->owner, packet);
 470 }
 471
 472 /* RFC 2461 */
 473
 474 static void route_neighborsol(node_t *source, vpn_packet_t *packet) {
 475         struct ip6_hdr ip6;
 476         struct nd_neighbor_solicit ns;
 477         struct nd_opt_hdr opt;
 478         subnet_t *subnet;
 479         uint16_t checksum;
 480         bool has_opt;
 481
 482         struct {
 483                 struct in6_addr ip6_src;        /* source address */
 484                 struct in6_addr ip6_dst;        /* destination address */
 485                 uint32_t length;
 486                 uint32_t next;
 487         } pseudo;
 488
 489         if(!checklength(source, packet, ether_size + ip6_size + ns_size))
 490                 return;
 491
 492         has_opt = packet->len >= ether_size + ip6_size + ns_size + opt_size + ETH_ALEN;
 493
 494         if(source != myself) {
 495                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Got neighbor solicitation request from %s (%s) while in router mode!", source->name, source->hostname);
 496                 return;
 497         }
 498
 499         /* Copy headers from packet to structs on the stack */
 500
 501         memcpy(&ip6, packet->data + ether_size, ip6_size);
 502         memcpy(&ns, packet->data + ether_size + ip6_size, ns_size);
 503         if(has_opt)
 504                 memcpy(&opt, packet->data + ether_size + ip6_size + ns_size, opt_size);
 505
 506         /* First, snatch the source address from the neighbor solicitation packet */
 507
 508         if(overwrite_mac)
 509                 memcpy(mymac.x, packet->data + ETH_ALEN, ETH_ALEN);
 510
 511         /* Check if this is a valid neighbor solicitation request */
 512
 513         if(ns.nd_ns_hdr.icmp6_type != ND_NEIGHBOR_SOLICIT ||
 514            (has_opt && opt.nd_opt_type != ND_OPT_SOURCE_LINKADDR)) {
 515                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Cannot route packet: received unknown type neighbor solicitation request");
 516                 return;
 517         }
 518
 519         /* Create pseudo header */
 520
 521         pseudo.ip6_src = ip6.ip6_src;
 522         pseudo.ip6_dst = ip6.ip6_dst;
 523         if(has_opt)
 524                 pseudo.length = htonl(ns_size + opt_size + ETH_ALEN);
 525         else
 526                 pseudo.length = htonl(ns_size);
 527         pseudo.next = htonl(IPPROTO_ICMPV6);
 528
 529         /* Generate checksum */
 530
 531         checksum = inet_checksum(&pseudo, sizeof(pseudo), ~0);
 532         checksum = inet_checksum(&ns, ns_size, checksum);
 533         if(has_opt) {
 534                 checksum = inet_checksum(&opt, opt_size, checksum);
 535                 checksum = inet_checksum(packet->data + ether_size + ip6_size + ns_size + opt_size, ETH_ALEN, checksum);
 536         }
 537
 538         if(checksum) {
 539                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Cannot route packet: checksum error for neighbor solicitation request");
 540                 return;
 541         }
 542
 543         /* Check if the IPv6 address exists on the VPN */
 544
 545         subnet = lookup_subnet_ipv6((ipv6_t *) &ns.nd_ns_target);
 546
 547         if(!subnet) {
 548                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Cannot route packet: neighbor solicitation request for unknown address %hx:%hx:%hx:%hx:%hx:%hx:%hx:%hx",
 549                                    ntohs(((uint16_t *) &ns.nd_ns_target)[0]),
 550                                    ntohs(((uint16_t *) &ns.nd_ns_target)[1]),
 551                                    ntohs(((uint16_t *) &ns.nd_ns_target)[2]),
 552                                    ntohs(((uint16_t *) &ns.nd_ns_target)[3]),
 553                                    ntohs(((uint16_t *) &ns.nd_ns_target)[4]),
 554                                    ntohs(((uint16_t *) &ns.nd_ns_target)[5]),
 555                                    ntohs(((uint16_t *) &ns.nd_ns_target)[6]),
 556                                    ntohs(((uint16_t *) &ns.nd_ns_target)[7]));
 557
 558                 return;
 559         }
 560
 561         /* Check if it is for our own subnet */
 562
 563         if(subnet->owner == myself)
 564                 return;                                 /* silently ignore */
 565
 566         /* Create neighbor advertation reply */
 567
 568         memcpy(packet->data, packet->data + ETH_ALEN, ETH_ALEN);        /* copy destination address */
 569         packet->data[ETH_ALEN * 2 - 1] ^= 0xFF; /* mangle source address so it looks like it's not from us */
 570
 571         ip6.ip6_dst = ip6.ip6_src;                      /* swap destination and source protocoll address */
 572         ip6.ip6_src = ns.nd_ns_target;
 573
 574         if(has_opt)
 575                 memcpy(packet->data + ether_size + ip6_size + ns_size + opt_size, packet->data + ETH_ALEN, ETH_ALEN);   /* add fake source hard addr */
 576
 577         ns.nd_ns_cksum = 0;
 578         ns.nd_ns_type = ND_NEIGHBOR_ADVERT;
 579         ns.nd_ns_reserved = htonl(0x40000000UL);        /* Set solicited flag */
 580         opt.nd_opt_type = ND_OPT_TARGET_LINKADDR;
 581
 582         /* Create pseudo header */
 583
 584         pseudo.ip6_src = ip6.ip6_src;
 585         pseudo.ip6_dst = ip6.ip6_dst;
 586         if(has_opt)
 587                 pseudo.length = htonl(ns_size + opt_size + ETH_ALEN);
 588         else
 589                 pseudo.length = htonl(ns_size);
 590         pseudo.next = htonl(IPPROTO_ICMPV6);
 591
 592         /* Generate checksum */
 593
 594         checksum = inet_checksum(&pseudo, sizeof(pseudo), ~0);
 595         checksum = inet_checksum(&ns, ns_size, checksum);
 596         if(has_opt) {
 597                 checksum = inet_checksum(&opt, opt_size, checksum);
 598                 checksum = inet_checksum(packet->data + ether_size + ip6_size + ns_size + opt_size, ETH_ALEN, checksum);
 599         }
 600
 601         ns.nd_ns_hdr.icmp6_cksum = checksum;
 602
 603         /* Copy structs on stack back to packet */
 604
 605         memcpy(packet->data + ether_size, &ip6, ip6_size);
 606         memcpy(packet->data + ether_size + ip6_size, &ns, ns_size);
 607         if(has_opt)
 608                 memcpy(packet->data + ether_size + ip6_size + ns_size, &opt, opt_size);
 609
 610         send_packet(source, packet);
 611 }
 612
 613 static void route_ipv6(node_t *source, vpn_packet_t *packet) {
 614         if(!checklength(source, packet, ether_size + ip6_size))
 615                 return;
 616
 617         if(packet->data[20] == IPPROTO_ICMPV6 && checklength(source, packet, ether_size + ip6_size + icmp6_size) && packet->data[54] == ND_NEIGHBOR_SOLICIT) {
 618                 route_neighborsol(source, packet);
 619                 return;
 620         }
 621
 622         if(packet->data[38] == 255)
 623                 broadcast_packet(source, packet);
 624         else
 625                 route_ipv6_unicast(source, packet);
 626 }
 627
 628 /* RFC 826 */
 629
 630 static void route_arp(node_t *source, vpn_packet_t *packet) {
 631         struct ether_arp arp;
 632         subnet_t *subnet;
 633         struct in_addr addr;
 634
 635         if(!checklength(source, packet, ether_size + arp_size))
 636                 return;
 637
 638         if(source != myself) {
 639                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Got ARP request from %s (%s) while in router mode!", source->name, source->hostname);
 640                 return;
 641         }
 642
 643         /* First, snatch the source address from the ARP packet */
 644
 645         if(overwrite_mac)
 646                 memcpy(mymac.x, packet->data + ETH_ALEN, ETH_ALEN);
 647
 648         /* Copy headers from packet to structs on the stack */
 649
 650         memcpy(&arp, packet->data + ether_size, arp_size);
 651
 652         /* Check if this is a valid ARP request */
 653
 654         if(ntohs(arp.arp_hrd) != ARPHRD_ETHER || ntohs(arp.arp_pro) != ETH_P_IP ||
 655            arp.arp_hln != ETH_ALEN || arp.arp_pln != sizeof(addr) || ntohs(arp.arp_op) != ARPOP_REQUEST) {
 656                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Cannot route packet: received unknown type ARP request");
 657                 return;
 658         }
 659
 660         /* Check if the IPv4 address exists on the VPN */
 661
 662         subnet = lookup_subnet_ipv4((ipv4_t *) &arp.arp_tpa);
 663
 664         if(!subnet) {
 665                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Cannot route packet: ARP request for unknown address %d.%d.%d.%d",
 666                                    arp.arp_tpa[0], arp.arp_tpa[1], arp.arp_tpa[2],
 667                                    arp.arp_tpa[3]);
 668                 return;
 669         }
 670
 671         /* Check if it is for our own subnet */
 672
 673         if(subnet->owner == myself)
 674                 return;                                 /* silently ignore */
 675
 676         memcpy(packet->data, packet->data + ETH_ALEN, ETH_ALEN);        /* copy destination address */
 677         packet->data[ETH_ALEN * 2 - 1] ^= 0xFF; /* mangle source address so it looks like it's not from us */
 678
 679         memcpy(&addr, arp.arp_tpa, sizeof(addr));       /* save protocol addr */
 680         memcpy(arp.arp_tpa, arp.arp_spa, sizeof(addr)); /* swap destination and source protocol address */
 681         memcpy(arp.arp_spa, &addr, sizeof(addr));       /* ... */
 682
 683         memcpy(arp.arp_tha, arp.arp_sha, ETH_ALEN);     /* set target hard/proto addr */
 684         memcpy(arp.arp_sha, packet->data + ETH_ALEN, ETH_ALEN); /* add fake source hard addr */
 685         arp.arp_op = htons(ARPOP_REPLY);
 686
 687         /* Copy structs on stack back to packet */
 688
 689         memcpy(packet->data + ether_size, &arp, arp_size);
 690
 691         send_packet(source, packet);
 692 }
 693
 694 static void route_mac(node_t *source, vpn_packet_t *packet) {
 695         subnet_t *subnet;
 696         mac_t dest;
 697
 698         /* Learn source address */
 699
 700         if(source == myself) {
 701                 mac_t src;
 702                 memcpy(&src, &packet->data[6], sizeof src);
 703                 learn_mac(&src);
 704         }
 705
 706         /* Lookup destination address */
 707
 708         memcpy(&dest, &packet->data[0], sizeof dest);
 709         subnet = lookup_subnet_mac(NULL, &dest);
 710
 711         if(!subnet) {
 712                 broadcast_packet(source, packet);
 713                 return;
 714         }
 715
 716         if(subnet->owner == source) {
 717                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Packet looping back to %s (%s)!", source->name, source->hostname);
 718                 return;
 719         }
 720
 721         // Handle packets larger than PMTU
 722
 723         node_t *via = (subnet->owner->via == myself) ? subnet->owner->nexthop : subnet->owner->via;
 724
 725         if(via && packet->len > via->mtu && via != myself) {
 726                 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);
 727                 uint16_t type = packet->data[12] << 8 | packet->data[13];
 728                 if(type == ETH_P_IP && packet->len > 590) {
 729                         if(packet->data[20] & 0x40) {
 730                                 packet->len = via->mtu;
 731                                 route_ipv4_unreachable(source, packet, ICMP_DEST_UNREACH, ICMP_FRAG_NEEDED);
 732                         } else {
 733                                 fragment_ipv4_packet(via, packet);
 734                         }
 735                         return;
 736                 } else if(type == ETH_P_IPV6 && packet->len > 1294) {
 737                         packet->len = via->mtu;
 738                         route_ipv6_unreachable(source, packet, ICMP6_PACKET_TOO_BIG, 0);
 739                         return;
 740                 }
 741         }
 742
 743         send_packet(subnet->owner, packet);
 744 }
 745
 746 void route(node_t *source, vpn_packet_t *packet) {
 747         if(!checklength(source, packet, ether_size))
 748                 return;
 749
 750         switch (routing_mode) {
 751                 case RMODE_ROUTER:
 752                         {
 753                                 uint16_t type = packet->data[12] << 8 | packet->data[13];
 754
 755                                 switch (type) {
 756                                         case ETH_P_ARP:
 757                                                 route_arp(source, packet);
 758                                                 break;
 759
 760                                         case ETH_P_IP:
 761                                                 route_ipv4(source, packet);
 762                                                 break;
 763
 764                                         case ETH_P_IPV6:
 765                                                 route_ipv6(source, packet);
 766                                                 break;
 767
 768                                         default:
 769                                                 ifdebug(TRAFFIC) logger(LOG_WARNING, "Cannot route packet from %s (%s): unknown type %hx", source->name, source->hostname, type);
 770                                                 break;
 771                                 }
 772                         }
 773                         break;
 774
 775                 case RMODE_SWITCH:
 776                         route_mac(source, packet);
 777                         break;
 778
 779                 case RMODE_HUB:
 780                         broadcast_packet(source, packet);
 781                         break;
 782         }
 783 }