www.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
  52 /* RFC 1071 */
  53
  54 static uint16_t inet_checksum(void *data, int len, uint16_t prevsum)
  55 {
  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 {
 105         subnet_t *subnet;
 106         avl_node_t *node;
 107         connection_t *c;
 108
 109         cp();
 110
 111         subnet = lookup_subnet_mac(address);
 112
 113         /* If we don't know this MAC address yet, store it */
 114
 115         if(!subnet) {
 116                 ifdebug(TRAFFIC) logger(LOG_INFO, _("Learned new MAC address %hx:%hx:%hx:%hx:%hx:%hx"),
 117                                    address->x[0], address->x[1], address->x[2], address->x[3],
 118                                    address->x[4], address->x[5]);
 119
 120                 subnet = new_subnet();
 121                 subnet->type = SUBNET_MAC;
 122                 subnet->expires = now + macexpire;
 123                 subnet->net.mac.address = *address;
 124                 subnet_add(myself, subnet);
 125
 126                 /* And tell all other tinc daemons it's our MAC */
 127
 128                 for(node = connection_tree->head; node; node = node->next) {
 129                         c = node->data;
 130                         if(c->status.active)
 131                                 send_add_subnet(c, subnet);
 132                 }
 133         }
 134
 135         if(subnet->expires)
 136                 subnet->expires = now + macexpire;
 137 }
 138
 139 void age_subnets(void)
 140 {
 141         subnet_t *s;
 142         connection_t *c;
 143         avl_node_t *node, *next, *node2;
 144
 145         cp();
 146
 147         for(node = myself->subnet_tree->head; node; node = next) {
 148                 next = node->next;
 149                 s = node->data;
 150                 if(s->expires && s->expires < now) {
 151                         ifdebug(TRAFFIC) {
 152                                 char netstr[MAXNETSTR];
 153                                 if(net2str(netstr, sizeof netstr, s))
 154                                         logger(LOG_INFO, _("Subnet %s expired"), netstr);
 155                         }
 156
 157                         for(node2 = connection_tree->head; node2; node2 = node2->next) {
 158                                 c = node2->data;
 159                                 if(c->status.active)
 160                                         send_del_subnet(c, s);
 161                         }
 162
 163                         subnet_del(myself, s);
 164                 }
 165         }
 166 }
 167
 168 /* RFC 792 */
 169
 170 static void route_ipv4_unreachable(node_t *source, vpn_packet_t *packet, uint8_t type, uint8_t code)
 171 {
 172         struct ip ip = {0};
 173         struct icmp icmp = {0};
 174
 175         struct in_addr ip_src;
 176         struct in_addr ip_dst;
 177         uint32_t oldlen;
 178
 179         if(ratelimit(3))
 180                 return;
 181
 182         cp();
 183
 184         /* Swap Ethernet source and destination addresses */
 185
 186         swap_mac_addresses(packet);
 187
 188         /* Copy headers from packet into properly aligned structs on the stack */
 189
 190         memcpy(&ip, packet->data + ether_size, ip_size);
 191
 192         /* Remember original source and destination */
 193
 194         ip_src = ip.ip_src;
 195         ip_dst = ip.ip_dst;
 196
 197         oldlen = packet->len - ether_size;
 198
 199         if(type == ICMP_DEST_UNREACH && code == ICMP_FRAG_NEEDED)
 200                 icmp.icmp_nextmtu = htons(packet->len - ether_size);
 201
 202         if(oldlen >= IP_MSS - ip_size - icmp_size)
 203                 oldlen = IP_MSS - ip_size - icmp_size;
 204
 205         /* Copy first part of original contents to ICMP message */
 206
 207         memmove(packet->data + ether_size + ip_size + icmp_size, packet->data + ether_size, oldlen);
 208
 209         /* Fill in IPv4 header */
 210
 211         ip.ip_v = 4;
 212         ip.ip_hl = ip_size / 4;
 213         ip.ip_tos = 0;
 214         ip.ip_len = htons(ip_size + icmp_size + oldlen);
 215         ip.ip_id = 0;
 216         ip.ip_off = 0;
 217         ip.ip_ttl = 255;
 218         ip.ip_p = IPPROTO_ICMP;
 219         ip.ip_sum = 0;
 220         ip.ip_src = ip_dst;
 221         ip.ip_dst = ip_src;
 222
 223         ip.ip_sum = inet_checksum(&ip, ip_size, ~0);
 224
 225         /* Fill in ICMP header */
 226
 227         icmp.icmp_type = type;
 228         icmp.icmp_code = code;
 229         icmp.icmp_cksum = 0;
 230
 231         icmp.icmp_cksum = inet_checksum(&icmp, icmp_size, ~0);
 232         icmp.icmp_cksum = inet_checksum(packet->data + ether_size + ip_size + icmp_size, oldlen, icmp.icmp_cksum);
 233
 234         /* Copy structs on stack back to packet */
 235
 236         memcpy(packet->data + ether_size, &ip, ip_size);
 237         memcpy(packet->data + ether_size + ip_size, &icmp, icmp_size);
 238
 239         packet->len = ether_size + ip_size + icmp_size + oldlen;
 240
 241         send_packet(source, packet);
 242 }
 243
 244 /* RFC 791 */
 245
 246 static void fragment_ipv4_packet(node_t *dest, vpn_packet_t *packet) {
 247         struct ip ip;
 248         vpn_packet_t fragment;
 249         int len, maxlen, todo;
 250         uint8_t *offset;
 251         uint16_t ip_off, origf;
 252
 253         cp();
 254
 255         memcpy(&ip, packet->data + ether_size, ip_size);
 256         fragment.priority = packet->priority;
 257
 258         if(ip.ip_hl != ip_size / 4)
 259                 return;
 260
 261         todo = ntohs(ip.ip_len) - ip_size;
 262
 263         if(ether_size + ip_size + todo != packet->len) {
 264                 ifdebug(TRAFFIC) logger(LOG_WARNING, _("Length of packet (%d) doesn't match length in IPv4 header (%zd)"), packet->len, ether_size + ip_size + todo);
 265                 return;
 266         }
 267
 268         ifdebug(TRAFFIC) logger(LOG_INFO, _("Fragmenting packet of %d bytes to %s (%s)"), packet->len, dest->name, dest->hostname);
 269
 270         offset = packet->data + ether_size + ip_size;
 271         maxlen = (dest->mtu - ether_size - ip_size) & ~0x7;
 272         ip_off = ntohs(ip.ip_off);
 273         origf = ip_off & ~IP_OFFMASK;
 274         ip_off &= IP_OFFMASK;
 275
 276         while(todo) {
 277                 len = todo > maxlen ? maxlen : todo;
 278                 memcpy(fragment.data + ether_size + ip_size, offset, len);
 279                 todo -= len;
 280                 offset += len;
 281
 282                 ip.ip_len = htons(ip_size + len);
 283                 ip.ip_off = htons(ip_off | origf | (todo ? IP_MF : 0));
 284                 ip.ip_sum = 0;
 285                 ip.ip_sum = inet_checksum(&ip, ip_size, ~0);
 286                 memcpy(fragment.data, packet->data, ether_size);
 287                 memcpy(fragment.data + ether_size, &ip, ip_size);
 288                 fragment.len = ether_size + ip_size + len;
 289
 290                 send_packet(dest, &fragment);
 291
 292                 ip_off += len / 8;
 293         }
 294 }
 295
 296 static void route_ipv4_unicast(node_t *source, vpn_packet_t *packet)
 297 {
 298         subnet_t *subnet;
 299         node_t *via;
 300         ipv4_t dest;
 301
 302         cp();
 303
 304         memcpy(&dest, &packet->data[30], sizeof dest);
 305         subnet = lookup_subnet_ipv4(&dest);
 306
 307         if(!subnet) {
 308                 ifdebug(TRAFFIC) logger(LOG_WARNING, _("Cannot route packet from %s (%s): unknown IPv4 destination address %d.%d.%d.%d"),
 309                                 source->name, source->hostname,
 310                                 dest.x[0],
 311                                 dest.x[1],
 312                                 dest.x[2],
 313                                 dest.x[3]);
 314
 315                 route_ipv4_unreachable(source, packet, ICMP_DEST_UNREACH, ICMP_NET_UNKNOWN);
 316                 return;
 317         }
 318
 319         if(subnet->owner == source) {
 320                 ifdebug(TRAFFIC) logger(LOG_WARNING, _("Packet looping back to %s (%s)!"), source->name, source->hostname);
 321                 return;
 322         }
 323
 324         if(!subnet->owner->status.reachable)
 325                 route_ipv4_unreachable(source, packet, ICMP_DEST_UNREACH, ICMP_NET_UNREACH);
 326
 327         if(priorityinheritance)
 328                 packet->priority = packet->data[15];
 329
 330         via = (subnet->owner->via == myself) ? subnet->owner->nexthop : subnet->owner->via;
 331
 332         if(via && packet->len > via->mtu && via != myself) {
 333                 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);
 334                 if(packet->data[20] & 0x40) {
 335                         packet->len = via->mtu;
 336                         route_ipv4_unreachable(source, packet, ICMP_DEST_UNREACH, ICMP_FRAG_NEEDED);
 337                 } else {
 338                         fragment_ipv4_packet(via, packet);
 339                 }
 340
 341                 return;
 342         }
 343
 344         send_packet(subnet->owner, packet);
 345 }
 346
 347 static void route_ipv4(node_t *source, vpn_packet_t *packet)
 348 {
 349         cp();
 350
 351         if(!checklength(source, packet, ether_size + ip_size))
 352                 return;
 353
 354         if(((packet->data[30] & 0xf0) == 0xe0) || (
 355                         packet->data[30] == 255 &&
 356                         packet->data[31] == 255 &&
 357                         packet->data[32] == 255 &&
 358                         packet->data[33] == 255))
 359                 broadcast_packet(source, packet);
 360         else
 361                 route_ipv4_unicast(source, packet);
 362 }
 363
 364 /* RFC 2463 */
 365
 366 static void route_ipv6_unreachable(node_t *source, vpn_packet_t *packet, uint8_t type, uint8_t code)
 367 {
 368         struct ip6_hdr ip6;
 369         struct icmp6_hdr icmp6 = {0};
 370         uint16_t checksum;
 371
 372         struct {
 373                 struct in6_addr ip6_src;        /* source address */
 374                 struct in6_addr ip6_dst;        /* destination address */
 375                 uint32_t length;
 376                 uint32_t next;
 377         } pseudo;
 378
 379         if(ratelimit(3))
 380                 return;
 381
 382         cp();
 383
 384         /* Swap Ethernet source and destination addresses */
 385
 386         swap_mac_addresses(packet);
 387
 388         /* Copy headers from packet to structs on the stack */
 389
 390         memcpy(&ip6, packet->data + ether_size, ip6_size);
 391
 392         /* Remember original source and destination */
 393
 394         pseudo.ip6_src = ip6.ip6_dst;
 395         pseudo.ip6_dst = ip6.ip6_src;
 396
 397         pseudo.length = packet->len - ether_size;
 398
 399         if(type == ICMP6_PACKET_TOO_BIG)
 400                 icmp6.icmp6_mtu = htonl(pseudo.length);
 401
 402         if(pseudo.length >= IP_MSS - ip6_size - icmp6_size)
 403                 pseudo.length = IP_MSS - ip6_size - icmp6_size;
 404
 405         /* Copy first part of original contents to ICMP message */
 406
 407         memmove(packet->data + ether_size + ip6_size + icmp6_size, packet->data + ether_size, pseudo.length);
 408
 409         /* Fill in IPv6 header */
 410
 411         ip6.ip6_flow = htonl(0x60000000UL);
 412         ip6.ip6_plen = htons(icmp6_size + pseudo.length);
 413         ip6.ip6_nxt = IPPROTO_ICMPV6;
 414         ip6.ip6_hlim = 255;
 415         ip6.ip6_src = pseudo.ip6_src;
 416         ip6.ip6_dst = pseudo.ip6_dst;
 417
 418         /* Fill in ICMP header */
 419
 420         icmp6.icmp6_type = type;
 421         icmp6.icmp6_code = code;
 422         icmp6.icmp6_cksum = 0;
 423
 424         /* Create pseudo header */
 425
 426         pseudo.length = htonl(icmp6_size + pseudo.length);
 427         pseudo.next = htonl(IPPROTO_ICMPV6);
 428
 429         /* Generate checksum */
 430
 431         checksum = inet_checksum(&pseudo, sizeof(pseudo), ~0);
 432         checksum = inet_checksum(&icmp6, icmp6_size, checksum);
 433         checksum = inet_checksum(packet->data + ether_size + ip6_size + icmp6_size, ntohl(pseudo.length) - icmp6_size, checksum);
 434
 435         icmp6.icmp6_cksum = checksum;
 436
 437         /* Copy structs on stack back to packet */
 438
 439         memcpy(packet->data + ether_size, &ip6, ip6_size);
 440         memcpy(packet->data + ether_size + ip6_size, &icmp6, icmp6_size);
 441
 442         packet->len = ether_size + ip6_size + ntohl(pseudo.length);
 443
 444         send_packet(source, packet);
 445 }
 446
 447 static void route_ipv6_unicast(node_t *source, vpn_packet_t *packet)
 448 {
 449         subnet_t *subnet;
 450         node_t *via;
 451         ipv6_t dest;
 452
 453         cp();
 454
 455         memcpy(&dest, &packet->data[38], sizeof dest);
 456         subnet = lookup_subnet_ipv6(&dest);
 457
 458         if(!subnet) {
 459                 ifdebug(TRAFFIC) logger(LOG_WARNING, _("Cannot route packet from %s (%s): unknown IPv6 destination address %hx:%hx:%hx:%hx:%hx:%hx:%hx:%hx"),
 460                                 source->name, source->hostname,
 461                                 ntohs(dest.x[0]),
 462                                 ntohs(dest.x[1]),
 463                                 ntohs(dest.x[2]),
 464                                 ntohs(dest.x[3]),
 465                                 ntohs(dest.x[4]),
 466                                 ntohs(dest.x[5]),
 467                                 ntohs(dest.x[6]),
 468                                 ntohs(dest.x[7]));
 469
 470                 route_ipv6_unreachable(source, packet, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_ADDR);
 471                 return;
 472         }
 473
 474         if(subnet->owner == source) {
 475                 ifdebug(TRAFFIC) logger(LOG_WARNING, _("Packet looping back to %s (%s)!"), source->name, source->hostname);
 476                 return;
 477         }
 478
 479         if(!subnet->owner->status.reachable)
 480                 route_ipv6_unreachable(source, packet, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_NOROUTE);
 481
 482         via = (subnet->owner->via == myself) ? subnet->owner->nexthop : subnet->owner->via;
 483
 484         if(via && packet->len > via->mtu && via != myself) {
 485                 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);
 486                 packet->len = via->mtu;
 487                 route_ipv6_unreachable(source, packet, ICMP6_PACKET_TOO_BIG, 0);
 488                 return;
 489         }
 490
 491         send_packet(subnet->owner, packet);
 492 }
 493
 494 /* RFC 2461 */
 495
 496 static void route_neighborsol(node_t *source, vpn_packet_t *packet)
 497 {
 498         struct ip6_hdr ip6;
 499         struct nd_neighbor_solicit ns;
 500         struct nd_opt_hdr opt;
 501         subnet_t *subnet;
 502         uint16_t checksum;
 503         bool has_opt;
 504
 505         struct {
 506                 struct in6_addr ip6_src;        /* source address */
 507                 struct in6_addr ip6_dst;        /* destination address */
 508                 uint32_t length;
 509                 uint32_t next;
 510         } pseudo;
 511
 512         cp();
 513
 514         if(!checklength(source, packet, ether_size + ip6_size + ns_size))
 515                 return;
 516
 517         has_opt = packet->len >= ether_size + ip6_size + ns_size + opt_size + ETH_ALEN;
 518
 519         if(source != myself) {
 520                 ifdebug(TRAFFIC) logger(LOG_WARNING, _("Got neighbor solicitation request from %s (%s) while in router mode!"), source->name, source->hostname);
 521                 return;
 522         }
 523
 524         /* Copy headers from packet to structs on the stack */
 525
 526         memcpy(&ip6, packet->data + ether_size, ip6_size);
 527         memcpy(&ns, packet->data + ether_size + ip6_size, ns_size);
 528         if(has_opt)
 529                 memcpy(&opt, packet->data + ether_size + ip6_size + ns_size, opt_size);
 530
 531         /* First, snatch the source address from the neighbor solicitation packet */
 532
 533         if(overwrite_mac)
 534                 memcpy(mymac.x, packet->data + ETH_ALEN, ETH_ALEN);
 535
 536         /* Check if this is a valid neighbor solicitation request */
 537
 538         if(ns.nd_ns_hdr.icmp6_type != ND_NEIGHBOR_SOLICIT ||
 539            (has_opt && opt.nd_opt_type != ND_OPT_SOURCE_LINKADDR)) {
 540                 ifdebug(TRAFFIC) logger(LOG_WARNING, _("Cannot route packet: received unknown type neighbor solicitation request"));
 541                 return;
 542         }
 543
 544         /* Create pseudo header */
 545
 546         pseudo.ip6_src = ip6.ip6_src;
 547         pseudo.ip6_dst = ip6.ip6_dst;
 548         if(has_opt)
 549                 pseudo.length = htonl(ns_size + opt_size + ETH_ALEN);
 550         else
 551                 pseudo.length = htonl(ns_size);
 552         pseudo.next = htonl(IPPROTO_ICMPV6);
 553
 554         /* Generate checksum */
 555
 556         checksum = inet_checksum(&pseudo, sizeof(pseudo), ~0);
 557         checksum = inet_checksum(&ns, ns_size, checksum);
 558         if(has_opt) {
 559                 checksum = inet_checksum(&opt, opt_size, checksum);
 560                 checksum = inet_checksum(packet->data + ether_size + ip6_size + ns_size + opt_size, ETH_ALEN, checksum);
 561         }
 562
 563         if(checksum) {
 564                 ifdebug(TRAFFIC) logger(LOG_WARNING, _("Cannot route packet: checksum error for neighbor solicitation request"));
 565                 return;
 566         }
 567
 568         /* Check if the IPv6 address exists on the VPN */
 569
 570         subnet = lookup_subnet_ipv6((ipv6_t *) &ns.nd_ns_target);
 571
 572         if(!subnet) {
 573                 ifdebug(TRAFFIC) logger(LOG_WARNING, _("Cannot route packet: neighbor solicitation request for unknown address %hx:%hx:%hx:%hx:%hx:%hx:%hx:%hx"),
 574                                    ntohs(((uint16_t *) &ns.nd_ns_target)[0]),
 575                                    ntohs(((uint16_t *) &ns.nd_ns_target)[1]),
 576                                    ntohs(((uint16_t *) &ns.nd_ns_target)[2]),
 577                                    ntohs(((uint16_t *) &ns.nd_ns_target)[3]),
 578                                    ntohs(((uint16_t *) &ns.nd_ns_target)[4]),
 579                                    ntohs(((uint16_t *) &ns.nd_ns_target)[5]),
 580                                    ntohs(((uint16_t *) &ns.nd_ns_target)[6]),
 581                                    ntohs(((uint16_t *) &ns.nd_ns_target)[7]));
 582
 583                 return;
 584         }
 585
 586         /* Check if it is for our own subnet */
 587
 588         if(subnet->owner == myself)
 589                 return;                                 /* silently ignore */
 590
 591         /* Create neighbor advertation reply */
 592
 593         memcpy(packet->data, packet->data + ETH_ALEN, ETH_ALEN);        /* copy destination address */
 594         packet->data[ETH_ALEN * 2 - 1] ^= 0xFF; /* mangle source address so it looks like it's not from us */
 595
 596         ip6.ip6_dst = ip6.ip6_src;                      /* swap destination and source protocoll address */
 597         ip6.ip6_src = ns.nd_ns_target;
 598
 599         if(has_opt)
 600                 memcpy(packet->data + ether_size + ip6_size + ns_size + opt_size, packet->data + ETH_ALEN, ETH_ALEN);   /* add fake source hard addr */
 601
 602         ns.nd_ns_cksum = 0;
 603         ns.nd_ns_type = ND_NEIGHBOR_ADVERT;
 604         ns.nd_ns_reserved = htonl(0x40000000UL);        /* Set solicited flag */
 605         opt.nd_opt_type = ND_OPT_TARGET_LINKADDR;
 606
 607         /* Create pseudo header */
 608
 609         pseudo.ip6_src = ip6.ip6_src;
 610         pseudo.ip6_dst = ip6.ip6_dst;
 611         if(has_opt)
 612                 pseudo.length = htonl(ns_size + opt_size + ETH_ALEN);
 613         else
 614                 pseudo.length = htonl(ns_size);
 615         pseudo.next = htonl(IPPROTO_ICMPV6);
 616
 617         /* Generate checksum */
 618
 619         checksum = inet_checksum(&pseudo, sizeof(pseudo), ~0);
 620         checksum = inet_checksum(&ns, ns_size, checksum);
 621         if(has_opt) {
 622                 checksum = inet_checksum(&opt, opt_size, checksum);
 623                 checksum = inet_checksum(packet->data + ether_size + ip6_size + ns_size + opt_size, ETH_ALEN, checksum);
 624         }
 625
 626         ns.nd_ns_hdr.icmp6_cksum = checksum;
 627
 628         /* Copy structs on stack back to packet */
 629
 630         memcpy(packet->data + ether_size, &ip6, ip6_size);
 631         memcpy(packet->data + ether_size + ip6_size, &ns, ns_size);
 632         if(has_opt)
 633                 memcpy(packet->data + ether_size + ip6_size + ns_size, &opt, opt_size);
 634
 635         send_packet(source, packet);
 636 }
 637
 638 static void route_ipv6(node_t *source, vpn_packet_t *packet)
 639 {
 640         cp();
 641
 642         if(!checklength(source, packet, ether_size + ip6_size))
 643                 return;
 644
 645         if(packet->data[20] == IPPROTO_ICMPV6 && checklength(source, packet, ether_size + ip6_size + icmp6_size) && packet->data[54] == ND_NEIGHBOR_SOLICIT) {
 646                 route_neighborsol(source, packet);
 647                 return;
 648         }
 649
 650         if(packet->data[38] == 255)
 651                 broadcast_packet(source, packet);
 652         else
 653                 route_ipv6_unicast(source, packet);
 654 }
 655
 656 /* RFC 826 */
 657
 658 static void route_arp(node_t *source, vpn_packet_t *packet)
 659 {
 660         struct ether_arp arp;
 661         subnet_t *subnet;
 662         struct in_addr addr;
 663
 664         cp();
 665
 666         if(!checklength(source, packet, ether_size + arp_size))
 667                 return;
 668
 669         if(source != myself) {
 670                 ifdebug(TRAFFIC) logger(LOG_WARNING, _("Got ARP request from %s (%s) while in router mode!"), source->name, source->hostname);
 671                 return;
 672         }
 673
 674         /* First, snatch the source address from the ARP packet */
 675
 676         if(overwrite_mac)
 677                 memcpy(mymac.x, packet->data + ETH_ALEN, ETH_ALEN);
 678
 679         /* Copy headers from packet to structs on the stack */
 680
 681         memcpy(&arp, packet->data + ether_size, arp_size);
 682
 683         /* Check if this is a valid ARP request */
 684
 685         if(ntohs(arp.arp_hrd) != ARPHRD_ETHER || ntohs(arp.arp_pro) != ETH_P_IP ||
 686            arp.arp_hln != ETH_ALEN || arp.arp_pln != sizeof(addr) || ntohs(arp.arp_op) != ARPOP_REQUEST) {
 687                 ifdebug(TRAFFIC) logger(LOG_WARNING, _("Cannot route packet: received unknown type ARP request"));
 688                 return;
 689         }
 690
 691         /* Check if the IPv4 address exists on the VPN */
 692
 693         subnet = lookup_subnet_ipv4((ipv4_t *) &arp.arp_tpa);
 694
 695         if(!subnet) {
 696                 ifdebug(TRAFFIC) logger(LOG_WARNING, _("Cannot route packet: ARP request for unknown address %d.%d.%d.%d"),
 697                                    arp.arp_tpa[0], arp.arp_tpa[1], arp.arp_tpa[2],
 698                                    arp.arp_tpa[3]);
 699                 return;
 700         }
 701
 702         /* Check if it is for our own subnet */
 703
 704         if(subnet->owner == myself)
 705                 return;                                 /* silently ignore */
 706
 707         memcpy(packet->data, packet->data + ETH_ALEN, ETH_ALEN);        /* copy destination address */
 708         packet->data[ETH_ALEN * 2 - 1] ^= 0xFF; /* mangle source address so it looks like it's not from us */
 709
 710         memcpy(&addr, arp.arp_tpa, sizeof(addr));       /* save protocol addr */
 711         memcpy(arp.arp_tpa, arp.arp_spa, sizeof(addr)); /* swap destination and source protocol address */
 712         memcpy(arp.arp_spa, &addr, sizeof(addr));       /* ... */
 713
 714         memcpy(arp.arp_tha, arp.arp_sha, ETH_ALEN);     /* set target hard/proto addr */
 715         memcpy(arp.arp_sha, packet->data + ETH_ALEN, ETH_ALEN); /* add fake source hard addr */
 716         arp.arp_op = htons(ARPOP_REPLY);
 717
 718         /* Copy structs on stack back to packet */
 719
 720         memcpy(packet->data + ether_size, &arp, arp_size);
 721
 722         send_packet(source, packet);
 723 }
 724
 725 static void route_mac(node_t *source, vpn_packet_t *packet)
 726 {
 727         subnet_t *subnet;
 728         mac_t dest;
 729
 730         cp();
 731
 732
 733         /* Learn source address */
 734
 735         if(source == myself) {
 736                 mac_t src;
 737                 memcpy(&src, &packet->data[6], sizeof src);
 738                 learn_mac(&src);
 739         }
 740
 741         /* Lookup destination address */
 742
 743         memcpy(&dest, &packet->data[0], sizeof dest);
 744         subnet = lookup_subnet_mac(&dest);
 745
 746         if(!subnet) {
 747                 broadcast_packet(source, packet);
 748                 return;
 749         }
 750
 751         if(subnet->owner == source) {
 752                 ifdebug(TRAFFIC) logger(LOG_WARNING, _("Packet looping back to %s (%s)!"), source->name, source->hostname);
 753                 return;
 754         }
 755
 756         // Handle packets larger than PMTU
 757
 758         node_t *via = (subnet->owner->via == myself) ? subnet->owner->nexthop : subnet->owner->via;
 759
 760         if(via && packet->len > via->mtu && via != myself) {
 761                 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);
 762                 uint16_t type = packet->data[12] << 8 | packet->data[13];
 763                 if(type == ETH_P_IP) {
 764                         if(packet->data[20] & 0x40) {
 765                                 packet->len = via->mtu;
 766                                 route_ipv4_unreachable(source, packet, ICMP_DEST_UNREACH, ICMP_FRAG_NEEDED);
 767                         } else {
 768                                 fragment_ipv4_packet(via, packet);
 769                         }
 770                         return;
 771                 } else if(type == ETH_P_IPV6) {
 772                         packet->len = via->mtu;
 773                         route_ipv6_unreachable(source, packet, ICMP6_PACKET_TOO_BIG, 0);
 774                         return;
 775                 }
 776         }
 777
 778         send_packet(subnet->owner, packet);
 779 }
 780
 781
 782 void route(node_t *source, vpn_packet_t *packet)
 783 {
 784         cp();
 785
 786         if(!checklength(source, packet, ether_size))
 787                 return;
 788
 789         switch (routing_mode) {
 790                 case RMODE_ROUTER:
 791                         {
 792                                 uint16_t type = packet->data[12] << 8 | packet->data[13];
 793
 794                                 switch (type) {
 795                                         case ETH_P_ARP:
 796                                                 route_arp(source, packet);
 797                                                 break;
 798
 799                                         case ETH_P_IP:
 800                                                 route_ipv4(source, packet);
 801                                                 break;
 802
 803                                         case ETH_P_IPV6:
 804                                                 route_ipv6(source, packet);
 805                                                 break;
 806
 807                                         default:
 808                                                 ifdebug(TRAFFIC) logger(LOG_WARNING, _("Cannot route packet from %s (%s): unknown type %hx"), source->name, source->hostname, type);
 809                                                 break;
 810                                 }
 811                         }
 812                         break;
 813
 814                 case RMODE_SWITCH:
 815                         route_mac(source, packet);
 816                         break;
 817
 818                 case RMODE_HUB:
 819                         broadcast_packet(source, packet);
 820                         break;
 821         }
 822 }