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         uint16_t *p = data;
  56         uint32_t checksum = prevsum ^ 0xFFFF;
  57
  58         while(len >= 2) {
  59                 checksum += *p++;
  60                 len -= 2;
  61         }
  62
  63         if(len)
  64                 checksum += *(uint8_t *)p;
  65
  66         while(checksum >> 16)
  67                 checksum = (checksum & 0xFFFF) + (checksum >> 16);
  68
  69         return ~checksum;
  70 }
  71
  72 static bool ratelimit(int frequency) {
  73         static time_t lasttime = 0;
  74         static int count = 0;
  75
  76         if(lasttime == now) {
  77                 if(++count > frequency)
  78                         return true;
  79         } else {
  80                 lasttime = now;
  81                 count = 0;
  82         }
  83
  84         return false;
  85 }
  86
  87 static bool checklength(node_t *source, vpn_packet_t *packet, length_t length) {
  88         if(packet->len < length) {
  89                 ifdebug(TRAFFIC) logger(LOG_WARNING, _("Got too short packet from %s (%s)"), source->name, source->hostname);
  90                 return false;
  91         } else
  92                 return true;
  93 }
  94
  95 static void swap_mac_addresses(vpn_packet_t *packet) {
  96         mac_t tmp;
  97         memcpy(&tmp, &packet->data[0], sizeof tmp);
  98         memcpy(&packet->data[0], &packet->data[6], sizeof tmp);
  99         memcpy(&packet->data[6], &tmp, sizeof tmp);
 100 }
 101
 102 static void learn_mac(mac_t *address) {
 103         subnet_t *subnet;
 104         avl_node_t *node;
 105         connection_t *c;
 106
 107         cp();
 108
 109         subnet = lookup_subnet_mac(address);
 110
 111         /* If we don't know this MAC address yet, store it */
 112
 113         if(!subnet) {
 114                 ifdebug(TRAFFIC) logger(LOG_INFO, _("Learned new MAC address %hx:%hx:%hx:%hx:%hx:%hx"),
 115                                    address->x[0], address->x[1], address->x[2], address->x[3],
 116                                    address->x[4], address->x[5]);
 117
 118                 subnet = new_subnet();
 119                 subnet->type = SUBNET_MAC;
 120                 subnet->expires = now + macexpire;
 121                 subnet->net.mac.address = *address;
 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         cp();
 143
 144         for(node = myself->subnet_tree->head; node; node = next) {
 145                 next = node->next;
 146                 s = node->data;
 147                 if(s->expires && s->expires < now) {
 148                         ifdebug(TRAFFIC) {
 149                                 char netstr[MAXNETSTR];
 150                                 if(net2str(netstr, sizeof netstr, s))
 151                                         logger(LOG_INFO, _("Subnet %s expired"), netstr);
 152                         }
 153
 154                         for(node2 = connection_tree->head; node2; node2 = node2->next) {
 155                                 c = node2->data;
 156                                 if(c->status.active)
 157                                         send_del_subnet(c, s);
 158                         }
 159
 160                         subnet_del(myself, s);
 161                 }
 162         }
 163 }
 164
 165 /* RFC 792 */
 166
 167 static void route_ipv4_unreachable(node_t *source, vpn_packet_t *packet, uint8_t type, uint8_t code) {
 168         struct ip ip = {0};
 169         struct icmp icmp = {0};
 170
 171         struct in_addr ip_src;
 172         struct in_addr ip_dst;
 173         uint32_t oldlen;
 174
 175         if(ratelimit(3))
 176                 return;
 177
 178         cp();
 179
 180         /* Swap Ethernet source and destination addresses */
 181
 182         swap_mac_addresses(packet);
 183
 184         /* Copy headers from packet into properly aligned structs on the stack */
 185
 186         memcpy(&ip, packet->data + ether_size, ip_size);
 187
 188         /* Remember original source and destination */
 189
 190         ip_src = ip.ip_src;
 191         ip_dst = ip.ip_dst;
 192
 193         oldlen = packet->len - ether_size;
 194
 195         if(type == ICMP_DEST_UNREACH && code == ICMP_FRAG_NEEDED)
 196                 icmp.icmp_nextmtu = htons(packet->len - ether_size);
 197
 198         if(oldlen >= IP_MSS - ip_size - icmp_size)
 199                 oldlen = IP_MSS - ip_size - icmp_size;
 200
 201         /* Copy first part of original contents to ICMP message */
 202
 203         memmove(packet->data + ether_size + ip_size + icmp_size, packet->data + ether_size, oldlen);
 204
 205         /* Fill in IPv4 header */
 206
 207         ip.ip_v = 4;
 208         ip.ip_hl = ip_size / 4;
 209         ip.ip_tos = 0;
 210         ip.ip_len = htons(ip_size + icmp_size + oldlen);
 211         ip.ip_id = 0;
 212         ip.ip_off = 0;
 213         ip.ip_ttl = 255;
 214         ip.ip_p = IPPROTO_ICMP;
 215         ip.ip_sum = 0;
 216         ip.ip_src = ip_dst;
 217         ip.ip_dst = ip_src;
 218
 219         ip.ip_sum = inet_checksum(&ip, ip_size, ~0);
 220
 221         /* Fill in ICMP header */
 222
 223         icmp.icmp_type = type;
 224         icmp.icmp_code = code;
 225         icmp.icmp_cksum = 0;
 226
 227         icmp.icmp_cksum = inet_checksum(&icmp, icmp_size, ~0);
 228         icmp.icmp_cksum = inet_checksum(packet->data + ether_size + ip_size + icmp_size, oldlen, icmp.icmp_cksum);
 229
 230         /* Copy structs on stack back to packet */
 231
 232         memcpy(packet->data + ether_size, &ip, ip_size);
 233         memcpy(packet->data + ether_size + ip_size, &icmp, icmp_size);
 234
 235         packet->len = ether_size + ip_size + icmp_size + oldlen;
 236
 237         send_packet(source, packet);
 238 }
 239
 240 /* RFC 791 */
 241
 242 static void fragment_ipv4_packet(node_t *dest, vpn_packet_t *packet) {
 243         struct ip ip;
 244         vpn_packet_t fragment;
 245         int len, maxlen, todo;
 246         uint8_t *offset;
 247         uint16_t ip_off, origf;
 248
 249         cp();
 250
 251         memcpy(&ip, packet->data + ether_size, ip_size);
 252         fragment.priority = packet->priority;
 253
 254         if(ip.ip_hl != ip_size / 4)
 255                 return;
 256
 257         todo = ntohs(ip.ip_len) - ip_size;
 258
 259         if(ether_size + ip_size + todo != packet->len) {
 260                 ifdebug(TRAFFIC) logger(LOG_WARNING, _("Length of packet (%d) doesn't match length in IPv4 header (%zd)"), packet->len, ether_size + ip_size + todo);
 261                 return;
 262         }
 263
 264         ifdebug(TRAFFIC) logger(LOG_INFO, _("Fragmenting packet of %d bytes to %s (%s)"), packet->len, dest->name, dest->hostname);
 265
 266         offset = packet->data + ether_size + ip_size;
 267         maxlen = (dest->mtu - ether_size - ip_size) & ~0x7;
 268         ip_off = ntohs(ip.ip_off);
 269         origf = ip_off & ~IP_OFFMASK;
 270         ip_off &= IP_OFFMASK;
 271
 272         while(todo) {
 273                 len = todo > maxlen ? maxlen : todo;
 274                 memcpy(fragment.data + ether_size + ip_size, offset, len);
 275                 todo -= len;
 276                 offset += len;
 277
 278                 ip.ip_len = htons(ip_size + len);
 279                 ip.ip_off = htons(ip_off | origf | (todo ? IP_MF : 0));
 280                 ip.ip_sum = 0;
 281                 ip.ip_sum = inet_checksum(&ip, ip_size, ~0);
 282                 memcpy(fragment.data, packet->data, ether_size);
 283                 memcpy(fragment.data + ether_size, &ip, ip_size);
 284                 fragment.len = ether_size + ip_size + len;
 285
 286                 send_packet(dest, &fragment);
 287
 288                 ip_off += len / 8;
 289         }
 290 }
 291
 292 static void route_ipv4_unicast(node_t *source, vpn_packet_t *packet) {
 293         subnet_t *subnet;
 294         node_t *via;
 295         ipv4_t dest;
 296
 297         cp();
 298
 299         memcpy(&dest, &packet->data[30], sizeof dest);
 300         subnet = lookup_subnet_ipv4(&dest);
 301
 302         if(!subnet) {
 303                 ifdebug(TRAFFIC) logger(LOG_WARNING, _("Cannot route packet from %s (%s): unknown IPv4 destination address %d.%d.%d.%d"),
 304                                 source->name, source->hostname,
 305                                 dest.x[0],
 306                                 dest.x[1],
 307                                 dest.x[2],
 308                                 dest.x[3]);
 309
 310                 route_ipv4_unreachable(source, packet, ICMP_DEST_UNREACH, ICMP_NET_UNKNOWN);
 311                 return;
 312         }
 313
 314         if(subnet->owner == source) {
 315                 ifdebug(TRAFFIC) logger(LOG_WARNING, _("Packet looping back to %s (%s)!"), source->name, source->hostname);
 316                 return;
 317         }
 318
 319         if(!subnet->owner->status.reachable)
 320                 route_ipv4_unreachable(source, packet, ICMP_DEST_UNREACH, ICMP_NET_UNREACH);
 321
 322         if(priorityinheritance)
 323                 packet->priority = packet->data[15];
 324
 325         via = (subnet->owner->via == myself) ? subnet->owner->nexthop : subnet->owner->via;
 326
 327         if(via && packet->len > via->mtu && via != myself) {
 328                 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);
 329                 if(packet->data[20] & 0x40) {
 330                         packet->len = via->mtu;
 331                         route_ipv4_unreachable(source, packet, ICMP_DEST_UNREACH, ICMP_FRAG_NEEDED);
 332                 } else {
 333                         fragment_ipv4_packet(via, packet);
 334                 }
 335
 336                 return;
 337         }
 338
 339         send_packet(subnet->owner, packet);
 340 }
 341
 342 static void route_ipv4(node_t *source, vpn_packet_t *packet) {
 343         cp();
 344
 345         if(!checklength(source, packet, ether_size + ip_size))
 346                 return;
 347
 348         if(((packet->data[30] & 0xf0) == 0xe0) || (
 349                         packet->data[30] == 255 &&
 350                         packet->data[31] == 255 &&
 351                         packet->data[32] == 255 &&
 352                         packet->data[33] == 255))
 353                 broadcast_packet(source, packet);
 354         else
 355                 route_ipv4_unicast(source, packet);
 356 }
 357
 358 /* RFC 2463 */
 359
 360 static void route_ipv6_unreachable(node_t *source, vpn_packet_t *packet, uint8_t type, uint8_t code) {
 361         struct ip6_hdr ip6;
 362         struct icmp6_hdr icmp6 = {0};
 363         uint16_t checksum;
 364
 365         struct {
 366                 struct in6_addr ip6_src;        /* source address */
 367                 struct in6_addr ip6_dst;        /* destination address */
 368                 uint32_t length;
 369                 uint32_t next;
 370         } pseudo;
 371
 372         if(ratelimit(3))
 373                 return;
 374
 375         cp();
 376
 377         /* Swap Ethernet source and destination addresses */
 378
 379         swap_mac_addresses(packet);
 380
 381         /* Copy headers from packet to structs on the stack */
 382
 383         memcpy(&ip6, packet->data + ether_size, ip6_size);
 384
 385         /* Remember original source and destination */
 386
 387         pseudo.ip6_src = ip6.ip6_dst;
 388         pseudo.ip6_dst = ip6.ip6_src;
 389
 390         pseudo.length = packet->len - ether_size;
 391
 392         if(type == ICMP6_PACKET_TOO_BIG)
 393                 icmp6.icmp6_mtu = htonl(pseudo.length);
 394
 395         if(pseudo.length >= IP_MSS - ip6_size - icmp6_size)
 396                 pseudo.length = IP_MSS - ip6_size - icmp6_size;
 397
 398         /* Copy first part of original contents to ICMP message */
 399
 400         memmove(packet->data + ether_size + ip6_size + icmp6_size, packet->data + ether_size, pseudo.length);
 401
 402         /* Fill in IPv6 header */
 403
 404         ip6.ip6_flow = htonl(0x60000000UL);
 405         ip6.ip6_plen = htons(icmp6_size + pseudo.length);
 406         ip6.ip6_nxt = IPPROTO_ICMPV6;
 407         ip6.ip6_hlim = 255;
 408         ip6.ip6_src = pseudo.ip6_src;
 409         ip6.ip6_dst = pseudo.ip6_dst;
 410
 411         /* Fill in ICMP header */
 412
 413         icmp6.icmp6_type = type;
 414         icmp6.icmp6_code = code;
 415         icmp6.icmp6_cksum = 0;
 416
 417         /* Create pseudo header */
 418
 419         pseudo.length = htonl(icmp6_size + pseudo.length);
 420         pseudo.next = htonl(IPPROTO_ICMPV6);
 421
 422         /* Generate checksum */
 423
 424         checksum = inet_checksum(&pseudo, sizeof(pseudo), ~0);
 425         checksum = inet_checksum(&icmp6, icmp6_size, checksum);
 426         checksum = inet_checksum(packet->data + ether_size + ip6_size + icmp6_size, ntohl(pseudo.length) - icmp6_size, checksum);
 427
 428         icmp6.icmp6_cksum = checksum;
 429
 430         /* Copy structs on stack back to packet */
 431
 432         memcpy(packet->data + ether_size, &ip6, ip6_size);
 433         memcpy(packet->data + ether_size + ip6_size, &icmp6, icmp6_size);
 434
 435         packet->len = ether_size + ip6_size + ntohl(pseudo.length);
 436
 437         send_packet(source, packet);
 438 }
 439
 440 static void route_ipv6_unicast(node_t *source, vpn_packet_t *packet) {
 441         subnet_t *subnet;
 442         node_t *via;
 443         ipv6_t dest;
 444
 445         cp();
 446
 447         memcpy(&dest, &packet->data[38], sizeof dest);
 448         subnet = lookup_subnet_ipv6(&dest);
 449
 450         if(!subnet) {
 451                 ifdebug(TRAFFIC) logger(LOG_WARNING, _("Cannot route packet from %s (%s): unknown IPv6 destination address %hx:%hx:%hx:%hx:%hx:%hx:%hx:%hx"),
 452                                 source->name, source->hostname,
 453                                 ntohs(dest.x[0]),
 454                                 ntohs(dest.x[1]),
 455                                 ntohs(dest.x[2]),
 456                                 ntohs(dest.x[3]),
 457                                 ntohs(dest.x[4]),
 458                                 ntohs(dest.x[5]),
 459                                 ntohs(dest.x[6]),
 460                                 ntohs(dest.x[7]));
 461
 462                 route_ipv6_unreachable(source, packet, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_ADDR);
 463                 return;
 464         }
 465
 466         if(subnet->owner == source) {
 467                 ifdebug(TRAFFIC) logger(LOG_WARNING, _("Packet looping back to %s (%s)!"), source->name, source->hostname);
 468                 return;
 469         }
 470
 471         if(!subnet->owner->status.reachable)
 472                 route_ipv6_unreachable(source, packet, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_NOROUTE);
 473
 474         via = (subnet->owner->via == myself) ? subnet->owner->nexthop : subnet->owner->via;
 475
 476         if(via && packet->len > via->mtu && via != myself) {
 477                 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);
 478                 packet->len = via->mtu;
 479                 route_ipv6_unreachable(source, packet, ICMP6_PACKET_TOO_BIG, 0);
 480                 return;
 481         }
 482
 483         send_packet(subnet->owner, packet);
 484 }
 485
 486 /* RFC 2461 */
 487
 488 static void route_neighborsol(node_t *source, vpn_packet_t *packet) {
 489         struct ip6_hdr ip6;
 490         struct nd_neighbor_solicit ns;
 491         struct nd_opt_hdr opt;
 492         subnet_t *subnet;
 493         uint16_t checksum;
 494         bool has_opt;
 495
 496         struct {
 497                 struct in6_addr ip6_src;        /* source address */
 498                 struct in6_addr ip6_dst;        /* destination address */
 499                 uint32_t length;
 500                 uint32_t next;
 501         } pseudo;
 502
 503         cp();
 504
 505         if(!checklength(source, packet, ether_size + ip6_size + ns_size))
 506                 return;
 507
 508         has_opt = packet->len >= ether_size + ip6_size + ns_size + opt_size + ETH_ALEN;
 509
 510         if(source != myself) {
 511                 ifdebug(TRAFFIC) logger(LOG_WARNING, _("Got neighbor solicitation request from %s (%s) while in router mode!"), source->name, source->hostname);
 512                 return;
 513         }
 514
 515         /* Copy headers from packet to structs on the stack */
 516
 517         memcpy(&ip6, packet->data + ether_size, ip6_size);
 518         memcpy(&ns, packet->data + ether_size + ip6_size, ns_size);
 519         if(has_opt)
 520                 memcpy(&opt, packet->data + ether_size + ip6_size + ns_size, opt_size);
 521
 522         /* First, snatch the source address from the neighbor solicitation packet */
 523
 524         if(overwrite_mac)
 525                 memcpy(mymac.x, packet->data + ETH_ALEN, ETH_ALEN);
 526
 527         /* Check if this is a valid neighbor solicitation request */
 528
 529         if(ns.nd_ns_hdr.icmp6_type != ND_NEIGHBOR_SOLICIT ||
 530            (has_opt && opt.nd_opt_type != ND_OPT_SOURCE_LINKADDR)) {
 531                 ifdebug(TRAFFIC) logger(LOG_WARNING, _("Cannot route packet: received unknown type neighbor solicitation request"));
 532                 return;
 533         }
 534
 535         /* Create pseudo header */
 536
 537         pseudo.ip6_src = ip6.ip6_src;
 538         pseudo.ip6_dst = ip6.ip6_dst;
 539         if(has_opt)
 540                 pseudo.length = htonl(ns_size + opt_size + ETH_ALEN);
 541         else
 542                 pseudo.length = htonl(ns_size);
 543         pseudo.next = htonl(IPPROTO_ICMPV6);
 544
 545         /* Generate checksum */
 546
 547         checksum = inet_checksum(&pseudo, sizeof(pseudo), ~0);
 548         checksum = inet_checksum(&ns, ns_size, checksum);
 549         if(has_opt) {
 550                 checksum = inet_checksum(&opt, opt_size, checksum);
 551                 checksum = inet_checksum(packet->data + ether_size + ip6_size + ns_size + opt_size, ETH_ALEN, checksum);
 552         }
 553
 554         if(checksum) {
 555                 ifdebug(TRAFFIC) logger(LOG_WARNING, _("Cannot route packet: checksum error for neighbor solicitation request"));
 556                 return;
 557         }
 558
 559         /* Check if the IPv6 address exists on the VPN */
 560
 561         subnet = lookup_subnet_ipv6((ipv6_t *) &ns.nd_ns_target);
 562
 563         if(!subnet) {
 564                 ifdebug(TRAFFIC) logger(LOG_WARNING, _("Cannot route packet: neighbor solicitation request for unknown address %hx:%hx:%hx:%hx:%hx:%hx:%hx:%hx"),
 565                                    ntohs(((uint16_t *) &ns.nd_ns_target)[0]),
 566                                    ntohs(((uint16_t *) &ns.nd_ns_target)[1]),
 567                                    ntohs(((uint16_t *) &ns.nd_ns_target)[2]),
 568                                    ntohs(((uint16_t *) &ns.nd_ns_target)[3]),
 569                                    ntohs(((uint16_t *) &ns.nd_ns_target)[4]),
 570                                    ntohs(((uint16_t *) &ns.nd_ns_target)[5]),
 571                                    ntohs(((uint16_t *) &ns.nd_ns_target)[6]),
 572                                    ntohs(((uint16_t *) &ns.nd_ns_target)[7]));
 573
 574                 return;
 575         }
 576
 577         /* Check if it is for our own subnet */
 578
 579         if(subnet->owner == myself)
 580                 return;                                 /* silently ignore */
 581
 582         /* Create neighbor advertation reply */
 583
 584         memcpy(packet->data, packet->data + ETH_ALEN, ETH_ALEN);        /* copy destination address */
 585         packet->data[ETH_ALEN * 2 - 1] ^= 0xFF; /* mangle source address so it looks like it's not from us */
 586
 587         ip6.ip6_dst = ip6.ip6_src;                      /* swap destination and source protocoll address */
 588         ip6.ip6_src = ns.nd_ns_target;
 589
 590         if(has_opt)
 591                 memcpy(packet->data + ether_size + ip6_size + ns_size + opt_size, packet->data + ETH_ALEN, ETH_ALEN);   /* add fake source hard addr */
 592
 593         ns.nd_ns_cksum = 0;
 594         ns.nd_ns_type = ND_NEIGHBOR_ADVERT;
 595         ns.nd_ns_reserved = htonl(0x40000000UL);        /* Set solicited flag */
 596         opt.nd_opt_type = ND_OPT_TARGET_LINKADDR;
 597
 598         /* Create pseudo header */
 599
 600         pseudo.ip6_src = ip6.ip6_src;
 601         pseudo.ip6_dst = ip6.ip6_dst;
 602         if(has_opt)
 603                 pseudo.length = htonl(ns_size + opt_size + ETH_ALEN);
 604         else
 605                 pseudo.length = htonl(ns_size);
 606         pseudo.next = htonl(IPPROTO_ICMPV6);
 607
 608         /* Generate checksum */
 609
 610         checksum = inet_checksum(&pseudo, sizeof(pseudo), ~0);
 611         checksum = inet_checksum(&ns, ns_size, checksum);
 612         if(has_opt) {
 613                 checksum = inet_checksum(&opt, opt_size, checksum);
 614                 checksum = inet_checksum(packet->data + ether_size + ip6_size + ns_size + opt_size, ETH_ALEN, checksum);
 615         }
 616
 617         ns.nd_ns_hdr.icmp6_cksum = checksum;
 618
 619         /* Copy structs on stack back to packet */
 620
 621         memcpy(packet->data + ether_size, &ip6, ip6_size);
 622         memcpy(packet->data + ether_size + ip6_size, &ns, ns_size);
 623         if(has_opt)
 624                 memcpy(packet->data + ether_size + ip6_size + ns_size, &opt, opt_size);
 625
 626         send_packet(source, packet);
 627 }
 628
 629 static void route_ipv6(node_t *source, vpn_packet_t *packet) {
 630         cp();
 631
 632         if(!checklength(source, packet, ether_size + ip6_size))
 633                 return;
 634
 635         if(packet->data[20] == IPPROTO_ICMPV6 && checklength(source, packet, ether_size + ip6_size + icmp6_size) && packet->data[54] == ND_NEIGHBOR_SOLICIT) {
 636                 route_neighborsol(source, packet);
 637                 return;
 638         }
 639
 640         if(packet->data[38] == 255)
 641                 broadcast_packet(source, packet);
 642         else
 643                 route_ipv6_unicast(source, packet);
 644 }
 645
 646 /* RFC 826 */
 647
 648 static void route_arp(node_t *source, vpn_packet_t *packet) {
 649         struct ether_arp arp;
 650         subnet_t *subnet;
 651         struct in_addr addr;
 652
 653         cp();
 654
 655         if(!checklength(source, packet, ether_size + arp_size))
 656                 return;
 657
 658         if(source != myself) {
 659                 ifdebug(TRAFFIC) logger(LOG_WARNING, _("Got ARP request from %s (%s) while in router mode!"), source->name, source->hostname);
 660                 return;
 661         }
 662
 663         /* First, snatch the source address from the ARP packet */
 664
 665         if(overwrite_mac)
 666                 memcpy(mymac.x, packet->data + ETH_ALEN, ETH_ALEN);
 667
 668         /* Copy headers from packet to structs on the stack */
 669
 670         memcpy(&arp, packet->data + ether_size, arp_size);
 671
 672         /* Check if this is a valid ARP request */
 673
 674         if(ntohs(arp.arp_hrd) != ARPHRD_ETHER || ntohs(arp.arp_pro) != ETH_P_IP ||
 675            arp.arp_hln != ETH_ALEN || arp.arp_pln != sizeof(addr) || ntohs(arp.arp_op) != ARPOP_REQUEST) {
 676                 ifdebug(TRAFFIC) logger(LOG_WARNING, _("Cannot route packet: received unknown type ARP request"));
 677                 return;
 678         }
 679
 680         /* Check if the IPv4 address exists on the VPN */
 681
 682         subnet = lookup_subnet_ipv4((ipv4_t *) &arp.arp_tpa);
 683
 684         if(!subnet) {
 685                 ifdebug(TRAFFIC) logger(LOG_WARNING, _("Cannot route packet: ARP request for unknown address %d.%d.%d.%d"),
 686                                    arp.arp_tpa[0], arp.arp_tpa[1], arp.arp_tpa[2],
 687                                    arp.arp_tpa[3]);
 688                 return;
 689         }
 690
 691         /* Check if it is for our own subnet */
 692
 693         if(subnet->owner == myself)
 694                 return;                                 /* silently ignore */
 695
 696         memcpy(packet->data, packet->data + ETH_ALEN, ETH_ALEN);        /* copy destination address */
 697         packet->data[ETH_ALEN * 2 - 1] ^= 0xFF; /* mangle source address so it looks like it's not from us */
 698
 699         memcpy(&addr, arp.arp_tpa, sizeof(addr));       /* save protocol addr */
 700         memcpy(arp.arp_tpa, arp.arp_spa, sizeof(addr)); /* swap destination and source protocol address */
 701         memcpy(arp.arp_spa, &addr, sizeof(addr));       /* ... */
 702
 703         memcpy(arp.arp_tha, arp.arp_sha, ETH_ALEN);     /* set target hard/proto addr */
 704         memcpy(arp.arp_sha, packet->data + ETH_ALEN, ETH_ALEN); /* add fake source hard addr */
 705         arp.arp_op = htons(ARPOP_REPLY);
 706
 707         /* Copy structs on stack back to packet */
 708
 709         memcpy(packet->data + ether_size, &arp, arp_size);
 710
 711         send_packet(source, packet);
 712 }
 713
 714 static void route_mac(node_t *source, vpn_packet_t *packet) {
 715         subnet_t *subnet;
 716         mac_t dest;
 717
 718         cp();
 719
 720
 721         /* Learn source address */
 722
 723         if(source == myself) {
 724                 mac_t src;
 725                 memcpy(&src, &packet->data[6], sizeof src);
 726                 learn_mac(&src);
 727         }
 728
 729         /* Lookup destination address */
 730
 731         memcpy(&dest, &packet->data[0], sizeof dest);
 732         subnet = lookup_subnet_mac(&dest);
 733
 734         if(!subnet) {
 735                 broadcast_packet(source, packet);
 736                 return;
 737         }
 738
 739         if(subnet->owner == source) {
 740                 ifdebug(TRAFFIC) logger(LOG_WARNING, _("Packet looping back to %s (%s)!"), source->name, source->hostname);
 741                 return;
 742         }
 743
 744         // Handle packets larger than PMTU
 745
 746         node_t *via = (subnet->owner->via == myself) ? subnet->owner->nexthop : subnet->owner->via;
 747
 748         if(via && packet->len > via->mtu && via != myself) {
 749                 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);
 750                 uint16_t type = packet->data[12] << 8 | packet->data[13];
 751                 if(type == ETH_P_IP) {
 752                         if(packet->data[20] & 0x40) {
 753                                 packet->len = via->mtu;
 754                                 route_ipv4_unreachable(source, packet, ICMP_DEST_UNREACH, ICMP_FRAG_NEEDED);
 755                         } else {
 756                                 fragment_ipv4_packet(via, packet);
 757                         }
 758                         return;
 759                 } else if(type == ETH_P_IPV6) {
 760                         packet->len = via->mtu;
 761                         route_ipv6_unreachable(source, packet, ICMP6_PACKET_TOO_BIG, 0);
 762                         return;
 763                 }
 764         }
 765
 766         send_packet(subnet->owner, packet);
 767 }
 768
 769
 770 void route(node_t *source, vpn_packet_t *packet) {
 771         cp();
 772
 773         if(!checklength(source, packet, ether_size))
 774                 return;
 775
 776         switch (routing_mode) {
 777                 case RMODE_ROUTER:
 778                         {
 779                                 uint16_t type = packet->data[12] << 8 | packet->data[13];
 780
 781                                 switch (type) {
 782                                         case ETH_P_ARP:
 783                                                 route_arp(source, packet);
 784                                                 break;
 785
 786                                         case ETH_P_IP:
 787                                                 route_ipv4(source, packet);
 788                                                 break;
 789
 790                                         case ETH_P_IPV6:
 791                                                 route_ipv6(source, packet);
 792                                                 break;
 793
 794                                         default:
 795                                                 ifdebug(TRAFFIC) logger(LOG_WARNING, _("Cannot route packet from %s (%s): unknown type %hx"), source->name, source->hostname, type);
 796                                                 break;
 797                                 }
 798                         }
 799                         break;
 800
 801                 case RMODE_SWITCH:
 802                         route_mac(source, packet);
 803                         break;
 804
 805                 case RMODE_HUB:
 806                         broadcast_packet(source, packet);
 807                         break;
 808         }
 809 }