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

   1 /*
   2     route.c -- routing
   3     Copyright (C) 2000-2005 Ivo Timmermans,
   4                   2000-2012 Guus Sliepen <guus@tinc-vpn.org>
   5
   6     This program is free software; you can redistribute it and/or modify
   7     it under the terms of the GNU General Public License as published by
   8     the Free Software Foundation; either version 2 of the License, or
   9     (at your option) any later version.
  10
  11     This program is distributed in the hope that it will be useful,
  12     but WITHOUT ANY WARRANTY; without even the implied warranty of
  13     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14     GNU General Public License for more details.
  15
  16     You should have received a copy of the GNU General Public License along
  17     with this program; if not, write to the Free Software Foundation, Inc.,
  18     51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  19 */
  20
  21 #include "system.h"
  22
  23 #include "connection.h"
  24 #include "control_common.h"
  25 #include "ethernet.h"
  26 #include "ipv4.h"
  27 #include "ipv6.h"
  28 #include "logger.h"
  29 #include "meta.h"
  30 #include "net.h"
  31 #include "protocol.h"
  32 #include "route.h"
  33 #include "subnet.h"
  34 #include "utils.h"
  35
  36 rmode_t routing_mode = RMODE_ROUTER;
  37 fmode_t forwarding_mode = FMODE_INTERNAL;
  38 bmode_t broadcast_mode = BMODE_MST;
  39 bool decrement_ttl = false;
  40 bool directonly = false;
  41 bool priorityinheritance = false;
  42 int macexpire = 600;
  43 bool overwrite_mac = false;
  44 mac_t mymac = {{0xFE, 0xFD, 0, 0, 0, 0}};
  45 bool pcap = false;
  46
  47 /* Sizes of various headers */
  48
  49 static const size_t ether_size = sizeof(struct ether_header);
  50 static const size_t arp_size = sizeof(struct ether_arp);
  51 static const size_t ip_size = sizeof(struct ip);
  52 static const size_t icmp_size = sizeof(struct icmp) - sizeof(struct ip);
  53 static const size_t ip6_size = sizeof(struct ip6_hdr);
  54 static const size_t icmp6_size = sizeof(struct icmp6_hdr);
  55 static const size_t ns_size = sizeof(struct nd_neighbor_solicit);
  56 static const size_t opt_size = sizeof(struct nd_opt_hdr);
  57
  58 #ifndef MAX
  59 #define MAX(a, b) ((a) > (b) ? (a) : (b))
  60 #endif
  61
  62 static struct event age_subnets_event;
  63
  64 /* RFC 1071 */
  65
  66 static uint16_t inet_checksum(void *data, int len, uint16_t prevsum) {
  67         uint16_t *p = data;
  68         uint32_t checksum = prevsum ^ 0xFFFF;
  69
  70         while(len >= 2) {
  71                 checksum += *p++;
  72                 len -= 2;
  73         }
  74
  75         if(len)
  76                 checksum += *(uint8_t *)p;
  77
  78         while(checksum >> 16)
  79                 checksum = (checksum & 0xFFFF) + (checksum >> 16);
  80
  81         return ~checksum;
  82 }
  83
  84 static bool ratelimit(int frequency) {
  85         static time_t lasttime = 0;
  86         static int count = 0;
  87         time_t now = time(NULL);
  88
  89         if(lasttime == now) {
  90                 if(count >= frequency)
  91                         return true;
  92         } else {
  93                 lasttime = now;
  94                 count = 0;
  95         }
  96
  97         count++;
  98         return false;
  99 }
 100
 101 static bool checklength(node_t *source, vpn_packet_t *packet, length_t length) {
 102         if(packet->len < length) {
 103                 logger(DEBUG_TRAFFIC, LOG_WARNING, "Got too short packet from %s (%s)", source->name, source->hostname);
 104                 return false;
 105         } else
 106                 return true;
 107 }
 108
 109 static void clamp_mss(const node_t *source, const node_t *via, vpn_packet_t *packet) {
 110         if(!source || !via || !(via->options & OPTION_CLAMP_MSS))
 111                 return;
 112
 113         uint16_t mtu = source->mtu;
 114         if(via != myself && via->mtu < mtu)
 115                 mtu = via->mtu;
 116
 117         /* Find TCP header */
 118         int start = 0;
 119         uint16_t type = packet->data[12] << 8 | packet->data[13];
 120
 121         if(type == ETH_P_IP && packet->data[23] == 6)
 122                 start = 14 + (packet->data[14] & 0xf) * 4;
 123         else if(type == ETH_P_IPV6 && packet->data[20] == 6)
 124                 start = 14 + 40;
 125
 126         if(!start || packet->len <= start + 20)
 127                 return;
 128
 129         /* Use data offset field to calculate length of options field */
 130         int len = ((packet->data[start + 12] >> 4) - 5) * 4;
 131
 132         if(packet->len < start + 20 + len)
 133                 return;
 134
 135         /* Search for MSS option header */
 136         for(int i = 0; i < len;) {
 137                 if(packet->data[start + 20 + i] == 0)
 138                         break;
 139
 140                 if(packet->data[start + 20 + i] == 1) {
 141                         i++;
 142                         continue;
 143                 }
 144
 145                 if(i > len - 2 || i > len - packet->data[start + 21 + i])
 146                         break;
 147
 148                 if(packet->data[start + 20 + i] != 2) {
 149                         if(packet->data[start + 21 + i] < 2)
 150                                 break;
 151                         i += packet->data[start + 21 + i];
 152                         continue;
 153                 }
 154
 155                 if(packet->data[start + 21] != 4)
 156                         break;
 157
 158                 /* Found it */
 159                 uint16_t oldmss = packet->data[start + 22 + i] << 8 | packet->data[start + 23 + i];
 160                 uint16_t newmss = mtu - start - 20;
 161                 uint16_t csum = packet->data[start + 16] << 8 | packet->data[start + 17];
 162
 163                 if(oldmss <= newmss)
 164                         break;
 165
 166                 logger(DEBUG_TRAFFIC, LOG_INFO, "Clamping MSS of packet from %s to %s to %d", source->name, via->name, newmss);
 167
 168                 /* Update the MSS value and the checksum */
 169                 packet->data[start + 22 + i] = newmss >> 8;
 170                 packet->data[start + 23 + i] = newmss & 0xff;
 171                 csum ^= 0xffff;
 172                 csum -= oldmss;
 173                 csum += newmss;
 174                 csum ^= 0xffff;
 175                 packet->data[start + 16] = csum >> 8;
 176                 packet->data[start + 17] = csum & 0xff;
 177                 break;
 178         }
 179 }
 180
 181 static void swap_mac_addresses(vpn_packet_t *packet) {
 182         mac_t tmp;
 183         memcpy(&tmp, &packet->data[0], sizeof tmp);
 184         memcpy(&packet->data[0], &packet->data[6], sizeof tmp);
 185         memcpy(&packet->data[6], &tmp, sizeof tmp);
 186 }
 187
 188 static void age_subnets(int fd, short events, void *data) {
 189         bool left = false;
 190         time_t now = time(NULL);
 191
 192         for splay_each(subnet_t, s, myself->subnet_tree) {
 193                 if(s->expires && s->expires < now) {
 194                         if(debug_level >= DEBUG_TRAFFIC) {
 195                                 char netstr[MAXNETSTR];
 196                                 if(net2str(netstr, sizeof netstr, s))
 197                                         logger(DEBUG_TRAFFIC, LOG_INFO, "Subnet %s expired", netstr);
 198                         }
 199
 200                         for list_each(connection_t, c, connection_list)
 201                                 if(c->status.active)
 202                                         send_del_subnet(c, s);
 203
 204                         subnet_del(myself, s);
 205                 } else {
 206                         if(s->expires)
 207                                 left = true;
 208                 }
 209         }
 210
 211         if(left)
 212                 event_add(&age_subnets_event, &(struct timeval){10, 0});
 213 }
 214
 215 static void learn_mac(mac_t *address) {
 216         subnet_t *subnet = lookup_subnet_mac(myself, address);
 217
 218         /* If we don't know this MAC address yet, store it */
 219
 220         if(!subnet) {
 221                 logger(DEBUG_TRAFFIC, LOG_INFO, "Learned new MAC address %hx:%hx:%hx:%hx:%hx:%hx",
 222                                    address->x[0], address->x[1], address->x[2], address->x[3],
 223                                    address->x[4], address->x[5]);
 224
 225                 subnet = new_subnet();
 226                 subnet->type = SUBNET_MAC;
 227                 subnet->expires = time(NULL) + macexpire;
 228                 subnet->net.mac.address = *address;
 229                 subnet->weight = 10;
 230                 subnet_add(myself, subnet);
 231                 subnet_update(myself, subnet, true);
 232
 233                 /* And tell all other tinc daemons it's our MAC */
 234
 235                 for list_each(connection_t, c, connection_list)
 236                         if(c->status.active)
 237                                 send_add_subnet(c, subnet);
 238
 239                 if(!timeout_initialized(&age_subnets_event))
 240                         timeout_set(&age_subnets_event, age_subnets, NULL);
 241                 event_add(&age_subnets_event, &(struct timeval){10, 0});
 242         } else {
 243                 if(subnet->expires)
 244                         subnet->expires = time(NULL) + macexpire;
 245         }
 246 }
 247
 248 /* RFC 792 */
 249
 250 static void route_ipv4_unreachable(node_t *source, vpn_packet_t *packet, uint8_t type, uint8_t code) {
 251         struct ip ip = {0};
 252         struct icmp icmp = {0};
 253
 254         struct in_addr ip_src;
 255         struct in_addr ip_dst;
 256         uint32_t oldlen;
 257
 258         if(ratelimit(3))
 259                 return;
 260
 261         /* Swap Ethernet source and destination addresses */
 262
 263         swap_mac_addresses(packet);
 264
 265         /* Copy headers from packet into properly aligned structs on the stack */
 266
 267         memcpy(&ip, packet->data + ether_size, ip_size);
 268
 269         /* Remember original source and destination */
 270
 271         ip_src = ip.ip_src;
 272         ip_dst = ip.ip_dst;
 273
 274         oldlen = packet->len - ether_size;
 275
 276         if(type == ICMP_DEST_UNREACH && code == ICMP_FRAG_NEEDED)
 277                 icmp.icmp_nextmtu = htons(packet->len - ether_size);
 278
 279         if(oldlen >= IP_MSS - ip_size - icmp_size)
 280                 oldlen = IP_MSS - ip_size - icmp_size;
 281
 282         /* Copy first part of original contents to ICMP message */
 283
 284         memmove(packet->data + ether_size + ip_size + icmp_size, packet->data + ether_size, oldlen);
 285
 286         /* Fill in IPv4 header */
 287
 288         ip.ip_v = 4;
 289         ip.ip_hl = ip_size / 4;
 290         ip.ip_tos = 0;
 291         ip.ip_len = htons(ip_size + icmp_size + oldlen);
 292         ip.ip_id = 0;
 293         ip.ip_off = 0;
 294         ip.ip_ttl = 255;
 295         ip.ip_p = IPPROTO_ICMP;
 296         ip.ip_sum = 0;
 297         ip.ip_src = ip_dst;
 298         ip.ip_dst = ip_src;
 299
 300         ip.ip_sum = inet_checksum(&ip, ip_size, ~0);
 301
 302         /* Fill in ICMP header */
 303
 304         icmp.icmp_type = type;
 305         icmp.icmp_code = code;
 306         icmp.icmp_cksum = 0;
 307
 308         icmp.icmp_cksum = inet_checksum(&icmp, icmp_size, ~0);
 309         icmp.icmp_cksum = inet_checksum(packet->data + ether_size + ip_size + icmp_size, oldlen, icmp.icmp_cksum);
 310
 311         /* Copy structs on stack back to packet */
 312
 313         memcpy(packet->data + ether_size, &ip, ip_size);
 314         memcpy(packet->data + ether_size + ip_size, &icmp, icmp_size);
 315
 316         packet->len = ether_size + ip_size + icmp_size + oldlen;
 317
 318         send_packet(source, packet);
 319 }
 320
 321 /* RFC 791 */
 322
 323 static void fragment_ipv4_packet(node_t *dest, vpn_packet_t *packet) {
 324         struct ip ip;
 325         vpn_packet_t fragment;
 326         int len, maxlen, todo;
 327         uint8_t *offset;
 328         uint16_t ip_off, origf;
 329
 330         memcpy(&ip, packet->data + ether_size, ip_size);
 331         fragment.priority = packet->priority;
 332
 333         if(ip.ip_hl != ip_size / 4)
 334                 return;
 335
 336         todo = ntohs(ip.ip_len) - ip_size;
 337
 338         if(ether_size + ip_size + todo != packet->len) {
 339                 logger(DEBUG_TRAFFIC, LOG_WARNING, "Length of packet (%d) doesn't match length in IPv4 header (%d)", packet->len, (int)(ether_size + ip_size + todo));
 340                 return;
 341         }
 342
 343         logger(DEBUG_TRAFFIC, LOG_INFO, "Fragmenting packet of %d bytes to %s (%s)", packet->len, dest->name, dest->hostname);
 344
 345         offset = packet->data + ether_size + ip_size;
 346         maxlen = (dest->mtu - ether_size - ip_size) & ~0x7;
 347         ip_off = ntohs(ip.ip_off);
 348         origf = ip_off & ~IP_OFFMASK;
 349         ip_off &= IP_OFFMASK;
 350
 351         while(todo) {
 352                 len = todo > maxlen ? maxlen : todo;
 353                 memcpy(fragment.data + ether_size + ip_size, offset, len);
 354                 todo -= len;
 355                 offset += len;
 356
 357                 ip.ip_len = htons(ip_size + len);
 358                 ip.ip_off = htons(ip_off | origf | (todo ? IP_MF : 0));
 359                 ip.ip_sum = 0;
 360                 ip.ip_sum = inet_checksum(&ip, ip_size, ~0);
 361                 memcpy(fragment.data, packet->data, ether_size);
 362                 memcpy(fragment.data + ether_size, &ip, ip_size);
 363                 fragment.len = ether_size + ip_size + len;
 364
 365                 send_packet(dest, &fragment);
 366
 367                 ip_off += len / 8;
 368         }
 369 }
 370
 371 static void route_ipv4_unicast(node_t *source, vpn_packet_t *packet) {
 372         subnet_t *subnet;
 373         node_t *via;
 374         ipv4_t dest;
 375
 376         memcpy(&dest, &packet->data[30], sizeof dest);
 377         subnet = lookup_subnet_ipv4(&dest);
 378
 379         if(!subnet) {
 380                 logger(DEBUG_TRAFFIC, LOG_WARNING, "Cannot route packet from %s (%s): unknown IPv4 destination address %d.%d.%d.%d",
 381                                 source->name, source->hostname,
 382                                 dest.x[0],
 383                                 dest.x[1],
 384                                 dest.x[2],
 385                                 dest.x[3]);
 386
 387                 route_ipv4_unreachable(source, packet, ICMP_DEST_UNREACH, ICMP_NET_UNKNOWN);
 388                 return;
 389         }
 390
 391         if(subnet->owner == source) {
 392                 logger(DEBUG_TRAFFIC, LOG_WARNING, "Packet looping back to %s (%s)!", source->name, source->hostname);
 393                 return;
 394         }
 395
 396         if(!subnet->owner->status.reachable)
 397                 return route_ipv4_unreachable(source, packet, ICMP_DEST_UNREACH, ICMP_NET_UNREACH);
 398
 399         if(forwarding_mode == FMODE_OFF && source != myself && subnet->owner != myself)
 400                 return route_ipv4_unreachable(source, packet, ICMP_DEST_UNREACH, ICMP_NET_ANO);
 401
 402         if(priorityinheritance)
 403                 packet->priority = packet->data[15];
 404
 405         via = (subnet->owner->via == myself) ? subnet->owner->nexthop : subnet->owner->via;
 406
 407         if(via == source) {
 408                 logger(DEBUG_TRAFFIC, LOG_ERR, "Routing loop for packet from %s (%s)!", source->name, source->hostname);
 409                 return;
 410         }
 411
 412         if(directonly && subnet->owner != via)
 413                 return route_ipv4_unreachable(source, packet, ICMP_DEST_UNREACH, ICMP_NET_ANO);
 414
 415         if(via && packet->len > MAX(via->mtu, 590) && via != myself) {
 416                 logger(DEBUG_TRAFFIC, LOG_INFO, "Packet for %s (%s) length %d larger than MTU %d", subnet->owner->name, subnet->owner->hostname, packet->len, via->mtu);
 417                 if(packet->data[20] & 0x40) {
 418                         packet->len = MAX(via->mtu, 590);
 419                         route_ipv4_unreachable(source, packet, ICMP_DEST_UNREACH, ICMP_FRAG_NEEDED);
 420                 } else {
 421                         fragment_ipv4_packet(via, packet);
 422                 }
 423
 424                 return;
 425         }
 426
 427         clamp_mss(source, via, packet);
 428
 429         send_packet(subnet->owner, packet);
 430 }
 431
 432 static void route_ipv4(node_t *source, vpn_packet_t *packet) {
 433         if(!checklength(source, packet, ether_size + ip_size))
 434                 return;
 435
 436         if(broadcast_mode && (((packet->data[30] & 0xf0) == 0xe0) || (
 437                         packet->data[30] == 255 &&
 438                         packet->data[31] == 255 &&
 439                         packet->data[32] == 255 &&
 440                         packet->data[33] == 255)))
 441                 broadcast_packet(source, packet);
 442         else
 443                 route_ipv4_unicast(source, packet);
 444 }
 445
 446 /* RFC 2463 */
 447
 448 static void route_ipv6_unreachable(node_t *source, vpn_packet_t *packet, uint8_t type, uint8_t code) {
 449         struct ip6_hdr ip6;
 450         struct icmp6_hdr icmp6 = {0};
 451         uint16_t checksum;
 452
 453         struct {
 454                 struct in6_addr ip6_src;        /* source address */
 455                 struct in6_addr ip6_dst;        /* destination address */
 456                 uint32_t length;
 457                 uint32_t next;
 458         } pseudo;
 459
 460         if(ratelimit(3))
 461                 return;
 462
 463         /* Swap Ethernet source and destination addresses */
 464
 465         swap_mac_addresses(packet);
 466
 467         /* Copy headers from packet to structs on the stack */
 468
 469         memcpy(&ip6, packet->data + ether_size, ip6_size);
 470
 471         /* Remember original source and destination */
 472
 473         pseudo.ip6_src = ip6.ip6_dst;
 474         pseudo.ip6_dst = ip6.ip6_src;
 475
 476         pseudo.length = packet->len - ether_size;
 477
 478         if(type == ICMP6_PACKET_TOO_BIG)
 479                 icmp6.icmp6_mtu = htonl(pseudo.length);
 480
 481         if(pseudo.length >= IP_MSS - ip6_size - icmp6_size)
 482                 pseudo.length = IP_MSS - ip6_size - icmp6_size;
 483
 484         /* Copy first part of original contents to ICMP message */
 485
 486         memmove(packet->data + ether_size + ip6_size + icmp6_size, packet->data + ether_size, pseudo.length);
 487
 488         /* Fill in IPv6 header */
 489
 490         ip6.ip6_flow = htonl(0x60000000UL);
 491         ip6.ip6_plen = htons(icmp6_size + pseudo.length);
 492         ip6.ip6_nxt = IPPROTO_ICMPV6;
 493         ip6.ip6_hlim = 255;
 494         ip6.ip6_src = pseudo.ip6_src;
 495         ip6.ip6_dst = pseudo.ip6_dst;
 496
 497         /* Fill in ICMP header */
 498
 499         icmp6.icmp6_type = type;
 500         icmp6.icmp6_code = code;
 501         icmp6.icmp6_cksum = 0;
 502
 503         /* Create pseudo header */
 504
 505         pseudo.length = htonl(icmp6_size + pseudo.length);
 506         pseudo.next = htonl(IPPROTO_ICMPV6);
 507
 508         /* Generate checksum */
 509
 510         checksum = inet_checksum(&pseudo, sizeof pseudo, ~0);
 511         checksum = inet_checksum(&icmp6, icmp6_size, checksum);
 512         checksum = inet_checksum(packet->data + ether_size + ip6_size + icmp6_size, ntohl(pseudo.length) - icmp6_size, checksum);
 513
 514         icmp6.icmp6_cksum = checksum;
 515
 516         /* Copy structs on stack back to packet */
 517
 518         memcpy(packet->data + ether_size, &ip6, ip6_size);
 519         memcpy(packet->data + ether_size + ip6_size, &icmp6, icmp6_size);
 520
 521         packet->len = ether_size + ip6_size + ntohl(pseudo.length);
 522
 523         send_packet(source, packet);
 524 }
 525
 526 static void route_ipv6_unicast(node_t *source, vpn_packet_t *packet) {
 527         subnet_t *subnet;
 528         node_t *via;
 529         ipv6_t dest;
 530
 531         memcpy(&dest, &packet->data[38], sizeof dest);
 532         subnet = lookup_subnet_ipv6(&dest);
 533
 534         if(!subnet) {
 535                 logger(DEBUG_TRAFFIC, LOG_WARNING, "Cannot route packet from %s (%s): unknown IPv6 destination address %hx:%hx:%hx:%hx:%hx:%hx:%hx:%hx",
 536                                 source->name, source->hostname,
 537                                 ntohs(dest.x[0]),
 538                                 ntohs(dest.x[1]),
 539                                 ntohs(dest.x[2]),
 540                                 ntohs(dest.x[3]),
 541                                 ntohs(dest.x[4]),
 542                                 ntohs(dest.x[5]),
 543                                 ntohs(dest.x[6]),
 544                                 ntohs(dest.x[7]));
 545
 546                 route_ipv6_unreachable(source, packet, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_ADDR);
 547                 return;
 548         }
 549
 550         if(subnet->owner == source) {
 551                 logger(DEBUG_TRAFFIC, LOG_WARNING, "Packet looping back to %s (%s)!", source->name, source->hostname);
 552                 return;
 553         }
 554
 555         if(!subnet->owner->status.reachable)
 556                 return route_ipv6_unreachable(source, packet, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_NOROUTE);
 557
 558         if(forwarding_mode == FMODE_OFF && source != myself && subnet->owner != myself)
 559                 return route_ipv6_unreachable(source, packet, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_ADMIN);
 560
 561         via = (subnet->owner->via == myself) ? subnet->owner->nexthop : subnet->owner->via;
 562
 563         if(via == source) {
 564                 logger(DEBUG_TRAFFIC, LOG_ERR, "Routing loop for packet from %s (%s)!", source->name, source->hostname);
 565                 return;
 566         }
 567
 568         if(directonly && subnet->owner != via)
 569                 return route_ipv6_unreachable(source, packet, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_ADMIN);
 570
 571         if(via && packet->len > MAX(via->mtu, 1294) && via != myself) {
 572                 logger(DEBUG_TRAFFIC, LOG_INFO, "Packet for %s (%s) length %d larger than MTU %d", subnet->owner->name, subnet->owner->hostname, packet->len, via->mtu);
 573                 packet->len = MAX(via->mtu, 1294);
 574                 route_ipv6_unreachable(source, packet, ICMP6_PACKET_TOO_BIG, 0);
 575                 return;
 576         }
 577
 578         clamp_mss(source, via, packet);
 579
 580         send_packet(subnet->owner, packet);
 581 }
 582
 583 /* RFC 2461 */
 584
 585 static void route_neighborsol(node_t *source, vpn_packet_t *packet) {
 586         struct ip6_hdr ip6;
 587         struct nd_neighbor_solicit ns;
 588         struct nd_opt_hdr opt;
 589         subnet_t *subnet;
 590         uint16_t checksum;
 591         bool has_opt;
 592
 593         struct {
 594                 struct in6_addr ip6_src;
 595                 struct in6_addr ip6_dst;
 596                 uint32_t length;
 597                 uint32_t next;
 598         } pseudo;
 599
 600         if(!checklength(source, packet, ether_size + ip6_size + ns_size))
 601                 return;
 602
 603         has_opt = packet->len >= ether_size + ip6_size + ns_size + opt_size + ETH_ALEN;
 604
 605         if(source != myself) {
 606                 logger(DEBUG_TRAFFIC, LOG_WARNING, "Got neighbor solicitation request from %s (%s) while in router mode!", source->name, source->hostname);
 607                 return;
 608         }
 609
 610         /* Copy headers from packet to structs on the stack */
 611
 612         memcpy(&ip6, packet->data + ether_size, ip6_size);
 613         memcpy(&ns, packet->data + ether_size + ip6_size, ns_size);
 614         if(has_opt)
 615                 memcpy(&opt, packet->data + ether_size + ip6_size + ns_size, opt_size);
 616
 617         /* First, snatch the source address from the neighbor solicitation packet */
 618
 619         if(overwrite_mac)
 620                 memcpy(mymac.x, packet->data + ETH_ALEN, ETH_ALEN);
 621
 622         /* Check if this is a valid neighbor solicitation request */
 623
 624         if(ns.nd_ns_hdr.icmp6_type != ND_NEIGHBOR_SOLICIT ||
 625            (has_opt && opt.nd_opt_type != ND_OPT_SOURCE_LINKADDR)) {
 626                 logger(DEBUG_TRAFFIC, LOG_WARNING, "Cannot route packet: received unknown type neighbor solicitation request");
 627                 return;
 628         }
 629
 630         /* Create pseudo header */
 631
 632         pseudo.ip6_src = ip6.ip6_src;
 633         pseudo.ip6_dst = ip6.ip6_dst;
 634         if(has_opt)
 635                 pseudo.length = htonl(ns_size + opt_size + ETH_ALEN);
 636         else
 637                 pseudo.length = htonl(ns_size);
 638         pseudo.next = htonl(IPPROTO_ICMPV6);
 639
 640         /* Generate checksum */
 641
 642         checksum = inet_checksum(&pseudo, sizeof pseudo, ~0);
 643         checksum = inet_checksum(&ns, ns_size, checksum);
 644         if(has_opt) {
 645                 checksum = inet_checksum(&opt, opt_size, checksum);
 646                 checksum = inet_checksum(packet->data + ether_size + ip6_size + ns_size + opt_size, ETH_ALEN, checksum);
 647         }
 648
 649         if(checksum) {
 650                 logger(DEBUG_TRAFFIC, LOG_WARNING, "Cannot route packet: checksum error for neighbor solicitation request");
 651                 return;
 652         }
 653
 654         /* Check if the IPv6 address exists on the VPN */
 655
 656         subnet = lookup_subnet_ipv6((ipv6_t *) &ns.nd_ns_target);
 657
 658         if(!subnet) {
 659                 logger(DEBUG_TRAFFIC, LOG_WARNING, "Cannot route packet: neighbor solicitation request for unknown address %hx:%hx:%hx:%hx:%hx:%hx:%hx:%hx",
 660                                    ntohs(((uint16_t *) &ns.nd_ns_target)[0]),
 661                                    ntohs(((uint16_t *) &ns.nd_ns_target)[1]),
 662                                    ntohs(((uint16_t *) &ns.nd_ns_target)[2]),
 663                                    ntohs(((uint16_t *) &ns.nd_ns_target)[3]),
 664                                    ntohs(((uint16_t *) &ns.nd_ns_target)[4]),
 665                                    ntohs(((uint16_t *) &ns.nd_ns_target)[5]),
 666                                    ntohs(((uint16_t *) &ns.nd_ns_target)[6]),
 667                                    ntohs(((uint16_t *) &ns.nd_ns_target)[7]));
 668
 669                 return;
 670         }
 671
 672         /* Check if it is for our own subnet */
 673
 674         if(subnet->owner == myself)
 675                 return;                                          /* silently ignore */
 676
 677         /* Create neighbor advertation reply */
 678
 679         memcpy(packet->data, packet->data + ETH_ALEN, ETH_ALEN); /* copy destination address */
 680         packet->data[ETH_ALEN * 2 - 1] ^= 0xFF;                  /* mangle source address so it looks like it's not from us */
 681
 682         ip6.ip6_dst = ip6.ip6_src;                               /* swap destination and source protocoll address */
 683         ip6.ip6_src = ns.nd_ns_target;
 684
 685         if(has_opt)
 686                 memcpy(packet->data + ether_size + ip6_size + ns_size + opt_size, packet->data + ETH_ALEN, ETH_ALEN);   /* add fake source hard addr */
 687
 688         ns.nd_ns_cksum = 0;
 689         ns.nd_ns_type = ND_NEIGHBOR_ADVERT;
 690         ns.nd_ns_reserved = htonl(0x40000000UL);                 /* Set solicited flag */
 691         opt.nd_opt_type = ND_OPT_TARGET_LINKADDR;
 692
 693         /* Create pseudo header */
 694
 695         pseudo.ip6_src = ip6.ip6_src;
 696         pseudo.ip6_dst = ip6.ip6_dst;
 697         if(has_opt)
 698                 pseudo.length = htonl(ns_size + opt_size + ETH_ALEN);
 699         else
 700                 pseudo.length = htonl(ns_size);
 701         pseudo.next = htonl(IPPROTO_ICMPV6);
 702
 703         /* Generate checksum */
 704
 705         checksum = inet_checksum(&pseudo, sizeof pseudo, ~0);
 706         checksum = inet_checksum(&ns, ns_size, checksum);
 707         if(has_opt) {
 708                 checksum = inet_checksum(&opt, opt_size, checksum);
 709                 checksum = inet_checksum(packet->data + ether_size + ip6_size + ns_size + opt_size, ETH_ALEN, checksum);
 710         }
 711
 712         ns.nd_ns_hdr.icmp6_cksum = checksum;
 713
 714         /* Copy structs on stack back to packet */
 715
 716         memcpy(packet->data + ether_size, &ip6, ip6_size);
 717         memcpy(packet->data + ether_size + ip6_size, &ns, ns_size);
 718         if(has_opt)
 719                 memcpy(packet->data + ether_size + ip6_size + ns_size, &opt, opt_size);
 720
 721         send_packet(source, packet);
 722 }
 723
 724 static void route_ipv6(node_t *source, vpn_packet_t *packet) {
 725         if(!checklength(source, packet, ether_size + ip6_size))
 726                 return;
 727
 728         if(packet->data[20] == IPPROTO_ICMPV6 && checklength(source, packet, ether_size + ip6_size + icmp6_size) && packet->data[54] == ND_NEIGHBOR_SOLICIT) {
 729                 route_neighborsol(source, packet);
 730                 return;
 731         }
 732
 733         if(broadcast_mode && packet->data[38] == 255)
 734                 broadcast_packet(source, packet);
 735         else
 736                 route_ipv6_unicast(source, packet);
 737 }
 738
 739 /* RFC 826 */
 740
 741 static void route_arp(node_t *source, vpn_packet_t *packet) {
 742         struct ether_arp arp;
 743         subnet_t *subnet;
 744         struct in_addr addr;
 745
 746         if(!checklength(source, packet, ether_size + arp_size))
 747                 return;
 748
 749         if(source != myself) {
 750                 logger(DEBUG_TRAFFIC, LOG_WARNING, "Got ARP request from %s (%s) while in router mode!", source->name, source->hostname);
 751                 return;
 752         }
 753
 754         /* First, snatch the source address from the ARP packet */
 755
 756         if(overwrite_mac)
 757                 memcpy(mymac.x, packet->data + ETH_ALEN, ETH_ALEN);
 758
 759         /* Copy headers from packet to structs on the stack */
 760
 761         memcpy(&arp, packet->data + ether_size, arp_size);
 762
 763         /* Check if this is a valid ARP request */
 764
 765         if(ntohs(arp.arp_hrd) != ARPHRD_ETHER || ntohs(arp.arp_pro) != ETH_P_IP ||
 766            arp.arp_hln != ETH_ALEN || arp.arp_pln != sizeof addr || ntohs(arp.arp_op) != ARPOP_REQUEST) {
 767                 logger(DEBUG_TRAFFIC, LOG_WARNING, "Cannot route packet: received unknown type ARP request");
 768                 return;
 769         }
 770
 771         /* Check if the IPv4 address exists on the VPN */
 772
 773         subnet = lookup_subnet_ipv4((ipv4_t *) &arp.arp_tpa);
 774
 775         if(!subnet) {
 776                 logger(DEBUG_TRAFFIC, LOG_WARNING, "Cannot route packet: ARP request for unknown address %d.%d.%d.%d",
 777                                    arp.arp_tpa[0], arp.arp_tpa[1], arp.arp_tpa[2],
 778                                    arp.arp_tpa[3]);
 779                 return;
 780         }
 781
 782         /* Check if it is for our own subnet */
 783
 784         if(subnet->owner == myself)
 785                 return;                                          /* silently ignore */
 786
 787         memcpy(packet->data, packet->data + ETH_ALEN, ETH_ALEN); /* copy destination address */
 788         packet->data[ETH_ALEN * 2 - 1] ^= 0xFF;                  /* mangle source address so it looks like it's not from us */
 789
 790         memcpy(&addr, arp.arp_tpa, sizeof addr);                 /* save protocol addr */
 791         memcpy(arp.arp_tpa, arp.arp_spa, sizeof addr);           /* swap destination and source protocol address */
 792         memcpy(arp.arp_spa, &addr, sizeof addr);                 /* ... */
 793
 794         memcpy(arp.arp_tha, arp.arp_sha, ETH_ALEN);              /* set target hard/proto addr */
 795         memcpy(arp.arp_sha, packet->data + ETH_ALEN, ETH_ALEN);  /* add fake source hard addr */
 796         arp.arp_op = htons(ARPOP_REPLY);
 797
 798         /* Copy structs on stack back to packet */
 799
 800         memcpy(packet->data + ether_size, &arp, arp_size);
 801
 802         send_packet(source, packet);
 803 }
 804
 805 static void route_mac(node_t *source, vpn_packet_t *packet) {
 806         subnet_t *subnet;
 807         mac_t dest;
 808
 809         /* Learn source address */
 810
 811         if(source == myself) {
 812                 mac_t src;
 813                 memcpy(&src, &packet->data[6], sizeof src);
 814                 learn_mac(&src);
 815         }
 816
 817         /* Lookup destination address */
 818
 819         memcpy(&dest, &packet->data[0], sizeof dest);
 820         subnet = lookup_subnet_mac(NULL, &dest);
 821
 822         if(!subnet) {
 823                 broadcast_packet(source, packet);
 824                 return;
 825         }
 826
 827         if(subnet->owner == source) {
 828                 logger(DEBUG_TRAFFIC, LOG_WARNING, "Packet looping back to %s (%s)!", source->name, source->hostname);
 829                 return;
 830         }
 831
 832         if(forwarding_mode == FMODE_OFF && source != myself && subnet->owner != myself)
 833                 return;
 834
 835         // Handle packets larger than PMTU
 836
 837         node_t *via = (subnet->owner->via == myself) ? subnet->owner->nexthop : subnet->owner->via;
 838
 839         if(directonly && subnet->owner != via)
 840                 return;
 841
 842         if(via && packet->len > via->mtu && via != myself) {
 843                 logger(DEBUG_TRAFFIC, LOG_INFO, "Packet for %s (%s) length %d larger than MTU %d", subnet->owner->name, subnet->owner->hostname, packet->len, via->mtu);
 844                 uint16_t type = packet->data[12] << 8 | packet->data[13];
 845                 if(type == ETH_P_IP && packet->len > 590) {
 846                         if(packet->data[20] & 0x40) {
 847                                 packet->len = via->mtu;
 848                                 route_ipv4_unreachable(source, packet, ICMP_DEST_UNREACH, ICMP_FRAG_NEEDED);
 849                         } else {
 850                                 fragment_ipv4_packet(via, packet);
 851                         }
 852                         return;
 853                 } else if(type == ETH_P_IPV6 && packet->len > 1294) {
 854                         packet->len = via->mtu;
 855                         route_ipv6_unreachable(source, packet, ICMP6_PACKET_TOO_BIG, 0);
 856                         return;
 857                 }
 858         }
 859
 860         clamp_mss(source, via, packet);
 861
 862         send_packet(subnet->owner, packet);
 863 }
 864
 865 static void send_pcap(vpn_packet_t *packet) {
 866         pcap = false;
 867
 868         for list_each(connection_t, c, connection_list) {
 869                 if(!c->status.pcap)
 870                         continue;
 871
 872                 pcap = true;
 873                 int len = packet->len;
 874                 if(c->outmaclength && c->outmaclength < len)
 875                         len = c->outmaclength;
 876
 877                 if(send_request(c, "%d %d %d", CONTROL, REQ_PCAP, len))
 878                         send_meta(c, (char *)packet->data, len);
 879         }
 880 }
 881
 882 static bool do_decrement_ttl(node_t *source, vpn_packet_t *packet) {
 883         uint16_t type = packet->data[12] << 8 | packet->data[13];
 884
 885         switch (type) {
 886                 case ETH_P_IP:
 887                         if(!checklength(source, packet, 14 + 32))
 888                                 return false;
 889
 890                         if(packet->data[22] < 1) {
 891                                 if(packet->data[25] != IPPROTO_ICMP || packet->data[46] != ICMP_TIME_EXCEEDED)
 892                                         route_ipv4_unreachable(source, packet, ICMP_TIME_EXCEEDED, ICMP_EXC_TTL);
 893                                 return false;
 894                         }
 895
 896                         uint16_t old = packet->data[22] << 8 | packet->data[23];
 897                         packet->data[22]--;
 898                         uint16_t new = packet->data[22] << 8 | packet->data[23];
 899
 900                         uint32_t checksum = packet->data[24] << 8 | packet->data[25];
 901                         checksum += old + (~new & 0xFFFF);
 902                         while(checksum >> 16)
 903                                 checksum = (checksum & 0xFFFF) + (checksum >> 16);
 904                         packet->data[24] = checksum >> 8;
 905                         packet->data[25] = checksum & 0xff;
 906
 907                         return true;
 908
 909                 case ETH_P_IPV6:
 910                         if(!checklength(source, packet, 14 + 40))
 911                                 return false;
 912
 913                         if(packet->data[21] < 1) {
 914                                 if(packet->data[20] != IPPROTO_ICMPV6 || packet->data[54] != ICMP6_TIME_EXCEEDED)
 915                                         route_ipv6_unreachable(source, packet, ICMP6_TIME_EXCEEDED, ICMP6_TIME_EXCEED_TRANSIT);
 916                                 return false;
 917                         }
 918
 919                         packet->data[21]--;
 920
 921                         return true;
 922
 923                 default:
 924                         return true;
 925         }
 926 }
 927
 928 void route(node_t *source, vpn_packet_t *packet) {
 929         if(pcap)
 930                 send_pcap(packet);
 931
 932         if(forwarding_mode == FMODE_KERNEL && source != myself) {
 933                 send_packet(myself, packet);
 934                 return;
 935         }
 936
 937         if(!checklength(source, packet, ether_size))
 938                 return;
 939
 940         if(decrement_ttl && source != myself)
 941                 if(!do_decrement_ttl(source, packet))
 942                         return;
 943
 944         uint16_t type = packet->data[12] << 8 | packet->data[13];
 945
 946         switch (routing_mode) {
 947                 case RMODE_ROUTER:
 948                         switch (type) {
 949                                 case ETH_P_ARP:
 950                                         route_arp(source, packet);
 951                                         break;
 952
 953                                 case ETH_P_IP:
 954                                         route_ipv4(source, packet);
 955                                         break;
 956
 957                                 case ETH_P_IPV6:
 958                                         route_ipv6(source, packet);
 959                                         break;
 960
 961                                 default:
 962                                         logger(DEBUG_TRAFFIC, LOG_WARNING, "Cannot route packet from %s (%s): unknown type %hx", source->name, source->hostname, type);
 963                                         break;
 964                         }
 965                         break;
 966
 967                 case RMODE_SWITCH:
 968                         route_mac(source, packet);
 969                         break;
 970
 971                 case RMODE_HUB:
 972                         broadcast_packet(source, packet);
 973                         break;
 974         }
 975 }