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

   1 /*
   2     route.c -- routing
   3     Copyright (C) 2000-2005 Ivo Timmermans,
   4                   2000-2013 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 static bool do_decrement_ttl(node_t *source, vpn_packet_t *packet);
  59
  60 #ifndef MAX
  61 #define MAX(a, b) ((a) > (b) ? (a) : (b))
  62 #endif
  63
  64 static timeout_t age_subnets_timeout;
  65
  66 /* RFC 1071 */
  67
  68 static uint16_t inet_checksum(void *data, int len, uint16_t prevsum) {
  69         uint16_t *p = data;
  70         uint32_t checksum = prevsum ^ 0xFFFF;
  71
  72         while(len >= 2) {
  73                 checksum += *p++;
  74                 len -= 2;
  75         }
  76
  77         if(len)
  78                 checksum += *(uint8_t *)p;
  79
  80         while(checksum >> 16)
  81                 checksum = (checksum & 0xFFFF) + (checksum >> 16);
  82
  83         return ~checksum;
  84 }
  85
  86 static bool ratelimit(int frequency) {
  87         static time_t lasttime = 0;
  88         static int count = 0;
  89
  90         if(lasttime == now.tv_sec) {
  91                 if(count >= frequency)
  92                         return true;
  93         } else {
  94                 lasttime = now.tv_sec;
  95                 count = 0;
  96         }
  97
  98         count++;
  99         return false;
 100 }
 101
 102 static bool checklength(node_t *source, vpn_packet_t *packet, length_t length) {
 103         if(packet->len < length) {
 104                 logger(DEBUG_TRAFFIC, LOG_WARNING, "Got too short packet from %s (%s)", source->name, source->hostname);
 105                 return false;
 106         } else
 107                 return true;
 108 }
 109
 110 static void clamp_mss(const node_t *source, const node_t *via, vpn_packet_t *packet) {
 111         if(!source || !via || !(via->options & OPTION_CLAMP_MSS))
 112                 return;
 113
 114         uint16_t mtu = source->mtu;
 115         if(via != myself && via->mtu < mtu)
 116                 mtu = via->mtu;
 117
 118         /* Find TCP header */
 119         int start = ether_size;
 120         uint16_t type = DATA(packet)[12] << 8 | DATA(packet)[13];
 121
 122         if(type == ETH_P_8021Q) {
 123                 start += 4;
 124                 type = DATA(packet)[16] << 8 | DATA(packet)[17];
 125         }
 126
 127         if(type == ETH_P_IP && DATA(packet)[start + 9] == 6)
 128                 start += (DATA(packet)[start] & 0xf) * 4;
 129         else if(type == ETH_P_IPV6 && DATA(packet)[start + 6] == 6)
 130                 start += 40;
 131         else
 132                 return;
 133
 134         if(packet->len <= start + 20)
 135                 return;
 136
 137         /* Use data offset field to calculate length of options field */
 138         int len = ((DATA(packet)[start + 12] >> 4) - 5) * 4;
 139
 140         if(packet->len < start + 20 + len)
 141                 return;
 142
 143         /* Search for MSS option header */
 144         for(int i = 0; i < len;) {
 145                 if(DATA(packet)[start + 20 + i] == 0)
 146                         break;
 147
 148                 if(DATA(packet)[start + 20 + i] == 1) {
 149                         i++;
 150                         continue;
 151                 }
 152
 153                 if(i > len - 2 || i > len - DATA(packet)[start + 21 + i])
 154                         break;
 155
 156                 if(DATA(packet)[start + 20 + i] != 2) {
 157                         if(DATA(packet)[start + 21 + i] < 2)
 158                                 break;
 159                         i += DATA(packet)[start + 21 + i];
 160                         continue;
 161                 }
 162
 163                 if(DATA(packet)[start + 21] != 4)
 164                         break;
 165
 166                 /* Found it */
 167                 uint16_t oldmss = DATA(packet)[start + 22 + i] << 8 | DATA(packet)[start + 23 + i];
 168                 uint16_t newmss = mtu - start - 20;
 169                 uint32_t csum = DATA(packet)[start + 16] << 8 | DATA(packet)[start + 17];
 170
 171                 if(oldmss <= newmss)
 172                         break;
 173
 174                 logger(DEBUG_TRAFFIC, LOG_INFO, "Clamping MSS of packet from %s to %s to %d", source->name, via->name, newmss);
 175
 176                 /* Update the MSS value and the checksum */
 177                 DATA(packet)[start + 22 + i] = newmss >> 8;
 178                 DATA(packet)[start + 23 + i] = newmss & 0xff;
 179                 csum ^= 0xffff;
 180                 csum += oldmss ^ 0xffff;
 181                 csum += newmss;
 182                 csum = (csum & 0xffff) + (csum >> 16);
 183                 csum += csum >> 16;
 184                 csum ^= 0xffff;
 185                 DATA(packet)[start + 16] = csum >> 8;
 186                 DATA(packet)[start + 17] = csum;
 187                 break;
 188         }
 189 }
 190
 191 static void swap_mac_addresses(vpn_packet_t *packet) {
 192         mac_t tmp;
 193         memcpy(&tmp, &DATA(packet)[0], sizeof tmp);
 194         memcpy(&DATA(packet)[0], &DATA(packet)[6], sizeof tmp);
 195         memcpy(&DATA(packet)[6], &tmp, sizeof tmp);
 196 }
 197
 198 static void age_subnets(void *data) {
 199         bool left = false;
 200
 201         for splay_each(subnet_t, s, myself->subnet_tree) {
 202                 if(s->expires && s->expires < now.tv_sec) {
 203                         if(debug_level >= DEBUG_TRAFFIC) {
 204                                 char netstr[MAXNETSTR];
 205                                 if(net2str(netstr, sizeof netstr, s))
 206                                         logger(DEBUG_TRAFFIC, LOG_INFO, "Subnet %s expired", netstr);
 207                         }
 208
 209                         for list_each(connection_t, c, connection_list)
 210                                 if(c->edge)
 211                                         send_del_subnet(c, s);
 212
 213                         subnet_del(myself, s);
 214                 } else {
 215                         if(s->expires)
 216                                 left = true;
 217                 }
 218         }
 219
 220         if(left)
 221                 timeout_set(&age_subnets_timeout, &(struct timeval){10, rand() % 100000});
 222 }
 223
 224 static void learn_mac(mac_t *address) {
 225         subnet_t *subnet = lookup_subnet_mac(myself, address);
 226
 227         /* If we don't know this MAC address yet, store it */
 228
 229         if(!subnet) {
 230                 logger(DEBUG_TRAFFIC, LOG_INFO, "Learned new MAC address %x:%x:%x:%x:%x:%x",
 231                                    address->x[0], address->x[1], address->x[2], address->x[3],
 232                                    address->x[4], address->x[5]);
 233
 234                 subnet = new_subnet();
 235                 subnet->type = SUBNET_MAC;
 236                 subnet->expires = now.tv_sec + macexpire;
 237                 subnet->net.mac.address = *address;
 238                 subnet->weight = 10;
 239                 subnet_add(myself, subnet);
 240                 subnet_update(myself, subnet, true);
 241
 242                 /* And tell all other tinc daemons it's our MAC */
 243
 244                 for list_each(connection_t, c, connection_list)
 245                         if(c->edge)
 246                                 send_add_subnet(c, subnet);
 247
 248                 timeout_add(&age_subnets_timeout, age_subnets, NULL, &(struct timeval){10, rand() % 100000});
 249         } else {
 250                 if(subnet->expires)
 251                         subnet->expires = now.tv_sec + macexpire;
 252         }
 253 }
 254
 255 static void route_broadcast(node_t *source, vpn_packet_t *packet) {
 256         if(decrement_ttl && source != myself)
 257                 if(!do_decrement_ttl(source, packet))
 258                         return;
 259
 260         broadcast_packet(source, packet);
 261 }
 262
 263 /* RFC 792 */
 264
 265 static void route_ipv4_unreachable(node_t *source, vpn_packet_t *packet, length_t ether_size, uint8_t type, uint8_t code) {
 266         struct ip ip = {0};
 267         struct icmp icmp = {0};
 268
 269         struct in_addr ip_src;
 270         struct in_addr ip_dst;
 271         uint32_t oldlen;
 272
 273         if(ratelimit(3))
 274                 return;
 275
 276         /* Swap Ethernet source and destination addresses */
 277
 278         swap_mac_addresses(packet);
 279
 280         /* Copy headers from packet into properly aligned structs on the stack */
 281
 282         memcpy(&ip, DATA(packet) + ether_size, ip_size);
 283
 284         /* Remember original source and destination */
 285
 286         ip_src = ip.ip_src;
 287         ip_dst = ip.ip_dst;
 288
 289         /* Try to reply with an IP address assigned to the local machine */
 290
 291         if (type == ICMP_TIME_EXCEEDED && code == ICMP_EXC_TTL) {
 292                 int sockfd = socket(AF_INET, SOCK_DGRAM, 0);
 293                 if (sockfd != -1) {
 294                         struct sockaddr_in addr;
 295                         memset(&addr, 0, sizeof(addr));
 296                         addr.sin_family = AF_INET;
 297                         addr.sin_addr = ip.ip_src;
 298                         if (!connect(sockfd, (const struct sockaddr*) &addr, sizeof(addr))) {
 299                                 memset(&addr, 0, sizeof(addr));
 300                                 addr.sin_family = AF_INET;
 301                                 socklen_t addrlen = sizeof(addr);
 302                                 if (!getsockname(sockfd, (struct sockaddr*) &addr, &addrlen) && addrlen <= sizeof(addr)) {
 303                                         ip_dst = addr.sin_addr;
 304                                 }
 305                         }
 306                         close(sockfd);
 307                 }
 308         }
 309
 310         oldlen = packet->len - ether_size;
 311
 312         if(type == ICMP_DEST_UNREACH && code == ICMP_FRAG_NEEDED)
 313                 icmp.icmp_nextmtu = htons(packet->len - ether_size);
 314
 315         if(oldlen >= IP_MSS - ip_size - icmp_size)
 316                 oldlen = IP_MSS - ip_size - icmp_size;
 317
 318         /* Copy first part of original contents to ICMP message */
 319
 320         memmove(DATA(packet) + ether_size + ip_size + icmp_size, DATA(packet) + ether_size, oldlen);
 321
 322         /* Fill in IPv4 header */
 323
 324         ip.ip_v = 4;
 325         ip.ip_hl = ip_size / 4;
 326         ip.ip_tos = 0;
 327         ip.ip_len = htons(ip_size + icmp_size + oldlen);
 328         ip.ip_id = 0;
 329         ip.ip_off = 0;
 330         ip.ip_ttl = 255;
 331         ip.ip_p = IPPROTO_ICMP;
 332         ip.ip_sum = 0;
 333         ip.ip_src = ip_dst;
 334         ip.ip_dst = ip_src;
 335
 336         ip.ip_sum = inet_checksum(&ip, ip_size, ~0);
 337
 338         /* Fill in ICMP header */
 339
 340         icmp.icmp_type = type;
 341         icmp.icmp_code = code;
 342         icmp.icmp_cksum = 0;
 343
 344         icmp.icmp_cksum = inet_checksum(&icmp, icmp_size, ~0);
 345         icmp.icmp_cksum = inet_checksum(DATA(packet) + ether_size + ip_size + icmp_size, oldlen, icmp.icmp_cksum);
 346
 347         /* Copy structs on stack back to packet */
 348
 349         memcpy(DATA(packet) + ether_size, &ip, ip_size);
 350         memcpy(DATA(packet) + ether_size + ip_size, &icmp, icmp_size);
 351
 352         packet->len = ether_size + ip_size + icmp_size + oldlen;
 353
 354         send_packet(source, packet);
 355 }
 356
 357 /* RFC 791 */
 358
 359 static void fragment_ipv4_packet(node_t *dest, vpn_packet_t *packet, length_t ether_size) {
 360         struct ip ip;
 361         vpn_packet_t fragment;
 362         int len, maxlen, todo;
 363         uint8_t *offset;
 364         uint16_t ip_off, origf;
 365
 366         memcpy(&ip, DATA(packet) + ether_size, ip_size);
 367         fragment.priority = packet->priority;
 368         fragment.offset = DEFAULT_PACKET_OFFSET;
 369
 370         if(ip.ip_hl != ip_size / 4)
 371                 return;
 372
 373         todo = ntohs(ip.ip_len) - ip_size;
 374
 375         if(ether_size + ip_size + todo != packet->len) {
 376                 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));
 377                 return;
 378         }
 379
 380         logger(DEBUG_TRAFFIC, LOG_INFO, "Fragmenting packet of %d bytes to %s (%s)", packet->len, dest->name, dest->hostname);
 381
 382         offset = DATA(packet) + ether_size + ip_size;
 383         maxlen = (dest->mtu - ether_size - ip_size) & ~0x7;
 384         ip_off = ntohs(ip.ip_off);
 385         origf = ip_off & ~IP_OFFMASK;
 386         ip_off &= IP_OFFMASK;
 387
 388         while(todo) {
 389                 len = todo > maxlen ? maxlen : todo;
 390                 memcpy(DATA(&fragment) + ether_size + ip_size, offset, len);
 391                 todo -= len;
 392                 offset += len;
 393
 394                 ip.ip_len = htons(ip_size + len);
 395                 ip.ip_off = htons(ip_off | origf | (todo ? IP_MF : 0));
 396                 ip.ip_sum = 0;
 397                 ip.ip_sum = inet_checksum(&ip, ip_size, ~0);
 398                 memcpy(DATA(&fragment), DATA(packet), ether_size);
 399                 memcpy(DATA(&fragment) + ether_size, &ip, ip_size);
 400                 fragment.len = ether_size + ip_size + len;
 401
 402                 send_packet(dest, &fragment);
 403
 404                 ip_off += len / 8;
 405         }
 406 }
 407
 408 static void route_ipv4(node_t *source, vpn_packet_t *packet) {
 409         if(!checklength(source, packet, ether_size + ip_size))
 410                 return;
 411
 412         subnet_t *subnet;
 413         node_t *via;
 414         ipv4_t dest;
 415
 416         memcpy(&dest, &DATA(packet)[30], sizeof dest);
 417         subnet = lookup_subnet_ipv4(&dest);
 418
 419         if(!subnet) {
 420                 logger(DEBUG_TRAFFIC, LOG_WARNING, "Cannot route packet from %s (%s): unknown IPv4 destination address %d.%d.%d.%d",
 421                                 source->name, source->hostname,
 422                                 dest.x[0],
 423                                 dest.x[1],
 424                                 dest.x[2],
 425                                 dest.x[3]);
 426
 427                 route_ipv4_unreachable(source, packet, ether_size, ICMP_DEST_UNREACH, ICMP_NET_UNKNOWN);
 428                 return;
 429         }
 430
 431         if (!subnet->owner) {
 432                 route_broadcast(source, packet);
 433                 return;
 434         }
 435
 436         if(subnet->owner == source) {
 437                 logger(DEBUG_TRAFFIC, LOG_WARNING, "Packet looping back to %s (%s)!", source->name, source->hostname);
 438                 return;
 439         }
 440
 441         if(!subnet->owner->status.reachable)
 442                 return route_ipv4_unreachable(source, packet, ether_size, ICMP_DEST_UNREACH, ICMP_NET_UNREACH);
 443
 444         if(forwarding_mode == FMODE_OFF && source != myself && subnet->owner != myself)
 445                 return route_ipv4_unreachable(source, packet, ether_size, ICMP_DEST_UNREACH, ICMP_NET_ANO);
 446
 447         if(decrement_ttl && source != myself && subnet->owner != myself)
 448                 if(!do_decrement_ttl(source, packet))
 449                         return;
 450
 451         if(priorityinheritance)
 452                 packet->priority = DATA(packet)[15];
 453
 454         via = (subnet->owner->via == myself) ? subnet->owner->nexthop : subnet->owner->via;
 455
 456         if(via == source) {
 457                 logger(DEBUG_TRAFFIC, LOG_ERR, "Routing loop for packet from %s (%s)!", source->name, source->hostname);
 458                 return;
 459         }
 460
 461         if(directonly && subnet->owner != via)
 462                 return route_ipv4_unreachable(source, packet, ether_size, ICMP_DEST_UNREACH, ICMP_NET_ANO);
 463
 464         if(via && packet->len > MAX(via->mtu, 590) && via != myself) {
 465                 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);
 466                 if(DATA(packet)[20] & 0x40) {
 467                         packet->len = MAX(via->mtu, 590);
 468                         route_ipv4_unreachable(source, packet, ether_size, ICMP_DEST_UNREACH, ICMP_FRAG_NEEDED);
 469                 } else {
 470                         fragment_ipv4_packet(via, packet, ether_size);
 471                 }
 472
 473                 return;
 474         }
 475
 476         clamp_mss(source, via, packet);
 477
 478         send_packet(subnet->owner, packet);
 479 }
 480
 481 /* RFC 2463 */
 482
 483 static void route_ipv6_unreachable(node_t *source, vpn_packet_t *packet, length_t ether_size, uint8_t type, uint8_t code) {
 484         struct ip6_hdr ip6;
 485         struct icmp6_hdr icmp6 = {0};
 486         uint16_t checksum;
 487
 488         struct {
 489                 struct in6_addr ip6_src;        /* source address */
 490                 struct in6_addr ip6_dst;        /* destination address */
 491                 uint32_t length;
 492                 uint32_t next;
 493         } pseudo;
 494
 495         if(ratelimit(3))
 496                 return;
 497
 498         /* Swap Ethernet source and destination addresses */
 499
 500         swap_mac_addresses(packet);
 501
 502         /* Copy headers from packet to structs on the stack */
 503
 504         memcpy(&ip6, DATA(packet) + ether_size, ip6_size);
 505
 506         /* Remember original source and destination */
 507
 508         pseudo.ip6_src = ip6.ip6_dst;
 509         pseudo.ip6_dst = ip6.ip6_src;
 510
 511         /* Try to reply with an IP address assigned to the local machine */
 512
 513         if (type == ICMP6_TIME_EXCEEDED && code == ICMP6_TIME_EXCEED_TRANSIT) {
 514                 int sockfd = socket(AF_INET6, SOCK_DGRAM, 0);
 515                 if (sockfd != -1) {
 516                         struct sockaddr_in6 addr;
 517                         memset(&addr, 0, sizeof(addr));
 518                         addr.sin6_family = AF_INET6;
 519                         addr.sin6_addr = ip6.ip6_src;
 520                         if (!connect(sockfd, (const struct sockaddr*) &addr, sizeof(addr))) {
 521                                 memset(&addr, 0, sizeof(addr));
 522                                 addr.sin6_family = AF_INET6;
 523                                 socklen_t addrlen = sizeof(addr);
 524                                 if (!getsockname(sockfd, (struct sockaddr*) &addr, &addrlen) && addrlen <= sizeof(addr)) {
 525                                         pseudo.ip6_src = addr.sin6_addr;
 526                                 }
 527                         }
 528                         close(sockfd);
 529                 }
 530         }
 531
 532         pseudo.length = packet->len - ether_size;
 533
 534         if(type == ICMP6_PACKET_TOO_BIG)
 535                 icmp6.icmp6_mtu = htonl(pseudo.length);
 536
 537         if(pseudo.length >= IP_MSS - ip6_size - icmp6_size)
 538                 pseudo.length = IP_MSS - ip6_size - icmp6_size;
 539
 540         /* Copy first part of original contents to ICMP message */
 541
 542         memmove(DATA(packet) + ether_size + ip6_size + icmp6_size, DATA(packet) + ether_size, pseudo.length);
 543
 544         /* Fill in IPv6 header */
 545
 546         ip6.ip6_flow = htonl(0x60000000UL);
 547         ip6.ip6_plen = htons(icmp6_size + pseudo.length);
 548         ip6.ip6_nxt = IPPROTO_ICMPV6;
 549         ip6.ip6_hlim = 255;
 550         ip6.ip6_src = pseudo.ip6_src;
 551         ip6.ip6_dst = pseudo.ip6_dst;
 552
 553         /* Fill in ICMP header */
 554
 555         icmp6.icmp6_type = type;
 556         icmp6.icmp6_code = code;
 557         icmp6.icmp6_cksum = 0;
 558
 559         /* Create pseudo header */
 560
 561         pseudo.length = htonl(icmp6_size + pseudo.length);
 562         pseudo.next = htonl(IPPROTO_ICMPV6);
 563
 564         /* Generate checksum */
 565
 566         checksum = inet_checksum(&pseudo, sizeof pseudo, ~0);
 567         checksum = inet_checksum(&icmp6, icmp6_size, checksum);
 568         checksum = inet_checksum(DATA(packet) + ether_size + ip6_size + icmp6_size, ntohl(pseudo.length) - icmp6_size, checksum);
 569
 570         icmp6.icmp6_cksum = checksum;
 571
 572         /* Copy structs on stack back to packet */
 573
 574         memcpy(DATA(packet) + ether_size, &ip6, ip6_size);
 575         memcpy(DATA(packet) + ether_size + ip6_size, &icmp6, icmp6_size);
 576
 577         packet->len = ether_size + ip6_size + ntohl(pseudo.length);
 578
 579         send_packet(source, packet);
 580 }
 581
 582 static void route_neighborsol(node_t *source, vpn_packet_t *packet);
 583
 584 static void route_ipv6(node_t *source, vpn_packet_t *packet) {
 585         if(!checklength(source, packet, ether_size + ip6_size))
 586                 return;
 587
 588         if(DATA(packet)[20] == IPPROTO_ICMPV6 && checklength(source, packet, ether_size + ip6_size + icmp6_size) && DATA(packet)[54] == ND_NEIGHBOR_SOLICIT) {
 589                 route_neighborsol(source, packet);
 590                 return;
 591         }
 592
 593         subnet_t *subnet;
 594         node_t *via;
 595         ipv6_t dest;
 596
 597         memcpy(&dest, &DATA(packet)[38], sizeof dest);
 598         subnet = lookup_subnet_ipv6(&dest);
 599
 600         if(!subnet) {
 601                 logger(DEBUG_TRAFFIC, LOG_WARNING, "Cannot route packet from %s (%s): unknown IPv6 destination address %hx:%hx:%hx:%hx:%hx:%hx:%hx:%hx",
 602                                 source->name, source->hostname,
 603                                 ntohs(dest.x[0]),
 604                                 ntohs(dest.x[1]),
 605                                 ntohs(dest.x[2]),
 606                                 ntohs(dest.x[3]),
 607                                 ntohs(dest.x[4]),
 608                                 ntohs(dest.x[5]),
 609                                 ntohs(dest.x[6]),
 610                                 ntohs(dest.x[7]));
 611
 612                 route_ipv6_unreachable(source, packet, ether_size, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_ADDR);
 613                 return;
 614         }
 615
 616         if (!subnet->owner) {
 617                 route_broadcast(source, packet);
 618                 return;
 619         }
 620
 621         if(subnet->owner == source) {
 622                 logger(DEBUG_TRAFFIC, LOG_WARNING, "Packet looping back to %s (%s)!", source->name, source->hostname);
 623                 return;
 624         }
 625
 626         if(!subnet->owner->status.reachable)
 627                 return route_ipv6_unreachable(source, packet, ether_size, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_NOROUTE);
 628
 629         if(forwarding_mode == FMODE_OFF && source != myself && subnet->owner != myself)
 630                 return route_ipv6_unreachable(source, packet, ether_size, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_ADMIN);
 631
 632         if(decrement_ttl && source != myself && subnet->owner != myself)
 633                 if(!do_decrement_ttl(source, packet))
 634                         return;
 635
 636         via = (subnet->owner->via == myself) ? subnet->owner->nexthop : subnet->owner->via;
 637
 638         if(via == source) {
 639                 logger(DEBUG_TRAFFIC, LOG_ERR, "Routing loop for packet from %s (%s)!", source->name, source->hostname);
 640                 return;
 641         }
 642
 643         if(directonly && subnet->owner != via)
 644                 return route_ipv6_unreachable(source, packet, ether_size, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_ADMIN);
 645
 646         if(via && packet->len > MAX(via->mtu, 1294) && via != myself) {
 647                 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);
 648                 packet->len = MAX(via->mtu, 1294);
 649                 route_ipv6_unreachable(source, packet, ether_size, ICMP6_PACKET_TOO_BIG, 0);
 650                 return;
 651         }
 652
 653         clamp_mss(source, via, packet);
 654
 655         send_packet(subnet->owner, packet);
 656 }
 657
 658 /* RFC 2461 */
 659
 660 static void route_neighborsol(node_t *source, vpn_packet_t *packet) {
 661         struct ip6_hdr ip6;
 662         struct nd_neighbor_solicit ns;
 663         struct nd_opt_hdr opt;
 664         subnet_t *subnet;
 665         uint16_t checksum;
 666         bool has_opt;
 667
 668         struct {
 669                 struct in6_addr ip6_src;
 670                 struct in6_addr ip6_dst;
 671                 uint32_t length;
 672                 uint32_t next;
 673         } pseudo;
 674
 675         if(!checklength(source, packet, ether_size + ip6_size + ns_size))
 676                 return;
 677
 678         has_opt = packet->len >= ether_size + ip6_size + ns_size + opt_size + ETH_ALEN;
 679
 680         if(source != myself) {
 681                 logger(DEBUG_TRAFFIC, LOG_WARNING, "Got neighbor solicitation request from %s (%s) while in router mode!", source->name, source->hostname);
 682                 return;
 683         }
 684
 685         /* Copy headers from packet to structs on the stack */
 686
 687         memcpy(&ip6, DATA(packet) + ether_size, ip6_size);
 688         memcpy(&ns, DATA(packet) + ether_size + ip6_size, ns_size);
 689         if(has_opt)
 690                 memcpy(&opt, DATA(packet) + ether_size + ip6_size + ns_size, opt_size);
 691
 692         /* First, snatch the source address from the neighbor solicitation packet */
 693
 694         if(overwrite_mac)
 695                 memcpy(mymac.x, DATA(packet) + ETH_ALEN, ETH_ALEN);
 696
 697         /* Check if this is a valid neighbor solicitation request */
 698
 699         if(ns.nd_ns_hdr.icmp6_type != ND_NEIGHBOR_SOLICIT ||
 700            (has_opt && opt.nd_opt_type != ND_OPT_SOURCE_LINKADDR)) {
 701                 logger(DEBUG_TRAFFIC, LOG_WARNING, "Cannot route packet: received unknown type neighbor solicitation request");
 702                 return;
 703         }
 704
 705         /* Create pseudo header */
 706
 707         pseudo.ip6_src = ip6.ip6_src;
 708         pseudo.ip6_dst = ip6.ip6_dst;
 709         if(has_opt)
 710                 pseudo.length = htonl(ns_size + opt_size + ETH_ALEN);
 711         else
 712                 pseudo.length = htonl(ns_size);
 713         pseudo.next = htonl(IPPROTO_ICMPV6);
 714
 715         /* Generate checksum */
 716
 717         checksum = inet_checksum(&pseudo, sizeof pseudo, ~0);
 718         checksum = inet_checksum(&ns, ns_size, checksum);
 719         if(has_opt) {
 720                 checksum = inet_checksum(&opt, opt_size, checksum);
 721                 checksum = inet_checksum(DATA(packet) + ether_size + ip6_size + ns_size + opt_size, ETH_ALEN, checksum);
 722         }
 723
 724         if(checksum) {
 725                 logger(DEBUG_TRAFFIC, LOG_WARNING, "Cannot route packet: checksum error for neighbor solicitation request");
 726                 return;
 727         }
 728
 729         /* Check if the IPv6 address exists on the VPN */
 730
 731         subnet = lookup_subnet_ipv6((ipv6_t *) &ns.nd_ns_target);
 732
 733         if(!subnet) {
 734                 logger(DEBUG_TRAFFIC, LOG_WARNING, "Cannot route packet: neighbor solicitation request for unknown address %hx:%hx:%hx:%hx:%hx:%hx:%hx:%hx",
 735                                    ntohs(((uint16_t *) &ns.nd_ns_target)[0]),
 736                                    ntohs(((uint16_t *) &ns.nd_ns_target)[1]),
 737                                    ntohs(((uint16_t *) &ns.nd_ns_target)[2]),
 738                                    ntohs(((uint16_t *) &ns.nd_ns_target)[3]),
 739                                    ntohs(((uint16_t *) &ns.nd_ns_target)[4]),
 740                                    ntohs(((uint16_t *) &ns.nd_ns_target)[5]),
 741                                    ntohs(((uint16_t *) &ns.nd_ns_target)[6]),
 742                                    ntohs(((uint16_t *) &ns.nd_ns_target)[7]));
 743
 744                 return;
 745         }
 746
 747         /* Check if it is for our own subnet */
 748
 749         if(subnet->owner == myself)
 750                 return;                                          /* silently ignore */
 751
 752         if(decrement_ttl)
 753                 if(!do_decrement_ttl(source, packet))
 754                         return;
 755
 756         /* Create neighbor advertation reply */
 757
 758         memcpy(DATA(packet), DATA(packet) + ETH_ALEN, ETH_ALEN); /* copy destination address */
 759         DATA(packet)[ETH_ALEN * 2 - 1] ^= 0xFF;                  /* mangle source address so it looks like it's not from us */
 760
 761         ip6.ip6_dst = ip6.ip6_src;                               /* swap destination and source protocoll address */
 762         ip6.ip6_src = ns.nd_ns_target;
 763
 764         if(has_opt)
 765                 memcpy(DATA(packet) + ether_size + ip6_size + ns_size + opt_size, DATA(packet) + ETH_ALEN, ETH_ALEN);   /* add fake source hard addr */
 766
 767         ns.nd_ns_cksum = 0;
 768         ns.nd_ns_type = ND_NEIGHBOR_ADVERT;
 769         ns.nd_ns_reserved = htonl(0x40000000UL);                 /* Set solicited flag */
 770         opt.nd_opt_type = ND_OPT_TARGET_LINKADDR;
 771
 772         /* Create pseudo header */
 773
 774         pseudo.ip6_src = ip6.ip6_src;
 775         pseudo.ip6_dst = ip6.ip6_dst;
 776         if(has_opt)
 777                 pseudo.length = htonl(ns_size + opt_size + ETH_ALEN);
 778         else
 779                 pseudo.length = htonl(ns_size);
 780         pseudo.next = htonl(IPPROTO_ICMPV6);
 781
 782         /* Generate checksum */
 783
 784         checksum = inet_checksum(&pseudo, sizeof pseudo, ~0);
 785         checksum = inet_checksum(&ns, ns_size, checksum);
 786         if(has_opt) {
 787                 checksum = inet_checksum(&opt, opt_size, checksum);
 788                 checksum = inet_checksum(DATA(packet) + ether_size + ip6_size + ns_size + opt_size, ETH_ALEN, checksum);
 789         }
 790
 791         ns.nd_ns_hdr.icmp6_cksum = checksum;
 792
 793         /* Copy structs on stack back to packet */
 794
 795         memcpy(DATA(packet) + ether_size, &ip6, ip6_size);
 796         memcpy(DATA(packet) + ether_size + ip6_size, &ns, ns_size);
 797         if(has_opt)
 798                 memcpy(DATA(packet) + ether_size + ip6_size + ns_size, &opt, opt_size);
 799
 800         send_packet(source, packet);
 801 }
 802
 803 /* RFC 826 */
 804
 805 static void route_arp(node_t *source, vpn_packet_t *packet) {
 806         struct ether_arp arp;
 807         subnet_t *subnet;
 808         struct in_addr addr;
 809
 810         if(!checklength(source, packet, ether_size + arp_size))
 811                 return;
 812
 813         if(source != myself) {
 814                 logger(DEBUG_TRAFFIC, LOG_WARNING, "Got ARP request from %s (%s) while in router mode!", source->name, source->hostname);
 815                 return;
 816         }
 817
 818         /* First, snatch the source address from the ARP packet */
 819
 820         if(overwrite_mac)
 821                 memcpy(mymac.x, DATA(packet) + ETH_ALEN, ETH_ALEN);
 822
 823         /* Copy headers from packet to structs on the stack */
 824
 825         memcpy(&arp, DATA(packet) + ether_size, arp_size);
 826
 827         /* Check if this is a valid ARP request */
 828
 829         if(ntohs(arp.arp_hrd) != ARPHRD_ETHER || ntohs(arp.arp_pro) != ETH_P_IP ||
 830            arp.arp_hln != ETH_ALEN || arp.arp_pln != sizeof addr || ntohs(arp.arp_op) != ARPOP_REQUEST) {
 831                 logger(DEBUG_TRAFFIC, LOG_WARNING, "Cannot route packet: received unknown type ARP request");
 832                 return;
 833         }
 834
 835         /* Check if the IPv4 address exists on the VPN */
 836
 837         subnet = lookup_subnet_ipv4((ipv4_t *) &arp.arp_tpa);
 838
 839         if(!subnet) {
 840                 logger(DEBUG_TRAFFIC, LOG_WARNING, "Cannot route packet: ARP request for unknown address %d.%d.%d.%d",
 841                                    arp.arp_tpa[0], arp.arp_tpa[1], arp.arp_tpa[2],
 842                                    arp.arp_tpa[3]);
 843                 return;
 844         }
 845
 846         /* Check if it is for our own subnet */
 847
 848         if(subnet->owner == myself)
 849                 return;                                          /* silently ignore */
 850
 851         if(decrement_ttl)
 852                 if(!do_decrement_ttl(source, packet))
 853                         return;
 854
 855         memcpy(&addr, arp.arp_tpa, sizeof addr);                 /* save protocol addr */
 856         memcpy(arp.arp_tpa, arp.arp_spa, sizeof addr);           /* swap destination and source protocol address */
 857         memcpy(arp.arp_spa, &addr, sizeof addr);                 /* ... */
 858
 859         memcpy(arp.arp_tha, arp.arp_sha, ETH_ALEN);              /* set target hard/proto addr */
 860         memcpy(arp.arp_sha, DATA(packet) + ETH_ALEN, ETH_ALEN);  /* set source hard/proto addr */
 861         arp.arp_sha[ETH_ALEN - 1] ^= 0xFF;                       /* for consistency with route_packet() */
 862         arp.arp_op = htons(ARPOP_REPLY);
 863
 864         /* Copy structs on stack back to packet */
 865
 866         memcpy(DATA(packet) + ether_size, &arp, arp_size);
 867
 868         send_packet(source, packet);
 869 }
 870
 871 static void route_mac(node_t *source, vpn_packet_t *packet) {
 872         subnet_t *subnet;
 873         mac_t dest;
 874
 875         /* Learn source address */
 876
 877         if(source == myself) {
 878                 mac_t src;
 879                 memcpy(&src, &DATA(packet)[6], sizeof src);
 880                 learn_mac(&src);
 881         }
 882
 883         /* Lookup destination address */
 884
 885         memcpy(&dest, &DATA(packet)[0], sizeof dest);
 886         subnet = lookup_subnet_mac(NULL, &dest);
 887
 888         if(!subnet || !subnet->owner) {
 889                 route_broadcast(source, packet);
 890                 return;
 891         }
 892
 893         if(subnet->owner == source) {
 894                 logger(DEBUG_TRAFFIC, LOG_WARNING, "Packet looping back to %s (%s)!", source->name, source->hostname);
 895                 return;
 896         }
 897
 898         if(forwarding_mode == FMODE_OFF && source != myself && subnet->owner != myself)
 899                 return;
 900
 901         if(decrement_ttl && source != myself && subnet->owner != myself)
 902                 if(!do_decrement_ttl(source, packet))
 903                         return;
 904
 905         uint16_t type = DATA(packet)[12] << 8 | DATA(packet)[13];
 906
 907         if(priorityinheritance && type == ETH_P_IP && packet->len >= ether_size + ip_size)
 908                 packet->priority = DATA(packet)[15];
 909
 910         // Handle packets larger than PMTU
 911
 912         node_t *via = (subnet->owner->via == myself) ? subnet->owner->nexthop : subnet->owner->via;
 913
 914         if(directonly && subnet->owner != via)
 915                 return;
 916
 917         if(via && packet->len > via->mtu && via != myself) {
 918                 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);
 919                 length_t ethlen = 14;
 920
 921                 if(type == ETH_P_8021Q) {
 922                         type = DATA(packet)[16] << 8 | DATA(packet)[17];
 923                         ethlen += 4;
 924                 }
 925
 926                 if(type == ETH_P_IP && packet->len > 576 + ethlen) {
 927                         if(DATA(packet)[6 + ethlen] & 0x40) {
 928                                 packet->len = via->mtu;
 929                                 route_ipv4_unreachable(source, packet, ethlen, ICMP_DEST_UNREACH, ICMP_FRAG_NEEDED);
 930                         } else {
 931                                 fragment_ipv4_packet(via, packet, ethlen);
 932                         }
 933                         return;
 934                 } else if(type == ETH_P_IPV6 && packet->len > 1280 + ethlen) {
 935                         packet->len = via->mtu;
 936                         route_ipv6_unreachable(source, packet, ethlen, ICMP6_PACKET_TOO_BIG, 0);
 937                         return;
 938                 }
 939         }
 940
 941         clamp_mss(source, via, packet);
 942
 943         send_packet(subnet->owner, packet);
 944 }
 945
 946 static void send_pcap(vpn_packet_t *packet) {
 947         pcap = false;
 948
 949         for list_each(connection_t, c, connection_list) {
 950                 if(!c->status.pcap)
 951                         continue;
 952
 953                 pcap = true;
 954                 int len = packet->len;
 955                 if(c->outmaclength && c->outmaclength < len)
 956                         len = c->outmaclength;
 957
 958                 if(send_request(c, "%d %d %d", CONTROL, REQ_PCAP, len))
 959                         send_meta(c, (char *)DATA(packet), len);
 960         }
 961 }
 962
 963 static bool do_decrement_ttl(node_t *source, vpn_packet_t *packet) {
 964         uint16_t type = DATA(packet)[12] << 8 | DATA(packet)[13];
 965         length_t ethlen = ether_size;
 966
 967         if(type == ETH_P_8021Q) {
 968                 type = DATA(packet)[16] << 8 | DATA(packet)[17];
 969                 ethlen += 4;
 970         }
 971
 972         switch (type) {
 973                 case ETH_P_IP:
 974                         if(!checklength(source, packet, ethlen + ip_size))
 975                                 return false;
 976
 977                         if(DATA(packet)[ethlen + 8] <= 1) {
 978                                 if(DATA(packet)[ethlen + 11] != IPPROTO_ICMP || DATA(packet)[ethlen + 32] != ICMP_TIME_EXCEEDED)
 979                                         route_ipv4_unreachable(source, packet, ethlen, ICMP_TIME_EXCEEDED, ICMP_EXC_TTL);
 980                                 return false;
 981                         }
 982
 983                         uint16_t old = DATA(packet)[ethlen + 8] << 8 | DATA(packet)[ethlen + 9];
 984                         DATA(packet)[ethlen + 8]--;
 985                         uint16_t new = DATA(packet)[ethlen + 8] << 8 | DATA(packet)[ethlen + 9];
 986
 987                         uint32_t checksum = DATA(packet)[ethlen + 10] << 8 | DATA(packet)[ethlen + 11];
 988                         checksum += old + (~new & 0xFFFF);
 989                         while(checksum >> 16)
 990                                 checksum = (checksum & 0xFFFF) + (checksum >> 16);
 991                         DATA(packet)[ethlen + 10] = checksum >> 8;
 992                         DATA(packet)[ethlen + 11] = checksum & 0xff;
 993
 994                         return true;
 995
 996                 case ETH_P_IPV6:
 997                         if(!checklength(source, packet, ethlen + ip6_size))
 998                                 return false;
 999
1000                         if(DATA(packet)[ethlen + 7] <= 1) {
1001                                 if(DATA(packet)[ethlen + 6] != IPPROTO_ICMPV6 || DATA(packet)[ethlen + 40] != ICMP6_TIME_EXCEEDED)
1002                                         route_ipv6_unreachable(source, packet, ethlen, ICMP6_TIME_EXCEEDED, ICMP6_TIME_EXCEED_TRANSIT);
1003                                 return false;
1004                         }
1005
1006                         DATA(packet)[ethlen + 7]--;
1007
1008                         return true;
1009
1010                 default:
1011                         return true;
1012         }
1013 }
1014
1015 void route(node_t *source, vpn_packet_t *packet) {
1016         if(pcap)
1017                 send_pcap(packet);
1018
1019         if(forwarding_mode == FMODE_KERNEL && source != myself) {
1020                 send_packet(myself, packet);
1021                 return;
1022         }
1023
1024         if(!checklength(source, packet, ether_size))
1025                 return;
1026
1027         uint16_t type = DATA(packet)[12] << 8 | DATA(packet)[13];
1028
1029         switch (routing_mode) {
1030                 case RMODE_ROUTER:
1031                         switch (type) {
1032                                 case ETH_P_ARP:
1033                                         route_arp(source, packet);
1034                                         break;
1035
1036                                 case ETH_P_IP:
1037                                         route_ipv4(source, packet);
1038                                         break;
1039
1040                                 case ETH_P_IPV6:
1041                                         route_ipv6(source, packet);
1042                                         break;
1043
1044                                 default:
1045                                         logger(DEBUG_TRAFFIC, LOG_WARNING, "Cannot route packet from %s (%s): unknown type %hx", source->name, source->hostname, type);
1046                                         break;
1047                         }
1048                         break;
1049
1050                 case RMODE_SWITCH:
1051                         route_mac(source, packet);
1052                         break;
1053
1054                 case RMODE_HUB:
1055                         route_broadcast(source, packet);
1056                         break;
1057         }
1058 }