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