-static void clamp_mss(const node_t *source, const node_t *via, vpn_packet_t *packet) {
- if(!source || !via || !(via->options & OPTION_CLAMP_MSS))
- return;
-
- uint16_t mtu = source->mtu;
- if(via != myself && via->mtu < mtu)
- mtu = via->mtu;
-
- /* Find TCP header */
- int start = 0;
- uint16_t type = packet->data[12] << 8 | packet->data[13];
-
- if(type == ETH_P_IP && packet->data[23] == 6)
- start = 14 + (packet->data[14] & 0xf) * 4;
- else if(type == ETH_P_IPV6 && packet->data[20] == 6)
- start = 14 + 40;
-
- if(!start || packet->len <= start + 20)
- return;
-
- /* Use data offset field to calculate length of options field */
- int len = ((packet->data[start + 12] >> 4) - 5) * 4;
-
- if(packet->len < start + 20 + len)
- return;
-
- /* Search for MSS option header */
- for(int i = 0; i < len;) {
- if(packet->data[start + 20 + i] == 0)
- break;
-
- if(packet->data[start + 20 + i] == 1) {
- i++;
- continue;
- }
-
- if(i > len - 2 || i > len - packet->data[start + 21 + i])
- break;
-
- if(packet->data[start + 20 + i] != 2) {
- if(packet->data[start + 21 + i] < 2)
- break;
- i += packet->data[start + 21 + i];
- continue;
- }
-
- if(packet->data[start + 21] != 4)
- break;
-
- /* Found it */
- uint16_t oldmss = packet->data[start + 22 + i] << 8 | packet->data[start + 23 + i];
- uint16_t newmss = mtu - start - 20;
- uint16_t csum = packet->data[start + 16] << 8 | packet->data[start + 17];
-
- if(oldmss <= newmss)
- break;
-
- ifdebug(TRAFFIC) logger(LOG_INFO, "Clamping MSS of packet from %s to %s to %d", source->name, via->name, newmss);
-
- /* Update the MSS value and the checksum */
- packet->data[start + 22 + i] = newmss >> 8;
- packet->data[start + 23 + i] = newmss & 0xff;
- csum ^= 0xffff;
- csum -= oldmss;
- csum += newmss;
- csum ^= 0xffff;
- packet->data[start + 16] = csum >> 8;
- packet->data[start + 17] = csum & 0xff;
- break;
- }
-}
-
-static void swap_mac_addresses(vpn_packet_t *packet) {
- mac_t tmp;
- memcpy(&tmp, &packet->data[0], sizeof tmp);
- memcpy(&packet->data[0], &packet->data[6], sizeof tmp);
- memcpy(&packet->data[6], &tmp, sizeof tmp);
-}
-
-static void learn_mac(mac_t *address) {
- subnet_t *subnet;
- avl_node_t *node;
- connection_t *c;
-
- subnet = lookup_subnet_mac(myself, address);
-
- /* If we don't know this MAC address yet, store it */
-
- if(!subnet) {
- ifdebug(TRAFFIC) logger(LOG_INFO, "Learned new MAC address %hx:%hx:%hx:%hx:%hx:%hx",
- address->x[0], address->x[1], address->x[2], address->x[3],
- address->x[4], address->x[5]);
-
- subnet = new_subnet();
- subnet->type = SUBNET_MAC;
- subnet->expires = now + macexpire;
- subnet->net.mac.address = *address;
- subnet->weight = 10;
- subnet_add(myself, subnet);
- subnet_update(myself, subnet, true);
-
- /* And tell all other tinc daemons it's our MAC */
-
- for(node = connection_tree->head; node; node = node->next) {
- c = node->data;
- if(c->status.active)
- send_add_subnet(c, subnet);
- }
- }
-
- if(subnet->expires)
- subnet->expires = now + macexpire;
-}
-
-void age_subnets(void) {
- subnet_t *s;
- connection_t *c;
- avl_node_t *node, *next, *node2;
-
- for(node = myself->subnet_tree->head; node; node = next) {
- next = node->next;
- s = node->data;
- if(s->expires && s->expires < now) {
- ifdebug(TRAFFIC) {
- char netstr[MAXNETSTR];
- if(net2str(netstr, sizeof netstr, s))
- logger(LOG_INFO, "Subnet %s expired", netstr);
- }
-
- for(node2 = connection_tree->head; node2; node2 = node2->next) {
- c = node2->data;
- if(c->status.active)
- send_del_subnet(c, s);
- }
-
- subnet_update(myself, s, false);
- subnet_del(myself, s);
- }
- }
-}
-
-/* RFC 792 */
-
-static void route_ipv4_unreachable(node_t *source, vpn_packet_t *packet, uint8_t type, uint8_t code) {
- struct ip ip = {0};
- struct icmp icmp = {0};
-
- struct in_addr ip_src;
- struct in_addr ip_dst;
- uint32_t oldlen;
-
- if(ratelimit(3))
- return;
-
- /* Swap Ethernet source and destination addresses */
-
- swap_mac_addresses(packet);
-
- /* Copy headers from packet into properly aligned structs on the stack */
-
- memcpy(&ip, packet->data + ether_size, ip_size);
-
- /* Remember original source and destination */
-
- ip_src = ip.ip_src;
- ip_dst = ip.ip_dst;
-
- oldlen = packet->len - ether_size;
-
- if(type == ICMP_DEST_UNREACH && code == ICMP_FRAG_NEEDED)
- icmp.icmp_nextmtu = htons(packet->len - ether_size);
-
- if(oldlen >= IP_MSS - ip_size - icmp_size)
- oldlen = IP_MSS - ip_size - icmp_size;
-
- /* Copy first part of original contents to ICMP message */
-
- memmove(packet->data + ether_size + ip_size + icmp_size, packet->data + ether_size, oldlen);
-
- /* Fill in IPv4 header */
-
- ip.ip_v = 4;
- ip.ip_hl = ip_size / 4;
- ip.ip_tos = 0;
- ip.ip_len = htons(ip_size + icmp_size + oldlen);
- ip.ip_id = 0;
- ip.ip_off = 0;
- ip.ip_ttl = 255;
- ip.ip_p = IPPROTO_ICMP;
- ip.ip_sum = 0;
- ip.ip_src = ip_dst;
- ip.ip_dst = ip_src;
-
- ip.ip_sum = inet_checksum(&ip, ip_size, ~0);
-
- /* Fill in ICMP header */
-
- icmp.icmp_type = type;
- icmp.icmp_code = code;
- icmp.icmp_cksum = 0;
-
- icmp.icmp_cksum = inet_checksum(&icmp, icmp_size, ~0);
- icmp.icmp_cksum = inet_checksum(packet->data + ether_size + ip_size + icmp_size, oldlen, icmp.icmp_cksum);
-
- /* Copy structs on stack back to packet */
-
- memcpy(packet->data + ether_size, &ip, ip_size);
- memcpy(packet->data + ether_size + ip_size, &icmp, icmp_size);
-
- packet->len = ether_size + ip_size + icmp_size + oldlen;
-
- send_packet(source, packet);
-}
-
-/* RFC 791 */
-
-static void fragment_ipv4_packet(node_t *dest, vpn_packet_t *packet) {
- struct ip ip;
- vpn_packet_t fragment;
- int len, maxlen, todo;
- uint8_t *offset;
- uint16_t ip_off, origf;
-
- memcpy(&ip, packet->data + ether_size, ip_size);
- fragment.priority = packet->priority;
-
- if(ip.ip_hl != ip_size / 4)
- return;
-
- todo = ntohs(ip.ip_len) - ip_size;
-
- if(ether_size + ip_size + todo != packet->len) {
- ifdebug(TRAFFIC) logger(LOG_WARNING, "Length of packet (%d) doesn't match length in IPv4 header (%zd)", packet->len, ether_size + ip_size + todo);
- return;
- }
-
- ifdebug(TRAFFIC) logger(LOG_INFO, "Fragmenting packet of %d bytes to %s (%s)", packet->len, dest->name, dest->hostname);
-
- offset = packet->data + ether_size + ip_size;
- maxlen = (dest->mtu - ether_size - ip_size) & ~0x7;
- ip_off = ntohs(ip.ip_off);
- origf = ip_off & ~IP_OFFMASK;
- ip_off &= IP_OFFMASK;
-
- while(todo) {
- len = todo > maxlen ? maxlen : todo;
- memcpy(fragment.data + ether_size + ip_size, offset, len);
- todo -= len;
- offset += len;
-
- ip.ip_len = htons(ip_size + len);
- ip.ip_off = htons(ip_off | origf | (todo ? IP_MF : 0));
- ip.ip_sum = 0;
- ip.ip_sum = inet_checksum(&ip, ip_size, ~0);
- memcpy(fragment.data, packet->data, ether_size);
- memcpy(fragment.data + ether_size, &ip, ip_size);
- fragment.len = ether_size + ip_size + len;
-
- send_packet(dest, &fragment);
-
- ip_off += len / 8;
- }
-}
-
-static void route_ipv4_unicast(node_t *source, vpn_packet_t *packet) {
- subnet_t *subnet;
- node_t *via;
- ipv4_t dest;
-
- memcpy(&dest, &packet->data[30], sizeof dest);
- subnet = lookup_subnet_ipv4(&dest);
-
- if(!subnet) {
- ifdebug(TRAFFIC) logger(LOG_WARNING, "Cannot route packet from %s (%s): unknown IPv4 destination address %d.%d.%d.%d",
- source->name, source->hostname,
- dest.x[0],
- dest.x[1],
- dest.x[2],
- dest.x[3]);
-
- route_ipv4_unreachable(source, packet, ICMP_DEST_UNREACH, ICMP_NET_UNKNOWN);
- return;
- }
-
- if(subnet->owner == source) {
- ifdebug(TRAFFIC) logger(LOG_WARNING, "Packet looping back to %s (%s)!", source->name, source->hostname);
- return;
- }
-
- if(!subnet->owner->status.reachable)
- return route_ipv4_unreachable(source, packet, ICMP_DEST_UNREACH, ICMP_NET_UNREACH);
-
- if(forwarding_mode == FMODE_OFF && source != myself && subnet->owner != myself)
- return route_ipv4_unreachable(source, packet, ICMP_DEST_UNREACH, ICMP_NET_ANO);
-
- if(priorityinheritance)
- packet->priority = packet->data[15];
-
- via = (subnet->owner->via == myself) ? subnet->owner->nexthop : subnet->owner->via;
-
- if(directonly && subnet->owner != via)
- return route_ipv4_unreachable(source, packet, ICMP_DEST_UNREACH, ICMP_NET_ANO);
-
- if(via && packet->len > max(via->mtu, 590) && via != myself) {
- ifdebug(TRAFFIC) logger(LOG_INFO, "Packet for %s (%s) length %d larger than MTU %d", subnet->owner->name, subnet->owner->hostname, packet->len, via->mtu);
- if(packet->data[20] & 0x40) {
- packet->len = max(via->mtu, 590);
- route_ipv4_unreachable(source, packet, ICMP_DEST_UNREACH, ICMP_FRAG_NEEDED);
- } else {
- fragment_ipv4_packet(via, packet);
- }
-
- return;
- }
-
- clamp_mss(source, via, packet);
-
- send_packet(subnet->owner, packet);
-}
-
-static void route_ipv4(node_t *source, vpn_packet_t *packet) {
- if(!checklength(source, packet, ether_size + ip_size))
- return;
-
- if(((packet->data[30] & 0xf0) == 0xe0) || (
- packet->data[30] == 255 &&
- packet->data[31] == 255 &&
- packet->data[32] == 255 &&
- packet->data[33] == 255))
- broadcast_packet(source, packet);
- else
- route_ipv4_unicast(source, packet);
-}
-
-/* RFC 2463 */
-
-static void route_ipv6_unreachable(node_t *source, vpn_packet_t *packet, uint8_t type, uint8_t code) {
- struct ip6_hdr ip6;
- struct icmp6_hdr icmp6 = {0};
- uint16_t checksum;
-
- struct {
- struct in6_addr ip6_src; /* source address */
- struct in6_addr ip6_dst; /* destination address */
- uint32_t length;
- uint32_t next;
- } pseudo;
-
- if(ratelimit(3))
- return;
-
- /* Swap Ethernet source and destination addresses */
-
- swap_mac_addresses(packet);
-
- /* Copy headers from packet to structs on the stack */
-
- memcpy(&ip6, packet->data + ether_size, ip6_size);
-
- /* Remember original source and destination */
-
- pseudo.ip6_src = ip6.ip6_dst;
- pseudo.ip6_dst = ip6.ip6_src;
-
- pseudo.length = packet->len - ether_size;
-
- if(type == ICMP6_PACKET_TOO_BIG)
- icmp6.icmp6_mtu = htonl(pseudo.length);
-
- if(pseudo.length >= IP_MSS - ip6_size - icmp6_size)
- pseudo.length = IP_MSS - ip6_size - icmp6_size;
-
- /* Copy first part of original contents to ICMP message */
-
- memmove(packet->data + ether_size + ip6_size + icmp6_size, packet->data + ether_size, pseudo.length);
-
- /* Fill in IPv6 header */
-
- ip6.ip6_flow = htonl(0x60000000UL);
- ip6.ip6_plen = htons(icmp6_size + pseudo.length);
- ip6.ip6_nxt = IPPROTO_ICMPV6;
- ip6.ip6_hlim = 255;
- ip6.ip6_src = pseudo.ip6_src;
- ip6.ip6_dst = pseudo.ip6_dst;
-
- /* Fill in ICMP header */
-
- icmp6.icmp6_type = type;
- icmp6.icmp6_code = code;
- icmp6.icmp6_cksum = 0;
-
- /* Create pseudo header */
-
- pseudo.length = htonl(icmp6_size + pseudo.length);
- pseudo.next = htonl(IPPROTO_ICMPV6);
-
- /* Generate checksum */
-
- checksum = inet_checksum(&pseudo, sizeof(pseudo), ~0);
- checksum = inet_checksum(&icmp6, icmp6_size, checksum);
- checksum = inet_checksum(packet->data + ether_size + ip6_size + icmp6_size, ntohl(pseudo.length) - icmp6_size, checksum);
-
- icmp6.icmp6_cksum = checksum;
-
- /* Copy structs on stack back to packet */
-
- memcpy(packet->data + ether_size, &ip6, ip6_size);
- memcpy(packet->data + ether_size + ip6_size, &icmp6, icmp6_size);
-
- packet->len = ether_size + ip6_size + ntohl(pseudo.length);
-
- send_packet(source, packet);
-}
-
-static void route_ipv6_unicast(node_t *source, vpn_packet_t *packet) {
- subnet_t *subnet;
- node_t *via;
- ipv6_t dest;