+rmode_t routing_mode = RMODE_ROUTER;
+bool priorityinheritance = false;
+int macexpire = 600;
+bool overwrite_mac = false;
+mac_t mymac = {{0xFE, 0xFD, 0, 0, 0, 0}};
+
+/* Sizes of various headers */
+
+static const size_t ether_size = sizeof(struct ether_header);
+static const size_t arp_size = sizeof(struct ether_arp);
+static const size_t ip_size = sizeof(struct ip);
+static const size_t icmp_size = sizeof(struct icmp) - sizeof(struct ip);
+static const size_t ip6_size = sizeof(struct ip6_hdr);
+static const size_t icmp6_size = sizeof(struct icmp6_hdr);
+static const size_t ns_size = sizeof(struct nd_neighbor_solicit);
+static const size_t opt_size = sizeof(struct nd_opt_hdr);
+
+static struct event age_subnets_event;
+
+/* RFC 1071 */
+
+static uint16_t inet_checksum(void *data, int len, uint16_t prevsum)
+{
+ uint16_t *p = data;
+ uint32_t checksum = prevsum ^ 0xFFFF;
+
+ while(len >= 2) {
+ checksum += *p++;
+ len -= 2;
+ }
+
+ if(len)
+ checksum += *(uint8_t *)p;
+
+ while(checksum >> 16)
+ checksum = (checksum & 0xFFFF) + (checksum >> 16);
+
+ return ~checksum;
+}
+
+static bool ratelimit(int frequency) {
+ static time_t lasttime = 0;
+ static int count = 0;
+ time_t now = time(NULL);
+
+ if(lasttime == now) {
+ if(++count > frequency)
+ return true;
+ } else {
+ lasttime = now;
+ count = 0;
+ }
+
+ return false;
+}
+
+static bool checklength(node_t *source, vpn_packet_t *packet, length_t length) {
+ if(packet->len < length) {
+ ifdebug(TRAFFIC) logger(LOG_WARNING, _("Got too short packet from %s (%s)"), source->name, source->hostname);
+ return false;
+ } else
+ return true;
+}
+
+static void age_subnets(int fd, short events, void *data)
+{
+ subnet_t *s;
+ connection_t *c;
+ splay_node_t *node, *next, *node2;
+ bool left = false;
+ time_t now = time(NULL);
+
+ cp();
+
+ 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_del(myself, s);
+ } else {
+ if(s->expires)
+ left = true;
+ }
+ }
+
+ if(left)
+ event_add(&age_subnets_event, &(struct timeval){10, 0});
+}
+
+static void learn_mac(mac_t *address)
+{
+ subnet_t *subnet;
+ splay_node_t *node;
+ connection_t *c;
+
+ cp();
+
+ subnet = lookup_subnet_mac(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 = time(NULL) + macexpire;
+ subnet->net.mac.address = *address;
+ subnet_add(myself, subnet);
+
+ /* 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(!timeout_initialized(&age_subnets_event))
+ timeout_set(&age_subnets_event, age_subnets, NULL);
+ event_add(&age_subnets_event, &(struct timeval){10, 0});
+ } else {
+ if(subnet->expires)
+ subnet->expires = time(NULL) + macexpire;
+ }
+}
+
+static void route_mac(node_t *source, vpn_packet_t *packet)
+{
+ subnet_t *subnet;
+ mac_t dest;
+
+ cp();
+
+
+ /* Learn source address */
+
+ if(source == myself) {
+ mac_t src;
+ memcpy(&src, &packet->data[6], sizeof src);
+ learn_mac(&src);
+ }
+
+ /* Lookup destination address */
+
+ memcpy(&dest, &packet->data[0], sizeof dest);
+ subnet = lookup_subnet_mac(&dest);
+
+ if(!subnet) {
+ broadcast_packet(source, packet);
+ return;
+ }
+
+ if(subnet->owner == source) {
+ ifdebug(TRAFFIC) logger(LOG_WARNING, _("Packet looping back to %s (%s)!"), source->name, source->hostname);
+ return;
+ }
+
+ send_packet(subnet->owner, packet);
+}
+
+/* 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;
+
+ cp();
+
+ /* 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);
+}