+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);
+
+/* 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;
+
+ 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 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;
+
+ 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 = now + 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(subnet->expires)
+ subnet->expires = now + macexpire;
+}
+
+void age_subnets(void)
+{
+ subnet_t *s;
+ connection_t *c;
+ avl_node_t *node, *next, *node2;
+
+ 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);
+ }
+ }
+}
+
+/* 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();
+
+ /* 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;
+
+ cp();
+
+ 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;
+ }
+}