+rmode_t routing_mode = RMODE_ROUTER;
+fmode_t forwarding_mode = FMODE_INTERNAL;
+bmode_t broadcast_mode = BMODE_MST;
+bool decrement_ttl = false;
+bool directonly = false;
+bool priorityinheritance = false;
+int macexpire = 600;
+bool overwrite_mac = false;
+mac_t mymac = {{0xFE, 0xFD, 0, 0, 0, 0}};
+bool pcap = false;
+
+/* 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);
+
+#ifndef MAX
+#define MAX(a, b) ((a) > (b) ? (a) : (b))
+#endif
+
+static timeout_t age_subnets_timeout;
+
+/* 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.tv_sec) {
+ if(count >= frequency)
+ return true;
+ } else {
+ lasttime = now.tv_sec;
+ count = 0;
+ }
+
+ count++;
+ return false;
+}
+
+static bool checklength(node_t *source, vpn_packet_t *packet, length_t length) {
+ if(packet->len < length) {
+ logger(DEBUG_TRAFFIC, 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, &DATA(packet)[0], sizeof tmp);
+ memcpy(&DATA(packet)[0], &DATA(packet)[6], sizeof tmp);
+ memcpy(&DATA(packet)[6], &tmp, sizeof tmp);
+}
+
+/* RFC 792 */
+
+static void route_ipv4_unreachable(node_t *source, vpn_packet_t *packet, length_t ether_size, 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, DATA(packet) + ether_size, ip_size);
+
+ /* Remember original source and destination */
+
+ ip_src = ip.ip_src;
+ ip_dst = ip.ip_dst;
+
+ /* Try to reply with an IP address assigned to the local machine */
+
+ if (type == ICMP_TIME_EXCEEDED && code == ICMP_EXC_TTL) {
+ int sockfd = socket(AF_INET, SOCK_DGRAM, 0);
+ if (sockfd != -1) {
+ struct sockaddr_in addr;
+ memset(&addr, 0, sizeof(addr));
+ addr.sin_family = AF_INET;
+ addr.sin_addr = ip.ip_src;
+ if (!connect(sockfd, (const struct sockaddr*) &addr, sizeof(addr))) {
+ memset(&addr, 0, sizeof(addr));
+ addr.sin_family = AF_INET;
+ socklen_t addrlen = sizeof(addr);
+ if (!getsockname(sockfd, (struct sockaddr*) &addr, &addrlen) && addrlen <= sizeof(addr)) {
+ ip_dst = addr.sin_addr;
+ }
+ }
+ close(sockfd);
+ }
+ }
+
+ 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(DATA(packet) + ether_size + ip_size + icmp_size, DATA(packet) + 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(DATA(packet) + ether_size + ip_size + icmp_size, oldlen, icmp.icmp_cksum);
+
+ /* Copy structs on stack back to packet */
+
+ memcpy(DATA(packet) + ether_size, &ip, ip_size);
+ memcpy(DATA(packet) + ether_size + ip_size, &icmp, icmp_size);
+
+ packet->len = ether_size + ip_size + icmp_size + oldlen;
+
+ send_packet(source, packet);
+}
+
+/* RFC 2463 */
+
+static void route_ipv6_unreachable(node_t *source, vpn_packet_t *packet, length_t ether_size, 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, DATA(packet) + ether_size, ip6_size);
+
+ /* Remember original source and destination */
+
+ pseudo.ip6_src = ip6.ip6_dst;
+ pseudo.ip6_dst = ip6.ip6_src;
+
+ /* Try to reply with an IP address assigned to the local machine */
+
+ if (type == ICMP6_TIME_EXCEEDED && code == ICMP6_TIME_EXCEED_TRANSIT) {
+ int sockfd = socket(AF_INET6, SOCK_DGRAM, 0);
+ if (sockfd != -1) {
+ struct sockaddr_in6 addr;
+ memset(&addr, 0, sizeof(addr));
+ addr.sin6_family = AF_INET6;
+ addr.sin6_addr = ip6.ip6_src;
+ if (!connect(sockfd, (const struct sockaddr*) &addr, sizeof(addr))) {
+ memset(&addr, 0, sizeof(addr));
+ addr.sin6_family = AF_INET6;
+ socklen_t addrlen = sizeof(addr);
+ if (!getsockname(sockfd, (struct sockaddr*) &addr, &addrlen) && addrlen <= sizeof(addr)) {
+ pseudo.ip6_src = addr.sin6_addr;
+ }
+ }
+ close(sockfd);
+ }
+ }
+
+ 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(DATA(packet) + ether_size + ip6_size + icmp6_size, DATA(packet) + 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(DATA(packet) + ether_size + ip6_size + icmp6_size, ntohl(pseudo.length) - icmp6_size, checksum);
+
+ icmp6.icmp6_cksum = checksum;
+
+ /* Copy structs on stack back to packet */
+
+ memcpy(DATA(packet) + ether_size, &ip6, ip6_size);
+ memcpy(DATA(packet) + ether_size + ip6_size, &icmp6, icmp6_size);
+
+ packet->len = ether_size + ip6_size + ntohl(pseudo.length);
+
+ send_packet(source, packet);
+}
+
+static bool do_decrement_ttl(node_t *source, vpn_packet_t *packet) {
+ uint16_t type = DATA(packet)[12] << 8 | DATA(packet)[13];
+ length_t ethlen = ether_size;
+
+ if(type == ETH_P_8021Q) {
+ type = DATA(packet)[16] << 8 | DATA(packet)[17];
+ ethlen += 4;
+ }
+
+ switch (type) {
+ case ETH_P_IP:
+ if(!checklength(source, packet, ethlen + ip_size))
+ return false;
+
+ if(DATA(packet)[ethlen + 8] <= 1) {
+ if(DATA(packet)[ethlen + 11] != IPPROTO_ICMP || DATA(packet)[ethlen + 32] != ICMP_TIME_EXCEEDED)
+ route_ipv4_unreachable(source, packet, ethlen, ICMP_TIME_EXCEEDED, ICMP_EXC_TTL);
+ return false;
+ }
+
+ uint16_t old = DATA(packet)[ethlen + 8] << 8 | DATA(packet)[ethlen + 9];
+ DATA(packet)[ethlen + 8]--;
+ uint16_t new = DATA(packet)[ethlen + 8] << 8 | DATA(packet)[ethlen + 9];
+
+ uint32_t checksum = DATA(packet)[ethlen + 10] << 8 | DATA(packet)[ethlen + 11];
+ checksum += old + (~new & 0xFFFF);
+ while(checksum >> 16)
+ checksum = (checksum & 0xFFFF) + (checksum >> 16);
+ DATA(packet)[ethlen + 10] = checksum >> 8;
+ DATA(packet)[ethlen + 11] = checksum & 0xff;
+
+ return true;
+
+ case ETH_P_IPV6:
+ if(!checklength(source, packet, ethlen + ip6_size))
+ return false;
+
+ if(DATA(packet)[ethlen + 7] <= 1) {
+ if(DATA(packet)[ethlen + 6] != IPPROTO_ICMPV6 || DATA(packet)[ethlen + 40] != ICMP6_TIME_EXCEEDED)
+ route_ipv6_unreachable(source, packet, ethlen, ICMP6_TIME_EXCEEDED, ICMP6_TIME_EXCEED_TRANSIT);
+ return false;
+ }
+
+ DATA(packet)[ethlen + 7]--;
+
+ return true;
+
+ default:
+ return true;
+ }
+}
+
+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 = ether_size;
+ uint16_t type = DATA(packet)[12] << 8 | DATA(packet)[13];
+
+ if(type == ETH_P_8021Q) {
+ start += 4;
+ type = DATA(packet)[16] << 8 | DATA(packet)[17];
+ }
+
+ if(type == ETH_P_IP && DATA(packet)[start + 9] == 6)
+ start += (DATA(packet)[start] & 0xf) * 4;
+ else if(type == ETH_P_IPV6 && DATA(packet)[start + 6] == 6)
+ start += 40;
+ else
+ return;
+
+ if(packet->len <= start + 20)
+ return;
+
+ /* Use data offset field to calculate length of options field */
+ int len = ((DATA(packet)[start + 12] >> 4) - 5) * 4;
+
+ if(packet->len < start + 20 + len)
+ return;
+
+ /* Search for MSS option header */
+ for(int i = 0; i < len;) {
+ if(DATA(packet)[start + 20 + i] == 0)
+ break;
+
+ if(DATA(packet)[start + 20 + i] == 1) {
+ i++;
+ continue;
+ }
+
+ if(i > len - 2 || i > len - DATA(packet)[start + 21 + i])
+ break;
+
+ if(DATA(packet)[start + 20 + i] != 2) {
+ if(DATA(packet)[start + 21 + i] < 2)
+ break;
+ i += DATA(packet)[start + 21 + i];
+ continue;
+ }
+
+ if(DATA(packet)[start + 21] != 4)
+ break;
+
+ /* Found it */
+ uint16_t oldmss = DATA(packet)[start + 22 + i] << 8 | DATA(packet)[start + 23 + i];
+ uint16_t newmss = mtu - start - 20;
+ uint32_t csum = DATA(packet)[start + 16] << 8 | DATA(packet)[start + 17];
+
+ if(oldmss <= newmss)
+ break;
+
+ logger(DEBUG_TRAFFIC, LOG_INFO, "Clamping MSS of packet from %s to %s to %d", source->name, via->name, newmss);
+
+ /* Update the MSS value and the checksum */
+ DATA(packet)[start + 22 + i] = newmss >> 8;
+ DATA(packet)[start + 23 + i] = newmss & 0xff;
+ csum ^= 0xffff;
+ csum += oldmss ^ 0xffff;
+ csum += newmss;
+ csum = (csum & 0xffff) + (csum >> 16);
+ csum += csum >> 16;
+ csum ^= 0xffff;
+ DATA(packet)[start + 16] = csum >> 8;
+ DATA(packet)[start + 17] = csum;
+ break;
+ }
+}
+
+static void age_subnets(void *data) {
+ bool left = false;
+
+ for splay_each(subnet_t, s, myself->subnet_tree) {
+ if(s->expires && s->expires < now.tv_sec) {
+ if(debug_level >= DEBUG_TRAFFIC) {
+ char netstr[MAXNETSTR];
+ if(net2str(netstr, sizeof netstr, s))
+ logger(DEBUG_TRAFFIC, LOG_INFO, "Subnet %s expired", netstr);
+ }
+
+ for list_each(connection_t, c, connection_list)
+ if(c->edge)
+ send_del_subnet(c, s);
+
+ subnet_del(myself, s);
+ } else {
+ if(s->expires)
+ left = true;
+ }
+ }
+
+ if(left)
+ timeout_set(&age_subnets_timeout, &(struct timeval){10, rand() % 100000});
+}
+
+static void learn_mac(mac_t *address) {
+ subnet_t *subnet = lookup_subnet_mac(myself, address);
+
+ /* If we don't know this MAC address yet, store it */
+
+ if(!subnet) {
+ logger(DEBUG_TRAFFIC, LOG_INFO, "Learned new MAC address %x:%x:%x:%x:%x:%x",
+ 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.tv_sec + 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 list_each(connection_t, c, connection_list)
+ if(c->edge)
+ send_add_subnet(c, subnet);
+
+ timeout_add(&age_subnets_timeout, age_subnets, NULL, &(struct timeval){10, rand() % 100000});
+ } else {
+ if(subnet->expires)
+ subnet->expires = now.tv_sec + macexpire;
+ }
+}
+
+static void route_broadcast(node_t *source, vpn_packet_t *packet) {
+ if(decrement_ttl && source != myself)
+ if(!do_decrement_ttl(source, packet))
+ return;
+
+ broadcast_packet(source, packet);
+}
+
+/* RFC 791 */
+
+static void fragment_ipv4_packet(node_t *dest, vpn_packet_t *packet, length_t ether_size) {
+ struct ip ip;
+ vpn_packet_t fragment;
+ int len, maxlen, todo;
+ uint8_t *offset;
+ uint16_t ip_off, origf;
+
+ memcpy(&ip, DATA(packet) + ether_size, ip_size);
+ fragment.priority = packet->priority;
+ fragment.offset = DEFAULT_PACKET_OFFSET;
+
+ if(ip.ip_hl != ip_size / 4)
+ return;
+
+ todo = ntohs(ip.ip_len) - ip_size;
+
+ if(ether_size + ip_size + todo != packet->len) {
+ 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));
+ return;
+ }
+
+ logger(DEBUG_TRAFFIC, LOG_INFO, "Fragmenting packet of %d bytes to %s (%s)", packet->len, dest->name, dest->hostname);
+
+ offset = DATA(packet) + 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;