+static void try_fix_mtu(node_t *n) {
+ if(n->mtuprobes < 0)
+ return;
+
+ if(n->mtuprobes == 20 || n->minmtu >= n->maxmtu) {
+ if(n->minmtu > n->maxmtu)
+ n->minmtu = n->maxmtu;
+ else
+ n->maxmtu = n->minmtu;
+ n->mtu = n->minmtu;
+ logger(DEBUG_TRAFFIC, LOG_INFO, "Fixing MTU of %s (%s) to %d after %d probes", n->name, n->hostname, n->mtu, n->mtuprobes);
+ n->mtuprobes = -1;
+ }
+}
+
+static void udp_probe_timeout_handler(void *data) {
+ node_t *n = data;
+ if(!n->status.udp_confirmed)
+ return;
+
+ logger(DEBUG_TRAFFIC, LOG_INFO, "Too much time has elapsed since last UDP ping response from %s (%s), stopping UDP communication", n->name, n->hostname);
+ n->status.udp_confirmed = false;
+ n->maxrecentlen = 0;
+ n->mtuprobes = 0;
+ n->minmtu = 0;
+ n->maxmtu = MTU;
+}
+
+static void send_udp_probe_reply(node_t *n, vpn_packet_t *packet, length_t len) {
+ if(!n->status.sptps && !n->status.validkey) {
+ logger(DEBUG_TRAFFIC, LOG_INFO, "Trying to send UDP probe reply to %s (%s) but we don't have his key yet", n->name, n->hostname);
+ return;
+ }
+
+ /* Type 2 probe replies were introduced in protocol 17.3 */
+ if ((n->options >> 24) >= 3) {
+ DATA(packet)[0] = 2;
+ uint16_t len16 = htons(len);
+ memcpy(DATA(packet) + 1, &len16, 2);
+ packet->len = MIN_PROBE_SIZE;
+ logger(DEBUG_TRAFFIC, LOG_INFO, "Sending type 2 probe reply length %u to %s (%s)", len, n->name, n->hostname);
+
+ } else {
+ /* Legacy protocol: n won't understand type 2 probe replies. */
+ DATA(packet)[0] = 1;
+ logger(DEBUG_TRAFFIC, LOG_INFO, "Sending type 1 probe reply length %u to %s (%s)", len, n->name, n->hostname);
+ }
+
+ /* Temporarily set udp_confirmed, so that the reply is sent
+ back exactly the way it came in. */
+
+ bool udp_confirmed = n->status.udp_confirmed;
+ n->status.udp_confirmed = true;
+ send_udppacket(n, packet);
+ n->status.udp_confirmed = udp_confirmed;
+}
+
+static void udp_probe_h(node_t *n, vpn_packet_t *packet, length_t len) {
+ if(!DATA(packet)[0]) {
+ logger(DEBUG_TRAFFIC, LOG_INFO, "Got UDP probe request %d from %s (%s)", packet->len, n->name, n->hostname);
+ return send_udp_probe_reply(n, packet, len);
+ }
+
+ if (DATA(packet)[0] == 2) {
+ // It's a type 2 probe reply, use the length field inside the packet
+ uint16_t len16;
+ memcpy(&len16, DATA(packet) + 1, 2);
+ len = ntohs(len16);
+ }
+
+ logger(DEBUG_TRAFFIC, LOG_INFO, "Got type %d UDP probe reply %d from %s (%s)", DATA(packet)[0], len, n->name, n->hostname);
+
+ /* It's a valid reply: now we know bidirectional communication
+ is possible using the address and socket that the reply
+ packet used. */
+ n->status.udp_confirmed = true;
+
+ // Reset the UDP ping timer.
+ n->udp_ping_sent = now;
+
+ if(udp_discovery) {
+ timeout_del(&n->udp_ping_timeout);
+ timeout_add(&n->udp_ping_timeout, &udp_probe_timeout_handler, n, &(struct timeval){udp_discovery_timeout, 0});
+ }
+
+ if(len > n->maxmtu) {
+ logger(DEBUG_TRAFFIC, LOG_INFO, "Increase in PMTU to %s (%s) detected, restarting PMTU discovery", n->name, n->hostname);
+ n->minmtu = len;
+ n->maxmtu = MTU;
+ /* Set mtuprobes to 1 so that try_mtu() doesn't reset maxmtu */
+ n->mtuprobes = 1;
+ return;
+ } else if(n->mtuprobes < 0 && len == n->maxmtu) {
+ /* We got a maxmtu sized packet, confirming the PMTU is still valid. */
+ n->mtuprobes = -1;
+ n->mtu_ping_sent = now;
+ }
+
+ /* If applicable, raise the minimum supported MTU */
+
+ if(n->minmtu < len) {
+ n->minmtu = len;
+ try_fix_mtu(n);
+ }
+}
+
+static length_t compress_packet(uint8_t *dest, const uint8_t *source, length_t len, int level) {
+ if(level == 0) {
+ memcpy(dest, source, len);
+ return len;
+ } else if(level == 10) {
+#ifdef HAVE_LZO
+ lzo_uint lzolen = MAXSIZE;
+ lzo1x_1_compress(source, len, dest, &lzolen, lzo_wrkmem);
+ return lzolen;
+#else
+ return -1;
+#endif
+ } else if(level < 10) {
+#ifdef HAVE_ZLIB
+ unsigned long destlen = MAXSIZE;
+ if(compress2(dest, &destlen, source, len, level) == Z_OK)
+ return destlen;
+ else
+#endif
+ return -1;
+ } else {
+#ifdef HAVE_LZO
+ lzo_uint lzolen = MAXSIZE;
+ lzo1x_999_compress(source, len, dest, &lzolen, lzo_wrkmem);
+ return lzolen;
+#else
+ return -1;
+#endif
+ }
+
+ return -1;
+}
+
+static length_t uncompress_packet(uint8_t *dest, const uint8_t *source, length_t len, int level) {
+ if(level == 0) {
+ memcpy(dest, source, len);
+ return len;
+ } else if(level > 9) {
+#ifdef HAVE_LZO
+ lzo_uint lzolen = MAXSIZE;
+ if(lzo1x_decompress_safe(source, len, dest, &lzolen, NULL) == LZO_E_OK)
+ return lzolen;
+ else
+#endif
+ return -1;
+ }
+#ifdef HAVE_ZLIB
+ else {
+ unsigned long destlen = MAXSIZE;
+ if(uncompress(dest, &destlen, source, len) == Z_OK)
+ return destlen;
+ else
+ return -1;
+ }
+#endif
+
+ return -1;
+}
+