+static void mtu_probe_h(meshlink_handle_t *mesh, node_t *n, vpn_packet_t *packet, uint16_t len) {
+ if(len < 64) {
+ logger(mesh, MESHLINK_WARNING, "Got too short MTU probe length %d from %s", packet->len, n->name);
+ return;
+ }
+
+ logger(mesh, MESHLINK_DEBUG, "Got MTU probe length %d from %s", packet->len, n->name);
+
+ if(!packet->data[0]) {
+ /* It's a probe request, send back a reply */
+
+ packet->data[0] = 1;
+
+ /* 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(mesh, n, packet);
+ n->status.udp_confirmed = udp_confirmed;
+ } else {
+ /* It's a valid reply: now we know bidirectional communication
+ is possible using the address and socket that the reply
+ packet used. */
+
+ if(!n->status.udp_confirmed) {
+ char *address, *port;
+ sockaddr2str(&n->address, &address, &port);
+ send_request(mesh, n->nexthop->connection, NULL, "%d %s %s . -1 -1 -1 0 %s %s", ANS_KEY, n->name, n->name, address, port);
+ free(address);
+ free(port);
+ n->status.udp_confirmed = true;
+ }