- After the initial discovery, a fourth packet is added to each batch with a
- size larger than the currently known PMTU, to test if the PMTU has increased.
-
- In case local discovery is enabled, another packet is added to each batch,
- which will be broadcast to the local network.
-
-*/
-
-static void send_mtu_probe_handler(event_loop_t *loop, void *data) {
- meshlink_handle_t *mesh = loop->data;
- node_t *n = data;
- int timeout = 1;
-
- n->mtuprobes++;
-
- if(!n->status.reachable || !n->status.validkey) {
- logger(mesh, MESHLINK_INFO, "Trying to send MTU probe to unreachable or rekeying node %s (%s)", n->name, n->hostname);
- n->mtuprobes = 0;
- return;
- }
-
- if(n->mtuprobes > 32) {
- if(!n->minmtu) {
- n->mtuprobes = 31;
- timeout = mesh->pinginterval;
- goto end;
- }
-
- logger(mesh, MESHLINK_INFO, "%s (%s) did not respond to UDP ping, restarting PMTU discovery", n->name, n->hostname);
- n->status.udp_confirmed = false;
- n->mtuprobes = 1;
- n->minmtu = 0;
- n->maxmtu = MTU;
- }
-
- if(n->mtuprobes >= 10 && n->mtuprobes < 32 && !n->minmtu) {
- logger(mesh, MESHLINK_INFO, "No response to MTU probes from %s (%s)", n->name, n->hostname);
- n->mtuprobes = 31;
- }
-
- if(n->mtuprobes == 30 || (n->mtuprobes < 30 && n->minmtu >= n->maxmtu)) {
- if(n->minmtu > n->maxmtu)
- n->minmtu = n->maxmtu;
- else
- n->maxmtu = n->minmtu;
- n->mtu = n->minmtu;
- logger(mesh, MESHLINK_INFO, "Fixing MTU of %s (%s) to %d after %d probes", n->name, n->hostname, n->mtu, n->mtuprobes);
- n->mtuprobes = 31;
- }
-
- if(n->mtuprobes == 31) {
- timeout = mesh->pinginterval;
- goto end;
- } else if(n->mtuprobes == 32) {
- timeout = mesh->pingtimeout;
- }
-
- for(int i = 0; i < 4 + mesh->localdiscovery; i++) {
- int len;
-
- if(i == 0) {
- if(n->mtuprobes < 30 || n->maxmtu + 8 >= MTU)
- continue;
- len = n->maxmtu + 8;
- } else if(n->maxmtu <= n->minmtu) {
- len = n->maxmtu;
- } else {
- len = n->minmtu + 1 + rand() % (n->maxmtu - n->minmtu);
- }
-
- if(len < 64)
- len = 64;
-
- vpn_packet_t packet;
- packet.probe = true;
- memset(packet.data, 0, 14);
- randomize(packet.data + 14, len - 14);
- packet.len = len;
- n->status.broadcast = i >= 4 && n->mtuprobes <= 10 && n->prevedge;
-
- logger(mesh, MESHLINK_INFO, "Sending MTU probe length %d to %s (%s)", len, n->name, n->hostname);
-
- send_udppacket(mesh, n, &packet);
- }
-
- n->status.broadcast = false;
- n->probe_counter = 0;
- gettimeofday(&n->probe_time, NULL);
-
- /* Calculate the packet loss of incoming traffic by comparing the rate of
- packets received to the rate with which the sequence number has increased.
- */
-
- if(n->received > n->prev_received)
- n->packetloss = 1.0 - (n->received - n->prev_received) / (float)(n->received_seqno - n->prev_received_seqno);
- else
- n->packetloss = n->received_seqno <= n->prev_received_seqno;
-
- n->prev_received_seqno = n->received_seqno;
- n->prev_received = n->received;
-
-end:
- timeout_set(&mesh->loop, &n->mtutimeout, &(struct timeval){timeout, rand() % 100000});
-}
-
-void send_mtu_probe(meshlink_handle_t *mesh, node_t *n) {
- timeout_add(&mesh->loop, &n->mtutimeout, send_mtu_probe_handler, n, &(struct timeval){1, 0});
- send_mtu_probe_handler(&mesh->loop, n);
-}
-
-static void mtu_probe_h(meshlink_handle_t *mesh, node_t *n, vpn_packet_t *packet, uint16_t len) {
- logger(mesh, MESHLINK_INFO, "Got MTU probe length %d from %s (%s)", packet->len, n->name, n->hostname);
-
- 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. */
-
- n->status.udp_confirmed = true;
-
- /* If we haven't established the PMTU yet, restart the discovery process. */
-
- if(n->mtuprobes > 30) {
- if (len == n->maxmtu + 8) {
- logger(mesh, MESHLINK_INFO, "Increase in PMTU to %s (%s) detected, restarting PMTU discovery", n->name, n->hostname);
- n->maxmtu = MTU;
- n->mtuprobes = 10;
- return;
- }
-
- if(n->minmtu)
- n->mtuprobes = 30;
- else
- n->mtuprobes = 1;
- }
-
- /* If applicable, raise the minimum supported MTU */
-
- if(len > n->maxmtu)
- len = n->maxmtu;
- if(n->minmtu < len)
- n->minmtu = len;
-
- /* Calculate RTT and bandwidth.
- The RTT is the time between the MTU probe burst was sent and the first
- reply is received. The bandwidth is measured using the time between the
- arrival of the first and third probe reply.
- */
-
- struct timeval now, diff;
- gettimeofday(&now, NULL);
- timersub(&now, &n->probe_time, &diff);
-
- n->probe_counter++;
-
- if(n->probe_counter == 1) {
- n->rtt = diff.tv_sec + diff.tv_usec * 1e-6;
- n->probe_time = now;
- } else if(n->probe_counter == 3) {
- n->bandwidth = 2.0 * len / (diff.tv_sec + diff.tv_usec * 1e-6);
- logger(mesh, MESHLINK_DEBUG, "%s (%s) RTT %.2f ms, burst bandwidth %.3f Mbit/s, rx packet loss %.2f %%", n->name, n->hostname, n->rtt * 1e3, n->bandwidth * 8e-6, n->packetloss * 1e2);
- }
- }
-}