Don't send MTU probes smaller than 512 bytes.

[tinc] / src / net_packet.c

diff --git a/src/net_packet.c b/src/net_packet.c
index 2f15bb4..626114c 100644 (file)
--- a/src/net_packet.c
+++ b/src/net_packet.c
@@ -69,7 +69,7 @@ static void try_fix_mtu(node_t *n) {
        if(n->mtuprobes < 0)
                return;
 
-       if(n->mtuprobes == 90 || n->minmtu >= n->maxmtu) {
+       if(n->mtuprobes == 20 || n->minmtu >= n->maxmtu) {
                if(n->minmtu > n->maxmtu)
                        n->minmtu = n->maxmtu;
                else
@@ -141,10 +141,10 @@ static void udp_probe_h(node_t *n, vpn_packet_t *packet, length_t len) {
                        timeout_add(&n->udp_ping_timeout, &udp_probe_timeout_handler, n, &(struct timeval){udp_discovery_timeout, 0});
                }
 
-               if(probelen >= n->maxmtu + 8) {
+               if(probelen >= n->maxmtu + 1) {
                        logger(DEBUG_TRAFFIC, LOG_INFO, "Increase in PMTU to %s (%s) detected, restarting PMTU discovery", n->name, n->hostname);
                        n->maxmtu = MTU;
-                       n->mtuprobes = 30;
+                       n->mtuprobes = 0;
                        return;
                }
 
@@ -897,8 +897,8 @@ static void try_mtu(node_t *n) {
                return;
        }
 
-       /* mtuprobes == 0..89: initial discovery, send bursts with 1 second interval, mtuprobes++
-          mtuprobes ==    90: fix MTU, and go to -1
+       /* mtuprobes == 0..19: initial discovery, send bursts with 1 second interval, mtuprobes++
+          mtuprobes ==    20: fix MTU, and go to -1
           mtuprobes ==    -1: send one >maxmtu probe every pingtimeout */
 
        struct timeval now;
@@ -919,21 +919,21 @@ static void try_mtu(node_t *n) {
        if(n->mtuprobes < 0) {
                /* After the initial discovery, we only send one >maxmtu probe
                   to detect PMTU increases. */
-               if(n->maxmtu + 8 < MTU)
-                       send_udp_probe_packet(n, n->maxmtu + 8);
+               if(n->maxmtu + 1 < MTU)
+                       send_udp_probe_packet(n, n->maxmtu + 1);
        } else {
                /* Decreasing the number of probes per cycle might make the algorithm react faster to lost packets,
                   but it will typically increase convergence time in the no-loss case. */
                const length_t probes_per_cycle = 8;
 
                /* This magic value was determined using math simulations.
-                  It will result in a 1339-byte first probe, followed (if there was a reply) by a 1417-byte probe.
-                  Since 1417 is just below the range of tinc MTUs over typical networks,
+                  It will result in a 1329-byte first probe, followed (if there was a reply) by a 1407-byte probe.
+                  Since 1407 is just below the range of tinc MTUs over typical networks,
                   this fine-tuning allows tinc to cover a lot of ground very quickly. */
-               const float multiplier = 0.982;
+               const float multiplier = 0.97;
 
                const float cycle_position = probes_per_cycle - (n->mtuprobes % probes_per_cycle) - 1;
-               const length_t minmtu = MAX(n->minmtu, 64);
+               const length_t minmtu = MAX(n->minmtu, 512);
                const float interval = n->maxmtu - minmtu;
 
                /* The core of the discovery algorithm is this exponential.