static void send_udp_probe_packet(node_t *n, int len) {
vpn_packet_t packet;
- packet.offset = DEFAULT_PACKET_OFFSET;
- memset(DATA(&packet), 0, 14);
if(len > sizeof(packet.data)) {
logger(DEBUG_TRAFFIC, LOG_INFO, "Truncating probe length %d to %s (%s)", len, n->name, n->hostname);
len = sizeof(packet.data);
}
+ packet.offset = DEFAULT_PACKET_OFFSET;
+ memset(DATA(&packet), 0, 14);
randomize(DATA(&packet) + 14, len - 14);
packet.len = len;
packet.priority = 0;
const length_t minmtu = MAX(n->minmtu, 512);
const float interval = n->maxmtu - minmtu;
- /* The core of the discovery algorithm is this exponential.
- It produces very large probes early in the cycle, and then it very quickly decreases the probe size.
- This reflects the fact that in the most difficult cases, we don't get any feedback for probes that
- are too large, and therefore we need to concentrate on small offsets so that we can quickly converge
- on the precise MTU as we are approaching it.
- The last probe of the cycle is always 1 byte in size - this is to make sure we'll get at least one
- reply per cycle so that we can make progress. */
- const length_t offset = powf(interval, multiplier * cycle_position / (probes_per_cycle - 1));
+ length_t offset = 0;
+
+ /* powf can be underflowed if n->maxmtu is less than 512 due to the minmtu MAX bound */
+ if(interval > 0) {
+ /* The core of the discovery algorithm is this exponential.
+ It produces very large probes early in the cycle, and then it very quickly decreases the probe size.
+ This reflects the fact that in the most difficult cases, we don't get any feedback for probes that
+ are too large, and therefore we need to concentrate on small offsets so that we can quickly converge
+ on the precise MTU as we are approaching it.
+ The last probe of the cycle is always 1 byte in size - this is to make sure we'll get at least one
+ reply per cycle so that we can make progress. */
+ offset = powf(interval, multiplier * cycle_position / (probes_per_cycle - 1));
+ }
length_t maxmtu = n->maxmtu;
send_udp_probe_packet(n, minmtu + offset);