Files
gluetun/internal/pmtud/test/mtu.go
T
Quentin McGaw be92aa2ac4 Path MTU discovery fixes and improvements (#3109)
- Existing option `WIREGUARD_MTU` , if set, disables PMTUD and is used
- New option `PMTUD_ICMP_ADDRESSES=1.1.1.1,8.8.8.8` and `PMTUD_TCP_ADDRESSES=1.1.1.1:443,8.8.8.8:443`
- ICMP PMTUD now targets external-by-default IP addresses
- New TCP PMTUD (binary search only) as a second MTU confirmation and fallback mechanism.
- Force set TCP MSS to MTU - IP header - TCP base header - "magic 20 bytes" 🎆
- Fix #3108
2026-02-14 19:40:34 -05:00

37 lines
1.2 KiB
Go

package test
import "math"
// MakeMTUsToTest determines a slice of MTU values to test
// between minMTU and maxMTU inclusive. It creates an MTU
// slice of length up to 11 MTUs such that:
// - the first element is the minMTU
// - the last element is the maxMTU
// - elements in-between are separated as close to each other
// The number 11 is chosen to find the final MTU in 3 searches,
// with a total search space of 1728 MTUs which is enough;
// to find it in 2 searches requires 37 parallel queries which
// could be blocked by firewalls.
func MakeMTUsToTest(minMTU, maxMTU uint32) (mtus []uint32) {
const mtusLength = 11 // find the final MTU in 3 searches
diff := maxMTU - minMTU
switch {
case minMTU > maxMTU:
panic("minMTU > maxMTU")
case diff <= mtusLength:
mtus = make([]uint32, 0, diff)
for mtu := minMTU; mtu <= maxMTU; mtu++ {
mtus = append(mtus, mtu)
}
default:
step := float64(diff) / float64(mtusLength-1)
mtus = make([]uint32, 0, mtusLength)
for mtu := float64(minMTU); len(mtus) < mtusLength-1; mtu += step {
mtus = append(mtus, uint32(math.Round(mtu)))
}
mtus = append(mtus, maxMTU) // last element is the maxMTU
}
return mtus
}