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wgengine: drop wireguard MTU to 1280 bytes. 

Signed-off-by: David Anderson <danderson@tailscale.com>
pull/305/head
David Anderson 2020-04-14 16:36:17 -07:00
parent b925e18f70
commit afbfe4f217
1 changed files with 11 additions and 1 deletions
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12
wgengine/userspace.go
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@ -34,6 +34,16 @@ import (
"tailscale.com/wgengine/packet" "tailscale.com/wgengine/packet"
) )
// minimalMTU is the MTU we set on tailscale's tuntap
// interface. wireguard-go defaults to 1420 bytes, which only works if
// the "outer" MTU is 1500 bytes. This breaks on DSL connections
// (typically 1492 MTU) and on GCE (1460 MTU?!).
//
// 1280 is the smallest MTU allowed for IPv6, which is a sensible
// "probably works everywhere" setting until we develop proper PMTU
// discovery.
const minimalMTU = 1280
type userspaceEngine struct { type userspaceEngine struct {
logf logger.Logf logf logger.Logf
reqCh chan struct{} reqCh chan struct{}
@ -84,7 +94,7 @@ func NewUserspaceEngine(logf logger.Logf, tunname string, listenPort uint16) (En
logf("Starting userspace wireguard engine with tun device %q", tunname) logf("Starting userspace wireguard engine with tun device %q", tunname)
tundev, err := tun.CreateTUN(tunname, device.DefaultMTU) tundev, err := tun.CreateTUN(tunname, minimalMTU)
if err != nil { if err != nil {
diagnoseTUNFailure(logf) diagnoseTUNFailure(logf)
logf("CreateTUN: %v", err) logf("CreateTUN: %v", err)