From 35f13442ef6696a877d96957502cd9b0de69b8cf Mon Sep 17 00:00:00 2001
From: "Jason A. Donenfeld" <Jason@zx2c4.com>
Date: Tue, 5 Mar 2019 01:00:06 +0100
Subject: ifaceconfig: set MTU and monitor for auto mtu changes

---
 service/ifaceconfig.go | 53 +++++++++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 52 insertions(+), 1 deletion(-)

(limited to 'service/ifaceconfig.go')

diff --git a/service/ifaceconfig.go b/service/ifaceconfig.go
index 4569b0ab..b2f93b70 100644
--- a/service/ifaceconfig.go
+++ b/service/ifaceconfig.go
@@ -59,10 +59,11 @@ func bindSocketRoute(family winipcfg.AddressFamily, device *device.Device, ourLu
 	return nil
 }
 
-func monitorDefaultRoutes(device *device.Device, guid *windows.GUID) (*winipcfg.RouteChangeCallback, error) {
+func monitorDefaultRoutes(device *device.Device, autoMTU bool, guid *windows.GUID) (*winipcfg.RouteChangeCallback, error) {
 	ourLuid, err := winipcfg.InterfaceGuidToLuid(guid)
 	lastLuid4 := uint64(0)
 	lastLuid6 := uint64(0)
+	lastMtu := uint32(0)
 	if err != nil {
 		return nil, err
 	}
@@ -75,6 +76,50 @@ func monitorDefaultRoutes(device *device.Device, guid *windows.GUID) (*winipcfg.
 		if err != nil {
 			return err
 		}
+		if !autoMTU {
+			return nil
+		}
+		mtu := uint32(0)
+		if lastLuid4 != 0 {
+			iface, err := winipcfg.InterfaceFromLUID(lastLuid4)
+			if err != nil {
+				return err
+			}
+			if iface.Mtu > 0 {
+				mtu = iface.Mtu
+			}
+		}
+		if lastLuid6 != 0 {
+			iface, err := winipcfg.InterfaceFromLUID(lastLuid6)
+			if err != nil {
+				return err
+			}
+			if iface.Mtu > 0 && iface.Mtu < mtu {
+				mtu = iface.Mtu
+			}
+		}
+		if mtu > 0 && (lastMtu == 0 || lastMtu != mtu) {
+			//TODO: makesure wireguard-go knows about all MTU changes
+			iface, err := winipcfg.GetIpInterface(ourLuid, winipcfg.AF_INET)
+			if err != nil {
+				return err
+			}
+			iface.NlMtu = mtu - 80
+			err = iface.Set()
+			if err != nil {
+				return err
+			}
+			iface, err = winipcfg.GetIpInterface(ourLuid, winipcfg.AF_INET6)
+			if err != nil {
+				return err
+			}
+			iface.NlMtu = mtu - 80
+			err = iface.Set()
+			if err != nil {
+				return err
+			}
+			lastMtu = mtu
+		}
 		return nil
 	}
 	err = doIt()
@@ -204,6 +249,9 @@ func configureInterface(conf *conf.Config, guid *windows.GUID) error {
 		ipif.UseAutomaticMetric = false
 		ipif.Metric = 0
 	}
+	if conf.Interface.Mtu > 0 {
+		ipif.NlMtu = uint32(conf.Interface.Mtu)
+	}
 	err = ipif.Set()
 	if err != nil {
 		return err
@@ -217,6 +265,9 @@ func configureInterface(conf *conf.Config, guid *windows.GUID) error {
 		ipif.UseAutomaticMetric = false
 		ipif.Metric = 0
 	}
+	if conf.Interface.Mtu > 0 {
+		ipif.NlMtu = uint32(conf.Interface.Mtu)
+	}
 	ipif.DadTransmits = 0
 	ipif.RouterDiscoveryBehavior = winipcfg.RouterDiscoveryDisabled
 	err = ipif.Set()
-- 
cgit v1.2.3-59-g8ed1b