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/* SPDX-License-Identifier: MIT
*
* Copyright (C) 2019-2022 WireGuard LLC. All Rights Reserved.
*/
package tunnel
import (
"golang.org/x/sys/windows"
"golang.zx2c4.com/wireguard/windows/tunnel/winipcfg"
)
func findDefaultLUID(family winipcfg.AddressFamily, ourLUID winipcfg.LUID, lastLUID *winipcfg.LUID, lastIndex *uint32) error {
r, err := winipcfg.GetIPForwardTable2(family)
if err != nil {
return err
}
lowestMetric := ^uint32(0)
index := uint32(0)
luid := winipcfg.LUID(0)
for i := range r {
if r[i].DestinationPrefix.PrefixLength != 0 || r[i].InterfaceLUID == ourLUID {
continue
}
ifrow, err := r[i].InterfaceLUID.Interface()
if err != nil || ifrow.OperStatus != winipcfg.IfOperStatusUp {
continue
}
iface, err := r[i].InterfaceLUID.IPInterface(family)
if err != nil {
continue
}
if r[i].Metric+iface.Metric < lowestMetric {
lowestMetric = r[i].Metric + iface.Metric
index = r[i].InterfaceIndex
luid = r[i].InterfaceLUID
}
}
if luid == *lastLUID && index == *lastIndex {
return nil
}
*lastLUID = luid
*lastIndex = index
return nil
}
func monitorMTU(family winipcfg.AddressFamily, ourLUID winipcfg.LUID) ([]winipcfg.ChangeCallback, error) {
var minMTU uint32
if family == windows.AF_INET {
minMTU = 576
} else if family == windows.AF_INET6 {
minMTU = 1280
}
lastLUID := winipcfg.LUID(0)
lastIndex := ^uint32(0)
lastMTU := uint32(0)
doIt := func() error {
err := findDefaultLUID(family, ourLUID, &lastLUID, &lastIndex)
if err != nil {
return err
}
mtu := uint32(0)
if lastLUID != 0 {
iface, err := lastLUID.Interface()
if err != nil {
return err
}
if iface.MTU > 0 {
mtu = iface.MTU
}
}
if mtu > 0 && lastMTU != mtu {
iface, err := ourLUID.IPInterface(family)
if err != nil {
return err
}
iface.NLMTU = mtu - 80
if iface.NLMTU < minMTU {
iface.NLMTU = minMTU
}
err = iface.Set()
if err != nil {
return err
}
lastMTU = mtu
}
return nil
}
err := doIt()
if err != nil {
return nil, err
}
cbr, err := winipcfg.RegisterRouteChangeCallback(func(notificationType winipcfg.MibNotificationType, route *winipcfg.MibIPforwardRow2) {
if route != nil && route.DestinationPrefix.PrefixLength == 0 {
doIt()
}
})
if err != nil {
return nil, err
}
cbi, err := winipcfg.RegisterInterfaceChangeCallback(func(notificationType winipcfg.MibNotificationType, iface *winipcfg.MibIPInterfaceRow) {
if notificationType == winipcfg.MibParameterNotification {
doIt()
}
})
if err != nil {
cbr.Unregister()
return nil, err
}
return []winipcfg.ChangeCallback{cbr, cbi}, nil
}
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