wintun: don't try to flush interface, but rather delete

tun/tun_windows.go

@@ -65,30 +65,22 @@ func CreateTUN(ifname string) (TUNDevice, error) {
 
 	// Does an interface with this name already exist?
 	wt, err = wintun.GetInterface(ifname, 0)
-	if wt == nil {
+	if err == nil {
-		// Interface does not exist or an error occurred. Create one.
+		// If so, we delete it, in case it has weird residual configuration.
+		_, _, err = wt.DeleteInterface(0)
+		if err != nil {
+			return nil, fmt.Errorf("Unable to delete already existing Wintun interface: %v", err)
+		}
+	}
 	wt, _, err = wintun.CreateInterface("WireGuard Tunnel Adapter", 0)
 	if err != nil {
-			return nil, fmt.Errorf("wintun.CreateInterface: %v", err)
+		return nil, fmt.Errorf("Unable to create Wintun interface: %v", err)
-		}
-	} else if err != nil {
-		// Foreign interface with the same name found.
-		// We could create a Wintun interface under a temporary name. But, should our
-		// process die without deleting this interface first, the interface would remain
-		// orphaned.
-		return nil, fmt.Errorf("wintun.GetInterface: %v", err)
 	}
 
 	err = wt.SetInterfaceName(ifname)
 	if err != nil {
 		wt.DeleteInterface(0)
-		return nil, fmt.Errorf("wintun.SetInterfaceName: %v", err)
+		return nil, fmt.Errorf("Unable to set name of Wintun interface: %v", err)
-	}
-
-	err = wt.FlushInterface()
-	if err != nil {
-		wt.DeleteInterface(0)
-		return nil, fmt.Errorf("wintun.FlushInterface: %v", err)
 	}
 
 	return &NativeTun{

tun/wintun/wintun_windows.go

@@ -470,15 +470,6 @@ func (wintun *Wintun) DeleteInterface(hwndParent uintptr) (bool, bool, error) {
 	return false, false, nil
 }
 
-//
-// FlushInterface removes all properties from the interface and gives it only a very
-// vanilla IPv4 and IPv6 configuration with no addresses of any sort assigned.
-//
-func (wintun *Wintun) FlushInterface() error {
-	//TODO: implement me!
-	return nil
-}
-
 //
 // checkReboot checks device install parameters if a system reboot is required.
 //