wintun: use nci.dll directly instead of buggy netshell

tun/wintun/nci/nci_windows.go

@@ -0,0 +1,28 @@
+/* SPDX-License-Identifier: MIT
+ *
+ * Copyright (C) 2019 WireGuard LLC. All Rights Reserved.
+ */
+
+package nci
+
+import "golang.org/x/sys/windows"
+
+//sys	nciSetConnectionName(guid *windows.GUID, newName *uint16) (ret error) = nci.NciSetConnectionName
+//sys	nciGetConnectionName(guid *windows.GUID, destName *uint16, inDestNameBytes uint32, outDestNameBytes *uint32) (ret error) = nci.NciGetConnectionName
+
+func SetConnectionName(guid *windows.GUID, newName string) error {
+	newName16, err := windows.UTF16PtrFromString(newName)
+	if err != nil {
+		return err
+	}
+	return nciSetConnectionName(guid, newName16)
+}
+
+func ConnectionName(guid *windows.GUID) (string, error) {
+	var name [0x400]uint16
+	err := nciGetConnectionName(guid, &name[0], uint32(len(name)*2), nil)
+	if err != nil {
+		return "", err
+	}
+	return windows.UTF16ToString(name[:]), nil
+}