wintun: rename device using undocumented API that netsh.exe uses

tun/wintun/netshell/netshell_windows.go

@@ -0,0 +1,32 @@
+/* SPDX-License-Identifier: MIT
+ *
+ * Copyright (C) 2019 WireGuard LLC. All Rights Reserved.
+ */
+
+package netshell
+
+import (
+	"syscall"
+	"unsafe"
+
+	"golang.org/x/sys/windows"
+)
+
+var (
+	modnetshell = windows.NewLazySystemDLL("netshell.dll")
+	procHrRenameConnection = modnetshell.NewProc("HrRenameConnection")
+)
+
+func HrRenameConnection(guid *windows.GUID, newName *uint16) (err error) {
+	err = procHrRenameConnection.Find()
+	if err != nil {
+		// Missing from servercore, so we can't presume it's always there.
+		return
+	}
+
+	ret, _, _ := syscall.Syscall(procHrRenameConnection.Addr(), 2, uintptr(unsafe.Pointer(guid)), uintptr(unsafe.Pointer(newName)), 0)
+	if ret != 0 {
+		err = syscall.Errno(ret)
+	}
+	return
+}