tun_windows: Introduce preliminary TUN interface creation

Signed-off-by: Simon Rozman <simon@rozman.si>

tun/ztun_windows.go

@@ -0,0 +1,49 @@
+// Code generated by 'go generate'; DO NOT EDIT.
+
+package tun
+
+import (
+	"syscall"
+	"unsafe"
+
+	"golang.org/x/sys/windows"
+)
+
+var _ unsafe.Pointer
+
+// Do the interface allocations only once for common
+// Errno values.
+const (
+	errnoERROR_IO_PENDING = 997
+)
+
+var (
+	errERROR_IO_PENDING error = syscall.Errno(errnoERROR_IO_PENDING)
+)
+
+// errnoErr returns common boxed Errno values, to prevent
+// allocations at runtime.
+func errnoErr(e syscall.Errno) error {
+	switch e {
+	case 0:
+		return nil
+	case errnoERROR_IO_PENDING:
+		return errERROR_IO_PENDING
+	}
+	// TODO: add more here, after collecting data on the common
+	// error values see on Windows. (perhaps when running
+	// all.bat?)
+	return e
+}
+
+var (
+	modole32 = windows.NewLazySystemDLL("ole32.dll")
+
+	procCLSIDFromString = modole32.NewProc("CLSIDFromString")
+)
+
+func clsidFromString(lpsz *uint16, pclsid *windows.GUID) (hr int32) {
+	r0, _, _ := syscall.Syscall(procCLSIDFromString.Addr(), 2, uintptr(unsafe.Pointer(lpsz)), uintptr(unsafe.Pointer(pclsid)), 0)
+	hr = int32(r0)
+	return
+}