EPERM           = Errno(0x1)
	EPFNOSUPPORT    = Errno(0x7b)
	EPIPE           = Errno(0x20)
	EPROTO          = Errno(0x47)
	EPROTONOSUPPORT = Errno(0x78)
	EPROTOTYPE      = Errno(0x62)
	ERANGE          = Errno(0x22)
	EREMCHG         = Errno(0x52)
	EREMOTE         = Errno(0x42)
	ERESTART        = Errno(0x5b)
	EROFS           = Errno(0x1e)
	ESHUTDOWN       = Errno(0x8f)
	ESOCKTNOSUPPORT = Errno(0x79)

func GetsockoptString(fd, level, opt int) (string, error) {
	buf := make([]byte, 256)
	vallen := _Socklen(len(buf))
	err := getsockopt(fd, level, opt, unsafe.Pointer(&buf[0]), &vallen)
	if err != nil {
		if err == ERANGE {
			buf = make([]byte, vallen)
			err = getsockopt(fd, level, opt, unsafe.Pointer(&buf[0]), &vallen)
		}
		if err != nil {
			return "", err
		}
	}
	return ByteSliceToString(buf[:vallen]), nil