func readRawConn(c syscall.RawConn, b []byte) (int, error) {
	var operr error
	var n int
	err := c.Read(func(s uintptr) bool {
		n, operr = syscall.Read(int(s), b)
		if operr == syscall.EAGAIN {
			return false
		}
		return true
	})
	if err != nil {
		return n, err
	}
	return n, operr
}

func writeRawConn(c syscall.RawConn, b []byte) error {
	var operr error
	err := c.Write(func(s uintptr) bool {

	if err != nil {
		t.Fatal(err)
	}

	var operr error
	err = wconn.Write(func(s uintptr) bool {
		_, operr = syscall.Write(syscallDescriptor(s), []byte{'b'})
		return operr != syscall.EAGAIN
	})
	if err != nil {
		t.Fatal(err)
	}
	if operr != nil {
		t.Fatal(err)
	}

	var n int
	buf := make([]byte, 1)
	err = rconn.Read(func(s uintptr) bool {
		n, operr = syscall.Read(syscallDescriptor(s), buf)