if !ok {
		ln.Close()
		return nil, 0, fmt.Errorf("invalid listen address: %q", ln.Addr().String())
	}

	return ln, tcpAddr.Port, nil
}

type multipleControls []func(network, addr string, conn syscall.RawConn) error

func (mcs multipleControls) Control(network, addr string, conn syscall.RawConn) error {
	for _, c := range mcs {
		if err := c(network, addr, conn); err != nil {
			return err
		}
	}