if ok, err := multicastRIBContains(ip); err != nil {
		return err
	} else if !ok {
		return fmt.Errorf("%s not found in multicast rib", ip.String())
	}
	la := c.LocalAddr()
	if la, ok := la.(*UDPAddr); !ok || la.Port == 0 {
		return fmt.Errorf("got %v; want a proper address with non-zero port number", la)
	}
	return nil
}

func multicastRIBContains(ip IP) (bool, error) {
	switch runtime.GOOS {