if err != nil {
		err = &OpError{Op: "route", Net: "ip+net", Source: nil, Addr: nil, Err: err}
	}
	return ifat, err
}

// MulticastAddrs returns a list of multicast, joined group addresses
// for a specific interface.
func (ifi *Interface) MulticastAddrs() ([]Addr, error) {
	if ifi == nil {
		return nil, &OpError{Op: "route", Net: "ip+net", Source: nil, Addr: nil, Err: errInvalidInterface}
	}

	if err != nil {
		t.Fatal(err)
	}
	uniStats, err := validateInterfaceUnicastAddrs(ifat)
	if err != nil {
		t.Fatal(err)
	}
	var multiStats routeStats
	for _, ifi := range ift {
		ifmat, err := ifi.MulticastAddrs()
		if err != nil {
			t.Fatal(ifi, err)
		}
		stats, err := validateInterfaceMulticastAddrs(ifmat)
		if err != nil {
			t.Fatal(ifi, err)
		}
		multiStats.ipv4 += stats.ipv4