index := aa.IfIndex
		if index == 0 { // ipv6IfIndex is a substitute for ifIndex
			index = aa.Ipv6IfIndex
		}
		if ifi == nil || ifi.Index == int(index) {
			for pmul := aa.FirstMulticastAddress; pmul != nil; pmul = pmul.Next {
				sa, err := pmul.Address.Sockaddr.Sockaddr()
				if err != nil {
					return nil, os.NewSyscallError("sockaddr", err)
				}
				switch sa := sa.(type) {
				case *syscall.SockaddrInet4: