I have a “smart” washer and dryer. When the dryer starts, I get radvd warnings that it received Router Solicitation packets with invalid code=6 or code=168. If have determined that they can come on either the input chain or forward chain. Not knowing what they are for I am tempted to block them. Should I? Any ideas what they are for? BTW, the washer doesn’t seem to cause the problem.
As they are claimed as invalid, RouterOS doesn’t handle them anyway. So if you block them, nothing will change effectively, except that your log won’t be full of them.
Perhaps the traffic is meant to be LAN to LAN, the smart dryer telling the smart washer that the clothes are to fukking wet and damn well do a better job next time on the rinse cycle!! 
Or it is trying to find a master device in the network so it can combine all data and publish on Facebook how dirty are your clothes this time…
absolutely gold 
I enjoyed the comments. For whatever it might be worth, I also figured out the dryer also sends out ICMP type 135 (Neighbor Solicitation), code 0 packets without problems and it does not seem to send out any Router Solicitation packets other than codes 6 and 168.