IPv6 neighbor discovery breaks when igmp_snooping is enabled on the br-lan device.
After the 6.0[.1] Upgrade, my IPv6 was partially broken, one host on my network worked, and hosts could talk to each other, pings could reach the internet, but the replies didnt make it back.
I discovered ip -6 neigh showed lots of failures resolving the hosts,
- tcpdump -eni br-lan icmp6 # showed it was sending neighbour solicitation but the device wasn't receiving them with a tcpdump there
- tcpdump -eni lan2 icmp6 # showed the icmp packets from the host that was pinging google, but not the solicitation packets I expected from above
Looking at my /etc/config/network I saw I had option igmp_snooping '1' I tried setting this to 0 and IPv6 started working again.
I have a multicast feed from my ISP that i'd like to be able to use without flooding all of the ports, but this is more important.