odhcpd IPv6 NDP + macOS don't play together

[golddranks]

I'm just cross-posting this issue here, because it's more relevant here. I feel like it has been languishing in the main OpenWRT repo for years.

openwrt/openwrt#7561

The gist is that odhcpd seems to use ULA to send neighbor solicitation messages, when ULA is set up. MacOS doesn't respond to these messages, and fails to communicate its IPv6 address to the router. (In case of SLAAC). Everything works when ULA is disabled; MacOS seems to respond to messages that have LLA as the source address.

It would be better, if there were an option to force LLA. Currently having an ULA set up in the router settings basically prevents one from using MacOS in the network.