core Expose radvd option nat64prefix (PREF64) in GUI

Expose the nat64prefix option in Router Advertisements in the GUI. This is an alternative to the existing DNS64 support in Unbound, which breaks DNSSEC. Support for this option appeared in radvd 2.20, which was added in OPNSense 25.1.

The option is added in the Router Advertisements advanced options section. I kept the lowercase naming to match the option in the config, but it does look a bit out of place in the GUI this way.

I did not add the AdvValidLifeTime option within as it conflicts with an existing advanced option with the same name. I also did not add any input validation, but can add some if this is requested.

Fixes #7487

Feb 05 '25 21:02 darses

Ideally we want to do this but we need to move the RA page to MVC/API first, which is going to be on the roadmao for 25.7 most likely.

Feb 12 '25 09:02 fichtner

@fichtner Now that the MVC migration is no longer in scope (per https://github.com/opnsense/core/issues/8351), could you take another look into this PR with the hope of merging it in 25.7?

Jul 10 '25 20:07 darses