Add pref64 support (RFC8781)

[zajdee]

This pull requests adds support for the pref64 option, as defined in RFC8781. Its configuration is part of the interface config section and has only two parameters: the nat64prefix and the optional AdvValidLifetime, the prefix valid lifetime (which should not be smaller than the MaxRtrAdvInterval).

interface eth0
{
        nat64prefix 64:ff9b::/96
        {
                AdvValidLifetime 1800;
        };
};

[stappersg]

After seening additional commits, I marked this merge request as Work In Progress.

[zajdee]

Hi @stappersg, so far the implementation seems to be working, I have removed one extra space and added a documentation entry.
What's the current process regarding workflow testing and review? I'd like to know if you want more to be added or if you have comments to the code added that I should work on.

Thank you.

[robbat2]

• reviewed code and enabled the workflow after that review (sorry, have to check because of other projects where PRs contained malicious payloads that used CPU in workflow).
• Left comments on improvements, mostly style; functionality seems fine.

[zajdee]

Hi @robbat2,
thank you for all the valuable inputs.

• I have updated the code according to your code review (also had to amend the original commits as I have used an incorrect e-mail address there) and also simplified it (nat64prefix_init_defaults now sets the default value of AdvValidLifetime).
• There also was an unknown option 38 reported when radvd was running in debug mode, therefore I have skipped option 38 checking in process.c.
• Finally I have added option 38 parsing to radvdump.

Could you please re-run the workflows to ensure I didn't break things? Thanks.

[stappersg]

Could you please re-run the workflows to ensure I didn't break things?

Re-run triggered.

[zajdee]

Hi gents,
I have further cleaned up the code and have nothing more to add/remove right now.
If there will be further changes needed based on your code review or as a result of the workflow checks, I will incorporate those.
Otherwise it's ready to be merged.

Thank you for your time reviewing this pull request.

[stappersg]

Re-run triggered

[stappersg]

I have further cleaned up the code and have nothing more to add/remove right now.

I have removed the Work In Progress marker from the title of this merge request.

[robbat2]

LGTM. Thanks for your contribution.

[Neustradamus]

2024-12-31: radvd 2.20 has been released with this nice PR, thanks to @zajdee :)
Never too late!