Re: [RFC net-next] ipv6: update NUD_FAILED neighbors from NA messages

[Lawrence Lee]

On Thu Aug 27, 2026 at 9:05 AM UTC, Ido Schimmel wrote:
> On Tue, Aug 25, 2026 at 06:07:44PM +0000, Lawrence Lee wrote:
> > Sorry I should have been more specific before. Maybe a better way to 
> > phrase it is that this would be analogous to IPv4 in the sense that it 
> > allows NUD_FAILED neighbors to change states upon receipt of a NA, but 
> > by using NUD_STALE it remains consistent with RFC9131 Section 6.1.1.
>
> I think that your setup is quite unique and I don't necessarily agree
> with the statements regarding the CPU load, but it doesn't change my
> conclusion: IMO it makes sense to transition from FAILED to STALE when
> receiving NAs (most likely unsolicited given FAILED state).
>
> Mention in the commit message that trying to resolve FAILED neighbours
> by periodically probing them (e.g., using NTF_EXT_MANAGED) adds extra
> work compared to having the kernel stop ignoring the information that
> it's getting via NAs. Also mention that the approach taken here is more
> conservative than IPv4, which by default transitions FAILED neighbours
> to STALE upon receiving GARPs.

I will be sure to mention these points in the message. Is it appropriate 
to credit you with a 'Suggested-By' tag in the commit messages as well?  
I'm not sure what the proper attribution convention is here for commit 
message content.

> Note that you also need to update the RFC 9131 comment in
> ndisc_recv_na() and the description of accept_untracked_na in
> Documentation/networking/ip-sysctl.rst. In addition, please add a test
> case in tools/testing/selftests/net/ndisc_unsolicited_na_test.sh
>
> Before submitting, please read:
> https://docs.kernel.org/next/process/maintainer-netdev.html
>
> Run the CI checks locally:
> https://github.com/linux-netdev/nipa#running-locally
>
> And LLM review:
> https://github.com/sashiko-dev/sashiko#1-local-review-recommended
>
> Thanks

Will do, thanks for the suggestions. I will submit a patch once the tree 
re-opens.