Re: [PATCH 1/2 net v4] ipv6: addrconf: fix temp address generation after prefix deprecation

[Fernando Fernandez Mancera <fmancera@suse.de>]

On 5/13/26 9:17 AM, Ido Schimmel wrote:
> On Tue, May 12, 2026 at 05:01:17PM -0700, Jakub Kicinski wrote:
>> On Mon, 11 May 2026 14:26:45 +0200 Fernando Fernandez Mancera wrote:
>>> When a router temporarily deprecates an IPv6 prefix (either by sending a
>>> Router Advertisement with Preferred Lifetime = 0 or by letting the
>>> lifetime expire) and later restores it, the kernel permanently loses its
>>> ability to generate temporary privacy addresses (RFC 8981) for that
>>> prefix.
>>>
>>> This happens because the address worker attempts to generate a
>>> replacement temporary address when the current one nears expiration. As
>>> the base prefix is deprecated already, the generation fails after
>>> marking the temporary address as already having spawned a replacement
>>> (ifp->regen_count++).
>>>
>>> When the router eventually restores the prefix, the temporary address
>>> becomes active again. However, once it naturally expires, the address
>>> worker sees this temporary address already tried to generate one and
>>> skips the regeneration.
>>>
>>> Fix this by checking if all temporary addresses for a given prefix have
>>> already tried to spawn a replacement when processing a new RA. If so,
>>> spawn a new temporary address.
>>>
>>> Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
>>
>> No feedback on the patch itself, but I wanted to check - Ido, do you
>> think this is worth handling as a fix? Sounds like this scenario never
>> worked.
> 
> No, I think we should target net-next. The scenario never worked and the
> fix has the potential to cause other issues.
> 

That is fine for me too.

> Fernando, please wait with the next version. I need some time to go over
> the Sashiko feedback.

Sure thing, no need to rush it.

Thanks Ido!