Re: Problem with IPv6 privacy addresses in 7.0

On 5/28/26 13:29, Fernando Fernandez Mancera wrote:
> On 5/28/26 1:12 PM, Stefano Brivio wrote:
>> On Thu, 28 May 2026 12:46:05 +0200
>> Fernando Fernandez Mancera <[email protected]> wrote:
>>> On 5/28/26 7:38 AM, Stefano Brivio wrote:
>
>> - regardless of this, would there be a way to make NetworkManager
>>    robust to the order?
>>
>>    I'm asking this because yes, strictly speaking, you might say this
>>    change breaks userspace (NetworkManager), but at the same time it
>>    fixes another part of it (pasta), and changing it back would break
>>    pasta again (in a way we can't really fix).
>
> Ugh, that is a mess.

Well, yes, but one that happens regularly. :-D

The problem here is that it was reported only some months after the
culprit landed, as fixing the regression through a revert or so could
now cause a bigger regression. Do we assume this to be the case here? It
sounds like pasta would "only" be broken about as much as it was before
-- then a revert or something like that is the right solution to get
back to the status quo. Or does pasta already depend on the new behavior
somehow and would now break even more if we reverted the culprit? Then
it's really a mess. :-/

But there are ways to fix even this, it's just that most of them are
ugly. Like adding some bit somewhere to /proc/ or so that a fixed
NetworkManager (if it's the only affected app) could flip by default to
change the things from the old behavior to the new one; and one pasta
could check that bit and warn. Config options are also an option, but
that's even uglier.

>>    Now, I suppose NetworkManager is much more universally used and it's
>>    definitely a more mature project so it's a bigger userspace breakage,
>>    but at the same time it's a ton of containers (Podman uses pasta by
>>    default, Docker/moby optionally via rootlesskit) we might introduce a
>>    regression for.
> 
> I think the main argument here is: while we know it is affecting
> NetworkManager, we cannot know if it is breaking something else. The
> kernel rule is usually "do not break userspace" and this is likely
> considered a regression from my understanding. Cc'ing Thorsten as he is
> an expert on regressions.

From the mail at the top of the thread it definitely sounds like one.

Ciao, Thorsten