Re: [PATCH] netfilter: use per-cpu recursive spinlock (v6)

Patrick McHardy
2009-04-16T16:59:28Z

Linus Torvalds wrote:
> Guys, this whole discussion has just been filled with crazy crap. Can
> somebody even explain why we care so deeply about some counters for
> something that we just _deleted_ and that have random values anyway?
>
> I can see the counters being interesting while a firewall is active, but I
> sure don't see what's so wonderfully interesting after-the-fact about a
> counter on something that NO LONGER EXISTS that it has to be somehow
> "exactly right".

They're copied to userspace after replacing the ruleset, associated with
the rules that are still active after the change and then added to the
current counters in a second operation. The end result is that the
counters are accurate for rules not changed.

> Show of hands, here: tell me a single use that really _requires_ those
> exact counters of a netfilter rule that got deleted and is no longer
> active?

People use netfilter for accounting quite a lot. Having dynamic updates
is also not uncommon, so this might actually matter.