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Date:   Mon, 11 May 2020 12:50:02 +0300
From:   Paul Blakey <>
To:     Pablo Neira Ayuso <>
Cc:     Oz Shlomo <>, Roi Dayan <>,, Saeed Mahameed <>,
Subject: Re: [PATCH net] netfilter: flowtable: Fix expired flow not being
 deleted from software

On 5/11/2020 11:42 AM, Pablo Neira Ayuso wrote:
> On Mon, May 11, 2020 at 10:24:44AM +0300, Paul Blakey wrote:
>> On 5/11/2020 1:26 AM, Pablo Neira Ayuso wrote:
>>> On Wed, May 06, 2020 at 02:27:29PM +0300, Paul Blakey wrote:
>>>> Once a flow is considered expired, it is marked as DYING, and
>>>> scheduled a delete from hardware. The flow will be deleted from
>>>> software, in the next gc_step after hardware deletes the flow
>>>> (and flow is marked DEAD). Till that happens, the flow's timeout
>>>> might be updated from a previous scheduled stats, or software packets
>>>> (refresh). This will cause the gc_step to no longer consider the flow
>>>> expired, and it will not be deleted from software.
>>>> Fix that by looking at the DYING flag as in deciding
>>>> a flow should be deleted from software.
>>> Would this work for you?
>>> The idea is to skip the refresh if this has already expired.
>>> Thanks.
>> The idea is ok, but timeout check + update isn't atomic (need atomic_inc_unlesss
>> or something like that), and there is also
>> the hardware stats which if comes too late (after gc finds it expired) might
>> bring a flow back to life.
> Right. Once the entry has expired, there should not be a way turning
> back.
> I'm attaching a new sketch, it's basically using the teardown state to
> specify that the gc already made the decision to remove this entry.
> Thanks.

Looks fine to me, are you submitting that instead?

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