netdev - Re: [PATCH net] netfilter: flowtable: Fix expired flow not being deleted from software

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Message-ID: <b3a54d5e-bb00-3306-c064-5c85806560e1@mellanox.com>
Date:   Mon, 11 May 2020 12:50:02 +0300
From:   Paul Blakey <paulb@...lanox.com>
To:     Pablo Neira Ayuso <pablo@...filter.org>
Cc:     Oz Shlomo <ozsh@...lanox.com>, Roi Dayan <roid@...lanox.com>,
        netdev@...r.kernel.org, Saeed Mahameed <saeedm@...lanox.com>,
        netfilter-devel@...r.kernel.org
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?