netdev - Re: [PATCH nf-next] netfilter: flowtable: separate replace, destroy and stats to different workqueues

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Date:   Fri, 26 Mar 2021 10:51:49 -0300
From:   Marcelo Ricardo Leitner <marcelo.leitner@...il.com>
To:     Oz Shlomo <ozsh@...dia.com>
Cc:     Pablo Neira Ayuso <pablo@...filter.org>, netdev@...r.kernel.org,
        netfilter-devel@...r.kernel.org,
        Saeed Mahameed <saeedm@...dia.com>,
        Paul Blakey <paulb@...dia.com>
Subject: Re: [PATCH nf-next] netfilter: flowtable: separate replace, destroy
 and stats to different workqueues

On Thu, Mar 25, 2021 at 10:46:12AM +0200, Oz Shlomo wrote:
> Hi Marcelo,
> 
> On 3/24/2021 11:20 PM, Marcelo Ricardo Leitner wrote:
> > Maybe I'm just missing it but I'm not seeing how removals would only
> > happen after the entry is actually offloaded. As in, if the add queue
> > is very long, and the datapath see a FIN, seems the next gc iteration
> > could try to remove it before it's actually offloaded. I think this is
> > what Pablo meant on his original reply here too, then his idea on
> > having add/del to work with the same queue.
> > 
> 
> The work item will not be allocated if the hw offload is pending.
> 
> nf_flow_offload_work_alloc()
> 	if (test_and_set_bit(NF_FLOW_HW_PENDING, &flow->flags))
> 		return NULL;

Ahá! Right, and with that there can only be 1 flow_offload_work for a
flow at a time, so it can't fetch stats for a flow that is still to be
offloaded too. Got it.

Thanks,
Marcelo