netdev - Re: [PATCH net 2/2] net/sched: act_ct: Set offload timeout when setting the offload bit

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Message-ID: <20200729171044.GI3307@localhost.localdomain>
Date:   Wed, 29 Jul 2020 14:10:44 -0300
From:   Marcelo Ricardo Leitner <marcelo.leitner@...il.com>
To:     Roi Dayan <roid@...lanox.com>
Cc:     netdev@...r.kernel.org, pablo@...filter.org,
        Paul Blakey <paulb@...lanox.com>, Oz Shlomo <ozsh@...lanox.com>
Subject: Re: [PATCH net 2/2] net/sched: act_ct: Set offload timeout when
 setting the offload bit

On Wed, Jul 29, 2020 at 03:55:53PM +0300, Roi Dayan wrote:
> 
> 
> On 2020-07-28 5:42 PM, Marcelo Ricardo Leitner wrote:
> > On Tue, Jul 28, 2020 at 02:57:59PM +0300, Roi Dayan wrote:
> >> On heavily loaded systems the GC can take time to go over all existing
> >> conns and reset their timeout. At that time other calls like from
> >> nf_conntrack_in() can call of nf_ct_is_expired() and see the conn as
> >> expired. To fix this when we set the offload bit we should also reset
> >> the timeout instead of counting on GC to finish first iteration over
> >> all conns before the initial timeout.
> >>
> >> Fixes: 64ff70b80fd4 ("net/sched: act_ct: Offload established connections to flow table")
> >> Signed-off-by: Roi Dayan <roid@...lanox.com>
> >> Reviewed-by: Oz Shlomo <ozsh@...lanox.com>
> >> ---
> >>  net/sched/act_ct.c | 2 ++
> >>  1 file changed, 2 insertions(+)
> >>
> >> diff --git a/net/sched/act_ct.c b/net/sched/act_ct.c
> >> index e9f3576cbf71..650c2d78a346 100644
> >> --- a/net/sched/act_ct.c
> >> +++ b/net/sched/act_ct.c
> >> @@ -366,6 +366,8 @@ static void tcf_ct_flow_table_add(struct tcf_ct_flow_table *ct_ft,
> > 
> > Extra context line:
> > 	err = flow_offload_add(&ct_ft->nf_ft, entry);
> >>  	if (err)
> >>  		goto err_add;
> >>  
> >> +	nf_ct_offload_timeout(ct);
> >> +
> > 
> > What about adding this to flow_offload_add() instead?
> > It is already adjusting the flow_offload timeout there and then it
> > also effective for nft.
> > 
> 
> As you said, in flow_offload_add() we adjust the flow timeout.
> Here we adjust the conn timeout.
> So it's outside flow_offload_add() which only touch the flow struct.
> I guess it's like conn offload bit is set outside here and for nft.

Right, but

> What do you think?

I don't see why it can't update both. flow_offload_fixup_ct_timeout(),
called by flow_offload_del(), is updating ct->timeout already. It
looks consistent to me to update it in _add as well then. 

> 
> >>  	return;
> >>  
> >>  err_add:
> >> -- 
> >> 2.8.4
> >>