netdev - Re: [PATCH net 1/1] net/sched: act_ct: Fix flow table lookup failure with no originating ifindex

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Date:   Thu, 17 Feb 2022 20:27:08 -0300
From:   Marcelo Ricardo Leitner <marcelo.leitner@...il.com>
To:     Pablo Neira Ayuso <pablo@...filter.org>
Cc:     Paul Blakey <paulb@...dia.com>, dev@...nvswitch.org,
        netdev@...r.kernel.org, Jamal Hadi Salim <jhs@...atatu.com>,
        davem@...emloft.net, Jiri Pirko <jiri@...dia.com>,
        Cong Wang <xiyou.wangcong@...il.com>,
        Jakub Kicinski <kuba@...nel.org>,
        netfilter-devel@...r.kernel.org,
        Jozsef Kadlecsik <kadlec@...filter.org>,
        Oz Shlomo <ozsh@...dia.com>, Vlad Buslov <vladbu@...dia.com>,
        Roi Dayan <roid@...dia.com>,
        Ariel Levkovich <lariel@...dia.com>, coreteam@...filter.org
Subject: Re: [PATCH net 1/1] net/sched: act_ct: Fix flow table lookup failure
 with no originating ifindex

On Thu, Feb 17, 2022 at 02:55:27PM +0100, Pablo Neira Ayuso wrote:
> On Thu, Feb 17, 2022 at 11:34:24AM +0200, Paul Blakey wrote:
> > After cited commit optimizted hw insertion, flow table entries are
> > populated with ifindex information which was intended to only be used
> > for HW offload. This tuple ifindex is hashed in the flow table key, so
> > it must be filled for lookup to be successful. But tuple ifindex is only
> > relevant for the netfilter flowtables (nft), so it's not filled in
> > act_ct flow table lookup, resulting in lookup failure, and no SW
> > offload and no offload teardown for TCP connection FIN/RST packets.
> > 
> > To fix this, allow flow tables that don't hash the ifindex.
> > Netfilter flow tables will keep using ifindex for a more specific
> > offload, while act_ct will not.
> 
> Using iif == zero should be enough to specify not set?

You mean, when searching, if search input iif == zero, to simply not
check it? That seems dangerous somehow.