linux-kernel - Re: [PATCH net-next RFC] netfilter: flowtable: add CT metadata action for nft flowtables

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Message-ID: <aMpuwRiqBtG7ps30@calendula>
Date: Wed, 17 Sep 2025 10:18:09 +0200
From: Pablo Neira Ayuso <pablo@...filter.org>
To: Elad Yifee <eladwf@...il.com>
Cc: Jozsef Kadlecsik <kadlec@...filter.org>,
	Florian Westphal <fw@...len.de>, Phil Sutter <phil@....cc>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	Simon Horman <horms@...nel.org>, netfilter-devel@...r.kernel.org,
	coreteam@...filter.org, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH net-next RFC] netfilter: flowtable: add CT metadata
 action for nft flowtables

On Wed, Sep 17, 2025 at 06:10:10AM +0300, Elad Yifee wrote:
> On Wed, Sep 17, 2025 at 1:39 AM Pablo Neira Ayuso <pablo@...filter.org> wrote:
> >
> > May I ask, where is the software plane extension for this feature?
> > Will you add it for net/sched/act_ct.c?
> >
> >
> > Adding the hardware offload feature only is a deal breaker IMO.
> Software plane: This doesn’t add a new user feature, it just surfaces
> existing CT state to offload so the software plane already exists
> today via nft/TC. In software you can already set/match ct mark/labels
> (e.g., tag flows), and once offloaded the exporter snapshots that so a
> driver can map the tag to a HW queue/class if it wants per-flow QoS in
> hardware. Drivers that don’t need it can simply accept and ignore the
> metadata.

Hm, flowtable software datapath cannot do ct marks/label at this time.

> act_ct.c: Yes - I’ll include a small common helper so TC and nft
> flowtable offloads produce identical CT metadata.
> 
> If there’s no objection to the direction, I’ll respin with:
> - the common helper
> - act_ct switched to it
> - nft flowtable exporter appending CT metadata

Just to make sure we are on the same page: Software plane has to match
the capabilities of the hardware offload plan, new features must work
first in the software plane, then extend the hardware offload plane to
support it.