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

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Message-ID: <aMnnKsqCGw5JFVrD@calendula>
Date: Wed, 17 Sep 2025 00:39:38 +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 Tue, Sep 16, 2025 at 07:49:34PM +0300, Elad Yifee wrote:
> Hi all,
> 
> One caveat: this change will cause some existing drivers to start
> returning -EOPNOTSUPP, since they walk the action list and treat any
> unknown action as fatal in their default switch. In other words, adding
> CT metadata unconditionally would break offload in those drivers until
> they are updated.
> 
> Follow-up patches will therefore be needed to make drivers either parse
> or safely ignore FLOW_ACTION_CT_METADATA. Because this action is only
> advisory, it should be harmless for drivers that don’t use it to simply
> accept and no-op it.
> 
> Just flagging this up front: the core patch by itself will break some
> drivers, and additional work is required to make them tolerant of the
> new metadata.

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.