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

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Message-ID: <CA+SN3spZ7Q4zqpgiDbdE5T7pb8PWceUf5bGH+oHLEz6XhT9H+g@mail.gmail.com>
Date: Wed, 17 Sep 2025 20:33:49 +0300
From: Elad Yifee <eladwf@...il.com>
To: Pablo Neira Ayuso <pablo@...filter.org>
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 11:18 AM Pablo Neira Ayuso <pablo@...filter.org> wrote:
> 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.

Thanks - I see what you meant now.

This isn’t a new feature that needs to be implemented in software
first. We’re not introducing new user semantics, matches, or actions
in nft/TC. no datapath changes (including the flowtable software
offload fast path). The change only surfaces existing CT state
(mark/labels/dir) as FLOW_ACTION_CT_METADATA at the hardware offload
boundary so drivers can use it for per-flow QoS, or simply ignore it.

When a flow stays in software, behavior remains exactly as today,
software QoS continues to use existing tools (nft/TC setting
skb->priority/mark, qdiscs, etc.). There’s no SW-HW mismatch
introduced here.