netdev - Re: [net] ixgbe: fix parsing of TC actions for HW offload

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Message-ID: <20180531200122.dipwlgbo5lpzvzig@mace-windu.eideo.cz>
Date:   Thu, 31 May 2018 22:01:22 +0200
From:   Ondřej Hlavatý <ohlavaty@...hat.com>
To:     David Miller <davem@...emloft.net>
Cc:     jeffrey.t.kirsher@...el.com, netdev@...r.kernel.org,
        nhorman@...hat.com, sassmann@...hat.com, jogreene@...hat.com,
        jhs@...atatu.com, jiri@...nulli.us
Subject: Re: [net] ixgbe: fix parsing of TC actions for HW offload

On 31.05., David Miller wrote:
> From: Jeff Kirsher <jeffrey.t.kirsher@...el.com>
> Date: Wed, 30 May 2018 11:01:34 -0700
> 
> > From: Ondřej Hlavatý <ohlavaty@...hat.com>
> > 
> > The previous code was optimistic, accepting the offload of whole action
> > chain when there was a single known action (drop/redirect). This results
> > in offloading a rule which should not be offloaded, because its behavior
> > cannot be reproduced in the hardware.
> > 
> 
> This introduces a new warning with gcc-8.1.1 on Fedora 28.

Indeed. Sorry for noticing that it was introduced by my patch. The
issue is pretty obvious - empty action chain will not select a queue. As
the Flow Director rules always need to explicitly set a queue index when
they match (as far as I'm concerned), the correct solution should be to
just reject empty chains for offload as well. I will prepare v2 soon.

Ondřej