netdev - Re: [PATCH] net: veth: do not manipulate GRO when using XDP

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Message-ID: <87zfv3q0hb.fsf@toke.dk>
Date: Tue, 12 Mar 2024 10:10:40 +0100
From: Toke Høiland-Jørgensen <toke@...hat.com>
To: Ignat Korchagin <ignat@...udflare.com>, "David S . Miller"
 <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski
 <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
 netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Cc: kernel-team@...udflare.com, Ignat Korchagin <ignat@...udflare.com>
Subject: Re: [PATCH] net: veth: do not manipulate GRO when using XDP

Ignat Korchagin <ignat@...udflare.com> writes:

> Commit d3256efd8e8b ("veth: allow enabling NAPI even without XDP") tried to fix
> the fact that GRO was not possible without XDP, because veth did not use NAPI
> without XDP. However, it also introduced the behaviour that GRO is always
> enabled, when XDP is enabled.
>
> While it might be desired for most cases, it is confusing for the user at best
> as the GRO flag sudddenly changes, when an XDP program is attached. It also
> introduces some complexities in state management as was partially addressed in
> commit fe9f801355f0 ("net: veth: clear GRO when clearing XDP even when down").
>
> But the biggest problem is that it is not possible to disable GRO at all, when
> an XDP program is attached, which might be needed for some use cases.
>
> Fix this by not touching the GRO flag on XDP enable/disable as the code already
> supports switching to NAPI if either GRO or XDP is requested.

Sounds reasonable

Reviewed-by: Toke Høiland-Jørgensen <toke@...hat.com>