netdev - Re: [PATCH v4 iwl-net] i40e: Prevent setting MTU if greater than MFS

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Message-ID: <7b612db6-cec6-4873-8a38-fb4c97192aa2@criteo.com>
Date: Thu, 14 Mar 2024 19:04:17 +0100
From: Erwan Velu <e.velu@...teo.com>
To: Brett Creeley <bcreeley@....com>, Erwan Velu <erwanaliasr1@...il.com>
Cc: Jesse Brandeburg <jesse.brandeburg@...el.com>,
 Tony Nguyen <anthony.l.nguyen@...el.com>,
 "David S. Miller" <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>,
 Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
 intel-wired-lan@...ts.osuosl.org, netdev@...r.kernel.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4 iwl-net] i40e: Prevent setting MTU if greater than MFS

Le 14/03/2024 à 18:55, Brett Creeley a écrit :
> [...]
> AFAIK there is no API for a user to change the max_mtu, so the only way
> the device's MFS would need to change is if it's done during
> initialization time, which should be done before netdev registration 
> anyway.

Sorry Brett, I was probably unclear and please note that I'm not a 
network developer, just a user that faced a bug.

My initial though was to check the mfs size in i40e_change_mtu() and if 
mfs is too small, then let's increase it.

Maybe just resetting it at init time to the largest value (which seems 
to be the default fw behavior) is a best approach.

I'd love to ear from Intel dev that knows this driver/cards/fw better on 
what's the best approach here.

Erwan,