linux-kernel - Re: [PATCH] i40e: Prevent setting MTU if greater than MFS

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Message-ID: <d9529518-c6f5-c64f-d635-95da64ed6d65@intel.com>
Date: Wed, 6 Mar 2024 16:27:36 -0800
From: Tony Nguyen <anthony.l.nguyen@...el.com>
To: Erwan Velu <erwanaliasr1@...il.com>
CC: Erwan Velu <e.velu@...teo.com>, Jesse Brandeburg
	<jesse.brandeburg@...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] i40e: Prevent setting MTU if greater than MFS

On 3/4/2024 6:22 PM, Erwan Velu wrote:
> I was also wondering if I shouldn't subtract I40E_PACKET_HDR_PAD from
> the mfs to be more accurate, can you confirm this ?

Yes, you're correct, we should take the packet header out however...

> If one can have a look at what is the exact procedure to fix the MFS
> size when too small, that would be lovely/ideal in addition to my
> patch.

.. as you allude to here, we should resolve the MFS size issue.

You were on that right track (as mentioned in your commit message)

 > To fix this case, it would have been ideal to increase the MFS,
 > via i40e_aqc_opc_set_mac_config, but I didn't found a reliable way to 
do it.

The ice driver is doing this with the ice_aq_set_mac_cfg() call. You 
should be able to model the same here.

Thanks,
Tony