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

[Tony Nguyen]

On 2/27/2024 11:27 AM, Erwan Velu wrote:
> Commit 6871a7de705b6f6a4046f0d19da9bcd689c3bc8e from iPXE project is
> setting the MFS to 0x600 = 1536.
>
> At boot time the i40e driver complains about it with
> the following message but continues.
>
> 	MFS for port 1 has been set below the default: 600
>
> If the MTU size is increased, the driver accept it but large packets will not
> be processed by the firmware generating tx_errors. The issue is pretty
> silent for users. i.e doing TCP in such context will generates lots of
> retransmissions until the proper window size (below 1500) will be used.
>
> 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.
>
> At least, this commit prevents setting up an MTU greater than the current MFS.
> It will avoid being in the position of having an MTU set to 9000 on the
> netdev with a firmware refusing packets larger than 1536.
>
> A typical trace looks like the following :
> [  377.548696] i40e 0000:5d:00.0 eno5: Error changing mtu to 9000 which is greater than the current mfs: 1536
>
> Signed-off-by: Erwan Velu <e.velu@xxxxxxxxxx>

The Author and Sign-off needs to be fixed; they don't match.

WARNING: From:/Signed-off-by: email address mismatch: 'From: Erwan Velu 
<erwanaliasr1@xxxxxxxxx>' != 'Signed-off-by: Erwan Velu <e.velu@xxxxxxxxxx>'

Thanks,
Tony