netdev - Re: [PATCH net-next] net: Make RX-FCS and LRO mutually exclusive

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Date:   Mon, 5 Mar 2018 17:46:49 +0200
From:   Gal Pressman <galp@...lanox.com>
To:     David Miller <davem@...emloft.net>
Cc:     netdev@...r.kernel.org, tariqt@...lanox.com
Subject: Re: [PATCH net-next] net: Make RX-FCS and LRO mutually exclusive

On 05-Mar-18 17:27, David Miller wrote:
> From: Gal Pressman <galp@...lanox.com>
> Date: Sun,  4 Mar 2018 14:12:04 +0200
> 
>> LRO and RX-FCS offloads cannot be enabled at the same time since it is
>> not clear what should happen to the FCS of each coalesced packet.
>> The FCS is not really part of the TCP payload, hence cannot be merged
>> into one big packet. On the other hand, providing one big LRO packet
>> with one FCS contradicts the RX-FCS feature goal.
>>
>> Use the fix features mechanism in order to prevent intersection of the
>> features and drop LRO in case RX-FCS is requested.
>>
>> Enabling RX-FCS while LRO is enabled will result in:
>> $ ethtool -K ens6 rx-fcs on
>> Actual changes:
>> large-receive-offload: off [requested on]
>> rx-fcs: on
>>
>> Signed-off-by: Gal Pressman <galp@...lanox.com>
>> Reviewed-by: Tariq Toukan <tariqt@...lanox.com>
> 
> Agreed, having these two options enabled at the same time doesn't
> make any sense.
> 
> Applied.
> 
> Probably need to add the same restriction for HW GRO.
> 

I agree, I'll submit another patch to restrict it too.