linux-kernel - Re: [PATCH net-next v5] cadence: Add LSO support.

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Date:   Mon, 14 Nov 2016 12:30:38 -0500 (EST)
From:   David Miller <davem@...emloft.net>
To:     rafalo@...ence.com
Cc:     nicolas.ferre@...el.com, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH net-next v5] cadence: Add LSO support.

From: Rafal Ozieblo <rafalo@...ence.com>
Date: Mon, 14 Nov 2016 09:32:34 +0000

>> If UFO is in use it should not silently disable UDP checksums.
>> 
>> If you cannot support UFO with proper checksumming, then you cannot enable support for that feature.
> 
> According Cadence Gigabit Ethernet MAC documentation:
> 
> "Hardware will not calculate the UDP checksum or modify the UDP checksum field. Therefore software
> must set a value of zero in the checksum field in the UDP header (in the first payload buffer)
> to indicate to the receiver that the UDP datagram does not include a checksum."
> 
> It is hardware requirement.

I do not doubt that it is a hardware restriction.

But I am saying that you cannot enable this feature under Linux if
this is how it operates on your hardware.