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SubjectRe: [PATCH net-next v5] cadence: Add LSO support.
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On Mon, 2016-11-14 at 09:32 +0000, Rafal Ozieblo wrote:
> From: David Miller [mailto:davem@davemloft.net]
> Sent: 10 listopada 2016 18:01
> To: Rafal Ozieblo
> Cc: nicolas.ferre@atmel.com; netdev@vger.kernel.org; linux-kernel@vger.kernel.org
> Subject: Re: [PATCH net-next v5]] cadence: Add LSO support.
>
> From: Rafal Ozieblo <rafalo@cadence.com>
> Date: Wed, 9 Nov 2016 13:41:02 +0000
>
> > First, please remove the spurious closing bracket in your Subject line in future submittions.
> >
> >> + if (is_udp) /* is_udp is only set when (is_lso) is checked */
> >> + /* zero UDP checksum, not calculated by h/w for UFO */
> >> + udp_hdr(skb)->check = 0;
> >
> > This is really not ok.
> >
> > 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.

Then do not claim NETIF_F_UFO suport in the driver, if hardware is
absolutely not capable of handling this.

Linux stack will provide proper udp checksum.

Almost no driver sets NETIF_F_UFO.





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