netdev - Re: Generic TSO (was Re: [net-next PATCH 0/2] GENEVE/VXLAN: Enable outer Tx checksum by default)

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Message-ID: <56E3239B.7080009@solarflare.com>
Date:	Fri, 11 Mar 2016 19:59:23 +0000
From:	Edward Cree <ecree@...arflare.com>
To:	Tom Herbert <tom@...bertland.com>
CC:	Linux Kernel Network Developers <netdev@...r.kernel.org>
Subject: Re: Generic TSO (was Re: [net-next PATCH 0/2] GENEVE/VXLAN: Enable
 outer Tx checksum by default)

On 11/03/16 19:57, Tom Herbert wrote:
> On Fri, Mar 11, 2016 at 11:20 AM, Edward Cree <ecree@...arflare.com> wrote:
>> Tom,
>>
>> Are you planning to / working on implementing this?  If not, I might have a
>> crack at it; I've talked to our firmware guys and (provisionally) we think
>> we can support it in current sfc hardware.
>> Or were there any blocking problems raised in the thread?  My understanding
>> of the IP ID issue was that it only matters for the inner frame, because
>> the rest aren't TCP (so hopefully no-one is doing SLHC on them).  But I may
>> have missed something.
>>
> Right, then the interface would need to just include the offset of the
> IP ID. But doesn't this break using LCO with GSO though-- i.e. the
> outer checksum and inner checksum still need to be updated per packet
> so we need to tell device where outer checksum(s) is.
No, outer checksum shouldn't change: IP ID is protected by inner IP header
checksum, which device will edit.  No?

-Ed