netdev - Re: [PATCH net-next 6/8] net: gre: Implement LCO for GRE over IPv4

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Message-ID: <5693FC5B.3060904@solarflare.com>
Date:	Mon, 11 Jan 2016 19:02:51 +0000
From:	Edward Cree <ecree@...arflare.com>
To:	Alexander Duyck <alexander.duyck@...il.com>
CC:	David Laight <David.Laight@...lab.com>,
	David Miller <davem@...emloft.net>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	"linux-net-drivers@...arflare.com" <linux-net-drivers@...arflare.com>,
	"tom@...bertland.com" <tom@...bertland.com>
Subject: Re: [PATCH net-next 6/8] net: gre: Implement LCO for GRE over IPv4

On 11/01/16 18:39, Alexander Duyck wrote:
> On Mon, Jan 11, 2016 at 5:21 AM, Edward Cree <ecree@...arflare.com> wrote:
>> csum_fold complements, so if the sum comes to (say) 0x1fffe, it will return ~0xffff which is 0.
>>
>> Next version of patch will mangle 0 for both branches.
> Actually you may want to go the other way on that.  If they weren't
> flipping the checksum value for GRE before why should we start doing
> that now?  I'm pretty sure the checksum mangling is a very UDP centric
> thing.  There is no need to introduce it to other protocols.
Good catch, you're quite right.

-ed