netdev - Re: [PATCH net-next 0/5] virtio-net: Add SCTP checksum offload support

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Message-ID: <6bc762f6-d6fb-5471-2893-a888cce199f9@redhat.com>
Date:   Tue, 17 Apr 2018 16:35:18 -0400
From:   Vlad Yasevich <vyasevic@...hat.com>
To:     Marcelo Ricardo Leitner <marcelo.leitner@...il.com>,
        Vladislav Yasevich <vyasevich@...il.com>
Cc:     netdev@...r.kernel.org, linux-sctp@...r.kernel.org,
        virtualization@...ts.linux-foundation.org, mst@...hat.com,
        jasowang@...hat.com, nhorman@...driver.com
Subject: Re: [PATCH net-next 0/5] virtio-net: Add SCTP checksum offload
 support

On 04/02/2018 10:47 AM, Marcelo Ricardo Leitner wrote:
> On Mon, Apr 02, 2018 at 09:40:01AM -0400, Vladislav Yasevich wrote:
>> Now that we have SCTP offload capabilities in the kernel, we can add
>> them to virtio as well.  First step is SCTP checksum.
> 
> Thanks.
> 
>> As for GSO, the way sctp GSO is currently implemented buys us nothing
>> in added support to virtio.  To add true GSO, would require a lot of
>> re-work inside of SCTP and would require extensions to the virtio
>> net header to carry extra sctp data.
> 
> Can you please elaborate more on this? Is this because SCTP GSO relies
> on the gso skb format for knowing how to segment it instead of having
> a list of sizes?
> 

it's mainly because all the true segmentation, placing data into chunks,
has already happened.  All that GSO does is allow for higher bundling
rate between VMs. If that is all SCTP GSO ever going to do, that fine,
but the goal is to do real GSO eventually and potentially reduce the
amount of memory copying we are doing.
If we do that, any current attempt at GSO in virtio would have to be
depricated and we'd need GSO2 or something like that.

This is why, after doing the GSO support, I decided not to include it.

-vlad

>   Marcelo
>