netdev - Re: [PATCH v2 0/7] net: Support checksum in UDP tunnels

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Date:	Wed, 4 Jun 2014 16:46:04 -0700
From:	Jesse Gross <jesse@...ira.com>
To:	Tom Herbert <therbert@...gle.com>
Cc:	David Miller <davem@...emloft.net>, netdev <netdev@...r.kernel.org>
Subject: Re: [PATCH v2 0/7] net: Support checksum in UDP tunnels

On Wed, Jun 4, 2014 at 4:11 PM, Tom Herbert <therbert@...gle.com> wrote:
> On Wed, Jun 4, 2014 at 3:28 PM, Jesse Gross <jesse@...ira.com> wrote:
>> On Sun, Jun 1, 2014 at 9:00 PM, Tom Herbert <therbert@...gle.com> wrote:
>>> This patch series adds support for using checksums in UDP tunnels. With
>>> this it is possible that two or more checksums may be set within the
>>> same packet and we would like to do that efficiently.
>>
>> Do you also plan to implement double checksum offload in the absence
>> of TSO? I know it is functionally correct now but it's not offloaded.
>
> We'd need HW support for that (like NETIF_F_HW_CSUM2). I think there
> is some justification in light of tunneling protocols over UDP that
> carry sensitive data, like virtual network ID, and don't otherwise
> have any provision at L3 to detect data corruption (e.g. vxlan).
>
> To implement, I think this is just another pair of checksum offsets
> (csum_start, csum_offset) (CHECKSUM_PARTIAL2?) that a driver would
> implement. Both csum_start and csum_offset could also be stored in 8
> bits (right shifted to give values up to 510) if there are concerns
> about space in TX descriptors.
>
> Are any vendors interested in this functionality?

My guess is that you won't get too many vendors to respond here but
without going into specifics, I know that a few are planning this. I
guess there isn't too much benefit until the hardware exists (which is
a different situation from GSO) but I was just wondering if you were
planning on building out the infrastructure.
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