[virtio-dev] Re: [virtio-comment] Re: [PATCH v10] virtio-net: support inner header hash

[Parav Pandit <parav@nvidia.com>]

On 3/15/2023 8:10 AM, Michael S. Tsirkin wrote:
> On Tue, Mar 14, 2023 at 11:23:55PM -0400, Parav Pandit wrote:
>> If not, for now it may be better to skip vxlan and nvegre as they inherently
>> have unique outer header UDP src port based on the inner header.
> 
> So what's left, GRE?  GRE is actually different, in that it's not IP at
> all.
Sorry, I wrongly wrote nvegre above.

IPoIP, GRE and NVGRE are left.

vxlan and geneve has the udp src entropy.

> 
Not sure I understand "its not IP at all".

GRE has outer IP header + GRE header with the key to identify the flow.
The key is effectively the hash for the flow.

> So if we are talking about GRE, hash is indeed not calculated at all at
> the moment, right?  
Hash of the outer IP header of the src and dst IP can be still 
calculated currently for GRE when the optional key is not present.

> And I would say a natural first step for GRE is
> actually adding a hash type that will support this protocol.
>
For GRE and NVGRE GRE_header.key as the flow/hash identifier should work 
without inner header hash.
Older version of the GRE doesn't have key, so inner header hash is useful.

> How about doing that? It seems like this should be a small step
> and completely uncontroversial.

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