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

["Michael S. Tsirkin" <mst@redhat.com>]

On Wed, Mar 15, 2023 at 09:19:43PM +0800, Heng Qi wrote:
> > Any encapsulation technology that includes UDP/L4 header likely do not
> > prefer based on the inner header. This is because the outer header src
> > port entropy is added based on the inner header.
> > 
> > I was not able to follow the discussion in v9 that you had with Michael.
> > Did you conclude if this is needed for vxlan too?
> > 
> > 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.
> 
> Symmetric hashing ignores the order of the five-tuples when calculating the
> hash, that is, using (a1,a2,p1,p2) and (a2,a1,p2,p1) respectively can
> calculate the same hash.
> There is a scenario that the two directions client1->client2 and
> client2->client1 of the same flow may pass through different tunnels.
> In order to allow the data in two directions to be processed by the same
> CPU, we need to calculate a symmetric hash based on the inner packet header.
> Sorry I didn't mention this earlier just to avoid introducing the concept of
> symmetric hashing.

But the hash is already there in the port. Is it then maybe just
the question of ignoring the IP addresses when hashing?

-- 
MST


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