[ovs-dev] lookups in OVS data path

Jesse Gross jesse at nicira.com
Fri Feb 1 18:00:11 UTC 2013

On Fri, Feb 1, 2013 at 2:19 AM, SDN learn <sdn.learn at gmail.com> wrote:
> Hello OVS experts,
> I'm new to OVS and trying to understand a few things...
> 1. When packet comes in, there is a lookup for outer-IP/L4 in vport-gre.c
> (for GRE overlay). Then GRE key is matched.
> Finally, at some point later, there is a look up for inner IP/L4 before
> inner IP/L4/payload is sent to "action" port.
> Is that correct? If yes, why do we need multi stage lookup policies? Isn't
> that inefficient...any issues in combining them into a single wider lookup?

We're transitioning to a single lookup in the master branch.  However,
it is to expose more information to userspace, not because the
efficiency is much different.

> 2. When OVS terminates outer-IP/overlay header etc, the inner-IP+payload is
> sent to hypervisor...how does the hypervisor associate this packet to a
> particular Virtual-Machine instance.
> Does OF controller select a different "action" port for each VM?

Yes, each VM has a different port.

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