[ovs-dev] [PATCH v7 4/7] ovn: add egress loopback capability

[Ben Pfaff]

On Fri, Jan 06, 2017 at 12:00:31PM -0800, Mickey Spiegel wrote:
> This patch adds the capability to force loopback at the end of the
> egress pipeline.  A new flags.force_egress_loopback symbol is defined,
> along with corresponding flags bits.  When flags.force_egress_loopback
> is set, at OFTABLE_LOG_TO_PHY, instead of the packet being sent out to
> the peer patch port or out the outport, the packet is forced back to
> the beginning of the ingress pipeline with inport = outport.  All
> other registers are cleared, as if the packet just arrived on that
> inport.
> 
> This capability is needed in order to implement some of the east/west
> distributed NAT flows.
> 
> Note: The existing flags.loopback allows a packet to go from the end
> of the ingress pipeline to the beginning of the egress pipeline with
> outport = inport, which is different.
> 
> Initially, there are no tests incorporated in this patch.  This
> functionality is tested in a subsequent distributed NAT flows patch.
> Tests specific to egress loopback may be added once the capability
> to inject a packet with one of the flags bits set is added.
> 
> Signed-off-by: Mickey Spiegel <mickeys.dev at gmail.com>

I don't really understand this yet.

Does this need to be a flag or can it be an action, i.e. one that
immediately jumps back to the beginning of the ingress pipeline.  Then
we don't need hard-coded flags, we can just have used-defined register
bits, etc.

This needs real documentation in ovn-sb.xml instead of just being added
to a list.