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

[Mickey Spiegel]

On Fri, Jan 6, 2017 at 3:57 PM, Ben Pfaff <blp at ovn.org> wrote:

> 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.
>

Since I am figuring out whether to do egress loopback at the end of
the egress pipeline, I could get rid of the FORCE_EGRESS_LOOPBACK
flag and use an action instead.

I think I still need the EGRESS_LOOPBACK_OCCURRED bit to avoid
the packet getting dropped in table 1 because the logical router receives
a packet with its own IP address as source.

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