On Mon, Jan 9, 2017 at 2:22 PM, Ben Pfaff <[email protected]> wrote:

> On Fri, Jan 06, 2017 at 04:28:00PM -0800, Mickey Spiegel wrote:
> > On Fri, Jan 6, 2017 at 3:57 PM, Ben Pfaff <[email protected]> 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 <[email protected]>
> > >
> > > 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.
>
> OK.
>
> > 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.
>
> I think that could be avoided, too, with a little more adjustment.
> First, instead of zeroing all the registers, maintain them (and then
> zero registers that should be zeroed using OVN logical actions).
> Second, use some designated bit in a register for this particular
> purpose.
>
> (In case it is not clear, my preference, overall, is to put policy, as
> much as possible, into the logical flow table instead of into the
> mechanism that surrounds it.)
>

Probably the register bit setting should be within the clone.
Are you OK with setting a specific register bit in an OVN action definition?

Mickey
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