[openstack-dev] [neutron][networking-sfc] API clarification questions

Giuseppe (Pino) de Candia gdecandia at midokura.com
Wed Oct 28 08:14:31 UTC 2015

On Wed, Oct 28, 2015 at 4:20 PM, Russell Bryant <rbryant at redhat.com> wrote:

> I read through the proposed SFC API here:
> http://docs.openstack.org/developer/networking-sfc/api.html
> I'm looking at implementing what would be required to support this API
> in OVN.  I have a prototype, but I had to make some pretty big
> assumptions, so I wanted to clarify the intent of the API.
> First, does it assume that all of the neutron ports in a chain are on
> the same Neutron network?  That keeps things simple.  If its intended to
> allow a chain of ports on different networks, is it just required that
> you pick ports that all have addresses routable from one port to the
> next in the chain?  An arbitrary set of ports can't always work, so
> there has to be some bounds around what set of ports are valid to be in
> a chain.

Hi Russell,

We have similarly been experimenting with a MidoNet implementation of the

I hope there's no restriction on the location of the Neutron ports in a

In terms of addresses, I believe the API is lacking (or we use a
chain_parameter?) a way to indicate the service insertion model:
- L2 - The service can accept packets sent from any MAC (service NIC in
promiscuous mode). The MAC address may be used to identify where the packet
came from before it entered the chain.
- L3 -  The service expects packets to be routed to it. So the destination
MAC of the packet must be set to the service's NIC's MAC.

Any thoughts on this?

> Second, where is it expected that the match is applied?  The API for
> creating a port chain doesn't associate the chain with a network, but
> just matching "globally" doesn't make any sense.  If all ports are
> expected to be on the same network, is the match applied for any traffic
> entering that network from any port?

Here's what we were thinking for MidoNet:

use the logical_source_port in the flow classifier: when we render the SFC
API in MidoNet's models we will associate the chain with the source port.

Our packet pipeline (for packets egressing the VM) is:

   1. Port Mirroring
   2. Service Chaining
   3. Filtering (Port Security, anti-spoofing, Security Groups)

Do you think we can standardise on a single order in all implementations?
We'd be happy to change the order if it makes sense.

> I'm in Tokyo this week, so if the group working on this would like to
> talk in person, that would be great too.

I'd love to be included.

Great topic, thanks!


> --
> Russell Bryant
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