[openstack-dev] [neutron] blueprint ovs-firewall-driver: OVS implementation of security groups

Amir Sadoughi amir.sadoughi at RACKSPACE.COM
Mon Jun 9 20:08:26 UTC 2014


The 80% distinction came from a discussion I had at summit, representing that the majority of features described by the current security groups could be implemented today with OVS without connection tracking. It’s not based on any mathematical calculation… more of a pseudo-application of Pareto’s principle. :)

Correct, the OVS tcp_flags feature will be used to implement an emulated statefulness for TCP flows whereas non-TCP flows would use the source-port-range-min, source-port-range-max extended API to implement stateless flows.

Performance measurements would have to come after implementations are made for the proposed blueprint. Although, benchmarks of the two existing FirewallDriver implementations can be done today. We can measure number of concurrent connections until failure, overall bandwidth as percentage of line rate, etc. Are there any other specific metrics you would like to see in the benchmark?


On Jun 3, 2014, at 2:51 AM, Salvatore Orlando <sorlando at nicira.com<mailto:sorlando at nicira.com>> wrote:

I would like to understand how did we get to this 80%/20% distinction.
In other terms, it seems conntrack's RELATED features won't be supported for non-tcp traffic. What about the ESTABLISHED feature? The blueprint specs refers to tcp_flags=ack.
Or will that be supported through the source port matching extension which is being promoted?

More comments inline.

On 3 June 2014 01:22, Amir Sadoughi <amir.sadoughi at rackspace.com<mailto:amir.sadoughi at rackspace.com>> wrote:
Hi all,

In the Neutron weekly meeting today[0], we discussed the ovs-firewall-driver blueprint[1]. Moving forward, OVS features today will give us "80%" of the iptables security groups behavior. Specifically, OVS lacks connection tracking so it won’t have a RELATED feature or stateful rules for non-TCP flows. (OVS connection tracking is currently under development, to be released by 2015[2]). To make the “20%" difference more explicit to the operator and end user, we have proposed feature configuration to provide security group rules API validation that would validate based on connection tracking ability, for example.

I am stilly generally skeptic of API changes which surface backend details on user-facing APIs. I understand why you are proposing this however, and I think it would be good to get first an assessment of the benefits brought by such a change before making a call on changing API behaviour to reflect security group implementation on the backend.

Several ideas floated up during the chat today, I wanted to expand the discussion to the mailing list for further debate. Some ideas include:
- marking ovs-firewall-driver as experimental in Juno
- What does it mean to be marked as “experimental”?

In this case experimental would be a way to say "not 100% functional".  You would not expect a public service provider exposing neutron APIs backed by this driver, but maybe in some private deployments where the missing features are not a concern it could be used.

- performance improvements under a new OVS firewall driver untested so far (vthapar is working on this)

>From the last comment in your post it seems you already have proof of the performance improvement, perhaps you can add those to the "Performance Impact" section on the spec.

- incomplete implementation will cause confusion, educational burden

It's more about technical debt in my opinion, but this is not necessarily the case.

- debugging OVS is new to users compared to debugging old iptables

This won't be a concern as long as we have good documentation to back the implementation.
As Neutron is usually sloppy with documentation - then it's a concern.

- waiting for upstream OVS to implement (OpenStack K- or even L- cycle)

In my humble opinion, merging the blueprint for Juno will provide us a viable, more performant security groups implementation than what we have available today.


[0] http://eavesdrop.openstack.org/meetings/networking/2014/networking.2014-06-02-21.01.log.html
[1] https://review.openstack.org/#/c/89712/
[2] http://openvswitch.org/pipermail/dev/2014-May/040567.html

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