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On 1/29/19 1:25 AM, Duarte Cardoso, Igor wrote:
>
> Hi Neutron,
>
>  
>
> I've been internally collaborating on the ``dvr_bridge`` L3 agent mode
> [1][2][3] work (David Shaughnessy, Xubo Zhang), which allows the L3
> agent to make use of Open vSwitch / OpenFlow to implement
> ``distributed`` IPv4 Routers thus bypassing kernel namespaces and
> iptables and opening the door for higher performance by keeping
> packets in OVS for longer.
>
>  
>
> I want to share a few questions in order to gather feedback from you.
> I understand parts of these questions may have been answered in the
> past before my involvement, but I believe it's still important to
> revisit and clarify them. This can impact how long it's going to take
> to complete the work and whether it can make it to stein-3.
>
>  
>
> 1. Should OVS support also be added to the legacy router?
>
> And if so, would it make more sense to have a new variable (not
> ``agent_mode``) to specify what backend to use (OVS or kernel) instead
> of creating more combinations?
>
Personally, I would like to see all routers implemented completely in
the OVS data path. We can't do everything at once, so the DVR-first
approach here seems reasonable to me. As to the question of config
flags, agent_mode has a specific meaning. It effectively tells the agent
what role it's playing (SNAT, SNAT_HA, etc.), not how to do it.
dvr_bridge isn't a new mode, it's really a change to the backend
implementation of the router (ie the "how"). Because of that, I'm
partial to an "agent_mode" flag which will toggle the router
implementation between OVS and namespace implementations.
>
>  
>
> 2. What is expected in terms of CI for this? Regarding testing, what
> should this first patch include apart from the unit tests? (since the
> l3_agent.ini needs to be configured differently).
>
>  
>
> 3. What problems can be anticipated by having the same agent managing
> both kernel and OVS powered routers (depending on whether they were
> created as ``distributed``)?
>
> We are experimenting with different ways of decoupling RouterInfo
> (mainly as part of the L3 agent refactor patch) and haven't been able
> to find the right balance yet. On one end we have an agent that is
> still coupled with kernel-based RouterInfo, and on the other end we
> have an agent that either only accepts OVS-based RouterInfos or only
> kernel-based RouterInfos depending on the ``agent_mode``.
>
>  
>
> We'd also appreciate reviews on the 2 patches [4][5]. The L3 refactor
> one should be able to pass Zuul after a recheck.
>
>  
>
> [1] Spec:
> https://blueprints.launchpad.net/neutron/+spec/openflow-based-dvr
>
> [2] RFE: https://bugs.launchpad.net/neutron/+bug/1705536
>
> [3] Gerrit topic:
> https://review.openstack.org/#/q/topic:dvr_bridge+(status:open+OR+status:merged)
>
> [4] L3 agent refactor patch: https://review.openstack.org/#/c/528336/29
>
> [5] dvr_bridge patch: https://review.openstack.org/#/c/472289/17
>
>  
>
> Thank you!
>
>  
>
> Best regards,
>
> Igor D.C.
>
>  
>
-Ryan
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