[openstack-dev] [neutron] Are routed TAP interfaces (and DHCP for them) in scope for Neutron?

Neil Jerram Neil.Jerram at metaswitch.com
Tue Apr 21 07:05:00 UTC 2015

I haven't yet had any responses to this, so reflagging it in case it was 
just missed in the helter skelter of activity that is the openstack-dev 
mailing list...

On the other hand, if I need to describe more clearly what I'm on about, 
please don't be afraid to say that!

Any comments and steer would be appreciated, even if they're more of a 
high level gut feel, than an exhaustive treatment.


On 16/04/15 15:12, Neil Jerram wrote:
> I have a Neutron DHCP agent patch whose purpose is to launch dnsmasq
> with options such that it works (=> provides DHCP service) for TAP
> interfaces that are _not_ bridged to the DHCP interface (ns-XXX).  For
> the sake of being concrete, this involves:
> - creating the ns-XXX interface as a dummy, instead of as a veth pair
> - launching dnsmasq with --bind-dynamic --listen=ns-XXX --listen=tap*
> --bridge-interface=ns-XXX,tap*
> - not running in a separate namespace
> - running the DHCP agent on every compute host, instead of only on the
> network node
> - using the relevant subnet's gateway IP on the ns-XXX interface (on
> every host), instead of allocating a different IP for each ns-XXX
> interface.
> I proposed a spec for this in the Kilo cycle [1], but it didn't get
> enough traction, and I'm now wondering what to do with this
> work/function.  Specifically, whether to look again at integrating it
> into Neutron during the Liberty cycle, or whether to maintain an
> independent DHCP agent for my project outside the upstream Neutron tree.
>   I would very much appreciate any comments or advice on this.
> For answering that last question, I suspect the biggest factor is
> whether routed TAP interfaces - i.e. forms of networking implementation
> that rely on routing data between VMs instead of bridging it - is in
> scope for Neutron, at all.  If it is, I understand that there could be a
> lot more detail to work on, such as how it meshes with other Neutron
> features such as DVR and the IPAM work, and that it might end up being
> quite different from the blueprint linked below.  But it would be good
> to know whether this would ultimately be in scope and of interest for
> Neutron at all.
> Please do let me now what you think.
> Many thanks,
>      Neil
> [1] https://blueprints.launchpad.net/neutron/+spec/dhcp-for-routed-ifs

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