Thanks for your reply, Kevin, and sorry for the delay in following up.
On 21/04/15 09:40, Kevin Benton wrote:
Is it compatible with overlapping IPs? i.e. Will it give two different
VMs the same IP address if the reservations are setup that way?
No, not as I've described it below, and as we've implemented Calico so
far. Calico's first target is a shared address space without
overlapping IPs, so that we can handle everything within the default
namespace.
But we do also anticipate a future Calico release to support private
address spaces with overlapping IPs, while still routing all VM data
rather than bridging. That will need the private address TAP interfaces
to go into a separate namespace (per address space), and have their data
routed there; and we'd run a Dnsmasq in that namespace to provide that
space's IP addresses.
Within each namespace - whether the default one or private ones - we'd
still use the other changes I've described below for how the DHCP agent
creates the ns-XXX interface and launches Dnsmasq.
Does that make sense? Do you think that this kind of approach could be
in scope under the Neutron umbrella, as an alternative to bridging the
TAP interfaces?
Thanks,
Neil
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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