[ovs-dev] [PATCH v4] OVN localport type support

Daniel Alvarez Sanchez dalvarez at redhat.com
Fri May 19 14:26:14 UTC 2017


Thanks a lot Ben for your review!

On Fri, May 19, 2017 at 12:16 AM, Ben Pfaff <blp at ovn.org> wrote:

> On Wed, May 10, 2017 at 08:35:45AM +0000, Daniel Alvarez wrote:
> > This patch introduces a new type of OVN ports called "localport".
> > These ports will be present in every hypervisor and may have the
> > same IP/MAC addresses. They are not bound to any chassis and traffic
> > to these ports will never go through a tunnel.
> >
> > Its main use case is the OpenStack metadata API support which relies
> > on a local agent running on every hypervisor and serving metadata to
> > VM's locally. This service is described in detail at [0].
> >
> > An example to illustrate the purpose of this patch:
> >
> > - One logical switch sw0 with 2 ports (p1, p2) and 1 localport (lp)
> > - Two hypervisors: HV1 and HV2
> > - p1 in HV1 (OVS port with external-id:iface-id="p1")
> > - p2 in HV2 (OVS port with external-id:iface-id="p2")
> > - lp in both hypevisors (OVS port with external-id:iface-id="lp")
> > - p1 should be able to reach p2 and viceversa
> > - lp on HV1 should be able to reach p1 but not p2
> > - lp on HV2 should be able to reach p2 but not p1
> >
> > Explicit drop rules are inserted in table 32 with priority 150
> > in order to prevent traffic originated at a localport to go over
> > a tunnel.
> >
> > [0] https://review.openstack.org/#/c/452811/
> >
> > Signed-off-by: Daniel Alvarez <dalvarez at redhat.com>
>
> Thanks for working on this!
>
> This seems reasonable, but I'm torn about one aspect of it.  I'm not
> sure whether my concern is a kind of premature optimization or not, so
> let me just describe it and we can discuss.
>
> This adds code that iterates over every local lport (suppose there are N
> of them), which is nested inside a function that is executed for every
> port relevant to the local hypervisor (suppose there are M of them).
> That's O(N*M) time.  But the inner loop is only doing something useful
> for localport logical ports, and normally there would only be 1 or so of
> those; at any rate a constant number.  So in theory this could run in
> O(M) time.
>
> I see at least two ways to fix the problem, if it's a problem, but I
> don't know whether it's worth fixing.  Daniel?  Russell?  (Others?)
>
> Yes, I also thought about this but I don't know either if it's a problem
or not.
If we want to impose at most one logical localport per datapath then we
would have O(M) time (mimic localnet ports) but that's something I didn't
want to do unless you think it makes more sense.


> Thanks,
>
> Ben.
>


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