[ovs-dev] OvS on OpenVZ

Eric Murray emurray.uml at gmail.com
Wed Feb 3 11:58:03 PST 2010


Thank you for such a quick response.

I am using OpenvSwitch version 0.90.7.

For the time being I am trying to allow virtual machines to communicate with
each other through a datapath, and assigning a physical nic to the datapath
for the VM's to communicate to another machine connected via crossover
cable.

I'm trying to get an OpenvSwitch system running so that I can try developing
some applications on network processors, specifically the Netronome NFEi8k.
I'm working for Professor Luo at UMass Lowell.

I was able to successfully communicate from a virtual machine to the outside
world with the regular linux bridge, but I have not been able to repeat this
experiment using OpenvSwitch.

When using the ovs-dpctl utility to remove interfaces from a given datapath,
I get the warning:

            Feb 03 14:32:34|00124|dpif|WARN|dp0: failed to query port eth1:
No such file or directory

While brcompatd reports:

           Feb 03 14:47:52|00020|brcompatd|INFO|kernel reported network
device eth1 removed but a device by that name exists (XS Tools 5.0.0?)


Could this warning be related to the problem I'm having with accessing the
outside world from a VM?


The bridge compatibility issues I mentioned are that the brctl commands do
not work correctly. When I try to add an interface using the brctl command I
get:

[root at pr10 openvswitch-0.90.7]# brctl addif br0 eth1
Feb 03 14:49:16|00021|brcompatd|INFO|add-if br0 eth1: success
Feb 03 14:49:16|00022|brcompatd|ERR|ovs-appctl exited with error (exit
status 1)
Feb 03 14:49:16|00023|brcompatd|INFO|ovs-appctl wrote to stderr:
cat: /usr/local/var/run/ovs-vswitchd.pid: No such file or directory
Error connecting to "/usr/local/var/run/ovs-vswitchd..ctl": No such file or
directory
ovs-appctl: no targets specified (use --help for help)
Feb 03 14:49:16|00024|brcompatd|INFO|reload command executed in 4 ms
Feb 03 14:49:16|00025|brcompatd|INFO|add-if br0 eth1: success
Feb 03 14:49:16|00026|brcompatd|ERR|ovs-appctl exited with error (exit
status 1)
Feb 03 14:49:16|00027|brcompatd|INFO|ovs-appctl wrote to stderr:
cat: /usr/local/var/run/ovs-vswitchd.pid: No such file or directory
Error connecting to "/usr/local/var/run/ovs-vswitchd..ctl": No such file or
directory
ovs-appctl: no targets specified (use --help for help)
Feb 03 14:49:16|00028|brcompatd|INFO|reload command executed in 4 ms
can't add eth1 to bridge br0: No child processes


I'm not sure if I'll actually end up needing to use the legacy bridge
compatibility functionality, but any advice you can give me as to meeting
the goal I mentioned above (sending packets out from a VM) would be greatly
appreciated.

Thanks,

Eric Murray


On Tue, Feb 2, 2010 at 4:57 PM, Ben Pfaff <blp at nicira.com> wrote:

> On Tue, Feb 02, 2010 at 04:48:06PM -0500, Eric Murray wrote:
> > I'm experimenting with OpenvSwitch on OpenVZ. The OpenvSwitch homepage
> does
> > not state whether or not OpenVZ is supported, but I figured I might as
> well
> > ask and gain some perspective.
> >
> > I've noticed the bridge compatibility functionality does not work on
> OpenVZ,
>
> Can you give any more details, e.g. what you tried, what you expected to
> happen, and what actually happened?
>
> What version of OVS are you testing?
>
> > and also that the following error message occurs when an interface is
> > added or removed from a datapath:
> >
> > Feb 02 16:23:40|00001|netdev|INFO|RTM_GETLINK failed (Invalid argument),
> > obtaining netdev stats via proc (you are probably running a pre-2.6.19
> > kernel)
>
> That's not an error, it just means that you have an old kernel and so
> the code is falling back to less-efficient means of obtaining some
> statistics.  Perhaps we should disable or downgrade the message's
> severity, since I'm pretty sure that it works.
>
> > I'm running OpenVZ's stable version, which is on the 2.6.18 kernel, but I
> > was not seeing this message when running Xen on the same machine.
>
> Xen kernels have some backported functionality.  Perhaps this is part of
> what has been backported.
>
> > Please let me know if it is worthwhile to try to get OpenvSwitch to work
> > normally on OpenVZ, and where would be a good place in the source code to
> > look for the source of the problems.
>
> Bridge compatibility is mainly in datapath/brc_*.c and
> vswitchd/ovs-brcompatd.c.
>
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