[Openstack] Nested Open vSwitch Bridges

Aaron Rosen arosen at nicira.com
Tue Apr 30 23:55:58 UTC 2013


Also, the security group stuff locks down the port to be the mac+ip of the
quantum port mac+ip. If you create a new bridge and add ethX to it you'll
also have to set the mac on your bridge to be the same as ethX (which is
the mac that quantum handed out).

Aaron


On Tue, Apr 30, 2013 at 4:25 PM, Salvatore Orlando <sorlando at nicira.com>wrote:

> Hi Joe,
>
> are you using the OVS plugin with GRE overlays?
> In that case your problem might be the fact that the plugin pushes a OVS
> flow entry which applies the 'local' vlan tag only to packet directed to
> the VM's mac [1]
>
> To me, this does not look like a bug; it's probably intended behaviour, as
> it kind of implements mac spoofing prevention. In the future we might also
> expect stricter anti-spoof checking; on the other side a change
> for administratively enabling promiscuos mode might be welcome - this
> should allow you to do nested OVS.
>
> Salvatore
>
> [1]
> https://github.com/openstack/quantum/blob/master/quantum/plugins/openvswitch/agent/ovs_quantum_agent.py#L448
>
>
>
> On 30 April 2013 22:08, Joe Topjian <joe.topjian at cybera.ca> wrote:
>
>> Hello,
>>
>> I have OpenStack (Grizzly) up and running with Quantum. I'm using the
>> Open vSwitch plugin, per-tenant routing, and network namespaces. As far as
>> I'm aware, this is all set up correctly as instances that I create are able
>> to retrieve an IP address via DHCP, reach the metadata server, and reach
>> the outside internet.
>>
>> The issue that I'm running into is that when I install Open vSwitch on
>> the instance itself, I'm unable to create working bridges. For example:
>>
>> ovs-vsctl add-br br-eth0
>> ovs-vsctl add-port br-eth0 eth0
>> (swap IPs from eth0 to br-eth0, kill dhcp, etc etc)
>>
>> Traffic isn't flowing properly, though.
>>
>> If I run a continuous ping and run tcpdump on both the instance and the
>> tap interface on the controller, I see arp requests going out of the
>> instance, being received on the tap interface, the tap interface sending a
>> reply, but the reply never reaching the instance.
>>
>> However, I have found that if I create a bridge with the same MAC as the
>> interface that I'm adding to the bridge, traffic flows correctly:
>>
>> ovs-vsctl set bridge br-eth0 other-config:hwaddr=aa:bb:cc:00:11:22
>>
>> My best guess is that there's something (L2) blocking the flow of
>> traffic, but I'm not exactly sure where to start looking. I think it's safe
>> to assume that Open vSwitch on the OpenStack servers is doing the blocking
>> but I think it's Quantum that's implementing the blocking since if I use
>> Open vSwitch with nova-network, this problem doesn't happen.
>>
>> Does anyone have any pointers? Or even a fix?
>>
>> Thanks,
>> Joe
>>
>> --
>> Joe Topjian
>> Systems Administrator
>> Cybera Inc.
>>
>> www.cybera.ca
>>
>> Cybera is a not-for-profit organization that works to spur and support
>> innovation, for the economic benefit of Alberta, through the use
>> of cyberinfrastructure.
>>
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