[openstack-dev] [neutron] Why neutron-openvswitch-agent use linux-bridge?

Kyle Mestery (kmestery) kmestery at cisco.com
Wed Nov 27 19:38:14 UTC 2013


On Nov 27, 2013, at 1:29 PM, George Shuklin <george.shuklin at gmail.com> wrote:

> Thank you for reply!
> 
> Few more question:
> 
> AFAIK bridge tools is not very fast (compare to OVS), so adding them between OVS and tap (instead of yet another OVS switch) is kinda slow everything down. Why just not use yet another openvswitch switch to connect tap to veth devices?
> 
> Why iptables, not internal openvswitch flow rules? Those rules allows to filter packets on L2-L4 headers and operates very fast. Is some iptables-only features used in ova-agent?
> 
George:

There is work ongoing now to implement security groups using
OVS flow rules in the OVS agent with the ML2 plugin. That would
do what you're looking at above. Stay tuned on this, the authors
of these patches hope to have some WIP code available soon.

Thanks,
Kyle

> Thanks.
> 
> 27.11.2013 20:55 пользователь "Lorin Hochstein" <lorin at nimbisservices.com> написал:
> Hi George:
> 
> 
> 
> On Wed, Nov 27, 2013 at 1:45 PM, George Shuklin <george.shuklin at gmail.com> wrote:
> Good day.
> 
> I looking at the internals of bridge layout of openvswitch agent at http://docs.openstack.org/network-admin/admin/content/figures/2/figures/under-the-hood-scenario-1-ovs-compute.png
> and wondering, why this scheme is so complicated and why it use linux bridge and vethes with openvswitch together? Why no just plug tap device directly to openvswitch bridge without intermediate brctl bridge?
> 
> I guess that was caused by some important consideration, but I unable to find any documents about this.
> 
> If someone know reasons for that complex construction with different bridges, please response.
> 
> 
> If you look a little further down on the page with that figure, the documentation reads
> 
> Ideally, the TAP device vnet0 would be connected directly to the integration bridge, br-int. Unfortunately, this isn't possible because of how OpenStack security groups are currently implemented. OpenStack uses iptables rules on the TAP devices such as vnet0 to implement security groups, and Open vSwitch is not compatible with iptables rules that are applied directly on TAP devices that are connected to an Open vSwitch port.
> 
> 
> Take care,
> 
> Lorin
> 
> 
> 
> -- 
> Lorin Hochstein
> Lead Architect - Cloud Services
> Nimbis Services, Inc.
> www.nimbisservices.com
> 
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