openvswitch agent should use veths instead of patch ports

[Robert Kukura]

The Open vSwitch FAQ at http://openvswitch.org/cgi-bin/gitweb.cgi?p=openvswitch;a=blob_plain;f=FAQ;hb=HEAD contains the following:

Q: What features are not available in the Open vSwitch kernel datapath
   that ships as part of the upstream Linux kernel?

A: The kernel module in upstream Linux 3.3 and later does not include
   the following features:

       - Bridge compatibility, that is, support for the ovs-brcompatd
         daemon that (if you enable it) lets "brctl" and other Linux
         bridge tools transparently work with Open vSwitch instead.

         We do not expect bridge compatibility to ever be available in
         upstream Linux. If you need bridge compatibility, use the
         kernel module from the Open vSwitch distribution instead of the
         upstream Linux kernel module.

       - Tunnel virtual ports, that is, interfaces with type "gre",
         "ipsec_gre", "capwap". It is possible to create tunnels in
         Linux and attach them to Open vSwitch as system devices.
         However, they cannot be dynamically created through the OVSDB
         protocol or set the tunnel ids as a flow action.

         Work is in progress in adding these features to the upstream
         Linux version of the Open vSwitch kernel module. For now, if
         you need these features, use the kernel module from the Open
         vSwitch distribution instead of the upstream Linux kernel
         module.

       - Patch virtual ports, that is, interfaces with type "patch".
         You can use Linux "veth" devices as a substitute.

         We don't have any plans to add patch ports upstream.

Operating systems such as Fedora that only support the "Open vSwitch kernel datapath that ships as part of the upstream Linux kernel" do not currently support GRE tunnelling with the openvswitch plugin due to the lack of both tunnel virtual ports and patch virtual ports. Since there are plans to add the former but not the latter to the upstream kernel, the openvswitch agent should be changed to use veth devices instead of patch port to link the integration bridge with the tunnel bridge. This would enable GRE networks to be supported on these systems as soon as the planned support for tunnel virtual ports is in the upstream Linux kernel.

[dan wendlandt (danwent)]

Bob, I don't believe we're planning on doing this for Folsom. If you think it needs to be done for Folsom, let's coordinate ASAP.

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/19294

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/27054

[Robert Kukura (rkukura)]

The patch above expired 9 months ago, and since then patch port support has been added to the upstream Linux kernel OVS implementation, so I'm changing this to "won't fix".