[ovs-dev] VXLAN ports not working with latest master

[Ethan Jackson]

> Yes, I'd like to help here. Can you shoot me any ideas you may have?
> I've been looking at this in my free time today. Tomorrow I should be
> able to dedicate most of the day to it.

Ok sounds good.  Thanks for taking this on.

So at a high level, conceptually what we need to do is fairly straight
forward.  Instead of creating a vxlan tnl_backer, like we do for the
other tunnel types.  We need to create a vxlan tnl_backer per dest
port.  All vxlan ports using the same dest port, will share this
backer.

So to start off we need to make some minor netdev-vport changes.
netdev_vport_get_dpif_port() needs to return special dpif port names
for VXLAN ports which embed the dst port number.  I.E. instead of
"vxlan_system" which it returns now, it would return "vxlan_sys_8472"
or "vxlan_sys_4321" depending on what the dest port is.  This done,
ofproto-dpif and dpif-linux will know that they should be using
different tnl_backers.  Also, dpif-linux needs to get the dst port
from the netdev_tunnel_config and set it in the options if nonzero.

The hardest part to deal with will be ofproto-dpif.  We're now
breaking the assumption that a port's dpif_port can never change once
created. Therefore, simply creating and deleting tnl_backers at ofport
creation and deletion time will be insufficient as it will not
properly deal with dst port config changes.

My tentative solution to the problem is to decouple port creation and
deletion from tnl_backer management.  Specifically, I think we should
remove may_dpif_port_del(), and stop doing dpif_port_del() of
tnl_backers in the port_del() and port_destruct() functions.  Instead
we should centralize all of this in a run function near the
reconfiguration code.  We should loop through all ofports and
tnl_backers associated with a dpif_backer. For any ofports whose dst
port has changed, we should change their odp_port to the appropriate
tnl_backer, or create it if necessary.  Once done, we can delete any
tnl_backers which are no longer used by any ofports.

Hopefully that is all clear.  Let me know if you think the strategy
won't work, or could be enhanced in some way.  Thanks again for
volunteering to have a look at this.

Ethan