[ovs-dev] [RFC PATCH] datapath: allow tunnels to be created with rtnetlink

[Jiri Benc]

On Wed, 7 Dec 2016 16:35:59 -0800, Pravin Shelar wrote:
> In compat mode, OVS tunnel devices are not used in same way as LWT,
> since OVS do support kernel version that does not have core LWT
> support. Therefore we have to use legacy vport APIs to create these
> ports.

I see. Yes, that's unfortunate.

> There might be a way to configure the device, once it is
> created, using rtnetlink API but would complicate the code. So I think
> in such cases like GPE we could to add code to the legacy code.

Could we just support the newest shiniest features only with lwtunnel
capable kernel? Kernel 4.3 is out for more than a year already, that's
a long time. And several more months will pass before this is available
in an Open vSwitch release.

What about:
- always preferring the out of tree module (whatever capabilities it
  has)
	- first try rtnetlink
	- if it fails, try genetlink
	- if it fails (but the out of tree module is there), just don't
	  bother with kernel
- then try the in kernel module
	- first rtnetlink
	- if it fails then genetlink

This way, we would accommodate most of the stuff. With old kernels,
VXLAN-GPE wouldn't be available even with the out of tree module (but
I think that's it, I can't think of any other feature unavailable at
this point; of course, more may be added in the future).

Is this really that bad? It's (relatively) simply to implement, the out
of tree module does not diverge from the in kernel one too much, and I
don't think the requirement for lwtunnels capable kernel for the newest
features is unreasonable.

Thanks,

 Jiri