[ovs-dev] [PATCH] dpif: Ensure ERSPAN GRE support

[Jiri Benc]

On Fri, 1 Jun 2018 11:23:12 -0700, William Tu wrote:
> Looking at the dpif_netlink_rtnl_probe_oot_tunnels(), since now we
> added ERSPAN feature, instead of probing geneve module,
> we should probe ip_gre module with a nlattr of ERSPAN (ex: HWID).
> If it does not return -ENOSUPPORT, then use the upstream ip_gre module.

That doesn't make sense. That function is used solely to determine
whether the out of (kernel) tree modules are loaded. If they are, ovs
prefers them.

Note that the features do not come into play here: if there are out of
tree modules present, they are used. It's very well possible that the
running kernel has more features but it's irrelevant.

It doesn't matter in which way the code determines whether there are
out of tree modules loaded or not. Probing for geneve thus works just
fine and there's no need to change it.

> And the next added feature should change this function to determine
> whether to use compat mode or not.  Do I understand it right?

No. The out of tree modules are preferred, irrespective of the
supported features.

 Jiri