[ovs-dev] [PATCH v2] Add experimental support for TUNNEL SRC/DST.

[Jesse Gross]

On Wed, Dec 12, 2012 at 6:34 AM, Jarno Rajahalme
<jarno.rajahalme at nsn.com> wrote:
> This version adds odp-level support for tunnel metadata.
>
> Currently it seems the datapath expects userspace to specify all the
> tunnel fields, or none of them.  IMO, it would be better to use of
> configured values as defaults, allowing flow entries to provide only
> some of the fields (e.g., tun_dst).
>
> This is obviously similar to how any other field changes are viewed
> at the OF level, but tunnel metadata is different since packets don't
> have the metadata when they arrive on a normal port, but the tunnel
> metadata is figured out only when the output port is determined
> (which may be taken from a register if I'm not mistaken).
>
> So, is the design intent that the userspace code digs the missing
> values from the tunnel configuration data?  Currently, it seems that
> data is readily available in the datapath when it is needed, but maybe
> doing it "once" on the userspace is better than figuring out which
> values to use on the datapath for each packet separately?

The configuration information is no longer going to be available at
the kernel level soon.  This will allow userspace to be more flexible
about the policies that it implements.

Please separate out the ODP changes from the OpenFlow changes.  I
can't apply the OpenFlow portions until all of the issues that I
mentioned before have been resolved but I could apply the ODP
component now.

Is the ODP code based on the patch that I linked to before?  If so, it
makes some changes that I don't understand, particularly things like
dropping comments and unit tests.

In any case, flags should be converted between userspace and kernel.
The same set of flags happen to be defined now with the same values
but it shouldn't be assumed that is the case.  In particular, if there
are different versions of userspace and kernel then new flags that the
other side doesn't know about shouldn't just get carried over.  This
can result in not being able to setup flows properly.