[ovs-discuss] Overlapping rules with identical actions

Bithika Khargharia bithika at gmail.com
Wed Sep 5 16:16:59 UTC 2012


Thank you Ben.

I am trying to figure out what happens in the following scenario.

OVERLAP flag is not set. Rule 1 has been installed that has an idle timeout
value. Before Rule 1 has expired, an overlapping Rule 2 (same priority,
same idle timeout) came in.

1. Would Rule 1 be deleted and Rule 2 installed?
                                       OR
2. Would Rule 1 continue to stay (because idle timeout is not up yet) and
Rule 2  is also installed.

I would assume 2 because by the time Rule 2 came in, the idle timeout value
of Rule 1 would have been updated and hence shorter than that of Rule 1. So
technically they are not overlapping. But I wanted to verify that  first.

Thanks
Bithika

On Tue, Sep 4, 2012 at 5:33 PM, Ben Pfaff <blp at nicira.com> wrote:

> On Tue, Sep 04, 2012 at 05:25:26PM -0400, Bithika Khargharia wrote:
> > If the OFPFF_CHECK_OVERLAP flag is not set and a Controller (erroneously)
> > sends an Openflow rule that has *both* identical match conditions &
> > identical actions to that of an existing rule how would OVS handle this?
> > Would the new rule still overwrite the old rule or is there an
> inexpensive
> > way of determining this case, rejecting the new rule and notifying an
> error
> > to the Controller?
>
> If the new and old rule have the same priority, the new rule
> overwrites the old rule.
>
> If the new and old rule have different priorities, there is no
> conflict: the new rule will be added to the flow table, the old rule
> will still be in the flow table.
>
> OpenFlow doesn't provide an option for other behavior.
>
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