[ovs-dev] [PATCH v1] ofproto: Fix OVS crash when packets hit Openflow rules with certain combinations of nested actions

[Ben Pfaff]

On Thu, Sep 05, 2019 at 11:12:26PM +0530, Anil Kumar Koli wrote:
> > * We can't get rid of ofproto_mutex in do_bundle_commit(), or drop it
> >   temporarily around flow translation (i.e. the call to
> >   ofproto_packet_out_start()), because it might need to revert all the
> >   flow table changes and dropping the mutex would allow other threads to
> >   race in and make conflicting changes
> 
> But it seems that the issue happens on ofproto_packet_out_finish() and not on
> ofproto_packet_out_start(). So, the flow translation should be OK under the
> ofproto_mutex and revert is still possible under the mutex.
> The only thing we need to take out of the mutex is real action execution by
> the datapath triggered by ofproto_packet_out_finish(). Callers never check the
> status of this function so it should be not so hard.
> 
> So, possible solution:
> * Move ofproto_packet_out_finish() out of ofproto_mutex in all the callers:
>   * It's easy for handle_packet_out()
>   * For do_bundle_commit() we could temporary store all the ofproto_packet_out
>     entities and finish them later.
> 
> Am I missing something?  Is there reason for ofproto_packet_out_finish() to
> require ofproto_mutex?
> 
> Ben, Anil, what do you think?
> 
> Best regards, Ilya Maximets.

This does seem like a reasonable solution.  Do you want to take a shot
at implementing it?  I promise to review a patch much more quickly than
I responded to the thread :-(