On Fri, Sep 30, 2011 at 09:25:00AM -0700, Ben Pfaff wrote:
> Ideally, in-band control would be able to do this by setting up a
> flow.  What if we abandoned the idea of looking into the L7 packet
> contents and instead set up two flows:
> 
>       * One that matches UDP from port 67 to port 68 directed to the
>           local port's MAC.  This should catch unicast DHCP replies,
>           which is the ordinary case.
> 
>       * One that matches UDP from port 67 to port 68 directed to
>           Ethernet broadcast.  This catches broadcast DHCP replies,
>           which are odd cases like DHCP clients that set the
>           "BROADCAST" bit in the request, DHCP servers that always
>           broadcast DHCP replies (which is allowed by the RFCs), and
>           some DHCP relay cases.
> 
> The only problem is that the latter is overbroad.  We could drop the
> latter rule.  It probably wouldn't cause problems very often, but when
> they did happen they'd be difficult to debug.

Another idea: move the in-band rules to an extra table (as we've
discussed before) and then in the latter case output to OFPP_LOCAL and
resubmit to table 0.  Then you could potentially get duplicates sent
to the local port but that's probably not a big deal.
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