[pox-dev] Dealing with buffer ID = -1, i.e. no buffered packet

[Sam Russell]

Sounds good to me. I've just got back from leave so trying to catch up on
work before jumping back into this, but I think that's right - I had to
explain to a colleague that 4294967295 isn't a valid buffer ID - having the
None value will make this much easier. I need to start playing with betta
more - and adding your comments to my projects to make them utilise POX
more appropriately

On Tue, Oct 9, 2012 at 3:09 PM, Murphy McCauley
<murphy.mccauley at gmail.com>wrote:

> Hey, Sam.
>
> l2_learning hasn't been updated for this, but check out l2_pairs in the
> betta branch, which uses the fact that packet_out and flow_mod can now be
> passed a packet_in as "data", and they should both "do the right thing".
>
> I think this addresses your problem.  Feedback?
>
> Also, note that in betta, buffer ID of -1 on the wire comes out as None in
> Python.  I think this is more intuitive, and saying it was "-1" was always
> questionable anyway, since the buffer ID field is unsigned.
>
> -- Murphy
>
> On Oct 8, 2012, at 6:59 PM, Sam Russell wrote:
>
> I've been working with a vendor implementation of OpenFlow that I can't
> give any detail about other than to say that they don't buffer packets
> coming in, and they set the buffer ID field to -1.
>
> The good news is that they seem to follow the spec correctly, ignore the
> miss_send_len field and send the whole packet to the controller, but they
> do seem to rely on packet_in messages to make sure the first packet in a
> flow gets delivered.
>
> I've modified l2_learning.py to handle this, not sure if I'm supposed to
> add attachments here, but the main functions are below. This appears to
> work on the new implementation, and I think it would be a useful addition
> to POX as FloodLight apparently handles this out of the box ;)
>
> Is this a good way to deal with it, or is there a better one (possibly
> already implemented in POX somewhere?)
>
>  def _handle_PacketIn (self, event):
> [..]
>     def flood ():
>       """ Floods the packet """
>       msg = of.ofp_packet_out()
>       if event.ofp.buffer_id == -1:
>         #log.warning("Not flooding unbuffered packet on %s",
>         #            dpidToStr(event.dpid))
>         #return
>
>         # Ideally we'll set a flow to flood AND send to controller
>         #    for multicast packets, but for now we'll just make
>         #    sure that they can get through
>         # If buffer ID == -1 then we have the whole packet
>         msg._set_data(packet)
>
>       if time.time() - self.connection.connect_time > FLOOD_DELAY:
>         # Only flood if we've been connected for a little while...
>         #log.debug("%i: flood %s -> %s", event.dpid, packet.src,
> packet.dst)
>         msg.actions.append(of.ofp_action_output(port = of.OFPP_FLOOD))
>       else:
>         pass
>         #log.info("Holding down flood for %s", dpidToStr(event.dpid))
>       msg.buffer_id = event.ofp.buffer_id
>       msg.in_port = event.port
>       self.connection.send(msg)
> [..]
>         # 6
>         log.debug("installing flow for %s.%i -> %s.%i" %
>                   (packet.src, event.port, packet.dst, port))
>         msg = of.ofp_flow_mod()
>         msg.match = of.ofp_match.from_packet(packet)
>         msg.idle_timeout = 10
>         msg.hard_timeout = 30
>         msg.actions.append(of.ofp_action_output(port = port))
>         msg.buffer_id = event.ofp.buffer_id # 6a
>         self.connection.send(msg)
>
>         if event.ofp.buffer_id == -1:
>           # do a packet send message too since we can't tag this on the
>           #    mod_flow message
>           msg = of.ofp_packet_out()
>           msg._set_data(packet)
>           msg.actions.append(of.ofp_action_output(port = port))
>           msg.buffer_id = event.ofp.buffer_id
>           msg.in_port = event.port
>           self.connection.send(msg)
>
>
>
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