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

[Murphy McCauley]

Another note is that I've updated l2_learning and I think it should now just work for you.

-- Murphy

On Oct 8, 2012, at 7:11 PM, Sam Russell wrote:

> 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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