[pox-dev] POX - TCP redirection flows

[chenli]

Dear Murphy,


Thanks again for your kindly clarifying.

But sometimes I got error message when I delete flows from controller using
the OFPFC_DELETE in ofp_flow_mod object like below:

Exception while handling Connection!PacketIn...

Traceback (most recent call last):
  File "/pox/pox/lib/revent/revent.py", line 233, in raiseEventNoErrors
    return self.raiseEvent(event, *args, **kw)
  File "/pox/pox/lib/revent/revent.py", line 280, in raiseEvent
    rv = event._invoke(handler, *args, **kw)
  File "/pox/pox/lib/revent/revent.py", line 158, in _invoke
    return handler(self, *args, **kw)
  File "/pox/pox/forwarding/test_wayne2.py", line 97, in _handle_PacketIn
    packet = event.parse()
  File "/pox/pox/openflow/__init__.py", line 162, in parse
    self._parsed = ethernet(self.data)
  File "/pox/pox/lib/packet/ethernet.py", line 102, in __init__
    self.parse(raw)
  File "/pox/pox/lib/packet/ethernet.py", line 124, in parse
    self.next = ethernet.type_parsers[self.type](raw[ethernet.MIN_LEN:],
self)
  File "/pox/pox/lib/packet/ipv4.py", line 96, in __init__
    self.parse(raw)
  File "/pox/pox/lib/packet/ipv4.py", line 153, in parse
    self.next = udp(raw=raw[self.hl*4:length], prev=self)
  File "/pox/pox/lib/packet/udp.py", line 70, in __init__
    self.parse(raw)
  File "/pox/pox/lib/packet/udp.py", line 100, in parse
    self.next = dhcp(raw=raw[udp.MIN_LEN:],prev=self)
  File "/pox/pox/lib/packet/dhcp.py", line 135, in __init__
    self.parse(raw)
  File "/pox/pox/lib/packet/dhcp.py", line 205, in parse
    self.parseOptions()
  File "/pox/pox/lib/packet/dhcp.py", line 215, in parseOptions
    (opt_val[0],))
TypeError: %u format: a number is required, not str

Did this error caused by the interlaced time between packet come to
controller and delete flows from controller?

Thanks again and sorry for bothering you to clarify my questions.


2013/5/18 Murphy McCauley <murphy.mccauley at gmail.com>

> On May 18, 2013, at 4:16 AM, chenli wrote:
> > But I want to ask why during the connection between OpenFlow switch and
> POX controller, POX command line usually dump some information like below:
> >
> > [packet                 ] (dhcp parse) warning DHCP packet data too
> short to parse header: data len 86
> >
> > Is this invoke by the arp broadcast or the other problems?
>
> I've added this to the POX manual FAQ under the heading "What are these
> log messages from the packet subsystem?":
> https://openflow.stanford.edu/display/ONL/POX+Wiki
>
> Generally this is caused by a packet being sent to the controller due to a
> table miss.  Switches usually default to not sending the entire packet --
> they only send the first part (often the first 128 bytes).  This is enough
> to see the MAC addresses, ethertype, VLAN, IP header, etc.  But it's often
> NOT enough to, for example, hold an entire DHCP message.
>
> Thus, when a DHCP message gets sent to the controller, if POX tries to
> parse it, it often finds it can't and issues a message like this.  Unless
> you're actually trying to examine the DHCP message, however, this isn't
> indicative of any problem, which is why the message comes out at INFO level
> and not WARN level (despite the fact that the message itself contains the
> word "warning", which is a holdover from long ago).
>
> I routinely switch the packet subsystem to warning log level (log.level
> --packet=WARN).
>
> -- Murphy
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