A likely candidate...
send_packet() appears to be victim to a copy/paste error or something. The end
of it is duplicated and it's sending the packet_out message twice. The first
time works. The switch sends the buffered packet referenced by the buffer_id,
and then throws away the buffer. The second time... the switch has thrown away
the buffer, so you get the OFPBRC_BUFFER_EMPTY error.
This is mostly harmless, but fixing it is as simple as removing the duplicate
send.
Examining the OpenFlow traffic with Wireshark, you'll likely see two
packet_outs sent back to back with the same XID, which is suspicious.
-- Murphy
On Sep 16, 2014, at 10:25 AM, Choma Joshua <joshua.ch...@gmail.com> wrote:
>
> Hi
>
> I am using the Ubuntu 12.04.5 LTS, Oracle VM VirtualBox and Virtual Machine
> Image (OVF format, 64-bit, Mininet 2.0).
>
> General
>
> Name: Mininet
> Operating System:Ubuntu (32 bit)
>
> System
> Base Memory: 512 MB
> Boot order: Floppy, CD/DVD, Hard Disk
> Acceleration: PAE/NX
>
> Display
> Video Memory: 12 MB
> Remote Desktop Server: Disabled
> Video Capture: Disabled
>
> I am at the "Open Hub Code and Begin" step and the error i am getting is:
>
> INFO:openflow.of_01:[00-00-00-00-00-01 1] connected
> DEBUG:misc.of_tutorial:Controlling [00-00-00-00-00-01 1]
> ERROR:openflow.of_01:[00-00-00-00-00-01 1] OpenFlow Error:
> [00-00-00-00-00-01 1] Error: header:
> [00-00-00-00-00-01 1] Error: version: 1
> [00-00-00-00-00-01 1] Error: type: 1 (OFPT_ERROR)
> [00-00-00-00-00-01 1] Error: length: 36
> [00-00-00-00-00-01 1] Error: xid: 6
> [00-00-00-00-00-01 1] Error: type: OFPET_BAD_REQUEST (1)
> [00-00-00-00-00-01 1] Error: code: OFPBRC_BUFFER_EMPTY (7)
> [00-00-00-00-00-01 1] Error: datalen: 24
>
>
> I have been using the POX code below:
>
> from pox.core import core
> import pox.openflow.libopenflow_01 as of
> import re
>
> log = core.getLogger()
>
>
>
> class Tutorial (object):
> """
> A Tutorial object is created for each switch that connects.
> A Connection object for that switch is passed to the __init__ function.
> """
> def __init__ (self, connection):
> # Keep track of the connection to the switch so that we can
> # send it messages!
> self.connection = connection
>
> # This binds our PacketIn event listener
> connection.addListeners(self)
>
> # Use this table to keep track of which ethernet address is on
> # which switch port (keys are MACs, values are ports).
> self.mac_to_port = {}
> self.matrix={} # this will keep track of the traffic matrix.
> # matrix[i][j]=number of times a packet from i went to j
>
> def send_packet (self,buffer_id, raw_data, out_port, in_port):
> """
> Sends a packet out of the specified switch port.
> If buffer_id is a valid buffer on the switch, use that. Otherwise , send
> the raw data in a raw data.
> The "in_port" is the port number that the packet arrived on. Use
> OFPP_NONE if you are generating this packet
> """
> msg = of.ofp_packet_out()
> msg.in_port = in_port
> if buffer_id != -1 and buffer_id is not None:
> # We got a buffer ID from the switch, use that
> msg.buffer_id = buffer_id
> else:
> # No buffer ID from switch -- we got the raw data
> if raw_data is None:
> # No raw_data specified -- nothing to send!
> return
> msg.data = raw_data
> action = of.ofp_action_output(port = out_port)
> msg.actions.append(action)
>
> # Send message to switch
> self.connection.send(msg)
>
>
>
> # Send message to switch
> self.connection.send(msg)
>
>
> def act_like_hub (self, packet, packet_in):
> """
> Implement hub-like behavior -- send all packets to all ports besides
> the input port.
> """
> #Flood packet on all port
> self.send_packet(packet_in.buffer_id, packet_in.data, of.OFPP_FLOOD,
> packet_in.in_port)
> # Note that if we didn't get a valid buffer_id, a slightly better
> # implementation would check that we got the full data before
> # sending it (len(packet_in.data) should be == packet_in.total_len)).
>
>
> def act_like_switch (self, packet, packet_in):
> """
> Implement switch-like behavior.
> """
>
> """ # DELETE THIS LINE TO START WORKING ON THIS (AND THE ONE BELOW!) #
>
> # Here's some psuedocode to start you off implementing a learning
> # switch. You'll need to rewrite it as real Python code.
>
> # Learn the port for the source MAC
> self.mac_to_port ... <add or update entry>
>
> if the port associated with the destination MAC of the packet is known:
> # Send packet out the associated port
> self.resend_packet(packet_in, ...)
>
> # Once you have the above working, try pushing a flow entry
> # instead of resending the packet (comment out the above and
> # uncomment and complete the below.)
>
>
> log.debug("Installing flow...")
> # Maybe the log statement should have source/destination/port?
>
> #msg = of.ofp_flow_mod()
> #
> ## Set fields to match received packet
> #msg.match = of.ofp_match.from_packet(packet)
> #
> #< Set other fields of flow_mod (timeouts? buffer_id?) >
> #
> #< Add an output action, and send -- similar to resend_packet() >
>
> else:
> # Flood the packet out everything but the input port
> # This part looks familiar, right?
> self.resend_packet(packet_in, of.OFPP_ALL)
>
> """ # DELETE THIS LINE TO START WORKING ON THIS #
> # Learn the port for the source MAC
> self.mac_to_port[packet.src]=packet_in.in_port
> # Add the entry to the traffic matrix
> if self.mac_to_port.get(packet.dst)!=None:
> # Send packet out the associated port
> self.send_packet(packet_in.buffer_id, packet_in.data,
> self.mac_to_port[packet.dst],packet_in.in_port)
> else:
> # Flood the packet out everything but the input port (same as hub)
> self.send_packet(packet_in.buffer_id, packet_in.data, of.OFPP_FLOOD,
> packet_in.in_port)
>
>
> def _handle_PacketIn (self, event):
> """
> Handles packet in messages from the switch.
> ''""
>
> packet = event.parsed # This is the parsed packet data.
> if not packet.parsed:
> log.warning("Ignoring incomplete packet")
> return
>
> packet_in = event.ofp # The actual ofp_packet_in message.
>
> # Comment out the following line and uncomment the one after
> # when starting the exercise.
> self.act_like_hub(packet, packet_in)
> #self.act_like_switch(packet, packet_in)
>
>
>
> def launch ():
> """
> Starts the component
> """
> def start_switch (event):
> log.debug("Controlling %s" % (event.connection,))
> Tutorial(event.connection)
> core.openflow.addListenerByName("ConnectionUp", start_switch)
>
>
>
>
> Please do assist with the error, i am new to mininet.
>
> Regards
> Joshua Choma
> South Africa, University of Witwatersrand
>
>
> _______________________________________________
> openflow-discuss mailing list
> openflow-discuss@lists.stanford.edu
> https://mailman.stanford.edu/mailman/listinfo/openflow-discuss
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