[pox-dev] send packet from controller

Mon Jul 22 02:14:12 PDT 2013

If you mean the field eth_packet.dst yes, I've set it as 00:00:00:00:00:01
the mac address of the host h1.

2013/7/22 Murphy McCauley <murphy.mccauley at gmail.com>

> Are you setting the ethernet destination address correctly?
>
> On Jul 21, 2013, at 3:23 PM, Silvia Fichera wrote:
>
> Dear Murphy,
> I am still experiencing problems to send packets from controller to host.
> I tried to send UDP packet via packet_out and they are correctly sent and
> received from the host (I can see using tcpdump from receiving host) but if
> I try to open a socket with python to read the data, I receive nothing in
> the socket even if tcpdump keeps seeing the packets.
>
> Then I tried to communicate from host to host (opening two xterm from
> mininet). If I use netcat listening for data communication is perfect. If I
> try to receive data with python sockets I receive the following tcpdump
> output (python or netcat send, tcpdump and python listen):
>
> IP 10.0.0.2.12345 > 10.0.0.1.12345: UDP, length 14
> IP 10.0.0.1 > 10.0.0.2: ICMP 10.0.0.1 udp port 12345 unreachable, length
> 50
>
> I can see the process listening to the port by lsof -i :12345
> If I put netcat listening to the port, the packet arrives correctly.
> I also tried to change the ports but same result.
>
> Is it maybe a problem of the low-level python socket binding? I am using
> simply
> s= socket.socket(socket.AF_INET, soket.SOCK_DGRAM)
> s.bind((host,port))
> data, addr = sock.recv(10)
>
> Eventually, I tried in both my ubuntu+mininet installation and in the
> virtual machine of mininet (mininet 2.0 with ubuntu 12.10 64 bit) without
> success.
>
> Thanks for support
>
> regards
>
>
>
>
> 2013/7/21 Murphy McCauley <murphy.mccauley at gmail.com>
>
>> If you have any switches, then you'll have received a ConnectionUp event
>> when they connect.  You can save a reference to the Connection object into
>> your own variable at this point.  Lots of the example components do this
>> (e.g., l2_learning more or less does it).
>>
>> You can also get the connections later from the OpenFlow nexus, e.g.,
>> using the core.openflow.connections collection which holds a Connection for
>> each connected switch (you can either enumerate it, or you can get
>> connections by their DPID).  There's also the related
>> core.openflow.sendToDPID(dpid, data) method if you know the DPID you want
>> to send to.
>>
>> -- Murphy
>>
>> On Jul 20, 2013, at 3:57 PM, Silvia Fichera wrote:
>>
>> Thanks for the summary.
>> I was planning to use the packet_out but I am missing the connection
>> object (I saw this is usually taken from an event). Can I create a
>> connection object (to link controller and a switch) starting the
>> communication from the controller?
>>
>>
>> 2013/7/20 Murphy McCauley <murphy.mccauley at gmail.com>
>>
>>> Let me try restating.
>>>
>>> Imagine you have a hardware switch.  It has some ports which connect it
>>> to other switches and hosts and stuff -- it makes a network (call this the
>>> "data network" for lack of a better term).
>>>
>>> So if it's an OpenFlow switch, where is the controller in this picture?
>>>
>>> One type configuration, the controller can be anywhere on the data
>>> network.  It communicates with the switch over IP, so why not?  You have
>>> OpenFlow mixed with normal traffic all over your network.  (This is often
>>> called "in band control")
>>>
>>> In another type of configuration (out of band control), you set aside
>>> one port on each switch as "special", and use this port to connect to the
>>> controller.  The special port is *not* a part of the data network.  You
>>> might say it's part of a control or management network.  No normal
>>> forwarding ever takes place over this port -- *only* OpenFlow.
>>>
>>>
>>> If your setup looks like the first configuration, a controller can
>>> easily send arbitrary traffic over the data network using plain old socket
>>> programming.  But if your configuration is similar to the second option,
>>> there's no direct way for the controller to send to or receive from the
>>> data network.  The only way it can do it is over OpenFlow -- by instructing
>>> one of the switches to send data (via a packet out) and having the switch
>>> send data to the controller (via packet in).
>>>
>>> Of course, even in the second configuration, you could run a cable
>>> between a second interface on the controller and a normal port on the
>>> switch.  That way you have two cables between switch and controller -- one
>>> on the management network and one on the data network.
>>>
>>>
>>> Hope that helps.
>>>
>>> -- Murphy
>>>
>>> On Jul 20, 2013, at 8:49 AM, Silvia Fichera wrote:
>>>
>>> >  In which case, there's no way to send except via a datapath or a
>>> host which actually is.
>>> Can you clarify this sentence?
>>>
>>> Am I following the right way to send packets from the controller to
>>> hosts through switches, so using my network, or do I miss something?
>>>
>>>
>>> 2013/7/20 Murphy McCauley <murphy.mccauley at gmail.com>
>>>
>>>> If I'm understanding correctly, the problem is that the controller
>>>> isn't necessarily *on* the data network.  In Mininet, for example, it is
>>>> often the case that the controller and the datapaths are linked essentially
>>>> by a separate management network, and this is not an unusual case in the
>>>> real world either.  In which case, there's no way to send except via a
>>>> datapath or a host which actually is.
>>>>
>>>> Hope that helps.
>>>>
>>>> -- Murphy
>>>>
>>>> On Jul 19, 2013, at 3:39 PM, Silvia Fichera wrote:
>>>>
>>>> Hello,
>>>> I am having trouble sending packets from l3_learning controller to host.
>>>> I would like to send UDP packets but if I try to use normal socket from
>>>> controller I see no traffic (I minotired it with wireshark on all switches)
>>>> unless I send to itself (127.0.0.1).  I was also trying to make a switch
>>>> sending the controller generated packet in this way:
>>>>
>>>> http://lists.noxrepo.org/pipermail/pox-dev-noxrepo.org/2012-October/000281.html
>>>>
>>>> Although I have no traffic too.
>>>> I guess the problem is that I am missing something like
>>>>
>>>>  self.connection.send(msg)
>>>>
>>>> but I don't have any datapath connection with any switch since I want
>>>> to start the communication from the controller.
>>>> Is there an easier way to send these udp packets?
>>>>
>>>> thanks
>>>>
>>>> --
>>>> Silvia Fichera
>>>>
>>>>
>>>>
>>>
>>>
>>> --
>>> Silvia Fichera
>>>
>>>
>>>
>>
>>
>> --
>> Silvia Fichera
>>
>>
>>
>
>
> --
> Silvia Fichera
>
>
>

-- 
Silvia Fichera
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.noxrepo.org/pipermail/pox-dev-noxrepo.org/attachments/20130722/d9cebee9/attachment-0002.htm>