[pox-dev] Create TCP packet

[Silvia Fichera]

You are right! I want to pretend that a connection is open.
I've done this:

def send_tcp(seqNum, srcMAC, dstMAC,srcIP,dstIP,srcPort,dstPort,inport):
   tcp_packet = tcp()
   tcp_packet.srcport = dstPort
   tcp_packet.dstport = srcPort
   tcp_packet.len = tcp.MIN_LEN+20
   tcp_packet.win=1
   tcp_packet._setflag(tcp_packet.SYN_flag,1)
   tcp_packet._setflag(tcp_packet.ACK_flag,1)
   tcp_packet.seq=0
   tcp_packet.ack=1
   ipv4_packet = ipv4()
   ipv4_packet.iplen = ipv4.MIN_LEN + tcp_packet.len
   ipv4_packet.protocol = ipv4.TCP_PROTOCOL
   ipv4_packet.dstip = IPAddr(dstIP)
   ipv4_packet.srcip = IPAddr(srcIP)
   ipv4_packet.set_payload(tcp_packet)
   eth_packet = ethernet()
   eth_packet.set_payload(ipv4_packet)
   eth_packet.src = srcMAC #MAC Controller
   eth_packet.dst = dstMAC
   eth_packet.type = ethernet.IP_TYPE
   msg = of.ofp_packet_out(data = eth_packet)
   msg.actions.append(of.ofp_action_output(port = inport))
   for connection in core.openflow.connections:
       connection.send(msg)

Here the controller aswers to a SYN packet with a SYN/ACK packet via
packet_out.  But I still have a problem...
I've done a wireshark capture and in the information about this packet it
tells me:

  Packet Out (CSM) (78B) => 45506 > 5001 [SYN, ACK] Seq=0 Ack=0 Win=1,
bogus TCP header length (0, must be at least 20)

wich fields I'm forgetting to set? And why, if I setted ack=1 it is 0?




2013/11/25 Murphy McCauley <murphy.mccauley at gmail.com>

> The .win attribute of the TCP class should be an integer, and it's just
> put into the 16-bit window field verbatim.  IIRC, in the absence of window
> scaling, this is just the number of bytes (beyond whatever is being ACKed)
> that you're willing to receive.  (If you're just trying to get a client to
> think a connection is open, I think you can probably just set it to 1 -- 0
> may not be a good idea.)
>
> I'd check the RFC or a good TCP reference for additional information.  Or
> just try it. :)
>
> -- Murphy
>
> On Nov 25, 2013, at 12:38 AM, Silvia Fichera <fichera.sil at gmail.com>
> wrote:
>
> > Hi all,
> > I would like send a TCP - SYN/ACK packet from the controller to one host.
> > I already know how to buid UDP packet and send it in flooding, so I
> think I can follow the same way with TCP fields.
> > I need to set a minimal congestion window as I can receive only the ACK.
> Is it measured in bit? How much should be the right dimension?
> >
> > Thanks
> >
> > --
> > Silvia Fichera
>
>


-- 
Silvia Fichera
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.noxrepo.org/pipermail/pox-dev-noxrepo.org/attachments/20131126/9c357eab/attachment-0002.htm>