I'm not sure what you're trying to do, so it's hard for me to give too much
advice.
Why is leaving the ARP flows installed a problem?
Maybe it would make sense to not install flows for the ARP packets, and instead
to simply output them using send_openflow() (that is, forward them from inside
NOX instead of on the switch)? You pay for this in terms of ARP latency,
controller<->switch traffic, and computation on the controller, of course,
though maybe not enough to make much difference to you.
-- Murphy
On Nov 28, 2010, at 4:22 PM, K Singh wrote:
> Hi,
>
> I modified the code below for function def forward_l2_packet(...) in
> pyswitch.py.
>
> def forward_l2_packet(dpid, inport, packet, buf, bufid):
>
> dstaddr = packet.dst.tostring()
> if not ord(dstaddr[0]) & 1 and inst.st[dpid].has_key(dstaddr):
> prt = inst.st[dpid][dstaddr]
> if prt[0] == inport:
> log.err('**warning** learned port = inport', system="pyswitch")
> inst.send_openflow(dpid, bufid, buf, openflow.OFPP_FLOOD, inport)
> else:
> # We know the outport, set up a flow
> log.msg('installing flow for ' + str(packet), system="pyswitch")
> flow = extract_flow(packet)
> flow[core.IN_PORT] = inport
> actions = [[openflow.OFPAT_OUTPUT, [0, prt[0]]]]
> # openflow.OFP_FLOW_PERMANENT
> renewflag = flowpacketdecision(dpid, flow, packet, inport, buf)
> print "renewflag",renewflag
> #print packet
> if renewflag == 1:
> inst.install_datapath_flow(dpid, flow, CACHE_TIMEOUT,5,
> actions,bufid, openflow.OFP_DEFAULT_PRIORITY,inport, buf)
>
> else:
> # haven't learned destination MAC. Flood
> inst.send_openflow(dpid, bufid, buf, openflow.OFPP_FLOOD, inport)
>
>
> The red highlighted part is where i made changes. I am making decision on
> setting flow based on port numbers whose logic is in flowpacketdecision(...).
> If the function returns 1 i renew or set the flow else i reject the packet
> and wait for another packet to come.
>
> But this logic, fails for ARP packet. Because in my flowpacketdecision(..) i
> am checking for TCP/UDP packet and renewing/setting the flow. If i receive
> ARP packet then in the current code it is not renewing/setting the flow. This
> means i cant proceed with TCP/UDP code anyways connection timeout when tested
> in iperf.
>
> If i check for ARP packets and set the reneweflag = 1 then anyways the flow
> is getting set irrespective of my logic. I even tried commenting the
> timer_callback function which removes the MAC entries so that ARP message are
> not sent again after initially learning about MAC addresses. It didnt work.
> Is there anyway I can block the ARP messages once transmitted and then only
> have TCP/UDP messages flowing in the network.
>
> --
> Regards,
> Kavitesh Singh.
>
> _______________________________________________
> nox-dev mailing list
> nox-dev@noxrepo.org
> http://noxrepo.org/mailman/listinfo/nox-dev_noxrepo.org
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