Specifically in order to avoid creating loops, an output action will generally not go back out of the incoming port. If you do really want to do this, you must add an output action that outputs to the OFPP_IN_PORT virtual port. If you check the spec, it describes OFPP_IN_PORT as "Send the packet out the input port. This virtual port must be explicitly used in order to send back out of the input port."
-- Murphy On Mar 30, 2012, at 5:09 PM, Vishal wrote: > Hi, > > I have 2 openvswitches: OVS1 and OVS2 > > OVS1, port 3 is connected to OVS2's port 3 > > so, I set up a rule, saying traffic_matching_some_condition, when received on > port 3 send it back to port 3 (for both the switches, in pyswitch, handle > packet in). > > The above should in theory, cause a packet to ping pong between the two > interfaces until the hard time out. --> essentially, it's forcibly creating a > loop. > > > I achieve this by setting -> out_port = 3 (instead of prt[0] for the matching > flow) in pyswitch. > actions = [[openflow.OFPAT_OUTPUT, [0, out_port]]] > inst.install_datapath_flow(dpid, flow, CACHE_TIMEOUT, > openflow.OFP_FLOW_PERMANENT, > actions, bufid, > openflow.OFP_DEFAULT_PRIORITY, inport, buf) > > > When I look at Flow Mod for this flow, it correctly sets the port to 3. > > The problem is that the actual packet is not being sent by the switch back > to the port on which it was received. > > On wireshark, I see that number of packets on each switch is same as number > of packets generated by one client host connected to one of the switches. > > Is there a mechanism to prevent such looping in the openv switch or am i > doing something wrong ? > > Regards, > Vishal
