Add comments and cleanup

Uebung1/controller_1_4.py

@@ -1,3 +1,6 @@
+# Abgabe von:
+# Jutta Seth, Janek Schoffit, Eva Högner
+# Problem 1.4 (Packet-based IP Anycast)
 from ryu.base import app_manager
 from ryu.controller import ofp_event
 from ryu.controller.handler import CONFIG_DISPATCHER, MAIN_DISPATCHER
@@ -23,8 +26,10 @@ class L3Switch(app_manager.RyuApp):
         self.mac_to_port = {}
         self.port_to_mac = {}
         self.ip_to_mac = {}
+
+        # Define the ports for anycast round robin
         self.anycastPorts = [1, 3, 4]
-        self.anycastIndex = 0
+        self.anycastIndex = 0 # round robin index for the ports array
 
     @set_ev_cls(ofp_event.EventOFPSwitchFeatures, CONFIG_DISPATCHER)
     def switch_features_handler(self, ev):
@@ -190,18 +195,10 @@ class L3Switch(app_manager.RyuApp):
         else:
             out_port = ofproto.OFPP_FLOOD
 
-        actions = [parser.OFPActionOutput(out_port)]
+        # add_flow removed, otherwise the controller wouldn't receive new packets
+        # for the anycast switching.
 
-        # install a flow to avoid packet_in next time
-        if out_port != ofproto.OFPP_FLOOD:
-            match = parser.OFPMatch(in_port=in_port, eth_dst=frame.dst)
-            # verify if we have a valid buffer_id, if yes avoid to send both
-            # flow_mod & packet_out
-            #if buffer_id != ofproto.OFP_NO_BUFFER:
-            #    self.add_flow(datapath, 1, match, actions, buffer_id)
-            #    return
-            #else:
-            #    self.add_flow(datapath, 1, match, actions)
+        actions = [parser.OFPActionOutput(out_port)]
         data = None
         if buffer_id == ofproto.OFP_NO_BUFFER:
             data = packet.data
@@ -210,6 +207,7 @@ class L3Switch(app_manager.RyuApp):
                                   in_port=in_port, actions=actions, data=data)
         datapath.send_msg(out)
 
+    # Get the next port where a package should be forwarded
     def anycast_next(self):
         if self.anycastIndex >= 2:
             self.anycastIndex = 0
@@ -221,8 +219,10 @@ class L3Switch(app_manager.RyuApp):
         ofproto = datapath.ofproto
         parser = datapath.ofproto_parser
 
+        # Select a port
         port = self.anycast_next()
 
+        # Send the package without adding a flow
         packet.get_protocols(ethernet.ethernet)[0].dst = self.port_to_mac[dpid][str(port)]
         self.send_packet(datapath, port, packet)
 
@@ -273,6 +273,7 @@ class L3Switch(app_manager.RyuApp):
                 icmp_pkt = pkt.get_protocol(icmp.icmp)
                 if icmp_pkt:
                     self.do_icmp(datapath, in_port, eth, ipv4_pkt, icmp_pkt)
+            # Do anycast if the package contains the anycast dst-IP
             if ipv4_pkt.dst == "10.0.0.100":
                 self.do_anycast(datapath, dpid, pkt, eth, in_port, msg.buffer_id)
                 return