ryu.patch

diff --git a/ryu/app/simple_switch.py b/ryu/app/simple_switch.py
index 33c4f7d0..40cabf9a 100644
--- a/ryu/app/simple_switch.py
+++ b/ryu/app/simple_switch.py
@@ -27,7 +27,9 @@ from ryu.lib.mac import haddr_to_bin
 from ryu.lib.packet import packet
 from ryu.lib.packet import ethernet
 from ryu.lib.packet import ether_types
-
+from datetime import datetime
+import time
+import threading
 
 class SimpleSwitch(app_manager.RyuApp):
     OFP_VERSIONS = [ofproto_v1_0.OFP_VERSION]
@@ -35,6 +37,11 @@ class SimpleSwitch(app_manager.RyuApp):
     def __init__(self, *args, **kwargs):
         super(SimpleSwitch, self).__init__(*args, **kwargs)
         self.mac_to_port = {}
+        self.measurements = []
+        self.lastPacketReceived = self.getCurrentMicroSeconds()
+        thread = threading.Thread(target=self.checkFileWriteNecessary)
+        thread.daemon = True
+        thread.start()
 
     def add_flow(self, datapath, in_port, dst, src, actions):
         ofproto = datapath.ofproto
@@ -50,9 +57,39 @@ class SimpleSwitch(app_manager.RyuApp):
             flags=ofproto.OFPFF_SEND_FLOW_REM, actions=actions)
         datapath.send_msg(mod)
 
+    def writeToFile(self):
+        measurementsToWrite = self.measurements.copy()
+        self.measurements = []
+        f = open("ryu_times.txt", "a+")
+        for measurement in measurementsToWrite:
+            f.write(str(measurement[0]) + (" in " if measurement[1] else " out ") + str(measurement[2]) + "\n")
+        f.flush()
+        f.close()
+
+    def checkFileWriteNecessary(self):
+        time.sleep(3)
+        if self.getCurrentMicroSeconds() - self.lastPacketReceived > 1000000 * 3 and len(self.measurements) > 0:
+            self.writeToFile()
+        
+        thread = threading.Thread(target=self.checkFileWriteNecessary)
+        thread.daemon = True
+        thread.start()
+    
+    def getCurrentMicroSeconds(self):
+        return int(datetime.timestamp(datetime.now()) * 1000000)
+
+
+    @set_ev_cls(ofp_event.EventOFPEchoRequest, MAIN_DISPATCHER)
+    def _ech_request_handler(self, ev):
+        msg = ev.msg
+        self.measurements.append([msg.xid, True, self.getCurrentMicroSeconds()])
+        self.measurements.append([msg.xid, False, self.getCurrentMicroSeconds()])
+
     @set_ev_cls(ofp_event.EventOFPPacketIn, MAIN_DISPATCHER)
     def _packet_in_handler(self, ev):
+        self.lastPacketReceived = self.getCurrentMicroSeconds()
         msg = ev.msg
+        self.measurements.append([msg.xid, True, self.lastPacketReceived])
         datapath = msg.datapath
         ofproto = datapath.ofproto
 
@@ -81,8 +118,8 @@ class SimpleSwitch(app_manager.RyuApp):
         actions = [datapath.ofproto_parser.OFPActionOutput(out_port)]
 
         # install a flow to avoid packet_in next time
-        if out_port != ofproto.OFPP_FLOOD:
-            self.add_flow(datapath, msg.in_port, dst, src, actions)
+        #if out_port != ofproto.OFPP_FLOOD:
+        #    self.add_flow(datapath, msg.in_port, dst, src, actions)
 
         data = None
         if msg.buffer_id == ofproto.OFP_NO_BUFFER:
@@ -91,6 +128,10 @@ class SimpleSwitch(app_manager.RyuApp):
         out = datapath.ofproto_parser.OFPPacketOut(
             datapath=datapath, buffer_id=msg.buffer_id, in_port=msg.in_port,
             actions=actions, data=data)
+        out.set_xid(msg.xid)
+        self.logger.info("%s %s", out.xid, msg.xid)
+        
+        self.measurements.append([msg.xid, False, self.getCurrentMicroSeconds()])
         datapath.send_msg(out)
 
     @set_ev_cls(ofp_event.EventOFPPortStatus, MAIN_DISPATCHER)