From 5dac2f97025b61af3bfa33f3c167851d4969171b Mon Sep 17 00:00:00 2001
From: structix <structix@noreply.schoffit.net>
Date: Thu, 19 May 2022 13:16:49 +0000
Subject: [PATCH] Fix first ping package packet loss

---
 example.py | 37 +++++++++++++++++++++++--------------
 1 file changed, 23 insertions(+), 14 deletions(-)

diff --git a/example.py b/example.py
index 50a7479..ba86ebb 100644
--- a/example.py
+++ b/example.py
@@ -200,8 +200,6 @@ class L3Switch(app_manager.RyuApp):
         # 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)
-            self.logger.info(actions)
-            self.logger.info(match)
             # 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:
@@ -222,27 +220,37 @@ class L3Switch(app_manager.RyuApp):
         parser = datapath.ofproto_parser
 
         if ipv4_pkt.dst in self.ip_to_mac[dpid]:
+            # GEt mac and port of the given destination
             dstMac = self.ip_to_mac[dpid][ipv4_pkt.dst]
+            out_port = self.mac_to_port[dpid][dstMac]
         else:
-            self.send_arp(datapath, 1, self.MAC_ADDR, ipv4_pkt.src, "FF:FF:FF:FF:FF:FF", ipv4_pkt.dst, ofproto.OFPP_FLOOD)
-            return
+            # Send an arp request and define mac and port
+            # so we're able to apply the following actions
+            # on the packet.
+            out_port = ofproto.OFPP_FLOOD
+            dstMac = "FF:FF:FF:FF:FF:FF"
+            self.send_arp(datapath, 1, self.MAC_ADDR, ipv4_pkt.src, dstMac, ipv4_pkt.dst, out_port)
 
-        out_port = self.mac_to_port[dpid][dstMac]
+        # Actions are applied in the same order as defined in the list.
+        # OFPActionOutput terminates the chain. So this call should be the last action.
         actions = [parser.OFPActionDecNwTtl(), #decrease TTL count
             parser.OFPActionSetField(eth_src=self.MAC_ADDR), # set own mac as source
             parser.OFPActionSetField(eth_dst=dstMac), # set dst from arp request
             parser.OFPActionOutput(out_port)] # forward packet through out_port
 
-        # install a flow to avoid packet_in next time
-        match = parser.OFPMatch(in_port=in_port, ipv4_dst=ipv4_pkt.dst, eth_type=0x0800) #onlz match ipv4 packets
+        # Only install a flow if we#re in the first case (specific mac and out_port)
+        if ipv4_pkt.dst in self.ip_to_mac[dpid]:
+            # install a flow to avoid packet_in next time
+            match = parser.OFPMatch(in_port=in_port, ipv4_dst=ipv4_pkt.dst, eth_type=0x0800) #onlz match ipv4 packets
+
+            # 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)
 
-        # 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)
         data = None
         if buffer_id == ofproto.OFP_NO_BUFFER:
             data = packet.data
@@ -301,6 +309,7 @@ class L3Switch(app_manager.RyuApp):
                 if icmp_pkt:
                     self.do_icmp(datapath, in_port, eth, ipv4_pkt, icmp_pkt)
             else:
+                # forward the package into a different subnet
                 self.do_l3_switch(datapath, dpid, pkt, eth, ipv4_pkt, in_port, msg.buffer_id)