Adding IPv4 rate tracer
diff --git a/helper/tracers/ipv4-l3-tracer.h b/helper/tracers/ipv4-l3-tracer.h
new file mode 100644
index 0000000..e5f3c74
--- /dev/null
+++ b/helper/tracers/ipv4-l3-tracer.h
@@ -0,0 +1,90 @@
+/* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil -*- */
+/*
+ * Copyright (c) 2011 UCLA
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation;
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
+ *
+ * Author:  Alexander Afanasyev <alexander.afanasyev@ucla.edu>
+ */
+
+#ifndef IPV4_L3_TRACER_H
+#define IPV4_L3_TRACER_H
+
+#include "ns3/ptr.h"
+#include "ns3/simple-ref-count.h"
+#include "ns3/ipv4-l3-protocol.h"
+
+namespace ns3 {
+
+class Node;
+
+class Ipv4L3Tracer : public SimpleRefCount<Ipv4L3Tracer>
+{
+public:
+  Ipv4L3Tracer (Ptr<Node> node);
+  virtual ~Ipv4L3Tracer () { };
+
+  void
+  Connect ();
+  
+  virtual void
+  PrintHeader (std::ostream &os) const = 0;
+
+  virtual void
+  Print (std::ostream &os) const = 0;
+  
+  virtual void
+  Rx  (std::string context,
+       Ptr<const Packet>, Ptr<Ipv4>,  uint32_t) = 0;
+
+  virtual void
+  Tx   (std::string context,
+        Ptr<const Packet>, Ptr<Ipv4>,  uint32_t) = 0;
+
+  virtual void
+  Drop (std::string context,
+        const Ipv4Header &, Ptr<const Packet>, Ipv4L3Protocol::DropReason, Ptr<Ipv4>, uint32_t) = 0;
+
+protected:
+  std::string m_node;
+  Ptr<Node> m_nodePtr;
+
+  struct Stats
+  {
+    void Reset ()
+    {
+      m_in = 0;
+      m_out = 0;
+      m_drop = 0;
+    }
+    
+    uint64_t m_in;
+    uint64_t m_out;
+    uint64_t m_drop;
+  };
+};
+
+inline std::ostream&
+operator << (std::ostream &os, const Ipv4L3Tracer &tracer)
+{
+  os << "# ";
+  tracer.PrintHeader (os);
+  os << "\n";
+  tracer.Print (os);
+  return os;
+}
+
+} // namespace ns3
+
+#endif // IPV4_L3_TRACER_H