apps+model+utils: Implementing Interest/Data hop counting using new PacketTag
diff --git a/model/fw/ndn-forwarding-strategy.cc b/model/fw/ndn-forwarding-strategy.cc
index 4bab0a1..0e773f9 100644
--- a/model/fw/ndn-forwarding-strategy.cc
+++ b/model/fw/ndn-forwarding-strategy.cc
@@ -37,6 +37,8 @@
 #include "ns3/boolean.h"
 #include "ns3/string.h"
 
+#include "ns3/ndnSIM/utils/ndn-fw-hop-count-tag.h"
+
 #include <boost/ref.hpp>
 #include <boost/foreach.hpp>
 #include <boost/lambda/lambda.hpp>
@@ -171,7 +173,13 @@
   boost::tie (contentObject, contentObjectHeader, payload) = m_contentStore->Lookup (header);
   if (contentObject != 0)
     {
-      NS_ASSERT (contentObjectHeader != 0);      
+      NS_ASSERT (contentObjectHeader != 0);
+
+      FwHopCountTag hopCountTag;
+      if (origPacket->PeekPacketTag (hopCountTag))
+        {
+          contentObject->AddPacketTag (hopCountTag);
+        }
 
       pitEntry->AddIncoming (inFace/*, Seconds (1.0)*/);
 
@@ -223,8 +231,20 @@
     }
   else
     {
-      // Add or update entry in the content store
-      m_contentStore->Add (header, payload);
+      FwHopCountTag hopCountTag;
+      if (payload->PeekPacketTag (hopCountTag))
+        {
+          Ptr<Packet> payloadCopy = payload->Copy ();
+          payloadCopy->RemovePacketTag (hopCountTag);
+          
+          // Add or update entry in the content store
+          m_contentStore->Add (header, payloadCopy);
+        }
+      else
+        {
+          // Add or update entry in the content store
+          m_contentStore->Add (header, payload); // no need for extra copy
+        }
     }
 
   while (pitEntry != 0)
diff --git a/model/ndn-face.cc b/model/ndn-face.cc
index f91fc19..4ae7ee9 100644
--- a/model/ndn-face.cc
+++ b/model/ndn-face.cc
@@ -32,7 +32,7 @@
 #include "ns3/random-variable.h"
 #include "ns3/pointer.h"
 
-// #include "ns3/weights-path-stretch-tag.h"
+#include "ns3/ndnSIM/utils/ndn-fw-hop-count-tag.h"
 
 #include <boost/ref.hpp>
 
@@ -55,11 +55,6 @@
                    MakeUintegerAccessor (&Face::m_id),
                    MakeUintegerChecker<uint32_t> ())
 
-    // .AddAttribute ("MetricTagging", "Enable metric tagging (path-stretch calculation)",
-    //                BooleanValue (false),
-    //                MakeBooleanAccessor (&Face::m_enableMetricTagging),
-    //                MakeBooleanChecker ())
-
     .AddTraceSource ("NdnTx", "Transmitted packet trace",
                      MakeTraceSourceAccessor (&Face::m_txTrace))
     .AddTraceSource ("NdnRx", "Received packet trace",
@@ -81,7 +76,6 @@
   , m_ifup (false)
   , m_id ((uint32_t)-1)
   , m_metric (0)
-  // , m_enableMetricTagging (false)
 {
   NS_LOG_FUNCTION (this);
 
@@ -128,23 +122,13 @@
       return false;
     }
 
-  // if (m_enableMetricTagging)
-  //   {
-  //     // update path information
-  //     Ptr<const WeightsPathStretchTag> origTag = packet->RemovePacketTag<WeightsPathStretchTag> ();
-  //     Ptr<WeightsPathStretchTag> tag;
-  //     if (origTag == 0)
-  //       {
-  //         tag = CreateObject<WeightsPathStretchTag> (); // create a new tag
-  //       }
-  //     else
-  //       {
-  //         tag = CreateObject<WeightsPathStretchTag> (*origTag); // will update existing tag
-  //       }
-
-  //     tag->AddPathInfo (m_node, GetMetric ());
-  //     packet->AddPacketTag (tag);
-  //   }
+  FwHopCountTag hopCount;
+  bool tagExists = packet->RemovePacketTag (hopCount);
+  if (tagExists)
+    {
+      hopCount.Increment ();
+      packet->AddPacketTag (hopCount);
+    }
 
   bool ok = SendImpl (packet);
   if (ok)
diff --git a/model/ndn-face.h b/model/ndn-face.h
index acb1c90..f5aba0f 100644
--- a/model/ndn-face.h
+++ b/model/ndn-face.h
@@ -215,8 +215,6 @@
   uint32_t m_id; ///< \brief id of the interface in Ndn stack (per-node uniqueness)
   uint32_t m_metric; ///< \brief metric of the face
 
-  // bool m_enableMetricTagging;
-
   TracedCallback<Ptr<const Packet> > m_txTrace;
   TracedCallback<Ptr<const Packet> > m_rxTrace;
   TracedCallback<Ptr<const Packet> > m_dropTrace;