ns-3-patch-tapbridge-linkup.diff

--- ./src/tap-bridge/model/tap-bridge.cc	2013-07-22 04:03:53.671898613 +0200
+++ ./src/tap-bridge/model/tap-bridge.cc	2013-07-19 08:36:33.963029004 +0200
@@ -674,6 +674,7 @@ TapBridge::CreateTap (void)
              NS_LOG_INFO ("Underlying ns-3 device will continue to use default address, what can lead to connectivity errors");
            }
         }
+      NotifyLinkUp ();
       return;  
     }
 }
@@ -1064,18 +1065,25 @@ TapBridge::GetMtu (void) const
   return m_mtu;
 }
 
+void
+TapBridge::NotifyLinkUp (void)
+{
+  m_linkUp = true;
+  m_linkChangeCallbacks ();
+}
 
 bool 
 TapBridge::IsLinkUp (void) const
 {
   NS_LOG_FUNCTION_NOARGS ();
-  return true;
+  return m_linkUp;
 }
 
 void 
 TapBridge::AddLinkChangeCallback (Callback<void> callback)
 {
   NS_LOG_FUNCTION_NOARGS ();
+  m_linkChangeCallbacks.ConnectWithoutContext (callback);
 }
 
 bool 

--- ./src/tap-bridge/model/tap-bridge.h	2013-07-22 04:03:53.671898613 +0200
+++ ./src/tap-bridge/model/tap-bridge.h	2013-07-19 08:11:22.510991547 +0200
@@ -291,6 +291,8 @@ private:
    */
   Ptr<Packet> Filter (Ptr<Packet> packet, Address *src, Address *dst, uint16_t *type);
 
+  void NotifyLinkUp (void);
+
   /**
    * \internal
    *
@@ -463,6 +465,22 @@ private:
    * multithreaded apps is not a good thing.
    */
   uint32_t m_nodeId;
+
+  /**
+   * \internal
+   *
+   * Flag indicating whether or not the link is up.  In this case,
+   * whether or not ns-3 is connected to the underlying TAP device
+   * with a file descriptor.
+   */
+  bool m_linkUp;
+
+  /**
+   * \internal
+   *
+   * Callbacks to fire if the link changes state (up or down).
+   */
+  TracedCallback<> m_linkChangeCallbacks;
 };
 
 } // namespace ns3