the protocol number field is a 16 bit integer, not a 32 bit integer

src/node/net-device.cc

@@ -197,7 +197,7 @@ NetDevice::GetChannel (void) const
 
 // Receive packets from below
 bool
-NetDevice::ForwardUp(const Packet& p, uint32_t param, const Address &from)
+NetDevice::ForwardUp(const Packet& p, uint16_t param, const Address &from)
 {
   bool retval = false;
 

src/node/net-device.h

@@ -251,7 +251,7 @@ public:
    * forwards it to the higher layers by calling this method
    * which is responsible for passing it up to the Rx callback.
    */
-  bool ForwardUp (const Packet& p, uint32_t param, const Address &address);
+  bool ForwardUp (const Packet& p, uint16_t param, const Address &address);
 
 
   /**