diff -r dacc57c5d31f src/devices/bridge/bridge-net-device.cc
--- a/src/devices/bridge/bridge-net-device.cc	Thu Aug 07 10:13:54 2008 -0700
+++ b/src/devices/bridge/bridge-net-device.cc	Thu Aug 07 10:47:53 2008 -0700
@@ -59,7 +59,7 @@ BridgeNetDevice::BridgeNetDevice ()
 }
 
 void
-BridgeNetDevice::ReceiveFromDevice (Ptr<NetDevice> incomingPort, Ptr<Packet> packet, uint16_t protocol,
+BridgeNetDevice::ReceiveFromDevice (Ptr<NetDevice> incomingPort, Ptr<const Packet> packet, uint16_t protocol,
                                     Address const &src, Address const &dst, PacketType packetType)
 {
   NS_LOG_FUNCTION_NOARGS ();
@@ -95,7 +95,7 @@ BridgeNetDevice::ReceiveFromDevice (Ptr<
 }
 
 void
-BridgeNetDevice::ForwardUnicast (Ptr<NetDevice> incomingPort, Ptr<Packet> packet,
+BridgeNetDevice::ForwardUnicast (Ptr<NetDevice> incomingPort, Ptr<const Packet> packet,
                                  uint16_t protocol, Mac48Address src, Mac48Address dst)
 {
   NS_LOG_DEBUG ("LearningBridgeForward (incomingPort=" << incomingPort->GetName ()
@@ -128,7 +128,7 @@ BridgeNetDevice::ForwardUnicast (Ptr<Net
 }
 
 void
-BridgeNetDevice::ForwardBroadcast (Ptr<NetDevice> incomingPort, Ptr<Packet> packet,
+BridgeNetDevice::ForwardBroadcast (Ptr<NetDevice> incomingPort, Ptr<const Packet> packet,
                                         uint16_t protocol, Mac48Address src, Mac48Address dst)
 {
   NS_LOG_DEBUG ("LearningBridgeForward (incomingPort=" << incomingPort->GetName ()
diff -r dacc57c5d31f src/devices/bridge/bridge-net-device.h
--- a/src/devices/bridge/bridge-net-device.h	Thu Aug 07 10:13:54 2008 -0700
+++ b/src/devices/bridge/bridge-net-device.h	Thu Aug 07 10:47:53 2008 -0700
@@ -72,11 +72,11 @@ protected:
 protected:
   virtual void DoDispose (void);
 
-  void ReceiveFromDevice (Ptr<NetDevice> device, Ptr<Packet> packet, uint16_t protocol,
+  void ReceiveFromDevice (Ptr<NetDevice> device, Ptr<const Packet> packet, uint16_t protocol,
                           Address const &source, Address const &destination, PacketType packetType);
-  void ForwardUnicast (Ptr<NetDevice> incomingPort, Ptr<Packet> packet,
+  void ForwardUnicast (Ptr<NetDevice> incomingPort, Ptr<const Packet> packet,
                        uint16_t protocol, Mac48Address src, Mac48Address dst);
-  void ForwardBroadcast (Ptr<NetDevice> incomingPort, Ptr<Packet> packet,
+  void ForwardBroadcast (Ptr<NetDevice> incomingPort, Ptr<const Packet> packet,
                          uint16_t protocol, Mac48Address src, Mac48Address dst);
   void Learn (Mac48Address source, Ptr<NetDevice> port);
   Ptr<NetDevice> GetLearnedState (Mac48Address source);
diff -r dacc57c5d31f src/internet-stack/arp-l3-protocol.cc
--- a/src/internet-stack/arp-l3-protocol.cc	Thu Aug 07 10:13:54 2008 -0700
+++ b/src/internet-stack/arp-l3-protocol.cc	Thu Aug 07 10:47:53 2008 -0700
@@ -117,10 +117,12 @@ ArpL3Protocol::FindCache (Ptr<NetDevice>
 }
 
 void 
-ArpL3Protocol::Receive(Ptr<NetDevice> device, Ptr<Packet> packet, uint16_t protocol, const Address &from,
+ArpL3Protocol::Receive(Ptr<NetDevice> device, Ptr<const Packet> p, uint16_t protocol, const Address &from,
                        const Address &to, NetDevice::PacketType packetType)
 {
   NS_LOG_FUNCTION_NOARGS ();
+
+  Ptr<Packet> packet = p->Copy ();
 
   Ptr<ArpCache> cache = FindCache (device);
   ArpHeader arp;
diff -r dacc57c5d31f src/internet-stack/arp-l3-protocol.h
--- a/src/internet-stack/arp-l3-protocol.h	Thu Aug 07 10:13:54 2008 -0700
+++ b/src/internet-stack/arp-l3-protocol.h	Thu Aug 07 10:47:53 2008 -0700
@@ -54,7 +54,7 @@ public:
   /**
    * \brief Receive a packet
    */
-  void Receive(Ptr<NetDevice> device, Ptr<Packet> p, uint16_t protocol, const Address &from, const Address &to,
+  void Receive(Ptr<NetDevice> device, Ptr<const Packet> p, uint16_t protocol, const Address &from, const Address &to,
                NetDevice::PacketType packetType);
   /**
    * \brief Perform an ARP lookup
diff -r dacc57c5d31f src/internet-stack/ipv4-l3-protocol.cc
--- a/src/internet-stack/ipv4-l3-protocol.cc	Thu Aug 07 10:13:54 2008 -0700
+++ b/src/internet-stack/ipv4-l3-protocol.cc	Thu Aug 07 10:47:53 2008 -0700
@@ -449,12 +449,14 @@ Ipv4L3Protocol::FindInterfaceForDevice (
 }  
 
 void 
-Ipv4L3Protocol::Receive( Ptr<NetDevice> device, Ptr<Packet> packet, uint16_t protocol, const Address &from,
+Ipv4L3Protocol::Receive( Ptr<NetDevice> device, Ptr<const Packet> p, uint16_t protocol, const Address &from,
                          const Address &to, NetDevice::PacketType packetType)
 {
-  NS_LOG_FUNCTION (this << &device << packet << protocol <<  from);
+  NS_LOG_FUNCTION (this << &device << p << protocol <<  from);
 
   NS_LOG_LOGIC ("Packet from " << from << " received on node " << m_node->GetId ());
+
+  Ptr<Packet> packet = p->Copy ();
 
   uint32_t index = 0;
   Ptr<Ipv4Interface> ipv4Interface;
diff -r dacc57c5d31f src/internet-stack/ipv4-l3-protocol.h
--- a/src/internet-stack/ipv4-l3-protocol.h	Thu Aug 07 10:13:54 2008 -0700
+++ b/src/internet-stack/ipv4-l3-protocol.h	Thu Aug 07 10:47:53 2008 -0700
@@ -83,7 +83,7 @@ public:
    *    - implement a per-NetDevice ARP cache
    *    - send back arp replies on the right device
    */
-  void Receive( Ptr<NetDevice> device, Ptr<Packet> p, uint16_t protocol, const Address &from,
+  void Receive( Ptr<NetDevice> device, Ptr<const Packet> p, uint16_t protocol, const Address &from,
                 const Address &to, NetDevice::PacketType packetType);
 
   /**
diff -r dacc57c5d31f src/node/net-device.h
--- a/src/node/net-device.h	Thu Aug 07 10:13:54 2008 -0700
+++ b/src/node/net-device.h	Thu Aug 07 10:47:53 2008 -0700
@@ -274,7 +274,7 @@ public:
    * \returns true if the callback could handle the packet successfully, false
    *          otherwise.
    */
-  typedef Callback<bool,Ptr<NetDevice>,Ptr<Packet>,uint16_t,const Address &> ReceiveCallback;
+  typedef Callback<bool,Ptr<NetDevice>,Ptr<const Packet>,uint16_t,const Address &> ReceiveCallback;
 
   /**
    * \param cb callback to invoke whenever a packet has been received and must
@@ -296,7 +296,7 @@ public:
    * \returns true if the callback could handle the packet successfully, false
    *          otherwise.
    */
-  typedef Callback< bool, Ptr<NetDevice>, Ptr<Packet>, uint16_t,
+  typedef Callback< bool, Ptr<NetDevice>, Ptr<const Packet>, uint16_t,
                     const Address &, const Address &, PacketType > PromiscReceiveCallback;
 
   /**
diff -r dacc57c5d31f src/node/node.cc
--- a/src/node/node.cc	Thu Aug 07 10:13:54 2008 -0700
+++ b/src/node/node.cc	Thu Aug 07 10:47:53 2008 -0700
@@ -222,7 +222,7 @@ Node::UnregisterProtocolHandler (Protoco
 }
 
 bool
-Node::PromiscReceiveFromDevice (Ptr<NetDevice> device, Ptr<Packet> packet, uint16_t protocol,
+Node::PromiscReceiveFromDevice (Ptr<NetDevice> device, Ptr<const Packet> packet, uint16_t protocol,
                                 const Address &from, const Address &to, NetDevice::PacketType packetType)
 {
   NS_LOG_FUNCTION(device->GetName ());
@@ -230,7 +230,7 @@ Node::PromiscReceiveFromDevice (Ptr<NetD
 }
 
 bool
-Node::NonPromiscReceiveFromDevice (Ptr<NetDevice> device, Ptr<Packet> packet, uint16_t protocol,
+Node::NonPromiscReceiveFromDevice (Ptr<NetDevice> device, Ptr<const Packet> packet, uint16_t protocol,
                                    const Address &from)
 {
   NS_LOG_FUNCTION(device->GetName ());
@@ -238,15 +238,11 @@ Node::NonPromiscReceiveFromDevice (Ptr<N
 }
 
 bool
-Node::ReceiveFromDevice (Ptr<NetDevice> device, Ptr<Packet> packet, uint16_t protocol,
+Node::ReceiveFromDevice (Ptr<NetDevice> device, Ptr<const Packet> packet, uint16_t protocol,
                          const Address &from, const Address &to, NetDevice::PacketType packetType, bool promiscuous)
 {
   NS_LOG_FUNCTION(device->GetName ());
   bool found = false;
-  // if there are (potentially) multiple handlers, we need to copy the
-  // packet before passing it to each handler, because handlers may
-  // modify it.
-  bool copyNeeded = (m_handlers.size () > 1);
 
   for (ProtocolHandlerList::iterator i = m_handlers.begin ();
        i != m_handlers.end (); i++)
@@ -259,7 +255,7 @@ Node::ReceiveFromDevice (Ptr<NetDevice> 
             {
               if (promiscuous == i->promiscuous)
                 {
-                  i->handler (device, (copyNeeded ? packet->Copy () : packet), protocol, from, to, packetType);
+                  i->handler (device, packet->Copy (), protocol, from, to, packetType);
                   found = true;
                 }
             }
diff -r dacc57c5d31f src/node/node.h
--- a/src/node/node.h	Thu Aug 07 10:13:54 2008 -0700
+++ b/src/node/node.h	Thu Aug 07 10:47:53 2008 -0700
@@ -145,7 +145,7 @@ public:
    *                   this value is only valid for promiscuous mode
    *                   protocol handlers.
    */
-  typedef Callback<void,Ptr<NetDevice>, Ptr<Packet>,uint16_t,const Address &,
+  typedef Callback<void,Ptr<NetDevice>, Ptr<const Packet>,uint16_t,const Address &,
                    const Address &, NetDevice::PacketType> ProtocolHandler;
   /**
    * \param handler the handler to register
@@ -189,10 +189,10 @@ private:
    */
   virtual void NotifyDeviceAdded (Ptr<NetDevice> device);
 
-  bool NonPromiscReceiveFromDevice (Ptr<NetDevice> device, Ptr<Packet>, uint16_t protocol, const Address &from);
-  bool PromiscReceiveFromDevice (Ptr<NetDevice> device, Ptr<Packet>, uint16_t protocol,
+  bool NonPromiscReceiveFromDevice (Ptr<NetDevice> device, Ptr<const Packet>, uint16_t protocol, const Address &from);
+  bool PromiscReceiveFromDevice (Ptr<NetDevice> device, Ptr<const Packet>, uint16_t protocol,
                                  const Address &from, const Address &to, NetDevice::PacketType packetType);
-  bool ReceiveFromDevice (Ptr<NetDevice> device, Ptr<Packet>, uint16_t protocol,
+  bool ReceiveFromDevice (Ptr<NetDevice> device, Ptr<const Packet>, uint16_t protocol,
                           const Address &from, const Address &to, NetDevice::PacketType packetType, bool promisc);
 
   void Construct (void);
diff -r dacc57c5d31f src/node/packet-socket.cc
--- a/src/node/packet-socket.cc	Thu Aug 07 10:13:54 2008 -0700
+++ b/src/node/packet-socket.cc	Thu Aug 07 10:47:53 2008 -0700
@@ -344,7 +344,7 @@ PacketSocket::SendTo (Ptr<Packet> p, uin
 }
 
 void 
-PacketSocket::ForwardUp (Ptr<NetDevice> device, Ptr<Packet> packet, 
+PacketSocket::ForwardUp (Ptr<NetDevice> device, Ptr<const Packet> packet, 
                          uint16_t protocol, const Address &from,
                          const Address &to, NetDevice::PacketType packetType)
 {
@@ -369,7 +369,7 @@ PacketSocket::ForwardUp (Ptr<NetDevice> 
       SocketAddressTag tag;
       tag.SetAddress (address);
       packet->AddTag (tag);
-      m_deliveryQueue.push (packet);
+      m_deliveryQueue.push (packet->Copy ());
       m_rxAvailable += packet->GetSize ();
       NS_LOG_LOGIC ("UID is " << packet->GetUid() << " PacketSocket " << this);
       NotifyDataRecv ();
diff -r dacc57c5d31f src/node/packet-socket.h
--- a/src/node/packet-socket.h	Thu Aug 07 10:13:54 2008 -0700
+++ b/src/node/packet-socket.h	Thu Aug 07 10:47:53 2008 -0700
@@ -103,7 +103,7 @@ public:
     Address &fromAddress);
 
 private:
-  void ForwardUp (Ptr<NetDevice> device, Ptr<Packet> packet, 
+  void ForwardUp (Ptr<NetDevice> device, Ptr<const Packet> packet, 
                   uint16_t protocol, const Address &from, const Address &to,
                   NetDevice::PacketType packetType);
   int DoBind (const PacketSocketAddress &address);