src/network/model/packet.cc
changeset 6823 a27f86fb4e55
parent 6775 0783f42a364b
child 6968 4b68e211540c
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/network/model/packet.cc	Mon Feb 21 09:11:37 2011 -0800
@@ -0,0 +1,1327 @@
+/* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
+/*
+ * Copyright (c) 2005,2006 INRIA
+ *
+ * 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: Mathieu Lacage <mathieu.lacage@sophia.inria.fr>
+ */
+#include "packet.h"
+#include "ns3/assert.h"
+#include "ns3/log.h"
+#include "ns3/simulator.h"
+#include "ns3/test.h"
+#include <string>
+#include <stdarg.h>
+
+NS_LOG_COMPONENT_DEFINE ("Packet");
+
+namespace ns3 {
+
+uint32_t Packet::m_globalUid = 0;
+
+TypeId 
+ByteTagIterator::Item::GetTypeId (void) const
+{
+  return m_tid;
+}
+uint32_t 
+ByteTagIterator::Item::GetStart (void) const
+{
+  return m_start;
+}
+uint32_t 
+ByteTagIterator::Item::GetEnd (void) const
+{
+  return m_end;
+}
+void 
+ByteTagIterator::Item::GetTag (Tag &tag) const
+{
+  if (tag.GetInstanceTypeId () != GetTypeId ())
+    {
+      NS_FATAL_ERROR ("The tag you provided is not of the right type.");
+    }
+  tag.Deserialize (m_buffer);
+}
+ByteTagIterator::Item::Item (TypeId tid, uint32_t start, uint32_t end, TagBuffer buffer)
+  : m_tid (tid),
+    m_start (start),
+    m_end (end),
+    m_buffer (buffer)
+{
+}
+bool
+ByteTagIterator::HasNext (void) const
+{
+  return m_current.HasNext ();
+}
+ByteTagIterator::Item
+ByteTagIterator::Next (void)
+{
+  ByteTagList::Iterator::Item i = m_current.Next ();
+  return ByteTagIterator::Item (i.tid,
+                                i.start-m_current.GetOffsetStart (),
+                                i.end-m_current.GetOffsetStart (),
+                                i.buf);
+}
+ByteTagIterator::ByteTagIterator (ByteTagList::Iterator i)
+  : m_current (i)
+{
+}
+
+
+PacketTagIterator::PacketTagIterator (const struct PacketTagList::TagData *head)
+  : m_current (head)
+{
+}
+bool
+PacketTagIterator::HasNext (void) const
+{
+  return m_current != 0;
+}
+PacketTagIterator::Item
+PacketTagIterator::Next (void)
+{
+  NS_ASSERT (HasNext ());
+  const struct PacketTagList::TagData *prev = m_current;
+  m_current = m_current->next;
+  return PacketTagIterator::Item (prev);
+}
+
+PacketTagIterator::Item::Item (const struct PacketTagList::TagData *data)
+  : m_data (data)
+{
+}
+TypeId
+PacketTagIterator::Item::GetTypeId (void) const
+{
+  return m_data->tid;
+}
+void
+PacketTagIterator::Item::GetTag (Tag &tag) const
+{
+  NS_ASSERT (tag.GetInstanceTypeId () == m_data->tid);
+  tag.Deserialize (TagBuffer ((uint8_t*)m_data->data, (uint8_t*)m_data->data+PACKET_TAG_MAX_SIZE));
+}
+
+
+Ptr<Packet> 
+Packet::Copy (void) const
+{
+  // we need to invoke the copy constructor directly
+  // rather than calling Create because the copy constructor
+  // is private.
+  return Ptr<Packet> (new Packet (*this), false);
+}
+
+Packet::Packet ()
+  : m_buffer (),
+    m_byteTagList (),
+    m_packetTagList (),
+    /* The upper 32 bits of the packet id in 
+     * metadata is for the system id. For non-
+     * distributed simulations, this is simply 
+     * zero.  The lower 32 bits are for the 
+     * global UID
+     */
+    m_metadata (static_cast<uint64_t> (Simulator::GetSystemId ()) << 32 | m_globalUid, 0),
+    m_nixVector (0)
+{
+  m_globalUid++;
+}
+
+Packet::Packet (const Packet &o)
+  : m_buffer (o.m_buffer),
+    m_byteTagList (o.m_byteTagList),
+    m_packetTagList (o.m_packetTagList),
+    m_metadata (o.m_metadata)
+{
+  o.m_nixVector ? m_nixVector = o.m_nixVector->Copy ()
+    : m_nixVector = 0;
+}
+
+Packet &
+Packet::operator = (const Packet &o)
+{
+  if (this == &o)
+    {
+      return *this;
+    }
+  m_buffer = o.m_buffer;
+  m_byteTagList = o.m_byteTagList;
+  m_packetTagList = o.m_packetTagList;
+  m_metadata = o.m_metadata;
+  o.m_nixVector ? m_nixVector = o.m_nixVector->Copy () 
+    : m_nixVector = 0;
+  return *this;
+}
+
+Packet::Packet (uint32_t size)
+  : m_buffer (size),
+    m_byteTagList (),
+    m_packetTagList (),
+    /* The upper 32 bits of the packet id in 
+     * metadata is for the system id. For non-
+     * distributed simulations, this is simply 
+     * zero.  The lower 32 bits are for the 
+     * global UID
+     */
+    m_metadata (static_cast<uint64_t> (Simulator::GetSystemId ()) << 32 | m_globalUid, size),
+    m_nixVector (0)
+{
+  m_globalUid++;
+}
+Packet::Packet (uint8_t const *buffer, uint32_t size, bool magic)
+  : m_buffer (0, false),
+    m_byteTagList (),
+    m_packetTagList (),
+    m_metadata (0,0),
+    m_nixVector (0)
+{
+  NS_ASSERT (magic);
+  Deserialize (buffer, size);
+}
+
+Packet::Packet (uint8_t const*buffer, uint32_t size)
+  : m_buffer (),
+    m_byteTagList (),
+    m_packetTagList (),
+    /* The upper 32 bits of the packet id in 
+     * metadata is for the system id. For non-
+     * distributed simulations, this is simply 
+     * zero.  The lower 32 bits are for the 
+     * global UID
+     */
+    m_metadata (static_cast<uint64_t> (Simulator::GetSystemId ()) << 32 | m_globalUid, size),
+    m_nixVector (0)
+{
+  m_globalUid++;
+  m_buffer.AddAtStart (size);
+  Buffer::Iterator i = m_buffer.Begin ();
+  i.Write (buffer, size);
+}
+
+Packet::Packet (const Buffer &buffer,  const ByteTagList &byteTagList, 
+                const PacketTagList &packetTagList, const PacketMetadata &metadata)
+  : m_buffer (buffer),
+    m_byteTagList (byteTagList),
+    m_packetTagList (packetTagList),
+    m_metadata (metadata),
+    m_nixVector (0)
+{
+}
+
+Ptr<Packet>
+Packet::CreateFragment (uint32_t start, uint32_t length) const
+{
+  NS_LOG_FUNCTION (this << start << length);
+  Buffer buffer = m_buffer.CreateFragment (start, length);
+  NS_ASSERT (m_buffer.GetSize () >= start + length);
+  uint32_t end = m_buffer.GetSize () - (start + length);
+  PacketMetadata metadata = m_metadata.CreateFragment (start, end);
+  // again, call the constructor directly rather than
+  // through Create because it is private.
+  return Ptr<Packet> (new Packet (buffer, m_byteTagList, m_packetTagList, metadata), false);
+}
+
+void
+Packet::SetNixVector (Ptr<NixVector> nixVector)
+{
+  m_nixVector = nixVector;
+}
+
+Ptr<NixVector>
+Packet::GetNixVector (void) const
+{
+  return m_nixVector;
+} 
+
+void
+Packet::AddHeader (const Header &header)
+{
+  uint32_t size = header.GetSerializedSize ();
+  NS_LOG_FUNCTION (this << header.GetInstanceTypeId ().GetName () << size);
+  uint32_t orgStart = m_buffer.GetCurrentStartOffset ();
+  bool resized = m_buffer.AddAtStart (size);
+  if (resized)
+    {
+      m_byteTagList.AddAtStart (m_buffer.GetCurrentStartOffset () + size - orgStart,
+                                m_buffer.GetCurrentStartOffset () + size);
+    }
+  header.Serialize (m_buffer.Begin ());
+  m_metadata.AddHeader (header, size);
+}
+uint32_t
+Packet::RemoveHeader (Header &header)
+{
+  uint32_t deserialized = header.Deserialize (m_buffer.Begin ());
+  NS_LOG_FUNCTION (this << header.GetInstanceTypeId ().GetName () << deserialized);
+  m_buffer.RemoveAtStart (deserialized);
+  m_metadata.RemoveHeader (header, deserialized);
+  return deserialized;
+}
+uint32_t
+Packet::PeekHeader (Header &header) const
+{
+  uint32_t deserialized = header.Deserialize (m_buffer.Begin ());
+  NS_LOG_FUNCTION (this << header.GetInstanceTypeId ().GetName () << deserialized);
+  return deserialized;
+}
+void
+Packet::AddTrailer (const Trailer &trailer)
+{
+  uint32_t size = trailer.GetSerializedSize ();
+  NS_LOG_FUNCTION (this << trailer.GetInstanceTypeId ().GetName () << size);
+  uint32_t orgStart = m_buffer.GetCurrentStartOffset ();
+  bool resized = m_buffer.AddAtEnd (size);
+  if (resized)
+    {
+      m_byteTagList.AddAtEnd (m_buffer.GetCurrentStartOffset () - orgStart,
+                              m_buffer.GetCurrentEndOffset () - size);
+    }
+  Buffer::Iterator end = m_buffer.End ();
+  trailer.Serialize (end);
+  m_metadata.AddTrailer (trailer, size);
+}
+uint32_t
+Packet::RemoveTrailer (Trailer &trailer)
+{
+  uint32_t deserialized = trailer.Deserialize (m_buffer.End ());
+  NS_LOG_FUNCTION (this << trailer.GetInstanceTypeId ().GetName () << deserialized);
+  m_buffer.RemoveAtEnd (deserialized);
+  m_metadata.RemoveTrailer (trailer, deserialized);
+  return deserialized;
+}
+uint32_t
+Packet::PeekTrailer (Trailer &trailer)
+{
+  uint32_t deserialized = trailer.Deserialize (m_buffer.End ());
+  NS_LOG_FUNCTION (this << trailer.GetInstanceTypeId ().GetName () << deserialized);
+  return deserialized;
+}
+
+void 
+Packet::AddAtEnd (Ptr<const Packet> packet)
+{
+  NS_LOG_FUNCTION (this << packet << packet->GetSize ());
+  uint32_t aStart = m_buffer.GetCurrentStartOffset ();
+  uint32_t bEnd = packet->m_buffer.GetCurrentEndOffset ();
+  m_buffer.AddAtEnd (packet->m_buffer);
+  uint32_t appendPrependOffset = m_buffer.GetCurrentEndOffset () - packet->m_buffer.GetSize ();
+  m_byteTagList.AddAtEnd (m_buffer.GetCurrentStartOffset () - aStart, 
+                          appendPrependOffset);
+  ByteTagList copy = packet->m_byteTagList;
+  copy.AddAtStart (m_buffer.GetCurrentEndOffset () - bEnd,
+                   appendPrependOffset);
+  m_byteTagList.Add (copy);
+  m_metadata.AddAtEnd (packet->m_metadata);
+}
+void
+Packet::AddPaddingAtEnd (uint32_t size)
+{
+  NS_LOG_FUNCTION (this << size);
+  uint32_t orgEnd = m_buffer.GetCurrentEndOffset ();
+  bool resized = m_buffer.AddAtEnd (size);
+  if (resized)
+    {
+      m_byteTagList.AddAtEnd (m_buffer.GetCurrentEndOffset () - orgEnd,
+                              m_buffer.GetCurrentEndOffset () - size);
+    }
+  m_metadata.AddPaddingAtEnd (size);
+}
+void 
+Packet::RemoveAtEnd (uint32_t size)
+{
+  NS_LOG_FUNCTION (this << size);
+  m_buffer.RemoveAtEnd (size);
+  m_metadata.RemoveAtEnd (size);
+}
+void 
+Packet::RemoveAtStart (uint32_t size)
+{
+  NS_LOG_FUNCTION (this << size);
+  m_buffer.RemoveAtStart (size);
+  m_metadata.RemoveAtStart (size);
+}
+
+void 
+Packet::RemoveAllByteTags (void)
+{
+  NS_LOG_FUNCTION (this);
+  m_byteTagList.RemoveAll ();
+}
+
+uint8_t const *
+Packet::PeekData (void) const
+{
+  NS_LOG_FUNCTION (this);
+  uint32_t oldStart = m_buffer.GetCurrentStartOffset ();
+  uint8_t const * data = m_buffer.PeekData ();
+  uint32_t newStart = m_buffer.GetCurrentStartOffset ();
+ 
+  // Update tag offsets if buffer offsets were changed
+  const_cast<ByteTagList &>(m_byteTagList).AddAtStart (newStart - oldStart, newStart);
+  return data;
+}
+
+uint32_t 
+Packet::CopyData (uint8_t *buffer, uint32_t size) const
+{
+  return m_buffer.CopyData (buffer, size);
+}
+
+void
+Packet::CopyData(std::ostream *os, uint32_t size) const
+{
+  return m_buffer.CopyData (os, size);
+}
+
+uint64_t 
+Packet::GetUid (void) const
+{
+  return m_metadata.GetUid ();
+}
+
+void 
+Packet::PrintByteTags (std::ostream &os) const
+{
+  ByteTagIterator i = GetByteTagIterator ();
+  while (i.HasNext ())
+    {
+      ByteTagIterator::Item item = i.Next ();
+      os << item.GetTypeId ().GetName () << " [" << item.GetStart () << "-" << item.GetEnd () << "]";
+      Callback<ObjectBase *> constructor = item.GetTypeId ().GetConstructor ();
+      if (constructor.IsNull ())
+        {
+          if (i.HasNext ())
+            {
+              os << " ";
+            }
+          continue;
+        }
+      Tag *tag = dynamic_cast<Tag *> (constructor ());
+      NS_ASSERT (tag != 0);
+      os << " ";
+      item.GetTag (*tag);
+      tag->Print (os);
+      if (i.HasNext ())
+        {
+          os << " ";
+        }
+      delete tag;
+    }
+}
+
+void 
+Packet::Print (std::ostream &os) const
+{
+  PacketMetadata::ItemIterator i = m_metadata.BeginItem (m_buffer);
+  while (i.HasNext ())
+    {
+      PacketMetadata::Item item = i.Next ();
+      if (item.isFragment)
+        {
+          switch (item.type) {
+            case PacketMetadata::Item::PAYLOAD:
+              os << "Payload";
+              break;
+            case PacketMetadata::Item::HEADER:
+            case PacketMetadata::Item::TRAILER:
+              os << item.tid.GetName ();
+              break;
+            }
+          os << " Fragment [" << item.currentTrimedFromStart<<":"
+             << (item.currentTrimedFromStart + item.currentSize) << "]";
+        }
+      else
+        {
+          switch (item.type) {
+            case PacketMetadata::Item::PAYLOAD:
+              os << "Payload (size=" << item.currentSize << ")";
+              break;
+            case PacketMetadata::Item::HEADER:
+            case PacketMetadata::Item::TRAILER:
+              os << item.tid.GetName () << " (";
+              {
+                NS_ASSERT (item.tid.HasConstructor ());
+                Callback<ObjectBase *> constructor = item.tid.GetConstructor ();
+                NS_ASSERT (!constructor.IsNull ());
+                ObjectBase *instance = constructor ();
+                NS_ASSERT (instance != 0);
+                Chunk *chunk = dynamic_cast<Chunk *> (instance);
+                NS_ASSERT (chunk != 0);
+                chunk->Deserialize (item.current);
+                chunk->Print (os);
+                delete chunk;
+              }
+              os << ")";
+              break;
+            }
+        }
+      if (i.HasNext ())
+        {
+          os << " ";
+        }
+    }
+#if 0
+  // The code below will work only if headers and trailers
+  // define the right attributes which is not the case for
+  // now. So, as a temporary measure, we use the 
+  // headers' and trailers' Print method as shown above.
+  PacketMetadata::ItemIterator i = m_metadata.BeginItem (m_buffer);
+  while (i.HasNext ())
+    {
+      PacketMetadata::Item item = i.Next ();
+      if (item.isFragment)
+        {
+          switch (item.type) {
+            case PacketMetadata::Item::PAYLOAD:
+              os << "Payload";
+              break;
+            case PacketMetadata::Item::HEADER:
+            case PacketMetadata::Item::TRAILER:
+              os << item.tid.GetName ();
+              break;
+            }
+          os << " Fragment [" << item.currentTrimedFromStart<<":"
+             << (item.currentTrimedFromStart + item.currentSize) << "]";
+        }
+      else
+        {
+          switch (item.type) {
+            case PacketMetadata::Item::PAYLOAD:
+              os << "Payload (size=" << item.currentSize << ")";
+              break;
+            case PacketMetadata::Item::HEADER:
+            case PacketMetadata::Item::TRAILER:
+              os << item.tid.GetName () << "(";
+              {
+                NS_ASSERT (item.tid.HasConstructor ());
+                Callback<ObjectBase *> constructor = item.tid.GetConstructor ();
+                NS_ASSERT (constructor.IsNull ());
+                ObjectBase *instance = constructor ();
+                NS_ASSERT (instance != 0);
+                Chunk *chunk = dynamic_cast<Chunk *> (instance);
+                NS_ASSERT (chunk != 0);
+                chunk->Deserialize (item.current);
+                for (uint32_t j = 0; j < item.tid.GetAttributeN (); j++)
+                  {
+                    std::string attrName = item.tid.GetAttributeName (j);
+                    std::string value;
+                    bool ok = chunk->GetAttribute (attrName, value);
+                    NS_ASSERT (ok);
+                    os << attrName << "=" << value;
+                    if ((j + 1) < item.tid.GetAttributeN ())
+                      {
+                        os << ",";
+                      }
+                  }
+              }
+              os << ")";
+              break;
+            }
+        }
+      if (i.HasNext ())
+        {
+          os << " ";
+        }
+    }
+#endif
+}
+
+PacketMetadata::ItemIterator 
+Packet::BeginItem (void) const
+{
+  return m_metadata.BeginItem (m_buffer);
+}
+
+void
+Packet::EnablePrinting (void)
+{
+  NS_LOG_FUNCTION_NOARGS ();
+  PacketMetadata::Enable ();
+}
+
+void
+Packet::EnableChecking (void)
+{
+  NS_LOG_FUNCTION_NOARGS ();
+  PacketMetadata::EnableChecking ();
+}
+
+uint32_t Packet::GetSerializedSize (void) const
+{
+  uint32_t size = 0;
+
+  if (m_nixVector)
+    {
+      // increment total size by the size of the nix-vector
+      // ensuring 4-byte boundary
+      size += ((m_nixVector->GetSerializedSize () + 3) & (~3));
+
+      // add 4-bytes for entry of total length of nix-vector
+      size += 4;
+    }
+  else
+    {
+      // if no nix-vector, still have to add 4-bytes
+      // to account for the entry of total size for 
+      // nix-vector in the buffer
+      size += 4;
+    }
+
+  //Tag size
+  //XXX
+  //size += m_tags.GetSerializedSize ();
+
+  // increment total size by size of meta-data 
+  // ensuring 4-byte boundary
+  size += ((m_metadata.GetSerializedSize () + 3) & (~3));
+
+  // add 4-bytes for entry of total length of meta-data
+  size += 4;
+
+  // increment total size by size of buffer 
+  // ensuring 4-byte boundary
+  size += ((m_buffer.GetSerializedSize () + 3) & (~3));
+
+  // add 4-bytes for entry of total length of buffer 
+  size += 4;
+
+  return size;
+}
+
+uint32_t 
+Packet::Serialize (uint8_t* buffer, uint32_t maxSize) const
+{
+  uint32_t* p = reinterpret_cast<uint32_t *> (buffer);
+  uint32_t size = 0;
+
+  // if nix-vector exists, serialize it
+  if (m_nixVector)
+    {
+      uint32_t nixSize = m_nixVector->GetSerializedSize ();
+      if (size + nixSize <= maxSize)
+        {
+          // put the total length of nix-vector in the
+          // buffer. this includes 4-bytes for total 
+          // length itself
+          *p++ = nixSize + 4;
+          size += nixSize;
+
+          // serialize the nix-vector
+          uint32_t serialized = 
+            m_nixVector->Serialize (p, nixSize);
+          if (serialized)
+            {
+              // increment p by nixSize bytes
+              // ensuring 4-byte boundary
+              p += ((nixSize+3) & (~3)) / 4;
+            }
+          else
+            {
+              return 0;
+            }
+        }
+      else 
+        {
+          return 0;
+        }
+    }
+  else
+    { 
+      // no nix vector, set zero length, 
+      // ie 4-bytes, since it must include 
+      // length for itself
+      if (size + 4 <= maxSize)
+        {
+          size += 4;
+          *p++ = 4;
+        }
+      else
+        {
+          return 0;
+        }
+    }
+
+  // Serialize Tags
+  // XXX
+
+  // Serialize Metadata
+  uint32_t metaSize = m_metadata.GetSerializedSize ();
+  if (size + metaSize <= maxSize)
+    {
+      // put the total length of metadata in the
+      // buffer. this includes 4-bytes for total 
+      // length itself
+      *p++ = metaSize + 4;
+      size += metaSize;
+
+      // serialize the metadata
+      uint32_t serialized = 
+        m_metadata.Serialize (reinterpret_cast<uint8_t *> (p), metaSize); 
+      if (serialized)
+        {
+          // increment p by metaSize bytes
+          // ensuring 4-byte boundary
+          p += ((metaSize+3) & (~3)) / 4;
+        }
+      else
+        {
+          return 0;
+        }
+    }
+  else
+    {
+      return 0;
+    }
+
+  // Serialize the packet contents
+  uint32_t bufSize = m_buffer.GetSerializedSize ();
+  if (size + bufSize <= maxSize)
+    {
+      // put the total length of the buffer in the
+      // buffer. this includes 4-bytes for total 
+      // length itself
+      *p++ = bufSize + 4;
+      size += bufSize;
+
+      // serialize the buffer
+      uint32_t serialized = 
+        m_buffer.Serialize (reinterpret_cast<uint8_t *> (p), bufSize);
+      if (serialized)
+        {
+          // increment p by bufSize bytes
+          // ensuring 4-byte boundary
+          p += ((bufSize+3) & (~3)) / 4;
+        }
+      else 
+        {
+          return 0;
+        }
+    }
+  else
+    {
+      return 0;
+    }
+
+  // Serialized successfully
+  return 1;
+}
+
+uint32_t 
+Packet::Deserialize (const uint8_t* buffer, uint32_t size)
+{
+  NS_LOG_FUNCTION (this);
+
+  const uint32_t* p = reinterpret_cast<const uint32_t *> (buffer);
+
+  // read nix-vector
+  NS_ASSERT (!m_nixVector);
+  uint32_t nixSize = *p++;
+
+  // if size less than nixSize, the buffer 
+  // will be overrun, assert
+  NS_ASSERT (size >= nixSize);
+
+  size -= nixSize;
+
+  if (nixSize > 4)
+    {
+      Ptr<NixVector> nix = Create<NixVector> ();
+      uint32_t nixDeserialized = nix->Deserialize (p, nixSize);
+      if (!nixDeserialized)
+        {
+          // nix-vector not deserialized
+          // completely
+          return 0;
+        }
+      m_nixVector = nix;
+      // increment p by nixSize ensuring
+      // 4-byte boundary
+      p += ((((nixSize - 4) + 3) & (~3)) / 4);
+    }
+
+  // read tags
+  //XXX
+  //uint32_t tagsDeserialized = m_tags.Deserialize (buffer.Begin ());
+  //buffer.RemoveAtStart (tagsDeserialized);
+
+  // read metadata
+  uint32_t metaSize = *p++;
+
+  // if size less than metaSize, the buffer 
+  // will be overrun, assert
+  NS_ASSERT (size >= metaSize);
+
+  size -= metaSize;
+
+  uint32_t metadataDeserialized = 
+    m_metadata.Deserialize (reinterpret_cast<const uint8_t *> (p), metaSize);
+  if (!metadataDeserialized)
+    {
+      // meta-data not deserialized 
+      // completely
+      return 0;
+    }
+  // increment p by metaSize ensuring 
+  // 4-byte boundary
+  p += ((((metaSize - 4) + 3) & (~3)) / 4);
+
+  // read buffer contents
+  uint32_t bufSize = *p++;
+
+  // if size less than bufSize, the buffer 
+  // will be overrun, assert
+  NS_ASSERT (size >= bufSize);
+
+  size -= bufSize;
+
+  uint32_t bufferDeserialized =
+    m_buffer.Deserialize (reinterpret_cast<const uint8_t *> (p), bufSize);
+  if (!bufferDeserialized)
+    {
+      // buffer not deserialized 
+      // completely
+      return 0;
+    }
+
+  // return zero if did not deserialize the 
+  // number of expected bytes
+  return (size == 0);
+}
+
+void 
+Packet::AddByteTag (const Tag &tag) const
+{
+  NS_LOG_FUNCTION (this << tag.GetInstanceTypeId ().GetName () << tag.GetSerializedSize ());
+  ByteTagList *list = const_cast<ByteTagList *> (&m_byteTagList);
+  TagBuffer buffer = list->Add (tag.GetInstanceTypeId (), tag.GetSerializedSize (), 
+                                m_buffer.GetCurrentStartOffset (),
+                                m_buffer.GetCurrentEndOffset ());
+  tag.Serialize (buffer);
+}
+ByteTagIterator 
+Packet::GetByteTagIterator (void) const
+{
+  return ByteTagIterator (m_byteTagList.Begin (m_buffer.GetCurrentStartOffset (), m_buffer.GetCurrentEndOffset ()));
+}
+
+bool 
+Packet::FindFirstMatchingByteTag (Tag &tag) const
+{
+  TypeId tid = tag.GetInstanceTypeId ();
+  ByteTagIterator i = GetByteTagIterator ();
+  while (i.HasNext ())
+    {
+      ByteTagIterator::Item item = i.Next ();
+      if (tid == item.GetTypeId ())
+        {
+          item.GetTag (tag);
+          return true;
+        }
+    }
+  return false;
+}
+
+void 
+Packet::AddPacketTag (const Tag &tag) const
+{
+  NS_LOG_FUNCTION (this << tag.GetInstanceTypeId ().GetName () << tag.GetSerializedSize ());
+  m_packetTagList.Add (tag);
+}
+bool 
+Packet::RemovePacketTag (Tag &tag)
+{
+  NS_LOG_FUNCTION (this << tag.GetInstanceTypeId ().GetName () << tag.GetSerializedSize ());
+  bool found = m_packetTagList.Remove (tag);
+  return found;
+}
+bool 
+Packet::PeekPacketTag (Tag &tag) const
+{
+  bool found = m_packetTagList.Peek (tag);
+  return found;
+}
+void 
+Packet::RemoveAllPacketTags (void)
+{
+  NS_LOG_FUNCTION (this);
+  m_packetTagList.RemoveAll ();
+}
+
+void 
+Packet::PrintPacketTags (std::ostream &os) const
+{
+  PacketTagIterator i = GetPacketTagIterator ();
+  while (i.HasNext ())
+    {
+      PacketTagIterator::Item item = i.Next ();
+      NS_ASSERT (item.GetTypeId ().HasConstructor ());
+      Callback<ObjectBase *> constructor = item.GetTypeId ().GetConstructor ();
+      NS_ASSERT (!constructor.IsNull ());
+      ObjectBase *instance = constructor ();
+      Tag *tag = dynamic_cast<Tag *> (instance);
+      NS_ASSERT (tag != 0);
+      item.GetTag (*tag);
+      tag->Print (os);
+      delete tag;
+      if (i.HasNext ())
+        {
+          os << " ";
+        }
+    }
+}
+
+PacketTagIterator 
+Packet::GetPacketTagIterator (void) const
+{
+  return PacketTagIterator (m_packetTagList.Head ());
+}
+
+std::ostream& operator<< (std::ostream& os, const Packet &packet)
+{
+  packet.Print (os);
+  return os;
+}
+
+//-----------------------------------------------------------------------------
+// Unit tests
+//-----------------------------------------------------------------------------
+namespace {
+
+class ATestTagBase : public Tag
+{
+public:
+  ATestTagBase () : m_error (false) {}
+  bool m_error;
+};
+
+template <int N>
+class ATestTag : public ATestTagBase
+{
+public:
+  static TypeId GetTypeId (void) {
+    std::ostringstream oss;
+    oss << "anon::ATestTag<" << N << ">";
+    static TypeId tid = TypeId (oss.str ().c_str ())
+      .SetParent<Tag> ()
+      .AddConstructor<ATestTag<N> > ()
+      .HideFromDocumentation ()
+    ;
+    return tid;
+  }
+  virtual TypeId GetInstanceTypeId (void) const {
+    return GetTypeId ();
+  }
+  virtual uint32_t GetSerializedSize (void) const {
+    return N;
+  }
+  virtual void Serialize (TagBuffer buf) const {
+    for (uint32_t i = 0; i < N; ++i)
+      {
+        buf.WriteU8 (N);
+      }
+  }
+  virtual void Deserialize (TagBuffer buf) {
+    for (uint32_t i = 0; i < N; ++i)
+      {
+        uint8_t v = buf.ReadU8 ();
+        if (v != N)
+          {
+            m_error = true;
+          }
+      }
+  }
+  virtual void Print (std::ostream &os) const {
+    os << N;
+  }
+  ATestTag ()
+    : ATestTagBase () {}
+};
+
+class ATestHeaderBase : public Header
+{
+public:
+  ATestHeaderBase () : Header (), m_error (false) {}
+  bool m_error;
+};
+
+template <int N>
+class ATestHeader : public ATestHeaderBase
+{
+public:
+  static TypeId GetTypeId (void) {
+    std::ostringstream oss;
+    oss << "anon::ATestHeader<" << N << ">";
+    static TypeId tid = TypeId (oss.str ().c_str ())
+      .SetParent<Header> ()
+      .AddConstructor<ATestHeader<N> > ()
+      .HideFromDocumentation ()
+    ;
+    return tid;
+  }
+  virtual TypeId GetInstanceTypeId (void) const {
+    return GetTypeId ();
+  }
+  virtual uint32_t GetSerializedSize (void) const {
+    return N;
+  }
+  virtual void Serialize (Buffer::Iterator iter) const {
+    for (uint32_t i = 0; i < N; ++i)
+      {
+        iter.WriteU8 (N);
+      }
+  }
+  virtual uint32_t Deserialize (Buffer::Iterator iter) {
+    for (uint32_t i = 0; i < N; ++i)
+      {
+        uint8_t v = iter.ReadU8 ();
+        if (v != N)
+          {
+            m_error = true;
+          }
+      }
+    return N;
+  }
+  virtual void Print (std::ostream &os) const {
+  }
+  ATestHeader ()
+    : ATestHeaderBase () {}
+
+};
+
+class ATestTrailerBase : public Trailer
+{
+public:
+  ATestTrailerBase () : Trailer (), m_error (false) {}
+  bool m_error;
+};
+
+template <int N>
+class ATestTrailer : public ATestTrailerBase
+{
+public:
+  static TypeId GetTypeId (void) {
+    std::ostringstream oss;
+    oss << "anon::ATestTrailer<" << N << ">";
+    static TypeId tid = TypeId (oss.str ().c_str ())
+      .SetParent<Header> ()
+      .AddConstructor<ATestTrailer<N> > ()
+      .HideFromDocumentation ()
+    ;
+    return tid;
+  }
+  virtual TypeId GetInstanceTypeId (void) const {
+    return GetTypeId ();
+  }
+  virtual uint32_t GetSerializedSize (void) const {
+    return N;
+  }
+  virtual void Serialize (Buffer::Iterator iter) const {
+    iter.Prev (N);
+    for (uint32_t i = 0; i < N; ++i)
+      {
+        iter.WriteU8 (N);
+      }
+  }
+  virtual uint32_t Deserialize (Buffer::Iterator iter) {
+    iter.Prev (N);
+    for (uint32_t i = 0; i < N; ++i)
+      {
+        uint8_t v = iter.ReadU8 ();
+        if (v != N)
+          {
+            m_error = true;
+          }
+      }
+    return N;
+  }
+  virtual void Print (std::ostream &os) const {
+  }
+  ATestTrailer ()
+    : ATestTrailerBase () {}
+
+};
+
+
+struct Expected
+{
+  Expected (uint32_t n_, uint32_t start_, uint32_t end_)
+    : n (n_), start (start_), end (end_) {}
+
+  uint32_t n;
+  uint32_t start;
+  uint32_t end;
+};
+
+}
+
+// tag name, start, end
+#define E(a,b,c) a,b,c
+
+#define CHECK(p, n, ...)                                \
+  DoCheck (p, __FILE__, __LINE__, n, __VA_ARGS__)
+
+class PacketTest : public TestCase
+{
+public:
+  PacketTest ();
+  virtual void DoRun (void);
+private:
+  void DoCheck (Ptr<const Packet> p, const char *file, int line, uint32_t n, ...);
+};
+
+
+PacketTest::PacketTest ()
+  : TestCase ("Packet") {
+}
+
+void
+PacketTest::DoCheck (Ptr<const Packet> p, const char *file, int line, uint32_t n, ...)
+{
+  std::vector<struct Expected> expected;
+  va_list ap;
+  va_start (ap, n);
+  for (uint32_t k = 0; k < n; ++k)
+    {
+      uint32_t N = va_arg (ap, uint32_t);
+      uint32_t start = va_arg (ap, uint32_t);
+      uint32_t end = va_arg (ap, uint32_t);
+      expected.push_back (Expected (N, start, end));
+    }
+  va_end (ap);
+
+  ByteTagIterator i = p->GetByteTagIterator ();
+  uint32_t j = 0;
+  while (i.HasNext () && j < expected.size ())
+    {
+      ByteTagIterator::Item item = i.Next ();
+      struct Expected e = expected[j];
+      std::ostringstream oss;
+      oss << "anon::ATestTag<" << e.n << ">";
+      NS_TEST_EXPECT_MSG_EQ_INTERNAL (item.GetTypeId ().GetName (), oss.str (), "trivial", file, line);
+      NS_TEST_EXPECT_MSG_EQ_INTERNAL (item.GetStart (), e.start, "trivial", file, line);
+      NS_TEST_EXPECT_MSG_EQ_INTERNAL (item.GetEnd (), e.end, "trivial", file, line);
+      ATestTagBase *tag = dynamic_cast<ATestTagBase *> (item.GetTypeId ().GetConstructor () ());
+      NS_TEST_EXPECT_MSG_NE (tag, 0, "trivial");
+      item.GetTag (*tag);
+      NS_TEST_EXPECT_MSG_EQ (tag->m_error, false, "trivial");
+      delete tag;
+      j++;
+    }
+  NS_TEST_EXPECT_MSG_EQ (i.HasNext (), false, "Nothing left");
+  NS_TEST_EXPECT_MSG_EQ (j, expected.size (), "Size match");
+}
+
+void
+PacketTest::DoRun (void)
+{
+  Ptr<Packet> pkt1 = Create<Packet> (reinterpret_cast<const uint8_t*> ("hello"), 5);
+  Ptr<Packet> pkt2 = Create<Packet> (reinterpret_cast<const uint8_t*> (" world"), 6);
+  Ptr<Packet> packet = Create<Packet> ();
+  packet->AddAtEnd (pkt1);
+  packet->AddAtEnd (pkt2);
+
+  NS_TEST_EXPECT_MSG_EQ (packet->GetSize (), 11, "trivial");
+
+  uint8_t *buf = new uint8_t[packet->GetSize ()];
+  packet->CopyData (buf, packet->GetSize ());
+
+  std::string msg = std::string (reinterpret_cast<const char *>(buf),
+                                 packet->GetSize ());
+  delete [] buf;
+
+  NS_TEST_EXPECT_MSG_EQ (msg, "hello world", "trivial");
+
+
+  Ptr<const Packet> p = Create<Packet> (1000);
+
+  p->AddByteTag (ATestTag<1> ());
+  CHECK (p, 1, E (1, 0, 1000));
+  Ptr<const Packet> copy = p->Copy ();
+  CHECK (copy, 1, E (1, 0, 1000));
+
+  p->AddByteTag (ATestTag<2> ());
+  CHECK (p, 2, E (1, 0, 1000), E(2, 0, 1000));
+  CHECK (copy, 1, E (1, 0, 1000));
+
+  {
+    Packet c0 = *copy;
+    Packet c1 = *copy;
+    c0 = c1;
+    CHECK (&c0, 1, E (1, 0, 1000));
+    CHECK (&c1, 1, E (1, 0, 1000));
+    CHECK (copy, 1, E (1, 0, 1000));
+    c0.AddByteTag (ATestTag<10> ());
+    CHECK (&c0, 2, E (1, 0, 1000), E (10, 0, 1000));
+    CHECK (&c1, 1, E (1, 0, 1000));
+    CHECK (copy, 1, E (1, 0, 1000));
+  }
+
+  Ptr<Packet> frag0 = p->CreateFragment (0, 10);
+  Ptr<Packet> frag1 = p->CreateFragment (10, 90);
+  Ptr<const Packet> frag2 = p->CreateFragment (100, 900);
+  frag0->AddByteTag (ATestTag<3> ());
+  CHECK (frag0, 3, E (1, 0, 10), E(2, 0, 10), E (3, 0, 10));
+  frag1->AddByteTag (ATestTag<4> ());
+  CHECK (frag1, 3, E (1, 0, 90), E(2, 0, 90), E (4, 0, 90));
+  frag2->AddByteTag (ATestTag<5> ());
+  CHECK (frag2, 3, E (1, 0, 900), E(2, 0, 900), E (5, 0, 900));
+
+  frag1->AddAtEnd (frag2);
+  CHECK (frag1, 6, E (1, 0, 90), E(2, 0, 90), E (4, 0, 90), E (1, 90, 990), E(2, 90, 990), E (5, 90, 990));
+
+  CHECK (frag0, 3, E (1, 0, 10), E(2, 0, 10), E (3, 0, 10));
+  frag0->AddAtEnd (frag1);
+  CHECK (frag0, 9, 
+         E (1, 0, 10), E(2, 0, 10), E (3, 0, 10),
+         E (1, 10, 100), E(2, 10, 100), E (4, 10, 100), 
+         E (1, 100, 1000), E(2, 100, 1000), E (5, 100, 1000));
+
+
+  // force caching a buffer of the right size.
+  frag0 = Create<Packet> (1000);
+  frag0->AddHeader (ATestHeader<10> ());
+  frag0 = 0;
+
+  p = Create<Packet> (1000);
+  p->AddByteTag (ATestTag<20> ());
+  CHECK (p, 1, E (20, 0, 1000));
+  frag0 = p->CreateFragment (10, 90);
+  CHECK (p, 1, E (20, 0, 1000));
+  CHECK (frag0, 1, E (20, 0, 90));
+  p = 0;
+  frag0->AddHeader (ATestHeader<10> ());
+  CHECK (frag0, 1, E (20, 10, 100));
+
+  {
+    Ptr<Packet> tmp = Create<Packet> (100);
+    tmp->AddByteTag (ATestTag<20> ());
+    CHECK (tmp, 1, E (20, 0, 100));
+    tmp->AddHeader (ATestHeader<10> ());
+    CHECK (tmp, 1, E (20, 10, 110));
+    ATestHeader<10> h;
+    tmp->RemoveHeader (h);
+    CHECK (tmp, 1, E (20, 0, 100));
+    tmp->AddHeader (ATestHeader<10> ());
+    CHECK (tmp, 1, E (20, 10, 110));
+
+    tmp = Create<Packet> (100);
+    tmp->AddByteTag (ATestTag<20> ());
+    CHECK (tmp, 1, E (20, 0, 100));
+    tmp->AddTrailer (ATestTrailer<10> ());
+    CHECK (tmp, 1, E (20, 0, 100));
+    ATestTrailer<10> t;
+    tmp->RemoveTrailer (t);
+    CHECK (tmp, 1, E (20, 0, 100));
+    tmp->AddTrailer (ATestTrailer<10> ());
+    CHECK (tmp, 1, E (20, 0, 100));
+
+  }
+
+  {
+    Ptr<Packet> tmp = Create<Packet> (0);
+    tmp->AddHeader (ATestHeader<156> ());
+    tmp->AddByteTag (ATestTag<20> ());
+    CHECK (tmp, 1, E (20, 0, 156));
+    tmp->RemoveAtStart (120);
+    CHECK (tmp, 1, E (20, 0, 36));
+    Ptr<Packet> a = Create<Packet> (0);
+    a->AddAtEnd (tmp);
+    CHECK (a, 1, E (20, 0, 36));
+  }
+
+  {
+    Ptr<Packet> tmp = Create<Packet> (0);
+    tmp->AddByteTag (ATestTag<20> ());
+    CHECK (tmp, 0, E (20, 0, 0));
+  }
+  {
+    Ptr<Packet> tmp = Create<Packet> (1000);
+    tmp->AddByteTag (ATestTag<20> ());
+    CHECK (tmp, 1, E (20, 0, 1000));
+    tmp->RemoveAtStart (1000);
+    CHECK (tmp, 0,  E (0,0,0));
+    Ptr<Packet> a = Create<Packet> (10);
+    a->AddByteTag (ATestTag<10> ());
+    CHECK (a, 1, E (10, 0, 10));
+    tmp->AddAtEnd (a);
+    CHECK (tmp, 1, E (10, 0, 10));
+  }
+
+  {
+    Packet p;
+    ATestTag<10> a;
+    p.AddPacketTag (a);
+    NS_TEST_EXPECT_MSG_EQ (p.PeekPacketTag (a), true, "trivial");
+    ATestTag<11> b;
+    p.AddPacketTag (b);
+    NS_TEST_EXPECT_MSG_EQ (p.PeekPacketTag (b), true, "trivial");
+    NS_TEST_EXPECT_MSG_EQ (p.PeekPacketTag (a), true, "trivial");
+    Packet copy = p;
+    NS_TEST_EXPECT_MSG_EQ (copy.PeekPacketTag (b), true, "trivial");
+    NS_TEST_EXPECT_MSG_EQ (copy.PeekPacketTag (a), true, "trivial");
+    ATestTag<12> c;
+    NS_TEST_EXPECT_MSG_EQ (copy.PeekPacketTag (c), false, "trivial");
+    copy.AddPacketTag (c);
+    NS_TEST_EXPECT_MSG_EQ (copy.PeekPacketTag (c), true, "trivial");
+    NS_TEST_EXPECT_MSG_EQ (copy.PeekPacketTag (b), true, "trivial");
+    NS_TEST_EXPECT_MSG_EQ (copy.PeekPacketTag (a), true, "trivial");
+    NS_TEST_EXPECT_MSG_EQ (p.PeekPacketTag (c), false, "trivial");
+    copy.RemovePacketTag (b);
+    NS_TEST_EXPECT_MSG_EQ (copy.PeekPacketTag (b), false, "trivial");
+    NS_TEST_EXPECT_MSG_EQ (p.PeekPacketTag (b), true, "trivial");
+    p.RemovePacketTag (a);
+    NS_TEST_EXPECT_MSG_EQ (p.PeekPacketTag (a), false, "trivial");
+    NS_TEST_EXPECT_MSG_EQ (copy.PeekPacketTag (a), true, "trivial");
+    NS_TEST_EXPECT_MSG_EQ (p.PeekPacketTag (c), false, "trivial");
+    NS_TEST_EXPECT_MSG_EQ (copy.PeekPacketTag (c), true, "trivial");
+    p.RemoveAllPacketTags ();
+    NS_TEST_EXPECT_MSG_EQ (p.PeekPacketTag (b), false, "trivial");
+  }
+
+  {
+    // bug 572
+    Ptr<Packet> tmp = Create<Packet> (1000);
+    tmp->AddByteTag (ATestTag<20> ());
+    CHECK (tmp, 1, E (20, 0, 1000));
+    tmp->AddHeader (ATestHeader<2> ());
+    CHECK (tmp, 1, E (20, 2, 1002));
+    tmp->RemoveAtStart (1);
+    CHECK (tmp, 1, E (20, 1, 1001));
+#if 0
+    tmp->PeekData ();
+    CHECK (tmp, 1, E (20, 1, 1001));
+#endif
+  }
+}
+//-----------------------------------------------------------------------------
+class PacketTestSuite : public TestSuite
+{
+public:
+  PacketTestSuite ();
+};
+
+PacketTestSuite::PacketTestSuite ()
+  : TestSuite ("packet", UNIT)
+{
+  AddTestCase (new PacketTest);
+}
+
+static PacketTestSuite g_packetTestSuite;
+
+
+} // namespace ns3