packet.h

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/*
 * 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>
 */
#ifndef PACKET_H
#define PACKET_H
 
#include "buffer.h"
#include "byte-tag-list.h"
#include "header.h"
#include "nix-vector.h"
#include "packet-metadata.h"
#include "packet-tag-list.h"
#include "tag.h"
#include "trailer.h"
 
#include "ns3/assert.h"
#include "ns3/callback.h"
#include "ns3/mac48-address.h"
#include "ns3/ptr.h"
 
#include <stdint.h>
 
namespace ns3
{
 
// Forward declaration
class Address;
 
/**
 * \ingroup network
 * \defgroup packet Packet
 */
 
/**
 * \ingroup packet
 * \brief Iterator over the set of byte tags in a packet
 *
 * This is a java-style iterator.
 */
class ByteTagIterator
{
  public:
    /**
     * \brief Identifies a byte tag and a set of bytes within a packet
     * to which the tag applies.
     */
    class Item
    {
      public:
        /**
         * \returns the ns3::TypeId associated to this tag.
         */
        TypeId GetTypeId() const;
        /**
         * \returns the index of the first byte tagged by this tag.
         *
         * \brief The index is an offset from the start of the packet.
         */
        uint32_t GetStart() const;
        /**
         * \returns the index of the last byte tagged by this tag.
         *
         * \brief The index is an offset from the start of the packet.
         */
        uint32_t GetEnd() const;
        /**
         * \brief Read the requested tag and store it in the user-provided tag instance.
         *
         * \param tag the user tag to which the data should be copied.
         *
         * This method will crash if the type of the tag provided
         * by the user does not match the type of the underlying tag.
         */
        void GetTag(Tag& tag) const;
 
      private:
        /// Friend class
        friend class ByteTagIterator;
        /**
         * \brief Constructor
         * \param tid the ns3::TypeId associated to this tag.
         * \param start the index of the first byte tagged by this tag.
         * \param end the index of the last byte tagged by this tag.
         * \param buffer the buffer associated with this tag.
         */
        Item(TypeId tid, uint32_t start, uint32_t end, TagBuffer buffer);
 
        TypeId m_tid;       //!< the ns3::TypeId associated to this tag.
        uint32_t m_start;   //!< the index of the first byte tagged by this tag.
        uint32_t m_end;     //!< the index of the last byte tagged by this tag.
        TagBuffer m_buffer; //!< the buffer associated with this tag.
    };
 
    /**
     * \returns true if calling Next is safe, false otherwise.
     */
    bool HasNext() const;
    /**
     * \returns the next item found and prepare for the next one.
     */
    Item Next();
 
  private:
    /// Friend class
    friend class Packet;
    /**
     * Copy Constructor
     * \param i object to copy
     */
    ByteTagIterator(ByteTagList::Iterator i);
    ByteTagList::Iterator m_current; //!< actual position over the set of byte tags in a packet
};
 
/**
 * \ingroup packet
 * \brief Iterator over the set of packet tags in a packet
 *
 * This is a java-style iterator.
 */
class PacketTagIterator
{
  public:
    /**
     * Identifies a packet tag within a packet.
     */
    class Item
    {
      public:
        /**
         * \returns the ns3::TypeId associated to this tag.
         */
        TypeId GetTypeId() const;
        /**
         * Read the requested tag and store it in the user-provided tag instance.
         *
         * \param tag the user tag to which the data should be copied.
         *
         * This method will crash if the type of the tag provided
         * by the user does not match the type of the underlying tag.
         */
        void GetTag(Tag& tag) const;
 
      private:
        /// Friend class
        friend class PacketTagIterator;
        /**
         * Constructor
         * \param data the data to copy.
         */
        Item(const PacketTagList::TagData* data);
        const PacketTagList::TagData* m_data; //!< the tag data
    };
 
    /**
     * \returns true if calling Next is safe, false otherwise.
     */
    bool HasNext() const;
    /**
     * \returns the next item found and prepare for the next one.
     */
    Item Next();
 
  private:
    /// Friend class
    friend class Packet;
    /**
     * Constructor
     * \param head head of the items
     */
    PacketTagIterator(const PacketTagList::TagData* head);
    const PacketTagList::TagData* m_current; //!< actual position over the set of tags in a packet
};
 
/**
 * \ingroup packet
 * \brief network packets
 *
 * Each network packet contains a byte buffer, a set of byte tags, a set of
 * packet tags, and metadata.
 *
 * - The byte buffer stores the serialized content of the headers and trailers
 * added to a packet. The serialized representation of these headers is expected
 * to match that of real network packets bit for bit (although nothing
 * forces you to do this) which means that the content of a packet buffer
 * is expected to be that of a real packet.
 *
 * - The metadata describes the type of the headers and trailers which
 * were serialized in the byte buffer. The maintenance of metadata is
 * optional and disabled by default. To enable it, you must call
 * Packet::EnablePrinting and this will allow you to get non-empty
 * output from Packet::Print. If you wish to only enable
 * checking of metadata, and do not need any printing capability, you can
 * call Packet::EnableChecking: its runtime cost is lower than
 * Packet::EnablePrinting.
 *
 * - The set of tags contain simulation-specific information which cannot
 * be stored in the packet byte buffer because the protocol headers or trailers
 * have no standard-conformant field for this information. So-called
 * 'byte' tags are used to tag a subset of the bytes in the packet byte buffer
 * while 'packet' tags are used to tag the packet itself. The main difference
 * between these two kinds of tags is what happens when packets are copied,
 * fragmented, and reassembled: 'byte' tags follow bytes while 'packet' tags
 * follow packets. Another important difference between these two kinds of tags
 * is that byte tags cannot be removed and are expected to be written once,
 * and read many times, while packet tags are expected to be written once,
 * read many times, and removed exactly once. An example of a 'byte'
 * tag is a FlowIdTag which contains a flow id and is set by the application
 * generating traffic. An example of a 'packet' tag is a cross-layer
 * qos class id set by an application and processed by a lower-level MAC
 * layer.
 *
 * Implementing a new type of Header or Trailer for a new protocol is
 * pretty easy and is a matter of creating a subclass of the ns3::Header
 * or of the ns3::Trailer base class, and implementing the methods
 * described in their respective API documentation.
 *
 * Implementing a new type of Tag requires roughly the same amount of
 * work and this work is described in the ns3::Tag API documentation.
 *
 * The performance aspects copy-on-write semantics of the
 * Packet API are discussed in \ref packetperf
 */
class Packet : public SimpleRefCount<Packet>
{
  public:
    /**
     * \brief Create an empty packet with a new uid (as returned
     * by getUid).
     */
    Packet();
    /**
     * \brief Copy constructor
     * \param o object to copy
     */
    Packet(const Packet& o);
    /**
     * \brief Basic assignment
     * \param o object to copy
     * \return the copied object
     */
    Packet& operator=(const Packet& o);
    /**
     * \brief Create a packet with a zero-filled payload.
     *
     * The memory necessary for the payload is not allocated:
     * it will be allocated at any later point if you attempt
     * to fragment this packet or to access the zero-filled
     * bytes. The packet is allocated with a new uid (as
     * returned by getUid).
     *
     * \param size the size of the zero-filled payload
     */
    Packet(uint32_t size);
    /**
     * \brief Create a new packet from the serialized buffer.
     *
     * This new packet
     * is identical to the serialized packet contained in the buffer
     * and is magically deserialized for you
     *
     * \param buffer the serialized packet to be created
     * \param size the size of the packet for deserialization
     * \param magic allows packet deserialization;
     *        asserts when set to false
     */
    Packet(const uint8_t* buffer, uint32_t size, bool magic);
    /**
     * \brief Create a packet with payload filled with the content
     * of this buffer.
     *
     * The input data is copied: the input
     * buffer is untouched.
     *
     * \param buffer the data to store in the packet.
     * \param size the size of the input buffer.
     */
    Packet(const uint8_t* buffer, uint32_t size);
    /**
     * \brief Create a new packet which contains a fragment of the original
     * packet.
     *
     * The returned packet shares the same uid as this packet.
     *
     * \param start offset from start of packet to start of fragment to create
     * \param length length of fragment to create
     * \returns a fragment of the original packet
     */
    Ptr<Packet> CreateFragment(uint32_t start, uint32_t length) const;
    /**
     * \brief Returns the the size in bytes of the packet (including the zero-filled
     * initial payload).
     *
     * \returns the size in bytes of the packet
     */
    inline uint32_t GetSize() const;
    /**
     * \brief Add header to this packet.
     *
     * This method invokes the
     * Header::GetSerializedSize and Header::Serialize
     * methods to reserve space in the buffer and request the
     * header to serialize itself in the packet buffer.
     *
     * \param header a reference to the header to add to this packet.
     */
    void AddHeader(const Header& header);
    /**
     * \brief Deserialize and remove the header from the internal buffer.
     *
     * This method invokes Header::Deserialize (begin) and should be used for
     * fixed-length headers.
     *
     * \param header a reference to the header to remove from the internal buffer.
     * \returns the number of bytes removed from the packet.
     */
    uint32_t RemoveHeader(Header& header);
    /**
     * \brief Deserialize and remove the header from the internal buffer.
     *
     * This method invokes Header::Deserialize (begin, end) and should be
     * used for variable-length headers (where the size is determined somehow
     * by the caller).
     *
     * \param header a reference to the header to remove from the internal buffer.
     * \param size number of bytes to deserialize
     * \returns the number of bytes removed from the packet.
     */
    uint32_t RemoveHeader(Header& header, uint32_t size);
    /**
     * \brief Deserialize but does _not_ remove the header from the internal buffer.
     * s
     * This method invokes Header::Deserialize.
     *
     * \param header a reference to the header to read from the internal buffer.
     * \returns the number of bytes read from the packet.
     */
    uint32_t PeekHeader(Header& header) const;
    /**
     * \brief Deserialize but does _not_ remove the header from the internal buffer.
     * s
     * This method invokes Header::Deserialize (begin, end) and should be used
     * for variable-length headers (where the size is determined somehow
     * by the caller).
     *
     * \param header a reference to the header to read from the internal buffer.
     * \param size number of bytes to deserialize
     * \returns the number of bytes read from the packet.
     */
    uint32_t PeekHeader(Header& header, uint32_t size) const;
    /**
     * \brief Add trailer to this packet.
     *
     * This method invokes the
     * Trailer::GetSerializedSize and Trailer::Serialize
     * methods to reserve space in the buffer and request the trailer
     * to serialize itself in the packet buffer.
     *
     * \param trailer a reference to the trailer to add to this packet.
     */
    void AddTrailer(const Trailer& trailer);
    /**
     * \brief Remove a deserialized trailer from the internal buffer.
     *
     * This method invokes the Deserialize method.
     *
     * \param trailer a reference to the trailer to remove from the internal buffer.
     * \returns the number of bytes removed from the end of the packet.
     */
    uint32_t RemoveTrailer(Trailer& trailer);
    /**
     * \brief Deserialize but does _not_ remove a trailer from the internal buffer.
     *
     * This method invokes the Trailer::Deserialize method.
     *
     * \param trailer a reference to the trailer to read from the internal buffer.
     * \returns the number of bytes read from the end of the packet.
     */
    uint32_t PeekTrailer(Trailer& trailer);
 
    /**
     * \brief Concatenate the input packet at the end of the current
     * packet.
     *
     * This does not alter the uid of either packet.
     *
     * \param packet packet to concatenate
     */
    void AddAtEnd(Ptr<const Packet> packet);
    /**
     * \brief Add a zero-filled padding to the packet.
     *
     * \param size number of padding bytes to add.
     */
    void AddPaddingAtEnd(uint32_t size);
    /**
     * \brief Remove size bytes from the end of the current packet.
     *
     * It is safe to remove more bytes than are present in
     * the packet.
     *
     * \param size number of bytes from remove
     */
    void RemoveAtEnd(uint32_t size);
    /**
     * \brief Remove size bytes from the start of the current packet.
     *
     * It is safe to remove more bytes than are present in
     * the packet.
     *
     * \param size number of bytes from remove
     */
    void RemoveAtStart(uint32_t size);
 
    /**
     * \brief Copy the packet contents to a byte buffer.
     *
     * \param buffer a pointer to a byte buffer where the packet data
     *        should be copied.
     * \param size the size of the byte buffer.
     * \returns the number of bytes read from the packet
     *
     * No more than \b size bytes will be copied by this function.
     */
    uint32_t CopyData(uint8_t* buffer, uint32_t size) const;
 
    /**
     * \brief Copy the packet contents to an output stream.
     *
     * \param os pointer to output stream in which we want
     *        to write the packet data.
     * \param size the maximum number of bytes we want to write
     *        in the output stream.
     */
    void CopyData(std::ostream* os, uint32_t size) const;
 
    /**
     * \brief performs a COW copy of the packet.
     *
     * \returns a COW copy of the packet.
     *
     * The returns packet will behave like an independent copy of
     * the original packet, even though they both share the
     * same datasets internally.
     */
    Ptr<Packet> Copy() const;
 
    /**
     * \brief Returns the packet's Uid.
     *
     * A packet is allocated a new uid when it is created
     * empty or with zero-filled payload.
     *
     * Note: This uid is an internal uid and cannot be counted on to
     * provide an accurate counter of how many "simulated packets" of a
     * particular protocol are in the system. It is not trivial to make
     * this uid into such a counter, because of questions such as what
     * should the uid be when the packet is sent over broadcast media, or
     * when fragmentation occurs. If a user wants to trace actual packet
     * counts, he or she should look at e.g. the IP ID field or transport
     * sequence numbers, or other packet or frame counters at other
     * protocol layers.
     *
     * \returns an integer identifier which uniquely
     *          identifies this packet.
     */
    uint64_t GetUid() const;
 
    /**
     * \brief Print the packet contents.
     *
     * \param os output stream in which the data should be printed.
     *
     * Iterate over the headers and trailers present in this packet,
     * from the first header to the last trailer and invoke, for
     * each of them, the user-provided method Header::DoPrint or
     * Trailer::DoPrint methods.
     */
    void Print(std::ostream& os) const;
 
    /**
     * \brief Return a string representation of the packet
     *
     * An empty string is returned if you haven't called EnablePrinting ()
     *
     * \return String representation
     */
    std::string ToString() const;
 
    /**
     * \brief Returns an iterator which points to the first 'item'
     * stored in this buffer.
     *
     * Note that this iterator will point
     * to an empty array of items if you don't call EnablePrinting
     * or EnableChecking before.
     *
     * \returns an iterator
     *
     * \sa EnablePrinting EnableChecking
     */
    PacketMetadata::ItemIterator BeginItem() const;
 
    /**
     * \brief Enable printing packets metadata.
     *
     * By default, packets do not keep around enough metadata to
     * perform the operations requested by the Print methods. If you
     * want to be able the Packet::Print method,
     * you need to invoke this method at least once during the
     * simulation setup and before any packet is created.
     */
    static void EnablePrinting();
    /**
     * \brief Enable packets metadata checking.
     *
     * The packet metadata is also used to perform extensive
     * sanity checks at runtime when performing operations on a
     * Packet. For example, this metadata is used to verify that
     * when you remove a header from a packet, this same header
     * was actually present at the front of the packet. These
     * errors will be detected and will abort the program.
     */
    static void EnableChecking();
 
    /**
     * \brief Returns number of bytes required for packet
     * serialization.
     *
     * \returns number of bytes required for packet
     * serialization
     *
     * For packet serialization, the total size is checked
     * in order to determine the size of the buffer
     * required for serialization
     */
    uint32_t GetSerializedSize() const;
 
    /**
     * \brief Serialize a packet, tags, and metadata into a byte buffer.
     *
     * \param buffer a raw byte buffer to which the packet will be serialized
     * \param maxSize the max size of the buffer for bounds checking
     *
     * \returns one if all data were serialized, zero if buffer size was too small.
     */
    uint32_t Serialize(uint8_t* buffer, uint32_t maxSize) const;
 
    /**
     * \brief Tag each byte included in this packet with a new byte tag.
     *
     * \param tag the new tag to add to this packet
     *
     * Note that adding a tag is a const operation which is pretty
     * un-intuitive. The rationale is that the content and behavior of
     * a packet is _not_ changed when a tag is added to a packet: any
     * code which was not aware of the new tag is going to work just
     * the same if the new tag is added. The real reason why adding a
     * tag was made a const operation is to allow a trace sink which gets
     * a packet to tag the packet, even if the packet is const (and most
     * trace sources should use const packets because it would be
     * totally evil to allow a trace sink to modify the content of a
     * packet).
     */
    void AddByteTag(const Tag& tag) const;
 
    /**
     * \brief Tag the indicated byte range of this packet with a new byte tag.
     *
     * As parameters for this method, we do not use indexes, but byte position.
     * Moreover, as there is no 0-th position, the first position is 1.
     *
     * As example, if you want to tag the first 10 bytes, you have to call
     * the method in this way:
     *
     * \code{.cpp}
         Ptr<Packet> p = ... ;
         SomeTag tag;
         p->AddByteTag (tag, 1, 10);
       \endcode
     *
     * \param tag the new tag to add to this packet
     * \param start the position of the first byte tagged by this tag
     * \param end the position of the last byte tagged by this tag
     */
    void AddByteTag(const Tag& tag, uint32_t start, uint32_t end) const;
    /**
     * \brief Returns an iterator over the set of byte tags included in this packet
     *
     * \returns an iterator over the set of byte tags included in this packet.
     */
    ByteTagIterator GetByteTagIterator() const;
    /**
     * \brief Finds the first tag matching the parameter Tag type
     *
     * \param tag the byte tag type to search in this packet
     * \returns true if the requested tag type was found, false otherwise.
     *
     * If the requested tag type is found, it is copied in the user's
     * provided tag instance.
     */
    bool FindFirstMatchingByteTag(Tag& tag) const;
 
    /**
     * \brief Remove all byte tags stored in this packet.
     */
    void RemoveAllByteTags();
 
    /**
     * \param os output stream in which the data should be printed.
     *
     * \brief Iterate over the byte tags present in this packet, and
     * invoke the Print method of each tag stored in the packet.
     */
    void PrintByteTags(std::ostream& os) const;
 
    /**
     * \brief Add a packet tag.
     *
     * \param tag the packet tag type to add.
     *
     * Note that this method is const, that is, it does not
     * modify the state of this packet, which is fairly
     * un-intuitive.  See AddByteTag"()" discussion.
     */
    void AddPacketTag(const Tag& tag) const;
    /**
     * \brief Remove a packet tag.
     *
     * \param tag the packet tag type to remove from this packet.
     *        The tag parameter is set to the value of the tag found.
     * \returns true if the requested tag is found, false
     *          otherwise.
     */
    bool RemovePacketTag(Tag& tag);
    /**
     * \brief Replace the value of a packet tag.
     *
     * \param tag the packet tag type to replace.  To get the old
     *        value of the tag, use PeekPacketTag first.
     * \returns true if the requested tag is found, false otherwise.
     *        If the tag isn't found, Add is performed instead (so
     *        the packet is guaranteed to have the new tag value
     *        either way).
     */
    bool ReplacePacketTag(Tag& tag);
    /**
     * \brief Search a matching tag and call Tag::Deserialize if it is found.
     *
     * \param tag the tag to search in this packet
     * \returns true if the requested tag is found, false
     *          otherwise.
     */
    bool PeekPacketTag(Tag& tag) const;
    /**
     * \brief Remove all packet tags.
     */
    void RemoveAllPacketTags();
 
    /**
     * \brief Print the list of packet tags.
     *
     * \param os the stream on which to print the tags.
     *
     * \sa Packet::AddPacketTag, Packet::RemovePacketTag, Packet::PeekPacketTag,
     *  Packet::RemoveAllPacketTags
     */
    void PrintPacketTags(std::ostream& os) const;
 
    /**
     * \brief Returns an object which can be used to iterate over the list of
     *  packet tags.
     *
     * \returns an object which can be used to iterate over the list of
     *  packet tags.
     */
    PacketTagIterator GetPacketTagIterator() const;
 
    /**
     * \brief Set the packet nix-vector.
     *
     * \note Note: This function supports a temporary solution
     * to a specific problem in this generic class, i.e.
     * how to associate something specific like nix-vector
     * with a packet.  This design methodology
     * should _not_ be followed, and is only here as an
     * impetus to fix this general issue.
     *
     * \warning For real this function is not const, as it is the
     * setter for a mutable variable member. The const qualifier
     * is needed to set a private mutable variable of const objects.
     *
     * \param nixVector the nix vector
     */
    void SetNixVector(Ptr<NixVector> nixVector) const;
    /**
     * \brief Get the packet nix-vector.
     *
     * See the comment on SetNixVector
     *
     * \returns the Nix vector
     */
    Ptr<NixVector> GetNixVector() const;
 
    /**
     * TracedCallback signature for Ptr<Packet>
     *
     * \param [in] packet The packet.
     */
    typedef void (*TracedCallback)(Ptr<const Packet> packet);
 
    /**
     * TracedCallback signature for packet and Address.
     *
     * \param [in] packet The packet.
     * \param [in] address The address.
     */
    typedef void (*AddressTracedCallback)(Ptr<const Packet> packet, const Address& address);
 
    /**
     * TracedCallback signature for packet and source/destination addresses.
     *
     * \param [in] packet The packet.
     * \param [in] srcAddress The source address.
     * \param [in] destAddress The destination address.
     */
    typedef void (*TwoAddressTracedCallback)(const Ptr<const Packet> packet,
                                             const Address& srcAddress,
                                             const Address& destAddress);
 
    /**
     * TracedCallback signature for packet and Mac48Address.
     *
     * \param [in] packet The packet.
     * \param [in] mac The Mac48Address.
     */
    typedef void (*Mac48AddressTracedCallback)(Ptr<const Packet> packet, Mac48Address mac);
 
    /**
     * TracedCallback signature for changes in packet size.
     *
     * \param [in] oldSize The previous packet's size.
     * \param [in] newSize The actual packet's size.
     */
    typedef void (*SizeTracedCallback)(uint32_t oldSize, uint32_t newSize);
 
    /**
     * TracedCallback signature for packet and SINR.
     *
     * \param [in] packet The packet.
     * \param [in] sinr The received SINR.
     */
    typedef void (*SinrTracedCallback)(Ptr<const Packet> packet, double sinr);
 
  private:
    /**
     * \brief Constructor
     * \param buffer the packet buffer
     * \param byteTagList the ByteTag list
     * \param packetTagList the packet's Tag list
     * \param metadata the packet's metadata
     */
    Packet(const Buffer& buffer,
           const ByteTagList& byteTagList,
           const PacketTagList& packetTagList,
           const PacketMetadata& metadata);
 
    /**
     * \brief Deserializes a packet.
     * \param [in] buffer the input buffer.
     * \param [in] size the buffer size.
     * \returns the number of deserialized bytes.
     */
    uint32_t Deserialize(const uint8_t* buffer, uint32_t size);
 
    Buffer m_buffer;               //!< the packet buffer (it's actual contents)
    ByteTagList m_byteTagList;     //!< the ByteTag list
    PacketTagList m_packetTagList; //!< the packet's Tag list
    PacketMetadata m_metadata;     //!< the packet's metadata
 
    /* Please see comments above about nix-vector */
    mutable Ptr<NixVector> m_nixVector; //!< the packet's Nix vector
 
    static uint32_t m_globalUid; //!< Global counter of packets Uid
};
 
/**
 * \brief Stream insertion operator.
 *
 * \param os the stream
 * \param packet the packet
 * \returns a reference to the stream
 */
std::ostream& operator<<(std::ostream& os, const Packet& packet);
 
/**
 * \ingroup network
 * \defgroup packetperf Packet Performance
 * The current implementation of the byte buffers and tag list is based
 * on COW (Copy On Write. An introduction to COW can be found in Scott
 * Meyer's "More Effective C++", items 17 and 29). What this means is that
 * copying packets without modifying them is very cheap (in terms of cpu
 * and memory usage) and modifying them can be also very cheap. What is
 * key for proper COW implementations is being
 * able to detect when a given modification of the state of a packet triggers
 * a full copy of the data prior to the modification: COW systems need
 * to detect when an operation is "dirty".
 *
 * Dirty operations:
 *   - ns3::Packet::AddHeader
 *   - ns3::Packet::AddTrailer
 *   - both versions of ns3::Packet::AddAtEnd
 *   - ns3::Packet::RemovePacketTag
 *   - ns3::Packet::ReplacePacketTag
 *
 * Non-dirty operations:
 *   - ns3::Packet::AddPacketTag
 *   - ns3::Packet::PeekPacketTag
 *   - ns3::Packet::RemoveAllPacketTags
 *   - ns3::Packet::AddByteTag
 *   - ns3::Packet::FindFirstMatchingByteTag
 *   - ns3::Packet::RemoveAllByteTags
 *   - ns3::Packet::RemoveHeader
 *   - ns3::Packet::RemoveTrailer
 *   - ns3::Packet::CreateFragment
 *   - ns3::Packet::RemoveAtStart
 *   - ns3::Packet::RemoveAtEnd
 *   - ns3::Packet::CopyData
 *
 * Dirty operations will always be slower than non-dirty operations,
 * sometimes by several orders of magnitude. However, even the
 * dirty operations have been optimized for common use-cases which
 * means that most of the time, these operations will not trigger
 * data copies and will thus be still very fast.
 */
 
} // namespace ns3
 
/****************************************************
 *  Implementation of inline methods for performance
 ****************************************************/
 
namespace ns3
{
 
uint32_t
Packet::GetSize() const
{
    return m_buffer.GetSize();
}
 
} // namespace ns3
 
#endif /* PACKET_H */