Attachment #3108 for bug #2924

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* ``bool DoEnqueue (Ptr<QueueDiscItem> item)``:  Enqueue a packet
* ``Ptr<QueueDiscItem> DoDequeue (void)``:  Dequeue a packet
* ``Ptr<const QueueDiscItem> DoPeek (void) const``: Peek a packet
* ``bool CheckConfig (void) const``: Check if the configuration is correct
* ``void InitializeParams (void)``: Initialize queue disc parameters

and may override the default implementation of the following method:

* ``Ptr<const QueueDiscItem> DoPeek (void) const``: Peek the next packet to extract

The default implementation of the ``DoPeek`` method is based on the qdisc_peek_dequeued
function of the Linux kernel, which dequeues a packet and retains it in the
queue disc as a requeued packet. This approach is recommended
especially for queue discs for which it is not obvious what is the next
packet that will be dequeued (e.g., queue discs having multiple internal
queues or child queue discs or queue discs that drop packets after dequeue).
Consequently, if a queue disc queries a child queue disc with the ``Peek`` method,
then it has to use the ``DequeuePeeked`` method instead of the ``Dequeue`` method
to actually dequeue the peeked packet from the child queue disc.

The C++ base class QueueDisc implements:

* methods to add/get a single queue, class or filter and methods to get the number \




  return m_dropNext;
}

Ptr<const QueueDiscItem>
CoDelQueueDisc::DoPeek (void)
{
  NS_LOG_FUNCTION (this);

  Ptr<const QueueDiscItem> item = PeekDequeued ();

  if (!item)
    {
      NS_LOG_LOGIC ("Queue empty");
      return 0;
    }

  NS_LOG_LOGIC ("Number packets " << GetInternalQueue (0)->GetNPackets ());
  NS_LOG_LOGIC ("Number bytes " << GetInternalQueue (0)->GetNBytes ());

  return item;
}

bool
CoDelQueueDisc::CoDelTimeAfter (uint32_t a, uint32_t b)
{

(-)a/src/traffic-control/model/codel-queue-disc.h (-1 lines)

Lines 124-130 private:	Link Here

124

*/

124

*/

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  virtual Ptr<QueueDiscItem> DoDequeue (void);

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  virtual Ptr<QueueDiscItem> DoDequeue (void);

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  virtual Ptr<const QueueDiscItem> DoPeek (void);

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  virtual bool CheckConfig (void);

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  virtual bool CheckConfig (void);

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/**

129

/**




  return item;
}

Ptr<const QueueDiscItem>
FqCoDelQueueDisc::DoPeek (void)
{
  NS_LOG_FUNCTION (this);

  return PeekDequeued ();
}

bool
FqCoDelQueueDisc::CheckConfig (void)
{

(-)a/src/traffic-control/model/fq-codel-queue-disc.h (-1 lines)

Lines 133-139 public:	Link Here

133

private:

133

private:

134

  virtual bool DoEnqueue (Ptr<QueueDiscItem> item);

134

  virtual bool DoEnqueue (Ptr<QueueDiscItem> item);

135

  virtual Ptr<QueueDiscItem> DoDequeue (void);

135

  virtual Ptr<QueueDiscItem> DoDequeue (void);

136

  virtual Ptr<const QueueDiscItem> DoPeek (void);

137

  virtual bool CheckConfig (void);

136

  virtual bool CheckConfig (void);

138

  virtual void InitializeParams (void);

137

  virtual void InitializeParams (void);

139

138




  return item;
}

Ptr<const QueueDiscItem>
PieQueueDisc::DoPeek ()
{
  NS_LOG_FUNCTION (this);

  Ptr<const QueueDiscItem> item = PeekDequeued ();

  if (!item)
    {
      NS_LOG_LOGIC ("Queue empty");
      return 0;
    }

  NS_LOG_LOGIC ("Number packets " << GetInternalQueue (0)->GetNPackets ());
  NS_LOG_LOGIC ("Number bytes " << GetInternalQueue (0)->GetNBytes ());

  return item;
}

bool
PieQueueDisc::CheckConfig (void)
{

(-)a/src/traffic-control/model/pie-queue-disc.h (-1 lines)

Lines 107-113 protected:	Link Here

107

private:

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private:

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  virtual bool DoEnqueue (Ptr<QueueDiscItem> item);

108

  virtual bool DoEnqueue (Ptr<QueueDiscItem> item);

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  virtual Ptr<QueueDiscItem> DoDequeue (void);

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  virtual Ptr<QueueDiscItem> DoDequeue (void);

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  virtual Ptr<const QueueDiscItem> DoPeek (void);

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  virtual bool CheckConfig (void);

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  virtual bool CheckConfig (void);

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/**

112

/**

(-)a/src/traffic-control/model/queue-disc.cc (-1 / +1 lines)

Lines 877-883 QueueDisc::Peek (void)	Link Here

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Ptr<const QueueDiscItem>

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Ptr<const QueueDiscItem>

880

QueueDisc::PeekDequeued (void)

880

QueueDisc::DoPeek (void)

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  NS_LOG_FUNCTION (this);

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  NS_LOG_FUNCTION (this);

883




  /**
   * Request the queue discipline to extract a packet. This function only updates
   * the statistics and calls the (private) DoDequeue function, which must be
   * implemented by derived classes. Use DequeuePeeked instead of this method if
   * the queue disc has been previously queried with Peek.
   * \return 0 if the operation was not successful; the item otherwise.
   */
  Ptr<QueueDiscItem> Dequeue (void);

  /**
   * Get a copy of the next packet the queue discipline will extract, without
   * actually extracting the packet. This function only calls the (private)
   * DoPeek function.
   * \return 0 if the operation was not successful; the item otherwise.
   */
  Ptr<const QueueDiscItem> Peek (void);

  /**
   * Extract from the queue disc the packet that has been dequeued by calling
   * Peek, if any, or dequeue a packet, otherwise. Use this method instead of
   * Dequeue if the queue disc has been previously queried with Peek.
   *
   * \return 0 if the operation was not successful; the item otherwise.
   */

   */
  bool Mark (Ptr<QueueDiscItem> item, const char* reason);

  /**
   * Dequeue a packet and retain it in the queue disc as a requeued packet.
   * The packet is not traced as requeued, nor is the total count of requeued
   * packets increased. The dequeued packet is not counted in the backlog of
   * the queue disc and is actually extracted from the queue disc by calling
   * DequeuePeeked. Queue discs can point their DoPeek method to this one. This
   * is recommended especially for queue discs for which it is not obvious what
   * is the next packet that will be dequeued (e.g., queue discs having multiple
   * internal queues or child queue discs or queue discs that drop packets
   * after dequeue).
   *
   * \return 0 if the operation was not successful; the item otherwise.
   */
  Ptr<const QueueDiscItem> PeekDequeued (void);

private:
  /**
   * \brief Copy constructor

  virtual Ptr<QueueDiscItem> DoDequeue (void) = 0;

  /**
   * \brief Return a copy of the next packet the queue disc will extract.
   *
   * The implementation of this method is based on the qdisc_peek_dequeued
   * function of the Linux kernel, which dequeues a packet and retains it in the
   * queue disc as a requeued packet. The packet is not traced as requeued, nor
   * is the total count of requeued packets increased. The dequeued packet is
   * not counted in the backlog of the queue disc and is actually extracted from
   * the queue disc by calling DequeuePeeked. This approach is recommended
   * especially for queue discs for which it is not obvious what is the next
   * packet that will be dequeued (e.g., queue discs having multiple internal
   * queues or child queue discs or queue discs that drop packets after dequeue).
   * Subclasses can however provide their own implementation of this method that
   * overrides the default one.
   *
   * \return 0 if the operation was not successful; the packet otherwise.
   */
  virtual Ptr<const QueueDiscItem> DoPeek (void);

  /**
   * Check whether the current configuration is correct. Default objects (such




  return retval;
}

Ptr<const QueueDiscItem>
TbfQueueDisc::DoPeek ()
{
  NS_LOG_FUNCTION (this);

  Ptr<const QueueDiscItem> item = PeekDequeued ();

  if (!item)
    {
      NS_LOG_LOGIC ("No packet returned");
      return 0;
    }

  NS_LOG_LOGIC ("Current queue size: " << GetNPackets () << " packets, " << GetNBytes () << " bytes");

  return item;
}

Ptr<QueueDiscItem>
TbfQueueDisc::DoDequeue (void)
{

(-)a/src/traffic-control/model/tbf-queue-disc.h (-1 lines)

Lines 149-155 private:	Link Here

149

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  virtual bool DoEnqueue (Ptr<QueueDiscItem> item);

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  virtual bool DoEnqueue (Ptr<QueueDiscItem> item);

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  virtual Ptr<QueueDiscItem> DoDequeue (void);

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  virtual Ptr<QueueDiscItem> DoDequeue (void);

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  virtual Ptr<const QueueDiscItem> DoPeek (void);

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  virtual bool CheckConfig (void);

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  virtual bool CheckConfig (void);

154

  virtual void InitializeParams (void);

153

  virtual void InitializeParams (void);

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