recipient-block-ack-agreement.cc

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/* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
/*
 * Copyright (c) 2020 Universita' degli Studi di Napoli Federico II
 *
 * 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: Stefano Avallone <stavallo@unina.it>
 */

#include "ns3/log.h"
#include "ns3/packet.h"
#include "recipient-block-ack-agreement.h"
#include "wifi-mac-queue-item.h"
#include "wifi-utils.h"
#include "mac-rx-middle.h"
#include "ctrl-headers.h"
#include <algorithm>

namespace ns3 {

NS_LOG_COMPONENT_DEFINE ("RecipientBlockAckAgreement");

bool
RecipientBlockAckAgreement::Compare::operator() (const Key& a, const Key& b) const
{
  return ((a.first - *a.second + SEQNO_SPACE_SIZE) % SEQNO_SPACE_SIZE)
         < ((b.first - *b.second + SEQNO_SPACE_SIZE) % SEQNO_SPACE_SIZE);
}

RecipientBlockAckAgreement::RecipientBlockAckAgreement (Mac48Address originator, bool amsduSupported,
                                                        uint8_t tid, uint16_t bufferSize, uint16_t timeout,
                                                        uint16_t startingSeq, bool htSupported)
  : BlockAckAgreement (originator, tid)
{
  NS_LOG_FUNCTION (this << originator << amsduSupported << +tid << bufferSize
                   << timeout << startingSeq << htSupported);

  m_amsduSupported = amsduSupported;
  m_bufferSize = bufferSize;
  m_timeout = timeout;
  m_startingSeq = startingSeq;
  m_htSupported = htSupported;

  m_scoreboard.Init (startingSeq, bufferSize);
  m_winStartB = startingSeq;
  m_winSizeB = bufferSize;
}

RecipientBlockAckAgreement::~RecipientBlockAckAgreement ()
{
  NS_LOG_FUNCTION_NOARGS ();
  m_bufferedMpdus.clear ();
  m_rxMiddle = 0;
}

void
RecipientBlockAckAgreement::SetMacRxMiddle (const Ptr<MacRxMiddle> rxMiddle)
{
  NS_LOG_FUNCTION (this << rxMiddle);
  m_rxMiddle = rxMiddle;
}

void
RecipientBlockAckAgreement::PassBufferedMpdusUntilFirstLost (void)
{
  NS_LOG_FUNCTION (this);

  // There cannot be old MPDUs in the buffer (we just check the MPDU with the
  // highest sequence number)
  NS_ASSERT (m_bufferedMpdus.empty () ||
             GetDistance (m_bufferedMpdus.rbegin ()->first.first, m_winStartB) < SEQNO_SPACE_HALF_SIZE);
  
  auto it = m_bufferedMpdus.begin ();

  while (it != m_bufferedMpdus.end () && it->first.first == m_winStartB)
    {
      NS_LOG_DEBUG ("Forwarding up: " << *it->second);
      m_rxMiddle->Receive (it->second);
      it = m_bufferedMpdus.erase (it);
      m_winStartB = (m_winStartB + 1) % SEQNO_SPACE_SIZE;
    }
}

void
RecipientBlockAckAgreement::PassBufferedMpdusWithSeqNumberLessThan (uint16_t newWinStartB)
{
  NS_LOG_FUNCTION (this << newWinStartB);

  // There cannot be old MPDUs in the buffer (we just check the MPDU with the
  // highest sequence number)
  NS_ASSERT (m_bufferedMpdus.empty () ||
             GetDistance (m_bufferedMpdus.rbegin ()->first.first, m_winStartB) < SEQNO_SPACE_HALF_SIZE);
  
  auto it = m_bufferedMpdus.begin ();

  while (it != m_bufferedMpdus.end ()
         && GetDistance (it->first.first, m_winStartB) < GetDistance (newWinStartB, m_winStartB))
    {
      NS_LOG_DEBUG ("Forwarding up: " << *it->second);
      m_rxMiddle->Receive (it->second);
      it = m_bufferedMpdus.erase (it);
    }
  m_winStartB = newWinStartB;
}

void
RecipientBlockAckAgreement::NotifyReceivedMpdu (Ptr<WifiMacQueueItem> mpdu)
{
  NS_LOG_FUNCTION (this << *mpdu);

  uint16_t mpduSeqNumber = mpdu->GetHeader ().GetSequenceNumber ();
  uint16_t distance = GetDistance (mpduSeqNumber, m_scoreboard.GetWinStart ());

  /* Update the scoreboard (see Section 10.24.7.3 of 802.11-2016) */
  if (distance < m_scoreboard.GetWinSize ())
    {
      // set to 1 the bit in position SN within the bitmap
      m_scoreboard.At (distance) = true;
    }
  else if (distance < SEQNO_SPACE_HALF_SIZE)
    {
      m_scoreboard.Advance (distance - m_scoreboard.GetWinSize () + 1);
      m_scoreboard.At (m_scoreboard.GetWinSize () - 1) = true;
    }

  distance = GetDistance (mpduSeqNumber, m_winStartB);

  /* Update the receive reordering buffer (see Section 10.24.7.6.2 of 802.11-2016) */
  if (distance < m_winSizeB)
    {
      // 1. Store the received MPDU in the buffer, if no MSDU with the same sequence
      // number is already present
      m_bufferedMpdus.insert ({{mpdu->GetHeader ().GetSequenceNumber (), &m_winStartB}, mpdu});

      // 2. Pass MSDUs or A-MSDUs up to the next MAC process if they are stored in
      // the buffer in order of increasing value of the Sequence Number subfield
      // starting with the MSDU or A-MSDU that has SN=WinStartB
      // 3. Set WinStartB to the value of the Sequence Number subfield of the last
      // MSDU or A-MSDU that was passed up to the next MAC process plus one.
      PassBufferedMpdusUntilFirstLost ();
    }
  else if (distance < SEQNO_SPACE_HALF_SIZE)
    {
      // 1. Store the received MPDU in the buffer, if no MSDU with the same sequence
      // number is already present
      m_bufferedMpdus.insert ({{mpdu->GetHeader ().GetSequenceNumber (), &m_winStartB}, mpdu});

      // 2. Set WinEndB = SN
      // 3. Set WinStartB = WinEndB – WinSizeB + 1
      // 4. Pass any complete MSDUs or A-MSDUs stored in the buffer with Sequence Number
      // subfield values that are lower than the new value of WinStartB up to the next
      // MAC process in order of increasing Sequence Number subfield value. Gaps may
      // exist in the Sequence Number subfield values of the MSDUs or A-MSDUs that are
      // passed up to the next MAC process.
      PassBufferedMpdusWithSeqNumberLessThan (mpdu->GetHeader ().GetSequenceNumber () - m_winSizeB + 1);

      // 5. Pass MSDUs or A-MSDUs stored in the buffer up to the next MAC process in
      // order of increasing value of the Sequence Number subfield starting with
      // WinStartB and proceeding sequentially until there is no buffered MSDU or
      // A-MSDU for the next sequential Sequence Number subfield value
      PassBufferedMpdusUntilFirstLost ();
    }
}

void
RecipientBlockAckAgreement::Flush (void)
{
  NS_LOG_FUNCTION (this);
  PassBufferedMpdusWithSeqNumberLessThan (m_scoreboard.GetWinStart ());
  PassBufferedMpdusUntilFirstLost ();
}

void
RecipientBlockAckAgreement::NotifyReceivedBar (uint16_t startingSequenceNumber)
{
  NS_LOG_FUNCTION (this << startingSequenceNumber);

  uint16_t distance = GetDistance (startingSequenceNumber, m_scoreboard.GetWinStart ());

  /* Update the scoreboard (see Section 10.24.7.3 of 802.11-2016) */
  if (distance > 0 && distance < m_scoreboard.GetWinSize ())
    {
      // advance by SSN - WinStartR, so that WinStartR becomes equal to SSN
      m_scoreboard.Advance (distance);
      NS_ASSERT (m_scoreboard.GetWinStart () == startingSequenceNumber);
    }
  else if (distance > 0 && distance < SEQNO_SPACE_HALF_SIZE)
    {
      // reset the window and set WinStartR to SSN
      m_scoreboard.Reset (startingSequenceNumber);
    }

  distance = GetDistance (startingSequenceNumber, m_winStartB);

  /* Update the receive reordering buffer (see Section 10.24.7.6.2 of 802.11-2016) */
  if (distance > 0 && distance < SEQNO_SPACE_HALF_SIZE)
    {
      // 1. set WinStartB = SSN
      // 3. Pass any complete MSDUs or A-MSDUs stored in the buffer with Sequence
      // Number subfield values that are lower than the new value of WinStartB up to
      // the next MAC process in order of increasing Sequence Number subfield value
      PassBufferedMpdusWithSeqNumberLessThan (startingSequenceNumber);

      // 4. Pass MSDUs or A-MSDUs stored in the buffer up to the next MAC process
      // in order of increasing Sequence Number subfield value starting with
      // SN=WinStartB and proceeding sequentially until there is no buffered MSDU
      // or A-MSDU for the next sequential Sequence Number subfield value
      PassBufferedMpdusUntilFirstLost ();
    }
}

void
RecipientBlockAckAgreement::FillBlockAckBitmap (CtrlBAckResponseHeader *blockAckHeader, std::size_t index) const
{
  NS_LOG_FUNCTION (this << blockAckHeader << index);
  if (blockAckHeader->IsBasic ())
    {
      NS_FATAL_ERROR ("Basic block ack is not supported.");
    }
  else if (blockAckHeader->IsMultiTid ())
    {
      NS_FATAL_ERROR ("Multi-tid block ack is not supported.");
    }
  else if (blockAckHeader->IsCompressed () || blockAckHeader->IsExtendedCompressed ()
           || blockAckHeader->IsMultiSta ())
    {
      // The Starting Sequence Number subfield of the Block Ack Starting Sequence
      // Control subfield of the BlockAck frame shall be set to any value in the
      // range (WinEndR – 63) to WinStartR (Sec. 10.24.7.5 of 802.11-2016).
      // We set it to WinStartR
      uint16_t ssn = m_scoreboard.GetWinStart ();
      NS_LOG_DEBUG ("SSN=" << ssn);
      blockAckHeader->SetStartingSequence (ssn, index);
      blockAckHeader->ResetBitmap (index);

      for (std::size_t i = 0; i < m_scoreboard.GetWinSize (); i++)
        {
          if (m_scoreboard.At (i))
            {
              blockAckHeader->SetReceivedPacket ((ssn + i) % SEQNO_SPACE_SIZE, index);
            }
        }
    }
}


} //namespace ns3