block-ack-manager.cc

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/*
 * Copyright (c) 2009, 2010 MIRKO BANCHI
 *
 * 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: Mirko Banchi <mk.banchi@gmail.com>
 */
 
#include "block-ack-manager.h"
 
#include "ctrl-headers.h"
#include "mac-rx-middle.h"
#include "mgt-action-headers.h"
#include "qos-utils.h"
#include "wifi-mac-queue.h"
#include "wifi-tx-vector.h"
#include "wifi-utils.h"
 
#include "ns3/log.h"
#include "ns3/simulator.h"
 
#include <algorithm>
#include <optional>
 
namespace ns3
{
 
NS_LOG_COMPONENT_DEFINE("BlockAckManager");
 
NS_OBJECT_ENSURE_REGISTERED(BlockAckManager);
 
TypeId
BlockAckManager::GetTypeId()
{
    static TypeId tid =
        TypeId("ns3::BlockAckManager")
            .SetParent<Object>()
            .SetGroupName("Wifi")
            .AddConstructor<BlockAckManager>()
            .AddTraceSource("AgreementState",
                            "The state of the ADDBA handshake",
                            MakeTraceSourceAccessor(&BlockAckManager::m_originatorAgreementState),
                            "ns3::BlockAckManager::AgreementStateTracedCallback");
    return tid;
}
 
BlockAckManager::BlockAckManager()
{
    NS_LOG_FUNCTION(this);
}
 
BlockAckManager::~BlockAckManager()
{
    NS_LOG_FUNCTION(this);
}
 
void
BlockAckManager::DoDispose()
{
    NS_LOG_FUNCTION(this);
    m_originatorAgreements.clear();
    m_queue = nullptr;
}
 
BlockAckManager::OriginatorAgreementOptConstRef
BlockAckManager::GetAgreementAsOriginator(const Mac48Address& recipient, uint8_t tid) const
{
    NS_LOG_FUNCTION(this << recipient << +tid);
    if (auto it = m_originatorAgreements.find({recipient, tid}); it != m_originatorAgreements.end())
    {
        return std::cref(it->second.first);
    }
 
    return std::nullopt;
}
 
BlockAckManager::RecipientAgreementOptConstRef
BlockAckManager::GetAgreementAsRecipient(const Mac48Address& originator, uint8_t tid) const
{
    NS_LOG_FUNCTION(this << originator << +tid);
    if (auto it = m_recipientAgreements.find({originator, tid}); it != m_recipientAgreements.end())
    {
        return std::cref(it->second);
    }
 
    return std::nullopt;
}
 
void
BlockAckManager::CreateOriginatorAgreement(const MgtAddBaRequestHeader& reqHdr,
                                           const Mac48Address& recipient,
                                           bool htSupported)
{
    NS_LOG_FUNCTION(this << reqHdr << recipient << htSupported);
    const uint8_t tid = reqHdr.GetTid();
    OriginatorBlockAckAgreement agreement(recipient, tid);
    agreement.SetStartingSequence(reqHdr.GetStartingSequence());
    /* For now we assume that originator doesn't use this field. Use of this field
       is mandatory only for recipient */
    agreement.SetBufferSize(reqHdr.GetBufferSize());
    agreement.SetTimeout(reqHdr.GetTimeout());
    agreement.SetAmsduSupport(reqHdr.IsAmsduSupported());
    agreement.SetHtSupported(htSupported);
    if (reqHdr.IsImmediateBlockAck())
    {
        agreement.SetImmediateBlockAck();
    }
    else
    {
        agreement.SetDelayedBlockAck();
    }
    agreement.SetState(OriginatorBlockAckAgreement::PENDING);
    m_originatorAgreementState(Simulator::Now(),
                               recipient,
                               tid,
                               OriginatorBlockAckAgreement::PENDING);
    if (auto existingAgreement = GetAgreementAsOriginator(recipient, tid))
    {
        NS_ASSERT_MSG(existingAgreement->get().IsReset(),
                      "Existing agreement must be in RESET state");
    }
    m_originatorAgreements.insert_or_assign({recipient, tid},
                                            std::make_pair(std::move(agreement), PacketQueue{}));
    m_blockPackets(recipient, tid);
}
 
void
BlockAckManager::DestroyOriginatorAgreement(const Mac48Address& recipient, uint8_t tid)
{
    NS_LOG_FUNCTION(this << recipient << +tid);
    auto it = m_originatorAgreements.find({recipient, tid});
    if (it != m_originatorAgreements.end())
    {
        m_originatorAgreements.erase(it);
    }
}
 
void
BlockAckManager::UpdateOriginatorAgreement(const MgtAddBaResponseHeader& respHdr,
                                           const Mac48Address& recipient,
                                           uint16_t startingSeq)
{
    NS_LOG_FUNCTION(this << respHdr << recipient << startingSeq);
    uint8_t tid = respHdr.GetTid();
    auto it = m_originatorAgreements.find({recipient, tid});
    if (it != m_originatorAgreements.end())
    {
        OriginatorBlockAckAgreement& agreement = it->second.first;
        agreement.SetBufferSize(respHdr.GetBufferSize());
        agreement.SetTimeout(respHdr.GetTimeout());
        agreement.SetAmsduSupport(respHdr.IsAmsduSupported());
        agreement.SetStartingSequence(startingSeq);
        agreement.InitTxWindow();
        if (respHdr.IsImmediateBlockAck())
        {
            agreement.SetImmediateBlockAck();
        }
        else
        {
            agreement.SetDelayedBlockAck();
        }
        if (!it->second.first.IsEstablished())
        {
            m_originatorAgreementState(Simulator::Now(),
                                       recipient,
                                       tid,
                                       OriginatorBlockAckAgreement::ESTABLISHED);
        }
        agreement.SetState(OriginatorBlockAckAgreement::ESTABLISHED);
        if (agreement.GetTimeout() != 0)
        {
            Time timeout = MicroSeconds(1024 * agreement.GetTimeout());
            agreement.m_inactivityEvent = Simulator::Schedule(timeout,
                                                              &BlockAckManager::InactivityTimeout,
                                                              this,
                                                              recipient,
                                                              tid);
        }
    }
    m_unblockPackets(recipient, tid);
}
 
void
BlockAckManager::CreateRecipientAgreement(const MgtAddBaResponseHeader& respHdr,
                                          const Mac48Address& originator,
                                          uint16_t startingSeq,
                                          bool htSupported,
                                          Ptr<MacRxMiddle> rxMiddle)
{
    NS_LOG_FUNCTION(this << respHdr << originator << startingSeq << htSupported << rxMiddle);
    uint8_t tid = respHdr.GetTid();
 
    RecipientBlockAckAgreement agreement(originator,
                                         respHdr.IsAmsduSupported(),
                                         tid,
                                         respHdr.GetBufferSize(),
                                         respHdr.GetTimeout(),
                                         startingSeq,
                                         htSupported);
    agreement.SetMacRxMiddle(rxMiddle);
    if (respHdr.IsImmediateBlockAck())
    {
        agreement.SetImmediateBlockAck();
    }
    else
    {
        agreement.SetDelayedBlockAck();
    }
 
    m_recipientAgreements.insert_or_assign({originator, tid}, agreement);
}
 
void
BlockAckManager::DestroyRecipientAgreement(const Mac48Address& originator, uint8_t tid)
{
    NS_LOG_FUNCTION(this << originator << tid);
 
    if (auto agreementIt = m_recipientAgreements.find({originator, tid});
        agreementIt != m_recipientAgreements.end())
    {
        // forward up the buffered MPDUs before destroying the agreement
        agreementIt->second.Flush();
        m_recipientAgreements.erase(agreementIt);
    }
}
 
void
BlockAckManager::StorePacket(Ptr<WifiMpdu> mpdu)
{
    NS_LOG_FUNCTION(this << *mpdu);
    NS_ASSERT(mpdu->GetHeader().IsQosData());
 
    uint8_t tid = mpdu->GetHeader().GetQosTid();
    Mac48Address recipient = mpdu->GetHeader().GetAddr1();
 
    auto agreementIt = m_originatorAgreements.find({recipient, tid});
    NS_ASSERT(agreementIt != m_originatorAgreements.end());
 
    uint16_t mpduDist =
        agreementIt->second.first.GetDistance(mpdu->GetHeader().GetSequenceNumber());
 
    if (mpduDist >= SEQNO_SPACE_HALF_SIZE)
    {
        NS_LOG_DEBUG("Got an old packet. Do nothing");
        return;
    }
 
    // store the packet and keep the list sorted in increasing order of sequence number
    // with respect to the starting sequence number
    auto it = agreementIt->second.second.rbegin();
    while (it != agreementIt->second.second.rend())
    {
        if (mpdu->GetHeader().GetSequenceControl() == (*it)->GetHeader().GetSequenceControl())
        {
            NS_LOG_DEBUG("Packet already in the queue of the BA agreement");
            return;
        }
 
        uint16_t dist =
            agreementIt->second.first.GetDistance((*it)->GetHeader().GetSequenceNumber());
 
        if (mpduDist > dist || (mpduDist == dist && mpdu->GetHeader().GetFragmentNumber() >
                                                        (*it)->GetHeader().GetFragmentNumber()))
        {
            break;
        }
 
        it++;
    }
    agreementIt->second.second.insert(it.base(), mpdu);
    agreementIt->second.first.NotifyTransmittedMpdu(mpdu);
}
 
uint32_t
BlockAckManager::GetNBufferedPackets(const Mac48Address& recipient, uint8_t tid) const
{
    NS_LOG_FUNCTION(this << recipient << +tid);
    auto it = m_originatorAgreements.find({recipient, tid});
    if (it == m_originatorAgreements.end())
    {
        return 0;
    }
    return it->second.second.size();
}
 
void
BlockAckManager::SetBlockAckThreshold(uint8_t nPackets)
{
    NS_LOG_FUNCTION(this << +nPackets);
    m_blockAckThreshold = nPackets;
}
 
BlockAckManager::PacketQueueI
BlockAckManager::HandleInFlightMpdu(uint8_t linkId,
                                    PacketQueueI mpduIt,
                                    MpduStatus status,
                                    const OriginatorAgreementsI& it,
                                    const Time& now)
{
    NS_LOG_FUNCTION(this << linkId << **mpduIt << +static_cast<uint8_t>(status));
 
    if (!(*mpduIt)->IsQueued())
    {
        // MPDU is not in the EDCA queue (e.g., its lifetime expired and it was
        // removed by another method), remove from the queue of in flight MPDUs
        NS_LOG_DEBUG("MPDU is not stored in the EDCA queue, drop MPDU");
        return it->second.second.erase(mpduIt);
    }
 
    if (status == ACKNOWLEDGED)
    {
        // the MPDU has to be dequeued from the EDCA queue
        return it->second.second.erase(mpduIt);
    }
 
    const WifiMacHeader& hdr = (*mpduIt)->GetHeader();
 
    NS_ASSERT(hdr.GetAddr1() == it->first.first);
    NS_ASSERT(hdr.IsQosData() && hdr.GetQosTid() == it->first.second);
 
    if (it->second.first.GetDistance(hdr.GetSequenceNumber()) >= SEQNO_SPACE_HALF_SIZE)
    {
        NS_LOG_DEBUG("Old packet. Remove from the EDCA queue, too");
        if (!m_droppedOldMpduCallback.IsNull())
        {
            m_droppedOldMpduCallback(*mpduIt);
        }
        m_queue->Remove(*mpduIt);
        return it->second.second.erase(mpduIt);
    }
 
    std::optional<PacketQueueI> prevIt;
    if (mpduIt != it->second.second.begin())
    {
        prevIt = std::prev(mpduIt);
    }
 
    if (m_queue->TtlExceeded(*mpduIt, now))
    {
        // WifiMacQueue::TtlExceeded() has removed the MPDU from the EDCA queue
        // and fired the Expired trace source, which called NotifyDiscardedMpdu,
        // which removed this MPDU (and possibly others) from the in flight queue as well
        NS_LOG_DEBUG("MSDU lifetime expired, drop MPDU");
        return (prevIt.has_value() ? std::next(prevIt.value()) : it->second.second.begin());
    }
 
    if (status == STAY_INFLIGHT)
    {
        // the MPDU has to stay in flight, do nothing
        return ++mpduIt;
    }
 
    NS_ASSERT(status == TO_RETRANSMIT);
    (*mpduIt)->GetHeader().SetRetry();
    (*mpduIt)->ResetInFlight(linkId); // no longer in flight; will be if retransmitted
 
    return it->second.second.erase(mpduIt);
}
 
void
BlockAckManager::NotifyGotAck(uint8_t linkId, Ptr<const WifiMpdu> mpdu)
{
    NS_LOG_FUNCTION(this << linkId << *mpdu);
    NS_ASSERT(mpdu->GetHeader().IsQosData());
 
    Mac48Address recipient = mpdu->GetOriginal()->GetHeader().GetAddr1();
    uint8_t tid = mpdu->GetHeader().GetQosTid();
 
    auto it = m_originatorAgreements.find({recipient, tid});
    NS_ASSERT(it != m_originatorAgreements.end());
    NS_ASSERT(it->second.first.IsEstablished());
 
    it->second.first.NotifyAckedMpdu(mpdu);
 
    // remove the acknowledged frame from the queue of outstanding packets
    for (auto queueIt = it->second.second.begin(); queueIt != it->second.second.end(); ++queueIt)
    {
        if ((*queueIt)->GetHeader().GetSequenceNumber() == mpdu->GetHeader().GetSequenceNumber())
        {
            m_queue->DequeueIfQueued({*queueIt});
            HandleInFlightMpdu(linkId, queueIt, ACKNOWLEDGED, it, Simulator::Now());
            break;
        }
    }
}
 
void
BlockAckManager::NotifyMissedAck(uint8_t linkId, Ptr<WifiMpdu> mpdu)
{
    NS_LOG_FUNCTION(this << linkId << *mpdu);
    NS_ASSERT(mpdu->GetHeader().IsQosData());
 
    Mac48Address recipient = mpdu->GetOriginal()->GetHeader().GetAddr1();
    uint8_t tid = mpdu->GetHeader().GetQosTid();
 
    auto it = m_originatorAgreements.find({recipient, tid});
    NS_ASSERT(it != m_originatorAgreements.end());
    NS_ASSERT(it->second.first.IsEstablished());
 
    // remove the frame from the queue of outstanding packets (it will be re-inserted
    // if retransmitted)
    for (auto queueIt = it->second.second.begin(); queueIt != it->second.second.end(); ++queueIt)
    {
        if ((*queueIt)->GetHeader().GetSequenceNumber() == mpdu->GetHeader().GetSequenceNumber())
        {
            HandleInFlightMpdu(linkId, queueIt, TO_RETRANSMIT, it, Simulator::Now());
            break;
        }
    }
}
 
std::pair<uint16_t, uint16_t>
BlockAckManager::NotifyGotBlockAck(uint8_t linkId,
                                   const CtrlBAckResponseHeader& blockAck,
                                   const Mac48Address& recipient,
                                   const std::set<uint8_t>& tids,
                                   size_t index)
{
    NS_LOG_FUNCTION(this << linkId << blockAck << recipient << index);
 
    NS_ABORT_MSG_IF(blockAck.IsBasic(), "Basic Block Ack is not supported");
    NS_ABORT_MSG_IF(blockAck.IsMultiTid(), "Multi-TID Block Ack is not supported");
 
    uint8_t tid = blockAck.GetTidInfo(index);
    // If this is a Multi-STA Block Ack with All-ack context (TID equal to 14),
    // use the TID passed by the caller.
    if (tid == 14)
    {
        NS_ASSERT(blockAck.GetAckType(index) && tids.size() == 1);
        tid = *tids.begin();
    }
 
    auto it = m_originatorAgreements.find({recipient, tid});
    if (it == m_originatorAgreements.end() || !it->second.first.IsEstablished())
    {
        return {0, 0};
    }
 
    uint16_t nSuccessfulMpdus = 0;
    uint16_t nFailedMpdus = 0;
 
    if (it->second.first.m_inactivityEvent.IsRunning())
    {
        /* Upon reception of a BlockAck frame, the inactivity timer at the
            originator must be reset.
            For more details see section 11.5.3 in IEEE802.11e standard */
        it->second.first.m_inactivityEvent.Cancel();
        Time timeout = MicroSeconds(1024 * it->second.first.GetTimeout());
        it->second.first.m_inactivityEvent =
            Simulator::Schedule(timeout, &BlockAckManager::InactivityTimeout, this, recipient, tid);
    }
 
    NS_ASSERT(blockAck.IsCompressed() || blockAck.IsExtendedCompressed() || blockAck.IsMultiSta());
    Time now = Simulator::Now();
    std::list<Ptr<const WifiMpdu>> acked;
 
    for (auto queueIt = it->second.second.begin(); queueIt != it->second.second.end();)
    {
        uint16_t currentSeq = (*queueIt)->GetHeader().GetSequenceNumber();
        NS_LOG_DEBUG("Current seq=" << currentSeq);
        if (blockAck.IsPacketReceived(currentSeq, index))
        {
            it->second.first.NotifyAckedMpdu(*queueIt);
            nSuccessfulMpdus++;
            if (!m_txOkCallback.IsNull())
            {
                m_txOkCallback(*queueIt);
            }
            acked.emplace_back(*queueIt);
            queueIt = HandleInFlightMpdu(linkId, queueIt, ACKNOWLEDGED, it, now);
        }
        else
        {
            ++queueIt;
        }
    }
 
    // Dequeue all acknowledged MPDUs at once
    m_queue->DequeueIfQueued(acked);
 
    // Remaining outstanding MPDUs have not been acknowledged
    for (auto queueIt = it->second.second.begin(); queueIt != it->second.second.end();)
    {
        // transmission actually failed if the MPDU is inflight only on the same link on
        // which we received the BlockAck frame
        auto linkIds = (*queueIt)->GetInFlightLinkIds();
 
        if (linkIds.size() == 1 && *linkIds.begin() == linkId)
        {
            nFailedMpdus++;
            if (!m_txFailedCallback.IsNull())
            {
                m_txFailedCallback(*queueIt);
            }
            queueIt = HandleInFlightMpdu(linkId, queueIt, TO_RETRANSMIT, it, now);
            continue;
        }
 
        queueIt = HandleInFlightMpdu(linkId, queueIt, STAY_INFLIGHT, it, now);
    }
 
    return {nSuccessfulMpdus, nFailedMpdus};
}
 
void
BlockAckManager::NotifyMissedBlockAck(uint8_t linkId, const Mac48Address& recipient, uint8_t tid)
{
    NS_LOG_FUNCTION(this << linkId << recipient << +tid);
 
    auto it = m_originatorAgreements.find({recipient, tid});
    if (it == m_originatorAgreements.end() || !it->second.first.IsEstablished())
    {
        return;
    }
 
    Time now = Simulator::Now();
 
    // remove all packets from the queue of outstanding packets (they will be
    // re-inserted if retransmitted)
    for (auto mpduIt = it->second.second.begin(); mpduIt != it->second.second.end();)
    {
        // MPDUs that were transmitted on another link shall stay inflight
        auto linkIds = (*mpduIt)->GetInFlightLinkIds();
        if (!linkIds.contains(linkId))
        {
            mpduIt = HandleInFlightMpdu(linkId, mpduIt, STAY_INFLIGHT, it, now);
            continue;
        }
        mpduIt = HandleInFlightMpdu(linkId, mpduIt, TO_RETRANSMIT, it, now);
    }
}
 
void
BlockAckManager::NotifyDiscardedMpdu(Ptr<const WifiMpdu> mpdu)
{
    NS_LOG_FUNCTION(this << *mpdu);
 
    if (!mpdu->GetHeader().IsQosData())
    {
        NS_LOG_DEBUG("Not a QoS Data frame");
        return;
    }
 
    if (!mpdu->GetHeader().IsRetry() && !mpdu->IsInFlight())
    {
        NS_LOG_DEBUG("This frame has never been transmitted");
        return;
    }
 
    Mac48Address recipient = mpdu->GetOriginal()->GetHeader().GetAddr1();
    uint8_t tid = mpdu->GetHeader().GetQosTid();
    auto it = m_originatorAgreements.find({recipient, tid});
    if (it == m_originatorAgreements.end() || !it->second.first.IsEstablished())
    {
        NS_LOG_DEBUG("No established Block Ack agreement");
        return;
    }
 
    uint16_t currStartingSeq = it->second.first.GetStartingSequence();
    if (QosUtilsIsOldPacket(currStartingSeq, mpdu->GetHeader().GetSequenceNumber()))
    {
        NS_LOG_DEBUG("Discarded an old frame");
        return;
    }
 
    // actually advance the transmit window
    it->second.first.NotifyDiscardedMpdu(mpdu);
 
    // remove old MPDUs from the EDCA queue and from the in flight queue
    // (including the given MPDU which became old after advancing the transmit window)
    for (auto mpduIt = it->second.second.begin(); mpduIt != it->second.second.end();)
    {
        if (it->second.first.GetDistance((*mpduIt)->GetHeader().GetSequenceNumber()) >=
            SEQNO_SPACE_HALF_SIZE)
        {
            NS_LOG_DEBUG("Dropping old MPDU: " << **mpduIt);
            m_queue->DequeueIfQueued({*mpduIt});
            if (!m_droppedOldMpduCallback.IsNull())
            {
                m_droppedOldMpduCallback(*mpduIt);
            }
            mpduIt = it->second.second.erase(mpduIt);
        }
        else
        {
            break; // MPDUs are in increasing order of sequence number in the in flight queue
        }
    }
 
    // schedule a BlockAckRequest
    NS_LOG_DEBUG("Schedule a Block Ack Request for agreement (" << recipient << ", " << +tid
                                                                << ")");
 
    WifiMacHeader hdr;
    hdr.SetType(WIFI_MAC_CTL_BACKREQ);
    hdr.SetAddr1(recipient);
    hdr.SetAddr2(mpdu->GetOriginal()->GetHeader().GetAddr2());
    hdr.SetDsNotTo();
    hdr.SetDsNotFrom();
    hdr.SetNoRetry();
    hdr.SetNoMoreFragments();
 
    ScheduleBar(GetBlockAckReqHeader(recipient, tid), hdr);
}
 
void
BlockAckManager::NotifyGotBlockAckRequest(const Mac48Address& originator,
                                          uint8_t tid,
                                          uint16_t startingSeq)
{
    NS_LOG_FUNCTION(this << originator << tid << startingSeq);
    auto it = m_recipientAgreements.find({originator, tid});
    if (it == m_recipientAgreements.end())
    {
        return;
    }
    it->second.NotifyReceivedBar(startingSeq);
}
 
void
BlockAckManager::NotifyGotMpdu(Ptr<const WifiMpdu> mpdu)
{
    NS_LOG_FUNCTION(this << *mpdu);
    auto originator = mpdu->GetOriginal()->GetHeader().GetAddr2();
    NS_ASSERT(mpdu->GetHeader().IsQosData());
    auto tid = mpdu->GetHeader().GetQosTid();
 
    auto it = m_recipientAgreements.find({originator, tid});
    if (it == m_recipientAgreements.end())
    {
        return;
    }
    it->second.NotifyReceivedMpdu(mpdu);
}
 
CtrlBAckRequestHeader
BlockAckManager::GetBlockAckReqHeader(const Mac48Address& recipient, uint8_t tid) const
{
    NS_LOG_FUNCTION(this << recipient << +tid);
    auto it = m_originatorAgreements.find({recipient, tid});
    NS_ASSERT(it != m_originatorAgreements.end());
 
    CtrlBAckRequestHeader reqHdr;
    reqHdr.SetType((*it).second.first.GetBlockAckReqType());
    reqHdr.SetTidInfo(tid);
    reqHdr.SetStartingSequence((*it).second.first.GetStartingSequence());
    return reqHdr;
}
 
void
BlockAckManager::ScheduleBar(const CtrlBAckRequestHeader& reqHdr, const WifiMacHeader& hdr)
{
    NS_LOG_FUNCTION(this << reqHdr << hdr);
 
    uint8_t tid = reqHdr.GetTidInfo();
 
    WifiContainerQueueId queueId(WIFI_CTL_QUEUE, WIFI_UNICAST, hdr.GetAddr1(), std::nullopt);
    auto pkt = Create<Packet>();
    pkt->AddHeader(reqHdr);
    Ptr<WifiMpdu> item = nullptr;
 
    // if a BAR for the given agreement is present, replace it with the new one
    while ((item = m_queue->PeekByQueueId(queueId, item)))
    {
        if (item->GetHeader().IsBlockAckReq() && item->GetHeader().GetAddr1() == hdr.GetAddr1())
        {
            CtrlBAckRequestHeader otherHdr;
            item->GetPacket()->PeekHeader(otherHdr);
            if (otherHdr.GetTidInfo() == tid)
            {
                auto bar = Create<WifiMpdu>(pkt, hdr, item->GetTimestamp());
                // replace item with bar
                m_queue->Replace(item, bar);
                return;
            }
        }
    }
 
    m_queue->Enqueue(Create<WifiMpdu>(pkt, hdr));
}
 
const std::list<BlockAckManager::AgreementKey>&
BlockAckManager::GetSendBarIfDataQueuedList() const
{
    return m_sendBarIfDataQueued;
}
 
void
BlockAckManager::AddToSendBarIfDataQueuedList(const Mac48Address& recipient, uint8_t tid)
{
    NS_LOG_FUNCTION(this << recipient << tid);
    // do nothing if the given pair is already in the list
    if (std::find(m_sendBarIfDataQueued.begin(),
                  m_sendBarIfDataQueued.end(),
                  BlockAckManager::AgreementKey{recipient, tid}) == m_sendBarIfDataQueued.end())
    {
        m_sendBarIfDataQueued.emplace_back(recipient, tid);
    }
}
 
void
BlockAckManager::RemoveFromSendBarIfDataQueuedList(const Mac48Address& recipient, uint8_t tid)
{
    NS_LOG_FUNCTION(this << recipient << tid);
    m_sendBarIfDataQueued.remove({recipient, tid});
}
 
void
BlockAckManager::InactivityTimeout(const Mac48Address& recipient, uint8_t tid)
{
    NS_LOG_FUNCTION(this << recipient << +tid);
    m_blockAckInactivityTimeout(recipient, tid, true);
}
 
void
BlockAckManager::NotifyOriginatorAgreementEstablished(const Mac48Address& recipient,
                                                      uint8_t tid,
                                                      uint16_t startingSeq)
{
    NS_LOG_FUNCTION(this << recipient << +tid << startingSeq);
    auto it = m_originatorAgreements.find({recipient, tid});
    NS_ASSERT(it != m_originatorAgreements.end());
    if (!it->second.first.IsEstablished())
    {
        m_originatorAgreementState(Simulator::Now(),
                                   recipient,
                                   tid,
                                   OriginatorBlockAckAgreement::ESTABLISHED);
    }
    it->second.first.SetState(OriginatorBlockAckAgreement::ESTABLISHED);
    it->second.first.SetStartingSequence(startingSeq);
}
 
void
BlockAckManager::NotifyOriginatorAgreementRejected(const Mac48Address& recipient, uint8_t tid)
{
    NS_LOG_FUNCTION(this << recipient << +tid);
    auto it = m_originatorAgreements.find({recipient, tid});
    NS_ASSERT(it != m_originatorAgreements.end());
    if (!it->second.first.IsRejected())
    {
        m_originatorAgreementState(Simulator::Now(),
                                   recipient,
                                   tid,
                                   OriginatorBlockAckAgreement::REJECTED);
    }
    it->second.first.SetState(OriginatorBlockAckAgreement::REJECTED);
    m_unblockPackets(recipient, tid);
}
 
void
BlockAckManager::NotifyOriginatorAgreementNoReply(const Mac48Address& recipient, uint8_t tid)
{
    NS_LOG_FUNCTION(this << recipient << +tid);
    auto it = m_originatorAgreements.find({recipient, tid});
    NS_ASSERT(it != m_originatorAgreements.end());
    if (!it->second.first.IsNoReply())
    {
        m_originatorAgreementState(Simulator::Now(),
                                   recipient,
                                   tid,
                                   OriginatorBlockAckAgreement::NO_REPLY);
    }
    it->second.first.SetState(OriginatorBlockAckAgreement::NO_REPLY);
    m_unblockPackets(recipient, tid);
}
 
void
BlockAckManager::NotifyOriginatorAgreementReset(const Mac48Address& recipient, uint8_t tid)
{
    NS_LOG_FUNCTION(this << recipient << +tid);
    auto it = m_originatorAgreements.find({recipient, tid});
    NS_ASSERT(it != m_originatorAgreements.end());
    if (!it->second.first.IsReset())
    {
        m_originatorAgreementState(Simulator::Now(),
                                   recipient,
                                   tid,
                                   OriginatorBlockAckAgreement::RESET);
    }
    it->second.first.SetState(OriginatorBlockAckAgreement::RESET);
}
 
void
BlockAckManager::SetQueue(const Ptr<WifiMacQueue> queue)
{
    NS_LOG_FUNCTION(this << queue);
    m_queue = queue;
}
 
bool
BlockAckManager::NeedBarRetransmission(uint8_t tid, const Mac48Address& recipient)
{
    auto it = m_originatorAgreements.find({recipient, tid});
    if (it == m_originatorAgreements.end() || !it->second.first.IsEstablished())
    {
        // If the inactivity timer has expired, QosTxop::SendDelbaFrame has been called and
        // has destroyed the agreement, hence we get here and correctly return false
        return false;
    }
 
    Time now = Simulator::Now();
 
    // A BAR needs to be retransmitted if there is at least a non-expired in flight MPDU
    for (auto mpduIt = it->second.second.begin(); mpduIt != it->second.second.end();)
    {
        // remove MPDU if old or with expired lifetime
        mpduIt = HandleInFlightMpdu(SINGLE_LINK_OP_ID, mpduIt, STAY_INFLIGHT, it, now);
 
        if (mpduIt != it->second.second.begin())
        {
            // the MPDU has not been removed
            return true;
        }
    }
 
    return false;
}
 
void
BlockAckManager::SetBlockAckInactivityCallback(Callback<void, Mac48Address, uint8_t, bool> callback)
{
    NS_LOG_FUNCTION(this << &callback);
    m_blockAckInactivityTimeout = callback;
}
 
void
BlockAckManager::SetBlockDestinationCallback(Callback<void, Mac48Address, uint8_t> callback)
{
    NS_LOG_FUNCTION(this << &callback);
    m_blockPackets = callback;
}
 
void
BlockAckManager::SetUnblockDestinationCallback(Callback<void, Mac48Address, uint8_t> callback)
{
    NS_LOG_FUNCTION(this << &callback);
    m_unblockPackets = callback;
}
 
void
BlockAckManager::SetTxOkCallback(TxOk callback)
{
    m_txOkCallback = callback;
}
 
void
BlockAckManager::SetTxFailedCallback(TxFailed callback)
{
    m_txFailedCallback = callback;
}
 
void
BlockAckManager::SetDroppedOldMpduCallback(DroppedOldMpdu callback)
{
    m_droppedOldMpduCallback = callback;
}
 
uint16_t
BlockAckManager::GetRecipientBufferSize(const Mac48Address& recipient, uint8_t tid) const
{
    uint16_t size = 0;
    auto it = m_originatorAgreements.find({recipient, tid});
    if (it != m_originatorAgreements.end())
    {
        size = it->second.first.GetBufferSize();
    }
    return size;
}
 
uint16_t
BlockAckManager::GetOriginatorStartingSequence(const Mac48Address& recipient, uint8_t tid) const
{
    uint16_t seqNum = 0;
    auto it = m_originatorAgreements.find({recipient, tid});
    if (it != m_originatorAgreements.end())
    {
        seqNum = it->second.first.GetStartingSequence();
    }
    return seqNum;
}
 
} // namespace ns3