sta-wifi-mac.cc

Go to the documentation of this file.

/*
 * Copyright (c) 2006, 2009 INRIA
 * Copyright (c) 2009 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
 *
 * Authors: Mathieu Lacage <mathieu.lacage@sophia.inria.fr>
 *          Mirko Banchi <mk.banchi@gmail.com>
 */
 
#include "sta-wifi-mac.h"
 
#include "channel-access-manager.h"
#include "frame-exchange-manager.h"
#include "mgt-action-headers.h"
#include "mgt-headers.h"
#include "qos-txop.h"
#include "snr-tag.h"
#include "wifi-assoc-manager.h"
#include "wifi-mac-queue.h"
#include "wifi-net-device.h"
#include "wifi-phy.h"
 
#include "ns3/attribute-container.h"
#include "ns3/eht-configuration.h"
#include "ns3/emlsr-manager.h"
#include "ns3/he-configuration.h"
#include "ns3/ht-configuration.h"
#include "ns3/log.h"
#include "ns3/packet.h"
#include "ns3/pair.h"
#include "ns3/pointer.h"
#include "ns3/random-variable-stream.h"
#include "ns3/simulator.h"
#include "ns3/string.h"
 
#include <iterator>
#include <numeric>
#include <sstream>
 
namespace ns3
{
 
NS_LOG_COMPONENT_DEFINE("StaWifiMac");
 
NS_OBJECT_ENSURE_REGISTERED(StaWifiMac);
 
TypeId
StaWifiMac::GetTypeId()
{
    static TypeId tid =
        TypeId("ns3::StaWifiMac")
            .SetParent<WifiMac>()
            .SetGroupName("Wifi")
            .AddConstructor<StaWifiMac>()
            .AddAttribute("ProbeRequestTimeout",
                          "The duration to actively probe the channel.",
                          TimeValue(Seconds(0.05)),
                          MakeTimeAccessor(&StaWifiMac::m_probeRequestTimeout),
                          MakeTimeChecker())
            .AddAttribute("WaitBeaconTimeout",
                          "The duration to dwell on a channel while passively scanning for beacon",
                          TimeValue(MilliSeconds(120)),
                          MakeTimeAccessor(&StaWifiMac::m_waitBeaconTimeout),
                          MakeTimeChecker())
            .AddAttribute("AssocRequestTimeout",
                          "The interval between two consecutive association request attempts.",
                          TimeValue(Seconds(0.5)),
                          MakeTimeAccessor(&StaWifiMac::m_assocRequestTimeout),
                          MakeTimeChecker())
            .AddAttribute("MaxMissedBeacons",
                          "Number of beacons which much be consecutively missed before "
                          "we attempt to restart association.",
                          UintegerValue(10),
                          MakeUintegerAccessor(&StaWifiMac::m_maxMissedBeacons),
                          MakeUintegerChecker<uint32_t>())
            .AddAttribute(
                "ActiveProbing",
                "If true, we send probe requests. If false, we don't."
                "NOTE: if more than one STA in your simulation is using active probing, "
                "you should enable it at a different simulation time for each STA, "
                "otherwise all the STAs will start sending probes at the same time resulting in "
                "collisions. "
                "See bug 1060 for more info.",
                BooleanValue(false),
                MakeBooleanAccessor(&StaWifiMac::SetActiveProbing, &StaWifiMac::GetActiveProbing),
                MakeBooleanChecker())
            .AddAttribute("ProbeDelay",
                          "Delay (in microseconds) to be used prior to transmitting a "
                          "Probe frame during active scanning.",
                          StringValue("ns3::UniformRandomVariable[Min=50.0|Max=250.0]"),
                          MakePointerAccessor(&StaWifiMac::m_probeDelay),
                          MakePointerChecker<RandomVariableStream>())
            .AddAttribute(
                "PowerSaveMode",
                "Enable/disable power save mode on the given link. The power management mode is "
                "actually changed when the AP acknowledges a frame sent with the Power Management "
                "field set to the value corresponding to the requested mode",
                TypeId::ATTR_GET | TypeId::ATTR_SET, // do not set at construction time
                PairValue<BooleanValue, UintegerValue>(),
                MakePairAccessor<BooleanValue, UintegerValue>(&StaWifiMac::SetPowerSaveMode),
                MakePairChecker<BooleanValue, UintegerValue>(MakeBooleanChecker(),
                                                             MakeUintegerChecker<uint8_t>()))
            .AddAttribute("PmModeSwitchTimeout",
                          "If switching to a new Power Management mode is not completed within "
                          "this amount of time, make another attempt at switching Power "
                          "Management mode.",
                          TimeValue(Seconds(0.1)),
                          MakeTimeAccessor(&StaWifiMac::m_pmModeSwitchTimeout),
                          MakeTimeChecker())
            .AddTraceSource("Assoc",
                            "Associated with an access point. If this is an MLD that associated "
                            "with an AP MLD, the AP MLD address is provided.",
                            MakeTraceSourceAccessor(&StaWifiMac::m_assocLogger),
                            "ns3::Mac48Address::TracedCallback")
            .AddTraceSource("LinkSetupCompleted",
                            "A link was setup in the context of ML setup with an AP MLD. "
                            "Provides ID of the setup link and AP MAC address",
                            MakeTraceSourceAccessor(&StaWifiMac::m_setupCompleted),
                            "ns3::StaWifiMac::LinkSetupCallback")
            .AddTraceSource("DeAssoc",
                            "Association with an access point lost. If this is an MLD "
                            "that disassociated with an AP MLD, the AP MLD address is provided.",
                            MakeTraceSourceAccessor(&StaWifiMac::m_deAssocLogger),
                            "ns3::Mac48Address::TracedCallback")
            .AddTraceSource("LinkSetupCanceled",
                            "A link setup in the context of ML setup with an AP MLD was torn down. "
                            "Provides ID of the setup link and AP MAC address",
                            MakeTraceSourceAccessor(&StaWifiMac::m_setupCanceled),
                            "ns3::StaWifiMac::LinkSetupCallback",
                            TypeId::OBSOLETE,
                            "Disassociation only occurs at MLD level; use DeAssoc trace.")
            .AddTraceSource("BeaconArrival",
                            "Time of beacons arrival from associated AP",
                            MakeTraceSourceAccessor(&StaWifiMac::m_beaconArrival),
                            "ns3::Time::TracedCallback")
            .AddTraceSource("ReceivedBeaconInfo",
                            "Information about every received Beacon frame",
                            MakeTraceSourceAccessor(&StaWifiMac::m_beaconInfo),
                            "ns3::ApInfo::TracedCallback");
    return tid;
}
 
StaWifiMac::StaWifiMac()
    : m_state(UNASSOCIATED),
      m_aid(0),
      m_assocRequestEvent()
{
    NS_LOG_FUNCTION(this);
 
    // Let the lower layers know that we are acting as a non-AP STA in
    // an infrastructure BSS.
    SetTypeOfStation(STA);
}
 
void
StaWifiMac::DoInitialize()
{
    NS_LOG_FUNCTION(this);
    // an EMLSR client must perform ML setup by using its main PHY
    if (m_assocManager && m_emlsrManager)
    {
        auto mainPhyId = m_emlsrManager->GetMainPhyId();
        auto linkId = GetLinkForPhy(mainPhyId);
        NS_ASSERT(linkId);
        m_assocManager->SetAttribute(
            "AllowedLinks",
            AttributeContainerValue<UintegerValue>(std::list<uint8_t>{*linkId}));
    }
    if (m_emlsrManager)
    {
        m_emlsrManager->Initialize();
    }
    StartScanning();
    NS_ABORT_IF(!TraceConnectWithoutContext("AckedMpdu", MakeCallback(&StaWifiMac::TxOk, this)));
    WifiMac::DoInitialize();
}
 
void
StaWifiMac::DoDispose()
{
    NS_LOG_FUNCTION(this);
    if (m_assocManager)
    {
        m_assocManager->Dispose();
    }
    m_assocManager = nullptr;
    if (m_emlsrManager)
    {
        m_emlsrManager->Dispose();
    }
    m_emlsrManager = nullptr;
    WifiMac::DoDispose();
}
 
StaWifiMac::~StaWifiMac()
{
    NS_LOG_FUNCTION(this);
}
 
StaWifiMac::StaLinkEntity::~StaLinkEntity()
{
    NS_LOG_FUNCTION_NOARGS();
}
 
std::unique_ptr<WifiMac::LinkEntity>
StaWifiMac::CreateLinkEntity() const
{
    return std::make_unique<StaLinkEntity>();
}
 
StaWifiMac::StaLinkEntity&
StaWifiMac::GetLink(uint8_t linkId) const
{
    return static_cast<StaLinkEntity&>(WifiMac::GetLink(linkId));
}
 
StaWifiMac::StaLinkEntity&
StaWifiMac::GetStaLink(const std::unique_ptr<WifiMac::LinkEntity>& link) const
{
    return static_cast<StaLinkEntity&>(*link);
}
 
int64_t
StaWifiMac::AssignStreams(int64_t stream)
{
    NS_LOG_FUNCTION(this << stream);
    m_probeDelay->SetStream(stream);
    auto currentStream = stream + 1;
    currentStream += WifiMac::AssignStreams(currentStream);
    return (currentStream - stream);
}
 
void
StaWifiMac::SetAssocManager(Ptr<WifiAssocManager> assocManager)
{
    NS_LOG_FUNCTION(this << assocManager);
    m_assocManager = assocManager;
    m_assocManager->SetStaWifiMac(this);
}
 
void
StaWifiMac::SetEmlsrManager(Ptr<EmlsrManager> emlsrManager)
{
    NS_LOG_FUNCTION(this << emlsrManager);
    m_emlsrManager = emlsrManager;
    m_emlsrManager->SetWifiMac(this);
}
 
Ptr<EmlsrManager>
StaWifiMac::GetEmlsrManager() const
{
    return m_emlsrManager;
}
 
uint16_t
StaWifiMac::GetAssociationId() const
{
    NS_ASSERT_MSG(IsAssociated(), "This station is not associated to any AP");
    return m_aid;
}
 
void
StaWifiMac::SetActiveProbing(bool enable)
{
    NS_LOG_FUNCTION(this << enable);
    m_activeProbing = enable;
    if (m_state == SCANNING)
    {
        NS_LOG_DEBUG("STA is still scanning, reset scanning process");
        StartScanning();
    }
}
 
bool
StaWifiMac::GetActiveProbing() const
{
    return m_activeProbing;
}
 
void
StaWifiMac::SetWifiPhys(const std::vector<Ptr<WifiPhy>>& phys)
{
    NS_LOG_FUNCTION(this);
    WifiMac::SetWifiPhys(phys);
    for (auto& phy : phys)
    {
        phy->SetCapabilitiesChangedCallback(
            MakeCallback(&StaWifiMac::PhyCapabilitiesChanged, this));
    }
}
 
WifiScanParams::Channel
StaWifiMac::GetCurrentChannel(uint8_t linkId) const
{
    auto phy = GetWifiPhy(linkId);
    uint16_t width = phy->GetOperatingChannel().IsOfdm() ? 20 : phy->GetChannelWidth();
    uint8_t ch = phy->GetOperatingChannel().GetPrimaryChannelNumber(width, phy->GetStandard());
    return {ch, phy->GetPhyBand()};
}
 
void
StaWifiMac::NotifyEmlsrModeChanged(const std::set<uint8_t>& linkIds)
{
    std::stringstream ss;
    if (g_log.IsEnabled(ns3::LOG_FUNCTION))
    {
        std::copy(linkIds.cbegin(), linkIds.cend(), std::ostream_iterator<uint16_t>(ss, " "));
    }
    NS_LOG_FUNCTION(this << ss.str());
 
    for (const auto& [linkId, lnk] : GetLinks())
    {
        auto& link = GetStaLink(lnk);
 
        if (linkIds.contains(linkId))
        {
            // EMLSR mode enabled
            link.emlsrEnabled = true;
            link.pmMode = WIFI_PM_ACTIVE;
        }
        else
        {
            // EMLSR mode disabled
            if (link.emlsrEnabled)
            {
                link.pmMode = WIFI_PM_POWERSAVE;
            }
            link.emlsrEnabled = false;
        }
    }
}
 
bool
StaWifiMac::IsEmlsrLink(uint8_t linkId) const
{
    return GetLink(linkId).emlsrEnabled;
}
 
void
StaWifiMac::SendProbeRequest(uint8_t linkId)
{
    NS_LOG_FUNCTION(this << linkId);
    WifiMacHeader hdr;
    hdr.SetType(WIFI_MAC_MGT_PROBE_REQUEST);
    hdr.SetAddr1(Mac48Address::GetBroadcast());
    hdr.SetAddr2(GetFrameExchangeManager(linkId)->GetAddress());
    hdr.SetAddr3(Mac48Address::GetBroadcast());
    hdr.SetDsNotFrom();
    hdr.SetDsNotTo();
    Ptr<Packet> packet = Create<Packet>();
    MgtProbeRequestHeader probe;
    probe.Get<Ssid>() = GetSsid();
    auto supportedRates = GetSupportedRates(linkId);
    probe.Get<SupportedRates>() = supportedRates.rates;
    probe.Get<ExtendedSupportedRatesIE>() = supportedRates.extendedRates;
    if (GetHtSupported())
    {
        probe.Get<ExtendedCapabilities>() = GetExtendedCapabilities();
        probe.Get<HtCapabilities>() = GetHtCapabilities(linkId);
    }
    if (GetVhtSupported(linkId))
    {
        probe.Get<VhtCapabilities>() = GetVhtCapabilities(linkId);
    }
    if (GetHeSupported())
    {
        probe.Get<HeCapabilities>() = GetHeCapabilities(linkId);
    }
    if (GetEhtSupported())
    {
        probe.Get<EhtCapabilities>() = GetEhtCapabilities(linkId);
    }
    packet->AddHeader(probe);
 
    if (!GetQosSupported())
    {
        GetTxop()->Queue(packet, hdr);
    }
    // "A QoS STA that transmits a Management frame determines access category used
    // for medium access in transmission of the Management frame as follows
    // (If dot11QMFActivated is false or not present)
    // — If the Management frame is individually addressed to a non-QoS STA, category
    //   AC_BE should be selected.
    // — If category AC_BE was not selected by the previous step, category AC_VO
    //   shall be selected." (Sec. 10.2.3.2 of 802.11-2020)
    else
    {
        GetVOQueue()->Queue(packet, hdr);
    }
}
 
std::variant<MgtAssocRequestHeader, MgtReassocRequestHeader>
StaWifiMac::GetAssociationRequest(bool isReassoc, uint8_t linkId) const
{
    NS_LOG_FUNCTION(this << isReassoc << +linkId);
 
    std::variant<MgtAssocRequestHeader, MgtReassocRequestHeader> mgtFrame;
 
    if (isReassoc)
    {
        MgtReassocRequestHeader reassoc;
        reassoc.SetCurrentApAddress(GetBssid(linkId));
        mgtFrame = std::move(reassoc);
    }
    else
    {
        mgtFrame = MgtAssocRequestHeader();
    }
 
    // lambda to set the fields of the (Re)Association Request
    auto fill = [&](auto&& frame) {
        frame.template Get<Ssid>() = GetSsid();
        auto supportedRates = GetSupportedRates(linkId);
        frame.template Get<SupportedRates>() = supportedRates.rates;
        frame.template Get<ExtendedSupportedRatesIE>() = supportedRates.extendedRates;
        frame.Capabilities() = GetCapabilities(linkId);
        frame.SetListenInterval(0);
        if (GetHtSupported())
        {
            frame.template Get<ExtendedCapabilities>() = GetExtendedCapabilities();
            frame.template Get<HtCapabilities>() = GetHtCapabilities(linkId);
        }
        if (GetVhtSupported(linkId))
        {
            frame.template Get<VhtCapabilities>() = GetVhtCapabilities(linkId);
        }
        if (GetHeSupported())
        {
            frame.template Get<HeCapabilities>() = GetHeCapabilities(linkId);
        }
        if (GetEhtSupported())
        {
            frame.template Get<EhtCapabilities>() = GetEhtCapabilities(linkId);
        }
    };
 
    std::visit(fill, mgtFrame);
    return mgtFrame;
}
 
MultiLinkElement
StaWifiMac::GetMultiLinkElement(bool isReassoc, uint8_t linkId) const
{
    NS_LOG_FUNCTION(this << isReassoc << +linkId);
 
    MultiLinkElement multiLinkElement(MultiLinkElement::BASIC_VARIANT);
    // The Common info field of the Basic Multi-Link element carried in the (Re)Association
    // Request frame shall include the MLD MAC address, the MLD Capabilities and Operations,
    // and the EML Capabilities subfields, and shall not include the Link ID Info, the BSS
    // Parameters Change Count, and the Medium Synchronization Delay Information subfields
    // (Sec. 35.3.5.4 of 802.11be D2.0)
    // TODO Add the MLD Capabilities and Operations subfield
    multiLinkElement.SetMldMacAddress(GetAddress());
 
    if (m_emlsrManager) // EMLSR Manager is only installed if EMLSR is activated
    {
        multiLinkElement.SetEmlsrSupported(true);
        TimeValue time;
        m_emlsrManager->GetAttribute("EmlsrPaddingDelay", time);
        multiLinkElement.SetEmlsrPaddingDelay(time.Get());
        m_emlsrManager->GetAttribute("EmlsrTransitionDelay", time);
        multiLinkElement.SetEmlsrTransitionDelay(time.Get());
        // When the Transition Timeout subfield is included in a frame sent by a non-AP STA
        // affiliated with a non-AP MLD, the Transition Timeout subfield is reserved
        // (Section 9.4.2.312.2.3 of 802.11be D2.3)
        // The Medium Synchronization Delay Information subfield in the Common Info subfield is
        // not present if the Basic Multi-Link element is sent by a non-AP STA. (Section
        // 9.4.2.312.2.3 of 802.11be D3.1)
    }
 
    // The MLD Capabilities And Operations subfield is present in the Common Info field of the
    // Basic Multi-Link element carried in Beacon, Probe Response, (Re)Association Request, and
    // (Re)Association Response frames. (Sec. 9.4.2.312.2.3 of 802.11be D3.1)
    auto& mldCapabilities = multiLinkElement.GetCommonInfoBasic().m_mldCapabilities;
    mldCapabilities.emplace();
    mldCapabilities->maxNSimultaneousLinks = GetNLinks() - 1; // assuming STR for now
    mldCapabilities->srsSupport = 0;
 
    auto ehtConfiguration = GetEhtConfiguration();
    NS_ASSERT(ehtConfiguration);
    EnumValue<WifiTidToLinkMappingNegSupport> negSupport;
    ehtConfiguration->GetAttributeFailSafe("TidToLinkMappingNegSupport", negSupport);
 
    mldCapabilities->tidToLinkMappingSupport = static_cast<uint8_t>(negSupport.Get());
    mldCapabilities->freqSepForStrApMld = 0; // not supported yet
    mldCapabilities->aarSupport = 0;         // not supported yet
 
    // For each requested link in addition to the link on which the (Re)Association Request
    // frame is transmitted, the Link Info field of the Basic Multi-Link element carried
    // in the (Re)Association Request frame shall contain the corresponding Per-STA Profile
    // subelement(s).
    for (const auto& [index, link] : GetLinks())
    {
        const auto& staLink = GetStaLink(link);
 
        if (index != linkId && staLink.bssid.has_value())
        {
            multiLinkElement.AddPerStaProfileSubelement();
            auto& perStaProfile = multiLinkElement.GetPerStaProfile(
                multiLinkElement.GetNPerStaProfileSubelements() - 1);
            // The Link ID subfield of the STA Control field of the Per-STA Profile subelement
            // for the corresponding non-AP STA that requests a link for multi-link (re)setup
            // with the AP MLD is set to the link ID of the AP affiliated with the AP MLD that
            // is operating on that link. The link ID is obtained during multi-link discovery
            perStaProfile.SetLinkId(index);
            // For each Per-STA Profile subelement included in the Link Info field, the
            // Complete Profile subfield of the STA Control field shall be set to 1
            perStaProfile.SetCompleteProfile();
            // The MAC Address Present subfield indicates the presence of the STA MAC Address
            // subfield in the STA Info field and is set to 1 if the STA MAC Address subfield
            // is present in the STA Info field; otherwise set to 0. An STA sets this subfield
            // to 1 when the element carries complete profile.
            perStaProfile.SetStaMacAddress(staLink.feManager->GetAddress());
            perStaProfile.SetAssocRequest(GetAssociationRequest(isReassoc, index));
        }
    }
 
    return multiLinkElement;
}
 
std::vector<TidToLinkMapping>
StaWifiMac::GetTidToLinkMappingElements(WifiTidToLinkMappingNegSupport apNegSupport)
{
    NS_LOG_FUNCTION(this << apNegSupport);
 
    auto ehtConfig = GetEhtConfiguration();
    NS_ASSERT(ehtConfig);
 
    EnumValue<WifiTidToLinkMappingNegSupport> negSupport;
    ehtConfig->GetAttributeFailSafe("TidToLinkMappingNegSupport", negSupport);
 
    NS_ABORT_MSG_IF(negSupport.Get() == WifiTidToLinkMappingNegSupport::NOT_SUPPORTED,
                    "Cannot request TID-to-Link Mapping if negotiation is not supported");
 
    // store the mappings, so that we can enforce them when the AP MLD accepts them
    m_dlTidLinkMappingInAssocReq = ehtConfig->GetTidLinkMapping(WifiDirection::DOWNLINK);
    m_ulTidLinkMappingInAssocReq = ehtConfig->GetTidLinkMapping(WifiDirection::UPLINK);
 
    bool mappingValidForNegType1 = TidToLinkMappingValidForNegType1(m_dlTidLinkMappingInAssocReq,
                                                                    m_ulTidLinkMappingInAssocReq);
    NS_ABORT_MSG_IF(
        negSupport.Get() == WifiTidToLinkMappingNegSupport::SAME_LINK_SET &&
            !mappingValidForNegType1,
        "Mapping TIDs to distinct link sets is incompatible with negotiation support of 1");
 
    if (apNegSupport == WifiTidToLinkMappingNegSupport::SAME_LINK_SET && !mappingValidForNegType1)
    {
        // If the TID-to-link Mapping Negotiation Support subfield value received from a peer
        // MLD is equal to 1, the MLD that initiates a TID-to-link mapping negotiation with the
        // peer MLD shall send only the TID-to-link Mapping element where all TIDs are mapped to
        // the same link set (Sec. 35.3.7.1.3 of 802.11be D3.1). We use default mapping to meet
        // this requirement.
        NS_LOG_DEBUG("Using default mapping because AP MLD advertised negotiation support of 1");
        m_dlTidLinkMappingInAssocReq.clear();
        m_ulTidLinkMappingInAssocReq.clear();
    }
 
    std::vector<TidToLinkMapping> ret(1);
 
    ret.back().m_control.direction = WifiDirection::DOWNLINK;
 
    // lambda to fill the last TID-to-Link Mapping IE in the vector to return
    auto fillIe = [&ret](const auto& mapping) {
        ret.back().m_control.defaultMapping = mapping.empty();
 
        for (const auto& [tid, linkSet] : mapping)
        {
            // At any point in time, a TID shall always be mapped to at least one setup link both
            // in DL and UL, which means that a TID-to-link mapping change is only valid and
            // successful if it will not result in having any TID for which the link set for DL
            // or UL is made of zero setup links (Sec. 35.3.7.1.1 of 802.11be D3.1)
            NS_ABORT_MSG_IF(linkSet.empty(), "Cannot map a TID to an empty link set");
            ret.back().SetLinkMappingOfTid(tid, linkSet);
        }
    };
 
    fillIe(m_dlTidLinkMappingInAssocReq);
 
    if (m_ulTidLinkMappingInAssocReq == m_dlTidLinkMappingInAssocReq)
    {
        ret.back().m_control.direction = WifiDirection::BOTH_DIRECTIONS;
        return ret;
    }
 
    ret.emplace_back();
    ret.back().m_control.direction = WifiDirection::UPLINK;
    fillIe(m_ulTidLinkMappingInAssocReq);
 
    return ret;
}
 
void
StaWifiMac::SendAssociationRequest(bool isReassoc)
{
    // find the link where the (Re)Association Request has to be sent
    auto it = GetLinks().cbegin();
    while (it != GetLinks().cend())
    {
        if (GetStaLink(it->second).sendAssocReq)
        {
            break;
        }
        it++;
    }
    NS_ABORT_MSG_IF(it == GetLinks().cend(),
                    "No link selected to send the (Re)Association Request");
    uint8_t linkId = it->first;
    auto& link = GetLink(linkId);
    NS_ABORT_MSG_IF(!link.bssid.has_value(),
                    "No BSSID set for the link on which the (Re)Association Request is to be sent");
 
    NS_LOG_FUNCTION(this << *link.bssid << isReassoc);
    WifiMacHeader hdr;
    hdr.SetType(isReassoc ? WIFI_MAC_MGT_REASSOCIATION_REQUEST : WIFI_MAC_MGT_ASSOCIATION_REQUEST);
    hdr.SetAddr1(*link.bssid);
    hdr.SetAddr2(link.feManager->GetAddress());
    hdr.SetAddr3(*link.bssid);
    hdr.SetDsNotFrom();
    hdr.SetDsNotTo();
    Ptr<Packet> packet = Create<Packet>();
 
    auto frame = GetAssociationRequest(isReassoc, linkId);
 
    // include a Multi-Link Element if this device has multiple links (independently
    // of how many links will be setup) and the AP is a multi-link device;
    // if the AP MLD  has indicated a support of TID-to-link mapping negotiation, also
    // include the TID-to-link Mapping element(s)
    if (GetNLinks() > 1 &&
        GetWifiRemoteStationManager(linkId)->GetMldAddress(*link.bssid).has_value())
    {
        auto addMle = [&](auto&& frame) {
            frame.template Get<MultiLinkElement>() = GetMultiLinkElement(isReassoc, linkId);
        };
        std::visit(addMle, frame);
 
        WifiTidToLinkMappingNegSupport negSupport;
        if (const auto& mldCapabilities =
                GetWifiRemoteStationManager(linkId)->GetStationMldCapabilities(*link.bssid);
            mldCapabilities && (negSupport = static_cast<WifiTidToLinkMappingNegSupport>(
                                    mldCapabilities->get().tidToLinkMappingSupport)) >
                                   WifiTidToLinkMappingNegSupport::NOT_SUPPORTED)
        {
            auto addTlm = [&](auto&& frame) {
                frame.template Get<TidToLinkMapping>() = GetTidToLinkMappingElements(negSupport);
            };
            std::visit(addTlm, frame);
        }
    }
 
    if (!isReassoc)
    {
        packet->AddHeader(std::get<MgtAssocRequestHeader>(frame));
    }
    else
    {
        packet->AddHeader(std::get<MgtReassocRequestHeader>(frame));
    }
 
    if (!GetQosSupported())
    {
        GetTxop()->Queue(packet, hdr);
    }
    // "A QoS STA that transmits a Management frame determines access category used
    // for medium access in transmission of the Management frame as follows
    // (If dot11QMFActivated is false or not present)
    // — If the Management frame is individually addressed to a non-QoS STA, category
    //   AC_BE should be selected.
    // — If category AC_BE was not selected by the previous step, category AC_VO
    //   shall be selected." (Sec. 10.2.3.2 of 802.11-2020)
    else if (!GetWifiRemoteStationManager(linkId)->GetQosSupported(*link.bssid))
    {
        GetBEQueue()->Queue(packet, hdr);
    }
    else
    {
        GetVOQueue()->Queue(packet, hdr);
    }
 
    if (m_assocRequestEvent.IsRunning())
    {
        m_assocRequestEvent.Cancel();
    }
    m_assocRequestEvent =
        Simulator::Schedule(m_assocRequestTimeout, &StaWifiMac::AssocRequestTimeout, this);
}
 
void
StaWifiMac::TryToEnsureAssociated()
{
    NS_LOG_FUNCTION(this);
    switch (m_state)
    {
    case ASSOCIATED:
        return;
    case SCANNING:
        /* we have initiated active or passive scanning, continue to wait
           and gather beacons or probe responses until the scanning timeout
         */
        break;
    case UNASSOCIATED:
        /* we were associated but we missed a bunch of beacons
         * so we should assume we are not associated anymore.
         * We try to initiate a scan now.
         */
        m_linkDown();
        StartScanning();
        break;
    case WAIT_ASSOC_RESP:
        /* we have sent an association request so we do not need to
           re-send an association request right now. We just need to
           wait until either assoc-request-timeout or until
           we get an association response.
         */
        break;
    case REFUSED:
        /* we have sent an association request and received a negative
           association response. We wait until someone restarts an
           association with a given SSID.
         */
        break;
    }
}
 
void
StaWifiMac::StartScanning()
{
    NS_LOG_FUNCTION(this);
    SetState(SCANNING);
    NS_ASSERT(m_assocManager);
 
    WifiScanParams scanParams;
    scanParams.ssid = GetSsid();
    for (const auto& [id, link] : GetLinks())
    {
        WifiScanParams::ChannelList channel{
            (link->phy->HasFixedPhyBand()) ? WifiScanParams::Channel{0, link->phy->GetPhyBand()}
                                           : WifiScanParams::Channel{0, WIFI_PHY_BAND_UNSPECIFIED}};
 
        scanParams.channelList.push_back(channel);
    }
    if (m_activeProbing)
    {
        scanParams.type = WifiScanType::ACTIVE;
        scanParams.probeDelay = MicroSeconds(m_probeDelay->GetValue());
        scanParams.minChannelTime = scanParams.maxChannelTime = m_probeRequestTimeout;
    }
    else
    {
        scanParams.type = WifiScanType::PASSIVE;
        scanParams.maxChannelTime = m_waitBeaconTimeout;
    }
 
    m_assocManager->StartScanning(std::move(scanParams));
}
 
void
StaWifiMac::ScanningTimeout(const std::optional<ApInfo>& bestAp)
{
    NS_LOG_FUNCTION(this);
 
    if (!bestAp.has_value())
    {
        NS_LOG_DEBUG("Exhausted list of candidate AP; restart scanning");
        StartScanning();
        return;
    }
 
    NS_LOG_DEBUG("Attempting to associate with AP: " << *bestAp);
    UpdateApInfo(bestAp->m_frame, bestAp->m_apAddr, bestAp->m_bssid, bestAp->m_linkId);
    // reset info on links to setup
    for (auto& [id, link] : GetLinks())
    {
        auto& staLink = GetStaLink(link);
        staLink.sendAssocReq = false;
        staLink.bssid = std::nullopt;
    }
    // send Association Request on the link where the Beacon/Probe Response was received
    GetLink(bestAp->m_linkId).sendAssocReq = true;
    GetLink(bestAp->m_linkId).bssid = bestAp->m_bssid;
    std::shared_ptr<CommonInfoBasicMle> mleCommonInfo;
    // update info on links to setup (11be MLDs only)
    const auto& mle =
        std::visit([](auto&& frame) { return frame.template Get<MultiLinkElement>(); },
                   bestAp->m_frame);
    std::map<uint8_t, uint8_t> swapInfo;
    for (const auto& [localLinkId, apLinkId, bssid] : bestAp->m_setupLinks)
    {
        NS_ASSERT_MSG(mle, "We get here only for ML setup");
        NS_LOG_DEBUG("Setting up link (local ID=" << +localLinkId << ", AP ID=" << +apLinkId
                                                  << ")");
        GetLink(localLinkId).bssid = bssid;
        if (!mleCommonInfo)
        {
            mleCommonInfo = std::make_shared<CommonInfoBasicMle>(mle->GetCommonInfoBasic());
        }
        GetWifiRemoteStationManager(localLinkId)->AddStationMleCommonInfo(bssid, mleCommonInfo);
        swapInfo.emplace(localLinkId, apLinkId);
    }
 
    SwapLinks(swapInfo);
 
    // lambda to get beacon interval from Beacon or Probe Response
    auto getBeaconInterval = [](auto&& frame) {
        using T = std::decay_t<decltype(frame)>;
        if constexpr (std::is_same_v<T, MgtBeaconHeader> ||
                      std::is_same_v<T, MgtProbeResponseHeader>)
        {
            return MicroSeconds(frame.GetBeaconIntervalUs());
        }
        else
        {
            NS_ABORT_MSG("Unexpected frame type");
            return Seconds(0);
        }
    };
    Time beaconInterval = std::visit(getBeaconInterval, bestAp->m_frame);
    Time delay = beaconInterval * m_maxMissedBeacons;
    // restart beacon watchdog
    RestartBeaconWatchdog(delay);
 
    SetState(WAIT_ASSOC_RESP);
    SendAssociationRequest(false);
}
 
void
StaWifiMac::AssocRequestTimeout()
{
    NS_LOG_FUNCTION(this);
    SetState(WAIT_ASSOC_RESP);
    SendAssociationRequest(false);
}
 
void
StaWifiMac::MissedBeacons()
{
    NS_LOG_FUNCTION(this);
 
    if (m_beaconWatchdogEnd > Simulator::Now())
    {
        if (m_beaconWatchdog.IsRunning())
        {
            m_beaconWatchdog.Cancel();
        }
        m_beaconWatchdog = Simulator::Schedule(m_beaconWatchdogEnd - Simulator::Now(),
                                               &StaWifiMac::MissedBeacons,
                                               this);
        return;
    }
    NS_LOG_DEBUG("beacon missed");
    // We need to switch to the UNASSOCIATED state. However, if we are receiving a frame, wait
    // until the RX is completed (otherwise, crashes may occur if we are receiving a MU frame
    // because its reception requires the STA-ID). We need to check that a PHY is operating on
    // the given link, because this may (temporarily) not be the case for EMLSR clients.
    Time delay = Seconds(0);
    for (const auto& [id, link] : GetLinks())
    {
        if (link->phy && link->phy->IsStateRx())
        {
            delay = std::max(delay, link->phy->GetDelayUntilIdle());
        }
    }
    Simulator::Schedule(delay, &StaWifiMac::Disassociated, this);
}
 
void
StaWifiMac::Disassociated()
{
    NS_LOG_FUNCTION(this);
 
    Mac48Address apAddr; // the AP address to trace (MLD address in case of ML setup)
 
    for (const auto& [id, link] : GetLinks())
    {
        auto& bssid = GetStaLink(link).bssid;
        if (bssid)
        {
            apAddr = GetWifiRemoteStationManager(id)->GetMldAddress(*bssid).value_or(*bssid);
        }
        bssid = std::nullopt; // link is no longer setup
    }
 
    NS_LOG_DEBUG("Set state to UNASSOCIATED and start scanning");
    SetState(UNASSOCIATED);
    // cancel the association request timer (see issue #862)
    m_assocRequestEvent.Cancel();
    m_deAssocLogger(apAddr);
    m_aid = 0; // reset AID
    TryToEnsureAssociated();
}
 
void
StaWifiMac::RestartBeaconWatchdog(Time delay)
{
    NS_LOG_FUNCTION(this << delay);
 
    m_beaconWatchdogEnd = std::max(Simulator::Now() + delay, m_beaconWatchdogEnd);
    if (Simulator::GetDelayLeft(m_beaconWatchdog) < delay && m_beaconWatchdog.IsExpired())
    {
        NS_LOG_DEBUG("really restart watchdog.");
        m_beaconWatchdog = Simulator::Schedule(delay, &StaWifiMac::MissedBeacons, this);
    }
}
 
bool
StaWifiMac::IsAssociated() const
{
    return m_state == ASSOCIATED;
}
 
bool
StaWifiMac::IsWaitAssocResp() const
{
    return m_state == WAIT_ASSOC_RESP;
}
 
std::set<uint8_t>
StaWifiMac::GetSetupLinkIds() const
{
    if (!IsAssociated())
    {
        return {};
    }
 
    std::set<uint8_t> linkIds;
    for (const auto& [id, link] : GetLinks())
    {
        if (GetStaLink(link).bssid)
        {
            linkIds.insert(id);
        }
    }
    return linkIds;
}
 
Mac48Address
StaWifiMac::DoGetLocalAddress(const Mac48Address& remoteAddr) const
{
    auto linkIds = GetSetupLinkIds();
    NS_ASSERT_MSG(!linkIds.empty(), "Not associated");
    uint8_t linkId = *linkIds.begin();
    return GetFrameExchangeManager(linkId)->GetAddress();
}
 
bool
StaWifiMac::CanForwardPacketsTo(Mac48Address to) const
{
    return IsAssociated();
}
 
void
StaWifiMac::Enqueue(Ptr<Packet> packet, Mac48Address to)
{
    NS_LOG_FUNCTION(this << packet << to);
    if (!CanForwardPacketsTo(to))
    {
        NotifyTxDrop(packet);
        TryToEnsureAssociated();
        return;
    }
    WifiMacHeader hdr;
 
    // If we are not a QoS AP then we definitely want to use AC_BE to
    // transmit the packet. A TID of zero will map to AC_BE (through \c
    // QosUtilsMapTidToAc()), so we use that as our default here.
    uint8_t tid = 0;
 
    // For now, an AP that supports QoS does not support non-QoS
    // associations, and vice versa. In future the AP model should
    // support simultaneously associated QoS and non-QoS STAs, at which
    // point there will need to be per-association QoS state maintained
    // by the association state machine, and consulted here.
    if (GetQosSupported())
    {
        hdr.SetType(WIFI_MAC_QOSDATA);
        hdr.SetQosAckPolicy(WifiMacHeader::NORMAL_ACK);
        hdr.SetQosNoEosp();
        hdr.SetQosNoAmsdu();
        // Transmission of multiple frames in the same TXOP is not
        // supported for now
        hdr.SetQosTxopLimit(0);
 
        // Fill in the QoS control field in the MAC header
        tid = QosUtilsGetTidForPacket(packet);
        // Any value greater than 7 is invalid and likely indicates that
        // the packet had no QoS tag, so we revert to zero, which'll
        // mean that AC_BE is used.
        if (tid > 7)
        {
            tid = 0;
        }
        hdr.SetQosTid(tid);
    }
    else
    {
        hdr.SetType(WIFI_MAC_DATA);
    }
    if (GetQosSupported())
    {
        hdr.SetNoOrder(); // explicitly set to 0 for the time being since HT control field is not
                          // yet implemented (set it to 1 when implemented)
    }
 
    // the Receiver Address (RA) and the Transmitter Address (TA) are the MLD addresses only for
    // non-broadcast data frames exchanged between two MLDs
    auto linkIds = GetSetupLinkIds();
    NS_ASSERT(!linkIds.empty());
    uint8_t linkId = *linkIds.begin();
    if (const auto apMldAddr = GetWifiRemoteStationManager(linkId)->GetMldAddress(GetBssid(linkId)))
    {
        hdr.SetAddr1(*apMldAddr);
        hdr.SetAddr2(GetAddress());
    }
    else
    {
        hdr.SetAddr1(GetBssid(linkId));
        hdr.SetAddr2(GetFrameExchangeManager(linkId)->GetAddress());
    }
 
    hdr.SetAddr3(to);
    hdr.SetDsNotFrom();
    hdr.SetDsTo();
 
    if (GetQosSupported())
    {
        // Sanity check that the TID is valid
        NS_ASSERT(tid < 8);
        GetQosTxop(tid)->Queue(packet, hdr);
    }
    else
    {
        GetTxop()->Queue(packet, hdr);
    }
}
 
void
StaWifiMac::BlockTxOnLink(uint8_t linkId, WifiQueueBlockedReason reason)
{
    NS_LOG_FUNCTION(this << linkId << reason);
 
    auto bssid = GetBssid(linkId);
    auto apAddress = GetWifiRemoteStationManager(linkId)->GetMldAddress(bssid).value_or(bssid);
 
    BlockUnicastTxOnLinks(reason, apAddress, {linkId});
    // the only type of broadcast frames that a non-AP STA can send are management frames
    for (const auto& [acIndex, ac] : wifiAcList)
    {
        GetMacQueueScheduler()->BlockQueues(reason,
                                            acIndex,
                                            {WIFI_MGT_QUEUE},
                                            Mac48Address::GetBroadcast(),
                                            GetFrameExchangeManager(linkId)->GetAddress(),
                                            {},
                                            {linkId});
    }
}
 
void
StaWifiMac::UnblockTxOnLink(std::set<uint8_t> linkIds, WifiQueueBlockedReason reason)
{
    std::stringstream ss;
    std::copy(linkIds.cbegin(), linkIds.cend(), std::ostream_iterator<uint16_t>(ss, " "));
    NS_LOG_FUNCTION(this << ss.str() << reason);
 
    const auto linkId = *linkIds.cbegin();
    const auto bssid = GetBssid(linkId);
    const auto apAddress =
        GetWifiRemoteStationManager(linkId)->GetMldAddress(bssid).value_or(bssid);
 
    UnblockUnicastTxOnLinks(reason, apAddress, linkIds);
    // the only type of broadcast frames that a non-AP STA can send are management frames
    for (const auto& [acIndex, ac] : wifiAcList)
    {
        GetMacQueueScheduler()->UnblockQueues(reason,
                                              acIndex,
                                              {WIFI_MGT_QUEUE},
                                              Mac48Address::GetBroadcast(),
                                              GetFrameExchangeManager(linkId)->GetAddress(),
                                              {},
                                              linkIds);
    }
}
 
void
StaWifiMac::Receive(Ptr<const WifiMpdu> mpdu, uint8_t linkId)
{
    NS_LOG_FUNCTION(this << *mpdu << +linkId);
    // consider the MAC header of the original MPDU (makes a difference for data frames only)
    const WifiMacHeader* hdr = &mpdu->GetOriginal()->GetHeader();
    Ptr<const Packet> packet = mpdu->GetPacket();
    NS_ASSERT(!hdr->IsCtl());
    Mac48Address myAddr = hdr->IsData() ? Mac48Address::ConvertFrom(GetDevice()->GetAddress())
                                        : GetFrameExchangeManager(linkId)->GetAddress();
    if (hdr->GetAddr3() == myAddr)
    {
        NS_LOG_LOGIC("packet sent by us.");
        return;
    }
    if (hdr->GetAddr1() != myAddr && !hdr->GetAddr1().IsGroup())
    {
        NS_LOG_LOGIC("packet is not for us");
        NotifyRxDrop(packet);
        return;
    }
    if (hdr->IsData())
    {
        if (!IsAssociated())
        {
            NS_LOG_LOGIC("Received data frame while not associated: ignore");
            NotifyRxDrop(packet);
            return;
        }
        if (!(hdr->IsFromDs() && !hdr->IsToDs()))
        {
            NS_LOG_LOGIC("Received data frame not from the DS: ignore");
            NotifyRxDrop(packet);
            return;
        }
        std::set<Mac48Address> apAddresses; // link addresses of AP
        for (auto id : GetSetupLinkIds())
        {
            apAddresses.insert(GetBssid(id));
        }
        if (!apAddresses.contains(mpdu->GetHeader().GetAddr2()))
        {
            NS_LOG_LOGIC("Received data frame not from the BSS we are associated with: ignore");
            NotifyRxDrop(packet);
            return;
        }
        if (!hdr->HasData())
        {
            NS_LOG_LOGIC("Received (QoS) Null Data frame: ignore");
            NotifyRxDrop(packet);
            return;
        }
        if (hdr->IsQosData())
        {
            if (hdr->IsQosAmsdu())
            {
                NS_ASSERT(apAddresses.contains(mpdu->GetHeader().GetAddr3()));
                DeaggregateAmsduAndForward(mpdu);
                packet = nullptr;
            }
            else
            {
                ForwardUp(packet, hdr->GetAddr3(), hdr->GetAddr1());
            }
        }
        else
        {
            ForwardUp(packet, hdr->GetAddr3(), hdr->GetAddr1());
        }
        return;
    }
 
    switch (hdr->GetType())
    {
    case WIFI_MAC_MGT_PROBE_REQUEST:
    case WIFI_MAC_MGT_ASSOCIATION_REQUEST:
    case WIFI_MAC_MGT_REASSOCIATION_REQUEST:
        // This is a frame aimed at an AP, so we can safely ignore it.
        NotifyRxDrop(packet);
        break;
 
    case WIFI_MAC_MGT_BEACON:
        ReceiveBeacon(mpdu, linkId);
        break;
 
    case WIFI_MAC_MGT_PROBE_RESPONSE:
        ReceiveProbeResp(mpdu, linkId);
        break;
 
    case WIFI_MAC_MGT_ASSOCIATION_RESPONSE:
    case WIFI_MAC_MGT_REASSOCIATION_RESPONSE:
        ReceiveAssocResp(mpdu, linkId);
        break;
 
    case WIFI_MAC_MGT_ACTION:
        if (auto [category, action] = WifiActionHeader::Peek(packet);
            category == WifiActionHeader::PROTECTED_EHT &&
            action.protectedEhtAction ==
                WifiActionHeader::PROTECTED_EHT_EML_OPERATING_MODE_NOTIFICATION)
        {
            // this is handled by the EMLSR Manager
            break;
        }
 
    default:
        // Invoke the receive handler of our parent class to deal with any
        // other frames. Specifically, this will handle Block Ack-related
        // Management Action frames.
        WifiMac::Receive(mpdu, linkId);
    }
 
    if (m_emlsrManager)
    {
        m_emlsrManager->NotifyMgtFrameReceived(mpdu, linkId);
    }
}
 
void
StaWifiMac::ReceiveBeacon(Ptr<const WifiMpdu> mpdu, uint8_t linkId)
{
    NS_LOG_FUNCTION(this << *mpdu << +linkId);
    const WifiMacHeader& hdr = mpdu->GetHeader();
    NS_ASSERT(hdr.IsBeacon());
 
    NS_LOG_DEBUG("Beacon received");
    MgtBeaconHeader beacon;
    mpdu->GetPacket()->PeekHeader(beacon);
    const auto& capabilities = beacon.Capabilities();
    NS_ASSERT(capabilities.IsEss());
    bool goodBeacon;
    if (IsWaitAssocResp() || IsAssociated())
    {
        // we have to process this Beacon only if sent by the AP we are associated
        // with or from which we are waiting an Association Response frame
        auto bssid = GetLink(linkId).bssid;
        goodBeacon = bssid.has_value() && (hdr.GetAddr3() == *bssid);
    }
    else
    {
        // we retain this Beacon as candidate AP if the supported rates fit the
        // configured BSS membership selector
        goodBeacon = CheckSupportedRates(beacon, linkId);
    }
 
    SnrTag snrTag;
    bool found = mpdu->GetPacket()->PeekPacketTag(snrTag);
    NS_ASSERT(found);
    ApInfo apInfo = {.m_bssid = hdr.GetAddr3(),
                     .m_apAddr = hdr.GetAddr2(),
                     .m_snr = snrTag.Get(),
                     .m_frame = std::move(beacon),
                     .m_channel = {GetCurrentChannel(linkId)},
                     .m_linkId = linkId};
 
    if (!m_beaconInfo.IsEmpty())
    {
        m_beaconInfo(apInfo);
    }
 
    if (!goodBeacon)
    {
        NS_LOG_LOGIC("Beacon is not for us");
        return;
    }
    if (m_state == ASSOCIATED)
    {
        m_beaconArrival(Simulator::Now());
        Time delay = MicroSeconds(std::get<MgtBeaconHeader>(apInfo.m_frame).GetBeaconIntervalUs() *
                                  m_maxMissedBeacons);
        RestartBeaconWatchdog(delay);
        UpdateApInfo(apInfo.m_frame, hdr.GetAddr2(), hdr.GetAddr3(), linkId);
    }
    else
    {
        NS_LOG_DEBUG("Beacon received from " << hdr.GetAddr2());
        m_assocManager->NotifyApInfo(std::move(apInfo));
    }
}
 
void
StaWifiMac::ReceiveProbeResp(Ptr<const WifiMpdu> mpdu, uint8_t linkId)
{
    NS_LOG_FUNCTION(this << *mpdu << +linkId);
    const WifiMacHeader& hdr = mpdu->GetHeader();
    NS_ASSERT(hdr.IsProbeResp());
 
    NS_LOG_DEBUG("Probe response received from " << hdr.GetAddr2());
    MgtProbeResponseHeader probeResp;
    mpdu->GetPacket()->PeekHeader(probeResp);
    if (!CheckSupportedRates(probeResp, linkId))
    {
        return;
    }
    SnrTag snrTag;
    bool found = mpdu->GetPacket()->PeekPacketTag(snrTag);
    NS_ASSERT(found);
    m_assocManager->NotifyApInfo(ApInfo{.m_bssid = hdr.GetAddr3(),
                                        .m_apAddr = hdr.GetAddr2(),
                                        .m_snr = snrTag.Get(),
                                        .m_frame = std::move(probeResp),
                                        .m_channel = {GetCurrentChannel(linkId)},
                                        .m_linkId = linkId});
}
 
void
StaWifiMac::ReceiveAssocResp(Ptr<const WifiMpdu> mpdu, uint8_t linkId)
{
    NS_LOG_FUNCTION(this << *mpdu << +linkId);
    const WifiMacHeader& hdr = mpdu->GetHeader();
    NS_ASSERT(hdr.IsAssocResp() || hdr.IsReassocResp());
 
    if (m_state != WAIT_ASSOC_RESP)
    {
        return;
    }
 
    std::optional<Mac48Address> apMldAddress;
    MgtAssocResponseHeader assocResp;
    mpdu->GetPacket()->PeekHeader(assocResp);
    if (m_assocRequestEvent.IsRunning())
    {
        m_assocRequestEvent.Cancel();
    }
    if (assocResp.GetStatusCode().IsSuccess())
    {
        m_aid = assocResp.GetAssociationId();
        NS_LOG_DEBUG((hdr.IsReassocResp() ? "reassociation done" : "association completed"));
        UpdateApInfo(assocResp, hdr.GetAddr2(), hdr.GetAddr3(), linkId);
        NS_ASSERT(GetLink(linkId).bssid.has_value() && *GetLink(linkId).bssid == hdr.GetAddr3());
        SetBssid(hdr.GetAddr3(), linkId);
        SetState(ASSOCIATED);
        if ((GetNLinks() > 1) && assocResp.Get<MultiLinkElement>().has_value())
        {
            // this is an ML setup, trace the setup link
            m_setupCompleted(linkId, hdr.GetAddr3());
            apMldAddress = GetWifiRemoteStationManager(linkId)->GetMldAddress(hdr.GetAddr3());
            NS_ASSERT(apMldAddress);
 
            if (const auto& mldCapabilities =
                    GetWifiRemoteStationManager(linkId)->GetStationMldCapabilities(hdr.GetAddr3());
                mldCapabilities && static_cast<WifiTidToLinkMappingNegSupport>(
                                       mldCapabilities->get().tidToLinkMappingSupport) >
                                       WifiTidToLinkMappingNegSupport::NOT_SUPPORTED)
            {
                // the AP MLD supports TID-to-Link Mapping negotiation, hence we included
                // TID-to-Link Mapping element(s) in the Association Request.
                if (assocResp.Get<TidToLinkMapping>().empty())
                {
                    // The AP MLD did not include a TID-to-Link Mapping element in the Association
                    // Response, hence it accepted the mapping, which we can now store.
                    UpdateTidToLinkMapping(*apMldAddress,
                                           WifiDirection::DOWNLINK,
                                           m_dlTidLinkMappingInAssocReq);
                    UpdateTidToLinkMapping(*apMldAddress,
                                           WifiDirection::UPLINK,
                                           m_ulTidLinkMappingInAssocReq);
 
                    // Apply the negotiated TID-to-Link Mapping (if any) for UL direction
                    ApplyTidLinkMapping(*apMldAddress, WifiDirection::UPLINK);
                }
            }
        }
        else
        {
            m_assocLogger(hdr.GetAddr3());
        }
        if (!m_linkUp.IsNull())
        {
            m_linkUp();
        }
    }
    else
    {
        // If the link on which the (Re)Association Request frame was received cannot be
        // accepted by the AP MLD, the AP MLD shall treat the multi-link (re)setup as a
        // failure and shall not accept any requested links. If the link on which the
        // (Re)Association Request frame was received is accepted by the AP MLD, the
        // multi-link (re)setup is successful. (Sec. 35.3.5.1 of 802.11be D3.1)
        NS_LOG_DEBUG("association refused");
        SetState(REFUSED);
        StartScanning();
        return;
    }
 
    // if this is an MLD, check if we can setup (other) links
    if (GetNLinks() > 1)
    {
        // create a list of all local Link IDs. IDs are removed as we find a corresponding
        // Per-STA Profile Subelements indicating successful association. Links with
        // remaining IDs are not setup
        std::list<uint8_t> setupLinks;
        for (const auto& [id, link] : GetLinks())
        {
            setupLinks.push_back(id);
        }
        if (assocResp.GetStatusCode().IsSuccess())
        {
            setupLinks.remove(linkId);
        }
 
        // if a Multi-Link Element is present, check its content
        if (const auto& mle = assocResp.Get<MultiLinkElement>())
        {
            NS_ABORT_MSG_IF(!GetLink(linkId).bssid.has_value(),
                            "The link on which the Association Response was received "
                            "is not a link we requested to setup");
            NS_ABORT_MSG_IF(linkId != mle->GetLinkIdInfo(),
                            "The link ID of the AP that transmitted the Association "
                            "Response does not match the stored link ID");
            NS_ABORT_MSG_IF(GetWifiRemoteStationManager(linkId)->GetMldAddress(hdr.GetAddr2()) !=
                                mle->GetMldMacAddress(),
                            "The AP MLD MAC address in the received Multi-Link Element does not "
                            "match the address stored in the station manager for link "
                                << +linkId);
            // process the Per-STA Profile Subelements in the Multi-Link Element
            for (std::size_t elem = 0; elem < mle->GetNPerStaProfileSubelements(); elem++)
            {
                auto& perStaProfile = mle->GetPerStaProfile(elem);
                uint8_t apLinkId = perStaProfile.GetLinkId();
                auto it = GetLinks().find(apLinkId);
                uint8_t staLinkid = 0;
                std::optional<Mac48Address> bssid;
                NS_ABORT_MSG_IF(it == GetLinks().cend() ||
                                    !(bssid = GetLink((staLinkid = it->first)).bssid).has_value(),
                                "Setup for AP link ID " << apLinkId << " was not requested");
                NS_ABORT_MSG_IF(*bssid != perStaProfile.GetStaMacAddress(),
                                "The BSSID in the Per-STA Profile for link ID "
                                    << +staLinkid << " does not match the stored BSSID");
                NS_ABORT_MSG_IF(
                    GetWifiRemoteStationManager(staLinkid)->GetMldAddress(
                        perStaProfile.GetStaMacAddress()) != mle->GetMldMacAddress(),
                    "The AP MLD MAC address in the received Multi-Link Element does not "
                    "match the address stored in the station manager for link "
                        << +staLinkid);
                // process the Association Response contained in this Per-STA Profile
                MgtAssocResponseHeader assoc = perStaProfile.GetAssocResponse();
                if (assoc.GetStatusCode().IsSuccess())
                {
                    NS_ABORT_MSG_IF(m_aid != 0 && m_aid != assoc.GetAssociationId(),
                                    "AID should be the same for all the links");
                    m_aid = assoc.GetAssociationId();
                    NS_LOG_DEBUG("Setup on link " << staLinkid << " completed");
                    UpdateApInfo(assoc, *bssid, *bssid, staLinkid);
                    SetBssid(*bssid, staLinkid);
                    m_setupCompleted(staLinkid, *bssid);
                    SetState(ASSOCIATED);
                    apMldAddress = GetWifiRemoteStationManager(staLinkid)->GetMldAddress(*bssid);
                    if (!m_linkUp.IsNull())
                    {
                        m_linkUp();
                    }
                }
                // remove the ID of the link we setup
                setupLinks.remove(staLinkid);
            }
        }
        // remaining links in setupLinks are not setup and hence must be disabled
        for (const auto& id : setupLinks)
        {
            GetLink(id).bssid = std::nullopt;
            GetLink(id).phy->SetOffMode();
        }
        if (apMldAddress)
        {
            // this is an ML setup, trace the MLD address of the AP (only once)
            m_assocLogger(*apMldAddress);
        }
    }
 
    // the station that associated with the AP may have dissociated and then associated again.
    // In this case, the station may store packets from the previous period in which it was
    // associated. Have the station restart access if it has packets queued.
    for (const auto& [id, link] : GetLinks())
    {
        if (GetStaLink(link).bssid)
        {
            if (const auto txop = GetTxop())
            {
                txop->StartAccessAfterEvent(id,
                                            Txop::DIDNT_HAVE_FRAMES_TO_TRANSMIT,
                                            Txop::CHECK_MEDIUM_BUSY);
            }
            for (const auto& [acIndex, ac] : wifiAcList)
            {
                if (const auto edca = GetQosTxop(acIndex))
                {
                    edca->StartAccessAfterEvent(id,
                                                Txop::DIDNT_HAVE_FRAMES_TO_TRANSMIT,
                                                Txop::CHECK_MEDIUM_BUSY);
                }
            }
        }
    }
 
    SetPmModeAfterAssociation(linkId);
}
 
void
StaWifiMac::SetPmModeAfterAssociation(uint8_t linkId)
{
    NS_LOG_FUNCTION(this << linkId);
 
    // STAs operating on setup links may need to transition to a new PM mode after the
    // acknowledgement of the Association Response. For this purpose, we connect a callback to
    // the PHY TX begin trace to catch the Ack transmitted after the Association Response.
    CallbackBase cb = Callback<void, WifiConstPsduMap, WifiTxVector, double>(
        [=, this](WifiConstPsduMap psduMap, WifiTxVector txVector, double /* txPowerW */) {
            NS_ASSERT_MSG(psduMap.size() == 1 && psduMap.begin()->second->GetNMpdus() == 1 &&
                              psduMap.begin()->second->GetHeader(0).IsAck(),
                          "Expected a Normal Ack after Association Response frame");
 
            auto ackDuration =
                WifiPhy::CalculateTxDuration(psduMap, txVector, GetLink(linkId).phy->GetPhyBand());
 
            for (const auto& [id, lnk] : GetLinks())
            {
                auto& link = GetStaLink(lnk);
 
                if (!link.bssid)
                {
                    // link has not been setup
                    continue;
                }
 
                if (id == linkId)
                {
                    /**
                     * When a link becomes enabled for a non-AP STA that is affiliated with a
                     * non-AP MLD after successful association with an AP MLD with (Re)Association
                     * Request/Response  frames transmitted on that link [..], the power management
                     * mode of the non-AP STA, immediately after the acknowledgement of the
                     * (Re)Association Response frame [..], is active mode.
                     * (Sec. 35.3.7.1.4 of 802.11be D3.0)
                     */
                    // if the user requested this link to be in powersave mode, we have to
                    // switch PM mode
                    if (link.pmMode == WIFI_PM_POWERSAVE)
                    {
                        Simulator::Schedule(ackDuration,
                                            &StaWifiMac::SetPowerSaveMode,
                                            this,
                                            std::pair<bool, uint8_t>{true, id});
                    }
                    link.pmMode = WIFI_PM_ACTIVE;
                }
                else
                {
                    /**
                     * When a link becomes enabled for a non-AP STA that is affiliated with a
                     * non-AP MLD after successful association with an AP MLD with (Re)Association
                     * Request/Response frames transmitted on another link [..], the power
                     * management mode of the non-AP STA, immediately after the acknowledgement of
                     * the (Re)Association Response frame [..], is power save mode, and its power
                     * state is doze. (Sec. 35.3.7.1.4 of 802.11be D3.0)
                     */
                    // if the user requested this link to be in active mode, we have to
                    // switch PM mode
                    if (link.pmMode == WIFI_PM_ACTIVE)
                    {
                        Simulator::Schedule(ackDuration,
                                            &StaWifiMac::SetPowerSaveMode,
                                            this,
                                            std::pair<bool, uint8_t>{false, id});
                    }
                    link.pmMode = WIFI_PM_POWERSAVE;
                }
            }
        });
 
    // connect the callback to the PHY TX begin trace to catch the Ack and disconnect
    // after its transmission begins
    auto phy = GetLink(linkId).phy;
    phy->TraceConnectWithoutContext("PhyTxPsduBegin", cb);
    Simulator::Schedule(phy->GetSifs() + NanoSeconds(1),
                        [=]() { phy->TraceDisconnectWithoutContext("PhyTxPsduBegin", cb); });
}
 
bool
StaWifiMac::CheckSupportedRates(std::variant<MgtBeaconHeader, MgtProbeResponseHeader> frame,
                                uint8_t linkId)
{
    NS_LOG_FUNCTION(this << +linkId);
 
    // lambda to invoke on the current frame variant
    auto check = [&](auto&& mgtFrame) -> bool {
        // check supported rates
        NS_ASSERT(mgtFrame.template Get<SupportedRates>());
        const auto rates = AllSupportedRates{*mgtFrame.template Get<SupportedRates>(),
                                             mgtFrame.template Get<ExtendedSupportedRatesIE>()};
        for (const auto& selector : GetWifiPhy(linkId)->GetBssMembershipSelectorList())
        {
            if (!rates.IsBssMembershipSelectorRate(selector))
            {
                NS_LOG_DEBUG("Supported rates do not fit with the BSS membership selector");
                return false;
            }
        }
 
        return true;
    };
 
    return std::visit(check, frame);
}
 
void
StaWifiMac::UpdateApInfo(const MgtFrameType& frame,
                         const Mac48Address& apAddr,
                         const Mac48Address& bssid,
                         uint8_t linkId)
{
    NS_LOG_FUNCTION(this << frame.index() << apAddr << bssid << +linkId);
 
    // ERP Information is not present in Association Response frames
    const std::optional<ErpInformation>* erpInformation = nullptr;
 
    if (const auto* beacon = std::get_if<MgtBeaconHeader>(&frame))
    {
        erpInformation = &beacon->Get<ErpInformation>();
    }
    else if (const auto* probe = std::get_if<MgtProbeResponseHeader>(&frame))
    {
        erpInformation = &probe->Get<ErpInformation>();
    }
 
    // lambda processing Information Elements included in all frame types
    auto commonOps = [&](auto&& frame) {
        const auto& capabilities = frame.Capabilities();
        NS_ASSERT(frame.template Get<SupportedRates>());
        const auto rates = AllSupportedRates{*frame.template Get<SupportedRates>(),
                                             frame.template Get<ExtendedSupportedRatesIE>()};
        for (const auto& mode : GetWifiPhy(linkId)->GetModeList())
        {
            if (rates.IsSupportedRate(mode.GetDataRate(GetWifiPhy(linkId)->GetChannelWidth())))
            {
                GetWifiRemoteStationManager(linkId)->AddSupportedMode(apAddr, mode);
                if (rates.IsBasicRate(mode.GetDataRate(GetWifiPhy(linkId)->GetChannelWidth())))
                {
                    GetWifiRemoteStationManager(linkId)->AddBasicMode(mode);
                }
            }
        }
 
        bool isShortPreambleEnabled = capabilities.IsShortPreamble();
        if (erpInformation && erpInformation->has_value() && GetErpSupported(linkId))
        {
            isShortPreambleEnabled &= !(*erpInformation)->GetBarkerPreambleMode();
            if ((*erpInformation)->GetUseProtection() != 0)
            {
                GetWifiRemoteStationManager(linkId)->SetUseNonErpProtection(true);
            }
            else
            {
                GetWifiRemoteStationManager(linkId)->SetUseNonErpProtection(false);
            }
            if (capabilities.IsShortSlotTime() == true)
            {
                // enable short slot time
                GetWifiPhy(linkId)->SetSlot(MicroSeconds(9));
            }
            else
            {
                // disable short slot time
                GetWifiPhy(linkId)->SetSlot(MicroSeconds(20));
            }
        }
        GetWifiRemoteStationManager(linkId)->SetShortPreambleEnabled(isShortPreambleEnabled);
        GetWifiRemoteStationManager(linkId)->SetShortSlotTimeEnabled(
            capabilities.IsShortSlotTime());
 
        if (!GetQosSupported())
        {
            return;
        }
        /* QoS station */
        bool qosSupported = false;
        const auto& edcaParameters = frame.template Get<EdcaParameterSet>();
        if (edcaParameters.has_value())
        {
            qosSupported = true;
            // The value of the TXOP Limit field is specified as an unsigned integer, with the least
            // significant octet transmitted first, in units of 32 μs.
            SetEdcaParameters({AC_BE,
                               edcaParameters->GetBeCWmin(),
                               edcaParameters->GetBeCWmax(),
                               edcaParameters->GetBeAifsn(),
                               32 * MicroSeconds(edcaParameters->GetBeTxopLimit())},
                              linkId);
            SetEdcaParameters({AC_BK,
                               edcaParameters->GetBkCWmin(),
                               edcaParameters->GetBkCWmax(),
                               edcaParameters->GetBkAifsn(),
                               32 * MicroSeconds(edcaParameters->GetBkTxopLimit())},
                              linkId);
            SetEdcaParameters({AC_VI,
                               edcaParameters->GetViCWmin(),
                               edcaParameters->GetViCWmax(),
                               edcaParameters->GetViAifsn(),
                               32 * MicroSeconds(edcaParameters->GetViTxopLimit())},
                              linkId);
            SetEdcaParameters({AC_VO,
                               edcaParameters->GetVoCWmin(),
                               edcaParameters->GetVoCWmax(),
                               edcaParameters->GetVoAifsn(),
                               32 * MicroSeconds(edcaParameters->GetVoTxopLimit())},
                              linkId);
        }
        GetWifiRemoteStationManager(linkId)->SetQosSupport(apAddr, qosSupported);
 
        if (!GetHtSupported())
        {
            return;
        }
        /* HT station */
        if (const auto& htCapabilities = frame.template Get<HtCapabilities>();
            htCapabilities.has_value())
        {
            if (!htCapabilities->IsSupportedMcs(0))
            {
                GetWifiRemoteStationManager(linkId)->RemoveAllSupportedMcs(apAddr);
            }
            else
            {
                GetWifiRemoteStationManager(linkId)->AddStationHtCapabilities(apAddr,
                                                                              *htCapabilities);
            }
        }
        // TODO: process ExtendedCapabilities
        // ExtendedCapabilities extendedCapabilities = frame.GetExtendedCapabilities ();
 
        // we do not return if VHT is not supported because HE STAs operating in
        // the 2.4 GHz band do not support VHT
        if (GetVhtSupported(linkId))
        {
            const auto& vhtCapabilities = frame.template Get<VhtCapabilities>();
            // we will always fill in RxHighestSupportedLgiDataRate field at TX, so this can be used
            // to check whether it supports VHT
            if (vhtCapabilities.has_value() &&
                vhtCapabilities->GetRxHighestSupportedLgiDataRate() > 0)
            {
                GetWifiRemoteStationManager(linkId)->AddStationVhtCapabilities(apAddr,
                                                                               *vhtCapabilities);
                // const auto& vhtOperation = frame.GetVhtOperation ();
                for (const auto& mcs : GetWifiPhy(linkId)->GetMcsList(WIFI_MOD_CLASS_VHT))
                {
                    if (vhtCapabilities->IsSupportedRxMcs(mcs.GetMcsValue()))
                    {
                        GetWifiRemoteStationManager(linkId)->AddSupportedMcs(apAddr, mcs);
                    }
                }
            }
        }
 
        if (!GetHeSupported())
        {
            return;
        }
        /* HE station */
        const auto& heCapabilities = frame.template Get<HeCapabilities>();
        if (heCapabilities.has_value() && heCapabilities->GetSupportedMcsAndNss() != 0)
        {
            GetWifiRemoteStationManager(linkId)->AddStationHeCapabilities(apAddr, *heCapabilities);
            for (const auto& mcs : GetWifiPhy(linkId)->GetMcsList(WIFI_MOD_CLASS_HE))
            {
                if (heCapabilities->IsSupportedRxMcs(mcs.GetMcsValue()))
                {
                    GetWifiRemoteStationManager(linkId)->AddSupportedMcs(apAddr, mcs);
                }
            }
            if (const auto& heOperation = frame.template Get<HeOperation>();
                heOperation.has_value())
            {
                GetHeConfiguration()->SetAttribute("BssColor",
                                                   UintegerValue(heOperation->GetBssColor()));
            }
        }
 
        const auto& muEdcaParameters = frame.template Get<MuEdcaParameterSet>();
        if (muEdcaParameters.has_value())
        {
            SetMuEdcaParameters({AC_BE,
                                 muEdcaParameters->GetMuCwMin(AC_BE),
                                 muEdcaParameters->GetMuCwMax(AC_BE),
                                 muEdcaParameters->GetMuAifsn(AC_BE),
                                 muEdcaParameters->GetMuEdcaTimer(AC_BE)},
                                linkId);
            SetMuEdcaParameters({AC_BK,
                                 muEdcaParameters->GetMuCwMin(AC_BK),
                                 muEdcaParameters->GetMuCwMax(AC_BK),
                                 muEdcaParameters->GetMuAifsn(AC_BK),
                                 muEdcaParameters->GetMuEdcaTimer(AC_BK)},
                                linkId);
            SetMuEdcaParameters({AC_VI,
                                 muEdcaParameters->GetMuCwMin(AC_VI),
                                 muEdcaParameters->GetMuCwMax(AC_VI),
                                 muEdcaParameters->GetMuAifsn(AC_VI),
                                 muEdcaParameters->GetMuEdcaTimer(AC_VI)},
                                linkId);
            SetMuEdcaParameters({AC_VO,
                                 muEdcaParameters->GetMuCwMin(AC_VO),
                                 muEdcaParameters->GetMuCwMax(AC_VO),
                                 muEdcaParameters->GetMuAifsn(AC_VO),
                                 muEdcaParameters->GetMuEdcaTimer(AC_VO)},
                                linkId);
        }
 
        if (!GetEhtSupported())
        {
            return;
        }
        /* EHT station */
        const auto& ehtCapabilities = frame.template Get<EhtCapabilities>();
        // TODO: once we support non constant rate managers, we should add checks here whether EHT
        // is supported by the peer
        GetWifiRemoteStationManager(linkId)->AddStationEhtCapabilities(apAddr, *ehtCapabilities);
 
        if (const auto& mle = frame.template Get<MultiLinkElement>(); mle && m_emlsrManager)
        {
            if (mle->HasEmlCapabilities())
            {
                m_emlsrManager->SetTransitionTimeout(mle->GetTransitionTimeout());
            }
            if (const auto& common = mle->GetCommonInfoBasic(); common.m_mediumSyncDelayInfo)
            {
                m_emlsrManager->SetMediumSyncDuration(common.GetMediumSyncDelayTimer());
                m_emlsrManager->SetMediumSyncOfdmEdThreshold(common.GetMediumSyncOfdmEdThreshold());
                m_emlsrManager->SetMediumSyncMaxNTxops(common.GetMediumSyncMaxNTxops());
            }
        }
    };
 
    // process Information Elements included in the current frame variant
    std::visit(commonOps, frame);
}
 
void
StaWifiMac::SetPowerSaveMode(const std::pair<bool, uint8_t>& enableLinkIdPair)
{
    const auto [enable, linkId] = enableLinkIdPair;
    NS_LOG_FUNCTION(this << enable << linkId);
 
    auto& link = GetLink(linkId);
 
    if (!IsAssociated())
    {
        NS_LOG_DEBUG("Not associated yet, record the PM mode to switch to upon association");
        link.pmMode = enable ? WIFI_PM_POWERSAVE : WIFI_PM_ACTIVE;
        return;
    }
 
    if (!link.bssid)
    {
        NS_LOG_DEBUG("Link " << +linkId << " has not been setup, ignore request");
        return;
    }
 
    if ((enable && link.pmMode == WIFI_PM_POWERSAVE) || (!enable && link.pmMode == WIFI_PM_ACTIVE))
    {
        NS_LOG_DEBUG("No PM mode change needed");
        return;
    }
 
    link.pmMode = enable ? WIFI_PM_SWITCHING_TO_PS : WIFI_PM_SWITCHING_TO_ACTIVE;
 
    // reschedule a call to this function to make sure that the PM mode switch
    // is eventually completed
    Simulator::Schedule(m_pmModeSwitchTimeout,
                        &StaWifiMac::SetPowerSaveMode,
                        this,
                        enableLinkIdPair);
 
    if (HasFramesToTransmit(linkId))
    {
        NS_LOG_DEBUG("Next transmitted frame will be sent with PM=" << enable);
        return;
    }
 
    // No queued frames. Enqueue a Data Null frame to inform the AP of the PM mode change
    WifiMacHeader hdr(WIFI_MAC_DATA_NULL);
 
    hdr.SetAddr1(GetBssid(linkId));
    hdr.SetAddr2(GetFrameExchangeManager(linkId)->GetAddress());
    hdr.SetAddr3(GetBssid(linkId));
    hdr.SetDsNotFrom();
    hdr.SetDsTo();
    enable ? hdr.SetPowerManagement() : hdr.SetNoPowerManagement();
    if (GetQosSupported())
    {
        GetQosTxop(AC_BE)->Queue(Create<WifiMpdu>(Create<Packet>(), hdr));
    }
    else
    {
        m_txop->Queue(Create<WifiMpdu>(Create<Packet>(), hdr));
    }
}
 
WifiPowerManagementMode
StaWifiMac::GetPmMode(uint8_t linkId) const
{
    return GetLink(linkId).pmMode;
}
 
void
StaWifiMac::TxOk(Ptr<const WifiMpdu> mpdu)
{
    NS_LOG_FUNCTION(this << *mpdu);
 
    auto linkId = GetLinkIdByAddress(mpdu->GetHeader().GetAddr2());
 
    if (!linkId)
    {
        // the given MPDU may be the original copy containing MLD addresses and not carrying
        // a valid PM bit (which is set on the aliases).
        auto linkIds = mpdu->GetInFlightLinkIds();
        NS_ASSERT_MSG(!linkIds.empty(),
                      "The TA of the acked MPDU (" << *mpdu
                                                   << ") is not a link "
                                                      "address and the MPDU is not inflight");
        // in case the ack'ed MPDU is inflight on multiple links, we cannot really know if
        // it was received by the AP on all links or only on some links. Hence, we only
        // consider the first link ID in the set, given that in the most common case of MPDUs
        // that cannot be sent concurrently on multiple links, there will be only one link ID
        linkId = *linkIds.begin();
        mpdu = GetTxopQueue(mpdu->GetQueueAc())->GetAlias(mpdu, *linkId);
    }
 
    auto& link = GetLink(*linkId);
    const WifiMacHeader& hdr = mpdu->GetHeader();
 
    // we received an acknowledgment while switching PM mode; the PM mode change is effective now
    if (hdr.IsPowerManagement() && link.pmMode == WIFI_PM_SWITCHING_TO_PS)
    {
        link.pmMode = WIFI_PM_POWERSAVE;
    }
    else if (!hdr.IsPowerManagement() && link.pmMode == WIFI_PM_SWITCHING_TO_ACTIVE)
    {
        link.pmMode = WIFI_PM_ACTIVE;
    }
}
 
AllSupportedRates
StaWifiMac::GetSupportedRates(uint8_t linkId) const
{
    AllSupportedRates rates;
    for (const auto& mode : GetWifiPhy(linkId)->GetModeList())
    {
        uint64_t modeDataRate = mode.GetDataRate(GetWifiPhy(linkId)->GetChannelWidth());
        NS_LOG_DEBUG("Adding supported rate of " << modeDataRate);
        rates.AddSupportedRate(modeDataRate);
    }
    if (GetHtSupported())
    {
        for (const auto& selector : GetWifiPhy(linkId)->GetBssMembershipSelectorList())
        {
            rates.AddBssMembershipSelectorRate(selector);
        }
    }
    return rates;
}
 
CapabilityInformation
StaWifiMac::GetCapabilities(uint8_t linkId) const
{
    CapabilityInformation capabilities;
    capabilities.SetShortPreamble(GetWifiPhy(linkId)->GetShortPhyPreambleSupported() ||
                                  GetErpSupported(linkId));
    capabilities.SetShortSlotTime(GetShortSlotTimeSupported() && GetErpSupported(linkId));
    return capabilities;
}
 
void
StaWifiMac::SetState(MacState value)
{
    m_state = value;
}
 
void
StaWifiMac::SetEdcaParameters(const EdcaParams& params, uint8_t linkId)
{
    Ptr<QosTxop> edca = GetQosTxop(params.ac);
    edca->SetMinCw(params.cwMin, linkId);
    edca->SetMaxCw(params.cwMax, linkId);
    edca->SetAifsn(params.aifsn, linkId);
    edca->SetTxopLimit(params.txopLimit, linkId);
}
 
void
StaWifiMac::SetMuEdcaParameters(const MuEdcaParams& params, uint8_t linkId)
{
    Ptr<QosTxop> edca = GetQosTxop(params.ac);
    edca->SetMuCwMin(params.cwMin, linkId);
    edca->SetMuCwMax(params.cwMax, linkId);
    edca->SetMuAifsn(params.aifsn, linkId);
    edca->SetMuEdcaTimer(params.muEdcaTimer, linkId);
}
 
void
StaWifiMac::PhyCapabilitiesChanged()
{
    NS_LOG_FUNCTION(this);
    if (IsAssociated())
    {
        NS_LOG_DEBUG("PHY capabilities changed: send reassociation request");
        SetState(WAIT_ASSOC_RESP);
        SendAssociationRequest(true);
    }
}
 
/**
 * Initial configuration:
 *
 *        ┌───┬───┬───┐        ┌────┐       ┌───────┐
 * Link A │FEM│RSM│CAM│◄──────►│Main├──────►│Channel│
 *        │   │   │   │        │PHY │       │   A   │
 *        └───┴───┴───┘        └────┘       └───────┘
 *
 *        ┌───┬───┬───┐        ┌────┐       ┌───────┐
 * Link B │FEM│RSM│CAM│        │Aux │       │Channel│
 *        │   │   │   │◄──────►│PHY ├──────►│   B   │
 *        └───┴───┴───┘        └────┘       └───────┘
 *
 * A link switching/swapping is notified by the EMLSR Manager and the Channel Access Manager
 * (CAM) notifies us that a first PHY (i.e., the Main PHY) switches to Channel B. We connect
 * the Main PHY to the MAC stack B:
 *
 *
 *        ┌───┬───┬───┐        ┌────┐       ┌───────┐
 * Link A │FEM│RSM│CAM│   ┌───►│Main├───┐   │Channel│
 *        │   │   │   │   │    │PHY │   │   │   A   │
 *        └───┴───┴───┘   │    └────┘   │   └───────┘
 *                        │             │
 *        ┌───┬───┬───┐   │    ┌────┐   │   ┌───────┐
 * Link B │FEM│RSM│CAM│◄──┘    │Aux │   └──►│Channel│
 *        │   │   │   │◄─ ─ ─ ─│PHY ├──────►│   B   │
 *        └───┴───┴───┘INACTIVE└────┘       └───────┘
 *
 * MAC stack B keeps a PHY listener associated with the Aux PHY, even though it is inactive,
 * meaning that the PHY listener will only notify channel switches (no CCA, no RX).
 * If the EMLSR Manager requested a link switching, this configuration will be kept until
 * further requests. If the EMLSR Manager requested a link swapping, link B's CAM will be
 * notified by its (inactive) PHY listener upon the channel switch performed by the Aux PHY.
 * In this case, we remove the inactive PHY listener and connect the Aux PHY to MAC stack A:
 *
 *        ┌───┬───┬───┐        ┌────┐       ┌───────┐
 * Link A │FEM│RSM│CAM│◄─┐ ┌──►│Main├───┐   │Channel│
 *        │   │   │   │  │ │   │PHY │ ┌─┼──►│   A   │
 *        └───┴───┴───┘  │ │   └────┘ │ │   └───────┘
 *                       │ │          │ │
 *        ┌───┬───┬───┐  │ │   ┌────┐ │ │   ┌───────┐
 * Link B │FEM│RSM│CAM│◄─┼─┘   │Aux │ │ └──►│Channel│
 *        │   │   │   │  └────►│PHY ├─┘     │   B   │
 *        └───┴───┴───┘        └────┘       └───────┘
 */
 
void
StaWifiMac::NotifySwitchingEmlsrLink(Ptr<WifiPhy> phy, uint8_t linkId, Time delay)
{
    NS_LOG_FUNCTION(this << phy << linkId << delay.As(Time::US));
 
    // If the PHY is switching channel to operate on another link, then it is no longer operating
    // on the current link. If any link (other than the current link) points to the PHY that is
    // switching channel, reset the phy pointer of the link
    for (auto& [id, link] : GetLinks())
    {
        if (link->phy == phy && id != linkId)
        {
            link->phy = nullptr;
        }
    }
 
    // lambda to connect the PHY to the new link
    auto connectPhy = [=, this]() mutable {
        auto& newLink = GetLink(linkId);
        // The MAC stack associated with the new link uses the given PHY
        newLink.phy = phy;
        // Setup a PHY listener for the given PHY on the CAM associated with the new link
        newLink.channelAccessManager->SetupPhyListener(phy);
        NS_ASSERT(m_emlsrManager);
        if (m_emlsrManager->GetCamStateReset())
        {
            newLink.channelAccessManager->ResetState();
        }
        // Disconnect the FEM on the new link from the current PHY
        newLink.feManager->ResetPhy();
        // Connect the FEM on the new link to the given PHY
        newLink.feManager->SetWifiPhy(phy);
        // Connect the station manager on the new link to the given PHY
        newLink.stationManager->SetupPhy(phy);
    };
 
    // if there is no PHY operating on the new link, connect the PHY to the new link now.
    // Otherwise, wait until the channel switch is completed, so that the PHY operating on the new
    // link can possibly continue receiving frames in the meantime.
    if (!GetLink(linkId).phy)
    {
        connectPhy();
    }
    else
    {
        Simulator::Schedule(delay, connectPhy);
    }
}
 
void
StaWifiMac::NotifyChannelSwitching(uint8_t linkId)
{
    NS_LOG_FUNCTION(this << +linkId);
 
    WifiMac::NotifyChannelSwitching(linkId);
 
    if (IsInitialized() && IsAssociated())
    {
        Disassociated();
    }
 
    // notify association manager
    m_assocManager->NotifyChannelSwitched(linkId);
}
 
std::ostream&
operator<<(std::ostream& os, const StaWifiMac::ApInfo& apInfo)
{
    os << "BSSID=" << apInfo.m_bssid << ", AP addr=" << apInfo.m_apAddr << ", SNR=" << apInfo.m_snr
       << ", Channel={" << apInfo.m_channel.number << "," << apInfo.m_channel.band
       << "}, Link ID=" << +apInfo.m_linkId << ", Frame=[";
    std::visit([&os](auto&& frame) { frame.Print(os); }, apInfo.m_frame);
    os << "]";
    return os;
}
 
} // namespace ns3