wifi: EMLSR client switches to listening mode as soon as it is notified of the MAC header of an MPDU that is not addressed to it

src/wifi/model/eht/advanced-emlsr-manager.cc

@@ -67,6 +67,32 @@ AdvancedEmlsrManager::~AdvancedEmlsrManager()
     NS_LOG_FUNCTION_NOARGS();
 }
 
+void
+AdvancedEmlsrManager::DoDispose()
+{
+    NS_LOG_FUNCTION(this);
+    for (auto phy : GetStaMac()->GetDevice()->GetPhys())
+    {
+        phy->TraceDisconnectWithoutContext(
+            "PhyRxMacHeaderEnd",
+            MakeCallback(&AdvancedEmlsrManager::ReceivedMacHdr, this).Bind(phy));
+    }
+    DefaultEmlsrManager::DoDispose();
+}
+
+void
+AdvancedEmlsrManager::DoSetWifiMac(Ptr<StaWifiMac> mac)
+{
+    NS_LOG_FUNCTION(this << mac);
+
+    for (auto phy : GetStaMac()->GetDevice()->GetPhys())
+    {
+        phy->TraceConnectWithoutContext(
+            "PhyRxMacHeaderEnd",
+            MakeCallback(&AdvancedEmlsrManager::ReceivedMacHdr, this).Bind(phy));
+    }
+}
+
 Time
 AdvancedEmlsrManager::GetDelayUntilAccessRequest(uint8_t linkId)
 {
@@ -162,4 +188,36 @@ AdvancedEmlsrManager::GetDelayUntilAccessRequest(uint8_t linkId)
     return Time{0};
 }
 
+void
+AdvancedEmlsrManager::ReceivedMacHdr(Ptr<WifiPhy> phy,
+                                     const WifiMacHeader& macHdr,
+                                     const WifiTxVector& txVector,
+                                     Time psduDuration)
+{
+    auto linkId = GetStaMac()->GetLinkForPhy(phy);
+    if (!linkId.has_value())
+    {
+        return;
+    }
+    NS_LOG_FUNCTION(this << *linkId << macHdr << txVector << psduDuration.As(Time::MS));
+
+    auto& ongoingTxopEnd = GetEhtFem(*linkId)->GetOngoingTxopEndEvent();
+
+    if (m_useNotifiedMacHdr && ongoingTxopEnd.IsPending() &&
+        macHdr.GetAddr1() != GetEhtFem(*linkId)->GetAddress() && !macHdr.GetAddr1().IsBroadcast() &&
+        !(macHdr.IsCts() && macHdr.GetAddr1() == GetEhtFem(*linkId)->GetBssid() /* CTS-to-self */))
+    {
+        // the EMLSR client is no longer involved in the TXOP and switching to listening mode
+        ongoingTxopEnd.Cancel();
+        // this method is a callback connected to the PhyRxMacHeaderEnd trace source of WifiPhy
+        // and is called within a for loop that executes all the callbacks. The call to NotifyTxop
+        // below leads the main PHY to be connected back to the primary link, thus
+        // the ResetPhy() method of the FEM on the non-primary link is called, which disconnects
+        // another callback (FEM::ReceivedMacHdr) from the PhyRxMacHeaderEnd trace source of
+        // the main PHY, thus invalidating the list of callbacks on which the for loop iterates.
+        // Hence, schedule the call to NotifyTxopEnd to execute it outside such for loop.
+        Simulator::ScheduleNow(&AdvancedEmlsrManager::NotifyTxopEnd, this, *linkId, false, false);
+    }
+}
+
 } // namespace ns3

src/wifi/model/eht/advanced-emlsr-manager.h

@@ -44,6 +44,24 @@ class AdvancedEmlsrManager : public DefaultEmlsrManager
 
     Time GetDelayUntilAccessRequest(uint8_t linkId) override;
 
+  protected:
+    void DoDispose() override;
+    void DoSetWifiMac(Ptr<StaWifiMac> mac) override;
+
+    /**
+     * Possibly take actions when notified of the MAC header of the MPDU being received by the
+     * given PHY.
+     *
+     * \param phy the given PHY
+     * \param macHdr the MAC header of the MPDU being received
+     * \param txVector the TXVECTOR used to transmit the PSDU
+     * \param psduDuration the remaining duration of the PSDU
+     */
+    void ReceivedMacHdr(Ptr<WifiPhy> phy,
+                        const WifiMacHeader& macHdr,
+                        const WifiTxVector& txVector,
+                        Time psduDuration);
+
   private:
     bool m_useNotifiedMacHdr; //!< whether to use the information about the MAC header of
                               //!< the MPDU being received (if notified by the PHY)

src/wifi/model/eht/eht-frame-exchange-manager.cc

@@ -1163,6 +1163,12 @@ EhtFrameExchangeManager::CheckEmlsrClientStartingTxop(const WifiMacHeader& hdr,
     return true;
 }
 
+EventId&
+EhtFrameExchangeManager::GetOngoingTxopEndEvent()
+{
+    return m_ongoingTxopEnd;
+}
+
 void
 EhtFrameExchangeManager::PsduRxError(Ptr<const WifiPsdu> psdu)
 {

src/wifi/model/eht/eht-frame-exchange-manager.h

@@ -126,6 +126,12 @@ class EhtFrameExchangeManager : public HeFrameExchangeManager
      */
     void EmlsrSwitchToListening(const Mac48Address& address, const Time& delay);
 
+    /**
+     * \return a reference to the event indicating the possible end of the current TXOP (of
+     *         which this device is not the holder)
+     */
+    EventId& GetOngoingTxopEndEvent();
+
   protected:
     void DoDispose() override;
     void RxStartIndication(WifiTxVector txVector, Time psduDuration) override;

src/wifi/model/eht/emlsr-manager.cc

@@ -177,6 +177,13 @@ EmlsrManager::SetWifiMac(Ptr<StaWifiMac> mac)
     m_staMac->TraceConnectWithoutContext("AckedMpdu", MakeCallback(&EmlsrManager::TxOk, this));
     m_staMac->TraceConnectWithoutContext("DroppedMpdu",
                                          MakeCallback(&EmlsrManager::TxDropped, this));
+    DoSetWifiMac(mac);
+}
+
+void
+EmlsrManager::DoSetWifiMac(Ptr<StaWifiMac> mac)
+{
+    NS_LOG_FUNCTION(this << mac);
 }
 
 void

src/wifi/model/eht/emlsr-manager.h

@@ -280,6 +280,13 @@ class EmlsrManager : public Object
   protected:
     void DoDispose() override;
 
+    /**
+     * Allow subclasses to take actions when the MAC is set.
+     *
+     * \param mac the wifi MAC
+     */
+    virtual void DoSetWifiMac(Ptr<StaWifiMac> mac);
+
     /**
      * \return the MAC of the non-AP MLD managed by this EMLSR Manager.
      */