wifi: STAs not responding to a MU PPDU need to be protected again in the same TXOP

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

@@ -504,6 +504,23 @@ HeFrameExchangeManager::CtsTimeout(Ptr<WifiMpdu> rts, const WifiTxVector& txVect
     m_psduMap.clear();
 }
 
+void
+HeFrameExchangeManager::TransmissionSucceeded()
+{
+    NS_LOG_FUNCTION(this);
+
+    // A multi-user transmission may succeed even if some stations did not respond.
+    // Remove such stations from the set of stations for which protection is not needed
+    // in the current TXOP.
+    for (const auto& address : m_txTimer.GetStasExpectedToRespond())
+    {
+        NS_LOG_DEBUG(address << " did not respond, hence it is no longer protected");
+        m_protectedStas.erase(address);
+    }
+
+    VhtFrameExchangeManager::TransmissionSucceeded();
+}
+
 void
 HeFrameExchangeManager::SendPsduMap()
 {

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

@@ -163,6 +163,7 @@ class HeFrameExchangeManager : public VhtFrameExchangeManager
     void NavResetTimeout() override;
     void StartProtection(const WifiTxParameters& txParams) override;
     void ProtectionCompleted() override;
+    void TransmissionSucceeded() override;
 
     /**
      * Clear the TXOP holder if the intra-BSS NAV counted down to zero (includes the case