From 6a2e56c9fe3258b1ae6baef85c3c975da4d22d6b Mon Sep 17 00:00:00 2001
From: Stefano Avallone <stavallo@unina.it>
Date: Fri, 15 Sep 2023 19:28:02 +0200
Subject: [PATCH] wifi: Allow creation of A-MSDUs containing a single MSDU

---
 src/wifi/model/wifi-mpdu.cc | 17 +++++++++++++----
 src/wifi/model/wifi-mpdu.h  |  4 +++-
 2 files changed, 16 insertions(+), 5 deletions(-)

diff --git a/src/wifi/model/wifi-mpdu.cc b/src/wifi/model/wifi-mpdu.cc
index efaaefa29..5f10b1bc4 100644
--- a/src/wifi/model/wifi-mpdu.cc
+++ b/src/wifi/model/wifi-mpdu.cc
@@ -174,9 +174,15 @@ WifiMpdu::GetProtocolDataUnit() const
 void
 WifiMpdu::Aggregate(Ptr<const WifiMpdu> msdu)
 {
-    NS_ASSERT(msdu);
-    NS_LOG_FUNCTION(this << *msdu);
-    NS_ABORT_MSG_IF(!msdu->GetHeader().IsQosData() || msdu->GetHeader().IsQosAmsdu(),
+    if (msdu)
+    {
+        NS_LOG_FUNCTION(this << *msdu);
+    }
+    else
+    {
+        NS_LOG_FUNCTION(this);
+    }
+    NS_ABORT_MSG_IF(msdu && (!msdu->GetHeader().IsQosData() || msdu->GetHeader().IsQosAmsdu()),
                     "Only QoS data frames that do not contain an A-MSDU can be aggregated");
     NS_ABORT_MSG_IF(!std::holds_alternative<OriginalInfo>(m_instanceInfo),
                     "This method can only be called on the original version of the MPDU");
@@ -206,7 +212,10 @@ WifiMpdu::Aggregate(Ptr<const WifiMpdu> msdu)
         // to be set to the BSSID, but neither Address 1 nor Address 2 contain the
         // BSSID. Hence, it is left up to the caller to set these Address fields.
     }
-    DoAggregate(msdu);
+    if (msdu)
+    {
+        DoAggregate(msdu);
+    }
 }
 
 void
diff --git a/src/wifi/model/wifi-mpdu.h b/src/wifi/model/wifi-mpdu.h
index da6025d8a..b79849fe1 100644
--- a/src/wifi/model/wifi-mpdu.h
+++ b/src/wifi/model/wifi-mpdu.h
@@ -131,7 +131,9 @@ class WifiMpdu : public SimpleRefCount<WifiMpdu>
     /**
      * \brief Aggregate the MSDU contained in the given MPDU to this MPDU (thus
      *        constituting an A-MSDU). Note that the given MPDU cannot contain
-     *        an A-MSDU.
+     *        an A-MSDU. If the given MPDU is a null pointer, the effect of this
+     *        call is to add only an A-MSDU subframe header, thus producing an A-MSDU
+     *        containing a single MSDU.
      * \param msdu the MPDU containing the MSDU to aggregate
      */
     void Aggregate(Ptr<const WifiMpdu> msdu);