wifi: Add a WifiPsdu method to check if a PSDU is setting the NAV

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

@@ -1110,13 +1110,8 @@ FrameExchangeManager::UpdateNav(Ptr<const WifiPsdu> psdu, const WifiTxVector& tx
 {
     NS_LOG_FUNCTION(this << psdu << txVector);
 
-    if (psdu->GetHeader(0).GetRawDuration() > 32767)
+    if (!psdu->HasNav())
     {
-        // When the contents of a received Duration/ID field, treated as an unsigned
-        // integer, are greater than 32 768, the contents are interpreted as appropriate
-        // for the frame type and subtype or ignored if the receiving MAC entity does
-        // not have a defined interpretation for that type and subtype (IEEE 802.11-2016
-        // sec. 10.27.3)
         return;
     }
 

src/wifi/model/wifi-psdu.cc

@@ -139,6 +139,16 @@ WifiPsdu::GetAddr2() const
     return ta;
 }
 
+bool
+WifiPsdu::HasNav() const
+{
+    // When the contents of a received Duration/ID field, treated as an unsigned integer,
+    // are greater than 32 768, the contents are interpreted as appropriate for the frame
+    // type and subtype or ignored if the receiving MAC entity does not have a defined
+    // interpretation for that type and subtype (IEEE 802.11-2016 sec. 10.27.3)
+    return (m_mpduList.at(0)->GetHeader().GetRawDuration() & 0x8000) == 0;
+}
+
 Time
 WifiPsdu::GetDuration() const
 {

src/wifi/model/wifi-psdu.h

@@ -144,6 +144,11 @@ class WifiPsdu : public SimpleRefCount<WifiPsdu>
      */
     Mac48Address GetAddr2() const;
 
+    /**
+     * \return true if the Duration/ID field contains a value for setting the NAV
+     */
+    bool HasNav() const;
+
     /**
      * Get the duration from the Duration/ID field, which is common to all the MPDUs
      * \return the duration from the Duration/ID field.