wifi: mobility initialization and caching in WifiPhy

src/wifi/model/wifi-phy.cc

@@ -363,6 +363,31 @@ WifiPhy::~WifiPhy()
     NS_LOG_FUNCTION(this);
 }
 
+void
+WifiPhy::DoInitialize()
+{
+    NS_LOG_FUNCTION(this);
+
+    // This method ensures that the local mobility model pointer holds
+    // a pointer to the Node's aggregated mobility model (if one exists)
+    // in the case that the user has not directly called SetMobility()
+    // on this WifiPhy during simulation setup.  If the mobility model
+    // needs to be added or changed during simulation runtime, users must
+    // call SetMobility() on this object.
+
+    if (!m_mobility)
+    {
+        NS_ABORT_MSG_UNLESS(m_device && m_device->GetNode(),
+                            "Either install a MobilityModel on this object or ensure that this "
+                            "object is part of a Node and NetDevice");
+        m_mobility = m_device->GetNode()->GetObject<MobilityModel>();
+        if (!m_mobility)
+        {
+            NS_LOG_WARN("Mobility not found, propagation models might not work properly");
+        }
+    }
+}
+
 void
 WifiPhy::DoDispose()
 {
@@ -592,14 +617,7 @@ WifiPhy::SetMobility(const Ptr<MobilityModel> mobility)
 Ptr<MobilityModel>
 WifiPhy::GetMobility() const
 {
-    if (m_mobility)
-    {
-        return m_mobility;
-    }
-    else
-    {
-        return m_device->GetNode()->GetObject<MobilityModel>();
-    }
+    return m_mobility;
 }
 
 void

src/wifi/model/wifi-phy.h

@@ -1132,6 +1132,7 @@ class WifiPhy : public Object
     virtual WifiSpectrumBand GetBand(uint16_t bandWidth, uint8_t bandIndex = 0);
 
   protected:
+    void DoInitialize() override;
     void DoDispose() override;
 
     /**