Fix for Bug project-chip#36731. (project-chip#36880)

Add CloseActiveConnections() call in TCPBase::Close(), which
is called as part of Server::Shutdown().
Active connections should be closed as part of Server shutdown.
This allows the TCPConnectionState to also close the associated
TCPEndpoint object as part of this shutdown flow.

Previously, the CloseActiveConnections() call was present in the
TCPBase destructor alone.

Add test for Connection Close() and checking for TCPEndPoint.

src/transport/raw/ActiveTCPConnectionState.h

@@ -62,7 +62,10 @@ struct ActiveTCPConnectionState
 
     void Free()
     {
-        mEndPoint->Free();
+        if (mEndPoint)
+        {
+            mEndPoint->Free();
+        }
         mPeerAddr = PeerAddress::Uninitialized();
         mEndPoint = nullptr;
         mReceived = nullptr;

src/transport/raw/TCP.cpp

@@ -55,14 +55,8 @@ constexpr int kListenBacklogSize = 2;
 
 TCPBase::~TCPBase()
 {
-    if (mListenSocket != nullptr)
-    {
-        // endpoint is only non null if it is initialized and listening
-        mListenSocket->Free();
-        mListenSocket = nullptr;
-    }
-
-    CloseActiveConnections();
+    // Call Close to free the listening socket and close all active connections.
+    Close();
 }
 
 void TCPBase::CloseActiveConnections()
@@ -125,6 +119,9 @@ void TCPBase::Close()
         mListenSocket->Free();
         mListenSocket = nullptr;
     }
+
+    CloseActiveConnections();
+
     mState = TCPState::kNotReady;
 }
 

src/transport/raw/tests/TestTCP.cpp

@@ -610,6 +610,29 @@ TEST_F(TestTCP, HandleConnCloseCalledTest6)
     HandleConnCloseTest(addr);
 }
 
+TEST_F(TestTCP, CheckTCPEndpointAfterCloseTest)
+{
+    TCPImpl tcp;
+
+    IPAddress addr;
+    IPAddress::FromString("::1", addr);
+
+    MockTransportMgrDelegate gMockTransportMgrDelegate(mIOContext);
+    gMockTransportMgrDelegate.InitializeMessageTest(tcp, addr);
+    gMockTransportMgrDelegate.ConnectTest(tcp, addr);
+
+    Transport::PeerAddress lPeerAddress = Transport::PeerAddress::TCP(addr, gChipTCPPort);
+    void * state                        = TestAccess::FindActiveConnection(tcp, lPeerAddress);
+    ASSERT_NE(state, nullptr);
+    TCPEndPoint * lEndPoint = TestAccess::GetEndpoint(state);
+    ASSERT_NE(lEndPoint, nullptr);
+
+    // Call Close and check the TCPEndpoint
+    tcp.Close();
+    lEndPoint = TestAccess::GetEndpoint(state);
+    ASSERT_EQ(lEndPoint, nullptr);
+}
+
 TEST_F(TestTCP, CheckProcessReceivedBuffer)
 {
     TCPImpl tcp;