[net] Delete CNetMessage copy constructor/assignment op

src/net.h

@@ -236,6 +236,14 @@ public:
     std::string m_type;
 
     CNetMessage(CDataStream&& recv_in) : m_recv(std::move(recv_in)) {}
+    // Only one CNetMessage object will exist for the same message on either
+    // the receive or processing queue. For performance reasons we therefore
+    // delete the copy constructor and assignment operator to avoid the
+    // possibility of copying CNetMessage objects.
+    CNetMessage(CNetMessage&&) = default;
+    CNetMessage(const CNetMessage&) = delete;
+    CNetMessage& operator=(CNetMessage&&) = default;
+    CNetMessage& operator=(const CNetMessage&) = delete;
 
     void SetVersion(int nVersionIn)
     {