Add extract_metadata to main PDU classes

include/tins/icmp.h

@@ -92,6 +92,14 @@ public:
         ADDRESS_MASK_REPLY = 18
     };
 
+    /**
+     * \brief Extracts metadata for this protocol based on the buffer provided
+     *
+     * \param buffer Pointer to a buffer
+     * \param total_sz Size of the buffer pointed by buffer
+     */
+    static metadata extract_metadata(const uint8_t *buffer, uint32_t total_sz);
+
     /**
      * \brief Creates an instance of ICMP.
      *