add _update_header method to messages.py

app/src/async_stream.py

@@ -117,6 +117,7 @@ class AsyncStream():
                         await self.remoteStream.__async_write()
 
             if self.remoteStream:
+                self.remoteStream._update_header(self._forward_buffer)
                 hex_dump_memory(logging.INFO,
                                 f'Forward to {self.remoteStream.addr}:',
                                 self._forward_buffer,

app/src/messages.py

@@ -74,6 +74,9 @@ class Message(metaclass=IterRegistry):
         # to our _recv_buffer
         return  # pragma: no cover
 
+    def _update_header(self, _forward_buffer):
+        return
+
     '''
     Our puplic methods
     '''