Copy of the rest of the buffer when receiving network data

Otherwise the whole ByteString with the message (that has been already
processed) is retained until more data is received, unnecessarily
occupying memory, possibly for long time periods.
Signed-off-by: Petr Pudlak <pudlak@google.com>
Reviewed-by: Klaus Aehlig <aehlig@google.com>

src/Ganeti/UDSServer.hs

@@ -308,7 +308,9 @@ recvMsg s = do
     if B.null ibuf      -- if old buffer didn't contain a full message
                         -- then we read from network:
       then recvUpdate (clientConfig s) (rsocket s) cbuf
-      else return (imsg, B.tail ibuf)   -- else we return data from our buffer
+      -- else we return data from our buffer, copying it so that the whole
+      -- message isn't retained and can be garbage collected
+      else return (imsg, B.copy (B.tail ibuf))
   writeIORef (rbuf s) nbuf
   return $ UTF8.toString msg