Print a meaningful error when -M is used but SO_MARK is not supported

diff --git a/mtr.c b/mtr.c
index cad2ca03a478e35119ccdb22d8144c16c8f329cd..417caf66583dfde68ef04319fb0823391023fefe 100644 (file)
--- a/mtr.c
+++ b/mtr.c
@@ -491,6 +491,10 @@ void parse_arg (int argc, char **argv)
         exit(EXIT_FAILURE);
       }
       break;
+#else
+    case 'M':
+      fprintf( stderr, "SO_MARK not enabled.\n" );
+      break;
 #endif
     }
   }