With an error if it is an unknown option.
Signed-off-by: Matthieu Baerts <matthieu.baerts@tessares.net>
Signed-off-by: Mat Martineau <mathew.j.martineau@linux.intel.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
        fullmesh_tests
 }
 
+# [$1: error message]
 usage()
 {
+       if [ -n "${1}" ]; then
+               echo "${1}"
+               ret=1
+       fi
+
        echo "mptcp_join usage:"
        echo "  -f subflows_tests"
        echo "  -e subflows_error_tests"
        echo "  -C enable data checksum"
        echo "  -i use ip mptcp"
        echo "  -h help"
+
+       exit ${ret}
 }
 
 sin=$(mktemp)
                        ;;
                i)
                        ;;
-               h | *)
+               h)
                        usage
                        ;;
+               *)
+                       usage "Unknown option: -${opt}"
+                       ;;
        esac
 done