From: Quentin Monnet <quentin.monnet@netronome.com>
Date: Tue, 28 Nov 2017 17:44:30 -0800
Subject: tools: bpftool: make error message from getopt_long() JSON-friendly
Patch-mainline: v4.15-rc3
Git-commit: 146882a37da7aa566c7ec088b42c6495d769f2ba
References: bsc#1109837

If `getopt_long()` meets an unknown option, it prints its own error
message to standard error output. While this does not strictly break
JSON output, it is the only case bpftool prints something to standard
error output if JSON output is required. All other errors are printed on
standard output as JSON objects, so that an external program does not
have to parse stderr.

This is changed by setting the global variable `opterr` to 0.
Furthermore, p_err() is used to reproduce the error message in a more
JSON-friendly way, so that users still get to know what the erroneous
option is.

Signed-off-by: Quentin Monnet <quentin.monnet@netronome.com>
Acked-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Thomas Bogendoerfer <tbogendoerfer@suse.de>
---
 tools/bpf/bpftool/main.c |    7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

--- a/tools/bpf/bpftool/main.c
+++ b/tools/bpf/bpftool/main.c
@@ -288,6 +288,7 @@ int main(int argc, char **argv)
 	hash_init(prog_table.table);
 	hash_init(map_table.table);
 
+	opterr = 0;
 	while ((opt = getopt_long(argc, argv, "Vhpjf",
 				  options, NULL)) >= 0) {
 		switch (opt) {
@@ -313,7 +314,11 @@ int main(int argc, char **argv)
 			show_pinned = true;
 			break;
 		default:
-			usage();
+			p_err("unrecognized option '%s'", argv[optind - 1]);
+			if (json_output)
+				clean_and_exit(-1);
+			else
+				usage();
 		}
 	}