tools: bpftool: add JSON output for bpftool batch file FILE command

`bpftool batch file FILE` takes FILE as an argument and executes all the
bpftool commands it finds inside (or stops if an error occurs).

To obtain a consistent JSON output, create a root JSON array, then for
each command create a new object containing two fields: one with the
command arguments, the other with the output (which is the JSON object
that the command would have produced, if called on its own).

Signed-off-by: Quentin Monnet <quentin.monnet@netronome.com>
Acked-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

tools/bpf/bpftool/main.c

@@ -155,6 +155,7 @@ static int do_batch(int argc, char **argv)
 	int n_argc;
 	FILE *fp;
 	int err;
+	int i;
 
 	if (argc < 2) {
 		err("too few parameters for batch\n");
@@ -174,6 +175,8 @@ static int do_batch(int argc, char **argv)
 		return -1;
 	}
 
+	if (json_output)
+		jsonw_start_array(json_wtr);
 	while (fgets(buf, sizeof(buf), fp)) {
 		if (strlen(buf) == sizeof(buf) - 1) {
 			errno = E2BIG;
@@ -197,7 +200,21 @@ static int do_batch(int argc, char **argv)
 		if (!n_argc)
 			continue;
 
+		if (json_output) {
+			jsonw_start_object(json_wtr);
+			jsonw_name(json_wtr, "command");
+			jsonw_start_array(json_wtr);
+			for (i = 0; i < n_argc; i++)
+				jsonw_string(json_wtr, n_argv[i]);
+			jsonw_end_array(json_wtr);
+			jsonw_name(json_wtr, "output");
+		}
+
 		err = cmd_select(cmds, n_argc, n_argv, do_help);
+
+		if (json_output)
+			jsonw_end_object(json_wtr);
+
 		if (err)
 			goto err_close;
 
@@ -214,6 +231,9 @@ static int do_batch(int argc, char **argv)
 err_close:
 	fclose(fp);
 
+	if (json_output)
+		jsonw_end_array(json_wtr);
+
 	return err;
 }