libifupdown: execute: add lif_maybe_try_executor()

cmd/ifupdown.c

@@ -28,7 +28,9 @@ struct match_options {
 };
 
 static bool up;
-static struct lif_execute_opts exec_opts = {};
+static struct lif_execute_opts exec_opts = {
+	.executor_path = EXECUTOR_PATH,
+};
 
 void
 ifupdown_usage(void)

libifupdown/execute.c

@@ -73,3 +73,19 @@ lif_file_is_executable(const char *path)
 
 	return access(path, X_OK);
 }
+
+bool
+lif_maybe_run_executor(const struct lif_execute_opts *opts, char *const envp[], const char *executor)
+{
+	if (opts->verbose)
+		fprintf(stderr, "ifupdown: attempting to run %s executor\n", executor);
+
+	char pathbuf[4096];
+
+	snprintf(pathbuf, sizeof pathbuf, "%s/%s", opts->executor_path, executor);
+
+	if (!lif_file_is_executable(pathbuf))
+		return true;
+
+	return lif_execute_fmt(opts, envp, "%s", pathbuf);
+}

libifupdown/execute.h

@@ -22,9 +22,11 @@
 struct lif_execute_opts {
 	bool verbose;
 	bool mock;
+	const char *executor_path;
 };
 
 extern bool lif_execute_fmt(const struct lif_execute_opts *opts, char *const envp[], const char *fmt, ...);
 extern bool lif_file_is_executable(const char *path);
+extern bool lif_maybe_run_executor(const struct lif_execute_opts *opts, char *const envp[], const char *executor);
 
 #endif