Added a method to plugin_loader_t to add 'static' plugin features

This allows daemons and other components to register plugin features
like those provided by plugins (following the same lifecycle).

The added features are internally handled like they were added by a
plugin.

src/libstrongswan/plugins/plugin_loader.c

@@ -104,6 +104,78 @@ static void plugin_entry_destroy(plugin_entry_t *entry)
 	free(entry);
 }
 
+/**
+ * Wrapper for static plugin features
+ */
+typedef struct {
+
+	/**
+	 * Implements plugin_t interface
+	 */
+	plugin_t public;
+
+	/**
+	 * Name of the module registering these features
+	 */
+	char *name;
+
+	/**
+	 * Static plugin features
+	 */
+	plugin_feature_t *features;
+
+	/**
+	 * Number of plugin features
+	 */
+	int count;
+
+} static_features_t;
+
+METHOD(plugin_t, get_static_name, char*,
+	static_features_t *this)
+{
+	return this->name;
+}
+
+METHOD(plugin_t, get_static_features, int,
+	static_features_t *this, plugin_feature_t *features[])
+{
+	*features = this->features;
+	return this->count;
+}
+
+METHOD(plugin_t, static_destroy, void,
+	static_features_t *this)
+{
+	free(this->features);
+	free(this->name);
+	free(this);
+}
+
+/**
+ * Create a wrapper around static plugin features.
+ */
+static plugin_t *static_features_create(const char *name,
+										plugin_feature_t features[], int count)
+{
+	static_features_t *this;
+
+	INIT(this,
+		.public = {
+			.get_name = _get_static_name,
+			.get_features = _get_static_features,
+			.destroy = _static_destroy,
+		},
+		.name = strdup(name),
+		.features = calloc(count, sizeof(plugin_feature_t)),
+		.count = count,
+	);
+
+	memcpy(this->features, features, sizeof(plugin_feature_t) * count);
+
+	return &this->public;
+}
+
 /**
  * Compare function for hashtable of loaded features.
  */
@@ -554,6 +626,24 @@ static void purge_plugins(private_plugin_loader_t *this)
 	enumerator->destroy(enumerator);
 }
 
+METHOD(plugin_loader_t, add_static_features, void,
+	private_plugin_loader_t *this, const char *name,
+	plugin_feature_t features[], int count, bool critical)
+{
+	plugin_entry_t *entry;
+	plugin_t *plugin;
+
+	plugin = static_features_create(name, features, count);
+
+	INIT(entry,
+		.plugin = plugin,
+		.critical = critical,
+		.loaded = linked_list_create(),
+		.failed = linked_list_create(),
+	);
+	this->plugins->insert_last(this->plugins, entry);
+}
+
 METHOD(plugin_loader_t, load_plugins, bool,
 	private_plugin_loader_t *this, char *path, char *list)
 {
@@ -740,6 +830,7 @@ plugin_loader_t *plugin_loader_create()
 
 	INIT(this,
 		.public = {
+			.add_static_features = _add_static_features,
 			.load = _load_plugins,
 			.reload = _reload,
 			.unload = _unload,