Registration of the MOSQ_EVT_CONTROL plugin event is now handled globally.

This means only a single plugin can register for a given $CONTROL topic.

ChangeLog.txt

@@ -37,6 +37,9 @@ Broker:
 - Return protocol error if a client attemps to subscribe to a shared
   subscription and also sets no-local.
 - Log protocol version and ciphers that a client negotiates when connecting.
+- Registration of the MOSQ_EVT_CONTROL plugin event is now handled globally
+  across the broker, so only a single plugin can register for a given $CONTROL
+  topic.
 
 Client library:
 - Add MOSQ_OPT_DISABLE_SOCKETPAIR to allow the disabling of the socketpair

src/control.c

@@ -36,12 +36,15 @@ int control__process(struct mosquitto *context, struct mosquitto_msg_store *stor
 	mosquitto_property *properties = NULL;
 	int rc = MOSQ_ERR_SUCCESS;
 
-	if(db.config->per_listener_settings){
+	/* Check global plugins and non-per-listener settings first */
+	opts = &db.config->security_options;
+	HASH_FIND(hh, opts->plugin_callbacks.control, stored->topic, strlen(stored->topic), cb_found);
+
+	/* If not found, check for per-listener plugins. */
+	if(cb_found == NULL && db.config->per_listener_settings){
 		opts = &context->listener->security_options;
-	}else{
-		opts = &db.config->security_options;
+		HASH_FIND(hh, opts->plugin_callbacks.control, stored->topic, strlen(stored->topic), cb_found);
 	}
-	HASH_FIND(hh, opts->plugin_callbacks.control, stored->topic, strlen(stored->topic), cb_found);
 	if(cb_found){
 		memset(&event_data, 0, sizeof(event_data));
 		event_data.client = context;
@@ -75,9 +78,10 @@ int control__process(struct mosquitto *context, struct mosquitto_msg_store *stor
 }
 #endif
 
-int control__register_callback(struct mosquitto__security_options *opts, MOSQ_FUNC_generic_callback cb_func, const char *topic, void *userdata)
+int control__register_callback(MOSQ_FUNC_generic_callback cb_func, const char *topic, void *userdata)
 {
 #ifdef WITH_CONTROL
+	struct mosquitto__security_options *opts;
 	struct mosquitto__callback *cb_found, *cb_new;
 	size_t topic_len;
 
@@ -88,6 +92,8 @@ int control__register_callback(struct mosquitto__security_options *opts, MOSQ_FU
 		return MOSQ_ERR_INVAL;
 	}
 
+	opts = &db.config->security_options;
+
 	HASH_FIND(hh, opts->plugin_callbacks.control, topic, topic_len, cb_found);
 	if(cb_found){
 		return MOSQ_ERR_ALREADY_EXISTS;
@@ -112,9 +118,11 @@ int control__register_callback(struct mosquitto__security_options *opts, MOSQ_FU
 #endif
 }
 
-int control__unregister_callback(struct mosquitto__security_options *opts, MOSQ_FUNC_generic_callback cb_func, const char *topic)
+int control__unregister_callback(MOSQ_FUNC_generic_callback cb_func, const char *topic)
 {
 #ifdef WITH_CONTROL
+	struct mosquitto__security_options *opts;
+
 	struct mosquitto__callback *cb_found;
 	size_t topic_len;
 
@@ -123,6 +131,8 @@ int control__unregister_callback(struct mosquitto__security_options *opts, MOSQ_
 	if(topic_len == 0 || topic_len > 65535) return MOSQ_ERR_INVAL;
 	if(strncmp(topic, "$CONTROL/", strlen("$CONTROL/"))) return MOSQ_ERR_INVAL;
 
+	opts = &db.config->security_options;
+
 	HASH_FIND(hh, opts->plugin_callbacks.control, topic, topic_len, cb_found);
 	if(cb_found && cb_found->cb == cb_func){
 		HASH_DELETE(hh, opts->plugin_callbacks.control, cb_found);

src/mosquitto_broker_internal.h

@@ -723,8 +723,8 @@ int connect__on_authorised(struct mosquitto *context, void *auth_data_out, uint1
 int control__process(struct mosquitto *context, struct mosquitto_msg_store *stored);
 void control__cleanup(void);
 #endif
-int control__register_callback(struct mosquitto__security_options *opts, MOSQ_FUNC_generic_callback cb_func, const char *topic, void *userdata);
-int control__unregister_callback(struct mosquitto__security_options *opts, MOSQ_FUNC_generic_callback cb_func, const char *topic);
+int control__register_callback(MOSQ_FUNC_generic_callback cb_func, const char *topic, void *userdata);
+int control__unregister_callback(MOSQ_FUNC_generic_callback cb_func, const char *topic);
 
 
 /* ============================================================

src/plugin.c

@@ -267,7 +267,7 @@ int mosquitto_callback_register(
 			cb_base = &security_options->plugin_callbacks.ext_auth_continue;
 			break;
 		case MOSQ_EVT_CONTROL:
-			return control__register_callback(security_options, cb_func, event_data, userdata);
+			return control__register_callback(cb_func, event_data, userdata);
 			break;
 		case MOSQ_EVT_MESSAGE:
 			cb_base = &security_options->plugin_callbacks.message;
@@ -340,7 +340,7 @@ int mosquitto_callback_unregister(
 			cb_base = &security_options->plugin_callbacks.ext_auth_continue;
 			break;
 		case MOSQ_EVT_CONTROL:
-			return control__unregister_callback(security_options, cb_func, event_data);
+			return control__unregister_callback(cb_func, event_data);
 			break;
 		case MOSQ_EVT_MESSAGE:
 			cb_base = &security_options->plugin_callbacks.message;