config: bus reconnect support

Add support for reconnecting to the bus when it restarts.

config/config.c

@@ -36,10 +36,10 @@
                     /* the above comment lies.  there is no better way. */
 #include "input.h"
 #include "inputstr.h"
-#include "config.h"
+#include "hotplug.h"
 #include "os.h"
 
-#define MATCH_RULE "type='method_call',interface='org.x.config.input'"
+#define CONFIG_MATCH_RULE "type='method_call',interface='org.x.config.input'"
 
 #define MALFORMED_MSG "[config] malformed message, dropping"
 #define MALFORMED_MESSAGE() { DebugF(MALFORMED_MSG "\n"); \
@@ -50,6 +50,9 @@
                                   ret = BadValue; \
                                   goto unwind; }
 
+/* How often to attempt reconnecting when we get booted off the bus. */
+#define RECONNECT_DELAY 10000 /* in ms */
+
 struct config_data {
     int fd;
     DBusConnection *connection;
@@ -59,6 +62,8 @@ struct config_data {
 
 static struct config_data *configData;
 
+static CARD32 configReconnect(OsTimerPtr timer, CARD32 time, pointer arg);
+
 static void
 configWakeupHandler(pointer blockData, int err, pointer pReadMask)
 {
@@ -73,6 +78,18 @@ configBlockHandler(pointer data, struct timeval **tv, pointer pReadMask)
 {
 }
 
+static void
+configTeardown(void)
+{
+    if (configData) {
+        RemoveGeneralSocket(configData->fd);
+        RemoveBlockAndWakeupHandlers(configBlockHandler, configWakeupHandler,
+                                     configData);
+        xfree(configData);
+        configData = NULL;
+    }
+}
+
 static int
 configAddDevice(DBusMessage *message, DBusMessageIter *iter, DBusError *error)
 {
@@ -226,8 +243,6 @@ configMessage(DBusConnection *connection, DBusMessage *message, void *closure)
             ret = configAddDevice(message, &iter, &error);
         else if (strcmp(dbus_message_get_member(message), "remove") == 0)
             ret = configRemoveDevice(message, &iter, &error);
-    }
-
         if (ret != BadDrawable && ret != BadAlloc) {
             reply = dbus_message_new_method_return(message);
             dbus_message_iter_init_append(reply, &iter);
@@ -244,6 +259,7 @@ configMessage(DBusConnection *connection, DBusMessage *message, void *closure)
 
             dbus_message_unref(reply);
         }
+    }
 
     dbus_error_free(&error);
 
@@ -255,16 +271,40 @@ configMessage(DBusConnection *connection, DBusMessage *message, void *closure)
         return DBUS_HANDLER_RESULT_HANDLED;
 }
 
-void
+/**
-configInitialise()
+ * This is a filter, which only handles the disconnected signal, which
+ * doesn't go to the normal message handling function.  This takes
+ * precedence over the message handling function, so have have to be
+ * careful to ignore anything we don't want to deal with here.
+ *
+ * Yes, this is brutally stupid.
+ */
+static DBusHandlerResult
+configFilter(DBusConnection *connection, DBusMessage *message, void *closure)
+{
+    if (dbus_message_is_signal(message, DBUS_INTERFACE_LOCAL,
+                                    "Disconnected")) {
+        ErrorF("[dbus] disconnected from bus\n");
+        TimerSet(NULL, 0, RECONNECT_DELAY, configReconnect, NULL);
+        configTeardown();
+        return DBUS_HANDLER_RESULT_HANDLED;
+    }
+
+    return DBUS_HANDLER_RESULT_NOT_YET_HANDLED;
+}
+
+static Bool
+configSetup(void)
 {
     DBusError error;
     DBusObjectPathVTable vtable = { .message_function = configMessage };
 
     if (!configData)
         configData = (struct config_data *) xcalloc(sizeof(struct config_data), 1);
-    if (!configData)
+    if (!configData) {
-        return;
+        ErrorF("[dbus] failed to allocate data struct.\n");
+        return FALSE;
+    }
 
     dbus_error_init(&error);
     configData->connection = dbus_bus_get(DBUS_BUS_SYSTEM, &error);
@@ -272,15 +312,20 @@ configInitialise()
         ErrorF("[dbus] some kind of error occurred: %s (%s)\n", error.name,
                 error.message);
         dbus_error_free(&error);
-        return;
+        xfree(configData);
+        configData = NULL;
+        return FALSE;
     }
 
+    dbus_connection_set_exit_on_disconnect(configData->connection, FALSE);
+
     if (!dbus_connection_get_unix_fd(configData->connection, &configData->fd)) {
         dbus_connection_unref(configData->connection);
         ErrorF("[dbus] couldn't get fd for bus\n");
         dbus_error_free(&error);
-        configData->fd = -1;
+        xfree(configData);
-        return;
+        configData = NULL;
+        return FALSE;
     }
 
     snprintf(configData->busname, sizeof(configData->busname),
@@ -291,12 +336,13 @@ configInitialise()
                error.name, error.message);
         dbus_error_free(&error);
         dbus_connection_unref(configData->connection);
-        configData->fd = -1;
+        xfree(configData);
-        return;
+        configData = NULL;
+        return FALSE;
     }
 
     /* blocks until we get a reply. */
-    dbus_bus_add_match(configData->connection, MATCH_RULE, &error);
+    dbus_bus_add_match(configData->connection, CONFIG_MATCH_RULE, &error);
     if (dbus_error_is_set(&error)) {
         ErrorF("[dbus] couldn't match X.Org rule: %s (%s)\n", error.name,
                error.message);
@@ -304,8 +350,25 @@ configInitialise()
         dbus_bus_release_name(configData->connection, configData->busname,
                               &error);
         dbus_connection_unref(configData->connection);
-        configData->fd = -1;
+        xfree(configData);
-        return;
+        configData = NULL;
+        return FALSE;
+    }
+
+    if (!dbus_connection_add_filter(configData->connection, configFilter,
+                                    configData, NULL)) {
+        
+        ErrorF("[dbus] couldn't add signal filter: %s (%s)\n", error.name,
+               error.message);
+        dbus_error_free(&error);
+        dbus_bus_release_name(configData->connection, configData->busname,
+                              &error);
+        dbus_bus_remove_match(configData->connection, CONFIG_MATCH_RULE,
+                              &error);
+        dbus_connection_unref(configData->connection);
+        xfree(configData);
+        configData = NULL;
+        return FALSE;
     }
 
     snprintf(configData->busobject, sizeof(configData->busobject),
@@ -314,13 +377,15 @@ configInitialise()
                                               configData->busobject, &vtable,
                                               configData->connection)) {
         ErrorF("[dbus] couldn't register object path\n");
-        configData->fd = -1;
         dbus_bus_release_name(configData->connection, configData->busname,
                               &error);
-        dbus_bus_remove_match(configData->connection, MATCH_RULE, &error);
+        dbus_bus_remove_match(configData->connection, CONFIG_MATCH_RULE,
+                              &error);
         dbus_connection_unref(configData->connection);
         dbus_error_free(&error);
-        return;
+        xfree(configData);
+        configData = NULL;
+        return FALSE;
     }
 
     DebugF("[dbus] registered object path %s\n", configData->busobject);
@@ -330,6 +395,23 @@ configInitialise()
 
     RegisterBlockAndWakeupHandlers(configBlockHandler, configWakeupHandler,
                                    configData);
+
+    return TRUE;
+}
+
+static CARD32
+configReconnect(OsTimerPtr timer, CARD32 time, pointer arg)
+{
+    if (configSetup())
+        return 0;
+    else
+        return RECONNECT_DELAY;
+}
+
+void
+configInitialise()
+{
+    TimerSet(NULL, 0, 1, configReconnect, NULL);
 }
 
 void
@@ -341,16 +423,15 @@ configFini()
         dbus_error_init(&error);
         dbus_connection_unregister_object_path(configData->connection,
                                                configData->busobject);
-        dbus_bus_remove_match(configData->connection, MATCH_RULE, &error);
+        dbus_connection_remove_filter(configData->connection, configFilter,
+                                      configData);
+        dbus_bus_remove_match(configData->connection, CONFIG_MATCH_RULE,
+                              &error);
         dbus_bus_release_name(configData->connection, configData->busname,
                               &error);
         dbus_connection_unref(configData->connection);
-        RemoveGeneralSocket(configData->fd);
-        RemoveBlockAndWakeupHandlers(configBlockHandler, configWakeupHandler,
-                                     configData);
-        xfree(configData);
-        configData = NULL;
         dbus_error_free(&error);
+        configTeardown();
     }
 }