Plug a mem leak
[platform/upstream/glib.git] / gio / gdbusprivate.c
index 3dfb829..91942a9 100644 (file)
@@ -40,6 +40,7 @@
 #include "giostream.h"
 #include "gsocketcontrolmessage.h"
 #include "gsocketconnection.h"
+#include "gsocketoutputstream.h"
 
 #ifdef G_OS_UNIX
 #include "gunixfdmessage.h"
@@ -386,16 +387,19 @@ struct GDBusWorker
   /* used for writing */
   GMutex                             *write_lock;
   GQueue                             *write_queue;
-  gboolean                            write_is_pending;
+  gint                                num_writes_pending;
   guint64                             write_num_messages_written;
   GList                              *write_pending_flushes;
 };
 
+/* ---------------------------------------------------------------------------------------------------- */
+
 typedef struct
 {
   GMutex *mutex;
   GCond *cond;
   guint64 number_to_wait_for;
+  GError *error;
 } FlushData;
 
 struct _MessageToWriteData ;
@@ -403,6 +407,14 @@ typedef struct _MessageToWriteData MessageToWriteData;
 
 static void message_to_write_data_free (MessageToWriteData *data);
 
+static void read_message_print_transport_debug (gssize bytes_read,
+                                                GDBusWorker *worker);
+
+static void write_message_print_transport_debug (gssize bytes_written,
+                                                 MessageToWriteData *data);
+
+/* ---------------------------------------------------------------------------------------------------- */
+
 static GDBusWorker *
 _g_dbus_worker_ref (GDBusWorker *worker)
 {
@@ -433,6 +445,8 @@ _g_dbus_worker_unref (GDBusWorker *worker)
       g_queue_foreach (worker->write_queue, (GFunc) message_to_write_data_free, NULL);
       g_queue_free (worker->write_queue);
 
+      g_free (worker->read_buffer);
+
       g_free (worker);
     }
 }
@@ -454,12 +468,12 @@ _g_dbus_worker_emit_message_received (GDBusWorker  *worker,
     worker->message_received_callback (worker, message, worker->user_data);
 }
 
-static gboolean
+static GDBusMessageFilterResult
 _g_dbus_worker_emit_message_about_to_be_sent (GDBusWorker  *worker,
                                               GDBusMessage *message)
 {
-  gboolean ret;
-  ret = FALSE;
+  GDBusMessageFilterResult ret;
+  ret = G_DBUS_MESSAGE_FILTER_RESULT_NO_EFFECT;
   if (!worker->stopped)
     ret = worker->message_about_to_be_sent_callback (worker, message, worker->user_data);
   return ret;
@@ -646,6 +660,8 @@ _g_dbus_worker_do_read_cb (GInputStream  *input_stream,
       goto out;
     }
 
+  read_message_print_transport_debug (bytes_read, worker);
+
   worker->read_buffer_cur_size += bytes_read;
   if (worker->read_buffer_bytes_wanted == worker->read_buffer_cur_size)
     {
@@ -701,6 +717,7 @@ _g_dbus_worker_do_read_cb (GInputStream  *input_stream,
           if (worker->read_fd_list != NULL)
             {
               g_dbus_message_set_unix_fd_list (message, worker->read_fd_list);
+              g_object_unref (worker->read_fd_list);
               worker->read_fd_list = NULL;
             }
 #endif
@@ -803,14 +820,20 @@ _g_dbus_worker_do_read (GDBusWorker *worker)
 
 struct _MessageToWriteData
 {
+  GDBusWorker  *worker;
   GDBusMessage *message;
   gchar        *blob;
   gsize         blob_size;
+
+  gsize               total_written;
+  GSimpleAsyncResult *simple;
+
 };
 
 static void
 message_to_write_data_free (MessageToWriteData *data)
 {
+  _g_dbus_worker_unref (data->worker);
   g_object_unref (data->message);
   g_free (data->blob);
   g_free (data);
@@ -818,126 +841,297 @@ message_to_write_data_free (MessageToWriteData *data)
 
 /* ---------------------------------------------------------------------------------------------------- */
 
+static void write_message_continue_writing (MessageToWriteData *data);
+
 /* called in private thread shared by all GDBusConnection instances (without write-lock held) */
-static gboolean
-write_message (GDBusWorker         *worker,
-               MessageToWriteData  *data,
-               GError             **error)
+static void
+write_message_async_cb (GObject      *source_object,
+                        GAsyncResult *res,
+                        gpointer      user_data)
 {
-  gboolean ret;
-  GList *l;
-  GList *ll;
+  MessageToWriteData *data = user_data;
+  GSimpleAsyncResult *simple;
+  gssize bytes_written;
+  GError *error;
+
+  /* Note: we can't access data->simple after calling g_async_result_complete () because the
+   * callback can free @data and we're not completing in idle. So use a copy of the pointer.
+   */
+  simple = data->simple;
 
-  g_return_val_if_fail (data->blob_size > 16, FALSE);
+  error = NULL;
+  bytes_written = g_output_stream_write_finish (G_OUTPUT_STREAM (source_object),
+                                                res,
+                                                &error);
+  if (bytes_written == -1)
+    {
+      g_simple_async_result_set_from_error (simple, error);
+      g_error_free (error);
+      g_simple_async_result_complete (simple);
+      g_object_unref (simple);
+      goto out;
+    }
+  g_assert (bytes_written > 0); /* zero is never returned */
 
-  ret = FALSE;
+  write_message_print_transport_debug (bytes_written, data);
 
-  /* First, the initial 16 bytes - special case UNIX sockets here
-   * since it may involve writing an ancillary message with file
-   * descriptors
+  data->total_written += bytes_written;
+  g_assert (data->total_written <= data->blob_size);
+  if (data->total_written == data->blob_size)
+    {
+      g_simple_async_result_complete (simple);
+      g_object_unref (simple);
+      goto out;
+    }
+
+  write_message_continue_writing (data);
+
+ out:
+  ;
+}
+
+/* called in private thread shared by all GDBusConnection instances (without write-lock held) */
+static gboolean
+on_socket_ready (GSocket      *socket,
+                 GIOCondition  condition,
+                 gpointer      user_data)
+{
+  MessageToWriteData *data = user_data;
+  write_message_continue_writing (data);
+  return FALSE; /* remove source */
+}
+
+/* called in private thread shared by all GDBusConnection instances (without write-lock held) */
+static void
+write_message_continue_writing (MessageToWriteData *data)
+{
+  GOutputStream *ostream;
+  GSimpleAsyncResult *simple;
+#ifdef G_OS_UNIX
+  GUnixFDList *fd_list;
+#endif
+
+  /* Note: we can't access data->simple after calling g_async_result_complete () because the
+   * callback can free @data and we're not completing in idle. So use a copy of the pointer.
    */
+  simple = data->simple;
+
+  ostream = g_io_stream_get_output_stream (data->worker->stream);
 #ifdef G_OS_UNIX
-  {
-    GOutputVector vector;
-    GSocketControlMessage *message;
-    GUnixFDList *fd_list;
-    gssize bytes_written;
+  fd_list = g_dbus_message_get_unix_fd_list (data->message);
+#endif
 
-    fd_list = g_dbus_message_get_unix_fd_list (data->message);
+  g_assert (!g_output_stream_has_pending (ostream));
+  g_assert_cmpint (data->total_written, <, data->blob_size);
 
-    message = NULL;
-    if (fd_list != NULL)
-      {
-        if (!G_IS_UNIX_CONNECTION (worker->stream))
-          {
-            g_set_error (error,
-                         G_IO_ERROR,
-                         G_IO_ERROR_INVALID_ARGUMENT,
-                         "Tried sending a file descriptor on unsupported stream of type %s",
-                         g_type_name (G_TYPE_FROM_INSTANCE (worker->stream)));
-            goto out;
-          }
-        else if (!(worker->capabilities & G_DBUS_CAPABILITY_FLAGS_UNIX_FD_PASSING))
-          {
-            g_set_error_literal (error,
-                                 G_IO_ERROR,
-                                 G_IO_ERROR_INVALID_ARGUMENT,
-                                 "Tried sending a file descriptor but remote peer does not support this capability");
-            goto out;
-          }
-        message = g_unix_fd_message_new_with_fd_list (fd_list);
-      }
+  if (FALSE)
+    {
+    }
+#ifdef G_OS_UNIX
+  else if (G_IS_SOCKET_OUTPUT_STREAM (ostream) && data->total_written == 0)
+    {
+      GOutputVector vector;
+      GSocketControlMessage *control_message;
+      gssize bytes_written;
+      GError *error;
 
-    vector.buffer = data->blob;
-    vector.size = 16;
-
-    bytes_written = g_socket_send_message (worker->socket,
-                                           NULL, /* address */
-                                           &vector,
-                                           1,
-                                           message != NULL ? &message : NULL,
-                                           message != NULL ? 1 : 0,
-                                           G_SOCKET_MSG_NONE,
-                                           worker->cancellable,
-                                           error);
-    if (bytes_written == -1)
-      {
-        g_prefix_error (error, _("Error writing first 16 bytes of message to socket: "));
-        if (message != NULL)
-          g_object_unref (message);
-        goto out;
-      }
-    if (message != NULL)
-      g_object_unref (message);
+      vector.buffer = data->blob;
+      vector.size = data->blob_size;
 
-    if (bytes_written < 16)
-      {
-        /* TODO: I think this needs to be handled ... are we guaranteed that the ancillary
-         * messages are sent?
-         */
-        g_assert_not_reached ();
-      }
-  }
-#else
-  /* write the first 16 bytes (guaranteed to return an error if everything can't be written) */
-  if (!g_output_stream_write_all (g_io_stream_get_output_stream (worker->stream),
-                                  (const gchar *) data->blob,
-                                  16,
-                                  NULL, /* bytes_written */
-                                  worker->cancellable, /* cancellable */
-                                  error))
-    goto out;
-#endif
+      control_message = NULL;
+      if (fd_list != NULL && g_unix_fd_list_get_length (fd_list) > 0)
+        {
+          if (!(data->worker->capabilities & G_DBUS_CAPABILITY_FLAGS_UNIX_FD_PASSING))
+            {
+              g_simple_async_result_set_error (simple,
+                                               G_IO_ERROR,
+                                               G_IO_ERROR_FAILED,
+                                               "Tried sending a file descriptor but remote peer does not support this capability");
+              g_simple_async_result_complete (simple);
+              g_object_unref (simple);
+              goto out;
+            }
+          control_message = g_unix_fd_message_new_with_fd_list (fd_list);
+        }
 
-  /* Then write the rest of the message (guaranteed to return an error if everything can't be written) */
-  if (!g_output_stream_write_all (g_io_stream_get_output_stream (worker->stream),
-                                  (const gchar *) data->blob + 16,
-                                  data->blob_size - 16,
-                                  NULL, /* bytes_written */
-                                  worker->cancellable, /* cancellable */
-                                  error))
-    goto out;
+      error = NULL;
+      bytes_written = g_socket_send_message (data->worker->socket,
+                                             NULL, /* address */
+                                             &vector,
+                                             1,
+                                             control_message != NULL ? &control_message : NULL,
+                                             control_message != NULL ? 1 : 0,
+                                             G_SOCKET_MSG_NONE,
+                                             data->worker->cancellable,
+                                             &error);
+      if (control_message != NULL)
+        g_object_unref (control_message);
 
-  ret = TRUE;
+      if (bytes_written == -1)
+        {
+          /* Handle WOULD_BLOCK by waiting until there's room in the buffer */
+          if (g_error_matches (error, G_IO_ERROR, G_IO_ERROR_WOULD_BLOCK))
+            {
+              GSource *source;
+              source = g_socket_create_source (data->worker->socket,
+                                               G_IO_OUT | G_IO_HUP | G_IO_ERR,
+                                               data->worker->cancellable);
+              g_source_set_callback (source,
+                                     (GSourceFunc) on_socket_ready,
+                                     data,
+                                     NULL); /* GDestroyNotify */
+              g_source_attach (source, g_main_context_get_thread_default ());
+              g_source_unref (source);
+              g_error_free (error);
+              goto out;
+            }
+          g_simple_async_result_set_from_error (simple, error);
+          g_error_free (error);
+          g_simple_async_result_complete (simple);
+          g_object_unref (simple);
+          goto out;
+        }
+      g_assert (bytes_written > 0); /* zero is never returned */
 
-  /* wake up pending flushes */
-  g_mutex_lock (worker->write_lock);
-  worker->write_num_messages_written += 1;
-  for (l = worker->write_pending_flushes; l != NULL; l = ll)
+      write_message_print_transport_debug (bytes_written, data);
+
+      data->total_written += bytes_written;
+      g_assert (data->total_written <= data->blob_size);
+      if (data->total_written == data->blob_size)
+        {
+          g_simple_async_result_complete (simple);
+          g_object_unref (simple);
+          goto out;
+        }
+
+      write_message_continue_writing (data);
+    }
+#endif
+  else
     {
-      FlushData *f = l->data;
-      ll = l->next;
+#ifdef G_OS_UNIX
+      if (fd_list != NULL)
+        {
+          g_simple_async_result_set_error (simple,
+                                           G_IO_ERROR,
+                                           G_IO_ERROR_FAILED,
+                                           "Tried sending a file descriptor on unsupported stream of type %s",
+                                           g_type_name (G_TYPE_FROM_INSTANCE (ostream)));
+          g_simple_async_result_complete (simple);
+          g_object_unref (simple);
+          goto out;
+        }
+#endif
 
-      if (f->number_to_wait_for == worker->write_num_messages_written)
+      g_output_stream_write_async (ostream,
+                                   (const gchar *) data->blob + data->total_written,
+                                   data->blob_size - data->total_written,
+                                   G_PRIORITY_DEFAULT,
+                                   data->worker->cancellable,
+                                   write_message_async_cb,
+                                   data);
+    }
+ out:
+  ;
+}
+
+/* called in private thread shared by all GDBusConnection instances (without write-lock held) */
+static void
+write_message_async (GDBusWorker         *worker,
+                     MessageToWriteData  *data,
+                     GAsyncReadyCallback  callback,
+                     gpointer             user_data)
+{
+  data->simple = g_simple_async_result_new (NULL,
+                                            callback,
+                                            user_data,
+                                            write_message_async);
+  data->total_written = 0;
+  write_message_continue_writing (data);
+}
+
+/* called in private thread shared by all GDBusConnection instances (without write-lock held) */
+static gboolean
+write_message_finish (GAsyncResult   *res,
+                      GError        **error)
+{
+  g_warn_if_fail (g_simple_async_result_get_source_tag (G_SIMPLE_ASYNC_RESULT (res)) == write_message_async);
+  if (g_simple_async_result_propagate_error (G_SIMPLE_ASYNC_RESULT (res), error))
+    return FALSE;
+  else
+    return TRUE;
+}
+/* ---------------------------------------------------------------------------------------------------- */
+
+static void maybe_write_next_message (GDBusWorker *worker);
+
+typedef struct
+{
+  GDBusWorker *worker;
+  GList *flushers;
+} FlushAsyncData;
+
+/* called in private thread shared by all GDBusConnection instances (without write-lock held) */
+static void
+ostream_flush_cb (GObject      *source_object,
+                  GAsyncResult *res,
+                  gpointer      user_data)
+{
+  FlushAsyncData *data = user_data;
+  GError *error;
+  GList *l;
+
+  error = NULL;
+  g_output_stream_flush_finish (G_OUTPUT_STREAM (source_object),
+                                res,
+                                &error);
+
+  if (error == NULL)
+    {
+      if (G_UNLIKELY (_g_dbus_debug_transport ()))
         {
-          g_mutex_lock (f->mutex);
-          g_cond_signal (f->cond);
-          g_mutex_unlock (f->mutex);
-          worker->write_pending_flushes = g_list_delete_link (worker->write_pending_flushes, l);
+          _g_dbus_debug_print_lock ();
+          g_print ("========================================================================\n"
+                   "GDBus-debug:Transport:\n"
+                   "  ---- FLUSHED stream of type %s\n",
+                   g_type_name (G_TYPE_FROM_INSTANCE (g_io_stream_get_output_stream (data->worker->stream))));
+          _g_dbus_debug_print_unlock ();
         }
     }
-  g_mutex_unlock (worker->write_lock);
 
+  g_assert (data->flushers != NULL);
+  for (l = data->flushers; l != NULL; l = l->next)
+    {
+      FlushData *f = l->data;
+
+      f->error = error != NULL ? g_error_copy (error) : NULL;
+
+      g_mutex_lock (f->mutex);
+      g_cond_signal (f->cond);
+      g_mutex_unlock (f->mutex);
+    }
+  g_list_free (data->flushers);
+
+  if (error != NULL)
+    g_error_free (error);
+
+  /* OK, cool, finally kick off the next write */
+  maybe_write_next_message (data->worker);
+
+  _g_dbus_worker_unref (data->worker);
+  g_free (data);
+}
+
+/* called in private thread shared by all GDBusConnection instances (without write-lock held) */
+static void
+message_written (GDBusWorker *worker,
+                 MessageToWriteData *message_data)
+{
+  GList *l;
+  GList *ll;
+  GList *flushers;
+
+  /* first log the fact that we wrote a message */
   if (G_UNLIKELY (_g_dbus_debug_message ()))
     {
       gchar *s;
@@ -945,66 +1139,171 @@ write_message (GDBusWorker         *worker,
       g_print ("========================================================================\n"
                "GDBus-debug:Message:\n"
                "  >>>> SENT D-Bus message (%" G_GSIZE_FORMAT " bytes)\n",
-               data->blob_size);
-      s = g_dbus_message_print (data->message, 2);
+               message_data->blob_size);
+      s = g_dbus_message_print (message_data->message, 2);
       g_print ("%s", s);
       g_free (s);
       if (G_UNLIKELY (_g_dbus_debug_payload ()))
         {
-          s = _g_dbus_hexdump (data->blob, data->blob_size, 2);
+          s = _g_dbus_hexdump (message_data->blob, message_data->blob_size, 2);
           g_print ("%s\n", s);
           g_free (s);
         }
       _g_dbus_debug_print_unlock ();
     }
 
- out:
-  return ret;
+  /* then first wake up pending flushes and, if needed, flush the stream */
+  flushers = NULL;
+  g_mutex_lock (worker->write_lock);
+  worker->write_num_messages_written += 1;
+  for (l = worker->write_pending_flushes; l != NULL; l = ll)
+    {
+      FlushData *f = l->data;
+      ll = l->next;
+
+      if (f->number_to_wait_for == worker->write_num_messages_written)
+        {
+          flushers = g_list_append (flushers, f);
+          worker->write_pending_flushes = g_list_delete_link (worker->write_pending_flushes, l);
+        }
+    }
+  g_mutex_unlock (worker->write_lock);
+
+  if (flushers != NULL)
+    {
+      FlushAsyncData *data;
+      data = g_new0 (FlushAsyncData, 1);
+      data->worker = _g_dbus_worker_ref (worker);
+      data->flushers = flushers;
+      /* flush the stream before writing the next message */
+      g_output_stream_flush_async (g_io_stream_get_output_stream (worker->stream),
+                                   G_PRIORITY_DEFAULT,
+                                   worker->cancellable,
+                                   ostream_flush_cb,
+                                   data);
+    }
+  else
+    {
+      /* kick off the next write! */
+      maybe_write_next_message (worker);
+    }
 }
 
-/* ---------------------------------------------------------------------------------------------------- */
+/* called in private thread shared by all GDBusConnection instances (without write-lock held) */
+static void
+write_message_cb (GObject       *source_object,
+                  GAsyncResult  *res,
+                  gpointer       user_data)
+{
+  MessageToWriteData *data = user_data;
+  GError *error;
+
+  g_mutex_lock (data->worker->write_lock);
+  data->worker->num_writes_pending -= 1;
+  g_mutex_unlock (data->worker->write_lock);
+
+  error = NULL;
+  if (!write_message_finish (res, &error))
+    {
+      /* TODO: handle */
+      _g_dbus_worker_emit_disconnected (data->worker, TRUE, error);
+      g_error_free (error);
+    }
+
+  /* this function will also kick of the next write (it might need to
+   * flush so writing the next message might happen much later
+   * e.g. async)
+   */
+  message_written (data->worker, data);
+
+  message_to_write_data_free (data);
+}
 
 /* called in private thread shared by all GDBusConnection instances (without write-lock held) */
-static gboolean
-write_message_in_idle_cb (gpointer user_data)
+static void
+maybe_write_next_message (GDBusWorker *worker)
 {
-  GDBusWorker *worker = user_data;
-  gboolean more_writes_are_pending;
   MessageToWriteData *data;
-  gboolean message_was_dropped;
-  GError *error;
+
+ write_next:
 
   g_mutex_lock (worker->write_lock);
   data = g_queue_pop_head (worker->write_queue);
-  g_assert (data != NULL);
-  more_writes_are_pending = (g_queue_get_length (worker->write_queue) > 0);
-  worker->write_is_pending = more_writes_are_pending;
+  if (data != NULL)
+    worker->num_writes_pending += 1;
   g_mutex_unlock (worker->write_lock);
 
   /* Note that write_lock is only used for protecting the @write_queue
-   * and @write_is_pending fields of the GDBusWorker struct ... which we
+   * and @num_writes_pending fields of the GDBusWorker struct ... which we
    * need to modify from arbitrary threads in _g_dbus_worker_send_message().
    *
    * Therefore, it's fine to drop it here when calling back into user
    * code and then writing the message out onto the GIOStream since this
    * function only runs on the worker thread.
    */
-  message_was_dropped = _g_dbus_worker_emit_message_about_to_be_sent (worker, data->message);
-  if (G_LIKELY (!message_was_dropped))
+  if (data != NULL)
     {
-      error = NULL;
-      if (!write_message (worker,
-                          data,
-                          &error))
+      GDBusMessageFilterResult filter_result;
+      guchar *new_blob;
+      gsize new_blob_size;
+      GError *error;
+
+      filter_result = _g_dbus_worker_emit_message_about_to_be_sent (worker, data->message);
+      switch (filter_result)
         {
-          /* TODO: handle */
-          _g_dbus_worker_emit_disconnected (worker, TRUE, error);
-          g_error_free (error);
+        case G_DBUS_MESSAGE_FILTER_RESULT_NO_EFFECT:
+          /* do nothing */
+          break;
+
+        case G_DBUS_MESSAGE_FILTER_RESULT_MESSAGE_CONSUMED:
+          /* drop message */
+          g_mutex_lock (worker->write_lock);
+          worker->num_writes_pending -= 1;
+          g_mutex_unlock (worker->write_lock);
+          message_to_write_data_free (data);
+          goto write_next;
+
+        case G_DBUS_MESSAGE_FILTER_RESULT_MESSAGE_ALTERED:
+          /* reencode altered message */
+          error = NULL;
+          new_blob = g_dbus_message_to_blob (data->message,
+                                             &new_blob_size,
+                                             worker->capabilities,
+                                             &error);
+          if (new_blob == NULL)
+            {
+              /* if filter make the GDBusMessage unencodeable, just complain on stderr and send
+               * the old message instead
+               */
+              g_warning ("Error encoding GDBusMessage with serial %d altered by filter function: %s",
+                         g_dbus_message_get_serial (data->message),
+                         error->message);
+              g_error_free (error);
+            }
+          else
+            {
+              g_free (data->blob);
+              data->blob = (gchar *) new_blob;
+              data->blob_size = new_blob_size;
+            }
+          break;
         }
+
+      write_message_async (worker,
+                           data,
+                           write_message_cb,
+                           data);
     }
-  message_to_write_data_free (data);
+}
 
-  return more_writes_are_pending;
+/* called in private thread shared by all GDBusConnection instances (without write-lock held) */
+static gboolean
+write_message_in_idle_cb (gpointer user_data)
+{
+  GDBusWorker *worker = user_data;
+  if (worker->num_writes_pending == 0)
+    maybe_write_next_message (worker);
+  return FALSE;
 }
 
 /* ---------------------------------------------------------------------------------------------------- */
@@ -1023,18 +1322,16 @@ _g_dbus_worker_send_message (GDBusWorker    *worker,
   g_return_if_fail (blob_len > 16);
 
   data = g_new0 (MessageToWriteData, 1);
+  data->worker = _g_dbus_worker_ref (worker);
   data->message = g_object_ref (message);
   data->blob = blob; /* steal! */
   data->blob_size = blob_len;
 
   g_mutex_lock (worker->write_lock);
   g_queue_push_tail (worker->write_queue, data);
-  if (!worker->write_is_pending)
+  if (worker->num_writes_pending == 0)
     {
       GSource *idle_source;
-
-      worker->write_is_pending = TRUE;
-
       idle_source = g_idle_source_new ();
       g_source_set_priority (idle_source, G_PRIORITY_DEFAULT);
       g_source_set_callback (idle_source,
@@ -1139,6 +1436,7 @@ _g_dbus_worker_flush_sync (GDBusWorker    *worker,
   FlushData *data;
 
   data = NULL;
+  ret = TRUE;
 
   /* if the queue is empty, there's nothing to wait for */
   g_mutex_lock (worker->write_lock);
@@ -1158,29 +1456,33 @@ _g_dbus_worker_flush_sync (GDBusWorker    *worker,
       g_cond_wait (data->cond, data->mutex);
       g_mutex_unlock (data->mutex);
 
-      /* note:the element is removed from worker->write_pending_flushes in write_message() */
+      /* note:the element is removed from worker->write_pending_flushes in flush_cb() above */
       g_cond_free (data->cond);
       g_mutex_free (data->mutex);
+      if (data->error != NULL)
+        {
+          ret = FALSE;
+          g_propagate_error (error, data->error);
+        }
       g_free (data);
     }
 
-  ret = g_output_stream_flush (g_io_stream_get_output_stream (worker->stream),
-                               cancellable,
-                               error);
   return ret;
 }
 
 /* ---------------------------------------------------------------------------------------------------- */
 
 #define G_DBUS_DEBUG_AUTHENTICATION (1<<0)
-#define G_DBUS_DEBUG_MESSAGE        (1<<1)
-#define G_DBUS_DEBUG_PAYLOAD        (1<<2)
-#define G_DBUS_DEBUG_CALL           (1<<3)
-#define G_DBUS_DEBUG_SIGNAL         (1<<4)
-#define G_DBUS_DEBUG_INCOMING       (1<<5)
-#define G_DBUS_DEBUG_EMISSION       (1<<6)
-#define G_DBUS_DEBUG_ADDRESS        (1<<7)
-#define G_DBUS_DEBUG_ALL            0xffffffff
+#define G_DBUS_DEBUG_TRANSPORT      (1<<1)
+#define G_DBUS_DEBUG_MESSAGE        (1<<2)
+#define G_DBUS_DEBUG_PAYLOAD        (1<<3)
+#define G_DBUS_DEBUG_CALL           (1<<4)
+#define G_DBUS_DEBUG_SIGNAL         (1<<5)
+#define G_DBUS_DEBUG_INCOMING       (1<<6)
+#define G_DBUS_DEBUG_RETURN         (1<<7)
+#define G_DBUS_DEBUG_EMISSION       (1<<8)
+#define G_DBUS_DEBUG_ADDRESS        (1<<9)
+
 static gint _gdbus_debug_flags = 0;
 
 gboolean
@@ -1191,6 +1493,13 @@ _g_dbus_debug_authentication (void)
 }
 
 gboolean
+_g_dbus_debug_transport (void)
+{
+  _g_dbus_initialize ();
+  return (_gdbus_debug_flags & G_DBUS_DEBUG_TRANSPORT) != 0;
+}
+
+gboolean
 _g_dbus_debug_message (void)
 {
   _g_dbus_initialize ();
@@ -1226,6 +1535,13 @@ _g_dbus_debug_incoming (void)
 }
 
 gboolean
+_g_dbus_debug_return (void)
+{
+  _g_dbus_initialize ();
+  return (_gdbus_debug_flags & G_DBUS_DEBUG_RETURN) != 0;
+}
+
+gboolean
 _g_dbus_debug_emission (void)
 {
   _g_dbus_initialize ();
@@ -1276,31 +1592,22 @@ _g_dbus_initialize (void)
       debug = g_getenv ("G_DBUS_DEBUG");
       if (debug != NULL)
         {
-          gchar **tokens;
-          guint n;
-          tokens = g_strsplit (debug, ",", 0);
-          for (n = 0; tokens[n] != NULL; n++)
-            {
-              if (g_strcmp0 (tokens[n], "authentication") == 0)
-                _gdbus_debug_flags |= G_DBUS_DEBUG_AUTHENTICATION;
-              else if (g_strcmp0 (tokens[n], "message") == 0)
-                _gdbus_debug_flags |= G_DBUS_DEBUG_MESSAGE;
-              else if (g_strcmp0 (tokens[n], "payload") == 0) /* implies `message' */
-                _gdbus_debug_flags |= (G_DBUS_DEBUG_MESSAGE | G_DBUS_DEBUG_PAYLOAD);
-              else if (g_strcmp0 (tokens[n], "call") == 0)
-                _gdbus_debug_flags |= G_DBUS_DEBUG_CALL;
-              else if (g_strcmp0 (tokens[n], "signal") == 0)
-                _gdbus_debug_flags |= G_DBUS_DEBUG_SIGNAL;
-              else if (g_strcmp0 (tokens[n], "incoming") == 0)
-                _gdbus_debug_flags |= G_DBUS_DEBUG_INCOMING;
-              else if (g_strcmp0 (tokens[n], "emission") == 0)
-                _gdbus_debug_flags |= G_DBUS_DEBUG_EMISSION;
-              else if (g_strcmp0 (tokens[n], "address") == 0)
-                _gdbus_debug_flags |= G_DBUS_DEBUG_ADDRESS;
-              else if (g_strcmp0 (tokens[n], "all") == 0)
-                _gdbus_debug_flags |= G_DBUS_DEBUG_ALL;
-            }
-          g_strfreev (tokens);
+          const GDebugKey keys[] = {
+            { "authentication", G_DBUS_DEBUG_AUTHENTICATION },
+            { "transport",      G_DBUS_DEBUG_TRANSPORT      },
+            { "message",        G_DBUS_DEBUG_MESSAGE        },
+            { "payload",        G_DBUS_DEBUG_PAYLOAD        },
+            { "call",           G_DBUS_DEBUG_CALL           },
+            { "signal",         G_DBUS_DEBUG_SIGNAL         },
+            { "incoming",       G_DBUS_DEBUG_INCOMING       },
+            { "return",         G_DBUS_DEBUG_RETURN         },
+            { "emission",       G_DBUS_DEBUG_EMISSION       },
+            { "address",        G_DBUS_DEBUG_ADDRESS        }
+          };
+
+          _gdbus_debug_flags = g_parse_debug_string (debug, keys, G_N_ELEMENTS (keys));
+          if (_gdbus_debug_flags & G_DBUS_DEBUG_PAYLOAD)
+            _gdbus_debug_flags |= G_DBUS_DEBUG_MESSAGE;
         }
 
       g_once_init_leave (&initialized, 1);
@@ -1444,3 +1751,76 @@ _g_dbus_enum_to_string (GType enum_type, gint value)
 }
 
 /* ---------------------------------------------------------------------------------------------------- */
+
+static void
+write_message_print_transport_debug (gssize bytes_written,
+                                     MessageToWriteData *data)
+{
+  if (G_LIKELY (!_g_dbus_debug_transport ()))
+    goto out;
+
+  _g_dbus_debug_print_lock ();
+  g_print ("========================================================================\n"
+           "GDBus-debug:Transport:\n"
+           "  >>>> WROTE %" G_GSIZE_FORMAT " bytes of message with serial %d and\n"
+           "       size %" G_GSIZE_FORMAT " from offset %" G_GSIZE_FORMAT " on a %s\n",
+           bytes_written,
+           g_dbus_message_get_serial (data->message),
+           data->blob_size,
+           data->total_written,
+           g_type_name (G_TYPE_FROM_INSTANCE (g_io_stream_get_output_stream (data->worker->stream))));
+  _g_dbus_debug_print_unlock ();
+ out:
+  ;
+}
+
+/* ---------------------------------------------------------------------------------------------------- */
+
+static void
+read_message_print_transport_debug (gssize bytes_read,
+                                    GDBusWorker *worker)
+{
+  gsize size;
+  gint32 serial;
+  gint32 message_length;
+
+  if (G_LIKELY (!_g_dbus_debug_transport ()))
+    goto out;
+
+  size = bytes_read + worker->read_buffer_cur_size;
+  serial = 0;
+  message_length = 0;
+  if (size >= 16)
+    message_length = g_dbus_message_bytes_needed ((guchar *) worker->read_buffer, size, NULL);
+  if (size >= 1)
+    {
+      switch (worker->read_buffer[0])
+        {
+        case 'l':
+          if (size >= 12)
+            serial = GUINT32_FROM_LE (((guint32 *) worker->read_buffer)[2]);
+          break;
+        case 'B':
+          if (size >= 12)
+            serial = GUINT32_FROM_BE (((guint32 *) worker->read_buffer)[2]);
+          break;
+        default:
+          /* an error will be set elsewhere if this happens */
+          goto out;
+        }
+    }
+
+    _g_dbus_debug_print_lock ();
+  g_print ("========================================================================\n"
+           "GDBus-debug:Transport:\n"
+           "  <<<< READ %" G_GSIZE_FORMAT " bytes of message with serial %d and\n"
+           "       size %d to offset %" G_GSIZE_FORMAT " from a %s\n",
+           bytes_read,
+           serial,
+           message_length,
+           worker->read_buffer_cur_size,
+           g_type_name (G_TYPE_FROM_INSTANCE (g_io_stream_get_input_stream (worker->stream))));
+  _g_dbus_debug_print_unlock ();
+ out:
+  ;
+}