[glib] GDBus: Only rewrite serial number if g_dbus_message_get_serial() returns 0

[David Zeuthen <davidz src gnome org>]

commit acc9bb24033cdb93be6b9c00012f86ac56904cc9
Author: David Zeuthen <davidz redhat com>
Date:   Wed Jul 7 11:02:08 2010 -0400

    GDBus: Only rewrite serial number if g_dbus_message_get_serial() returns 0
    
    While this a dangerous thing to allow (collissions, reply_serial not
    matching up etc.), the added flexibility makes this a good trade-off -
    for example, with this feature, it's now a lot easier to build message
    routers.
    
    Signed-off-by: David Zeuthen <davidz redhat com>

 gio/gdbusconnection.c        |   27 ++++++++++++++++++++-------
 gio/tests/gdbus-connection.c |    3 +++
 2 files changed, 23 insertions(+), 7 deletions(-)
---
diff --git a/gio/gdbusconnection.c b/gio/gdbusconnection.c
index e853281..9b94d1d 100644
--- a/gio/gdbusconnection.c
+++ b/gio/gdbusconnection.c
@@ -1026,7 +1026,11 @@ g_dbus_connection_send_message_unlocked (GDBusConnection   *connection,
   if (blob == NULL)
     goto out;
 
-  serial_to_use = ++connection->priv->last_serial; /* TODO: handle overflow */
+  serial_to_use = g_dbus_message_get_serial (message);
+  if (serial_to_use == 0)
+    {
+      serial_to_use = ++connection->priv->last_serial; /* TODO: handle overflow */
+    }
 
   switch (blob[0])
     {
@@ -1079,8 +1083,11 @@ g_dbus_connection_send_message_unlocked (GDBusConnection   *connection,
  *
  * Asynchronously sends @message to the peer represented by @connection.
  *
- * If @out_serial is not %NULL, then the serial number assigned to
- * @message by @connection will be written to this location prior to
+ * If g_dbus_message_get_serial() returns non-zero for @message, then
+ * that value is used for the message serial number. Otherwise a
+ * serial number will be assigned by @connection and set on @message
+ * via g_dbus_message_set_serial(). If @out_serial is not %NULL, then
+ * the serial number used will be written to this location prior to
  * submitting the message to the underlying transport.
  *
  * If @connection is closed then the operation will fail with
@@ -1392,8 +1399,11 @@ g_dbus_connection_send_message_with_reply_unlocked (GDBusConnection     *connect
  *
  * Asynchronously sends @message to the peer represented by @connection.
  *
- * If @out_serial is not %NULL, then the serial number assigned to
- * @message by @connection will be written to this location prior to
+ * If g_dbus_message_get_serial() returns non-zero for @message, then
+ * that value is used for the message serial number. Otherwise a
+ * serial number will be assigned by @connection and set on @message
+ * via g_dbus_message_set_serial(). If @out_serial is not %NULL, then
+ * the serial number used will be written to this location prior to
  * submitting the message to the underlying transport.
  *
  * If @connection is closed then the operation will fail with
@@ -1525,8 +1535,11 @@ send_message_with_reply_sync_cb (GDBusConnection *connection,
  * timeout is reached. See g_dbus_connection_send_message_with_reply()
  * for the asynchronous version of this method.
  *
- * If @out_serial is not %NULL, then the serial number assigned to
- * @message by @connection will be written to this location prior to
+ * If g_dbus_message_get_serial() returns non-zero for @message, then
+ * that value is used for the message serial number. Otherwise a
+ * serial number will be assigned by @connection and set on @message
+ * via g_dbus_message_set_serial(). If @out_serial is not %NULL, then
+ * the serial number used will be written to this location prior to
  * submitting the message to the underlying transport.
  *
  * If @connection is closed then the operation will fail with
diff --git a/gio/tests/gdbus-connection.c b/gio/tests/gdbus-connection.c
index 01113ee..3c63cae 100644
--- a/gio/tests/gdbus-connection.c
+++ b/gio/tests/gdbus-connection.c
@@ -618,12 +618,14 @@ test_connection_filter (void)
   while (data.num_handled == 0)
     g_thread_yield ();
 
+  g_dbus_message_set_serial (m, 0);
   g_dbus_connection_send_message (c, m, &data.serial, &error);
   g_assert_no_error (error);
 
   while (data.num_handled == 1)
     g_thread_yield ();
 
+  g_dbus_message_set_serial (m, 0);
   r = g_dbus_connection_send_message_with_reply_sync (c,
                                                       m,
                                                       -1,
@@ -637,6 +639,7 @@ test_connection_filter (void)
 
   g_dbus_connection_remove_filter (c, filter_id);
 
+  g_dbus_message_set_serial (m, 0);
   r = g_dbus_connection_send_message_with_reply_sync (c,
                                                       m,
                                                       -1,