The ifupdown plugin causes the keyfile plugin to break if there is a connection managed by ifupdown (/etc/network/interfaces) and the keyfile plugin is loaded after ifupdown as specified in /etc/NetworkManager/nm-system-settings.conf by default. The reason for this behaviour is the signal emission to unmanaged_specs_changed in the udev_device_added method of plugins/ifupdown/plugin.c:
        if (ALWAYS_UNMANAGE || priv->unmanage_well_known)
                g_signal_emit_by_name (G_OBJECT (self), NM_SYSTEM_CONFIG_INTERFACE_UNMANAGED_SPECS_CHANGED);

The signal is handled by nm-sysconfig-settings.c:unmanaged_specs_changed, which calls nm_system_config_interface_get_unmanaged_specs, which in turn calls load_connections. load_connections iterates all plugins which have already been loaded (only ifupdown), gets all connections and then sets priv->connections_loaded = TRUE; All further calls to load_connections do nothing if this variable is set. Therefore the connections managed by keyfile (and potentially other sysconfig plugins in the future) are invisible to NetworkManager.

A workaround is to change the order of the plugins and make sure ifupdown is the last.

Ubuntu Lucid suffers from this bug. I would like to get the workaround into Ubuntu as a SRU. Can someone from Gnome help with that?

+ Trace 224241