nm_config_data_get_connection_default() gets called a lot.
In an example profiling run activating a 100 devices it thus shows up to consume 13.3% of the CPU time. That's mainly due to the overhead of
g_key_file_get_string() (interestingly, it is due to
glib_gettext() to construct the
GError message). Anyway, it sucks.
Add our own lookup index for these values and use binary search.