select function ob libbsc. A "polling" flag is used to enable polling.
In this case select() will not sleep until file descriptor events occurr
or nearest timer expires. Also a return value will indicate if there was
an event that has been handled. If there was an event, the application
decides to poll again and don't wait.
In case for bsc_hack, the polling flag is not set. select will sleep as
usual.
(Andreas Eversberg)
One can use add_timer or schedule_timer to add a timer. After
the timeout time has been reached the callback will be called.
One can call add_time/schedule_timer and del_timer from within
the callback.
Harald Welte
Holger Freyther