Altera TSE driver and example program for lwIP (1.3.2)

For those who uses sys_timeout() as a general purpose timer -

I’ve found that under certain circumstances lwip timeouts become extremely inaccurate. The reason is that sys_timeout() effectively schedules the handler not relative to the current time (result of sys_now()), but relative to the moment, when previous handler was called (stored in timers.c: static u32_t timeouts_last_time)

This does not affect internal lwip timers because they always reschedule themselves inside timeout handler routine, i.e. when timeouts_last_time is equal to sys_now(). On the contrary, if one calls sys_timeout() in arbitrary moment in time, say, inside UDP packet handler, difference between sys_now() and timeouts_last_time may be large. In such a case effective timeout value will be shorter by (sys_now() - timeouts_last_time) and all subsequent timeouts will be offset by the same value.

This can be fixed at the cost of extra sys_now() call by inserting

msecs += sys_now() - timeouts_last_time;

in the very beginning of void sys_timeout(u32_t msecs, sys_timeout_handler handler, void *arg).

Igor