[libmicrohttpd] minor issue with epoll+external select+no_timeout

[Marcos Pindado Sebastian]

Hi,

I want to share this little issue I had while implementing an external select 
webserver.
Case: daemon configured with MHD_USE_EPOLL_LINUX_ONLY plus EXTERNAL_SELECT.

The typical example for the external select is:

MHD_start_daemon (epoll)
while (1)
 {
   MHD_get_fdset (...)
   MHD_get_timeout(...)
   select(fds, timeout)
   MHD_run
}

Well, the example worked as far as I noticed that timeout had value 0 (not 
null), meaning not waiting at all. When I changed it to NULL then the example 
stopped working, because the program got blocked in the select statement not 
being notified of incoming connections.
The problem is, MHD_start_daemon, creates the epollFD before the listen-socket 
is set up. So, get_fdset returns a well epoll-fd without any listen socket 
attached just after start_daemon returns.

The solution for this is very simple, call MHD_run one time after the daemon is 
started and before the select-loop:

MHD_start_daemon (epoll)
MHD_run // => The listen socket is attached to the epollFD 
while (1)
 {select/run}


Thanks for your work!
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