Hi,
On Sun, 20 Feb 2000 16:48:04 +0200 (EET), Julian Anastasov
<uli@linux.tu-varna.acad.bg> said:
> I have played these days with accept() and sigwaitinfo().
> It seems that for single threaded server we have to:
> 1. setup listening socket: O_ASYNC|O_NONBLOCK, SETOWN my_pid,
> signals (SIGIO, SIGRTMIN...), etc.
> In the loop:
> 2. accept() the connection
> 3. fcntl(connected_socket,F_SETFL,O_NONBLOCK|O_ASYNC|O_RDWR)
> 4. fcntl(connected_socket,F_SETSIG,sig)
> 5. fcntl(connected_socket,F_SETOWN,again_my_pid)
> 6. read(connected_socket...), sigwaitinfo()
> It is possible between points 2 and 5 the data for
> the connected socket to arrive. So, I had to put an extra
> read() after F_SETOWN to detect this condition.
Yes. I'm looking at adding a F_SETFAST() fcntl, which will do a
F_SETFL, F_SETSIG and F_SETOWN at once on the socket, and return a
poll struct indicating any outstanding IO on the socket so that you
don't have to do a speculative read() to detect data arrived before you
made the fcntl call.
> My proposal: is it possible to add SO_INHERITOWN or other
> socket/file (F_COPYOWN) option suitable for listening sockets
> with the main goal to let sys_accept() to copy the fd owner after
> get_fd(2.2.x) or sock_map_fd(2.3.x) in net/socket.c.
Definitely a good idea --- a lot of other O/Ses already have something
like that. We can inherit socket options the same way, of course, which
will be useful for a lot of services.
> I haven't made a patch yet. I need more opinions
> about this problem. May be I'm wrong? Are there any other
> things that can be inherited from the listening socket
> using the new option or only the f_owner is enough?
TCP_CORK, linger options, all sorts of others.
--Stephen
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