Re: A possible bug with non-blocking sockets and SIGIO

[Matthias Scheler <tron%zhadum.org.uk@localhost>]

On Thu, Feb 17, 2011 at 10:58:10AM +0300, Dmitry Matveev wrote:
> I have discovered a bug (at least it looks like a bug) in NetBSD's
> socket layer.

I disagree, see below.

> Background information
> ----------------------
> 
> Suppose there is a single-threaded server. It uses SIGIO to maintain
> incoming connections and data from clients.

Using SIGIO is bad idea in general. Please use poll(2) or
kqueue(2) + kevent(2) instead.

> Server process does not receive SIGIO on incoming data on the client
> socket.

Because you never setup the acceptor socket to do so.

Here are my comment about your source code:

        void incoming_data (int i) {
            if (i != SIGIO)
                exit (0);

It is not safe to use exit(3) from a signal handler, please use
_exit(2) instead.

            g_client = accept_client (g_server);
            CLOG ("client accepted");

Here is your problem. You newer setup asynchronous I/O on this socket.
You need to use fcntl(2) to set O_ASYNC just as you do on the
acceptor socket.

        Kind regards

-- 
Matthias Scheler                                  http://zhadum.org.uk/