eliminating a syscall on accept()+ioctl() combo

[Jilles Tjoelker]

On Mon, Aug 01, 2011 at 08:11:04AM +0200, Vlad Galu wrote:
> On Jul 31, 2011, at 9:59 PM, Bernard van Gastel wrote:
> > I want to reduce the number of syscalls for my networking
> > application. The app handles incoming connections with the
> > 'accept()' system call. Is there a way to specify to accept() that
> > the newly created file descriptors should be non-blocking (FIONBIO)?
> > This will avoid an ioctl() after the accept(). Thanks!

> You can make your listening socket non-blocking. Newly created file
> descriptors will inherit that property. However, that will require you
> to select()/poll()/kqueue() for that descriptor as well, instead of
> simply blocking in accept().

This is documented FreeBSD behaviour and common across BSDs, but is not
portable. POSIX leaves it unspecified what the non-blocking state of the
new socket is and in fact Linux always makes the new socket blocking
(unless you request non-blocking using their new accept4() call).

Because this portability issue can be very subtle, I suggest not blindly
relying on it.

-- 
Jilles Tjoelker