Re: In-kernel process exit hooks?

[David Young <dyoung%pobox.com@localhost>]

On Fri, Jan 08, 2016 at 12:26:14PM +0700, Robert Elz wrote:
>     Date:        Fri, 8 Jan 2016 11:22:28 +0800 (PHT)
>     From:        Paul Goyette <paul%vps1.whooppee.com@localhost>
>     Message-ID:  <Pine.NEB.4.64.1601081115270.22533%vps1.whooppee.com@localhost>
> 
>   | Is there a "supported" interface for detaching the file (or descriptor) 
>   | from the process without closing it?
> 
> Inside the kernel you want to follow the exact same procedure as would
> be done by
> 
> 		newfd = dup(oldfd);
> 		close(oldfd);
> 
> except instead of dup (and assigning to a newfd in the process) we
> take the file reference and stick it in filemon.   There's nothing
> magic about this step.  What magic there is (though barely worthy of
> the title) would be in ensuring that filemon properly releases the file
> when it is closing.

Years ago I added to gre(4) an ioctl that a user thread can use to
delegate to the kernel a UDP socket that carries tunnel traffic.  I
think that that code should cover at least the dup(2) part of Robert's
suggestion.

Dave

-- 
David Young
dyoung%pobox.com@localhost    Urbana, IL    (217) 721-9981