[asterisk-dev] asterisk ast_close_fds_above_n, wtf?

[Tilghman Lesher]

On Tuesday 17 May 2011 13:20:22 Paul Albrecht wrote:
> Thought I'd start a separate thread because since some folks can't look
> at patches submitted to the list...

All developers who have commit rights to the code aren't allowed to look at
unlicensed patches.  It's a policy meant to protect the project from
"tainting" the minds of developers who may unconsciously use code they see
that is not licensed for inclusion under our licensing scheme.

> Here's my question: Why is asterisk supporting code, essentially the
> solaris closefrom system call, to close file descriptors over exec
> system calls?
> 
> This approach has been rejected by the glibc maintainer:
> 
> http://sourceware.org/bugzilla/show_bug.cgi?id=10353

Correct, because it really needs to be a kernel interface, as implemented
on Solaris.  Because it's possible for a program to go directly to the
kernel to open file descriptors, instead of through the library, the
library cannot reliably verify that it has tracked all file descriptors.

> And as linux provides a satisfactory method to close file descriptors it
> creates prior to exec'ing a program or script:
> 
> http://udrepper.livejournal.com/20407.html
> 
> what's the point another interface?

That's wonderful.... for Linux, as long as you're running kernel 2.6.27 or 
above.  What if you're running FreeBSD?  Or Mac OS X?  Or Solaris?  Or
CentOS 5.5 (a kernel less than 2.6.27)?  Those systems don't support 
setting the CLOEXEC flag concurrently with the system call that opens
the file descriptor.  You still have the same problem.  Asterisk supports
all of these systems, so it needs a solution that works on all of these
systems.

-- 
Tilghman