Bug or feature ...

[Clint Byrum]

Excerpts from Kees Cook's message of Wed Apr 06 15:14:38 -0700 2011:
> On Wed, Apr 06, 2011 at 02:53:46PM -0700, Kees Cook wrote:
> > On Wed, Apr 06, 2011 at 05:35:07PM -0400, Scott Kitterman wrote:
> > > He offers this as a test case:
> > 
> > I can confirm the behavior difference between maverick and natty by doing
> > this:
> > 
> > while ./testcase.pl ; do echo -n . ; done
> > 
> > On maverick, this runs forever. Natty immediately fails:
> > 
> > Parent 792
> > 
> > Child 793
> > .bind: Address already in use at ./testcase.pl line 9.
> > 
> > 
> > I hope this is a Net::Server delta and not a kernel delta.
> 
> This looks like a kernel bug to me. I can reproduce it with C as well.
> 
> $ ./testcase
> parent: 3781
> before:
> tcp        0      0 0.0.0.0:12345           0.0.0.0:*               LISTEN     
> after:
> child: 3786
> 
> $ ./testcase
> bind: Address already in use

This looks suspiciously similar to an occasional race condition we've been seeing in VMs with udev:

https://bugs.launchpad.net/ubuntu/+source/udev/+bug/712026