[lxc-devel] [PATCH v2] fix console stdin,stdout,stderr fds

[Serge Hallyn]

Quoting Dwight Engen (dwight.engen at oracle.com):
> On Fri, 7 Mar 2014 17:58:07 -0600
> Serge Hallyn <serge.hallyn at ubuntu.com> wrote:
> 
> > Quoting Dwight Engen (dwight.engen at oracle.com):
> > > On Fri, 7 Mar 2014 17:01:17 -0600
> > > Serge Hallyn <serge.hallyn at ubuntu.com> wrote:
> > > 
> > > > Quoting Dwight Engen (dwight.engen at oracle.com):
> > > > > +	if (lxc_console_set_stdfds(handler) < 0)
> > > > > +		goto out_warn_father;
> > > > > +
> > > > >  	close(handler->sigfd);
> > > > >  
> > > > > +	if (lxc_check_inherited(handler->conf))
> > > > > +		return -1;
> > > > > +
> > > > 
> > > > Hi,
> > > > 
> > > > so the reason why the lxc_check_inherited() was where it
> > > > was, was because at this point we've called tmp_proc_umount().
> > > > So in some cases /proc won't be mounted, and lxc_check_inherited()
> > > > finds the fds to close under /proc
> > > 
> > > Ahh okay that makes sense, good catch. So it seems like I should
> > > leave lxc_check_inherited() where it was and then just put the call
> > > to lxc_console_set_stdfds() just before it since it looks like
> > > check_inherited() will leave 0,1,2 alone and close the original fds.
> > > Does that sound reasonable?
> > 
> > Yeah, that sounds good.
> > 
> > thanks,
> > -serge
> 
> Hi Serge, I noticed that just doing the above means that stdin,out,err
> will be changed for the start hook, is that going to be a problem? If
> so, then maybe what we can do is arrange for check_inherited() ignore
> the console pty's as well and do the set_stdfds() after the hook runs?

Since the start hook runs out of the container's filesystem, I think
it is fine to have them run under the container's pty.  (Keeping in
mind that the stdout is dup'd to a pipe, while stdin and stderr are
unchanged)

Does that make sense?

-serge