Re: [PATCH 2/2] net: Implement SO_PEERCGROUP

[Vivek Goyal <vgoyal-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>]

On Thu, Mar 13, 2014 at 04:17:55PM -0400, Vivek Goyal wrote:
> On Thu, Mar 13, 2014 at 04:06:49PM -0400, Vivek Goyal wrote:
> > On Thu, Mar 13, 2014 at 12:58:14PM -0700, Andy Lutomirski wrote:
> > > On Thu, Mar 13, 2014 at 12:53 PM, Vivek Goyal <vgoyal-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org> wrote:
> > > > On Thu, Mar 13, 2014 at 10:55:16AM -0700, Andy Lutomirski wrote:
> > > >
> > > > [..]
> > > >> >> 2. Docker is a container system, so use the "container" (aka
> > > >> >> namespace) APIs.  There are probably several clever things that could
> > > >> >> be done with /proc/<pid>/ns.
> > > >> >
> > > >> > pid is racy, if it weren't I would simply go straight
> > > >> > to /proc/<pid>/cgroups ...
> > > >>
> > > >> How about:
> > > >>
> > > >> open("/proc/self/ns/ipc", O_RDONLY);
> > > >> send the result over SCM_RIGHTS?
> > > >
> > > > As I don't know I will ask. So what will server now do with this file
> > > > descriptor of client's ipc namespace.
> > > >
> > > > IOW, what information/identifier does it contain which can be
> > > > used to map to pre-configrued per container/per namespace policies.
> > > 
> > > Inode number, which will match that assigned to the container at runtime.
> > > 
> > 
> > But what would I do with this inode number. I am assuming this is
> > generated dynamically when respective namespace was created. To me
> > this is like assigning a pid dynamically and one does not create
> > policies in user space based on pid. Similarly I will not be able
> > to create policies based on an inode number which is generated
> > dynamically.
> > 
> > For it to be useful, it should map to something more static which
> > user space understands.
> 
> Or could we do following.
> 
> open("/proc/self/cgroup", O_RDONLY);
> send the result over SCM_RIGHTS

I guess that would not work. Client should be able to create a file,
fake cgroup information and send fd.

Thanks
Vivek