Re: RFC: netfilter: nf_conntrack: add support for "conntrack zones"

[Matt Helsley <matthltc-r/Jw6+rmf7HQT0dZR+AlfA@public.gmane.org>]

On Tue, Feb 23, 2010 at 12:00:55PM -0800, Eric W. Biederman wrote:
> jamal <hadi-fAAogVwAN2Kw5LPnMra/2Q@public.gmane.org> writes:
> 
> > Added Daniel to the discussion..
> >
> > On Tue, 2010-02-23 at 06:07 -0800, Eric W. Biederman wrote:
> >> jamal <hadi-fAAogVwAN2Kw5LPnMra/2Q@public.gmane.org> writes:
> >
> >> > Does the point after sys_setns(fd) allow me to do io inside
> >> > ns <name>? Can i do open() and get a fd from ns <name>?
> >> 
> >> Yes.  My intention is that current->nsproxy->net_ns be changed.
> >> We can already change it in unshare so this is feasible.
> >
> > I like it if it makes it as easy as it sounds;-> With lxc,
> > i essentially have to create a proxy process inside the
> > namespace that i use unix domain to open fds inside the ns.
> > Do i still need that?
> 
> That point of the mount to hold a persistent reference to the
> namespace without using a process.

I think technicaly it's still held using processes, only now it's
much more indirect:

netns <- mount <- mount namespace(s) <- process(es)

The big difference is we'd be waiting for all the processes
sharing that mount (or dups of it in multiple mount namespaces) to
exit too -- not just those sharing the netns.

Using a mount requires keeping names for the namespaces themselves
in the kernel which is a problem we've largely avoided so far.
The nscgroup is an example of the messes that creates, I think. And it
further complicates c/r -- we'd need to checkpoint and recreate the
names of the namespaces too. So we'll need a namespace for the names of
the namespaces to make restart reliable won't we? Makes my head spin...

Cheers,
	-Matt Helsley