Re: [RFC PATCH net-next v2 0/5] netns: allow to identify peer netns

[Nicolas Dichtel]

Le 26/09/2014 03:58, Cong Wang a Ãcrit :
> On Thu, Sep 25, 2014 at 1:53 AM, Nicolas Dichtel
> <nicolas.dichtel@xxxxxxxxx> wrote:
> > Le 24/09/2014 18:48, Cong Wang a Ãcrit :
> >
> > > On Wed, Sep 24, 2014 at 9:31 AM, Nicolas Dichtel
> > > <nicolas.dichtel@xxxxxxxxx> wrote:
> > > > > I think in this case your ID's are still available, but aren't you
> > > > > providing a new way
> > > > > for the inner netns device to escape which we are trying to avoid?
> > > >
> > > >
> > > > It's why the ids depend on user ns. Only if user ns are the same we allow
> > > > to
> > > > get an id for a peer netns.
> > >
> > >
> > > Too late, userns is relatively new, relying on it breaks our existing
> > > assumption.
> > I don't get your point. netns has been added in kernel after user ns:
> > acce292c82d4 user namespace: add the framework => 2.6.23
> > 5f256becd868 [NET]: Basic network namespace infrastructure. => 2.6.24
>
> Was it complete on 2.6.x? I doubt...
>
> https://lkml.org/lkml/2014/8/20/826
>
>     As at Linux 3.8, most relevant subsystems supported  user  namesâ
>         paces,  but  a number of filesystems did not have the infrastrucâ
>         ture needed to map user and group IDs  between  user  namespaces.
>         Linux  3.9  added the required infrastructure support for many of
>         the remaining unsupported filesystems (Plan 9 (9P),  Andrew  File
>         System  (AFS),  Ceph,  CIFS,  CODA,  NFS, and OCFS2).  Linux 3.11
>         added support the last of the unsupported major filesystems, XFS.
>
>
> > In the kernel, each netns is linked with a user ns.
>
> Are you saying every time we create a netns we have a new userns?
> This doesn't make sense for me.
No. I mean that each netns depends on a userns.
See include/net/net_namespace.h:
struct net {
[snip]
        struct user_namespace   *user_ns;       /* Owning user namespace */
[snip]
}
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