netdev - Re: cross namespace interface notification for tun devices

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Message-ID: <CAM_iQpVvDNRbtj_47_3XXa_ezyrT=a_VzDtK5SCR9a4_2Gqw9w@mail.gmail.com>
Date:   Tue, 19 Sep 2017 13:40:49 -0700
From:   Cong Wang <xiyou.wangcong@...il.com>
To:     "Jason A. Donenfeld" <Jason@...c4.com>
Cc:     Netdev <netdev@...r.kernel.org>, Mathias <mathias@...l-andersen.dk>
Subject: Re: cross namespace interface notification for tun devices

On Mon, Sep 18, 2017 at 11:47 AM, Jason A. Donenfeld <Jason@...c4.com> wrote:
> Hey guys,
>
> It's possible to create a tun device in a process in namespace A and
> then move that interface to namespace B. The controlling process in A
> needs to receive notifications on when the interface is brought up or
> down. It can receive these notifications via netlink while the
> interface lives in A but not when it moves to B.

By "notification" I assume you mean netlink notification.

>
> Any tricks or APIs to get around this?

The question is why does the process in A still care about
the device sitting in B?

Also, the process should be able to receive a last notification
on IFF_UP|IFF_RUNNING before device is finally moved to B.
After this point, it should not have any relation to netns A
any more, like the device were completely gone.