netdev - Re: loosing netdevices with namespaces and unshare?

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Message-ID: <20170601070031.mdycexartsu33fyd@nataraja>
Date:   Thu, 1 Jun 2017 09:00:31 +0200
From:   Harald Welte <laforge@...monks.org>
To:     "Eric W. Biederman" <ebiederm@...ssion.com>
Cc:     Cong Wang <xiyou.wangcong@...il.com>,
        Linux Kernel Network Developers <netdev@...r.kernel.org>
Subject: Re: loosing netdevices with namespaces and unshare?

Hi Eric,

On Thu, Jun 01, 2017 at 01:32:49AM -0500, Eric W. Biederman wrote:

> If a network device does not implement rntl_link_ops it is returned to
> the initial network namespace.   Anything else will loose physical
> devices.

Thanks a lot for your statement.  This is a big relief, my line of
thinking thus is confirmed:  We shall not loose physical devices.

> Only for pure software based devices do we delete them.  Perhaps your
> sub interface implements rtnl_link_ops?  Either that or something is
> still holding a reference to your network namespace, which would prevent
> the network device from being returned.

My question is how to debug this further?  Monitoring
/proc/*/ns/net* showed that the ID of the namespace is gone after
terminating my processes in the namespace.  Short of adding printk() or
playing with kprobes: to the related kernel code, how can I track the
reference count or get an idea who might hold references?

Regards,
	Harald
-- 
- Harald Welte <laforge@...monks.org>           http://laforge.gnumonks.org/
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