netdev - Re: xfrm, ip tunnel: non released device reference upon device unregistration

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Date:   Sun, 4 Feb 2018 15:32:52 +0200
From:   Eyal Birger <eyal.birger@...il.com>
To:     steffen.klassert@...unet.com
Cc:     netdev@...r.kernel.org, herbert@...dor.apana.org.au,
        davem@...emloft.net, shmulik@...anetworks.com
Subject: Re: xfrm, ip tunnel: non released device reference upon device
 unregistration

On Sun, 4 Feb 2018 13:21:18 +0200
Eyal Birger <eyal.birger@...il.com> wrote:

> Hi,
> 
> We've encountered a non released device reference upon device
> unregistration which seems to stem from xfrm policy code.
> 
> The setup includes:
> - an underlay device (e.g. eth0) using IPv4
> - an xfrm IPv6 over IPv4 tunnel routed via the underlay device
> - an ipip6 tunnel over the xfrm IPv6 tunnel
> 
> When tearing down the underlay device, after traffic had passed via
> the ipip6 tunnel, log messages of the following form are observed:
> 
> unregister_netdevice: waiting for eth0 to become free. Usage count = 2
> 
> The below synthetic script reproduces this consistently on a fresh
> ubuntu vm running net-next v4.15-6066-ge9522a5:

Minor correction: net-next version v4.15-10442-g617aebe

Eyal.