Subject: Re: waiting for ppp0 to become free (Re: ppp0 out of control)

From: Andre Tomt <[email-masked]>
Date: Wed, 26 Jan 2005 11:02:54 +0100

Janos Farkas wrote:
> On 2005-01-21 at 15:44:44, Aurélien GÉRÔME wrote:
> 
>>I am running 2.6.10 from kernel.org on Debian Sid ppc/x86, the same
>>issue occurs with 2.6.9. Though, 2.6.8.1 and previous are fine.
>>
>>When my ISP connection via PPPoE (kernel side) goes down, reconnection
>>does not occur, and the kernel displays continuous:
>>
>>kernel: unregister_netdevice: waiting for ppp0 to become free. Usage count = 1
> 
> 
> BTW, I have seen many cases when this symptom annoyed me too, the last
> one is that my shutdown scripts tried unloading the network driver
> modules.  Is your setup doing this by any chance?  In my case,
> apparently there were conntrack entries keeping the device in use,
> which is almost useless when preparing to shutdown :)
> 
> OTOH, I couldn't find a way to flush those conntracks, so I worked
> around it by not rmmoding ethernet drivers.
> 
> In your case, it's probably conntrack too, I'd presume you are using
> that PPPoE machine as a masquerading gateway, which by definition needs
> connection tracking...  I'm not sure either if this is a "real" change,
> I only vaguely recollect as some moons earlier this wasn't a problem in
> 2.6.
> 

Here's some data I've collected on a possible related or identical one.

So far it seems related to interface removal. I've seen this recently on 
vlan interfaces, since ifupdown on my systems kill vlan devices on ifdown.

In my cases I've not been able to reproduce without ipv6 loaded in the 
kernel, and it only seems to happen when lo/loopback is taken offline 
first (ifdown -a here does it in that order..)

A shutdown rrmod-type takedown of a NIC would probably be run after 
"ifdown -a", hence after lo is down, thats why I suspect it to be the 
same problem.

I still have a binary search to do for pinpointing what broke it, though.