Bug#809166: networking.service does not prevent ifdown with network file systems

[Martin Pitt]

Hey Guus,

Guus Sliepen [2016-01-13 16:30 +0100]:
> Ugh. That's totally wrong. Why doesn't LTSP tell NetworkManager itself
> to stop messing with eth0? Instead of adding a stanza to /e/n/i, just
> write this to /etc/NetworkManager/NetworkManager.conf:
> 
> [keyfile]
> unmanaged-devices=interface-name=eth0

I guess it could do that. This is currently done in

  https://sources.debian.net/src/ltsp/5.5.5-1/client/share/ltsp/init-ltsp.d/50-interfaces/

and it could be equally well writing to NetworkManager.conf.

> 
> > This use case actually got broken
> > by the overzealous patch in #809169 which added this:
> > 
> >    down
> > +    /bin/ip link set dev %iface% down 2>/dev/null || true \
> > +        if (iface_is_link())
> > 
> > for "manual" interfaces. I. e. "ifdown eth0" on the above "manual"
> > interface example would actually down the interface. This isn't
> > documented behaviour, and breaks this (IMHO) valid use case to mark an
> > interface as "please leave me alone".
> 
> I'd say that the latter use case is invalid.

I do agree it's inelegant, but these LTSP versions are out there.

But independently of that: Do you actually think it is right that
"ifdown" on a manual interface without any "down" command downs it?
That isn't documented and hasn't happened until 0.8.4, and IMHO that's
overzealous and might break other setups too.

> > [open-iscsi]
> Oh god. That's also completely wrong.

Heh, amen :-/ As I said, we'll fix that.

> What I am willing to do is to add the keyword "no-auto-down" to
> interface stanza's, which will prevent the interface from being brought
> down using "ifdown -a".

In the interest of backward compatibility, it would perhaps make more
sense to add a keyword "auto-down" which will then "down" a manual
interface on ifdown? This would then be a shortcut for

  iface eth0 inet manual
     down ifconfig $IFACE down

Thanks,

Martin
-- 
Martin Pitt                        | http://www.piware.de
Ubuntu Developer (www.ubuntu.com)  | Debian Developer  (www.debian.org)
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