Comment 4 for bug 925511

On Tuesday 07 February 2012 09:19 PM, Serge Hallyn wrote:
> @Ritesh,
>
> the dnsmasq for the lxc bridge explicitly binds only lxcbr0. So if that
> fails, then your other dnsmasq has already bound all interfaces.

Yes. Because I had dnsmasq installed by default. From the dnsmasq.conf
file's documentation, it says:

# On systems which support it, dnsmasq binds the wildcard address,
# even when it is listening on only some interfaces. It then discards
# requests that it shouldn't reply to. This has the advantage of
# working even when interfaces come and go and change address. If you
# want dnsmasq to really bind only the interfaces it is listening on,
# uncomment this option. About the only time you may need this is when
# running another nameserver on the same machine.
#bind-interfaces

So any machine, where dnsmasq is installed, will bind to all the
interfaces. This is the _default_ behavior, as installed.

libvirt was doing something similar.
http://anonscm.debian.org/gitweb/?p=pkg-libvirt/libvirt.git;a=blob;f=debian/README.Debian;h=6248662c56111c4ec4a5b2c0887059ddfb5fdda6;hb=HEAD

They bind dnsmasq to the loopback interface. Since LXC's bridge also has
similar purpose, it could try to do similar things.

>
> If /etc/init.d/lxc fails to start now, then lxcbr0 never had dhcp
> before. If you're not using lxcbr0 for your containers, then you can
> simply set USE_LXC_BRIDGE="false" in /etc/default/lxc.
I haven't started using it yet. So I'm not sure how it has been behaving
up till now.

> If do want to use lxcbr0, then you should change your other dnsmasq to
> not bind all interfaces.
Yes. But would you want this to be a default?

Or actually, just adding a similar documentation into LXC's
README.Debian will also suffice. No?

> A third alternative, I suppose, would be that you want to use lxcbr0 but
> your statically assign addresses to your containers. We could add a
> USE_LXC_BRIDGE_DNSMASQ variable to /etc/default/lxc to support that use
> case. If that is what you want, please open a new bug against lxc and
> I'll add it.

--
Ritesh Raj Sarraf | http://people.debian.org/~rrs
Debian - The Universal Operating System