Re: VPN + dnsmasq = split dns?

[Olav Morken <olavmrk gmail com>]

On Thu, Nov 27, 2014 at 07:24:13 -0500, Pavel Simerda wrote:
> > > Odd...  I'm not quite sure why it would be happening that way.  In any
> > > case, NM should only be doing split DNS when 'dns=dnsmasq' is set *and*
> > > the VPN sends a domain name to NetworkManager.  So I'd expect to see
> > > your #1 case above also do "local" VPN DNS servers, with the DHCP
> > > servers as fallback.
> >
> > After investigating this, I think I have found the cause of the behavior:
> >
> > Ubuntu carries a patch[1] which disables split DNS when it notices
> > that it is on a VPN connection with a default route. This makes sense,
> > since otherwise users of Ubuntu wouldn't be able to connect to VPNs as
> > long as they are running dnsmasq (which they are by default).
>
> I don't think it makes sense. Running a local DNS cache is good for
> other reasons as well and I don't see a reason to drop dnsmasq just
> because you are connected to a VPN. Or did I misunderstand? What
> exactly is the problem with upstream NM and could we have a bug
> report for it?

Ubuntu doesn't drop dnsmasq when running on a VPN. By default, Network
Manager assumes that if you are running dnsmasq you want split DNS
with your VPN. That includes if you have a default route over your
VPN. Since that breaks DNS when you connect to your VPN, Ubuntu has a
fix for it, which involves disabling split DNS in that case. My
problem was that the fix wasn't complete.

I certainly think that the "split DNS with default route"-problem
would be something that should probably be fixed in Network Manager as
well, unless dnsmasq is only supposed to be used with split DNS. If I
understand correctly dnsmasq is the only DNS backend that implements
split DNS with Network Manager at the moment, but if any others
implemented it, they would probably need the same fix.

However, since I don't run a "pure" Network Manager, I do not have the
ability to test its behavior, so I don't think I can open a bug for
this.

Best regards,
Olav Morken