[Pkg-utopia-maintainers] Bug#795023: [network-manager] Bricks DNS when disconnecting from a VPN, separately ignores instruction not to use VPN DNS servers

[Julian Gilbey]

On Thu, Aug 20, 2015 at 09:20:10PM +0100, OmegaPhil wrote:
> Package: network-manager
> Version: 1.0.4-1
> 
> I have played around with this some more - the idea with the work VPN
> connection is not that it takes over everything, but simply that one
> particular IP address gets routed to it - everything else works as normal.
> 
> This is why I'm ignoring routes etc, with 'Automatic (VPN) addresses
> only' used with the intention of not fiddling with the current DNS
> configuration, which is failing.
> 
> The workaround is to manually set 'DNS servers' and 'Search domains' to
> the normal values outside of the VPN, rather than leaving them blank,
> which Network Manager can't seem to cope with.

I can confirm that something like this is still happening with
network-manager 1.46.0-1 (Debian testing machine), when using
network-manager-strongswan: before switching on the VPN,
/etc/resolv.conf reads:

nameserver 192.168.0.1
nameserver 0.0.0.0

then with the VPN on, it becomes

# Generated by NetworkManager
nameserver <VPN nameserver redacted>
nameserver <VPN nameserver redacted>

but after the VPN is switched off, it collapses to just one line:

# Generated by NetworkManager

making DNS lookups impossible.  Manually reverting /etc/resolv.conf to
its original state restores normal networking.

Best wishes,

   Julian