Re: DNS from wifi not removed when switching to wire after suspend/resume

[Dan Williams <dcbw redhat com>]

On Wed, 2009-11-18 at 08:46 +0000, Frederik Himpe wrote:
> On Tue, 17 Nov 2009 14:34:16 -0800, Dan Williams wrote:
> 
> >> Looking at resolvconf's man page, I guess that NetworkManager only
> >> calls networkmanager -a, which will add stuff to resolvconf, but does
> >> not call resolvconf -d first to clean up the outdated entries.
> >> 
> >> This seems to happen in src/named-manager/nm-named-manager.c in
> >> dispatch_resolvconf.
> >> 
> >> I can indeed reproduce the problem by running resolvconf -a
> >> NetworkManager and then sending a new nameserver: it will simply be
> >> added to resolv.conf without removing the old one.
> > 
> > Ah, maybe we should call -d unconditionally before calling -a.  That
> > might explain a few things.
> 
> I did some more tests, and it seems I was totally wrong. resolvconf -a 
> really overwrites the settings for the chosen interface. So it seems 
> there is no problem in NetworkManager itself.
> 
> I guess the problem comes from an interaction problem with some Mandriva 
> scripts, maybe from when I did not yet have all connections disabled in 
> Mandriva's networking tools. I had a file
> /var/run/resolvconf/interface/eth0 which contained the faulty resolv.conf 
> entries. Removing this file, so that only
> /var/run/resolvconf/interface/NetworkManager exists, fixes this.

Ah, thanks for investigating that.

> >> Actually, I'm surprised to see that NM always calls resolvonf with the
> >> name NetworkManager as INTERFACE name. I rather expected it to call it
> >> with the UUID or interface name of the connection, so that it simply
> >> calls resolvonf -a UUID (or IFNAME) for every connection which comes
> >> online, and resolvconf -d UUID/IFNAME for every connection going down.
> >> But I guess you don't want this because NM wants to take complete
> >> control of resolv.conf instead of letting the contents be managed by
> >> resolvconf?
> > 
> > It's mainly to kludge in support for resolvconf; I'm not sure the
> > original patch had that in it it.  That sounds like a good improvement
> > though, but we need to figure out a few things first...
> > 
> > Like VPNs.  If I connect wifi (and send those nameservers to resolvconf)
> > then connect a VPN (and send those), then plug in a wired cable (and
> > send those), aren't the VPN's nameservers now not used?  NM will ensure
> > they do get used.
> 
> resolvonf will merge the different nameserver entries for all 
> connections, and add all nameserver entries according to the order 
> configured in /etc/resolvconf/interface-order. In Debian this files looks 
> like this:
> lo.inet*
> lo.dnsmasq
> lo.pdnsd
> lo.!(pdns|pdns-recursor)
> lo
> tun*
> tap*
> hso*
> eth*
> ath*
> wlan*
> ppp*
> *
> 
> In Mandriva it looks like this:
> lo.inet*
> lo.dnsmasq
> lo.pdnsd
> lo.!(pdns|pdns-recursor)
> lo
> tun*
> tap*
> *
> 
> They removed the entries for wired and wireless connections because they 
> patched resolvconf to use the metric value for those interfaces to order 
> the nameservers.

Ah!  This has been quite informative.  Thanks.

Dan