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

[Frederik Himpe <fhimpe telenet be>]

On Tue, 17 Nov 2009 12:55:00 -0800, Dan Williams wrote:

> On Tue, 2009-11-17 at 08:13 +0000, Frederik Himpe wrote:
>> I'm using NetworkManager 0.7.996 (git 20091021 snapshot) on Mandriva,
>> built with dhclient and resolvconf support.
>> 
>> I have a wireless connection to my AP at home and a wired DHCP
>> connection configured in networkmanager, both set to autoconnect and
>> available to all users. At home, networkmanager connects to my wireless
>> AP automatically. Then I suspend my system and resume it at work, where
>> it's docked and has a wired DHCP connection. NetworkManager connects
>> automatically to the wired connection, and deactivates the wlan0
>> connection, however NetworkManager just adds the DNS servers from my
>> wired connection at work to resolv.conf without removing the DNS server
>> from my wireless home connection. This results in long waits when
>> resolving hostnames.
> 
> Nov 17 08:56:27 defected NetworkManager: <info> (eth0): writing
> resolv.conf to /sbin/resolvconf
> 
> Until we figure out how resolvconf is interacting with NM here, or until
> we add more debugging to NM to figure out what's going on and what
> exactly NM is writing to resolvconf (which I'm pretty sure is correct),
> if you move /sbin/resolvconf out of the way, does allowing NM to write
> /etc/resolv.conf directly make things work again?

OK, I will test this tomorrow and I'll let you know.

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resolvconf -d first to clean up the outdated entries.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.

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?

-- 
Frederik Himpe