Re: Question about DNS managemer lifecycle

On Fri, 2020-10-30 at 13:45 +0000, Frederic Martinsons wrote:
Hello NM hackers,

I'm tracking a nasty bug in dnsmasq (possibly introduced by us
because of patches) and it is triggered during shutdown (while
systemd stop all services). 

Tracking this, I activated traces of NetworkManager and it seems that
dnsmasq (the dns manager I used) is not stopped by NetworkManager. I
patched NM to print refcount of all objects and I see that
NMDnsManager has refcount at 2 after calling nm_dns_manager_stop in

I would like to have information about DNS manger lifecycle since I
see a comment in NM merge requests which seem telling that it may be
done on purpose (to not stop dnsmasq) , I'm talking about the
following comment:

By the way, I use NetworkManager 1.26.4 and dnsmasq 2.82.

Thank you very much for any help you can provide.


when restarting (or only stopping) NetworkManager, it leaves the
interfaces up, in an attempt not to disrupt your connectivity. So,
there is a point in leaving the dnsmasq instance running. Restarting
NetworkManager (with it's aim to not disrupt connectivity) has many
coerner cases where it doesn't work overly well. So restarting
NetworkManager should not be done on a regular basis.

Leaving the dnsmasq instance running can be problematic, because after
restart the dnsmasq instance is no longer a child process (we cannot
waitpid on it). Also, in general it might be undesirable. On the other
hand, stopping NetworkManager and breaking DNS is also undesirable.

The code, and in particular commit [1] makes an effort to get that
right. But it's not entirely clear whether the dnsmasq instance should
be left running or not.


If you find a bug, we would gladly accept patches. As to what is the
optimal/desired behahavior, that is up for discussion.

A better solution would be to extend "dns=dnsmasq" option to run the
dnsmasq instance as a separate service (which would work well when
using systemd, but it might be harder on systems without systemd).
It not likely that somebody invests the effort of improving
dns=dnsmasq, especially since an improved DNS plugin already exists:


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