Global nameservers or alternative to / change in FallbackNameservers

[Richard Sent <richard@freakingpenguin.com>]

Hi all,

I'm using Connman with --nodnsproxy on a virtual private server where
the DNS servers discovered via DHCP have inconsistent availability. I
thought I could resolve this by setting FallbackNameservers. However,
this setting is only used when DHCP does not provide DNS at all, as
opposed to my initial thinking of using it as a fallback in case the
DHCP discovered DNS servers fail.

> # List of fallback nameservers separated by "," used if no
> # nameservers are otherwise provided by the service. The
> # nameserver entries must be in numeric format, host
> # names are ignored.
> # FallbackNameservers =

This results in a resolv.conf containing only the nonfunctional DHCP
discovered DNS servers and not my fallback DNS. I could configure
nameservers on a per-connection basis, but this is frustrating to have
to do on a system that could be deployed to different hosters that may
enumerate the network interfaces differently.

There does seem to be some demand for a way to set global nameservers,
as opposed to per-connection [1]. This case is even worse to do manually
because it discusses a laptop which roams between connections
constantly.

If breaking backwards compatibility with the old FallbackNameservers
behavior is considered unacceptable, I propose a GlobalNameservers
setting in connman.conf.

I do see a line in service-api.txt that implies global nameservers are
in fact already a thing, but can't find any other references to them.
This comment was added back in 2010, before FallbackNameservers was
added.

> Global nameservers are automatically added to this
> list. The array represents a sorted list of the
> current nameservers. The first one has the highest
> priority and is used by default.

Thanks

[1]: https://www.antixforum.com/forums/topic/set-default-dns-for-all-users-ethernet-wifi-connections/

-- 
Take it easy,
Richard Sent
Making my computer weirder one commit at a time.