Port/improve Mono's managed Dns implementation?

[stephentoub]

@migueldeicaza highlighted to me today that Mono has a managed DNS implementation:
https://github.com/mono/mono/tree/0bcbe39b148bb498742fc68416f8293ccd350fb6/mcs/class/System/Mono.Net.Dns
We should look into whether it would make sense to port and improve upon that, so as to be able to avoid depending on the DNS resolution capabilities built into specific OSes (e.g. we rely on Windows for its overlapped I/O support, but an equivalent doesn't exist built-in on Linux, and so there our async support is based on queueing work items that in turn invoke the synchronous APIs).

cc: @migueldeicaza, @geoffkizer

[ghost]

What are the restrictions in it for not being able to run on mobile device: https://github.com/mono/mono/blob/2f211770198d741a35cf1f713e639cc66505db44/mcs/class/System/System.Net/Dns.cs#L47 ?

[stephentoub]

@marek-safar, did I understand you correctly when we chatted that the aforementioned code isn't really production quality? I believe you said it's not really used by anyone (off by default), has known impactful bugs, etc.?

[marek-safar]

@stephentoub you can find the code under https://github.com/mono/mono/tree/master/mcs/class/System/Mono.Net.Dns the main entry point is SimpleResolver.cs. It's an opt-in feature enabled via an environment variable called MONO_DNS. Looking at the history you can see we didn't touch it much recently ;-)

[migueldeicaza]

It lacks some of the new features, like secure DNS, but it is a starting point.

[karelz]

Duplicate of #19443