[dns-operations] good async DNS library

[Florian Weimer]

* Klaus Darilion:

> My current task is to monitor zone freshness on our Anycast cloud. So,
> every second, I send SOA requests to every of our 30 global nodes and
> check the received serial.
>
> I currently use Net::DNS::Async as sequential scanning takes to long -
> hence with async. I patched Async to allow sending also to non-standard
> ports (with only 1 unicast IP, but multiple name server processes, I
> have to use different ports). But there is still the problem that
> Timeouts are only with 1 second granularity, but I need timeouts < 1s.
>
> That's why I look for a good replacement of Net::DNS::Async.

In this case, you probably want to take over the packet processing
completely and only use a preexisting DNS packet builder and parser.
It's probably easier to write the event dispatching yourself than to
figure out how to get the desired behavior from some existing DNS
library and integrate that with an event-handling loop of your choice.

Thanks,
Florian