DNS using Name Service Switch module and Casper

[Vasily Postnicov]

Hello. I wrote a simple daemon called ZeroDNS which provides functionality
similar to multicast DNS, namely it discovers other participating machines
over the LAN and stores their hostname and IPv4 address pairs.

Here is a NSS module which allows the system to use information from that
daemon:
https://github.com/shamazmazum/nss-zero-dns

You need to modify /etc/nsswitch.conf, changing the line 'hosts: files dns'
to 'hosts: files dns zerodns'.

It all works on FreeBSD 12.2-RELEASE, but sometimes not on 13.0-CURRENT.
For example, ping(8) just blocks when trying to ping a host whose name is
resolvable with ZeroDNS. Turns out that programs built with casper support
(like ping(8) and some others) stop working with my NSS module (they just
block trying to resolve the name).

Is there some kind of manual on how to write casper-compatible NSS modules?