dora VS comfydns

Powerdns and dnsdist are incredible projects with a lot of features. Dnsdist has particularly added a lot of flexibility with ebpf/lua support.

Shameless plug in related space that I was able to get open sourced is Dora a rust written DHCP server.

https://github.com/bluecatengineering/dora

Disclaimer: Opinions mine. Work at a DNS, DHCP, IPAM company.

It's because the RFC is fairly short but DNS as a live system is very very complicated. Plus not everything is BIND anyway and you'll find weird things even from large providers.

I wrote https://github.com/jmhertlein/comfydns from scratch, just using the RFCs, and what I got when I was "done" was something that mostly worked. Like surprisingly well. But then I just kept finding a small trickle of issues for certain sites.

One that got me was console.aws.amazon.com. It has 4 CNAMEs in the resolution path and (iirc) one weird but was somewhere along there, you get an NXDOMAIN response but still get a CNAME record back. Is thus allowed by the rfc? IMO, no. I was discarding anything that came back with NXDOMAIN (really, NAME_ERROR - Nxdomain is bind parlance). But alas, it's AWS, and 8.8.8.8 resolves it fine, so what am I to do?

So I added a heuristic thats similarly not-incorrect per the RFC where if I get a NAME_ERROR back, as long as the message has records that match my SNAME, I still treat it as a successful query, cache the records, and continue my search.

So... yeah. Lots of weird shit like that. Just mixes of being too defensive in what you accept and then in some cases not defensive enough - I've found searches that resolve for 8.8.8.8 but if I comb through it manually in DIG, I get back results that are clearly a misconfiguration and then I have to come up with some heuristic that rejects them while still being universally applicable.

So yeah. Fun times. I love DNS. (not sarcasm! I promise).