djbdns

One thing I noticed while using your code as a reference for a project I worked on several weeks ago is that it doesn't record the state before following the pointer, so unless the pointer you follow eventually leads to another pointer that brings it back to where you were, you can't simulate recursion. I'm referring to lines 1286-1288 in codec.c, FWIW. Obviously, you only need to support jumping back per RFC1035 and your code supports both jumping back AND forward, so I'm just telling you this for idle chitchat and so that you know that your code was helpful and I appreciate you putting it out there. Thanks! Edit: Also, before I forget, this implementation uses recursion even though it's not necessary. https://github.com/google/gopacket/blob/3eaba08943250fd21252... Between your code, the one linked to above, and djbdns I was totally conf

Label compression is pretty common, I think all of the big name server implementations do it by default. Amazon Route 53 definitely does it - I wrote the code! But my favorite thing about DNS label compression is probably this quote from DJB's code where he implemented it ... https://github.com/abh/djbdns/blob/0715ca5de14ad5eae2c779c53...

It's interesting to read the sources[1] of lots of djb's[2] code, as he often works around problems with (or perhaps dislikes the style of) standard libraries by re-implementing parts. [1] https://github.com/abh/djbdns/blob/master/str_len.c [2] http://cr.yp.to/djb.html

axfrdns is a confusing mis-nomer; the daemon handles all TCP DNS queries too. TinyDNS will truncate any UDP response that doesn't fit in 500 bytes (it also doesn't implement EDNS0), leaving it to be handled by axfrdns. That's about 4% of all DNS responses going on my data. And with apologies for the domain name; http://dnsneedsfuckingtcp.info/ . To generalize my point; DOS is a very significant risk to DNS server availability these days, and the first and best defense is to have a fast server (Knot's target of 500k qps is in the right ballpark). djbdns is single threaded, single process and doesn't even use epoll/kqueue, it's just not up to it and tops out within a few 10k qps, axfrdns won't get close to that. https://github.com/abh/djbdns/blob/master/byte_copy.c is a good example of my earlier point too; last time I profiled tinydns it s