it nearly fully implements the rfc1035:
- resolver-side recursion
- cache
- following types: a, ns, cname, hinfo, mx, ptr, soa, txt
- in-addr.arpa (get hostname by ip)
each dns-lookup returns a dns-message record.
Note it does at least one thing wrong (besides what's noted in PLT's
documentation):
> (dns-get-address "macon" "ftp.uni-tuebingen.de")
"8.115.111.102"
(The original version also does this. I assume it has something to do
with recursive queries.)