µDNS supports most of the domain name system used in the wild. It adheres to strict conventions. Failing early and hard. It is mostly implemented in the pure fragment of OCaml (no mutation, isolated IO, no exceptions).

Legacy resource record types are not dealt with, and there is no plan to support ISDN, MAILA, MAILB, WKS, MB, NULL, HINFO, ... . AXFR is only handled via TCP connections. The only resource class supported is IN (the Internet). Truncated hmac in TSIG are not supported (always the full length of the hash algorithm is used).

Please read the blog article for a more detailed overview.