The Dhall config

The schema

A config is a record of zones, each a list of Record union members. The interpreter evaluates the whole program at startup, then walks the normal form into the server's in-memory zone table.

let Record = < A     : { name : Text, ttl : Natural, value : Text }
           | AAAA  : { name : Text, ttl : Natural, value : Text }
           | CNAME : { name : Text, ttl : Natural, value : Text }
           | TXT   : { name : Text, ttl : Natural, value : Text }
           | MX    : { name : Text, ttl : Natural, priority : Natural, exchange : Text }
           | NS    : { name : Text, ttl : Natural, value : Text }
           | SOA   : { name : Text, ttl : Natural, mname : Text, rname : Text
                     , serial : Natural, refresh : Natural, retry : Natural
                     , expire : Natural, minimum : Natural }
           | CAA   : { name : Text, ttl : Natural, flags : Natural, tag : Text, value : Text } >
in  let Zone   = { name : Text, records : List Record }
in  let Config = { zones : List Zone }

Owner names are relative to the zone (@ / "" = apex). rdata target names (CNAME/NS value, MX exchange, SOA mname/rname) are absolute FQDNs with a trailing dot.

Verified before it binds

• The config is a Dhall program, not a file — so it is typechecked against its schema before the server ever binds a port.
• A typo in a record is a type error (e.g. a bad union label or value), reported at load.
• See config.example.dhall for a full two-zone example.