The pure interface to the client part of uDns.
Various helper modules to do with side effects are available from Dns_client_lwt, Dns_client_unix and so forth.
type 'key query_state constraint 'key = 'a Dns.Rr_map.keyquery_state is parameterized over the query type, so the type of the representation of the answer depends on what the name server was asked to provide. See Dns_map.k for a list of response types. The first element (the int32) in most of the tuples is the Time-To-Live (TTL) field returned from the server, which you can use to calculate when you should request fresh information in case you are writing a long-running application.
val make_query :
(int -> Cstruct.t) ->
Dns.proto ->
[ `None | `Auto | `Manual of Dns.Edns.t ] ->
'a Domain_name.t ->
'query_type Dns.Rr_map.key ->
Cstruct.t * 'query_type Dns.Rr_map.key query_statemake_query rng protocol name query_type is query, query_state where query is the serialized DNS query to send to the name server, and query_state is the information required to validate the response.
val parse_response :
'query_type Dns.Rr_map.key query_state ->
Cstruct.t ->
([ `Data of 'query_type
| `Partial
| `No_data of [ `raw ] Domain_name.t * Dns.Soa.t
| `No_domain of [ `raw ] Domain_name.t * Dns.Soa.t ],
[ `Msg of string ])
resultparse_response query_state response is the information contained in response parsed using query_state when the query was successful, or an `Msg message if the response did not match the query_state (or if the query failed).
In a TCP usage context the `Partial means there are more bytes to be read in order to parse correctly. This can happen due to short reads or if the server (or something along the route) chunks its responses into multiple individual packets. In that case you should concatenate response and the next received data and call this function again.
In a UDP usage context the `Partial means information was lost, due to an incomplete packet.