Module Dns_client_unix.Transport

A flow module based on blocking I/O on top of the Unix socket API.

TODO: Implement the connect timeout.

type context

A context is a network connection initialized by T.connect

type +'a io = 'a

io is the type of an effect. 'err is a polymorphic variant.

type io_addr = Unix.inet_addr * int

An address for a given context type, usually this will consist of IP address + a TCP/IP or UDP/IP port number, but for some context types it can carry additional information for purposes of cryptographic verification. TODO at least that would be nice in the future. TODO

type ns_addr = [ `TCP | `UDP ] * io_addr

TODO well this is kind of crude; it's a tuple to prevent having to do endless amounts of currying things when implementing context types, and we need to know the protocol used so we can prefix packets for DNS-over-TCP and set correct socket options etc. therefore we can't just use the opaque io_addr. TODO

type stack = unit

A stack with which to connect, e.g. IPv4.tcpv4

type t

The abstract state of a DNS client.

val create : ?⁠nameserver:ns_addr -> timeout:int64 -> stack -> t

create ~nameserver ~timeout stack creates the state record of the DNS client. We use timeout (ns) as a cumulative time budget for connect and request timeouts.

val nameserver : t -> ns_addr

The address of a nameserver that is supposed to work with the underlying context, can be used if the user does not want to bother with configuring their own.

val rng : int -> Cstruct.t

rng t is a random number generator.

val clock : unit -> int64

clock t is the monotonic clock.

val connect : ?⁠nameserver:ns_addr -> t -> (context, [> `Msg of string ]) Stdlib.result io

connect addr is a new connection (context) to addr, or an error.

val send : context -> Cstruct.t -> (unit, [> `Msg of string ]) Stdlib.result io

send context buffer sends buffer to the context upstream.

val recv : context -> (Cstruct.t, [> `Msg of string ]) Stdlib.result io

recv context tries to read a buffer from the context downstream.

val close : context -> unit io

close context closes the context, freeing up resources.

val bind : 'a io -> ('a -> 'b io) -> 'b io

a.k.a. >>=

val lift : 'a -> 'a io