75 lines
2.4 KiB
OCaml
75 lines
2.4 KiB
OCaml
open Lwt.Infix
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module Transport (R : Mirage_random.S) (C : Mirage_clock.MCLOCK) (Time : Mirage_time.S) = struct
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type +'a io = 'a Lwt.t
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type io_addr = Ipaddr.V4.t * int
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module Dispatcher = Dispatcher.Make(R)(C)(Time)
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type stack = Dispatcher.t * (src_port:int -> dst:Ipaddr.V4.t -> dst_port:int -> Cstruct.t -> (unit, [ `Msg of string ]) result Lwt.t) * (Udp_packet.t * Cstruct.t) Lwt_mvar.t
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module IM = Map.Make(Int)
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type t = {
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protocol : Dns.proto ;
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nameserver : io_addr ;
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stack : stack ;
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timeout_ns : int64 ;
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mutable requests : Cstruct.t Lwt_condition.t IM.t ;
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}
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type context = t
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let nameservers { protocol ; nameserver ; _ } = protocol, [ nameserver ]
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let rng = R.generate ?g:None
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let clock = C.elapsed_ns
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let rec read t =
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let _, _, answer = t.stack in
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Lwt_mvar.take answer >>= fun (_, data) ->
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if Cstruct.length data > 2 then begin
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match IM.find_opt (Cstruct.BE.get_uint16 data 0) t.requests with
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| Some cond -> Lwt_condition.broadcast cond data
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| None -> ()
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end;
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read t
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let create ?nameservers ~timeout stack =
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let protocol, nameserver = match nameservers with
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| None | Some (_, []) -> invalid_arg "no nameserver found"
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| Some (proto, ns :: _) -> proto, ns
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in
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let t =
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{ protocol ; nameserver ; stack ; timeout_ns = timeout ; requests = IM.empty }
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in
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Lwt.async (fun () -> read t);
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t
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let with_timeout timeout_ns f =
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let timeout = Time.sleep_ns timeout_ns >|= fun () -> Error (`Msg "DNS request timeout") in
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Lwt.pick [ f ; timeout ]
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let connect (t : t) = Lwt.return (Ok (t.protocol, t))
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let send_recv (ctx : context) buf : (Cstruct.t, [> `Msg of string ]) result Lwt.t =
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let dst, dst_port = ctx.nameserver in
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let router, send_udp, _ = ctx.stack in
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let src_port, evict =
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My_nat.free_udp_port router.nat ~src:router.config.our_ip ~dst ~dst_port:53
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in
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let id = Cstruct.BE.get_uint16 buf 0 in
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with_timeout ctx.timeout_ns
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(let cond = Lwt_condition.create () in
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ctx.requests <- IM.add id cond ctx.requests;
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(send_udp ~src_port ~dst ~dst_port buf >|= Rresult.R.open_error_msg) >>= function
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| Ok () -> Lwt_condition.wait cond >|= fun dns_response -> Ok dns_response
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| Error _ as e -> Lwt.return e) >|= fun result ->
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ctx.requests <- IM.remove id ctx.requests;
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evict ();
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result
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let close _ = Lwt.return_unit
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let bind = Lwt.bind
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let lift = Lwt.return
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end
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