eio(client): 'run' inject stack

Make `run` function inject stack parameter. Address reviewer comments.

eio/client/dns_client_eio.ml

@@ -1,14 +1,18 @@
-module E = Eio
-
-type env = <
-  clock         : E.Time.clock ;
-  net           : E.Net.t;
-  fs            : E.Dir.t;
-  secure_random : E.Flow.source;
->
+type 'a env = <
+  clock         : Eio.Time.clock ;
+  net           : Eio.Net.t ;
+  fs            : Eio.Fs.dir Eio.Path.t ;
+  secure_random : Eio.Flow.source;
+  ..
+> as 'a
 
 type io_addr = Ipaddr.t * int
-type stack = env * E.Switch.t 
+type stack = {
+  sw            : Eio.Switch.t;
+  clock         : Eio.Time.clock;
+  net           : Eio.Net.t;
+  resolv_conf   : Eio.Fs.dir Eio.Path.t
+}
 
 module Transport : Dns_client.S 
   with type io_addr = io_addr
@@ -18,7 +22,7 @@ module Transport : Dns_client.S
   type nonrec io_addr = io_addr
   type nonrec stack = stack
   type +'a io = 'a
-  type context = E.Net.stream_socket
+  type context = <Eio.Net.stream_socket; Eio.Flow.close>
 
   type nameservers = 
     | Static of io_addr Queue.t
@@ -30,17 +34,15 @@ module Transport : Dns_client.S
   type t = {
     nameservers : nameservers ;
     timeout_ns  : int64 ;      (* Timeout in nano seconds *)
-    env         : env;
-    sw          : E.Switch.t ;
-    mutex       : E.Mutex.t ;
+    stack       : stack;
+    mutex       : Eio.Mutex.t ;
   }
 
-  let read_file env file =
-    match E.Dir.load env#fs file with
+  let read_file file =
+    match Eio.Path.load file with
     | content -> Ok content
-    | exception e -> 
-      let err = "Error while reading file: " ^ file ^ ". " ^ (Printexc.to_string e) in  
-      Error (`Msg err)
+    | exception e ->
+      Fmt.error_msg "Error while reading file %a: %a" Eio.Path.pp file Fmt.exn e
 
   (* Prioritises IPv6 nameservers before IPv4 nameservers so that we 
      are more conformant with the happy eyballs RFC when implementing it. 
@@ -71,7 +73,7 @@ module Transport : Dns_client.S
     |> List.map (fun ip -> ip, 53) 
     |> ipv6_first_queue 
 
-  let create ?nameservers ~timeout (env, sw) = 
+  let create ?nameservers ~timeout stack = 
     let nameservers = 
       match nameservers with
       | Some (proto, ns) -> begin 
@@ -87,7 +89,7 @@ module Transport : Dns_client.S
         let nameservers, digest = 
           match 
             let ( let* ) = Result.bind in
-            let* data = read_file env "/etc/resolv.conf" in
+            let* data = read_file stack.resolv_conf in
             let* ips = decode_resolv_conf data in
             Ok (ips, Digest.string data)
           with
@@ -96,8 +98,8 @@ module Transport : Dns_client.S
         in
         (Resolv_conf { nameservers; digest })
     in
-    let mutex = E.Mutex.create () in
-    { nameservers; timeout_ns = timeout; env; sw; mutex }
+    let mutex = Eio.Mutex.create () in
+    { nameservers; timeout_ns = timeout; stack;  mutex }
 
   let nameservers0 
       { nameservers = 
@@ -130,7 +132,7 @@ module Transport : Dns_client.S
           resolv_conf.digest <- None;
           resolv_conf.nameservers <- default_resolvers ()
       in 
-      match read_file t.env "/etc/resolv.conf", resolv_conf.digest with
+      match read_file t.stack.resolv_conf, resolv_conf.digest with
       | Ok data, Some d ->
         let digest = Digest.string data in 
         if Digest.equal digest d then () else decode_update data digest
@@ -154,17 +156,17 @@ module Transport : Dns_client.S
     if n >= Queue.length ns_q then 
       Error (`Msg "Unable to connect to specified nameservers")
     else
-      let (ip, port) = E.Mutex.use_ro t.mutex @@ fun () -> Queue.peek ns_q in
-      let ip = ipaddr_octects ip |> E.Net.Ipaddr.of_raw in
+      let (ip, port) = Eio.Mutex.use_ro t.mutex @@ fun () -> Queue.peek ns_q in
+      let ip = ipaddr_octects ip |> Eio.Net.Ipaddr.of_raw in
       let stream = `Tcp (ip, port) in
       try 
         let timeout = Duration.to_f t.timeout_ns in
-        E.Time.with_timeout_exn t.env#clock timeout @@ fun () ->
-        let flow = E.Net.connect ~sw:t.sw t.env#net stream in 
+        Eio.Time.with_timeout_exn t.stack.clock timeout @@ fun () ->
+        let flow = Eio.Net.connect ~sw:t.stack.sw t.stack.net stream in 
         Ok flow
-      with E.Time.Timeout ->
+      with Eio.Time.Timeout ->
         (* Push the non responsive nameserver to the back of the queue. *)
-        let ns = E.Mutex.use_rw ~protect:true t.mutex @@ fun () -> Queue.pop ns_q in
+        let ns = Eio.Mutex.use_rw ~protect:true t.mutex @@ fun () -> Queue.pop ns_q in
         Queue.push ns ns_q;         
         try_ns_connection t (n + 1) ns_q
 
@@ -176,23 +178,34 @@ module Transport : Dns_client.S
   let send_recv ctx dns_query =
     if Cstruct.length dns_query > 4 then 
       try
-        let src = E.Flow.cstruct_source [dns_query] in
-        E.Flow.copy src ctx;
+        let src = Eio.Flow.cstruct_source [dns_query] in
+        Eio.Flow.copy src ctx;
         let dns_response = Cstruct.create 2048 in 
-        let got = E.Flow.read ctx dns_response in
+        let got = Eio.Flow.read ctx dns_response in
         Ok (Cstruct.sub dns_response 0 got)
       with e -> Error (`Msg (Printexc.to_string e))
     else
       Error (`Msg "Invalid DNS query packet (data length <= 4)")
 
-  let close flow = try E.Flow.close flow with _ -> () 
+  let close flow = Eio.Flow.close flow 
   let bind a f = f a
   let lift v = v  
 end 
 
-module Client = Dns_client.Make(Transport)
 module type DNS_CLIENT = module type of Dns_client.Make(Transport)
 
-let run env (f:(module DNS_CLIENT) -> 'a) =
-  Mirage_crypto_rng_eio.run (module Mirage_crypto_rng.Fortuna) env @@ fun () ->
-  f (module Client)
+module Client = Dns_client.Make(Transport)
+
+let run ?(resolv_conf = "/etc/resolv.conf") env (f: Transport.stack -> (module DNS_CLIENT) -> 'a) =
+  Mirage_crypto_rng_eio.run (module Mirage_crypto_rng.Fortuna) env (fun () ->
+    Eio.Switch.run (fun sw ->
+      let stack = {
+          sw;
+          clock=env#clock;
+          net = env#net;
+          resolv_conf = Eio.Path.(env#fs / resolv_conf)
+      }
+      in
+      f stack (module Client)
+    )
+  )

eio/client/dns_client_eio.mli

@@ -1,15 +1,19 @@
-type env = <
+type 'a env = <
   clock         : Eio.Time.clock ;
   net           : Eio.Net.t ;
-  fs            : Eio.Dir.t ;
+  fs            : Eio.Fs.dir Eio.Path.t ;
   secure_random : Eio.Flow.source ;
->
+  ..
+> as 'a
 
 module Transport : Dns_client.S 
   with type io_addr = Ipaddr.t * int 
-   and type stack   = env * Eio.Switch.t 
    and type +'a io  = 'a
 
 module type DNS_CLIENT = module type of Dns_client.Make(Transport)
 
-val run : < env; ..> -> ((module DNS_CLIENT) -> 'a) -> 'a
+val run : 
+  ?resolv_conf:string
+  -> _ env 
+  -> (Transport.stack -> (module DNS_CLIENT) -> 'a) 
+  -> 'a

eio/client/ohost.ml

@@ -8,10 +8,8 @@ let (let+) r f = Result.map f r
 
 let display_host_ips h_name = 
   Eio_main.run @@ fun env -> 
-  Eio.Switch.run @@ fun sw -> 
-  Dns_client_eio.run env @@ fun (module Client) ->   
-  let env = (env :> Dns_client_eio.env) in
-  let c = Client.create (env, sw) in
+  Dns_client_eio.run env @@ fun stack (module Client) ->   
+  let c = Client.create stack in
   let domain = Domain_name.(host_exn (of_string_exn h_name)) in
   let ipv4 = 
     let+ addr = Client.gethostbyname c domain in