eio(client): implement send_recv

Author: bikallem

eio/client/dns_client_eio.ml

@@ -1,10 +1,10 @@
+open Eio
+
 module Transport : Dns_client.S 
   with type io_addr = Ipaddr.t * int
-   and type stack = (Eio.Stdenv.t * Eio.Switch.t)
+   and type stack = (Stdenv.t * Switch.t)
    and type +'a io = 'a  
 = struct 
-  open Eio
-
   type io_addr = Ipaddr.t * int
   type stack = (Stdenv.t * Eio.Switch.t)
   type +'a io = 'a
@@ -58,8 +58,6 @@ module Transport : Dns_client.S
     |> List.map (fun ip -> ip, 53) 
     |> ipv6_first_queue 
 
-  let ( let* ) = Result.bind
-
   let create ?nameservers ~timeout (env, sw) = 
     let nameservers = 
       match nameservers with
@@ -75,6 +73,7 @@ module Transport : Dns_client.S
       | None ->
         let nameservers, digest = 
           match 
+            let ( let* ) = Result.bind in
             let* data = read_file env "/etc/resolv.conf" in
             let* ips = decode_resolv_conf data in
             Ok (ips, Digest.string data)
@@ -160,35 +159,19 @@ module Transport : Dns_client.S
     nameservers0 t
     |> try_ns_connection t 0
 
-  (* let handle_received_data data = *) 
-  (*   let len = Cstruct.length data in *) 
-  (*   if len > 2 then *)
-  (*     let len' = Cstruct.BE.get_uint16 data 0 in *) 
-  (*     if len - 2 >= len' then *)
-  (*       let packet, rest = *) 
-  (*         if len - 2 = len *)
-  (*         then data, Cstruct.empty *) 
-  (*         else Cstruct.split data (len' + 2) *)
-  (*       in *) 
-  (*       let id = *) 
-  (*   else *) 
-
-  (* let rec read_loop buf ctx = *) 
-  (*   try *)
-
-  let send_recv _ctx  _tx =  failwith ""
-    (* if Cstruct.length tx > 4 then *) 
-    (*   try *)
-    (*     let tx = Flow.cstruct_source [tx] in *)
-    (*     Flow.copy src tx; *)
-    (*     let recv_buffer = Cstruct.create 2048 in *)
-    (*     match Flow.read ctx recv_buffer with *)
-    (*     | _got -> *) 
-    (* else *)
-    (*   Error (`Msg "invalid DNS packet(data length <= 4)") *)
+  let send_recv ctx dns_query =
+    if Cstruct.length dns_query > 4 then 
+      try
+        let src = Flow.cstruct_source [dns_query] in
+        Flow.copy src ctx;
+        let dns_response = Cstruct.create 2048 in 
+        let got = 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 Flow.close flow with _ -> ()
-  
+  let close flow = try Flow.close flow with _ -> () 
   let bind a f = f a
   let lift v = v  
 end