unikernel/duniverse/ocaml-dns/unix/client/ohost.ml

@@ -0,0 +1,36 @@
+let () =
+  Mirage_crypto_rng_unix.use_default ();
+  let t = Dns_client_unix.create () in
+  let domain = Domain_name.(host_exn (of_string_exn Sys.argv.(1))) in
+  let ipv4 =
+    match Dns_client_unix.gethostbyname t domain with
+    | Ok addr -> Fmt.pr "%a has address %a\n"
+                   Domain_name.pp domain Ipaddr.V4.pp addr ; Ok ()
+    | Error _ as err -> err
+  in
+  let ipv6 =
+    match Dns_client_unix.gethostbyname6 t domain with
+    | Ok addr -> Fmt.pr "%a has IPv6 address %a\n"
+                   Domain_name.pp domain Ipaddr.V6.pp addr ; Ok ()
+    | Error _ as err -> err
+  in
+  let mx =
+    match Dns_client_unix.getaddrinfo t Mx domain with
+    | Ok (_ttl, resp) ->
+      Fmt.pr "%a\n"
+        (Fmt.list (fun ppf -> Fmt.pf ppf "%a mail is handled by %a"
+                      Domain_name.pp domain
+                      Dns.Mx.pp)) (Dns.Rr_map.Mx_set.elements resp) ;
+      Ok ()
+    | Error _ as err -> err
+  in
+  let results = [ ipv4 ; ipv6 ; mx ] in
+  let is_error = (function Error _ -> true | Ok _ -> false) in
+  match List.find_opt is_error results with
+  | None | Some Ok _ -> () (* no errors *)
+  | Some (Error `Msg msg) -> (* at least one error *)
+    if List.for_all is_error results then
+      (* Everything failed; print an error message *)
+      ( Fmt.epr "Host %a not found: @[<v>%s@]\n"
+          Domain_name.pp domain msg ;
+        exit 1)