add close_notify as raw SSL_shutdown

this is needed for sending EOF, aka one-way shutdown.

Author: Christopher Zimmermann

Diff for: src/lwt_ssl.ml

@@ -161,6 +161,13 @@ let wait_write (fd, s) =
     Plain -> Lwt_unix.wait_write fd
   | SSL _ -> Lwt_unix.yield ()
 
+let close_notify (fd, s) =
+  match s with
+    Plain ->
+    Lwt.fail_invalid_arg
+      "Lwt_ssl.close_notify: Expected SSL, but got Plain connection"
+  | SSL s -> repeat_call fd (fun () -> Ssl.close_notify s)
+
 let ssl_shutdown (fd, s) =
   match s with
     Plain -> Lwt.return_unit

Diff for: src/lwt_ssl.mli

@@ -74,6 +74,7 @@ val close : socket -> unit Lwt.t
 val in_channel_of_descr : ?buffer:Lwt_bytes.t -> socket -> Lwt_io.input_channel
 val out_channel_of_descr : ?buffer:Lwt_bytes.t -> socket -> Lwt_io.output_channel
 
+val close_notify : socket -> int Lwt.t
 val ssl_shutdown : socket -> unit Lwt.t
 
 val abort : socket -> exn -> unit