Remove SHUTDOWNABLE signature

This follows the clarification that `V1_LWT.close` follows the behaviour
of the Mirage tcp/ip stack i.e. it signals a "shutdown" to the remote
(like sending an `Eof`) while leaving the resources allocated and
the connection up. Implementations which associate extra resources with
a connection (such as a file descriptor or socket buffers) need provide
some other cleanup method (e.g. a `disconnect` function)

Fixes mirage#16

Signed-off-by: David Scott <dave@recoil.org>

lib/mirage_flow.mli

@@ -46,8 +46,8 @@ val copy:
 
 val proxy:
   (module V1.CLOCK)
-  -> (module Mirage_flow_s.SHUTDOWNABLE with type flow = 'a) -> 'a
-  -> (module Mirage_flow_s.SHUTDOWNABLE with type flow = 'b) -> 'b
+  -> (module V1_LWT.FLOW with type flow = 'a) -> 'a
+  -> (module V1_LWT.FLOW with type flow = 'b) -> 'b
   -> unit -> [ `Ok of (CopyStats.t * CopyStats.t) | `Error of [ `Msg of string ] ] Lwt.t
 (** [proxy (module Clock) (module A) a (module B) b ()] proxies data between
     [a] and [b] until both sides close. If either direction encounters an error

lib/mirage_flow_proxy.ml

@@ -17,17 +17,14 @@
 open Lwt
 
 let proxy (module Clock: V1.CLOCK)
-    (type a) (module A: Mirage_flow_s.SHUTDOWNABLE with type flow = a) (a: a)
-    (type b) (module B: Mirage_flow_s.SHUTDOWNABLE with type flow = b) (b: b)
+    (type a) (module A: V1_LWT.FLOW with type flow = a) (a: a)
+    (type b) (module B: V1_LWT.FLOW with type flow = b) (b: b)
     () =
   let a2b =
     let t = Mirage_flow_copy.start (module Clock) (module A) a (module B) b () in
     Mirage_flow_copy.wait t
     >>= fun result ->
-    A.shutdown_read a
-    >>= fun () ->
-    B.shutdown_write b
-    >>= fun () ->
+    let _ = B.close b in (* signal Eof to the remote *)
     let stats = Mirage_flow_copy.stats t in
     match result with
     | `Ok () -> return (`Ok stats)
@@ -36,10 +33,7 @@ let proxy (module Clock: V1.CLOCK)
     let t = Mirage_flow_copy.start (module Clock) (module B) b (module A) a () in
     Mirage_flow_copy.wait t
     >>= fun result ->
-    B.shutdown_read b
-    >>= fun () ->
-    A.shutdown_write a
-    >>= fun () ->
+    let _ = A.close a in (* signal Eof to the remote *)
     let stats = Mirage_flow_copy.stats t in
     match result with
     | `Ok () -> return (`Ok stats)

lib/mirage_flow_s.mli

@@ -1,5 +1,6 @@
 (*
  * Copyright (C) 2015 David Scott <dave.scott@unikernel.com>
+ * Copyright (C) 2016 Docker Inc
  *
  * Permission to use, copy, modify, and distribute this software for any
  * purpose with or without fee is hereby granted, provided that the above
@@ -15,14 +16,11 @@
  *
  *)
 
-module type SHUTDOWNABLE = sig
+module type DISCONNECTABLE = sig
   include V1_LWT.FLOW
 
-  val shutdown_write: flow -> unit io
-  (** Close the [write] direction of the flow, flushing any buffered data and
-      causing future calls to [read] by the peer to return [`Eof]. *)
-
-  val shutdown_read: flow -> unit io
-  (** Close the [read] direction of the flow, such that future calls to [write]
-      by the peer will return [`Eof] *)
+  val disconnect: flow -> unit io
+  (** Close the flow and immediately release any local resources allocated for
+      it. This will drop any remaining in-flight data (see [close] for more
+      graceful shutdown) *)
 end