Provide Write errors to upper layers

Author: Kai Ruhnau

src/Microsoft.AspNet.Server.Kestrel/Http/SocketOutput.cs

@@ -27,19 +27,22 @@ public SocketOutput(KestrelThread thread, UvTcpStreamHandle socket)
             _socket = socket;
         }
 
-        public Task WriteAsync(ArraySegment<byte> buffer)
+        public async Task WriteAsync(ArraySegment<byte> buffer)
         {
             //TODO: need buffering that works
             var copy = new byte[buffer.Count];
             Array.Copy(buffer.Array, buffer.Offset, copy, 0, buffer.Count);
             var arraySegment = new ArraySegment<byte>(copy);
 
             KestrelTrace.Log.ConnectionWrite(0, buffer.Count);
-            var req = new UvWriteReq(
+            using (var req = new UvWriteReq(
                 _thread.Loop,
                 _socket,
-                arraySegment);
-            return _thread.PostAsync(req.Write);
+                arraySegment))
+            {
+                await _thread.PostAsync(req.Write);
+                await req.Task;
+            }
         }
 
         public bool Flush(Action drained)

src/Microsoft.AspNet.Server.Kestrel/Networking/UvWriteRequest.cs

@@ -4,6 +4,7 @@
 using System;
 using System.Collections.Generic;
 using System.Runtime.InteropServices;
+using System.Threading.Tasks;
 
 namespace Microsoft.AspNet.Server.Kestrel.Networking
 {
@@ -20,6 +21,8 @@ public class UvWriteReq : UvMemoryResource
         private readonly GCHandle[] _bufferHandles;
         private readonly GCHandle _bufferArrayHandle;
 
+        private readonly TaskCompletionSource<int> _tcs;
+
         public UvWriteReq(
             UvLoopHandle loop,
             UvTcpStreamHandle stream,
@@ -37,43 +40,38 @@ public UvWriteReq(
             _uvBuffers[0] = new UvBuffer(
                 _bufferHandles[0].AddrOfPinnedObject() + buffer.Offset,
                 buffer.Count);
+
+            _tcs = new TaskCompletionSource<int>();
         }
 
         private static int GetSize()
         {
             return UnsafeNativeMethods.uv_req_size(RequestType.WRITE);
         }
 
+        public Task Task => _tcs.Task;
+
         public void Write()
         {
-            try
-            {
-                _stream.Validate();
-                Validate();
-                Libuv.ThrowOnError(UnsafeNativeMethods.uv_write(
-                    this,
-                    _stream.Handle,
-                    _uvBuffers,
-                    _uvBuffers.Length,
-                    _uv_write_cb));
-            }
-            catch
-            {
-                Dispose();
-                throw;
-            }
+            _stream.Validate();
+            Validate();
+            Libuv.ThrowOnError(UnsafeNativeMethods.uv_write(
+                this,
+                _stream.Handle,
+                _uvBuffers,
+                _uvBuffers.Length,
+                _uv_write_cb));
         }
 
         private void UvWriteCb(IntPtr ptr, int status)
         {
             KestrelTrace.Log.ConnectionWriteCallback(0, status);
 
-            Dispose();
-
-            if (status == -125 || status == -4081) // UV_ECANCELED on Unix and Windows
-                return;
+            var exception = Libuv.ExceptionForError(status);
+            if (exception == null)
+                _tcs.SetResult(0);
             else
-                Libuv.ThrowOnError(status);
+                _tcs.SetException(exception);
         }
 
         protected override bool ReleaseHandle()