Use IOCP on secondary listener threads on Windows

Addresses #679

src/Microsoft.AspNetCore.Server.Kestrel/Http/ListenerPrimary.cs

@@ -3,6 +3,7 @@
 
 using System;
 using System.Collections.Generic;
+using System.Runtime.InteropServices;
 using System.Threading.Tasks;
 using Microsoft.AspNetCore.Server.Kestrel.Infrastructure;
 using Microsoft.AspNetCore.Server.Kestrel.Networking;
@@ -11,7 +12,7 @@ using Microsoft.Extensions.Logging;
 namespace Microsoft.AspNetCore.Server.Kestrel.Http
 {
     /// <summary>
-    /// A primary listener waits for incoming connections on a specified socket. Incoming 
+    /// A primary listener waits for incoming connections on a specified socket. Incoming
     /// connections may be passed to a secondary listener to handle.
     /// </summary>
     public abstract class ListenerPrimary : Listener
@@ -19,8 +20,10 @@ namespace Microsoft.AspNetCore.Server.Kestrel.Http
         private readonly List<UvPipeHandle> _dispatchPipes = new List<UvPipeHandle>();
         private int _dispatchIndex;
         private string _pipeName;
+        private IntPtr _fileCompletionInfoPtr;
+        private bool _tryDetachFromIOCP = PlatformApis.IsWindows;
 
-        // this message is passed to write2 because it must be non-zero-length, 
+        // this message is passed to write2 because it must be non-zero-length,
         // but it has no other functional significance
         private readonly ArraySegment<ArraySegment<byte>> _dummyMessage = new ArraySegment<ArraySegment<byte>>(new[] { new ArraySegment<byte>(new byte[] { 1, 2, 3, 4 }) });
 
@@ -37,6 +40,13 @@ namespace Microsoft.AspNetCore.Server.Kestrel.Http
         {
             _pipeName = pipeName;
 
+            if (_fileCompletionInfoPtr == IntPtr.Zero)
+            {
+                var fileCompletionInfo = new FILE_COMPLETION_INFORMATION() { Key = IntPtr.Zero, Port = IntPtr.Zero };
+                _fileCompletionInfoPtr = Marshal.AllocHGlobal(Marshal.SizeOf(fileCompletionInfo));
+                Marshal.StructureToPtr(fileCompletionInfo, _fileCompletionInfoPtr, false);
+            }
+
             await StartAsync(address, thread).ConfigureAwait(false);
 
             await Thread.PostAsync(state => ((ListenerPrimary)state).PostCallback(),
@@ -85,6 +95,7 @@ namespace Microsoft.AspNetCore.Server.Kestrel.Http
             }
             else
             {
+                DetachFromIOCP(socket);
                 var dispatchPipe = _dispatchPipes[index];
                 var write = new UvWriteReq(Log);
                 write.Init(Thread.Loop);
@@ -92,7 +103,7 @@ namespace Microsoft.AspNetCore.Server.Kestrel.Http
                     dispatchPipe,
                     _dummyMessage,
                     socket,
-                    (write2, status, error, state) => 
+                    (write2, status, error, state) =>
                     {
                         write2.Dispose();
                         ((UvStreamHandle)state).Dispose();
@@ -101,12 +112,59 @@ namespace Microsoft.AspNetCore.Server.Kestrel.Http
             }
         }
 
+        private void DetachFromIOCP(UvHandle handle)
+        {
+            if (!_tryDetachFromIOCP)
+            {
+                return;
+            }
+
+            // https://msdn.microsoft.com/en-us/library/windows/hardware/ff728840(v=vs.85).aspx
+            const int FileReplaceCompletionInformation = 61;
+            // https://msdn.microsoft.com/en-us/library/cc704588.aspx
+            const uint STATUS_INVALID_INFO_CLASS = 0xC0000003;
+
+            var statusBlock = new IO_STATUS_BLOCK();
+            var socket = IntPtr.Zero;
+            Thread.Loop.Libuv.uv_fileno(handle, ref socket);
+
+            if (NtSetInformationFile(socket, out statusBlock, _fileCompletionInfoPtr,
+                (uint)Marshal.SizeOf<FILE_COMPLETION_INFORMATION>(), FileReplaceCompletionInformation) == STATUS_INVALID_INFO_CLASS)
+            {
+                // Replacing IOCP information is only supported on Windows 8.1 or newer
+                _tryDetachFromIOCP = false;
+            }
+        }
+
+        private struct IO_STATUS_BLOCK
+        {
+            uint status;
+            ulong information;
+        }
+
+        private struct FILE_COMPLETION_INFORMATION
+        {
+            public IntPtr Port;
+            public IntPtr Key;
+        }
+
+        [DllImport("NtDll.dll")]
+        private static extern uint NtSetInformationFile(IntPtr FileHandle,
+                out IO_STATUS_BLOCK IoStatusBlock, IntPtr FileInformation, uint Length,
+                int FileInformationClass);
+
         public override async Task DisposeAsync()
         {
             // Call base first so the ListenSocket gets closed and doesn't
             // try to dispatch connections to closed pipes.
             await base.DisposeAsync().ConfigureAwait(false);
 
+            if (_fileCompletionInfoPtr != IntPtr.Zero)
+            {
+                Marshal.FreeHGlobal(_fileCompletionInfoPtr);
+                _fileCompletionInfoPtr = IntPtr.Zero;
+            }
+
             if (Thread.FatalError == null && ListenPipe != null)
             {
                 await Thread.PostAsync(state =>