Enable TCP Loopback Fast Path (Windows)

Enable TCP Loopback Fast Path; where the IP layer is skipped, for lower
latency for localhost comms, like HttpPlatformHandler+IIS reverse proxy

http://blogs.technet.com/b/wincat/archive/2012/12/05/fast-tcp-loopback-performance-and-low-latency-with-windows-server-2012-tcp-loopback-fast-path.aspx

Have to do it this way due to open issue in libuv

Loopback fast path: libuv/libuv#489

Related: "Confirm HttpPlatformHandler uses Fast TCP Loopback"
aspnet/IISIntegration#29

src/Microsoft.AspNetCore.Server.Kestrel/Networking/Libuv.cs

@@ -27,6 +27,7 @@ namespace Microsoft.AspNetCore.Server.Kestrel.Networking
                 _uv_stop = NativeDarwinMonoMethods.uv_stop;
                 _uv_ref = NativeDarwinMonoMethods.uv_ref;
                 _uv_unref = NativeDarwinMonoMethods.uv_unref;
+                _uv_fileno = NativeDarwinMonoMethods.uv_fileno;
                 _uv_close = NativeDarwinMonoMethods.uv_close;
                 _uv_async_init = NativeDarwinMonoMethods.uv_async_init;
                 _uv_async_send = NativeDarwinMonoMethods.uv_async_send;
@@ -68,6 +69,7 @@ namespace Microsoft.AspNetCore.Server.Kestrel.Networking
                 _uv_stop = NativeMethods.uv_stop;
                 _uv_ref = NativeMethods.uv_ref;
                 _uv_unref = NativeMethods.uv_unref;
+                _uv_fileno = NativeMethods.uv_fileno;
                 _uv_close = NativeMethods.uv_close;
                 _uv_async_init = NativeMethods.uv_async_init;
                 _uv_async_send = NativeMethods.uv_async_send;
@@ -177,6 +179,15 @@ namespace Microsoft.AspNetCore.Server.Kestrel.Networking
             _uv_unref(handle);
         }
 
+        [UnmanagedFunctionPointer(CallingConvention.Cdecl)]
+        protected delegate int uv_fileno_func(UvHandle handle, ref IntPtr socket);
+        protected uv_fileno_func _uv_fileno;
+        public int uv_fileno(UvHandle handle, ref IntPtr socket)
+        {
+            handle.Validate();
+            return Check(_uv_fileno(handle, ref socket));
+        }
+
         [UnmanagedFunctionPointer(CallingConvention.Cdecl)]
         public delegate void uv_close_cb(IntPtr handle);
         protected Action<IntPtr, uv_close_cb> _uv_close;
@@ -221,6 +232,40 @@ namespace Microsoft.AspNetCore.Server.Kestrel.Networking
         {
             handle.Validate();
             Check(_uv_tcp_bind(handle, ref addr, flags));
+            if (PlatformApis.IsWindows)
+            {
+                tcp_bind_windows_extras(handle);
+            }
+        }
+
+        private unsafe void tcp_bind_windows_extras(UvTcpHandle handle)
+        {
+            const int SIO_LOOPBACK_FAST_PATH = -1744830448; // IOC_IN | IOC_WS2 | 16;
+            const int WSAEOPNOTSUPP = 10000 + 45; // (WSABASEERR+45)
+            const int SOCKET_ERROR = -1;
+
+            var socket = IntPtr.Zero;
+            Check(_uv_fileno(handle, ref socket));
+
+            // Enable loopback fast-path for lower latency for localhost comms, like HttpPlatformHandler fronting
+            // http://blogs.technet.com/b/wincat/archive/2012/12/05/fast-tcp-loopback-performance-and-low-latency-with-windows-server-2012-tcp-loopback-fast-path.aspx
+            // https://github.com/libuv/libuv/issues/489
+            var optionValue = 1;
+            uint dwBytes = 0u;
+
+            var result = NativeMethods.WSAIoctl(socket, SIO_LOOPBACK_FAST_PATH, &optionValue, sizeof(int), null, 0, out dwBytes, IntPtr.Zero, IntPtr.Zero);
+            if (result == SOCKET_ERROR)
+            {
+                var errorId = NativeMethods.WSAGetLastError();
+                if (errorId == WSAEOPNOTSUPP)
+                {
+                    // This system is not >= Windows Server 2012, and the call is not supported.
+                }
+                else
+                {
+                    Check(errorId);
+                }
+            }
         }
 
         protected Func<UvTcpHandle, IntPtr, int> _uv_tcp_open;
@@ -501,6 +546,9 @@ namespace Microsoft.AspNetCore.Server.Kestrel.Networking
             [DllImport("libuv", CallingConvention = CallingConvention.Cdecl)]
             public static extern void uv_unref(UvHandle handle);
 
+            [DllImport("libuv", CallingConvention = CallingConvention.Cdecl)]
+            public static extern int uv_fileno(UvHandle handle, ref IntPtr socket);
+
             [DllImport("libuv", CallingConvention = CallingConvention.Cdecl)]
             public static extern void uv_close(IntPtr handle, uv_close_cb close_cb);
 
@@ -587,6 +635,22 @@ namespace Microsoft.AspNetCore.Server.Kestrel.Networking
 
             [DllImport("libuv", CallingConvention = CallingConvention.Cdecl)]
             unsafe public static extern int uv_walk(UvLoopHandle loop, uv_walk_cb walk_cb, IntPtr arg);
+
+            [DllImport("WS2_32.dll", CallingConvention = CallingConvention.Winapi)]
+            unsafe public static extern int WSAIoctl(
+                IntPtr socket,
+                int dwIoControlCode,
+                int* lpvInBuffer,
+                uint cbInBuffer,
+                int* lpvOutBuffer,
+                int cbOutBuffer,
+                out uint lpcbBytesReturned,
+                IntPtr lpOverlapped,
+                IntPtr lpCompletionRoutine
+            );
+            
+            [DllImport("WS2_32.dll", CallingConvention = CallingConvention.Winapi)]
+            public static extern int WSAGetLastError();
         }
 
         private static class NativeDarwinMonoMethods
@@ -609,6 +673,9 @@ namespace Microsoft.AspNetCore.Server.Kestrel.Networking
             [DllImport("__Internal", CallingConvention = CallingConvention.Cdecl)]
             public static extern void uv_unref(UvHandle handle);
 
+            [DllImport("__Internal", CallingConvention = CallingConvention.Cdecl)]
+            public static extern int uv_fileno(UvHandle handle, ref IntPtr socket);
+
             [DllImport("__Internal", CallingConvention = CallingConvention.Cdecl)]
             public static extern void uv_close(IntPtr handle, uv_close_cb close_cb);
 

test/Microsoft.AspNetCore.Server.KestrelTests/EngineTests.cs

@@ -14,6 +14,7 @@ using Microsoft.AspNetCore.Http.Features;
 using Microsoft.AspNetCore.Server.Kestrel;
 using Microsoft.AspNetCore.Server.Kestrel.Filter;
 using Microsoft.AspNetCore.Server.Kestrel.Infrastructure;
+using Microsoft.AspNetCore.Server.Kestrel.Networking;
 using Microsoft.AspNetCore.Testing.xunit;
 using Microsoft.Extensions.Logging;
 using Xunit;
@@ -118,6 +119,22 @@ namespace Microsoft.AspNetCore.Server.KestrelTests
 
             Console.WriteLine("Started");
             var socket = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);
+            if (PlatformApis.IsWindows)
+            {
+                const int SIO_LOOPBACK_FAST_PATH = (-1744830448);
+                var optionInValue = BitConverter.GetBytes(1);
+                try
+                {
+                    socket.IOControl(SIO_LOOPBACK_FAST_PATH, optionInValue, null);
+                }
+                catch
+                {
+                    // If the operating system version on this machine did
+                    // not support SIO_LOOPBACK_FAST_PATH (i.e. version
+                    // prior to Windows 8 / Windows Server 2012), handle the exception
+                }
+            }
+            socket.NoDelay = true;
             socket.Connect(new IPEndPoint(IPAddress.Loopback, port));
             socket.Send(Encoding.ASCII.GetBytes("POST / HTTP/1.0\r\n\r\nHello World"));
             socket.Shutdown(SocketShutdown.Send);
@@ -475,6 +492,22 @@ namespace Microsoft.AspNetCore.Server.KestrelTests
             using (var server = new TestServer(App, testContext))
             {
                 var socket = new Socket(SocketType.Stream, ProtocolType.Tcp);
+                if (PlatformApis.IsWindows)
+                {
+                    const int SIO_LOOPBACK_FAST_PATH = (-1744830448);
+                    var optionInValue = BitConverter.GetBytes(1);
+                    try
+                    {
+                        socket.IOControl(SIO_LOOPBACK_FAST_PATH, optionInValue, null);
+                    }
+                    catch
+                    {
+                        // If the operating system version on this machine did
+                        // not support SIO_LOOPBACK_FAST_PATH (i.e. version
+                        // prior to Windows 8 / Windows Server 2012), handle the exception
+                    }
+                }
+                socket.NoDelay = true;
                 socket.Connect(IPAddress.Loopback, server.Port);
                 await Task.Delay(200);
                 socket.Dispose();

test/Microsoft.AspNetCore.Server.KestrelTests/MultipleLoopTests.cs

@@ -235,6 +235,22 @@ namespace Microsoft.AspNetCore.Server.KestrelTests
                     serverConnectionPipeAcceptedEvent.WaitOne();
 
                     var socket = new Socket(SocketType.Stream, ProtocolType.IP);
+                    if (PlatformApis.IsWindows)
+                    {
+                        const int SIO_LOOPBACK_FAST_PATH = (-1744830448);
+                        var optionInValue = BitConverter.GetBytes(1);
+                        try
+                        {
+                            socket.IOControl(SIO_LOOPBACK_FAST_PATH, optionInValue, null);
+                        }
+                        catch
+                        {
+                            // If the operating system version on this machine did
+                            // not support SIO_LOOPBACK_FAST_PATH (i.e. version
+                            // prior to Windows 8 / Windows Server 2012), handle the exception
+                        }
+                    }
+                    socket.NoDelay = true;
                     socket.Connect(IPAddress.Loopback, 54321);
                     socket.Send(new byte[] { 6, 7, 8, 9 });
                     socket.Shutdown(SocketShutdown.Send);

test/Microsoft.AspNetCore.Server.KestrelTests/NetworkingTests.cs

@@ -93,6 +93,22 @@ namespace Microsoft.AspNetCore.Server.KestrelTests
                     AddressFamily.InterNetwork,
                     SocketType.Stream,
                     ProtocolType.Tcp);
+                if (PlatformApis.IsWindows)
+                {
+                    const int SIO_LOOPBACK_FAST_PATH = (-1744830448);
+                    var optionInValue = BitConverter.GetBytes(1);
+                    try
+                    {
+                        socket.IOControl(SIO_LOOPBACK_FAST_PATH, optionInValue, null);
+                    }
+                    catch
+                    {
+                        // If the operating system version on this machine did
+                        // not support SIO_LOOPBACK_FAST_PATH (i.e. version
+                        // prior to Windows 8 / Windows Server 2012), handle the exception
+                    }
+                }
+                socket.NoDelay = true;
 #if DNX451
                 await Task.Factory.FromAsync(
                     socket.BeginConnect,
@@ -147,6 +163,22 @@ namespace Microsoft.AspNetCore.Server.KestrelTests
                     AddressFamily.InterNetwork,
                     SocketType.Stream,
                     ProtocolType.Tcp);
+                if (PlatformApis.IsWindows)
+                {
+                    const int SIO_LOOPBACK_FAST_PATH = (-1744830448);
+                    var optionInValue = BitConverter.GetBytes(1);
+                    try
+                    {
+                        socket.IOControl(SIO_LOOPBACK_FAST_PATH, optionInValue, null);
+                    }
+                    catch
+                    {
+                        // If the operating system version on this machine did
+                        // not support SIO_LOOPBACK_FAST_PATH (i.e. version
+                        // prior to Windows 8 / Windows Server 2012), handle the exception
+                    }
+                }
+                socket.NoDelay = true;
 #if DNX451
                 await Task.Factory.FromAsync(
                     socket.BeginConnect,
@@ -234,6 +266,22 @@ namespace Microsoft.AspNetCore.Server.KestrelTests
                     AddressFamily.InterNetwork,
                     SocketType.Stream,
                     ProtocolType.Tcp);
+                if (PlatformApis.IsWindows)
+                {
+                    const int SIO_LOOPBACK_FAST_PATH = (-1744830448);
+                    var optionInValue = BitConverter.GetBytes(1);
+                    try
+                    {
+                        socket.IOControl(SIO_LOOPBACK_FAST_PATH, optionInValue, null);
+                    }
+                    catch
+                    {
+                        // If the operating system version on this machine did
+                        // not support SIO_LOOPBACK_FAST_PATH (i.e. version
+                        // prior to Windows 8 / Windows Server 2012), handle the exception
+                    }
+                }
+                socket.NoDelay = true;
 #if DNX451
                 await Task.Factory.FromAsync(
                     socket.BeginConnect,

test/Microsoft.AspNetCore.Server.KestrelTests/TestConnection.cs

@@ -8,6 +8,7 @@ using System.Net;
 using System.Net.Sockets;
 using System.Text;
 using System.Threading.Tasks;
+using Microsoft.AspNetCore.Server.Kestrel.Networking;
 using Xunit;
 
 namespace Microsoft.AspNetCore.Server.KestrelTests
@@ -29,6 +30,22 @@ namespace Microsoft.AspNetCore.Server.KestrelTests
         public void Create(int port)
         {
             _socket = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);
+            if (PlatformApis.IsWindows)
+            {
+                const int SIO_LOOPBACK_FAST_PATH = (-1744830448);
+                var optionInValue = BitConverter.GetBytes(1);
+                try
+                {
+                    _socket.IOControl(SIO_LOOPBACK_FAST_PATH, optionInValue, null);
+                }
+                catch
+                {
+                    // If the operating system version on this machine did
+                    // not support SIO_LOOPBACK_FAST_PATH (i.e. version
+                    // prior to Windows 8 / Windows Server 2012), handle the exception
+                }
+            }
+            _socket.NoDelay = true;
             _socket.Connect(new IPEndPoint(IPAddress.Loopback, port));
 
             _stream = new NetworkStream(_socket, false);