loopback fast-path and zero-copy send (Windows)

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

@@ -27,6 +27,7 @@ public Libuv()
                 _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 @@ public Libuv()
                 _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;
@@ -172,6 +174,15 @@ public void unref(UvHandle handle)
             _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;
@@ -216,6 +227,54 @@ public void tcp_bind(UvTcpHandle handle, ref SockAddr addr, int flags)
         {
             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 SOL_SOCKET = 0xffff; // options for socket level
+            const int SO_SNDBUF = 0x1001; // send buffer size
+            const int WSAEOPNOTSUPP = 10000 + 45; // (WSABASEERR+45)
+            const int SOCKET_ERROR = -1;
+
+            IntPtr 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
+            int True = -1;
+            uint dwBytes = 0;
+
+            var result = NativeMethods.WSAIoctl(socket, SIO_LOOPBACK_FAST_PATH, &True, 4, 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);
+                }
+            }
+
+            // Only use application buffers for send buffer don't buffer at winsock level 
+            // i.e. don't copy the data twice as overlapped I/O and multiple sends are used
+            // https://github.com/libuv/libuv/issues/74
+            int zero = 0;
+            result = NativeMethods.setsockopt(socket, SOL_SOCKET, SO_SNDBUF, (char*)&zero, sizeof(int));
+            if (result == SOCKET_ERROR)
+            {
+                var errorId = NativeMethods.WSAGetLastError();
+                Check(errorId);
+            }
         }
 
         protected Func<UvTcpHandle, IntPtr, int> _uv_tcp_open;
@@ -496,6 +555,9 @@ private static class NativeMethods
             [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);
 
@@ -582,6 +644,25 @@ private static class NativeMethods
 
             [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)]
+            public unsafe static extern int setsockopt(IntPtr s, int level, int optname, char* optval, int optlen);
+
+            [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
@@ -604,6 +685,9 @@ private static class NativeDarwinMonoMethods
             [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);