Added support for unix domain sockets to the sockets transport

src/Servers/Kestrel/Core/src/KestrelServerOptions.cs

@@ -3,6 +3,7 @@
 
 using System;
 using System.Collections.Generic;
+using System.IO;
 using System.Linq;
 using System.Net;
 using System.Security.Cryptography.X509Certificates;
@@ -295,7 +296,8 @@ public void ListenUnixSocket(string socketPath, Action<ListenOptions> configure)
             {
                 throw new ArgumentNullException(nameof(socketPath));
             }
-            if (socketPath.Length == 0 || socketPath[0] != '/')
+
+            if (!Path.IsPathRooted(socketPath))
             {
                 throw new ArgumentException(CoreStrings.UnixSocketPathMustBeAbsolute, nameof(socketPath));
             }

src/Servers/Kestrel/Transport.Sockets/src/SocketConnectionListener.cs

@@ -31,10 +31,6 @@ internal SocketConnectionListener(
             SocketTransportOptions options,
             ISocketsTrace trace)
         {
-            Debug.Assert(endpoint != null);
-            Debug.Assert(endpoint is IPEndPoint);
-            Debug.Assert(trace != null);
-
             EndPoint = endpoint;
             _trace = trace;
             _options = options;
@@ -66,9 +62,12 @@ internal void Bind()
                 throw new InvalidOperationException(SocketsStrings.TransportAlreadyBound);
             }
 
-            // TODO: Add support for UnixDomainSocket
+            Socket listenSocket;
+
+            // Unix domain sockets are unspecified
+            var protocolType = EndPoint is UnixDomainSocketEndPoint ? ProtocolType.Unspecified : ProtocolType.Tcp;
 
-            var listenSocket = new Socket(EndPoint.AddressFamily, SocketType.Stream, ProtocolType.Tcp);
+            listenSocket = new Socket(EndPoint.AddressFamily, SocketType.Stream, protocolType);
 
             // Kestrel expects IPv6Any to bind to both IPv6 and IPv4
             if (EndPoint is IPEndPoint ip && ip.Address == IPAddress.IPv6Any)
@@ -99,7 +98,12 @@ public async ValueTask<ConnectionContext> AcceptAsync(CancellationToken cancella
                 try
                 {
                     var acceptSocket = await _listenSocket.AcceptAsync();
-                    acceptSocket.NoDelay = _options.NoDelay;
+
+                    // Only apply no delay to Tcp based endpoints
+                    if (acceptSocket.LocalEndPoint is IPEndPoint)
+                    {
+                        acceptSocket.NoDelay = _options.NoDelay;
+                    }
 
                     var connection = new SocketConnection(acceptSocket, _memoryPool, _schedulers[_schedulerIndex], _trace, _options.MaxReadBufferSize, _options.MaxWriteBufferSize);
 

src/Servers/Kestrel/test/FunctionalTests/UnixDomainSocketsTests.cs

@@ -0,0 +1,117 @@
+// Copyright (c) .NET Foundation. All rights reserved.
+// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
+
+using System;
+using System.Buffers;
+using System.IO;
+using System.Linq;
+using System.Net.Sockets;
+using System.Text;
+using System.Threading.Tasks;
+using Microsoft.AspNetCore.Builder;
+using Microsoft.AspNetCore.Connections;
+using Microsoft.AspNetCore.Connections.Features;
+using Microsoft.AspNetCore.Hosting;
+using Microsoft.AspNetCore.Testing;
+using Microsoft.AspNetCore.Testing.xunit;
+using Xunit;
+
+namespace Microsoft.AspNetCore.Server.Kestrel.FunctionalTests
+{
+    public class UnixDomainSocketsTest : TestApplicationErrorLoggerLoggedTest
+    {
+#if LIBUV
+        [OSSkipCondition(OperatingSystems.Windows, SkipReason = "Libuv does not support unix domain sockets on Windows.")]
+#else
+        [OSSkipCondition(OperatingSystems.Windows, WindowsVersions.Win7, WindowsVersions.Win8, WindowsVersions.Win81, WindowsVersions.Win2008R2, SkipReason = "UnixDomainSocketEndPoint is not supported on older versions of Windows")]
+#endif
+        [ConditionalFact]
+        public async Task TestUnixDomainSocket()
+        {
+            var path = Path.GetTempFileName();
+
+            Delete(path);
+
+            try
+            {
+                async Task EchoServer(ConnectionContext connection)
+                {
+                    // For graceful shutdown
+                    var notificationFeature = connection.Features.Get<IConnectionLifetimeNotificationFeature>();
+
+                    try
+                    {
+                        while (true)
+                        {
+                            var result = await connection.Transport.Input.ReadAsync(notificationFeature.ConnectionClosedRequested);
+
+                            if (result.IsCompleted)
+                            {
+                                break;
+                            }
+
+                            await connection.Transport.Output.WriteAsync(result.Buffer.ToArray());
+
+                            connection.Transport.Input.AdvanceTo(result.Buffer.End);
+                        }
+                    }
+                    catch (OperationCanceledException)
+                    {
+
+                    }
+                }
+
+                var hostBuilder = TransportSelector.GetWebHostBuilder()
+                    .UseKestrel(o =>
+                    {
+                        o.ListenUnixSocket(path, builder =>
+                        {
+                            builder.Run(EchoServer);
+                        });
+                    })
+                    .ConfigureServices(AddTestLogging)
+                    .Configure(c => { });
+
+                using (var host = hostBuilder.Build())
+                {
+                    await host.StartAsync();
+
+                    using (var socket = new Socket(AddressFamily.Unix, SocketType.Stream, ProtocolType.Unspecified))
+                    {
+                        await socket.ConnectAsync(new UnixDomainSocketEndPoint(path));
+
+                        var data = Encoding.ASCII.GetBytes("Hello World");
+                        await socket.SendAsync(data, SocketFlags.None);
+
+                        var buffer = new byte[data.Length];
+                        var read = 0;
+                        while (read < data.Length)
+                        {
+                            read += await socket.ReceiveAsync(buffer.AsMemory(read, buffer.Length - read), SocketFlags.None);
+                        }
+
+                        Assert.Equal(data, buffer);
+                    }
+
+                    await host.StopAsync();
+                }
+            }
+            finally
+            {
+                Delete(path);
+            }
+        }
+
+        private static void Delete(string path)
+        {
+            try
+            {
+                File.Delete(path);
+            }
+            catch (FileNotFoundException)
+            {
+
+            }
+        }
+    }
+}