Merge pull request #2272 from aspnet/release/2.1

Mark HTTP/2 as not supported with an AppContext switch override.

samples/Http2SampleApp/Program.cs

@@ -1,4 +1,4 @@
-using System.Globalization;
+using System;
 using System.IO;
 using System.Net;
 using Microsoft.AspNetCore.Hosting;
@@ -13,6 +13,8 @@ namespace Http2SampleApp
     {
         public static void Main(string[] args)
         {
+            AppContext.SetSwitch("Switch.Microsoft.AspNetCore.Server.Kestrel.Experimental.Http2", isEnabled: true);
+
             var hostBuilder = new WebHostBuilder()
                 .ConfigureLogging((_, factory) =>
                 {

samples/Http2SampleApp/Startup.cs

@@ -1,7 +1,3 @@
-using System;
-using System.Collections.Generic;
-using System.Linq;
-using System.Threading.Tasks;
 using Microsoft.AspNetCore.Builder;
 using Microsoft.AspNetCore.Hosting;
 using Microsoft.AspNetCore.Http;
@@ -11,18 +7,16 @@ namespace Http2SampleApp
 {
     public class Startup
     {
-        // This method gets called by the runtime. Use this method to add services to the container.
-        // For more information on how to configure your application, visit https://go.microsoft.com/fwlink/?LinkID=398940
+
         public void ConfigureServices(IServiceCollection services)
         {
         }
 
-        // This method gets called by the runtime. Use this method to configure the HTTP request pipeline.
         public void Configure(IApplicationBuilder app, IHostingEnvironment env)
         {
-            app.Run(async (context) =>
+            app.Run(context =>
             {
-                await context.Response.WriteAsync("Hello World!");
+                return context.Response.WriteAsync("Hello World! " + context.Request.Protocol);
             });
         }
     }

src/Kestrel.Core/CoreStrings.resx

@@ -495,4 +495,7 @@
   <data name="MultipleCertificateSources" xml:space="preserve">
     <value>The endpoint {endpointName} specified multiple certificate sources.</value>
   </data>
+  <data name="Http2NotSupported" xml:space="preserve">
+    <value>HTTP/2 support is experimental, see https://go.microsoft.com/fwlink/?linkid=866785 to enable it.</value>
+  </data>
 </root>

src/Kestrel.Core/ListenOptions.cs

@@ -19,13 +19,18 @@ namespace Microsoft.AspNetCore.Server.Kestrel.Core
     /// </summary>
     public class ListenOptions : IEndPointInformation, IConnectionBuilder
     {
+        internal const string Http2ExperimentSwitch = "Switch.Microsoft.AspNetCore.Server.Kestrel.Experimental.Http2";
+
         private FileHandleType _handleType;
+        private HttpProtocols _protocols = HttpProtocols.Http1;
+        internal bool _isHttp2Supported;
         private readonly List<Func<ConnectionDelegate, ConnectionDelegate>> _components = new List<Func<ConnectionDelegate, ConnectionDelegate>>();
 
         internal ListenOptions(IPEndPoint endPoint)
         {
             Type = ListenType.IPEndPoint;
             IPEndPoint = endPoint;
+            AppContext.TryGetSwitch(Http2ExperimentSwitch, out _isHttp2Supported);
         }
 
         internal ListenOptions(string socketPath)
@@ -122,8 +127,20 @@ namespace Microsoft.AspNetCore.Server.Kestrel.Core
         /// <summary>
         /// The protocols enabled on this endpoint.
         /// </summary>
-        /// <remarks>Defaults to HTTP/1.x only.</remarks>
-        public HttpProtocols Protocols { get; set; } = HttpProtocols.Http1;
+        /// <remarks>Defaults to HTTP/1.x only. HTTP/2 support is experimental, see
+        /// https://go.microsoft.com/fwlink/?linkid=866785 to enable it.</remarks>
+        public HttpProtocols Protocols
+        {
+            get => _protocols;
+            set
+            {
+                if (!_isHttp2Supported && (value == HttpProtocols.Http1AndHttp2 || value == HttpProtocols.Http2))
+                {
+                    throw new NotSupportedException(CoreStrings.Http2NotSupported);
+                }
+                _protocols = value;
+            }
+        }
 
         /// <summary>
         /// Gets the <see cref="List{IConnectionAdapter}"/> that allows each connection <see cref="System.IO.Stream"/>

src/Kestrel.Core/Properties/CoreStrings.Designer.cs

@@ -1774,6 +1774,20 @@ namespace Microsoft.AspNetCore.Server.Kestrel.Core
         internal static string FormatMultipleCertificateSources(object endpointName)
             => string.Format(CultureInfo.CurrentCulture, GetString("MultipleCertificateSources", "endpointName"), endpointName);
 
+        /// <summary>
+        /// HTTP/2 support is experimental, see https://go.microsoft.com/fwlink/?linkid=866785 to enable it.
+        /// </summary>
+        internal static string Http2NotSupported
+        {
+            get => GetString("Http2NotSupported");
+        }
+
+        /// <summary>
+        /// HTTP/2 support is experimental, see https://go.microsoft.com/fwlink/?linkid=866785 to enable it.
+        /// </summary>
+        internal static string FormatHttp2NotSupported()
+            => GetString("Http2NotSupported");
+
         private static string GetString(string name, params string[] formatterNames)
         {
             var value = _resourceManager.GetString(name);

test/Kestrel.Core.Tests/ListenOptionsTests.cs

@@ -1,6 +1,7 @@
 // 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.Net;
 using Xunit;
 
@@ -14,5 +15,15 @@ namespace Microsoft.AspNetCore.Server.Kestrel.Core.Tests
             var listenOptions = new ListenOptions(new IPEndPoint(IPAddress.Loopback, 0));
             Assert.Equal(HttpProtocols.Http1, listenOptions.Protocols);
         }
+
+        [Fact]
+        public void Http2DisabledByDefault()
+        {
+            var listenOptions = new ListenOptions(new IPEndPoint(IPAddress.Loopback, 0));
+            var ex = Assert.Throws<NotSupportedException>(() => listenOptions.Protocols = HttpProtocols.Http1AndHttp2);
+            Assert.Equal(CoreStrings.Http2NotSupported, ex.Message);
+            ex = Assert.Throws<NotSupportedException>(() => listenOptions.Protocols = HttpProtocols.Http2);
+            Assert.Equal(CoreStrings.Http2NotSupported, ex.Message);
+        }
     }
 }

test/Kestrel.FunctionalTests/HttpProtocolSelectionTests.cs

@@ -48,7 +48,11 @@ namespace Microsoft.AspNetCore.Server.Kestrel.FunctionalTests
             var builder = TransportSelector.GetWebHostBuilder()
                 .UseKestrel(options =>
                 {
-                    options.Listen(IPAddress.Loopback, 0, listenOptions => listenOptions.Protocols = serverProtocols);
+                    options.Listen(IPAddress.Loopback, 0, listenOptions =>
+                    {
+                        listenOptions._isHttp2Supported = true;
+                        listenOptions.Protocols = serverProtocols;
+                    });
                 })
                 .Configure(app => app.Run(context => Task.CompletedTask));
 
@@ -75,7 +79,11 @@ namespace Microsoft.AspNetCore.Server.Kestrel.FunctionalTests
 
             var builder = TransportSelector.GetWebHostBuilder()
                 .ConfigureLogging(loggingBuilder => loggingBuilder.AddProvider(loggerProvider.Object))
-                .UseKestrel(options => options.Listen(IPAddress.Loopback, 0, listenOptions => listenOptions.Protocols = serverProtocols))
+                .UseKestrel(options => options.Listen(IPAddress.Loopback, 0, listenOptions =>
+                {
+                    listenOptions._isHttp2Supported = true;
+                    listenOptions.Protocols = serverProtocols;
+                }))
                 .Configure(app => app.Run(context => Task.CompletedTask));
 
             using (var host = builder.Build())