HTTP/3: Change alt-svc protocol to h3 and add upgrade test

src/Servers/Kestrel/Core/src/Internal/Http/HttpProtocol.cs

@@ -1194,17 +1194,17 @@ private HttpResponseHeaders CreateResponseHeaders(bool appCompleted)
                 }
             }
 
-            // TODO allow customization of this.
-            // Chrome is using h3-29 for protocol ID as of 12/2020. This is likely to be the alt-svc
-            // value until HTTP/3 is finalized.
-            // More info: https://blog.chromium.org/2020/10/chrome-is-deploying-http3-and-ietf-quic.html
             if (ServerOptions.EnableAltSvc && _httpVersion < Http.HttpVersion.Http3)
             {
+                // TODO: Perf. Avoid allocating enumerator and property's LINQ.
+                // https://github.com/dotnet/aspnetcore/issues/34468
                 foreach (var option in ServerOptions.ListenOptions)
                 {
                     if ((option.Protocols & HttpProtocols.Http3) == HttpProtocols.Http3)
                     {
-                        responseHeaders.HeaderAltSvc = $"h3-29=\":{option.IPEndPoint!.Port}\"; ma=84600";
+                        // TODO: Perf. Create string once instead of per-request.
+                        // https://github.com/dotnet/aspnetcore/issues/34468
+                        responseHeaders.HeaderAltSvc = $"h3=\":{option.IPEndPoint!.Port}\"; ma=84600";
                         break;
                     }
                 }

src/Servers/Kestrel/Transport.Quic/test/Microsoft.AspNetCore.Server.Kestrel.Transport.Quic.Tests.csproj

@@ -14,6 +14,11 @@
     <Content Include="$(KestrelSharedSourceRoot)test\TestCertificates\*.pfx" LinkBase="shared\TestCertificates" CopyToOutputDirectory="PreserveNewest" />
   </ItemGroup>
 
+  <ItemGroup>
+    <!-- Required for QUIC & HTTP/3 in .NET 6 - https://github.com/dotnet/runtime/pull/55332 -->
+    <RuntimeHostConfigurationOption Include="System.Net.SocketsHttpHandler.Http3Support" Value="true" />
+  </ItemGroup>
+
   <ItemGroup>
     <Reference Include="Microsoft.AspNetCore.Http" />
     <Reference Include="Microsoft.AspNetCore.Server.Kestrel.Core" />

src/Servers/Kestrel/Transport.Quic/test/WebHostTests.cs

@@ -152,6 +152,73 @@ public async Task Listen_Http3AndSocketsCoexistOnSameEndpoint_ClientSuccess()
             await host.StopAsync().DefaultTimeout();
         }
 
+        [ConditionalFact]
+        [MsQuicSupported]
+        public async Task Listen_Http3AndSocketsCoexistOnSameEndpoint_AltSvcEnabled_Upgrade()
+        {
+            // Arrange
+            var builder = GetHostBuilder()
+                .ConfigureWebHost(webHostBuilder =>
+                {
+                    webHostBuilder
+                        .UseKestrel(o =>
+                        {
+                            o.EnableAltSvc = true;
+                            o.Listen(IPAddress.Parse("127.0.0.1"), 0, listenOptions =>
+                            {
+                                listenOptions.Protocols = Core.HttpProtocols.Http1AndHttp2AndHttp3;
+                                listenOptions.UseHttps();
+                            });
+                        })
+                        .Configure(app =>
+                        {
+                            app.Run(async context =>
+                            {
+                                await context.Response.WriteAsync("hello, world");
+                            });
+                        });
+                })
+                .ConfigureServices(AddTestLogging);
+
+            using var host = builder.Build();
+            await host.StartAsync().DefaultTimeout();
+
+            var httpClientHandler = new HttpClientHandler();
+            httpClientHandler.ServerCertificateCustomValidationCallback = HttpClientHandler.DangerousAcceptAnyServerCertificateValidator;
+
+            using (var client = new HttpClient(httpClientHandler))
+            {
+                // Act
+                var request1 = new HttpRequestMessage(HttpMethod.Get, $"https://127.0.0.1:{host.GetPort()}/");
+                request1.VersionPolicy = HttpVersionPolicy.RequestVersionOrHigher;
+                var response1 = await client.SendAsync(request1).DefaultTimeout();
+
+                // Assert
+                response1.EnsureSuccessStatusCode();
+                Assert.Equal(HttpVersion.Version20, response1.Version);
+                var responseText1 = await response1.Content.ReadAsStringAsync().DefaultTimeout();
+                Assert.Equal("hello, world", responseText1);
+
+                Assert.True(response1.Headers.TryGetValues("alt-svc", out var altSvcValues));
+                Assert.Single(altSvcValues, @$"h3="":{host.GetPort()}""; ma=84600");
+
+                // Act
+                var request2 = new HttpRequestMessage(HttpMethod.Get, $"https://127.0.0.1:{host.GetPort()}/");
+                request2.VersionPolicy = HttpVersionPolicy.RequestVersionOrHigher;
+                var response2 = await client.SendAsync(request2).DefaultTimeout();
+
+                // Assert
+                response2.EnsureSuccessStatusCode();
+                Assert.Equal(HttpVersion.Version30, response2.Version);
+                var responseText2 = await response2.Content.ReadAsStringAsync().DefaultTimeout();
+                Assert.Equal("hello, world", responseText2);
+
+                Assert.False(response2.Headers.Contains("alt-svc"));
+            }
+
+            await host.StopAsync().DefaultTimeout();
+        }
+
         private static async Task CallHttp3AndHttp1EndpointsAsync(int http3Port, int http1Port)
         {
             // HTTP/3

src/Servers/Kestrel/test/InMemory.FunctionalTests/ResponseTests.cs

@@ -4106,7 +4106,7 @@ await connection.Receive(
                         $"HTTP/1.1 200 OK",
                         "Content-Length: 0",
                         $"Date: {server.Context.DateHeaderValue}",
-                        @"Alt-Svc: h3-29="":1""; ma=84600",
+                        @"Alt-Svc: h3="":1""; ma=84600",
                         "",
                         "");
                 }