Turn HTTP/3 on by default in Kestrel (#44217)

Author: JamesNK

src/Servers/Kestrel/Core/src/ListenOptions.cs

@@ -16,7 +16,7 @@ namespace Microsoft.AspNetCore.Server.Kestrel.Core;
 /// </summary>
 public class ListenOptions : IConnectionBuilder, IMultiplexedConnectionBuilder
 {
-    internal const HttpProtocols DefaultHttpProtocols = HttpProtocols.Http1AndHttp2;
+    internal const HttpProtocols DefaultHttpProtocols = HttpProtocols.Http1AndHttp2AndHttp3;
 
     internal readonly List<Func<ConnectionDelegate, ConnectionDelegate>> _middleware = new List<Func<ConnectionDelegate, ConnectionDelegate>>();
     internal readonly List<Func<MultiplexedConnectionDelegate, MultiplexedConnectionDelegate>> _multiplexedMiddleware = new List<Func<MultiplexedConnectionDelegate, MultiplexedConnectionDelegate>>();

src/Servers/Kestrel/Core/test/KestrelServerOptionsTests.cs

@@ -28,7 +28,7 @@ public void ConfigureEndpointDefaultsAppliesToNewEndpoints()
         var options = new KestrelServerOptions();
         options.ListenLocalhost(5000);
 
-        Assert.Equal(HttpProtocols.Http1AndHttp2, options.CodeBackedListenOptions[0].Protocols);
+        Assert.Equal(ListenOptions.DefaultHttpProtocols, options.CodeBackedListenOptions[0].Protocols);
 
         options.ConfigureEndpointDefaults(opt =>
         {

src/Servers/Kestrel/Core/test/ListenOptionsTests.cs

@@ -16,7 +16,7 @@ public class ListenOptionsTests
     public void ProtocolsDefault()
     {
         var listenOptions = new ListenOptions(new IPEndPoint(IPAddress.Loopback, 0));
-        Assert.Equal(HttpProtocols.Http1AndHttp2, listenOptions.Protocols);
+        Assert.Equal(ListenOptions.DefaultHttpProtocols, listenOptions.Protocols);
     }
 
     [Fact]

src/Servers/Kestrel/Kestrel/test/KestrelConfigurationLoaderTests.cs

@@ -633,7 +633,7 @@ private void EndpointConfigSectionCanSetProtocols(string input, HttpProtocols ex
         serverOptions.ConfigureEndpointDefaults(opt =>
         {
             // Kestrel default.
-            Assert.Equal(HttpProtocols.Http1AndHttp2, opt.Protocols);
+            Assert.Equal(ListenOptions.DefaultHttpProtocols, opt.Protocols);
             ranDefault = true;
         });
 
@@ -663,14 +663,14 @@ private void EndpointConfigSectionCanSetProtocols(string input, HttpProtocols ex
             .LocalhostEndpoint(5002, opt =>
             {
                 // Kestrel default.
-                Assert.Equal(HttpProtocols.Http1AndHttp2, opt.Protocols);
+                Assert.Equal(ListenOptions.DefaultHttpProtocols, opt.Protocols);
                 ran2 = true;
             })
             .Load();
         serverOptions.ListenAnyIP(0, opt =>
         {
             // Kestrel default.
-            Assert.Equal(HttpProtocols.Http1AndHttp2, opt.Protocols);
+            Assert.Equal(ListenOptions.DefaultHttpProtocols, opt.Protocols);
             ran3 = true;
         });
 
@@ -1038,13 +1038,15 @@ public void Reload_IdentifiesEndpointsWithChangedDefaults()
 
         var (endpointsToStop, endpointsToStart) = serverOptions.ConfigurationLoader.Reload();
 
-        Assert.Single(endpointsToStop);
-        Assert.Single(endpointsToStart);
+        // NonDefaultProtocol is unchanged and doesn't need to be stopped/started
+        var stopEndpoint = Assert.Single(endpointsToStop);
+        var startEndpoint = Assert.Single(endpointsToStart);
+
+        Assert.Equal(5000, stopEndpoint.IPEndPoint.Port);
+        Assert.Equal(ListenOptions.DefaultHttpProtocols, stopEndpoint.Protocols);
 
-        Assert.Equal(5000, endpointsToStop[0].IPEndPoint.Port);
-        Assert.Equal(HttpProtocols.Http1AndHttp2, endpointsToStop[0].Protocols);
-        Assert.Equal(5000, endpointsToStart[0].IPEndPoint.Port);
-        Assert.Equal(HttpProtocols.Http1, endpointsToStart[0].Protocols);
+        Assert.Equal(5000, startEndpoint.IPEndPoint.Port);
+        Assert.Equal(HttpProtocols.Http1, startEndpoint.Protocols);
     }
 
     [Fact]