Add SslApplicationProtocol.Http3

src/libraries/System.Net.Http/src/System/Net/Http/SocketsHttpHandler/Http3Connection.cs

@@ -20,9 +20,6 @@ namespace System.Net.Http
     [SupportedOSPlatform("macos")]
     internal sealed class Http3Connection : HttpConnectionBase
     {
-        // TODO: once HTTP/3 is standardized, create APIs for this.
-        public static readonly SslApplicationProtocol Http3ApplicationProtocol = new SslApplicationProtocol("h3");
-
         private readonly HttpConnectionPool _pool;
         private readonly HttpAuthority? _origin;
         private readonly HttpAuthority _authority;

src/libraries/System.Net.Http/src/System/Net/Http/SocketsHttpHandler/HttpConnectionPool.cs

@@ -295,21 +295,10 @@ public HttpConnectionPool(HttpConnectionPoolManager poolManager, HttpConnectionK
         [SupportedOSPlatformGuard("Windows")]
         internal static bool IsHttp3Supported() => (OperatingSystem.IsLinux() && !OperatingSystem.IsAndroid()) || OperatingSystem.IsWindows() || OperatingSystem.IsMacOS();
 
-        private static readonly List<SslApplicationProtocol> s_http3ApplicationProtocols = CreateHttp3ApplicationProtocols();
+        private static readonly List<SslApplicationProtocol> s_http3ApplicationProtocols = new List<SslApplicationProtocol>() { SslApplicationProtocol.Http3, SslApplicationProtocol.Http2, SslApplicationProtocol.Http11 };
         private static readonly List<SslApplicationProtocol> s_http2ApplicationProtocols = new List<SslApplicationProtocol>() { SslApplicationProtocol.Http2, SslApplicationProtocol.Http11 };
         private static readonly List<SslApplicationProtocol> s_http2OnlyApplicationProtocols = new List<SslApplicationProtocol>() { SslApplicationProtocol.Http2 };
 
-        private static List<SslApplicationProtocol> CreateHttp3ApplicationProtocols()
-        {
-            if (IsHttp3Supported())
-            {
-                // TODO: Once the HTTP/3 versions are part of SslApplicationProtocol, see https://github.com/dotnet/runtime/issues/1293, move this back to field initialization.
-                return new List<SslApplicationProtocol>() { Http3Connection.Http3ApplicationProtocol };
-            }
-
-            return null!;
-        }
-
         private static SslClientAuthenticationOptions ConstructSslOptions(HttpConnectionPoolManager poolManager, string sslHostName)
         {
             Debug.Assert(sslHostName != null);

src/libraries/System.Net.Security/ref/System.Net.Security.cs

@@ -118,8 +118,9 @@ public readonly struct SslClientHelloInfo
     {
         private readonly object _dummy;
         private readonly int _dummyPrimitive;
-        public static readonly System.Net.Security.SslApplicationProtocol Http11;
+        public static readonly System.Net.Security.SslApplicationProtocol Http3;
         public static readonly System.Net.Security.SslApplicationProtocol Http2;
+        public static readonly System.Net.Security.SslApplicationProtocol Http11;
         public SslApplicationProtocol(byte[] protocol) { throw null; }
         public SslApplicationProtocol(string protocol) { throw null; }
         public System.ReadOnlyMemory<byte> Protocol { get { throw null; } }

src/libraries/System.Net.Security/src/System/Net/Security/SslApplicationProtocol.cs

@@ -10,13 +10,16 @@ namespace System.Net.Security
     public readonly struct SslApplicationProtocol : IEquatable<SslApplicationProtocol>
     {
         private static readonly Encoding s_utf8 = Encoding.GetEncoding(Encoding.UTF8.CodePage, EncoderFallback.ExceptionFallback, DecoderFallback.ExceptionFallback);
+        private static readonly byte[] s_http3Utf8 = new byte[] { 0x68, 0x33 }; // "h3"
         private static readonly byte[] s_http2Utf8 = new byte[] { 0x68, 0x32 }; // "h2"
         private static readonly byte[] s_http11Utf8 = new byte[] { 0x68, 0x74, 0x74, 0x70, 0x2f, 0x31, 0x2e, 0x31 }; // "http/1.1"
 
         // Refer to IANA on ApplicationProtocols: https://www.iana.org/assignments/tls-extensiontype-values/tls-extensiontype-values.xhtml#alpn-protocol-ids
-        // h2
+        /// <summary>Defines a <see cref="SslApplicationProtocol"/> instance for HTTP 3.0.</summary>
+        public static readonly SslApplicationProtocol Http3 = new SslApplicationProtocol(s_http3Utf8, copy: false);
+        /// <summary>Defines a <see cref="SslApplicationProtocol"/> instance for HTTP 2.0.</summary>
         public static readonly SslApplicationProtocol Http2 = new SslApplicationProtocol(s_http2Utf8, copy: false);
-        // http/1.1
+        /// <summary>Defines a <see cref="SslApplicationProtocol"/> instance for HTTP 1.1.</summary>
         public static readonly SslApplicationProtocol Http11 = new SslApplicationProtocol(s_http11Utf8, copy: false);
 
         private readonly byte[] _readOnlyProtocol;
@@ -77,6 +80,7 @@ public override string ToString()
             {
                 return
                     arr is null ? string.Empty :
+                    ReferenceEquals(arr, s_http3Utf8) ? "h3" :
                     ReferenceEquals(arr, s_http2Utf8) ? "h2" :
                     ReferenceEquals(arr, s_http11Utf8) ? "http/1.1" :
                     s_utf8.GetString(arr);

src/libraries/System.Net.Security/tests/UnitTests/SslApplicationProtocolTests.cs

@@ -13,6 +13,7 @@ public class SslApplicationProtocolTests
         [Fact]
         public void Constants_Values_AreCorrect()
         {
+            Assert.Equal(new SslApplicationProtocol(new byte[] { 0x68, 0x33 }), SslApplicationProtocol.Http3);
             Assert.Equal(new SslApplicationProtocol(new byte[] { 0x68, 0x32 }), SslApplicationProtocol.Http2);
             Assert.Equal(new SslApplicationProtocol(new byte[] { 0x68, 0x74, 0x74, 0x70, 0x2f, 0x31, 0x2e, 0x31 }), SslApplicationProtocol.Http11);
         }
@@ -75,6 +76,7 @@ public void ToString_Rendering_Succeeds()
         {
             Assert.Equal("http/1.1", SslApplicationProtocol.Http11.ToString());
             Assert.Equal("h2", SslApplicationProtocol.Http2.ToString());
+            Assert.Equal("h3", SslApplicationProtocol.Http3.ToString());
             Assert.Equal("hello", new SslApplicationProtocol("hello").ToString());
             Assert.Equal("0x0b 0xee", new SslApplicationProtocol(new byte[] { 0x0B, 0xEE }).ToString());
             Assert.Equal(string.Empty, default(SslApplicationProtocol).ToString());

src/libraries/System.Net.Security/tests/UnitTests/SslAuthenticationOptionsTests.cs

@@ -41,7 +41,7 @@ public void ApplicationProtocols_Get_Set_Succeeds()
             Assert.Null(_clientOptions.ApplicationProtocols);
             Assert.Null(_serverOptions.ApplicationProtocols);
 
-            List<SslApplicationProtocol> applnProtos = new List<SslApplicationProtocol> { SslApplicationProtocol.Http2, SslApplicationProtocol.Http11 };
+            List<SslApplicationProtocol> applnProtos = new List<SslApplicationProtocol> { SslApplicationProtocol.Http3, SslApplicationProtocol.Http2, SslApplicationProtocol.Http11 };
             _clientOptions.ApplicationProtocols = applnProtos;
             _serverOptions.ApplicationProtocols = applnProtos;