HttpClient to handle ws over h2

src/libraries/Common/src/System/Net/HttpKnownHeaderNames.TryGetHeaderName.cs

@@ -181,6 +181,9 @@ private static bool TryGetHeaderName<T>(
                     }
                     break;
 
+                case 9:
+                    potentialHeader = Protocol; goto TryMatch; // :protocol
+
                 case 10:
                     switch (charAt(key, startIndex))
                     {

src/libraries/Common/src/System/Net/HttpKnownHeaderNames.cs

@@ -55,6 +55,7 @@ internal static partial class HttpKnownHeaderNames
         public const string Origin = "Origin";
         public const string P3P = "P3P";
         public const string Pragma = "Pragma";
+        public const string Protocol = ":protocol";
         public const string ProxyAuthenticate = "Proxy-Authenticate";
         public const string ProxyAuthorization = "Proxy-Authorization";
         public const string ProxyConnection = "Proxy-Connection";

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

@@ -231,6 +231,7 @@ public HttpMethod(string method) { }
         public static System.Net.Http.HttpMethod Post { get { throw null; } }
         public static System.Net.Http.HttpMethod Put { get { throw null; } }
         public static System.Net.Http.HttpMethod Trace { get { throw null; } }
+        public static System.Net.Http.HttpMethod Connect { get { throw null; } }
         public bool Equals([System.Diagnostics.CodeAnalysis.NotNullWhen(true)] System.Net.Http.HttpMethod? other) { throw null; }
         public override bool Equals([System.Diagnostics.CodeAnalysis.NotNullWhen(true)] object? obj) { throw null; }
         public override int GetHashCode() { throw null; }

src/libraries/System.Net.Http/src/System/Net/Http/Headers/KnownHeaders.cs

@@ -12,6 +12,7 @@ internal static class KnownHeaders
         // If you add a new entry here, you need to add it to TryGetKnownHeader below as well.
 
         public static readonly KnownHeader PseudoStatus = new KnownHeader(":status", HttpHeaderType.Response, parser: null);
+        public static readonly KnownHeader PseudoProtocol = new KnownHeader(":protocol", HttpHeaderType.Request, parser: null);
         public static readonly KnownHeader Accept = new KnownHeader("Accept", HttpHeaderType.Request, MediaTypeHeaderParser.MultipleValuesParser, null, H2StaticTable.Accept, H3StaticTable.AcceptAny);
         public static readonly KnownHeader AcceptCharset = new KnownHeader("Accept-Charset", HttpHeaderType.Request, GenericHeaderParser.MultipleValueStringWithQualityParser, null, H2StaticTable.AcceptCharset);
         public static readonly KnownHeader AcceptEncoding = new KnownHeader("Accept-Encoding", HttpHeaderType.Request, GenericHeaderParser.MultipleValueStringWithQualityParser, null, H2StaticTable.AcceptEncoding, H3StaticTable.AcceptEncodingGzipDeflateBr);
@@ -244,7 +245,12 @@ public BytePtrAccessor(byte* p, int length)
                     break;
 
                 case 9:
-                    return ExpectCT; // Expect-CT
+                    switch (key[0] | 0x20)
+                    {
+                        case ':': return PseudoProtocol; // [:]protocol
+                        case 'e': return ExpectCT; // [E]xpect-CT
+                    }
+                    break;
 
                 case 10:
                     switch (key[0] | 0x20)

src/libraries/System.Net.Http/src/System/Net/Http/HttpMethod.cs

@@ -67,7 +67,7 @@ public static HttpMethod Patch
         // Don't expose CONNECT as static property, since it's used by the transport to connect to a proxy.
         // CONNECT is not used by users directly.
 
-        internal static HttpMethod Connect
+        public static HttpMethod Connect
         {
             get { return s_connectMethod; }
         }

src/libraries/System.Net.Http/src/System/Net/Http/HttpRequestMessage.cs

@@ -168,6 +168,22 @@ public override string ToString()
 
         internal bool WasRedirected() => (_sendStatus & MessageIsRedirect) != 0;
 
+        internal bool IsWebSocketRequest()
+        {
+            if (Headers.TryGetValues(":protocol", out IEnumerable<string>? values))
+            {
+                var valuesArray = (string[])values;
+                return valuesArray.Length > 0 && valuesArray[0] == "websocket";
+            }
+
+            if (Headers.TryGetValues("Upgrade", out values))
+            {
+                var valuesArray = (string[])values;
+                return valuesArray.Length > 0 && valuesArray[0] == "websocket";
+            }
+            return false;
+        }
+
         #region IDisposable Members
 
         protected virtual void Dispose(bool disposing)

src/libraries/System.Net.Http/src/System/Net/Http/SocketsHttpHandler/Http2Connection.cs

@@ -1899,7 +1899,7 @@ private enum SettingId : ushort
             EnableConnect = 0x7
         }
 
-        internal bool IsWebsocketEnabled { get; private set; } = false;
+        internal bool IsWebsocketEnabled { get; private set; } = true;
 
         // Note that this is safe to be called concurrently by multiple threads.
 

src/libraries/System.Net.Http/src/System/Net/Http/SocketsHttpHandler/Http2Stream.cs

@@ -634,7 +634,6 @@ private void OnStatus(int statusCode)
                         if (_response.RequestMessage != null && _response.RequestMessage.IsWebSocketRequest() && statusCode == 200)
                         {
                             _webSocketEstablished = true;
-                            return;
                         }
 
                         _responseProtocolState = ResponseProtocolState.ExpectingHeaders;