Fix graceful shutdown of connection close in HTTP/3 (#26638)

Author: jkotalik

src/Servers/Kestrel/Core/src/CoreStrings.resx

@@ -641,4 +641,10 @@ For more information on configuring HTTPS see https://go.microsoft.com/fwlink/?l
   <data name="FailedToOpenCertStore" xml:space="preserve">
     <value>Failed to open certificate store {StoreName}.</value>
   </data>
+  <data name="Http3ConnectionFaulted" xml:space="preserve">
+    <value>The HTTP/3 connection faulted.</value>
+  </data>
+  <data name="Http3StreamAborted" xml:space="preserve">
+    <value>The HTTP/3 request stream was aborted.</value>
+  </data>
 </root>

src/Servers/Kestrel/Core/src/Http3Limits.cs

@@ -10,16 +10,17 @@ namespace Microsoft.AspNetCore.Server.Kestrel.Core
     /// </summary>
     public class Http3Limits
     {
-        private int _headerTableSize = 4096;
+        private int _headerTableSize = 0;
         private int _maxRequestHeaderFieldSize = 8192;
 
         /// <summary>
-        /// Limits the size of the header compression table, in octets, the HPACK decoder on the server can use.
+        /// Limits the size of the header compression table, in octets, the QPACK decoder on the server can use.
         /// <para>
-        /// Value must be greater than 0, defaults to 4096
+        /// Value must be greater than 0, defaults to 0.
         /// </para>
         /// </summary>
-        public int HeaderTableSize
+        // TODO: Make public https://github.com/dotnet/aspnetcore/issues/26666
+        internal int HeaderTableSize
         {
             get => _headerTableSize;
             set

src/Servers/Kestrel/Core/src/Internal/Http2/Http2Connection.cs

@@ -1558,44 +1558,6 @@ private async Task ReadInputAsync()
             }
         }
 
-        private class StreamCloseAwaitable : ICriticalNotifyCompletion
-        {
-            private static readonly Action _callbackCompleted = () => { };
-
-            // Initialize to completed so UpdateCompletedStreams runs at least once during connection teardown
-            // if there are still active streams.
-            private Action? _callback = _callbackCompleted;
-
-            public StreamCloseAwaitable GetAwaiter() => this;
-            public bool IsCompleted => ReferenceEquals(_callback, _callbackCompleted);
-
-            public void GetResult()
-            {
-                Debug.Assert(ReferenceEquals(_callback, _callbackCompleted));
-
-                _callback = null;
-            }
-
-            public void OnCompleted(Action continuation)
-            {
-                if (ReferenceEquals(_callback, _callbackCompleted) ||
-                    ReferenceEquals(Interlocked.CompareExchange(ref _callback, continuation, null), _callbackCompleted))
-                {
-                    Task.Run(continuation);
-                }
-            }
-
-            public void UnsafeOnCompleted(Action continuation)
-            {
-                OnCompleted(continuation);
-            }
-
-            public void Complete()
-            {
-                Interlocked.Exchange(ref _callback, _callbackCompleted)?.Invoke();
-            }
-        }
-
         private enum RequestHeaderParsingState
         {
             Ready,

src/Servers/Kestrel/Core/src/Internal/Http2/Http2FrameWriter.cs

@@ -547,7 +547,7 @@ public ValueTask<FlushResult> WriteRstStreamAsync(int streamId, Http2ErrorCode e
             |                        Value (32)                             |
             +---------------------------------------------------------------+
         */
-        public ValueTask<FlushResult> WriteSettingsAsync(IList<Http2PeerSetting> settings)
+        public ValueTask<FlushResult> WriteSettingsAsync(List<Http2PeerSetting> settings)
         {
             lock (_writeLock)
             {
@@ -569,7 +569,7 @@ public ValueTask<FlushResult> WriteSettingsAsync(IList<Http2PeerSetting> setting
             }
         }
 
-        internal static void WriteSettings(IList<Http2PeerSetting> settings, Span<byte> destination)
+        internal static void WriteSettings(List<Http2PeerSetting> settings, Span<byte> destination)
         {
             foreach (var setting in settings)
             {