Send RST for canceled HTTP/2 writes #3007

Author: Tratcher

src/Kestrel.Core/Internal/Http2/Http2OutputProducer.cs

@@ -74,10 +74,11 @@ public void Dispose()
             }
         }
 
-        // Review: This is called when a CancellationToken fires mid-write. In HTTP/1.x, this aborts the entire connection.
-        // Should we do that here?
+        // This is called when a CancellationToken fires mid-write. In HTTP/1.x, this aborts the entire connection.
+        // For HTTP/2 we abort the stream.
         void IHttpOutputAborter.Abort(ConnectionAbortedException abortReason)
         {
+            _stream.ResetAndAbort(abortReason, Http2ErrorCode.INTERNAL_ERROR);
             Dispose();
         }
 

src/Kestrel.Core/Internal/Http2/Http2Stream.cs

@@ -427,7 +427,7 @@ protected override void ApplicationAbort()
             ResetAndAbort(abortReason, Http2ErrorCode.INTERNAL_ERROR);
         }
 
-        private void ResetAndAbort(ConnectionAbortedException abortReason, Http2ErrorCode error)
+        internal void ResetAndAbort(ConnectionAbortedException abortReason, Http2ErrorCode error)
         {
             // Future incoming frames will drain for a default grace period to avoid destabilizing the connection.
             var states = ApplyCompletionFlag(StreamCompletionFlags.Aborted);

test/Kestrel.InMemory.FunctionalTests/Http2/Http2StreamTests.cs

@@ -1998,5 +1998,90 @@ await ExpectAsync(Http2FrameType.HEADERS,
             await WaitForConnectionErrorAsync<HPackEncodingException>(ignoreNonGoAwayFrames: false, expectedLastStreamId: 1, Http2ErrorCode.INTERNAL_ERROR,
                 CoreStrings.HPackErrorNotEnoughBuffer);
         }
+
+        [Fact]
+        public async Task WriteAsync_PreCancelledCancellationToken_DoesNotAbort()
+        {
+            var headers = new[]
+            {
+                new KeyValuePair<string, string>(HeaderNames.Method, "GET"),
+                new KeyValuePair<string, string>(HeaderNames.Path, "/"),
+                new KeyValuePair<string, string>(HeaderNames.Scheme, "http"),
+            };
+            await InitializeConnectionAsync(async context =>
+            {
+                // The cancellation is checked at the start of WriteAsync and no application state is changed.
+                await Assert.ThrowsAsync<OperationCanceledException>(() => context.Response.WriteAsync("hello,", new CancellationToken(true)));
+                Assert.False(context.Response.HasStarted);
+            });
+
+            await StartStreamAsync(1, headers, endStream: true);
+
+            var headersFrame = await ExpectAsync(Http2FrameType.HEADERS,
+                withLength: 55,
+                withFlags: (byte)Http2HeadersFrameFlags.END_HEADERS,
+                withStreamId: 1);
+            await ExpectAsync(Http2FrameType.DATA,
+                withLength: 0,
+                withFlags: (byte)Http2DataFrameFlags.END_STREAM,
+                withStreamId: 1);
+
+            await StopConnectionAsync(expectedLastStreamId: 1, ignoreNonGoAwayFrames: false);
+
+            _hpackDecoder.Decode(headersFrame.PayloadSequence, endHeaders: false, handler: this);
+
+            Assert.Equal(3, _decodedHeaders.Count);
+            Assert.Contains("date", _decodedHeaders.Keys, StringComparer.OrdinalIgnoreCase);
+            Assert.Equal("200", _decodedHeaders[HeaderNames.Status]);
+            Assert.Equal("0", _decodedHeaders[HeaderNames.ContentLength]);
+        }
+
+        [Fact]
+        public async Task WriteAsync_CancellationTokenTriggeredDueToFlowControl_SendRST()
+        {
+            var cts = new CancellationTokenSource();
+            var writeStarted = new TaskCompletionSource<int>(TaskCreationOptions.RunContinuationsAsynchronously);
+            var headers = new[]
+            {
+                new KeyValuePair<string, string>(HeaderNames.Method, "GET"),
+                new KeyValuePair<string, string>(HeaderNames.Path, "/"),
+                new KeyValuePair<string, string>(HeaderNames.Scheme, "http"),
+            };
+            await InitializeConnectionAsync(async context =>
+            {
+                await context.Response.Body.FlushAsync(); // https://github.com/aspnet/KestrelHttpServer/issues/3031
+                var writeTask = context.Response.WriteAsync("hello,", cts.Token);
+                writeStarted.SetResult(0);
+                await Assert.ThrowsAsync<OperationCanceledException>(() => writeTask);
+            });
+
+            _clientSettings.InitialWindowSize = 0;
+            await SendSettingsAsync();
+            await ExpectAsync(Http2FrameType.SETTINGS,
+                withLength: 0,
+                withFlags: (byte)Http2SettingsFrameFlags.ACK,
+                withStreamId: 0);
+
+            await StartStreamAsync(1, headers, endStream: true);
+
+            var headersFrame = await ExpectAsync(Http2FrameType.HEADERS,
+                withLength: 37,
+                withFlags: (byte)Http2HeadersFrameFlags.END_HEADERS,
+                withStreamId: 1);
+
+            await writeStarted.Task;
+
+            cts.Cancel();
+
+            await WaitForStreamErrorAsync(1, Http2ErrorCode.INTERNAL_ERROR, null);
+
+            await StopConnectionAsync(expectedLastStreamId: 1, ignoreNonGoAwayFrames: false);
+
+            _hpackDecoder.Decode(headersFrame.PayloadSequence, endHeaders: false, handler: this);
+
+            Assert.Equal(2, _decodedHeaders.Count);
+            Assert.Contains("date", _decodedHeaders.Keys, StringComparer.OrdinalIgnoreCase);
+            Assert.Equal("200", _decodedHeaders[HeaderNames.Status]);
+        }
     }
 }