Process all buffers in the Http2Connection (#13921)

- Change method name to TryReadFrame instead of ReadFrame
- Make TryReadFrame slice the incoming buffer

Author: davidfowl

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

@@ -204,27 +204,17 @@ public async Task ProcessRequestsAsync<TContext>(IHttpApplication<TContext> appl
                 while (_isClosed == 0)
                 {
                     var result = await Input.ReadAsync();
-                    var readableBuffer = result.Buffer;
-                    var consumed = readableBuffer.Start;
-                    var examined = readableBuffer.Start;
+                    var buffer = result.Buffer;
 
                     // Call UpdateCompletedStreams() prior to frame processing in order to remove any streams that have exceded their drain timeouts.
                     UpdateCompletedStreams();
 
                     try
                     {
-                        if (!readableBuffer.IsEmpty)
+                        while (Http2FrameReader.TryReadFrame(ref buffer, _incomingFrame, _serverSettings.MaxFrameSize, out var framePayload))
                         {
-                            if (Http2FrameReader.ReadFrame(readableBuffer, _incomingFrame, _serverSettings.MaxFrameSize, out var framePayload))
-                            {
-                                Log.Http2FrameReceived(ConnectionId, _incomingFrame);
-                                consumed = examined = framePayload.End;
-                                await ProcessFrameAsync(application, framePayload);
-                            }
-                            else
-                            {
-                                examined = readableBuffer.End;
-                            }
+                            Log.Http2FrameReceived(ConnectionId, _incomingFrame);
+                            await ProcessFrameAsync(application, framePayload);
                         }
 
                         if (result.IsCompleted)
@@ -242,7 +232,7 @@ public async Task ProcessRequestsAsync<TContext>(IHttpApplication<TContext> appl
                     }
                     finally
                     {
-                        Input.AdvanceTo(consumed, examined);
+                        Input.AdvanceTo(buffer.Start, buffer.End);
 
                         UpdateConnectionState();
                     }

src/Servers/Kestrel/Core/src/Internal/Http2/Http2FrameReader.cs

@@ -31,16 +31,16 @@ internal static class Http2FrameReader
 
         public const int SettingSize = 6; // 2 bytes for the id, 4 bytes for the value.
 
-        public static bool ReadFrame(in ReadOnlySequence<byte> readableBuffer, Http2Frame frame, uint maxFrameSize, out ReadOnlySequence<byte> framePayload)
+        public static bool TryReadFrame(ref ReadOnlySequence<byte> buffer, Http2Frame frame, uint maxFrameSize, out ReadOnlySequence<byte> framePayload)
         {
             framePayload = ReadOnlySequence<byte>.Empty;
 
-            if (readableBuffer.Length < HeaderLength)
+            if (buffer.Length < HeaderLength)
             {
                 return false;
             }
 
-            var headerSlice = readableBuffer.Slice(0, HeaderLength);
+            var headerSlice = buffer.Slice(0, HeaderLength);
             var header = headerSlice.ToSpan();
 
             var payloadLength = (int)Bitshifter.ReadUInt24BigEndian(header);
@@ -51,7 +51,7 @@ public static bool ReadFrame(in ReadOnlySequence<byte> readableBuffer, Http2Fram
 
             // Make sure the whole frame is buffered
             var frameLength = HeaderLength + payloadLength;
-            if (readableBuffer.Length < frameLength)
+            if (buffer.Length < frameLength)
             {
                 return false;
             }
@@ -61,10 +61,11 @@ public static bool ReadFrame(in ReadOnlySequence<byte> readableBuffer, Http2Fram
             frame.Flags = header[FlagsOffset];
             frame.StreamId = (int)Bitshifter.ReadUInt31BigEndian(header.Slice(StreamIdOffset));
 
-            var extendedHeaderLength = ReadExtendedFields(frame, readableBuffer);
+            var extendedHeaderLength = ReadExtendedFields(frame, buffer);
 
             // The remaining payload minus the extra fields
-            framePayload = readableBuffer.Slice(HeaderLength + extendedHeaderLength, payloadLength - extendedHeaderLength);
+            framePayload = buffer.Slice(HeaderLength + extendedHeaderLength, payloadLength - extendedHeaderLength);
+            buffer = buffer.Slice(framePayload.End);
 
             return true;
         }

src/Servers/Kestrel/test/InMemory.FunctionalTests/Http2/Http2TestBase.cs

@@ -1112,12 +1112,13 @@ internal async Task<Http2FrameWithPayload> ReceiveFrameAsync(uint maxFrameSize =
                 var buffer = result.Buffer;
                 var consumed = buffer.Start;
                 var examined = buffer.Start;
+                var copyBuffer = buffer;
 
                 try
                 {
                     Assert.True(buffer.Length > 0);
 
-                    if (Http2FrameReader.ReadFrame(buffer, frame, maxFrameSize, out var framePayload))
+                    if (Http2FrameReader.TryReadFrame(ref buffer, frame, maxFrameSize, out var framePayload))
                     {
                         consumed = examined = framePayload.End;
                         frame.Payload = framePayload.ToArray();
@@ -1135,7 +1136,7 @@ internal async Task<Http2FrameWithPayload> ReceiveFrameAsync(uint maxFrameSize =
                 }
                 finally
                 {
-                    _bytesReceived += buffer.Slice(buffer.Start, consumed).Length;
+                    _bytesReceived += copyBuffer.Slice(copyBuffer.Start, consumed).Length;
                     _pair.Application.Input.AdvanceTo(consumed, examined);
                 }
             }

src/Servers/Kestrel/test/InMemory.FunctionalTests/Http2/TlsTests.cs

@@ -103,7 +103,7 @@ private async Task<Http2Frame> ReceiveFrameAsync(PipeReader reader)
 
                 try
                 {
-                    if (Http2FrameReader.ReadFrame(buffer, frame, 16_384, out var framePayload))
+                    if (Http2FrameReader.TryReadFrame(ref buffer, frame, 16_384, out var framePayload))
                     {
                         consumed = examined = framePayload.End;
                         return frame;