QuicStreamSequencer closes the connection on receipt of frames overlapping with buffered data.

net/quic/quic_stream_sequencer.h

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef NET_QUIC_QUIC_STREAM_SEQUENCER_H_
 #define NET_QUIC_QUIC_STREAM_SEQUENCER_H_
 
 #include <map>
 
 #include "base/basictypes.h"
@@ skipping 40 matching lines @@
 
   // Returns true if the sequncer has bytes available for reading.
   bool HasBytesToRead() const;
 
   // Returns true if the sequencer has delivered the fin.
   bool IsClosed() const;
 
   // Returns true if the sequencer has received this frame before.
   bool IsDuplicate(const QuicStreamFrame& frame) const;
 
+  // Returns true if |frame| contains data which overlaps buffered data
+  // (indicating an invalid stream frame has been received).
+  bool FrameOverlapsBufferedData(const QuicStreamFrame& frame) const;
+
   // Calls |ProcessRawData| on |stream_| for each buffered frame that may
   // be processed.
   void FlushBufferedFrames();
 
   // Blocks processing of frames until |FlushBufferedFrames| is called.
   void SetBlockedUntilFlush();
 
   size_t num_bytes_buffered() const { return num_bytes_buffered_; }
   QuicStreamOffset num_bytes_consumed() const { return num_bytes_consumed_; }
 
@@ skipping 17 matching lines @@
   // num_bytes_consumed_ and num_bytes_buffered_.
   void RecordBytesConsumed(size_t bytes_consumed);
 
   // The stream which owns this sequencer.
   ReliableQuicStream* stream_;
 
   // The last data consumed by the stream.
   QuicStreamOffset num_bytes_consumed_;
 
   // TODO(alyssar) use something better than strings.
+  // TODO(rjshade): In future we may support retransmission of partial stream
+  // frames, in which case we will have to allow receipt of overlapping frames.
+  // Maybe write new frames into a ring buffer, and keep track of consumed
+  // bytes, and gaps.
   typedef map<QuicStreamOffset, string> FrameMap;
 
   // Stores buffered frames (maps from sequence number -> frame data as string).
   FrameMap buffered_frames_;
 
   // The offset, if any, we got a stream termination for.  When this many bytes
   // have been processed, the sequencer will be closed.
   QuicStreamOffset close_offset_;
 
   // If true, the sequencer is blocked from passing data to the stream and will
   // buffer all new incoming data until FlushBufferedFrames is called.
   bool blocked_;
 
   // Tracks how many bytes the sequencer has buffered.
   size_t num_bytes_buffered_;
 
   // Count of the number of frames received.
   int num_frames_received_;
 
   // Count of the number of duplicate frames received.
   int num_duplicate_frames_received_;
 
   DISALLOW_COPY_AND_ASSIGN(QuicStreamSequencer);
 };
 
 }  // namespace net
 
 #endif  // NET_QUIC_QUIC_STREAM_SEQUENCER_H_