Fix flow control enforcement condition.

net/spdy/spdy_session.cc

 // 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.
 
 #include "net/spdy/spdy_session.h"
 
 #include <algorithm>
 #include <map>
 
 #include "base/basictypes.h"
@@ skipping 3186 matching lines @@
                           HIGHEST);
     session_unacked_recv_window_bytes_ = 0;
   }
 }
 
 void SpdySession::DecreaseRecvWindowSize(int32 delta_window_size) {
   CHECK(in_io_loop_);
   DCHECK_EQ(flow_control_state_, FLOW_CONTROL_STREAM_AND_SESSION);
   DCHECK_GE(delta_window_size, 1);
 
-  // Since we never decrease the initial receive window size,
-  // |delta_window_size| should never cause |recv_window_size_| to go
-  // negative. If we do, the receive window isn't being respected.
-  if (delta_window_size > session_recv_window_size_) {
+  // The receiving window size as the peer knows it is
+  // |session_recv_window_size_ - session_unacked_recv_window_bytes_|, if more
+  // data are sent by the peer, that means that the receive window is not being
+  // respected.
+  if (delta_window_size >
+      session_recv_window_size_ - session_unacked_recv_window_bytes_) {
     RecordProtocolErrorHistogram(PROTOCOL_ERROR_RECEIVE_WINDOW_VIOLATION);
     DoDrainSession(
         ERR_SPDY_FLOW_CONTROL_ERROR,
         "delta_window_size is " + base::IntToString(delta_window_size) +
             " in DecreaseRecvWindowSize, which is larger than the receive " +
             "window size of " + base::IntToString(session_recv_window_size_));
     return;
   }
 
   session_recv_window_size_ -= delta_window_size;
@@ skipping 46 matching lines @@
     if (!queue->empty()) {
       SpdyStreamId stream_id = queue->front();
       queue->pop_front();
       return stream_id;
     }
   }
   return 0;
 }
 
 }  // namespace net