net/quic/quic_flow_controller.h

   1 // Copyright 2014 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #ifndef NET_QUIC_QUIC_FLOW_CONTROLLER_H_
   6 #define NET_QUIC_QUIC_FLOW_CONTROLLER_H_
   7
   8 #include "base/basictypes.h"
   9 #include "net/base/net_export.h"
  10 #include "net/quic/quic_protocol.h"
  11
  12 namespace net {
  13
  14 namespace test {
  15 class QuicFlowControllerPeer;
  16 }  // namespace test
  17
  18 class QuicConnection;
  19
  20 const QuicStreamId kConnectionLevelId = 0;
  21
  22 // QuicFlowController allows a QUIC stream or connection to perform flow
  23 // control. The stream/connection owns a QuicFlowController which keeps track of
  24 // bytes sent/received, can tell the owner if it is flow control blocked, and
  25 // can send WINDOW_UPDATE or BLOCKED frames when needed.
  26 class NET_EXPORT_PRIVATE QuicFlowController {
  27  public:
  28   QuicFlowController(QuicConnection* connection,
  29                      QuicStreamId id,
  30                      Perspective perspective,
  31                      QuicStreamOffset send_window_offset,
  32                      QuicStreamOffset receive_window_offset,
  33                      bool should_auto_tune_receive_window);
  34
  35   ~QuicFlowController() {}
  36
  37   // Called when we see a new highest received byte offset from the peer, either
  38   // via a data frame or a RST.
  39   // Returns true if this call changes highest_received_byte_offset_, and false
  40   // in the case where |new_offset| is <= highest_received_byte_offset_.
  41   bool UpdateHighestReceivedOffset(QuicStreamOffset new_offset);
  42
  43   // Called when bytes received from the peer are consumed locally. This may
  44   // trigger the sending of a WINDOW_UPDATE frame using |connection|.
  45   void AddBytesConsumed(QuicByteCount bytes_consumed);
  46
  47   // Called when bytes are sent to the peer.
  48   void AddBytesSent(QuicByteCount bytes_sent);
  49
  50   // Set a new send window offset.
  51   // Returns true if this increases send_window_offset_ and is now blocked.
  52   bool UpdateSendWindowOffset(QuicStreamOffset new_send_window_offset);
  53
  54   // Returns the current available send window.
  55   QuicByteCount SendWindowSize() const;
  56
  57   // Send a BLOCKED frame if appropriate.
  58   void MaybeSendBlocked();
  59
  60   // Returns true if flow control send limits have been reached.
  61   bool IsBlocked() const;
  62
  63   // Returns true if flow control receive limits have been violated by the peer.
  64   bool FlowControlViolation();
  65
  66   QuicByteCount bytes_consumed() const { return bytes_consumed_; }
  67
  68   QuicStreamOffset highest_received_byte_offset() const {
  69     return highest_received_byte_offset_;
  70   }
  71
  72   void set_receive_window_size_limit(QuicByteCount receive_window_size_limit) {
  73     DCHECK_GE(receive_window_size_limit, receive_window_size_limit_);
  74     receive_window_size_limit_ = receive_window_size_limit;
  75   }
  76
  77   void set_auto_tune_receive_window(bool enable) {
  78     auto_tune_receive_window_ = enable;
  79   }
  80
  81   bool auto_tune_receive_window() { return auto_tune_receive_window_; }
  82
  83  private:
  84   friend class test::QuicFlowControllerPeer;
  85
  86   // Send a WINDOW_UPDATE frame if appropriate.
  87   void MaybeSendWindowUpdate();
  88
  89   // Auto-tune the max receive window size.
  90   void MaybeIncreaseMaxWindowSize();
  91
  92   // The parent connection, used to send connection close on flow control
  93   // violation, and WINDOW_UPDATE and BLOCKED frames when appropriate.
  94   // Not owned.
  95   QuicConnection* connection_;
  96
  97   // ID of stream this flow controller belongs to. This can be 0 if this is a
  98   // connection level flow controller.
  99   QuicStreamId id_;
 100
 101   // Tracks if this is owned by a server or a client.
 102   Perspective perspective_;
 103
 104   // Tracks number of bytes sent to the peer.
 105   QuicByteCount bytes_sent_;
 106
 107   // The absolute offset in the outgoing byte stream. If this offset is reached
 108   // then we become flow control blocked until we receive a WINDOW_UPDATE.
 109   QuicStreamOffset send_window_offset_;
 110
 111   // Overview of receive flow controller.
 112   //
 113   // 0=...===1=======2-------3 ...... FIN
 114   //         |<--- <= 4  --->|
 115   //
 116
 117   // 1) bytes_consumed_ - moves forward when data is read out of the
 118   //    stream.
 119   //
 120   // 2) highest_received_byte_offset_ - moves when data is received
 121   //    from the peer.
 122   //
 123   // 3) receive_window_offset_ - moves when WINDOW_UPDATE is sent.
 124   //
 125   // 4) receive_window_size_ - maximum allowed unread data (3 - 1).
 126   //    This value may be increased by auto-tuning.
 127   //
 128   // 5) receive_window_size_limit_ - limit on receive_window_size_;
 129   //    auto-tuning will not increase window size beyond this limit.
 130
 131   // Track number of bytes received from the peer, which have been consumed
 132   // locally.
 133   QuicByteCount bytes_consumed_;
 134
 135   // The highest byte offset we have seen from the peer. This could be the
 136   // highest offset in a data frame, or a final value in a RST.
 137   QuicStreamOffset highest_received_byte_offset_;
 138
 139
 140   // The absolute offset in the incoming byte stream. The peer should never send
 141   // us bytes which are beyond this offset.
 142   QuicStreamOffset receive_window_offset_;
 143
 144   // Largest size the receive window can grow to.
 145   QuicByteCount receive_window_size_;
 146
 147   // Upper limit on receive_window_size_;
 148   QuicByteCount receive_window_size_limit_;
 149
 150   // Used to dynamically enable receive window auto-tuning.
 151   bool auto_tune_receive_window_;
 152
 153   // Send window update when receive window size drops below this.
 154   QuicByteCount WindowUpdateThreshold();
 155
 156   // Keep track of the last time we sent a BLOCKED frame. We should only send
 157   // another when the number of bytes we have sent has changed.
 158   QuicStreamOffset last_blocked_send_window_offset_;
 159
 160   // Keep time of the last time a window update was sent.  We use this
 161   // as part of the receive window auto tuning.
 162   QuicTime prev_window_update_time_;
 163
 164   DISALLOW_COPY_AND_ASSIGN(QuicFlowController);
 165 };
 166
 167 }  // namespace net
 168
 169 #endif  // NET_QUIC_QUIC_FLOW_CONTROLLER_H_