1 // Copyright (c) 2012 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 // Responsible for generating packets on behalf of a QuicConnection. 6 // Packets are serialized just-in-time. Control frames are queued. 7 // Ack and Feedback frames will be requested from the Connection 8 // just-in-time. When a packet needs to be sent, the Generator 9 // will serialize a packet and pass it to QuicConnection::SendOrQueuePacket() 10 // 11 // The Generator's mode of operation is controlled by two conditions: 12 // 13 // 1) Is the Delegate writable? 14 // 15 // If the Delegate is not writable, then no operations will cause 16 // a packet to be serialized. In particular: 17 // * SetShouldSendAck will simply record that an ack is to be sent. 18 // * AddControlFram will enqueue the control frame. 19 // * ConsumeData will do nothing. 20 // 21 // If the Delegate is writable, then the behavior depends on the second 22 // condition: 23 // 24 // 2) Is the Generator in batch mode? 25 // 26 // If the Generator is NOT in batch mode, then each call to a write 27 // operation will serialize one or more packets. The contents will 28 // include any previous queued frames. If an ack should be sent 29 // but has not been sent, then the Delegate will be asked to create 30 // an Ack frame which will then be included in the packet. When 31 // the write call completes, the current packet will be serialized 32 // and sent to the Delegate, even if it is not full. 33 // 34 // If the Generator is in batch mode, then each write operation will 35 // add data to the "current" packet. When the current packet becomes 36 // full, it will be serialized and sent to the packet. When batch 37 // mode is ended via |FinishBatchOperations|, the current packet 38 // will be serialzied, even if it is not full. 39 // 40 // FEC behavior also depends on batch mode. In batch mode, FEC packets 41 // will be sent after |max_packets_per_group| have been sent, as well 42 // as after batch operations are complete. When not in batch mode, 43 // an FEC packet will be sent after each write call completes. 44 // 45 // TODO(rch): This behavior should probably be tuned. When not in batch 46 // mode, we should probably set a timer so that several independent 47 // operations can be grouped into the same FEC group. 48 // 49 // When an FEC packet is generated, it will be send to the Delegate, 50 // even if the Delegate has become unwritable after handling the 51 // data packet immediately proceeding the FEC packet. 52 53 #ifndef NET_QUIC_QUIC_PACKET_GENERATOR_H_ 54 #define NET_QUIC_QUIC_PACKET_GENERATOR_H_ 55 56 #include "net/quic/quic_packet_creator.h" 57 58 namespace net { 59 60 class NET_EXPORT_PRIVATE QuicPacketGenerator { 61 public: 62 class NET_EXPORT_PRIVATE DelegateInterface { 63 public: 64 virtual ~DelegateInterface() {} 65 virtual bool CanWrite(Retransmission retransmission, 66 HasRetransmittableData retransmittable, 67 IsHandshake handshake) = 0; 68 virtual QuicAckFrame* CreateAckFrame() = 0; 69 virtual QuicCongestionFeedbackFrame* CreateFeedbackFrame() = 0; 70 // Takes ownership of |packet.packet| and |packet.retransmittable_frames|. 71 virtual bool OnSerializedPacket(const SerializedPacket& packet) = 0; 72 }; 73 74 // Interface which gets callbacks from the QuicPacketGenerator at interesting 75 // points. Implementations must not mutate the state of the generator 76 // as a result of these callbacks. 77 class NET_EXPORT_PRIVATE DebugDelegateInterface { 78 public: 79 virtual ~DebugDelegateInterface() {} 80 81 // Called when a frame has been added to the current packet. 82 virtual void OnFrameAddedToPacket(const QuicFrame& frame) = 0; 83 }; 84 85 QuicPacketGenerator(DelegateInterface* delegate, 86 DebugDelegateInterface* debug_delegate, 87 QuicPacketCreator* creator); 88 89 virtual ~QuicPacketGenerator(); 90 91 void SetShouldSendAck(bool also_send_feedback); 92 void AddControlFrame(const QuicFrame& frame); 93 QuicConsumedData ConsumeData(QuicStreamId id, 94 base::StringPiece data, 95 QuicStreamOffset offset, 96 bool fin); 97 98 // Disables flushing. 99 void StartBatchOperations(); 100 // Enables flushing and flushes queued data. 101 void FinishBatchOperations(); 102 103 bool HasQueuedFrames() const; 104 105 void set_debug_delegate(DebugDelegateInterface* debug_delegate) { 106 debug_delegate_ = debug_delegate; 107 } 108 109 private: 110 void SendQueuedFrames(); 111 112 // Test to see if we have pending ack, feedback, or control frames. 113 bool HasPendingFrames() const; 114 // Test to see if the addition of a pending frame (which might be 115 // retransmittable) would still allow the resulting packet to be sent now. 116 bool CanSendWithNextPendingFrameAddition() const; 117 // Add exactly one pending frame, preferring ack over feedback over control 118 // frames. 119 bool AddNextPendingFrame(); 120 121 bool AddFrame(const QuicFrame& frame); 122 void SerializeAndSendPacket(); 123 124 DelegateInterface* delegate_; 125 DebugDelegateInterface* debug_delegate_; 126 127 QuicPacketCreator* packet_creator_; 128 QuicFrames queued_control_frames_; 129 bool should_flush_; 130 // Flags to indicate the need for just-in-time construction of a frame. 131 bool should_send_ack_; 132 bool should_send_feedback_; 133 // If we put a non-retransmittable frame (namley ack or feedback frame) in 134 // this packet, then we have to hold a reference to it until we flush (and 135 // serialize it). Retransmittable frames are referenced elsewhere so that they 136 // can later be (optionally) retransmitted. 137 scoped_ptr<QuicAckFrame> pending_ack_frame_; 138 scoped_ptr<QuicCongestionFeedbackFrame> pending_feedback_frame_; 139 140 DISALLOW_COPY_AND_ASSIGN(QuicPacketGenerator); 141 }; 142 143 } // namespace net 144 145 #endif // NET_QUIC_QUIC_PACKET_GENERATOR_H_ 146
