Adds an alarm for sending a QUIC FEC packet.

net/quic/quic_packet_generator.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.
 //
 // Responsible for generating packets on behalf of a QuicConnection.
 // Packets are serialized just-in-time.  Control frames are queued.
 // Ack and Feedback frames will be requested from the Connection
 // just-in-time.  When a packet needs to be sent, the Generator
 // will serialize a packet and pass it to QuicConnection::SendOrQueuePacket()
 //
@@ skipping 153 matching lines @@
 
   // Update the sequence number length to use in future packets as soon as it
   // can be safely changed.
   void UpdateSequenceNumberLength(
       QuicPacketSequenceNumber least_packet_awaited_by_peer,
       QuicPacketCount max_packets_in_flight);
 
   // Set the minimum number of bytes for the connection id length;
   void SetConnectionIdLength(uint32 length);
 
+  // Called when the FEC alarm fires.
+  void OnFecTimeout();
+
+  // Called after sending |sequence_number| to determine whether an FEC alarm
+  // should be set for sending out an FEC packet. Returns a positive and finite
+  // timeout if an FEC alarm should be set, and infinite if no alarm should be
+  // set. OnFecTimeout should be called to send the FEC packet when the alarm
+  // fires.
+  QuicTime::Delta GetFecTimeout(QuicPacketSequenceNumber sequence_number);
+
   // Sets the encryption level that will be applied to new packets.
   void set_encryption_level(EncryptionLevel level);
 
   // Sequence number of the last created packet, or 0 if no packets have been
   // created.
   QuicPacketSequenceNumber sequence_number() const;
 
   QuicByteCount max_packet_length() const;
 
   void set_max_packet_length(QuicByteCount length);
 
   void set_debug_delegate(DebugDelegate* debug_delegate) {
     debug_delegate_ = debug_delegate;
   }
 
-  QuicTime::Delta fec_timeout() { return fec_timeout_; }
-
  private:
   friend class test::QuicPacketGeneratorPeer;
 
   // Turn on FEC protection for subsequent packets in the generator.
   // If no FEC group is currently open in the creator, this method flushes any
   // queued frames in the generator and in the creator, and it then turns FEC on
   // in the creator. This method may be called with an open FEC group in the
   // creator, in which case, only the generator's state is altered.
   void MaybeStartFecProtection();
 
   // Serializes and calls the delegate on an FEC packet if one was under
   // construction in the creator. When |force| is false, it relies on the
   // creator being ready to send an FEC packet, otherwise FEC packet is sent
   // as long as one is under construction in the creator. Also tries to turn
   // off FEC protection in the creator if it's off in the generator.
   void MaybeSendFecPacketAndCloseGroup(bool force);
 
+  // Returns true if an FEC packet should be generated based on |force| and
+  // current state of the generator and the creator.
+  bool ShouldSendFecPacket(bool force);
+
   void SendQueuedFrames(bool flush);
 
   // Test to see if we have pending ack, feedback, or control frames.
   bool HasPendingFrames() const;
   // Test to see if the addition of a pending frame (which might be
   // retransmittable) would still allow the resulting packet to be sent now.
   bool CanSendWithNextPendingFrameAddition() const;
   // Add exactly one pending frame, preferring ack over feedback over control
   // frames.
   bool AddNextPendingFrame();
 
   bool AddFrame(const QuicFrame& frame);
 
   void SerializeAndSendPacket();
 
   DelegateInterface* delegate_;
   DebugDelegate* debug_delegate_;
 
   QuicPacketCreator packet_creator_;
   QuicFrames queued_control_frames_;
 
   // True if batch mode is currently enabled.
   bool batch_mode_;
 
-  // Timeout used for FEC alarm. Can be set to zero.
+  // Timeout used for FEC alarm. Can be set to zero initially or if the SRTT has
+  // not yet been set.
   QuicTime::Delta fec_timeout_;
 
   // True if FEC protection is on. The creator may have an open FEC group even
   // if this variable is false.
   bool should_fec_protect_;
 
   // Flags to indicate the need for just-in-time construction of a frame.
   bool should_send_ack_;
   bool should_send_feedback_;
   bool should_send_stop_waiting_;
   // If we put a non-retransmittable frame (namley ack or feedback frame) in
   // this packet, then we have to hold a reference to it until we flush (and
   // serialize it). Retransmittable frames are referenced elsewhere so that they
   // can later be (optionally) retransmitted.
   scoped_ptr<QuicAckFrame> pending_ack_frame_;
   scoped_ptr<QuicCongestionFeedbackFrame> pending_feedback_frame_;
   scoped_ptr<QuicStopWaitingFrame> pending_stop_waiting_frame_;
 
   // Stores notifiers that should be attached to the next serialized packet.
   base::hash_set<QuicAckNotifier*> ack_notifiers_;
 
   DISALLOW_COPY_AND_ASSIGN(QuicPacketGenerator);
 };
 
 }  // namespace net
 
 #endif  // NET_QUIC_QUIC_PACKET_GENERATOR_H_