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// 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.
// Accumulates frames for the next packet until more frames no longer fit or
// it's time to create a packet from them. Also provides packet creation of
// FEC packets based on previously created packets.
#include <utility>
#include <vector>
#include "base/memory/scoped_ptr.h"
#include "base/strings/string_piece.h"
#include "net/quic/quic_fec_group.h"
#include "net/quic/quic_framer.h"
#include "net/quic/quic_protocol.h"
namespace net {
namespace test {
class QuicPacketCreatorPeer;
class QuicAckNotifier;
class QuicRandom;
class QuicRandomBoolSource;
class NET_EXPORT_PRIVATE QuicPacketCreator : public QuicFecBuilderInterface {
// QuicRandom* required for packet entropy.
QuicPacketCreator(QuicConnectionId connection_id,
QuicFramer* framer,
QuicRandom* random_generator);
virtual ~QuicPacketCreator();
// QuicFecBuilderInterface
virtual void OnBuiltFecProtectedPayload(const QuicPacketHeader& header,
base::StringPiece payload) OVERRIDE;
// Turn on FEC protection for subsequently created packets. FEC should be
// enabled first (max_packets_per_fec_group should be non-zero) for FEC
// protection to start.
void StartFecProtectingPackets();
// Turn off FEC protection for subsequently created packets. If the creator
// has any open FEC group, call will fail. It is the caller's responsibility
// to flush out FEC packets in generation, and to verify with ShouldSendFec()
// that there is no open FEC group.
void StopFecProtectingPackets();
// Checks if it's time to send an FEC packet. |force_close| forces this to
// return true if an FEC group is open.
bool ShouldSendFec(bool force_close) const;
// Returns true if an FEC packet is under construction.
bool IsFecGroupOpen() const;
// Makes the framer not serialize the protocol version in sent packets.
void StopSendingVersion();
// 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,
QuicByteCount congestion_window);
// The overhead the framing will add for a packet with one frame.
static size_t StreamFramePacketOverhead(
QuicConnectionIdLength connection_id_length,
bool include_version,
QuicSequenceNumberLength sequence_number_length,
QuicStreamOffset offset,
InFecGroup is_in_fec_group);
bool HasRoomForStreamFrame(QuicStreamId id, QuicStreamOffset offset) const;
// Converts a raw payload to a frame which fits into the currently open
// packet if there is one. Returns the number of bytes consumed from data.
// If data is empty and fin is true, the expected behavior is to consume the
// fin but return 0.
size_t CreateStreamFrame(QuicStreamId id,
const IOVector& data,
QuicStreamOffset offset,
bool fin,
QuicFrame* frame);
// As above, but keeps track of an QuicAckNotifier that should be called when
// the packet that contains this stream frame is ACKed.
// The |notifier| is not owned by the QuicPacketGenerator and must outlive the
// generated packet.
size_t CreateStreamFrameWithNotifier(QuicStreamId id,
const IOVector& data,
QuicStreamOffset offset,
bool fin,
QuicAckNotifier* notifier,
QuicFrame* frame);
// Serializes all frames into a single packet. All frames must fit into a
// single packet. Also, sets the entropy hash of the serialized packet to a
// random bool and returns that value as a member of SerializedPacket.
// Never returns a RetransmittableFrames in SerializedPacket.
SerializedPacket SerializeAllFrames(const QuicFrames& frames);
// Re-serializes frames with the original packet's sequence number length.
// Used for retransmitting packets to ensure they aren't too long.
// Caller must ensure that any open FEC group is closed before calling this
// method.
SerializedPacket ReserializeAllFrames(
const QuicFrames& frames,
QuicSequenceNumberLength original_length);
// Returns true if there are frames pending to be serialized.
bool HasPendingFrames() const;
// Returns true if there are retransmittable frames pending to be serialized.
bool HasPendingRetransmittableFrames() const;
// Returns whether FEC protection is currently enabled. Note: Enabled does not
// mean that an FEC group is currently active; i.e., IsFecProtected() may
// still return false.
bool IsFecEnabled() const;
// Returns true if subsequent packets will be FEC protected. Note: True does
// not mean that an FEC packet is currently under construction; i.e.,
// fec_group_.get() may still be NULL, until MaybeStartFec() is called.
bool IsFecProtected() const;
// Returns the number of bytes which are available to be used by additional
// frames in the packet. Since stream frames are slightly smaller when they
// are the last frame in a packet, this method will return a different
// value than max_packet_size - PacketSize(), in this case.
size_t BytesFree() const;
// Returns the number of bytes that the packet will expand by if a new frame
// is added to the packet. If the last frame was a stream frame, it will
// expand slightly when a new frame is added, and this method returns the
// amount of expected expansion. If the packet is in an FEC group, no
// expansion happens and this method always returns zero.
size_t ExpansionOnNewFrame() const;
// Returns the number of bytes in the current packet, including the header,
// if serialized with the current frames. Adding a frame to the packet
// may change the serialized length of existing frames, as per the comment
// in BytesFree.
size_t PacketSize() const;
// TODO(jri): AddSavedFrame calls AddFrame, which only saves the frame
// if it is a stream frame, not other types of frames. Fix this API;
// add a AddNonSavedFrame method.
// Adds |frame| to the packet creator's list of frames to be serialized.
// Returns false if the frame doesn't fit into the current packet.
bool AddSavedFrame(const QuicFrame& frame);
// Serializes all frames which have been added and adds any which should be
// retransmitted to |retransmittable_frames| if it's not NULL. All frames must
// fit into a single packet. Sets the entropy hash of the serialized
// packet to a random bool and returns that value as a member of
// SerializedPacket. Also, sets |serialized_frames| in the SerializedPacket
// to the corresponding RetransmittableFrames if any frames are to be
// retransmitted.
SerializedPacket SerializePacket();
// Packetize FEC data. All frames must fit into a single packet. Also, sets
// the entropy hash of the serialized packet to a random bool and returns
// that value as a member of SerializedPacket.
SerializedPacket SerializeFec();
// Creates a packet with connection close frame. Caller owns the created
// packet. Also, sets the entropy hash of the serialized packet to a random
// bool and returns that value as a member of SerializedPacket.
SerializedPacket SerializeConnectionClose(
QuicConnectionCloseFrame* close_frame);
// Creates a version negotiation packet which supports |supported_versions|.
// Caller owns the created packet. Also, sets the entropy hash of the
// serialized packet to a random bool and returns that value as a member of
// SerializedPacket.
QuicEncryptedPacket* SerializeVersionNegotiationPacket(
const QuicVersionVector& supported_versions);
// Sets the encryption level that will be applied to new packets.
void set_encryption_level(EncryptionLevel level) {
encryption_level_ = level;
// Sequence number of the last created packet, or 0 if no packets have been
// created.
QuicPacketSequenceNumber sequence_number() const {
return sequence_number_;
void set_sequence_number(QuicPacketSequenceNumber s) {
sequence_number_ = s;
QuicConnectionIdLength connection_id_length() const {
return connection_id_length_;
QuicSequenceNumberLength next_sequence_number_length() const {
return next_sequence_number_length_;
void set_next_sequence_number_length(QuicSequenceNumberLength length) {
next_sequence_number_length_ = length;
size_t max_packet_length() const {
return max_packet_length_;
void set_max_packet_length(size_t length) {
// |max_packet_length_| should not be changed mid-packet or mid-FEC group.
DCHECK(fec_group_.get() == NULL && queued_frames_.empty());
max_packet_length_ = length;
// Returns current max number of packets covered by an FEC group.
size_t max_packets_per_fec_group() const {
return max_packets_per_fec_group_;
// Sets creator's max number of packets covered by an FEC group.
// Note: While there are no constraints on |max_packets_per_fec_group|,
// this setter enforces a min value of kLowestMaxPacketsPerFecGroup.
// To turn off FEC protection, use StopFecProtectingPackets().
void set_max_packets_per_fec_group(size_t max_packets_per_fec_group);
friend class test::QuicPacketCreatorPeer;
static bool ShouldRetransmit(const QuicFrame& frame);
// Updates sequence number and max packet lengths on a packet or FEC group
// boundary.
void MaybeUpdateLengths();
// Updates lengths and also starts an FEC group if FEC protection is on and
// there is not already an FEC group open.
InFecGroup MaybeUpdateLengthsAndStartFec();
void FillPacketHeader(QuicFecGroupNumber fec_group,
bool fec_flag,
QuicPacketHeader* header);
// Allows a frame to be added without creating retransmittable frames.
// Particularly useful for retransmits using SerializeAllFrames().
bool AddFrame(const QuicFrame& frame, bool save_retransmittable_frames);
// Adds a padding frame to the current packet only if the current packet
// contains a handshake message, and there is sufficient room to fit a
// padding frame.
void MaybeAddPadding();
QuicConnectionId connection_id_;
EncryptionLevel encryption_level_;
QuicFramer* framer_;
scoped_ptr<QuicRandomBoolSource> random_bool_source_;
QuicPacketSequenceNumber sequence_number_;
// If true, any created packets will be FEC protected.
bool should_fec_protect_;
QuicFecGroupNumber fec_group_number_;
scoped_ptr<QuicFecGroup> fec_group_;
// Controls whether protocol version should be included while serializing the
// packet.
bool send_version_in_packet_;
// Maximum length including headers and encryption (UDP payload length.)
size_t max_packet_length_;
// 0 indicates FEC is disabled.
size_t max_packets_per_fec_group_;
// Length of connection_id to send over the wire.
QuicConnectionIdLength connection_id_length_;
// Staging variable to hold next packet sequence number length. When sequence
// number length is to be changed, this variable holds the new length until
// a packet or FEC group boundary, when the creator's sequence_number_length_
// can be changed to this new value.
QuicSequenceNumberLength next_sequence_number_length_;
// Sequence number length for the current packet and for the current FEC group
// when FEC is enabled. Mutable so PacketSize() can adjust it when the packet
// is empty.
mutable QuicSequenceNumberLength sequence_number_length_;
// packet_size_ is mutable because it's just a cache of the current size.
// packet_size should never be read directly, use PacketSize() instead.
mutable size_t packet_size_;
QuicFrames queued_frames_;
scoped_ptr<RetransmittableFrames> queued_retransmittable_frames_;
} // namespace net