net/quic/quic_packet_creator.cc

   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 #include "net/quic/quic_packet_creator.h"
   6
   7 #include "base/basictypes.h"
   8 #include "base/logging.h"
   9 #include "net/quic/crypto/quic_random.h"
  10 #include "net/quic/quic_ack_notifier.h"
  11 #include "net/quic/quic_fec_group.h"
  12 #include "net/quic/quic_utils.h"
  13
  14 using base::StringPiece;
  15 using std::make_pair;
  16 using std::max;
  17 using std::min;
  18 using std::pair;
  19 using std::vector;
  20
  21 namespace net {
  22
  23 // A QuicRandom wrapper that gets a bucket of entropy and distributes it
  24 // bit-by-bit. Replenishes the bucket as needed. Not thread-safe. Expose this
  25 // class if single bit randomness is needed elsewhere.
  26 class QuicRandomBoolSource {
  27  public:
  28   // random: Source of entropy. Not owned.
  29   explicit QuicRandomBoolSource(QuicRandom* random)
  30       : random_(random),
  31         bit_bucket_(0),
  32         bit_mask_(0) {}
  33
  34   ~QuicRandomBoolSource() {}
  35
  36   // Returns the next random bit from the bucket.
  37   bool RandBool() {
  38     if (bit_mask_ == 0) {
  39       bit_bucket_ = random_->RandUint64();
  40       bit_mask_ = 1;
  41     }
  42     bool result = ((bit_bucket_ & bit_mask_) != 0);
  43     bit_mask_ <<= 1;
  44     return result;
  45   }
  46
  47  private:
  48   // Source of entropy.
  49   QuicRandom* random_;
  50   // Stored random bits.
  51   uint64 bit_bucket_;
  52   // The next available bit has "1" in the mask. Zero means empty bucket.
  53   uint64 bit_mask_;
  54
  55   DISALLOW_COPY_AND_ASSIGN(QuicRandomBoolSource);
  56 };
  57
  58 QuicPacketCreator::QuicPacketCreator(QuicConnectionId connection_id,
  59                                      QuicFramer* framer,
  60                                      QuicRandom* random_generator,
  61                                      bool is_server)
  62     : connection_id_(connection_id),
  63       framer_(framer),
  64       random_bool_source_(new QuicRandomBoolSource(random_generator)),
  65       sequence_number_(0),
  66       fec_group_number_(0),
  67       is_server_(is_server),
  68       send_version_in_packet_(!is_server),
  69       sequence_number_length_(options_.send_sequence_number_length),
  70       packet_size_(0) {
  71   framer_->set_fec_builder(this);
  72 }
  73
  74 QuicPacketCreator::~QuicPacketCreator() {
  75 }
  76
  77 void QuicPacketCreator::OnBuiltFecProtectedPayload(
  78     const QuicPacketHeader& header, StringPiece payload) {
  79   if (fec_group_.get()) {
  80     DCHECK_NE(0u, header.fec_group);
  81     fec_group_->Update(header, payload);
  82   }
  83 }
  84
  85 bool QuicPacketCreator::ShouldSendFec(bool force_close) const {
  86   return fec_group_.get() != NULL && fec_group_->NumReceivedPackets() > 0 &&
  87       (force_close ||
  88        fec_group_->NumReceivedPackets() >= options_.max_packets_per_fec_group);
  89 }
  90
  91 void QuicPacketCreator::MaybeStartFEC() {
  92   // Don't send FEC until QUIC_VERSION_15.
  93   if (framer_->version() > QUIC_VERSION_14 &&
  94       options_.max_packets_per_fec_group > 0 && fec_group_.get() == NULL) {
  95     DCHECK(queued_frames_.empty());
  96     // Set the fec group number to the sequence number of the next packet.
  97     fec_group_number_ = sequence_number() + 1;
  98     fec_group_.reset(new QuicFecGroup());
  99   }
 100 }
 101
 102 // Stops serializing version of the protocol in packets sent after this call.
 103 // A packet that is already open might send kQuicVersionSize bytes less than the
 104 // maximum packet size if we stop sending version before it is serialized.
 105 void QuicPacketCreator::StopSendingVersion() {
 106   DCHECK(send_version_in_packet_);
 107   send_version_in_packet_ = false;
 108   if (packet_size_ > 0) {
 109     DCHECK_LT(kQuicVersionSize, packet_size_);
 110     packet_size_ -= kQuicVersionSize;
 111   }
 112 }
 113
 114 void QuicPacketCreator::UpdateSequenceNumberLength(
 115       QuicPacketSequenceNumber least_packet_awaited_by_peer,
 116       QuicByteCount bytes_per_second) {
 117   DCHECK_LE(least_packet_awaited_by_peer, sequence_number_ + 1);
 118   // Since the packet creator will not change sequence number length mid FEC
 119   // group, include the size of an FEC group to be safe.
 120   const QuicPacketSequenceNumber current_delta =
 121       options_.max_packets_per_fec_group + sequence_number_ + 1
 122       - least_packet_awaited_by_peer;
 123   const uint64 congestion_window =
 124       bytes_per_second / options_.max_packet_length;
 125   const uint64 delta = max(current_delta, congestion_window);
 126
 127   options_.send_sequence_number_length =
 128       QuicFramer::GetMinSequenceNumberLength(delta * 4);
 129 }
 130
 131 bool QuicPacketCreator::HasRoomForStreamFrame(QuicStreamId id,
 132                                               QuicStreamOffset offset) const {
 133   return BytesFree() >
 134       QuicFramer::GetMinStreamFrameSize(framer_->version(), id, offset, true);
 135 }
 136
 137 // static
 138 size_t QuicPacketCreator::StreamFramePacketOverhead(
 139     QuicVersion version,
 140     QuicConnectionIdLength connection_id_length,
 141     bool include_version,
 142     QuicSequenceNumberLength sequence_number_length,
 143     InFecGroup is_in_fec_group) {
 144   return GetPacketHeaderSize(connection_id_length, include_version,
 145                              sequence_number_length, is_in_fec_group) +
 146       // Assumes this is a stream with a single lone packet.
 147       QuicFramer::GetMinStreamFrameSize(version, 1u, 0u, true);
 148 }
 149
 150 size_t QuicPacketCreator::CreateStreamFrame(QuicStreamId id,
 151                                             const IOVector& data,
 152                                             QuicStreamOffset offset,
 153                                             bool fin,
 154                                             QuicFrame* frame) {
 155   DCHECK_GT(options_.max_packet_length,
 156             StreamFramePacketOverhead(
 157                 framer_->version(), PACKET_8BYTE_CONNECTION_ID, kIncludeVersion,
 158                 PACKET_6BYTE_SEQUENCE_NUMBER, IN_FEC_GROUP));
 159   LOG_IF(DFATAL, !HasRoomForStreamFrame(id, offset))
 160       << "No room for Stream frame, BytesFree: " << BytesFree()
 161       << " MinStreamFrameSize: "
 162       << QuicFramer::GetMinStreamFrameSize(
 163           framer_->version(), id, offset, true);
 164
 165   if (data.Empty()) {
 166     LOG_IF(DFATAL, !fin)
 167         << "Creating a stream frame with no data or fin.";
 168     // Create a new packet for the fin, if necessary.
 169     *frame = QuicFrame(new QuicStreamFrame(id, true, offset, data));
 170     return 0;
 171   }
 172
 173   const size_t free_bytes = BytesFree();
 174   size_t bytes_consumed = 0;
 175   const size_t data_size = data.TotalBufferSize();
 176
 177   // When a STREAM frame is the last frame in a packet, it consumes two fewer
 178   // bytes of framing overhead.
 179   // Anytime more data is available than fits in with the extra two bytes,
 180   // the frame will be the last, and up to two extra bytes are consumed.
 181   // TODO(ianswett): If QUIC pads, the 1 byte PADDING frame does not fit when
 182   // 1 byte is available, because then the STREAM frame isn't the last.
 183
 184   // The minimum frame size(0 bytes of data) if it's not the last frame.
 185   size_t min_frame_size = QuicFramer::GetMinStreamFrameSize(
 186       framer_->version(), id, offset, false);
 187   // Check if it's the last frame in the packet.
 188   if (data_size + min_frame_size > free_bytes) {
 189     // The minimum frame size(0 bytes of data) if it is the last frame.
 190     size_t min_last_frame_size = QuicFramer::GetMinStreamFrameSize(
 191         framer_->version(), id, offset, true);
 192     bytes_consumed =
 193         min<size_t>(free_bytes - min_last_frame_size, data_size);
 194   } else {
 195     DCHECK_LT(data_size, BytesFree());
 196     bytes_consumed = data_size;
 197   }
 198
 199   bool set_fin = fin && bytes_consumed == data_size;  // Last frame.
 200   IOVector frame_data;
 201   frame_data.AppendIovecAtMostBytes(data.iovec(), data.Size(),
 202                                     bytes_consumed);
 203   DCHECK_EQ(frame_data.TotalBufferSize(), bytes_consumed);
 204   *frame = QuicFrame(new QuicStreamFrame(id, set_fin, offset, frame_data));
 205   return bytes_consumed;
 206 }
 207
 208 size_t QuicPacketCreator::CreateStreamFrameWithNotifier(
 209     QuicStreamId id,
 210     const IOVector& data,
 211     QuicStreamOffset offset,
 212     bool fin,
 213     QuicAckNotifier* notifier,
 214     QuicFrame* frame) {
 215   size_t bytes_consumed = CreateStreamFrame(id, data, offset, fin, frame);
 216
 217   // The frame keeps track of the QuicAckNotifier until it is serialized into
 218   // a packet. At that point the notifier is informed of the sequence number
 219   // of the packet that this frame was eventually sent in.
 220   frame->stream_frame->notifier = notifier;
 221
 222   return bytes_consumed;
 223 }
 224
 225 SerializedPacket QuicPacketCreator::ReserializeAllFrames(
 226     const QuicFrames& frames,
 227     QuicSequenceNumberLength original_length) {
 228   const QuicSequenceNumberLength start_length = sequence_number_length_;
 229   const QuicSequenceNumberLength start_options_length =
 230       options_.send_sequence_number_length;
 231   const QuicFecGroupNumber start_fec_group = fec_group_number_;
 232   const size_t start_max_packets_per_fec_group =
 233       options_.max_packets_per_fec_group;
 234
 235   // Temporarily set the sequence number length and disable FEC.
 236   sequence_number_length_ = original_length;
 237   options_.send_sequence_number_length = original_length;
 238   fec_group_number_ = 0;
 239   options_.max_packets_per_fec_group = 0;
 240
 241   // Serialize the packet and restore the fec and sequence number length state.
 242   SerializedPacket serialized_packet = SerializeAllFrames(frames);
 243   sequence_number_length_ = start_length;
 244   options_.send_sequence_number_length = start_options_length;
 245   fec_group_number_ = start_fec_group;
 246   options_.max_packets_per_fec_group = start_max_packets_per_fec_group;
 247
 248   return serialized_packet;
 249 }
 250
 251 SerializedPacket QuicPacketCreator::SerializeAllFrames(
 252     const QuicFrames& frames) {
 253   // TODO(satyamshekhar): Verify that this DCHECK won't fail. What about queued
 254   // frames from SendStreamData()[send_stream_should_flush_ == false &&
 255   // data.empty() == true] and retransmit due to RTO.
 256   DCHECK_EQ(0u, queued_frames_.size());
 257   LOG_IF(DFATAL, frames.empty())
 258       << "Attempt to serialize empty packet";
 259   for (size_t i = 0; i < frames.size(); ++i) {
 260     bool success = AddFrame(frames[i], false);
 261     DCHECK(success);
 262   }
 263   SerializedPacket packet = SerializePacket();
 264   DCHECK(packet.retransmittable_frames == NULL);
 265   return packet;
 266 }
 267
 268 bool QuicPacketCreator::HasPendingFrames() {
 269   return !queued_frames_.empty();
 270 }
 271
 272 size_t QuicPacketCreator::BytesFree() const {
 273   const size_t max_plaintext_size =
 274       framer_->GetMaxPlaintextSize(options_.max_packet_length);
 275   DCHECK_GE(max_plaintext_size, PacketSize());
 276
 277   // If the last frame in the packet is a stream frame, then it can be
 278   // two bytes smaller than if it were not the last.  So this means that
 279   // there are two fewer bytes available to the next frame in this case.
 280   bool has_trailing_stream_frame =
 281       !queued_frames_.empty() && queued_frames_.back().type == STREAM_FRAME;
 282   size_t expanded_packet_size = PacketSize() +
 283       (has_trailing_stream_frame ? kQuicStreamPayloadLengthSize : 0);
 284
 285   if (expanded_packet_size  >= max_plaintext_size) {
 286     return 0;
 287   }
 288   return max_plaintext_size - expanded_packet_size;
 289 }
 290
 291 size_t QuicPacketCreator::PacketSize() const {
 292   if (queued_frames_.empty()) {
 293     // Only adjust the sequence number length when the FEC group is not open,
 294     // to ensure no packets in a group are too large.
 295     if (fec_group_.get() == NULL ||
 296         fec_group_->NumReceivedPackets() == 0) {
 297       sequence_number_length_ = options_.send_sequence_number_length;
 298     }
 299     packet_size_ = GetPacketHeaderSize(options_.send_connection_id_length,
 300                                        send_version_in_packet_,
 301                                        sequence_number_length_,
 302                                        options_.max_packets_per_fec_group == 0 ?
 303                                            NOT_IN_FEC_GROUP : IN_FEC_GROUP);
 304   }
 305   return packet_size_;
 306 }
 307
 308 bool QuicPacketCreator::AddSavedFrame(const QuicFrame& frame) {
 309   return AddFrame(frame, true);
 310 }
 311
 312 SerializedPacket QuicPacketCreator::SerializePacket() {
 313   LOG_IF(DFATAL, queued_frames_.empty())
 314       << "Attempt to serialize empty packet";
 315   QuicPacketHeader header;
 316   FillPacketHeader(fec_group_number_, false, &header);
 317
 318   MaybeAddPadding();
 319
 320   size_t max_plaintext_size =
 321       framer_->GetMaxPlaintextSize(options_.max_packet_length);
 322   DCHECK_GE(max_plaintext_size, packet_size_);
 323   // ACK and CONNECTION_CLOSE Frames will be truncated only if they're
 324   // the first frame in the packet.  If truncation is to occur, then
 325   // GetSerializedFrameLength will have returned all bytes free.
 326   bool possibly_truncated =
 327       packet_size_ != max_plaintext_size ||
 328       queued_frames_.size() != 1 ||
 329       (queued_frames_.back().type == ACK_FRAME ||
 330        queued_frames_.back().type == CONNECTION_CLOSE_FRAME);
 331   SerializedPacket serialized =
 332       framer_->BuildDataPacket(header, queued_frames_, packet_size_);
 333   LOG_IF(DFATAL, !serialized.packet)
 334       << "Failed to serialize " << queued_frames_.size() << " frames.";
 335   // Because of possible truncation, we can't be confident that our
 336   // packet size calculation worked correctly.
 337   if (!possibly_truncated)
 338     DCHECK_EQ(packet_size_, serialized.packet->length());
 339
 340   packet_size_ = 0;
 341   queued_frames_.clear();
 342   serialized.retransmittable_frames = queued_retransmittable_frames_.release();
 343   return serialized;
 344 }
 345
 346 SerializedPacket QuicPacketCreator::SerializeFec() {
 347   DCHECK_LT(0u, fec_group_->NumReceivedPackets());
 348   DCHECK_EQ(0u, queued_frames_.size());
 349   QuicPacketHeader header;
 350   FillPacketHeader(fec_group_number_, true, &header);
 351   QuicFecData fec_data;
 352   fec_data.fec_group = fec_group_->min_protected_packet();
 353   fec_data.redundancy = fec_group_->payload_parity();
 354   SerializedPacket serialized = framer_->BuildFecPacket(header, fec_data);
 355   fec_group_.reset(NULL);
 356   fec_group_number_ = 0;
 357   packet_size_ = 0;
 358   LOG_IF(DFATAL, !serialized.packet)
 359       << "Failed to serialize fec packet for group:" << fec_data.fec_group;
 360   DCHECK_GE(options_.max_packet_length, serialized.packet->length());
 361   return serialized;
 362 }
 363
 364 SerializedPacket QuicPacketCreator::SerializeConnectionClose(
 365     QuicConnectionCloseFrame* close_frame) {
 366   QuicFrames frames;
 367   frames.push_back(QuicFrame(close_frame));
 368   return SerializeAllFrames(frames);
 369 }
 370
 371 QuicEncryptedPacket* QuicPacketCreator::SerializeVersionNegotiationPacket(
 372     const QuicVersionVector& supported_versions) {
 373   DCHECK(is_server_);
 374   QuicPacketPublicHeader header;
 375   header.connection_id = connection_id_;
 376   header.reset_flag = false;
 377   header.version_flag = true;
 378   header.versions = supported_versions;
 379   QuicEncryptedPacket* encrypted =
 380       framer_->BuildVersionNegotiationPacket(header, supported_versions);
 381   DCHECK(encrypted);
 382   DCHECK_GE(options_.max_packet_length, encrypted->length());
 383   return encrypted;
 384 }
 385
 386 void QuicPacketCreator::FillPacketHeader(QuicFecGroupNumber fec_group,
 387                                          bool fec_flag,
 388                                          QuicPacketHeader* header) {
 389   header->public_header.connection_id = connection_id_;
 390   header->public_header.reset_flag = false;
 391   header->public_header.version_flag = send_version_in_packet_;
 392   header->fec_flag = fec_flag;
 393   header->packet_sequence_number = ++sequence_number_;
 394   header->public_header.sequence_number_length = sequence_number_length_;
 395   header->entropy_flag = random_bool_source_->RandBool();
 396   header->is_in_fec_group = fec_group == 0 ? NOT_IN_FEC_GROUP : IN_FEC_GROUP;
 397   header->fec_group = fec_group;
 398 }
 399
 400 bool QuicPacketCreator::ShouldRetransmit(const QuicFrame& frame) {
 401   switch (frame.type) {
 402     case ACK_FRAME:
 403     case CONGESTION_FEEDBACK_FRAME:
 404     case PADDING_FRAME:
 405     case STOP_WAITING_FRAME:
 406       return false;
 407     default:
 408       return true;
 409   }
 410 }
 411
 412 bool QuicPacketCreator::AddFrame(const QuicFrame& frame,
 413                                  bool save_retransmittable_frames) {
 414   DVLOG(1) << "Adding frame: " << frame;
 415   size_t frame_len = framer_->GetSerializedFrameLength(
 416       frame, BytesFree(), queued_frames_.empty(), true,
 417       options()->send_sequence_number_length);
 418   if (frame_len == 0) {
 419     return false;
 420   }
 421   DCHECK_LT(0u, packet_size_);
 422   MaybeStartFEC();
 423   packet_size_ += frame_len;
 424   // If the last frame in the packet was a stream frame, then once we add the
 425   // new frame it's serialization will be two bytes larger.
 426   if (!queued_frames_.empty() && queued_frames_.back().type == STREAM_FRAME) {
 427     packet_size_ += kQuicStreamPayloadLengthSize;
 428   }
 429   if (save_retransmittable_frames && ShouldRetransmit(frame)) {
 430     if (queued_retransmittable_frames_.get() == NULL) {
 431       queued_retransmittable_frames_.reset(new RetransmittableFrames());
 432     }
 433     if (frame.type == STREAM_FRAME) {
 434       queued_frames_.push_back(
 435           queued_retransmittable_frames_->AddStreamFrame(frame.stream_frame));
 436     } else {
 437       queued_frames_.push_back(
 438           queued_retransmittable_frames_->AddNonStreamFrame(frame));
 439     }
 440   } else {
 441     queued_frames_.push_back(frame);
 442   }
 443   return true;
 444 }
 445
 446 void QuicPacketCreator::MaybeAddPadding() {
 447   if (BytesFree() == 0) {
 448     // Don't pad full packets.
 449     return;
 450   }
 451
 452   // If any of the frames in the current packet are on the crypto stream
 453   // then they contain handshake messagses, and we should pad them.
 454   bool is_handshake = false;
 455   for (size_t i = 0; i < queued_frames_.size(); ++i) {
 456     if (queued_frames_[i].type == STREAM_FRAME &&
 457         queued_frames_[i].stream_frame->stream_id == kCryptoStreamId) {
 458       is_handshake = true;
 459       break;
 460     }
 461   }
 462   if (!is_handshake) {
 463     return;
 464   }
 465
 466   QuicPaddingFrame padding;
 467   bool success = AddFrame(QuicFrame(&padding), false);
 468   DCHECK(success);
 469 }
 470
 471 }  // namespace net