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 <algorithm>
   8
   9 #include "base/basictypes.h"
  10 #include "base/logging.h"
  11 #include "net/quic/crypto/quic_random.h"
  12 #include "net/quic/quic_ack_notifier.h"
  13 #include "net/quic/quic_data_writer.h"
  14 #include "net/quic/quic_fec_group.h"
  15 #include "net/quic/quic_utils.h"
  16
  17 using base::StringPiece;
  18 using std::make_pair;
  19 using std::max;
  20 using std::min;
  21 using std::pair;
  22 using std::vector;
  23
  24 namespace net {
  25
  26 namespace {
  27
  28 // Default max packets in an FEC group.
  29 static const size_t kDefaultMaxPacketsPerFecGroup = 10;
  30 // Lowest max packets in an FEC group.
  31 static const size_t kLowestMaxPacketsPerFecGroup = 2;
  32
  33 }  // namespace
  34
  35 // A QuicRandom wrapper that gets a bucket of entropy and distributes it
  36 // bit-by-bit. Replenishes the bucket as needed. Not thread-safe. Expose this
  37 // class if single bit randomness is needed elsewhere.
  38 class QuicRandomBoolSource {
  39  public:
  40   // random: Source of entropy. Not owned.
  41   explicit QuicRandomBoolSource(QuicRandom* random)
  42       : random_(random),
  43         bit_bucket_(0),
  44         bit_mask_(0) {}
  45
  46   ~QuicRandomBoolSource() {}
  47
  48   // Returns the next random bit from the bucket.
  49   bool RandBool() {
  50     if (bit_mask_ == 0) {
  51       bit_bucket_ = random_->RandUint64();
  52       bit_mask_ = 1;
  53     }
  54     bool result = ((bit_bucket_ & bit_mask_) != 0);
  55     bit_mask_ <<= 1;
  56     return result;
  57   }
  58
  59  private:
  60   // Source of entropy.
  61   QuicRandom* random_;
  62   // Stored random bits.
  63   uint64 bit_bucket_;
  64   // The next available bit has "1" in the mask. Zero means empty bucket.
  65   uint64 bit_mask_;
  66
  67   DISALLOW_COPY_AND_ASSIGN(QuicRandomBoolSource);
  68 };
  69
  70 QuicPacketCreator::QuicPacketCreator(QuicConnectionId connection_id,
  71                                      QuicFramer* framer,
  72                                      QuicRandom* random_generator)
  73     : connection_id_(connection_id),
  74       encryption_level_(ENCRYPTION_NONE),
  75       framer_(framer),
  76       random_bool_source_(new QuicRandomBoolSource(random_generator)),
  77       sequence_number_(0),
  78       should_fec_protect_(false),
  79       fec_group_number_(0),
  80       send_version_in_packet_(framer->perspective() == Perspective::IS_CLIENT),
  81       max_packets_per_fec_group_(kDefaultMaxPacketsPerFecGroup),
  82       connection_id_length_(PACKET_8BYTE_CONNECTION_ID),
  83       next_sequence_number_length_(PACKET_1BYTE_SEQUENCE_NUMBER),
  84       sequence_number_length_(next_sequence_number_length_),
  85       packet_size_(0) {
  86   SetMaxPacketLength(kDefaultMaxPacketSize);
  87 }
  88
  89 QuicPacketCreator::~QuicPacketCreator() {
  90 }
  91
  92 void QuicPacketCreator::OnBuiltFecProtectedPayload(
  93     const QuicPacketHeader& header, StringPiece payload) {
  94   if (fec_group_.get()) {
  95     DCHECK_NE(0u, header.fec_group);
  96     fec_group_->Update(encryption_level_, header, payload);
  97   }
  98 }
  99
 100 void QuicPacketCreator::SetEncrypter(EncryptionLevel level,
 101                                      QuicEncrypter* encrypter) {
 102   framer_->SetEncrypter(level, encrypter);
 103   max_plaintext_size_ = framer_->GetMaxPlaintextSize(max_packet_length_);
 104 }
 105
 106 void QuicPacketCreator::SetMaxPacketLength(QuicByteCount length) {
 107   // |max_packet_length_| should not be changed mid-packet or mid-FEC group.
 108   DCHECK(fec_group_.get() == nullptr && queued_frames_.empty());
 109   max_packet_length_ = length;
 110   max_plaintext_size_ = framer_->GetMaxPlaintextSize(max_packet_length_);
 111 }
 112
 113 void QuicPacketCreator::set_max_packets_per_fec_group(
 114     size_t max_packets_per_fec_group) {
 115   max_packets_per_fec_group_ = max(kLowestMaxPacketsPerFecGroup,
 116                                    max_packets_per_fec_group);
 117   DCHECK_LT(0u, max_packets_per_fec_group_);
 118 }
 119
 120 bool QuicPacketCreator::ShouldSendFec(bool force_close) const {
 121   DCHECK(!HasPendingFrames());
 122   return fec_group_.get() != nullptr && fec_group_->NumReceivedPackets() > 0 &&
 123          (force_close ||
 124           fec_group_->NumReceivedPackets() >= max_packets_per_fec_group_);
 125 }
 126
 127 bool QuicPacketCreator::IsFecGroupOpen() const {
 128   return fec_group_.get() != nullptr;
 129 }
 130
 131 void QuicPacketCreator::StartFecProtectingPackets() {
 132   if (!IsFecEnabled()) {
 133     LOG(DFATAL) << "Cannot start FEC protection when FEC is not enabled.";
 134     return;
 135   }
 136   // TODO(jri): This currently requires that the generator flush out any
 137   // pending frames when FEC protection is turned on. If current packet can be
 138   // converted to an FEC protected packet, do it. This will require the
 139   // generator to check if the resulting expansion still allows the incoming
 140   // frame to be added to the packet.
 141   if (HasPendingFrames()) {
 142     LOG(DFATAL) << "Cannot start FEC protection with pending frames.";
 143     return;
 144   }
 145   DCHECK(!should_fec_protect_);
 146   should_fec_protect_ = true;
 147 }
 148
 149 void QuicPacketCreator::StopFecProtectingPackets() {
 150   if (fec_group_.get() != nullptr) {
 151     LOG(DFATAL) << "Cannot stop FEC protection with open FEC group.";
 152     return;
 153   }
 154   DCHECK(should_fec_protect_);
 155   should_fec_protect_ = false;
 156   fec_group_number_ = 0;
 157 }
 158
 159 bool QuicPacketCreator::IsFecProtected() const {
 160   return should_fec_protect_;
 161 }
 162
 163 bool QuicPacketCreator::IsFecEnabled() const {
 164   return max_packets_per_fec_group_ > 0;
 165 }
 166
 167 InFecGroup QuicPacketCreator::MaybeUpdateLengthsAndStartFec() {
 168   if (fec_group_.get() != nullptr) {
 169     // Don't update any lengths when an FEC group is open, to ensure same
 170     // packet header size in all packets within a group.
 171     return IN_FEC_GROUP;
 172   }
 173   if (!queued_frames_.empty()) {
 174     // Don't change creator state if there are frames queued.
 175     return fec_group_.get() == nullptr ? NOT_IN_FEC_GROUP : IN_FEC_GROUP;
 176   }
 177
 178   // Update sequence number length only on packet and FEC group boundaries.
 179   sequence_number_length_ = next_sequence_number_length_;
 180
 181   if (!should_fec_protect_) {
 182     return NOT_IN_FEC_GROUP;
 183   }
 184   // Start a new FEC group since protection is on. Set the fec group number to
 185   // the sequence number of the next packet.
 186   fec_group_number_ = sequence_number() + 1;
 187   fec_group_.reset(new QuicFecGroup());
 188   return IN_FEC_GROUP;
 189 }
 190
 191 // Stops serializing version of the protocol in packets sent after this call.
 192 // A packet that is already open might send kQuicVersionSize bytes less than the
 193 // maximum packet size if we stop sending version before it is serialized.
 194 void QuicPacketCreator::StopSendingVersion() {
 195   DCHECK(send_version_in_packet_);
 196   send_version_in_packet_ = false;
 197   if (packet_size_ > 0) {
 198     DCHECK_LT(kQuicVersionSize, packet_size_);
 199     packet_size_ -= kQuicVersionSize;
 200   }
 201 }
 202
 203 void QuicPacketCreator::UpdateSequenceNumberLength(
 204       QuicPacketSequenceNumber least_packet_awaited_by_peer,
 205       QuicPacketCount max_packets_in_flight) {
 206   DCHECK_LE(least_packet_awaited_by_peer, sequence_number_ + 1);
 207   // Since the packet creator will not change sequence number length mid FEC
 208   // group, include the size of an FEC group to be safe.
 209   const QuicPacketSequenceNumber current_delta =
 210       max_packets_per_fec_group_ + sequence_number_ + 1
 211       - least_packet_awaited_by_peer;
 212   const uint64 delta = max(current_delta, max_packets_in_flight);
 213   next_sequence_number_length_ =
 214       QuicFramer::GetMinSequenceNumberLength(delta * 4);
 215 }
 216
 217 bool QuicPacketCreator::HasRoomForStreamFrame(QuicStreamId id,
 218                                               QuicStreamOffset offset) const {
 219   // TODO(jri): This is a simple safe decision for now, but make
 220   // is_in_fec_group a parameter. Same as with all public methods in
 221   // QuicPacketCreator.
 222   return BytesFree() >
 223       QuicFramer::GetMinStreamFrameSize(id, offset, true,
 224                                         should_fec_protect_ ? IN_FEC_GROUP :
 225                                                               NOT_IN_FEC_GROUP);
 226 }
 227
 228 // static
 229 size_t QuicPacketCreator::StreamFramePacketOverhead(
 230     QuicConnectionIdLength connection_id_length,
 231     bool include_version,
 232     QuicSequenceNumberLength sequence_number_length,
 233     QuicStreamOffset offset,
 234     InFecGroup is_in_fec_group) {
 235   return GetPacketHeaderSize(connection_id_length, include_version,
 236                              sequence_number_length, is_in_fec_group) +
 237       // Assumes this is a stream with a single lone packet.
 238       QuicFramer::GetMinStreamFrameSize(1u, offset, true, is_in_fec_group);
 239 }
 240
 241 size_t QuicPacketCreator::CreateStreamFrame(QuicStreamId id,
 242                                             const IOVector& data,
 243                                             QuicStreamOffset offset,
 244                                             bool fin,
 245                                             QuicFrame* frame) {
 246   DCHECK_GT(max_packet_length_, StreamFramePacketOverhead(
 247                 connection_id_length_, kIncludeVersion,
 248                 PACKET_6BYTE_SEQUENCE_NUMBER, offset, IN_FEC_GROUP));
 249
 250   InFecGroup is_in_fec_group = MaybeUpdateLengthsAndStartFec();
 251
 252   LOG_IF(DFATAL, !HasRoomForStreamFrame(id, offset))
 253       << "No room for Stream frame, BytesFree: " << BytesFree()
 254       << " MinStreamFrameSize: "
 255       << QuicFramer::GetMinStreamFrameSize(id, offset, true, is_in_fec_group);
 256
 257   if (data.Empty()) {
 258     LOG_IF(DFATAL, !fin)
 259         << "Creating a stream frame with no data or fin.";
 260     // Create a new packet for the fin, if necessary.
 261     *frame = QuicFrame(new QuicStreamFrame(id, true, offset, data));
 262     return 0;
 263   }
 264
 265   const size_t data_size = data.TotalBufferSize();
 266   size_t min_frame_size = QuicFramer::GetMinStreamFrameSize(
 267       id, offset, /* last_frame_in_packet= */ true, is_in_fec_group);
 268   size_t bytes_consumed = min<size_t>(BytesFree() - min_frame_size, data_size);
 269
 270   bool set_fin = fin && bytes_consumed == data_size;  // Last frame.
 271   IOVector frame_data;
 272   frame_data.AppendIovecAtMostBytes(data.iovec(), data.Size(),
 273                                     bytes_consumed);
 274   DCHECK_EQ(frame_data.TotalBufferSize(), bytes_consumed);
 275   *frame = QuicFrame(new QuicStreamFrame(id, set_fin, offset, frame_data));
 276   return bytes_consumed;
 277 }
 278
 279 SerializedPacket QuicPacketCreator::ReserializeAllFrames(
 280     const RetransmittableFrames& frames,
 281     QuicSequenceNumberLength original_length,
 282     char* buffer,
 283     size_t buffer_len) {
 284   DCHECK(fec_group_.get() == nullptr);
 285   const QuicSequenceNumberLength saved_length = sequence_number_length_;
 286   const QuicSequenceNumberLength saved_next_length =
 287       next_sequence_number_length_;
 288   const bool saved_should_fec_protect = should_fec_protect_;
 289   const EncryptionLevel default_encryption_level = encryption_level_;
 290
 291   // Temporarily set the sequence number length, stop FEC protection,
 292   // and change the encryption level.
 293   sequence_number_length_ = original_length;
 294   next_sequence_number_length_ = original_length;
 295   should_fec_protect_ = false;
 296   encryption_level_ = frames.encryption_level();
 297
 298   // Serialize the packet and restore the FEC and sequence number length state.
 299   SerializedPacket serialized_packet =
 300       SerializeAllFrames(frames.frames(), buffer, buffer_len);
 301   sequence_number_length_ = saved_length;
 302   next_sequence_number_length_ = saved_next_length;
 303   should_fec_protect_ = saved_should_fec_protect;
 304   encryption_level_ = default_encryption_level;
 305
 306   return serialized_packet;
 307 }
 308
 309 SerializedPacket QuicPacketCreator::SerializeAllFrames(const QuicFrames& frames,
 310                                                        char* buffer,
 311                                                        size_t buffer_len) {
 312   LOG_IF(DFATAL, !queued_frames_.empty()) << "Frames already queued.";
 313   LOG_IF(DFATAL, frames.empty())
 314       << "Attempt to serialize empty packet";
 315   for (const QuicFrame& frame : frames) {
 316     bool success = AddFrame(frame, false);
 317     DCHECK(success);
 318   }
 319   SerializedPacket packet = SerializePacket(buffer, buffer_len);
 320   DCHECK(packet.retransmittable_frames == nullptr);
 321   return packet;
 322 }
 323
 324 bool QuicPacketCreator::HasPendingFrames() const {
 325   return !queued_frames_.empty();
 326 }
 327
 328 bool QuicPacketCreator::HasPendingRetransmittableFrames() const {
 329   return queued_retransmittable_frames_.get() != nullptr &&
 330          !queued_retransmittable_frames_->frames().empty();
 331 }
 332
 333 size_t QuicPacketCreator::ExpansionOnNewFrame() const {
 334   // If packet is FEC protected, there's no expansion.
 335   if (should_fec_protect_) {
 336       return 0;
 337   }
 338   // If the last frame in the packet is a stream frame, then it will expand to
 339   // include the stream_length field when a new frame is added.
 340   bool has_trailing_stream_frame =
 341       !queued_frames_.empty() && queued_frames_.back().type == STREAM_FRAME;
 342   return has_trailing_stream_frame ? kQuicStreamPayloadLengthSize : 0;
 343 }
 344
 345 size_t QuicPacketCreator::BytesFree() const {
 346   DCHECK_GE(max_plaintext_size_, PacketSize());
 347   return max_plaintext_size_ - min(max_plaintext_size_, PacketSize()
 348                                    + ExpansionOnNewFrame());
 349 }
 350
 351 size_t QuicPacketCreator::PacketSize() const {
 352   if (!queued_frames_.empty()) {
 353     return packet_size_;
 354   }
 355   if (fec_group_.get() == nullptr) {
 356     // Update sequence number length on packet and FEC boundary.
 357     sequence_number_length_ = next_sequence_number_length_;
 358   }
 359   packet_size_ = GetPacketHeaderSize(
 360       connection_id_length_, send_version_in_packet_, sequence_number_length_,
 361       should_fec_protect_ ? IN_FEC_GROUP : NOT_IN_FEC_GROUP);
 362   return packet_size_;
 363 }
 364
 365 bool QuicPacketCreator::AddSavedFrame(const QuicFrame& frame) {
 366   return AddFrame(frame, true);
 367 }
 368
 369 SerializedPacket QuicPacketCreator::SerializePacket(
 370     char* encrypted_buffer,
 371     size_t encrypted_buffer_len) {
 372   DCHECK_LT(0u, encrypted_buffer_len);
 373   LOG_IF(DFATAL, queued_frames_.empty())
 374       << "Attempt to serialize empty packet";
 375   DCHECK_GE(sequence_number_ + 1, fec_group_number_);
 376   QuicPacketHeader header;
 377   FillPacketHeader(should_fec_protect_ ? fec_group_number_ : 0, false, &header);
 378
 379   MaybeAddPadding();
 380
 381   DCHECK_GE(max_plaintext_size_, packet_size_);
 382   // ACK Frames will be truncated due to length only if they're the only frame
 383   // in the packet, and if packet_size_ was set to max_plaintext_size_. If
 384   // truncation due to length occurred, then GetSerializedFrameLength will have
 385   // returned all bytes free.
 386   bool possibly_truncated_by_length = packet_size_ == max_plaintext_size_ &&
 387                                       queued_frames_.size() == 1 &&
 388                                       queued_frames_.back().type == ACK_FRAME;
 389   char buffer[kMaxPacketSize];
 390   scoped_ptr<QuicPacket> packet;
 391   // Use the packet_size_ instead of the buffer size to ensure smaller
 392   // packet sizes are properly used.
 393   scoped_ptr<char[]> large_buffer;
 394   if (packet_size_ <= kMaxPacketSize) {
 395     packet.reset(
 396         framer_->BuildDataPacket(header, queued_frames_, buffer, packet_size_));
 397   } else {
 398     large_buffer.reset(new char[packet_size_]);
 399     packet.reset(framer_->BuildDataPacket(header, queued_frames_,
 400                                           large_buffer.get(), packet_size_));
 401   }
 402   OnBuiltFecProtectedPayload(header, packet->FecProtectedData());
 403
 404   LOG_IF(DFATAL, packet == nullptr) << "Failed to serialize "
 405                                     << queued_frames_.size() << " frames.";
 406   // Because of possible truncation, we can't be confident that our
 407   // packet size calculation worked correctly.
 408   if (!possibly_truncated_by_length) {
 409     DCHECK_EQ(packet_size_, packet->length());
 410   }
 411   // Immediately encrypt the packet, to ensure we don't encrypt the same packet
 412   // sequence number multiple times.
 413   QuicEncryptedPacket* encrypted =
 414       framer_->EncryptPacket(encryption_level_, sequence_number_, *packet,
 415                              encrypted_buffer, encrypted_buffer_len);
 416   if (encrypted == nullptr) {
 417     LOG(DFATAL) << "Failed to encrypt packet number " << sequence_number_;
 418     return NoPacket();
 419   }
 420
 421   packet_size_ = 0;
 422   queued_frames_.clear();
 423   return SerializedPacket(header.packet_sequence_number,
 424                           header.public_header.sequence_number_length,
 425                           encrypted, QuicFramer::GetPacketEntropyHash(header),
 426                           queued_retransmittable_frames_.release());
 427 }
 428
 429 SerializedPacket QuicPacketCreator::SerializeFec(char* buffer,
 430                                                  size_t buffer_len) {
 431   DCHECK_LT(0u, buffer_len);
 432   if (fec_group_.get() == nullptr || fec_group_->NumReceivedPackets() <= 0) {
 433     LOG(DFATAL) << "SerializeFEC called but no group or zero packets in group.";
 434     // TODO(jri): Make this a public method of framer?
 435     return NoPacket();
 436   }
 437   DCHECK_EQ(0u, queued_frames_.size());
 438   QuicPacketHeader header;
 439   FillPacketHeader(fec_group_number_, true, &header);
 440   QuicFecData fec_data;
 441   fec_data.fec_group = fec_group_->min_protected_packet();
 442   fec_data.redundancy = fec_group_->payload_parity();
 443   scoped_ptr<QuicPacket> packet(framer_->BuildFecPacket(header, fec_data));
 444   fec_group_.reset(nullptr);
 445   packet_size_ = 0;
 446   LOG_IF(DFATAL, packet == nullptr)
 447       << "Failed to serialize fec packet for group:" << fec_data.fec_group;
 448   DCHECK_GE(max_packet_length_, packet->length());
 449   // Immediately encrypt the packet, to ensure we don't encrypt the same packet
 450   // sequence number multiple times.
 451   QuicEncryptedPacket* encrypted = framer_->EncryptPacket(
 452       encryption_level_, sequence_number_, *packet, buffer, buffer_len);
 453   if (encrypted == nullptr) {
 454     LOG(DFATAL) << "Failed to encrypt packet number " << sequence_number_;
 455     return NoPacket();
 456   }
 457   SerializedPacket serialized(
 458       header.packet_sequence_number,
 459       header.public_header.sequence_number_length, encrypted,
 460       QuicFramer::GetPacketEntropyHash(header), nullptr);
 461   serialized.is_fec_packet = true;
 462   return serialized;
 463 }
 464
 465 QuicEncryptedPacket* QuicPacketCreator::SerializeVersionNegotiationPacket(
 466     const QuicVersionVector& supported_versions) {
 467   DCHECK_EQ(Perspective::IS_SERVER, framer_->perspective());
 468   QuicPacketPublicHeader header;
 469   header.connection_id = connection_id_;
 470   header.reset_flag = false;
 471   header.version_flag = true;
 472   header.versions = supported_versions;
 473   QuicEncryptedPacket* encrypted =
 474       framer_->BuildVersionNegotiationPacket(header, supported_versions);
 475   DCHECK(encrypted);
 476   DCHECK_GE(max_packet_length_, encrypted->length());
 477   return encrypted;
 478 }
 479
 480 SerializedPacket QuicPacketCreator::NoPacket() {
 481   return SerializedPacket(0, PACKET_1BYTE_SEQUENCE_NUMBER, nullptr, 0, nullptr);
 482 }
 483
 484 void QuicPacketCreator::FillPacketHeader(QuicFecGroupNumber fec_group,
 485                                          bool fec_flag,
 486                                          QuicPacketHeader* header) {
 487   header->public_header.connection_id = connection_id_;
 488   header->public_header.connection_id_length = connection_id_length_;
 489   header->public_header.reset_flag = false;
 490   header->public_header.version_flag = send_version_in_packet_;
 491   header->fec_flag = fec_flag;
 492   header->packet_sequence_number = ++sequence_number_;
 493   header->public_header.sequence_number_length = sequence_number_length_;
 494   header->entropy_flag = random_bool_source_->RandBool();
 495   header->is_in_fec_group = fec_group == 0 ? NOT_IN_FEC_GROUP : IN_FEC_GROUP;
 496   header->fec_group = fec_group;
 497 }
 498
 499 bool QuicPacketCreator::ShouldRetransmit(const QuicFrame& frame) {
 500   switch (frame.type) {
 501     case ACK_FRAME:
 502     case PADDING_FRAME:
 503     case STOP_WAITING_FRAME:
 504       return false;
 505     default:
 506       return true;
 507   }
 508 }
 509
 510 bool QuicPacketCreator::AddFrame(const QuicFrame& frame,
 511                                  bool save_retransmittable_frames) {
 512   DVLOG(1) << "Adding frame: " << frame;
 513   InFecGroup is_in_fec_group = MaybeUpdateLengthsAndStartFec();
 514
 515   size_t frame_len = framer_->GetSerializedFrameLength(
 516       frame, BytesFree(), queued_frames_.empty(), true, is_in_fec_group,
 517       sequence_number_length_);
 518   if (frame_len == 0) {
 519     return false;
 520   }
 521   DCHECK_LT(0u, packet_size_);
 522   packet_size_ += ExpansionOnNewFrame() + frame_len;
 523
 524   if (save_retransmittable_frames && ShouldRetransmit(frame)) {
 525     if (queued_retransmittable_frames_.get() == nullptr) {
 526       queued_retransmittable_frames_.reset(
 527           new RetransmittableFrames(encryption_level_));
 528     }
 529     if (frame.type == STREAM_FRAME) {
 530       queued_frames_.push_back(
 531           queued_retransmittable_frames_->AddStreamFrame(frame.stream_frame));
 532     } else {
 533       queued_frames_.push_back(
 534           queued_retransmittable_frames_->AddNonStreamFrame(frame));
 535     }
 536   } else {
 537     queued_frames_.push_back(frame);
 538   }
 539   return true;
 540 }
 541
 542 void QuicPacketCreator::MaybeAddPadding() {
 543   if (BytesFree() == 0) {
 544     // Don't pad full packets.
 545     return;
 546   }
 547
 548   // Since ReserializeAllFrames does not populate queued_retransmittable_frames_
 549   // it's not sufficient to simply call
 550   // queued_retransmittable_frames_->HasCryptoHandshake().
 551   // TODO(rch): we should really make ReserializeAllFrames not be a special
 552   // case!
 553
 554   // If any of the frames in the current packet are on the crypto stream
 555   // then they contain handshake messagses, and we should pad them.
 556   bool is_handshake = false;
 557   for (const QuicFrame& frame : queued_frames_) {
 558     if (frame.type == STREAM_FRAME &&
 559         frame.stream_frame->stream_id == kCryptoStreamId) {
 560       is_handshake = true;
 561       break;
 562     }
 563   }
 564   if (!is_handshake) {
 565     return;
 566   }
 567
 568   QuicPaddingFrame padding;
 569   bool success = AddFrame(QuicFrame(&padding), false);
 570   DCHECK(success);
 571 }
 572
 573 }  // namespace net