net/quic/quic_packet_generator.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_generator.h"
   6
   7 #include "base/basictypes.h"
   8 #include "base/logging.h"
   9 #include "net/quic/quic_ack_notifier.h"
  10 #include "net/quic/quic_fec_group.h"
  11 #include "net/quic/quic_flags.h"
  12 #include "net/quic/quic_utils.h"
  13
  14 using base::StringPiece;
  15
  16 namespace net {
  17
  18 namespace {
  19
  20 // We want to put some space between a protected packet and the FEC packet to
  21 // avoid losing them both within the same loss episode. On the other hand, we
  22 // expect to be able to recover from any loss in about an RTT. We resolve this
  23 // tradeoff by sending an FEC packet atmost half an RTT, or equivalently, half
  24 // the max number of in-flight packets,  the first protected packet. Since we
  25 // don't want to delay an FEC packet past half an RTT, we set the max FEC group
  26 // size to be half the current congestion window.
  27 const float kMaxPacketsInFlightMultiplierForFecGroupSize = 0.5;
  28 const float kRttMultiplierForFecTimeout = 0.5;
  29
  30 // Minimum timeout for FEC alarm, set to half the minimum Tail Loss Probe
  31 // timeout of 10ms.
  32 const int64 kMinFecTimeoutMs = 5u;
  33
  34 }  // namespace
  35
  36 class QuicAckNotifier;
  37
  38 QuicPacketGenerator::QuicPacketGenerator(QuicConnectionId connection_id,
  39                                          QuicFramer* framer,
  40                                          QuicRandom* random_generator,
  41                                          DelegateInterface* delegate)
  42     : delegate_(delegate),
  43       debug_delegate_(nullptr),
  44       packet_creator_(connection_id, framer, random_generator),
  45       batch_mode_(false),
  46       fec_timeout_(QuicTime::Delta::Zero()),
  47       should_fec_protect_(false),
  48       // TODO(rtenneti): Add the ability to set a different policy.
  49       fec_send_policy_(FEC_ANY_TRIGGER),
  50       should_send_ack_(false),
  51       should_send_stop_waiting_(false),
  52       ack_queued_(false),
  53       stop_waiting_queued_(false) {
  54 }
  55
  56 QuicPacketGenerator::~QuicPacketGenerator() {
  57   for (QuicFrame& frame : queued_control_frames_) {
  58     switch (frame.type) {
  59       case PADDING_FRAME:
  60         delete frame.padding_frame;
  61         break;
  62       case STREAM_FRAME:
  63         delete frame.stream_frame;
  64         break;
  65       case ACK_FRAME:
  66         delete frame.ack_frame;
  67         break;
  68       case RST_STREAM_FRAME:
  69         delete frame.rst_stream_frame;
  70         break;
  71       case CONNECTION_CLOSE_FRAME:
  72         delete frame.connection_close_frame;
  73         break;
  74       case GOAWAY_FRAME:
  75         delete frame.goaway_frame;
  76         break;
  77       case WINDOW_UPDATE_FRAME:
  78         delete frame.window_update_frame;
  79         break;
  80       case BLOCKED_FRAME:
  81         delete frame.blocked_frame;
  82         break;
  83       case STOP_WAITING_FRAME:
  84         delete frame.stop_waiting_frame;
  85         break;
  86       case PING_FRAME:
  87         delete frame.ping_frame;
  88         break;
  89       case NUM_FRAME_TYPES:
  90         DCHECK(false) << "Cannot delete type: " << frame.type;
  91     }
  92   }
  93 }
  94
  95 void QuicPacketGenerator::OnCongestionWindowChange(
  96     QuicPacketCount max_packets_in_flight) {
  97   packet_creator_.set_max_packets_per_fec_group(
  98       static_cast<size_t>(kMaxPacketsInFlightMultiplierForFecGroupSize *
  99                           max_packets_in_flight));
 100 }
 101
 102 void QuicPacketGenerator::OnRttChange(QuicTime::Delta rtt) {
 103   fec_timeout_ = rtt.Multiply(kRttMultiplierForFecTimeout);
 104 }
 105
 106 void QuicPacketGenerator::SetShouldSendAck(bool also_send_stop_waiting) {
 107   if (ack_queued_) {
 108     // Ack already queued, nothing to do.
 109     return;
 110   }
 111
 112   if (also_send_stop_waiting && stop_waiting_queued_) {
 113     LOG(DFATAL) << "Should only ever be one pending stop waiting frame.";
 114     return;
 115   }
 116
 117   should_send_ack_ = true;
 118   should_send_stop_waiting_ = also_send_stop_waiting;
 119   SendQueuedFrames(/*flush=*/false, /*is_fec_timeout=*/false);
 120 }
 121
 122 void QuicPacketGenerator::AddControlFrame(const QuicFrame& frame) {
 123   queued_control_frames_.push_back(frame);
 124   SendQueuedFrames(/*flush=*/false, /*is_fec_timeout=*/false);
 125 }
 126
 127 QuicConsumedData QuicPacketGenerator::ConsumeData(
 128     QuicStreamId id,
 129     const IOVector& data_to_write,
 130     QuicStreamOffset offset,
 131     bool fin,
 132     FecProtection fec_protection,
 133     QuicAckNotifier::DelegateInterface* delegate) {
 134   bool has_handshake = id == kCryptoStreamId;
 135   // To make reasoning about crypto frames easier, we don't combine them with
 136   // other retransmittable frames in a single packet.
 137   const bool flush =
 138       has_handshake && packet_creator_.HasPendingRetransmittableFrames();
 139   SendQueuedFrames(flush, /*is_fec_timeout=*/false);
 140
 141   size_t total_bytes_consumed = 0;
 142   bool fin_consumed = false;
 143
 144   if (!packet_creator_.HasRoomForStreamFrame(id, offset)) {
 145     SerializeAndSendPacket();
 146   }
 147
 148   if (fec_protection == MUST_FEC_PROTECT) {
 149     MaybeStartFecProtection();
 150   }
 151
 152   // This notifier will be owned by the AckNotifierManager (or deleted below) if
 153   // not attached to a packet.
 154   QuicAckNotifier* notifier = nullptr;
 155   if (delegate != nullptr) {
 156     notifier = new QuicAckNotifier(delegate);
 157   }
 158
 159   IOVector data = data_to_write;
 160   size_t data_size = data.TotalBufferSize();
 161   if (!fin && (data_size == 0)) {
 162     LOG(DFATAL) << "Attempt to consume empty data without FIN.";
 163     return QuicConsumedData(0, false);
 164   }
 165
 166   int frames_created = 0;
 167   while (delegate_->ShouldGeneratePacket(
 168       HAS_RETRANSMITTABLE_DATA, has_handshake ? IS_HANDSHAKE : NOT_HANDSHAKE)) {
 169     QuicFrame frame;
 170     scoped_ptr<char[]> buffer;
 171     size_t bytes_consumed = packet_creator_.CreateStreamFrame(
 172         id, &data, offset + total_bytes_consumed, fin, &frame, &buffer);
 173     ++frames_created;
 174
 175     // We want to track which packet this stream frame ends up in.
 176     if (notifier != nullptr) {
 177       ack_notifiers_.push_back(notifier);
 178     }
 179
 180     if (!AddFrame(frame, buffer.get())) {
 181       LOG(DFATAL) << "Failed to add stream frame.";
 182       // Inability to add a STREAM frame creates an unrecoverable hole in a
 183       // the stream, so it's best to close the connection.
 184       delegate_->CloseConnection(QUIC_INTERNAL_ERROR, false);
 185       delete notifier;
 186       return QuicConsumedData(0, false);
 187     }
 188     // When AddFrame succeeds, it takes ownership of the buffer.
 189     ignore_result(buffer.release());
 190
 191     total_bytes_consumed += bytes_consumed;
 192     fin_consumed = fin && total_bytes_consumed == data_size;
 193     DCHECK(data.Empty() || packet_creator_.BytesFree() == 0u);
 194
 195     // TODO(ianswett): Restore packet reordering.
 196     if (!InBatchMode() || !packet_creator_.HasRoomForStreamFrame(id, offset)) {
 197       // TODO(rtenneti): remove MaybeSendFecPacketAndCloseGroup() from inside
 198       // SerializeAndSendPacket() and make it an explicit call here (and
 199       // elsewhere where we call SerializeAndSendPacket?).
 200       SerializeAndSendPacket();
 201     }
 202
 203     if (data.Empty()) {
 204       // We're done writing the data. Exit the loop.
 205       // We don't make this a precondition because we could have 0 bytes of data
 206       // if we're simply writing a fin.
 207       if (fec_protection == MUST_FEC_PROTECT) {
 208         // Turn off FEC protection when we're done writing protected data.
 209         DVLOG(1) << "Turning FEC protection OFF";
 210         should_fec_protect_ = false;
 211       }
 212       break;
 213     }
 214   }
 215
 216   if (notifier != nullptr && frames_created == 0) {
 217     // Safe to delete the AckNotifer as it was never attached to a packet.
 218     delete notifier;
 219   }
 220
 221   // Don't allow the handshake to be bundled with other retransmittable frames.
 222   if (has_handshake) {
 223     SendQueuedFrames(/*flush=*/true, /*is_fec_timeout=*/false);
 224   }
 225
 226   // Try to close FEC group since we've either run out of data to send or we're
 227   // blocked. If not in batch mode, force close the group.
 228   MaybeSendFecPacketAndCloseGroup(/*force=*/false, /*is_fec_timeout=*/false);
 229
 230   DCHECK(InBatchMode() || !packet_creator_.HasPendingFrames());
 231   return QuicConsumedData(total_bytes_consumed, fin_consumed);
 232 }
 233
 234 bool QuicPacketGenerator::CanSendWithNextPendingFrameAddition() const {
 235   DCHECK(HasPendingFrames());
 236   HasRetransmittableData retransmittable =
 237       (should_send_ack_ || should_send_stop_waiting_)
 238           ? NO_RETRANSMITTABLE_DATA
 239           : HAS_RETRANSMITTABLE_DATA;
 240   if (retransmittable == HAS_RETRANSMITTABLE_DATA) {
 241       DCHECK(!queued_control_frames_.empty());  // These are retransmittable.
 242   }
 243   return delegate_->ShouldGeneratePacket(retransmittable, NOT_HANDSHAKE);
 244 }
 245
 246 void QuicPacketGenerator::SendQueuedFrames(bool flush, bool is_fec_timeout) {
 247   // Only add pending frames if we are SURE we can then send the whole packet.
 248   while (HasPendingFrames() &&
 249          (flush || CanSendWithNextPendingFrameAddition())) {
 250     if (!AddNextPendingFrame()) {
 251       // Packet was full, so serialize and send it.
 252       SerializeAndSendPacket();
 253     }
 254   }
 255   if (packet_creator_.HasPendingFrames() && (flush || !InBatchMode())) {
 256     SerializeAndSendPacket();
 257   }
 258   MaybeSendFecPacketAndCloseGroup(flush, is_fec_timeout);
 259 }
 260
 261 void QuicPacketGenerator::MaybeStartFecProtection() {
 262   if (!packet_creator_.IsFecEnabled()) {
 263     return;
 264   }
 265   DVLOG(1) << "Turning FEC protection ON";
 266   should_fec_protect_ = true;
 267   if (packet_creator_.IsFecProtected()) {
 268     // Only start creator's FEC protection if not already on.
 269     return;
 270   }
 271   if (HasQueuedFrames()) {
 272     // TODO(jri): This currently requires that the generator flush out any
 273     // pending frames when FEC protection is turned on. If current packet can be
 274     // converted to an FEC protected packet, do it. This will require the
 275     // generator to check if the resulting expansion still allows the incoming
 276     // frame to be added to the packet.
 277     SendQueuedFrames(/*flush=*/true, /*is_fec_timeout=*/false);
 278   }
 279   packet_creator_.StartFecProtectingPackets();
 280   DCHECK(packet_creator_.IsFecProtected());
 281 }
 282
 283 void QuicPacketGenerator::MaybeSendFecPacketAndCloseGroup(bool force,
 284                                                           bool is_fec_timeout) {
 285   if (!ShouldSendFecPacket(force)) {
 286     return;
 287   }
 288
 289   // If we want to send FEC packet only when FEC alaram goes off and if it is
 290   // not a FEC timeout then close the group and dont send FEC packet.
 291   if (fec_send_policy_ == FEC_ALARM_TRIGGER && !is_fec_timeout) {
 292     ResetFecGroup();
 293   } else {
 294     // TODO(jri): SerializeFec can return a NULL packet, and this should
 295     // cause an early return, with a call to delegate_->OnPacketGenerationError.
 296     char buffer[kMaxPacketSize];
 297     SerializedPacket serialized_fec =
 298         packet_creator_.SerializeFec(buffer, kMaxPacketSize);
 299     DCHECK(serialized_fec.packet);
 300     delegate_->OnSerializedPacket(serialized_fec);
 301   }
 302   // Turn FEC protection off if creator's protection is on and the creator
 303   // does not have an open FEC group.
 304   // Note: We only wait until the frames queued in the creator are flushed;
 305   // pending frames in the generator will not keep us from turning FEC off.
 306   if (!should_fec_protect_ && !packet_creator_.IsFecGroupOpen()) {
 307     packet_creator_.StopFecProtectingPackets();
 308     DCHECK(!packet_creator_.IsFecProtected());
 309   }
 310 }
 311
 312 bool QuicPacketGenerator::ShouldSendFecPacket(bool force) {
 313   return packet_creator_.IsFecProtected() &&
 314          !packet_creator_.HasPendingFrames() &&
 315          packet_creator_.ShouldSendFec(force);
 316 }
 317
 318 void QuicPacketGenerator::ResetFecGroup() {
 319   DCHECK(packet_creator_.IsFecGroupOpen());
 320   packet_creator_.ResetFecGroup();
 321   delegate_->OnResetFecGroup();
 322 }
 323
 324 void QuicPacketGenerator::OnFecTimeout() {
 325   DCHECK(!InBatchMode());
 326   if (!ShouldSendFecPacket(true)) {
 327     LOG(DFATAL) << "No FEC packet to send on FEC timeout.";
 328     return;
 329   }
 330   // Flush out any pending frames in the generator and the creator, and then
 331   // send out FEC packet.
 332   SendQueuedFrames(/*flush=*/true, /*is_fec_timeout=*/true);
 333   MaybeSendFecPacketAndCloseGroup(/*force=*/true, /*is_fec_timeout=*/true);
 334 }
 335
 336 QuicTime::Delta QuicPacketGenerator::GetFecTimeout(
 337     QuicPacketSequenceNumber sequence_number) {
 338   // Do not set up FEC alarm for |sequence_number| it is not the first packet in
 339   // the current group.
 340   if (packet_creator_.IsFecGroupOpen() &&
 341       (sequence_number == packet_creator_.fec_group_number())) {
 342     return QuicTime::Delta::Max(
 343         fec_timeout_, QuicTime::Delta::FromMilliseconds(kMinFecTimeoutMs));
 344   }
 345   return QuicTime::Delta::Infinite();
 346 }
 347
 348 bool QuicPacketGenerator::InBatchMode() {
 349   return batch_mode_;
 350 }
 351
 352 void QuicPacketGenerator::StartBatchOperations() {
 353   batch_mode_ = true;
 354 }
 355
 356 void QuicPacketGenerator::FinishBatchOperations() {
 357   batch_mode_ = false;
 358   SendQueuedFrames(/*flush=*/false, /*is_fec_timeout=*/false);
 359 }
 360
 361 void QuicPacketGenerator::FlushAllQueuedFrames() {
 362   SendQueuedFrames(/*flush=*/true, /*is_fec_timeout=*/false);
 363 }
 364
 365 bool QuicPacketGenerator::HasQueuedFrames() const {
 366   return packet_creator_.HasPendingFrames() || HasPendingFrames();
 367 }
 368
 369 bool QuicPacketGenerator::HasPendingFrames() const {
 370   return should_send_ack_ || should_send_stop_waiting_ ||
 371          !queued_control_frames_.empty();
 372 }
 373
 374 bool QuicPacketGenerator::AddNextPendingFrame() {
 375   if (should_send_ack_) {
 376     delegate_->PopulateAckFrame(&pending_ack_frame_);
 377     ack_queued_ = true;
 378     // If we can't this add the frame now, then we still need to do so later.
 379     should_send_ack_ = !AddFrame(QuicFrame(&pending_ack_frame_), nullptr);
 380     // Return success if we have cleared out this flag (i.e., added the frame).
 381     // If we still need to send, then the frame is full, and we have failed.
 382     return !should_send_ack_;
 383   }
 384
 385   if (should_send_stop_waiting_) {
 386     delegate_->PopulateStopWaitingFrame(&pending_stop_waiting_frame_);
 387     stop_waiting_queued_ = true;
 388     // If we can't this add the frame now, then we still need to do so later.
 389     should_send_stop_waiting_ =
 390         !AddFrame(QuicFrame(&pending_stop_waiting_frame_), nullptr);
 391     // Return success if we have cleared out this flag (i.e., added the frame).
 392     // If we still need to send, then the frame is full, and we have failed.
 393     return !should_send_stop_waiting_;
 394   }
 395
 396   LOG_IF(DFATAL, queued_control_frames_.empty())
 397       << "AddNextPendingFrame called with no queued control frames.";
 398   if (!AddFrame(queued_control_frames_.back(), nullptr)) {
 399     // Packet was full.
 400     return false;
 401   }
 402   queued_control_frames_.pop_back();
 403   return true;
 404 }
 405
 406 bool QuicPacketGenerator::AddFrame(const QuicFrame& frame, char* buffer) {
 407   bool success = packet_creator_.AddSavedFrame(frame, buffer);
 408   if (success && debug_delegate_) {
 409     debug_delegate_->OnFrameAddedToPacket(frame);
 410   }
 411   return success;
 412 }
 413
 414 void QuicPacketGenerator::SerializeAndSendPacket() {
 415   char buffer[kMaxPacketSize];
 416   SerializedPacket serialized_packet =
 417       packet_creator_.SerializePacket(buffer, kMaxPacketSize);
 418   DCHECK(serialized_packet.packet);
 419
 420   // There may be AckNotifiers interested in this packet.
 421   serialized_packet.notifiers.swap(ack_notifiers_);
 422   ack_notifiers_.clear();
 423
 424   delegate_->OnSerializedPacket(serialized_packet);
 425   MaybeSendFecPacketAndCloseGroup(/*force=*/false, /*is_fec_timeout=*/false);
 426
 427   // The packet has now been serialized, so the frames are no longer queued.
 428   ack_queued_ = false;
 429   stop_waiting_queued_ = false;
 430 }
 431
 432 void QuicPacketGenerator::StopSendingVersion() {
 433   packet_creator_.StopSendingVersion();
 434 }
 435
 436 QuicPacketSequenceNumber QuicPacketGenerator::sequence_number() const {
 437   return packet_creator_.sequence_number();
 438 }
 439
 440 QuicByteCount QuicPacketGenerator::max_packet_length() const {
 441   return packet_creator_.max_packet_length();
 442 }
 443
 444 void QuicPacketGenerator::set_max_packet_length(QuicByteCount length) {
 445   packet_creator_.SetMaxPacketLength(length);
 446 }
 447
 448 QuicEncryptedPacket* QuicPacketGenerator::SerializeVersionNegotiationPacket(
 449     const QuicVersionVector& supported_versions) {
 450   return packet_creator_.SerializeVersionNegotiationPacket(supported_versions);
 451 }
 452
 453 SerializedPacket QuicPacketGenerator::ReserializeAllFrames(
 454     const RetransmittableFrames& frames,
 455     QuicSequenceNumberLength original_length,
 456     char* buffer,
 457     size_t buffer_len) {
 458   return packet_creator_.ReserializeAllFrames(frames, original_length, buffer,
 459                                               buffer_len);
 460 }
 461
 462 void QuicPacketGenerator::UpdateSequenceNumberLength(
 463       QuicPacketSequenceNumber least_packet_awaited_by_peer,
 464       QuicPacketCount max_packets_in_flight) {
 465   return packet_creator_.UpdateSequenceNumberLength(
 466       least_packet_awaited_by_peer, max_packets_in_flight);
 467 }
 468
 469 void QuicPacketGenerator::SetConnectionIdLength(uint32 length) {
 470   if (length == 0) {
 471     packet_creator_.set_connection_id_length(PACKET_0BYTE_CONNECTION_ID);
 472   } else if (length == 1) {
 473     packet_creator_.set_connection_id_length(PACKET_1BYTE_CONNECTION_ID);
 474   } else if (length <= 4) {
 475     packet_creator_.set_connection_id_length(PACKET_4BYTE_CONNECTION_ID);
 476   } else {
 477     packet_creator_.set_connection_id_length(PACKET_8BYTE_CONNECTION_ID);
 478   }
 479 }
 480
 481 void QuicPacketGenerator::set_encryption_level(EncryptionLevel level) {
 482   packet_creator_.set_encryption_level(level);
 483 }
 484
 485 void QuicPacketGenerator::SetEncrypter(EncryptionLevel level,
 486                                        QuicEncrypter* encrypter) {
 487   packet_creator_.SetEncrypter(level, encrypter);
 488 }
 489
 490 }  // namespace net