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       rtt_multiplier_for_fec_timeout_(kRttMultiplierForFecTimeout),
  48       should_fec_protect_(false),
  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       max_packet_length_(kDefaultMaxPacketSize) {}
  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 MTU_DISCOVERY_FRAME:
  69         delete frame.mtu_discovery_frame;
  70         break;
  71       case RST_STREAM_FRAME:
  72         delete frame.rst_stream_frame;
  73         break;
  74       case CONNECTION_CLOSE_FRAME:
  75         delete frame.connection_close_frame;
  76         break;
  77       case GOAWAY_FRAME:
  78         delete frame.goaway_frame;
  79         break;
  80       case WINDOW_UPDATE_FRAME:
  81         delete frame.window_update_frame;
  82         break;
  83       case BLOCKED_FRAME:
  84         delete frame.blocked_frame;
  85         break;
  86       case STOP_WAITING_FRAME:
  87         delete frame.stop_waiting_frame;
  88         break;
  89       case PING_FRAME:
  90         delete frame.ping_frame;
  91         break;
  92       case NUM_FRAME_TYPES:
  93         DCHECK(false) << "Cannot delete type: " << frame.type;
  94     }
  95   }
  96 }
  97
  98 void QuicPacketGenerator::OnCongestionWindowChange(
  99     QuicPacketCount max_packets_in_flight) {
 100   packet_creator_.set_max_packets_per_fec_group(
 101       static_cast<size_t>(kMaxPacketsInFlightMultiplierForFecGroupSize *
 102                           max_packets_in_flight));
 103 }
 104
 105 void QuicPacketGenerator::OnRttChange(QuicTime::Delta rtt) {
 106   fec_timeout_ = rtt.Multiply(rtt_multiplier_for_fec_timeout_);
 107 }
 108
 109 void QuicPacketGenerator::SetShouldSendAck(bool also_send_stop_waiting) {
 110   if (ack_queued_) {
 111     // Ack already queued, nothing to do.
 112     return;
 113   }
 114
 115   if (also_send_stop_waiting && stop_waiting_queued_) {
 116     LOG(DFATAL) << "Should only ever be one pending stop waiting frame.";
 117     return;
 118   }
 119
 120   should_send_ack_ = true;
 121   should_send_stop_waiting_ = also_send_stop_waiting;
 122   SendQueuedFrames(/*flush=*/false, /*is_fec_timeout=*/false);
 123 }
 124
 125 void QuicPacketGenerator::AddControlFrame(const QuicFrame& frame) {
 126   queued_control_frames_.push_back(frame);
 127   SendQueuedFrames(/*flush=*/false, /*is_fec_timeout=*/false);
 128 }
 129
 130 QuicConsumedData QuicPacketGenerator::ConsumeData(
 131     QuicStreamId id,
 132     const QuicIOVector& iov,
 133     QuicStreamOffset offset,
 134     bool fin,
 135     FecProtection fec_protection,
 136     QuicAckNotifier::DelegateInterface* delegate) {
 137   bool has_handshake = id == kCryptoStreamId;
 138   // To make reasoning about crypto frames easier, we don't combine them with
 139   // other retransmittable frames in a single packet.
 140   const bool flush =
 141       has_handshake && packet_creator_.HasPendingRetransmittableFrames();
 142   SendQueuedFrames(flush, /*is_fec_timeout=*/false);
 143
 144   size_t total_bytes_consumed = 0;
 145   bool fin_consumed = false;
 146
 147   if (!packet_creator_.HasRoomForStreamFrame(id, offset)) {
 148     SerializeAndSendPacket();
 149   }
 150
 151   if (fec_protection == MUST_FEC_PROTECT) {
 152     MaybeStartFecProtection();
 153   }
 154
 155   // This notifier will be owned by the AckNotifierManager (or deleted below) if
 156   // not attached to a packet.
 157   QuicAckNotifier* notifier = nullptr;
 158   if (delegate != nullptr) {
 159     notifier = new QuicAckNotifier(delegate);
 160   }
 161
 162   if (!fin && (iov.total_length == 0)) {
 163     LOG(DFATAL) << "Attempt to consume empty data without FIN.";
 164     return QuicConsumedData(0, false);
 165   }
 166
 167   int frames_created = 0;
 168   while (delegate_->ShouldGeneratePacket(
 169       HAS_RETRANSMITTABLE_DATA, has_handshake ? IS_HANDSHAKE : NOT_HANDSHAKE)) {
 170     QuicFrame frame;
 171     scoped_ptr<char[]> buffer;
 172     size_t bytes_consumed = packet_creator_.CreateStreamFrame(
 173         id, iov, total_bytes_consumed, offset + total_bytes_consumed, fin,
 174         &frame, &buffer);
 175     ++frames_created;
 176
 177     // We want to track which packet this stream frame ends up in.
 178     if (notifier != nullptr) {
 179       ack_notifiers_.push_back(notifier);
 180     }
 181
 182     if (!AddFrame(frame, buffer.get(), has_handshake)) {
 183       LOG(DFATAL) << "Failed to add stream frame.";
 184       // Inability to add a STREAM frame creates an unrecoverable hole in a
 185       // the stream, so it's best to close the connection.
 186       delegate_->CloseConnection(QUIC_INTERNAL_ERROR, false);
 187       delete notifier;
 188       return QuicConsumedData(0, false);
 189     }
 190     // When AddFrame succeeds, it takes ownership of the buffer.
 191     ignore_result(buffer.release());
 192
 193     total_bytes_consumed += bytes_consumed;
 194     fin_consumed = fin && total_bytes_consumed == iov.total_length;
 195     DCHECK(total_bytes_consumed == iov.total_length ||
 196            packet_creator_.BytesFree() == 0u);
 197
 198     if (!InBatchMode() || !packet_creator_.HasRoomForStreamFrame(id, offset)) {
 199       // TODO(rtenneti): remove MaybeSendFecPacketAndCloseGroup() from inside
 200       // SerializeAndSendPacket() and make it an explicit call here (and
 201       // elsewhere where we call SerializeAndSendPacket?).
 202       SerializeAndSendPacket();
 203     }
 204
 205     if (total_bytes_consumed == iov.total_length) {
 206       // We're done writing the data. Exit the loop.
 207       // We don't make this a precondition because we could have 0 bytes of data
 208       // if we're simply writing a fin.
 209       if (fec_protection == MUST_FEC_PROTECT) {
 210         // Turn off FEC protection when we're done writing protected data.
 211         DVLOG(1) << "Turning FEC protection OFF";
 212         should_fec_protect_ = false;
 213       }
 214       break;
 215     }
 216   }
 217
 218   if (notifier != nullptr && frames_created == 0) {
 219     // Safe to delete the AckNotifer as it was never attached to a packet.
 220     delete notifier;
 221   }
 222
 223   // Don't allow the handshake to be bundled with other retransmittable frames.
 224   if (has_handshake) {
 225     SendQueuedFrames(/*flush=*/true, /*is_fec_timeout=*/false);
 226   }
 227
 228   // Try to close FEC group since we've either run out of data to send or we're
 229   // blocked. If not in batch mode, force close the group.
 230   MaybeSendFecPacketAndCloseGroup(/*force=*/false, /*is_fec_timeout=*/false);
 231
 232   DCHECK(InBatchMode() || !packet_creator_.HasPendingFrames());
 233   return QuicConsumedData(total_bytes_consumed, fin_consumed);
 234 }
 235
 236 void QuicPacketGenerator::GenerateMtuDiscoveryPacket(
 237     QuicByteCount target_mtu,
 238     QuicAckNotifier::DelegateInterface* delegate) {
 239   // MTU discovery frames must be sent by themselves.
 240   DCHECK(!InBatchMode() && !packet_creator_.HasPendingFrames());
 241
 242   // If an ack notifier delegate is provided, register it.
 243   if (delegate) {
 244     QuicAckNotifier* ack_notifier = new QuicAckNotifier(delegate);
 245     // The notifier manager will take the ownership of the notifier after the
 246     // packet is sent.
 247     ack_notifiers_.push_back(ack_notifier);
 248   }
 249
 250   const QuicByteCount current_mtu = GetMaxPacketLength();
 251
 252   // The MTU discovery frame is allocated on the stack, since it is going to be
 253   // serialized within this function.
 254   QuicMtuDiscoveryFrame mtu_discovery_frame;
 255   QuicFrame frame(&mtu_discovery_frame);
 256
 257   // Send the probe packet with the new length.
 258   SetMaxPacketLength(target_mtu, /*force=*/true);
 259   const bool success = AddFrame(frame, nullptr, /*needs_padding=*/true);
 260   SerializeAndSendPacket();
 261   // The only reason AddFrame can fail is that the packet is too full to fit in
 262   // a ping.  This is not possible for any sane MTU.
 263   DCHECK(success);
 264
 265   // Reset the packet length back.
 266   SetMaxPacketLength(current_mtu, /*force=*/true);
 267 }
 268
 269 bool QuicPacketGenerator::CanSendWithNextPendingFrameAddition() const {
 270   DCHECK(HasPendingFrames());
 271   HasRetransmittableData retransmittable =
 272       (should_send_ack_ || should_send_stop_waiting_)
 273           ? NO_RETRANSMITTABLE_DATA
 274           : HAS_RETRANSMITTABLE_DATA;
 275   if (retransmittable == HAS_RETRANSMITTABLE_DATA) {
 276       DCHECK(!queued_control_frames_.empty());  // These are retransmittable.
 277   }
 278   return delegate_->ShouldGeneratePacket(retransmittable, NOT_HANDSHAKE);
 279 }
 280
 281 void QuicPacketGenerator::SendQueuedFrames(bool flush, bool is_fec_timeout) {
 282   // Only add pending frames if we are SURE we can then send the whole packet.
 283   while (HasPendingFrames() &&
 284          (flush || CanSendWithNextPendingFrameAddition())) {
 285     if (!AddNextPendingFrame()) {
 286       // Packet was full, so serialize and send it.
 287       SerializeAndSendPacket();
 288     }
 289   }
 290   if (packet_creator_.HasPendingFrames() && (flush || !InBatchMode())) {
 291     SerializeAndSendPacket();
 292   }
 293   MaybeSendFecPacketAndCloseGroup(flush, is_fec_timeout);
 294 }
 295
 296 void QuicPacketGenerator::MaybeStartFecProtection() {
 297   if (!packet_creator_.IsFecEnabled()) {
 298     return;
 299   }
 300   DVLOG(1) << "Turning FEC protection ON";
 301   should_fec_protect_ = true;
 302   if (packet_creator_.IsFecProtected()) {
 303     // Only start creator's FEC protection if not already on.
 304     return;
 305   }
 306   if (HasQueuedFrames()) {
 307     // TODO(jri): This currently requires that the generator flush out any
 308     // pending frames when FEC protection is turned on. If current packet can be
 309     // converted to an FEC protected packet, do it. This will require the
 310     // generator to check if the resulting expansion still allows the incoming
 311     // frame to be added to the packet.
 312     SendQueuedFrames(/*flush=*/true, /*is_fec_timeout=*/false);
 313   }
 314   packet_creator_.StartFecProtectingPackets();
 315   DCHECK(packet_creator_.IsFecProtected());
 316 }
 317
 318 void QuicPacketGenerator::MaybeSendFecPacketAndCloseGroup(bool force,
 319                                                           bool is_fec_timeout) {
 320   if (!ShouldSendFecPacket(force)) {
 321     return;
 322   }
 323
 324   // If we want to send FEC packet only when FEC alaram goes off and if it is
 325   // not a FEC timeout then close the group and dont send FEC packet.
 326   if (fec_send_policy_ == FEC_ALARM_TRIGGER && !is_fec_timeout) {
 327     ResetFecGroup();
 328   } else {
 329     // TODO(jri): SerializeFec can return a NULL packet, and this should
 330     // cause an early return, with a call to delegate_->OnPacketGenerationError.
 331     char buffer[kMaxPacketSize];
 332     SerializedPacket serialized_fec =
 333         packet_creator_.SerializeFec(buffer, kMaxPacketSize);
 334     DCHECK(serialized_fec.packet);
 335     delegate_->OnSerializedPacket(serialized_fec);
 336   }
 337   // Turn FEC protection off if creator's protection is on and the creator
 338   // does not have an open FEC group.
 339   // Note: We only wait until the frames queued in the creator are flushed;
 340   // pending frames in the generator will not keep us from turning FEC off.
 341   if (!should_fec_protect_ && !packet_creator_.IsFecGroupOpen()) {
 342     packet_creator_.StopFecProtectingPackets();
 343     DCHECK(!packet_creator_.IsFecProtected());
 344   }
 345 }
 346
 347 bool QuicPacketGenerator::ShouldSendFecPacket(bool force) {
 348   return packet_creator_.IsFecProtected() &&
 349          !packet_creator_.HasPendingFrames() &&
 350          packet_creator_.ShouldSendFec(force);
 351 }
 352
 353 void QuicPacketGenerator::ResetFecGroup() {
 354   DCHECK(packet_creator_.IsFecGroupOpen());
 355   packet_creator_.ResetFecGroup();
 356   delegate_->OnResetFecGroup();
 357 }
 358
 359 void QuicPacketGenerator::OnFecTimeout() {
 360   DCHECK(!InBatchMode());
 361   if (!ShouldSendFecPacket(true)) {
 362     LOG(DFATAL) << "No FEC packet to send on FEC timeout.";
 363     return;
 364   }
 365   // Flush out any pending frames in the generator and the creator, and then
 366   // send out FEC packet.
 367   SendQueuedFrames(/*flush=*/true, /*is_fec_timeout=*/true);
 368   MaybeSendFecPacketAndCloseGroup(/*force=*/true, /*is_fec_timeout=*/true);
 369 }
 370
 371 QuicTime::Delta QuicPacketGenerator::GetFecTimeout(
 372     QuicPacketSequenceNumber sequence_number) {
 373   // Do not set up FEC alarm for |sequence_number| it is not the first packet in
 374   // the current group.
 375   if (packet_creator_.IsFecGroupOpen() &&
 376       (sequence_number == packet_creator_.fec_group_number())) {
 377     return QuicTime::Delta::Max(
 378         fec_timeout_, QuicTime::Delta::FromMilliseconds(kMinFecTimeoutMs));
 379   }
 380   return QuicTime::Delta::Infinite();
 381 }
 382
 383 bool QuicPacketGenerator::InBatchMode() {
 384   return batch_mode_;
 385 }
 386
 387 void QuicPacketGenerator::StartBatchOperations() {
 388   batch_mode_ = true;
 389 }
 390
 391 void QuicPacketGenerator::FinishBatchOperations() {
 392   batch_mode_ = false;
 393   SendQueuedFrames(/*flush=*/false, /*is_fec_timeout=*/false);
 394 }
 395
 396 void QuicPacketGenerator::FlushAllQueuedFrames() {
 397   SendQueuedFrames(/*flush=*/true, /*is_fec_timeout=*/false);
 398 }
 399
 400 bool QuicPacketGenerator::HasQueuedFrames() const {
 401   return packet_creator_.HasPendingFrames() || HasPendingFrames();
 402 }
 403
 404 bool QuicPacketGenerator::HasPendingFrames() const {
 405   return should_send_ack_ || should_send_stop_waiting_ ||
 406          !queued_control_frames_.empty();
 407 }
 408
 409 bool QuicPacketGenerator::AddNextPendingFrame() {
 410   if (should_send_ack_) {
 411     delegate_->PopulateAckFrame(&pending_ack_frame_);
 412     ack_queued_ = true;
 413     // If we can't this add the frame now, then we still need to do so later.
 414     should_send_ack_ = !AddFrame(QuicFrame(&pending_ack_frame_), nullptr,
 415                                  /*needs_padding=*/false);
 416     // Return success if we have cleared out this flag (i.e., added the frame).
 417     // If we still need to send, then the frame is full, and we have failed.
 418     return !should_send_ack_;
 419   }
 420
 421   if (should_send_stop_waiting_) {
 422     delegate_->PopulateStopWaitingFrame(&pending_stop_waiting_frame_);
 423     stop_waiting_queued_ = true;
 424     // If we can't this add the frame now, then we still need to do so later.
 425     should_send_stop_waiting_ =
 426         !AddFrame(QuicFrame(&pending_stop_waiting_frame_), nullptr,
 427                   /*needs_padding=*/false);
 428     // Return success if we have cleared out this flag (i.e., added the frame).
 429     // If we still need to send, then the frame is full, and we have failed.
 430     return !should_send_stop_waiting_;
 431   }
 432
 433   LOG_IF(DFATAL, queued_control_frames_.empty())
 434       << "AddNextPendingFrame called with no queued control frames.";
 435   if (!AddFrame(queued_control_frames_.back(), nullptr,
 436                 /*needs_padding=*/false)) {
 437     // Packet was full.
 438     return false;
 439   }
 440   queued_control_frames_.pop_back();
 441   return true;
 442 }
 443
 444 bool QuicPacketGenerator::AddFrame(const QuicFrame& frame,
 445                                    char* buffer,
 446                                    bool needs_padding) {
 447   bool success = needs_padding
 448                      ? packet_creator_.AddPaddedSavedFrame(frame, buffer)
 449                      : packet_creator_.AddSavedFrame(frame, buffer);
 450   if (success && debug_delegate_) {
 451     debug_delegate_->OnFrameAddedToPacket(frame);
 452   }
 453   return success;
 454 }
 455
 456 void QuicPacketGenerator::SerializeAndSendPacket() {
 457   char buffer[kMaxPacketSize];
 458   SerializedPacket serialized_packet =
 459       packet_creator_.SerializePacket(buffer, kMaxPacketSize);
 460   if (serialized_packet.packet == nullptr) {
 461     LOG(DFATAL) << "Failed to SerializePacket. fec_policy:" << fec_send_policy_
 462                 << " should_fec_protect_:" << should_fec_protect_;
 463     delegate_->CloseConnection(QUIC_FAILED_TO_SERIALIZE_PACKET, false);
 464     return;
 465   }
 466
 467   // There may be AckNotifiers interested in this packet.
 468   serialized_packet.notifiers.swap(ack_notifiers_);
 469   ack_notifiers_.clear();
 470
 471   delegate_->OnSerializedPacket(serialized_packet);
 472   MaybeSendFecPacketAndCloseGroup(/*force=*/false, /*is_fec_timeout=*/false);
 473
 474   // Maximum packet size may be only enacted while no packet is currently being
 475   // constructed, so here we have a good opportunity to actually change it.
 476   if (packet_creator_.CanSetMaxPacketLength()) {
 477     packet_creator_.SetMaxPacketLength(max_packet_length_);
 478   }
 479
 480   // The packet has now been serialized, so the frames are no longer queued.
 481   ack_queued_ = false;
 482   stop_waiting_queued_ = false;
 483 }
 484
 485 void QuicPacketGenerator::StopSendingVersion() {
 486   packet_creator_.StopSendingVersion();
 487 }
 488
 489 QuicPacketSequenceNumber QuicPacketGenerator::sequence_number() const {
 490   return packet_creator_.sequence_number();
 491 }
 492
 493 QuicByteCount QuicPacketGenerator::GetMaxPacketLength() const {
 494   return max_packet_length_;
 495 }
 496
 497 QuicByteCount QuicPacketGenerator::GetCurrentMaxPacketLength() const {
 498   return packet_creator_.max_packet_length();
 499 }
 500
 501 void QuicPacketGenerator::SetMaxPacketLength(QuicByteCount length, bool force) {
 502   // If we cannot immediately set new maximum packet length, and the |force|
 503   // flag is set, we have to flush the contents of the queue and close existing
 504   // FEC group.
 505   if (!packet_creator_.CanSetMaxPacketLength() && force) {
 506     SendQueuedFrames(/*flush=*/true, /*is_fec_timeout=*/false);
 507     MaybeSendFecPacketAndCloseGroup(/*force=*/true, /*is_fec_timeout=*/false);
 508     DCHECK(packet_creator_.CanSetMaxPacketLength());
 509   }
 510
 511   max_packet_length_ = length;
 512   if (packet_creator_.CanSetMaxPacketLength()) {
 513     packet_creator_.SetMaxPacketLength(length);
 514   }
 515 }
 516
 517 QuicEncryptedPacket* QuicPacketGenerator::SerializeVersionNegotiationPacket(
 518     const QuicVersionVector& supported_versions) {
 519   return packet_creator_.SerializeVersionNegotiationPacket(supported_versions);
 520 }
 521
 522 SerializedPacket QuicPacketGenerator::ReserializeAllFrames(
 523     const RetransmittableFrames& frames,
 524     QuicSequenceNumberLength original_length,
 525     char* buffer,
 526     size_t buffer_len) {
 527   return packet_creator_.ReserializeAllFrames(frames, original_length, buffer,
 528                                               buffer_len);
 529 }
 530
 531 void QuicPacketGenerator::UpdateSequenceNumberLength(
 532       QuicPacketSequenceNumber least_packet_awaited_by_peer,
 533       QuicPacketCount max_packets_in_flight) {
 534   return packet_creator_.UpdateSequenceNumberLength(
 535       least_packet_awaited_by_peer, max_packets_in_flight);
 536 }
 537
 538 void QuicPacketGenerator::SetConnectionIdLength(uint32 length) {
 539   if (length == 0) {
 540     packet_creator_.set_connection_id_length(PACKET_0BYTE_CONNECTION_ID);
 541   } else if (length == 1) {
 542     packet_creator_.set_connection_id_length(PACKET_1BYTE_CONNECTION_ID);
 543   } else if (length <= 4) {
 544     packet_creator_.set_connection_id_length(PACKET_4BYTE_CONNECTION_ID);
 545   } else {
 546     packet_creator_.set_connection_id_length(PACKET_8BYTE_CONNECTION_ID);
 547   }
 548 }
 549
 550 void QuicPacketGenerator::set_encryption_level(EncryptionLevel level) {
 551   packet_creator_.set_encryption_level(level);
 552 }
 553
 554 void QuicPacketGenerator::SetEncrypter(EncryptionLevel level,
 555                                        QuicEncrypter* encrypter) {
 556   packet_creator_.SetEncrypter(level, encrypter);
 557 }
 558
 559 }  // namespace net