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// Copyright 2014 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.
#include "net/third_party/quiche/src/quic/core/quic_flow_controller.h"
#include <cstdint>
#include "net/third_party/quiche/src/quic/core/quic_connection.h"
#include "net/third_party/quiche/src/quic/core/quic_packets.h"
#include "net/third_party/quiche/src/quic/core/quic_session.h"
#include "net/third_party/quiche/src/quic/core/quic_utils.h"
#include "net/third_party/quiche/src/quic/platform/api/quic_bug_tracker.h"
#include "net/third_party/quiche/src/quic/platform/api/quic_flag_utils.h"
#include "net/third_party/quiche/src/quic/platform/api/quic_flags.h"
#include "net/third_party/quiche/src/quic/platform/api/quic_logging.h"
#include "net/third_party/quiche/src/quic/platform/api/quic_str_cat.h"
namespace quic {
#define ENDPOINT \
(perspective_ == Perspective::IS_SERVER ? "Server: " : "Client: ")
QuicFlowController::QuicFlowController(
QuicSession* session,
QuicStreamId id,
bool is_connection_flow_controller,
QuicStreamOffset send_window_offset,
QuicStreamOffset receive_window_offset,
QuicByteCount receive_window_size_limit,
bool should_auto_tune_receive_window,
QuicFlowControllerInterface* session_flow_controller)
: session_(session),
connection_(session->connection()),
id_(id),
is_connection_flow_controller_(is_connection_flow_controller),
perspective_(session->perspective()),
bytes_sent_(0),
send_window_offset_(send_window_offset),
bytes_consumed_(0),
highest_received_byte_offset_(0),
receive_window_offset_(receive_window_offset),
receive_window_size_(receive_window_offset),
receive_window_size_limit_(receive_window_size_limit),
auto_tune_receive_window_(should_auto_tune_receive_window),
session_flow_controller_(session_flow_controller),
last_blocked_send_window_offset_(0),
prev_window_update_time_(QuicTime::Zero()) {
DCHECK_LE(receive_window_size_, receive_window_size_limit_);
DCHECK_EQ(is_connection_flow_controller_,
QuicUtils::GetInvalidStreamId(
session_->connection()->transport_version()) == id_);
QUIC_DVLOG(1) << ENDPOINT << "Created flow controller for stream " << id_
<< ", setting initial receive window offset to: "
<< receive_window_offset_
<< ", max receive window to: " << receive_window_size_
<< ", max receive window limit to: "
<< receive_window_size_limit_
<< ", setting send window offset to: " << send_window_offset_;
}
void QuicFlowController::AddBytesConsumed(QuicByteCount bytes_consumed) {
bytes_consumed_ += bytes_consumed;
QUIC_DVLOG(1) << ENDPOINT << "Stream " << id_ << " consumed "
<< bytes_consumed_ << " bytes.";
MaybeSendWindowUpdate();
}
bool QuicFlowController::UpdateHighestReceivedOffset(
QuicStreamOffset new_offset) {
// Only update if offset has increased.
if (new_offset <= highest_received_byte_offset_) {
return false;
}
QUIC_DVLOG(1) << ENDPOINT << "Stream " << id_
<< " highest byte offset increased from "
<< highest_received_byte_offset_ << " to " << new_offset;
highest_received_byte_offset_ = new_offset;
return true;
}
void QuicFlowController::AddBytesSent(QuicByteCount bytes_sent) {
if (bytes_sent_ + bytes_sent > send_window_offset_) {
QUIC_BUG << ENDPOINT << "Stream " << id_ << " Trying to send an extra "
<< bytes_sent << " bytes, when bytes_sent = " << bytes_sent_
<< ", and send_window_offset_ = " << send_window_offset_;
bytes_sent_ = send_window_offset_;
// This is an error on our side, close the connection as soon as possible.
connection_->CloseConnection(
QUIC_FLOW_CONTROL_SENT_TOO_MUCH_DATA,
QuicStrCat(send_window_offset_ - (bytes_sent_ + bytes_sent),
"bytes over send window offset"),
ConnectionCloseBehavior::SEND_CONNECTION_CLOSE_PACKET);
return;
}
bytes_sent_ += bytes_sent;
QUIC_DVLOG(1) << ENDPOINT << "Stream " << id_ << " sent " << bytes_sent_
<< " bytes.";
}
bool QuicFlowController::FlowControlViolation() {
if (highest_received_byte_offset_ > receive_window_offset_) {
QUIC_DLOG(INFO) << ENDPOINT << "Flow control violation on stream " << id_
<< ", receive window offset: " << receive_window_offset_
<< ", highest received byte offset: "
<< highest_received_byte_offset_;
return true;
}
return false;
}
void QuicFlowController::MaybeIncreaseMaxWindowSize() {
// Core of receive window auto tuning. This method should be called before a
// WINDOW_UPDATE frame is sent. Ideally, window updates should occur close to
// once per RTT. If a window update happens much faster than RTT, it implies
// that the flow control window is imposing a bottleneck. To prevent this,
// this method will increase the receive window size (subject to a reasonable
// upper bound). For simplicity this algorithm is deliberately asymmetric, in
// that it may increase window size but never decreases.
// Keep track of timing between successive window updates.
QuicTime now = connection_->clock()->ApproximateNow();
QuicTime prev = prev_window_update_time_;
prev_window_update_time_ = now;
if (!prev.IsInitialized()) {
QUIC_DVLOG(1) << ENDPOINT << "first window update for stream " << id_;
return;
}
if (!auto_tune_receive_window_) {
return;
}
// Get outbound RTT.
QuicTime::Delta rtt =
connection_->sent_packet_manager().GetRttStats()->smoothed_rtt();
if (rtt.IsZero()) {
QUIC_DVLOG(1) << ENDPOINT << "rtt zero for stream " << id_;
return;
}
// Now we can compare timing of window updates with RTT.
QuicTime::Delta since_last = now - prev;
QuicTime::Delta two_rtt = 2 * rtt;
if (since_last >= two_rtt) {
// If interval between window updates is sufficiently large, there
// is no need to increase receive_window_size_.
return;
}
QuicByteCount old_window = receive_window_size_;
IncreaseWindowSize();
if (receive_window_size_ > old_window) {
QUIC_DVLOG(1) << ENDPOINT << "New max window increase for stream " << id_
<< " after " << since_last.ToMicroseconds()
<< " us, and RTT is " << rtt.ToMicroseconds()
<< "us. max wndw: " << receive_window_size_;
if (session_flow_controller_ != nullptr) {
session_flow_controller_->EnsureWindowAtLeast(
kSessionFlowControlMultiplier * receive_window_size_);
}
} else {
// TODO(ckrasic) - add a varz to track this (?).
QUIC_LOG_FIRST_N(INFO, 1)
<< ENDPOINT << "Max window at limit for stream " << id_ << " after "
<< since_last.ToMicroseconds() << " us, and RTT is "
<< rtt.ToMicroseconds() << "us. Limit size: " << receive_window_size_;
}
}
void QuicFlowController::IncreaseWindowSize() {
receive_window_size_ *= 2;
receive_window_size_ =
std::min(receive_window_size_, receive_window_size_limit_);
}
QuicByteCount QuicFlowController::WindowUpdateThreshold() {
return receive_window_size_ / 2;
}
void QuicFlowController::MaybeSendWindowUpdate() {
// Send WindowUpdate to increase receive window if
// (receive window offset - consumed bytes) < (max window / 2).
// This is behaviour copied from SPDY.
DCHECK_LE(bytes_consumed_, receive_window_offset_);
QuicStreamOffset available_window = receive_window_offset_ - bytes_consumed_;
QuicByteCount threshold = WindowUpdateThreshold();
if (!prev_window_update_time_.IsInitialized()) {
// Treat the initial window as if it is a window update, so if 1/2 the
// window is used in less than 2 RTTs, the window is increased.
prev_window_update_time_ = connection_->clock()->ApproximateNow();
}
if (available_window >= threshold) {
QUIC_DVLOG(1) << ENDPOINT << "Not sending WindowUpdate for stream " << id_
<< ", available window: " << available_window
<< " >= threshold: " << threshold;
return;
}
MaybeIncreaseMaxWindowSize();
UpdateReceiveWindowOffsetAndSendWindowUpdate(available_window);
}
void QuicFlowController::UpdateReceiveWindowOffsetAndSendWindowUpdate(
QuicStreamOffset available_window) {
// Update our receive window.
receive_window_offset_ += (receive_window_size_ - available_window);
QUIC_DVLOG(1) << ENDPOINT << "Sending WindowUpdate frame for stream " << id_
<< ", consumed bytes: " << bytes_consumed_
<< ", available window: " << available_window
<< ", and threshold: " << WindowUpdateThreshold()
<< ", and receive window size: " << receive_window_size_
<< ". New receive window offset is: " << receive_window_offset_;
SendWindowUpdate();
}
bool QuicFlowController::ShouldSendBlocked() {
if (SendWindowSize() != 0 ||
last_blocked_send_window_offset_ >= send_window_offset_) {
return false;
}
QUIC_DLOG(INFO) << ENDPOINT << "Stream " << id_
<< " is flow control blocked. "
<< "Send window: " << SendWindowSize()
<< ", bytes sent: " << bytes_sent_
<< ", send limit: " << send_window_offset_;
// The entire send_window has been consumed, we are now flow control
// blocked.
// Keep track of when we last sent a BLOCKED frame so that we only send one
// at a given send offset.
last_blocked_send_window_offset_ = send_window_offset_;
return true;
}
bool QuicFlowController::UpdateSendWindowOffset(
QuicStreamOffset new_send_window_offset) {
// Only update if send window has increased.
if (new_send_window_offset <= send_window_offset_) {
return false;
}
QUIC_DVLOG(1) << ENDPOINT << "UpdateSendWindowOffset for stream " << id_
<< " with new offset " << new_send_window_offset
<< " current offset: " << send_window_offset_
<< " bytes_sent: " << bytes_sent_;
// The flow is now unblocked but could have also been unblocked
// before. Return true iff this update caused a change from blocked
// to unblocked.
const bool was_previously_blocked = IsBlocked();
send_window_offset_ = new_send_window_offset;
return was_previously_blocked;
}
void QuicFlowController::EnsureWindowAtLeast(QuicByteCount window_size) {
if (receive_window_size_limit_ >= window_size) {
return;
}
QuicStreamOffset available_window = receive_window_offset_ - bytes_consumed_;
IncreaseWindowSize();
UpdateReceiveWindowOffsetAndSendWindowUpdate(available_window);
}
bool QuicFlowController::IsBlocked() const {
return SendWindowSize() == 0;
}
uint64_t QuicFlowController::SendWindowSize() const {
if (bytes_sent_ > send_window_offset_) {
return 0;
}
return send_window_offset_ - bytes_sent_;
}
void QuicFlowController::UpdateReceiveWindowSize(QuicStreamOffset size) {
DCHECK_LE(size, receive_window_size_limit_);
QUIC_DVLOG(1) << ENDPOINT << "UpdateReceiveWindowSize for stream " << id_
<< ": " << size;
if (receive_window_size_ != receive_window_offset_) {
QUIC_BUG << "receive_window_size_:" << receive_window_size_
<< " != receive_window_offset:" << receive_window_offset_;
return;
}
receive_window_size_ = size;
receive_window_offset_ = size;
}
void QuicFlowController::SendWindowUpdate() {
QuicStreamId id = id_;
if (is_connection_flow_controller_) {
id = QuicUtils::GetInvalidStreamId(connection_->transport_version());
}
session_->SendWindowUpdate(id, receive_window_offset_);
}
} // namespace quic