platform/network/network_state_notifier.cc

/*
 * Copyright (C) 2008 Apple Inc. All Rights Reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY APPLE INC. ``AS IS'' AND ANY
 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
 * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL APPLE INC. OR
 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
 * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
 * OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

#include "third_party/blink/renderer/platform/network/network_state_notifier.h"

#include <memory>

#include "net/nqe/effective_connection_type.h"
#include "net/nqe/network_quality_estimator_params.h"
#include "third_party/blink/public/common/client_hints/client_hints.h"
#include "third_party/blink/renderer/platform/scheduler/public/post_cross_thread_task.h"
#include "third_party/blink/renderer/platform/wtf/assertions.h"
#include "third_party/blink/renderer/platform/wtf/cross_thread_functional.h"
#include "third_party/blink/renderer/platform/wtf/functional.h"
#include "third_party/blink/renderer/platform/wtf/std_lib_extras.h"
#include "third_party/blink/renderer/platform/wtf/text/string_hash.h"
#include "third_party/blink/renderer/platform/wtf/threading.h"
#include "third_party/blink/renderer/platform/wtf/wtf.h"

namespace blink {

namespace {

// Typical HTTP RTT value corresponding to a given WebEffectiveConnectionType
// value. Taken from
// https://cs.chromium.org/chromium/src/net/nqe/network_quality_estimator_params.cc.
const base::TimeDelta kTypicalHttpRttEffectiveConnectionType
    [static_cast<size_t>(WebEffectiveConnectionType::kMaxValue) + 1] = {
        base::TimeDelta::FromMilliseconds(0),
        base::TimeDelta::FromMilliseconds(0),
        base::TimeDelta::FromMilliseconds(3600),
        base::TimeDelta::FromMilliseconds(1800),
        base::TimeDelta::FromMilliseconds(450),
        base::TimeDelta::FromMilliseconds(175)};

// Typical downlink throughput (in Mbps) value corresponding to a given
// WebEffectiveConnectionType value. Taken from
// https://cs.chromium.org/chromium/src/net/nqe/network_quality_estimator_params.cc.
const double kTypicalDownlinkMbpsEffectiveConnectionType
    [static_cast<size_t>(WebEffectiveConnectionType::kMaxValue) + 1] = {
        0, 0, 0.040, 0.075, 0.400, 1.600};

}  // namespace

NetworkStateNotifier& GetNetworkStateNotifier() {
  DEFINE_THREAD_SAFE_STATIC_LOCAL(NetworkStateNotifier, network_state_notifier,
                                  ());
  return network_state_notifier;
}

NetworkStateNotifier::ScopedNotifier::ScopedNotifier(
    NetworkStateNotifier& notifier)
    : notifier_(notifier) {
  DCHECK(IsMainThread());
  before_ = notifier_.has_override_ ? notifier_.override_ : notifier_.state_;
}

NetworkStateNotifier::ScopedNotifier::~ScopedNotifier() {
  DCHECK(IsMainThread());
  const NetworkState& after =
      notifier_.has_override_ ? notifier_.override_ : notifier_.state_;
  if ((after.type != before_.type ||
       after.max_bandwidth_mbps != before_.max_bandwidth_mbps ||
       after.effective_type != before_.effective_type ||
       after.http_rtt != before_.http_rtt ||
       after.transport_rtt != before_.transport_rtt ||
       after.downlink_throughput_mbps != before_.downlink_throughput_mbps ||
       after.save_data != before_.save_data) &&
      before_.connection_initialized) {
    notifier_.NotifyObservers(notifier_.connection_observers_,
                              ObserverType::kConnectionType, after);
  }
  if (after.on_line != before_.on_line && before_.on_line_initialized) {
    notifier_.NotifyObservers(notifier_.on_line_state_observers_,
                              ObserverType::kOnLineState, after);
  }
}

NetworkStateNotifier::NetworkStateObserverHandle::NetworkStateObserverHandle(
    NetworkStateNotifier* notifier,
    NetworkStateNotifier::ObserverType type,
    NetworkStateNotifier::NetworkStateObserver* observer,
    scoped_refptr<base::SingleThreadTaskRunner> task_runner)
    : notifier_(notifier),
      type_(type),
      observer_(observer),
      task_runner_(std::move(task_runner)) {}

NetworkStateNotifier::NetworkStateObserverHandle::
    ~NetworkStateObserverHandle() {
  notifier_->RemoveObserver(type_, observer_, std::move(task_runner_));
}

void NetworkStateNotifier::SetOnLine(bool on_line) {
  DCHECK(IsMainThread());
  ScopedNotifier notifier(*this);
  {
    MutexLocker locker(mutex_);
    state_.on_line_initialized = true;
    state_.on_line = on_line;
  }
}

void NetworkStateNotifier::SetWebConnection(WebConnectionType type,
                                            double max_bandwidth_mbps) {
  DCHECK(IsMainThread());
  ScopedNotifier notifier(*this);
  {
    MutexLocker locker(mutex_);
    state_.connection_initialized = true;
    state_.type = type;
    state_.max_bandwidth_mbps = max_bandwidth_mbps;
  }
}

void NetworkStateNotifier::SetNetworkQuality(WebEffectiveConnectionType type,
                                             base::TimeDelta http_rtt,
                                             base::TimeDelta transport_rtt,
                                             int downlink_throughput_kbps) {
  DCHECK(IsMainThread());
  ScopedNotifier notifier(*this);
  {
    MutexLocker locker(mutex_);

    state_.effective_type = type;
    state_.http_rtt = base::nullopt;
    state_.transport_rtt = base::nullopt;
    state_.downlink_throughput_mbps = base::nullopt;

    if (http_rtt.InMilliseconds() >= 0)
      state_.http_rtt = http_rtt;

    if (transport_rtt.InMilliseconds() >= 0)
      state_.transport_rtt = transport_rtt;

    if (downlink_throughput_kbps >= 0) {
      state_.downlink_throughput_mbps =
          static_cast<double>(downlink_throughput_kbps) / 1000;
    }
  }
}

void NetworkStateNotifier::SetNetworkQualityWebHoldback(
    WebEffectiveConnectionType type) {
  DCHECK(IsMainThread());
  if (type == WebEffectiveConnectionType::kTypeUnknown)
    return;
  ScopedNotifier notifier(*this);
  {
    MutexLocker locker(mutex_);

    state_.network_quality_web_holdback = type;
  }
}

std::unique_ptr<NetworkStateNotifier::NetworkStateObserverHandle>
NetworkStateNotifier::AddConnectionObserver(
    NetworkStateObserver* observer,
    scoped_refptr<base::SingleThreadTaskRunner> task_runner) {
  AddObserverToMap(connection_observers_, observer, task_runner);
  return std::make_unique<NetworkStateNotifier::NetworkStateObserverHandle>(
      this, ObserverType::kConnectionType, observer, task_runner);
}

void NetworkStateNotifier::SetSaveDataEnabled(bool enabled) {
  DCHECK(IsMainThread());
  ScopedNotifier notifier(*this);
  {
    MutexLocker locker(mutex_);
    state_.save_data = enabled;
  }
}

std::unique_ptr<NetworkStateNotifier::NetworkStateObserverHandle>
NetworkStateNotifier::AddOnLineObserver(
    NetworkStateObserver* observer,
    scoped_refptr<base::SingleThreadTaskRunner> task_runner) {
  AddObserverToMap(on_line_state_observers_, observer, task_runner);
  return std::make_unique<NetworkStateNotifier::NetworkStateObserverHandle>(
      this, ObserverType::kOnLineState, observer, task_runner);
}

void NetworkStateNotifier::SetNetworkConnectionInfoOverride(
    bool on_line,
    WebConnectionType type,
    base::Optional<WebEffectiveConnectionType> effective_type,
    int64_t http_rtt_msec,
    double max_bandwidth_mbps) {
  DCHECK(IsMainThread());
  ScopedNotifier notifier(*this);
  {
    MutexLocker locker(mutex_);
    has_override_ = true;
    override_.on_line_initialized = true;
    override_.on_line = on_line;
    override_.connection_initialized = true;
    override_.type = type;
    override_.max_bandwidth_mbps = max_bandwidth_mbps;

    if (!effective_type && http_rtt_msec > 0) {
      base::TimeDelta http_rtt(
          base::TimeDelta::FromMilliseconds(http_rtt_msec));
      // Threshold values taken from
      // net/nqe/network_quality_estimator_params.cc.
      if (http_rtt >= net::kHttpRttEffectiveConnectionTypeThresholds
                          [net::EFFECTIVE_CONNECTION_TYPE_SLOW_2G]) {
        effective_type = WebEffectiveConnectionType::kTypeSlow2G;
      } else if (http_rtt >= net::kHttpRttEffectiveConnectionTypeThresholds
                                 [net::EFFECTIVE_CONNECTION_TYPE_2G]) {
        effective_type = WebEffectiveConnectionType::kType2G;
      } else if (http_rtt >= net::kHttpRttEffectiveConnectionTypeThresholds
                                 [net::EFFECTIVE_CONNECTION_TYPE_3G]) {
        effective_type = WebEffectiveConnectionType::kType3G;
      } else {
        effective_type = WebEffectiveConnectionType::kType4G;
      }
    }
    override_.effective_type = effective_type
                                   ? effective_type.value()
                                   : WebEffectiveConnectionType::kTypeUnknown;
    override_.http_rtt = base::TimeDelta::FromMilliseconds(http_rtt_msec);
    override_.downlink_throughput_mbps = max_bandwidth_mbps;
  }
}

void NetworkStateNotifier::SetSaveDataEnabledOverride(bool enabled) {
  DCHECK(IsMainThread());
  ScopedNotifier notifier(*this);
  {
    MutexLocker locker(mutex_);
    has_override_ = true;
    override_.on_line_initialized = true;
    override_.connection_initialized = true;
    override_.save_data = enabled;
  }
}

void NetworkStateNotifier::ClearOverride() {
  DCHECK(IsMainThread());
  ScopedNotifier notifier(*this);
  {
    MutexLocker locker(mutex_);
    has_override_ = false;
  }
}

void NetworkStateNotifier::NotifyObservers(ObserverListMap& map,
                                           ObserverType type,
                                           const NetworkState& state) {
  DCHECK(IsMainThread());
  MutexLocker locker(mutex_);
  for (const auto& entry : map) {
    scoped_refptr<base::SingleThreadTaskRunner> task_runner = entry.key;
    PostCrossThreadTask(
        *task_runner, FROM_HERE,
        CrossThreadBindOnce(&NetworkStateNotifier::NotifyObserversOnTaskRunner,
                            CrossThreadUnretained(this),
                            CrossThreadUnretained(&map), type, task_runner,
                            state));
  }
}

void NetworkStateNotifier::NotifyObserversOnTaskRunner(
    ObserverListMap* map,
    ObserverType type,
    scoped_refptr<base::SingleThreadTaskRunner> task_runner,
    const NetworkState& state) {
  ObserverList* observer_list = LockAndFindObserverList(*map, task_runner);

  // The context could have been removed before the notification task got to
  // run.
  if (!observer_list)
    return;

  DCHECK(task_runner->RunsTasksInCurrentSequence());

  observer_list->iterating = true;

  for (wtf_size_t i = 0; i < observer_list->observers.size(); ++i) {
    // Observers removed during iteration are zeroed out, skip them.
    if (!observer_list->observers[i])
      continue;
    switch (type) {
      case ObserverType::kOnLineState:
        observer_list->observers[i]->OnLineStateChange(state.on_line);
        continue;
      case ObserverType::kConnectionType:
        observer_list->observers[i]->ConnectionChange(
            state.type, state.max_bandwidth_mbps, state.effective_type,
            state.http_rtt, state.transport_rtt, state.downlink_throughput_mbps,
            state.save_data);
        continue;
    }
    NOTREACHED();
  }

  observer_list->iterating = false;

  if (!observer_list->zeroed_observers.IsEmpty())
    CollectZeroedObservers(*map, observer_list, std::move(task_runner));
}

void NetworkStateNotifier::AddObserverToMap(
    ObserverListMap& map,
    NetworkStateObserver* observer,
    scoped_refptr<base::SingleThreadTaskRunner> task_runner) {
  DCHECK(task_runner->RunsTasksInCurrentSequence());
  DCHECK(observer);

  MutexLocker locker(mutex_);
  ObserverListMap::AddResult result =
      map.insert(std::move(task_runner), nullptr);
  if (result.is_new_entry)
    result.stored_value->value = std::make_unique<ObserverList>();

  DCHECK(result.stored_value->value->observers.Find(observer) == kNotFound);
  result.stored_value->value->observers.push_back(observer);
}

void NetworkStateNotifier::RemoveObserver(
    ObserverType type,
    NetworkStateObserver* observer,
    scoped_refptr<base::SingleThreadTaskRunner> task_runner) {
  switch (type) {
    case ObserverType::kConnectionType:
      RemoveObserverFromMap(connection_observers_, observer,
                            std::move(task_runner));
      break;
    case ObserverType::kOnLineState:
      RemoveObserverFromMap(on_line_state_observers_, observer,
                            std::move(task_runner));
      break;
  }
}

void NetworkStateNotifier::RemoveObserverFromMap(
    ObserverListMap& map,
    NetworkStateObserver* observer,
    scoped_refptr<base::SingleThreadTaskRunner> task_runner) {
  DCHECK(task_runner->RunsTasksInCurrentSequence());
  DCHECK(observer);

  ObserverList* observer_list = LockAndFindObserverList(map, task_runner);
  if (!observer_list)
    return;

  Vector<NetworkStateObserver*>& observers = observer_list->observers;
  wtf_size_t index = observers.Find(observer);
  if (index != kNotFound) {
    observers[index] = 0;
    observer_list->zeroed_observers.push_back(index);
  }

  if (!observer_list->iterating && !observer_list->zeroed_observers.IsEmpty())
    CollectZeroedObservers(map, observer_list, std::move(task_runner));
}

NetworkStateNotifier::ObserverList*
NetworkStateNotifier::LockAndFindObserverList(
    ObserverListMap& map,
    scoped_refptr<base::SingleThreadTaskRunner> task_runner) {
  MutexLocker locker(mutex_);
  ObserverListMap::iterator it = map.find(task_runner);
  return it == map.end() ? nullptr : it->value.get();
}

void NetworkStateNotifier::CollectZeroedObservers(
    ObserverListMap& map,
    ObserverList* list,
    scoped_refptr<base::SingleThreadTaskRunner> task_runner) {
  DCHECK(task_runner->RunsTasksInCurrentSequence());
  DCHECK(!list->iterating);

  // If any observers were removed during the iteration they will have
  // 0 values, clean them up.
  for (wtf_size_t i = 0; i < list->zeroed_observers.size(); ++i)
    list->observers.EraseAt(list->zeroed_observers[i]);

  list->zeroed_observers.clear();

  if (list->observers.IsEmpty()) {
    MutexLocker locker(mutex_);
    map.erase(task_runner);  // deletes list
  }
}

// static
String NetworkStateNotifier::EffectiveConnectionTypeToString(
    WebEffectiveConnectionType type) {
  DCHECK_GT(kWebEffectiveConnectionTypeMappingCount, static_cast<size_t>(type));
  return kWebEffectiveConnectionTypeMapping[static_cast<int>(type)];
}

double NetworkStateNotifier::GetRandomMultiplier(const String& host) const {
  // The random number should be a function of the hostname to reduce
  // cross-origin fingerprinting. The random number should also be a function
  // of randomized salt which is known only to the device. This prevents
  // origin from removing noise from the estimates.
  if (!host)
    return 1.0;

  unsigned hash = StringHash::GetHash(host) + RandomizationSalt();
  double random_multiplier = 0.9 + static_cast<double>((hash % 21)) * 0.01;
  DCHECK_LE(0.90, random_multiplier);
  DCHECK_GE(1.10, random_multiplier);
  return random_multiplier;
}

uint32_t NetworkStateNotifier::RoundRtt(
    const String& host,
    const base::Optional<base::TimeDelta>& rtt) const {
  if (!rtt.has_value()) {
    // RTT is unavailable. So, return the fastest value.
    return 0;
  }

  // Limit the maximum reported value and the granularity to reduce
  // fingerprinting.
  constexpr auto kMaxRtt = base::TimeDelta::FromSeconds(3);
  constexpr auto kGranularity = base::TimeDelta::FromMilliseconds(50);

  const base::TimeDelta modified_rtt =
      std::min(rtt.value() * GetRandomMultiplier(host), kMaxRtt);
  DCHECK_GE(modified_rtt, base::TimeDelta());
  return static_cast<uint32_t>(
      modified_rtt.RoundToMultiple(kGranularity).InMilliseconds());
}

double NetworkStateNotifier::RoundMbps(
    const String& host,
    const base::Optional<double>& downlink_mbps) const {
  // Limit the size of the buckets and the maximum reported value to reduce
  // fingerprinting.
  static const size_t kBucketSize = 50;
  static const double kMaxDownlinkKbps = 10.0 * 1000;

  double downlink_kbps = 0;
  if (!downlink_mbps.has_value()) {
    // Throughput is unavailable. So, return the fastest value.
    downlink_kbps = kMaxDownlinkKbps;
  } else {
    downlink_kbps = downlink_mbps.value() * 1000;
  }
  downlink_kbps *= GetRandomMultiplier(host);

  downlink_kbps = std::min(downlink_kbps, kMaxDownlinkKbps);

  DCHECK_LE(0, downlink_kbps);
  DCHECK_GE(kMaxDownlinkKbps, downlink_kbps);
  // Round down to the nearest kBucketSize kbps value.
  double downlink_kbps_rounded =
      std::round(downlink_kbps / kBucketSize) * kBucketSize;

  // Convert from Kbps to Mbps.
  return downlink_kbps_rounded / 1000;
}

base::Optional<WebEffectiveConnectionType>
NetworkStateNotifier::GetWebHoldbackEffectiveType() const {
  MutexLocker locker(mutex_);

  const NetworkState& state = has_override_ ? override_ : state_;
  // TODO (tbansal): Add a DCHECK to check that |state.on_line_initialized| is
  // true once https://crbug.com/728771 is fixed.
  return state.network_quality_web_holdback;
}

base::Optional<base::TimeDelta> NetworkStateNotifier::GetWebHoldbackHttpRtt()
    const {
  base::Optional<WebEffectiveConnectionType> override_ect =
      GetWebHoldbackEffectiveType();

  if (override_ect) {
    return kTypicalHttpRttEffectiveConnectionType[static_cast<size_t>(
        override_ect.value())];
  }
  return base::nullopt;
}

base::Optional<double>
NetworkStateNotifier::GetWebHoldbackDownlinkThroughputMbps() const {
  base::Optional<WebEffectiveConnectionType> override_ect =
      GetWebHoldbackEffectiveType();

  if (override_ect) {
    return kTypicalDownlinkMbpsEffectiveConnectionType[static_cast<size_t>(
        override_ect.value())];
  }
  return base::nullopt;
}

void NetworkStateNotifier::GetMetricsWithWebHoldback(
    WebConnectionType* type,
    double* downlink_max_mbps,
    WebEffectiveConnectionType* effective_type,
    base::Optional<base::TimeDelta>* http_rtt,
    base::Optional<double>* downlink_mbps,
    bool* save_data) const {
  MutexLocker locker(mutex_);
  const NetworkState& state = has_override_ ? override_ : state_;

  *type = state.type;
  *downlink_max_mbps = state.max_bandwidth_mbps;

  base::Optional<WebEffectiveConnectionType> override_ect =
      state.network_quality_web_holdback;
  if (override_ect) {
    *effective_type = override_ect.value();
    *http_rtt = kTypicalHttpRttEffectiveConnectionType[static_cast<size_t>(
        override_ect.value())];
    *downlink_mbps =
        kTypicalDownlinkMbpsEffectiveConnectionType[static_cast<size_t>(
            override_ect.value())];
  } else {
    *effective_type = state.effective_type;
    *http_rtt = state.http_rtt;
    *downlink_mbps = state.downlink_throughput_mbps;
  }
  *save_data = state.save_data;
}

}  // namespace blink