// Copyright (c) 2012 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/base/network_change_notifier.h"

#include <limits>
#include <unordered_set>

#include "base/macros.h"
#include "base/metrics/histogram_macros.h"
#include "base/stl_util.h"
#include "base/strings/string_util.h"
#include "base/synchronization/lock.h"
#include "base/threading/thread_checker.h"
#include "build/build_config.h"
#include "net/base/network_change_notifier_factory.h"
#include "net/base/network_interfaces.h"
#include "net/base/url_util.h"
#include "net/dns/dns_config_service.h"
#include "net/url_request/url_request.h"
#include "url/gurl.h"

#if defined(OS_ANDROID)
#include "base/metrics/histogram_functions.h"
#include "base/strings/string_number_conversions.h"
#include "net/android/network_library.h"
#endif

#if defined(OS_WIN)
#include "net/base/network_change_notifier_win.h"
#elif defined(OS_LINUX) && !defined(OS_CHROMEOS)
#include "net/base/network_change_notifier_linux.h"
#elif defined(OS_MACOSX)
#include "net/base/network_change_notifier_mac.h"
#endif

namespace net {

namespace {

// The actual singleton notifier.  The class contract forbids usage of the API
// in ways that would require us to place locks around access to this object.
// (The prohibition on global non-POD objects makes it tricky to do such a thing
// anyway.)
NetworkChangeNotifier* g_network_change_notifier = NULL;

// Class factory singleton.
NetworkChangeNotifierFactory* g_network_change_notifier_factory = NULL;

class MockNetworkChangeNotifier : public NetworkChangeNotifier {
 public:
  ConnectionType GetCurrentConnectionType() const override {
    return CONNECTION_UNKNOWN;
  }
};

}  // namespace

// static
bool NetworkChangeNotifier::test_notifications_only_ = false;
// static
const NetworkChangeNotifier::NetworkHandle
    NetworkChangeNotifier::kInvalidNetworkHandle = -1;

// The main observer class that records UMAs for network events.
class NetworkChangeNotifier::HistogramWatcher : public ConnectionTypeObserver,
                                                public IPAddressObserver,
                                                public DNSObserver,
                                                public NetworkChangeObserver {
 public:
  HistogramWatcher()
      : last_ip_address_change_(base::TimeTicks::Now()),
        last_connection_change_(base::TimeTicks::Now()),
        last_dns_change_(base::TimeTicks::Now()),
        last_network_change_(base::TimeTicks::Now()),
        last_connection_type_(CONNECTION_UNKNOWN),
        offline_packets_received_(0),
        bytes_read_since_last_connection_change_(0),
        peak_kbps_since_last_connection_change_(0) {}

  // Registers our three Observer implementations.  This is called from the
  // network thread so that our Observer implementations are also called
  // from the network thread.  This avoids multi-threaded race conditions
  // because the only other interface, |NotifyDataReceived| is also
  // only called from the network thread.
  void Init() {
    DCHECK(thread_checker_.CalledOnValidThread());
    DCHECK(g_network_change_notifier);
    AddConnectionTypeObserver(this);
    AddIPAddressObserver(this);
    AddDNSObserver(this);
    AddNetworkChangeObserver(this);
  }

  ~HistogramWatcher() override {
    DCHECK(thread_checker_.CalledOnValidThread());
    DCHECK(g_network_change_notifier);
    RemoveConnectionTypeObserver(this);
    RemoveIPAddressObserver(this);
    RemoveDNSObserver(this);
    RemoveNetworkChangeObserver(this);
  }

  // IPAddressObserver implementation.
  void OnIPAddressChanged() override {
    DCHECK(thread_checker_.CalledOnValidThread());
    UMA_HISTOGRAM_MEDIUM_TIMES("NCN.IPAddressChange",
                               SinceLast(&last_ip_address_change_));
    UMA_HISTOGRAM_MEDIUM_TIMES(
        "NCN.ConnectionTypeChangeToIPAddressChange",
        last_ip_address_change_ - last_connection_change_);
  }

  // ConnectionTypeObserver implementation.
  void OnConnectionTypeChanged(ConnectionType type) override {
    DCHECK(thread_checker_.CalledOnValidThread());
    base::TimeTicks now = base::TimeTicks::Now();
    int32_t kilobytes_read = bytes_read_since_last_connection_change_ / 1000;
    base::TimeDelta state_duration = SinceLast(&last_connection_change_);
    if (bytes_read_since_last_connection_change_) {
      switch (last_connection_type_) {
        case CONNECTION_UNKNOWN:
          UMA_HISTOGRAM_TIMES("NCN.CM.FirstReadOnUnknown",
                              first_byte_after_connection_change_);
          UMA_HISTOGRAM_TIMES("NCN.CM.FastestRTTOnUnknown",
                              fastest_RTT_since_last_connection_change_);
          break;
        case CONNECTION_ETHERNET:
          UMA_HISTOGRAM_TIMES("NCN.CM.FirstReadOnEthernet",
                              first_byte_after_connection_change_);
          UMA_HISTOGRAM_TIMES("NCN.CM.FastestRTTOnEthernet",
                              fastest_RTT_since_last_connection_change_);
          break;
        case CONNECTION_WIFI:
          UMA_HISTOGRAM_TIMES("NCN.CM.FirstReadOnWifi",
                              first_byte_after_connection_change_);
          UMA_HISTOGRAM_TIMES("NCN.CM.FastestRTTOnWifi",
                              fastest_RTT_since_last_connection_change_);
          break;
        case CONNECTION_2G:
          UMA_HISTOGRAM_TIMES("NCN.CM.FirstReadOn2G",
                              first_byte_after_connection_change_);
          UMA_HISTOGRAM_TIMES("NCN.CM.FastestRTTOn2G",
                              fastest_RTT_since_last_connection_change_);
          break;
        case CONNECTION_3G:
          UMA_HISTOGRAM_TIMES("NCN.CM.FirstReadOn3G",
                              first_byte_after_connection_change_);
          UMA_HISTOGRAM_TIMES("NCN.CM.FastestRTTOn3G",
                              fastest_RTT_since_last_connection_change_);
          break;
        case CONNECTION_4G:
          UMA_HISTOGRAM_TIMES("NCN.CM.FirstReadOn4G",
                              first_byte_after_connection_change_);
          UMA_HISTOGRAM_TIMES("NCN.CM.FastestRTTOn4G",
                              fastest_RTT_since_last_connection_change_);
          break;
        case CONNECTION_NONE:
          UMA_HISTOGRAM_TIMES("NCN.CM.FirstReadOnNone",
                              first_byte_after_connection_change_);
          UMA_HISTOGRAM_TIMES("NCN.CM.FastestRTTOnNone",
                              fastest_RTT_since_last_connection_change_);
          break;
        case CONNECTION_BLUETOOTH:
          UMA_HISTOGRAM_TIMES("NCN.CM.FirstReadOnBluetooth",
                              first_byte_after_connection_change_);
          UMA_HISTOGRAM_TIMES("NCN.CM.FastestRTTOnBluetooth",
                              fastest_RTT_since_last_connection_change_);
      }
    }
    if (peak_kbps_since_last_connection_change_) {
      switch (last_connection_type_) {
        case CONNECTION_UNKNOWN:
          UMA_HISTOGRAM_COUNTS_1M("NCN.CM.PeakKbpsOnUnknown",
                                  peak_kbps_since_last_connection_change_);
          break;
        case CONNECTION_ETHERNET:
          UMA_HISTOGRAM_COUNTS_1M("NCN.CM.PeakKbpsOnEthernet",
                                  peak_kbps_since_last_connection_change_);
          break;
        case CONNECTION_WIFI:
          UMA_HISTOGRAM_COUNTS_1M("NCN.CM.PeakKbpsOnWifi",
                                  peak_kbps_since_last_connection_change_);
          break;
        case CONNECTION_2G:
          UMA_HISTOGRAM_COUNTS_1M("NCN.CM.PeakKbpsOn2G",
                                  peak_kbps_since_last_connection_change_);
          break;
        case CONNECTION_3G:
          UMA_HISTOGRAM_COUNTS_1M("NCN.CM.PeakKbpsOn3G",
                                  peak_kbps_since_last_connection_change_);
          break;
        case CONNECTION_4G:
          UMA_HISTOGRAM_COUNTS_1M("NCN.CM.PeakKbpsOn4G",
                                  peak_kbps_since_last_connection_change_);
          break;
        case CONNECTION_NONE:
          UMA_HISTOGRAM_COUNTS_1M("NCN.CM.PeakKbpsOnNone",
                                  peak_kbps_since_last_connection_change_);
          break;
        case CONNECTION_BLUETOOTH:
          UMA_HISTOGRAM_COUNTS_1M("NCN.CM.PeakKbpsOnBluetooth",
                                  peak_kbps_since_last_connection_change_);
          break;
      }
    }
    switch (last_connection_type_) {
      case CONNECTION_UNKNOWN:
        UMA_HISTOGRAM_LONG_TIMES("NCN.CM.TimeOnUnknown", state_duration);
        UMA_HISTOGRAM_COUNTS_1M("NCN.CM.KBTransferedOnUnknown", kilobytes_read);
        break;
      case CONNECTION_ETHERNET:
        UMA_HISTOGRAM_LONG_TIMES("NCN.CM.TimeOnEthernet", state_duration);
        UMA_HISTOGRAM_COUNTS_1M("NCN.CM.KBTransferedOnEthernet",
                                kilobytes_read);
        break;
      case CONNECTION_WIFI:
        UMA_HISTOGRAM_LONG_TIMES("NCN.CM.TimeOnWifi", state_duration);
        UMA_HISTOGRAM_COUNTS_1M("NCN.CM.KBTransferedOnWifi", kilobytes_read);
        break;
      case CONNECTION_2G:
        UMA_HISTOGRAM_LONG_TIMES("NCN.CM.TimeOn2G", state_duration);
        UMA_HISTOGRAM_COUNTS_1M("NCN.CM.KBTransferedOn2G", kilobytes_read);
        break;
      case CONNECTION_3G:
        UMA_HISTOGRAM_LONG_TIMES("NCN.CM.TimeOn3G", state_duration);
        UMA_HISTOGRAM_COUNTS_1M("NCN.CM.KBTransferedOn3G", kilobytes_read);
        break;
      case CONNECTION_4G:
        UMA_HISTOGRAM_LONG_TIMES("NCN.CM.TimeOn4G", state_duration);
        UMA_HISTOGRAM_COUNTS_1M("NCN.CM.KBTransferedOn4G", kilobytes_read);
        break;
      case CONNECTION_NONE:
        UMA_HISTOGRAM_LONG_TIMES("NCN.CM.TimeOnNone", state_duration);
        UMA_HISTOGRAM_COUNTS_1M("NCN.CM.KBTransferedOnNone", kilobytes_read);
        break;
      case CONNECTION_BLUETOOTH:
        UMA_HISTOGRAM_LONG_TIMES("NCN.CM.TimeOnBluetooth", state_duration);
        UMA_HISTOGRAM_COUNTS_1M("NCN.CM.KBTransferedOnBluetooth",
                                kilobytes_read);
        break;
    }

    if (type != CONNECTION_NONE) {
      UMA_HISTOGRAM_MEDIUM_TIMES("NCN.OnlineChange", state_duration);

      if (offline_packets_received_) {
        if ((now - last_offline_packet_received_) <
            base::TimeDelta::FromSeconds(5)) {
          // We can compare this sum with the sum of NCN.OfflineDataRecv.
          UMA_HISTOGRAM_COUNTS_10000(
              "NCN.OfflineDataRecvAny5sBeforeOnline",
              offline_packets_received_);
        }

        UMA_HISTOGRAM_MEDIUM_TIMES("NCN.OfflineDataRecvUntilOnline",
                                   now - last_offline_packet_received_);
      }
    } else {
      UMA_HISTOGRAM_MEDIUM_TIMES("NCN.OfflineChange", state_duration);
    }

    LogOperatorCodeHistogram(type);

    UMA_HISTOGRAM_MEDIUM_TIMES(
        "NCN.IPAddressChangeToConnectionTypeChange",
        now - last_ip_address_change_);

    offline_packets_received_ = 0;
    bytes_read_since_last_connection_change_ = 0;
    peak_kbps_since_last_connection_change_ = 0;
    last_connection_type_ = type;
    polling_interval_ = base::TimeDelta::FromSeconds(1);
  }

  // DNSObserver implementation.
  void OnDNSChanged() override {
    DCHECK(thread_checker_.CalledOnValidThread());
    UMA_HISTOGRAM_MEDIUM_TIMES("NCN.DNSConfigChange",
                               SinceLast(&last_dns_change_));
  }

  // NetworkChangeObserver implementation.
  void OnNetworkChanged(ConnectionType type) override {
    DCHECK(thread_checker_.CalledOnValidThread());
    if (type != CONNECTION_NONE) {
      UMA_HISTOGRAM_MEDIUM_TIMES("NCN.NetworkOnlineChange",
                                 SinceLast(&last_network_change_));
    } else {
      UMA_HISTOGRAM_MEDIUM_TIMES("NCN.NetworkOfflineChange",
                                 SinceLast(&last_network_change_));
    }
  }

  // Record histogram data whenever we receive a packet. Should only be called
  // from the network thread.
  void NotifyDataReceived(const URLRequest& request, int bytes_read) {
    DCHECK(thread_checker_.CalledOnValidThread());
    if (IsLocalhost(request.url()) || !request.url().SchemeIsHTTPOrHTTPS()) {
      return;
    }

    base::TimeTicks now = base::TimeTicks::Now();
    base::TimeDelta request_duration = now - request.creation_time();
    if (bytes_read_since_last_connection_change_ == 0) {
      first_byte_after_connection_change_ = now - last_connection_change_;
      fastest_RTT_since_last_connection_change_ = request_duration;
    }
    bytes_read_since_last_connection_change_ += bytes_read;
    if (request_duration < fastest_RTT_since_last_connection_change_)
      fastest_RTT_since_last_connection_change_ = request_duration;
    // Ignore tiny transfers which will not produce accurate rates.
    // Ignore zero duration transfers which might cause divide by zero.
    if (bytes_read > 10000 &&
        request_duration > base::TimeDelta::FromMilliseconds(1) &&
        request.creation_time() > last_connection_change_) {
      int32_t kbps = static_cast<int32_t>(bytes_read * 8 /
                                          request_duration.InMilliseconds());
      if (kbps > peak_kbps_since_last_connection_change_)
        peak_kbps_since_last_connection_change_ = kbps;
    }

    if (last_connection_type_ != CONNECTION_NONE)
      return;

    UMA_HISTOGRAM_MEDIUM_TIMES("NCN.OfflineDataRecv",
                               now - last_connection_change_);
    offline_packets_received_++;
    last_offline_packet_received_ = now;

    if ((now - last_polled_connection_) > polling_interval_) {
      polling_interval_ *= 2;
      last_polled_connection_ = now;
      last_polled_connection_type_ = GetConnectionType();
    }
    if (last_polled_connection_type_ == CONNECTION_NONE) {
      UMA_HISTOGRAM_MEDIUM_TIMES("NCN.PollingOfflineDataRecv",
                                 now - last_connection_change_);
    }
  }

 private:
  static base::TimeDelta SinceLast(base::TimeTicks *last_time) {
    base::TimeTicks current_time = base::TimeTicks::Now();
    base::TimeDelta delta = current_time - *last_time;
    *last_time = current_time;
    return delta;
  }

  base::TimeTicks last_ip_address_change_;
  base::TimeTicks last_connection_change_;
  base::TimeTicks last_dns_change_;
  base::TimeTicks last_network_change_;
  base::TimeTicks last_offline_packet_received_;
  base::TimeTicks last_polled_connection_;
  // |polling_interval_| is initialized by |OnConnectionTypeChanged| on our
  // first transition to offline and on subsequent transitions.  Once offline,
  // |polling_interval_| doubles as offline data is received and we poll
  // with |GetConnectionType| to verify the connection
  // state.
  base::TimeDelta polling_interval_;
  // |last_connection_type_| is the last value passed to
  // |OnConnectionTypeChanged|.
  ConnectionType last_connection_type_;
  // |last_polled_connection_type_| is last result from calling
  // |GetConnectionType| in |NotifyDataReceived|.
  ConnectionType last_polled_connection_type_;
  // Count of how many times NotifyDataReceived() has been called while the
  // NetworkChangeNotifier thought network connection was offline.
  int32_t offline_packets_received_;
  // Number of bytes of network data received since last connectivity change.
  int32_t bytes_read_since_last_connection_change_;
  // Fastest round-trip-time (RTT) since last connectivity change. RTT measured
  // from URLRequest creation until first byte received.
  base::TimeDelta fastest_RTT_since_last_connection_change_;
  // Time between connectivity change and first network data byte received.
  base::TimeDelta first_byte_after_connection_change_;
  // Rough measurement of peak KB/s witnessed since last connectivity change.
  // The accuracy is decreased by ignoring these factors:
  // 1) Multiple URLRequests can occur concurrently.
  // 2) NotifyDataReceived() may be called repeatedly for one URLRequest.
  // 3) The transfer time includes at least one RTT while no bytes are read.
  // Erring on the conservative side is hopefully offset by taking the maximum.
  int32_t peak_kbps_since_last_connection_change_;

  base::ThreadChecker thread_checker_;

  DISALLOW_COPY_AND_ASSIGN(HistogramWatcher);
};

// NetworkState is thread safe.
class NetworkChangeNotifier::NetworkState {
 public:
  NetworkState() = default;
  ~NetworkState() = default;

  void GetDnsConfig(DnsConfig* config) const {
    base::AutoLock lock(lock_);
    *config = dns_config_;
  }

  void SetDnsConfig(const DnsConfig& dns_config) {
    base::AutoLock lock(lock_);
    dns_config_ = dns_config;
  }

 private:
  mutable base::Lock lock_;
  DnsConfig dns_config_;
};

NetworkChangeNotifier::NetworkChangeCalculatorParams::
    NetworkChangeCalculatorParams() = default;

// Calculates NetworkChange signal from IPAddress and ConnectionType signals.
class NetworkChangeNotifier::NetworkChangeCalculator
    : public ConnectionTypeObserver,
      public IPAddressObserver {
 public:
  explicit NetworkChangeCalculator(const NetworkChangeCalculatorParams& params)
      : params_(params),
        have_announced_(false),
        last_announced_connection_type_(CONNECTION_NONE),
        pending_connection_type_(CONNECTION_NONE) {}

  void Init() {
    DCHECK(thread_checker_.CalledOnValidThread());
    DCHECK(g_network_change_notifier);
    AddConnectionTypeObserver(this);
    AddIPAddressObserver(this);
  }

  ~NetworkChangeCalculator() override {
    DCHECK(thread_checker_.CalledOnValidThread());
    DCHECK(g_network_change_notifier);
    RemoveConnectionTypeObserver(this);
    RemoveIPAddressObserver(this);
  }

  // NetworkChangeNotifier::IPAddressObserver implementation.
  void OnIPAddressChanged() override {
    DCHECK(thread_checker_.CalledOnValidThread());
    base::TimeDelta delay = last_announced_connection_type_ == CONNECTION_NONE
        ? params_.ip_address_offline_delay_ : params_.ip_address_online_delay_;
    // Cancels any previous timer.
    timer_.Start(FROM_HERE, delay, this, &NetworkChangeCalculator::Notify);
  }

  // NetworkChangeNotifier::ConnectionTypeObserver implementation.
  void OnConnectionTypeChanged(ConnectionType type) override {
    DCHECK(thread_checker_.CalledOnValidThread());
    pending_connection_type_ = type;
    base::TimeDelta delay = last_announced_connection_type_ == CONNECTION_NONE
        ? params_.connection_type_offline_delay_
        : params_.connection_type_online_delay_;
    // Cancels any previous timer.
    timer_.Start(FROM_HERE, delay, this, &NetworkChangeCalculator::Notify);
  }

 private:
  void Notify() {
    DCHECK(thread_checker_.CalledOnValidThread());
    // Don't bother signaling about dead connections.
    if (have_announced_ &&
        (last_announced_connection_type_ == CONNECTION_NONE) &&
        (pending_connection_type_ == CONNECTION_NONE)) {
      return;
    }
    have_announced_ = true;
    last_announced_connection_type_ = pending_connection_type_;
    // Immediately before sending out an online signal, send out an offline
    // signal to perform any destructive actions before constructive actions.
    if (pending_connection_type_ != CONNECTION_NONE)
      NetworkChangeNotifier::NotifyObserversOfNetworkChange(CONNECTION_NONE);
    NetworkChangeNotifier::NotifyObserversOfNetworkChange(
        pending_connection_type_);
  }

  const NetworkChangeCalculatorParams params_;

  // Indicates if NotifyObserversOfNetworkChange has been called yet.
  bool have_announced_;
  // Last value passed to NotifyObserversOfNetworkChange.
  ConnectionType last_announced_connection_type_;
  // Value to pass to NotifyObserversOfNetworkChange when Notify is called.
  ConnectionType pending_connection_type_;
  // Used to delay notifications so duplicates can be combined.
  base::OneShotTimer timer_;

  base::ThreadChecker thread_checker_;

  DISALLOW_COPY_AND_ASSIGN(NetworkChangeCalculator);
};

NetworkChangeNotifier::~NetworkChangeNotifier() {
  network_change_calculator_.reset();
  DCHECK_EQ(this, g_network_change_notifier);
  g_network_change_notifier = NULL;
}

// static
NetworkChangeNotifierFactory* NetworkChangeNotifier::GetFactory() {
  return g_network_change_notifier_factory;
}

// static
void NetworkChangeNotifier::SetFactory(
    NetworkChangeNotifierFactory* factory) {
  CHECK(!g_network_change_notifier_factory);
  g_network_change_notifier_factory = factory;
}

// static
NetworkChangeNotifier* NetworkChangeNotifier::Create() {
  if (g_network_change_notifier_factory)
    return g_network_change_notifier_factory->CreateInstance();

#if defined(OS_WIN)
  NetworkChangeNotifierWin* network_change_notifier =
      new NetworkChangeNotifierWin();
  network_change_notifier->WatchForAddressChange();
  return network_change_notifier;
#elif defined(OS_CHROMEOS) || defined(OS_ANDROID)
  // ChromeOS and Android builds MUST use their own class factory.
#if !defined(OS_CHROMEOS)
  // TODO(oshima): ash_shell do not have access to chromeos'es
  // notifier yet. Re-enable this when chromeos'es notifier moved to
  // chromeos root directory. crbug.com/119298.
  CHECK(false);
#endif
  return NULL;
#elif defined(OS_LINUX)
  return new NetworkChangeNotifierLinux(std::unordered_set<std::string>());
#elif defined(OS_MACOSX)
  return new NetworkChangeNotifierMac();
#else
  NOTIMPLEMENTED();
  return NULL;
#endif
}

// static
bool NetworkChangeNotifier::HasNetworkChangeNotifier() {
  return g_network_change_notifier != nullptr;
}

// static
NetworkChangeNotifier::ConnectionType
NetworkChangeNotifier::GetConnectionType() {
  return g_network_change_notifier ?
      g_network_change_notifier->GetCurrentConnectionType() :
      CONNECTION_UNKNOWN;
}

// static
NetworkChangeNotifier::ConnectionSubtype
NetworkChangeNotifier::GetConnectionSubtype() {
  return g_network_change_notifier
             ? g_network_change_notifier->GetCurrentConnectionSubtype()
             : SUBTYPE_UNKNOWN;
}

// static
void NetworkChangeNotifier::GetMaxBandwidthAndConnectionType(
    double* max_bandwidth_mbps,
    ConnectionType* connection_type) {
  if (!g_network_change_notifier) {
    *connection_type = CONNECTION_UNKNOWN;
    *max_bandwidth_mbps =
        GetMaxBandwidthMbpsForConnectionSubtype(SUBTYPE_UNKNOWN);
    return;
  }

  g_network_change_notifier->GetCurrentMaxBandwidthAndConnectionType(
      max_bandwidth_mbps, connection_type);
}

// static
double NetworkChangeNotifier::GetMaxBandwidthMbpsForConnectionSubtype(
    ConnectionSubtype subtype) {
  switch (subtype) {
    case SUBTYPE_GSM:
      return 0.01;
    case SUBTYPE_IDEN:
      return 0.064;
    case SUBTYPE_CDMA:
      return 0.115;
    case SUBTYPE_1XRTT:
      return 0.153;
    case SUBTYPE_GPRS:
      return 0.237;
    case SUBTYPE_EDGE:
      return 0.384;
    case SUBTYPE_UMTS:
      return 2.0;
    case SUBTYPE_EVDO_REV_0:
      return 2.46;
    case SUBTYPE_EVDO_REV_A:
      return 3.1;
    case SUBTYPE_HSPA:
      return 3.6;
    case SUBTYPE_EVDO_REV_B:
      return 14.7;
    case SUBTYPE_HSDPA:
      return 14.3;
    case SUBTYPE_HSUPA:
      return 14.4;
    case SUBTYPE_EHRPD:
      return 21.0;
    case SUBTYPE_HSPAP:
      return 42.0;
    case SUBTYPE_LTE:
      return 100.0;
    case SUBTYPE_LTE_ADVANCED:
      return 100.0;
    case SUBTYPE_BLUETOOTH_1_2:
      return 1.0;
    case SUBTYPE_BLUETOOTH_2_1:
      return 3.0;
    case SUBTYPE_BLUETOOTH_3_0:
      return 24.0;
    case SUBTYPE_BLUETOOTH_4_0:
      return 1.0;
    case SUBTYPE_ETHERNET:
      return 10.0;
    case SUBTYPE_FAST_ETHERNET:
      return 100.0;
    case SUBTYPE_GIGABIT_ETHERNET:
      return 1000.0;
    case SUBTYPE_10_GIGABIT_ETHERNET:
      return 10000.0;
    case SUBTYPE_WIFI_B:
      return 11.0;
    case SUBTYPE_WIFI_G:
      return 54.0;
    case SUBTYPE_WIFI_N:
      return 600.0;
    case SUBTYPE_WIFI_AC:
      return 1300.0;
    case SUBTYPE_WIFI_AD:
      return 7000.0;
    case SUBTYPE_UNKNOWN:
      return std::numeric_limits<double>::infinity();
    case SUBTYPE_NONE:
      return 0.0;
    case SUBTYPE_OTHER:
      return std::numeric_limits<double>::infinity();
  }
  NOTREACHED();
  return std::numeric_limits<double>::infinity();
}

// static
bool NetworkChangeNotifier::AreNetworkHandlesSupported() {
  if (g_network_change_notifier) {
    return g_network_change_notifier->AreNetworkHandlesCurrentlySupported();
  }
  return false;
}

// static
void NetworkChangeNotifier::GetConnectedNetworks(NetworkList* network_list) {
  DCHECK(AreNetworkHandlesSupported());
  if (g_network_change_notifier) {
    g_network_change_notifier->GetCurrentConnectedNetworks(network_list);
  } else {
    network_list->clear();
  }
}

// static
NetworkChangeNotifier::ConnectionType
NetworkChangeNotifier::GetNetworkConnectionType(NetworkHandle network) {
  DCHECK(AreNetworkHandlesSupported());
  return g_network_change_notifier
             ? g_network_change_notifier->GetCurrentNetworkConnectionType(
                   network)
             : CONNECTION_UNKNOWN;
}

// static
NetworkChangeNotifier::NetworkHandle
NetworkChangeNotifier::GetDefaultNetwork() {
  DCHECK(AreNetworkHandlesSupported());
  return g_network_change_notifier
             ? g_network_change_notifier->GetCurrentDefaultNetwork()
             : kInvalidNetworkHandle;
}

// static
void NetworkChangeNotifier::GetDnsConfig(DnsConfig* config) {
  if (!g_network_change_notifier) {
    *config = DnsConfig();
  } else {
    g_network_change_notifier->network_state_->GetDnsConfig(config);
  }
}

// static
const char* NetworkChangeNotifier::ConnectionTypeToString(
    ConnectionType type) {
  static const char* const kConnectionTypeNames[] = {
    "CONNECTION_UNKNOWN",
    "CONNECTION_ETHERNET",
    "CONNECTION_WIFI",
    "CONNECTION_2G",
    "CONNECTION_3G",
    "CONNECTION_4G",
    "CONNECTION_NONE",
    "CONNECTION_BLUETOOTH"
  };
  static_assert(base::size(kConnectionTypeNames) ==
                    NetworkChangeNotifier::CONNECTION_LAST + 1,
                "ConnectionType name count should match");
  if (type < CONNECTION_UNKNOWN || type > CONNECTION_LAST) {
    NOTREACHED();
    return "CONNECTION_INVALID";
  }
  return kConnectionTypeNames[type];
}

// static
void NetworkChangeNotifier::NotifyDataReceived(const URLRequest& request,
                                               int bytes_read) {
  if (!g_network_change_notifier ||
      !g_network_change_notifier->histogram_watcher_) {
    return;
  }
  g_network_change_notifier->histogram_watcher_->NotifyDataReceived(request,
                                                                    bytes_read);
}

// static
void NetworkChangeNotifier::InitHistogramWatcher() {
  if (!g_network_change_notifier)
    return;
  g_network_change_notifier->histogram_watcher_.reset(new HistogramWatcher());
  g_network_change_notifier->histogram_watcher_->Init();
}

// static
void NetworkChangeNotifier::ShutdownHistogramWatcher() {
  if (!g_network_change_notifier)
    return;
  g_network_change_notifier->histogram_watcher_.reset();
}

// static
void NetworkChangeNotifier::FinalizingMetricsLogRecord() {
  if (!g_network_change_notifier)
    return;
  g_network_change_notifier->OnFinalizingMetricsLogRecord();
}

// static
void NetworkChangeNotifier::LogOperatorCodeHistogram(ConnectionType type) {
#if defined(OS_ANDROID)
  // On a connection type change to cellular, log the network operator MCC/MNC.
  // Log zero in other cases.
  unsigned mcc_mnc = 0;
  if (NetworkChangeNotifier::IsConnectionCellular(type)) {
    // Log zero if not perfectly converted.
    if (!base::StringToUint(android::GetTelephonyNetworkOperator(), &mcc_mnc)) {
      mcc_mnc = 0;
    }
  }
  base::UmaHistogramSparse("NCN.NetworkOperatorMCCMNC", mcc_mnc);
#endif
}

#if defined(OS_LINUX)
// static
const internal::AddressTrackerLinux*
NetworkChangeNotifier::GetAddressTracker() {
  return g_network_change_notifier ?
        g_network_change_notifier->GetAddressTrackerInternal() : NULL;
}
#endif

// static
bool NetworkChangeNotifier::IsOffline() {
  return GetConnectionType() == CONNECTION_NONE;
}

// static
bool NetworkChangeNotifier::IsConnectionCellular(ConnectionType type) {
  bool is_cellular = false;
  switch (type) {
    case CONNECTION_2G:
    case CONNECTION_3G:
    case CONNECTION_4G:
      is_cellular =  true;
      break;
    case CONNECTION_UNKNOWN:
    case CONNECTION_ETHERNET:
    case CONNECTION_WIFI:
    case CONNECTION_NONE:
    case CONNECTION_BLUETOOTH:
      is_cellular = false;
      break;
  }
  return is_cellular;
}

// static
NetworkChangeNotifier::ConnectionType
NetworkChangeNotifier::ConnectionTypeFromInterfaces() {
  NetworkInterfaceList interfaces;
  if (!GetNetworkList(&interfaces, EXCLUDE_HOST_SCOPE_VIRTUAL_INTERFACES))
    return CONNECTION_UNKNOWN;
  return ConnectionTypeFromInterfaceList(interfaces);
}

// static
NetworkChangeNotifier::ConnectionType
NetworkChangeNotifier::ConnectionTypeFromInterfaceList(
    const NetworkInterfaceList& interfaces) {
  bool first = true;
  ConnectionType result = CONNECTION_NONE;
  for (size_t i = 0; i < interfaces.size(); ++i) {
#if defined(OS_WIN)
    if (interfaces[i].friendly_name == "Teredo Tunneling Pseudo-Interface")
      continue;
#endif
#if defined(OS_MACOSX)
    // Ignore tunnel and airdrop interfaces.
    if (base::StartsWith(interfaces[i].friendly_name, "utun",
                         base::CompareCase::SENSITIVE) ||
        base::StartsWith(interfaces[i].friendly_name, "awdl",
                         base::CompareCase::SENSITIVE)) {
      continue;
    }
#endif

    // Remove VMware network interfaces as they're internal and should not be
    // used to determine the network connection type.
    if (base::ToLowerASCII(interfaces[i].friendly_name).find("vmnet") !=
        std::string::npos) {
      continue;
    }
    if (first) {
      first = false;
      result = interfaces[i].type;
    } else if (result != interfaces[i].type) {
      return CONNECTION_UNKNOWN;
    }
  }
  return result;
}

// static
NetworkChangeNotifier* NetworkChangeNotifier::CreateMock() {
  return new MockNetworkChangeNotifier();
}

void NetworkChangeNotifier::AddIPAddressObserver(IPAddressObserver* observer) {
  if (g_network_change_notifier)
    g_network_change_notifier->ip_address_observer_list_->AddObserver(observer);
}

void NetworkChangeNotifier::AddConnectionTypeObserver(
    ConnectionTypeObserver* observer) {
  if (g_network_change_notifier) {
    g_network_change_notifier->connection_type_observer_list_->AddObserver(
        observer);
  }
}

void NetworkChangeNotifier::AddDNSObserver(DNSObserver* observer) {
  if (g_network_change_notifier) {
    g_network_change_notifier->resolver_state_observer_list_->AddObserver(
        observer);
  }
}

void NetworkChangeNotifier::AddNetworkChangeObserver(
    NetworkChangeObserver* observer) {
  if (g_network_change_notifier) {
    g_network_change_notifier->network_change_observer_list_->AddObserver(
        observer);
  }
}

void NetworkChangeNotifier::AddMaxBandwidthObserver(
    MaxBandwidthObserver* observer) {
  if (g_network_change_notifier) {
    g_network_change_notifier->max_bandwidth_observer_list_->AddObserver(
        observer);
  }
}

void NetworkChangeNotifier::AddNetworkObserver(NetworkObserver* observer) {
  DCHECK(AreNetworkHandlesSupported());
  if (g_network_change_notifier) {
    g_network_change_notifier->network_observer_list_->AddObserver(observer);
  }
}

void NetworkChangeNotifier::RemoveIPAddressObserver(
    IPAddressObserver* observer) {
  if (g_network_change_notifier) {
    g_network_change_notifier->ip_address_observer_list_->RemoveObserver(
        observer);
  }
}

void NetworkChangeNotifier::RemoveConnectionTypeObserver(
    ConnectionTypeObserver* observer) {
  if (g_network_change_notifier) {
    g_network_change_notifier->connection_type_observer_list_->RemoveObserver(
        observer);
  }
}

void NetworkChangeNotifier::RemoveDNSObserver(DNSObserver* observer) {
  if (g_network_change_notifier) {
    g_network_change_notifier->resolver_state_observer_list_->RemoveObserver(
        observer);
  }
}

void NetworkChangeNotifier::RemoveNetworkChangeObserver(
    NetworkChangeObserver* observer) {
  if (g_network_change_notifier) {
    g_network_change_notifier->network_change_observer_list_->RemoveObserver(
        observer);
  }
}

void NetworkChangeNotifier::RemoveMaxBandwidthObserver(
    MaxBandwidthObserver* observer) {
  if (g_network_change_notifier) {
    g_network_change_notifier->max_bandwidth_observer_list_->RemoveObserver(
        observer);
  }
}

void NetworkChangeNotifier::RemoveNetworkObserver(NetworkObserver* observer) {
  DCHECK(AreNetworkHandlesSupported());
  if (g_network_change_notifier) {
    g_network_change_notifier->network_observer_list_->RemoveObserver(observer);
  }
}

// static
void NetworkChangeNotifier::NotifyObserversOfIPAddressChangeForTests() {
  if (g_network_change_notifier)
    g_network_change_notifier->NotifyObserversOfIPAddressChangeImpl();
}

// static
void NetworkChangeNotifier::NotifyObserversOfConnectionTypeChangeForTests(
    ConnectionType type) {
  if (g_network_change_notifier)
    g_network_change_notifier->NotifyObserversOfConnectionTypeChangeImpl(type);
}

// static
void NetworkChangeNotifier::NotifyObserversOfDNSChangeForTests() {
  if (g_network_change_notifier)
    g_network_change_notifier->NotifyObserversOfDNSChangeImpl();
}

// static
void NetworkChangeNotifier::NotifyObserversOfNetworkChangeForTests(
    ConnectionType type) {
  if (g_network_change_notifier)
    g_network_change_notifier->NotifyObserversOfNetworkChangeImpl(type);
}

// static
void NetworkChangeNotifier::NotifyObserversOfInitialDNSConfigReadForTests() {
  if (g_network_change_notifier)
    g_network_change_notifier->NotifyObserversOfInitialDNSConfigReadImpl();
}

// static
void NetworkChangeNotifier::NotifyObserversOfMaxBandwidthChangeForTests(
    double max_bandwidth_mbps,
    ConnectionType type) {
  if (g_network_change_notifier) {
    g_network_change_notifier->NotifyObserversOfMaxBandwidthChangeImpl(
        max_bandwidth_mbps, type);
  }
}

// static
void NetworkChangeNotifier::SetTestNotificationsOnly(bool test_only) {
  DCHECK(!g_network_change_notifier);
  NetworkChangeNotifier::test_notifications_only_ = test_only;
}

NetworkChangeNotifier::NetworkChangeNotifier(
    const NetworkChangeCalculatorParams& params
    /*= NetworkChangeCalculatorParams()*/)
    : ip_address_observer_list_(
          new base::ObserverListThreadSafe<IPAddressObserver>(
              base::ObserverListPolicy::EXISTING_ONLY)),
      connection_type_observer_list_(
          new base::ObserverListThreadSafe<ConnectionTypeObserver>(
              base::ObserverListPolicy::EXISTING_ONLY)),
      resolver_state_observer_list_(
          new base::ObserverListThreadSafe<DNSObserver>(
              base::ObserverListPolicy::EXISTING_ONLY)),
      network_change_observer_list_(
          new base::ObserverListThreadSafe<NetworkChangeObserver>(
              base::ObserverListPolicy::EXISTING_ONLY)),
      max_bandwidth_observer_list_(
          new base::ObserverListThreadSafe<MaxBandwidthObserver>(
              base::ObserverListPolicy::EXISTING_ONLY)),
      network_observer_list_(new base::ObserverListThreadSafe<NetworkObserver>(
          base::ObserverListPolicy::EXISTING_ONLY)),
      network_state_(new NetworkState()),
      network_change_calculator_(new NetworkChangeCalculator(params)) {
  DCHECK(!g_network_change_notifier);
  g_network_change_notifier = this;
  network_change_calculator_->Init();
}

#if defined(OS_LINUX)
const internal::AddressTrackerLinux*
NetworkChangeNotifier::GetAddressTrackerInternal() const {
  return NULL;
}
#endif

NetworkChangeNotifier::ConnectionSubtype
NetworkChangeNotifier::GetCurrentConnectionSubtype() const {
  return SUBTYPE_UNKNOWN;
}

void NetworkChangeNotifier::GetCurrentMaxBandwidthAndConnectionType(
    double* max_bandwidth_mbps,
    ConnectionType* connection_type) const {
  // This default implementation conforms to the NetInfo V3 specification but
  // should be overridden to provide specific bandwidth data based on the
  // platform.
  *connection_type = GetCurrentConnectionType();
  *max_bandwidth_mbps =
      *connection_type == CONNECTION_NONE
          ? GetMaxBandwidthMbpsForConnectionSubtype(SUBTYPE_NONE)
          : GetMaxBandwidthMbpsForConnectionSubtype(SUBTYPE_UNKNOWN);
}

bool NetworkChangeNotifier::AreNetworkHandlesCurrentlySupported() const {
  return false;
}

void NetworkChangeNotifier::GetCurrentConnectedNetworks(
    NetworkList* network_list) const {
  network_list->clear();
}

NetworkChangeNotifier::ConnectionType
NetworkChangeNotifier::GetCurrentNetworkConnectionType(
    NetworkHandle network) const {
  return CONNECTION_UNKNOWN;
}

NetworkChangeNotifier::NetworkHandle
NetworkChangeNotifier::GetCurrentDefaultNetwork() const {
  return kInvalidNetworkHandle;
}

// static
void NetworkChangeNotifier::NotifyObserversOfIPAddressChange() {
  if (g_network_change_notifier &&
      !NetworkChangeNotifier::test_notifications_only_) {
    g_network_change_notifier->NotifyObserversOfIPAddressChangeImpl();
  }
}

// static
void NetworkChangeNotifier::NotifyObserversOfConnectionTypeChange() {
  if (g_network_change_notifier &&
      !NetworkChangeNotifier::test_notifications_only_) {
    g_network_change_notifier->NotifyObserversOfConnectionTypeChangeImpl(
        GetConnectionType());
  }
}

// static
void NetworkChangeNotifier::NotifyObserversOfNetworkChange(
    ConnectionType type) {
  if (g_network_change_notifier &&
      !NetworkChangeNotifier::test_notifications_only_) {
    g_network_change_notifier->NotifyObserversOfNetworkChangeImpl(type);
  }
}

// static
void NetworkChangeNotifier::NotifyObserversOfMaxBandwidthChange(
    double max_bandwidth_mbps,
    ConnectionType type) {
  if (g_network_change_notifier &&
      !NetworkChangeNotifier::test_notifications_only_) {
    g_network_change_notifier->NotifyObserversOfMaxBandwidthChangeImpl(
        max_bandwidth_mbps, type);
  }
}

// static
void NetworkChangeNotifier::NotifyObserversOfDNSChange() {
  if (g_network_change_notifier &&
      !NetworkChangeNotifier::test_notifications_only_) {
    g_network_change_notifier->NotifyObserversOfDNSChangeImpl();
  }
}

// static
void NetworkChangeNotifier::NotifyObserversOfInitialDNSConfigRead() {
  if (g_network_change_notifier &&
      !NetworkChangeNotifier::test_notifications_only_) {
    g_network_change_notifier->NotifyObserversOfInitialDNSConfigReadImpl();
  }
}

// static
void NetworkChangeNotifier::NotifyObserversOfSpecificNetworkChange(
    NetworkChangeType type,
    NetworkHandle network) {
  if (g_network_change_notifier &&
      !NetworkChangeNotifier::test_notifications_only_) {
    g_network_change_notifier->NotifyObserversOfSpecificNetworkChangeImpl(
        type, network);
  }
}

// static
void NetworkChangeNotifier::SetDnsConfig(const DnsConfig& config) {
  if (!g_network_change_notifier)
    return;
  g_network_change_notifier->network_state_->SetDnsConfig(config);
  NotifyObserversOfDNSChange();
}

// static
void NetworkChangeNotifier::SetInitialDnsConfig(const DnsConfig& config) {
  if (!g_network_change_notifier)
    return;
#if DCHECK_IS_ON()
  // Verify we've never received a valid DnsConfig previously.
  DnsConfig old_config;
  g_network_change_notifier->network_state_->GetDnsConfig(&old_config);
  DCHECK(!old_config.IsValid());
#endif
  g_network_change_notifier->network_state_->SetDnsConfig(config);
  NotifyObserversOfInitialDNSConfigRead();
}

void NetworkChangeNotifier::NotifyObserversOfIPAddressChangeImpl() {
  ip_address_observer_list_->Notify(FROM_HERE,
                                    &IPAddressObserver::OnIPAddressChanged);
}

void NetworkChangeNotifier::NotifyObserversOfConnectionTypeChangeImpl(
    ConnectionType type) {
  connection_type_observer_list_->Notify(
      FROM_HERE, &ConnectionTypeObserver::OnConnectionTypeChanged, type);
}

void NetworkChangeNotifier::NotifyObserversOfNetworkChangeImpl(
    ConnectionType type) {
  network_change_observer_list_->Notify(
      FROM_HERE, &NetworkChangeObserver::OnNetworkChanged, type);
}

void NetworkChangeNotifier::NotifyObserversOfDNSChangeImpl() {
  resolver_state_observer_list_->Notify(FROM_HERE, &DNSObserver::OnDNSChanged);
}

void NetworkChangeNotifier::NotifyObserversOfInitialDNSConfigReadImpl() {
  resolver_state_observer_list_->Notify(FROM_HERE,
                                        &DNSObserver::OnInitialDNSConfigRead);
}

void NetworkChangeNotifier::NotifyObserversOfMaxBandwidthChangeImpl(
    double max_bandwidth_mbps,
    ConnectionType type) {
  max_bandwidth_observer_list_->Notify(
      FROM_HERE, &MaxBandwidthObserver::OnMaxBandwidthChanged,
      max_bandwidth_mbps, type);
}

void NetworkChangeNotifier::NotifyObserversOfSpecificNetworkChangeImpl(
    NetworkChangeType type,
    NetworkHandle network) {
  switch (type) {
    case CONNECTED:
      network_observer_list_->Notify(
          FROM_HERE, &NetworkObserver::OnNetworkConnected, network);
      break;
    case DISCONNECTED:
      network_observer_list_->Notify(
          FROM_HERE, &NetworkObserver::OnNetworkDisconnected, network);
      break;
    case SOON_TO_DISCONNECT:
      network_observer_list_->Notify(
          FROM_HERE, &NetworkObserver::OnNetworkSoonToDisconnect, network);
      break;
    case MADE_DEFAULT:
      network_observer_list_->Notify(
          FROM_HERE, &NetworkObserver::OnNetworkMadeDefault, network);
      break;
  }
}

NetworkChangeNotifier::DisableForTest::DisableForTest()
    : network_change_notifier_(g_network_change_notifier) {
  DCHECK(g_network_change_notifier);
  g_network_change_notifier = NULL;
}

NetworkChangeNotifier::DisableForTest::~DisableForTest() {
  DCHECK(!g_network_change_notifier);
  g_network_change_notifier = network_change_notifier_;
}

void NetworkChangeNotifier::DNSObserver::OnInitialDNSConfigRead() {
}

}  // namespace net