net/android/network_change_notifier_android.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 ////////////////////////////////////////////////////////////////////////////////
   6 // Threading considerations:
   7 //
   8 // This class is designed to meet various threading guarantees starting from the
   9 // ones imposed by NetworkChangeNotifier:
  10 // - The notifier can be constructed on any thread.
  11 // - GetCurrentConnectionType() can be called on any thread.
  12 //
  13 // The fact that this implementation of NetworkChangeNotifier is backed by a
  14 // Java side singleton class (see NetworkChangeNotifier.java) adds another
  15 // threading constraint:
  16 // - The calls to the Java side (stateful) object must be performed from a
  17 //   single thread. This object happens to be a singleton which is used on the
  18 //   application side on the main thread. Therefore all the method calls from
  19 //   the native NetworkChangeNotifierAndroid class to its Java counterpart are
  20 //   performed on the main thread.
  21 //
  22 // This leads to a design involving the following native classes:
  23 // 1) NetworkChangeNotifierFactoryAndroid ('factory')
  24 // 2) NetworkChangeNotifierDelegateAndroid ('delegate')
  25 // 3) NetworkChangeNotifierAndroid ('notifier')
  26 //
  27 // The factory constructs and owns the delegate. The factory is constructed and
  28 // destroyed on the main thread which makes it construct and destroy the
  29 // delegate on the main thread too. This guarantees that the calls to the Java
  30 // side are performed on the main thread.
  31 // Note that after the factory's construction, the factory's creation method can
  32 // be called from any thread since the delegate's construction (performing the
  33 // JNI calls) already happened on the main thread (when the factory was
  34 // constructed).
  35 //
  36 ////////////////////////////////////////////////////////////////////////////////
  37 // Propagation of network change notifications:
  38 //
  39 // When the factory is requested to create a new instance of the notifier, the
  40 // factory passes the delegate to the notifier (without transferring ownership).
  41 // Note that there is a one-to-one mapping between the factory and the
  42 // delegate as explained above. But the factory naturally creates multiple
  43 // instances of the notifier. That means that there is a one-to-many mapping
  44 // between delegate and notifier (i.e. a single delegate can be shared by
  45 // multiple notifiers).
  46 // At construction the notifier (which is also an observer) subscribes to
  47 // notifications fired by the delegate. These notifications, received by the
  48 // delegate (and forwarded to the notifier(s)), are sent by the Java side
  49 // notifier (see NetworkChangeNotifier.java) and are initiated by the Android
  50 // platform.
  51 // Notifications from the Java side always arrive on the main thread. The
  52 // delegate then forwards these notifications to the threads of each observer
  53 // (network change notifier). The network change notifier than processes the
  54 // state change, and notifies each of its observers on their threads.
  55 //
  56 // This can also be seen as:
  57 // Android platform -> NetworkChangeNotifier (Java) ->
  58 // NetworkChangeNotifierDelegateAndroid -> NetworkChangeNotifierAndroid.
  59
  60 #include "net/android/network_change_notifier_android.h"
  61
  62 #include "base/threading/thread.h"
  63 #include "net/base/address_tracker_linux.h"
  64 #include "net/dns/dns_config_service.h"
  65
  66 namespace net {
  67
  68 // Thread on which we can run DnsConfigService, which requires a TYPE_IO
  69 // message loop to monitor /system/etc/hosts.
  70 class NetworkChangeNotifierAndroid::DnsConfigServiceThread
  71     : public base::Thread {
  72  public:
  73   DnsConfigServiceThread()
  74       : base::Thread("DnsConfigService"),
  75         address_tracker_(base::Bind(base::DoNothing),
  76                          base::Bind(base::DoNothing),
  77                          // We're only interested in tunnel interface changes.
  78                          base::Bind(NotifyNetworkChangeNotifierObservers)) {}
  79
  80   ~DnsConfigServiceThread() override { Stop(); }
  81
  82   void Init() override {
  83     address_tracker_.Init();
  84     dns_config_service_ = DnsConfigService::CreateSystemService();
  85     dns_config_service_->WatchConfig(
  86         base::Bind(&NetworkChangeNotifier::SetDnsConfig));
  87   }
  88
  89   void CleanUp() override { dns_config_service_.reset(); }
  90
  91   static void NotifyNetworkChangeNotifierObservers() {
  92     NetworkChangeNotifier::NotifyObserversOfIPAddressChange();
  93     NetworkChangeNotifier::NotifyObserversOfConnectionTypeChange();
  94   }
  95
  96  private:
  97   scoped_ptr<DnsConfigService> dns_config_service_;
  98   // Used to detect tunnel state changes.
  99   internal::AddressTrackerLinux address_tracker_;
 100
 101   DISALLOW_COPY_AND_ASSIGN(DnsConfigServiceThread);
 102 };
 103
 104 NetworkChangeNotifierAndroid::~NetworkChangeNotifierAndroid() {
 105   delegate_->RemoveObserver(this);
 106 }
 107
 108 NetworkChangeNotifier::ConnectionType
 109 NetworkChangeNotifierAndroid::GetCurrentConnectionType() const {
 110   return delegate_->GetCurrentConnectionType();
 111 }
 112
 113 double NetworkChangeNotifierAndroid::GetCurrentMaxBandwidth() const {
 114   return delegate_->GetCurrentMaxBandwidth();
 115 }
 116
 117 void NetworkChangeNotifierAndroid::OnConnectionTypeChanged() {
 118   DnsConfigServiceThread::NotifyNetworkChangeNotifierObservers();
 119 }
 120
 121 void NetworkChangeNotifierAndroid::OnMaxBandwidthChanged(
 122     double max_bandwidth_mbps) {
 123   NetworkChangeNotifier::NotifyObserversOfMaxBandwidthChange(
 124       max_bandwidth_mbps);
 125 }
 126
 127 // static
 128 bool NetworkChangeNotifierAndroid::Register(JNIEnv* env) {
 129   return NetworkChangeNotifierDelegateAndroid::Register(env);
 130 }
 131
 132 NetworkChangeNotifierAndroid::NetworkChangeNotifierAndroid(
 133     NetworkChangeNotifierDelegateAndroid* delegate)
 134     : NetworkChangeNotifier(NetworkChangeCalculatorParamsAndroid()),
 135       delegate_(delegate),
 136       dns_config_service_thread_(new DnsConfigServiceThread()) {
 137   delegate_->AddObserver(this);
 138   dns_config_service_thread_->StartWithOptions(
 139       base::Thread::Options(base::MessageLoop::TYPE_IO, 0));
 140 }
 141
 142 // static
 143 NetworkChangeNotifier::NetworkChangeCalculatorParams
 144 NetworkChangeNotifierAndroid::NetworkChangeCalculatorParamsAndroid() {
 145   NetworkChangeCalculatorParams params;
 146   // IPAddressChanged is produced immediately prior to ConnectionTypeChanged
 147   // so delay IPAddressChanged so they get merged with the following
 148   // ConnectionTypeChanged signal.
 149   params.ip_address_offline_delay_ = base::TimeDelta::FromSeconds(1);
 150   params.ip_address_online_delay_ = base::TimeDelta::FromSeconds(1);
 151   params.connection_type_offline_delay_ = base::TimeDelta::FromSeconds(0);
 152   params.connection_type_online_delay_ = base::TimeDelta::FromSeconds(0);
 153   return params;
 154 }
 155
 156 }  // namespace net