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// 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 "base/basictypes.h"
#include "base/observer_list_threadsafe.h"
#include "base/time.h"
#include "net/base/net_export.h"
class GURL;
namespace net {
struct DnsConfig;
class HistogramWatcher;
class NetworkChangeNotifierFactory;
#if defined(OS_LINUX)
namespace internal {
class AddressTrackerLinux;
// NetworkChangeNotifier monitors the system for network changes, and notifies
// registered observers of those events. Observers may register on any thread,
// and will be called back on the thread from which they registered.
// NetworkChangeNotifiers are threadsafe, though they must be created and
// destroyed on the same thread.
class NET_EXPORT NetworkChangeNotifier {
// Using the terminology of the Network Information API:
enum ConnectionType {
CONNECTION_UNKNOWN = 0, // A connection exists, but its type is unknown.
CONNECTION_NONE = 6 // No connection.
class NET_EXPORT IPAddressObserver {
// Will be called when the IP address of the primary interface changes.
// This includes when the primary interface itself changes.
virtual void OnIPAddressChanged() = 0;
IPAddressObserver() {}
virtual ~IPAddressObserver() {}
class NET_EXPORT ConnectionTypeObserver {
// Will be called when the connection type of the system has changed.
// See NetworkChangeNotifier::GetConnectionType() for important caveats
// about the unreliability of using this signal to infer the ability to
// reach remote sites.
virtual void OnConnectionTypeChanged(ConnectionType type) = 0;
ConnectionTypeObserver() {}
virtual ~ConnectionTypeObserver() {}
class NET_EXPORT DNSObserver {
// Will be called when the DNS settings of the system may have changed.
// Use GetDnsConfig to obtain the current settings.
virtual void OnDNSChanged() = 0;
DNSObserver() {}
virtual ~DNSObserver() {}
class NET_EXPORT NetworkChangeObserver {
// OnNetworkChanged will be called when a change occurs to the host
// computer's hardware or software that affects the route network packets
// take to any network server. Some examples:
// 1. A network connection becoming available or going away. For example
// plugging or unplugging an Ethernet cable, WiFi or cellular modem
// connecting or disconnecting from a network, or a VPN tunnel being
// established or taken down.
// 2. An active network connection's IP address changes.
// 3. A change to the local IP routing tables.
// The signal shall only be produced when the change is complete. For
// example if a new network connection has become available, only give the
// signal once we think the O/S has finished establishing the connection
// (i.e. DHCP is done) to the point where the new connection is usable.
// The signal shall not be produced spuriously as it will be triggering some
// expensive operations, like socket pools closing all connections and
// sockets and then re-establishing them.
// |type| indicates the type of the active primary network connection after
// the change. Observers performing "constructive" activities like trying
// to establish a connection to a server should only do so when
// |type != CONNECTION_NONE|. Observers performing "destructive" activities
// like resetting already established server connections should only do so
// when |type == CONNECTION_NONE|. OnNetworkChanged will always be called
// with CONNECTION_NONE immediately prior to being called with an online
// state; this is done to make sure that destructive actions take place
// prior to constructive actions.
virtual void OnNetworkChanged(ConnectionType type) = 0;
NetworkChangeObserver() {}
virtual ~NetworkChangeObserver() {}
virtual ~NetworkChangeNotifier();
// See the description of NetworkChangeNotifier::GetConnectionType().
// Implementations must be thread-safe. Implementations must also be
// cheap as this could be called (repeatedly) from the network thread.
virtual ConnectionType GetCurrentConnectionType() const = 0;
// Replaces the default class factory instance of NetworkChangeNotifier class.
// The method will take over the ownership of |factory| object.
static void SetFactory(NetworkChangeNotifierFactory* factory);
// Creates the process-wide, platform-specific NetworkChangeNotifier. The
// caller owns the returned pointer. You may call this on any thread. You
// may also avoid creating this entirely (in which case nothing will be
// monitored), but if you do create it, you must do so before any other
// threads try to access the API below, and it must outlive all other threads
// which might try to use it.
static NetworkChangeNotifier* Create();
// Returns the connection type.
// A return value of |CONNECTION_NONE| is a pretty strong indicator that the
// user won't be able to connect to remote sites. However, another return
// value doesn't imply that the user will be able to connect to remote sites;
// even if some link is up, it is uncertain whether a particular connection
// attempt to a particular remote site will be successful.
// The returned value only describes the connection currently used by the
// device, and does not take into account other machines on the network. For
// example, if the device is connected using Wifi to a 3G gateway to access
// the internet, the connection type is CONNECTION_WIFI.
static ConnectionType GetConnectionType();
// Retrieve the last read DnsConfig. This could be expensive if the system has
// a large HOSTS file.
static void GetDnsConfig(DnsConfig* config);
#if defined(OS_LINUX)
// Returns the AddressTrackerLinux if present.
static const internal::AddressTrackerLinux* GetAddressTracker();
// Convenience method to determine if the user is offline.
// Returns true if there is currently no internet connection.
// A return value of |true| is a pretty strong indicator that the user
// won't be able to connect to remote sites. However, a return value of
// |false| is inconclusive; even if some link is up, it is uncertain
// whether a particular connection attempt to a particular remote site
// will be successfully.
static bool IsOffline();
// Returns true if |type| is a cellular connection.
// Returns false if |type| is CONNECTION_UNKNOWN, and thus, depending on the
// implementation of GetConnectionType(), it is possible that
// IsConnectionCellular(GetConnectionType()) returns false even if the
// current connection is cellular.
static bool IsConnectionCellular(ConnectionType type);
// Like Create(), but for use in tests. The mock object doesn't monitor any
// events, it merely rebroadcasts notifications when requested.
static NetworkChangeNotifier* CreateMock();
// Registers |observer| to receive notifications of network changes. The
// thread on which this is called is the thread on which |observer| will be
// called back with notifications. This is safe to call if Create() has not
// been called (as long as it doesn't race the Create() call on another
// thread), in which case it will simply do nothing.
static void AddIPAddressObserver(IPAddressObserver* observer);
static void AddConnectionTypeObserver(ConnectionTypeObserver* observer);
static void AddDNSObserver(DNSObserver* observer);
static void AddNetworkChangeObserver(NetworkChangeObserver* observer);
// Unregisters |observer| from receiving notifications. This must be called
// on the same thread on which AddObserver() was called. Like AddObserver(),
// this is safe to call if Create() has not been called (as long as it doesn't
// race the Create() call on another thread), in which case it will simply do
// nothing. Technically, it's also safe to call after the notifier object has
// been destroyed, if the call doesn't race the notifier's destruction, but
// there's no reason to use the API in this risky way, so don't do it.
static void RemoveIPAddressObserver(IPAddressObserver* observer);
static void RemoveConnectionTypeObserver(ConnectionTypeObserver* observer);
static void RemoveDNSObserver(DNSObserver* observer);
static void RemoveNetworkChangeObserver(NetworkChangeObserver* observer);
// Allow unit tests to trigger notifications.
static void NotifyObserversOfIPAddressChangeForTests() {
// Return a string equivalent to |type|.
static const char* ConnectionTypeToString(ConnectionType type);
// Let the NetworkChangeNotifier know we received some data.
// This is used strictly for producing histogram data about the accuracy of
// the NetworkChangenotifier's online detection.
static void NotifyDataReceived(const GURL& source);
// Register the Observer callbacks for producing histogram data. This
// should be called from the network thread to avoid race conditions.
static void InitHistogramWatcher();
// NetworkChanged signal is calculated from the IPAddressChanged and
// ConnectionTypeChanged signals. Delay parameters control how long to delay
// producing NetworkChanged signal after particular input signals so as to
// combine duplicates. In other words if an input signal is repeated within
// the corresponding delay period, only one resulting NetworkChange signal is
// produced.
struct NET_EXPORT NetworkChangeCalculatorParams {
// Controls delay after OnIPAddressChanged when transitioning from an
// offline state.
base::TimeDelta ip_address_offline_delay_;
// Controls delay after OnIPAddressChanged when transitioning from an
// online state.
base::TimeDelta ip_address_online_delay_;
// Controls delay after OnConnectionTypeChanged when transitioning from an
// offline state.
base::TimeDelta connection_type_offline_delay_;
// Controls delay after OnConnectionTypeChanged when transitioning from an
// online state.
base::TimeDelta connection_type_online_delay_;
explicit NetworkChangeNotifier(
const NetworkChangeCalculatorParams& params =
#if defined(OS_LINUX)
// Returns the AddressTrackerLinux if present.
// TODO(szym): Retrieve AddressMap from NetworkState.
virtual const internal::AddressTrackerLinux*
GetAddressTrackerInternal() const;
// Broadcasts a notification to all registered observers. Note that this
// happens asynchronously, even for observers on the current thread, even in
// tests.
static void NotifyObserversOfIPAddressChange();
static void NotifyObserversOfConnectionTypeChange();
static void NotifyObserversOfDNSChange();
static void NotifyObserversOfNetworkChange(ConnectionType type);
// Stores |config| in NetworkState and notifies observers.
static void SetDnsConfig(const DnsConfig& config);
friend class HostResolverImplDnsTest;
friend class NetworkChangeNotifierAndroidTest;
friend class NetworkChangeNotifierLinuxTest;
friend class NetworkChangeNotifierWinTest;
friend class URLFetcherMockDnsTest;
class NetworkState;
class NetworkChangeCalculator;
// Allows a second NetworkChangeNotifier to be created for unit testing, so
// the test suite can create a MockNetworkChangeNotifier, but platform
// specific NetworkChangeNotifiers can also be created for testing. To use,
// create an DisableForTest object, and then create the new
// NetworkChangeNotifier object. The NetworkChangeNotifier must be
// destroyed before the DisableForTest object, as its destruction will restore
// the original NetworkChangeNotifier.
class NET_EXPORT_PRIVATE DisableForTest {
// The original NetworkChangeNotifier to be restored on destruction.
NetworkChangeNotifier* network_change_notifier_;
const scoped_refptr<ObserverListThreadSafe<IPAddressObserver> >
const scoped_refptr<ObserverListThreadSafe<ConnectionTypeObserver> >
const scoped_refptr<ObserverListThreadSafe<DNSObserver> >
const scoped_refptr<ObserverListThreadSafe<NetworkChangeObserver> >
// The current network state. Hosts DnsConfig, exposed via GetDnsConfig.
scoped_ptr<NetworkState> network_state_;
// A little-piggy-back observer that simply logs UMA histogram data.
scoped_ptr<HistogramWatcher> histogram_watcher_;
// Computes NetworkChange signal from IPAddress and ConnectionType signals.
scoped_ptr<NetworkChangeCalculator> network_change_calculator_;
} // namespace net