Long live QNetworkInformation

The plugins are meant to indicate what they do support, meaning users of
QNetworkInformation can choose to not care about which plugin is used
and rather just request what they want.

Task-number: QTBUG-86966
Change-Id: Ie130e1791250ec2a4470e3ba7081d982654af06c
Reviewed-by: Timur Pocheptsov <timur.pocheptsov@qt.io>
Reviewed-by: Edward Welbourne <edward.welbourne@qt.io>

4 files changed, 759 insertions, 1 deletions

diff --git a/src/network/CMakeLists.txt b/src/network/CMakeLists.txt
index 8910f3fece..003e504c92 100644
--- a/src/network/CMakeLists.txt
+++ b/src/network/CMakeLists.txt
@@ -5,7 +5,7 @@
 #####################################################################
 
 qt_internal_add_module(Network
-    PLUGIN_TYPES networkaccessbackends
+    PLUGIN_TYPES networkaccessbackends networkinformationbackends
     SOURCES
         access/qabstractnetworkcache.cpp access/qabstractnetworkcache.h access/qabstractnetworkcache_p.h
         access/qhsts.cpp access/qhsts_p.h
@@ -30,6 +30,7 @@ qt_internal_add_module(Network
         kernel/qhostinfo.cpp kernel/qhostinfo.h kernel/qhostinfo_p.h
         kernel/qnetconmonitor_p.h
         kernel/qnetworkdatagram.cpp kernel/qnetworkdatagram.h kernel/qnetworkdatagram_p.h
+        kernel/qnetworkinformation.cpp kernel/qnetworkinformation_p.h kernel/qnetworkinformation.h
         kernel/qnetworkinterface.cpp kernel/qnetworkinterface.h kernel/qnetworkinterface_p.h
         kernel/qnetworkinterface_unix_p.h
         kernel/qnetworkproxy.cpp kernel/qnetworkproxy.h
diff --git a/src/network/kernel/qnetworkinformation.cpp b/src/network/kernel/qnetworkinformation.cpp
new file mode 100644
index 0000000000..2b0493ee26
--- /dev/null
+++ b/src/network/kernel/qnetworkinformation.cpp
@@ -0,0 +1,556 @@
+/****************************************************************************
+**
+** Copyright (C) 2021 The Qt Company Ltd.
+** Contact: https://www.qt.io/licensing/
+**
+** This file is part of the QtNetwork module of the Qt Toolkit.
+**
+** $QT_BEGIN_LICENSE:LGPL$
+** Commercial License Usage
+** Licensees holding valid commercial Qt licenses may use this file in
+** accordance with the commercial license agreement provided with the
+** Software or, alternatively, in accordance with the terms contained in
+** a written agreement between you and The Qt Company. For licensing terms
+** and conditions see https://www.qt.io/terms-conditions. For further
+** information use the contact form at https://www.qt.io/contact-us.
+**
+** GNU Lesser General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU Lesser
+** General Public License version 3 as published by the Free Software
+** Foundation and appearing in the file LICENSE.LGPL3 included in the
+** packaging of this file. Please review the following information to
+** ensure the GNU Lesser General Public License version 3 requirements
+** will be met: https://www.gnu.org/licenses/lgpl-3.0.html.
+**
+** GNU General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU
+** General Public License version 2.0 or (at your option) the GNU General
+** Public license version 3 or any later version approved by the KDE Free
+** Qt Foundation. The licenses are as published by the Free Software
+** Foundation and appearing in the file LICENSE.GPL2 and LICENSE.GPL3
+** included in the packaging of this file. Please review the following
+** information to ensure the GNU General Public License requirements will
+** be met: https://www.gnu.org/licenses/gpl-2.0.html and
+** https://www.gnu.org/licenses/gpl-3.0.html.
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+// #define DEBUG_LOADING
+
+#include "qnetworkinformation.h"
+#include <QtNetwork/private/qnetworkinformation_p.h>
+#include <QtNetwork/qnetworkinformation.h>
+
+#include <QtCore/private/qobject_p.h>
+#include <QtCore/qcoreapplication.h>
+#include <QtCore/qmutex.h>
+#include <QtCore/private/qfactoryloader_p.h>
+
+#include <algorithm>
+#include <memory>
+#include <mutex>
+
+QT_BEGIN_NAMESPACE
+Q_DECLARE_LOGGING_CATEGORY(lcNetInfo)
+Q_LOGGING_CATEGORY(lcNetInfo, "qt.network.info");
+
+Q_GLOBAL_STATIC_WITH_ARGS(QFactoryLoader, loader,
+                          (QNetworkInformationBackendFactory_iid,
+                           QStringLiteral("/networkinformationbackends")))
+
+struct QStaticNetworkInformationDataHolder
+{
+    QMutex instanceMutex;
+    std::unique_ptr<QNetworkInformation> instanceHolder;
+    QList<QNetworkInformationBackendFactory *> factories;
+};
+Q_GLOBAL_STATIC(QStaticNetworkInformationDataHolder, dataHolder);
+
+class QNetworkInformationPrivate : public QObjectPrivate
+{
+    Q_DECLARE_PUBLIC(QNetworkInformation)
+public:
+    QNetworkInformationPrivate(QNetworkInformationBackend *backend) : backend(backend) { }
+
+    static QNetworkInformation *create(QNetworkInformation::Features features);
+    static QNetworkInformation *create(QStringView name);
+    static QNetworkInformation *instance()
+    {
+        if (!dataHolder())
+            return nullptr;
+        QMutexLocker locker(&dataHolder->instanceMutex);
+        return dataHolder->instanceHolder.get();
+    }
+    static QStringList backendNames();
+    static void addToList(QNetworkInformationBackendFactory *factory);
+    static void removeFromList(QNetworkInformationBackendFactory *factory);
+
+private:
+    static bool initializeList();
+
+    std::unique_ptr<QNetworkInformationBackend> backend;
+    bool m_isOnline = true; // cached
+};
+
+bool QNetworkInformationPrivate::initializeList()
+{
+    if (!loader())
+        return false;
+    if (!dataHolder())
+        return false;
+    static QBasicMutex mutex;
+    QMutexLocker initLocker(&mutex);
+
+#if QT_CONFIG(library)
+    loader->update();
+#endif
+    // Instantiates the plugins (and registers the factories)
+    int index = 0;
+    while (loader->instance(index))
+        ++index;
+    initLocker.unlock();
+
+    // Now sort the list on number of features available (then name)
+    const auto featuresNameOrder = [](QNetworkInformationBackendFactory *a,
+                                      QNetworkInformationBackendFactory *b) {
+        if (!a || !b)
+            return a && !b;
+        auto aFeaturesSupported = qPopulationCount(unsigned(a->featuresSupported()));
+        auto bFeaturesSupported = qPopulationCount(unsigned(b->featuresSupported()));
+        return aFeaturesSupported > bFeaturesSupported
+                || (aFeaturesSupported == bFeaturesSupported
+                    && a->name().compare(b->name(), Qt::CaseInsensitive) < 0);
+    };
+    QMutexLocker instanceLocker(&dataHolder->instanceMutex);
+    std::sort(dataHolder->factories.begin(), dataHolder->factories.end(), featuresNameOrder);
+
+    return !dataHolder->factories.isEmpty();
+}
+
+void QNetworkInformationPrivate::addToList(QNetworkInformationBackendFactory *factory)
+{
+    // @note: factory is in the base class ctor
+    if (!dataHolder())
+        return;
+    QMutexLocker locker(&dataHolder->instanceMutex);
+    dataHolder->factories.append(factory);
+}
+
+void QNetworkInformationPrivate::removeFromList(QNetworkInformationBackendFactory *factory)
+{
+    // @note: factory is in the base class dtor
+    if (!dataHolder.exists())
+        return;
+    QMutexLocker locker(&dataHolder->instanceMutex);
+    dataHolder->factories.removeAll(factory);
+}
+
+QStringList QNetworkInformationPrivate::backendNames()
+{
+    if (!dataHolder())
+        return {};
+    if (!initializeList())
+        return {};
+
+    QMutexLocker locker(&dataHolder->instanceMutex);
+    const QList copy = dataHolder->factories;
+    locker.unlock();
+
+    QStringList result;
+    result.reserve(copy.size());
+    for (const auto *factory : copy)
+        result << factory->name();
+    return result;
+}
+
+QNetworkInformation *QNetworkInformationPrivate::create(QStringView name)
+{
+    if (!dataHolder())
+        return nullptr;
+    QMutexLocker locker(&dataHolder->instanceMutex);
+#ifdef DEBUG_LOADING
+    qDebug().nospace() << "create() called with name=\"" << name
+                       << "\". instanceHolder initialized? " << !!dataHolder->instanceHolder;
+#endif
+    if (dataHolder->instanceHolder)
+        return dataHolder->instanceHolder.get();
+
+    locker.unlock();
+    if (!initializeList()) {
+#ifdef DEBUG_LOADING
+        qDebug("Failed to initialize list, returning.");
+#endif
+        return nullptr;
+    }
+    locker.relock();
+
+    QNetworkInformationBackend *backend = nullptr;
+    if (!name.isEmpty()) {
+        const auto nameMatches = [name](QNetworkInformationBackendFactory *factory) {
+            return factory->name().compare(name, Qt::CaseInsensitive) == 0;
+        };
+        auto it = std::find_if(dataHolder->factories.cbegin(), dataHolder->factories.cend(),
+                               nameMatches);
+        if (it == dataHolder->factories.cend()) {
+#ifdef DEBUG_LOADING
+            if (dataHolder->factories.isEmpty()) {
+                qDebug("No plugins available");
+            } else {
+                QString listNames;
+                listNames.reserve(8 * dataHolder->factories.count());
+                for (const auto *factory : qAsConst(dataHolder->factories))
+                    listNames += factory->name() + QStringLiteral(", ");
+                listNames.chop(2);
+                qDebug().nospace() << "Couldn't find " << name << " in list with names: { "
+                                   << listNames << " }";
+            }
+#endif
+            return nullptr;
+        }
+#ifdef DEBUG_LOADING
+        qDebug() << "Creating instance using loader named " << (*it)->name();
+#endif
+        backend = (*it)->create({});
+    } else {
+#ifdef DEBUG_LOADING
+        qDebug() << "Creating instance using loader named" << dataHolder->factories.front()->name();
+#endif
+        if (!dataHolder->factories.isEmpty())
+            backend = dataHolder->factories.front()->create({});
+    }
+    if (!backend)
+        return nullptr;
+    dataHolder->instanceHolder.reset(new QNetworkInformation(backend));
+    Q_ASSERT(name.isEmpty()
+             || dataHolder->instanceHolder->backendName().compare(name, Qt::CaseInsensitive) == 0);
+    return dataHolder->instanceHolder.get();
+}
+
+QNetworkInformation *QNetworkInformationPrivate::create(QNetworkInformation::Features features)
+{
+    if (!dataHolder())
+        return nullptr;
+    QMutexLocker locker(&dataHolder->instanceMutex);
+#ifdef DEBUG_LOADING
+    qDebug().nospace() << "create() called with features=\"" << features
+                       << "\". instanceHolder initialized? " << !!dataHolder->instanceHolder;
+#endif
+    if (dataHolder->instanceHolder)
+        return dataHolder->instanceHolder.get();
+    if (features == 0)
+        return nullptr;
+
+    locker.unlock();
+    if (!initializeList()) {
+#ifdef DEBUG_LOADING
+        qDebug("Failed to initialize list, returning.");
+#endif
+        return nullptr;
+    }
+    locker.relock();
+
+    const auto supportsRequestedFeatures = [features](QNetworkInformationBackendFactory *factory) {
+        return factory && (factory->featuresSupported() & features) == features;
+    };
+
+    for (auto it = dataHolder->factories.cbegin(), end = dataHolder->factories.cend(); it != end;
+         ++it) {
+        it = std::find_if(it, end, supportsRequestedFeatures);
+        if (it == end) {
+#ifdef DEBUG_LOADING
+            if (dataHolder->factories.isEmpty()) {
+                qDebug("No plugins available");
+            } else {
+                QStringList names;
+                names.reserve(dataHolder->factories.count());
+                for (const auto *factory : qAsConst(dataHolder->factories))
+                    names += factory->name();
+                qDebug() << "None of the following backends has all the requested features:"
+                         << names << features;
+            }
+#endif
+            break;
+        }
+#ifdef DEBUG_LOADING
+        qDebug() << "Creating instance using loader named" << (*it)->name();
+#endif
+        if (QNetworkInformationBackend *backend = (*it)->create(features)) {
+            dataHolder->instanceHolder.reset(new QNetworkInformation(backend));
+            Q_ASSERT(dataHolder->instanceHolder->supports(features));
+            return dataHolder->instanceHolder.get();
+        }
+#ifdef DEBUG_LOADING
+        else {
+            qDebug() << "The factory returned a nullptr";
+        }
+#endif
+    }
+#ifdef DEBUG_LOADING
+    qDebug() << "Couldn't find/create an appropriate backend.";
+#endif
+    return nullptr;
+}
+
+/*!
+    \class QNetworkInformationBackend
+    \internal (Semi-private)
+    \brief QNetworkInformationBackend provides the interface with
+    which QNetworkInformation does all of its actual work.
+
+    Deriving from and implementing this class makes it a candidate
+    for use with QNetworkInformation. The derived class must, on
+    updates, call setters in the QNetworkInformationBackend which
+    will update the values and emit signals if the value has changed.
+
+    \sa QNetworkInformationBackendFactory
+*/
+
+/*!
+    \internal
+    Destroys base backend class.
+*/
+QNetworkInformationBackend::~QNetworkInformationBackend() = default;
+
+/*!
+    \fn QNetworkInformationBackend::name()
+
+    Backend name, return the same in
+    QNetworkInformationBackendFactory::name().
+*/
+
+/*!
+    \fn QNetworkInformation::Features QNetworkInformationBackend::featuresSupported()
+
+    Features supported, return the same in
+    QNetworkInformationBackendFactory::featuresSupported().
+*/
+
+/*!
+    \fn void QNetworkInformationBackend::reachabilityChanged()
+
+    You should not emit this signal manually, call setReachability()
+    instead which will emit this signal when the value changes.
+
+    \sa setReachability
+*/
+
+/*!
+    \fn void QNetworkInformationBackend::setReachability(QNetworkInformation::Reachability reachability)
+
+    Call this when reachability has changed. It will automatically
+    emit reachabilityChanged().
+
+    \sa setReachability
+*/
+
+/*!
+    \class QNetworkInformationBackendFactory
+    \internal (Semi-private)
+    \brief QNetworkInformationBackendFactory provides the interface
+    for creating instances of QNetworkInformationBackend.
+
+    Deriving from and implementing this class will let you register
+    your plugin with QNetworkInformation. It must provide some basic
+    information for querying information about the backend, and must
+    also create the backend if requested. If some pre-conditions for
+    the backend is not met it must return \nullptr.
+*/
+
+/*!
+    \internal
+    Adds the factory to an internal list.
+*/
+QNetworkInformationBackendFactory::QNetworkInformationBackendFactory()
+{
+    QNetworkInformationPrivate::addToList(this);
+}
+
+/*!
+    \internal
+    Removes the factory from an internal list.
+*/
+QNetworkInformationBackendFactory::~QNetworkInformationBackendFactory()
+{
+    QNetworkInformationPrivate::removeFromList(this);
+}
+
+/*!
+    \fn QString QNetworkInformationBackendFactory::name()
+
+    Backend name, return the same in
+    QNetworkInformationBackend::name().
+*/
+
+/*!
+    \fn QNetworkInformation::Features QNetworkInformationBackendFactory::featuresSupported()
+
+    Features supported, return the same in
+    QNetworkInformationBackend::featuresSupported().
+    The factory should not promise support for features that wouldn't
+    be available after creating the backend.
+*/
+
+/*!
+    \fn QNetworkInformationBackend *QNetworkInformationBackendFactory::create()
+
+    Create and return an instance of QNetworkInformationBackend. It
+    will be deallocated by QNetworkInformation on shutdown. If some
+    precondition is not met, meaning the backend would not function
+    correctly, then you must return \nullptr.
+*/
+
+/*!
+    \class QNetworkInformation
+    \since 6.1
+    \brief QNetworkInformation exposes various network information
+    through native backends.
+
+    QNetworkInformation provides a cross-platform interface to
+    network-related information through plugins.
+
+    Various plugins can have various functionality supported, and so
+    you can load() plugins based on which features are needed.
+
+    QNetworkInformation is a singleton and stays alive from the first
+    successful load() until application shutdown.
+
+    \sa QNetworkInformation::Feature
+*/
+
+/*!
+    \enum QNetworkInformation::Feature
+
+    Lists all of the features that a plugin may currently support.
+    This can be used in QNetworkInformation::load().
+
+    \value Reachability
+        If the plugin supports this feature then
+        the \c reachability property will be available.
+        See also QNetworkInformation::Reachability.
+*/
+
+/*!
+    \enum QNetworkInformation::Reachability
+
+    \value Unknown
+        If this value is returned then we may be connected but the OS
+        has still not confirmed full connectivity, or this features
+        is not supported.
+    \value Disconnected
+        Indicates that the system may have no connectivity at all.
+    \value Local
+        Indicates that the system is connected to a network, but it
+        might only be able to access devices on the local network.
+    \value Site
+        Indicates that the system is connected to a network, but it
+        might only be able to access devices on the local subnet or an
+        intranet.
+    \value Online
+        Indicates that the system is connected to a network and
+        able to access the Internet.
+
+    \sa QNetworkInformation::reachability
+*/
+
+/*!
+    \internal ctor
+*/
+QNetworkInformation::QNetworkInformation(QNetworkInformationBackend *backend)
+    : QObject(*(new QNetworkInformationPrivate(backend)))
+{
+    connect(backend, &QNetworkInformationBackend::reachabilityChanged, this,
+            [this]() { emit reachabilityChanged(d_func()->backend->m_reachability); });
+}
+
+/*!
+    \internal dtor
+*/
+QNetworkInformation::~QNetworkInformation() = default;
+
+/*!
+    \property QNetworkInformation::reachability
+    \brief The current state of the system's network connectivity.
+
+    Indicates the level of connectivity that can be expected. Do note
+    that this is only based on what the plugin/operating system
+    reports. In certain scenarios this is known to be wrong. For
+    example, on Windows the 'Online' check, by default, is performed
+    by Windows connecting to a Microsoft-owned server. If this server
+    is for any reason blocked then it will assume it does not have
+    Online reachability. Because of this you should not use this as a
+    pre-check before attempting to make a connection.
+*/
+
+QNetworkInformation::Reachability QNetworkInformation::reachability() const
+{
+    return d_func()->backend->m_reachability;
+}
+
+/*!
+    Returns the name of the currently loaded backend.
+*/
+QString QNetworkInformation::backendName() const
+{
+    return d_func()->backend->name();
+}
+
+/*!
+    Returns \c true if the currently loaded backend supports
+    \a features.
+*/
+bool QNetworkInformation::supports(Features features) const
+{
+    return (d_func()->backend->featuresSupported() & features) == features;
+}
+
+/*!
+    Attempts to load a backend whose name matches \a backend
+    (case insensitively).
+
+    Returns \c true if it managed to load the requested backend or
+    if it was already loaded. Returns \c false otherwise
+
+    \sa instance
+*/
+bool QNetworkInformation::load(QStringView backend)
+{
+    auto loadedBackend = QNetworkInformationPrivate::create(backend);
+    return loadedBackend && loadedBackend->backendName() == backend;
+}
+
+/*!
+    Load a backend which supports \a features.
+
+    Returns \c true if it managed to load the requested backend or
+    if it was already loaded. Returns \c false otherwise
+
+    \sa instance
+*/
+bool QNetworkInformation::load(Features features)
+{
+    auto loadedBackend = QNetworkInformationPrivate::create(features);
+    return loadedBackend && loadedBackend->supports(features);
+}
+
+/*!
+    Returns a list of the names of all currently available backends.
+*/
+QStringList QNetworkInformation::availableBackends()
+{
+    return QNetworkInformationPrivate::backendNames();
+}
+
+/*!
+    Returns a pointer to the instance of the QNetworkInformation,
+    if any.
+
+    \sa load()
+*/
+QNetworkInformation *QNetworkInformation::instance()
+{
+    return QNetworkInformationPrivate::instance();
+}
+
+QT_END_NAMESPACE
diff --git a/src/network/kernel/qnetworkinformation.h b/src/network/kernel/qnetworkinformation.h
new file mode 100644
index 0000000000..6321300f40
--- /dev/null
+++ b/src/network/kernel/qnetworkinformation.h
@@ -0,0 +1,96 @@
+/****************************************************************************
+**
+** Copyright (C) 2021 The Qt Company Ltd.
+** Contact: https://www.qt.io/licensing/
+**
+** This file is part of the QtNetwork module of the Qt Toolkit.
+**
+** $QT_BEGIN_LICENSE:LGPL$
+** Commercial License Usage
+** Licensees holding valid commercial Qt licenses may use this file in
+** accordance with the commercial license agreement provided with the
+** Software or, alternatively, in accordance with the terms contained in
+** a written agreement between you and The Qt Company. For licensing terms
+** and conditions see https://www.qt.io/terms-conditions. For further
+** information use the contact form at https://www.qt.io/contact-us.
+**
+** GNU Lesser General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU Lesser
+** General Public License version 3 as published by the Free Software
+** Foundation and appearing in the file LICENSE.LGPL3 included in the
+** packaging of this file. Please review the following information to
+** ensure the GNU Lesser General Public License version 3 requirements
+** will be met: https://www.gnu.org/licenses/lgpl-3.0.html.
+**
+** GNU General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU
+** General Public License version 2.0 or (at your option) the GNU General
+** Public license version 3 or any later version approved by the KDE Free
+** Qt Foundation. The licenses are as published by the Free Software
+** Foundation and appearing in the file LICENSE.GPL2 and LICENSE.GPL3
+** included in the packaging of this file. Please review the following
+** information to ensure the GNU General Public License requirements will
+** be met: https://www.gnu.org/licenses/gpl-2.0.html and
+** https://www.gnu.org/licenses/gpl-3.0.html.
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+#ifndef QNETWORKINFORMATION_H
+#define QNETWORKINFORMATION_H
+
+#include <QtNetwork/qtnetworkglobal.h>
+#include <QtCore/qobject.h>
+#include <QtCore/qstringview.h>
+#include <QtCore/qstringlist.h>
+
+QT_BEGIN_NAMESPACE
+
+class QNetworkInformationBackend;
+class QNetworkInformationPrivate;
+class Q_NETWORK_EXPORT QNetworkInformation : public QObject
+{
+    Q_OBJECT
+    Q_DECLARE_PRIVATE(QNetworkInformation)
+    Q_PROPERTY(Reachability reachability READ reachability)
+public:
+    enum class Reachability {
+        Unknown,
+        Disconnected,
+        Local,
+        Site,
+        Online,
+    };
+    Q_ENUM(Reachability)
+
+    enum class Feature {
+        Reachability = 0x1,
+    };
+    Q_ENUM(Feature)
+    Q_DECLARE_FLAGS(Features, Feature)
+
+    ~QNetworkInformation();
+
+    Reachability reachability() const;
+
+    QString backendName() const;
+
+    virtual bool supports(Features features) const;
+
+    static bool load(QStringView backend = {});
+    static bool load(Features features);
+    static QStringList availableBackends();
+    static QNetworkInformation *instance();
+
+Q_SIGNALS:
+    void reachabilityChanged(Reachability newReachability);
+
+private:
+    friend class QNetworkInformationPrivate;
+    QNetworkInformation(QNetworkInformationBackend *backend);
+};
+
+QT_END_NAMESPACE
+
+#endif
diff --git a/src/network/kernel/qnetworkinformation_p.h b/src/network/kernel/qnetworkinformation_p.h
new file mode 100644
index 0000000000..fc783fa079
--- /dev/null
+++ b/src/network/kernel/qnetworkinformation_p.h
@@ -0,0 +1,105 @@
+/****************************************************************************
+**
+** Copyright (C) 2021 The Qt Company Ltd.
+** Contact: https://www.qt.io/licensing/
+**
+** This file is part of the QtNetwork module of the Qt Toolkit.
+**
+** $QT_BEGIN_LICENSE:LGPL$
+** Commercial License Usage
+** Licensees holding valid commercial Qt licenses may use this file in
+** accordance with the commercial license agreement provided with the
+** Software or, alternatively, in accordance with the terms contained in
+** a written agreement between you and The Qt Company. For licensing terms
+** and conditions see https://www.qt.io/terms-conditions. For further
+** information use the contact form at https://www.qt.io/contact-us.
+**
+** GNU Lesser General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU Lesser
+** General Public License version 3 as published by the Free Software
+** Foundation and appearing in the file LICENSE.LGPL3 included in the
+** packaging of this file. Please review the following information to
+** ensure the GNU Lesser General Public License version 3 requirements
+** will be met: https://www.gnu.org/licenses/lgpl-3.0.html.
+**
+** GNU General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU
+** General Public License version 2.0 or (at your option) the GNU General
+** Public license version 3 or any later version approved by the KDE Free
+** Qt Foundation. The licenses are as published by the Free Software
+** Foundation and appearing in the file LICENSE.GPL2 and LICENSE.GPL3
+** included in the packaging of this file. Please review the following
+** information to ensure the GNU General Public License requirements will
+** be met: https://www.gnu.org/licenses/gpl-2.0.html and
+** https://www.gnu.org/licenses/gpl-3.0.html.
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+#ifndef QNETWORKINFORMATION_P_H
+#define QNETWORKINFORMATION_P_H
+
+//
+//  W A R N I N G
+//  -------------
+//
+// This file is not part of the Qt API. It exists for the convenience
+// of the Network Information API. This header file may change from
+// version to version without notice, or even be removed.
+//
+// We mean it.
+//
+
+#include <QtNetwork/private/qtnetworkglobal_p.h>
+
+#include <QtNetwork/qnetworkinformation.h>
+
+#include <QtCore/qloggingcategory.h>
+
+QT_BEGIN_NAMESPACE
+
+class Q_NETWORK_EXPORT QNetworkInformationBackend : public QObject
+{
+    Q_OBJECT
+public:
+    virtual ~QNetworkInformationBackend();
+
+    virtual QString name() const = 0;
+    virtual QNetworkInformation::Features featuresSupported() const = 0;
+
+Q_SIGNALS:
+    void reachabilityChanged();
+
+protected:
+    void setReachability(QNetworkInformation::Reachability reachability)
+    {
+        if (m_reachability != reachability) {
+            m_reachability = reachability;
+            emit reachabilityChanged();
+        }
+    }
+
+private:
+    QNetworkInformation::Reachability m_reachability = QNetworkInformation::Reachability::Unknown;
+
+    friend class QNetworkInformation;
+    friend class QNetworkInformationPrivate;
+};
+
+class Q_NETWORK_EXPORT QNetworkInformationBackendFactory : public QObject
+{
+    Q_OBJECT
+public:
+    QNetworkInformationBackendFactory();
+    virtual ~QNetworkInformationBackendFactory();
+    virtual QString name() const = 0;
+    virtual QNetworkInformationBackend *create(QNetworkInformation::Features requiredFeatures) const = 0;
+    virtual QNetworkInformation::Features featuresSupported() const = 0;
+};
+#define QNetworkInformationBackendFactory_iid "org.qt-project.Qt.NetworkInformationBackendFactory"
+Q_DECLARE_INTERFACE(QNetworkInformationBackendFactory, QNetworkInformationBackendFactory_iid);
+
+QT_END_NAMESPACE
+
+#endif