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// Copyright 2019 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.
#ifndef NET_DNS_SYSTEM_DNS_CONFIG_CHANGE_NOTIFIER_H_
#define NET_DNS_SYSTEM_DNS_CONFIG_CHANGE_NOTIFIER_H_
#include <memory>
#include "base/macros.h"
#include "base/memory/scoped_refptr.h"
#include "base/optional.h"
#include "base/sequenced_task_runner.h"
#include "net/base/net_export.h"
#include "net/dns/dns_config.h"
namespace net {
class DnsConfigService;
// Notifier that can be subscribed to to listen for changes to system DNS
// configuration. Expected to only be used internally to HostResolverManager and
// NetworkChangeNotifier. Other classes are expected to subscribe to
// NetworkChangeNotifier::AddDNSObserver() to subscribe to listen to both system
// config changes and configuration applied on top by Chrome.
//
// This class is thread and sequence safe except that RemoveObserver() must be
// called on the same sequence as the matched AddObserver() call.
//
// TODO(crbug.com/971411): Use this class in HostResolverManager.
class NET_EXPORT_PRIVATE SystemDnsConfigChangeNotifier {
public:
class Observer {
public:
// Called on loading new config, including the initial read once the first
// valid config has been read. If a config read encounters errors or an
// invalid config is read, will be invoked with |base::nullopt|. Only
// invoked when |config| changes.
virtual void OnSystemDnsConfigChanged(base::Optional<DnsConfig> config) = 0;
};
SystemDnsConfigChangeNotifier();
// Alternate constructor allowing specifying the underlying DnsConfigService.
// |dns_config_service| will only be interacted with and destroyed using
// |task_runner|. As required by DnsConfigService, blocking I/O may be
// performed on |task_runner|, so it must support blocking (i.e.
// base::MayBlock).
//
// |dns_config_service| may be null if system DNS config is disabled for the
// current platform. Calls against the created object will noop, and no
// notifications will ever be sent.
SystemDnsConfigChangeNotifier(
scoped_refptr<base::SequencedTaskRunner> task_runner,
std::unique_ptr<DnsConfigService> dns_config_service);
~SystemDnsConfigChangeNotifier();
// An added Observer will receive notifications on the sequence where
// AddObserver() was called. If the config has been successfully read before
// calling this method, a notification will be sent for that current config
// before any other notifications.
void AddObserver(Observer* observer);
// In order to ensure notifications immediately stop on calling
// RemoveObserver(), must be called on the same sequence where the associated
// AddObserver() was called.
void RemoveObserver(Observer* observer);
// Triggers invalidation and re-read of the current configuration (followed by
// notifications to registered Observers). For use only on platforms
// expecting network-stack-external notifications of DNS config changes.
void RefreshConfig();
void SetDnsConfigServiceForTesting(
std::unique_ptr<DnsConfigService> dns_config_service);
private:
class Core;
std::unique_ptr<Core, base::OnTaskRunnerDeleter> core_;
DISALLOW_COPY_AND_ASSIGN(SystemDnsConfigChangeNotifier);
};
} // namespace net
#endif // NET_DNS_SYSTEM_DNS_CONFIG_CHANGE_NOTIFIER_H_
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