234 lines
8.4 KiB
C
234 lines
8.4 KiB
C
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// Copyright 2012 The Chromium Authors
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// Use of this source code is governed by a BSD-style license that can be
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// found in the LICENSE file.
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#ifndef NET_DNS_DNS_CONFIG_SERVICE_H_
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#define NET_DNS_DNS_CONFIG_SERVICE_H_
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#include <map>
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#include <memory>
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#include "base/files/file_path.h"
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#include "base/memory/raw_ptr.h"
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#include "base/memory/weak_ptr.h"
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#include "base/sequence_checker.h"
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#include "base/time/time.h"
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#include "base/timer/timer.h"
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#include "net/base/net_export.h"
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#include "net/dns/dns_config.h"
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#include "net/dns/dns_hosts.h"
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#include "net/dns/serial_worker.h"
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#include "third_party/abseil-cpp/absl/types/optional.h"
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#include "url/gurl.h"
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namespace net {
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// Service for reading system DNS settings, on demand or when signalled by
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// internal watchers and NetworkChangeNotifier. This object is not thread-safe
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// and methods may perform blocking I/O so methods must be called on a sequence
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// that allows blocking (i.e. base::MayBlock).
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class NET_EXPORT_PRIVATE DnsConfigService {
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public:
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// Callback interface for the client, called on the same thread as
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// ReadConfig() and WatchConfig().
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typedef base::RepeatingCallback<void(const DnsConfig& config)> CallbackType;
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// DHCP and user-induced changes are on the order of seconds, so 150ms should
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// not add perceivable delay. On the other hand, config readers should finish
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// within 150ms with the rare exception of I/O block or extra large HOSTS.
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static const base::TimeDelta kInvalidationTimeout;
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// Creates the platform-specific DnsConfigService. May return |nullptr| if
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// reading system DNS settings is not supported on the current platform.
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static std::unique_ptr<DnsConfigService> CreateSystemService();
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DnsConfigService(const DnsConfigService&) = delete;
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DnsConfigService& operator=(const DnsConfigService&) = delete;
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virtual ~DnsConfigService();
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// Attempts to read the configuration. Will run |callback| when succeeded.
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// Can be called at most once.
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void ReadConfig(const CallbackType& callback);
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// Registers systems watchers. Will attempt to read config after watch starts,
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// but only if watchers started successfully. Will run |callback| iff config
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// changes from last call or has to be withdrawn. Can be called at most once.
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// Might require MessageLoopForIO.
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void WatchConfig(const CallbackType& callback);
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// Triggers invalidation and re-read of the current configuration (followed by
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// invocation of the callback). For use only on platforms expecting
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// network-stack-external notifications of DNS config changes.
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virtual void RefreshConfig();
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void set_watch_failed_for_testing(bool watch_failed) {
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watch_failed_ = watch_failed;
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}
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// Simulates a watcher trigger by calling OnConfigChanged().
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void TriggerOnConfigChangedForTesting(bool succeeded) {
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// Directly call ...Delayed() version to skip past delay logic.
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OnConfigChangedDelayed(succeeded);
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}
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protected:
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// Watcher to observe for changes to DNS config or HOSTS (via overriding
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// `Watch()` with platform specifics) and trigger necessary refreshes on
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// changes.
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class NET_EXPORT_PRIVATE Watcher {
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public:
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// `service` is expected to own the created Watcher and thus stay valid for
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// the lifetime of the created Watcher.
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explicit Watcher(DnsConfigService& service);
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virtual ~Watcher();
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Watcher(const Watcher&) = delete;
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Watcher& operator=(const Watcher&) = delete;
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virtual bool Watch() = 0;
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protected:
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// Hooks for detected changes. `succeeded` false to indicate that there was
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// an error watching for the change.
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void OnConfigChanged(bool succeeded);
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void OnHostsChanged(bool succeeded);
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void CheckOnCorrectSequence();
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private:
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void OnConfigChangedDelayed(bool success);
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// Back pointer. `this` is expected to be owned by `service_`, making this
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// raw pointer safe.
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const raw_ptr<DnsConfigService> service_;
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SEQUENCE_CHECKER(sequence_checker_);
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};
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// Reader of HOSTS files. In this base implementation, uses standard logic
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// appropriate to most platforms to read the HOSTS file located at
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// `hosts_file_path`.
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class NET_EXPORT_PRIVATE HostsReader : public SerialWorker {
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public:
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// `service` is expected to own the created reader and thus stay valid for
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// the lifetime of the created reader.
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HostsReader(base::FilePath::StringPieceType hosts_file_path,
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DnsConfigService& service);
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~HostsReader() override;
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HostsReader(const HostsReader&) = delete;
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HostsReader& operator=(const HostsReader&) = delete;
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protected:
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class NET_EXPORT_PRIVATE WorkItem : public SerialWorker::WorkItem {
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public:
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explicit WorkItem(std::unique_ptr<DnsHostsParser> dns_hosts_parser);
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~WorkItem() override;
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// Override if needed to implement platform-specific behavior, e.g. for a
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// platform-specific HOSTS format.
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virtual absl::optional<DnsHosts> ReadHosts();
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// Adds any necessary additional entries to the given `DnsHosts`. Returns
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// false on failure.
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//
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// Override if needed to implement platform-specific behavior.
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virtual bool AddAdditionalHostsTo(DnsHosts& in_out_dns_hosts);
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// SerialWorker::WorkItem:
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void DoWork() final;
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private:
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friend HostsReader;
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absl::optional<DnsHosts> hosts_;
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std::unique_ptr<DnsHostsParser> dns_hosts_parser_;
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};
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// SerialWorker:
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std::unique_ptr<SerialWorker::WorkItem> CreateWorkItem() override;
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bool OnWorkFinished(
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std::unique_ptr<SerialWorker::WorkItem> work_item) final;
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private:
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// Raw pointer to owning DnsConfigService. This must never be accessed
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// inside DoWork(), since service may be destroyed while SerialWorker is
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// running on worker thread.
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const raw_ptr<DnsConfigService> service_;
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const base::FilePath hosts_file_path_;
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};
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// On detecting config change, will post and wait `config_change_delay` before
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// triggering refreshes. Will trigger refreshes synchronously on nullopt.
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// Useful for platforms where multiple changes may be made and detected before
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// the config is stabilized and ready to be read.
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explicit DnsConfigService(base::FilePath::StringPieceType hosts_file_path,
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absl::optional<base::TimeDelta>
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config_change_delay = base::Milliseconds(50));
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// Immediately attempts to read the current configuration.
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virtual void ReadConfigNow() = 0;
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virtual void ReadHostsNow();
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// Registers system watchers. Returns true iff succeeds.
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virtual bool StartWatching() = 0;
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// Called when the current config (except hosts) has changed.
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void InvalidateConfig();
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// Called when the current hosts have changed.
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void InvalidateHosts();
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// Called with new config. |config|.hosts is ignored.
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void OnConfigRead(DnsConfig config);
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// Called with new hosts. Rest of the config is assumed unchanged.
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void OnHostsRead(DnsHosts hosts);
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SEQUENCE_CHECKER(sequence_checker_);
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private:
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// The timer counts from the last Invalidate* until complete config is read.
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void StartTimer();
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void OnTimeout();
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// Called when the config becomes complete. Stops the timer.
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void OnCompleteConfig();
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// Hooks for Watcher change notifications. `succeeded` false to indicate that
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// there was an error watching for the change.
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void OnConfigChanged(bool succeeded);
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void OnHostsChanged(bool succeeded);
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void OnConfigChangedDelayed(bool succeeded);
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CallbackType callback_;
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DnsConfig dns_config_;
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// True if any of the necessary watchers failed. In that case, the service
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// will communicate changes via OnTimeout, but will only send empty DnsConfig.
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bool watch_failed_ = false;
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// True after On*Read, before Invalidate*. Tells if the config is complete.
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bool have_config_ = false;
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bool have_hosts_ = false;
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// True if receiver needs to be updated when the config becomes complete.
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bool need_update_ = false;
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// True if the last config sent was empty (instead of |dns_config_|).
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// Set when |timer_| expires.
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bool last_sent_empty_ = true;
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const absl::optional<base::TimeDelta> config_change_delay_;
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const base::FilePath hosts_file_path_;
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// Created only if needed in ReadHostsNow() to avoid creating unnecessarily if
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// overridden for a platform-specific implementation.
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std::unique_ptr<HostsReader> hosts_reader_;
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// Started in Invalidate*, cleared in On*Read.
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base::OneShotTimer timer_;
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base::WeakPtrFactory<DnsConfigService> weak_factory_{this};
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};
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} // namespace net
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#endif // NET_DNS_DNS_CONFIG_SERVICE_H_
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