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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.
#ifndef NET_DNS_DNS_CONFIG_SERVICE_H_
#define NET_DNS_DNS_CONFIG_SERVICE_H_
#include <map>
#include <memory>
#include "base/macros.h"
#include "base/sequence_checker.h"
#include "base/time/time.h"
#include "base/timer/timer.h"
#include "net/base/net_export.h"
#include "net/dns/dns_config.h"
#include "net/dns/dns_hosts.h"
#include "url/gurl.h"
namespace net {
// Service for reading system DNS settings, on demand or when signalled by
// internal watchers and NetworkChangeNotifier. This object is not thread-safe
// and methods may perform blocking I/O so methods must be called on a sequence
// that allows blocking (i.e. base::MayBlock).
class NET_EXPORT_PRIVATE DnsConfigService {
public:
// Callback interface for the client, called on the same thread as
// ReadConfig() and WatchConfig().
typedef base::RepeatingCallback<void(const DnsConfig& config)> CallbackType;
// DHCP and user-induced changes are on the order of seconds, so 150ms should
// not add perceivable delay. On the other hand, config readers should finish
// within 150ms with the rare exception of I/O block or extra large HOSTS.
static const base::TimeDelta kInvalidationTimeout;
// Creates the platform-specific DnsConfigService. May return |nullptr| if
// reading system DNS settings is not supported on the current platform.
static std::unique_ptr<DnsConfigService> CreateSystemService();
DnsConfigService();
virtual ~DnsConfigService();
// Attempts to read the configuration. Will run |callback| when succeeded.
// Can be called at most once.
void ReadConfig(const CallbackType& callback);
// Registers systems watchers. Will attempt to read config after watch starts,
// but only if watchers started successfully. Will run |callback| iff config
// changes from last call or has to be withdrawn. Can be called at most once.
// Might require MessageLoopForIO.
void WatchConfig(const CallbackType& callback);
// Triggers invalidation and re-read of the current configuration (followed by
// invocation of the callback). For use only on platforms expecting
// network-stack-external notifications of DNS config changes.
virtual void RefreshConfig();
protected:
enum WatchStatus {
DNS_CONFIG_WATCH_STARTED = 0,
DNS_CONFIG_WATCH_FAILED_TO_START_CONFIG,
DNS_CONFIG_WATCH_FAILED_TO_START_HOSTS,
DNS_CONFIG_WATCH_FAILED_CONFIG,
DNS_CONFIG_WATCH_FAILED_HOSTS,
DNS_CONFIG_WATCH_MAX,
};
// Immediately attempts to read the current configuration.
virtual void ReadNow() = 0;
// Registers system watchers. Returns true iff succeeds.
virtual bool StartWatching() = 0;
// Called when the current config (except hosts) has changed.
void InvalidateConfig();
// Called when the current hosts have changed.
void InvalidateHosts();
// Called with new config. |config|.hosts is ignored.
void OnConfigRead(const DnsConfig& config);
// Called with new hosts. Rest of the config is assumed unchanged.
void OnHostsRead(const DnsHosts& hosts);
void set_watch_failed(bool value) { watch_failed_ = value; }
SEQUENCE_CHECKER(sequence_checker_);
private:
// The timer counts from the last Invalidate* until complete config is read.
void StartTimer();
void OnTimeout();
// Called when the config becomes complete. Stops the timer.
void OnCompleteConfig();
CallbackType callback_;
DnsConfig dns_config_;
// True if any of the necessary watchers failed. In that case, the service
// will communicate changes via OnTimeout, but will only send empty DnsConfig.
bool watch_failed_;
// True after On*Read, before Invalidate*. Tells if the config is complete.
bool have_config_;
bool have_hosts_;
// True if receiver needs to be updated when the config becomes complete.
bool need_update_;
// True if the last config sent was empty (instead of |dns_config_|).
// Set when |timer_| expires.
bool last_sent_empty_;
// Initialized and updated on Invalidate* call.
base::TimeTicks last_invalidate_config_time_;
base::TimeTicks last_invalidate_hosts_time_;
// Initialized and updated when |timer_| expires.
base::TimeTicks last_sent_empty_time_;
// Started in Invalidate*, cleared in On*Read.
base::OneShotTimer timer_;
DISALLOW_COPY_AND_ASSIGN(DnsConfigService);
};
} // namespace net
#endif // NET_DNS_DNS_CONFIG_SERVICE_H_
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