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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 <map>
#include <string>
#include <vector>
#include "base/gtest_prod_util.h"
#include "base/memory/scoped_ptr.h"
#include "base/memory/scoped_vector.h"
#include "base/threading/non_thread_safe.h"
#include "base/time/time.h"
#include "base/timer/timer.h"
// Needed on shared build with MSVS2010 to avoid multiple definitions of
// std::vector<IPEndPoint>.
#include "net/base/address_list.h"
#include "net/base/ip_endpoint.h" // win requires size of IPEndPoint
#include "net/base/net_export.h"
#include "net/dns/dns_hosts.h"
namespace base {
class Value;
namespace net {
// Always use 1 second timeout (followed by binary exponential backoff).
// TODO(szym): Remove code which reads timeout from system.
const unsigned kDnsTimeoutSeconds = 1;
// Classifies nameserver address lists for histograms.
class NET_EXPORT_PRIVATE NameServerClassifier {
// This is used in a histogram (AsyncDNS.NameServersType); add new entries
// right before MAX_VALUE.
enum NameServersType {
NameServersType GetNameServersType(
const std::vector<net::IPEndPoint>& nameservers) const;
struct NameServerTypeRule;
void AddRule(const char* pattern_string, NameServersType type);
NameServersType GetNameServerType(const IPAddressNumber& address) const;
static NameServersType MergeNameServersTypes(NameServersType a,
NameServersType b);
ScopedVector<NameServerTypeRule> rules_;
// DnsConfig stores configuration of the system resolver.
struct NET_EXPORT_PRIVATE DnsConfig {
virtual ~DnsConfig();
bool Equals(const DnsConfig& d) const;
bool EqualsIgnoreHosts(const DnsConfig& d) const;
void CopyIgnoreHosts(const DnsConfig& src);
// Returns a Value representation of |this|. Caller takes ownership of the
// returned Value. For performance reasons, the Value only contains the
// number of hosts rather than the full list.
base::Value* ToValue() const;
bool IsValid() const {
return !nameservers.empty();
// List of name server addresses.
std::vector<IPEndPoint> nameservers;
// Suffix search list; used on first lookup when number of dots in given name
// is less than |ndots|.
std::vector<std::string> search;
DnsHosts hosts;
// True if there are options set in the system configuration that are not yet
// supported by DnsClient.
bool unhandled_options;
// AppendToMultiLabelName: is suffix search performed for multi-label names?
// True, except on Windows where it can be configured.
bool append_to_multi_label_name;
// Indicates that source port randomization is required. This uses additional
// resources on some platforms.
bool randomize_ports;
// Resolver options; see man resolv.conf.
// Minimum number of dots before global resolution precedes |search|.
int ndots;
// Time between retransmissions, see res_state.retrans.
base::TimeDelta timeout;
// Maximum number of attempts, see res_state.retry.
int attempts;
// Round robin entries in |nameservers| for subsequent requests.
bool rotate;
// Enable EDNS0 extensions.
bool edns0;
// Indicates system configuration uses local IPv6 connectivity, e.g.,
// DirectAccess. This is exposed for HostResolver to skip IPv6 probes,
// as it may cause them to return incorrect results.
bool use_local_ipv6;
// Service for reading system DNS settings, on demand or when signalled by
// internal watchers and NetworkChangeNotifier.
class NET_EXPORT_PRIVATE DnsConfigService
: NON_EXPORTED_BASE(public base::NonThreadSafe) {
// Callback interface for the client, called on the same thread as
// ReadConfig() and WatchConfig().
typedef base::Callback<void(const DnsConfig& config)> CallbackType;
// Creates the platform-specific DnsConfigService.
static scoped_ptr<DnsConfigService> CreateSystemService();
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);
enum WatchStatus {
// 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; }
// 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<DnsConfigService> timer_;
NameServerClassifier classifier_;
} // namespace net