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      1 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
      2 // Use of this source code is governed by a BSD-style license that can be
      3 // found in the LICENSE file.
      4 
      5 #ifndef NET_DNS_DNS_CONFIG_SERVICE_H_
      6 #define NET_DNS_DNS_CONFIG_SERVICE_H_
      7 
      8 #include <map>
      9 #include <string>
     10 #include <vector>
     11 
     12 #include "base/gtest_prod_util.h"
     13 #include "base/memory/scoped_ptr.h"
     14 #include "base/threading/non_thread_safe.h"
     15 #include "base/time/time.h"
     16 #include "base/timer/timer.h"
     17 // Needed on shared build with MSVS2010 to avoid multiple definitions of
     18 // std::vector<IPEndPoint>.
     19 #include "net/base/address_list.h"
     20 #include "net/base/ip_endpoint.h"  // win requires size of IPEndPoint
     21 #include "net/base/net_export.h"
     22 #include "net/dns/dns_hosts.h"
     23 
     24 namespace base {
     25 class Value;
     26 }
     27 
     28 namespace net {
     29 
     30 // Always use 1 second timeout (followed by binary exponential backoff).
     31 // TODO(szym): Remove code which reads timeout from system.
     32 const unsigned kDnsTimeoutSeconds = 1;
     33 
     34 // DnsConfig stores configuration of the system resolver.
     35 struct NET_EXPORT_PRIVATE DnsConfig {
     36   DnsConfig();
     37   virtual ~DnsConfig();
     38 
     39   bool Equals(const DnsConfig& d) const;
     40 
     41   bool EqualsIgnoreHosts(const DnsConfig& d) const;
     42 
     43   void CopyIgnoreHosts(const DnsConfig& src);
     44 
     45   // Returns a Value representation of |this|.  Caller takes ownership of the
     46   // returned Value.  For performance reasons, the Value only contains the
     47   // number of hosts rather than the full list.
     48   base::Value* ToValue() const;
     49 
     50   bool IsValid() const {
     51     return !nameservers.empty();
     52   }
     53 
     54   // List of name server addresses.
     55   std::vector<IPEndPoint> nameservers;
     56   // Suffix search list; used on first lookup when number of dots in given name
     57   // is less than |ndots|.
     58   std::vector<std::string> search;
     59 
     60   DnsHosts hosts;
     61 
     62   // True if there are options set in the system configuration that are not yet
     63   // supported by DnsClient.
     64   bool unhandled_options;
     65 
     66   // AppendToMultiLabelName: is suffix search performed for multi-label names?
     67   // True, except on Windows where it can be configured.
     68   bool append_to_multi_label_name;
     69 
     70   // Indicates that source port randomization is required. This uses additional
     71   // resources on some platforms.
     72   bool randomize_ports;
     73 
     74   // Resolver options; see man resolv.conf.
     75 
     76   // Minimum number of dots before global resolution precedes |search|.
     77   int ndots;
     78   // Time between retransmissions, see res_state.retrans.
     79   base::TimeDelta timeout;
     80   // Maximum number of attempts, see res_state.retry.
     81   int attempts;
     82   // Round robin entries in |nameservers| for subsequent requests.
     83   bool rotate;
     84   // Enable EDNS0 extensions.
     85   bool edns0;
     86 
     87   // Indicates system configuration uses local IPv6 connectivity, e.g.,
     88   // DirectAccess. This is exposed for HostResolver to skip IPv6 probes,
     89   // as it may cause them to return incorrect results.
     90   bool use_local_ipv6;
     91 };
     92 
     93 
     94 // Service for reading system DNS settings, on demand or when signalled by
     95 // internal watchers and NetworkChangeNotifier.
     96 class NET_EXPORT_PRIVATE DnsConfigService
     97     : NON_EXPORTED_BASE(public base::NonThreadSafe) {
     98  public:
     99   // Callback interface for the client, called on the same thread as
    100   // ReadConfig() and WatchConfig().
    101   typedef base::Callback<void(const DnsConfig& config)> CallbackType;
    102 
    103   // Creates the platform-specific DnsConfigService.
    104   static scoped_ptr<DnsConfigService> CreateSystemService();
    105 
    106   DnsConfigService();
    107   virtual ~DnsConfigService();
    108 
    109   // Attempts to read the configuration. Will run |callback| when succeeded.
    110   // Can be called at most once.
    111   void ReadConfig(const CallbackType& callback);
    112 
    113   // Registers systems watchers. Will attempt to read config after watch starts,
    114   // but only if watchers started successfully. Will run |callback| iff config
    115   // changes from last call or has to be withdrawn. Can be called at most once.
    116   // Might require MessageLoopForIO.
    117   void WatchConfig(const CallbackType& callback);
    118 
    119  protected:
    120   enum WatchStatus {
    121     DNS_CONFIG_WATCH_STARTED = 0,
    122     DNS_CONFIG_WATCH_FAILED_TO_START_CONFIG,
    123     DNS_CONFIG_WATCH_FAILED_TO_START_HOSTS,
    124     DNS_CONFIG_WATCH_FAILED_CONFIG,
    125     DNS_CONFIG_WATCH_FAILED_HOSTS,
    126     DNS_CONFIG_WATCH_MAX,
    127   };
    128 
    129  // Immediately attempts to read the current configuration.
    130   virtual void ReadNow() = 0;
    131   // Registers system watchers. Returns true iff succeeds.
    132   virtual bool StartWatching() = 0;
    133 
    134   // Called when the current config (except hosts) has changed.
    135   void InvalidateConfig();
    136   // Called when the current hosts have changed.
    137   void InvalidateHosts();
    138 
    139   // Called with new config. |config|.hosts is ignored.
    140   void OnConfigRead(const DnsConfig& config);
    141   // Called with new hosts. Rest of the config is assumed unchanged.
    142   void OnHostsRead(const DnsHosts& hosts);
    143 
    144   void set_watch_failed(bool value) { watch_failed_ = value; }
    145 
    146  private:
    147   // The timer counts from the last Invalidate* until complete config is read.
    148   void StartTimer();
    149   void OnTimeout();
    150   // Called when the config becomes complete. Stops the timer.
    151   void OnCompleteConfig();
    152 
    153   CallbackType callback_;
    154 
    155   DnsConfig dns_config_;
    156 
    157   // True if any of the necessary watchers failed. In that case, the service
    158   // will communicate changes via OnTimeout, but will only send empty DnsConfig.
    159   bool watch_failed_;
    160   // True after On*Read, before Invalidate*. Tells if the config is complete.
    161   bool have_config_;
    162   bool have_hosts_;
    163   // True if receiver needs to be updated when the config becomes complete.
    164   bool need_update_;
    165   // True if the last config sent was empty (instead of |dns_config_|).
    166   // Set when |timer_| expires.
    167   bool last_sent_empty_;
    168 
    169   // Initialized and updated on Invalidate* call.
    170   base::TimeTicks last_invalidate_config_time_;
    171   base::TimeTicks last_invalidate_hosts_time_;
    172   // Initialized and updated when |timer_| expires.
    173   base::TimeTicks last_sent_empty_time_;
    174 
    175   // Started in Invalidate*, cleared in On*Read.
    176   base::OneShotTimer<DnsConfigService> timer_;
    177 
    178   DISALLOW_COPY_AND_ASSIGN(DnsConfigService);
    179 };
    180 
    181 }  // namespace net
    182 
    183 #endif  // NET_DNS_DNS_CONFIG_SERVICE_H_
    184