net/dns/dns_config_service.h

   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.h"
  16 #include "base/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   // AppendToMultiLabelName: is suffix search performed for multi-label names?
  63   // True, except on Windows where it can be configured.
  64   bool append_to_multi_label_name;
  65
  66   // Indicates that source port randomization is required. This uses additional
  67   // resources on some platforms.
  68   bool randomize_ports;
  69
  70   // Resolver options; see man resolv.conf.
  71
  72   // Minimum number of dots before global resolution precedes |search|.
  73   int ndots;
  74   // Time between retransmissions, see res_state.retrans.
  75   base::TimeDelta timeout;
  76   // Maximum number of attempts, see res_state.retry.
  77   int attempts;
  78   // Round robin entries in |nameservers| for subsequent requests.
  79   bool rotate;
  80   // Enable EDNS0 extensions.
  81   bool edns0;
  82 };
  83
  84
  85 // Service for reading system DNS settings, on demand or when signalled by
  86 // internal watchers and NetworkChangeNotifier.
  87 class NET_EXPORT_PRIVATE DnsConfigService
  88     : NON_EXPORTED_BASE(public base::NonThreadSafe) {
  89  public:
  90   // Callback interface for the client, called on the same thread as
  91   // ReadConfig() and WatchConfig().
  92   typedef base::Callback<void(const DnsConfig& config)> CallbackType;
  93
  94   // Creates the platform-specific DnsConfigService.
  95   static scoped_ptr<DnsConfigService> CreateSystemService();
  96
  97   DnsConfigService();
  98   virtual ~DnsConfigService();
  99
 100   // Attempts to read the configuration. Will run |callback| when succeeded.
 101   // Can be called at most once.
 102   void ReadConfig(const CallbackType& callback);
 103
 104   // Registers systems watchers. Will attempt to read config after watch starts,
 105   // but only if watchers started successfully. Will run |callback| iff config
 106   // changes from last call or has to be withdrawn. Can be called at most once.
 107   // Might require MessageLoopForIO.
 108   void WatchConfig(const CallbackType& callback);
 109
 110  protected:
 111   enum WatchStatus {
 112     DNS_CONFIG_WATCH_STARTED = 0,
 113     DNS_CONFIG_WATCH_FAILED_TO_START_CONFIG,
 114     DNS_CONFIG_WATCH_FAILED_TO_START_HOSTS,
 115     DNS_CONFIG_WATCH_FAILED_CONFIG,
 116     DNS_CONFIG_WATCH_FAILED_HOSTS,
 117     DNS_CONFIG_WATCH_MAX,
 118   };
 119
 120  // Immediately attempts to read the current configuration.
 121   virtual void ReadNow() = 0;
 122   // Registers system watchers. Returns true iff succeeds.
 123   virtual bool StartWatching() = 0;
 124
 125   // Called when the current config (except hosts) has changed.
 126   void InvalidateConfig();
 127   // Called when the current hosts have changed.
 128   void InvalidateHosts();
 129
 130   // Called with new config. |config|.hosts is ignored.
 131   void OnConfigRead(const DnsConfig& config);
 132   // Called with new hosts. Rest of the config is assumed unchanged.
 133   void OnHostsRead(const DnsHosts& hosts);
 134
 135   void set_watch_failed(bool value) { watch_failed_ = value; }
 136
 137  private:
 138   // The timer counts from the last Invalidate* until complete config is read.
 139   void StartTimer();
 140   void OnTimeout();
 141   // Called when the config becomes complete. Stops the timer.
 142   void OnCompleteConfig();
 143
 144   CallbackType callback_;
 145
 146   DnsConfig dns_config_;
 147
 148   // True if any of the necessary watchers failed. In that case, the service
 149   // will communicate changes via OnTimeout, but will only send empty DnsConfig.
 150   bool watch_failed_;
 151   // True after On*Read, before Invalidate*. Tells if the config is complete.
 152   bool have_config_;
 153   bool have_hosts_;
 154   // True if receiver needs to be updated when the config becomes complete.
 155   bool need_update_;
 156   // True if the last config sent was empty (instead of |dns_config_|).
 157   // Set when |timer_| expires.
 158   bool last_sent_empty_;
 159
 160   // Initialized and updated on Invalidate* call.
 161   base::TimeTicks last_invalidate_config_time_;
 162   base::TimeTicks last_invalidate_hosts_time_;
 163   // Initialized and updated when |timer_| expires.
 164   base::TimeTicks last_sent_empty_time_;
 165
 166   // Started in Invalidate*, cleared in On*Read.
 167   base::OneShotTimer<DnsConfigService> timer_;
 168
 169   DISALLOW_COPY_AND_ASSIGN(DnsConfigService);
 170 };
 171
 172 }  // namespace net
 173
 174 #endif  // NET_DNS_DNS_CONFIG_SERVICE_H_