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/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_