chrome/browser/net/dns_probe_service.cc

   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 #include "chrome/browser/net/dns_probe_service.h"
   6
   7 #include "base/metrics/field_trial.h"
   8 #include "base/metrics/histogram.h"
   9 #include "base/strings/string_number_conversions.h"
  10 #include "net/base/ip_endpoint.h"
  11 #include "net/base/net_util.h"
  12 #include "net/dns/dns_client.h"
  13 #include "net/dns/dns_config_service.h"
  14 #include "net/dns/dns_protocol.h"
  15
  16 using base::FieldTrialList;
  17 using base::StringToInt;
  18 using chrome_common_net::DnsProbeStatus;
  19 using net::DnsClient;
  20 using net::DnsConfig;
  21 using net::IPAddressNumber;
  22 using net::IPEndPoint;
  23 using net::ParseIPLiteralToNumber;
  24 using net::NetworkChangeNotifier;
  25
  26 namespace chrome_browser_net {
  27
  28 namespace {
  29
  30 // How long the DnsProbeService will cache the probe result for.
  31 // If it's older than this and we get a probe request, the service expires it
  32 // and starts a new probe.
  33 const int kMaxResultAgeMs = 5000;
  34
  35 // The public DNS servers used by the DnsProbeService to verify internet
  36 // connectivity.
  37 const char kGooglePublicDns1[] = "8.8.8.8";
  38 const char kGooglePublicDns2[] = "8.8.4.4";
  39
  40 IPEndPoint MakeDnsEndPoint(const std::string& dns_ip_literal) {
  41   IPAddressNumber dns_ip_number;
  42   bool rv = ParseIPLiteralToNumber(dns_ip_literal, &dns_ip_number);
  43   DCHECK(rv);
  44   return IPEndPoint(dns_ip_number, net::dns_protocol::kDefaultPort);
  45 }
  46
  47 DnsProbeStatus EvaluateResults(DnsProbeRunner::Result system_result,
  48                                DnsProbeRunner::Result public_result) {
  49   // If the system DNS is working, assume the domain doesn't exist.
  50   if (system_result == DnsProbeRunner::CORRECT)
  51     return chrome_common_net::DNS_PROBE_FINISHED_NXDOMAIN;
  52
  53   // If the system DNS is unknown (e.g. on Android), but the public server is
  54   // reachable, assume the domain doesn't exist.
  55   if (system_result == DnsProbeRunner::UNKNOWN &&
  56       public_result == DnsProbeRunner::CORRECT) {
  57     return chrome_common_net::DNS_PROBE_FINISHED_NXDOMAIN;
  58   }
  59
  60   // If the system DNS is not working but another public server is, assume the
  61   // DNS config is bad (or perhaps the DNS servers are down or broken).
  62   if (public_result == DnsProbeRunner::CORRECT)
  63     return chrome_common_net::DNS_PROBE_FINISHED_BAD_CONFIG;
  64
  65   // If the system DNS is not working and another public server is unreachable,
  66   // assume the internet connection is down (note that system DNS may be a
  67   // router on the LAN, so it may be reachable but returning errors.)
  68   if (public_result == DnsProbeRunner::UNREACHABLE)
  69     return chrome_common_net::DNS_PROBE_FINISHED_NO_INTERNET;
  70
  71   // Otherwise: the system DNS is not working and another public server is
  72   // responding but with errors or incorrect results.  This is an awkward case;
  73   // an invasive captive portal or a restrictive firewall may be intercepting
  74   // or rewriting DNS traffic, or the public server may itself be failing or
  75   // down.
  76   return chrome_common_net::DNS_PROBE_FINISHED_INCONCLUSIVE;
  77 }
  78
  79 void HistogramProbe(DnsProbeStatus status, base::TimeDelta elapsed) {
  80   DCHECK(chrome_common_net::DnsProbeStatusIsFinished(status));
  81
  82   UMA_HISTOGRAM_ENUMERATION("DnsProbe.ProbeResult", status,
  83                             chrome_common_net::DNS_PROBE_MAX);
  84   UMA_HISTOGRAM_MEDIUM_TIMES("DnsProbe.ProbeDuration", elapsed);
  85 }
  86
  87 }  // namespace
  88
  89 DnsProbeService::DnsProbeService()
  90     : state_(STATE_NO_RESULT) {
  91   NetworkChangeNotifier::AddDNSObserver(this);
  92   SetSystemClientToCurrentConfig();
  93   SetPublicClientToGooglePublicDns();
  94 }
  95
  96 DnsProbeService::~DnsProbeService() {
  97   NetworkChangeNotifier::RemoveDNSObserver(this);
  98 }
  99
 100 void DnsProbeService::ProbeDns(const DnsProbeService::ProbeCallback& callback) {
 101   pending_callbacks_.push_back(callback);
 102
 103   if (CachedResultIsExpired())
 104     ClearCachedResult();
 105
 106   switch (state_) {
 107     case STATE_NO_RESULT:
 108       StartProbes();
 109       break;
 110     case STATE_RESULT_CACHED:
 111       CallCallbacks();
 112       break;
 113     case STATE_PROBE_RUNNING:
 114       // Do nothing; probe is already running, and will call the callback.
 115       break;
 116   }
 117 }
 118
 119 void DnsProbeService::OnDNSChanged() {
 120   ClearCachedResult();
 121   SetSystemClientToCurrentConfig();
 122 }
 123
 124 void DnsProbeService::SetSystemClientForTesting(
 125     scoped_ptr<DnsClient> system_client) {
 126   system_runner_.SetClient(system_client.Pass());
 127 }
 128
 129 void DnsProbeService::SetPublicClientForTesting(
 130     scoped_ptr<DnsClient> public_client) {
 131   public_runner_.SetClient(public_client.Pass());
 132 }
 133
 134 void DnsProbeService::ClearCachedResultForTesting() {
 135   ClearCachedResult();
 136 }
 137
 138 void DnsProbeService::SetSystemClientToCurrentConfig() {
 139   DnsConfig system_config;
 140   NetworkChangeNotifier::GetDnsConfig(&system_config);
 141   system_config.search.clear();
 142   system_config.attempts = 1;
 143   system_config.randomize_ports = false;
 144
 145   scoped_ptr<DnsClient> system_client(DnsClient::CreateClient(NULL));
 146   system_client->SetConfig(system_config);
 147
 148   system_runner_.SetClient(system_client.Pass());
 149 }
 150
 151 void DnsProbeService::SetPublicClientToGooglePublicDns() {
 152   DnsConfig public_config;
 153   public_config.nameservers.push_back(MakeDnsEndPoint(kGooglePublicDns1));
 154   public_config.nameservers.push_back(MakeDnsEndPoint(kGooglePublicDns2));
 155   public_config.attempts = 1;
 156   public_config.randomize_ports = false;
 157
 158   scoped_ptr<DnsClient> public_client(DnsClient::CreateClient(NULL));
 159   public_client->SetConfig(public_config);
 160
 161   public_runner_.SetClient(public_client.Pass());
 162 }
 163
 164 void DnsProbeService::StartProbes() {
 165   DCHECK_EQ(STATE_NO_RESULT, state_);
 166
 167   DCHECK(!system_runner_.IsRunning());
 168   DCHECK(!public_runner_.IsRunning());
 169
 170   const base::Closure callback = base::Bind(&DnsProbeService::OnProbeComplete,
 171                                             base::Unretained(this));
 172   system_runner_.RunProbe(callback);
 173   public_runner_.RunProbe(callback);
 174   probe_start_time_ = base::Time::Now();
 175   state_ = STATE_PROBE_RUNNING;
 176
 177   DCHECK(system_runner_.IsRunning());
 178   DCHECK(public_runner_.IsRunning());
 179 }
 180
 181 void DnsProbeService::OnProbeComplete() {
 182   DCHECK_EQ(STATE_PROBE_RUNNING, state_);
 183
 184   if (system_runner_.IsRunning() || public_runner_.IsRunning())
 185     return;
 186
 187   cached_result_ = EvaluateResults(system_runner_.result(),
 188                                    public_runner_.result());
 189   state_ = STATE_RESULT_CACHED;
 190
 191   HistogramProbe(cached_result_, base::Time::Now() - probe_start_time_);
 192
 193   CallCallbacks();
 194 }
 195
 196 void DnsProbeService::CallCallbacks() {
 197   DCHECK_EQ(STATE_RESULT_CACHED, state_);
 198   DCHECK(chrome_common_net::DnsProbeStatusIsFinished(cached_result_));
 199   DCHECK(!pending_callbacks_.empty());
 200
 201   std::vector<ProbeCallback> callbacks;
 202   callbacks.swap(pending_callbacks_);
 203
 204   for (std::vector<ProbeCallback>::const_iterator i = callbacks.begin();
 205        i != callbacks.end(); ++i) {
 206     i->Run(cached_result_);
 207   }
 208 }
 209
 210 void DnsProbeService::ClearCachedResult() {
 211   if (state_ == STATE_RESULT_CACHED) {
 212     state_ = STATE_NO_RESULT;
 213     cached_result_ = chrome_common_net::DNS_PROBE_MAX;
 214   }
 215 }
 216
 217 bool DnsProbeService::CachedResultIsExpired() const {
 218   if (state_ != STATE_RESULT_CACHED)
 219     return false;
 220
 221   const base::TimeDelta kMaxResultAge =
 222       base::TimeDelta::FromMilliseconds(kMaxResultAgeMs);
 223   return base::Time::Now() - probe_start_time_ > kMaxResultAge;
 224 }
 225
 226 }  // namespace chrome_browser_net