net/dns/dns_config_service_win.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 "net/dns/dns_config_service_win.h"
   6
   7 #include <algorithm>
   8 #include <string>
   9
  10 #include "base/bind.h"
  11 #include "base/callback.h"
  12 #include "base/compiler_specific.h"
  13 #include "base/files/file_path.h"
  14 #include "base/files/file_path_watcher.h"
  15 #include "base/logging.h"
  16 #include "base/memory/scoped_ptr.h"
  17 #include "base/metrics/histogram_macros.h"
  18 #include "base/strings/string_split.h"
  19 #include "base/strings/string_util.h"
  20 #include "base/strings/utf_string_conversions.h"
  21 #include "base/synchronization/lock.h"
  22 #include "base/threading/non_thread_safe.h"
  23 #include "base/threading/thread_restrictions.h"
  24 #include "base/time/time.h"
  25 #include "base/win/registry.h"
  26 #include "base/win/scoped_handle.h"
  27 #include "base/win/windows_version.h"
  28 #include "net/base/net_util.h"
  29 #include "net/base/network_change_notifier.h"
  30 #include "net/dns/dns_hosts.h"
  31 #include "net/dns/dns_protocol.h"
  32 #include "net/dns/serial_worker.h"
  33 #include "url/url_canon.h"
  34
  35 #pragma comment(lib, "iphlpapi.lib")
  36
  37 namespace net {
  38
  39 namespace internal {
  40
  41 namespace {
  42
  43 // Interval between retries to parse config. Used only until parsing succeeds.
  44 const int kRetryIntervalSeconds = 5;
  45
  46 // Registry key paths.
  47 const wchar_t* const kTcpipPath =
  48     L"SYSTEM\\CurrentControlSet\\Services\\Tcpip\\Parameters";
  49 const wchar_t* const kTcpip6Path =
  50     L"SYSTEM\\CurrentControlSet\\Services\\Tcpip6\\Parameters";
  51 const wchar_t* const kDnscachePath =
  52     L"SYSTEM\\CurrentControlSet\\Services\\Dnscache\\Parameters";
  53 const wchar_t* const kPolicyPath =
  54     L"SOFTWARE\\Policies\\Microsoft\\Windows NT\\DNSClient";
  55 const wchar_t* const kPrimaryDnsSuffixPath =
  56     L"SOFTWARE\\Policies\\Microsoft\\System\\DNSClient";
  57 const wchar_t* const kNRPTPath =
  58     L"SOFTWARE\\Policies\\Microsoft\\Windows NT\\DNSClient\\DnsPolicyConfig";
  59
  60 enum HostsParseWinResult {
  61   HOSTS_PARSE_WIN_OK = 0,
  62   HOSTS_PARSE_WIN_UNREADABLE_HOSTS_FILE,
  63   HOSTS_PARSE_WIN_COMPUTER_NAME_FAILED,
  64   HOSTS_PARSE_WIN_IPHELPER_FAILED,
  65   HOSTS_PARSE_WIN_BAD_ADDRESS,
  66   HOSTS_PARSE_WIN_MAX  // Bounding values for enumeration.
  67 };
  68
  69 // Convenience for reading values using RegKey.
  70 class RegistryReader : public base::NonThreadSafe {
  71  public:
  72   explicit RegistryReader(const wchar_t* key) {
  73     // Ignoring the result. |key_.Valid()| will catch failures.
  74     key_.Open(HKEY_LOCAL_MACHINE, key, KEY_QUERY_VALUE);
  75   }
  76
  77   bool ReadString(const wchar_t* name,
  78                   DnsSystemSettings::RegString* out) const {
  79     DCHECK(CalledOnValidThread());
  80     out->set = false;
  81     if (!key_.Valid()) {
  82       // Assume that if the |key_| is invalid then the key is missing.
  83       return true;
  84     }
  85     LONG result = key_.ReadValue(name, &out->value);
  86     if (result == ERROR_SUCCESS) {
  87       out->set = true;
  88       return true;
  89     }
  90     return (result == ERROR_FILE_NOT_FOUND);
  91   }
  92
  93   bool ReadDword(const wchar_t* name,
  94                  DnsSystemSettings::RegDword* out) const {
  95     DCHECK(CalledOnValidThread());
  96     out->set = false;
  97     if (!key_.Valid()) {
  98       // Assume that if the |key_| is invalid then the key is missing.
  99       return true;
 100     }
 101     LONG result = key_.ReadValueDW(name, &out->value);
 102     if (result == ERROR_SUCCESS) {
 103       out->set = true;
 104       return true;
 105     }
 106     return (result == ERROR_FILE_NOT_FOUND);
 107   }
 108
 109  private:
 110   base::win::RegKey key_;
 111
 112   DISALLOW_COPY_AND_ASSIGN(RegistryReader);
 113 };
 114
 115 // Wrapper for GetAdaptersAddresses. Returns NULL if failed.
 116 scoped_ptr<IP_ADAPTER_ADDRESSES, base::FreeDeleter> ReadIpHelper(ULONG flags) {
 117   base::ThreadRestrictions::AssertIOAllowed();
 118
 119   scoped_ptr<IP_ADAPTER_ADDRESSES, base::FreeDeleter> out;
 120   ULONG len = 15000;  // As recommended by MSDN for GetAdaptersAddresses.
 121   UINT rv = ERROR_BUFFER_OVERFLOW;
 122   // Try up to three times.
 123   for (unsigned tries = 0; (tries < 3) && (rv == ERROR_BUFFER_OVERFLOW);
 124        tries++) {
 125     out.reset(static_cast<PIP_ADAPTER_ADDRESSES>(malloc(len)));
 126     memset(out.get(), 0, len);
 127     rv = GetAdaptersAddresses(AF_UNSPEC, flags, NULL, out.get(), &len);
 128   }
 129   if (rv != NO_ERROR)
 130     out.reset();
 131   return out.Pass();
 132 }
 133
 134 // Converts a base::string16 domain name to ASCII, possibly using punycode.
 135 // Returns true if the conversion succeeds and output is not empty. In case of
 136 // failure, |domain| might become dirty.
 137 bool ParseDomainASCII(base::StringPiece16 widestr, std::string* domain) {
 138   DCHECK(domain);
 139   if (widestr.empty())
 140     return false;
 141
 142   // Check if already ASCII.
 143   if (base::IsStringASCII(widestr)) {
 144     domain->assign(widestr.begin(), widestr.end());
 145     return true;
 146   }
 147
 148   // Otherwise try to convert it from IDN to punycode.
 149   const int kInitialBufferSize = 256;
 150   url::RawCanonOutputT<base::char16, kInitialBufferSize> punycode;
 151   if (!url::IDNToASCII(widestr.data(), widestr.length(), &punycode))
 152     return false;
 153
 154   // |punycode_output| should now be ASCII; convert it to a std::string.
 155   // (We could use UTF16ToASCII() instead, but that requires an extra string
 156   // copy. Since ASCII is a subset of UTF8 the following is equivalent).
 157   bool success = base::UTF16ToUTF8(punycode.data(), punycode.length(), domain);
 158   DCHECK(success);
 159   DCHECK(base::IsStringASCII(*domain));
 160   return success && !domain->empty();
 161 }
 162
 163 bool ReadDevolutionSetting(const RegistryReader& reader,
 164                            DnsSystemSettings::DevolutionSetting* setting) {
 165   return reader.ReadDword(L"UseDomainNameDevolution", &setting->enabled) &&
 166          reader.ReadDword(L"DomainNameDevolutionLevel", &setting->level);
 167 }
 168
 169 // Reads DnsSystemSettings from IpHelper and registry.
 170 ConfigParseWinResult ReadSystemSettings(DnsSystemSettings* settings) {
 171   settings->addresses = ReadIpHelper(GAA_FLAG_SKIP_ANYCAST |
 172                                      GAA_FLAG_SKIP_UNICAST |
 173                                      GAA_FLAG_SKIP_MULTICAST |
 174                                      GAA_FLAG_SKIP_FRIENDLY_NAME);
 175   if (!settings->addresses.get())
 176     return CONFIG_PARSE_WIN_READ_IPHELPER;
 177
 178   RegistryReader tcpip_reader(kTcpipPath);
 179   RegistryReader tcpip6_reader(kTcpip6Path);
 180   RegistryReader dnscache_reader(kDnscachePath);
 181   RegistryReader policy_reader(kPolicyPath);
 182   RegistryReader primary_dns_suffix_reader(kPrimaryDnsSuffixPath);
 183
 184   if (!policy_reader.ReadString(L"SearchList",
 185                                 &settings->policy_search_list)) {
 186     return CONFIG_PARSE_WIN_READ_POLICY_SEARCHLIST;
 187   }
 188
 189   if (!tcpip_reader.ReadString(L"SearchList", &settings->tcpip_search_list))
 190     return CONFIG_PARSE_WIN_READ_TCPIP_SEARCHLIST;
 191
 192   if (!tcpip_reader.ReadString(L"Domain", &settings->tcpip_domain))
 193     return CONFIG_PARSE_WIN_READ_DOMAIN;
 194
 195   if (!ReadDevolutionSetting(policy_reader, &settings->policy_devolution))
 196     return CONFIG_PARSE_WIN_READ_POLICY_DEVOLUTION;
 197
 198   if (!ReadDevolutionSetting(dnscache_reader, &settings->dnscache_devolution))
 199     return CONFIG_PARSE_WIN_READ_DNSCACHE_DEVOLUTION;
 200
 201   if (!ReadDevolutionSetting(tcpip_reader, &settings->tcpip_devolution))
 202     return CONFIG_PARSE_WIN_READ_TCPIP_DEVOLUTION;
 203
 204   if (!policy_reader.ReadDword(L"AppendToMultiLabelName",
 205                                &settings->append_to_multi_label_name)) {
 206     return CONFIG_PARSE_WIN_READ_APPEND_MULTILABEL;
 207   }
 208
 209   if (!primary_dns_suffix_reader.ReadString(L"PrimaryDnsSuffix",
 210                                             &settings->primary_dns_suffix)) {
 211     return CONFIG_PARSE_WIN_READ_PRIMARY_SUFFIX;
 212   }
 213
 214   base::win::RegistryKeyIterator nrpt_rules(HKEY_LOCAL_MACHINE, kNRPTPath);
 215   settings->have_name_resolution_policy = (nrpt_rules.SubkeyCount() > 0);
 216
 217   return CONFIG_PARSE_WIN_OK;
 218 }
 219
 220 // Default address of "localhost" and local computer name can be overridden
 221 // by the HOSTS file, but if it's not there, then we need to fill it in.
 222 HostsParseWinResult AddLocalhostEntries(DnsHosts* hosts) {
 223   const unsigned char kIPv4Localhost[] = { 127, 0, 0, 1 };
 224   const unsigned char kIPv6Localhost[] = { 0, 0, 0, 0, 0, 0, 0, 0,
 225                                            0, 0, 0, 0, 0, 0, 0, 1 };
 226   IPAddressNumber loopback_ipv4(kIPv4Localhost,
 227                                 kIPv4Localhost + arraysize(kIPv4Localhost));
 228   IPAddressNumber loopback_ipv6(kIPv6Localhost,
 229                                 kIPv6Localhost + arraysize(kIPv6Localhost));
 230
 231   // This does not override any pre-existing entries from the HOSTS file.
 232   hosts->insert(std::make_pair(DnsHostsKey("localhost", ADDRESS_FAMILY_IPV4),
 233                                loopback_ipv4));
 234   hosts->insert(std::make_pair(DnsHostsKey("localhost", ADDRESS_FAMILY_IPV6),
 235                                loopback_ipv6));
 236
 237   WCHAR buffer[MAX_PATH];
 238   DWORD size = MAX_PATH;
 239   std::string localname;
 240   if (!GetComputerNameExW(ComputerNameDnsHostname, buffer, &size) ||
 241       !ParseDomainASCII(buffer, &localname)) {
 242     return HOSTS_PARSE_WIN_COMPUTER_NAME_FAILED;
 243   }
 244   localname = base::ToLowerASCII(localname);
 245
 246   bool have_ipv4 =
 247       hosts->count(DnsHostsKey(localname, ADDRESS_FAMILY_IPV4)) > 0;
 248   bool have_ipv6 =
 249       hosts->count(DnsHostsKey(localname, ADDRESS_FAMILY_IPV6)) > 0;
 250
 251   if (have_ipv4 && have_ipv6)
 252     return HOSTS_PARSE_WIN_OK;
 253
 254   scoped_ptr<IP_ADAPTER_ADDRESSES, base::FreeDeleter> addresses =
 255       ReadIpHelper(GAA_FLAG_SKIP_ANYCAST |
 256                    GAA_FLAG_SKIP_DNS_SERVER |
 257                    GAA_FLAG_SKIP_MULTICAST |
 258                    GAA_FLAG_SKIP_FRIENDLY_NAME);
 259   if (!addresses.get())
 260     return HOSTS_PARSE_WIN_IPHELPER_FAILED;
 261
 262   // The order of adapters is the network binding order, so stick to the
 263   // first good adapter for each family.
 264   for (const IP_ADAPTER_ADDRESSES* adapter = addresses.get();
 265        adapter != NULL && (!have_ipv4 || !have_ipv6);
 266        adapter = adapter->Next) {
 267     if (adapter->OperStatus != IfOperStatusUp)
 268       continue;
 269     if (adapter->IfType == IF_TYPE_SOFTWARE_LOOPBACK)
 270       continue;
 271
 272     for (const IP_ADAPTER_UNICAST_ADDRESS* address =
 273              adapter->FirstUnicastAddress;
 274          address != NULL;
 275          address = address->Next) {
 276       IPEndPoint ipe;
 277       if (!ipe.FromSockAddr(address->Address.lpSockaddr,
 278                             address->Address.iSockaddrLength)) {
 279         return HOSTS_PARSE_WIN_BAD_ADDRESS;
 280       }
 281       if (!have_ipv4 && (ipe.GetFamily() == ADDRESS_FAMILY_IPV4)) {
 282         have_ipv4 = true;
 283         (*hosts)[DnsHostsKey(localname, ADDRESS_FAMILY_IPV4)] = ipe.address();
 284       } else if (!have_ipv6 && (ipe.GetFamily() == ADDRESS_FAMILY_IPV6)) {
 285         have_ipv6 = true;
 286         (*hosts)[DnsHostsKey(localname, ADDRESS_FAMILY_IPV6)] = ipe.address();
 287       }
 288     }
 289   }
 290   return HOSTS_PARSE_WIN_OK;
 291 }
 292
 293 // Watches a single registry key for changes.
 294 class RegistryWatcher : public base::NonThreadSafe {
 295  public:
 296   typedef base::Callback<void(bool succeeded)> CallbackType;
 297   RegistryWatcher() {}
 298
 299   bool Watch(const wchar_t* key, const CallbackType& callback) {
 300     DCHECK(CalledOnValidThread());
 301     DCHECK(!callback.is_null());
 302     DCHECK(callback_.is_null());
 303     callback_ = callback;
 304     if (key_.Open(HKEY_LOCAL_MACHINE, key, KEY_NOTIFY) != ERROR_SUCCESS)
 305       return false;
 306
 307     return key_.StartWatching(base::Bind(&RegistryWatcher::OnObjectSignaled,
 308                                          base::Unretained(this)));
 309   }
 310
 311   void OnObjectSignaled() {
 312     DCHECK(CalledOnValidThread());
 313     DCHECK(!callback_.is_null());
 314     if (key_.StartWatching(base::Bind(&RegistryWatcher::OnObjectSignaled,
 315                                       base::Unretained(this)))) {
 316       callback_.Run(true);
 317     } else {
 318       key_.Close();
 319       callback_.Run(false);
 320     }
 321   }
 322
 323  private:
 324   CallbackType callback_;
 325   base::win::RegKey key_;
 326
 327   DISALLOW_COPY_AND_ASSIGN(RegistryWatcher);
 328 };
 329
 330 // Returns true iff |address| is DNS address from IPv6 stateless discovery,
 331 // i.e., matches fec0:0:0:ffff::{1,2,3}.
 332 // http://tools.ietf.org/html/draft-ietf-ipngwg-dns-discovery
 333 bool IsStatelessDiscoveryAddress(const IPAddressNumber& address) {
 334   if (address.size() != kIPv6AddressSize)
 335     return false;
 336   const uint8 kPrefix[] = {
 337       0xfe, 0xc0, 0x00, 0x00, 0x00, 0x00, 0xff, 0xff,
 338       0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
 339   };
 340   return std::equal(kPrefix, kPrefix + arraysize(kPrefix),
 341                     address.begin()) && (address.back() < 4);
 342 }
 343
 344 // Returns the path to the HOSTS file.
 345 base::FilePath GetHostsPath() {
 346   TCHAR buffer[MAX_PATH];
 347   UINT rc = GetSystemDirectory(buffer, MAX_PATH);
 348   DCHECK(0 < rc && rc < MAX_PATH);
 349   return base::FilePath(buffer).Append(
 350       FILE_PATH_LITERAL("drivers\\etc\\hosts"));
 351 }
 352
 353 void ConfigureSuffixSearch(const DnsSystemSettings& settings,
 354                            DnsConfig* config) {
 355   // SearchList takes precedence, so check it first.
 356   if (settings.policy_search_list.set) {
 357     std::vector<std::string> search;
 358     if (ParseSearchList(settings.policy_search_list.value, &search)) {
 359       config->search.swap(search);
 360       return;
 361     }
 362     // Even if invalid, the policy disables the user-specified setting below.
 363   } else if (settings.tcpip_search_list.set) {
 364     std::vector<std::string> search;
 365     if (ParseSearchList(settings.tcpip_search_list.value, &search)) {
 366       config->search.swap(search);
 367       return;
 368     }
 369   }
 370
 371   // In absence of explicit search list, suffix search is:
 372   // [primary suffix, connection-specific suffix, devolution of primary suffix].
 373   // Primary suffix can be set by policy (primary_dns_suffix) or
 374   // user setting (tcpip_domain).
 375   //
 376   // The policy (primary_dns_suffix) can be edited via Group Policy Editor
 377   // (gpedit.msc) at Local Computer Policy => Computer Configuration
 378   // => Administrative Template => Network => DNS Client => Primary DNS Suffix.
 379   //
 380   // The user setting (tcpip_domain) can be configurred at Computer Name in
 381   // System Settings
 382   std::string primary_suffix;
 383   if ((settings.primary_dns_suffix.set &&
 384        ParseDomainASCII(settings.primary_dns_suffix.value, &primary_suffix)) ||
 385       (settings.tcpip_domain.set &&
 386        ParseDomainASCII(settings.tcpip_domain.value, &primary_suffix))) {
 387     // Primary suffix goes in front.
 388     config->search.insert(config->search.begin(), primary_suffix);
 389   } else {
 390     return;  // No primary suffix, hence no devolution.
 391   }
 392
 393   // Devolution is determined by precedence: policy > dnscache > tcpip.
 394   // |enabled|: UseDomainNameDevolution and |level|: DomainNameDevolutionLevel
 395   // are overridden independently.
 396   DnsSystemSettings::DevolutionSetting devolution = settings.policy_devolution;
 397
 398   if (!devolution.enabled.set)
 399     devolution.enabled = settings.dnscache_devolution.enabled;
 400   if (!devolution.enabled.set)
 401     devolution.enabled = settings.tcpip_devolution.enabled;
 402   if (devolution.enabled.set && (devolution.enabled.value == 0))
 403     return;  // Devolution disabled.
 404
 405   // By default devolution is enabled.
 406
 407   if (!devolution.level.set)
 408     devolution.level = settings.dnscache_devolution.level;
 409   if (!devolution.level.set)
 410     devolution.level = settings.tcpip_devolution.level;
 411
 412   // After the recent update, Windows will try to determine a safe default
 413   // value by comparing the forest root domain (FRD) to the primary suffix.
 414   // See http://support.microsoft.com/kb/957579 for details.
 415   // For now, if the level is not set, we disable devolution, assuming that
 416   // we will fallback to the system getaddrinfo anyway. This might cause
 417   // performance loss for resolutions which depend on the system default
 418   // devolution setting.
 419   //
 420   // If the level is explicitly set below 2, devolution is disabled.
 421   if (!devolution.level.set || devolution.level.value < 2)
 422     return;  // Devolution disabled.
 423
 424   // Devolve the primary suffix. This naive logic matches the observed
 425   // behavior (see also ParseSearchList). If a suffix is not valid, it will be
 426   // discarded when the fully-qualified name is converted to DNS format.
 427
 428   unsigned num_dots = std::count(primary_suffix.begin(),
 429                                  primary_suffix.end(), '.');
 430
 431   for (size_t offset = 0; num_dots >= devolution.level.value; --num_dots) {
 432     offset = primary_suffix.find('.', offset + 1);
 433     config->search.push_back(primary_suffix.substr(offset + 1));
 434   }
 435 }
 436
 437 }  // namespace
 438
 439 DnsSystemSettings::DnsSystemSettings()
 440     : policy_search_list(),
 441       tcpip_search_list(),
 442       tcpip_domain(),
 443       primary_dns_suffix(),
 444       policy_devolution(),
 445       dnscache_devolution(),
 446       tcpip_devolution(),
 447       append_to_multi_label_name(),
 448       have_name_resolution_policy(false) {
 449   policy_search_list.set = false;
 450   tcpip_search_list.set = false;
 451   tcpip_domain.set = false;
 452   primary_dns_suffix.set = false;
 453
 454   policy_devolution.enabled.set = false;
 455   policy_devolution.level.set = false;
 456   dnscache_devolution.enabled.set = false;
 457   dnscache_devolution.level.set = false;
 458   tcpip_devolution.enabled.set = false;
 459   tcpip_devolution.level.set = false;
 460
 461   append_to_multi_label_name.set = false;
 462 }
 463
 464 DnsSystemSettings::~DnsSystemSettings() {
 465 }
 466
 467 bool ParseSearchList(const base::string16& value,
 468                      std::vector<std::string>* output) {
 469   DCHECK(output);
 470   if (value.empty())
 471     return false;
 472
 473   output->clear();
 474
 475   // If the list includes an empty hostname (",," or ", ,"), it is terminated.
 476   // Although nslookup and network connection property tab ignore such
 477   // fragments ("a,b,,c" becomes ["a", "b", "c"]), our reference is getaddrinfo
 478   // (which sees ["a", "b"]). WMI queries also return a matching search list.
 479   for (const base::StringPiece16& t : base::SplitStringPiece(
 480            value, L",", base::TRIM_WHITESPACE, base::SPLIT_WANT_ALL)) {
 481     // Convert non-ASCII to punycode, although getaddrinfo does not properly
 482     // handle such suffixes.
 483     std::string parsed;
 484     if (!ParseDomainASCII(t, &parsed))
 485       break;
 486     output->push_back(parsed);
 487   }
 488   return !output->empty();
 489 }
 490
 491 ConfigParseWinResult ConvertSettingsToDnsConfig(
 492     const DnsSystemSettings& settings,
 493     DnsConfig* config) {
 494   *config = DnsConfig();
 495
 496   // Use GetAdapterAddresses to get effective DNS server order and
 497   // connection-specific DNS suffix. Ignore disconnected and loopback adapters.
 498   // The order of adapters is the network binding order, so stick to the
 499   // first good adapter.
 500   for (const IP_ADAPTER_ADDRESSES* adapter = settings.addresses.get();
 501        adapter != NULL && config->nameservers.empty();
 502        adapter = adapter->Next) {
 503     if (adapter->OperStatus != IfOperStatusUp)
 504       continue;
 505     if (adapter->IfType == IF_TYPE_SOFTWARE_LOOPBACK)
 506       continue;
 507
 508     for (const IP_ADAPTER_DNS_SERVER_ADDRESS* address =
 509              adapter->FirstDnsServerAddress;
 510          address != NULL;
 511          address = address->Next) {
 512       IPEndPoint ipe;
 513       if (ipe.FromSockAddr(address->Address.lpSockaddr,
 514                            address->Address.iSockaddrLength)) {
 515         if (IsStatelessDiscoveryAddress(ipe.address()))
 516           continue;
 517         // Override unset port.
 518         if (!ipe.port())
 519           ipe = IPEndPoint(ipe.address(), dns_protocol::kDefaultPort);
 520         config->nameservers.push_back(ipe);
 521       } else {
 522         return CONFIG_PARSE_WIN_BAD_ADDRESS;
 523       }
 524     }
 525
 526     // IP_ADAPTER_ADDRESSES in Vista+ has a search list at |FirstDnsSuffix|,
 527     // but it came up empty in all trials.
 528     // |DnsSuffix| stores the effective connection-specific suffix, which is
 529     // obtained via DHCP (regkey: Tcpip\Parameters\Interfaces\{XXX}\DhcpDomain)
 530     // or specified by the user (regkey: Tcpip\Parameters\Domain).
 531     std::string dns_suffix;
 532     if (ParseDomainASCII(adapter->DnsSuffix, &dns_suffix))
 533       config->search.push_back(dns_suffix);
 534   }
 535
 536   if (config->nameservers.empty())
 537     return CONFIG_PARSE_WIN_NO_NAMESERVERS;  // No point continuing.
 538
 539   // Windows always tries a multi-label name "as is" before using suffixes.
 540   config->ndots = 1;
 541
 542   if (!settings.append_to_multi_label_name.set) {
 543     // The default setting is true for XP, false for Vista+.
 544     if (base::win::GetVersion() >= base::win::VERSION_VISTA) {
 545       config->append_to_multi_label_name = false;
 546     } else {
 547       config->append_to_multi_label_name = true;
 548     }
 549   } else {
 550     config->append_to_multi_label_name =
 551         (settings.append_to_multi_label_name.value != 0);
 552   }
 553
 554   ConfigParseWinResult result = CONFIG_PARSE_WIN_OK;
 555   if (settings.have_name_resolution_policy) {
 556     config->unhandled_options = true;
 557     // TODO(szym): only set this to true if NRPT has DirectAccess rules.
 558     config->use_local_ipv6 = true;
 559     result = CONFIG_PARSE_WIN_UNHANDLED_OPTIONS;
 560   }
 561
 562   ConfigureSuffixSearch(settings, config);
 563   return result;
 564 }
 565
 566 // Watches registry and HOSTS file for changes. Must live on a thread which
 567 // allows IO.
 568 class DnsConfigServiceWin::Watcher
 569     : public NetworkChangeNotifier::IPAddressObserver {
 570  public:
 571   explicit Watcher(DnsConfigServiceWin* service) : service_(service) {}
 572   ~Watcher() override { NetworkChangeNotifier::RemoveIPAddressObserver(this); }
 573
 574   bool Watch() {
 575     RegistryWatcher::CallbackType callback =
 576         base::Bind(&DnsConfigServiceWin::OnConfigChanged,
 577                    base::Unretained(service_));
 578
 579     bool success = true;
 580
 581     // The Tcpip key must be present.
 582     if (!tcpip_watcher_.Watch(kTcpipPath, callback)) {
 583       LOG(ERROR) << "DNS registry watch failed to start.";
 584       success = false;
 585       UMA_HISTOGRAM_ENUMERATION("AsyncDNS.WatchStatus",
 586                                 DNS_CONFIG_WATCH_FAILED_TO_START_CONFIG,
 587                                 DNS_CONFIG_WATCH_MAX);
 588     }
 589
 590     // Watch for IPv6 nameservers.
 591     tcpip6_watcher_.Watch(kTcpip6Path, callback);
 592
 593     // DNS suffix search list and devolution can be configured via group
 594     // policy which sets this registry key. If the key is missing, the policy
 595     // does not apply, and the DNS client uses Tcpip and Dnscache settings.
 596     // If a policy is installed, DnsConfigService will need to be restarted.
 597     // BUG=99509
 598
 599     dnscache_watcher_.Watch(kDnscachePath, callback);
 600     policy_watcher_.Watch(kPolicyPath, callback);
 601
 602     if (!hosts_watcher_.Watch(GetHostsPath(), false,
 603                               base::Bind(&Watcher::OnHostsChanged,
 604                                          base::Unretained(this)))) {
 605       UMA_HISTOGRAM_ENUMERATION("AsyncDNS.WatchStatus",
 606                                 DNS_CONFIG_WATCH_FAILED_TO_START_HOSTS,
 607                                 DNS_CONFIG_WATCH_MAX);
 608       LOG(ERROR) << "DNS hosts watch failed to start.";
 609       success = false;
 610     } else {
 611       // Also need to observe changes to local non-loopback IP for DnsHosts.
 612       NetworkChangeNotifier::AddIPAddressObserver(this);
 613     }
 614     return success;
 615   }
 616
 617  private:
 618   void OnHostsChanged(const base::FilePath& path, bool error) {
 619     if (error)
 620       NetworkChangeNotifier::RemoveIPAddressObserver(this);
 621     service_->OnHostsChanged(!error);
 622   }
 623
 624   // NetworkChangeNotifier::IPAddressObserver:
 625   void OnIPAddressChanged() override {
 626     // Need to update non-loopback IP of local host.
 627     service_->OnHostsChanged(true);
 628   }
 629
 630   DnsConfigServiceWin* service_;
 631
 632   RegistryWatcher tcpip_watcher_;
 633   RegistryWatcher tcpip6_watcher_;
 634   RegistryWatcher dnscache_watcher_;
 635   RegistryWatcher policy_watcher_;
 636   base::FilePathWatcher hosts_watcher_;
 637
 638   DISALLOW_COPY_AND_ASSIGN(Watcher);
 639 };
 640
 641 // Reads config from registry and IpHelper. All work performed on WorkerPool.
 642 class DnsConfigServiceWin::ConfigReader : public SerialWorker {
 643  public:
 644   explicit ConfigReader(DnsConfigServiceWin* service)
 645       : service_(service),
 646         success_(false) {}
 647
 648  private:
 649   ~ConfigReader() override {}
 650
 651   void DoWork() override {
 652     // Should be called on WorkerPool.
 653     base::TimeTicks start_time = base::TimeTicks::Now();
 654     DnsSystemSettings settings = {};
 655     ConfigParseWinResult result = ReadSystemSettings(&settings);
 656     if (result == CONFIG_PARSE_WIN_OK)
 657       result = ConvertSettingsToDnsConfig(settings, &dns_config_);
 658     success_ = (result == CONFIG_PARSE_WIN_OK ||
 659                 result == CONFIG_PARSE_WIN_UNHANDLED_OPTIONS);
 660     UMA_HISTOGRAM_ENUMERATION("AsyncDNS.ConfigParseWin",
 661                               result, CONFIG_PARSE_WIN_MAX);
 662     UMA_HISTOGRAM_BOOLEAN("AsyncDNS.ConfigParseResult", success_);
 663     UMA_HISTOGRAM_TIMES("AsyncDNS.ConfigParseDuration",
 664                         base::TimeTicks::Now() - start_time);
 665   }
 666
 667   void OnWorkFinished() override {
 668     DCHECK(loop()->BelongsToCurrentThread());
 669     DCHECK(!IsCancelled());
 670     if (success_) {
 671       service_->OnConfigRead(dns_config_);
 672     } else {
 673       LOG(WARNING) << "Failed to read DnsConfig.";
 674       // Try again in a while in case DnsConfigWatcher missed the signal.
 675       base::MessageLoop::current()->PostDelayedTask(
 676           FROM_HERE,
 677           base::Bind(&ConfigReader::WorkNow, this),
 678           base::TimeDelta::FromSeconds(kRetryIntervalSeconds));
 679     }
 680   }
 681
 682   DnsConfigServiceWin* service_;
 683   // Written in DoWork(), read in OnWorkFinished(). No locking required.
 684   DnsConfig dns_config_;
 685   bool success_;
 686 };
 687
 688 // Reads hosts from HOSTS file and fills in localhost and local computer name if
 689 // necessary. All work performed on WorkerPool.
 690 class DnsConfigServiceWin::HostsReader : public SerialWorker {
 691  public:
 692   explicit HostsReader(DnsConfigServiceWin* service)
 693       : path_(GetHostsPath()),
 694         service_(service),
 695         success_(false) {
 696   }
 697
 698  private:
 699   ~HostsReader() override {}
 700
 701   void DoWork() override {
 702     base::TimeTicks start_time = base::TimeTicks::Now();
 703     HostsParseWinResult result = HOSTS_PARSE_WIN_UNREADABLE_HOSTS_FILE;
 704     if (ParseHostsFile(path_, &hosts_))
 705       result = AddLocalhostEntries(&hosts_);
 706     success_ = (result == HOSTS_PARSE_WIN_OK);
 707     UMA_HISTOGRAM_ENUMERATION("AsyncDNS.HostsParseWin",
 708                               result, HOSTS_PARSE_WIN_MAX);
 709     UMA_HISTOGRAM_BOOLEAN("AsyncDNS.HostParseResult", success_);
 710     UMA_HISTOGRAM_TIMES("AsyncDNS.HostsParseDuration",
 711                         base::TimeTicks::Now() - start_time);
 712   }
 713
 714   void OnWorkFinished() override {
 715     DCHECK(loop()->BelongsToCurrentThread());
 716     if (success_) {
 717       service_->OnHostsRead(hosts_);
 718     } else {
 719       LOG(WARNING) << "Failed to read DnsHosts.";
 720     }
 721   }
 722
 723   const base::FilePath path_;
 724   DnsConfigServiceWin* service_;
 725   // Written in DoWork, read in OnWorkFinished, no locking necessary.
 726   DnsHosts hosts_;
 727   bool success_;
 728
 729   DISALLOW_COPY_AND_ASSIGN(HostsReader);
 730 };
 731
 732 DnsConfigServiceWin::DnsConfigServiceWin()
 733     : config_reader_(new ConfigReader(this)),
 734       hosts_reader_(new HostsReader(this)) {}
 735
 736 DnsConfigServiceWin::~DnsConfigServiceWin() {
 737   config_reader_->Cancel();
 738   hosts_reader_->Cancel();
 739 }
 740
 741 void DnsConfigServiceWin::ReadNow() {
 742   config_reader_->WorkNow();
 743   hosts_reader_->WorkNow();
 744 }
 745
 746 bool DnsConfigServiceWin::StartWatching() {
 747   // TODO(szym): re-start watcher if that makes sense. http://crbug.com/116139
 748   watcher_.reset(new Watcher(this));
 749   UMA_HISTOGRAM_ENUMERATION("AsyncDNS.WatchStatus", DNS_CONFIG_WATCH_STARTED,
 750                             DNS_CONFIG_WATCH_MAX);
 751   return watcher_->Watch();
 752 }
 753
 754 void DnsConfigServiceWin::OnConfigChanged(bool succeeded) {
 755   InvalidateConfig();
 756   config_reader_->WorkNow();
 757   if (!succeeded) {
 758     LOG(ERROR) << "DNS config watch failed.";
 759     set_watch_failed(true);
 760     UMA_HISTOGRAM_ENUMERATION("AsyncDNS.WatchStatus",
 761                               DNS_CONFIG_WATCH_FAILED_CONFIG,
 762                               DNS_CONFIG_WATCH_MAX);
 763   }
 764 }
 765
 766 void DnsConfigServiceWin::OnHostsChanged(bool succeeded) {
 767   InvalidateHosts();
 768   if (succeeded) {
 769     hosts_reader_->WorkNow();
 770   } else {
 771     LOG(ERROR) << "DNS hosts watch failed.";
 772     set_watch_failed(true);
 773     UMA_HISTOGRAM_ENUMERATION("AsyncDNS.WatchStatus",
 774                               DNS_CONFIG_WATCH_FAILED_HOSTS,
 775                               DNS_CONFIG_WATCH_MAX);
 776   }
 777 }
 778
 779 }  // namespace internal
 780
 781 // static
 782 scoped_ptr<DnsConfigService> DnsConfigService::CreateSystemService() {
 783   return scoped_ptr<DnsConfigService>(new internal::DnsConfigServiceWin());
 784 }
 785
 786 }  // namespace net