src/net/dns/host_resolver_impl.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/host_resolver_impl.h"
   6
   7 #if defined(OS_WIN)
   8 #include <Winsock2.h>
   9 #elif defined(OS_POSIX)
  10 #include <netdb.h>
  11 #endif
  12
  13 #include <cmath>
  14 #include <utility>
  15 #include <vector>
  16
  17 #include "base/basictypes.h"
  18 #include "base/bind.h"
  19 #include "base/bind_helpers.h"
  20 #include "base/callback.h"
  21 #include "base/compiler_specific.h"
  22 #include "base/debug/debugger.h"
  23 #include "base/debug/stack_trace.h"
  24 #include "base/message_loop/message_loop_proxy.h"
  25 #include "base/metrics/field_trial.h"
  26 #include "base/metrics/histogram.h"
  27 #include "base/stl_util.h"
  28 #include "base/strings/string_util.h"
  29 #include "base/strings/utf_string_conversions.h"
  30 #include "base/threading/worker_pool.h"
  31 #include "base/time/time.h"
  32 #include "base/values.h"
  33 #include "net/base/address_family.h"
  34 #include "net/base/address_list.h"
  35 #include "net/base/dns_reloader.h"
  36 #include "net/base/dns_util.h"
  37 #include "net/base/host_port_pair.h"
  38 #include "net/base/ip_endpoint.h"
  39 #include "net/base/net_errors.h"
  40 #include "net/base/net_log.h"
  41 #include "net/base/net_util.h"
  42 #include "net/dns/address_sorter.h"
  43 #include "net/dns/dns_client.h"
  44 #include "net/dns/dns_config_service.h"
  45 #include "net/dns/dns_protocol.h"
  46 #include "net/dns/dns_response.h"
  47 #include "net/dns/dns_transaction.h"
  48 #include "net/dns/host_resolver_proc.h"
  49 #include "net/socket/client_socket_factory.h"
  50 #include "net/udp/datagram_client_socket.h"
  51
  52 #if defined(OS_WIN)
  53 #include "net/base/winsock_init.h"
  54 #endif
  55
  56 namespace net {
  57
  58 namespace {
  59
  60 // Limit the size of hostnames that will be resolved to combat issues in
  61 // some platform's resolvers.
  62 const size_t kMaxHostLength = 4096;
  63
  64 // Default TTL for successful resolutions with ProcTask.
  65 const unsigned kCacheEntryTTLSeconds = 60;
  66
  67 // Default TTL for unsuccessful resolutions with ProcTask.
  68 const unsigned kNegativeCacheEntryTTLSeconds = 0;
  69
  70 // Minimum TTL for successful resolutions with DnsTask.
  71 const unsigned kMinimumTTLSeconds = kCacheEntryTTLSeconds;
  72
  73 // We use a separate histogram name for each platform to facilitate the
  74 // display of error codes by their symbolic name (since each platform has
  75 // different mappings).
  76 const char kOSErrorsForGetAddrinfoHistogramName[] =
  77 #if defined(OS_WIN)
  78     "Net.OSErrorsForGetAddrinfo_Win";
  79 #elif defined(OS_MACOSX)
  80     "Net.OSErrorsForGetAddrinfo_Mac";
  81 #elif defined(OS_LINUX)
  82     "Net.OSErrorsForGetAddrinfo_Linux";
  83 #else
  84     "Net.OSErrorsForGetAddrinfo";
  85 #endif
  86
  87 // Gets a list of the likely error codes that getaddrinfo() can return
  88 // (non-exhaustive). These are the error codes that we will track via
  89 // a histogram.
  90 std::vector<int> GetAllGetAddrinfoOSErrors() {
  91   int os_errors[] = {
  92 #if defined(OS_POSIX)
  93 #if !defined(OS_FREEBSD)
  94 #if !defined(OS_ANDROID)
  95     // EAI_ADDRFAMILY has been declared obsolete in Android's and
  96     // FreeBSD's netdb.h.
  97     EAI_ADDRFAMILY,
  98 #endif
  99     // EAI_NODATA has been declared obsolete in FreeBSD's netdb.h.
 100     EAI_NODATA,
 101 #endif
 102     EAI_AGAIN,
 103     EAI_BADFLAGS,
 104     EAI_FAIL,
 105     EAI_FAMILY,
 106     EAI_MEMORY,
 107     EAI_NONAME,
 108     EAI_SERVICE,
 109     EAI_SOCKTYPE,
 110     EAI_SYSTEM,
 111 #elif defined(OS_WIN)
 112     // See: http://msdn.microsoft.com/en-us/library/ms738520(VS.85).aspx
 113     WSA_NOT_ENOUGH_MEMORY,
 114     WSAEAFNOSUPPORT,
 115     WSAEINVAL,
 116     WSAESOCKTNOSUPPORT,
 117     WSAHOST_NOT_FOUND,
 118     WSANO_DATA,
 119     WSANO_RECOVERY,
 120     WSANOTINITIALISED,
 121     WSATRY_AGAIN,
 122     WSATYPE_NOT_FOUND,
 123     // The following are not in doc, but might be to appearing in results :-(.
 124     WSA_INVALID_HANDLE,
 125 #endif
 126   };
 127
 128   // Ensure all errors are positive, as histogram only tracks positive values.
 129   for (size_t i = 0; i < arraysize(os_errors); ++i) {
 130     os_errors[i] = std::abs(os_errors[i]);
 131   }
 132
 133   return base::CustomHistogram::ArrayToCustomRanges(os_errors,
 134                                                     arraysize(os_errors));
 135 }
 136
 137 enum DnsResolveStatus {
 138   RESOLVE_STATUS_DNS_SUCCESS = 0,
 139   RESOLVE_STATUS_PROC_SUCCESS,
 140   RESOLVE_STATUS_FAIL,
 141   RESOLVE_STATUS_SUSPECT_NETBIOS,
 142   RESOLVE_STATUS_MAX
 143 };
 144
 145 void UmaAsyncDnsResolveStatus(DnsResolveStatus result) {
 146   UMA_HISTOGRAM_ENUMERATION("AsyncDNS.ResolveStatus",
 147                             result,
 148                             RESOLVE_STATUS_MAX);
 149 }
 150
 151 bool ResemblesNetBIOSName(const std::string& hostname) {
 152   return (hostname.size() < 16) && (hostname.find('.') == std::string::npos);
 153 }
 154
 155 // True if |hostname| ends with either ".local" or ".local.".
 156 bool ResemblesMulticastDNSName(const std::string& hostname) {
 157   DCHECK(!hostname.empty());
 158   const char kSuffix[] = ".local.";
 159   const size_t kSuffixLen = sizeof(kSuffix) - 1;
 160   const size_t kSuffixLenTrimmed = kSuffixLen - 1;
 161   if (hostname[hostname.size() - 1] == '.') {
 162     return hostname.size() > kSuffixLen &&
 163         !hostname.compare(hostname.size() - kSuffixLen, kSuffixLen, kSuffix);
 164   }
 165   return hostname.size() > kSuffixLenTrimmed &&
 166       !hostname.compare(hostname.size() - kSuffixLenTrimmed, kSuffixLenTrimmed,
 167                         kSuffix, kSuffixLenTrimmed);
 168 }
 169
 170 // Attempts to connect a UDP socket to |dest|:53.
 171 bool IsGloballyReachable(const IPAddressNumber& dest,
 172                          const BoundNetLog& net_log) {
 173   scoped_ptr<DatagramClientSocket> socket(
 174       ClientSocketFactory::GetDefaultFactory()->CreateDatagramClientSocket(
 175           DatagramSocket::DEFAULT_BIND,
 176           RandIntCallback(),
 177           net_log.net_log(),
 178           net_log.source()));
 179   int rv = socket->Connect(IPEndPoint(dest, 53));
 180   if (rv != OK)
 181     return false;
 182   IPEndPoint endpoint;
 183   rv = socket->GetLocalAddress(&endpoint);
 184   if (rv != OK)
 185     return false;
 186   DCHECK_EQ(ADDRESS_FAMILY_IPV6, endpoint.GetFamily());
 187   const IPAddressNumber& address = endpoint.address();
 188   bool is_link_local = (address[0] == 0xFE) && ((address[1] & 0xC0) == 0x80);
 189   if (is_link_local)
 190     return false;
 191   const uint8 kTeredoPrefix[] = { 0x20, 0x01, 0, 0 };
 192   bool is_teredo = std::equal(kTeredoPrefix,
 193                               kTeredoPrefix + arraysize(kTeredoPrefix),
 194                               address.begin());
 195   if (is_teredo)
 196     return false;
 197   return true;
 198 }
 199
 200 // Provide a common macro to simplify code and readability. We must use a
 201 // macro as the underlying HISTOGRAM macro creates static variables.
 202 #define DNS_HISTOGRAM(name, time) UMA_HISTOGRAM_CUSTOM_TIMES(name, time, \
 203     base::TimeDelta::FromMilliseconds(1), base::TimeDelta::FromHours(1), 100)
 204
 205 // A macro to simplify code and readability.
 206 #define DNS_HISTOGRAM_BY_PRIORITY(basename, priority, time) \
 207   do { \
 208     switch (priority) { \
 209       case HIGHEST: DNS_HISTOGRAM(basename "_HIGHEST", time); break; \
 210       case MEDIUM: DNS_HISTOGRAM(basename "_MEDIUM", time); break; \
 211       case LOW: DNS_HISTOGRAM(basename "_LOW", time); break; \
 212       case LOWEST: DNS_HISTOGRAM(basename "_LOWEST", time); break; \
 213       case IDLE: DNS_HISTOGRAM(basename "_IDLE", time); break; \
 214       default: NOTREACHED(); break; \
 215     } \
 216     DNS_HISTOGRAM(basename, time); \
 217   } while (0)
 218
 219 // Record time from Request creation until a valid DNS response.
 220 void RecordTotalTime(bool had_dns_config,
 221                      bool speculative,
 222                      base::TimeDelta duration) {
 223   if (had_dns_config) {
 224     if (speculative) {
 225       DNS_HISTOGRAM("AsyncDNS.TotalTime_speculative", duration);
 226     } else {
 227       DNS_HISTOGRAM("AsyncDNS.TotalTime", duration);
 228     }
 229   } else {
 230     if (speculative) {
 231       DNS_HISTOGRAM("DNS.TotalTime_speculative", duration);
 232     } else {
 233       DNS_HISTOGRAM("DNS.TotalTime", duration);
 234     }
 235   }
 236 }
 237
 238 void RecordTTL(base::TimeDelta ttl) {
 239   UMA_HISTOGRAM_CUSTOM_TIMES("AsyncDNS.TTL", ttl,
 240                              base::TimeDelta::FromSeconds(1),
 241                              base::TimeDelta::FromDays(1), 100);
 242 }
 243
 244 bool ConfigureAsyncDnsNoFallbackFieldTrial() {
 245   const bool kDefault = false;
 246
 247   // Configure the AsyncDns field trial as follows:
 248   // groups AsyncDnsNoFallbackA and AsyncDnsNoFallbackB: return true,
 249   // groups AsyncDnsA and AsyncDnsB: return false,
 250   // groups SystemDnsA and SystemDnsB: return false,
 251   // otherwise (trial absent): return default.
 252   std::string group_name = base::FieldTrialList::FindFullName("AsyncDns");
 253   if (!group_name.empty())
 254     return StartsWithASCII(group_name, "AsyncDnsNoFallback", false);
 255   return kDefault;
 256 }
 257
 258 //-----------------------------------------------------------------------------
 259
 260 AddressList EnsurePortOnAddressList(const AddressList& list, uint16 port) {
 261   if (list.empty() || list.front().port() == port)
 262     return list;
 263   return AddressList::CopyWithPort(list, port);
 264 }
 265
 266 // Returns true if |addresses| contains only IPv4 loopback addresses.
 267 bool IsAllIPv4Loopback(const AddressList& addresses) {
 268   for (unsigned i = 0; i < addresses.size(); ++i) {
 269     const IPAddressNumber& address = addresses[i].address();
 270     switch (addresses[i].GetFamily()) {
 271       case ADDRESS_FAMILY_IPV4:
 272         if (address[0] != 127)
 273           return false;
 274         break;
 275       case ADDRESS_FAMILY_IPV6:
 276         return false;
 277       default:
 278         NOTREACHED();
 279         return false;
 280     }
 281   }
 282   return true;
 283 }
 284
 285 // Creates NetLog parameters when the resolve failed.
 286 base::Value* NetLogProcTaskFailedCallback(uint32 attempt_number,
 287                                           int net_error,
 288                                           int os_error,
 289                                           NetLog::LogLevel /* log_level */) {
 290   base::DictionaryValue* dict = new base::DictionaryValue();
 291   if (attempt_number)
 292     dict->SetInteger("attempt_number", attempt_number);
 293
 294   dict->SetInteger("net_error", net_error);
 295
 296   if (os_error) {
 297     dict->SetInteger("os_error", os_error);
 298 #if defined(OS_POSIX)
 299     dict->SetString("os_error_string", gai_strerror(os_error));
 300 #elif defined(OS_WIN)
 301     // Map the error code to a human-readable string.
 302     LPWSTR error_string = NULL;
 303     int size = FormatMessage(FORMAT_MESSAGE_ALLOCATE_BUFFER |
 304                              FORMAT_MESSAGE_FROM_SYSTEM,
 305                              0,  // Use the internal message table.
 306                              os_error,
 307                              0,  // Use default language.
 308                              (LPWSTR)&error_string,
 309                              0,  // Buffer size.
 310                              0);  // Arguments (unused).
 311     dict->SetString("os_error_string", base::WideToUTF8(error_string));
 312     LocalFree(error_string);
 313 #endif
 314   }
 315
 316   return dict;
 317 }
 318
 319 // Creates NetLog parameters when the DnsTask failed.
 320 base::Value* NetLogDnsTaskFailedCallback(int net_error,
 321                                          int dns_error,
 322                                          NetLog::LogLevel /* log_level */) {
 323   base::DictionaryValue* dict = new base::DictionaryValue();
 324   dict->SetInteger("net_error", net_error);
 325   if (dns_error)
 326     dict->SetInteger("dns_error", dns_error);
 327   return dict;
 328 };
 329
 330 // Creates NetLog parameters containing the information in a RequestInfo object,
 331 // along with the associated NetLog::Source.
 332 base::Value* NetLogRequestInfoCallback(const NetLog::Source& source,
 333                                        const HostResolver::RequestInfo* info,
 334                                        NetLog::LogLevel /* log_level */) {
 335   base::DictionaryValue* dict = new base::DictionaryValue();
 336   source.AddToEventParameters(dict);
 337
 338   dict->SetString("host", info->host_port_pair().ToString());
 339   dict->SetInteger("address_family",
 340                    static_cast<int>(info->address_family()));
 341   dict->SetBoolean("allow_cached_response", info->allow_cached_response());
 342   dict->SetBoolean("is_speculative", info->is_speculative());
 343   return dict;
 344 }
 345
 346 // Creates NetLog parameters for the creation of a HostResolverImpl::Job.
 347 base::Value* NetLogJobCreationCallback(const NetLog::Source& source,
 348                                        const std::string* host,
 349                                        NetLog::LogLevel /* log_level */) {
 350   base::DictionaryValue* dict = new base::DictionaryValue();
 351   source.AddToEventParameters(dict);
 352   dict->SetString("host", *host);
 353   return dict;
 354 }
 355
 356 // Creates NetLog parameters for HOST_RESOLVER_IMPL_JOB_ATTACH/DETACH events.
 357 base::Value* NetLogJobAttachCallback(const NetLog::Source& source,
 358                                      RequestPriority priority,
 359                                      NetLog::LogLevel /* log_level */) {
 360   base::DictionaryValue* dict = new base::DictionaryValue();
 361   source.AddToEventParameters(dict);
 362   dict->SetString("priority", RequestPriorityToString(priority));
 363   return dict;
 364 }
 365
 366 // Creates NetLog parameters for the DNS_CONFIG_CHANGED event.
 367 base::Value* NetLogDnsConfigCallback(const DnsConfig* config,
 368                                      NetLog::LogLevel /* log_level */) {
 369   return config->ToValue();
 370 }
 371
 372 // The logging routines are defined here because some requests are resolved
 373 // without a Request object.
 374
 375 // Logs when a request has just been started.
 376 void LogStartRequest(const BoundNetLog& source_net_log,
 377                      const BoundNetLog& request_net_log,
 378                      const HostResolver::RequestInfo& info) {
 379   source_net_log.BeginEvent(
 380       NetLog::TYPE_HOST_RESOLVER_IMPL,
 381       request_net_log.source().ToEventParametersCallback());
 382
 383   request_net_log.BeginEvent(
 384       NetLog::TYPE_HOST_RESOLVER_IMPL_REQUEST,
 385       base::Bind(&NetLogRequestInfoCallback, source_net_log.source(), &info));
 386 }
 387
 388 // Logs when a request has just completed (before its callback is run).
 389 void LogFinishRequest(const BoundNetLog& source_net_log,
 390                       const BoundNetLog& request_net_log,
 391                       const HostResolver::RequestInfo& info,
 392                       int net_error) {
 393   request_net_log.EndEventWithNetErrorCode(
 394       NetLog::TYPE_HOST_RESOLVER_IMPL_REQUEST, net_error);
 395   source_net_log.EndEvent(NetLog::TYPE_HOST_RESOLVER_IMPL);
 396 }
 397
 398 // Logs when a request has been cancelled.
 399 void LogCancelRequest(const BoundNetLog& source_net_log,
 400                       const BoundNetLog& request_net_log,
 401                       const HostResolverImpl::RequestInfo& info) {
 402   request_net_log.AddEvent(NetLog::TYPE_CANCELLED);
 403   request_net_log.EndEvent(NetLog::TYPE_HOST_RESOLVER_IMPL_REQUEST);
 404   source_net_log.EndEvent(NetLog::TYPE_HOST_RESOLVER_IMPL);
 405 }
 406
 407 //-----------------------------------------------------------------------------
 408
 409 // Keeps track of the highest priority.
 410 class PriorityTracker {
 411  public:
 412   explicit PriorityTracker(RequestPriority initial_priority)
 413       : highest_priority_(initial_priority), total_count_(0) {
 414     memset(counts_, 0, sizeof(counts_));
 415   }
 416
 417   RequestPriority highest_priority() const {
 418     return highest_priority_;
 419   }
 420
 421   size_t total_count() const {
 422     return total_count_;
 423   }
 424
 425   void Add(RequestPriority req_priority) {
 426     ++total_count_;
 427     ++counts_[req_priority];
 428     if (highest_priority_ < req_priority)
 429       highest_priority_ = req_priority;
 430   }
 431
 432   void Remove(RequestPriority req_priority) {
 433     DCHECK_GT(total_count_, 0u);
 434     DCHECK_GT(counts_[req_priority], 0u);
 435     --total_count_;
 436     --counts_[req_priority];
 437     size_t i;
 438     for (i = highest_priority_; i > MINIMUM_PRIORITY && !counts_[i]; --i);
 439     highest_priority_ = static_cast<RequestPriority>(i);
 440
 441     // In absence of requests, default to MINIMUM_PRIORITY.
 442     if (total_count_ == 0)
 443       DCHECK_EQ(MINIMUM_PRIORITY, highest_priority_);
 444   }
 445
 446  private:
 447   RequestPriority highest_priority_;
 448   size_t total_count_;
 449   size_t counts_[NUM_PRIORITIES];
 450 };
 451
 452 }  // namespace
 453
 454 //-----------------------------------------------------------------------------
 455
 456 const unsigned HostResolverImpl::kMaximumDnsFailures = 16;
 457
 458 // Holds the data for a request that could not be completed synchronously.
 459 // It is owned by a Job. Canceled Requests are only marked as canceled rather
 460 // than removed from the Job's |requests_| list.
 461 class HostResolverImpl::Request {
 462  public:
 463   Request(const BoundNetLog& source_net_log,
 464           const BoundNetLog& request_net_log,
 465           const RequestInfo& info,
 466           RequestPriority priority,
 467           const CompletionCallback& callback,
 468           AddressList* addresses)
 469       : source_net_log_(source_net_log),
 470         request_net_log_(request_net_log),
 471         info_(info),
 472         priority_(priority),
 473         job_(NULL),
 474         callback_(callback),
 475         addresses_(addresses),
 476         request_time_(base::TimeTicks::Now()) {}
 477
 478   // Mark the request as canceled.
 479   void MarkAsCanceled() {
 480     job_ = NULL;
 481     addresses_ = NULL;
 482     callback_.Reset();
 483   }
 484
 485   bool was_canceled() const {
 486     return callback_.is_null();
 487   }
 488
 489   void set_job(Job* job) {
 490     DCHECK(job);
 491     // Identify which job the request is waiting on.
 492     job_ = job;
 493   }
 494
 495   // Prepare final AddressList and call completion callback.
 496   void OnComplete(int error, const AddressList& addr_list) {
 497     DCHECK(!was_canceled());
 498     if (error == OK)
 499       *addresses_ = EnsurePortOnAddressList(addr_list, info_.port());
 500     CompletionCallback callback = callback_;
 501     MarkAsCanceled();
 502     callback.Run(error);
 503   }
 504
 505   Job* job() const {
 506     return job_;
 507   }
 508
 509   // NetLog for the source, passed in HostResolver::Resolve.
 510   const BoundNetLog& source_net_log() {
 511     return source_net_log_;
 512   }
 513
 514   // NetLog for this request.
 515   const BoundNetLog& request_net_log() {
 516     return request_net_log_;
 517   }
 518
 519   const RequestInfo& info() const {
 520     return info_;
 521   }
 522
 523   RequestPriority priority() const { return priority_; }
 524
 525   base::TimeTicks request_time() const { return request_time_; }
 526
 527  private:
 528   BoundNetLog source_net_log_;
 529   BoundNetLog request_net_log_;
 530
 531   // The request info that started the request.
 532   const RequestInfo info_;
 533
 534   // TODO(akalin): Support reprioritization.
 535   const RequestPriority priority_;
 536
 537   // The resolve job that this request is dependent on.
 538   Job* job_;
 539
 540   // The user's callback to invoke when the request completes.
 541   CompletionCallback callback_;
 542
 543   // The address list to save result into.
 544   AddressList* addresses_;
 545
 546   const base::TimeTicks request_time_;
 547
 548   DISALLOW_COPY_AND_ASSIGN(Request);
 549 };
 550
 551 //------------------------------------------------------------------------------
 552
 553 // Calls HostResolverProc on the WorkerPool. Performs retries if necessary.
 554 //
 555 // Whenever we try to resolve the host, we post a delayed task to check if host
 556 // resolution (OnLookupComplete) is completed or not. If the original attempt
 557 // hasn't completed, then we start another attempt for host resolution. We take
 558 // the results from the first attempt that finishes and ignore the results from
 559 // all other attempts.
 560 //
 561 // TODO(szym): Move to separate source file for testing and mocking.
 562 //
 563 class HostResolverImpl::ProcTask
 564     : public base::RefCountedThreadSafe<HostResolverImpl::ProcTask> {
 565  public:
 566   typedef base::Callback<void(int net_error,
 567                               const AddressList& addr_list)> Callback;
 568
 569   ProcTask(const Key& key,
 570            const ProcTaskParams& params,
 571            const Callback& callback,
 572            const BoundNetLog& job_net_log)
 573       : key_(key),
 574         params_(params),
 575         callback_(callback),
 576         origin_loop_(base::MessageLoopProxy::current()),
 577         attempt_number_(0),
 578         completed_attempt_number_(0),
 579         completed_attempt_error_(ERR_UNEXPECTED),
 580         had_non_speculative_request_(false),
 581         net_log_(job_net_log) {
 582     if (!params_.resolver_proc.get())
 583       params_.resolver_proc = HostResolverProc::GetDefault();
 584     // If default is unset, use the system proc.
 585     if (!params_.resolver_proc.get())
 586       params_.resolver_proc = new SystemHostResolverProc();
 587   }
 588
 589   void Start() {
 590     DCHECK(origin_loop_->BelongsToCurrentThread());
 591     net_log_.BeginEvent(NetLog::TYPE_HOST_RESOLVER_IMPL_PROC_TASK);
 592     StartLookupAttempt();
 593   }
 594
 595   // Cancels this ProcTask. It will be orphaned. Any outstanding resolve
 596   // attempts running on worker threads will continue running. Only once all the
 597   // attempts complete will the final reference to this ProcTask be released.
 598   void Cancel() {
 599     DCHECK(origin_loop_->BelongsToCurrentThread());
 600
 601     if (was_canceled() || was_completed())
 602       return;
 603
 604     callback_.Reset();
 605     net_log_.EndEvent(NetLog::TYPE_HOST_RESOLVER_IMPL_PROC_TASK);
 606   }
 607
 608   void set_had_non_speculative_request() {
 609     DCHECK(origin_loop_->BelongsToCurrentThread());
 610     had_non_speculative_request_ = true;
 611   }
 612
 613   bool was_canceled() const {
 614     DCHECK(origin_loop_->BelongsToCurrentThread());
 615     return callback_.is_null();
 616   }
 617
 618   bool was_completed() const {
 619     DCHECK(origin_loop_->BelongsToCurrentThread());
 620     return completed_attempt_number_ > 0;
 621   }
 622
 623  private:
 624   friend class base::RefCountedThreadSafe<ProcTask>;
 625   ~ProcTask() {}
 626
 627   void StartLookupAttempt() {
 628     DCHECK(origin_loop_->BelongsToCurrentThread());
 629     base::TimeTicks start_time = base::TimeTicks::Now();
 630     ++attempt_number_;
 631     // Dispatch the lookup attempt to a worker thread.
 632     if (!base::WorkerPool::PostTask(
 633             FROM_HERE,
 634             base::Bind(&ProcTask::DoLookup, this, start_time, attempt_number_),
 635             true)) {
 636       NOTREACHED();
 637
 638       // Since we could be running within Resolve() right now, we can't just
 639       // call OnLookupComplete().  Instead we must wait until Resolve() has
 640       // returned (IO_PENDING).
 641       origin_loop_->PostTask(
 642           FROM_HERE,
 643           base::Bind(&ProcTask::OnLookupComplete, this, AddressList(),
 644                      start_time, attempt_number_, ERR_UNEXPECTED, 0));
 645       return;
 646     }
 647
 648     net_log_.AddEvent(
 649         NetLog::TYPE_HOST_RESOLVER_IMPL_ATTEMPT_STARTED,
 650         NetLog::IntegerCallback("attempt_number", attempt_number_));
 651
 652     // If we don't get the results within a given time, RetryIfNotComplete
 653     // will start a new attempt on a different worker thread if none of our
 654     // outstanding attempts have completed yet.
 655     if (attempt_number_ <= params_.max_retry_attempts) {
 656       origin_loop_->PostDelayedTask(
 657           FROM_HERE,
 658           base::Bind(&ProcTask::RetryIfNotComplete, this),
 659           params_.unresponsive_delay);
 660     }
 661   }
 662
 663   // WARNING: This code runs inside a worker pool. The shutdown code cannot
 664   // wait for it to finish, so we must be very careful here about using other
 665   // objects (like MessageLoops, Singletons, etc). During shutdown these objects
 666   // may no longer exist. Multiple DoLookups() could be running in parallel, so
 667   // any state inside of |this| must not mutate .
 668   void DoLookup(const base::TimeTicks& start_time,
 669                 const uint32 attempt_number) {
 670     AddressList results;
 671     int os_error = 0;
 672     // Running on the worker thread
 673     int error = params_.resolver_proc->Resolve(key_.hostname,
 674                                                key_.address_family,
 675                                                key_.host_resolver_flags,
 676                                                &results,
 677                                                &os_error);
 678
 679     origin_loop_->PostTask(
 680         FROM_HERE,
 681         base::Bind(&ProcTask::OnLookupComplete, this, results, start_time,
 682                    attempt_number, error, os_error));
 683   }
 684
 685   // Makes next attempt if DoLookup() has not finished (runs on origin thread).
 686   void RetryIfNotComplete() {
 687     DCHECK(origin_loop_->BelongsToCurrentThread());
 688
 689     if (was_completed() || was_canceled())
 690       return;
 691
 692     params_.unresponsive_delay *= params_.retry_factor;
 693     StartLookupAttempt();
 694   }
 695
 696   // Callback for when DoLookup() completes (runs on origin thread).
 697   void OnLookupComplete(const AddressList& results,
 698                         const base::TimeTicks& start_time,
 699                         const uint32 attempt_number,
 700                         int error,
 701                         const int os_error) {
 702     DCHECK(origin_loop_->BelongsToCurrentThread());
 703     // If results are empty, we should return an error.
 704     bool empty_list_on_ok = (error == OK && results.empty());
 705     UMA_HISTOGRAM_BOOLEAN("DNS.EmptyAddressListAndNoError", empty_list_on_ok);
 706     if (empty_list_on_ok)
 707       error = ERR_NAME_NOT_RESOLVED;
 708
 709     bool was_retry_attempt = attempt_number > 1;
 710
 711     // Ideally the following code would be part of host_resolver_proc.cc,
 712     // however it isn't safe to call NetworkChangeNotifier from worker threads.
 713     // So we do it here on the IO thread instead.
 714     if (error != OK && NetworkChangeNotifier::IsOffline())
 715       error = ERR_INTERNET_DISCONNECTED;
 716
 717     // If this is the first attempt that is finishing later, then record data
 718     // for the first attempt. Won't contaminate with retry attempt's data.
 719     if (!was_retry_attempt)
 720       RecordPerformanceHistograms(start_time, error, os_error);
 721
 722     RecordAttemptHistograms(start_time, attempt_number, error, os_error);
 723
 724     if (was_canceled())
 725       return;
 726
 727     NetLog::ParametersCallback net_log_callback;
 728     if (error != OK) {
 729       net_log_callback = base::Bind(&NetLogProcTaskFailedCallback,
 730                                     attempt_number,
 731                                     error,
 732                                     os_error);
 733     } else {
 734       net_log_callback = NetLog::IntegerCallback("attempt_number",
 735                                                  attempt_number);
 736     }
 737     net_log_.AddEvent(NetLog::TYPE_HOST_RESOLVER_IMPL_ATTEMPT_FINISHED,
 738                       net_log_callback);
 739
 740     if (was_completed())
 741       return;
 742
 743     // Copy the results from the first worker thread that resolves the host.
 744     results_ = results;
 745     completed_attempt_number_ = attempt_number;
 746     completed_attempt_error_ = error;
 747
 748     if (was_retry_attempt) {
 749       // If retry attempt finishes before 1st attempt, then get stats on how
 750       // much time is saved by having spawned an extra attempt.
 751       retry_attempt_finished_time_ = base::TimeTicks::Now();
 752     }
 753
 754     if (error != OK) {
 755       net_log_callback = base::Bind(&NetLogProcTaskFailedCallback,
 756                                     0, error, os_error);
 757     } else {
 758       net_log_callback = results_.CreateNetLogCallback();
 759     }
 760     net_log_.EndEvent(NetLog::TYPE_HOST_RESOLVER_IMPL_PROC_TASK,
 761                       net_log_callback);
 762
 763     callback_.Run(error, results_);
 764   }
 765
 766   void RecordPerformanceHistograms(const base::TimeTicks& start_time,
 767                                    const int error,
 768                                    const int os_error) const {
 769     DCHECK(origin_loop_->BelongsToCurrentThread());
 770     enum Category {  // Used in UMA_HISTOGRAM_ENUMERATION.
 771       RESOLVE_SUCCESS,
 772       RESOLVE_FAIL,
 773       RESOLVE_SPECULATIVE_SUCCESS,
 774       RESOLVE_SPECULATIVE_FAIL,
 775       RESOLVE_MAX,  // Bounding value.
 776     };
 777     int category = RESOLVE_MAX;  // Illegal value for later DCHECK only.
 778
 779     base::TimeDelta duration = base::TimeTicks::Now() - start_time;
 780     if (error == OK) {
 781       if (had_non_speculative_request_) {
 782         category = RESOLVE_SUCCESS;
 783         DNS_HISTOGRAM("DNS.ResolveSuccess", duration);
 784       } else {
 785         category = RESOLVE_SPECULATIVE_SUCCESS;
 786         DNS_HISTOGRAM("DNS.ResolveSpeculativeSuccess", duration);
 787       }
 788
 789       // Log DNS lookups based on |address_family|. This will help us determine
 790       // if IPv4 or IPv4/6 lookups are faster or slower.
 791       switch(key_.address_family) {
 792         case ADDRESS_FAMILY_IPV4:
 793           DNS_HISTOGRAM("DNS.ResolveSuccess_FAMILY_IPV4", duration);
 794           break;
 795         case ADDRESS_FAMILY_IPV6:
 796           DNS_HISTOGRAM("DNS.ResolveSuccess_FAMILY_IPV6", duration);
 797           break;
 798         case ADDRESS_FAMILY_UNSPECIFIED:
 799           DNS_HISTOGRAM("DNS.ResolveSuccess_FAMILY_UNSPEC", duration);
 800           break;
 801       }
 802     } else {
 803       if (had_non_speculative_request_) {
 804         category = RESOLVE_FAIL;
 805         DNS_HISTOGRAM("DNS.ResolveFail", duration);
 806       } else {
 807         category = RESOLVE_SPECULATIVE_FAIL;
 808         DNS_HISTOGRAM("DNS.ResolveSpeculativeFail", duration);
 809       }
 810       // Log DNS lookups based on |address_family|. This will help us determine
 811       // if IPv4 or IPv4/6 lookups are faster or slower.
 812       switch(key_.address_family) {
 813         case ADDRESS_FAMILY_IPV4:
 814           DNS_HISTOGRAM("DNS.ResolveFail_FAMILY_IPV4", duration);
 815           break;
 816         case ADDRESS_FAMILY_IPV6:
 817           DNS_HISTOGRAM("DNS.ResolveFail_FAMILY_IPV6", duration);
 818           break;
 819         case ADDRESS_FAMILY_UNSPECIFIED:
 820           DNS_HISTOGRAM("DNS.ResolveFail_FAMILY_UNSPEC", duration);
 821           break;
 822       }
 823       UMA_HISTOGRAM_CUSTOM_ENUMERATION(kOSErrorsForGetAddrinfoHistogramName,
 824                                        std::abs(os_error),
 825                                        GetAllGetAddrinfoOSErrors());
 826     }
 827     DCHECK_LT(category, static_cast<int>(RESOLVE_MAX));  // Be sure it was set.
 828
 829     UMA_HISTOGRAM_ENUMERATION("DNS.ResolveCategory", category, RESOLVE_MAX);
 830   }
 831
 832   void RecordAttemptHistograms(const base::TimeTicks& start_time,
 833                                const uint32 attempt_number,
 834                                const int error,
 835                                const int os_error) const {
 836     DCHECK(origin_loop_->BelongsToCurrentThread());
 837     bool first_attempt_to_complete =
 838         completed_attempt_number_ == attempt_number;
 839     bool is_first_attempt = (attempt_number == 1);
 840
 841     if (first_attempt_to_complete) {
 842       // If this was first attempt to complete, then record the resolution
 843       // status of the attempt.
 844       if (completed_attempt_error_ == OK) {
 845         UMA_HISTOGRAM_ENUMERATION(
 846             "DNS.AttemptFirstSuccess", attempt_number, 100);
 847       } else {
 848         UMA_HISTOGRAM_ENUMERATION(
 849             "DNS.AttemptFirstFailure", attempt_number, 100);
 850       }
 851     }
 852
 853     if (error == OK)
 854       UMA_HISTOGRAM_ENUMERATION("DNS.AttemptSuccess", attempt_number, 100);
 855     else
 856       UMA_HISTOGRAM_ENUMERATION("DNS.AttemptFailure", attempt_number, 100);
 857
 858     // If first attempt didn't finish before retry attempt, then calculate stats
 859     // on how much time is saved by having spawned an extra attempt.
 860     if (!first_attempt_to_complete && is_first_attempt && !was_canceled()) {
 861       DNS_HISTOGRAM("DNS.AttemptTimeSavedByRetry",
 862                     base::TimeTicks::Now() - retry_attempt_finished_time_);
 863     }
 864
 865     if (was_canceled() || !first_attempt_to_complete) {
 866       // Count those attempts which completed after the job was already canceled
 867       // OR after the job was already completed by an earlier attempt (so in
 868       // effect).
 869       UMA_HISTOGRAM_ENUMERATION("DNS.AttemptDiscarded", attempt_number, 100);
 870
 871       // Record if job is canceled.
 872       if (was_canceled())
 873         UMA_HISTOGRAM_ENUMERATION("DNS.AttemptCancelled", attempt_number, 100);
 874     }
 875
 876     base::TimeDelta duration = base::TimeTicks::Now() - start_time;
 877     if (error == OK)
 878       DNS_HISTOGRAM("DNS.AttemptSuccessDuration", duration);
 879     else
 880       DNS_HISTOGRAM("DNS.AttemptFailDuration", duration);
 881   }
 882
 883   // Set on the origin thread, read on the worker thread.
 884   Key key_;
 885
 886   // Holds an owning reference to the HostResolverProc that we are going to use.
 887   // This may not be the current resolver procedure by the time we call
 888   // ResolveAddrInfo, but that's OK... we'll use it anyways, and the owning
 889   // reference ensures that it remains valid until we are done.
 890   ProcTaskParams params_;
 891
 892   // The listener to the results of this ProcTask.
 893   Callback callback_;
 894
 895   // Used to post ourselves onto the origin thread.
 896   scoped_refptr<base::MessageLoopProxy> origin_loop_;
 897
 898   // Keeps track of the number of attempts we have made so far to resolve the
 899   // host. Whenever we start an attempt to resolve the host, we increase this
 900   // number.
 901   uint32 attempt_number_;
 902
 903   // The index of the attempt which finished first (or 0 if the job is still in
 904   // progress).
 905   uint32 completed_attempt_number_;
 906
 907   // The result (a net error code) from the first attempt to complete.
 908   int completed_attempt_error_;
 909
 910   // The time when retry attempt was finished.
 911   base::TimeTicks retry_attempt_finished_time_;
 912
 913   // True if a non-speculative request was ever attached to this job
 914   // (regardless of whether or not it was later canceled.
 915   // This boolean is used for histogramming the duration of jobs used to
 916   // service non-speculative requests.
 917   bool had_non_speculative_request_;
 918
 919   AddressList results_;
 920
 921   BoundNetLog net_log_;
 922
 923   DISALLOW_COPY_AND_ASSIGN(ProcTask);
 924 };
 925
 926 //-----------------------------------------------------------------------------
 927
 928 // Wraps a call to HaveOnlyLoopbackAddresses to be executed on the WorkerPool as
 929 // it takes 40-100ms and should not block initialization.
 930 class HostResolverImpl::LoopbackProbeJob {
 931  public:
 932   explicit LoopbackProbeJob(const base::WeakPtr<HostResolverImpl>& resolver)
 933       : resolver_(resolver),
 934         result_(false) {
 935     DCHECK(resolver.get());
 936     const bool kIsSlow = true;
 937     base::WorkerPool::PostTaskAndReply(
 938         FROM_HERE,
 939         base::Bind(&LoopbackProbeJob::DoProbe, base::Unretained(this)),
 940         base::Bind(&LoopbackProbeJob::OnProbeComplete, base::Owned(this)),
 941         kIsSlow);
 942   }
 943
 944   virtual ~LoopbackProbeJob() {}
 945
 946  private:
 947   // Runs on worker thread.
 948   void DoProbe() {
 949     result_ = HaveOnlyLoopbackAddresses();
 950   }
 951
 952   void OnProbeComplete() {
 953     if (!resolver_.get())
 954       return;
 955     resolver_->SetHaveOnlyLoopbackAddresses(result_);
 956   }
 957
 958   // Used/set only on origin thread.
 959   base::WeakPtr<HostResolverImpl> resolver_;
 960
 961   bool result_;
 962
 963   DISALLOW_COPY_AND_ASSIGN(LoopbackProbeJob);
 964 };
 965
 966 //-----------------------------------------------------------------------------
 967
 968 // Resolves the hostname using DnsTransaction.
 969 // TODO(szym): This could be moved to separate source file as well.
 970 class HostResolverImpl::DnsTask : public base::SupportsWeakPtr<DnsTask> {
 971  public:
 972   class Delegate {
 973    public:
 974     virtual void OnDnsTaskComplete(base::TimeTicks start_time,
 975                                    int net_error,
 976                                    const AddressList& addr_list,
 977                                    base::TimeDelta ttl) = 0;
 978
 979     // Called when the first of two jobs succeeds.  If the first completed
 980     // transaction fails, this is not called.  Also not called when the DnsTask
 981     // only needs to run one transaction.
 982     virtual void OnFirstDnsTransactionComplete() = 0;
 983
 984    protected:
 985     Delegate() {}
 986     virtual ~Delegate() {}
 987   };
 988
 989   DnsTask(DnsClient* client,
 990           const Key& key,
 991           Delegate* delegate,
 992           const BoundNetLog& job_net_log)
 993       : client_(client),
 994         key_(key),
 995         delegate_(delegate),
 996         net_log_(job_net_log),
 997         num_completed_transactions_(0),
 998         task_start_time_(base::TimeTicks::Now()) {
 999     DCHECK(client);
1000     DCHECK(delegate_);
1001   }
1002
1003   bool needs_two_transactions() const {
1004     return key_.address_family == ADDRESS_FAMILY_UNSPECIFIED;
1005   }
1006
1007   bool needs_another_transaction() const {
1008     return needs_two_transactions() && !transaction_aaaa_;
1009   }
1010
1011   void StartFirstTransaction() {
1012     DCHECK_EQ(0u, num_completed_transactions_);
1013     net_log_.BeginEvent(NetLog::TYPE_HOST_RESOLVER_IMPL_DNS_TASK);
1014     if (key_.address_family == ADDRESS_FAMILY_IPV6) {
1015       StartAAAA();
1016     } else {
1017       StartA();
1018     }
1019   }
1020
1021   void StartSecondTransaction() {
1022     DCHECK(needs_two_transactions());
1023     StartAAAA();
1024   }
1025
1026  private:
1027   void StartA() {
1028     DCHECK(!transaction_a_);
1029     DCHECK_NE(ADDRESS_FAMILY_IPV6, key_.address_family);
1030     transaction_a_ = CreateTransaction(ADDRESS_FAMILY_IPV4);
1031     transaction_a_->Start();
1032   }
1033
1034   void StartAAAA() {
1035     DCHECK(!transaction_aaaa_);
1036     DCHECK_NE(ADDRESS_FAMILY_IPV4, key_.address_family);
1037     transaction_aaaa_ = CreateTransaction(ADDRESS_FAMILY_IPV6);
1038     transaction_aaaa_->Start();
1039   }
1040
1041   scoped_ptr<DnsTransaction> CreateTransaction(AddressFamily family) {
1042     DCHECK_NE(ADDRESS_FAMILY_UNSPECIFIED, family);
1043     return client_->GetTransactionFactory()->CreateTransaction(
1044         key_.hostname,
1045         family == ADDRESS_FAMILY_IPV6 ? dns_protocol::kTypeAAAA :
1046                                         dns_protocol::kTypeA,
1047         base::Bind(&DnsTask::OnTransactionComplete, base::Unretained(this),
1048                    base::TimeTicks::Now()),
1049         net_log_);
1050   }
1051
1052   void OnTransactionComplete(const base::TimeTicks& start_time,
1053                              DnsTransaction* transaction,
1054                              int net_error,
1055                              const DnsResponse* response) {
1056     DCHECK(transaction);
1057     base::TimeDelta duration = base::TimeTicks::Now() - start_time;
1058     if (net_error != OK) {
1059       DNS_HISTOGRAM("AsyncDNS.TransactionFailure", duration);
1060       OnFailure(net_error, DnsResponse::DNS_PARSE_OK);
1061       return;
1062     }
1063
1064     DNS_HISTOGRAM("AsyncDNS.TransactionSuccess", duration);
1065     switch (transaction->GetType()) {
1066       case dns_protocol::kTypeA:
1067         DNS_HISTOGRAM("AsyncDNS.TransactionSuccess_A", duration);
1068         break;
1069       case dns_protocol::kTypeAAAA:
1070         DNS_HISTOGRAM("AsyncDNS.TransactionSuccess_AAAA", duration);
1071         break;
1072     }
1073
1074     AddressList addr_list;
1075     base::TimeDelta ttl;
1076     DnsResponse::Result result = response->ParseToAddressList(&addr_list, &ttl);
1077     UMA_HISTOGRAM_ENUMERATION("AsyncDNS.ParseToAddressList",
1078                               result,
1079                               DnsResponse::DNS_PARSE_RESULT_MAX);
1080     if (result != DnsResponse::DNS_PARSE_OK) {
1081       // Fail even if the other query succeeds.
1082       OnFailure(ERR_DNS_MALFORMED_RESPONSE, result);
1083       return;
1084     }
1085
1086     ++num_completed_transactions_;
1087     if (num_completed_transactions_ == 1) {
1088       ttl_ = ttl;
1089     } else {
1090       ttl_ = std::min(ttl_, ttl);
1091     }
1092
1093     if (transaction->GetType() == dns_protocol::kTypeA) {
1094       DCHECK_EQ(transaction_a_.get(), transaction);
1095       // Place IPv4 addresses after IPv6.
1096       addr_list_.insert(addr_list_.end(), addr_list.begin(), addr_list.end());
1097     } else {
1098       DCHECK_EQ(transaction_aaaa_.get(), transaction);
1099       // Place IPv6 addresses before IPv4.
1100       addr_list_.insert(addr_list_.begin(), addr_list.begin(), addr_list.end());
1101     }
1102
1103     if (needs_two_transactions() && num_completed_transactions_ == 1) {
1104       // No need to repeat the suffix search.
1105       key_.hostname = transaction->GetHostname();
1106       delegate_->OnFirstDnsTransactionComplete();
1107       return;
1108     }
1109
1110     if (addr_list_.empty()) {
1111       // TODO(szym): Don't fallback to ProcTask in this case.
1112       OnFailure(ERR_NAME_NOT_RESOLVED, DnsResponse::DNS_PARSE_OK);
1113       return;
1114     }
1115
1116     // If there are multiple addresses, and at least one is IPv6, need to sort
1117     // them.  Note that IPv6 addresses are always put before IPv4 ones, so it's
1118     // sufficient to just check the family of the first address.
1119     if (addr_list_.size() > 1 &&
1120         addr_list_[0].GetFamily() == ADDRESS_FAMILY_IPV6) {
1121       // Sort addresses if needed.  Sort could complete synchronously.
1122       client_->GetAddressSorter()->Sort(
1123           addr_list_,
1124           base::Bind(&DnsTask::OnSortComplete,
1125                      AsWeakPtr(),
1126                      base::TimeTicks::Now()));
1127     } else {
1128       OnSuccess(addr_list_);
1129     }
1130   }
1131
1132   void OnSortComplete(base::TimeTicks start_time,
1133                       bool success,
1134                       const AddressList& addr_list) {
1135     if (!success) {
1136       DNS_HISTOGRAM("AsyncDNS.SortFailure",
1137                     base::TimeTicks::Now() - start_time);
1138       OnFailure(ERR_DNS_SORT_ERROR, DnsResponse::DNS_PARSE_OK);
1139       return;
1140     }
1141
1142     DNS_HISTOGRAM("AsyncDNS.SortSuccess",
1143                   base::TimeTicks::Now() - start_time);
1144
1145     // AddressSorter prunes unusable destinations.
1146     if (addr_list.empty()) {
1147       LOG(WARNING) << "Address list empty after RFC3484 sort";
1148       OnFailure(ERR_NAME_NOT_RESOLVED, DnsResponse::DNS_PARSE_OK);
1149       return;
1150     }
1151
1152     OnSuccess(addr_list);
1153   }
1154
1155   void OnFailure(int net_error, DnsResponse::Result result) {
1156     DCHECK_NE(OK, net_error);
1157     net_log_.EndEvent(
1158         NetLog::TYPE_HOST_RESOLVER_IMPL_DNS_TASK,
1159         base::Bind(&NetLogDnsTaskFailedCallback, net_error, result));
1160     delegate_->OnDnsTaskComplete(task_start_time_, net_error, AddressList(),
1161                                  base::TimeDelta());
1162   }
1163
1164   void OnSuccess(const AddressList& addr_list) {
1165     net_log_.EndEvent(NetLog::TYPE_HOST_RESOLVER_IMPL_DNS_TASK,
1166                       addr_list.CreateNetLogCallback());
1167     delegate_->OnDnsTaskComplete(task_start_time_, OK, addr_list, ttl_);
1168   }
1169
1170   DnsClient* client_;
1171   Key key_;
1172
1173   // The listener to the results of this DnsTask.
1174   Delegate* delegate_;
1175   const BoundNetLog net_log_;
1176
1177   scoped_ptr<DnsTransaction> transaction_a_;
1178   scoped_ptr<DnsTransaction> transaction_aaaa_;
1179
1180   unsigned num_completed_transactions_;
1181
1182   // These are updated as each transaction completes.
1183   base::TimeDelta ttl_;
1184   // IPv6 addresses must appear first in the list.
1185   AddressList addr_list_;
1186
1187   base::TimeTicks task_start_time_;
1188
1189   DISALLOW_COPY_AND_ASSIGN(DnsTask);
1190 };
1191
1192 //-----------------------------------------------------------------------------
1193
1194 // Aggregates all Requests for the same Key. Dispatched via PriorityDispatch.
1195 class HostResolverImpl::Job : public PrioritizedDispatcher::Job,
1196                               public HostResolverImpl::DnsTask::Delegate {
1197  public:
1198   // Creates new job for |key| where |request_net_log| is bound to the
1199   // request that spawned it.
1200   Job(const base::WeakPtr<HostResolverImpl>& resolver,
1201       const Key& key,
1202       RequestPriority priority,
1203       const BoundNetLog& request_net_log)
1204       : resolver_(resolver),
1205         key_(key),
1206         priority_tracker_(priority),
1207         had_non_speculative_request_(false),
1208         had_dns_config_(false),
1209         num_occupied_job_slots_(0),
1210         dns_task_error_(OK),
1211         creation_time_(base::TimeTicks::Now()),
1212         priority_change_time_(creation_time_),
1213         net_log_(BoundNetLog::Make(request_net_log.net_log(),
1214                                    NetLog::SOURCE_HOST_RESOLVER_IMPL_JOB)) {
1215     request_net_log.AddEvent(NetLog::TYPE_HOST_RESOLVER_IMPL_CREATE_JOB);
1216
1217     net_log_.BeginEvent(
1218         NetLog::TYPE_HOST_RESOLVER_IMPL_JOB,
1219         base::Bind(&NetLogJobCreationCallback,
1220                    request_net_log.source(),
1221                    &key_.hostname));
1222   }
1223
1224   virtual ~Job() {
1225     if (is_running()) {
1226       // |resolver_| was destroyed with this Job still in flight.
1227       // Clean-up, record in the log, but don't run any callbacks.
1228       if (is_proc_running()) {
1229         proc_task_->Cancel();
1230         proc_task_ = NULL;
1231       }
1232       // Clean up now for nice NetLog.
1233       KillDnsTask();
1234       net_log_.EndEventWithNetErrorCode(NetLog::TYPE_HOST_RESOLVER_IMPL_JOB,
1235                                         ERR_ABORTED);
1236     } else if (is_queued()) {
1237       // |resolver_| was destroyed without running this Job.
1238       // TODO(szym): is there any benefit in having this distinction?
1239       net_log_.AddEvent(NetLog::TYPE_CANCELLED);
1240       net_log_.EndEvent(NetLog::TYPE_HOST_RESOLVER_IMPL_JOB);
1241     }
1242     // else CompleteRequests logged EndEvent.
1243
1244     // Log any remaining Requests as cancelled.
1245     for (RequestsList::const_iterator it = requests_.begin();
1246          it != requests_.end(); ++it) {
1247       Request* req = *it;
1248       if (req->was_canceled())
1249         continue;
1250       DCHECK_EQ(this, req->job());
1251       LogCancelRequest(req->source_net_log(), req->request_net_log(),
1252                        req->info());
1253     }
1254   }
1255
1256   // Add this job to the dispatcher.  If "at_head" is true, adds at the front
1257   // of the queue.
1258   void Schedule(bool at_head) {
1259     DCHECK(!is_queued());
1260     PrioritizedDispatcher::Handle handle;
1261     if (!at_head) {
1262       handle = resolver_->dispatcher_->Add(this, priority());
1263     } else {
1264       handle = resolver_->dispatcher_->AddAtHead(this, priority());
1265     }
1266     // The dispatcher could have started |this| in the above call to Add, which
1267     // could have called Schedule again. In that case |handle| will be null,
1268     // but |handle_| may have been set by the other nested call to Schedule.
1269     if (!handle.is_null()) {
1270       DCHECK(handle_.is_null());
1271       handle_ = handle;
1272     }
1273   }
1274
1275   void AddRequest(scoped_ptr<Request> req) {
1276     DCHECK_EQ(key_.hostname, req->info().hostname());
1277
1278     req->set_job(this);
1279     priority_tracker_.Add(req->priority());
1280
1281     req->request_net_log().AddEvent(
1282         NetLog::TYPE_HOST_RESOLVER_IMPL_JOB_ATTACH,
1283         net_log_.source().ToEventParametersCallback());
1284
1285     net_log_.AddEvent(
1286         NetLog::TYPE_HOST_RESOLVER_IMPL_JOB_REQUEST_ATTACH,
1287         base::Bind(&NetLogJobAttachCallback,
1288                    req->request_net_log().source(),
1289                    priority()));
1290
1291     // TODO(szym): Check if this is still needed.
1292     if (!req->info().is_speculative()) {
1293       had_non_speculative_request_ = true;
1294       if (proc_task_.get())
1295         proc_task_->set_had_non_speculative_request();
1296     }
1297
1298     requests_.push_back(req.release());
1299
1300     UpdatePriority();
1301   }
1302
1303   // Marks |req| as cancelled. If it was the last active Request, also finishes
1304   // this Job, marking it as cancelled, and deletes it.
1305   void CancelRequest(Request* req) {
1306     DCHECK_EQ(key_.hostname, req->info().hostname());
1307     DCHECK(!req->was_canceled());
1308
1309     // Don't remove it from |requests_| just mark it canceled.
1310     req->MarkAsCanceled();
1311     LogCancelRequest(req->source_net_log(), req->request_net_log(),
1312                      req->info());
1313
1314     priority_tracker_.Remove(req->priority());
1315     net_log_.AddEvent(NetLog::TYPE_HOST_RESOLVER_IMPL_JOB_REQUEST_DETACH,
1316                       base::Bind(&NetLogJobAttachCallback,
1317                                  req->request_net_log().source(),
1318                                  priority()));
1319
1320     if (num_active_requests() > 0) {
1321       UpdatePriority();
1322     } else {
1323       // If we were called from a Request's callback within CompleteRequests,
1324       // that Request could not have been cancelled, so num_active_requests()
1325       // could not be 0. Therefore, we are not in CompleteRequests().
1326       CompleteRequestsWithError(OK /* cancelled */);
1327     }
1328   }
1329
1330   // Called from AbortAllInProgressJobs. Completes all requests and destroys
1331   // the job. This currently assumes the abort is due to a network change.
1332   void Abort() {
1333     DCHECK(is_running());
1334     CompleteRequestsWithError(ERR_NETWORK_CHANGED);
1335   }
1336
1337   // If DnsTask present, abort it and fall back to ProcTask.
1338   void AbortDnsTask() {
1339     if (dns_task_) {
1340       KillDnsTask();
1341       dns_task_error_ = OK;
1342       StartProcTask();
1343     }
1344   }
1345
1346   // Called by HostResolverImpl when this job is evicted due to queue overflow.
1347   // Completes all requests and destroys the job.
1348   void OnEvicted() {
1349     DCHECK(!is_running());
1350     DCHECK(is_queued());
1351     handle_.Reset();
1352
1353     net_log_.AddEvent(NetLog::TYPE_HOST_RESOLVER_IMPL_JOB_EVICTED);
1354
1355     // This signals to CompleteRequests that this job never ran.
1356     CompleteRequestsWithError(ERR_HOST_RESOLVER_QUEUE_TOO_LARGE);
1357   }
1358
1359   // Attempts to serve the job from HOSTS. Returns true if succeeded and
1360   // this Job was destroyed.
1361   bool ServeFromHosts() {
1362     DCHECK_GT(num_active_requests(), 0u);
1363     AddressList addr_list;
1364     if (resolver_->ServeFromHosts(key(),
1365                                   requests_.front()->info(),
1366                                   &addr_list)) {
1367       // This will destroy the Job.
1368       CompleteRequests(
1369           HostCache::Entry(OK, MakeAddressListForRequest(addr_list)),
1370           base::TimeDelta());
1371       return true;
1372     }
1373     return false;
1374   }
1375
1376   const Key key() const {
1377     return key_;
1378   }
1379
1380   bool is_queued() const {
1381     return !handle_.is_null();
1382   }
1383
1384   bool is_running() const {
1385     return is_dns_running() || is_proc_running();
1386   }
1387
1388  private:
1389   void KillDnsTask() {
1390     if (dns_task_) {
1391       ReduceToOneJobSlot();
1392       dns_task_.reset();
1393     }
1394   }
1395
1396   // Reduce the number of job slots occupied and queued in the dispatcher
1397   // to one. If the second Job slot is queued in the dispatcher, cancels the
1398   // queued job. Otherwise, the second Job has been started by the
1399   // PrioritizedDispatcher, so signals it is complete.
1400   void ReduceToOneJobSlot() {
1401     DCHECK_GE(num_occupied_job_slots_, 1u);
1402     if (is_queued()) {
1403       resolver_->dispatcher_->Cancel(handle_);
1404       handle_.Reset();
1405     } else if (num_occupied_job_slots_ > 1) {
1406       resolver_->dispatcher_->OnJobFinished();
1407       --num_occupied_job_slots_;
1408     }
1409     DCHECK_EQ(1u, num_occupied_job_slots_);
1410   }
1411
1412   void UpdatePriority() {
1413     if (is_queued()) {
1414       if (priority() != static_cast<RequestPriority>(handle_.priority()))
1415         priority_change_time_ = base::TimeTicks::Now();
1416       handle_ = resolver_->dispatcher_->ChangePriority(handle_, priority());
1417     }
1418   }
1419
1420   AddressList MakeAddressListForRequest(const AddressList& list) const {
1421     if (requests_.empty())
1422       return list;
1423     return AddressList::CopyWithPort(list, requests_.front()->info().port());
1424   }
1425
1426   // PriorityDispatch::Job:
1427   virtual void Start() OVERRIDE {
1428     DCHECK_LE(num_occupied_job_slots_, 1u);
1429
1430     handle_.Reset();
1431     ++num_occupied_job_slots_;
1432
1433     if (num_occupied_job_slots_ == 2) {
1434       StartSecondDnsTransaction();
1435       return;
1436     }
1437
1438     DCHECK(!is_running());
1439
1440     net_log_.AddEvent(NetLog::TYPE_HOST_RESOLVER_IMPL_JOB_STARTED);
1441
1442     had_dns_config_ = resolver_->HaveDnsConfig();
1443
1444     base::TimeTicks now = base::TimeTicks::Now();
1445     base::TimeDelta queue_time = now - creation_time_;
1446     base::TimeDelta queue_time_after_change = now - priority_change_time_;
1447
1448     if (had_dns_config_) {
1449       DNS_HISTOGRAM_BY_PRIORITY("AsyncDNS.JobQueueTime", priority(),
1450                                 queue_time);
1451       DNS_HISTOGRAM_BY_PRIORITY("AsyncDNS.JobQueueTimeAfterChange", priority(),
1452                                 queue_time_after_change);
1453     } else {
1454       DNS_HISTOGRAM_BY_PRIORITY("DNS.JobQueueTime", priority(), queue_time);
1455       DNS_HISTOGRAM_BY_PRIORITY("DNS.JobQueueTimeAfterChange", priority(),
1456                                 queue_time_after_change);
1457     }
1458
1459     bool system_only =
1460         (key_.host_resolver_flags & HOST_RESOLVER_SYSTEM_ONLY) != 0;
1461
1462     // Caution: Job::Start must not complete synchronously.
1463     if (!system_only && had_dns_config_ &&
1464         !ResemblesMulticastDNSName(key_.hostname)) {
1465       StartDnsTask();
1466     } else {
1467       StartProcTask();
1468     }
1469   }
1470
1471   // TODO(szym): Since DnsTransaction does not consume threads, we can increase
1472   // the limits on |dispatcher_|. But in order to keep the number of WorkerPool
1473   // threads low, we will need to use an "inner" PrioritizedDispatcher with
1474   // tighter limits.
1475   void StartProcTask() {
1476     DCHECK(!is_dns_running());
1477     proc_task_ = new ProcTask(
1478         key_,
1479         resolver_->proc_params_,
1480         base::Bind(&Job::OnProcTaskComplete, base::Unretained(this),
1481                    base::TimeTicks::Now()),
1482         net_log_);
1483
1484     if (had_non_speculative_request_)
1485       proc_task_->set_had_non_speculative_request();
1486     // Start() could be called from within Resolve(), hence it must NOT directly
1487     // call OnProcTaskComplete, for example, on synchronous failure.
1488     proc_task_->Start();
1489   }
1490
1491   // Called by ProcTask when it completes.
1492   void OnProcTaskComplete(base::TimeTicks start_time,
1493                           int net_error,
1494                           const AddressList& addr_list) {
1495     DCHECK(is_proc_running());
1496
1497     if (!resolver_->resolved_known_ipv6_hostname_ &&
1498         net_error == OK &&
1499         key_.address_family == ADDRESS_FAMILY_UNSPECIFIED) {
1500       if (key_.hostname == "www.google.com") {
1501         resolver_->resolved_known_ipv6_hostname_ = true;
1502         bool got_ipv6_address = false;
1503         for (size_t i = 0; i < addr_list.size(); ++i) {
1504           if (addr_list[i].GetFamily() == ADDRESS_FAMILY_IPV6) {
1505             got_ipv6_address = true;
1506             break;
1507           }
1508         }
1509         UMA_HISTOGRAM_BOOLEAN("Net.UnspecResolvedIPv6", got_ipv6_address);
1510       }
1511     }
1512
1513     if (dns_task_error_ != OK) {
1514       base::TimeDelta duration = base::TimeTicks::Now() - start_time;
1515       if (net_error == OK) {
1516         DNS_HISTOGRAM("AsyncDNS.FallbackSuccess", duration);
1517         if ((dns_task_error_ == ERR_NAME_NOT_RESOLVED) &&
1518             ResemblesNetBIOSName(key_.hostname)) {
1519           UmaAsyncDnsResolveStatus(RESOLVE_STATUS_SUSPECT_NETBIOS);
1520         } else {
1521           UmaAsyncDnsResolveStatus(RESOLVE_STATUS_PROC_SUCCESS);
1522         }
1523         UMA_HISTOGRAM_CUSTOM_ENUMERATION("AsyncDNS.ResolveError",
1524                                          std::abs(dns_task_error_),
1525                                          GetAllErrorCodesForUma());
1526         resolver_->OnDnsTaskResolve(dns_task_error_);
1527       } else {
1528         DNS_HISTOGRAM("AsyncDNS.FallbackFail", duration);
1529         UmaAsyncDnsResolveStatus(RESOLVE_STATUS_FAIL);
1530       }
1531     }
1532
1533     base::TimeDelta ttl =
1534         base::TimeDelta::FromSeconds(kNegativeCacheEntryTTLSeconds);
1535     if (net_error == OK)
1536       ttl = base::TimeDelta::FromSeconds(kCacheEntryTTLSeconds);
1537
1538     // Don't store the |ttl| in cache since it's not obtained from the server.
1539     CompleteRequests(
1540         HostCache::Entry(net_error, MakeAddressListForRequest(addr_list)),
1541         ttl);
1542   }
1543
1544   void StartDnsTask() {
1545     DCHECK(resolver_->HaveDnsConfig());
1546     dns_task_.reset(new DnsTask(resolver_->dns_client_.get(), key_, this,
1547                                 net_log_));
1548
1549     dns_task_->StartFirstTransaction();
1550     // Schedule a second transaction, if needed.
1551     if (dns_task_->needs_two_transactions())
1552       Schedule(true);
1553   }
1554
1555   void StartSecondDnsTransaction() {
1556     DCHECK(dns_task_->needs_two_transactions());
1557     dns_task_->StartSecondTransaction();
1558   }
1559
1560   // Called if DnsTask fails. It is posted from StartDnsTask, so Job may be
1561   // deleted before this callback. In this case dns_task is deleted as well,
1562   // so we use it as indicator whether Job is still valid.
1563   void OnDnsTaskFailure(const base::WeakPtr<DnsTask>& dns_task,
1564                         base::TimeDelta duration,
1565                         int net_error) {
1566     DNS_HISTOGRAM("AsyncDNS.ResolveFail", duration);
1567
1568     if (dns_task == NULL)
1569       return;
1570
1571     dns_task_error_ = net_error;
1572
1573     // TODO(szym): Run ServeFromHosts now if nsswitch.conf says so.
1574     // http://crbug.com/117655
1575
1576     // TODO(szym): Some net errors indicate lack of connectivity. Starting
1577     // ProcTask in that case is a waste of time.
1578     if (resolver_->fallback_to_proctask_) {
1579       KillDnsTask();
1580       StartProcTask();
1581     } else {
1582       UmaAsyncDnsResolveStatus(RESOLVE_STATUS_FAIL);
1583       CompleteRequestsWithError(net_error);
1584     }
1585   }
1586
1587
1588   // HostResolverImpl::DnsTask::Delegate implementation:
1589
1590   virtual void OnDnsTaskComplete(base::TimeTicks start_time,
1591                                  int net_error,
1592                                  const AddressList& addr_list,
1593                                  base::TimeDelta ttl) OVERRIDE {
1594     DCHECK(is_dns_running());
1595
1596     base::TimeDelta duration = base::TimeTicks::Now() - start_time;
1597     if (net_error != OK) {
1598       OnDnsTaskFailure(dns_task_->AsWeakPtr(), duration, net_error);
1599       return;
1600     }
1601     DNS_HISTOGRAM("AsyncDNS.ResolveSuccess", duration);
1602     // Log DNS lookups based on |address_family|.
1603     switch(key_.address_family) {
1604       case ADDRESS_FAMILY_IPV4:
1605         DNS_HISTOGRAM("AsyncDNS.ResolveSuccess_FAMILY_IPV4", duration);
1606         break;
1607       case ADDRESS_FAMILY_IPV6:
1608         DNS_HISTOGRAM("AsyncDNS.ResolveSuccess_FAMILY_IPV6", duration);
1609         break;
1610       case ADDRESS_FAMILY_UNSPECIFIED:
1611         DNS_HISTOGRAM("AsyncDNS.ResolveSuccess_FAMILY_UNSPEC", duration);
1612         break;
1613     }
1614
1615     UmaAsyncDnsResolveStatus(RESOLVE_STATUS_DNS_SUCCESS);
1616     RecordTTL(ttl);
1617
1618     resolver_->OnDnsTaskResolve(OK);
1619
1620     base::TimeDelta bounded_ttl =
1621         std::max(ttl, base::TimeDelta::FromSeconds(kMinimumTTLSeconds));
1622
1623     CompleteRequests(
1624         HostCache::Entry(net_error, MakeAddressListForRequest(addr_list), ttl),
1625         bounded_ttl);
1626   }
1627
1628   virtual void OnFirstDnsTransactionComplete() OVERRIDE {
1629     DCHECK(dns_task_->needs_two_transactions());
1630     DCHECK_EQ(dns_task_->needs_another_transaction(), is_queued());
1631     // No longer need to occupy two dispatcher slots.
1632     ReduceToOneJobSlot();
1633
1634     // We already have a job slot at the dispatcher, so if the second
1635     // transaction hasn't started, reuse it now instead of waiting in the queue
1636     // for the second slot.
1637     if (dns_task_->needs_another_transaction())
1638       dns_task_->StartSecondTransaction();
1639   }
1640
1641   // Performs Job's last rites. Completes all Requests. Deletes this.
1642   void CompleteRequests(const HostCache::Entry& entry,
1643                         base::TimeDelta ttl) {
1644     CHECK(resolver_.get());
1645
1646     // This job must be removed from resolver's |jobs_| now to make room for a
1647     // new job with the same key in case one of the OnComplete callbacks decides
1648     // to spawn one. Consequently, the job deletes itself when CompleteRequests
1649     // is done.
1650     scoped_ptr<Job> self_deleter(this);
1651
1652     resolver_->RemoveJob(this);
1653
1654     if (is_running()) {
1655       if (is_proc_running()) {
1656         DCHECK(!is_queued());
1657         proc_task_->Cancel();
1658         proc_task_ = NULL;
1659       }
1660       KillDnsTask();
1661
1662       // Signal dispatcher that a slot has opened.
1663       resolver_->dispatcher_->OnJobFinished();
1664     } else if (is_queued()) {
1665       resolver_->dispatcher_->Cancel(handle_);
1666       handle_.Reset();
1667     }
1668
1669     if (num_active_requests() == 0) {
1670       net_log_.AddEvent(NetLog::TYPE_CANCELLED);
1671       net_log_.EndEventWithNetErrorCode(NetLog::TYPE_HOST_RESOLVER_IMPL_JOB,
1672                                         OK);
1673       return;
1674     }
1675
1676     net_log_.EndEventWithNetErrorCode(NetLog::TYPE_HOST_RESOLVER_IMPL_JOB,
1677                                       entry.error);
1678
1679     DCHECK(!requests_.empty());
1680
1681     if (entry.error == OK) {
1682       // Record this histogram here, when we know the system has a valid DNS
1683       // configuration.
1684       UMA_HISTOGRAM_BOOLEAN("AsyncDNS.HaveDnsConfig",
1685                             resolver_->received_dns_config_);
1686     }
1687
1688     bool did_complete = (entry.error != ERR_NETWORK_CHANGED) &&
1689                         (entry.error != ERR_HOST_RESOLVER_QUEUE_TOO_LARGE);
1690     if (did_complete)
1691       resolver_->CacheResult(key_, entry, ttl);
1692
1693     // Complete all of the requests that were attached to the job.
1694     for (RequestsList::const_iterator it = requests_.begin();
1695          it != requests_.end(); ++it) {
1696       Request* req = *it;
1697
1698       if (req->was_canceled())
1699         continue;
1700
1701       DCHECK_EQ(this, req->job());
1702       // Update the net log and notify registered observers.
1703       LogFinishRequest(req->source_net_log(), req->request_net_log(),
1704                        req->info(), entry.error);
1705       if (did_complete) {
1706         // Record effective total time from creation to completion.
1707         RecordTotalTime(had_dns_config_, req->info().is_speculative(),
1708                         base::TimeTicks::Now() - req->request_time());
1709       }
1710       req->OnComplete(entry.error, entry.addrlist);
1711
1712       // Check if the resolver was destroyed as a result of running the
1713       // callback. If it was, we could continue, but we choose to bail.
1714       if (!resolver_.get())
1715         return;
1716     }
1717   }
1718
1719   // Convenience wrapper for CompleteRequests in case of failure.
1720   void CompleteRequestsWithError(int net_error) {
1721     CompleteRequests(HostCache::Entry(net_error, AddressList()),
1722                      base::TimeDelta());
1723   }
1724
1725   RequestPriority priority() const {
1726     return priority_tracker_.highest_priority();
1727   }
1728
1729   // Number of non-canceled requests in |requests_|.
1730   size_t num_active_requests() const {
1731     return priority_tracker_.total_count();
1732   }
1733
1734   bool is_dns_running() const {
1735     return dns_task_.get() != NULL;
1736   }
1737
1738   bool is_proc_running() const {
1739     return proc_task_.get() != NULL;
1740   }
1741
1742   base::WeakPtr<HostResolverImpl> resolver_;
1743
1744   Key key_;
1745
1746   // Tracks the highest priority across |requests_|.
1747   PriorityTracker priority_tracker_;
1748
1749   bool had_non_speculative_request_;
1750
1751   // Distinguishes measurements taken while DnsClient was fully configured.
1752   bool had_dns_config_;
1753
1754   // Number of slots occupied by this Job in resolver's PrioritizedDispatcher.
1755   unsigned num_occupied_job_slots_;
1756
1757   // Result of DnsTask.
1758   int dns_task_error_;
1759
1760   const base::TimeTicks creation_time_;
1761   base::TimeTicks priority_change_time_;
1762
1763   BoundNetLog net_log_;
1764
1765   // Resolves the host using a HostResolverProc.
1766   scoped_refptr<ProcTask> proc_task_;
1767
1768   // Resolves the host using a DnsTransaction.
1769   scoped_ptr<DnsTask> dns_task_;
1770
1771   // All Requests waiting for the result of this Job. Some can be canceled.
1772   RequestsList requests_;
1773
1774   // A handle used in |HostResolverImpl::dispatcher_|.
1775   PrioritizedDispatcher::Handle handle_;
1776 };
1777
1778 //-----------------------------------------------------------------------------
1779
1780 HostResolverImpl::ProcTaskParams::ProcTaskParams(
1781     HostResolverProc* resolver_proc,
1782     size_t max_retry_attempts)
1783     : resolver_proc(resolver_proc),
1784       max_retry_attempts(max_retry_attempts),
1785       unresponsive_delay(base::TimeDelta::FromMilliseconds(6000)),
1786       retry_factor(2) {
1787   // Maximum of 4 retry attempts for host resolution.
1788   static const size_t kDefaultMaxRetryAttempts = 4u;
1789   if (max_retry_attempts == HostResolver::kDefaultRetryAttempts)
1790     max_retry_attempts = kDefaultMaxRetryAttempts;
1791 }
1792
1793 HostResolverImpl::ProcTaskParams::~ProcTaskParams() {}
1794
1795 HostResolverImpl::HostResolverImpl(const Options& options, NetLog* net_log)
1796     : max_queued_jobs_(0),
1797       proc_params_(NULL, options.max_retry_attempts),
1798       net_log_(net_log),
1799       default_address_family_(ADDRESS_FAMILY_UNSPECIFIED),
1800       received_dns_config_(false),
1801       num_dns_failures_(0),
1802       probe_ipv6_support_(true),
1803       use_local_ipv6_(false),
1804       resolved_known_ipv6_hostname_(false),
1805       additional_resolver_flags_(0),
1806       fallback_to_proctask_(true),
1807       weak_ptr_factory_(this),
1808       probe_weak_ptr_factory_(this) {
1809   if (options.enable_caching)
1810     cache_ = HostCache::CreateDefaultCache();
1811
1812   PrioritizedDispatcher::Limits job_limits = options.GetDispatcherLimits();
1813   dispatcher_.reset(new PrioritizedDispatcher(job_limits));
1814   max_queued_jobs_ = job_limits.total_jobs * 100u;
1815
1816   DCHECK_GE(dispatcher_->num_priorities(), static_cast<size_t>(NUM_PRIORITIES));
1817
1818 #if defined(OS_WIN)
1819   EnsureWinsockInit();
1820 #endif
1821 #if defined(OS_POSIX) && !defined(OS_MACOSX) && !defined(OS_ANDROID)
1822   new LoopbackProbeJob(weak_ptr_factory_.GetWeakPtr());
1823 #endif
1824   NetworkChangeNotifier::AddIPAddressObserver(this);
1825   NetworkChangeNotifier::AddDNSObserver(this);
1826 #if defined(OS_POSIX) && !defined(OS_MACOSX) && !defined(OS_OPENBSD) && \
1827     !defined(OS_ANDROID)
1828   EnsureDnsReloaderInit();
1829 #endif
1830
1831   {
1832     DnsConfig dns_config;
1833     NetworkChangeNotifier::GetDnsConfig(&dns_config);
1834     received_dns_config_ = dns_config.IsValid();
1835     // Conservatively assume local IPv6 is needed when DnsConfig is not valid.
1836     use_local_ipv6_ = !dns_config.IsValid() || dns_config.use_local_ipv6;
1837   }
1838
1839   fallback_to_proctask_ = !ConfigureAsyncDnsNoFallbackFieldTrial();
1840 }
1841
1842 HostResolverImpl::~HostResolverImpl() {
1843   // Prevent the dispatcher from starting new jobs.
1844   dispatcher_->SetLimitsToZero();
1845   // It's now safe for Jobs to call KillDsnTask on destruction, because
1846   // OnJobComplete will not start any new jobs.
1847   STLDeleteValues(&jobs_);
1848
1849   NetworkChangeNotifier::RemoveIPAddressObserver(this);
1850   NetworkChangeNotifier::RemoveDNSObserver(this);
1851 }
1852
1853 void HostResolverImpl::SetMaxQueuedJobs(size_t value) {
1854   DCHECK_EQ(0u, dispatcher_->num_queued_jobs());
1855   DCHECK_GT(value, 0u);
1856   max_queued_jobs_ = value;
1857 }
1858
1859 int HostResolverImpl::Resolve(const RequestInfo& info,
1860                               RequestPriority priority,
1861                               AddressList* addresses,
1862                               const CompletionCallback& callback,
1863                               RequestHandle* out_req,
1864                               const BoundNetLog& source_net_log) {
1865   DCHECK(addresses);
1866   DCHECK(CalledOnValidThread());
1867   DCHECK_EQ(false, callback.is_null());
1868
1869   // Check that the caller supplied a valid hostname to resolve.
1870   std::string labeled_hostname;
1871   if (!DNSDomainFromDot(info.hostname(), &labeled_hostname))
1872     return ERR_NAME_NOT_RESOLVED;
1873
1874   // Make a log item for the request.
1875   BoundNetLog request_net_log = BoundNetLog::Make(net_log_,
1876       NetLog::SOURCE_HOST_RESOLVER_IMPL_REQUEST);
1877
1878   LogStartRequest(source_net_log, request_net_log, info);
1879
1880   // Build a key that identifies the request in the cache and in the
1881   // outstanding jobs map.
1882   Key key = GetEffectiveKeyForRequest(info, request_net_log);
1883
1884   int rv = ResolveHelper(key, info, addresses, request_net_log);
1885   if (rv != ERR_DNS_CACHE_MISS) {
1886     LogFinishRequest(source_net_log, request_net_log, info, rv);
1887     RecordTotalTime(HaveDnsConfig(), info.is_speculative(), base::TimeDelta());
1888     return rv;
1889   }
1890
1891   // Next we need to attach our request to a "job". This job is responsible for
1892   // calling "getaddrinfo(hostname)" on a worker thread.
1893
1894   JobMap::iterator jobit = jobs_.find(key);
1895   Job* job;
1896   if (jobit == jobs_.end()) {
1897     job =
1898         new Job(weak_ptr_factory_.GetWeakPtr(), key, priority, request_net_log);
1899     job->Schedule(false);
1900
1901     // Check for queue overflow.
1902     if (dispatcher_->num_queued_jobs() > max_queued_jobs_) {
1903       Job* evicted = static_cast<Job*>(dispatcher_->EvictOldestLowest());
1904       DCHECK(evicted);
1905       evicted->OnEvicted();  // Deletes |evicted|.
1906       if (evicted == job) {
1907         rv = ERR_HOST_RESOLVER_QUEUE_TOO_LARGE;
1908         LogFinishRequest(source_net_log, request_net_log, info, rv);
1909         return rv;
1910       }
1911     }
1912     jobs_.insert(jobit, std::make_pair(key, job));
1913   } else {
1914     job = jobit->second;
1915   }
1916
1917   // Can't complete synchronously. Create and attach request.
1918   scoped_ptr<Request> req(new Request(
1919       source_net_log, request_net_log, info, priority, callback, addresses));
1920   if (out_req)
1921     *out_req = reinterpret_cast<RequestHandle>(req.get());
1922
1923   job->AddRequest(req.Pass());
1924   // Completion happens during Job::CompleteRequests().
1925   return ERR_IO_PENDING;
1926 }
1927
1928 int HostResolverImpl::ResolveHelper(const Key& key,
1929                                     const RequestInfo& info,
1930                                     AddressList* addresses,
1931                                     const BoundNetLog& request_net_log) {
1932   // The result of |getaddrinfo| for empty hosts is inconsistent across systems.
1933   // On Windows it gives the default interface's address, whereas on Linux it
1934   // gives an error. We will make it fail on all platforms for consistency.
1935   if (info.hostname().empty() || info.hostname().size() > kMaxHostLength)
1936     return ERR_NAME_NOT_RESOLVED;
1937
1938   int net_error = ERR_UNEXPECTED;
1939   if (ResolveAsIP(key, info, &net_error, addresses))
1940     return net_error;
1941   if (ServeFromCache(key, info, &net_error, addresses)) {
1942     request_net_log.AddEvent(NetLog::TYPE_HOST_RESOLVER_IMPL_CACHE_HIT);
1943     return net_error;
1944   }
1945   // TODO(szym): Do not do this if nsswitch.conf instructs not to.
1946   // http://crbug.com/117655
1947   if (ServeFromHosts(key, info, addresses)) {
1948     request_net_log.AddEvent(NetLog::TYPE_HOST_RESOLVER_IMPL_HOSTS_HIT);
1949     return OK;
1950   }
1951   return ERR_DNS_CACHE_MISS;
1952 }
1953
1954 int HostResolverImpl::ResolveFromCache(const RequestInfo& info,
1955                                        AddressList* addresses,
1956                                        const BoundNetLog& source_net_log) {
1957   DCHECK(CalledOnValidThread());
1958   DCHECK(addresses);
1959
1960   // Make a log item for the request.
1961   BoundNetLog request_net_log = BoundNetLog::Make(net_log_,
1962       NetLog::SOURCE_HOST_RESOLVER_IMPL_REQUEST);
1963
1964   // Update the net log and notify registered observers.
1965   LogStartRequest(source_net_log, request_net_log, info);
1966
1967   Key key = GetEffectiveKeyForRequest(info, request_net_log);
1968
1969   int rv = ResolveHelper(key, info, addresses, request_net_log);
1970   LogFinishRequest(source_net_log, request_net_log, info, rv);
1971   return rv;
1972 }
1973
1974 void HostResolverImpl::CancelRequest(RequestHandle req_handle) {
1975   DCHECK(CalledOnValidThread());
1976   Request* req = reinterpret_cast<Request*>(req_handle);
1977   DCHECK(req);
1978   Job* job = req->job();
1979   DCHECK(job);
1980   job->CancelRequest(req);
1981 }
1982
1983 void HostResolverImpl::SetDefaultAddressFamily(AddressFamily address_family) {
1984   DCHECK(CalledOnValidThread());
1985   default_address_family_ = address_family;
1986   probe_ipv6_support_ = false;
1987 }
1988
1989 AddressFamily HostResolverImpl::GetDefaultAddressFamily() const {
1990   return default_address_family_;
1991 }
1992
1993 void HostResolverImpl::SetDnsClientEnabled(bool enabled) {
1994   DCHECK(CalledOnValidThread());
1995 #if defined(ENABLE_BUILT_IN_DNS)
1996   if (enabled && !dns_client_) {
1997     SetDnsClient(DnsClient::CreateClient(net_log_));
1998   } else if (!enabled && dns_client_) {
1999     SetDnsClient(scoped_ptr<DnsClient>());
2000   }
2001 #endif
2002 }
2003
2004 HostCache* HostResolverImpl::GetHostCache() {
2005   return cache_.get();
2006 }
2007
2008 base::Value* HostResolverImpl::GetDnsConfigAsValue() const {
2009   // Check if async DNS is disabled.
2010   if (!dns_client_.get())
2011     return NULL;
2012
2013   // Check if async DNS is enabled, but we currently have no configuration
2014   // for it.
2015   const DnsConfig* dns_config = dns_client_->GetConfig();
2016   if (dns_config == NULL)
2017     return new base::DictionaryValue();
2018
2019   return dns_config->ToValue();
2020 }
2021
2022 bool HostResolverImpl::ResolveAsIP(const Key& key,
2023                                    const RequestInfo& info,
2024                                    int* net_error,
2025                                    AddressList* addresses) {
2026   DCHECK(addresses);
2027   DCHECK(net_error);
2028   IPAddressNumber ip_number;
2029   if (!ParseIPLiteralToNumber(key.hostname, &ip_number))
2030     return false;
2031
2032   DCHECK_EQ(key.host_resolver_flags &
2033       ~(HOST_RESOLVER_CANONNAME | HOST_RESOLVER_LOOPBACK_ONLY |
2034         HOST_RESOLVER_DEFAULT_FAMILY_SET_DUE_TO_NO_IPV6),
2035             0) << " Unhandled flag";
2036
2037   *net_error = OK;
2038   AddressFamily family = GetAddressFamily(ip_number);
2039   if (family == ADDRESS_FAMILY_IPV6 &&
2040       !probe_ipv6_support_ &&
2041       default_address_family_ == ADDRESS_FAMILY_IPV4) {
2042     // Don't return IPv6 addresses if default address family is set to IPv4,
2043     // and probes are disabled.
2044     *net_error = ERR_NAME_NOT_RESOLVED;
2045   } else if (key.address_family != ADDRESS_FAMILY_UNSPECIFIED &&
2046              key.address_family != family) {
2047     // Don't return IPv6 addresses for IPv4 queries, and vice versa.
2048     *net_error = ERR_NAME_NOT_RESOLVED;
2049   } else {
2050     *addresses = AddressList::CreateFromIPAddress(ip_number, info.port());
2051     if (key.host_resolver_flags & HOST_RESOLVER_CANONNAME)
2052       addresses->SetDefaultCanonicalName();
2053   }
2054   return true;
2055 }
2056
2057 bool HostResolverImpl::ServeFromCache(const Key& key,
2058                                       const RequestInfo& info,
2059                                       int* net_error,
2060                                       AddressList* addresses) {
2061   DCHECK(addresses);
2062   DCHECK(net_error);
2063   if (!info.allow_cached_response() || !cache_.get())
2064     return false;
2065
2066   const HostCache::Entry* cache_entry = cache_->Lookup(
2067       key, base::TimeTicks::Now());
2068   if (!cache_entry)
2069     return false;
2070
2071   *net_error = cache_entry->error;
2072   if (*net_error == OK) {
2073     if (cache_entry->has_ttl())
2074       RecordTTL(cache_entry->ttl);
2075     *addresses = EnsurePortOnAddressList(cache_entry->addrlist, info.port());
2076   }
2077   return true;
2078 }
2079
2080 bool HostResolverImpl::ServeFromHosts(const Key& key,
2081                                       const RequestInfo& info,
2082                                       AddressList* addresses) {
2083   DCHECK(addresses);
2084   if (!HaveDnsConfig())
2085     return false;
2086   addresses->clear();
2087
2088   // HOSTS lookups are case-insensitive.
2089   std::string hostname = base::StringToLowerASCII(key.hostname);
2090
2091   const DnsHosts& hosts = dns_client_->GetConfig()->hosts;
2092
2093   // If |address_family| is ADDRESS_FAMILY_UNSPECIFIED other implementations
2094   // (glibc and c-ares) return the first matching line. We have more
2095   // flexibility, but lose implicit ordering.
2096   // We prefer IPv6 because "happy eyeballs" will fall back to IPv4 if
2097   // necessary.
2098   if (key.address_family == ADDRESS_FAMILY_IPV6 ||
2099       key.address_family == ADDRESS_FAMILY_UNSPECIFIED) {
2100     DnsHosts::const_iterator it = hosts.find(
2101         DnsHostsKey(hostname, ADDRESS_FAMILY_IPV6));
2102     if (it != hosts.end())
2103       addresses->push_back(IPEndPoint(it->second, info.port()));
2104   }
2105
2106   if (key.address_family == ADDRESS_FAMILY_IPV4 ||
2107       key.address_family == ADDRESS_FAMILY_UNSPECIFIED) {
2108     DnsHosts::const_iterator it = hosts.find(
2109         DnsHostsKey(hostname, ADDRESS_FAMILY_IPV4));
2110     if (it != hosts.end())
2111       addresses->push_back(IPEndPoint(it->second, info.port()));
2112   }
2113
2114   // If got only loopback addresses and the family was restricted, resolve
2115   // again, without restrictions. See SystemHostResolverCall for rationale.
2116   if ((key.host_resolver_flags &
2117           HOST_RESOLVER_DEFAULT_FAMILY_SET_DUE_TO_NO_IPV6) &&
2118       IsAllIPv4Loopback(*addresses)) {
2119     Key new_key(key);
2120     new_key.address_family = ADDRESS_FAMILY_UNSPECIFIED;
2121     new_key.host_resolver_flags &=
2122         ~HOST_RESOLVER_DEFAULT_FAMILY_SET_DUE_TO_NO_IPV6;
2123     return ServeFromHosts(new_key, info, addresses);
2124   }
2125   return !addresses->empty();
2126 }
2127
2128 void HostResolverImpl::CacheResult(const Key& key,
2129                                    const HostCache::Entry& entry,
2130                                    base::TimeDelta ttl) {
2131   if (cache_.get())
2132     cache_->Set(key, entry, base::TimeTicks::Now(), ttl);
2133 }
2134
2135 void HostResolverImpl::RemoveJob(Job* job) {
2136   DCHECK(job);
2137   JobMap::iterator it = jobs_.find(job->key());
2138   if (it != jobs_.end() && it->second == job)
2139     jobs_.erase(it);
2140 }
2141
2142 void HostResolverImpl::SetHaveOnlyLoopbackAddresses(bool result) {
2143   if (result) {
2144     additional_resolver_flags_ |= HOST_RESOLVER_LOOPBACK_ONLY;
2145   } else {
2146     additional_resolver_flags_ &= ~HOST_RESOLVER_LOOPBACK_ONLY;
2147   }
2148 }
2149
2150 HostResolverImpl::Key HostResolverImpl::GetEffectiveKeyForRequest(
2151     const RequestInfo& info, const BoundNetLog& net_log) const {
2152   HostResolverFlags effective_flags =
2153       info.host_resolver_flags() | additional_resolver_flags_;
2154   AddressFamily effective_address_family = info.address_family();
2155
2156   if (info.address_family() == ADDRESS_FAMILY_UNSPECIFIED) {
2157     if (probe_ipv6_support_ && !use_local_ipv6_) {
2158       base::TimeTicks start_time = base::TimeTicks::Now();
2159       // Google DNS address.
2160       const uint8 kIPv6Address[] =
2161           { 0x20, 0x01, 0x48, 0x60, 0x48, 0x60, 0x00, 0x00,
2162             0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x88, 0x88 };
2163       IPAddressNumber address(kIPv6Address,
2164                               kIPv6Address + arraysize(kIPv6Address));
2165       BoundNetLog probe_net_log = BoundNetLog::Make(
2166           net_log.net_log(), NetLog::SOURCE_IPV6_REACHABILITY_CHECK);
2167       probe_net_log.BeginEvent(NetLog::TYPE_IPV6_REACHABILITY_CHECK,
2168                                net_log.source().ToEventParametersCallback());
2169       bool rv6 = IsGloballyReachable(address, probe_net_log);
2170       probe_net_log.EndEvent(NetLog::TYPE_IPV6_REACHABILITY_CHECK);
2171       if (rv6)
2172         net_log.AddEvent(NetLog::TYPE_HOST_RESOLVER_IMPL_IPV6_SUPPORTED);
2173
2174       UMA_HISTOGRAM_TIMES("Net.IPv6ConnectDuration",
2175                           base::TimeTicks::Now() - start_time);
2176       if (rv6) {
2177         UMA_HISTOGRAM_BOOLEAN("Net.IPv6ConnectSuccessMatch",
2178             default_address_family_ == ADDRESS_FAMILY_UNSPECIFIED);
2179       } else {
2180         UMA_HISTOGRAM_BOOLEAN("Net.IPv6ConnectFailureMatch",
2181             default_address_family_ != ADDRESS_FAMILY_UNSPECIFIED);
2182
2183         effective_address_family = ADDRESS_FAMILY_IPV4;
2184         effective_flags |= HOST_RESOLVER_DEFAULT_FAMILY_SET_DUE_TO_NO_IPV6;
2185       }
2186     } else {
2187       effective_address_family = default_address_family_;
2188     }
2189   }
2190
2191   return Key(info.hostname(), effective_address_family, effective_flags);
2192 }
2193
2194 void HostResolverImpl::AbortAllInProgressJobs() {
2195   // In Abort, a Request callback could spawn new Jobs with matching keys, so
2196   // first collect and remove all running jobs from |jobs_|.
2197   ScopedVector<Job> jobs_to_abort;
2198   for (JobMap::iterator it = jobs_.begin(); it != jobs_.end(); ) {
2199     Job* job = it->second;
2200     if (job->is_running()) {
2201       jobs_to_abort.push_back(job);
2202       jobs_.erase(it++);
2203     } else {
2204       DCHECK(job->is_queued());
2205       ++it;
2206     }
2207   }
2208
2209   // Pause the dispatcher so it won't start any new dispatcher jobs while
2210   // aborting the old ones.  This is needed so that it won't start the second
2211   // DnsTransaction for a job in |jobs_to_abort| if the DnsConfig just became
2212   // invalid.
2213   PrioritizedDispatcher::Limits limits = dispatcher_->GetLimits();
2214   dispatcher_->SetLimits(
2215       PrioritizedDispatcher::Limits(limits.reserved_slots.size(), 0));
2216
2217   // Life check to bail once |this| is deleted.
2218   base::WeakPtr<HostResolverImpl> self = weak_ptr_factory_.GetWeakPtr();
2219
2220   // Then Abort them.
2221   for (size_t i = 0; self.get() && i < jobs_to_abort.size(); ++i) {
2222     jobs_to_abort[i]->Abort();
2223     jobs_to_abort[i] = NULL;
2224   }
2225
2226   if (self)
2227     dispatcher_->SetLimits(limits);
2228 }
2229
2230 void HostResolverImpl::AbortDnsTasks() {
2231   // Pause the dispatcher so it won't start any new dispatcher jobs while
2232   // aborting the old ones.  This is needed so that it won't start the second
2233   // DnsTransaction for a job if the DnsConfig just changed.
2234   PrioritizedDispatcher::Limits limits = dispatcher_->GetLimits();
2235   dispatcher_->SetLimits(
2236       PrioritizedDispatcher::Limits(limits.reserved_slots.size(), 0));
2237
2238   for (JobMap::iterator it = jobs_.begin(); it != jobs_.end(); ++it)
2239     it->second->AbortDnsTask();
2240   dispatcher_->SetLimits(limits);
2241 }
2242
2243 void HostResolverImpl::TryServingAllJobsFromHosts() {
2244   if (!HaveDnsConfig())
2245     return;
2246
2247   // TODO(szym): Do not do this if nsswitch.conf instructs not to.
2248   // http://crbug.com/117655
2249
2250   // Life check to bail once |this| is deleted.
2251   base::WeakPtr<HostResolverImpl> self = weak_ptr_factory_.GetWeakPtr();
2252
2253   for (JobMap::iterator it = jobs_.begin(); self.get() && it != jobs_.end();) {
2254     Job* job = it->second;
2255     ++it;
2256     // This could remove |job| from |jobs_|, but iterator will remain valid.
2257     job->ServeFromHosts();
2258   }
2259 }
2260
2261 void HostResolverImpl::OnIPAddressChanged() {
2262   resolved_known_ipv6_hostname_ = false;
2263   // Abandon all ProbeJobs.
2264   probe_weak_ptr_factory_.InvalidateWeakPtrs();
2265   if (cache_.get())
2266     cache_->clear();
2267 #if defined(OS_POSIX) && !defined(OS_MACOSX) && !defined(OS_ANDROID)
2268   new LoopbackProbeJob(probe_weak_ptr_factory_.GetWeakPtr());
2269 #endif
2270   AbortAllInProgressJobs();
2271   // |this| may be deleted inside AbortAllInProgressJobs().
2272 }
2273
2274 void HostResolverImpl::OnDNSChanged() {
2275   DnsConfig dns_config;
2276   NetworkChangeNotifier::GetDnsConfig(&dns_config);
2277
2278   if (net_log_) {
2279     net_log_->AddGlobalEntry(
2280         NetLog::TYPE_DNS_CONFIG_CHANGED,
2281         base::Bind(&NetLogDnsConfigCallback, &dns_config));
2282   }
2283
2284   // TODO(szym): Remove once http://crbug.com/137914 is resolved.
2285   received_dns_config_ = dns_config.IsValid();
2286   // Conservatively assume local IPv6 is needed when DnsConfig is not valid.
2287   use_local_ipv6_ = !dns_config.IsValid() || dns_config.use_local_ipv6;
2288
2289   num_dns_failures_ = 0;
2290
2291   // We want a new DnsSession in place, before we Abort running Jobs, so that
2292   // the newly started jobs use the new config.
2293   if (dns_client_.get()) {
2294     dns_client_->SetConfig(dns_config);
2295     if (dns_client_->GetConfig())
2296       UMA_HISTOGRAM_BOOLEAN("AsyncDNS.DnsClientEnabled", true);
2297   }
2298
2299   // If the DNS server has changed, existing cached info could be wrong so we
2300   // have to drop our internal cache :( Note that OS level DNS caches, such
2301   // as NSCD's cache should be dropped automatically by the OS when
2302   // resolv.conf changes so we don't need to do anything to clear that cache.
2303   if (cache_.get())
2304     cache_->clear();
2305
2306   // Life check to bail once |this| is deleted.
2307   base::WeakPtr<HostResolverImpl> self = weak_ptr_factory_.GetWeakPtr();
2308
2309   // Existing jobs will have been sent to the original server so they need to
2310   // be aborted.
2311   AbortAllInProgressJobs();
2312
2313   // |this| may be deleted inside AbortAllInProgressJobs().
2314   if (self.get())
2315     TryServingAllJobsFromHosts();
2316 }
2317
2318 bool HostResolverImpl::HaveDnsConfig() const {
2319   // Use DnsClient only if it's fully configured and there is no override by
2320   // ScopedDefaultHostResolverProc.
2321   // The alternative is to use NetworkChangeNotifier to override DnsConfig,
2322   // but that would introduce construction order requirements for NCN and SDHRP.
2323   return (dns_client_.get() != NULL) && (dns_client_->GetConfig() != NULL) &&
2324          !(proc_params_.resolver_proc.get() == NULL &&
2325            HostResolverProc::GetDefault() != NULL);
2326 }
2327
2328 void HostResolverImpl::OnDnsTaskResolve(int net_error) {
2329   DCHECK(dns_client_);
2330   if (net_error == OK) {
2331     num_dns_failures_ = 0;
2332     return;
2333   }
2334   ++num_dns_failures_;
2335   if (num_dns_failures_ < kMaximumDnsFailures)
2336     return;
2337
2338   // Disable DnsClient until the next DNS change.  Must be done before aborting
2339   // DnsTasks, since doing so may start new jobs.
2340   dns_client_->SetConfig(DnsConfig());
2341
2342   // Switch jobs with active DnsTasks over to using ProcTasks.
2343   AbortDnsTasks();
2344
2345   UMA_HISTOGRAM_BOOLEAN("AsyncDNS.DnsClientEnabled", false);
2346   UMA_HISTOGRAM_CUSTOM_ENUMERATION("AsyncDNS.DnsClientDisabledReason",
2347                                    std::abs(net_error),
2348                                    GetAllErrorCodesForUma());
2349 }
2350
2351 void HostResolverImpl::SetDnsClient(scoped_ptr<DnsClient> dns_client) {
2352   // DnsClient and config must be updated before aborting DnsTasks, since doing
2353   // so may start new jobs.
2354   dns_client_ = dns_client.Pass();
2355   if (dns_client_ && !dns_client_->GetConfig() &&
2356       num_dns_failures_ < kMaximumDnsFailures) {
2357     DnsConfig dns_config;
2358     NetworkChangeNotifier::GetDnsConfig(&dns_config);
2359     dns_client_->SetConfig(dns_config);
2360     num_dns_failures_ = 0;
2361     if (dns_client_->GetConfig())
2362       UMA_HISTOGRAM_BOOLEAN("AsyncDNS.DnsClientEnabled", true);
2363   }
2364
2365   AbortDnsTasks();
2366 }
2367
2368 }  // namespace net