dbus/object_proxy.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 "dbus/bus.h"
   6
   7 #include "base/bind.h"
   8 #include "base/logging.h"
   9 #include "base/message_loop/message_loop.h"
  10 #include "base/metrics/histogram.h"
  11 #include "base/strings/string_piece.h"
  12 #include "base/strings/stringprintf.h"
  13 #include "base/task_runner_util.h"
  14 #include "base/threading/thread.h"
  15 #include "base/threading/thread_restrictions.h"
  16 #include "dbus/dbus_statistics.h"
  17 #include "dbus/message.h"
  18 #include "dbus/object_path.h"
  19 #include "dbus/object_proxy.h"
  20 #include "dbus/scoped_dbus_error.h"
  21 #include "dbus/util.h"
  22
  23 namespace dbus {
  24
  25 namespace {
  26
  27 const char kErrorServiceUnknown[] = "org.freedesktop.DBus.Error.ServiceUnknown";
  28 const char kErrorObjectUnknown[] = "org.freedesktop.DBus.Error.UnknownObject";
  29
  30 // Used for success ratio histograms. 1 for success, 0 for failure.
  31 const int kSuccessRatioHistogramMaxValue = 2;
  32
  33 // The path of D-Bus Object sending NameOwnerChanged signal.
  34 const char kDBusSystemObjectPath[] = "/org/freedesktop/DBus";
  35
  36 // The D-Bus Object interface.
  37 const char kDBusSystemObjectInterface[] = "org.freedesktop.DBus";
  38
  39 // The D-Bus Object address.
  40 const char kDBusSystemObjectAddress[] = "org.freedesktop.DBus";
  41
  42 // The NameOwnerChanged member in |kDBusSystemObjectInterface|.
  43 const char kNameOwnerChangedMember[] = "NameOwnerChanged";
  44
  45 // An empty function used for ObjectProxy::EmptyResponseCallback().
  46 void EmptyResponseCallbackBody(Response* /*response*/) {
  47 }
  48
  49 }  // namespace
  50
  51 ObjectProxy::ObjectProxy(Bus* bus,
  52                          const std::string& service_name,
  53                          const ObjectPath& object_path,
  54                          int options)
  55     : bus_(bus),
  56       service_name_(service_name),
  57       object_path_(object_path),
  58       ignore_service_unknown_errors_(
  59           options & IGNORE_SERVICE_UNKNOWN_ERRORS) {
  60 }
  61
  62 ObjectProxy::~ObjectProxy() {
  63 }
  64
  65 // Originally we tried to make |method_call| a const reference, but we
  66 // gave up as dbus_connection_send_with_reply_and_block() takes a
  67 // non-const pointer of DBusMessage as the second parameter.
  68 scoped_ptr<Response> ObjectProxy::CallMethodAndBlockWithErrorDetails(
  69     MethodCall* method_call, int timeout_ms, ScopedDBusError* error) {
  70   bus_->AssertOnDBusThread();
  71
  72   if (!bus_->Connect() ||
  73       !method_call->SetDestination(service_name_) ||
  74       !method_call->SetPath(object_path_))
  75     return scoped_ptr<Response>();
  76
  77   DBusMessage* request_message = method_call->raw_message();
  78
  79   // Send the message synchronously.
  80   const base::TimeTicks start_time = base::TimeTicks::Now();
  81   DBusMessage* response_message =
  82       bus_->SendWithReplyAndBlock(request_message, timeout_ms, error->get());
  83   // Record if the method call is successful, or not. 1 if successful.
  84   UMA_HISTOGRAM_ENUMERATION("DBus.SyncMethodCallSuccess",
  85                             response_message ? 1 : 0,
  86                             kSuccessRatioHistogramMaxValue);
  87   statistics::AddBlockingSentMethodCall(service_name_,
  88                                         method_call->GetInterface(),
  89                                         method_call->GetMember());
  90
  91   if (!response_message) {
  92     LogMethodCallFailure(method_call->GetInterface(),
  93                          method_call->GetMember(),
  94                          error->is_set() ? error->name() : "unknown error type",
  95                          error->is_set() ? error->message() : "");
  96     return scoped_ptr<Response>();
  97   }
  98   // Record time spent for the method call. Don't include failures.
  99   UMA_HISTOGRAM_TIMES("DBus.SyncMethodCallTime",
 100                       base::TimeTicks::Now() - start_time);
 101
 102   return Response::FromRawMessage(response_message);
 103 }
 104
 105 scoped_ptr<Response> ObjectProxy::CallMethodAndBlock(MethodCall* method_call,
 106                                                      int timeout_ms) {
 107   ScopedDBusError error;
 108   return CallMethodAndBlockWithErrorDetails(method_call, timeout_ms, &error);
 109 }
 110
 111 void ObjectProxy::CallMethod(MethodCall* method_call,
 112                              int timeout_ms,
 113                              ResponseCallback callback) {
 114   CallMethodWithErrorCallback(method_call, timeout_ms, callback,
 115                               base::Bind(&ObjectProxy::OnCallMethodError,
 116                                          this,
 117                                          method_call->GetInterface(),
 118                                          method_call->GetMember(),
 119                                          callback));
 120 }
 121
 122 void ObjectProxy::CallMethodWithErrorCallback(MethodCall* method_call,
 123                                               int timeout_ms,
 124                                               ResponseCallback callback,
 125                                               ErrorCallback error_callback) {
 126   bus_->AssertOnOriginThread();
 127
 128   const base::TimeTicks start_time = base::TimeTicks::Now();
 129
 130   if (!method_call->SetDestination(service_name_) ||
 131       !method_call->SetPath(object_path_)) {
 132     // In case of a failure, run the error callback with NULL.
 133     DBusMessage* response_message = NULL;
 134     base::Closure task = base::Bind(&ObjectProxy::RunResponseCallback,
 135                                     this,
 136                                     callback,
 137                                     error_callback,
 138                                     start_time,
 139                                     response_message);
 140     bus_->GetOriginTaskRunner()->PostTask(FROM_HERE, task);
 141     return;
 142   }
 143
 144   // Increment the reference count so we can safely reference the
 145   // underlying request message until the method call is complete. This
 146   // will be unref'ed in StartAsyncMethodCall().
 147   DBusMessage* request_message = method_call->raw_message();
 148   dbus_message_ref(request_message);
 149
 150   base::Closure task = base::Bind(&ObjectProxy::StartAsyncMethodCall,
 151                                   this,
 152                                   timeout_ms,
 153                                   request_message,
 154                                   callback,
 155                                   error_callback,
 156                                   start_time);
 157   statistics::AddSentMethodCall(service_name_,
 158                                 method_call->GetInterface(),
 159                                 method_call->GetMember());
 160
 161   // Wait for the response in the D-Bus thread.
 162   bus_->GetDBusTaskRunner()->PostTask(FROM_HERE, task);
 163 }
 164
 165 void ObjectProxy::ConnectToSignal(const std::string& interface_name,
 166                                   const std::string& signal_name,
 167                                   SignalCallback signal_callback,
 168                                   OnConnectedCallback on_connected_callback) {
 169   bus_->AssertOnOriginThread();
 170
 171   base::PostTaskAndReplyWithResult(
 172       bus_->GetDBusTaskRunner(),
 173       FROM_HERE,
 174       base::Bind(&ObjectProxy::ConnectToSignalInternal,
 175                  this,
 176                  interface_name,
 177                  signal_name,
 178                  signal_callback),
 179       base::Bind(on_connected_callback,
 180                  interface_name,
 181                  signal_name));
 182 }
 183
 184 void ObjectProxy::SetNameOwnerChangedCallback(
 185     NameOwnerChangedCallback callback) {
 186   bus_->AssertOnOriginThread();
 187
 188   name_owner_changed_callback_ = callback;
 189 }
 190
 191 void ObjectProxy::WaitForServiceToBeAvailable(
 192     WaitForServiceToBeAvailableCallback callback) {
 193   bus_->AssertOnOriginThread();
 194
 195   wait_for_service_to_be_available_callbacks_.push_back(callback);
 196   bus_->GetDBusTaskRunner()->PostTask(
 197       FROM_HERE,
 198       base::Bind(&ObjectProxy::WaitForServiceToBeAvailableInternal, this));
 199 }
 200
 201 void ObjectProxy::Detach() {
 202   bus_->AssertOnDBusThread();
 203
 204   if (bus_->is_connected())
 205     bus_->RemoveFilterFunction(&ObjectProxy::HandleMessageThunk, this);
 206
 207   for (std::set<std::string>::iterator iter = match_rules_.begin();
 208        iter != match_rules_.end(); ++iter) {
 209     ScopedDBusError error;
 210     bus_->RemoveMatch(*iter, error.get());
 211     if (error.is_set()) {
 212       // There is nothing we can do to recover, so just print the error.
 213       LOG(ERROR) << "Failed to remove match rule: " << *iter;
 214     }
 215   }
 216   match_rules_.clear();
 217 }
 218
 219 // static
 220 ObjectProxy::ResponseCallback ObjectProxy::EmptyResponseCallback() {
 221   return base::Bind(&EmptyResponseCallbackBody);
 222 }
 223
 224 ObjectProxy::OnPendingCallIsCompleteData::OnPendingCallIsCompleteData(
 225     ObjectProxy* in_object_proxy,
 226     ResponseCallback in_response_callback,
 227     ErrorCallback in_error_callback,
 228     base::TimeTicks in_start_time)
 229     : object_proxy(in_object_proxy),
 230       response_callback(in_response_callback),
 231       error_callback(in_error_callback),
 232       start_time(in_start_time) {
 233 }
 234
 235 ObjectProxy::OnPendingCallIsCompleteData::~OnPendingCallIsCompleteData() {
 236 }
 237
 238 void ObjectProxy::StartAsyncMethodCall(int timeout_ms,
 239                                        DBusMessage* request_message,
 240                                        ResponseCallback response_callback,
 241                                        ErrorCallback error_callback,
 242                                        base::TimeTicks start_time) {
 243   bus_->AssertOnDBusThread();
 244
 245   if (!bus_->Connect() || !bus_->SetUpAsyncOperations()) {
 246     // In case of a failure, run the error callback with NULL.
 247     DBusMessage* response_message = NULL;
 248     base::Closure task = base::Bind(&ObjectProxy::RunResponseCallback,
 249                                     this,
 250                                     response_callback,
 251                                     error_callback,
 252                                     start_time,
 253                                     response_message);
 254     bus_->GetOriginTaskRunner()->PostTask(FROM_HERE, task);
 255
 256     dbus_message_unref(request_message);
 257     return;
 258   }
 259
 260   DBusPendingCall* pending_call = NULL;
 261
 262   bus_->SendWithReply(request_message, &pending_call, timeout_ms);
 263
 264   // Prepare the data we'll be passing to OnPendingCallIsCompleteThunk().
 265   // The data will be deleted in OnPendingCallIsCompleteThunk().
 266   OnPendingCallIsCompleteData* data =
 267       new OnPendingCallIsCompleteData(this, response_callback, error_callback,
 268                                       start_time);
 269
 270   // This returns false only when unable to allocate memory.
 271   const bool success = dbus_pending_call_set_notify(
 272       pending_call,
 273       &ObjectProxy::OnPendingCallIsCompleteThunk,
 274       data,
 275       NULL);
 276   CHECK(success) << "Unable to allocate memory";
 277   dbus_pending_call_unref(pending_call);
 278
 279   // It's now safe to unref the request message.
 280   dbus_message_unref(request_message);
 281 }
 282
 283 void ObjectProxy::OnPendingCallIsComplete(DBusPendingCall* pending_call,
 284                                           ResponseCallback response_callback,
 285                                           ErrorCallback error_callback,
 286                                           base::TimeTicks start_time) {
 287   bus_->AssertOnDBusThread();
 288
 289   DBusMessage* response_message = dbus_pending_call_steal_reply(pending_call);
 290   base::Closure task = base::Bind(&ObjectProxy::RunResponseCallback,
 291                                   this,
 292                                   response_callback,
 293                                   error_callback,
 294                                   start_time,
 295                                   response_message);
 296   bus_->GetOriginTaskRunner()->PostTask(FROM_HERE, task);
 297 }
 298
 299 void ObjectProxy::RunResponseCallback(ResponseCallback response_callback,
 300                                       ErrorCallback error_callback,
 301                                       base::TimeTicks start_time,
 302                                       DBusMessage* response_message) {
 303   bus_->AssertOnOriginThread();
 304
 305   bool method_call_successful = false;
 306   if (!response_message) {
 307     // The response is not received.
 308     error_callback.Run(NULL);
 309   } else if (dbus_message_get_type(response_message) ==
 310              DBUS_MESSAGE_TYPE_ERROR) {
 311     // This will take |response_message| and release (unref) it.
 312     scoped_ptr<ErrorResponse> error_response(
 313         ErrorResponse::FromRawMessage(response_message));
 314     error_callback.Run(error_response.get());
 315     // Delete the message  on the D-Bus thread. See below for why.
 316     bus_->GetDBusTaskRunner()->PostTask(
 317         FROM_HERE,
 318         base::Bind(&base::DeletePointer<ErrorResponse>,
 319                    error_response.release()));
 320   } else {
 321     // This will take |response_message| and release (unref) it.
 322     scoped_ptr<Response> response(Response::FromRawMessage(response_message));
 323     // The response is successfully received.
 324     response_callback.Run(response.get());
 325     // The message should be deleted on the D-Bus thread for a complicated
 326     // reason:
 327     //
 328     // libdbus keeps track of the number of bytes in the incoming message
 329     // queue to ensure that the data size in the queue is manageable. The
 330     // bookkeeping is partly done via dbus_message_unref(), and immediately
 331     // asks the client code (Chrome) to stop monitoring the underlying
 332     // socket, if the number of bytes exceeds a certian number, which is set
 333     // to 63MB, per dbus-transport.cc:
 334     //
 335     //   /* Try to default to something that won't totally hose the system,
 336     //    * but doesn't impose too much of a limitation.
 337     //    */
 338     //   transport->max_live_messages_size = _DBUS_ONE_MEGABYTE * 63;
 339     //
 340     // The monitoring of the socket is done on the D-Bus thread (see Watch
 341     // class in bus.cc), hence we should stop the monitoring from D-Bus
 342     // thread, not from the current thread here, which is likely UI thread.
 343     bus_->GetDBusTaskRunner()->PostTask(
 344         FROM_HERE,
 345         base::Bind(&base::DeletePointer<Response>, response.release()));
 346
 347     method_call_successful = true;
 348     // Record time spent for the method call. Don't include failures.
 349     UMA_HISTOGRAM_TIMES("DBus.AsyncMethodCallTime",
 350                         base::TimeTicks::Now() - start_time);
 351   }
 352   // Record if the method call is successful, or not. 1 if successful.
 353   UMA_HISTOGRAM_ENUMERATION("DBus.AsyncMethodCallSuccess",
 354                             method_call_successful,
 355                             kSuccessRatioHistogramMaxValue);
 356 }
 357
 358 void ObjectProxy::OnPendingCallIsCompleteThunk(DBusPendingCall* pending_call,
 359                                                void* user_data) {
 360   OnPendingCallIsCompleteData* data =
 361       reinterpret_cast<OnPendingCallIsCompleteData*>(user_data);
 362   ObjectProxy* self = data->object_proxy;
 363   self->OnPendingCallIsComplete(pending_call,
 364                                 data->response_callback,
 365                                 data->error_callback,
 366                                 data->start_time);
 367   delete data;
 368 }
 369
 370 bool ObjectProxy::ConnectToNameOwnerChangedSignal() {
 371   bus_->AssertOnDBusThread();
 372
 373   if (!bus_->Connect() || !bus_->SetUpAsyncOperations())
 374     return false;
 375
 376   bus_->AddFilterFunction(&ObjectProxy::HandleMessageThunk, this);
 377
 378   // Add a match_rule listening NameOwnerChanged for the well-known name
 379   // |service_name_|.
 380   const std::string name_owner_changed_match_rule =
 381       base::StringPrintf(
 382           "type='signal',interface='org.freedesktop.DBus',"
 383           "member='NameOwnerChanged',path='/org/freedesktop/DBus',"
 384           "sender='org.freedesktop.DBus',arg0='%s'",
 385           service_name_.c_str());
 386
 387   const bool success =
 388       AddMatchRuleWithoutCallback(name_owner_changed_match_rule,
 389                                   "org.freedesktop.DBus.NameOwnerChanged");
 390
 391   // Try getting the current name owner. It's not guaranteed that we can get
 392   // the name owner at this moment, as the service may not yet be started. If
 393   // that's the case, we'll get the name owner via NameOwnerChanged signal,
 394   // as soon as the service is started.
 395   UpdateNameOwnerAndBlock();
 396
 397   return success;
 398 }
 399
 400 bool ObjectProxy::ConnectToSignalInternal(const std::string& interface_name,
 401                                           const std::string& signal_name,
 402                                           SignalCallback signal_callback) {
 403   bus_->AssertOnDBusThread();
 404
 405   if (!ConnectToNameOwnerChangedSignal())
 406     return false;
 407
 408   const std::string absolute_signal_name =
 409       GetAbsoluteMemberName(interface_name, signal_name);
 410
 411   // Add a match rule so the signal goes through HandleMessage().
 412   const std::string match_rule =
 413       base::StringPrintf("type='signal', interface='%s', path='%s'",
 414                          interface_name.c_str(),
 415                          object_path_.value().c_str());
 416   return AddMatchRuleWithCallback(match_rule,
 417                                   absolute_signal_name,
 418                                   signal_callback);
 419 }
 420
 421 void ObjectProxy::WaitForServiceToBeAvailableInternal() {
 422   bus_->AssertOnDBusThread();
 423
 424   if (!ConnectToNameOwnerChangedSignal()) {  // Failed to connect to the signal.
 425     const bool service_is_ready = false;
 426     bus_->GetOriginTaskRunner()->PostTask(
 427         FROM_HERE,
 428         base::Bind(&ObjectProxy::RunWaitForServiceToBeAvailableCallbacks,
 429                    this, service_is_ready));
 430     return;
 431   }
 432
 433   const bool service_is_available = !service_name_owner_.empty();
 434   if (service_is_available) {  // Service is already available.
 435     bus_->GetOriginTaskRunner()->PostTask(
 436         FROM_HERE,
 437         base::Bind(&ObjectProxy::RunWaitForServiceToBeAvailableCallbacks,
 438                    this, service_is_available));
 439     return;
 440   }
 441 }
 442
 443 DBusHandlerResult ObjectProxy::HandleMessage(
 444     DBusConnection* connection,
 445     DBusMessage* raw_message) {
 446   bus_->AssertOnDBusThread();
 447
 448   if (dbus_message_get_type(raw_message) != DBUS_MESSAGE_TYPE_SIGNAL)
 449     return DBUS_HANDLER_RESULT_NOT_YET_HANDLED;
 450
 451   // raw_message will be unrefed on exit of the function. Increment the
 452   // reference so we can use it in Signal.
 453   dbus_message_ref(raw_message);
 454   scoped_ptr<Signal> signal(
 455       Signal::FromRawMessage(raw_message));
 456
 457   // Verify the signal comes from the object we're proxying for, this is
 458   // our last chance to return DBUS_HANDLER_RESULT_NOT_YET_HANDLED and
 459   // allow other object proxies to handle instead.
 460   const ObjectPath path = signal->GetPath();
 461   if (path != object_path_) {
 462     if (path.value() == kDBusSystemObjectPath &&
 463         signal->GetMember() == kNameOwnerChangedMember) {
 464       // Handle NameOwnerChanged separately
 465       return HandleNameOwnerChanged(signal.Pass());
 466     }
 467     return DBUS_HANDLER_RESULT_NOT_YET_HANDLED;
 468   }
 469
 470   const std::string interface = signal->GetInterface();
 471   const std::string member = signal->GetMember();
 472
 473   statistics::AddReceivedSignal(service_name_, interface, member);
 474
 475   // Check if we know about the signal.
 476   const std::string absolute_signal_name = GetAbsoluteMemberName(
 477       interface, member);
 478   MethodTable::const_iterator iter = method_table_.find(absolute_signal_name);
 479   if (iter == method_table_.end()) {
 480     // Don't know about the signal.
 481     return DBUS_HANDLER_RESULT_NOT_YET_HANDLED;
 482   }
 483   VLOG(1) << "Signal received: " << signal->ToString();
 484
 485   std::string sender = signal->GetSender();
 486   if (service_name_owner_ != sender) {
 487     LOG(ERROR) << "Rejecting a message from a wrong sender.";
 488     UMA_HISTOGRAM_COUNTS("DBus.RejectedSignalCount", 1);
 489     return DBUS_HANDLER_RESULT_NOT_YET_HANDLED;
 490   }
 491
 492   const base::TimeTicks start_time = base::TimeTicks::Now();
 493   if (bus_->HasDBusThread()) {
 494     // Post a task to run the method in the origin thread.
 495     // Transfer the ownership of |signal| to RunMethod().
 496     // |released_signal| will be deleted in RunMethod().
 497     Signal* released_signal = signal.release();
 498     bus_->GetOriginTaskRunner()->PostTask(FROM_HERE,
 499                                           base::Bind(&ObjectProxy::RunMethod,
 500                                                      this,
 501                                                      start_time,
 502                                                      iter->second,
 503                                                      released_signal));
 504   } else {
 505     const base::TimeTicks start_time = base::TimeTicks::Now();
 506     // If the D-Bus thread is not used, just call the callback on the
 507     // current thread. Transfer the ownership of |signal| to RunMethod().
 508     Signal* released_signal = signal.release();
 509     RunMethod(start_time, iter->second, released_signal);
 510   }
 511
 512   // We don't return DBUS_HANDLER_RESULT_HANDLED for signals because other
 513   // objects may be interested in them. (e.g. Signals from org.freedesktop.DBus)
 514   return DBUS_HANDLER_RESULT_NOT_YET_HANDLED;
 515 }
 516
 517 void ObjectProxy::RunMethod(base::TimeTicks start_time,
 518                             std::vector<SignalCallback> signal_callbacks,
 519                             Signal* signal) {
 520   bus_->AssertOnOriginThread();
 521
 522   for (std::vector<SignalCallback>::iterator iter = signal_callbacks.begin();
 523        iter != signal_callbacks.end(); ++iter)
 524     iter->Run(signal);
 525
 526   // Delete the message on the D-Bus thread. See comments in
 527   // RunResponseCallback().
 528   bus_->GetDBusTaskRunner()->PostTask(
 529       FROM_HERE,
 530       base::Bind(&base::DeletePointer<Signal>, signal));
 531
 532   // Record time spent for handling the signal.
 533   UMA_HISTOGRAM_TIMES("DBus.SignalHandleTime",
 534                       base::TimeTicks::Now() - start_time);
 535 }
 536
 537 DBusHandlerResult ObjectProxy::HandleMessageThunk(
 538     DBusConnection* connection,
 539     DBusMessage* raw_message,
 540     void* user_data) {
 541   ObjectProxy* self = reinterpret_cast<ObjectProxy*>(user_data);
 542   return self->HandleMessage(connection, raw_message);
 543 }
 544
 545 void ObjectProxy::LogMethodCallFailure(
 546     const base::StringPiece& interface_name,
 547     const base::StringPiece& method_name,
 548     const base::StringPiece& error_name,
 549     const base::StringPiece& error_message) const {
 550   if (ignore_service_unknown_errors_ &&
 551       (error_name == kErrorServiceUnknown || error_name == kErrorObjectUnknown))
 552     return;
 553   logging::LogSeverity severity = logging::LOG_ERROR;
 554   // "UnknownObject" indicates that an object or service is no longer available,
 555   // e.g. a Shill network service has gone out of range. Treat these as warnings
 556   // not errors.
 557   if (error_name == kErrorObjectUnknown)
 558     severity = logging::LOG_WARNING;
 559   std::ostringstream msg;
 560   msg << "Failed to call method: " << interface_name << "." << method_name
 561       << ": object_path= " << object_path_.value()
 562       << ": " << error_name << ": " << error_message;
 563   logging::LogAtLevel(severity, msg.str());
 564 }
 565
 566 void ObjectProxy::OnCallMethodError(const std::string& interface_name,
 567                                     const std::string& method_name,
 568                                     ResponseCallback response_callback,
 569                                     ErrorResponse* error_response) {
 570   if (error_response) {
 571     // Error message may contain the error message as string.
 572     MessageReader reader(error_response);
 573     std::string error_message;
 574     reader.PopString(&error_message);
 575     LogMethodCallFailure(interface_name,
 576                          method_name,
 577                          error_response->GetErrorName(),
 578                          error_message);
 579   }
 580   response_callback.Run(NULL);
 581 }
 582
 583 bool ObjectProxy::AddMatchRuleWithCallback(
 584     const std::string& match_rule,
 585     const std::string& absolute_signal_name,
 586     SignalCallback signal_callback) {
 587   DCHECK(!match_rule.empty());
 588   DCHECK(!absolute_signal_name.empty());
 589   bus_->AssertOnDBusThread();
 590
 591   if (match_rules_.find(match_rule) == match_rules_.end()) {
 592     ScopedDBusError error;
 593     bus_->AddMatch(match_rule, error.get());
 594     if (error.is_set()) {
 595       LOG(ERROR) << "Failed to add match rule \"" << match_rule << "\". Got "
 596                  << error.name() << ": " << error.message();
 597       return false;
 598     } else {
 599       // Store the match rule, so that we can remove this in Detach().
 600       match_rules_.insert(match_rule);
 601       // Add the signal callback to the method table.
 602       method_table_[absolute_signal_name].push_back(signal_callback);
 603       return true;
 604     }
 605   } else {
 606     // We already have the match rule.
 607     method_table_[absolute_signal_name].push_back(signal_callback);
 608     return true;
 609   }
 610 }
 611
 612 bool ObjectProxy::AddMatchRuleWithoutCallback(
 613     const std::string& match_rule,
 614     const std::string& absolute_signal_name) {
 615   DCHECK(!match_rule.empty());
 616   DCHECK(!absolute_signal_name.empty());
 617   bus_->AssertOnDBusThread();
 618
 619   if (match_rules_.find(match_rule) != match_rules_.end())
 620     return true;
 621
 622   ScopedDBusError error;
 623   bus_->AddMatch(match_rule, error.get());
 624   if (error.is_set()) {
 625     LOG(ERROR) << "Failed to add match rule \"" << match_rule << "\". Got "
 626                << error.name() << ": " << error.message();
 627     return false;
 628   }
 629   // Store the match rule, so that we can remove this in Detach().
 630   match_rules_.insert(match_rule);
 631   return true;
 632 }
 633
 634 void ObjectProxy::UpdateNameOwnerAndBlock() {
 635   bus_->AssertOnDBusThread();
 636   // Errors should be suppressed here, as the service may not be yet running
 637   // when connecting to signals of the service, which is just fine.
 638   // The ObjectProxy will be notified when the service is launched via
 639   // NameOwnerChanged signal. See also comments in ConnectToSignalInternal().
 640   service_name_owner_ =
 641       bus_->GetServiceOwnerAndBlock(service_name_, Bus::SUPPRESS_ERRORS);
 642 }
 643
 644 DBusHandlerResult ObjectProxy::HandleNameOwnerChanged(
 645     scoped_ptr<Signal> signal) {
 646   DCHECK(signal);
 647   bus_->AssertOnDBusThread();
 648
 649   // Confirm the validity of the NameOwnerChanged signal.
 650   if (signal->GetMember() == kNameOwnerChangedMember &&
 651       signal->GetInterface() == kDBusSystemObjectInterface &&
 652       signal->GetSender() == kDBusSystemObjectAddress) {
 653     MessageReader reader(signal.get());
 654     std::string name, old_owner, new_owner;
 655     if (reader.PopString(&name) &&
 656         reader.PopString(&old_owner) &&
 657         reader.PopString(&new_owner) &&
 658         name == service_name_) {
 659       service_name_owner_ = new_owner;
 660       bus_->GetOriginTaskRunner()->PostTask(
 661           FROM_HERE,
 662           base::Bind(&ObjectProxy::RunNameOwnerChangedCallback,
 663                      this, old_owner, new_owner));
 664
 665       const bool service_is_available = !service_name_owner_.empty();
 666       if (service_is_available) {
 667         bus_->GetOriginTaskRunner()->PostTask(
 668             FROM_HERE,
 669             base::Bind(&ObjectProxy::RunWaitForServiceToBeAvailableCallbacks,
 670                        this, service_is_available));
 671       }
 672     }
 673   }
 674
 675   // Always return unhandled to let other object proxies handle the same
 676   // signal.
 677   return DBUS_HANDLER_RESULT_NOT_YET_HANDLED;
 678 }
 679
 680 void ObjectProxy::RunNameOwnerChangedCallback(const std::string& old_owner,
 681                                               const std::string& new_owner) {
 682   bus_->AssertOnOriginThread();
 683   if (!name_owner_changed_callback_.is_null())
 684     name_owner_changed_callback_.Run(old_owner, new_owner);
 685 }
 686
 687 void ObjectProxy::RunWaitForServiceToBeAvailableCallbacks(
 688     bool service_is_available) {
 689   bus_->AssertOnOriginThread();
 690
 691   std::vector<WaitForServiceToBeAvailableCallback> callbacks;
 692   callbacks.swap(wait_for_service_to_be_available_callbacks_);
 693   for (size_t i = 0; i < callbacks.size(); ++i)
 694     callbacks[i].Run(service_is_available);
 695 }
 696
 697 }  // namespace dbus