blob: c2cf962e87d3d1977826787087f49a6334d5eb41 [file] [log] [blame]
// Copyright 2013 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include <atomic>
#include <memory>
#include <utility>
#include "base/callback.h"
#include "base/compiler_specific.h"
#include "base/component_export.h"
#include "base/containers/queue.h"
#include "base/memory/ref_counted.h"
#include "base/memory/weak_ptr.h"
#include "base/optional.h"
#include "base/sequence_checker.h"
#include "base/sequenced_task_runner.h"
#include "mojo/public/cpp/bindings/connection_group.h"
#include "mojo/public/cpp/bindings/message.h"
#include "mojo/public/cpp/bindings/sequence_local_sync_event_watcher.h"
#include "mojo/public/cpp/bindings/sync_handle_watcher.h"
#include "mojo/public/cpp/system/core.h"
#include "mojo/public/cpp/system/handle_signal_tracker.h"
#include "mojo/public/cpp/system/simple_watcher.h"
namespace base {
class Lock;
namespace mojo {
// The Connector class is responsible for performing read/write operations on a
// MessagePipe. It writes messages it receives through the MessageReceiver
// interface that it subclasses, and it forwards messages it reads through the
// MessageReceiver interface assigned as its incoming receiver.
// NOTE:
// - MessagePipe I/O is non-blocking.
// - Sending messages can be configured to be thread safe (please see comments
// of the constructor). Other than that, the object should only be accessed
// on the creating sequence.
class COMPONENT_EXPORT(MOJO_CPP_BINDINGS) Connector : public MessageReceiver {
enum ConnectorConfig {
// Connector::Accept() is only called from a single sequence.
// Connector::Accept() is allowed to be called from multiple sequences.
// Determines how this Connector should behave with respect to serialization
// of outgoing messages.
enum class OutgoingSerializationMode {
// Lazy serialization. The Connector prefers to transmit serialized messages
// only when it knows its peer endpoint is remote. This ensures outgoing
// requests are unserialized by default (when possible, i.e. when generated
// bindings support it) and serialized only if and when necessary.
// Eager serialization. The Connector always prefers serialized messages,
// ensuring that interface calls will be serialized immediately before
// sending on the Connector.
// Determines how this Connector should behave with respect to serialization
// of incoming messages.
enum class IncomingSerializationMode {
// Accepts and dispatches either serialized or unserialized messages. This
// is the only mode that should be used in production.
// Accepts either serialized or unserialized messages, but always forces
// serialization (if applicable) before dispatch. Should be used only in
// test environments to coerce the lazy serialization of a message after
// transmission.
// The Connector takes ownership of |message_pipe|.
Connector(ScopedMessagePipeHandle message_pipe,
ConnectorConfig config,
scoped_refptr<base::SequencedTaskRunner> runner);
~Connector() override;
// Sets outgoing serialization mode.
void SetOutgoingSerializationMode(OutgoingSerializationMode mode);
void SetIncomingSerializationMode(IncomingSerializationMode mode);
// Sets the receiver to handle messages read from the message pipe. The
// Connector will read messages from the pipe regardless of whether or not an
// incoming receiver has been set.
void set_incoming_receiver(MessageReceiver* receiver) {
incoming_receiver_ = receiver;
// Errors from incoming receivers will force the connector into an error
// state, where no more messages will be processed. This method is used
// during testing to prevent that from happening.
void set_enforce_errors_from_incoming_receiver(bool enforce) {
enforce_errors_from_incoming_receiver_ = enforce;
// If set to |true|, this Connector will always dispatch messages to its
// receiver as soon as they're read off the pipe, rather than scheduling
// individual dispatch tasks for each message.
void set_force_immediate_dispatch(bool force) {
force_immediate_dispatch_ = force;
// Sets the error handler to receive notifications when an error is
// encountered while reading from the pipe or waiting to read from the pipe.
void set_connection_error_handler(base::OnceClosure error_handler) {
connection_error_handler_ = std::move(error_handler);
// Returns true if an error was encountered while reading from the pipe or
// waiting to read from the pipe.
bool encountered_error() const {
return error_;
// Closes the pipe. The connector is put into a quiescent state.
// Please note that this method shouldn't be called unless it results from an
// explicit request of the user of bindings (e.g., the user sets an
// InterfacePtr to null or closes a Binding).
void CloseMessagePipe();
// Releases the pipe. Connector is put into a quiescent state.
ScopedMessagePipeHandle PassMessagePipe();
// Enters the error state. The upper layer may do this for unrecoverable
// issues such as invalid messages are received. If a connection error handler
// has been set, it will be called asynchronously.
// It is a no-op if the connector is already in the error state or there isn't
// a bound message pipe. Otherwise, it closes the message pipe, which notifies
// the other end and also prevents potential danger (say, the caller raises
// an error because it believes the other end is malicious). In order to
// appear to the user that the connector still binds to a message pipe, it
// creates a new message pipe, closes one end and binds to the other.
void RaiseError();
// Is the connector bound to a MessagePipe handle?
bool is_valid() const {
return message_pipe_.is_valid();
// Adds this object to a ConnectionGroup identified by |ref|. All receiving
// pipe endpoints decoded from inbound messages on this MultiplexRouter will
// be added to the same group.
void SetConnectionGroup(ConnectionGroup::Ref ref);
// Waits for the next message on the pipe, blocking until one arrives,
// |deadline| elapses, or an error happens. Returns |true| if a message has
// been delivered, |false| otherwise.
bool WaitForIncomingMessage(MojoDeadline deadline);
// See Binding for details of pause/resume.
void PauseIncomingMethodCallProcessing();
void ResumeIncomingMethodCallProcessing();
// MessageReceiver implementation:
bool PrefersSerializedMessages() override;
bool Accept(Message* message) override;
MessagePipeHandle handle() const {
return message_pipe_.get();
// Allows |message_pipe_| to be watched while others perform sync handle
// watching on the same sequence. Please see comments of
// SyncHandleWatcher::AllowWokenUpBySyncWatchOnSameThread().
void AllowWokenUpBySyncWatchOnSameThread();
// Whether currently the control flow is inside the sync handle watcher
// callback.
// It always returns false after CloseMessagePipe()/PassMessagePipe().
bool during_sync_handle_watcher_callback() const {
return sync_handle_watcher_callback_count_ > 0;
base::SequencedTaskRunner* task_runner() const { return task_runner_.get(); }
// Sets the tag used by the heap profiler.
// |tag| must be a const string literal.
void SetWatcherHeapProfilerTag(const char* tag);
// Allows testing environments to override the default serialization behavior
// of newly constructed Connector instances. Must be called before any
// Connector instances are constructed.
static void OverrideDefaultSerializationBehaviorForTesting(
OutgoingSerializationMode outgoing_mode,
IncomingSerializationMode incoming_mode);
class ActiveDispatchTracker;
class RunLoopNestingObserver;
// Callback of mojo::SimpleWatcher.
void OnWatcherHandleReady(MojoResult result);
// Callback of SyncHandleWatcher.
void OnSyncHandleWatcherHandleReady(MojoResult result);
void OnHandleReadyInternal(MojoResult result);
void WaitToReadMore();
// Attempts to read a single Message from the pipe. Returns |MOJO_RESULT_OK|
// and a valid message in |*message| iff a message was successfully read and
// prepared for dispatch.
MojoResult ReadMessage(Message* message);
// Dispatches |message| to the receiver. Returns |true| if the message was
// accepted by the receiver, and |false| otherwise (e.g. if it failed
// validation).
bool DispatchMessage(Message message);
// Used to schedule dispatch of a single message from the front of
// |dispatch_queue_|. Returns |true| if the dispatch succeeded and |false|
// otherwise (e.g. if the message failed validation).
bool DispatchNextMessageInQueue();
// Dispatches all queued messages to the receiver immediately. This is
// necessary to ensure proper ordering when beginning to wait for a sync
// response, because new incoming messages need to be dispatched as they
// arrive. Returns |true| if all queued messages were successfully dispatched,
// and |false| if any dispatch fails.
bool DispatchAllQueuedMessages();
// Reads all available messages off of the pipe, possibly dispatching one or
// more of them depending on the state of the Connector when this is called.
void ReadAllAvailableMessages();
// If |force_pipe_reset| is true, this method replaces the existing
// |message_pipe_| with a dummy message pipe handle (whose peer is closed).
// If |force_async_handler| is true, |connection_error_handler_| is called
// asynchronously.
void HandleError(bool force_pipe_reset, bool force_async_handler);
// Cancels any calls made to |waiter_|.
void CancelWait();
void EnsureSyncWatcherExists();
// Indicates whether this Connector should immediately dispatch any message
// it reads off the pipe, rather than queuing and/or scheduling an
// asynchronous dispatch operation per message.
bool should_dispatch_messages_immediately() const {
return force_immediate_dispatch_ || during_sync_handle_watcher_callback();
base::OnceClosure connection_error_handler_;
ScopedMessagePipeHandle message_pipe_;
MessageReceiver* incoming_receiver_ = nullptr;
scoped_refptr<base::SequencedTaskRunner> task_runner_;
std::unique_ptr<SimpleWatcher> handle_watcher_;
base::Optional<HandleSignalTracker> peer_remoteness_tracker_;
std::atomic<bool> error_;
bool drop_writes_ = false;
bool enforce_errors_from_incoming_receiver_ = true;
bool paused_ = false;
// See |set_force_immediate_dispatch()|.
bool force_immediate_dispatch_;
// Messages which have been read off the pipe but not yet dispatched. This
// exists so that we can schedule individual dispatch tasks for each read
// message in parallel rather than having to do it in series as each message
// is read off the pipe.
base::queue<Message> dispatch_queue_;
// Indicates whether a non-fatal pipe error (i.e. peer closure and no more
// incoming messages) was detected while |dispatch_queue_| was non-empty.
// When |true|, ensures that an error will be propagated outward as soon as
// |dispatch_queue_| is fully flushed.
bool pending_error_dispatch_ = false;
OutgoingSerializationMode outgoing_serialization_mode_;
IncomingSerializationMode incoming_serialization_mode_;
// If sending messages is allowed from multiple sequences, |lock_| is used to
// protect modifications to |message_pipe_| and |drop_writes_|.
base::Optional<base::Lock> lock_;
std::unique_ptr<SyncHandleWatcher> sync_watcher_;
std::unique_ptr<SequenceLocalSyncEventWatcher> dispatch_queue_watcher_;
bool allow_woken_up_by_others_ = false;
// If non-zero, currently the control flow is inside the sync handle watcher
// callback.
size_t sync_handle_watcher_callback_count_ = 0;
base::Lock connected_lock_;
bool connected_ = true;
// The tag used to track heap allocations that originated from a Watcher
// notification.
const char* heap_profiler_tag_ = "unknown interface";
// A cached pointer to the RunLoopNestingObserver for the thread on which this
// Connector was created.
RunLoopNestingObserver* const nesting_observer_;
// |true| iff the Connector is currently dispatching a message. Used to detect
// nested dispatch operations.
bool is_dispatching_ = false;
#if defined(ENABLE_IPC_FUZZER)
std::unique_ptr<MessageReceiver> message_dumper_;
// A reference to the ConnectionGroup to which this Connector belongs, if any.
ConnectionGroup::Ref connection_group_;
// Create a single weak ptr and use it everywhere, to avoid the malloc/free
// cost of creating a new weak ptr whenever it is needed.
// NOTE: This weak pointer is invalidated when the message pipe is closed or
// transferred (i.e., when |connected_| is set to false).
base::WeakPtr<Connector> weak_self_;
base::WeakPtrFactory<Connector> weak_factory_{this};
} // namespace mojo