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channel_posix.cc
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// Copyright 2016 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 "mojo/core/channel.h"
#include <errno.h>
#include <sys/socket.h>
#include <algorithm>
#include <limits>
#include <memory>
#include "base/bind.h"
#include "base/containers/queue.h"
#include "base/location.h"
#include "base/macros.h"
#include "base/memory/ref_counted.h"
#include "base/message_loop/message_loop_current.h"
#include "base/message_loop/message_pump_for_io.h"
#include "base/synchronization/lock.h"
#include "base/task_runner.h"
#include "build/build_config.h"
#include "mojo/core/core.h"
#include "mojo/public/cpp/platform/socket_utils_posix.h"
#if !defined(OS_NACL)
#include <sys/uio.h>
#endif
namespace mojo {
namespace core {
namespace {
const size_t kMaxBatchReadCapacity = 256 * 1024;
// A view over a Channel::Message object. The write queue uses these since
// large messages may need to be sent in chunks.
class MessageView {
public:
// Owns |message|. |offset| indexes the first unsent byte in the message.
MessageView(Channel::MessagePtr message, size_t offset)
: message_(std::move(message)),
offset_(offset),
handles_(message_->TakeHandles()) {
DCHECK(!message_->data_num_bytes() || message_->data_num_bytes() > offset_);
}
MessageView(MessageView&& other) { *this = std::move(other); }
MessageView& operator=(MessageView&& other) = default;
~MessageView() {}
const void* data() const {
return static_cast<const char*>(message_->data()) + offset_;
}
size_t data_num_bytes() const { return message_->data_num_bytes() - offset_; }
size_t data_offset() const { return offset_; }
void advance_data_offset(size_t num_bytes) {
if (num_bytes) {
DCHECK_GT(message_->data_num_bytes(), offset_ + num_bytes);
offset_ += num_bytes;
}
}
std::vector<PlatformHandleInTransit> TakeHandles() {
return std::move(handles_);
}
Channel::MessagePtr TakeMessage() { return std::move(message_); }
void SetHandles(std::vector<PlatformHandleInTransit> handles) {
handles_ = std::move(handles);
}
size_t num_handles_sent() { return num_handles_sent_; }
void set_num_handles_sent(size_t num_handles_sent) {
num_handles_sent_ = num_handles_sent;
}
private:
Channel::MessagePtr message_;
size_t offset_;
std::vector<PlatformHandleInTransit> handles_;
size_t num_handles_sent_ = 0;
DISALLOW_COPY_AND_ASSIGN(MessageView);
};
class ChannelPosix : public Channel,
public base::MessageLoopCurrent::DestructionObserver,
public base::MessagePumpForIO::FdWatcher {
public:
ChannelPosix(Delegate* delegate,
ConnectionParams connection_params,
HandlePolicy handle_policy,
scoped_refptr<base::TaskRunner> io_task_runner)
: Channel(delegate, handle_policy),
self_(this),
io_task_runner_(io_task_runner) {
if (connection_params.server_endpoint().is_valid())
server_ = connection_params.TakeServerEndpoint();
else
socket_ = connection_params.TakeEndpoint().TakePlatformHandle().TakeFD();
CHECK(server_.is_valid() || socket_.is_valid());
}
void Start() override {
if (io_task_runner_->RunsTasksInCurrentSequence()) {
StartOnIOThread();
} else {
io_task_runner_->PostTask(
FROM_HERE, base::BindOnce(&ChannelPosix::StartOnIOThread, this));
}
}
void ShutDownImpl() override {
// Always shut down asynchronously when called through the public interface.
io_task_runner_->PostTask(
FROM_HERE, base::BindOnce(&ChannelPosix::ShutDownOnIOThread, this));
}
void Write(MessagePtr message) override {
bool write_error = false;
{
base::AutoLock lock(write_lock_);
if (reject_writes_)
return;
if (outgoing_messages_.empty()) {
if (!WriteNoLock(MessageView(std::move(message), 0)))
reject_writes_ = write_error = true;
} else {
outgoing_messages_.emplace_back(std::move(message), 0);
}
}
if (write_error) {
// Invoke OnWriteError() asynchronously on the IO thread, in case Write()
// was called by the delegate, in which case we should not re-enter it.
io_task_runner_->PostTask(
FROM_HERE, base::BindOnce(&ChannelPosix::OnWriteError, this,
Error::kDisconnected));
}
}
void LeakHandle() override {
DCHECK(io_task_runner_->RunsTasksInCurrentSequence());
leak_handle_ = true;
}
bool GetReadPlatformHandles(const void* payload,
size_t payload_size,
size_t num_handles,
const void* extra_header,
size_t extra_header_size,
std::vector<PlatformHandle>* handles,
bool* deferred) override {
if (num_handles > std::numeric_limits<uint16_t>::max())
return false;
if (incoming_fds_.size() < num_handles)
return true;
handles->resize(num_handles);
for (size_t i = 0; i < num_handles; ++i) {
handles->at(i) = PlatformHandle(std::move(incoming_fds_.front()));
incoming_fds_.pop_front();
}
return true;
}
private:
~ChannelPosix() override {
DCHECK(!read_watcher_);
DCHECK(!write_watcher_);
}
void StartOnIOThread() {
DCHECK(!read_watcher_);
DCHECK(!write_watcher_);
read_watcher_.reset(
new base::MessagePumpForIO::FdWatchController(FROM_HERE));
base::MessageLoopCurrent::Get()->AddDestructionObserver(this);
if (server_.is_valid()) {
base::MessageLoopCurrentForIO::Get()->WatchFileDescriptor(
server_.platform_handle().GetFD().get(), false /* persistent */,
base::MessagePumpForIO::WATCH_READ, read_watcher_.get(), this);
} else {
write_watcher_.reset(
new base::MessagePumpForIO::FdWatchController(FROM_HERE));
base::MessageLoopCurrentForIO::Get()->WatchFileDescriptor(
socket_.get(), true /* persistent */,
base::MessagePumpForIO::WATCH_READ, read_watcher_.get(), this);
base::AutoLock lock(write_lock_);
FlushOutgoingMessagesNoLock();
}
}
void WaitForWriteOnIOThread() {
base::AutoLock lock(write_lock_);
WaitForWriteOnIOThreadNoLock();
}
void WaitForWriteOnIOThreadNoLock() {
if (pending_write_)
return;
if (!write_watcher_)
return;
if (io_task_runner_->RunsTasksInCurrentSequence()) {
pending_write_ = true;
base::MessageLoopCurrentForIO::Get()->WatchFileDescriptor(
socket_.get(), false /* persistent */,
base::MessagePumpForIO::WATCH_WRITE, write_watcher_.get(), this);
} else {
io_task_runner_->PostTask(
FROM_HERE,
base::BindOnce(&ChannelPosix::WaitForWriteOnIOThread, this));
}
}
void ShutDownOnIOThread() {
base::MessageLoopCurrent::Get()->RemoveDestructionObserver(this);
read_watcher_.reset();
write_watcher_.reset();
if (leak_handle_) {
ignore_result(socket_.release());
server_.TakePlatformHandle().release();
} else {
socket_.reset();
ignore_result(server_.TakePlatformHandle());
}
#if defined(OS_IOS)
fds_to_close_.clear();
#endif
// May destroy the |this| if it was the last reference.
self_ = nullptr;
}
// base::MessageLoopCurrent::DestructionObserver:
void WillDestroyCurrentMessageLoop() override {
DCHECK(io_task_runner_->RunsTasksInCurrentSequence());
if (self_)
ShutDownOnIOThread();
}
// base::MessagePumpForIO::FdWatcher:
void OnFileCanReadWithoutBlocking(int fd) override {
if (server_.is_valid()) {
CHECK_EQ(fd, server_.platform_handle().GetFD().get());
#if !defined(OS_NACL)
read_watcher_.reset();
base::MessageLoopCurrent::Get()->RemoveDestructionObserver(this);
AcceptSocketConnection(server_.platform_handle().GetFD().get(), &socket_);
ignore_result(server_.TakePlatformHandle());
if (!socket_.is_valid()) {
OnError(Error::kConnectionFailed);
return;
}
StartOnIOThread();
#else
NOTREACHED();
#endif
return;
}
CHECK_EQ(fd, socket_.get());
bool validation_error = false;
bool read_error = false;
size_t next_read_size = 0;
size_t buffer_capacity = 0;
size_t total_bytes_read = 0;
size_t bytes_read = 0;
do {
buffer_capacity = next_read_size;
char* buffer = GetReadBuffer(&buffer_capacity);
DCHECK_GT(buffer_capacity, 0u);
std::vector<base::ScopedFD> incoming_fds;
ssize_t read_result =
SocketRecvmsg(socket_.get(), buffer, buffer_capacity, &incoming_fds);
for (auto& incoming_fd : incoming_fds)
incoming_fds_.emplace_back(std::move(incoming_fd));
if (read_result > 0) {
bytes_read = static_cast<size_t>(read_result);
total_bytes_read += bytes_read;
if (!OnReadComplete(bytes_read, &next_read_size)) {
read_error = true;
validation_error = true;
break;
}
} else if (read_result == 0 ||
(errno != EAGAIN && errno != EWOULDBLOCK)) {
read_error = true;
break;
} else {
// We expect more data but there is none to read. The
// FileDescriptorWatcher will wake us up again once there is.
DCHECK(errno == EAGAIN || errno == EWOULDBLOCK);
return;
}
} while (bytes_read == buffer_capacity &&
total_bytes_read < kMaxBatchReadCapacity && next_read_size > 0);
if (read_error) {
// Stop receiving read notifications.
read_watcher_.reset();
if (validation_error)
OnError(Error::kReceivedMalformedData);
else
OnError(Error::kDisconnected);
}
}
void OnFileCanWriteWithoutBlocking(int fd) override {
bool write_error = false;
{
base::AutoLock lock(write_lock_);
pending_write_ = false;
if (!FlushOutgoingMessagesNoLock())
reject_writes_ = write_error = true;
}
if (write_error)
OnWriteError(Error::kDisconnected);
}
// Attempts to write a message directly to the channel. If the full message
// cannot be written, it's queued and a wait is initiated to write the message
// ASAP on the I/O thread.
bool WriteNoLock(MessageView message_view) {
if (server_.is_valid()) {
outgoing_messages_.emplace_front(std::move(message_view));
return true;
}
size_t bytes_written = 0;
std::vector<PlatformHandleInTransit> handles = message_view.TakeHandles();
size_t num_handles = handles.size();
size_t handles_written = message_view.num_handles_sent();
do {
message_view.advance_data_offset(bytes_written);
ssize_t result;
if (handles_written < num_handles) {
iovec iov = {const_cast<void*>(message_view.data()),
message_view.data_num_bytes()};
size_t num_handles_to_send =
std::min(num_handles - handles_written, kMaxSendmsgHandles);
std::vector<base::ScopedFD> fds(num_handles_to_send);
for (size_t i = 0; i < num_handles_to_send; ++i)
fds[i] = handles[i + handles_written].TakeHandle().TakeFD();
// TODO: Handle lots of handles.
result = SendmsgWithHandles(socket_.get(), &iov, 1, fds);
if (result >= 0) {
#if defined(OS_IOS)
// There is a bug in XNU which makes it dangerous to close
// a file descriptor while it is in transit. So instead we
// store the file descriptor in a set and send a message to
// the recipient, which is queued AFTER the message that
// sent the FD. The recipient will reply to the message,
// letting us know that it is now safe to close the file
// descriptor. For more information, see:
// http://crbug.com/298276
MessagePtr fds_message(new Channel::Message(
sizeof(int) * fds.size(), 0, Message::MessageType::HANDLES_SENT));
int* fd_data = reinterpret_cast<int*>(fds_message->mutable_payload());
for (size_t i = 0; i < fds.size(); ++i)
fd_data[i] = fds[i].get();
outgoing_messages_.emplace_back(std::move(fds_message), 0);
{
base::AutoLock l(fds_to_close_lock_);
for (auto& fd : fds)
fds_to_close_.emplace_back(std::move(fd));
}
#endif // defined(OS_IOS)
handles_written += num_handles_to_send;
DCHECK_LE(handles_written, num_handles);
message_view.set_num_handles_sent(handles_written);
} else {
// Message transmission failed, so pull the FDs back into |handles|
// so they can be held by the Message again.
for (size_t i = 0; i < fds.size(); ++i) {
handles[i + handles_written] =
PlatformHandleInTransit(PlatformHandle(std::move(fds[i])));
}
}
} else {
result = SocketWrite(socket_.get(), message_view.data(),
message_view.data_num_bytes());
}
if (result < 0) {
if (errno != EAGAIN &&
errno != EWOULDBLOCK
#if defined(OS_IOS)
// On iOS if sendmsg() is trying to send fds between processes and
// there isn't enough room in the output buffer to send the fd
// structure over atomically then EMSGSIZE is returned.
//
// EMSGSIZE presents a problem since the system APIs can only call
// us when there's room in the socket buffer and not when there is
// "enough" room.
//
// The current behavior is to return to the event loop when EMSGSIZE
// is received and hopefull service another FD. This is however
// still technically a busy wait since the event loop will call us
// right back until the receiver has read enough data to allow
// passing the FD over atomically.
&& errno != EMSGSIZE
#endif
) {
return false;
}
message_view.SetHandles(std::move(handles));
outgoing_messages_.emplace_front(std::move(message_view));
WaitForWriteOnIOThreadNoLock();
return true;
}
bytes_written = static_cast<size_t>(result);
} while (handles_written < num_handles ||
bytes_written < message_view.data_num_bytes());
return FlushOutgoingMessagesNoLock();
}
bool FlushOutgoingMessagesNoLock() {
base::circular_deque<MessageView> messages;
std::swap(outgoing_messages_, messages);
while (!messages.empty()) {
if (!WriteNoLock(std::move(messages.front())))
return false;
messages.pop_front();
if (!outgoing_messages_.empty()) {
// The message was requeued by WriteNoLock(), so we have to wait for
// pipe to become writable again. Repopulate the message queue and exit.
// If sending the message triggered any control messages, they may be
// in |outgoing_messages_| in addition to or instead of the message
// being sent.
std::swap(messages, outgoing_messages_);
while (!messages.empty()) {
outgoing_messages_.push_front(std::move(messages.back()));
messages.pop_back();
}
return true;
}
}
return true;
}
#if defined(OS_IOS)
bool OnControlMessage(Message::MessageType message_type,
const void* payload,
size_t payload_size,
std::vector<PlatformHandle> handles) override {
switch (message_type) {
case Message::MessageType::HANDLES_SENT: {
if (payload_size == 0)
break;
MessagePtr message(new Channel::Message(
payload_size, 0, Message::MessageType::HANDLES_SENT_ACK));
memcpy(message->mutable_payload(), payload, payload_size);
Write(std::move(message));
return true;
}
case Message::MessageType::HANDLES_SENT_ACK: {
size_t num_fds = payload_size / sizeof(int);
if (num_fds == 0 || payload_size % sizeof(int) != 0)
break;
const int* fds = reinterpret_cast<const int*>(payload);
if (!CloseHandles(fds, num_fds))
break;
return true;
}
default:
break;
}
return false;
}
// Closes handles referenced by |fds|. Returns false if |num_fds| is 0, or if
// |fds| does not match a sequence of handles in |fds_to_close_|.
bool CloseHandles(const int* fds, size_t num_fds) {
base::AutoLock l(fds_to_close_lock_);
if (!num_fds)
return false;
auto start = std::find_if(
fds_to_close_.begin(), fds_to_close_.end(),
[&fds](const base::ScopedFD& fd) { return fd.get() == fds[0]; });
if (start == fds_to_close_.end())
return false;
auto it = start;
size_t i = 0;
// The FDs in the message should match a sequence of handles in
// |fds_to_close_|.
// TODO(wez): Consider making |fds_to_close_| a circular_deque<>
// for greater efficiency? Or assign a unique Id to each FD-containing
// message, and map that to a vector of FDs to close, to avoid the
// need for this traversal? Id could even be the first FD in the message.
for (; i < num_fds && it != fds_to_close_.end(); i++, ++it) {
if (it->get() != fds[i])
return false;
}
if (i != num_fds)
return false;
// Close the FDs by erase()ing their ScopedFDs.
fds_to_close_.erase(start, it);
return true;
}
#endif // defined(OS_IOS)
void OnWriteError(Error error) {
DCHECK(io_task_runner_->RunsTasksInCurrentSequence());
DCHECK(reject_writes_);
if (error == Error::kDisconnected) {
// If we can't write because the pipe is disconnected then continue
// reading to fetch any in-flight messages, relying on end-of-stream to
// signal the actual disconnection.
if (read_watcher_) {
write_watcher_.reset();
return;
}
}
OnError(error);
}
// Keeps the Channel alive at least until explicit shutdown on the IO thread.
scoped_refptr<Channel> self_;
// We may be initialized with a server socket, in which case this will be
// valid until it accepts an incoming connection.
PlatformChannelServerEndpoint server_;
// The socket over which to communicate. May be passed in at construction time
// or accepted over |server_|.
base::ScopedFD socket_;
scoped_refptr<base::TaskRunner> io_task_runner_;
// These watchers must only be accessed on the IO thread.
std::unique_ptr<base::MessagePumpForIO::FdWatchController> read_watcher_;
std::unique_ptr<base::MessagePumpForIO::FdWatchController> write_watcher_;
base::circular_deque<base::ScopedFD> incoming_fds_;
// Protects |pending_write_| and |outgoing_messages_|.
base::Lock write_lock_;
bool pending_write_ = false;
bool reject_writes_ = false;
base::circular_deque<MessageView> outgoing_messages_;
bool leak_handle_ = false;
#if defined(OS_IOS)
base::Lock fds_to_close_lock_;
std::vector<base::ScopedFD> fds_to_close_;
#endif // defined(OS_IOS)
DISALLOW_COPY_AND_ASSIGN(ChannelPosix);
};
} // namespace
// static
scoped_refptr<Channel> Channel::Create(
Delegate* delegate,
ConnectionParams connection_params,
HandlePolicy handle_policy,
scoped_refptr<base::TaskRunner> io_task_runner) {
return new ChannelPosix(delegate, std::move(connection_params), handle_policy,
io_task_runner);
}
} // namespace core
} // namespace mojo