mojo/edk/system/broker_posix.cc

// 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/edk/system/broker.h"

#include <fcntl.h>
#include <unistd.h>

#include <utility>

#include "base/logging.h"
#include "mojo/edk/embedder/embedder_internal.h"
#include "mojo/edk/embedder/platform_channel_utils_posix.h"
#include "mojo/edk/embedder/platform_handle_utils.h"
#include "mojo/edk/embedder/platform_shared_buffer.h"
#include "mojo/edk/embedder/scoped_platform_handle.h"
#include "mojo/edk/system/broker_messages.h"
#include "mojo/edk/system/channel.h"

namespace mojo {
namespace edk {

namespace {

Channel::MessagePtr WaitForBrokerMessage(
    const ScopedPlatformHandle& platform_handle,
    BrokerMessageType expected_type,
    size_t expected_num_handles,
    size_t expected_data_size,
    std::vector<ScopedPlatformHandle>* incoming_handles) {
  Channel::MessagePtr message(new Channel::Message(
      sizeof(BrokerMessageHeader) + expected_data_size, expected_num_handles));
  base::circular_deque<ScopedPlatformHandle> incoming_platform_handles;
  ssize_t read_result = PlatformChannelRecvmsg(
      platform_handle, const_cast<void*>(message->data()),
      message->data_num_bytes(), &incoming_platform_handles, true /* block */);
  bool error = false;
  if (read_result < 0) {
    PLOG(ERROR) << "Recvmsg error";
    error = true;
  } else if (static_cast<size_t>(read_result) != message->data_num_bytes()) {
    LOG(ERROR) << "Invalid node channel message";
    error = true;
  } else if (incoming_platform_handles.size() != expected_num_handles) {
    LOG(ERROR) << "Received unexpected number of handles";
    error = true;
  }

  if (error)
    return nullptr;

  const BrokerMessageHeader* header =
      reinterpret_cast<const BrokerMessageHeader*>(message->payload());
  if (header->type != expected_type) {
    LOG(ERROR) << "Unexpected message";
    return nullptr;
  }

  incoming_handles->resize(incoming_platform_handles.size());
  std::move(incoming_platform_handles.begin(), incoming_platform_handles.end(),
            incoming_handles->begin());

  return message;
}

}  // namespace

Broker::Broker(ScopedPlatformHandle platform_handle)
    : sync_channel_(std::move(platform_handle)) {
  CHECK(sync_channel_.is_valid());

  // Mark the channel as blocking.
  int flags = fcntl(sync_channel_.get().handle, F_GETFL);
  PCHECK(flags != -1);
  flags = fcntl(sync_channel_.get().handle, F_SETFL, flags & ~O_NONBLOCK);
  PCHECK(flags != -1);

  // Wait for the first message, which should contain a handle.
  std::vector<ScopedPlatformHandle> incoming_platform_handles;
  if (WaitForBrokerMessage(sync_channel_, BrokerMessageType::INIT, 1, 0,
                           &incoming_platform_handles)) {
    parent_channel_ = std::move(incoming_platform_handles[0]);
  }
}

Broker::~Broker() = default;

ScopedPlatformHandle Broker::GetParentPlatformHandle() {
  return std::move(parent_channel_);
}

scoped_refptr<PlatformSharedBuffer> Broker::GetSharedBuffer(size_t num_bytes) {
  base::AutoLock lock(lock_);

  BufferRequestData* buffer_request;
  Channel::MessagePtr out_message = CreateBrokerMessage(
      BrokerMessageType::BUFFER_REQUEST, 0, 0, &buffer_request);
  buffer_request->size = num_bytes;
  ssize_t write_result = PlatformChannelWrite(
      sync_channel_, out_message->data(), out_message->data_num_bytes());
  if (write_result < 0) {
    PLOG(ERROR) << "Error sending sync broker message";
    return nullptr;
  } else if (static_cast<size_t>(write_result) !=
             out_message->data_num_bytes()) {
    LOG(ERROR) << "Error sending complete broker message";
    return nullptr;
  }

  std::vector<ScopedPlatformHandle> incoming_platform_handles;
  Channel::MessagePtr message = WaitForBrokerMessage(
      sync_channel_, BrokerMessageType::BUFFER_RESPONSE, 2,
      sizeof(BufferResponseData), &incoming_platform_handles);
  if (message) {
    const BufferResponseData* data;
    if (!GetBrokerMessageData(message.get(), &data))
      return nullptr;
    base::UnguessableToken guid =
        base::UnguessableToken::Deserialize(data->guid_high, data->guid_low);
    return PlatformSharedBuffer::CreateFromPlatformHandlePair(
        num_bytes, guid, std::move(incoming_platform_handles[0]),
        std::move(incoming_platform_handles[1]));
  }

  return nullptr;
}

}  // namespace edk
}  // namespace mojo