ipc/ipc_channel_reader.cc

// Copyright (c) 2012 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 "ipc/ipc_channel_reader.h"

#include <stddef.h>

#include <algorithm>

#include "base/message_loop/message_loop.h"
#include "ipc/ipc_listener.h"
#include "ipc/ipc_logging.h"
#include "ipc/ipc_message.h"
#include "ipc/ipc_message_attachment_set.h"
#include "ipc/ipc_message_macros.h"

namespace IPC {
namespace internal {

ChannelReader::ChannelReader(Listener* listener)
  : listener_(listener),
    max_input_buffer_size_(Channel::kMaximumReadBufferSize) {
  memset(input_buf_, 0, sizeof(input_buf_));
}

ChannelReader::~ChannelReader() {
  DCHECK(blocked_ids_.empty());
}

ChannelReader::DispatchState ChannelReader::ProcessIncomingMessages() {
  while (true) {
    int bytes_read = 0;
    ReadState read_state = ReadData(input_buf_, Channel::kReadBufferSize,
                                    &bytes_read);
    if (read_state == READ_FAILED)
      return DISPATCH_ERROR;
    if (read_state == READ_PENDING)
      return DISPATCH_FINISHED;

    DCHECK(bytes_read > 0);
    if (!TranslateInputData(input_buf_, bytes_read))
      return DISPATCH_ERROR;

    DispatchState state = DispatchMessages();
    if (state != DISPATCH_FINISHED)
      return state;
  }
}

ChannelReader::DispatchState ChannelReader::AsyncReadComplete(int bytes_read) {
  if (!TranslateInputData(input_buf_, bytes_read))
    return DISPATCH_ERROR;

  return DispatchMessages();
}

bool ChannelReader::IsInternalMessage(const Message& m) {
  return m.routing_id() == MSG_ROUTING_NONE &&
      m.type() >= Channel::CLOSE_FD_MESSAGE_TYPE &&
      m.type() <= Channel::HELLO_MESSAGE_TYPE;
}

bool ChannelReader::IsHelloMessage(const Message& m) {
  return m.routing_id() == MSG_ROUTING_NONE &&
      m.type() == Channel::HELLO_MESSAGE_TYPE;
}

void ChannelReader::CleanUp() {
  if (!blocked_ids_.empty()) {
    StopObservingAttachmentBroker();
    blocked_ids_.clear();
  }
}

void ChannelReader::DispatchMessage(Message* m) {
  EmitLogBeforeDispatch(*m);
  listener_->OnMessageReceived(*m);
  HandleDispatchError(*m);
}

bool ChannelReader::TranslateInputData(const char* input_data,
                                       int input_data_len) {
  const char* p;
  const char* end;

  // Possibly combine with the overflow buffer to make a larger buffer.
  if (input_overflow_buf_.empty()) {
    p = input_data;
    end = input_data + input_data_len;
  } else {
    if (!CheckMessageSize(input_overflow_buf_.size() + input_data_len))
      return false;
    input_overflow_buf_.append(input_data, input_data_len);
    p = input_overflow_buf_.data();
    end = p + input_overflow_buf_.size();
  }

  size_t next_message_size = 0;

  // Dispatch all complete messages in the data buffer.
  while (p < end) {
    Message::NextMessageInfo info;
    Message::FindNext(p, end, &info);
    if (info.message_found) {
      int pickle_len = static_cast<int>(info.pickle_end - p);
      Message translated_message(p, pickle_len);

      if (!HandleTranslatedMessage(&translated_message, info.attachment_ids))
        return false;

      p = info.message_end;
    } else {
      // Last message is partial.
      next_message_size = info.message_size;
      if (!CheckMessageSize(next_message_size))
        return false;
      break;
    }
  }

  // Account for the case where last message's byte is in the next data chunk.
  size_t next_message_buffer_size = next_message_size ?
      next_message_size + Channel::kReadBufferSize - 1:
      0;

  // Save any partial data in the overflow buffer.
  if (p != input_overflow_buf_.data())
    input_overflow_buf_.assign(p, end - p);

  if (!input_overflow_buf_.empty()) {
    // We have something in the overflow buffer, which means that we will
    // append the next data chunk (instead of parsing it directly). So we
    // resize the buffer to fit the next message, to avoid repeatedly
    // growing the buffer as we receive all message' data chunks.
    if (next_message_buffer_size > input_overflow_buf_.capacity()) {
      input_overflow_buf_.reserve(next_message_buffer_size);
    }
  }

  // Trim the buffer if we can
  if (next_message_buffer_size < max_input_buffer_size_ &&
      input_overflow_buf_.size() < max_input_buffer_size_ &&
      input_overflow_buf_.capacity() > max_input_buffer_size_) {
    // std::string doesn't really have a method to shrink capacity to
    // a specific value, so we have to swap with another string.
    std::string trimmed_buf;
    trimmed_buf.reserve(max_input_buffer_size_);
    if (trimmed_buf.capacity() > max_input_buffer_size_) {
      // Since we don't control how much space reserve() actually reserves,
      // we have to go other way around and change the max size to avoid
      // getting into the outer if() again.
      max_input_buffer_size_ = trimmed_buf.capacity();
    }
    trimmed_buf.assign(input_overflow_buf_.data(),
                       input_overflow_buf_.size());
    input_overflow_buf_.swap(trimmed_buf);
  }

  if (input_overflow_buf_.empty() && !DidEmptyInputBuffers())
    return false;
  return true;
}

bool ChannelReader::HandleTranslatedMessage(
    Message* translated_message,
    const AttachmentIdVector& attachment_ids) {
  // Immediately handle internal messages.
  if (IsInternalMessage(*translated_message)) {
    EmitLogBeforeDispatch(*translated_message);
    HandleInternalMessage(*translated_message);
    HandleDispatchError(*translated_message);
    return true;
  }

  translated_message->set_sender_pid(GetSenderPID());

  // Immediately handle attachment broker messages.
  if (DispatchAttachmentBrokerMessage(*translated_message)) {
    // Ideally, the log would have been emitted prior to dispatching the
    // message, but that would require this class to know more about the
    // internals of attachment brokering, which should be avoided.
    EmitLogBeforeDispatch(*translated_message);
    HandleDispatchError(*translated_message);
    return true;
  }

  return HandleExternalMessage(translated_message, attachment_ids);
}

bool ChannelReader::HandleExternalMessage(
    Message* external_message,
    const AttachmentIdVector& attachment_ids) {
  for (const auto& id : attachment_ids)
    external_message->AddPlaceholderBrokerableAttachmentWithId(id);

  if (!GetNonBrokeredAttachments(external_message))
    return false;

  // If there are no queued messages, attempt to immediately dispatch the
  // newly translated message.
  if (queued_messages_.empty()) {
    DCHECK(blocked_ids_.empty());
    AttachmentIdSet blocked_ids = GetBrokeredAttachments(external_message);

    if (blocked_ids.empty()) {
      DispatchMessage(external_message);
      return true;
    }

    blocked_ids_.swap(blocked_ids);
    StartObservingAttachmentBroker();
  }

  // Make a deep copy of |external_message| to add to the queue.
  scoped_ptr<Message> m(new Message(*external_message));
  queued_messages_.push_back(m.release());
  return true;
}

void ChannelReader::HandleDispatchError(const Message& message) {
  if (message.dispatch_error())
    listener_->OnBadMessageReceived(message);
}

void ChannelReader::EmitLogBeforeDispatch(const Message& message) {
#ifdef IPC_MESSAGE_LOG_ENABLED
  std::string name;
  Logging::GetInstance()->GetMessageText(message.type(), &name, &message, NULL);
  TRACE_EVENT_WITH_FLOW1("ipc,toplevel", "ChannelReader::DispatchInputData",
                         message.flags(), TRACE_EVENT_FLAG_FLOW_IN, "name",
                         name);
#else
  TRACE_EVENT_WITH_FLOW2("ipc,toplevel", "ChannelReader::DispatchInputData",
                         message.flags(), TRACE_EVENT_FLAG_FLOW_IN, "class",
                         IPC_MESSAGE_ID_CLASS(message.type()), "line",
                         IPC_MESSAGE_ID_LINE(message.type()));
#endif
}

bool ChannelReader::DispatchAttachmentBrokerMessage(const Message& message) {
#if USE_ATTACHMENT_BROKER
  if (IsAttachmentBrokerEndpoint() && GetAttachmentBroker()) {
    return GetAttachmentBroker()->OnMessageReceived(message);
  }
#endif  // USE_ATTACHMENT_BROKER

  return false;
}

ChannelReader::DispatchState ChannelReader::DispatchMessages() {
  while (!queued_messages_.empty()) {
    if (!blocked_ids_.empty())
      return DISPATCH_WAITING_ON_BROKER;

    Message* m = queued_messages_.front();

    AttachmentIdSet blocked_ids = GetBrokeredAttachments(m);
    if (!blocked_ids.empty()) {
      blocked_ids_.swap(blocked_ids);
      StartObservingAttachmentBroker();
      return DISPATCH_WAITING_ON_BROKER;
    }

    DispatchMessage(m);
    queued_messages_.erase(queued_messages_.begin());
  }
  return DISPATCH_FINISHED;
}

ChannelReader::AttachmentIdSet ChannelReader::GetBrokeredAttachments(
    Message* msg) {
  std::set<BrokerableAttachment::AttachmentId> blocked_ids;

#if USE_ATTACHMENT_BROKER
  MessageAttachmentSet* set = msg->attachment_set();
  std::vector<scoped_refptr<IPC::BrokerableAttachment>>
      brokerable_attachments_copy(set->GetBrokerableAttachments());
  for (const auto& attachment : brokerable_attachments_copy) {
    if (attachment->NeedsBrokering()) {
      AttachmentBroker* broker = GetAttachmentBroker();
      DCHECK(broker);
      scoped_refptr<BrokerableAttachment> brokered_attachment;
      bool result = broker->GetAttachmentWithId(attachment->GetIdentifier(),
                                                &brokered_attachment);
      if (!result) {
        blocked_ids.insert(attachment->GetIdentifier());
        continue;
      }

      set->ReplacePlaceholderWithAttachment(brokered_attachment);
    }
  }
#endif  // USE_ATTACHMENT_BROKER

  return blocked_ids;
}

void ChannelReader::ReceivedBrokerableAttachmentWithId(
    const BrokerableAttachment::AttachmentId& id) {
  if (blocked_ids_.empty())
    return;

  auto it = find(blocked_ids_.begin(), blocked_ids_.end(), id);
  if (it != blocked_ids_.end())
    blocked_ids_.erase(it);

  if (blocked_ids_.empty()) {
    StopObservingAttachmentBroker();
    DispatchMessages();
  }
}

void ChannelReader::StartObservingAttachmentBroker() {
#if USE_ATTACHMENT_BROKER
  GetAttachmentBroker()->AddObserver(
      this, base::MessageLoopForIO::current()->task_runner());
#endif  // USE_ATTACHMENT_BROKER
}

void ChannelReader::StopObservingAttachmentBroker() {
#if USE_ATTACHMENT_BROKER
  GetAttachmentBroker()->RemoveObserver(this);
#endif  // USE_ATTACHMENT_BROKER
}

bool ChannelReader::CheckMessageSize(size_t size) {
  if (size <= Channel::kMaximumMessageSize) {
    return true;
  }
  input_overflow_buf_.clear();
  LOG(ERROR) << "IPC message is too big: " << size;
  return false;
}

}  // namespace internal
}  // namespace IPC