platform_system_core/libappfuse/FuseBridgeLoop.cc

/*
 * Copyright (C) 2016 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specic language governing permissions and
 * limitations under the License.
 */

#include "libappfuse/FuseBridgeLoop.h"

#include <android-base/logging.h>
#include <android-base/unique_fd.h>

namespace android {

bool FuseBridgeLoop::Start(
    int raw_dev_fd, int raw_proxy_fd, FuseBridgeLoop::Callback* callback) {
  base::unique_fd dev_fd(raw_dev_fd);
  base::unique_fd proxy_fd(raw_proxy_fd);
  fuse::FuseBuffer buffer;
  size_t open_count = 0;

  LOG(DEBUG) << "Start fuse loop.";
  while (true) {
    if (!buffer.request.Read(dev_fd)) {
      return false;
    }

    const uint32_t opcode = buffer.request.header.opcode;
    LOG(VERBOSE) << "Read a fuse packet, opcode=" << opcode;
    switch (opcode) {
      case FUSE_FORGET:
        // Do not reply to FUSE_FORGET.
        continue;

      case FUSE_LOOKUP:
      case FUSE_GETATTR:
      case FUSE_OPEN:
      case FUSE_READ:
      case FUSE_WRITE:
      case FUSE_RELEASE:
      case FUSE_FSYNC:
        if (!buffer.request.Write(proxy_fd)) {
          LOG(ERROR) << "Failed to write a request to the proxy.";
          return false;
        }
        if (!buffer.response.Read(proxy_fd)) {
          LOG(ERROR) << "Failed to read a response from the proxy.";
          return false;
        }
        break;

      case FUSE_INIT:
        buffer.HandleInit();
        break;

      default:
        buffer.HandleNotImpl();
        break;
    }

    if (!buffer.response.Write(dev_fd)) {
      LOG(ERROR) << "Failed to write a response to the device.";
      return false;
    }

    switch (opcode) {
      case FUSE_INIT:
        callback->OnMount();
        break;
      case FUSE_OPEN:
        if (buffer.response.header.error == fuse::kFuseSuccess) {
          open_count++;
        }
        break;
      case FUSE_RELEASE:
        if (open_count != 0) {
            open_count--;
        } else {
            LOG(WARNING) << "Unexpected FUSE_RELEASE before opening a file.";
            break;
        }
        if (open_count == 0) {
          return true;
        }
        break;
    }
  }
}

namespace fuse {

bool StartFuseBridgeLoop(
    int raw_dev_fd, int raw_proxy_fd, FuseBridgeLoopCallback* callback) {
  return FuseBridgeLoop().Start(raw_dev_fd, raw_proxy_fd, callback);
}

}  // namespace fuse
}  // namespace android