sdk/lib/sys/component/llcpp/outgoing_directory.cc

// Copyright 2022 The Fuchsia 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 <lib/svc/dir.h>
#include <lib/sys/component/llcpp/constants.h>
#include <lib/sys/component/llcpp/handlers.h>
#include <lib/sys/component/llcpp/outgoing_directory.h>
#include <lib/zx/status.h>
#include <zircon/assert.h>
#include <zircon/errors.h>
#include <zircon/process.h>
#include <zircon/processargs.h>
#include <zircon/types.h>

#include <memory>
#include <sstream>

namespace component {

OutgoingDirectory OutgoingDirectory::Create(async_dispatcher_t* dispatcher) {
  ZX_ASSERT_MSG(dispatcher != nullptr, "OutgoingDirectory::Create received nullptr |dispatcher|.");

  svc_dir_t* root = nullptr;
  // It's safe to ignore return value here since the function always returns
  // ZX_OK.
  (void)svc_dir_create_without_serve(&root);

  return OutgoingDirectory(dispatcher, root);
}

OutgoingDirectory::OutgoingDirectory(async_dispatcher_t* dispatcher, svc_dir_t* root)
    : dispatcher_(dispatcher), root_(root) {}

OutgoingDirectory::OutgoingDirectory(OutgoingDirectory&& other) noexcept
    : dispatcher_(other.dispatcher_), root_(other.root_) {
  other.dispatcher_ = nullptr;
  other.root_ = nullptr;
}

OutgoingDirectory& OutgoingDirectory::operator=(OutgoingDirectory&& other) noexcept {
  dispatcher_ = other.dispatcher_;
  root_ = other.root_;

  other.dispatcher_ = nullptr;
  other.root_ = nullptr;

  return *this;
}

OutgoingDirectory::~OutgoingDirectory() {
  if (root_) {
    svc_dir_destroy(root_);
  }
}

zx::status<> OutgoingDirectory::Serve(fidl::ServerEnd<fuchsia_io::Directory> directory_server_end) {
  if (!directory_server_end.is_valid()) {
    return zx::error_status(ZX_ERR_BAD_HANDLE);
  }

  zx_status_t status =
      svc_dir_serve(root_, dispatcher_, directory_server_end.TakeHandle().release());
  if (status != ZX_OK) {
    return zx::error_status(status);
  }

  return zx::make_status(status);
}

zx::status<> OutgoingDirectory::ServeFromStartupInfo() {
  fidl::ServerEnd<fuchsia_io::Directory> directory_request(
      zx::channel(zx_take_startup_handle(PA_DIRECTORY_REQUEST)));
  return Serve(std::move(directory_request));
}

zx::status<> OutgoingDirectory::AddProtocol(AnyHandler handler, cpp17::string_view name) {
  return AddProtocolAt(std::move(handler), kServiceDirectory, name);
}

zx::status<> OutgoingDirectory::AddProtocolAt(AnyHandler handler, cpp17::string_view path,
                                              cpp17::string_view name) {
  // More thorough path validation is done in |svc_add_service|.
  if (path.empty() || name.empty()) {
    return zx::error_status(ZX_ERR_INVALID_ARGS);
  }

  std::string directory_entry(path);
  std::string protocol_entry(name);
  if (registered_handlers_.count(directory_entry) != 0 &&
      registered_handlers_[directory_entry].count(protocol_entry) != 0) {
    return zx::make_status(ZX_ERR_ALREADY_EXISTS);
  }

  // |svc_dir_add_service_by_path| takes in a void* |context| that is passed to
  // the |handler| callback passed as the last argument to the function call.
  // The context will first be stored in the heap for this path, then a pointer
  // to it will be passed to this function. The callback, in this case |OnConnect|,
  // will then cast the void* type to OnConnectContext*.
  auto context = std::make_unique<OnConnectContext>(
      OnConnectContext{.handler = std::move(handler), .self = this});
  zx_status_t status =
      svc_dir_add_service(root_, directory_entry.c_str(), name.data(), context.get(), OnConnect);

  auto& directory_handlers = registered_handlers_[directory_entry];
  directory_handlers[protocol_entry] = std::move(context);

  return zx::make_status(status);
}

zx::status<> OutgoingDirectory::AddDirectory(fidl::ClientEnd<fuchsia_io::Directory> remote_dir,
                                             cpp17::string_view directory_name) {
  if (!remote_dir.is_valid()) {
    return zx::error_status(ZX_ERR_BAD_HANDLE);
  }
  if (directory_name.empty()) {
    return zx::error_status(ZX_ERR_INVALID_ARGS);
  }

  zx_status_t status =
      svc_dir_add_directory(root_, directory_name.data(), remote_dir.TakeChannel().release());
  return zx::make_status(status);
}

zx::status<> OutgoingDirectory::AddService(ServiceHandler handler, cpp17::string_view service,
                                           cpp17::string_view instance) {
  if (service.empty() || instance.empty()) {
    return zx::error_status(ZX_ERR_INVALID_ARGS);
  }

  auto handlers = handler.TakeMemberHandlers();
  if (handlers.empty()) {
    return zx::make_status(ZX_ERR_INVALID_ARGS);
  }

  std::string basepath = MakePath(service, instance);
  for (auto& [member_name, member_handler] : handlers) {
    zx::status<> status = AddProtocolAt(std::move(member_handler), basepath, member_name);
    if (status.is_error()) {
      // If we encounter an error with any of the instance members, scrub entire
      // directory entry.
      registered_handlers_.erase(basepath);
      return status;
    }
  }

  return zx::ok();
}

zx::status<> OutgoingDirectory::RemoveProtocol(cpp17::string_view name) {
  return RemoveProtocolAt(kServiceDirectory, name);
}

zx::status<> OutgoingDirectory::RemoveProtocolAt(cpp17::string_view directory,
                                                 cpp17::string_view name) {
  std::string key(directory);

  if (registered_handlers_.count(key) == 0) {
    return zx::make_status(ZX_ERR_NOT_FOUND);
  }

  auto& svc_root_handlers = registered_handlers_[key];
  std::string entry_key = std::string(name);
  if (svc_root_handlers.count(entry_key) == 0) {
    return zx::make_status(ZX_ERR_NOT_FOUND);
  }

  // Remove svc_dir_t entry first so that no new connections are attempted on
  // handler after we remove the pointer to it in |svc_root_handlers|.
  zx_status_t status = svc_dir_remove_service(root_, kServiceDirectory, name.data());
  if (status != ZX_OK) {
    return zx::make_status(status);
  }

  // If teardown is managed, e.g. through |AddProtocol| overload for `fidl::Server<T>*`,
  // then close all active connections.
  UnbindAllConnections(name);

  // Now that all active connections have been closed, and no new connections
  // are being accepted under |name|, it's safe to remove the handlers.
  svc_root_handlers.erase(entry_key);

  return zx::ok();
}

zx::status<> OutgoingDirectory::RemoveService(cpp17::string_view service,
                                              cpp17::string_view instance) {
  std::string path = MakePath(service, instance);
  if (registered_handlers_.count(path) == 0) {
    return zx::make_status(ZX_ERR_NOT_FOUND);
  }

  // Remove svc_dir_t entry first so that channels close _before_ we remove
  // pointer values out from underneath handlers.
  std::string service_path =
      std::string(kServiceDirectory) + std::string(kSvcPathDelimiter) + std::string(service);
  zx_status_t status = svc_dir_remove_service_by_path(root_, service_path.c_str(), instance.data());

  // Now it's safe to remove entry from map.
  registered_handlers_.erase(path);

  return zx::make_status(status);
}

zx::status<> OutgoingDirectory::RemoveDirectory(cpp17::string_view directory_name) {
  zx_status_t status = svc_dir_remove_directory(root_, directory_name.data());
  return zx::make_status(status);
}

void OutgoingDirectory::OnConnect(void* raw_context, const char* service_name, zx_handle_t handle) {
  OnConnectContext* context = reinterpret_cast<OnConnectContext*>(raw_context);
  (context->handler)(zx::channel(handle));
}

void OutgoingDirectory::AppendUnbindConnectionCallback(const std::string& name,
                                                       UnbindConnectionCallback callback) {
  unbind_protocol_callbacks_[name].emplace_back(std::move(callback));
}

void OutgoingDirectory::UnbindAllConnections(cpp17::string_view name) {
  auto key = std::string(name);
  auto iterator = unbind_protocol_callbacks_.find(key);
  if (iterator != unbind_protocol_callbacks_.end()) {
    std::vector<UnbindConnectionCallback>& callbacks = iterator->second;
    for (auto& cb : callbacks) {
      cb();
    }
    unbind_protocol_callbacks_.erase(iterator);
  }
}

std::string OutgoingDirectory::MakePath(cpp17::string_view service, cpp17::string_view instance) {
  std::stringstream path;
  path << kServiceDirectory << kSvcPathDelimiter << service << kSvcPathDelimiter << instance;
  return path.str();
}

}  // namespace component