[Chromoting] Refactor the host policy watcher so that policies can easily be added.

remoting/host/policy_hack/nat_policy_win.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.
-
-// Most of this code is copied from various classes in
-// src/chrome/browser/policy. In particular, look at
-//
-//   configuration_policy_provider_delegate_win.{h,cc}
-//   configuration_policy_loader_win.{h,cc}
-//
-// This is a reduction of the functionality in those classes.
-
-#include "remoting/host/policy_hack/nat_policy.h"
-
-#include <userenv.h>
-
-#include "base/compiler_specific.h"
-#include "base/memory/scoped_ptr.h"
-#include "base/message_loop_proxy.h"
-#include "base/string16.h"
-#include "base/synchronization/waitable_event.h"
-#include "base/utf_string_conversions.h"
-#include "base/values.h"
-#include "base/win/object_watcher.h"
-#include "base/win/registry.h"
-
-// userenv.dll is required for RegisterGPNotification().
-#pragma comment(lib, "userenv.lib")
-
-using base::win::RegKey;
-
-namespace remoting {
-namespace policy_hack {
-
-namespace {
-
-const wchar_t kRegistrySubKey[] = L"SOFTWARE\\Policies\\Google\\Chrome";
-
-}  // namespace
-
-class NatPolicyWin :
-  public NatPolicy,
-  public base::win::ObjectWatcher::Delegate {
- public:
-  explicit NatPolicyWin(scoped_refptr<base::SingleThreadTaskRunner> task_runner)
-      : NatPolicy(task_runner),
-        user_policy_changed_event_(false, false),
-        machine_policy_changed_event_(false, false),
-        user_policy_watcher_failed_(false),
-        machine_policy_watcher_failed_(false) {
-  }
-
-  virtual ~NatPolicyWin() {
-  }
-
-  virtual void StartWatchingInternal() OVERRIDE {
-    DCHECK(OnPolicyThread());
-
-    if (!RegisterGPNotification(user_policy_changed_event_.handle(), false)) {
-      PLOG(WARNING) << "Failed to register user group policy notification";
-      user_policy_watcher_failed_ = true;
-    }
-
-    if (!RegisterGPNotification(machine_policy_changed_event_.handle(), true)) {
-      PLOG(WARNING) << "Failed to register machine group policy notification.";
-      machine_policy_watcher_failed_ = true;
-    }
-
-    Reload();
-  }
-
-  virtual void StopWatchingInternal() OVERRIDE {
-    DCHECK(OnPolicyThread());
-
-    if (!UnregisterGPNotification(user_policy_changed_event_.handle())) {
-      PLOG(WARNING) << "Failed to unregister user group policy notification";
-    }
-
-    if (!UnregisterGPNotification(machine_policy_changed_event_.handle())) {
-      PLOG(WARNING) <<
-          "Failed to unregister machine group policy notification.";
-    }
-
-    user_policy_watcher_.StopWatching();
-    machine_policy_watcher_.StopWatching();
-  }
-
- private:
-  // Updates the watchers and schedules the reload task if appropriate.
-  void SetupWatches() {
-    DCHECK(OnPolicyThread());
-
-    if (!user_policy_watcher_failed_ &&
-        !user_policy_watcher_.GetWatchedObject() &&
-        !user_policy_watcher_.StartWatching(
-            user_policy_changed_event_.handle(), this)) {
-      LOG(WARNING) << "Failed to start watch for user policy change event";
-      user_policy_watcher_failed_ = true;
-    }
-
-    if (!machine_policy_watcher_failed_ &&
-        !machine_policy_watcher_.GetWatchedObject() &&
-        !machine_policy_watcher_.StartWatching(
-            machine_policy_changed_event_.handle(), this)) {
-      LOG(WARNING) << "Failed to start watch for machine policy change event";
-      machine_policy_watcher_failed_ = true;
-     }
-
-    if (user_policy_watcher_failed_ || machine_policy_watcher_failed_) {
-      ScheduleFallbackReloadTask();
-    }
-  }
-
-  bool GetRegistryPolicyInteger(const string16& value_name,
-                                uint32* result) const {
-    DWORD value = 0;
-    RegKey policy_key(HKEY_LOCAL_MACHINE, kRegistrySubKey, KEY_READ);
-    if (policy_key.ReadValueDW(value_name.c_str(), &value) == ERROR_SUCCESS) {
-      *result = value;
-      return true;
-    }
-
-    if (policy_key.Open(HKEY_CURRENT_USER, kRegistrySubKey, KEY_READ) ==
-        ERROR_SUCCESS) {
-      if (policy_key.ReadValueDW(value_name.c_str(), &value) == ERROR_SUCCESS) {
-        *result = value;
-        return true;
-      }
-    }
-    return false;
-  }
-
-  bool GetRegistryPolicyBoolean(const string16& value_name,
-                                bool* result) const {
-    uint32 local_result = 0;
-    bool ret = GetRegistryPolicyInteger(value_name, &local_result);
-    if (ret)
-      *result = local_result != 0;
-    return ret;
-  }
-
-  base::DictionaryValue* Load() {
-    base::DictionaryValue* policy = new base::DictionaryValue();
-
-    bool bool_value;
-    const string16 name(ASCIIToUTF16(kNatPolicyName));
-    if (GetRegistryPolicyBoolean(name, &bool_value)) {
-      policy->SetBoolean(kNatPolicyName, bool_value);
-    }
-
-    return policy;
-  }
-
-  // Post a reload notification and update the watch machinery.
-  void Reload() {
-    DCHECK(OnPolicyThread());
-    SetupWatches();
-    scoped_ptr<DictionaryValue> new_policy(Load());
-    UpdateNatPolicy(new_policy.get());
-  }
-
-  // ObjectWatcher::Delegate overrides:
-  virtual void OnObjectSignaled(HANDLE object) {
-    DCHECK(OnPolicyThread());
-    DCHECK(object == user_policy_changed_event_.handle() ||
-           object == machine_policy_changed_event_.handle())
-        << "unexpected object signaled policy reload, obj = "
-        << std::showbase << std::hex << object;
-    Reload();
-  }
-
-  base::WaitableEvent user_policy_changed_event_;
-  base::WaitableEvent machine_policy_changed_event_;
-  base::win::ObjectWatcher user_policy_watcher_;
-  base::win::ObjectWatcher machine_policy_watcher_;
-  bool user_policy_watcher_failed_;
-  bool machine_policy_watcher_failed_;
-};
-
-NatPolicy* NatPolicy::Create(
-    scoped_refptr<base::SingleThreadTaskRunner> task_runner) {
-  return new NatPolicyWin(task_runner);
-}
-
-}  // namespace policy_hack
-}  // namespace remoting