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* Copyright (C) 2018 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
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* See the License for the specific language governing permissions and
* limitations under the License.
#define LOG_TAG "resolv"
#include "ResolverEventReporter.h"
#include <android-base/logging.h>
#include <android/binder_manager.h>
using aidl::android::net::metrics::INetdEventListener;
ResolverEventReporter& ResolverEventReporter::getInstance() {
// It should be initialized only once.
static ResolverEventReporter instance;
// Add framework metrics listener. Because the binder service "netd_listener" may be launched
// later than Netd, try to get binder handler in every instance query if any. The framework
// metrics listener should be added only once if it has been already added successfully.
return instance;
ResolverEventReporter::ListenerSet ResolverEventReporter::getListeners() const {
return getListenersImpl();
int ResolverEventReporter::addListener(const std::shared_ptr<INetdEventListener>& listener) {
return addListenerImpl(listener);
// TODO: Consider registering metrics listener from framework and remove this function.
// Currently, the framework listener "netd_listener" is shared by netd and libnetd_resolv.
// Consider breaking it into two listeners. Once it has done, may let framework register
// the listener proactively.
void ResolverEventReporter::addDefaultListener() {
std::lock_guard lock(mMutex);
static bool added = false;
if (added) return;
// Use the non-blocking call AServiceManager_checkService in order not to delay DNS
// lookup threads when the netd_listener service is not ready.
ndk::SpAIBinder binder = ndk::SpAIBinder(AServiceManager_checkService("netd_listener"));
std::shared_ptr<INetdEventListener> listener = INetdEventListener::fromBinder(binder);
if (listener == nullptr) return;
if (!addListenerImplLocked(listener)) added = true;
void ResolverEventReporter::handleBinderDied(const void* who) {
std::lock_guard lock(mMutex);
// Use the raw binder pointer address to be the identification of dead binder. Treat "who"
// which passes the raw address of dead binder as an identification only.
auto found = std::find_if(mListeners.begin(), mListeners.end(),
[=](const auto& it) { return static_cast<void*>(it.get()) == who; });
if (found != mListeners.end()) mListeners.erase(found);
ResolverEventReporter::ListenerSet ResolverEventReporter::getListenersImpl() const {
std::lock_guard lock(mMutex);
return mListeners;
int ResolverEventReporter::addListenerImpl(const std::shared_ptr<INetdEventListener>& listener) {
std::lock_guard lock(mMutex);
return addListenerImplLocked(listener);
int ResolverEventReporter::addListenerImplLocked(
const std::shared_ptr<INetdEventListener>& listener) {
if (listener == nullptr) {
LOG(ERROR) << "The listener should not be null";
return -EINVAL;
for (const auto& it : mListeners) {
if (it->asBinder().get() == listener->asBinder().get()) {
LOG(WARNING) << "The listener was already subscribed";
return -EEXIST;
static AIBinder_DeathRecipient* deathRecipient = nullptr;
if (deathRecipient == nullptr) {
// The AIBinder_DeathRecipient object is used to manage all death recipients for multiple
// binder objects. It doesn't released because there should have at least one binder object
// from framework.
// TODO: Considering to remove death recipient for the binder object from framework because
// it doesn't need death recipient actually.
deathRecipient = AIBinder_DeathRecipient_new([](void* cookie) {
// Pass the raw binder pointer address to be the cookie of the death recipient. While the death
// notification is fired, the cookie is used for identifying which binder was died. Because
// the NDK binder doesn't pass dead binder pointer to binder death handler, the binder death
// handler can't know who was died via wp<IBinder>. The reason for wp<IBinder> is not passed
// is that NDK binder can't transform a wp<IBinder> to a wp<AIBinder> in some cases.
// See more information in b/128712772.
auto binder = listener->asBinder().get();
auto cookie = static_cast<void*>(listener.get()); // Used for dead binder identification.
binder_status_t status = AIBinder_linkToDeath(binder, deathRecipient, cookie);
if (STATUS_OK != status) {
LOG(ERROR) << "Failed to register death notification for INetdEventListener";
return -EAGAIN;
return 0;