resolver_test: Subscribe to death notification of service IDnsResolver

#define LOG_TAG "resolv_integration_test"

#include <android-base/logging.h>

#include <android-base/parseint.h>

#include <android-base/stringprintf.h>

#include <android-base/unique_fd.h>

class ResolverTest : public ::testing::Test {

  public:

    ResolverTest() {

        // Use a shared static DNS listener for all tests to avoid registering lots of listeners

        // which may be released late until process terminated. Currently, registered DNS listener

        // is removed by binder death notification which is fired when the process hosting an

        // IBinder has gone away. If every test in ResolverTest registers its DNS listener, Netd

        // may temporarily hold lots of dead listeners until the unit test process terminates.

        // TODO: Perhaps add an unregistering listener binder call or fork a listener process which

        // could be terminated earlier.

        static android::sp<DnsMetricsListener> listener =

                new DnsMetricsListener(TEST_NETID /*monitor specific network*/);

        mDnsMetricsListener = listener;

    static void SetUpTestCase() {

        // Get binder service.

        // Note that |mDnsClient| is not used for getting binder service in this static function.

        // The reason is that wants to keep |mDnsClient| as a non-static data member. |mDnsClient|

        // which sets up device network configuration could be independent from every test.

        // TODO: Perhaps add a static function in class DnsResponderClient to get binder service.

        auto resolvBinder =

                android::defaultServiceManager()->getService(android::String16("dnsresolver"));

        auto resolvService = android::interface_cast<android::net::IDnsResolver>(resolvBinder);

        ASSERT_NE(nullptr, resolvService.get());

        // Subscribe the death recipient to the service IDnsResolver for detecting Netd death.

        sResolvDeathRecipient = new ResolvDeathRecipient();

        ASSERT_EQ(android::NO_ERROR, resolvBinder->linkToDeath(sResolvDeathRecipient));

        // Subscribe the DNS listener for verifying DNS metrics event contents.

        sDnsMetricsListener = new DnsMetricsListener(TEST_NETID /*monitor specific network*/);

        ASSERT_TRUE(resolvService->registerEventListener(sDnsMetricsListener).isOk());

        // Start the binder thread pool for listening DNS metrics events and receiving death

        // recipient.

        android::ProcessState::self()->startThreadPool();

    }

  protected:

        std::string addr;       // ipv4/v6 address

    };

    void SetUp() {

        mDnsClient.SetUp();

        // Register the shared static DNS listener which may have been registered in previous test

        // ResolverTest.

        // TODO: Move the registration to SetUpTestCase which is called once before the first test.

        auto status = mDnsClient.resolvService()->registerEventListener(mDnsMetricsListener);

        ASSERT_TRUE(status.isOk() || status.serviceSpecificErrorCode() == EEXIST /*ignore*/);

    class ResolvDeathRecipient : public android::IBinder::DeathRecipient {

      public:

        ~ResolvDeathRecipient() override = default;

        // Start the binder thread pool for listening DNS metrics events.

        android::ProcessState::self()->startThreadPool();

        // GTEST assertion macros are not invoked for generating a test failure in the death

        // recipient because the macros can't indicate failed test if Netd died between tests.

        // Moreover, continuing testing may have no meaningful after Netd death. Therefore, the

        // death recipient aborts process by GTEST_LOG_(FATAL) once Netd died.

        void binderDied(const android::wp<android::IBinder>& /*who*/) override {

            constexpr char errorMessage[] = "Netd service died";

            LOG(ERROR) << errorMessage;

            GTEST_LOG_(FATAL) << errorMessage;

        }

    };

    void SetUp() { mDnsClient.SetUp(); }

    void TearDown() { mDnsClient.TearDown(); }

    void StartDns(test::DNSResponder& dns, const std::vector<DnsRecord>& records) {

    bool WaitForNat64Prefix(ExpectNat64PrefixStatus status,

                            std::chrono::milliseconds timeout = std::chrono::milliseconds(1000)) {

        return mDnsMetricsListener->waitForNat64Prefix(status, timeout);

        return sDnsMetricsListener->waitForNat64Prefix(status, timeout);

    }

    DnsResponderClient mDnsClient;

    android::sp<DnsMetricsListener> mDnsMetricsListener;  // Initialized in constructor.

    static constexpr char kLocalHost[] = "localhost";

    static constexpr char kLocalHostAddr[] = "127.0.0.1";

    static constexpr char kIp6LocalHost[] = "ip6-localhost";

    static constexpr char kIp6LocalHostAddr[] = "::1";

    static constexpr char kHelloExampleCom[] = "hello.example.com.";

    // Use a shared static DNS listener for all tests to avoid registering lots of listeners

    // which may be released late until process terminated. Currently, registered DNS listener

    // is removed by binder death notification which is fired when the process hosting an

    // IBinder has gone away. If every test in ResolverTest registers its DNS listener, Netd

    // may temporarily hold lots of dead listeners until the unit test process terminates.

    // TODO: Perhaps add an unregistering listener binder call or fork a listener process which

    // could be terminated earlier.

    static android::sp<DnsMetricsListener> sDnsMetricsListener;  // Initialized in SetUpTestCase.

    // Use a shared static death recipient to monitor the service death. The static death

    // recipient could monitor the death not only during the test but also between tests.

    static android::sp<ResolvDeathRecipient>

            sResolvDeathRecipient;  // Initialized in SetUpTestCase.

};

// Initialize static member of class.

android::sp<DnsMetricsListener> ResolverTest::sDnsMetricsListener;

android::sp<ResolverTest::ResolvDeathRecipient> ResolverTest::sResolvDeathRecipient;

TEST_F(ResolverTest, GetHostByName) {

    constexpr char nonexistent_host_name[] = "nonexistent.example.com.";