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Commit 74e8f525 authored by Mike Yu's avatar Mike Yu Committed by Automerger Merge Worker
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Merge "Set maximum attempt for opportunistic mode private DNS validation" am:... 

Merge "Set maximum attempt for opportunistic mode private DNS validation" am: b977d1ac am: 23b798f2 am: 4ee609d4

Original change: https://android-review.googlesource.com/c/platform/packages/modules/DnsResolver/+/1723079

Change-Id: Ia7712bd09ce6ced71ec67f0412db3b4711bcb173
parents 2d29eac4 4ee609d4

DnsTlsDispatcher.cpp

+6 −6
Original line number Diff line number Diff line
@@ -331,15 +331,15 @@ bool DnsTlsDispatcher::Transport::checkRevalidationNecessary(DnsTlsTransport::Re 


    if (code == DnsTlsTransport::Response::network_error) {

        continuousfailureCount++;

        LOG(WARNING) << "continuousfailureCount incremented: network_error, count = "

        LOG(DEBUG) << "continuousfailureCount incremented: network_error, count = "

                   << continuousfailureCount;

    } else if (latencyTooHigh) {

        continuousfailureCount++;

        LOG(WARNING) << "continuousfailureCount incremented: latency too High, count = "

        LOG(DEBUG) << "continuousfailureCount incremented: latency too High, count = "

                   << continuousfailureCount;

    } else {

    } else if (continuousfailureCount > 0) {

        continuousfailureCount = 0;

        LOG(WARNING) << "continuousfailureCount reset";

        LOG(DEBUG) << "continuousfailureCount reset";

    }



    // triggerThreshold must be greater than 0 because the value of revalidationEnabled is true.

PrivateDnsConfiguration.cpp

+43 −21
Original line number Diff line number Diff line
@@ -61,6 +61,11 @@ bool parseServer(const char* server, sockaddr_storage* parsed) { 
    return true;

}



// Returns true if the IPrivateDnsServer was created when the mode was opportunistic.

bool isForOpportunisticMode(const PrivateDnsConfiguration::ServerIdentity& identity) {

    return identity.provider.empty();

}



int PrivateDnsConfiguration::set(int32_t netId, uint32_t mark,

                                 const std::vector<std::string>& servers, const std::string& name,

                                 const std::string& caCert) {
@@ -202,20 +207,11 @@ void PrivateDnsConfiguration::startValidation(const ServerIdentity& identity, un 


        const bool avoidBadPrivateDns =

                Experiments::getInstance()->getFlag("avoid_bad_private_dns", 0);

        std::optional<int64_t> latencyThreshold;

        if (avoidBadPrivateDns) {

        const int maxLatency = Experiments::getInstance()->getFlag(

                "max_private_dns_latency_threshold_ms", kMaxPrivateDnsLatencyThresholdMs);

        const int minLatency = Experiments::getInstance()->getFlag(

                "min_private_dns_latency_threshold_ms", kMinPrivateDnsLatencyThresholdMs);

            const auto do53Latency = resolv_stats_get_average_response_time(netId, PROTO_UDP);

            const int target =

                    do53Latency.has_value() ? (3 * do53Latency.value().count() / 1000) : 0;



            // The time is limited to the range [minLatency, maxLatency].

            latencyThreshold = std::clamp(target, minLatency, maxLatency);

        }

        const bool isOpportunisticMode = server.name.empty();

        std::optional<int64_t> latencyThreshold;



        // cat /proc/sys/net/ipv4/tcp_syn_retries yields "6".

        //
@@ -232,7 +228,20 @@ void PrivateDnsConfiguration::startValidation(const ServerIdentity& identity, un 
        // (6 SYNs per ip, 4 ips per validation pass, 24 passes per day).

        auto backoff = mBackoffBuilder.build();



        while (true) {

        for (int attempt = 1; /**/; ++attempt) {

            // Because the time between two probes is at least one minute, there might already be

            // some traffic sent to Do53 servers during the time. Update latencyThreshold every

            // time before the probe.

            if (avoidBadPrivateDns && isForOpportunisticMode(identity)) {

                const auto do53Latency = resolv_stats_get_average_response_time(netId, PROTO_UDP);

                const int target = do53Latency.has_value()

                                           ? (3 * do53Latency.value().count() / 1000)

                                           : minLatency;



                // The threshold is limited to the range [minLatency, maxLatency].

                latencyThreshold = std::clamp(target, minLatency, maxLatency);

            }



            // ::validate() is a blocking call that performs network operations.

            // It can take milliseconds to minutes, up to the SYN retry limit.

            LOG(WARNING) << "Validating DnsTlsServer " << server.toIpString() << " with mark 0x"
@@ -241,20 +250,28 @@ void PrivateDnsConfiguration::startValidation(const ServerIdentity& identity, un 
            Stopwatch stopwatch;

            const bool gotAnswer = DnsTlsTransport::validate(server, server.validationMark());

            const int32_t timeTaken = saturate_cast<int32_t>(stopwatch.timeTakenUs() / 1000);

            LOG(WARNING) << fmt::format("validateDnsTlsServer returned {} for {}, took {}ms",

                                        gotAnswer, server.toIpString(), timeTaken);

            LOG(WARNING) << fmt::format(

                    "validateDnsTlsServer returned {} for {}, took {}ms, attempt {}", gotAnswer,

                    server.toIpString(), timeTaken, attempt);



            // Prevent from endlessly sending traffic on the network in opportunistic mode.

            bool maxAttemptsReached = false;

            if (avoidBadPrivateDns && attempt >= kOpportunisticModeMaxAttempts &&

                isForOpportunisticMode(identity)) {

                maxAttemptsReached = true;

                LOG(WARNING) << "Max attempts reached: " << kOpportunisticModeMaxAttempts;

            }



            const int64_t targetTime = latencyThreshold.value_or(INT64_MAX);

            bool latencyTooHigh = false;

            if (isOpportunisticMode && timeTaken > targetTime) {

                latencyTooHigh = true;

            const bool latencyTooHigh = timeTaken > targetTime;

            if (latencyTooHigh) {

                LOG(WARNING) << "validateDnsTlsServer took too long: threshold is " << targetTime

                             << "ms";

            }



            // TODO: combine these boolean variables into a bitwise variable.

            const bool needs_reeval = this->recordPrivateDnsValidation(

                    identity, netId, gotAnswer, isRevalidation, latencyTooHigh);

                    identity, netId, gotAnswer, isRevalidation, latencyTooHigh, maxAttemptsReached);



            if (!needs_reeval) {

                break;
@@ -305,7 +322,8 @@ void PrivateDnsConfiguration::sendPrivateDnsValidationEvent(const ServerIdentity 


bool PrivateDnsConfiguration::recordPrivateDnsValidation(const ServerIdentity& identity,

                                                         unsigned netId, bool gotAnswer,

                                                         bool isRevalidation, bool latencyTooHigh) {

                                                         bool isRevalidation, bool latencyTooHigh,

                                                         bool maxAttemptsReached) {

    constexpr bool NEEDS_REEVALUATION = true;

    constexpr bool DONT_REEVALUATE = false;
@@ -336,6 +354,10 @@ bool PrivateDnsConfiguration::recordPrivateDnsValidation(const ServerIdentity& i 
        reevaluationStatus = DONT_REEVALUATE;

    }



    if (maxAttemptsReached) {

        reevaluationStatus = DONT_REEVALUATE;

    }



    bool success = gotAnswer;

    auto& tracker = netPair->second;

    auto serverPair = tracker.find(identity);

PrivateDnsConfiguration.h

+5 −2
Original line number Diff line number Diff line
@@ -98,6 +98,9 @@ class PrivateDnsConfiguration { 
    static constexpr int kMaxPrivateDnsLatencyThresholdMs = 2000;

    static constexpr int kMinPrivateDnsLatencyThresholdMs = 500;



    // (Opportunistic mode only) The maximum attempts to send a probe to a private DNS server.

    static constexpr int kOpportunisticModeMaxAttempts = 3;



    PrivateDnsConfiguration() = default;



    // Launchs a thread to run the validation for |server| on the network |netId|.
@@ -106,8 +109,8 @@ class PrivateDnsConfiguration { 
            REQUIRES(mPrivateDnsLock);



    bool recordPrivateDnsValidation(const ServerIdentity& identity, unsigned netId, bool success,

                                    bool isRevalidation, bool latencyTooHigh)

            EXCLUDES(mPrivateDnsLock);

                                    bool isRevalidation, bool latencyTooHigh,

                                    bool maxAttemptsReached) EXCLUDES(mPrivateDnsLock);



    void sendPrivateDnsValidationEvent(const ServerIdentity& identity, unsigned netId, bool success)

            REQUIRES(mPrivateDnsLock);

PrivateDnsConfigurationTest.cpp

+52 −0
Original line number Diff line number Diff line
@@ -156,6 +156,8 @@ class PrivateDnsConfigurationTest : public ::testing::Test { 
    static constexpr char kBackend[] = "127.0.2.1";

    static constexpr char kServer1[] = "127.0.2.2";

    static constexpr char kServer2[] = "127.0.2.3";

    static constexpr int kOpportunisticModeMaxAttempts =

            PrivateDnsConfiguration::kOpportunisticModeMaxAttempts;



    MockObserver mObserver;

    PrivateDnsConfiguration mPdc;
@@ -284,6 +286,56 @@ TEST_F(PrivateDnsConfigurationTest, ValidationProbingTime) { 
    backend.setResponseDelayMs(0);

}



// Tests that Private DNS validation won't be endless if the server works and it's slow.

TEST_F(PrivateDnsConfigurationTest, ValidationMaxProbes) {

    ScopedSystemProperty sp1(kMinPrivateDnsLatencyThresholdMsFlag, "100");

    ScopedSystemProperty sp2(kMaxPrivateDnsLatencyThresholdMsFlag, "200");

    const int serverLatencyMs = 300;



    // TODO: Complete STRICT test after the dependency of DnsTlsFrontend is removed.

    static const struct TestConfig {

        std::string dnsMode;

        bool avoidBadPrivateDns;

        Validation expectedValidationResult;

        int expectedProbes;

    } testConfigs[] = {

            // clang-format off

            {"OPPORTUNISTIC", false, Validation::success, 1},

            {"OPPORTUNISTIC", true,  Validation::fail,    kOpportunisticModeMaxAttempts},

            // clang-format on

    };



    for (const auto& config : testConfigs) {

        SCOPED_TRACE(

                fmt::format("testConfig: [{}, {}]", config.dnsMode, config.avoidBadPrivateDns));



        ScopedSystemProperty sp3(kAvoidBadPrivateDnsFlag, (config.avoidBadPrivateDns ? "1" : "0"));

        forceExperimentsInstanceUpdate();

        backend.setResponseDelayMs(serverLatencyMs);



        testing::InSequence seq;

        EXPECT_CALL(mObserver, onValidationStateUpdate(kServer1, Validation::in_process, kNetId))

                .Times(config.expectedProbes);

        EXPECT_CALL(mObserver,

                    onValidationStateUpdate(kServer1, config.expectedValidationResult, kNetId));



        EXPECT_EQ(mPdc.set(kNetId, kMark, {kServer1}, {}, {}), 0);

        expectPrivateDnsStatus(PrivateDnsMode::OPPORTUNISTIC);



        // probing time + backoff delay

        const int expectedValidationTimeMs =

                config.expectedProbes * serverLatencyMs + (config.expectedProbes - 1) * 1000;

        ASSERT_TRUE(PollForCondition([&]() { return mObserver.runningThreads == 0; },

                                     std::chrono::milliseconds(expectedValidationTimeMs + 1000)));



        // Reset the state for the next round.

        mPdc.clear(kNetId);

        testing::Mock::VerifyAndClearExpectations(&mObserver);

    }



    backend.setResponseDelayMs(0);

}



TEST_F(PrivateDnsConfigurationTest, ValidationBlock) {

    backend.setDeferredResp(true);