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Commit 32637fbc authored by Yan Yan's avatar Yan Yan
Browse files

VCN: Ignore packet loss detection when there is too few traffic 

When the expected received packet number is smaller than 10, the
packet loss detection result will be ignored because the sample
size is too small to ensure a reliable result.

This patch also fixes the bug where the detector does not update
ths packet loss threshold when carrier config updates

Bug: 332598276
Test: atest FrameworksVcnTests && atest CtsVcnTestCases
Change-Id: Iccc47e83c48699d139029420572e2a2616c357cd
parent 6bc811da

services/core/java/com/android/server/vcn/routeselection/IpSecPacketLossDetector.java

+15 −1
Original line number Diff line number Diff line
@@ -64,6 +64,12 @@ public class IpSecPacketLossDetector extends NetworkMetricMonitor { 


    private static final int PACKET_LOSS_PERCENT_UNAVAILABLE = -1;



    // Ignore the packet loss detection result if the expected packet number is smaller than 10.

    // Solarwinds NPM uses 10 ICMP echos to calculate packet loss rate (as per

    // https://thwack.solarwinds.com/products/network-performance-monitor-npm/f/forum/63829/how-is-packet-loss-calculated)

    @VisibleForTesting(visibility = Visibility.PRIVATE)

    static final int MIN_VALID_EXPECTED_RX_PACKET_NUM = 10;



    @Retention(RetentionPolicy.SOURCE)

    @IntDef(

            prefix = {"PACKET_LOSS_"},
@@ -85,6 +91,8 @@ public class IpSecPacketLossDetector extends NetworkMetricMonitor { 
     * <ul>

     *   <li>The replay window did not proceed and thus all packets might have been delivered out of

     *       order

     *   <li>The expected received packet number is too small and thus the detection result is not

     *       reliable

     *   <li>There are unexpected errors

     * </ul>

     */
@@ -113,7 +121,7 @@ public class IpSecPacketLossDetector extends NetworkMetricMonitor { 
    private static final int MAX_SEQ_NUM_INCREASE_DEFAULT_DISABLED = -1;



    private long mPollIpSecStateIntervalMs;

    private final int mPacketLossRatePercentThreshold;

    private int mPacketLossRatePercentThreshold;

    private int mMaxSeqNumIncreasePerSecond;



    @NonNull private final Handler mHandler;
@@ -273,6 +281,7 @@ public class IpSecPacketLossDetector extends NetworkMetricMonitor { 
        mPollIpSecStateIntervalMs = getPollIpSecStateIntervalMs(carrierConfig);



        if (Flags.handleSeqNumLeap()) {

            mPacketLossRatePercentThreshold = getPacketLossRatePercentThreshold(carrierConfig);

            mMaxSeqNumIncreasePerSecond = getMaxSeqNumIncreasePerSecond(carrierConfig);

        }

    }
@@ -476,6 +485,11 @@ public class IpSecPacketLossDetector extends NetworkMetricMonitor { 
                            + " actualPktCntDiff: "

                            + actualPktCntDiff);



            if (Flags.handleSeqNumLeap() && expectedPktCntDiff < MIN_VALID_EXPECTED_RX_PACKET_NUM) {

                // The sample size is too small to ensure a reliable detection result

                return PacketLossCalculationResult.invalid();

            }



            if (expectedPktCntDiff < 0

                    || expectedPktCntDiff == 0

                    || actualPktCntDiff < 0

tests/vcn/java/com/android/server/vcn/routeselection/IpSecPacketLossDetectorTest.java

+16 −0
Original line number Diff line number Diff line
@@ -20,6 +20,7 @@ import static android.net.vcn.VcnManager.VCN_NETWORK_SELECTION_IPSEC_PACKET_LOSS 
import static android.net.vcn.VcnManager.VCN_NETWORK_SELECTION_MAX_SEQ_NUM_INCREASE_PER_SECOND_KEY;

import static android.net.vcn.VcnManager.VCN_NETWORK_SELECTION_POLL_IPSEC_STATE_INTERVAL_SECONDS_KEY;



import static com.android.server.vcn.routeselection.IpSecPacketLossDetector.MIN_VALID_EXPECTED_RX_PACKET_NUM;

import static com.android.server.vcn.routeselection.IpSecPacketLossDetector.getMaxSeqNumIncreasePerSecond;

import static com.android.server.vcn.util.PersistableBundleUtils.PersistableBundleWrapper;
@@ -436,6 +437,21 @@ public class IpSecPacketLossDetectorTest extends NetworkEvaluationTestBase { 
                mTransformStateInitial, 3000, 2000, 2000, PacketLossCalculationResult.invalid());

    }



    @Test

    public void testGetPacketLossRate_expectedPacketNumTooFew() throws Exception {

        final int oldRxNo = 4096;

        final int oldPktCnt = 4096;

        final int pktCntDiff = MIN_VALID_EXPECTED_RX_PACKET_NUM - 1;

        final byte[] bitmapReceiveAll = newReplayBitmap(4096);



        final IpSecTransformState oldState =

                newTransformState(oldRxNo, oldPktCnt, bitmapReceiveAll);

        final IpSecTransformState newState =

                newTransformState(oldRxNo + pktCntDiff, oldPktCnt + pktCntDiff, bitmapReceiveAll);



        checkGetPacketLossRate(oldState, newState, PacketLossCalculationResult.invalid());

    }



    @Test

    public void testGetPacketLossRate_againstInitialState() throws Exception {

        checkGetPacketLossRate(mTransformStateInitial, 7000, 7001, 4096, 0);