diff --git a/Tethering/tests/integration/base/android/net/TetheringTester.java b/Tethering/tests/integration/base/android/net/TetheringTester.java
index ae39b24..1c0803e 100644
--- a/Tethering/tests/integration/base/android/net/TetheringTester.java
+++ b/Tethering/tests/integration/base/android/net/TetheringTester.java
@@ -628,7 +628,7 @@
         return false;
     }
 
-    private void sendUploadPacket(ByteBuffer packet) throws Exception {
+    public void sendUploadPacket(ByteBuffer packet) throws Exception {
         mDownstreamReader.sendResponse(packet);
     }
 
@@ -680,4 +680,12 @@
 
         return verifyPacketNotNull("Download fail", getDownloadPacket(filter));
     }
+
+    // Send DHCPDISCOVER to DHCP server to see if DHCP server is still alive to handle
+    // the upcoming DHCP packets. This method should be only used when we know the DHCP
+    // server has been created successfully before.
+    public boolean testDhcpServerAlive(final MacAddress mac) throws Exception {
+        sendDhcpDiscover(mac.toByteArray());
+        return getNextDhcpPacket() != null;
+    }
 }
diff --git a/Tethering/tests/integration/src/android/net/EthernetTetheringTest.java b/Tethering/tests/integration/src/android/net/EthernetTetheringTest.java
index 55854e2..21927df 100644
--- a/Tethering/tests/integration/src/android/net/EthernetTetheringTest.java
+++ b/Tethering/tests/integration/src/android/net/EthernetTetheringTest.java
@@ -39,6 +39,7 @@
 import static com.android.net.module.util.NetworkStackConstants.IPV4_LENGTH_OFFSET;
 
 import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertFalse;
 import static org.junit.Assert.assertNotNull;
 import static org.junit.Assert.assertTrue;
 import static org.junit.Assert.fail;
@@ -839,4 +840,41 @@
                 REMOTE_NAT64_ADDR /* downloadSrcIp */, clatIp6 /* downloadDstIp */,
                 tester, true /* isClat */);
     }
+
+    private static final byte[] ZeroLengthDhcpPacket = new byte[] {
+            // scapy.Ether(
+            //   dst="ff:ff:ff:ff:ff:ff")
+            // scapy.IP(
+            //   dst="255.255.255.255")
+            // scapy.UDP(sport=68, dport=67)
+            /* Ethernet Header */
+            (byte) 0xff, (byte) 0xff, (byte) 0xff, (byte) 0xff, (byte) 0xff, (byte) 0xff,
+            (byte) 0xe0, (byte) 0x4f, (byte) 0x43, (byte) 0xe6, (byte) 0xfb, (byte) 0xd2,
+            (byte) 0x08, (byte) 0x00,
+            /* Ip header */
+            (byte) 0x45, (byte) 0x00, (byte) 0x00, (byte) 0x1c, (byte) 0x00, (byte) 0x01,
+            (byte) 0x00, (byte) 0x00, (byte) 0x40, (byte) 0x11, (byte) 0xb6, (byte) 0x58,
+            (byte) 0x64, (byte) 0x4f, (byte) 0x60, (byte) 0x29, (byte) 0xff, (byte) 0xff,
+            (byte) 0xff, (byte) 0xff,
+            /* UDP header */
+            (byte) 0x00, (byte) 0x44, (byte) 0x00, (byte) 0x43,
+            (byte) 0x00, (byte) 0x08, (byte) 0x3a, (byte) 0xdf
+    };
+
+    @Test
+    public void testTetherZeroLengthDhcpPacket() throws Exception {
+        final TetheringTester tester = initTetheringTester(toList(TEST_IP4_ADDR),
+                toList(TEST_IP4_DNS));
+        tester.createTetheredDevice(TEST_MAC, false /* hasIpv6 */);
+
+        // Send a zero-length DHCP packet to upstream DHCP server.
+        final ByteBuffer packet = ByteBuffer.wrap(ZeroLengthDhcpPacket);
+        tester.sendUploadPacket(packet);
+
+        // Send DHCPDISCOVER packet from another downstream tethered device to verify that upstream
+        // DHCP server has closed the listening socket and stopped reading, then we will not receive
+        // any DHCPOFFER in this case.
+        final MacAddress macAddress = MacAddress.fromString("11:22:33:44:55:66");
+        assertFalse(tester.testDhcpServerAlive(macAddress));
+    }
 }
diff --git a/Tethering/tests/privileged/src/com/android/networkstack/tethering/ConntrackSocketTest.java b/Tethering/tests/privileged/src/com/android/networkstack/tethering/ConntrackSocketTest.java
index b3fb3e4..81d4fbe 100644
--- a/Tethering/tests/privileged/src/com/android/networkstack/tethering/ConntrackSocketTest.java
+++ b/Tethering/tests/privileged/src/com/android/networkstack/tethering/ConntrackSocketTest.java
@@ -106,6 +106,7 @@
                 ConntrackMessage.Tuple tuple = ctmsg.tupleOrig;
 
                 if (nlmsghdr.nlmsg_type == (NFNL_SUBSYS_CTNETLINK << 8 | IPCTNL_MSG_CT_NEW)
+                        && tuple != null
                         && tuple.protoNum == IPPROTO_TCP
                         && tuple.srcIp.equals(local.getAddress())
                         && tuple.dstIp.equals(remote.getAddress())
diff --git a/framework/src/android/net/NetworkCapabilities.java b/framework/src/android/net/NetworkCapabilities.java
index 3cc9c65..92e9599 100644
--- a/framework/src/android/net/NetworkCapabilities.java
+++ b/framework/src/android/net/NetworkCapabilities.java
@@ -1348,6 +1348,18 @@
     }
 
     /**
+     * Gets the transports as an int. Internal callers only.
+     *
+     * Prefer getTransportTypes/hasTransportType if not immediately collapsing back into a scalar.
+     *
+     * @return a long integer representing the transport types.
+     * @hide
+     */
+    public long getTransportTypesInternal() {
+        return mTransportTypes;
+    }
+
+    /**
      * Sets all the transports set on this {@code NetworkCapability} instance.
      * This overwrites any existing transports.
      *
diff --git a/service/jni/com_android_server_BpfNetMaps.cpp b/service/jni/com_android_server_BpfNetMaps.cpp
index 77cffda..9ced44e 100644
--- a/service/jni/com_android_server_BpfNetMaps.cpp
+++ b/service/jni/com_android_server_BpfNetMaps.cpp
@@ -54,6 +54,10 @@
   if (!isOk(status)) {
     uid_t uid = getuid();
     ALOGE("BpfNetMaps jni init failure as uid=%d", uid);
+    // We probably only ever get called from system_server (ie. AID_SYSTEM)
+    // or from tests, and never from network_stack (ie. AID_NETWORK_STACK).
+    // However, if we ever do add calls from production network_stack code
+    // we do want to make sure this initializes correctly.
     // TODO: Fix tests to not use this jni lib, so we can unconditionally abort()
     if (uid == AID_SYSTEM || uid == AID_NETWORK_STACK) abort();
   }
diff --git a/service/jni/com_android_server_connectivity_ClatCoordinator.cpp b/service/jni/com_android_server_connectivity_ClatCoordinator.cpp
index 8d909ed..d966070 100644
--- a/service/jni/com_android_server_connectivity_ClatCoordinator.cpp
+++ b/service/jni/com_android_server_connectivity_ClatCoordinator.cpp
@@ -90,11 +90,6 @@
 
 #undef ALOGF
 
-bool isGsiImage() {
-    // this implementation matches 2 other places in the codebase (same function name too)
-    return !access("/system/system_ext/etc/init/init.gsi.rc", F_OK);
-}
-
 static const char* kClatdDir = "/apex/com.android.tethering/bin/for-system";
 static const char* kClatdBin = "/apex/com.android.tethering/bin/for-system/clatd";
 
@@ -135,14 +130,6 @@
 
 #undef V2
 
-    // HACK: Some old vendor kernels lack ~5.10 backport of 'bpffs selinux genfscon' support.
-    // This is *NOT* supported, but let's allow, at least for now, U+ GSI to boot on them.
-    // (without this hack pixel5 R vendor + U gsi breaks)
-    if (isGsiImage() && !bpf::isAtLeastKernelVersion(5, 10, 0)) {
-        ALOGE("GSI with *BAD* pre-5.10 kernel lacking bpffs selinux genfscon support.");
-        return;
-    }
-
     if (fatal) abort();
 }
 
diff --git a/service/jni/onload.cpp b/service/jni/onload.cpp
index 4bbaae6..ed74430 100644
--- a/service/jni/onload.cpp
+++ b/service/jni/onload.cpp
@@ -38,11 +38,11 @@
         return JNI_ERR;
     }
 
-    if (register_com_android_server_BpfNetMaps(env) < 0) {
-        return JNI_ERR;
-    }
-
     if (android::modules::sdklevel::IsAtLeastT()) {
+        if (register_com_android_server_BpfNetMaps(env) < 0) {
+            return JNI_ERR;
+        }
+
         if (register_com_android_server_connectivity_ClatCoordinator(env) < 0) {
             return JNI_ERR;
         }
diff --git a/service/src/com/android/server/connectivity/NetworkDiagnostics.java b/service/src/com/android/server/connectivity/NetworkDiagnostics.java
index 4eba74b..15d0925 100644
--- a/service/src/com/android/server/connectivity/NetworkDiagnostics.java
+++ b/service/src/com/android/server/connectivity/NetworkDiagnostics.java
@@ -19,6 +19,9 @@
 import static android.system.OsConstants.*;
 
 import static com.android.net.module.util.NetworkStackConstants.ICMP_HEADER_LEN;
+import static com.android.net.module.util.NetworkStackConstants.IPV4_HEADER_MIN_LEN;
+import static com.android.net.module.util.NetworkStackConstants.IPV6_HEADER_LEN;
+import static com.android.net.module.util.NetworkStackConstants.IPV6_MIN_MTU;
 
 import android.annotation.NonNull;
 import android.annotation.Nullable;
@@ -35,6 +38,7 @@
 import android.system.Os;
 import android.system.StructTimeval;
 import android.text.TextUtils;
+import android.util.Log;
 import android.util.Pair;
 
 import com.android.internal.util.IndentingPrintWriter;
@@ -174,7 +178,7 @@
         }
     }
 
-    private final Map<InetAddress, Measurement> mIcmpChecks = new HashMap<>();
+    private final Map<Pair<InetAddress, Integer>, Measurement> mIcmpChecks = new HashMap<>();
     private final Map<Pair<InetAddress, InetAddress>, Measurement> mExplicitSourceIcmpChecks =
             new HashMap<>();
     private final Map<InetAddress, Measurement> mDnsUdpChecks = new HashMap<>();
@@ -207,17 +211,21 @@
             mLinkProperties.addDnsServer(TEST_DNS6);
         }
 
+        final int mtu = mLinkProperties.getMtu();
         for (RouteInfo route : mLinkProperties.getRoutes()) {
             if (route.getType() == RouteInfo.RTN_UNICAST && route.hasGateway()) {
                 InetAddress gateway = route.getGateway();
-                prepareIcmpMeasurement(gateway);
+                // Use mtu in the route if exists. Otherwise, use the one in the link property.
+                final int routeMtu = route.getMtu();
+                prepareIcmpMeasurements(gateway, (routeMtu > 0) ? routeMtu : mtu);
                 if (route.isIPv6Default()) {
                     prepareExplicitSourceIcmpMeasurements(gateway);
                 }
             }
         }
+
         for (InetAddress nameserver : mLinkProperties.getDnsServers()) {
-            prepareIcmpMeasurement(nameserver);
+            prepareIcmpMeasurements(nameserver, mtu);
             prepareDnsMeasurement(nameserver);
 
             // Unlike the DnsResolver which doesn't do certificate validation in opportunistic mode,
@@ -263,11 +271,50 @@
                 localAddr.getHostAddress(), inetSockAddr.getPort());
     }
 
-    private void prepareIcmpMeasurement(InetAddress target) {
-        if (!mIcmpChecks.containsKey(target)) {
-            Measurement measurement = new Measurement();
-            measurement.thread = new Thread(new IcmpCheck(target, 0, measurement));
-            mIcmpChecks.put(target, measurement);
+    private static int getHeaderLen(@NonNull InetAddress target) {
+        // Convert IPv4 mapped v6 address to v4 if any.
+        try {
+            final InetAddress addr = InetAddress.getByAddress(target.getAddress());
+            // An ICMPv6 header is technically 4 bytes, but the implementation in IcmpCheck#run()
+            // will always fill in another 4 bytes padding in the v6 diagnostic packets, so the size
+            // before icmp data is always 8 bytes in the implementation of ICMP diagnostics for both
+            // v4 and v6 packets. Thus, it's fine to use the v4 header size in the length
+            // calculation.
+            if (addr instanceof Inet6Address) {
+                return IPV6_HEADER_LEN + ICMP_HEADER_LEN;
+            }
+        } catch (UnknownHostException e) {
+            Log.e(TAG, "Create InetAddress fail(" + target + "): " + e);
+        }
+
+        return IPV4_HEADER_MIN_LEN + ICMP_HEADER_LEN;
+    }
+
+    private void prepareIcmpMeasurements(@NonNull InetAddress target, int targetNetworkMtu) {
+        // Test with different size payload ICMP.
+        // 1. Test with 0 payload.
+        addPayloadIcmpMeasurement(target, 0);
+        final int header = getHeaderLen(target);
+        // 2. Test with full size MTU.
+        addPayloadIcmpMeasurement(target, targetNetworkMtu - header);
+        // 3. If v6, make another measurement with the full v6 min MTU, unless that's what
+        //    was done above.
+        if ((target instanceof Inet6Address) && (targetNetworkMtu != IPV6_MIN_MTU)) {
+            addPayloadIcmpMeasurement(target, IPV6_MIN_MTU - header);
+        }
+    }
+
+    private void addPayloadIcmpMeasurement(@NonNull InetAddress target, int payloadLen) {
+        // This can happen if the there is no mtu filled(which is 0) in the link property.
+        // The value becomes negative after minus header length.
+        if (payloadLen < 0) return;
+
+        final Pair<InetAddress, Integer> lenTarget =
+                new Pair<>(target, Integer.valueOf(payloadLen));
+        if (!mIcmpChecks.containsKey(lenTarget)) {
+            final Measurement measurement = new Measurement();
+            measurement.thread = new Thread(new IcmpCheck(target, payloadLen, measurement));
+            mIcmpChecks.put(lenTarget, measurement);
         }
     }
 
@@ -336,8 +383,8 @@
         ArrayList<Measurement> measurements = new ArrayList(totalMeasurementCount());
 
         // Sort measurements IPv4 first.
-        for (Map.Entry<InetAddress, Measurement> entry : mIcmpChecks.entrySet()) {
-            if (entry.getKey() instanceof Inet4Address) {
+        for (Map.Entry<Pair<InetAddress, Integer>, Measurement> entry : mIcmpChecks.entrySet()) {
+            if (entry.getKey().first instanceof Inet4Address) {
                 measurements.add(entry.getValue());
             }
         }
@@ -359,8 +406,8 @@
         }
 
         // IPv6 measurements second.
-        for (Map.Entry<InetAddress, Measurement> entry : mIcmpChecks.entrySet()) {
-            if (entry.getKey() instanceof Inet6Address) {
+        for (Map.Entry<Pair<InetAddress, Integer>, Measurement> entry : mIcmpChecks.entrySet()) {
+            if (entry.getKey().first instanceof Inet6Address) {
                 measurements.add(entry.getValue());
             }
         }
diff --git a/tests/cts/net/src/android/net/cts/NetworkScoreTest.kt b/tests/cts/net/src/android/net/cts/NetworkScoreTest.kt
index fcfecad..2704dd3 100644
--- a/tests/cts/net/src/android/net/cts/NetworkScoreTest.kt
+++ b/tests/cts/net/src/android/net/cts/NetworkScoreTest.kt
@@ -30,6 +30,7 @@
 import android.os.Build
 import android.os.Handler
 import android.os.HandlerThread
+import android.util.Log
 import androidx.test.InstrumentationRegistry
 import com.android.compatibility.common.util.SystemUtil.runWithShellPermissionIdentity
 import com.android.testutils.DevSdkIgnoreRule.IgnoreUpTo
@@ -41,6 +42,7 @@
 import org.junit.Before
 import org.junit.Test
 import org.junit.runner.RunWith
+import java.util.Collections
 
 // This test doesn't really have a constraint on how fast the methods should return. If it's
 // going to fail, it will simply wait forever, so setting a high timeout lowers the flake ratio
@@ -64,10 +66,11 @@
 @IgnoreUpTo(Build.VERSION_CODES.R)
 @RunWith(DevSdkIgnoreRunner::class)
 class NetworkScoreTest {
+    private val TAG = javaClass.simpleName
     private val mCm = testContext.getSystemService(ConnectivityManager::class.java)
-    private val mHandlerThread = HandlerThread("${javaClass.simpleName} handler thread")
+    private val mHandlerThread = HandlerThread("$TAG handler thread")
     private val mHandler by lazy { Handler(mHandlerThread.looper) }
-    private val agentsToCleanUp = mutableListOf<NetworkAgent>()
+    private val agentsToCleanUp = Collections.synchronizedList(mutableListOf<NetworkAgent>())
     private val callbacksToCleanUp = mutableListOf<TestableNetworkCallback>()
 
     @Before
@@ -83,15 +86,18 @@
                     .addTransportType(NetworkCapabilities.TRANSPORT_TEST).build(), cb, mHandler
             )
         }
+        Log.i(TAG, "Teardown on thread ${System.identityHashCode(Thread.currentThread())} " +
+                "cleaning up ${agentsToCleanUp.size} agents")
         agentsToCleanUp.forEach {
+            Log.i(TAG, "Unregister agent for net ${it.network}")
             it.unregister()
             agentCleanUpCb.eventuallyExpect<CallbackEntry.Lost> { cb -> cb.network == it.network }
         }
         mCm.unregisterNetworkCallback(agentCleanUpCb)
 
+        callbacksToCleanUp.forEach { mCm.unregisterNetworkCallback(it) }
         mHandlerThread.quitSafely()
         mHandlerThread.join()
-        callbacksToCleanUp.forEach { mCm.unregisterNetworkCallback(it) }
     }
 
     // Returns a networkCallback that sends onAvailable on the best network with TRANSPORT_TEST.
@@ -145,6 +151,8 @@
         val agent = object : NetworkAgent(context, looper, "NetworkScore test agent", nc,
                 LinkProperties(), score, config, NetworkProvider(context, looper,
                 "NetworkScore test provider")) {}.also {
+            Log.i(TAG, "Add on thread ${System.identityHashCode(Thread.currentThread())} " +
+                    "agent to clean up $it")
             agentsToCleanUp.add(it)
         }
         runWithShellPermissionIdentity({ agent.register() }, MANAGE_TEST_NETWORKS)