diff --git a/bpf_progs/bpf_shared.h b/bpf_progs/bpf_shared.h
index a6e78b6..9a246a6 100644
--- a/bpf_progs/bpf_shared.h
+++ b/bpf_progs/bpf_shared.h
@@ -132,6 +132,7 @@
     RESTRICTED_MATCH = (1 << 5),
     LOW_POWER_STANDBY_MATCH = (1 << 6),
     IIF_MATCH = (1 << 7),
+    LOCKDOWN_VPN_MATCH = (1 << 8),
 };
 
 enum BpfPermissionMatch {
diff --git a/bpf_progs/netd.c b/bpf_progs/netd.c
index f3f675f..76911f4 100644
--- a/bpf_progs/netd.c
+++ b/bpf_progs/netd.c
@@ -214,9 +214,16 @@
             return BPF_DROP;
         }
     }
-    if (direction == BPF_INGRESS && (uidRules & IIF_MATCH)) {
-        // Drops packets not coming from lo nor the allowlisted interface
-        if (allowed_iif && skb->ifindex != 1 && skb->ifindex != allowed_iif) {
+    if (direction == BPF_INGRESS && skb->ifindex != 1) {
+        if (uidRules & IIF_MATCH) {
+            if (allowed_iif && skb->ifindex != allowed_iif) {
+                // Drops packets not coming from lo nor the allowed interface
+                // allowed interface=0 is a wildcard and does not drop packets
+                return BPF_DROP_UNLESS_DNS;
+            }
+        } else if (uidRules & LOCKDOWN_VPN_MATCH) {
+            // Drops packets not coming from lo and rule does not have IIF_MATCH but has
+            // LOCKDOWN_VPN_MATCH
             return BPF_DROP_UNLESS_DNS;
         }
     }
diff --git a/framework/src/android/net/ConnectivityManager.java b/framework/src/android/net/ConnectivityManager.java
index a174fe3..4ecc8a1 100644
--- a/framework/src/android/net/ConnectivityManager.java
+++ b/framework/src/android/net/ConnectivityManager.java
@@ -982,6 +982,16 @@
     @SystemApi(client = MODULE_LIBRARIES)
     public static final int FIREWALL_CHAIN_LOW_POWER_STANDBY = 5;
 
+    /**
+     * Firewall chain used for lockdown VPN.
+     * Denylist of apps that cannot receive incoming packets except on loopback because they are
+     * subject to an always-on VPN which is not currently connected.
+     *
+     * @see #BLOCKED_REASON_LOCKDOWN_VPN
+     * @hide
+     */
+    public static final int FIREWALL_CHAIN_LOCKDOWN_VPN = 6;
+
     /** @hide */
     @Retention(RetentionPolicy.SOURCE)
     @IntDef(flag = false, prefix = "FIREWALL_CHAIN_", value = {
@@ -989,7 +999,8 @@
         FIREWALL_CHAIN_STANDBY,
         FIREWALL_CHAIN_POWERSAVE,
         FIREWALL_CHAIN_RESTRICTED,
-        FIREWALL_CHAIN_LOW_POWER_STANDBY
+        FIREWALL_CHAIN_LOW_POWER_STANDBY,
+        FIREWALL_CHAIN_LOCKDOWN_VPN
     })
     public @interface FirewallChain {}
     // LINT.ThenChange(packages/modules/Connectivity/service/native/include/Common.h)
diff --git a/service/jni/com_android_server_BpfNetMaps.cpp b/service/jni/com_android_server_BpfNetMaps.cpp
index f13c68d..7b1f59c 100644
--- a/service/jni/com_android_server_BpfNetMaps.cpp
+++ b/service/jni/com_android_server_BpfNetMaps.cpp
@@ -133,12 +133,16 @@
 
 static jint native_addUidInterfaceRules(JNIEnv* env, jobject clazz, jstring ifName,
                                     jintArray jUids) {
-    const ScopedUtfChars ifNameUtf8(env, ifName);
-    if (ifNameUtf8.c_str() == nullptr) {
-        return -EINVAL;
+    // Null ifName is a wildcard to allow apps to receive packets on all interfaces and ifIndex is
+    // set to 0.
+    int ifIndex;
+    if (ifName != nullptr) {
+        const ScopedUtfChars ifNameUtf8(env, ifName);
+        const std::string interfaceName(ifNameUtf8.c_str());
+        ifIndex = if_nametoindex(interfaceName.c_str());
+    } else {
+        ifIndex = 0;
     }
-    const std::string interfaceName(ifNameUtf8.c_str());
-    const int ifIndex = if_nametoindex(interfaceName.c_str());
 
     ScopedIntArrayRO uids(env, jUids);
     if (uids.get() == nullptr) {
diff --git a/service/native/TrafficController.cpp b/service/native/TrafficController.cpp
index 473c9e3..5581c40 100644
--- a/service/native/TrafficController.cpp
+++ b/service/native/TrafficController.cpp
@@ -98,6 +98,7 @@
     FLAG_MSG_TRANS(matchType, RESTRICTED_MATCH, match);
     FLAG_MSG_TRANS(matchType, LOW_POWER_STANDBY_MATCH, match);
     FLAG_MSG_TRANS(matchType, IIF_MATCH, match);
+    FLAG_MSG_TRANS(matchType, LOCKDOWN_VPN_MATCH, match);
     if (match) {
         return StringPrintf("Unknown match: %u", match);
     }
@@ -286,16 +287,13 @@
 }
 
 Status TrafficController::addRule(uint32_t uid, UidOwnerMatchType match, uint32_t iif) {
-    // iif should be non-zero if and only if match == MATCH_IIF
-    if (match == IIF_MATCH && iif == 0) {
-        return statusFromErrno(EINVAL, "Interface match must have nonzero interface index");
-    } else if (match != IIF_MATCH && iif != 0) {
+    if (match != IIF_MATCH && iif != 0) {
         return statusFromErrno(EINVAL, "Non-interface match must have zero interface index");
     }
     auto oldMatch = mUidOwnerMap.readValue(uid);
     if (oldMatch.ok()) {
         UidOwnerValue newMatch = {
-                .iif = iif ? iif : oldMatch.value().iif,
+                .iif = (match == IIF_MATCH) ? iif : oldMatch.value().iif,
                 .rule = oldMatch.value().rule | match,
         };
         RETURN_IF_NOT_OK(mUidOwnerMap.writeValue(uid, newMatch, BPF_ANY));
@@ -335,6 +333,8 @@
             return ALLOWLIST;
         case LOW_POWER_STANDBY:
             return ALLOWLIST;
+        case LOCKDOWN:
+            return DENYLIST;
         case NONE:
         default:
             return DENYLIST;
@@ -360,6 +360,9 @@
         case LOW_POWER_STANDBY:
             res = updateOwnerMapEntry(LOW_POWER_STANDBY_MATCH, uid, rule, type);
             break;
+        case LOCKDOWN:
+            res = updateOwnerMapEntry(LOCKDOWN_VPN_MATCH, uid, rule, type);
+            break;
         case NONE:
         default:
             ALOGW("Unknown child chain: %d", chain);
@@ -399,9 +402,6 @@
 
 Status TrafficController::addUidInterfaceRules(const int iif,
                                                const std::vector<int32_t>& uidsToAdd) {
-    if (!iif) {
-        return statusFromErrno(EINVAL, "Interface rule must specify interface");
-    }
     std::lock_guard guard(mMutex);
 
     for (auto uid : uidsToAdd) {
diff --git a/service/native/TrafficControllerTest.cpp b/service/native/TrafficControllerTest.cpp
index 9529cae..ad53cb8 100644
--- a/service/native/TrafficControllerTest.cpp
+++ b/service/native/TrafficControllerTest.cpp
@@ -307,6 +307,7 @@
     checkUidOwnerRuleForChain(POWERSAVE, POWERSAVE_MATCH);
     checkUidOwnerRuleForChain(RESTRICTED, RESTRICTED_MATCH);
     checkUidOwnerRuleForChain(LOW_POWER_STANDBY, LOW_POWER_STANDBY_MATCH);
+    checkUidOwnerRuleForChain(LOCKDOWN, LOCKDOWN_VPN_MATCH);
     ASSERT_EQ(-EINVAL, mTc.changeUidOwnerRule(NONE, TEST_UID, ALLOW, ALLOWLIST));
     ASSERT_EQ(-EINVAL, mTc.changeUidOwnerRule(INVALID_CHAIN, TEST_UID, ALLOW, ALLOWLIST));
 }
@@ -491,6 +492,70 @@
     checkEachUidValue({10001, 10002}, IIF_MATCH);
 }
 
+TEST_F(TrafficControllerTest, TestAddUidInterfaceFilteringRulesWithWildcard) {
+    // iif=0 is a wildcard
+    int iif = 0;
+    // Add interface rule with wildcard to uids
+    ASSERT_TRUE(isOk(mTc.addUidInterfaceRules(iif, {1000, 1001})));
+    expectUidOwnerMapValues({1000, 1001}, IIF_MATCH, iif);
+}
+
+TEST_F(TrafficControllerTest, TestRemoveUidInterfaceFilteringRulesWithWildcard) {
+    // iif=0 is a wildcard
+    int iif = 0;
+    // Add interface rule with wildcard to two uids
+    ASSERT_TRUE(isOk(mTc.addUidInterfaceRules(iif, {1000, 1001})));
+    expectUidOwnerMapValues({1000, 1001}, IIF_MATCH, iif);
+
+    // Remove interface rule from one of the uids
+    ASSERT_TRUE(isOk(mTc.removeUidInterfaceRules({1000})));
+    expectUidOwnerMapValues({1001}, IIF_MATCH, iif);
+    checkEachUidValue({1001}, IIF_MATCH);
+
+    // Remove interface rule from the remaining uid
+    ASSERT_TRUE(isOk(mTc.removeUidInterfaceRules({1001})));
+    expectMapEmpty(mFakeUidOwnerMap);
+}
+
+TEST_F(TrafficControllerTest, TestUidInterfaceFilteringRulesWithWildcardAndExistingMatches) {
+    // Set up existing DOZABLE_MATCH and POWERSAVE_MATCH rule
+    ASSERT_TRUE(isOk(updateUidOwnerMaps({1000}, DOZABLE_MATCH,
+                                        TrafficController::IptOpInsert)));
+    ASSERT_TRUE(isOk(updateUidOwnerMaps({1000}, POWERSAVE_MATCH,
+                                        TrafficController::IptOpInsert)));
+
+    // iif=0 is a wildcard
+    int iif = 0;
+    // Add interface rule with wildcard to the existing uid
+    ASSERT_TRUE(isOk(mTc.addUidInterfaceRules(iif, {1000})));
+    expectUidOwnerMapValues({1000}, POWERSAVE_MATCH | DOZABLE_MATCH | IIF_MATCH, iif);
+
+    // Remove interface rule with wildcard from the existing uid
+    ASSERT_TRUE(isOk(mTc.removeUidInterfaceRules({1000})));
+    expectUidOwnerMapValues({1000}, POWERSAVE_MATCH | DOZABLE_MATCH, 0);
+}
+
+TEST_F(TrafficControllerTest, TestUidInterfaceFilteringRulesWithWildcardAndNewMatches) {
+    // iif=0 is a wildcard
+    int iif = 0;
+    // Set up existing interface rule with wildcard
+    ASSERT_TRUE(isOk(mTc.addUidInterfaceRules(iif, {1000})));
+
+    // Add DOZABLE_MATCH and POWERSAVE_MATCH rule to the existing uid
+    ASSERT_TRUE(isOk(updateUidOwnerMaps({1000}, DOZABLE_MATCH,
+                                        TrafficController::IptOpInsert)));
+    ASSERT_TRUE(isOk(updateUidOwnerMaps({1000}, POWERSAVE_MATCH,
+                                        TrafficController::IptOpInsert)));
+    expectUidOwnerMapValues({1000}, POWERSAVE_MATCH | DOZABLE_MATCH | IIF_MATCH, iif);
+
+    // Remove DOZABLE_MATCH and POWERSAVE_MATCH rule from the existing uid
+    ASSERT_TRUE(isOk(updateUidOwnerMaps({1000}, DOZABLE_MATCH,
+                                        TrafficController::IptOpDelete)));
+    ASSERT_TRUE(isOk(updateUidOwnerMaps({1000}, POWERSAVE_MATCH,
+                                        TrafficController::IptOpDelete)));
+    expectUidOwnerMapValues({1000}, IIF_MATCH, iif);
+}
+
 TEST_F(TrafficControllerTest, TestGrantInternetPermission) {
     std::vector<uid_t> appUids = {TEST_UID, TEST_UID2, TEST_UID3};
 
diff --git a/service/native/include/Common.h b/service/native/include/Common.h
index dc44845..847acec 100644
--- a/service/native/include/Common.h
+++ b/service/native/include/Common.h
@@ -35,6 +35,7 @@
     POWERSAVE = 3,
     RESTRICTED = 4,
     LOW_POWER_STANDBY = 5,
+    LOCKDOWN = 6,
     INVALID_CHAIN
 };
 // LINT.ThenChange(packages/modules/Connectivity/framework/src/android/net/ConnectivityManager.java)
diff --git a/service/src/com/android/server/ConnectivityService.java b/service/src/com/android/server/ConnectivityService.java
index d17ff0f..5bac1a1 100644
--- a/service/src/com/android/server/ConnectivityService.java
+++ b/service/src/com/android/server/ConnectivityService.java
@@ -5974,6 +5974,10 @@
                     + Arrays.toString(ranges) + "): netd command failed: " + e);
         }
 
+        if (SdkLevel.isAtLeastT()) {
+            mPermissionMonitor.updateVpnLockdownUidRanges(requireVpn, ranges);
+        }
+
         for (final NetworkAgentInfo nai : mNetworkAgentInfos) {
             final boolean curMetered = nai.networkCapabilities.isMetered();
             maybeNotifyNetworkBlocked(nai, curMetered, curMetered,
@@ -7739,8 +7743,8 @@
             NetworkAgentInfo nai) {
         final String oldIface = getVpnIsolationInterface(nai, nai.networkCapabilities, oldLp);
         final String newIface = getVpnIsolationInterface(nai, nai.networkCapabilities, newLp);
-        final boolean wasFiltering = requiresVpnAllowRule(oldIface);
-        final boolean needsFiltering = requiresVpnAllowRule(newIface);
+        final boolean wasFiltering = requiresVpnAllowRule(nai, oldLp, oldIface);
+        final boolean needsFiltering = requiresVpnAllowRule(nai, newLp, newIface);
 
         if (!wasFiltering && !needsFiltering) {
             // Nothing to do.
@@ -7753,11 +7757,19 @@
         }
 
         final Set<UidRange> ranges = nai.networkCapabilities.getUidRanges();
+        if (ranges == null || ranges.isEmpty()) {
+            return;
+        }
+
         final int vpnAppUid = nai.networkCapabilities.getOwnerUid();
         // TODO: this create a window of opportunity for apps to receive traffic between the time
         // when the old rules are removed and the time when new rules are added. To fix this,
         // make eBPF support two allowlisted interfaces so here new rules can be added before the
         // old rules are being removed.
+
+        // Null iface given to onVpnUidRangesAdded/Removed is a wildcard to allow apps to receive
+        // packets on all interfaces. This is required to accept incoming traffic in Lockdown mode
+        // by overriding the Lockdown blocking rule.
         if (wasFiltering) {
             mPermissionMonitor.onVpnUidRangesRemoved(oldIface, ranges, vpnAppUid);
         }
@@ -8081,9 +8093,13 @@
     /**
      * Returns whether we need to set interface filtering rule or not
      */
-    private boolean requiresVpnAllowRule(String filterIface) {
-        // Allow rules are only needed if VPN isolation is enabled.
-        return filterIface != null;
+    private boolean requiresVpnAllowRule(NetworkAgentInfo nai, LinkProperties lp,
+            String filterIface) {
+        // Only filter if lp has an interface.
+        if (lp == null || lp.getInterfaceName() == null) return false;
+        // Before T, allow rules are only needed if VPN isolation is enabled.
+        // T and After T, allow rules are needed for all VPNs.
+        return filterIface != null || (nai.isVPN() && SdkLevel.isAtLeastT());
     }
 
     private static UidRangeParcel[] toUidRangeStableParcels(final @NonNull Set<UidRange> ranges) {
@@ -8213,8 +8229,8 @@
             }
             final String oldIface = getVpnIsolationInterface(nai, prevNc, nai.linkProperties);
             final String newIface = getVpnIsolationInterface(nai, newNc, nai.linkProperties);
-            final boolean wasFiltering = requiresVpnAllowRule(oldIface);
-            final boolean shouldFilter = requiresVpnAllowRule(newIface);
+            final boolean wasFiltering = requiresVpnAllowRule(nai, nai.linkProperties, oldIface);
+            final boolean shouldFilter = requiresVpnAllowRule(nai, nai.linkProperties, newIface);
             // For VPN uid interface filtering, old ranges need to be removed before new ranges can
             // be added, due to the range being expanded and stored as individual UIDs. For example
             // the UIDs might be updated from [0, 99999] to ([0, 10012], [10014, 99999]) which means
@@ -8226,6 +8242,10 @@
             // above, where the addition of new ranges happens before the removal of old ranges.
             // TODO Fix this window by computing an accurate diff on Set<UidRange>, so the old range
             // to be removed will never overlap with the new range to be added.
+
+            // Null iface given to onVpnUidRangesAdded/Removed is a wildcard to allow apps to
+            // receive packets on all interfaces. This is required to accept incoming traffic in
+            // Lockdown mode by overriding the Lockdown blocking rule.
             if (wasFiltering && !prevRanges.isEmpty()) {
                 mPermissionMonitor.onVpnUidRangesRemoved(oldIface, prevRanges,
                         prevNc.getOwnerUid());
diff --git a/service/src/com/android/server/connectivity/PermissionMonitor.java b/service/src/com/android/server/connectivity/PermissionMonitor.java
index 8d99cb4..e4a2c20 100755
--- a/service/src/com/android/server/connectivity/PermissionMonitor.java
+++ b/service/src/com/android/server/connectivity/PermissionMonitor.java
@@ -23,6 +23,9 @@
 import static android.Manifest.permission.UPDATE_DEVICE_STATS;
 import static android.content.pm.PackageInfo.REQUESTED_PERMISSION_GRANTED;
 import static android.content.pm.PackageManager.GET_PERMISSIONS;
+import static android.net.ConnectivityManager.FIREWALL_CHAIN_LOCKDOWN_VPN;
+import static android.net.ConnectivityManager.FIREWALL_RULE_ALLOW;
+import static android.net.ConnectivityManager.FIREWALL_RULE_DENY;
 import static android.net.ConnectivitySettingsManager.UIDS_ALLOWED_ON_RESTRICTED_NETWORKS;
 import static android.net.INetd.PERMISSION_INTERNET;
 import static android.net.INetd.PERMISSION_NETWORK;
@@ -37,6 +40,7 @@
 import static com.android.net.module.util.CollectionUtils.toIntArray;
 
 import android.annotation.NonNull;
+import android.annotation.Nullable;
 import android.content.BroadcastReceiver;
 import android.content.Context;
 import android.content.Intent;
@@ -74,7 +78,6 @@
 import com.android.server.BpfNetMaps;
 
 import java.util.ArrayList;
-import java.util.HashMap;
 import java.util.HashSet;
 import java.util.List;
 import java.util.Map;
@@ -108,10 +111,19 @@
     @GuardedBy("this")
     private final SparseIntArray mUidToNetworkPerm = new SparseIntArray();
 
-    // Keys are active non-bypassable and fully-routed VPN's interface name, Values are uid ranges
-    // for apps under the VPN
+    // NonNull keys are active non-bypassable and fully-routed VPN's interface name, Values are uid
+    // ranges for apps under the VPNs which enable interface filtering.
+    // If key is null, Values are uid ranges for apps under the VPNs which are connected but do not
+    // enable interface filtering.
     @GuardedBy("this")
-    private final Map<String, Set<UidRange>> mVpnUidRanges = new HashMap<>();
+    private final Map<String, Set<UidRange>> mVpnInterfaceUidRanges = new ArrayMap<>();
+
+    // Items are uid ranges for apps under the VPN Lockdown
+    // Ranges were given through ConnectivityManager#setRequireVpnForUids, and ranges are allowed to
+    // have duplicates. Also, it is allowed to give ranges that are already subject to lockdown.
+    // So we need to maintain uid range with multiset.
+    @GuardedBy("this")
+    private final MultiSet<UidRange> mVpnLockdownUidRanges = new MultiSet<>();
 
     // A set of appIds for apps across all users on the device. We track appIds instead of uids
     // directly to reduce its size and also eliminate the need to update this set when user is
@@ -201,6 +213,38 @@
         }
     }
 
+    private static class MultiSet<T> {
+        private final Map<T, Integer> mMap = new ArrayMap<>();
+
+        /**
+         * Returns the number of key in the set before this addition.
+         */
+        public int add(T key) {
+            final int oldCount = mMap.getOrDefault(key, 0);
+            mMap.put(key, oldCount + 1);
+            return oldCount;
+        }
+
+        /**
+         * Return the number of key in the set before this removal.
+         */
+        public int remove(T key) {
+            final int oldCount = mMap.getOrDefault(key, 0);
+            if (oldCount == 0) {
+                Log.wtf(TAG, "Attempt to remove non existing key = " + key.toString());
+            } else if (oldCount == 1) {
+                mMap.remove(key);
+            } else {
+                mMap.put(key, oldCount - 1);
+            }
+            return oldCount;
+        }
+
+        public Set<T> getSet() {
+            return mMap.keySet();
+        }
+    }
+
     public PermissionMonitor(@NonNull final Context context, @NonNull final INetd netd,
             @NonNull final BpfNetMaps bpfNetMaps) {
         this(context, netd, bpfNetMaps, new Dependencies());
@@ -626,16 +670,26 @@
     }
 
     private synchronized void updateVpnUid(int uid, boolean add) {
-        for (Map.Entry<String, Set<UidRange>> vpn : mVpnUidRanges.entrySet()) {
+        // Apps that can use restricted networks can always bypass VPNs.
+        if (hasRestrictedNetworksPermission(uid)) {
+            return;
+        }
+        for (Map.Entry<String, Set<UidRange>> vpn : mVpnInterfaceUidRanges.entrySet()) {
             if (UidRange.containsUid(vpn.getValue(), uid)) {
                 final Set<Integer> changedUids = new HashSet<>();
                 changedUids.add(uid);
-                removeBypassingUids(changedUids, -1 /* vpnAppUid */);
                 updateVpnUidsInterfaceRules(vpn.getKey(), changedUids, add);
             }
         }
     }
 
+    private synchronized void updateLockdownUid(int uid, boolean add) {
+        if (UidRange.containsUid(mVpnLockdownUidRanges.getSet(), uid)
+                && !hasRestrictedNetworksPermission(uid)) {
+            updateLockdownUidRule(uid, add);
+        }
+    }
+
     /**
      * This handles both network and traffic permission, because there is no overlap in actual
      * values, where network permission is NETWORK or SYSTEM, and traffic permission is INTERNET
@@ -729,9 +783,10 @@
 
         // If the newly-installed package falls within some VPN's uid range, update Netd with it.
         // This needs to happen after the mUidToNetworkPerm update above, since
-        // removeBypassingUids() in updateVpnUid() depends on mUidToNetworkPerm to check if the
-        // package can bypass VPN.
+        // hasRestrictedNetworksPermission() in updateVpnUid() and updateLockdownUid() depends on
+        // mUidToNetworkPerm to check if the package can bypass VPN.
         updateVpnUid(uid, true /* add */);
+        updateLockdownUid(uid, true /* add */);
         mAllApps.add(appId);
 
         // Log package added.
@@ -775,9 +830,10 @@
 
         // If the newly-removed package falls within some VPN's uid range, update Netd with it.
         // This needs to happen before the mUidToNetworkPerm update below, since
-        // removeBypassingUids() in updateVpnUid() depends on mUidToNetworkPerm to check if the
-        // package can bypass VPN.
+        // hasRestrictedNetworksPermission() in updateVpnUid() and updateLockdownUid() depends on
+        // mUidToNetworkPerm to check if the package can bypass VPN.
         updateVpnUid(uid, false /* add */);
+        updateLockdownUid(uid, false /* add */);
         // If the package has been removed from all users on the device, clear it form mAllApps.
         if (mPackageManager.getNameForUid(uid) == null) {
             mAllApps.remove(appId);
@@ -859,48 +915,100 @@
     /**
      * Called when a new set of UID ranges are added to an active VPN network
      *
-     * @param iface The active VPN network's interface name
+     * @param iface The active VPN network's interface name. Null iface indicates that the app is
+     *              allowed to receive packets on all interfaces.
      * @param rangesToAdd The new UID ranges to be added to the network
      * @param vpnAppUid The uid of the VPN app
      */
-    public synchronized void onVpnUidRangesAdded(@NonNull String iface, Set<UidRange> rangesToAdd,
+    public synchronized void onVpnUidRangesAdded(@Nullable String iface, Set<UidRange> rangesToAdd,
             int vpnAppUid) {
         // Calculate the list of new app uids under the VPN due to the new UID ranges and update
         // Netd about them. Because mAllApps only contains appIds instead of uids, the result might
         // be an overestimation if an app is not installed on the user on which the VPN is running,
-        // but that's safe.
+        // but that's safe: if an app is not installed, it cannot receive any packets, so dropping
+        // packets to that UID is fine.
         final Set<Integer> changedUids = intersectUids(rangesToAdd, mAllApps);
         removeBypassingUids(changedUids, vpnAppUid);
         updateVpnUidsInterfaceRules(iface, changedUids, true /* add */);
-        if (mVpnUidRanges.containsKey(iface)) {
-            mVpnUidRanges.get(iface).addAll(rangesToAdd);
+        if (mVpnInterfaceUidRanges.containsKey(iface)) {
+            mVpnInterfaceUidRanges.get(iface).addAll(rangesToAdd);
         } else {
-            mVpnUidRanges.put(iface, new HashSet<UidRange>(rangesToAdd));
+            mVpnInterfaceUidRanges.put(iface, new HashSet<UidRange>(rangesToAdd));
         }
     }
 
     /**
      * Called when a set of UID ranges are removed from an active VPN network
      *
-     * @param iface The VPN network's interface name
+     * @param iface The VPN network's interface name. Null iface indicates that the app is allowed
+     *              to receive packets on all interfaces.
      * @param rangesToRemove Existing UID ranges to be removed from the VPN network
      * @param vpnAppUid The uid of the VPN app
      */
-    public synchronized void onVpnUidRangesRemoved(@NonNull String iface,
+    public synchronized void onVpnUidRangesRemoved(@Nullable String iface,
             Set<UidRange> rangesToRemove, int vpnAppUid) {
         // Calculate the list of app uids that are no longer under the VPN due to the removed UID
         // ranges and update Netd about them.
         final Set<Integer> changedUids = intersectUids(rangesToRemove, mAllApps);
         removeBypassingUids(changedUids, vpnAppUid);
         updateVpnUidsInterfaceRules(iface, changedUids, false /* add */);
-        Set<UidRange> existingRanges = mVpnUidRanges.getOrDefault(iface, null);
+        Set<UidRange> existingRanges = mVpnInterfaceUidRanges.getOrDefault(iface, null);
         if (existingRanges == null) {
             loge("Attempt to remove unknown vpn uid Range iface = " + iface);
             return;
         }
         existingRanges.removeAll(rangesToRemove);
         if (existingRanges.size() == 0) {
-            mVpnUidRanges.remove(iface);
+            mVpnInterfaceUidRanges.remove(iface);
+        }
+    }
+
+    /**
+     * Called when UID ranges under VPN Lockdown are updated
+     *
+     * @param add {@code true} if the uids are to be added to the Lockdown, {@code false} if they
+     *        are to be removed from the Lockdown.
+     * @param ranges The updated UID ranges under VPN Lockdown. This function does not treat the VPN
+     *               app's UID in any special way. The caller is responsible for excluding the VPN
+     *               app UID from the passed-in ranges.
+     *               Ranges can have duplications and/or contain the range that is already subject
+     *               to lockdown. However, ranges can not have overlaps with other ranges including
+     *               ranges that are currently subject to lockdown.
+     */
+    public synchronized void updateVpnLockdownUidRanges(boolean add, UidRange[] ranges) {
+        final Set<UidRange> affectedUidRanges = new HashSet<>();
+
+        for (final UidRange range : ranges) {
+            if (add) {
+                // Rule will be added if mVpnLockdownUidRanges does not have this uid range entry
+                // currently.
+                if (mVpnLockdownUidRanges.add(range) == 0) {
+                    affectedUidRanges.add(range);
+                }
+            } else {
+                // Rule will be removed if the number of the range in the set is 1 before the
+                // removal.
+                if (mVpnLockdownUidRanges.remove(range) == 1) {
+                    affectedUidRanges.add(range);
+                }
+            }
+        }
+
+        // mAllApps only contains appIds instead of uids. So the generated uid list might contain
+        // apps that are installed only on some users but not others. But that's safe: if an app is
+        // not installed, it cannot receive any packets, so dropping packets to that UID is fine.
+        final Set<Integer> affectedUids = intersectUids(affectedUidRanges, mAllApps);
+
+        // We skip adding rule to privileged apps and allow them to bypass incoming packet
+        // filtering. The behaviour is consistent with how lockdown works for outgoing packets, but
+        // the implementation is different: while ConnectivityService#setRequireVpnForUids does not
+        // exclude privileged apps from the prohibit routing rules used to implement outgoing packet
+        // filtering, privileged apps can still bypass outgoing packet filtering because the
+        // prohibit rules observe the protected from VPN bit.
+        for (final int uid: affectedUids) {
+            if (!hasRestrictedNetworksPermission(uid)) {
+                updateLockdownUidRule(uid, add);
+            }
         }
     }
 
@@ -939,7 +1047,7 @@
      */
     private void removeBypassingUids(Set<Integer> uids, int vpnAppUid) {
         uids.remove(vpnAppUid);
-        uids.removeIf(uid -> mUidToNetworkPerm.get(uid, PERMISSION_NONE) == PERMISSION_SYSTEM);
+        uids.removeIf(this::hasRestrictedNetworksPermission);
     }
 
     /**
@@ -948,6 +1056,7 @@
      *
      * This is to instruct netd to set up appropriate filtering rules for these uids, such that they
      * can only receive ingress packets from the VPN's tunnel interface (and loopback).
+     * Null iface set up a wildcard rule that allow app to receive packets on all interfaces.
      *
      * @param iface the interface name of the active VPN connection
      * @param add {@code true} if the uids are to be added to the interface, {@code false} if they
@@ -968,6 +1077,18 @@
         }
     }
 
+    private void updateLockdownUidRule(int uid, boolean add) {
+        try {
+            if (add) {
+                mBpfNetMaps.setUidRule(FIREWALL_CHAIN_LOCKDOWN_VPN, uid, FIREWALL_RULE_DENY);
+            } else {
+                mBpfNetMaps.setUidRule(FIREWALL_CHAIN_LOCKDOWN_VPN, uid, FIREWALL_RULE_ALLOW);
+            }
+        } catch (ServiceSpecificException e) {
+            loge("Failed to " + (add ? "add" : "remove") + " Lockdown rule: " + e);
+        }
+    }
+
     /**
      * Send the updated permission information to netd. Called upon package install/uninstall.
      *
@@ -1055,8 +1176,14 @@
 
     /** Should only be used by unit tests */
     @VisibleForTesting
-    public Set<UidRange> getVpnUidRanges(String iface) {
-        return mVpnUidRanges.get(iface);
+    public Set<UidRange> getVpnInterfaceUidRanges(String iface) {
+        return mVpnInterfaceUidRanges.get(iface);
+    }
+
+    /** Should only be used by unit tests */
+    @VisibleForTesting
+    public Set<UidRange> getVpnLockdownUidRanges() {
+        return mVpnLockdownUidRanges.getSet();
     }
 
     private synchronized void onSettingChanged() {
@@ -1121,7 +1248,7 @@
     public void dump(IndentingPrintWriter pw) {
         pw.println("Interface filtering rules:");
         pw.increaseIndent();
-        for (Map.Entry<String, Set<UidRange>> vpn : mVpnUidRanges.entrySet()) {
+        for (Map.Entry<String, Set<UidRange>> vpn : mVpnInterfaceUidRanges.entrySet()) {
             pw.println("Interface: " + vpn.getKey());
             pw.println("UIDs: " + vpn.getValue().toString());
             pw.println();
@@ -1129,6 +1256,14 @@
         pw.decreaseIndent();
 
         pw.println();
+        pw.println("Lockdown filtering rules:");
+        pw.increaseIndent();
+        for (final UidRange range : mVpnLockdownUidRanges.getSet()) {
+            pw.println("UIDs: " + range.toString());
+        }
+        pw.decreaseIndent();
+
+        pw.println();
         pw.println("Update logs:");
         pw.increaseIndent();
         mPermissionUpdateLogs.reverseDump(pw);
diff --git a/tests/unit/java/com/android/server/ConnectivityServiceTest.java b/tests/unit/java/com/android/server/ConnectivityServiceTest.java
index b7da17b..9961978 100644
--- a/tests/unit/java/com/android/server/ConnectivityServiceTest.java
+++ b/tests/unit/java/com/android/server/ConnectivityServiceTest.java
@@ -52,6 +52,9 @@
 import static android.net.ConnectivityManager.CONNECTIVITY_ACTION;
 import static android.net.ConnectivityManager.EXTRA_NETWORK_INFO;
 import static android.net.ConnectivityManager.EXTRA_NETWORK_TYPE;
+import static android.net.ConnectivityManager.FIREWALL_CHAIN_LOCKDOWN_VPN;
+import static android.net.ConnectivityManager.FIREWALL_RULE_ALLOW;
+import static android.net.ConnectivityManager.FIREWALL_RULE_DENY;
 import static android.net.ConnectivityManager.PROFILE_NETWORK_PREFERENCE_DEFAULT;
 import static android.net.ConnectivityManager.PROFILE_NETWORK_PREFERENCE_ENTERPRISE;
 import static android.net.ConnectivityManager.PROFILE_NETWORK_PREFERENCE_ENTERPRISE_NO_FALLBACK;
@@ -9502,6 +9505,46 @@
         b2.expectBroadcast();
     }
 
+    @Test
+    public void testLockdownSetFirewallUidRule() throws Exception {
+        // For ConnectivityService#setAlwaysOnVpnPackage.
+        mServiceContext.setPermission(
+                Manifest.permission.CONTROL_ALWAYS_ON_VPN, PERMISSION_GRANTED);
+        // Needed to call Vpn#setAlwaysOnPackage.
+        mServiceContext.setPermission(Manifest.permission.CONTROL_VPN, PERMISSION_GRANTED);
+        // Needed to call Vpn#isAlwaysOnPackageSupported.
+        mServiceContext.setPermission(NETWORK_SETTINGS, PERMISSION_GRANTED);
+
+        // Enable Lockdown
+        final ArrayList<String> allowList = new ArrayList<>();
+        mVpnManagerService.setAlwaysOnVpnPackage(PRIMARY_USER, ALWAYS_ON_PACKAGE,
+                true /* lockdown */, allowList);
+        waitForIdle();
+
+        // Lockdown rule is set to apps uids
+        verify(mBpfNetMaps).setUidRule(
+                eq(FIREWALL_CHAIN_LOCKDOWN_VPN), eq(APP1_UID), eq(FIREWALL_RULE_DENY));
+        verify(mBpfNetMaps).setUidRule(
+                eq(FIREWALL_CHAIN_LOCKDOWN_VPN), eq(APP2_UID), eq(FIREWALL_RULE_DENY));
+
+        reset(mBpfNetMaps);
+
+        // Disable lockdown
+        mVpnManagerService.setAlwaysOnVpnPackage(PRIMARY_USER, null, false /* lockdown */,
+                allowList);
+        waitForIdle();
+
+        // Lockdown rule is removed from apps uids
+        verify(mBpfNetMaps).setUidRule(
+                eq(FIREWALL_CHAIN_LOCKDOWN_VPN), eq(APP1_UID), eq(FIREWALL_RULE_ALLOW));
+        verify(mBpfNetMaps).setUidRule(
+                eq(FIREWALL_CHAIN_LOCKDOWN_VPN), eq(APP2_UID), eq(FIREWALL_RULE_ALLOW));
+
+        // Interface rules are not changed by Lockdown mode enable/disable
+        verify(mBpfNetMaps, never()).addUidInterfaceRules(any(), any());
+        verify(mBpfNetMaps, never()).removeUidInterfaceRules(any());
+    }
+
     /**
      * Test mutable and requestable network capabilities such as
      * {@link NetworkCapabilities#NET_CAPABILITY_TRUSTED} and
@@ -10373,7 +10416,7 @@
         verify(mBpfNetMaps, times(2)).addUidInterfaceRules(eq("tun0"), uidCaptor.capture());
         assertContainsExactly(uidCaptor.getAllValues().get(0), APP1_UID, APP2_UID);
         assertContainsExactly(uidCaptor.getAllValues().get(1), APP1_UID, APP2_UID);
-        assertTrue(mService.mPermissionMonitor.getVpnUidRanges("tun0").equals(vpnRange));
+        assertTrue(mService.mPermissionMonitor.getVpnInterfaceUidRanges("tun0").equals(vpnRange));
 
         mMockVpn.disconnect();
         waitForIdle();
@@ -10381,11 +10424,11 @@
         // Disconnected VPN should have interface rules removed
         verify(mBpfNetMaps).removeUidInterfaceRules(uidCaptor.capture());
         assertContainsExactly(uidCaptor.getValue(), APP1_UID, APP2_UID);
-        assertNull(mService.mPermissionMonitor.getVpnUidRanges("tun0"));
+        assertNull(mService.mPermissionMonitor.getVpnInterfaceUidRanges("tun0"));
     }
 
     @Test
-    public void testLegacyVpnDoesNotResultInInterfaceFilteringRule() throws Exception {
+    public void testLegacyVpnSetInterfaceFilteringRuleWithWildcard() throws Exception {
         LinkProperties lp = new LinkProperties();
         lp.setInterfaceName("tun0");
         lp.addRoute(new RouteInfo(new IpPrefix(Inet6Address.ANY, 0), null));
@@ -10395,13 +10438,29 @@
         mMockVpn.establish(lp, Process.SYSTEM_UID, vpnRange);
         assertVpnUidRangesUpdated(true, vpnRange, Process.SYSTEM_UID);
 
-        // Legacy VPN should not have interface rules set up
-        verify(mBpfNetMaps, never()).addUidInterfaceRules(any(), any());
+        // A connected Legacy VPN should have interface rules with null interface.
+        // Null Interface is a wildcard and this accepts traffic from all the interfaces.
+        // There are two expected invocations, one during the VPN initial connection,
+        // one during the VPN LinkProperties update.
+        ArgumentCaptor<int[]> uidCaptor = ArgumentCaptor.forClass(int[].class);
+        verify(mBpfNetMaps, times(2)).addUidInterfaceRules(
+                eq(null) /* iface */, uidCaptor.capture());
+        assertContainsExactly(uidCaptor.getAllValues().get(0), APP1_UID, APP2_UID, VPN_UID);
+        assertContainsExactly(uidCaptor.getAllValues().get(1), APP1_UID, APP2_UID, VPN_UID);
+        assertEquals(mService.mPermissionMonitor.getVpnInterfaceUidRanges(null /* iface */),
+                vpnRange);
+
+        mMockVpn.disconnect();
+        waitForIdle();
+
+        // Disconnected VPN should have interface rules removed
+        verify(mBpfNetMaps).removeUidInterfaceRules(uidCaptor.capture());
+        assertContainsExactly(uidCaptor.getValue(), APP1_UID, APP2_UID, VPN_UID);
+        assertNull(mService.mPermissionMonitor.getVpnInterfaceUidRanges(null /* iface */));
     }
 
     @Test
-    public void testLocalIpv4OnlyVpnDoesNotResultInInterfaceFilteringRule()
-            throws Exception {
+    public void testLocalIpv4OnlyVpnSetInterfaceFilteringRuleWithWildcard() throws Exception {
         LinkProperties lp = new LinkProperties();
         lp.setInterfaceName("tun0");
         lp.addRoute(new RouteInfo(new IpPrefix("192.0.2.0/24"), null, "tun0"));
@@ -10412,7 +10471,25 @@
         assertVpnUidRangesUpdated(true, vpnRange, Process.SYSTEM_UID);
 
         // IPv6 unreachable route should not be misinterpreted as a default route
-        verify(mBpfNetMaps, never()).addUidInterfaceRules(any(), any());
+        // A connected VPN should have interface rules with null interface.
+        // Null Interface is a wildcard and this accepts traffic from all the interfaces.
+        // There are two expected invocations, one during the VPN initial connection,
+        // one during the VPN LinkProperties update.
+        ArgumentCaptor<int[]> uidCaptor = ArgumentCaptor.forClass(int[].class);
+        verify(mBpfNetMaps, times(2)).addUidInterfaceRules(
+                eq(null) /* iface */, uidCaptor.capture());
+        assertContainsExactly(uidCaptor.getAllValues().get(0), APP1_UID, APP2_UID, VPN_UID);
+        assertContainsExactly(uidCaptor.getAllValues().get(1), APP1_UID, APP2_UID, VPN_UID);
+        assertEquals(mService.mPermissionMonitor.getVpnInterfaceUidRanges(null /* iface */),
+                vpnRange);
+
+        mMockVpn.disconnect();
+        waitForIdle();
+
+        // Disconnected VPN should have interface rules removed
+        verify(mBpfNetMaps).removeUidInterfaceRules(uidCaptor.capture());
+        assertContainsExactly(uidCaptor.getValue(), APP1_UID, APP2_UID, VPN_UID);
+        assertNull(mService.mPermissionMonitor.getVpnInterfaceUidRanges(null /* iface */));
     }
 
     @Test
diff --git a/tests/unit/java/com/android/server/connectivity/PermissionMonitorTest.java b/tests/unit/java/com/android/server/connectivity/PermissionMonitorTest.java
index fb821c3..ecd17ba 100644
--- a/tests/unit/java/com/android/server/connectivity/PermissionMonitorTest.java
+++ b/tests/unit/java/com/android/server/connectivity/PermissionMonitorTest.java
@@ -30,6 +30,9 @@
 import static android.content.pm.PackageInfo.REQUESTED_PERMISSION_REQUIRED;
 import static android.content.pm.PackageManager.GET_PERMISSIONS;
 import static android.content.pm.PackageManager.MATCH_ANY_USER;
+import static android.net.ConnectivityManager.FIREWALL_CHAIN_LOCKDOWN_VPN;
+import static android.net.ConnectivityManager.FIREWALL_RULE_ALLOW;
+import static android.net.ConnectivityManager.FIREWALL_RULE_DENY;
 import static android.net.ConnectivitySettingsManager.UIDS_ALLOWED_ON_RESTRICTED_NETWORKS;
 import static android.net.INetd.PERMISSION_INTERNET;
 import static android.net.INetd.PERMISSION_NETWORK;
@@ -761,8 +764,8 @@
                 MOCK_APPID1);
     }
 
-    @Test
-    public void testUidFilteringDuringVpnConnectDisconnectAndUidUpdates() throws Exception {
+    private void doTestuidFilteringDuringVpnConnectDisconnectAndUidUpdates(@Nullable String ifName)
+            throws Exception {
         doReturn(List.of(buildPackageInfo(SYSTEM_PACKAGE1, SYSTEM_APP_UID11, CHANGE_NETWORK_STATE,
                         CONNECTIVITY_USE_RESTRICTED_NETWORKS),
                 buildPackageInfo(MOCK_PACKAGE1, MOCK_UID11),
@@ -778,8 +781,8 @@
         final Set<UidRange> vpnRange2 = Set.of(new UidRange(MOCK_UID12, MOCK_UID12));
 
         // When VPN is connected, expect a rule to be set up for user app MOCK_UID11
-        mPermissionMonitor.onVpnUidRangesAdded("tun0", vpnRange1, VPN_UID);
-        verify(mBpfNetMaps).addUidInterfaceRules(eq("tun0"), aryEq(new int[]{MOCK_UID11}));
+        mPermissionMonitor.onVpnUidRangesAdded(ifName, vpnRange1, VPN_UID);
+        verify(mBpfNetMaps).addUidInterfaceRules(eq(ifName), aryEq(new int[]{MOCK_UID11}));
 
         reset(mBpfNetMaps);
 
@@ -787,27 +790,38 @@
         mPermissionMonitor.onPackageRemoved(MOCK_PACKAGE1, MOCK_UID11);
         verify(mBpfNetMaps).removeUidInterfaceRules(aryEq(new int[]{MOCK_UID11}));
         mPermissionMonitor.onPackageAdded(MOCK_PACKAGE1, MOCK_UID11);
-        verify(mBpfNetMaps).addUidInterfaceRules(eq("tun0"), aryEq(new int[]{MOCK_UID11}));
+        verify(mBpfNetMaps).addUidInterfaceRules(eq(ifName), aryEq(new int[]{MOCK_UID11}));
 
         reset(mBpfNetMaps);
 
         // During VPN uid update (vpnRange1 -> vpnRange2), ConnectivityService first deletes the
         // old UID rules then adds the new ones. Expect netd to be updated
-        mPermissionMonitor.onVpnUidRangesRemoved("tun0", vpnRange1, VPN_UID);
+        mPermissionMonitor.onVpnUidRangesRemoved(ifName, vpnRange1, VPN_UID);
         verify(mBpfNetMaps).removeUidInterfaceRules(aryEq(new int[] {MOCK_UID11}));
-        mPermissionMonitor.onVpnUidRangesAdded("tun0", vpnRange2, VPN_UID);
-        verify(mBpfNetMaps).addUidInterfaceRules(eq("tun0"), aryEq(new int[]{MOCK_UID12}));
+        mPermissionMonitor.onVpnUidRangesAdded(ifName, vpnRange2, VPN_UID);
+        verify(mBpfNetMaps).addUidInterfaceRules(eq(ifName), aryEq(new int[]{MOCK_UID12}));
 
         reset(mBpfNetMaps);
 
         // When VPN is disconnected, expect rules to be torn down
-        mPermissionMonitor.onVpnUidRangesRemoved("tun0", vpnRange2, VPN_UID);
+        mPermissionMonitor.onVpnUidRangesRemoved(ifName, vpnRange2, VPN_UID);
         verify(mBpfNetMaps).removeUidInterfaceRules(aryEq(new int[] {MOCK_UID12}));
-        assertNull(mPermissionMonitor.getVpnUidRanges("tun0"));
+        assertNull(mPermissionMonitor.getVpnInterfaceUidRanges(ifName));
     }
 
     @Test
-    public void testUidFilteringDuringPackageInstallAndUninstall() throws Exception {
+    public void testUidFilteringDuringVpnConnectDisconnectAndUidUpdates() throws Exception {
+        doTestuidFilteringDuringVpnConnectDisconnectAndUidUpdates("tun0");
+    }
+
+    @Test
+    public void testUidFilteringDuringVpnConnectDisconnectAndUidUpdatesWithWildcard()
+            throws Exception {
+        doTestuidFilteringDuringVpnConnectDisconnectAndUidUpdates(null /* ifName */);
+    }
+
+    private void doTestUidFilteringDuringPackageInstallAndUninstall(@Nullable String ifName) throws
+            Exception {
         doReturn(List.of(buildPackageInfo(SYSTEM_PACKAGE1, SYSTEM_APP_UID11, CHANGE_NETWORK_STATE,
                         NETWORK_STACK, CONNECTIVITY_USE_RESTRICTED_NETWORKS),
                 buildPackageInfo(SYSTEM_PACKAGE2, VPN_UID)))
@@ -818,12 +832,12 @@
         mPermissionMonitor.startMonitoring();
         final Set<UidRange> vpnRange = Set.of(UidRange.createForUser(MOCK_USER1),
                 UidRange.createForUser(MOCK_USER2));
-        mPermissionMonitor.onVpnUidRangesAdded("tun0", vpnRange, VPN_UID);
+        mPermissionMonitor.onVpnUidRangesAdded(ifName, vpnRange, VPN_UID);
 
         // Newly-installed package should have uid rules added
         addPackageForUsers(new UserHandle[]{MOCK_USER1, MOCK_USER2}, MOCK_PACKAGE1, MOCK_APPID1);
-        verify(mBpfNetMaps).addUidInterfaceRules(eq("tun0"), aryEq(new int[]{MOCK_UID11}));
-        verify(mBpfNetMaps).addUidInterfaceRules(eq("tun0"), aryEq(new int[]{MOCK_UID21}));
+        verify(mBpfNetMaps).addUidInterfaceRules(eq(ifName), aryEq(new int[]{MOCK_UID11}));
+        verify(mBpfNetMaps).addUidInterfaceRules(eq(ifName), aryEq(new int[]{MOCK_UID21}));
 
         // Removed package should have its uid rules removed
         mPermissionMonitor.onPackageRemoved(MOCK_PACKAGE1, MOCK_UID11);
@@ -831,6 +845,168 @@
         verify(mBpfNetMaps, never()).removeUidInterfaceRules(aryEq(new int[]{MOCK_UID21}));
     }
 
+    @Test
+    public void testUidFilteringDuringPackageInstallAndUninstall() throws Exception {
+        doTestUidFilteringDuringPackageInstallAndUninstall("tun0");
+    }
+
+    @Test
+    public void testUidFilteringDuringPackageInstallAndUninstallWithWildcard() throws Exception {
+        doTestUidFilteringDuringPackageInstallAndUninstall(null /* ifName */);
+    }
+
+    @Test
+    public void testLockdownUidFilteringWithLockdownEnableDisable() {
+        doReturn(List.of(buildPackageInfo(SYSTEM_PACKAGE1, SYSTEM_APP_UID11, CHANGE_NETWORK_STATE,
+                        CONNECTIVITY_USE_RESTRICTED_NETWORKS),
+                buildPackageInfo(MOCK_PACKAGE1, MOCK_UID11),
+                buildPackageInfo(MOCK_PACKAGE2, MOCK_UID12),
+                buildPackageInfo(SYSTEM_PACKAGE2, VPN_UID)))
+                .when(mPackageManager).getInstalledPackagesAsUser(eq(GET_PERMISSIONS), anyInt());
+        mPermissionMonitor.startMonitoring();
+        // Every app on user 0 except MOCK_UID12 are under VPN.
+        final UidRange[] vpnRange1 = {
+                new UidRange(0, MOCK_UID12 - 1),
+                new UidRange(MOCK_UID12 + 1, UserHandle.PER_USER_RANGE - 1)
+        };
+
+        // Add Lockdown uid range, expect a rule to be set up for user app MOCK_UID11
+        mPermissionMonitor.updateVpnLockdownUidRanges(true /* add */, vpnRange1);
+        verify(mBpfNetMaps)
+                .setUidRule(
+                        eq(FIREWALL_CHAIN_LOCKDOWN_VPN), eq(MOCK_UID11),
+                        eq(FIREWALL_RULE_DENY));
+        assertEquals(mPermissionMonitor.getVpnLockdownUidRanges(), Set.of(vpnRange1));
+
+        reset(mBpfNetMaps);
+
+        // Remove Lockdown uid range, expect rules to be torn down
+        mPermissionMonitor.updateVpnLockdownUidRanges(false /* false */, vpnRange1);
+        verify(mBpfNetMaps)
+                .setUidRule(eq(FIREWALL_CHAIN_LOCKDOWN_VPN), eq(MOCK_UID11),
+                        eq(FIREWALL_RULE_ALLOW));
+        assertTrue(mPermissionMonitor.getVpnLockdownUidRanges().isEmpty());
+    }
+
+    @Test
+    public void testLockdownUidFilteringWithLockdownEnableDisableWithMultiAdd() {
+        doReturn(List.of(buildPackageInfo(SYSTEM_PACKAGE1, SYSTEM_APP_UID11, CHANGE_NETWORK_STATE,
+                        CONNECTIVITY_USE_RESTRICTED_NETWORKS),
+                buildPackageInfo(MOCK_PACKAGE1, MOCK_UID11),
+                buildPackageInfo(SYSTEM_PACKAGE2, VPN_UID)))
+                .when(mPackageManager).getInstalledPackagesAsUser(eq(GET_PERMISSIONS), anyInt());
+        mPermissionMonitor.startMonitoring();
+        // MOCK_UID11 is under VPN.
+        final UidRange range = new UidRange(MOCK_UID11, MOCK_UID11);
+        final UidRange[] vpnRange = {range};
+
+        // Add Lockdown uid range at 1st time, expect a rule to be set up
+        mPermissionMonitor.updateVpnLockdownUidRanges(true /* add */, vpnRange);
+        verify(mBpfNetMaps)
+                .setUidRule(eq(FIREWALL_CHAIN_LOCKDOWN_VPN), eq(MOCK_UID11),
+                        eq(FIREWALL_RULE_DENY));
+        assertEquals(mPermissionMonitor.getVpnLockdownUidRanges(), Set.of(vpnRange));
+
+        reset(mBpfNetMaps);
+
+        // Add Lockdown uid range at 2nd time, expect a rule not to be set up because the uid
+        // already has the rule
+        mPermissionMonitor.updateVpnLockdownUidRanges(true /* add */, vpnRange);
+        verify(mBpfNetMaps, never()).setUidRule(anyInt(), anyInt(), anyInt());
+        assertEquals(mPermissionMonitor.getVpnLockdownUidRanges(), Set.of(vpnRange));
+
+        reset(mBpfNetMaps);
+
+        // Remove Lockdown uid range at 1st time, expect a rule not to be torn down because we added
+        // the range 2 times.
+        mPermissionMonitor.updateVpnLockdownUidRanges(false /* false */, vpnRange);
+        verify(mBpfNetMaps, never()).setUidRule(anyInt(), anyInt(), anyInt());
+        assertEquals(mPermissionMonitor.getVpnLockdownUidRanges(), Set.of(vpnRange));
+
+        reset(mBpfNetMaps);
+
+        // Remove Lockdown uid range at 2nd time, expect a rule to be torn down because we added
+        // twice and we removed twice.
+        mPermissionMonitor.updateVpnLockdownUidRanges(false /* false */, vpnRange);
+        verify(mBpfNetMaps)
+                .setUidRule(eq(FIREWALL_CHAIN_LOCKDOWN_VPN), eq(MOCK_UID11),
+                        eq(FIREWALL_RULE_ALLOW));
+        assertTrue(mPermissionMonitor.getVpnLockdownUidRanges().isEmpty());
+    }
+
+    @Test
+    public void testLockdownUidFilteringWithLockdownEnableDisableWithDuplicates() {
+        doReturn(List.of(buildPackageInfo(SYSTEM_PACKAGE1, SYSTEM_APP_UID11, CHANGE_NETWORK_STATE,
+                        CONNECTIVITY_USE_RESTRICTED_NETWORKS),
+                buildPackageInfo(MOCK_PACKAGE1, MOCK_UID11),
+                buildPackageInfo(SYSTEM_PACKAGE2, VPN_UID)))
+                .when(mPackageManager).getInstalledPackagesAsUser(eq(GET_PERMISSIONS), anyInt());
+        mPermissionMonitor.startMonitoring();
+        // MOCK_UID11 is under VPN.
+        final UidRange range = new UidRange(MOCK_UID11, MOCK_UID11);
+        final UidRange[] vpnRangeDuplicates = {range, range};
+        final UidRange[] vpnRange = {range};
+
+        // Add Lockdown uid ranges which contains duplicated uid ranges
+        mPermissionMonitor.updateVpnLockdownUidRanges(true /* add */, vpnRangeDuplicates);
+        verify(mBpfNetMaps)
+                .setUidRule(eq(FIREWALL_CHAIN_LOCKDOWN_VPN), eq(MOCK_UID11),
+                        eq(FIREWALL_RULE_DENY));
+        assertEquals(mPermissionMonitor.getVpnLockdownUidRanges(), Set.of(vpnRange));
+
+        reset(mBpfNetMaps);
+
+        // Remove Lockdown uid range at 1st time, expect a rule not to be torn down because uid
+        // ranges we added contains duplicated uid ranges.
+        mPermissionMonitor.updateVpnLockdownUidRanges(false /* false */, vpnRange);
+        verify(mBpfNetMaps, never()).setUidRule(anyInt(), anyInt(), anyInt());
+        assertEquals(mPermissionMonitor.getVpnLockdownUidRanges(), Set.of(vpnRange));
+
+        reset(mBpfNetMaps);
+
+        // Remove Lockdown uid range at 2nd time, expect a rule to be torn down.
+        mPermissionMonitor.updateVpnLockdownUidRanges(false /* false */, vpnRange);
+        verify(mBpfNetMaps)
+                .setUidRule(eq(FIREWALL_CHAIN_LOCKDOWN_VPN), eq(MOCK_UID11),
+                        eq(FIREWALL_RULE_ALLOW));
+        assertTrue(mPermissionMonitor.getVpnLockdownUidRanges().isEmpty());
+    }
+
+    @Test
+    public void testLockdownUidFilteringWithInstallAndUnInstall() {
+        doReturn(List.of(buildPackageInfo(SYSTEM_PACKAGE1, SYSTEM_APP_UID11, CHANGE_NETWORK_STATE,
+                        NETWORK_STACK, CONNECTIVITY_USE_RESTRICTED_NETWORKS),
+                buildPackageInfo(SYSTEM_PACKAGE2, VPN_UID)))
+                .when(mPackageManager).getInstalledPackagesAsUser(eq(GET_PERMISSIONS), anyInt());
+        doReturn(List.of(MOCK_USER1, MOCK_USER2)).when(mUserManager).getUserHandles(eq(true));
+
+        mPermissionMonitor.startMonitoring();
+        final UidRange[] vpnRange = {
+                UidRange.createForUser(MOCK_USER1),
+                UidRange.createForUser(MOCK_USER2)
+        };
+        mPermissionMonitor.updateVpnLockdownUidRanges(true /* add */, vpnRange);
+
+        // Installing package should add Lockdown rules
+        addPackageForUsers(new UserHandle[]{MOCK_USER1, MOCK_USER2}, MOCK_PACKAGE1, MOCK_APPID1);
+        verify(mBpfNetMaps)
+                .setUidRule(eq(FIREWALL_CHAIN_LOCKDOWN_VPN), eq(MOCK_UID11),
+                        eq(FIREWALL_RULE_DENY));
+        verify(mBpfNetMaps)
+                .setUidRule(eq(FIREWALL_CHAIN_LOCKDOWN_VPN), eq(MOCK_UID21),
+                        eq(FIREWALL_RULE_DENY));
+
+        reset(mBpfNetMaps);
+
+        // Uninstalling package should remove Lockdown rules
+        mPermissionMonitor.onPackageRemoved(MOCK_PACKAGE1, MOCK_UID11);
+        verify(mBpfNetMaps)
+                .setUidRule(eq(FIREWALL_CHAIN_LOCKDOWN_VPN), eq(MOCK_UID11),
+                        eq(FIREWALL_RULE_ALLOW));
+        verify(mBpfNetMaps, never())
+                .setUidRule(eq(FIREWALL_CHAIN_LOCKDOWN_VPN), eq(MOCK_UID21),
+                        eq(FIREWALL_RULE_ALLOW));
+    }
 
     // Normal package add/remove operations will trigger multiple intent for uids corresponding to
     // each user. To simulate generic package operations, the onPackageAdded/Removed will need to be