Populating local addresses to local_net_access_map

Whenever LinkProperties is added/modified/removes, we are updating local
network prefixes for the modified interface/addresses. These prefixes
are used by BPF egress and ingress cgroup hooks to disallow local
network packets if the calling application do not have required
permission.

Bug: 369815823
Test: Manually tested
Test: atest ConnectivityCoverageTests:android.net.connectivity.com.android.server.BpfNetMapsTest
Test: atest ConnectivityCoverageTests:android.net.connectivity.com.android.server.CSLocalNetworkProtectionTest
Change-Id: Ie592ecb948ae05a0a73f47d0573560eb705f6bcf
diff --git a/service/src/com/android/server/BpfNetMaps.java b/service/src/com/android/server/BpfNetMaps.java
index 4fae73a..ebb8de1 100644
--- a/service/src/com/android/server/BpfNetMaps.java
+++ b/service/src/com/android/server/BpfNetMaps.java
@@ -911,7 +911,7 @@
                     + "(" + iface + ")");
             return;
         }
-        LocalNetAccessKey localNetAccessKey = new LocalNetAccessKey(lpmBitlen, ifIndex,
+        final LocalNetAccessKey localNetAccessKey = new LocalNetAccessKey(lpmBitlen, ifIndex,
                 address, protocol, remotePort);
 
         try {
@@ -923,13 +923,43 @@
     }
 
     /**
-     * False if the configuration is disallowed.
-     *
+     * Remove configuration to local_net_access trie map.
+     * @param lpmBitlen prefix length that will be used for longest matching
+     * @param iface interface name
+     * @param address remote address. ipv4 addresses would be mapped to v6
+     * @param protocol required for longest match in special cases
+     * @param remotePort src/dst port for ingress/egress
+     */
+    @RequiresApi(Build.VERSION_CODES.CUR_DEVELOPMENT)
+    public void removeLocalNetAccess(final int lpmBitlen, final String iface,
+            final InetAddress address, final int protocol, final int remotePort) {
+        throwIfPre25Q2("removeLocalNetAccess is not available on pre-B devices");
+        final int ifIndex = mDeps.getIfIndex(iface);
+        if (ifIndex == 0) {
+            Log.e(TAG, "Failed to get if index, skip removeLocalNetAccess for " + address
+                    + "(" + iface + ")");
+            return;
+        }
+        final LocalNetAccessKey localNetAccessKey = new LocalNetAccessKey(lpmBitlen, ifIndex,
+                address, protocol, remotePort);
+
+        try {
+            sLocalNetAccessMap.deleteEntry(localNetAccessKey);
+        } catch (ErrnoException e) {
+            Log.e(TAG, "Failed to remove local network access for localNetAccessKey : "
+                    + localNetAccessKey);
+        }
+    }
+
+    /**
+     * Fetches value available in local_net_access bpf map for provided configuration
      * @param lpmBitlen  prefix length that will be used for longest matching
      * @param iface    interface name
      * @param address    remote address. ipv4 addresses would be mapped to v6
      * @param protocol   required for longest match in special cases
      * @param remotePort src/dst port for ingress/egress
+     * @return false if the configuration is disallowed, true if the configuration is absent i.e. it
+     * is not local network or if configuration is allowed like local dns servers.
      */
     @RequiresApi(Build.VERSION_CODES.CUR_DEVELOPMENT)
     public boolean getLocalNetAccess(final int lpmBitlen, final String iface,
@@ -941,10 +971,10 @@
                     + address + "(" + iface + ")");
             return true;
         }
-        LocalNetAccessKey localNetAccessKey = new LocalNetAccessKey(lpmBitlen, ifIndex,
+        final LocalNetAccessKey localNetAccessKey = new LocalNetAccessKey(lpmBitlen, ifIndex,
                 address, protocol, remotePort);
         try {
-            Bool value = sLocalNetAccessMap.getValue(localNetAccessKey);
+            final Bool value = sLocalNetAccessMap.getValue(localNetAccessKey);
             return value == null ? true : value.val;
         } catch (ErrnoException e) {
             Log.e(TAG, "Failed to find local network access configuration for "
@@ -972,10 +1002,10 @@
      * @param uid application uid that needs check if local network calls are blocked.
      */
     @RequiresApi(Build.VERSION_CODES.CUR_DEVELOPMENT)
-    public boolean getUidValueFromLocalNetBlockMap(final int uid) {
-        throwIfPre25Q2("getUidValueFromLocalNetBlockMap is not available on pre-B devices");
+    public boolean isUidBlockedFromUsingLocalNetwork(final int uid) {
+        throwIfPre25Q2("isUidBlockedFromUsingLocalNetwork is not available on pre-B devices");
         try {
-            Bool value = sLocalNetBlockedUidMap.getValue(new U32(uid));
+            final Bool value = sLocalNetBlockedUidMap.getValue(new U32(uid));
             return value == null ? false : value.val;
         } catch (ErrnoException e) {
             Log.e(TAG, "Failed to find uid(" + uid
diff --git a/service/src/com/android/server/ConnectivityService.java b/service/src/com/android/server/ConnectivityService.java
index 18801f0..2872751 100644
--- a/service/src/com/android/server/ConnectivityService.java
+++ b/service/src/com/android/server/ConnectivityService.java
@@ -109,8 +109,8 @@
 import static android.net.NetworkCapabilities.REDACT_FOR_ACCESS_FINE_LOCATION;
 import static android.net.NetworkCapabilities.REDACT_FOR_LOCAL_MAC_ADDRESS;
 import static android.net.NetworkCapabilities.REDACT_FOR_NETWORK_SETTINGS;
-import static android.net.NetworkCapabilities.RES_ID_UNSET;
 import static android.net.NetworkCapabilities.RES_ID_MATCH_ALL_RESERVATIONS;
+import static android.net.NetworkCapabilities.RES_ID_UNSET;
 import static android.net.NetworkCapabilities.TRANSPORT_CELLULAR;
 import static android.net.NetworkCapabilities.TRANSPORT_TEST;
 import static android.net.NetworkCapabilities.TRANSPORT_VPN;
@@ -146,6 +146,8 @@
 import static com.android.net.module.util.BpfUtils.BPF_CGROUP_UDP6_RECVMSG;
 import static com.android.net.module.util.BpfUtils.BPF_CGROUP_UDP6_SENDMSG;
 import static com.android.net.module.util.NetworkMonitorUtils.isPrivateDnsValidationRequired;
+import static com.android.net.module.util.NetworkStackConstants.IPV4_LOCAL_PREFIXES;
+import static com.android.net.module.util.NetworkStackConstants.MULTICAST_AND_BROADCAST_PREFIXES;
 import static com.android.net.module.util.PermissionUtils.enforceAnyPermissionOf;
 import static com.android.net.module.util.PermissionUtils.enforceNetworkStackPermission;
 import static com.android.net.module.util.PermissionUtils.enforceNetworkStackPermissionOr;
@@ -214,6 +216,7 @@
 import android.net.InetAddresses;
 import android.net.IpMemoryStore;
 import android.net.IpPrefix;
+import android.net.LinkAddress;
 import android.net.LinkProperties;
 import android.net.LocalNetworkConfig;
 import android.net.LocalNetworkInfo;
@@ -5683,6 +5686,7 @@
         // destroyed pending replacement they will be sent when it is disconnected.
         maybeDisableForwardRulesForDisconnectingNai(nai, false /* sendCallbacks */);
         updateIngressToVpnAddressFiltering(null, nai.linkProperties, nai);
+        updateLocalNetworkAddresses(null, nai.linkProperties);
         try {
             mNetd.networkDestroy(nai.network.getNetId());
         } catch (RemoteException | ServiceSpecificException e) {
@@ -9583,6 +9587,8 @@
 
         updateIngressToVpnAddressFiltering(newLp, oldLp, networkAgent);
 
+        updateLocalNetworkAddresses(newLp, oldLp);
+
         updateMtu(newLp, oldLp);
         // TODO - figure out what to do for clat
 //        for (LinkProperties lp : newLp.getStackedLinks()) {
@@ -9762,6 +9768,134 @@
     }
 
     /**
+     * Update Local Network Addresses to LocalNetAccess BPF map.
+     * @param newLp new link properties
+     * @param oldLp old link properties
+     */
+    private void updateLocalNetworkAddresses(@Nullable final LinkProperties newLp,
+            @NonNull final LinkProperties oldLp) {
+
+        // The maps are available only after 25Q2 release
+        if (!BpfNetMaps.isAtLeast25Q2()) {
+            return;
+        }
+
+        final CompareResult<String> interfaceDiff = new CompareResult<>(
+                oldLp != null ? oldLp.getAllInterfaceNames() : null,
+                newLp != null ? newLp.getAllInterfaceNames() : null);
+
+        for (final String iface : interfaceDiff.added) {
+            addLocalAddressesToBpfMap(iface, MULTICAST_AND_BROADCAST_PREFIXES);
+        }
+        for (final String iface : interfaceDiff.removed) {
+            removeLocalAddressesFromBpfMap(iface, MULTICAST_AND_BROADCAST_PREFIXES);
+        }
+
+        final CompareResult<LinkAddress> linkAddressDiff = new CompareResult<>(
+                oldLp != null ? oldLp.getLinkAddresses() : null,
+                newLp != null ? newLp.getLinkAddresses() : null);
+
+        List<IpPrefix> unicastLocalPrefixesToBeAdded = new ArrayList<>();
+        List<IpPrefix> unicastLocalPrefixesToBeRemoved = new ArrayList<>();
+
+        // Finding the list of local network prefixes that needs to be added
+        if (newLp != null) {
+            for (LinkAddress linkAddress : newLp.getLinkAddresses()) {
+                unicastLocalPrefixesToBeAdded.addAll(
+                        getLocalNetworkPrefixesForAddress(linkAddress));
+            }
+        }
+
+        for (LinkAddress linkAddress : linkAddressDiff.removed) {
+            unicastLocalPrefixesToBeRemoved.addAll(getLocalNetworkPrefixesForAddress(linkAddress));
+        }
+
+        // If newLp is not null, adding local network prefixes using interface name of newLp
+        if (newLp != null) {
+            addLocalAddressesToBpfMap(newLp.getInterfaceName(),
+                    new ArrayList<>(unicastLocalPrefixesToBeAdded));
+        }
+        if (oldLp != null) {
+            // excluding removal of ip prefixes that needs to be added for newLp, but also
+            // removed for oldLp.
+            if (newLp != null && Objects.equals(oldLp.getInterfaceName(),
+                    newLp.getInterfaceName())) {
+                unicastLocalPrefixesToBeRemoved.removeAll(unicastLocalPrefixesToBeAdded);
+            }
+            // removing ip local network prefixes because of change in link addresses.
+            removeLocalAddressesFromBpfMap(oldLp.getInterfaceName(),
+                    new ArrayList<>(unicastLocalPrefixesToBeRemoved));
+        }
+
+    }
+
+    /**
+     * Filters IpPrefix that are local prefixes and LinkAddress is part of them.
+     * @param linkAddress link address used for filtering
+     * @return list of IpPrefix that are local addresses.
+     */
+    private List<IpPrefix> getLocalNetworkPrefixesForAddress(LinkAddress linkAddress) {
+        List<IpPrefix> localPrefixes = new ArrayList<>();
+        if (linkAddress.isIpv6()) {
+            // For IPv6, if the prefix length is greater than zero then they are part of local
+            // network
+            if (linkAddress.getPrefixLength() != 0) {
+                localPrefixes.add(
+                        new IpPrefix(linkAddress.getAddress(), linkAddress.getPrefixLength()));
+            }
+        } else {
+            // For IPv4, if the linkAddress is part of IpPrefix adding prefix to result.
+            for (IpPrefix ipv4LocalPrefix : IPV4_LOCAL_PREFIXES) {
+                if (ipv4LocalPrefix.containsPrefix(
+                        new IpPrefix(linkAddress.getAddress(), linkAddress.getPrefixLength()))) {
+                    localPrefixes.add(ipv4LocalPrefix);
+                }
+            }
+        }
+        return localPrefixes;
+    }
+
+    /**
+     * Adds list of prefixes(addresses) to local network access map.
+     * @param iface interface name
+     * @param prefixes list of prefixes/addresses
+     */
+    private void addLocalAddressesToBpfMap(final String iface, final List<IpPrefix> prefixes) {
+        if (!BpfNetMaps.isAtLeast25Q2()) return;
+        for (IpPrefix prefix : prefixes) {
+            /*
+            Prefix length is used by LPM trie map(local_net_access_map) for performing longest
+            prefix matching, this length represents the maximum number of bits used for matching.
+            The interface index should always be matched which is 32-bit integer. For IPv6, prefix
+            length is calculated by adding the ip address prefix length along with interface index
+            making it (32 + length). IPv4 addresses are stored as ipv4-mapped-ipv6 which implies
+            first 96 bits are common for all ipv4 addresses. Hence, prefix length is calculated as
+            32(interface index) + 96 (common for ipv4-mapped-ipv6) + length.
+             */
+            final int prefixLengthConstant = (prefix.isIPv4() ? (32 + 96) : 32);
+            mBpfNetMaps.addLocalNetAccess(prefixLengthConstant + prefix.getPrefixLength(),
+                    iface, prefix.getAddress(), 0, 0, false);
+
+        }
+
+    }
+
+    /**
+     * Removes list of prefixes(addresses) from local network access map.
+     * @param iface interface name
+     * @param prefixes list of prefixes/addresses
+     */
+    private void removeLocalAddressesFromBpfMap(final String iface, final List<IpPrefix> prefixes) {
+        if (!BpfNetMaps.isAtLeast25Q2()) return;
+        for (IpPrefix prefix : prefixes) {
+            // The reasoning for prefix length is explained in addLocalAddressesToBpfMap()
+            final int prefixLengthConstant = (prefix.isIPv4() ? (32 + 96) : 32);
+            mBpfNetMaps.removeLocalNetAccess(prefixLengthConstant
+                    + prefix.getPrefixLength(), iface, prefix.getAddress(), 0, 0);
+        }
+    }
+
+    /**
      * Have netd update routes from oldLp to newLp.
      * @return true if routes changed between oldLp and newLp
      */
diff --git a/staticlibs/framework/com/android/net/module/util/NetworkStackConstants.java b/staticlibs/framework/com/android/net/module/util/NetworkStackConstants.java
index 026e985..8d7ae5c 100644
--- a/staticlibs/framework/com/android/net/module/util/NetworkStackConstants.java
+++ b/staticlibs/framework/com/android/net/module/util/NetworkStackConstants.java
@@ -23,6 +23,7 @@
 import java.net.Inet6Address;
 import java.net.InetAddress;
 import java.net.UnknownHostException;
+import java.util.List;
 
 /**
  * Network constants used by the network stack.
@@ -341,6 +342,26 @@
      */
     public static final String TEST_URL_EXPIRATION_TIME = "test_url_expiration_time";
 
+    /**
+     * List of IpPrefix that are local network prefixes.
+     */
+    public static final List<IpPrefix> IPV4_LOCAL_PREFIXES = List.of(
+            new IpPrefix("169.254.0.0/16"), // Link Local
+            new IpPrefix("100.64.0.0/10"),  // CGNAT
+            new IpPrefix("10.0.0.0/8"),     // RFC1918
+            new IpPrefix("172.16.0.0/12"),  // RFC1918
+            new IpPrefix("192.168.0.0/16")  // RFC1918
+    );
+
+    /**
+     * List of IpPrefix that are multicast and broadcast prefixes.
+     */
+    public static final List<IpPrefix> MULTICAST_AND_BROADCAST_PREFIXES = List.of(
+            new IpPrefix("224.0.0.0/4"),               // Multicast
+            new IpPrefix("ff00::/8"),                  // Multicast
+            new IpPrefix("255.255.255.255/32")         // Broadcast
+    );
+
     // TODO: Move to Inet4AddressUtils
     // See aosp/1455936: NetworkStackConstants can't depend on it as it causes jarjar-related issues
     // for users of both the net-utils-device-common and net-utils-framework-common libraries.
diff --git a/tests/unit/java/com/android/server/BpfNetMapsTest.java b/tests/unit/java/com/android/server/BpfNetMapsTest.java
index 73eb24d..fd92672 100644
--- a/tests/unit/java/com/android/server/BpfNetMapsTest.java
+++ b/tests/unit/java/com/android/server/BpfNetMapsTest.java
@@ -269,9 +269,11 @@
     public void testAddLocalNetAccessAfterVWithIncorrectInterface() throws Exception {
         assertTrue(mLocalNetAccessMap.isEmpty());
 
+        // wlan2 is an incorrect interface
         mBpfNetMaps.addLocalNetAccess(160, "wlan2",
                 Inet4Address.getByName("196.68.0.0"), 0, 0, true);
 
+        // As we tried to add incorrect interface, it would be skipped and map should be empty.
         assertTrue(mLocalNetAccessMap.isEmpty());
     }
 
@@ -302,6 +304,53 @@
 
     @Test
     @IgnoreAfter(Build.VERSION_CODES.VANILLA_ICE_CREAM)
+    public void testRemoveLocalNetAccessBeforeV() {
+        assertThrows(UnsupportedOperationException.class, () ->
+                mBpfNetMaps.removeLocalNetAccess(0, TEST_IF_NAME, Inet6Address.ANY, 0, 0));
+    }
+
+    @Test
+    @IgnoreUpTo(Build.VERSION_CODES.VANILLA_ICE_CREAM)
+    public void testRemoveLocalNetAccessAfterV() throws Exception {
+        assertTrue(mLocalNetAccessMap.isEmpty());
+
+        mBpfNetMaps.addLocalNetAccess(160, TEST_IF_NAME,
+                Inet4Address.getByName("196.68.0.0"), 0, 0, true);
+
+        assertNotNull(mLocalNetAccessMap.getValue(new LocalNetAccessKey(160, TEST_IF_INDEX,
+                Inet4Address.getByName("196.68.0.0"), 0, 0)));
+        assertNull(mLocalNetAccessMap.getValue(new LocalNetAccessKey(160, TEST_IF_INDEX,
+                Inet4Address.getByName("100.68.0.0"), 0, 0)));
+
+        mBpfNetMaps.removeLocalNetAccess(160, TEST_IF_NAME,
+                Inet4Address.getByName("196.68.0.0"), 0, 0);
+        assertNull(mLocalNetAccessMap.getValue(new LocalNetAccessKey(160, TEST_IF_INDEX,
+                Inet4Address.getByName("196.68.0.0"), 0, 0)));
+        assertNull(mLocalNetAccessMap.getValue(new LocalNetAccessKey(160, TEST_IF_INDEX,
+                Inet4Address.getByName("100.68.0.0"), 0, 0)));
+    }
+
+    @Test
+    @IgnoreUpTo(Build.VERSION_CODES.VANILLA_ICE_CREAM)
+    public void testRemoveLocalNetAccessAfterVWithIncorrectInterface() throws Exception {
+        assertTrue(mLocalNetAccessMap.isEmpty());
+
+        mBpfNetMaps.addLocalNetAccess(160, TEST_IF_NAME,
+                Inet4Address.getByName("196.68.0.0"), 0, 0, true);
+
+        assertNotNull(mLocalNetAccessMap.getValue(new LocalNetAccessKey(160, TEST_IF_INDEX,
+                Inet4Address.getByName("196.68.0.0"), 0, 0)));
+        assertNull(mLocalNetAccessMap.getValue(new LocalNetAccessKey(160, TEST_IF_INDEX,
+                Inet4Address.getByName("100.68.0.0"), 0, 0)));
+
+        mBpfNetMaps.removeLocalNetAccess(160, "wlan2",
+                Inet4Address.getByName("196.68.0.0"), 0, 0);
+        assertNotNull(mLocalNetAccessMap.getValue(new LocalNetAccessKey(160, TEST_IF_INDEX,
+                Inet4Address.getByName("196.68.0.0"), 0, 0)));
+    }
+
+    @Test
+    @IgnoreAfter(Build.VERSION_CODES.VANILLA_ICE_CREAM)
     public void testAddUidToLocalNetBlockMapBeforeV() {
         assertThrows(UnsupportedOperationException.class, () ->
                 mBpfNetMaps.addUidToLocalNetBlockMap(0));
@@ -309,9 +358,9 @@
 
     @Test
     @IgnoreAfter(Build.VERSION_CODES.VANILLA_ICE_CREAM)
-    public void testIsUidPresentInLocalNetBlockMapBeforeV() {
+    public void testIsUidBlockedFromUsingLocalNetworkBeforeV() {
         assertThrows(UnsupportedOperationException.class, () ->
-                mBpfNetMaps.getUidValueFromLocalNetBlockMap(0));
+                mBpfNetMaps.isUidBlockedFromUsingLocalNetwork(0));
     }
 
     @Test
@@ -339,18 +388,18 @@
 
     @Test
     @IgnoreUpTo(Build.VERSION_CODES.VANILLA_ICE_CREAM)
-    public void testIsUidPresentInLocalNetBlockMapAfterV() throws Exception {
+    public void testIsUidBlockedFromUsingLocalNetworkAfterV() throws Exception {
         final int uid0 = TEST_UIDS[0];
         final int uid1 = TEST_UIDS[1];
 
         assertTrue(mLocalNetAccessMap.isEmpty());
 
         mLocalNetBlockedUidMap.updateEntry(new U32(uid0), new Bool(true));
-        assertTrue(mBpfNetMaps.getUidValueFromLocalNetBlockMap(uid0));
-        assertFalse(mBpfNetMaps.getUidValueFromLocalNetBlockMap(uid1));
+        assertTrue(mBpfNetMaps.isUidBlockedFromUsingLocalNetwork(uid0));
+        assertFalse(mBpfNetMaps.isUidBlockedFromUsingLocalNetwork(uid1));
 
         mLocalNetBlockedUidMap.updateEntry(new U32(uid1), new Bool(true));
-        assertTrue(mBpfNetMaps.getUidValueFromLocalNetBlockMap(uid1));
+        assertTrue(mBpfNetMaps.isUidBlockedFromUsingLocalNetwork(uid1));
     }
 
     @Test
diff --git a/tests/unit/java/com/android/server/connectivityservice/CSLocalNetworkProtectionTest.kt b/tests/unit/java/com/android/server/connectivityservice/CSLocalNetworkProtectionTest.kt
new file mode 100644
index 0000000..73e7515
--- /dev/null
+++ b/tests/unit/java/com/android/server/connectivityservice/CSLocalNetworkProtectionTest.kt
@@ -0,0 +1,416 @@
+/*
+ * Copyright (C) 2023 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License")
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.android.server
+
+import android.net.InetAddresses
+import android.net.IpPrefix
+import android.net.LinkAddress
+import android.net.LinkProperties
+import android.net.NetworkCapabilities
+import android.net.NetworkCapabilities.NET_CAPABILITY_INTERNET
+import android.net.NetworkCapabilities.NET_CAPABILITY_NOT_VCN_MANAGED
+import android.net.NetworkCapabilities.NET_CAPABILITY_NOT_VPN
+import android.net.NetworkCapabilities.TRANSPORT_VPN
+import android.net.NetworkCapabilities.TRANSPORT_WIFI
+import android.net.NetworkRequest
+import android.os.Build
+import androidx.test.filters.SmallTest
+import com.android.testutils.DevSdkIgnoreRule.IgnoreUpTo
+import com.android.testutils.DevSdkIgnoreRunner
+import com.android.testutils.RecorderCallback.CallbackEntry.LinkPropertiesChanged
+import com.android.testutils.RecorderCallback.CallbackEntry.Lost
+import com.android.testutils.TestableNetworkCallback
+import org.junit.Test
+import org.junit.runner.RunWith
+import org.mockito.ArgumentMatchers.eq
+import org.mockito.Mockito.never
+import org.mockito.Mockito.verify
+
+private const val LONG_TIMEOUT_MS = 5_000
+private const val PREFIX_LENGTH_IPV4 = 32 + 96
+private const val PREFIX_LENGTH_IPV6 = 32
+private const val WIFI_IFNAME = "wlan0"
+private const val WIFI_IFNAME_2 = "wlan1"
+
+private val wifiNc = NetworkCapabilities.Builder()
+        .addTransportType(TRANSPORT_WIFI)
+        .addCapability(NET_CAPABILITY_INTERNET)
+        .addCapability(NET_CAPABILITY_NOT_VCN_MANAGED)
+        .build()
+
+private fun lp(iface: String, vararg linkAddresses: LinkAddress) = LinkProperties().apply {
+    interfaceName = iface
+    for (linkAddress in linkAddresses) {
+        addLinkAddress(linkAddress)
+    }
+}
+
+private fun nr(transport: Int) = NetworkRequest.Builder()
+        .clearCapabilities()
+        .addTransportType(transport).apply {
+            if (transport != TRANSPORT_VPN) {
+                addCapability(NET_CAPABILITY_NOT_VPN)
+            }
+        }.build()
+
+@DevSdkIgnoreRunner.MonitorThreadLeak
+@RunWith(DevSdkIgnoreRunner::class)
+@SmallTest
+@IgnoreUpTo(Build.VERSION_CODES.VANILLA_ICE_CREAM)
+class CSLocalNetworkProtectionTest : CSTest() {
+    private val LOCAL_IPV6_IP_ADDRESS_PREFIX = IpPrefix("fe80::1cf1:35ff:fe8c:db87/64")
+    private val LOCAL_IPV6_LINK_ADDRESS = LinkAddress(
+        LOCAL_IPV6_IP_ADDRESS_PREFIX.getAddress(),
+        LOCAL_IPV6_IP_ADDRESS_PREFIX.getPrefixLength()
+    )
+
+    private val LOCAL_IPV4_IP_ADDRESS_PREFIX_1 = IpPrefix("10.0.0.184/24")
+    private val LOCAL_IPV4_LINK_ADDRRESS_1 =
+        LinkAddress(
+            LOCAL_IPV4_IP_ADDRESS_PREFIX_1.getAddress(),
+            LOCAL_IPV4_IP_ADDRESS_PREFIX_1.getPrefixLength()
+        )
+
+    private val LOCAL_IPV4_IP_ADDRESS_PREFIX_2 = IpPrefix("10.0.255.184/24")
+    private val LOCAL_IPV4_LINK_ADDRRESS_2 =
+        LinkAddress(
+            LOCAL_IPV4_IP_ADDRESS_PREFIX_2.getAddress(),
+            LOCAL_IPV4_IP_ADDRESS_PREFIX_2.getPrefixLength()
+        )
+
+    @Test
+    fun testNetworkWithIPv6LocalAddress_AddressAddedToBpfMap() {
+        val nr = nr(TRANSPORT_WIFI)
+        val cb = TestableNetworkCallback()
+        cm.requestNetwork(nr, cb)
+
+        // Connecting to network with IPv6 local address in LinkProperties
+        val wifiLp = lp(WIFI_IFNAME, LOCAL_IPV6_LINK_ADDRESS)
+        val wifiAgent = Agent(nc = wifiNc, lp = wifiLp)
+        wifiAgent.connect()
+        cb.expectAvailableCallbacks(wifiAgent.network, validated = false)
+
+        // Multicast and Broadcast address should always be populated in local_net_access map
+        verifyPopulationOfMulticastAndBroadcastAddress()
+        // Verifying IPv6 address should be populated in local_net_access map
+        verify(bpfNetMaps).addLocalNetAccess(
+            eq(PREFIX_LENGTH_IPV6 + LOCAL_IPV6_IP_ADDRESS_PREFIX.getPrefixLength()),
+            eq(WIFI_IFNAME),
+            eq(LOCAL_IPV6_IP_ADDRESS_PREFIX.getAddress()),
+            eq(0),
+            eq(0),
+            eq(false)
+        )
+    }
+
+    @Test
+    fun testNetworkWithIPv4LocalAddress_AddressAddedToBpfMap() {
+        val nr = nr(TRANSPORT_WIFI)
+        val cb = TestableNetworkCallback()
+        cm.requestNetwork(nr, cb)
+
+        val wifiLp = lp(WIFI_IFNAME, LOCAL_IPV4_LINK_ADDRRESS_1)
+        val wifiAgent = Agent(nc = wifiNc, lp = wifiLp)
+        wifiAgent.connect()
+        cb.expectAvailableCallbacks(wifiAgent.network, validated = false)
+
+        // Multicast and Broadcast address should always be populated in local_net_access map
+        verifyPopulationOfMulticastAndBroadcastAddress()
+
+        // Verifying IPv4 matching prefix(10.0.0.0/8) should be populated in local_net_access map
+        verify(bpfNetMaps).addLocalNetAccess(
+            eq(PREFIX_LENGTH_IPV4 + 8),
+            eq(WIFI_IFNAME),
+            eq(InetAddresses.parseNumericAddress("10.0.0.0")),
+            eq(0),
+            eq(0),
+            eq(false)
+        )
+    }
+
+    @Test
+    fun testChangeLinkPropertiesWithDifferentLinkAddresses_AddressReplacedInBpfMap() {
+        val nr = nr(TRANSPORT_WIFI)
+        val cb = TestableNetworkCallback()
+        cm.requestNetwork(nr, cb)
+
+        val wifiLp = lp(WIFI_IFNAME, LOCAL_IPV6_LINK_ADDRESS)
+        val wifiAgent = Agent(nc = wifiNc, lp = wifiLp)
+        wifiAgent.connect()
+        cb.expectAvailableCallbacks(wifiAgent.network, validated = false)
+
+        // Multicast and Broadcast address should always be populated in local_net_access map
+        verifyPopulationOfMulticastAndBroadcastAddress()
+        // Verifying IPv6 address should be populated in local_net_access map
+        verify(bpfNetMaps).addLocalNetAccess(
+            eq(PREFIX_LENGTH_IPV6 + LOCAL_IPV6_IP_ADDRESS_PREFIX.getPrefixLength()),
+            eq(WIFI_IFNAME),
+            eq(LOCAL_IPV6_IP_ADDRESS_PREFIX.getAddress()),
+            eq(0),
+            eq(0),
+            eq(false)
+        )
+
+        // Updating Link Property from IPv6 in Link Address to IPv4 in Link Address
+        val wifiLp2 = lp(WIFI_IFNAME, LOCAL_IPV4_LINK_ADDRRESS_1)
+        wifiAgent.sendLinkProperties(wifiLp2)
+        cb.expect<LinkPropertiesChanged>(wifiAgent.network)
+
+        // Verifying IPv4 matching prefix(10.0.0.0/8) should be populated in local_net_access map
+        verify(bpfNetMaps).addLocalNetAccess(
+            eq(PREFIX_LENGTH_IPV4 + 8),
+            eq(WIFI_IFNAME),
+            eq(InetAddresses.parseNumericAddress("10.0.0.0")),
+            eq(0),
+            eq(0),
+            eq(false)
+        )
+        // Verifying IPv6 address should be removed from local_net_access map
+        verify(bpfNetMaps).removeLocalNetAccess(
+            eq(PREFIX_LENGTH_IPV6 + LOCAL_IPV6_IP_ADDRESS_PREFIX.getPrefixLength()),
+            eq(WIFI_IFNAME),
+            eq(LOCAL_IPV6_IP_ADDRESS_PREFIX.getAddress()),
+            eq(0),
+            eq(0)
+        )
+    }
+
+    @Test
+    fun testChangeLinkPropertiesWithLinkAddressesInSameRange_AddressIntactInBpfMap() {
+        val nr = nr(TRANSPORT_WIFI)
+        val cb = TestableNetworkCallback()
+        cm.requestNetwork(nr, cb)
+
+        val wifiLp = lp(WIFI_IFNAME, LOCAL_IPV4_LINK_ADDRRESS_1)
+        val wifiAgent = Agent(nc = wifiNc, lp = wifiLp)
+        wifiAgent.connect()
+        cb.expectAvailableCallbacks(wifiAgent.network, validated = false)
+
+        // Multicast and Broadcast address should always be populated in local_net_access map
+        verifyPopulationOfMulticastAndBroadcastAddress()
+        // Verifying IPv4 matching prefix(10.0.0.0/8) should be populated in local_net_access map
+        verify(bpfNetMaps).addLocalNetAccess(
+            eq(PREFIX_LENGTH_IPV4 + 8),
+            eq(WIFI_IFNAME),
+            eq(LOCAL_IPV4_IP_ADDRESS_PREFIX_1.getAddress()),
+            eq(0),
+            eq(0),
+            eq(false)
+        )
+
+        // Updating Link Property from one IPv4 to another IPv4 within same range(10.0.0.0/8)
+        val wifiLp2 = lp(WIFI_IFNAME, LOCAL_IPV4_LINK_ADDRRESS_2)
+        wifiAgent.sendLinkProperties(wifiLp2)
+        cb.expect<LinkPropertiesChanged>(wifiAgent.network)
+
+        // As both addresses below to same range, so no address should be removed from the map.
+        verify(bpfNetMaps, never()).removeLocalNetAccess(any(), any(), any(), any(), any())
+    }
+
+    @Test
+    fun testChangeLinkPropertiesWithDifferentInterface_AddressReplacedInBpfMap() {
+        val nr = nr(TRANSPORT_WIFI)
+        val cb = TestableNetworkCallback()
+        cm.requestNetwork(nr, cb)
+
+        val wifiLp = lp(WIFI_IFNAME, LOCAL_IPV6_LINK_ADDRESS)
+        val wifiAgent = Agent(nc = wifiNc, lp = wifiLp)
+        wifiAgent.connect()
+        cb.expectAvailableCallbacks(wifiAgent.network, validated = false)
+
+        // Multicast and Broadcast address should always be populated in local_net_access map
+        verifyPopulationOfMulticastAndBroadcastAddress()
+        // Verifying IPv6 address should be populated in local_net_access map
+        verify(bpfNetMaps).addLocalNetAccess(
+            eq(PREFIX_LENGTH_IPV6 + LOCAL_IPV6_IP_ADDRESS_PREFIX.getPrefixLength()),
+            eq(WIFI_IFNAME),
+            eq(LOCAL_IPV6_IP_ADDRESS_PREFIX.getAddress()),
+            eq(0),
+            eq(0),
+            eq(false)
+        )
+
+        // Updating Link Property by changing interface name which has IPv4 instead of IPv6
+        val wifiLp2 = lp(WIFI_IFNAME_2, LOCAL_IPV4_LINK_ADDRRESS_1)
+        wifiAgent.sendLinkProperties(wifiLp2)
+        cb.expect<LinkPropertiesChanged>(wifiAgent.network)
+
+        // Multicast and Broadcast address should be populated in local_net_access map for
+        // new interface
+        verifyPopulationOfMulticastAndBroadcastAddress(WIFI_IFNAME_2)
+        // Verifying IPv4 matching prefix(10.0.0.0/8) should be populated in local_net_access map
+        verify(bpfNetMaps).addLocalNetAccess(
+            eq(PREFIX_LENGTH_IPV4 + 8),
+            eq(WIFI_IFNAME_2),
+            eq(InetAddresses.parseNumericAddress("10.0.0.0")),
+            eq(0),
+            eq(0),
+            eq(false)
+        )
+        // Multicast and Broadcast address should be removed in local_net_access map for
+        // old interface
+        verifyRemovalOfMulticastAndBroadcastAddress()
+        // Verifying IPv6 address should be removed from local_net_access map
+        verify(bpfNetMaps).removeLocalNetAccess(
+            eq(PREFIX_LENGTH_IPV6 + LOCAL_IPV6_IP_ADDRESS_PREFIX.getPrefixLength()),
+            eq(WIFI_IFNAME),
+            eq(LOCAL_IPV6_IP_ADDRESS_PREFIX.getAddress()),
+            eq(0),
+            eq(0)
+        )
+    }
+
+    @Test
+    fun testAddingAnotherNetwork_AllAddressesAddedInBpfMap() {
+        val nr = nr(TRANSPORT_WIFI)
+        val cb = TestableNetworkCallback()
+        cm.requestNetwork(nr, cb)
+
+        val wifiLp = lp(WIFI_IFNAME, LOCAL_IPV6_LINK_ADDRESS)
+        val wifiAgent = Agent(nc = wifiNc, lp = wifiLp)
+        wifiAgent.connect()
+        cb.expectAvailableCallbacks(wifiAgent.network, validated = false)
+
+        // Multicast and Broadcast address should always be populated in local_net_access map
+        verifyPopulationOfMulticastAndBroadcastAddress()
+        // Verifying IPv6 address should be populated in local_net_access map
+        verify(bpfNetMaps).addLocalNetAccess(
+            eq(PREFIX_LENGTH_IPV6 + LOCAL_IPV6_IP_ADDRESS_PREFIX.getPrefixLength()),
+            eq(WIFI_IFNAME),
+            eq(LOCAL_IPV6_IP_ADDRESS_PREFIX.getAddress()),
+            eq(0),
+            eq(0),
+            eq(false)
+        )
+
+        // Adding another network with LinkProperty having IPv4 in LinkAddress
+        val wifiLp2 = lp(WIFI_IFNAME_2, LOCAL_IPV4_LINK_ADDRRESS_1)
+        val wifiAgent2 = Agent(nc = wifiNc, lp = wifiLp2)
+        wifiAgent2.connect()
+
+        // Multicast and Broadcast address should always be populated in local_net_access map
+        verifyPopulationOfMulticastAndBroadcastAddress(WIFI_IFNAME_2)
+        // Verifying IPv4 matching prefix(10.0.0.0/8) should be populated in local_net_access map
+        verify(bpfNetMaps).addLocalNetAccess(
+            eq(PREFIX_LENGTH_IPV4 + 8),
+            eq(WIFI_IFNAME_2),
+            eq(InetAddresses.parseNumericAddress("10.0.0.0")),
+            eq(0),
+            eq(0),
+            eq(false)
+        )
+        // Verifying nothing should be removed from local_net_access map
+        verify(bpfNetMaps, never()).removeLocalNetAccess(any(), any(), any(), any(), any())
+    }
+
+    @Test
+    fun testDestroyingNetwork_AddressesRemovedFromBpfMap() {
+        val nr = nr(TRANSPORT_WIFI)
+        val cb = TestableNetworkCallback()
+        cm.requestNetwork(nr, cb)
+
+        val wifiLp = lp(WIFI_IFNAME, LOCAL_IPV6_LINK_ADDRESS)
+        val wifiAgent = Agent(nc = wifiNc, lp = wifiLp)
+        wifiAgent.connect()
+        cb.expectAvailableCallbacks(wifiAgent.network, validated = false)
+
+        // Multicast and Broadcast address should always be populated in local_net_access map
+        verifyPopulationOfMulticastAndBroadcastAddress()
+        // Verifying IPv6 address should be populated in local_net_access map
+        verify(bpfNetMaps).addLocalNetAccess(
+            eq( PREFIX_LENGTH_IPV6 + LOCAL_IPV6_IP_ADDRESS_PREFIX.getPrefixLength()),
+            eq(WIFI_IFNAME),
+            eq(LOCAL_IPV6_IP_ADDRESS_PREFIX.getAddress()),
+            eq(0),
+            eq(0),
+            eq(false)
+        )
+
+        // Unregistering the network
+        wifiAgent.unregisterAfterReplacement(LONG_TIMEOUT_MS)
+        cb.expect<Lost>(wifiAgent.network)
+
+        // Multicast and Broadcast address should be removed in local_net_access map for
+        // old interface
+        verifyRemovalOfMulticastAndBroadcastAddress()
+        // Verifying IPv6 address should be removed from local_net_access map
+        verify(bpfNetMaps).removeLocalNetAccess(
+            eq(PREFIX_LENGTH_IPV6 + LOCAL_IPV6_IP_ADDRESS_PREFIX.getPrefixLength()),
+            eq(WIFI_IFNAME),
+            eq(LOCAL_IPV6_IP_ADDRESS_PREFIX.getAddress()),
+            eq(0),
+            eq(0)
+        )
+    }
+
+    // Verify if multicast and broadcast addresses have been added using addLocalNetAccess
+    fun verifyPopulationOfMulticastAndBroadcastAddress(
+        interfaceName: String = WIFI_IFNAME
+    ) {
+        verify(bpfNetMaps).addLocalNetAccess(
+            eq(PREFIX_LENGTH_IPV4 + 4),
+            eq(interfaceName),
+            eq(InetAddresses.parseNumericAddress("224.0.0.0")),
+            eq(0),
+            eq(0),
+            eq(false)
+        )
+        verify(bpfNetMaps).addLocalNetAccess(
+            eq(PREFIX_LENGTH_IPV6 + 8),
+            eq(interfaceName),
+            eq(InetAddresses.parseNumericAddress("ff00::")),
+            eq(0),
+            eq(0),
+            eq(false)
+        )
+        verify(bpfNetMaps).addLocalNetAccess(
+            eq(PREFIX_LENGTH_IPV4 + 32),
+            eq(interfaceName),
+            eq(InetAddresses.parseNumericAddress("255.255.255.255")),
+            eq(0),
+            eq(0),
+            eq(false)
+        )
+    }
+
+    // Verify if multicast and broadcast addresses have been removed using removeLocalNetAccess
+    fun verifyRemovalOfMulticastAndBroadcastAddress(
+        interfaceName: String = WIFI_IFNAME
+    ) {
+        verify(bpfNetMaps).removeLocalNetAccess(
+            eq(PREFIX_LENGTH_IPV4 + 4),
+            eq(interfaceName),
+            eq(InetAddresses.parseNumericAddress("224.0.0.0")),
+            eq(0),
+            eq(0)
+        )
+        verify(bpfNetMaps).removeLocalNetAccess(
+            eq(PREFIX_LENGTH_IPV6 + 8),
+            eq(interfaceName),
+            eq(InetAddresses.parseNumericAddress("ff00::")),
+            eq(0),
+            eq(0)
+        )
+        verify(bpfNetMaps).removeLocalNetAccess(
+            eq(PREFIX_LENGTH_IPV4 + 32),
+            eq(interfaceName),
+            eq(InetAddresses.parseNumericAddress("255.255.255.255")),
+            eq(0),
+            eq(0)
+        )
+    }
+}