diff --git a/Tethering/apishim/30/com/android/networkstack/tethering/apishim/api30/BpfCoordinatorShimImpl.java b/Tethering/apishim/30/com/android/networkstack/tethering/apishim/api30/BpfCoordinatorShimImpl.java
index e310fb6..33f1c29 100644
--- a/Tethering/apishim/30/com/android/networkstack/tethering/apishim/api30/BpfCoordinatorShimImpl.java
+++ b/Tethering/apishim/30/com/android/networkstack/tethering/apishim/api30/BpfCoordinatorShimImpl.java
@@ -179,6 +179,18 @@
     }
 
     @Override
+    public boolean addDevMap(int ifIndex) {
+        /* no op */
+        return false;
+    }
+
+    @Override
+    public boolean removeDevMap(int ifIndex) {
+        /* no op */
+        return false;
+    }
+
+    @Override
     public String toString() {
         return "Netd used";
     }
diff --git a/Tethering/apishim/31/com/android/networkstack/tethering/apishim/api31/BpfCoordinatorShimImpl.java b/Tethering/apishim/31/com/android/networkstack/tethering/apishim/api31/BpfCoordinatorShimImpl.java
index d7ce139..74ddcbc 100644
--- a/Tethering/apishim/31/com/android/networkstack/tethering/apishim/api31/BpfCoordinatorShimImpl.java
+++ b/Tethering/apishim/31/com/android/networkstack/tethering/apishim/api31/BpfCoordinatorShimImpl.java
@@ -36,6 +36,8 @@
 import com.android.networkstack.tethering.Tether4Key;
 import com.android.networkstack.tethering.Tether4Value;
 import com.android.networkstack.tethering.Tether6Value;
+import com.android.networkstack.tethering.TetherDevKey;
+import com.android.networkstack.tethering.TetherDevValue;
 import com.android.networkstack.tethering.TetherDownstream6Key;
 import com.android.networkstack.tethering.TetherLimitKey;
 import com.android.networkstack.tethering.TetherLimitValue;
@@ -85,6 +87,10 @@
     @Nullable
     private final BpfMap<TetherLimitKey, TetherLimitValue> mBpfLimitMap;
 
+    // BPF map of interface index mapping for XDP.
+    @Nullable
+    private final BpfMap<TetherDevKey, TetherDevValue> mBpfDevMap;
+
     // Tracking IPv4 rule count while any rule is using the given upstream interfaces. Used for
     // reducing the BPF map iteration query. The count is increased or decreased when the rule is
     // added or removed successfully on mBpfDownstream4Map. Counting the rules on downstream4 map
@@ -108,6 +114,7 @@
         mBpfUpstream6Map = deps.getBpfUpstream6Map();
         mBpfStatsMap = deps.getBpfStatsMap();
         mBpfLimitMap = deps.getBpfLimitMap();
+        mBpfDevMap = deps.getBpfDevMap();
 
         // Clear the stubs of the maps for handling the system service crash if any.
         // Doesn't throw the exception and clear the stubs as many as possible.
@@ -141,12 +148,18 @@
         } catch (ErrnoException e) {
             mLog.e("Could not clear mBpfLimitMap: " + e);
         }
+        try {
+            if (mBpfDevMap != null) mBpfDevMap.clear();
+        } catch (ErrnoException e) {
+            mLog.e("Could not clear mBpfDevMap: " + e);
+        }
     }
 
     @Override
     public boolean isInitialized() {
         return mBpfDownstream4Map != null && mBpfUpstream4Map != null && mBpfDownstream6Map != null
-                && mBpfUpstream6Map != null && mBpfStatsMap != null && mBpfLimitMap != null;
+                && mBpfUpstream6Map != null && mBpfStatsMap != null && mBpfLimitMap != null
+                && mBpfDevMap != null;
     }
 
     @Override
@@ -432,6 +445,32 @@
         return mRule4CountOnUpstream.get(ifIndex) != null;
     }
 
+    @Override
+    public boolean addDevMap(int ifIndex) {
+        if (!isInitialized()) return false;
+
+        try {
+            mBpfDevMap.updateEntry(new TetherDevKey(ifIndex), new TetherDevValue(ifIndex));
+        } catch (ErrnoException e) {
+            mLog.e("Could not add interface " + ifIndex + ": " + e);
+            return false;
+        }
+        return true;
+    }
+
+    @Override
+    public boolean removeDevMap(int ifIndex) {
+        if (!isInitialized()) return false;
+
+        try {
+            mBpfDevMap.deleteEntry(new TetherDevKey(ifIndex));
+        } catch (ErrnoException e) {
+            mLog.e("Could not delete interface " + ifIndex + ": " + e);
+            return false;
+        }
+        return true;
+    }
+
     private String mapStatus(BpfMap m, String name) {
         return name + "{" + (m != null ? "OK" : "ERROR") + "}";
     }
@@ -444,7 +483,8 @@
                 mapStatus(mBpfDownstream4Map, "mBpfDownstream4Map"),
                 mapStatus(mBpfUpstream4Map, "mBpfUpstream4Map"),
                 mapStatus(mBpfStatsMap, "mBpfStatsMap"),
-                mapStatus(mBpfLimitMap, "mBpfLimitMap")
+                mapStatus(mBpfLimitMap, "mBpfLimitMap"),
+                mapStatus(mBpfDevMap, "mBpfDevMap")
         });
     }
 
diff --git a/Tethering/apishim/common/com/android/networkstack/tethering/apishim/common/BpfCoordinatorShim.java b/Tethering/apishim/common/com/android/networkstack/tethering/apishim/common/BpfCoordinatorShim.java
index 79a628b..8a7a49c 100644
--- a/Tethering/apishim/common/com/android/networkstack/tethering/apishim/common/BpfCoordinatorShim.java
+++ b/Tethering/apishim/common/com/android/networkstack/tethering/apishim/common/BpfCoordinatorShim.java
@@ -166,5 +166,15 @@
      * TODO: consider using InterfaceParams to replace interface name.
      */
     public abstract boolean detachProgram(@NonNull String iface);
+
+    /**
+     * Add interface index mapping.
+     */
+    public abstract boolean addDevMap(int ifIndex);
+
+    /**
+     * Remove interface index mapping.
+     */
+    public abstract boolean removeDevMap(int ifIndex);
 }
 
diff --git a/Tethering/bpf_progs/offload.c b/Tethering/bpf_progs/offload.c
index 36f6783..6ff370c 100644
--- a/Tethering/bpf_progs/offload.c
+++ b/Tethering/bpf_progs/offload.c
@@ -767,8 +767,7 @@
 
 // ----- XDP Support -----
 
-DEFINE_BPF_MAP_GRW(tether_xdp_devmap, DEVMAP_HASH, uint32_t, uint32_t, 64,
-                   AID_NETWORK_STACK)
+DEFINE_BPF_MAP_GRW(tether_dev_map, DEVMAP_HASH, uint32_t, uint32_t, 64, AID_NETWORK_STACK)
 
 static inline __always_inline int do_xdp_forward6(struct xdp_md *ctx, const bool is_ethernet,
         const bool downstream) {
diff --git a/Tethering/src/com/android/networkstack/tethering/BpfCoordinator.java b/Tethering/src/com/android/networkstack/tethering/BpfCoordinator.java
index 2eed968..8adcbd9 100644
--- a/Tethering/src/com/android/networkstack/tethering/BpfCoordinator.java
+++ b/Tethering/src/com/android/networkstack/tethering/BpfCoordinator.java
@@ -72,6 +72,7 @@
 import java.util.HashMap;
 import java.util.HashSet;
 import java.util.LinkedHashMap;
+import java.util.LinkedHashSet;
 import java.util.Map;
 import java.util.Objects;
 import java.util.Set;
@@ -104,6 +105,7 @@
     private static final String TETHER_STATS_MAP_PATH = makeMapPath("stats");
     private static final String TETHER_LIMIT_MAP_PATH = makeMapPath("limit");
     private static final String TETHER_ERROR_MAP_PATH = makeMapPath("error");
+    private static final String TETHER_DEV_MAP_PATH = makeMapPath("dev");
 
     /** The names of all the BPF counters defined in bpf_tethering.h. */
     public static final String[] sBpfCounterNames = getBpfCounterNames();
@@ -220,6 +222,11 @@
     // Map for upstream and downstream pair.
     private final HashMap<String, HashSet<String>> mForwardingPairs = new HashMap<>();
 
+    // Set for upstream and downstream device map. Used for caching BPF dev map status and
+    // reduce duplicate adding or removing map operations. Use LinkedHashSet because the test
+    // BpfCoordinatorTest needs predictable iteration order.
+    private final Set<Integer> mDeviceMapSet = new LinkedHashSet<>();
+
     // Runnable that used by scheduling next polling of stats.
     private final Runnable mScheduledPollingTask = () -> {
         updateForwardedStats();
@@ -336,6 +343,18 @@
                 return null;
             }
         }
+
+        /** Get dev BPF map. */
+        @Nullable public BpfMap<TetherDevKey, TetherDevValue> getBpfDevMap() {
+            if (!isAtLeastS()) return null;
+            try {
+                return new BpfMap<>(TETHER_DEV_MAP_PATH,
+                    BpfMap.BPF_F_RDWR, TetherDevKey.class, TetherDevValue.class);
+            } catch (ErrnoException e) {
+                Log.e(TAG, "Cannot create dev map: " + e);
+                return null;
+            }
+        }
     }
 
     @VisibleForTesting
@@ -490,6 +509,9 @@
         }
         LinkedHashMap<Inet6Address, Ipv6ForwardingRule> rules = mIpv6ForwardingRules.get(ipServer);
 
+        // Add upstream and downstream interface index to dev map.
+        maybeAddDevMap(rule.upstreamIfindex, rule.downstreamIfindex);
+
         // When the first rule is added to an upstream, setup upstream forwarding and data limit.
         maybeSetLimit(rule.upstreamIfindex);
 
@@ -758,6 +780,11 @@
         dumpIpv4ForwardingRules(pw);
         pw.decreaseIndent();
 
+        pw.println("Device map:");
+        pw.increaseIndent();
+        dumpDevmap(pw);
+        pw.decreaseIndent();
+
         pw.println();
         pw.println("Forwarding counters:");
         pw.increaseIndent();
@@ -890,6 +917,31 @@
         }
     }
 
+    private void dumpDevmap(@NonNull IndentingPrintWriter pw) {
+        try (BpfMap<TetherDevKey, TetherDevValue> map = mDeps.getBpfDevMap()) {
+            if (map == null) {
+                pw.println("No devmap support");
+                return;
+            }
+            if (map.isEmpty()) {
+                pw.println("No interface index");
+                return;
+            }
+            pw.println("ifindex (iface) -> ifindex (iface)");
+            pw.increaseIndent();
+            map.forEach((k, v) -> {
+                // Only get upstream interface name. Just do the best to make the index readable.
+                // TODO: get downstream interface name because the index is either upstrema or
+                // downstream interface in dev map.
+                pw.println(String.format("%d (%s) -> %d (%s)", k.ifIndex, getIfName(k.ifIndex),
+                        v.ifIndex, getIfName(v.ifIndex)));
+            });
+        } catch (ErrnoException e) {
+            pw.println("Error dumping dev map: " + e);
+        }
+        pw.decreaseIndent();
+    }
+
     /** IPv6 forwarding rule class. */
     public static class Ipv6ForwardingRule {
         // The upstream6 and downstream6 rules are built as the following tables. Only raw ip
@@ -1229,6 +1281,7 @@
             final Tether4Value downstream4Value = makeTetherDownstream4Value(e, tetherClient,
                     upstreamIndex);
 
+            maybeAddDevMap(upstreamIndex, tetherClient.downstreamIfindex);
             maybeSetLimit(upstreamIndex);
             mBpfCoordinatorShim.tetherOffloadRuleAdd(UPSTREAM, upstream4Key, upstream4Value);
             mBpfCoordinatorShim.tetherOffloadRuleAdd(DOWNSTREAM, downstream4Key, downstream4Value);
@@ -1357,6 +1410,15 @@
         return false;
     }
 
+    // TODO: remove the index from map while the interface has been removed because the map size
+    // is 64 entries. See packages\modules\Connectivity\Tethering\bpf_progs\offload.c.
+    private void maybeAddDevMap(int upstreamIfindex, int downstreamIfindex) {
+        for (Integer index : new Integer[] {upstreamIfindex, downstreamIfindex}) {
+            if (mDeviceMapSet.contains(index)) continue;
+            if (mBpfCoordinatorShim.addDevMap(index)) mDeviceMapSet.add(index);
+        }
+    }
+
     private void forwardingPairAdd(@NonNull String intIface, @NonNull String extIface) {
         if (!mForwardingPairs.containsKey(extIface)) {
             mForwardingPairs.put(extIface, new HashSet<String>());
diff --git a/Tethering/src/com/android/networkstack/tethering/TetherDevKey.java b/Tethering/src/com/android/networkstack/tethering/TetherDevKey.java
new file mode 100644
index 0000000..4283c1b
--- /dev/null
+++ b/Tethering/src/com/android/networkstack/tethering/TetherDevKey.java
@@ -0,0 +1,31 @@
+/*
+ * Copyright (C) 2021 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.networkstack.tethering;
+
+import com.android.net.module.util.Struct;
+import com.android.net.module.util.Struct.Field;
+import com.android.net.module.util.Struct.Type;
+
+/** The key of BpfMap which is used for mapping interface index. */
+public class TetherDevKey extends Struct {
+    @Field(order = 0, type = Type.U32)
+    public final long ifIndex;  // interface index
+
+    public TetherDevKey(final long ifIndex) {
+        this.ifIndex = ifIndex;
+    }
+}
diff --git a/Tethering/src/com/android/networkstack/tethering/TetherDevValue.java b/Tethering/src/com/android/networkstack/tethering/TetherDevValue.java
new file mode 100644
index 0000000..1cd99b5
--- /dev/null
+++ b/Tethering/src/com/android/networkstack/tethering/TetherDevValue.java
@@ -0,0 +1,31 @@
+/*
+ * Copyright (C) 2021 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.networkstack.tethering;
+
+import com.android.net.module.util.Struct;
+import com.android.net.module.util.Struct.Field;
+import com.android.net.module.util.Struct.Type;
+
+/** The key of BpfMap which is used for mapping interface index. */
+public class TetherDevValue extends Struct {
+    @Field(order = 0, type = Type.U32)
+    public final long ifIndex;  // interface index
+
+    public TetherDevValue(final long ifIndex) {
+        this.ifIndex = ifIndex;
+    }
+}
diff --git a/Tethering/tests/unit/src/android/net/ip/IpServerTest.java b/Tethering/tests/unit/src/android/net/ip/IpServerTest.java
index 435cab5..ce69cb3 100644
--- a/Tethering/tests/unit/src/android/net/ip/IpServerTest.java
+++ b/Tethering/tests/unit/src/android/net/ip/IpServerTest.java
@@ -107,6 +107,8 @@
 import com.android.networkstack.tethering.Tether4Key;
 import com.android.networkstack.tethering.Tether4Value;
 import com.android.networkstack.tethering.Tether6Value;
+import com.android.networkstack.tethering.TetherDevKey;
+import com.android.networkstack.tethering.TetherDevValue;
 import com.android.networkstack.tethering.TetherDownstream6Key;
 import com.android.networkstack.tethering.TetherLimitKey;
 import com.android.networkstack.tethering.TetherLimitValue;
@@ -182,6 +184,7 @@
     @Mock private BpfMap<TetherUpstream6Key, Tether6Value> mBpfUpstream6Map;
     @Mock private BpfMap<TetherStatsKey, TetherStatsValue> mBpfStatsMap;
     @Mock private BpfMap<TetherLimitKey, TetherLimitValue> mBpfLimitMap;
+    @Mock private BpfMap<TetherDevKey, TetherDevValue> mBpfDevMap;
 
     @Captor private ArgumentCaptor<DhcpServingParamsParcel> mDhcpParamsCaptor;
 
@@ -334,6 +337,11 @@
                     public BpfMap<TetherLimitKey, TetherLimitValue> getBpfLimitMap() {
                         return mBpfLimitMap;
                     }
+
+                    @Nullable
+                    public BpfMap<TetherDevKey, TetherDevValue> getBpfDevMap() {
+                        return mBpfDevMap;
+                    }
                 };
         mBpfCoordinator = spy(new BpfCoordinator(mBpfDeps));
 
diff --git a/Tethering/tests/unit/src/com/android/networkstack/tethering/BpfCoordinatorTest.java b/Tethering/tests/unit/src/com/android/networkstack/tethering/BpfCoordinatorTest.java
index 233f6db..cc912f4 100644
--- a/Tethering/tests/unit/src/com/android/networkstack/tethering/BpfCoordinatorTest.java
+++ b/Tethering/tests/unit/src/com/android/networkstack/tethering/BpfCoordinatorTest.java
@@ -207,6 +207,7 @@
     @Mock private BpfMap<Tether4Key, Tether4Value> mBpfUpstream4Map;
     @Mock private BpfMap<TetherDownstream6Key, Tether6Value> mBpfDownstream6Map;
     @Mock private BpfMap<TetherUpstream6Key, Tether6Value> mBpfUpstream6Map;
+    @Mock private BpfMap<TetherDevKey, TetherDevValue> mBpfDevMap;
 
     // Late init since methods must be called by the thread that created this object.
     private TestableNetworkStatsProviderCbBinder mTetherStatsProviderCb;
@@ -284,6 +285,11 @@
                     public BpfMap<TetherLimitKey, TetherLimitValue> getBpfLimitMap() {
                         return mBpfLimitMap;
                     }
+
+                    @Nullable
+                    public BpfMap<TetherDevKey, TetherDevValue> getBpfDevMap() {
+                        return mBpfDevMap;
+                    }
             });
 
     @Before public void setUp() {
@@ -1368,12 +1374,9 @@
         coordinator.tetherOffloadClientAdd(mIpServer, clientInfo);
     }
 
-    // TODO: Test the IPv4 and IPv6 exist concurrently.
-    // TODO: Test the IPv4 rule delete failed.
-    @Test
-    @IgnoreUpTo(Build.VERSION_CODES.R)
-    public void testSetDataLimitOnRule4Change() throws Exception {
-        final BpfCoordinator coordinator = makeBpfCoordinator();
+    private void initBpfCoordinatorForRule4(final BpfCoordinator coordinator) throws Exception {
+        // Needed because addUpstreamIfindexToMap only updates upstream information when polling
+        // was started.
         coordinator.startPolling();
 
         // Needed because tetherOffloadRuleRemove of api31.BpfCoordinatorShimImpl only decreases
@@ -1387,6 +1390,15 @@
         coordinator.addUpstreamNameToLookupTable(UPSTREAM_IFINDEX, UPSTREAM_IFACE);
         setUpstreamInformationTo(coordinator);
         setDownstreamAndClientInformationTo(coordinator);
+    }
+
+    // TODO: Test the IPv4 and IPv6 exist concurrently.
+    // TODO: Test the IPv4 rule delete failed.
+    @Test
+    @IgnoreUpTo(Build.VERSION_CODES.R)
+    public void testSetDataLimitOnRule4Change() throws Exception {
+        final BpfCoordinator coordinator = makeBpfCoordinator();
+        initBpfCoordinatorForRule4(coordinator);
 
         // Applying a data limit to the current upstream does not take any immediate action.
         // The data limit could be only set on an upstream which has rules.
@@ -1445,4 +1457,41 @@
         verifyTetherOffloadGetAndClearStats(inOrder, UPSTREAM_IFINDEX);
         inOrder.verifyNoMoreInteractions();
     }
+
+    @Test
+    @IgnoreUpTo(Build.VERSION_CODES.R)
+    public void testAddDevMapRule6() throws Exception {
+        final BpfCoordinator coordinator = makeBpfCoordinator();
+
+        coordinator.addUpstreamNameToLookupTable(UPSTREAM_IFINDEX, UPSTREAM_IFACE);
+        final Ipv6ForwardingRule ruleA = buildTestForwardingRule(UPSTREAM_IFINDEX, NEIGH_A, MAC_A);
+        final Ipv6ForwardingRule ruleB = buildTestForwardingRule(UPSTREAM_IFINDEX, NEIGH_B, MAC_B);
+
+        coordinator.tetherOffloadRuleAdd(mIpServer, ruleA);
+        verify(mBpfDevMap).updateEntry(eq(new TetherDevKey(UPSTREAM_IFINDEX)),
+                eq(new TetherDevValue(UPSTREAM_IFINDEX)));
+        verify(mBpfDevMap).updateEntry(eq(new TetherDevKey(DOWNSTREAM_IFINDEX)),
+                eq(new TetherDevValue(DOWNSTREAM_IFINDEX)));
+        clearInvocations(mBpfDevMap);
+
+        coordinator.tetherOffloadRuleAdd(mIpServer, ruleB);
+        verify(mBpfDevMap, never()).updateEntry(any(), any());
+    }
+
+    @Test
+    @IgnoreUpTo(Build.VERSION_CODES.R)
+    public void testAddDevMapRule4() throws Exception {
+        final BpfCoordinator coordinator = makeBpfCoordinator();
+        initBpfCoordinatorForRule4(coordinator);
+
+        mConsumer.accept(makeTestConntrackEvent(IPCTNL_MSG_CT_NEW, IPPROTO_TCP));
+        verify(mBpfDevMap).updateEntry(eq(new TetherDevKey(UPSTREAM_IFINDEX)),
+                eq(new TetherDevValue(UPSTREAM_IFINDEX)));
+        verify(mBpfDevMap).updateEntry(eq(new TetherDevKey(DOWNSTREAM_IFINDEX)),
+                eq(new TetherDevValue(DOWNSTREAM_IFINDEX)));
+        clearInvocations(mBpfDevMap);
+
+        mConsumer.accept(makeTestConntrackEvent(IPCTNL_MSG_CT_NEW, IPPROTO_UDP));
+        verify(mBpfDevMap, never()).updateEntry(any(), any());
+    }
 }