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 eafa3ea..90b9b3f 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
@@ -28,7 +28,11 @@
 
 import com.android.networkstack.tethering.BpfCoordinator.Dependencies;
 import com.android.networkstack.tethering.BpfCoordinator.Ipv6ForwardingRule;
+import com.android.networkstack.tethering.TetherDownstream4Key;
+import com.android.networkstack.tethering.TetherDownstream4Value;
 import com.android.networkstack.tethering.TetherStatsValue;
+import com.android.networkstack.tethering.TetherUpstream4Key;
+import com.android.networkstack.tethering.TetherUpstream4Value;
 
 /**
  * Bpf coordinator class for API shims.
@@ -132,6 +136,32 @@
     }
 
     @Override
+    public boolean tetherOffloadRuleAdd(@NonNull TetherDownstream4Key key,
+            @NonNull TetherDownstream4Value value) {
+        /* no op */
+        return true;
+    }
+
+    @Override
+    public boolean tetherOffloadRuleRemove(@NonNull TetherDownstream4Key key) {
+        /* no op */
+        return true;
+    }
+
+    @Override
+    public boolean tetherOffloadRuleAdd(@NonNull TetherUpstream4Key key,
+            @NonNull TetherUpstream4Value value) {
+        /* no op */
+        return true;
+    }
+
+    @Override
+    public boolean tetherOffloadRuleRemove(@NonNull TetherUpstream4Key key) {
+        /* no op */
+        return true;
+    }
+
+    @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 c0d85ae..b9ce769 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
@@ -30,12 +30,16 @@
 import com.android.networkstack.tethering.BpfCoordinator.Dependencies;
 import com.android.networkstack.tethering.BpfCoordinator.Ipv6ForwardingRule;
 import com.android.networkstack.tethering.BpfMap;
+import com.android.networkstack.tethering.TetherDownstream4Key;
+import com.android.networkstack.tethering.TetherDownstream4Value;
 import com.android.networkstack.tethering.TetherDownstream6Key;
 import com.android.networkstack.tethering.TetherDownstream6Value;
 import com.android.networkstack.tethering.TetherLimitKey;
 import com.android.networkstack.tethering.TetherLimitValue;
 import com.android.networkstack.tethering.TetherStatsKey;
 import com.android.networkstack.tethering.TetherStatsValue;
+import com.android.networkstack.tethering.TetherUpstream4Key;
+import com.android.networkstack.tethering.TetherUpstream4Value;
 
 import java.io.FileDescriptor;
 
@@ -54,6 +58,16 @@
     @NonNull
     private final SharedLog mLog;
 
+    // BPF map of ingress queueing discipline which pre-processes the packets by the IPv4
+    // downstream rules.
+    @Nullable
+    private final BpfMap<TetherDownstream4Key, TetherDownstream4Value> mBpfDownstream4Map;
+
+    // BPF map of ingress queueing discipline which pre-processes the packets by the IPv4
+    // upstream rules.
+    @Nullable
+    private final BpfMap<TetherUpstream4Key, TetherUpstream4Value> mBpfUpstream4Map;
+
     // BPF map of ingress queueing discipline which pre-processes the packets by the IPv6
     // forwarding rules.
     @Nullable
@@ -69,6 +83,8 @@
 
     public BpfCoordinatorShimImpl(@NonNull final Dependencies deps) {
         mLog = deps.getSharedLog().forSubComponent(TAG);
+        mBpfDownstream4Map = deps.getBpfDownstream4Map();
+        mBpfUpstream4Map = deps.getBpfUpstream4Map();
         mBpfDownstream6Map = deps.getBpfDownstream6Map();
         mBpfStatsMap = deps.getBpfStatsMap();
         mBpfLimitMap = deps.getBpfLimitMap();
@@ -76,7 +92,8 @@
 
     @Override
     public boolean isInitialized() {
-        return mBpfDownstream6Map != null && mBpfStatsMap != null  && mBpfLimitMap != null;
+        return mBpfDownstream4Map != null && mBpfUpstream4Map != null && mBpfDownstream6Map != null
+                && mBpfStatsMap != null && mBpfLimitMap != null;
     }
 
     @Override
@@ -233,14 +250,85 @@
     }
 
     @Override
+    public boolean tetherOffloadRuleAdd(@NonNull TetherDownstream4Key key,
+            @NonNull TetherDownstream4Value value) {
+        if (!isInitialized()) return false;
+
+        try {
+            // The last used time field of the value is updated by the bpf program. Adding the same
+            // map pair twice causes the unexpected refresh. Must be fixed before starting the
+            // conntrack timeout extension implementation.
+            // TODO: consider using insertEntry.
+            mBpfDownstream4Map.updateEntry(key, value);
+        } catch (ErrnoException e) {
+            mLog.e("Could not update entry: ", e);
+            return false;
+        }
+        return true;
+    }
+
+    @Override
+    public boolean tetherOffloadRuleRemove(@NonNull TetherDownstream4Key key) {
+        if (!isInitialized()) return false;
+
+        try {
+            mBpfDownstream4Map.deleteEntry(key);
+        } catch (ErrnoException e) {
+            // Silent if the rule did not exist.
+            if (e.errno != OsConstants.ENOENT) {
+                mLog.e("Could not delete entry: ", e);
+                return false;
+            }
+        }
+        return true;
+    }
+
+    @Override
+    public boolean tetherOffloadRuleAdd(@NonNull TetherUpstream4Key key,
+            @NonNull TetherUpstream4Value value) {
+        if (!isInitialized()) return false;
+
+        try {
+            // The last used time field of the value is updated by the bpf program. Adding the same
+            // map pair twice causes the unexpected refresh. Must be fixed before starting the
+            // conntrack timeout extension implementation.
+            // TODO: consider using insertEntry.
+            mBpfUpstream4Map.updateEntry(key, value);
+        } catch (ErrnoException e) {
+            mLog.e("Could not update entry: ", e);
+            return false;
+        }
+        return true;
+    }
+
+    @Override
+    public boolean tetherOffloadRuleRemove(@NonNull TetherUpstream4Key key) {
+        if (!isInitialized()) return false;
+
+        try {
+            mBpfUpstream4Map.deleteEntry(key);
+        } catch (ErrnoException e) {
+            // Silent if the rule did not exist.
+            if (e.errno != OsConstants.ENOENT) {
+                mLog.e("Could not delete entry: ", e);
+                return false;
+            }
+        }
+        return true;
+    }
+
+    @Override
     public String toString() {
-        return "mBpfDownstream6Map{"
+        return "mBpfDownstream4Map{"
+                + (mBpfDownstream4Map != null ? "initialized" : "not initialized") + "}, "
+                + "mBpfUpstream4Map{"
+                + (mBpfUpstream4Map != null ? "initialized" : "not initialized") + "}, "
+                + "mBpfDownstream6Map{"
                 + (mBpfDownstream6Map != null ? "initialized" : "not initialized") + "}, "
                 + "mBpfStatsMap{"
                 + (mBpfStatsMap != null ? "initialized" : "not initialized") + "}, "
                 + "mBpfLimitMap{"
-                + (mBpfLimitMap != null ? "initialized" : "not initialized") + "} "
-                + "}";
+                + (mBpfLimitMap != null ? "initialized" : "not initialized") + "} ";
     }
 
     /**
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 61abfa3..36d2de1 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
@@ -23,7 +23,11 @@
 
 import com.android.networkstack.tethering.BpfCoordinator.Dependencies;
 import com.android.networkstack.tethering.BpfCoordinator.Ipv6ForwardingRule;
+import com.android.networkstack.tethering.TetherDownstream4Key;
+import com.android.networkstack.tethering.TetherDownstream4Value;
 import com.android.networkstack.tethering.TetherStatsValue;
+import com.android.networkstack.tethering.TetherUpstream4Key;
+import com.android.networkstack.tethering.TetherUpstream4Value;
 
 /**
  * Bpf coordinator class for API shims.
@@ -108,5 +112,27 @@
      */
     @Nullable
     public abstract TetherStatsValue tetherOffloadGetAndClearStats(int ifIndex);
+
+    /**
+     * Adds a tethering IPv4 downstream offload rule to BPF map.
+     */
+    public abstract boolean tetherOffloadRuleAdd(@NonNull TetherDownstream4Key key,
+            @NonNull TetherDownstream4Value value);
+
+    /**
+     * Deletes a tethering IPv4 downstream offload rule from the BPF map.
+     */
+    public abstract boolean tetherOffloadRuleRemove(@NonNull TetherDownstream4Key key);
+
+    /**
+     * Adds a tethering IPv4 upstream offload rule to BPF map.
+     */
+    public abstract boolean tetherOffloadRuleAdd(@NonNull TetherUpstream4Key key,
+            @NonNull TetherUpstream4Value value);
+
+    /**
+     * Deletes a tethering IPv4 upstream offload rule from the BPF map.
+     */
+    public abstract boolean tetherOffloadRuleRemove(@NonNull TetherUpstream4Key key);
 }
 
diff --git a/Tethering/src/com/android/networkstack/tethering/BpfCoordinator.java b/Tethering/src/com/android/networkstack/tethering/BpfCoordinator.java
index 717bf61..e4216d8 100644
--- a/Tethering/src/com/android/networkstack/tethering/BpfCoordinator.java
+++ b/Tethering/src/com/android/networkstack/tethering/BpfCoordinator.java
@@ -87,6 +87,10 @@
     private static final int DUMP_TIMEOUT_MS = 10_000;
     private static final MacAddress NULL_MAC_ADDRESS = MacAddress.fromString(
             "00:00:00:00:00:00");
+    private static final String TETHER_DOWNSTREAM4_MAP_PATH =
+            "/sys/fs/bpf/tethering/map_offload_tether_downstream4_map";
+    private static final String TETHER_UPSTREAM4_MAP_PATH =
+            "/sys/fs/bpf/tethering/map_offload_tether_upstream4_map";
     private static final String TETHER_DOWNSTREAM6_FS_PATH =
             "/sys/fs/bpf/tethering/map_offload_tether_downstream6_map";
     private static final String TETHER_STATS_MAP_PATH =
@@ -232,6 +236,30 @@
             return SdkLevel.isAtLeastS();
         }
 
+        /** Get downstream4 BPF map. */
+        @Nullable public BpfMap<TetherDownstream4Key, TetherDownstream4Value>
+                getBpfDownstream4Map() {
+            try {
+                return new BpfMap<>(TETHER_DOWNSTREAM4_MAP_PATH,
+                    BpfMap.BPF_F_RDWR, TetherDownstream4Key.class, TetherDownstream4Value.class);
+            } catch (ErrnoException e) {
+                Log.e(TAG, "Cannot create downstream4 map: " + e);
+                return null;
+            }
+        }
+
+        /** Get upstream4 BPF map. */
+        @Nullable public BpfMap<TetherUpstream4Key, TetherUpstream4Value>
+                getBpfUpstream4Map() {
+            try {
+                return new BpfMap<>(TETHER_UPSTREAM4_MAP_PATH,
+                    BpfMap.BPF_F_RDWR, TetherUpstream4Key.class, TetherUpstream4Value.class);
+            } catch (ErrnoException e) {
+                Log.e(TAG, "Cannot create upstream4 map: " + e);
+                return null;
+            }
+        }
+
         /** Get downstream6 BPF map. */
         @Nullable public BpfMap<TetherDownstream6Key, TetherDownstream6Value>
                 getBpfDownstream6Map() {
@@ -896,14 +924,12 @@
         @NonNull
         private TetherUpstream4Value makeTetherUpstream4Value(@NonNull ConntrackEvent e,
                 int upstreamIndex) {
-            // TODO: convert {src46, dst46} from ipv4 address (a.b.c.d) to ipv4-mapped address
-            // (::ffff:a.b.d.d).
             return new TetherUpstream4Value(upstreamIndex,
                     NULL_MAC_ADDRESS /* ethDstMac (rawip) */,
                     NULL_MAC_ADDRESS /* ethSrcMac (rawip) */, ETH_P_IP,
-                    NetworkStackConstants.ETHER_MTU, e.tupleReply.dstIp.getAddress(),
-                    e.tupleReply.srcIp.getAddress(), e.tupleReply.dstPort, e.tupleReply.srcPort,
-                    0 /* lastUsed, filled by bpf prog only */);
+                    NetworkStackConstants.ETHER_MTU, toIpv4MappedAddressBytes(e.tupleReply.dstIp),
+                    toIpv4MappedAddressBytes(e.tupleReply.srcIp), e.tupleReply.dstPort,
+                    e.tupleReply.srcPort, 0 /* lastUsed, filled by bpf prog only */);
         }
 
         @NonNull
@@ -916,6 +942,19 @@
                     0 /* lastUsed, filled by bpf prog only */);
         }
 
+        @NonNull
+        private byte[] toIpv4MappedAddressBytes(Inet4Address ia4) {
+            final byte[] addr4 = ia4.getAddress();
+            final byte[] addr6 = new byte[16];
+            addr6[10] = (byte) 0xff;
+            addr6[11] = (byte) 0xff;
+            addr6[12] = addr4[0];
+            addr6[13] = addr4[1];
+            addr6[14] = addr4[2];
+            addr6[15] = addr4[3];
+            return addr6;
+        }
+
         public void accept(ConntrackEvent e) {
             final ClientInfo tetherClient = getClientInfo(e.tupleOrig.srcIp);
             if (tetherClient == null) return;
@@ -929,7 +968,8 @@
 
             if (e.msgType == (NetlinkConstants.NFNL_SUBSYS_CTNETLINK << 8
                     | NetlinkConstants.IPCTNL_MSG_CT_DELETE)) {
-                // TODO: remove ingress and egress rules from BPF maps.
+                mBpfCoordinatorShim.tetherOffloadRuleRemove(upstream4Key);
+                mBpfCoordinatorShim.tetherOffloadRuleRemove(downstream4Key);
                 return;
             }
 
@@ -938,7 +978,8 @@
             final TetherDownstream4Value downstream4Value = makeTetherDownstream4Value(e,
                     tetherClient, upstreamIndex);
 
-            // TODO: insert ingress and egress rules to BPF maps.
+            mBpfCoordinatorShim.tetherOffloadRuleAdd(upstream4Key, upstream4Value);
+            mBpfCoordinatorShim.tetherOffloadRuleAdd(downstream4Key, downstream4Value);
         }
     }
 
diff --git a/Tethering/tests/unit/src/android/net/ip/IpServerTest.java b/Tethering/tests/unit/src/android/net/ip/IpServerTest.java
index e20e011..9b42c73 100644
--- a/Tethering/tests/unit/src/android/net/ip/IpServerTest.java
+++ b/Tethering/tests/unit/src/android/net/ip/IpServerTest.java
@@ -104,12 +104,16 @@
 import com.android.networkstack.tethering.BpfCoordinator.Ipv6ForwardingRule;
 import com.android.networkstack.tethering.BpfMap;
 import com.android.networkstack.tethering.PrivateAddressCoordinator;
+import com.android.networkstack.tethering.TetherDownstream4Key;
+import com.android.networkstack.tethering.TetherDownstream4Value;
 import com.android.networkstack.tethering.TetherDownstream6Key;
 import com.android.networkstack.tethering.TetherDownstream6Value;
 import com.android.networkstack.tethering.TetherLimitKey;
 import com.android.networkstack.tethering.TetherLimitValue;
 import com.android.networkstack.tethering.TetherStatsKey;
 import com.android.networkstack.tethering.TetherStatsValue;
+import com.android.networkstack.tethering.TetherUpstream4Key;
+import com.android.networkstack.tethering.TetherUpstream4Value;
 import com.android.networkstack.tethering.TetheringConfiguration;
 import com.android.testutils.DevSdkIgnoreRule;
 import com.android.testutils.DevSdkIgnoreRule.IgnoreAfter;
@@ -173,6 +177,8 @@
     @Mock private NetworkStatsManager mStatsManager;
     @Mock private TetheringConfiguration mTetherConfig;
     @Mock private ConntrackMonitor mConntrackMonitor;
+    @Mock private BpfMap<TetherDownstream4Key, TetherDownstream4Value> mBpfDownstream4Map;
+    @Mock private BpfMap<TetherUpstream4Key, TetherUpstream4Value> mBpfUpstream4Map;
     @Mock private BpfMap<TetherDownstream6Key, TetherDownstream6Value> mBpfDownstream6Map;
     @Mock private BpfMap<TetherStatsKey, TetherStatsValue> mBpfStatsMap;
     @Mock private BpfMap<TetherLimitKey, TetherLimitValue> mBpfLimitMap;
@@ -303,6 +309,18 @@
                     }
 
                     @Nullable
+                    public BpfMap<TetherDownstream4Key, TetherDownstream4Value>
+                            getBpfDownstream4Map() {
+                        return mBpfDownstream4Map;
+                    }
+
+                    @Nullable
+                    public BpfMap<TetherUpstream4Key, TetherUpstream4Value>
+                            getBpfUpstream4Map() {
+                        return mBpfUpstream4Map;
+                    }
+
+                    @Nullable
                     public BpfMap<TetherDownstream6Key, TetherDownstream6Value>
                             getBpfDownstream6Map() {
                         return mBpfDownstream6Map;
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 764e651..30b4bf4 100644
--- a/Tethering/tests/unit/src/com/android/networkstack/tethering/BpfCoordinatorTest.java
+++ b/Tethering/tests/unit/src/com/android/networkstack/tethering/BpfCoordinatorTest.java
@@ -158,6 +158,8 @@
     @Mock private IpServer mIpServer2;
     @Mock private TetheringConfiguration mTetherConfig;
     @Mock private ConntrackMonitor mConntrackMonitor;
+    @Mock private BpfMap<TetherDownstream4Key, TetherDownstream4Value> mBpfDownstream4Map;
+    @Mock private BpfMap<TetherUpstream4Key, TetherUpstream4Value> mBpfUpstream4Map;
     @Mock private BpfMap<TetherDownstream6Key, TetherDownstream6Value> mBpfDownstream6Map;
 
     // Late init since methods must be called by the thread that created this object.
@@ -203,6 +205,18 @@
                     }
 
                     @Nullable
+                    public BpfMap<TetherDownstream4Key, TetherDownstream4Value>
+                            getBpfDownstream4Map() {
+                        return mBpfDownstream4Map;
+                    }
+
+                    @Nullable
+                    public BpfMap<TetherUpstream4Key, TetherUpstream4Value>
+                            getBpfUpstream4Map() {
+                        return mBpfUpstream4Map;
+                    }
+
+                    @Nullable
                     public BpfMap<TetherDownstream6Key, TetherDownstream6Value>
                             getBpfDownstream6Map() {
                         return mBpfDownstream6Map;