diff --git a/staticlibs/Android.bp b/staticlibs/Android.bp
index 047d51e..513b201 100644
--- a/staticlibs/Android.bp
+++ b/staticlibs/Android.bp
@@ -116,6 +116,7 @@
         "device/com/android/net/module/util/JniUtil.java",
         "device/com/android/net/module/util/Struct.java",
         "device/com/android/net/module/util/TcUtils.java",
+        "device/com/android/net/module/util/bpf/*.java",
     ],
     sdk_version: "module_current",
     min_sdk_version: "29",
diff --git a/staticlibs/device/com/android/net/module/util/bpf/Tether4Key.java b/staticlibs/device/com/android/net/module/util/bpf/Tether4Key.java
new file mode 100644
index 0000000..638576f
--- /dev/null
+++ b/staticlibs/device/com/android/net/module/util/bpf/Tether4Key.java
@@ -0,0 +1,81 @@
+/*
+ * Copyright (C) 2020 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.net.module.util.bpf;
+
+import android.net.MacAddress;
+
+import androidx.annotation.NonNull;
+
+import com.android.net.module.util.Struct;
+import com.android.net.module.util.Struct.Field;
+import com.android.net.module.util.Struct.Type;
+
+import java.net.Inet4Address;
+import java.net.UnknownHostException;
+import java.util.Objects;
+
+/** Key type for downstream & upstream IPv4 forwarding maps. */
+public class Tether4Key extends Struct {
+    @Field(order = 0, type = Type.U32)
+    public final long iif;
+
+    @Field(order = 1, type = Type.EUI48)
+    public final MacAddress dstMac;
+
+    @Field(order = 2, type = Type.U8, padding = 1)
+    public final short l4proto;
+
+    @Field(order = 3, type = Type.ByteArray, arraysize = 4)
+    public final byte[] src4;
+
+    @Field(order = 4, type = Type.ByteArray, arraysize = 4)
+    public final byte[] dst4;
+
+    @Field(order = 5, type = Type.UBE16)
+    public final int srcPort;
+
+    @Field(order = 6, type = Type.UBE16)
+    public final int dstPort;
+
+    public Tether4Key(final long iif, @NonNull final MacAddress dstMac, final short l4proto,
+            final byte[] src4, final byte[] dst4, final int srcPort,
+            final int dstPort) {
+        Objects.requireNonNull(dstMac);
+
+        this.iif = iif;
+        this.dstMac = dstMac;
+        this.l4proto = l4proto;
+        this.src4 = src4;
+        this.dst4 = dst4;
+        this.srcPort = srcPort;
+        this.dstPort = dstPort;
+    }
+
+    @Override
+    public String toString() {
+        try {
+            return String.format(
+                    "iif: %d, dstMac: %s, l4proto: %d, src4: %s, dst4: %s, "
+                            + "srcPort: %d, dstPort: %d",
+                    iif, dstMac, l4proto,
+                    Inet4Address.getByAddress(src4), Inet4Address.getByAddress(dst4),
+                    Short.toUnsignedInt((short) srcPort), Short.toUnsignedInt((short) dstPort));
+        } catch (UnknownHostException | IllegalArgumentException e) {
+            return String.format("Invalid IP address", e);
+        }
+    }
+}
diff --git a/staticlibs/device/com/android/net/module/util/bpf/Tether4Value.java b/staticlibs/device/com/android/net/module/util/bpf/Tether4Value.java
new file mode 100644
index 0000000..de98766
--- /dev/null
+++ b/staticlibs/device/com/android/net/module/util/bpf/Tether4Value.java
@@ -0,0 +1,97 @@
+/*
+ * Copyright (C) 2020 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.net.module.util.bpf;
+
+import android.net.MacAddress;
+
+import androidx.annotation.NonNull;
+
+import com.android.net.module.util.Struct;
+import com.android.net.module.util.Struct.Field;
+import com.android.net.module.util.Struct.Type;
+
+import java.net.InetAddress;
+import java.net.UnknownHostException;
+import java.util.Objects;
+
+/** Value type for downstream & upstream IPv4 forwarding maps. */
+public class Tether4Value extends Struct {
+    @Field(order = 0, type = Type.U32)
+    public final long oif;
+
+    // The ethhdr struct which is defined in uapi/linux/if_ether.h
+    @Field(order = 1, type = Type.EUI48)
+    public final MacAddress ethDstMac;
+    @Field(order = 2, type = Type.EUI48)
+    public final MacAddress ethSrcMac;
+    @Field(order = 3, type = Type.UBE16)
+    public final int ethProto;  // Packet type ID field.
+
+    @Field(order = 4, type = Type.U16)
+    public final int pmtu;
+
+    @Field(order = 5, type = Type.ByteArray, arraysize = 16)
+    public final byte[] src46;
+
+    @Field(order = 6, type = Type.ByteArray, arraysize = 16)
+    public final byte[] dst46;
+
+    @Field(order = 7, type = Type.UBE16)
+    public final int srcPort;
+
+    @Field(order = 8, type = Type.UBE16)
+    public final int dstPort;
+
+    // TODO: consider using U64.
+    @Field(order = 9, type = Type.U63)
+    public final long lastUsed;
+
+    public Tether4Value(final long oif, @NonNull final MacAddress ethDstMac,
+            @NonNull final MacAddress ethSrcMac, final int ethProto, final int pmtu,
+            final byte[] src46, final byte[] dst46, final int srcPort,
+            final int dstPort, final long lastUsed) {
+        Objects.requireNonNull(ethDstMac);
+        Objects.requireNonNull(ethSrcMac);
+
+        this.oif = oif;
+        this.ethDstMac = ethDstMac;
+        this.ethSrcMac = ethSrcMac;
+        this.ethProto = ethProto;
+        this.pmtu = pmtu;
+        this.src46 = src46;
+        this.dst46 = dst46;
+        this.srcPort = srcPort;
+        this.dstPort = dstPort;
+        this.lastUsed = lastUsed;
+    }
+
+    @Override
+    public String toString() {
+        try {
+            return String.format(
+                    "oif: %d, ethDstMac: %s, ethSrcMac: %s, ethProto: %d, pmtu: %d, "
+                            + "src46: %s, dst46: %s, srcPort: %d, dstPort: %d, "
+                            + "lastUsed: %d",
+                    oif, ethDstMac, ethSrcMac, ethProto, pmtu,
+                    InetAddress.getByAddress(src46), InetAddress.getByAddress(dst46),
+                    Short.toUnsignedInt((short) srcPort), Short.toUnsignedInt((short) dstPort),
+                    lastUsed);
+        } catch (UnknownHostException | IllegalArgumentException e) {
+            return String.format("Invalid IP address", e);
+        }
+    }
+}