diff --git a/staticlibs/testutils/devicetests/com/android/testutils/NatExternalPacketForwarder.kt b/staticlibs/testutils/devicetests/com/android/testutils/NatExternalPacketForwarder.kt
deleted file mode 100644
index d7961a0..0000000
--- a/staticlibs/testutils/devicetests/com/android/testutils/NatExternalPacketForwarder.kt
+++ /dev/null
@@ -1,81 +0,0 @@
-/*
- * 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.testutils
-
-import java.io.FileDescriptor
-import java.net.InetAddress
-
-/**
- * A class that forwards packets from the external {@link TestNetworkInterface} to the internal
- * {@link TestNetworkInterface} with NAT. See {@link NatPacketForwarderBase} for detail.
- */
-class NatExternalPacketForwarder(
-    srcFd: FileDescriptor,
-    mtu: Int,
-    dstFd: FileDescriptor,
-    extAddr: InetAddress,
-    natMap: PacketBridge.NatMap
-) : NatPacketForwarderBase(srcFd, mtu, dstFd, extAddr, natMap) {
-
-    /**
-     * Rewrite addresses, ports and fix up checksums for packets received on the external
-     * interface.
-     *
-     * Incoming response from external interface which is being forwarded to the internal
-     * interface with translated address, e.g. 1.2.3.4:80 -> 8.8.8.8:1234
-     * will be translated into 8.8.8.8:80 -> 192.168.1.1:5678.
-     *
-     * For packets that are not an incoming response, do not forward them to the
-     * internal interface.
-     */
-    override fun preparePacketForForwarding(buf: ByteArray, len: Int, version: Int, proto: Int) {
-        val (addrPos, addrLen) = getAddressPositionAndLength(version)
-
-        // TODO: support one external address per ip version.
-        val extAddrBuf = mExtAddr.address
-        if (addrLen != extAddrBuf.size) throw IllegalStateException("Packet IP version mismatch")
-
-        // Get internal address by port.
-        val transportOffset =
-            if (version == 4) PacketReflector.IPV4_HEADER_LENGTH
-            else PacketReflector.IPV6_HEADER_LENGTH
-        val dstPort = getPortAt(buf, transportOffset + DESTINATION_PORT_OFFSET)
-        val intAddrInfo = synchronized(mNatMap) { mNatMap.fromExternalPort(dstPort) }
-        // No mapping, skip. This usually happens if the connection is initiated directly on
-        // the external interface, e.g. DNS64 resolution, network validation, etc.
-        if (intAddrInfo == null) return
-
-        val intAddrBuf = intAddrInfo.address.address
-        val intPort = intAddrInfo.port
-
-        // Copy the original destination to into the source address.
-        for (i in 0 until addrLen) {
-            buf[addrPos + i] = buf[addrPos + addrLen + i]
-        }
-
-        // Copy the internal address into the destination address.
-        for (i in 0 until addrLen) {
-            buf[addrPos + addrLen + i] = intAddrBuf[i]
-        }
-
-        // Copy the internal port into the destination port.
-        setPortAt(intPort, buf, transportOffset + DESTINATION_PORT_OFFSET)
-
-        // Fix IP and Transport layer checksum.
-        fixPacketChecksum(buf, len, version, proto.toByte())
-    }
-}
diff --git a/staticlibs/testutils/devicetests/com/android/testutils/NatInternalPacketForwarder.kt b/staticlibs/testutils/devicetests/com/android/testutils/NatInternalPacketForwarder.kt
deleted file mode 100644
index fa39d19..0000000
--- a/staticlibs/testutils/devicetests/com/android/testutils/NatInternalPacketForwarder.kt
+++ /dev/null
@@ -1,78 +0,0 @@
-/*
- * 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.testutils
-
-import java.io.FileDescriptor
-import java.net.InetAddress
-
-/**
- * A class that forwards packets from the internal {@link TestNetworkInterface} to the external
- * {@link TestNetworkInterface} with NAT. See {@link NatPacketForwarderBase} for detail.
- */
-class NatInternalPacketForwarder(
-    srcFd: FileDescriptor,
-    mtu: Int,
-    dstFd: FileDescriptor,
-    extAddr: InetAddress,
-    natMap: PacketBridge.NatMap
-) : NatPacketForwarderBase(srcFd, mtu, dstFd, extAddr, natMap) {
-
-    /**
-     * Rewrite addresses, ports and fix up checksums for packets received on the internal
-     * interface.
-     *
-     * Outgoing packet from the internal interface which is being forwarded to the
-     * external interface with translated address, e.g. 192.168.1.1:5678 -> 8.8.8.8:80
-     * will be translated into 8.8.8.8:1234 -> 1.2.3.4:80.
-     *
-     * The external port, e.g. 1234 in the above example, is the port number assigned by
-     * the forwarder when creating the mapping to identify the source address and port when
-     * the response is coming from the external interface. See {@link PacketBridge.NatMap}
-     * for detail.
-     */
-    override fun preparePacketForForwarding(buf: ByteArray, len: Int, version: Int, proto: Int) {
-        val (addrPos, addrLen) = getAddressPositionAndLength(version)
-
-        // TODO: support one external address per ip version.
-        val extAddrBuf = mExtAddr.address
-        if (addrLen != extAddrBuf.size) throw IllegalStateException("Packet IP version mismatch")
-
-        val srcAddr = getInetAddressAt(buf, addrPos, addrLen)
-
-        // Copy the original destination to into the source address.
-        for (i in 0 until addrLen) {
-            buf[addrPos + i] = buf[addrPos + addrLen + i]
-        }
-
-        // Copy the external address into the destination address.
-        for (i in 0 until addrLen) {
-            buf[addrPos + addrLen + i] = extAddrBuf[i]
-        }
-
-        // Add an entry to NAT mapping table.
-        val transportOffset =
-            if (version == 4) PacketReflector.IPV4_HEADER_LENGTH
-            else PacketReflector.IPV6_HEADER_LENGTH
-        val srcPort = getPortAt(buf, transportOffset)
-        val extPort = synchronized(mNatMap) { mNatMap.toExternalPort(srcAddr, srcPort, proto) }
-        // Copy the external port to into the source port.
-        setPortAt(extPort, buf, transportOffset)
-
-        // Fix IP and Transport layer checksum.
-        fixPacketChecksum(buf, len, version, proto.toByte())
-    }
-}
diff --git a/staticlibs/testutils/devicetests/com/android/testutils/PacketBridge.kt b/staticlibs/testutils/devicetests/com/android/testutils/PacketBridge.kt
index d50f78a..0d0cc06 100644
--- a/staticlibs/testutils/devicetests/com/android/testutils/PacketBridge.kt
+++ b/staticlibs/testutils/devicetests/com/android/testutils/PacketBridge.kt
@@ -16,6 +16,7 @@
 
 package com.android.testutils
 
+import android.annotation.SuppressLint
 import android.content.Context
 import android.net.ConnectivityManager
 import android.net.LinkAddress
@@ -31,29 +32,27 @@
 import java.net.InetAddress
 import libcore.io.IoUtils
 
-private const val MIN_PORT_NUMBER = 1025
-private const val MAX_PORT_NUMBER = 65535
-
 /**
- * A class that set up two {@link TestNetworkInterface} with NAT, and forward packets between them.
+ * A class that set up two {@link TestNetworkInterface}, and forward packets between them.
  *
- * See {@link NatPacketForwarder} for more detailed information.
+ * See {@link PacketForwarder} for more detailed information.
  */
+// TODO: Support multiple addresses.
 class PacketBridge(
     context: Context,
-    internalAddr: LinkAddress,
-    externalAddr: LinkAddress,
+    address: LinkAddress,
     dnsAddr: InetAddress
 ) {
-    private val natMap = NatMap()
     private val binder = Binder()
 
     private val cm = context.getSystemService(ConnectivityManager::class.java)!!
     private val tnm = context.getSystemService(TestNetworkManager::class.java)!!
 
-    // Create test networks.
-    private val internalIface = tnm.createTunInterface(listOf(internalAddr))
-    private val externalIface = tnm.createTunInterface(listOf(externalAddr))
+    // Create test networks. The needed permissions should be supplied by the callers.
+    @SuppressLint("MissingPermission")
+    private val internalIface = tnm.createTunInterface(listOf(address))
+    @SuppressLint("MissingPermission")
+    private val externalIface = tnm.createTunInterface(listOf(address))
 
     // Register test networks to ConnectivityService.
     private val internalNetworkCallback: TestableNetworkCallback
@@ -61,32 +60,20 @@
     val internalNetwork: Network
     val externalNetwork: Network
     init {
-        val (inCb, inNet) = createTestNetwork(internalIface, internalAddr, dnsAddr)
-        val (exCb, exNet) = createTestNetwork(externalIface, externalAddr, dnsAddr)
+        val (inCb, inNet) = createTestNetwork(internalIface, address, dnsAddr)
+        val (exCb, exNet) = createTestNetwork(externalIface, address, dnsAddr)
         internalNetworkCallback = inCb
         externalNetworkCallback = exCb
         internalNetwork = inNet
         externalNetwork = exNet
     }
 
-    // Setup the packet bridge.
+    // Set up the packet bridge.
     private val internalFd = internalIface.fileDescriptor.fileDescriptor
     private val externalFd = externalIface.fileDescriptor.fileDescriptor
 
-    private val pr1 = NatInternalPacketForwarder(
-        internalFd,
-        1500,
-        externalFd,
-        externalAddr.address,
-        natMap
-    )
-    private val pr2 = NatExternalPacketForwarder(
-        externalFd,
-        1500,
-        internalFd,
-        externalAddr.address,
-        natMap
-    )
+    private val pr1 = PacketForwarder(internalFd, 1500, externalFd)
+    private val pr2 = PacketForwarder(externalFd, 1500, internalFd)
 
     fun start() {
         IoUtils.setBlocking(internalFd, true /* blocking */)
@@ -130,44 +117,4 @@
         val network = testCb.expect<Available>().network
         return testCb to network
     }
-
-    /**
-     * A helper class to maintain the mappings between internal addresses/ports and external
-     * ports.
-     *
-     * This class assigns an unused external port number if the mapping between
-     * srcaddress:srcport:protocol and the external port does not exist yet.
-     *
-     * Note that this class is not thread-safe. The instance of the class needs to be
-     * synchronized in the callers when being used in multiple threads.
-     */
-    class NatMap {
-        data class AddressInfo(val address: InetAddress, val port: Int, val protocol: Int)
-
-        private val mToExternalPort = HashMap<AddressInfo, Int>()
-        private val mFromExternalPort = HashMap<Int, AddressInfo>()
-
-        // Skip well-known port 0~1024.
-        private var nextExternalPort = MIN_PORT_NUMBER
-
-        fun toExternalPort(addr: InetAddress, port: Int, protocol: Int): Int {
-            val info = AddressInfo(addr, port, protocol)
-            val extPort: Int
-            if (!mToExternalPort.containsKey(info)) {
-                extPort = nextExternalPort++
-                if (nextExternalPort > MAX_PORT_NUMBER) {
-                    throw IllegalStateException("Available ports are exhausted")
-                }
-                mToExternalPort[info] = extPort
-                mFromExternalPort[extPort] = info
-            } else {
-                extPort = mToExternalPort[info]!!
-            }
-            return extPort
-        }
-
-        fun fromExternalPort(port: Int): AddressInfo? {
-            return mFromExternalPort[port]
-        }
-    }
 }
diff --git a/staticlibs/testutils/devicetests/com/android/testutils/NatPacketForwarderBase.java b/staticlibs/testutils/devicetests/com/android/testutils/PacketForwarder.java
similarity index 62%
rename from staticlibs/testutils/devicetests/com/android/testutils/NatPacketForwarderBase.java
rename to staticlibs/testutils/devicetests/com/android/testutils/PacketForwarder.java
index 0a2b5d4..d8efb7d 100644
--- a/staticlibs/testutils/devicetests/com/android/testutils/NatPacketForwarderBase.java
+++ b/staticlibs/testutils/devicetests/com/android/testutils/PacketForwarder.java
@@ -30,16 +30,13 @@
 import android.system.Os;
 import android.util.Log;
 
-import androidx.annotation.GuardedBy;
-
 import java.io.FileDescriptor;
 import java.io.IOException;
-import java.net.InetAddress;
 import java.util.Objects;
 
 /**
  * A class that forwards packets from a {@link TestNetworkInterface} to another
- * {@link TestNetworkInterface} with NAT.
+ * {@link TestNetworkInterface}.
  *
  * For testing purposes, a {@link TestNetworkInterface} provides a {@link FileDescriptor}
  * which allows content injection on the test network. However, this could be hard to use
@@ -54,30 +51,14 @@
  *
  * To make it work, an internal interface and an external interface are defined, where
  * the client might send packets from the internal interface which are originated from
- * multiple addresses to a server that listens on the external address.
- *
- * When forwarding the outgoing packet on the internal interface, a simple NAT mechanism
- * is implemented during forwarding, which will swap the source and destination,
- * but replacing the source address with the external address,
- * e.g. 192.168.1.1:1234 -> 8.8.8.8:80 will be translated into 8.8.8.8:1234 -> 1.2.3.4:80.
- *
- * For the above example, a client who sends http request will have a hallucination that
- * it is talking to a remote server at 8.8.8.8. Also, the server listens on 1.2.3.4 will
- * have a different hallucination that the request is sent from a remote client at 8.8.8.8,
- * to a local address 1.2.3.4.
- *
- * And a NAT mapping is created at the time when the outgoing packet is forwarded.
- * With a different internal source port, the instance learned that when a response with the
- * destination port 1234, it should forward the packet to the internal address 192.168.1.1.
+ * multiple addresses to a server that listens on the different port.
  *
  * For the incoming packet received from external interface, for example a http response sent
  * from the http server, the same mechanism is applied but in a different direction,
- * where the source and destination will be swapped, and the source address will be replaced
- * with the internal address, which is obtained from the NAT mapping described above.
+ * where the source and destination will be swapped.
  */
-public abstract class NatPacketForwarderBase extends Thread {
-    private static final String TAG = "NatPacketForwarder";
-    static final int DESTINATION_PORT_OFFSET = 2;
+public class PacketForwarder extends Thread {
+    private static final String TAG = "PacketForwarder";
 
     // The source fd to read packets from.
     @NonNull
@@ -88,27 +69,12 @@
     // The destination fd to write packets to.
     @NonNull
     final FileDescriptor mDstFd;
-    // The NAT mapping table shared between two NatPacketForwarder instances to map from
-    // the source port to the associated internal address. The map can be read/write from two
-    // different threads on any given time whenever receiving packets on the
-    // {@link TestNetworkInterface}. Thus, synchronize on the object when reading/writing is needed.
-    @GuardedBy("mNatMap")
-    @NonNull
-    final PacketBridge.NatMap mNatMap;
-    // The address of the external interface. See {@link NatPacketForwarder}.
-    @NonNull
-    final InetAddress mExtAddr;
 
     /**
-     * Construct a {@link NatPacketForwarderBase}.
+     * Construct a {@link PacketForwarder}.
      *
      * This class reads packets from {@code srcFd} of a {@link TestNetworkInterface}, and
-     * forwards them to the {@code dstFd} of another {@link TestNetworkInterface} with
-     * NAT applied. See {@link NatPacketForwarderBase}.
-     *
-     * To apply NAT, the address of the external interface needs to be supplied through
-     * {@code extAddr} to identify the external interface. And a shared NAT mapping table,
-     * {@code natMap} is needed to be shared between these two instances.
+     * forwards them to the {@code dstFd} of another {@link TestNetworkInterface}.
      *
      * Note that this class is not useful if the instance is not managed by a
      * {@link PacketBridge} to set up a two-way communication.
@@ -116,29 +82,15 @@
      * @param srcFd   {@link FileDescriptor} to read packets from.
      * @param mtu     MTU of the test network.
      * @param dstFd   {@link FileDescriptor} to write packets to.
-     * @param extAddr the external address, which is the address of the external interface.
-     *                See {@link NatPacketForwarderBase}.
-     * @param natMap  the NAT mapping table shared between two {@link NatPacketForwarderBase}
-     *                instance.
      */
-    public NatPacketForwarderBase(@NonNull FileDescriptor srcFd, int mtu,
-            @NonNull FileDescriptor dstFd, @NonNull InetAddress extAddr,
-            @NonNull PacketBridge.NatMap natMap) {
+    public PacketForwarder(@NonNull FileDescriptor srcFd, int mtu,
+                           @NonNull FileDescriptor dstFd) {
         super(TAG);
         mSrcFd = Objects.requireNonNull(srcFd);
         mBuf = new byte[mtu];
         mDstFd = Objects.requireNonNull(dstFd);
-        mExtAddr = Objects.requireNonNull(extAddr);
-        mNatMap = Objects.requireNonNull(natMap);
     }
 
-    /**
-     * A method to prepare forwarding packets between two instances of {@link TestNetworkInterface},
-     * which includes re-write addresses, ports and fix up checksums.
-     * Subclasses should override this method to implement a simple NAT.
-     */
-    abstract void preparePacketForForwarding(@NonNull byte[] buf, int len, int version, int proto);
-
     private void forwardPacket(@NonNull byte[] buf, int len) {
         try {
             Os.write(mDstFd, buf, 0, len);
@@ -190,8 +142,9 @@
         if (len < ipHdrLen + transportHdrLen) {
             throw new IllegalStateException("Unexpected buffer length: " + len);
         }
-        // Re-write addresses, ports and fix up checksums.
-        preparePacketForForwarding(mBuf, len, version, proto);
+        // Swap addresses.
+        PacketReflectorUtil.swapAddresses(mBuf, version);
+
         // Send the packet to the destination fd.
         forwardPacket(mBuf, len);
     }
diff --git a/staticlibs/testutils/devicetests/com/android/testutils/PacketReflector.java b/staticlibs/testutils/devicetests/com/android/testutils/PacketReflector.java
index 69392d4..ce20d67 100644
--- a/staticlibs/testutils/devicetests/com/android/testutils/PacketReflector.java
+++ b/staticlibs/testutils/devicetests/com/android/testutils/PacketReflector.java
@@ -87,31 +87,6 @@
         mBuf = new byte[mtu];
     }
 
-    private static void swapBytes(@NonNull byte[] buf, int pos1, int pos2, int len) {
-        for (int i = 0; i < len; i++) {
-            byte b = buf[pos1 + i];
-            buf[pos1 + i] = buf[pos2 + i];
-            buf[pos2 + i] = b;
-        }
-    }
-
-    private static void swapAddresses(@NonNull byte[] buf, int version) {
-        int addrPos, addrLen;
-        switch (version) {
-            case 4:
-                addrPos = IPV4_ADDR_OFFSET;
-                addrLen = IPV4_ADDR_LENGTH;
-                break;
-            case 6:
-                addrPos = IPV6_ADDR_OFFSET;
-                addrLen = IPV6_ADDR_LENGTH;
-                break;
-            default:
-                throw new IllegalArgumentException();
-        }
-        swapBytes(buf, addrPos, addrPos + addrLen, addrLen);
-    }
-
     // Reflect TCP packets: swap the source and destination addresses, but don't change the ports.
     // This is used by the test to "connect to itself" through the VPN.
     private void processTcpPacket(@NonNull byte[] buf, int version, int len, int hdrLen) {
@@ -120,7 +95,7 @@
         }
 
         // Swap src and dst IP addresses.
-        swapAddresses(buf, version);
+        PacketReflectorUtil.swapAddresses(buf, version);
 
         // Send the packet back.
         writePacket(buf, len);
@@ -134,11 +109,11 @@
         }
 
         // Swap src and dst IP addresses.
-        swapAddresses(buf, version);
+        PacketReflectorUtil.swapAddresses(buf, version);
 
         // Swap dst and src ports.
         int portOffset = hdrLen;
-        swapBytes(buf, portOffset, portOffset + 2, 2);
+        PacketReflectorUtil.swapBytes(buf, portOffset, portOffset + 2, 2);
 
         // Send the packet back.
         writePacket(buf, len);
@@ -160,7 +135,7 @@
 
         // Swap src and dst IP addresses, and send the packet back.
         // This effectively pings the device to see if it replies.
-        swapAddresses(buf, version);
+        PacketReflectorUtil.swapAddresses(buf, version);
         writePacket(buf, len);
 
         // The device should have replied, and buf should now contain a ping response.
@@ -202,7 +177,7 @@
         }
 
         // Now swap the addresses again and reflect the packet. This sends a ping reply.
-        swapAddresses(buf, version);
+        PacketReflectorUtil.swapAddresses(buf, version);
         writePacket(buf, len);
     }
 
diff --git a/staticlibs/testutils/devicetests/com/android/testutils/PacketReflectorUtil.kt b/staticlibs/testutils/devicetests/com/android/testutils/PacketReflectorUtil.kt
index 498b1a3..ad259c5 100644
--- a/staticlibs/testutils/devicetests/com/android/testutils/PacketReflectorUtil.kt
+++ b/staticlibs/testutils/devicetests/com/android/testutils/PacketReflectorUtil.kt
@@ -112,3 +112,28 @@
         else -> throw IllegalArgumentException("Unsupported protocol: $protocol")
     }
 }
+
+fun swapBytes(buf: ByteArray, pos1: Int, pos2: Int, len: Int) {
+    for (i in 0 until len) {
+        val b = buf[pos1 + i]
+        buf[pos1 + i] = buf[pos2 + i]
+        buf[pos2 + i] = b
+    }
+}
+
+fun swapAddresses(buf: ByteArray, version: Int) {
+    val addrPos: Int
+    val addrLen: Int
+    when (version) {
+        4 -> {
+            addrPos = PacketReflector.IPV4_ADDR_OFFSET
+            addrLen = PacketReflector.IPV4_ADDR_LENGTH
+        }
+        6 -> {
+            addrPos = PacketReflector.IPV6_ADDR_OFFSET
+            addrLen = PacketReflector.IPV6_ADDR_LENGTH
+        }
+        else -> throw java.lang.IllegalArgumentException()
+    }
+    swapBytes(buf, addrPos, addrPos + addrLen, addrLen)
+}