diff --git a/staticlibs/tests/unit/Android.bp b/staticlibs/tests/unit/Android.bp
index 21e8c64..6e223bd 100644
--- a/staticlibs/tests/unit/Android.bp
+++ b/staticlibs/tests/unit/Android.bp
@@ -12,14 +12,15 @@
     min_sdk_version: "29",
     defaults: ["framework-connectivity-test-defaults"],
     static_libs: [
-        "net-utils-framework-common",
-        "net-utils-device-common-ip",
         "androidx.test.rules",
         "mockito-target-extended-minus-junit4",
-        "net-utils-device-common",
-        "net-utils-device-common-bpf",
-        "net-tests-utils",
         "netd-client",
+        "net-tests-utils",
+        "net-utils-framework-common",
+        "net-utils-device-common",
+        "net-utils-device-common-async",
+        "net-utils-device-common-bpf",
+        "net-utils-device-common-ip",
     ],
     libs: [
         "android.test.runner",
diff --git a/staticlibs/tests/unit/src/com/android/net/module/util/async/CircularByteBufferTest.java b/staticlibs/tests/unit/src/com/android/net/module/util/async/CircularByteBufferTest.java
new file mode 100644
index 0000000..01abee2
--- /dev/null
+++ b/staticlibs/tests/unit/src/com/android/net/module/util/async/CircularByteBufferTest.java
@@ -0,0 +1,267 @@
+/*
+ * Copyright (C) 2022 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.async;
+
+import static org.junit.Assert.assertArrayEquals;
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertTrue;
+import static org.junit.Assert.assertNotEquals;
+import static org.junit.Assert.fail;
+
+import androidx.test.filters.SmallTest;
+import androidx.test.runner.AndroidJUnit4;
+
+import org.junit.Test;
+import org.junit.runner.RunWith;
+
+@RunWith(AndroidJUnit4.class)
+@SmallTest
+public class CircularByteBufferTest {
+    @Test
+    public void writeBytes() {
+        final int capacity = 23;
+        CircularByteBuffer buffer = new CircularByteBuffer(capacity);
+        assertEquals(0, buffer.size());
+        assertEquals(0, buffer.getDirectReadSize());
+        assertEquals(capacity, buffer.freeSize());
+        assertEquals(capacity, buffer.getDirectWriteSize());
+
+        final byte[] writeBuffer = new byte[15];
+        buffer.writeBytes(writeBuffer, 0, writeBuffer.length);
+
+        assertEquals(writeBuffer.length, buffer.size());
+        assertEquals(writeBuffer.length, buffer.getDirectReadSize());
+        assertEquals(capacity - writeBuffer.length, buffer.freeSize());
+        assertEquals(capacity - writeBuffer.length, buffer.getDirectWriteSize());
+
+        buffer.clear();
+        assertEquals(0, buffer.size());
+        assertEquals(0, buffer.getDirectReadSize());
+        assertEquals(capacity, buffer.freeSize());
+        assertEquals(capacity, buffer.getDirectWriteSize());
+    }
+
+    @Test
+    public void writeBytes_withRollover() {
+        doTestReadWriteWithRollover(new BufferAccessor(false, false));
+    }
+
+    @Test
+    public void writeBytes_withFullBuffer() {
+        doTestReadWriteWithFullBuffer(new BufferAccessor(false, false));
+    }
+
+    @Test
+    public void directWriteBytes_withRollover() {
+        doTestReadWriteWithRollover(new BufferAccessor(true, true));
+    }
+
+    @Test
+    public void directWriteBytes_withFullBuffer() {
+        doTestReadWriteWithFullBuffer(new BufferAccessor(true, true));
+    }
+
+    private void doTestReadWriteWithFullBuffer(BufferAccessor accessor) {
+        CircularByteBuffer buffer = doTestReadWrite(accessor, 20, 5, 4);
+
+        assertEquals(0, buffer.size());
+        assertEquals(20, buffer.freeSize());
+    }
+
+    private void doTestReadWriteWithRollover(BufferAccessor accessor) {
+        // All buffer sizes are prime numbers to ensure that some read or write
+        // operations will roll over the end of the internal buffer.
+        CircularByteBuffer buffer = doTestReadWrite(accessor, 31, 13, 7);
+
+        assertNotEquals(0, buffer.size());
+    }
+
+    private CircularByteBuffer doTestReadWrite(BufferAccessor accessor,
+            final int capacity, final int writeLen, final int readLen) {
+        CircularByteBuffer buffer = new CircularByteBuffer(capacity);
+
+        final byte[] writeBuffer = new byte[writeLen + 2];
+        final byte[] peekBuffer = new byte[readLen + 2];
+        final byte[] readBuffer = new byte[readLen + 2];
+
+        final int numIterations = 1011;
+        final int maxRemaining = readLen - 1;
+
+        int currentWriteSymbol = 0;
+        int expectedReadSymbol = 0;
+        int expectedSize = 0;
+        int totalWritten = 0;
+        int totalRead = 0;
+
+        for (int i = 0; i < numIterations; i++) {
+            // Fill in with write buffers as much as possible.
+            while (buffer.freeSize() >= writeLen) {
+                currentWriteSymbol = fillTestBytes(writeBuffer, 1, writeLen, currentWriteSymbol);
+                accessor.writeBytes(buffer, writeBuffer, 1, writeLen);
+
+                expectedSize += writeLen;
+                totalWritten += writeLen;
+                assertEquals(expectedSize, buffer.size());
+                assertEquals(capacity - expectedSize, buffer.freeSize());
+            }
+
+            // Keep reading into read buffers while there's still data.
+            while (buffer.size() >= readLen) {
+                peekBuffer[1] = 0;
+                peekBuffer[2] = 0;
+                buffer.peekBytes(2, peekBuffer, 3, readLen - 2);
+                assertEquals(0, peekBuffer[1]);
+                assertEquals(0, peekBuffer[2]);
+
+                peekBuffer[2] = buffer.peek(1);
+
+                accessor.readBytes(buffer, readBuffer, 1, readLen);
+                peekBuffer[1] = readBuffer[1];
+
+                expectedReadSymbol = checkTestBytes(
+                    readBuffer, 1, readLen, expectedReadSymbol, totalRead);
+
+                assertArrayEquals(peekBuffer, readBuffer);
+
+                expectedSize -= readLen;
+                totalRead += readLen;
+                assertEquals(expectedSize, buffer.size());
+                assertEquals(capacity - expectedSize, buffer.freeSize());
+            }
+
+            if (buffer.size() > maxRemaining) {
+                fail("Too much data remaining: " + buffer.size());
+            }
+        }
+
+        final int maxWritten = capacity * numIterations;
+        final int minWritten = maxWritten / 2;
+        if (totalWritten < minWritten || totalWritten > maxWritten
+                || (totalWritten - totalRead) > maxRemaining) {
+            fail("Unexpected counts: read=" + totalRead + ", written=" + totalWritten
+                    + ", minWritten=" + minWritten + ", maxWritten=" + maxWritten);
+        }
+
+        return buffer;
+    }
+
+    @Test
+    public void readBytes_overflow() {
+        CircularByteBuffer buffer = new CircularByteBuffer(23);
+
+        final byte[] dataBuffer = new byte[15];
+        buffer.writeBytes(dataBuffer, 0, dataBuffer.length - 2);
+
+        try {
+            buffer.readBytes(dataBuffer, 0, dataBuffer.length);
+            assertTrue(false);
+        } catch (IllegalArgumentException e) {
+            // expected
+        }
+
+        assertEquals(13, buffer.size());
+        assertEquals(10, buffer.freeSize());
+    }
+
+    @Test
+    public void writeBytes_overflow() {
+        CircularByteBuffer buffer = new CircularByteBuffer(23);
+
+        final byte[] dataBuffer = new byte[15];
+        buffer.writeBytes(dataBuffer, 0, dataBuffer.length);
+
+        try {
+            buffer.writeBytes(dataBuffer, 0, dataBuffer.length);
+            assertTrue(false);
+        } catch (IllegalArgumentException e) {
+            // expected
+        }
+
+        assertEquals(15, buffer.size());
+        assertEquals(8, buffer.freeSize());
+    }
+
+    private static int fillTestBytes(byte[] buffer, int pos, int len, int startValue) {
+        for (int i = 0; i < len; i++) {
+            buffer[pos + i] = (byte) (startValue & 0xFF);
+            startValue = (startValue + 1) % 256;
+        }
+        return startValue;
+    }
+
+    private static int checkTestBytes(
+            byte[] buffer, int pos, int len, int startValue, int totalRead) {
+        for (int i = 0; i < len; i++) {
+            byte expectedValue = (byte) (startValue & 0xFF);
+            if (expectedValue != buffer[pos + i]) {
+                fail("Unexpected byte=" + (((int) buffer[pos + i]) & 0xFF)
+                        + ", expected=" + (((int) expectedValue) & 0xFF)
+                        + ", pos=" + (totalRead + i));
+            }
+            startValue = (startValue + 1) % 256;
+        }
+        return startValue;
+    }
+
+    private static final class BufferAccessor {
+        private final boolean mDirectRead;
+        private final boolean mDirectWrite;
+
+        BufferAccessor(boolean directRead, boolean directWrite) {
+            mDirectRead = directRead;
+            mDirectWrite = directWrite;
+        }
+
+        void writeBytes(CircularByteBuffer buffer, byte[] src, int pos, int len) {
+            if (mDirectWrite) {
+                while (len > 0) {
+                    if (buffer.getDirectWriteSize() == 0) {
+                        fail("Direct write size is zero: free=" + buffer.freeSize()
+                                + ", size=" + buffer.size());
+                    }
+                    int copyLen = Math.min(len, buffer.getDirectWriteSize());
+                    System.arraycopy(src, pos, buffer.getDirectWriteBuffer(),
+                        buffer.getDirectWritePos(), copyLen);
+                    buffer.accountForDirectWrite(copyLen);
+                    len -= copyLen;
+                    pos += copyLen;
+                }
+            } else {
+                buffer.writeBytes(src, pos, len);
+            }
+        }
+
+        void readBytes(CircularByteBuffer buffer, byte[] dst, int pos, int len) {
+            if (mDirectRead) {
+                while (len > 0) {
+                    if (buffer.getDirectReadSize() == 0) {
+                        fail("Direct read size is zero: free=" + buffer.freeSize()
+                                + ", size=" + buffer.size());
+                    }
+                    int copyLen = Math.min(len, buffer.getDirectReadSize());
+                    System.arraycopy(
+                        buffer.getDirectReadBuffer(), buffer.getDirectReadPos(), dst, pos, copyLen);
+                    buffer.accountForDirectRead(copyLen);
+                    len -= copyLen;
+                    pos += copyLen;
+                }
+            } else {
+                buffer.readBytes(dst, pos, len);
+            }
+        }
+    }
+}