diff --git a/staticlibs/device/com/android/net/module/util/BpfMap.java b/staticlibs/device/com/android/net/module/util/BpfMap.java
index 9df2b03..d45cace 100644
--- a/staticlibs/device/com/android/net/module/util/BpfMap.java
+++ b/staticlibs/device/com/android/net/module/util/BpfMap.java
@@ -194,9 +194,11 @@
     }
 
     private K getNextKeyInternal(@Nullable K key) throws ErrnoException {
-        final byte[] rawKey = getNextRawKey(
-                key == null ? null : key.writeToBytes());
-        if (rawKey == null) return null;
+        byte[] rawKey = new byte[mKeySize];
+
+        if (!nativeGetNextMapKey(mMapFd.getFd(),
+                                 key == null ? null : key.writeToBytes(),
+                                 rawKey)) return null;
 
         final ByteBuffer buffer = ByteBuffer.wrap(rawKey);
         buffer.order(ByteOrder.nativeOrder());
@@ -215,13 +217,6 @@
         return getNextKeyInternal(key);
     }
 
-    private byte[] getNextRawKey(@Nullable final byte[] key) throws ErrnoException {
-        byte[] nextKey = new byte[mKeySize];
-        if (nativeGetNextMapKey(mMapFd.getFd(), key, nextKey)) return nextKey;
-
-        return null;
-    }
-
     /** Get the first key of eBpf map. */
     @Override
     public K getFirstKey() throws ErrnoException {
@@ -233,30 +228,23 @@
     public boolean containsKey(@NonNull K key) throws ErrnoException {
         Objects.requireNonNull(key);
 
-        final byte[] rawValue = getRawValue(key.writeToBytes());
-        return rawValue != null;
+        byte[] rawValue = new byte[mValueSize];
+        return nativeFindMapEntry(mMapFd.getFd(), key.writeToBytes(), rawValue);
     }
 
     /** Retrieve a value from the map. Return null if there is no such key. */
     @Override
     public V getValue(@NonNull K key) throws ErrnoException {
         Objects.requireNonNull(key);
-        final byte[] rawValue = getRawValue(key.writeToBytes());
 
-        if (rawValue == null) return null;
+        byte[] rawValue = new byte[mValueSize];
+        if (!nativeFindMapEntry(mMapFd.getFd(), key.writeToBytes(), rawValue)) return null;
 
         final ByteBuffer buffer = ByteBuffer.wrap(rawValue);
         buffer.order(ByteOrder.nativeOrder());
         return Struct.parse(mValueClass, buffer);
     }
 
-    private byte[] getRawValue(final byte[] key) throws ErrnoException {
-        byte[] value = new byte[mValueSize];
-        if (nativeFindMapEntry(mMapFd.getFd(), key, value)) return value;
-
-        return null;
-    }
-
     /**
      * Iterate through the map and handle each key -> value retrieved base on the given BiConsumer.
      * The given BiConsumer may to delete the passed-in entry, but is not allowed to perform any
diff --git a/staticlibs/native/bpf_headers/include/bpf/BpfMap.h b/staticlibs/native/bpf_headers/include/bpf/BpfMap.h
index 51e6d16..847083e 100644
--- a/staticlibs/native/bpf_headers/include/bpf/BpfMap.h
+++ b/staticlibs/native/bpf_headers/include/bpf/BpfMap.h
@@ -29,6 +29,10 @@
 namespace android {
 namespace bpf {
 
+using base::Result;
+using base::unique_fd;
+using std::function;
+
 // This is a class wrapper for eBPF maps. The eBPF map is a special in-kernel
 // data structure that stores data in <Key, Value> pairs. It can be read/write
 // from userspace by passing syscalls with the map file descriptor. This class
@@ -80,7 +84,7 @@
     }
 #endif
 
-    base::Result<Key> getFirstKey() const {
+    Result<Key> getFirstKey() const {
         Key firstKey;
         if (getFirstMapKey(mMapFd, &firstKey)) {
             return ErrnoErrorf("Get firstKey map {} failed", mMapFd.get());
@@ -88,7 +92,7 @@
         return firstKey;
     }
 
-    base::Result<Key> getNextKey(const Key& key) const {
+    Result<Key> getNextKey(const Key& key) const {
         Key nextKey;
         if (getNextMapKey(mMapFd, &key, &nextKey)) {
             return ErrnoErrorf("Get next key of map {} failed", mMapFd.get());
@@ -96,14 +100,14 @@
         return nextKey;
     }
 
-    base::Result<void> writeValue(const Key& key, const Value& value, uint64_t flags) {
+    Result<void> writeValue(const Key& key, const Value& value, uint64_t flags) {
         if (writeToMapEntry(mMapFd, &key, &value, flags)) {
             return ErrnoErrorf("Write to map {} failed", mMapFd.get());
         }
         return {};
     }
 
-    base::Result<Value> readValue(const Key key) const {
+    Result<Value> readValue(const Key key) const {
         Value value;
         if (findMapEntry(mMapFd, &key, &value)) {
             return ErrnoErrorf("Read value of map {} failed", mMapFd.get());
@@ -111,7 +115,7 @@
         return value;
     }
 
-    base::Result<void> deleteValue(const Key& key) {
+    Result<void> deleteValue(const Key& key) {
         if (deleteMapEntry(mMapFd, &key)) {
             return ErrnoErrorf("Delete entry from map {} failed", mMapFd.get());
         }
@@ -119,7 +123,7 @@
     }
 
   protected:
-    [[clang::reinitializes]] base::Result<void> init(const char* path, int fd) {
+    [[clang::reinitializes]] Result<void> init(const char* path, int fd) {
         mMapFd.reset(fd);
         if (!mMapFd.ok()) {
             return ErrnoErrorf("Pinned map not accessible or does not exist: ({})", path);
@@ -134,7 +138,7 @@
 
   public:
     // Function that tries to get map from a pinned path.
-    [[clang::reinitializes]] base::Result<void> init(const char* path) {
+    [[clang::reinitializes]] Result<void> init(const char* path) {
         return init(path, mapRetrieveRW(path));
     }
 
@@ -144,7 +148,7 @@
     // this should only ever be used by test code, it is equivalent to:
     //   .reset(createMap(type, keysize, valuesize, max_entries, map_flags)
     // TODO: derive map_flags from BpfMap vs BpfMapRO
-    [[clang::reinitializes]] base::Result<void> resetMap(bpf_map_type map_type,
+    [[clang::reinitializes]] Result<void> resetMap(bpf_map_type map_type,
                                                          uint32_t max_entries,
                                                          uint32_t map_flags = 0) {
         mMapFd.reset(createMap(map_type, sizeof(Key), sizeof(Value), max_entries, map_flags));
@@ -155,30 +159,30 @@
 
     // Iterate through the map and handle each key retrieved based on the filter
     // without modification of map content.
-    base::Result<void> iterate(
-            const std::function<base::Result<void>(const Key& key, const BpfMap<Key, Value>& map)>&
-                    filter) const;
+    Result<void> iterate(
+            const function<Result<void>(const Key& key,
+                                        const BpfMap<Key, Value>& map)>& filter) const;
 
     // Iterate through the map and get each <key, value> pair, handle each <key,
     // value> pair based on the filter without modification of map content.
-    base::Result<void> iterateWithValue(
-            const std::function<base::Result<void>(const Key& key, const Value& value,
-                                                   const BpfMap<Key, Value>& map)>& filter) const;
+    Result<void> iterateWithValue(
+            const function<Result<void>(const Key& key, const Value& value,
+                                        const BpfMap<Key, Value>& map)>& filter) const;
 
     // Iterate through the map and handle each key retrieved based on the filter
-    base::Result<void> iterate(
-            const std::function<base::Result<void>(const Key& key, BpfMap<Key, Value>& map)>&
-                    filter);
+    Result<void> iterate(
+            const function<Result<void>(const Key& key,
+                                        BpfMap<Key, Value>& map)>& filter);
 
     // Iterate through the map and get each <key, value> pair, handle each <key,
     // value> pair based on the filter.
-    base::Result<void> iterateWithValue(
-            const std::function<base::Result<void>(const Key& key, const Value& value,
-                                                   BpfMap<Key, Value>& map)>& filter);
-
-    const base::unique_fd& getMap() const { return mMapFd; };
+    Result<void> iterateWithValue(
+            const function<Result<void>(const Key& key, const Value& value,
+                                        BpfMap<Key, Value>& map)>& filter);
 
 #ifdef BPF_MAP_MAKE_VISIBLE_FOR_TESTING
+    const unique_fd& getMap() const { return mMapFd; };
+
     // Copy assignment operator - due to need for fd duping, should not be used in non-test code.
     BpfMap<Key, Value>& operator=(const BpfMap<Key, Value>& other) {
         if (this != &other) mMapFd.reset(fcntl(other.mMapFd.get(), F_DUPFD_CLOEXEC, 0));
@@ -197,7 +201,7 @@
         return *this;
     }
 
-    void reset(base::unique_fd fd) = delete;
+    void reset(unique_fd fd) = delete;
 
 #ifdef BPF_MAP_MAKE_VISIBLE_FOR_TESTING
     // Note that unique_fd.reset() carefully saves and restores the errno,
@@ -216,7 +220,7 @@
 
     bool isValid() const { return mMapFd.ok(); }
 
-    base::Result<void> clear() {
+    Result<void> clear() {
         while (true) {
             auto key = getFirstKey();
             if (!key.ok()) {
@@ -233,28 +237,25 @@
         }
     }
 
-    base::Result<bool> isEmpty() const {
+    Result<bool> isEmpty() const {
         auto key = getFirstKey();
-        if (!key.ok()) {
-            // Return error code ENOENT means the map is empty
-            if (key.error().code() == ENOENT) return true;
-            return key.error();
-        }
-        return false;
+        if (key.ok()) return false;
+        if (key.error().code() == ENOENT) return true;
+        return key.error();
     }
 
   private:
-    base::unique_fd mMapFd;
+    unique_fd mMapFd;
 };
 
 template <class Key, class Value>
-base::Result<void> BpfMap<Key, Value>::iterate(
-        const std::function<base::Result<void>(const Key& key, const BpfMap<Key, Value>& map)>&
-                filter) const {
-    base::Result<Key> curKey = getFirstKey();
+Result<void> BpfMap<Key, Value>::iterate(
+        const function<Result<void>(const Key& key,
+                                    const BpfMap<Key, Value>& map)>& filter) const {
+    Result<Key> curKey = getFirstKey();
     while (curKey.ok()) {
-        const base::Result<Key>& nextKey = getNextKey(curKey.value());
-        base::Result<void> status = filter(curKey.value(), *this);
+        const Result<Key>& nextKey = getNextKey(curKey.value());
+        Result<void> status = filter(curKey.value(), *this);
         if (!status.ok()) return status;
         curKey = nextKey;
     }
@@ -263,15 +264,15 @@
 }
 
 template <class Key, class Value>
-base::Result<void> BpfMap<Key, Value>::iterateWithValue(
-        const std::function<base::Result<void>(const Key& key, const Value& value,
-                                               const BpfMap<Key, Value>& map)>& filter) const {
-    base::Result<Key> curKey = getFirstKey();
+Result<void> BpfMap<Key, Value>::iterateWithValue(
+        const function<Result<void>(const Key& key, const Value& value,
+                                    const BpfMap<Key, Value>& map)>& filter) const {
+    Result<Key> curKey = getFirstKey();
     while (curKey.ok()) {
-        const base::Result<Key>& nextKey = getNextKey(curKey.value());
-        base::Result<Value> curValue = readValue(curKey.value());
+        const Result<Key>& nextKey = getNextKey(curKey.value());
+        Result<Value> curValue = readValue(curKey.value());
         if (!curValue.ok()) return curValue.error();
-        base::Result<void> status = filter(curKey.value(), curValue.value(), *this);
+        Result<void> status = filter(curKey.value(), curValue.value(), *this);
         if (!status.ok()) return status;
         curKey = nextKey;
     }
@@ -280,12 +281,13 @@
 }
 
 template <class Key, class Value>
-base::Result<void> BpfMap<Key, Value>::iterate(
-        const std::function<base::Result<void>(const Key& key, BpfMap<Key, Value>& map)>& filter) {
-    base::Result<Key> curKey = getFirstKey();
+Result<void> BpfMap<Key, Value>::iterate(
+        const function<Result<void>(const Key& key,
+                                    BpfMap<Key, Value>& map)>& filter) {
+    Result<Key> curKey = getFirstKey();
     while (curKey.ok()) {
-        const base::Result<Key>& nextKey = getNextKey(curKey.value());
-        base::Result<void> status = filter(curKey.value(), *this);
+        const Result<Key>& nextKey = getNextKey(curKey.value());
+        Result<void> status = filter(curKey.value(), *this);
         if (!status.ok()) return status;
         curKey = nextKey;
     }
@@ -294,15 +296,15 @@
 }
 
 template <class Key, class Value>
-base::Result<void> BpfMap<Key, Value>::iterateWithValue(
-        const std::function<base::Result<void>(const Key& key, const Value& value,
-                                               BpfMap<Key, Value>& map)>& filter) {
-    base::Result<Key> curKey = getFirstKey();
+Result<void> BpfMap<Key, Value>::iterateWithValue(
+        const function<Result<void>(const Key& key, const Value& value,
+                                    BpfMap<Key, Value>& map)>& filter) {
+    Result<Key> curKey = getFirstKey();
     while (curKey.ok()) {
-        const base::Result<Key>& nextKey = getNextKey(curKey.value());
-        base::Result<Value> curValue = readValue(curKey.value());
+        const Result<Key>& nextKey = getNextKey(curKey.value());
+        Result<Value> curValue = readValue(curKey.value());
         if (!curValue.ok()) return curValue.error();
-        base::Result<void> status = filter(curKey.value(), curValue.value(), *this);
+        Result<void> status = filter(curKey.value(), curValue.value(), *this);
         if (!status.ok()) return status;
         curKey = nextKey;
     }
@@ -319,7 +321,7 @@
         : BpfMap<Key, Value>(pathname, BPF_F_RDONLY) {}
 
     // Function that tries to get map from a pinned path.
-    [[clang::reinitializes]] base::Result<void> init(const char* path) {
+    [[clang::reinitializes]] Result<void> init(const char* path) {
         return BpfMap<Key,Value>::init(path, mapRetrieveRO(path));
     }
 };
diff --git a/staticlibs/tests/unit/src/com/android/net/module/util/CollectionUtilsTest.kt b/staticlibs/tests/unit/src/com/android/net/module/util/CollectionUtilsTest.kt
index 9fb025b..e23f999 100644
--- a/staticlibs/tests/unit/src/com/android/net/module/util/CollectionUtilsTest.kt
+++ b/staticlibs/tests/unit/src/com/android/net/module/util/CollectionUtilsTest.kt
@@ -63,9 +63,6 @@
         assertEquals(0, CollectionUtils.indexOfSubArray(haystack, byteArrayOf()))
         assertEquals(-1, CollectionUtils.indexOfSubArray(byteArrayOf(), byteArrayOf(3, 2)))
         assertEquals(0, CollectionUtils.indexOfSubArray(byteArrayOf(), byteArrayOf()))
-        assertThrows(NullPointerException::class.java) {
-            CollectionUtils.indexOfSubArray(haystack, null)
-        }
     }
 
     @Test
diff --git a/staticlibs/testutils/devicetests/com/android/testutils/FakeDns.kt b/staticlibs/testutils/devicetests/com/android/testutils/FakeDns.kt
index 825d748..1f82a35 100644
--- a/staticlibs/testutils/devicetests/com/android/testutils/FakeDns.kt
+++ b/staticlibs/testutils/devicetests/com/android/testutils/FakeDns.kt
@@ -81,9 +81,9 @@
         var type = if (posType != -1) it.arguments[posType] as Int else TYPE_UNSPECIFIED
         val answer = getAnswer(hostname, type)
 
-        if (!answer?.addresses.isNullOrEmpty()) {
+        if (answer != null && !answer.addresses.isNullOrEmpty()) {
             Handler(Looper.getMainLooper()).post({ executor.execute({
-                    callback.onAnswer(answer?.addresses, 0); }) })
+                    callback.onAnswer(answer.addresses, 0); }) })
         }
     }
 
diff --git a/staticlibs/testutils/devicetests/com/android/testutils/NonNullTestUtils.java b/staticlibs/testutils/devicetests/com/android/testutils/NonNullTestUtils.java
new file mode 100644
index 0000000..463c470
--- /dev/null
+++ b/staticlibs/testutils/devicetests/com/android/testutils/NonNullTestUtils.java
@@ -0,0 +1,33 @@
+/*
+ * 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 android.annotation.NonNull;
+
+/**
+ * Utilities to help Kotlin test to verify java @NonNull code
+ */
+public class NonNullTestUtils {
+    /**
+     * This method allows Kotlin to pass nullable to @NonNull java code for testing.
+     * For Foo(@NonNull arg) java method, Kotlin can pass nullable variable by
+     * Foo(NonNullTestUtils.nullUnsafe(nullableVar)).
+     */
+    @NonNull public static <T> T nullUnsafe(T v) {
+        return v;
+    }
+}
diff --git a/staticlibs/testutils/devicetests/com/android/testutils/PacketBridge.kt b/staticlibs/testutils/devicetests/com/android/testutils/PacketBridge.kt
index da3508d..d50f78a 100644
--- a/staticlibs/testutils/devicetests/com/android/testutils/PacketBridge.kt
+++ b/staticlibs/testutils/devicetests/com/android/testutils/PacketBridge.kt
@@ -48,8 +48,8 @@
     private val natMap = NatMap()
     private val binder = Binder()
 
-    private val cm = context.getSystemService(ConnectivityManager::class.java)
-    private val tnm = context.getSystemService(TestNetworkManager::class.java)
+    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))
diff --git a/staticlibs/testutils/devicetests/com/android/testutils/TestNetworkTracker.kt b/staticlibs/testutils/devicetests/com/android/testutils/TestNetworkTracker.kt
index b743b6c..84fb47b 100644
--- a/staticlibs/testutils/devicetests/com/android/testutils/TestNetworkTracker.kt
+++ b/staticlibs/testutils/devicetests/com/android/testutils/TestNetworkTracker.kt
@@ -91,7 +91,7 @@
     lp: LinkProperties?,
     setupTimeoutMs: Long = 10_000L
 ): TestNetworkTracker {
-    val tnm = context.getSystemService(TestNetworkManager::class.java)
+    val tnm = context.getSystemService(TestNetworkManager::class.java)!!
     val iface = if (isAtLeastS()) tnm.createTunInterface(linkAddrs)
     else tnm.createTunInterface(linkAddrs.toTypedArray())
     val lpWithIface = if (lp == null) null else LinkProperties(lp).apply {
@@ -112,7 +112,7 @@
     val lp: LinkProperties?,
     setupTimeoutMs: Long
 ) : TestableNetworkCallback.HasNetwork {
-    private val cm = context.getSystemService(ConnectivityManager::class.java)
+    private val cm = context.getSystemService(ConnectivityManager::class.java)!!
     private val binder = Binder()
 
     private val networkCallback: NetworkCallback