diff --git a/Tethering/src/android/net/ip/IpServer.java b/Tethering/src/android/net/ip/IpServer.java
index 79d9a23..aaa36d2 100644
--- a/Tethering/src/android/net/ip/IpServer.java
+++ b/Tethering/src/android/net/ip/IpServer.java
@@ -60,6 +60,7 @@
 import android.os.Message;
 import android.os.RemoteException;
 import android.os.ServiceSpecificException;
+import android.util.ArraySet;
 import android.util.Log;
 import android.util.SparseArray;
 
@@ -899,7 +900,7 @@
     }
 
     private void configureLocalIPv6Routes(
-            HashSet<IpPrefix> deprecatedPrefixes, HashSet<IpPrefix> newPrefixes) {
+            ArraySet<IpPrefix> deprecatedPrefixes, ArraySet<IpPrefix> newPrefixes) {
         // [1] Remove the routes that are deprecated.
         if (!deprecatedPrefixes.isEmpty()) {
             removeRoutesFromLocalNetwork(getLocalRoutesFor(mIfaceName, deprecatedPrefixes));
@@ -907,7 +908,7 @@
 
         // [2] Add only the routes that have not previously been added.
         if (newPrefixes != null && !newPrefixes.isEmpty()) {
-            HashSet<IpPrefix> addedPrefixes = (HashSet) newPrefixes.clone();
+            ArraySet<IpPrefix> addedPrefixes = new ArraySet<IpPrefix>(newPrefixes);
             if (mLastRaParams != null) {
                 addedPrefixes.removeAll(mLastRaParams.prefixes);
             }
@@ -919,7 +920,7 @@
     }
 
     private void configureLocalIPv6Dns(
-            HashSet<Inet6Address> deprecatedDnses, HashSet<Inet6Address> newDnses) {
+            ArraySet<Inet6Address> deprecatedDnses, ArraySet<Inet6Address> newDnses) {
         // TODO: Is this really necessary? Can we not fail earlier if INetd cannot be located?
         if (mNetd == null) {
             if (newDnses != null) newDnses.clear();
@@ -940,7 +941,7 @@
 
         // [2] Add only the local DNS IP addresses that have not previously been added.
         if (newDnses != null && !newDnses.isEmpty()) {
-            final HashSet<Inet6Address> addedDnses = (HashSet) newDnses.clone();
+            final ArraySet<Inet6Address> addedDnses = new ArraySet<Inet6Address>(newDnses);
             if (mLastRaParams != null) {
                 addedDnses.removeAll(mLastRaParams.dnses);
             }
@@ -1547,7 +1548,7 @@
     // Accumulate routes representing "prefixes to be assigned to the local
     // interface", for subsequent modification of local_network routing.
     private static ArrayList<RouteInfo> getLocalRoutesFor(
-            String ifname, HashSet<IpPrefix> prefixes) {
+            String ifname, ArraySet<IpPrefix> prefixes) {
         final ArrayList<RouteInfo> localRoutes = new ArrayList<RouteInfo>();
         for (IpPrefix ipp : prefixes) {
             localRoutes.add(new RouteInfo(ipp, null, ifname, RTN_UNICAST));
@@ -1578,8 +1579,8 @@
     /** Get IPv6 prefixes from LinkProperties */
     @NonNull
     @VisibleForTesting
-    static HashSet<IpPrefix> getTetherableIpv6Prefixes(@NonNull Collection<LinkAddress> addrs) {
-        final HashSet<IpPrefix> prefixes = new HashSet<>();
+    static ArraySet<IpPrefix> getTetherableIpv6Prefixes(@NonNull Collection<LinkAddress> addrs) {
+        final ArraySet<IpPrefix> prefixes = new ArraySet<>();
         for (LinkAddress linkAddr : addrs) {
             if (linkAddr.getPrefixLength() != RFC7421_PREFIX_LENGTH) continue;
             prefixes.add(new IpPrefix(linkAddr.getAddress(), RFC7421_PREFIX_LENGTH));
@@ -1588,7 +1589,7 @@
     }
 
     @NonNull
-    private HashSet<IpPrefix> getTetherableIpv6Prefixes(@NonNull LinkProperties lp) {
+    private ArraySet<IpPrefix> getTetherableIpv6Prefixes(@NonNull LinkProperties lp) {
         return getTetherableIpv6Prefixes(lp.getLinkAddresses());
     }
 }
diff --git a/Tethering/src/android/net/ip/RouterAdvertisementDaemon.java b/Tethering/src/android/net/ip/RouterAdvertisementDaemon.java
index 50d6c4b..d848ea8 100644
--- a/Tethering/src/android/net/ip/RouterAdvertisementDaemon.java
+++ b/Tethering/src/android/net/ip/RouterAdvertisementDaemon.java
@@ -41,6 +41,7 @@
 import android.system.ErrnoException;
 import android.system.Os;
 import android.system.StructTimeval;
+import android.util.ArraySet;
 import android.util.Log;
 
 import com.android.internal.annotations.GuardedBy;
@@ -134,23 +135,23 @@
         public boolean hasDefaultRoute;
         public byte hopLimit;
         public int mtu;
-        public HashSet<IpPrefix> prefixes;
-        public HashSet<Inet6Address> dnses;
+        public ArraySet<IpPrefix> prefixes;
+        public ArraySet<Inet6Address> dnses;
 
         public RaParams() {
             hasDefaultRoute = false;
             hopLimit = DEFAULT_HOPLIMIT;
             mtu = IPV6_MIN_MTU;
-            prefixes = new HashSet<IpPrefix>();
-            dnses = new HashSet<Inet6Address>();
+            prefixes = new ArraySet<IpPrefix>();
+            dnses = new ArraySet<Inet6Address>();
         }
 
         public RaParams(RaParams other) {
             hasDefaultRoute = other.hasDefaultRoute;
             hopLimit = other.hopLimit;
             mtu = other.mtu;
-            prefixes = (HashSet) other.prefixes.clone();
-            dnses = (HashSet) other.dnses.clone();
+            prefixes = new ArraySet<IpPrefix>(other.prefixes);
+            dnses = new ArraySet<Inet6Address>(other.dnses);
         }
 
         /**