diff --git a/Tethering/src/com/android/networkstack/tethering/BpfCoordinator.java b/Tethering/src/com/android/networkstack/tethering/BpfCoordinator.java
index 4bd7e6a..9f542f4 100644
--- a/Tethering/src/com/android/networkstack/tethering/BpfCoordinator.java
+++ b/Tethering/src/com/android/networkstack/tethering/BpfCoordinator.java
@@ -90,7 +90,6 @@
 import java.net.NetworkInterface;
 import java.net.SocketException;
 import java.net.UnknownHostException;
-import java.nio.ByteBuffer;
 import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.Collection;
@@ -1258,12 +1257,18 @@
         pw.decreaseIndent();
     }
 
-    private IpPrefix longToPrefix(long ip64) {
-        final ByteBuffer prefixBuffer = ByteBuffer.allocate(IPV6_ADDR_LEN);
-        prefixBuffer.putLong(ip64);
+    /**
+     * Returns a /64 IpPrefix corresponding to the passed in byte array
+     *
+     * @param ip64 byte array to convert format
+     * @return the converted IpPrefix
+     */
+    @VisibleForTesting
+    public static IpPrefix bytesToPrefix(final byte[] ip64) {
         IpPrefix sourcePrefix;
+        byte[] prefixBytes = Arrays.copyOf(ip64, IPV6_ADDR_LEN);
         try {
-            sourcePrefix = new IpPrefix(InetAddress.getByAddress(prefixBuffer.array()), 64);
+            sourcePrefix = new IpPrefix(InetAddress.getByAddress(prefixBytes), 64);
         } catch (UnknownHostException e) {
             // Cannot happen. InetAddress.getByAddress can only throw an exception if the byte array
             // is the wrong length, but we allocate it with fixed length IPV6_ADDR_LEN.
@@ -1274,7 +1279,7 @@
 
     private String ipv6UpstreamRuleToString(TetherUpstream6Key key, Tether6Value value) {
         return String.format("%d(%s) [%s] [%s] -> %d(%s) %04x [%s] [%s]",
-                key.iif, getIfName(key.iif), key.dstMac, longToPrefix(key.src64), value.oif,
+                key.iif, getIfName(key.iif), key.dstMac, bytesToPrefix(key.src64), value.oif,
                 getIfName(value.oif), value.ethProto, value.ethSrcMac, value.ethDstMac);
     }
 
@@ -1570,7 +1575,7 @@
          */
         @NonNull
         public TetherUpstream6Key makeTetherUpstream6Key() {
-            long prefix64 = ByteBuffer.wrap(sourcePrefix.getRawAddress()).getLong();
+            final byte[] prefix64 = Arrays.copyOf(sourcePrefix.getRawAddress(), 8);
             return new TetherUpstream6Key(downstreamIfindex, inDstMac, prefix64);
         }
 
diff --git a/Tethering/src/com/android/networkstack/tethering/TetherUpstream6Key.java b/Tethering/src/com/android/networkstack/tethering/TetherUpstream6Key.java
index 36a1c3c..0cc3dd9 100644
--- a/Tethering/src/com/android/networkstack/tethering/TetherUpstream6Key.java
+++ b/Tethering/src/com/android/networkstack/tethering/TetherUpstream6Key.java
@@ -32,10 +32,10 @@
     @Field(order = 1, type = Type.EUI48, padding = 6)
     public final MacAddress dstMac; // Destination ethernet mac address (zeroed iff rawip ingress).
 
-    @Field(order = 2, type = Type.S64)
-    public final long src64; // The top 64-bits of the source ip.
+    @Field(order = 2, type = Type.ByteArray, arraysize = 8)
+    public final byte[] src64; // The top 64-bits of the source ip.
 
-    public TetherUpstream6Key(int iif, @NonNull final MacAddress dstMac, long src64) {
+    public TetherUpstream6Key(int iif, @NonNull final MacAddress dstMac, final byte[] src64) {
         Objects.requireNonNull(dstMac);
 
         this.iif = iif;
diff --git a/Tethering/tests/unit/src/com/android/networkstack/tethering/BpfCoordinatorTest.java b/Tethering/tests/unit/src/com/android/networkstack/tethering/BpfCoordinatorTest.java
index 6c1721e..01600b8 100644
--- a/Tethering/tests/unit/src/com/android/networkstack/tethering/BpfCoordinatorTest.java
+++ b/Tethering/tests/unit/src/com/android/networkstack/tethering/BpfCoordinatorTest.java
@@ -64,6 +64,7 @@
 import static com.android.networkstack.tethering.TetheringConfiguration.DEFAULT_TETHER_OFFLOAD_POLL_INTERVAL_MS;
 import static com.android.testutils.MiscAsserts.assertSameElements;
 
+import static org.junit.Assert.assertArrayEquals;
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertFalse;
 import static org.junit.Assert.assertNotNull;
@@ -166,7 +167,6 @@
 import java.net.Inet4Address;
 import java.net.Inet6Address;
 import java.net.InetAddress;
-import java.nio.ByteBuffer;
 import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.HashMap;
@@ -794,7 +794,7 @@
         if (!mDeps.isAtLeastS()) return;
         ArrayMap<TetherUpstream6Key, Tether6Value> expected = new ArrayMap<>();
         for (IpPrefix upstreamPrefix : upstreamPrefixes) {
-            long prefix64 = prefixToLong(upstreamPrefix);
+            final byte[] prefix64 = prefixToIp64(upstreamPrefix);
             final TetherUpstream6Key key = new TetherUpstream6Key(DOWNSTREAM_IFACE_PARAMS.index,
                     DOWNSTREAM_IFACE_PARAMS.macAddr, prefix64);
             final Tether6Value value = new Tether6Value(upstreamIfindex,
@@ -822,7 +822,7 @@
         if (!mDeps.isAtLeastS()) return;
         Set<TetherUpstream6Key> expected = new ArraySet<>();
         for (IpPrefix upstreamPrefix : upstreamPrefixes) {
-            long prefix64 = prefixToLong(upstreamPrefix);
+            final byte[] prefix64 = prefixToIp64(upstreamPrefix);
             final TetherUpstream6Key key = new TetherUpstream6Key(DOWNSTREAM_IFACE_PARAMS.index,
                     DOWNSTREAM_IFACE_PARAMS.macAddr, prefix64);
             expected.add(key);
@@ -1275,7 +1275,7 @@
     }
 
     @Test
-    public void testRuleMakeTetherDownstream6Key() throws Exception {
+    public void testIpv6DownstreamRuleMakeTetherDownstream6Key() throws Exception {
         final int mobileIfIndex = 100;
         final Ipv6DownstreamRule rule = buildTestDownstreamRule(mobileIfIndex, NEIGH_A, MAC_A);
 
@@ -1288,7 +1288,7 @@
     }
 
     @Test
-    public void testRuleMakeTether6Value() throws Exception {
+    public void testIpv6DownstreamRuleMakeTether6Value() throws Exception {
         final int mobileIfIndex = 100;
         final Ipv6DownstreamRule rule = buildTestDownstreamRule(mobileIfIndex, NEIGH_A, MAC_A);
 
@@ -1303,6 +1303,46 @@
     }
 
     @Test
+    public void testIpv6UpstreamRuleMakeTetherUpstream6Key() {
+        final byte[] bytes = new byte[]{(byte) 0x20, (byte) 0x01, (byte) 0x0d, (byte) 0xb8,
+                (byte) 0xab, (byte) 0xcd, (byte) 0xfe, (byte) 0x00};
+        final IpPrefix prefix = new IpPrefix("2001:db8:abcd:fe00::/64");
+        final Ipv6UpstreamRule rule = buildTestUpstreamRule(UPSTREAM_IFINDEX,
+                DOWNSTREAM_IFINDEX, prefix, DOWNSTREAM_MAC);
+
+        final TetherUpstream6Key key = rule.makeTetherUpstream6Key();
+        assertEquals(DOWNSTREAM_IFINDEX, key.iif);
+        assertEquals(DOWNSTREAM_MAC, key.dstMac);
+        assertArrayEquals(bytes, key.src64);
+        // iif (4) + dstMac (6) + padding (6) + src64 (8) = 24
+        assertEquals(24, key.writeToBytes().length);
+    }
+
+    @Test
+    public void testIpv6UpstreamRuleMakeTether6Value() {
+        final IpPrefix prefix = new IpPrefix("2001:db8:abcd:fe00::/64");
+        final Ipv6UpstreamRule rule = buildTestUpstreamRule(UPSTREAM_IFINDEX,
+                DOWNSTREAM_IFINDEX, prefix, DOWNSTREAM_MAC);
+
+        final Tether6Value value = rule.makeTether6Value();
+        assertEquals(UPSTREAM_IFINDEX, value.oif);
+        assertEquals(MAC_NULL, value.ethDstMac);
+        assertEquals(MAC_NULL, value.ethSrcMac);
+        assertEquals(ETH_P_IPV6, value.ethProto);
+        assertEquals(NetworkStackConstants.ETHER_MTU, value.pmtu);
+        // oif (4) + ethDstMac (6) + ethSrcMac (6) + ethProto (2) + pmtu (2) = 20
+        assertEquals(20, value.writeToBytes().length);
+    }
+
+    @Test
+    public void testBytesToPrefix() {
+        final byte[] bytes = new byte[]{(byte) 0x20, (byte) 0x01, (byte) 0x0d, (byte) 0xb8,
+                (byte) 0x00, (byte) 0x00, (byte) 0x12, (byte) 0x34};
+        final IpPrefix prefix = new IpPrefix("2001:db8:0:1234::/64");
+        assertEquals(prefix, BpfCoordinator.bytesToPrefix(bytes));
+    }
+
+    @Test
     public void testSetDataLimit() throws Exception {
         setupFunctioningNetdInterface();
 
@@ -2269,8 +2309,8 @@
                 100 /* nonzero, CT_NEW */);
     }
 
-    private static long prefixToLong(IpPrefix prefix) {
-        return ByteBuffer.wrap(prefix.getRawAddress()).getLong();
+    private static byte[] prefixToIp64(IpPrefix prefix) {
+        return Arrays.copyOf(prefix.getRawAddress(), 8);
     }
 
     void checkRule4ExistInUpstreamDownstreamMap() throws Exception {
@@ -2515,7 +2555,7 @@
         final Ipv6DownstreamRule rule = buildTestDownstreamRule(UPSTREAM_IFINDEX, NEIGH_A, MAC_A);
         mBpfDownstream6Map.insertEntry(rule.makeTetherDownstream6Key(), rule.makeTether6Value());
 
-        final long prefix64 = prefixToLong(UPSTREAM_PREFIX);
+        final byte[] prefix64 = prefixToIp64(UPSTREAM_PREFIX);
         final TetherUpstream6Key upstream6Key = new TetherUpstream6Key(DOWNSTREAM_IFINDEX,
                 DOWNSTREAM_MAC, prefix64);
         final Tether6Value upstream6Value = new Tether6Value(UPSTREAM_IFINDEX,