diff --git a/services/core/java/com/android/server/connectivity/Tethering.java b/services/core/java/com/android/server/connectivity/Tethering.java
index ca002fc..cc418ca 100644
--- a/services/core/java/com/android/server/connectivity/Tethering.java
+++ b/services/core/java/com/android/server/connectivity/Tethering.java
@@ -75,6 +75,7 @@
 import com.android.internal.util.StateMachine;
 import com.android.server.connectivity.tethering.IControlsTethering;
 import com.android.server.connectivity.tethering.IPv6TetheringCoordinator;
+import com.android.server.connectivity.tethering.TetheringConfiguration;
 import com.android.server.connectivity.tethering.TetherInterfaceStateMachine;
 import com.android.server.connectivity.tethering.UpstreamNetworkMonitor;
 import com.android.server.net.BaseNetworkObserver;
@@ -117,10 +118,6 @@
     // used to synchronize public access to members
     private final Object mPublicSync;
 
-    private static final Integer MOBILE_TYPE = new Integer(ConnectivityManager.TYPE_MOBILE);
-    private static final Integer HIPRI_TYPE = new Integer(ConnectivityManager.TYPE_MOBILE_HIPRI);
-    private static final Integer DUN_TYPE = new Integer(ConnectivityManager.TYPE_MOBILE_DUN);
-
     private final INetworkManagementService mNMService;
     private final INetworkStatsService mStatsService;
     private final INetworkPolicyManager mPolicyManager;
@@ -1688,119 +1685,4 @@
     private static String[] copy(String[] strarray) {
         return Arrays.copyOf(strarray, strarray.length);
     }
-
-    private static class TetheringConfiguration {
-        private static final int DUN_NOT_REQUIRED = 0;
-        private static final int DUN_REQUIRED = 1;
-        private static final int DUN_UNSPECIFIED = 2;
-
-        // USB is  192.168.42.1 and 255.255.255.0
-        // Wifi is 192.168.43.1 and 255.255.255.0
-        // BT is limited to max default of 5 connections. 192.168.44.1 to 192.168.48.1
-        // with 255.255.255.0
-        // P2P is 192.168.49.1 and 255.255.255.0
-        private static final String[] DHCP_DEFAULT_RANGE = {
-            "192.168.42.2", "192.168.42.254", "192.168.43.2", "192.168.43.254",
-            "192.168.44.2", "192.168.44.254", "192.168.45.2", "192.168.45.254",
-            "192.168.46.2", "192.168.46.254", "192.168.47.2", "192.168.47.254",
-            "192.168.48.2", "192.168.48.254", "192.168.49.2", "192.168.49.254",
-        };
-
-        private final String[] DEFAULT_IPV4_DNS = {"8.8.4.4", "8.8.8.8"};
-
-        public final String[] tetherableUsbRegexs;
-        public final String[] tetherableWifiRegexs;
-        public final String[] tetherableBluetoothRegexs;
-        public final boolean isDunRequired;
-        public final Collection<Integer> preferredUpstreamIfaceTypes;
-        public final String[] dhcpRanges;
-        public final String[] defaultIPv4DNS;
-
-        public TetheringConfiguration(Context ctx) {
-            tetherableUsbRegexs = ctx.getResources().getStringArray(
-                    com.android.internal.R.array.config_tether_usb_regexs);
-            tetherableWifiRegexs = ctx.getResources().getStringArray(
-                    com.android.internal.R.array.config_tether_wifi_regexs);
-            tetherableBluetoothRegexs = ctx.getResources().getStringArray(
-                    com.android.internal.R.array.config_tether_bluetooth_regexs);
-
-            isDunRequired = checkDunRequired(ctx);
-            preferredUpstreamIfaceTypes = getUpstreamIfaceTypes(ctx, isDunRequired);
-
-            dhcpRanges = getDhcpRanges(ctx);
-            defaultIPv4DNS = copy(DEFAULT_IPV4_DNS);
-        }
-
-        public boolean isUsb(String iface) {
-            for (String regex : tetherableUsbRegexs) {
-                if (iface.matches(regex)) return true;
-            }
-            return false;
-        }
-
-        public boolean isWifi(String iface) {
-            for (String regex : tetherableWifiRegexs) {
-                if (iface.matches(regex)) return true;
-            }
-            return false;
-        }
-
-        public boolean isBluetooth(String iface) {
-            for (String regex : tetherableBluetoothRegexs) {
-                if (iface.matches(regex)) return true;
-            }
-            return false;
-        }
-
-        private static boolean checkDunRequired(Context ctx) {
-            final TelephonyManager tm = ctx.getSystemService(TelephonyManager.class);
-            final int secureSetting =
-                    (tm != null) ? tm.getTetherApnRequired() : DUN_UNSPECIFIED;
-            return (secureSetting == DUN_REQUIRED);
-        }
-
-        private static Collection<Integer> getUpstreamIfaceTypes(Context ctx, boolean requiresDun) {
-            final int ifaceTypes[] = ctx.getResources().getIntArray(
-                    com.android.internal.R.array.config_tether_upstream_types);
-            final ArrayList<Integer> upstreamIfaceTypes = new ArrayList<>(ifaceTypes.length);
-            for (int i : ifaceTypes) {
-                upstreamIfaceTypes.add(i);
-            }
-
-            // Fix up upstream interface types for DUN or mobile.
-            // TODO: Perform this filtering step in the above for loop.
-            if (requiresDun) {
-                while (upstreamIfaceTypes.contains(MOBILE_TYPE)) {
-                    upstreamIfaceTypes.remove(MOBILE_TYPE);
-                }
-                while (upstreamIfaceTypes.contains(HIPRI_TYPE)) {
-                    upstreamIfaceTypes.remove(HIPRI_TYPE);
-                }
-                if (!upstreamIfaceTypes.contains(DUN_TYPE)) {
-                    upstreamIfaceTypes.add(DUN_TYPE);
-                }
-            } else {
-                while (upstreamIfaceTypes.contains(DUN_TYPE)) {
-                    upstreamIfaceTypes.remove(DUN_TYPE);
-                }
-                if (!upstreamIfaceTypes.contains(MOBILE_TYPE)) {
-                    upstreamIfaceTypes.add(MOBILE_TYPE);
-                }
-                if (!upstreamIfaceTypes.contains(HIPRI_TYPE)) {
-                    upstreamIfaceTypes.add(HIPRI_TYPE);
-                }
-            }
-
-            return upstreamIfaceTypes;
-        }
-
-        private static String[] getDhcpRanges(Context ctx) {
-            final String[] fromResource = ctx.getResources().getStringArray(
-                    com.android.internal.R.array.config_tether_dhcp_range);
-            if ((fromResource.length > 0) && (fromResource.length % 2 == 0)) {
-                return fromResource;
-            }
-            return copy(DHCP_DEFAULT_RANGE);
-        }
-    }
 }
diff --git a/services/core/java/com/android/server/connectivity/tethering/TetheringConfiguration.java b/services/core/java/com/android/server/connectivity/tethering/TetheringConfiguration.java
new file mode 100644
index 0000000..14d06cc
--- /dev/null
+++ b/services/core/java/com/android/server/connectivity/tethering/TetheringConfiguration.java
@@ -0,0 +1,163 @@
+/*
+ * Copyright (C) 2017 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.server.connectivity.tethering;
+
+import static android.net.ConnectivityManager.TYPE_MOBILE;
+import static android.net.ConnectivityManager.TYPE_MOBILE_DUN;
+import static android.net.ConnectivityManager.TYPE_MOBILE_HIPRI;
+
+import android.content.Context;
+import android.content.res.Resources;
+import android.telephony.TelephonyManager;
+import android.util.Log;
+
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.Collection;
+
+
+/**
+ * A utility class to encapsulate the various tethering configuration elements.
+ *
+ * This configuration data includes elements describing upstream properties
+ * (preferred and required types of upstream connectivity as well as default
+ * DNS servers to use if none are available) and downstream properties (such
+ * as regular expressions use to match suitable downstream interfaces and the
+ * DHCPv4 ranges to use).
+ *
+ * @hide
+ */
+public class TetheringConfiguration {
+    private static final String TAG = TetheringConfiguration.class.getSimpleName();
+
+    private static final int DUN_NOT_REQUIRED = 0;
+    private static final int DUN_REQUIRED = 1;
+    private static final int DUN_UNSPECIFIED = 2;
+
+    // USB is  192.168.42.1 and 255.255.255.0
+    // Wifi is 192.168.43.1 and 255.255.255.0
+    // BT is limited to max default of 5 connections. 192.168.44.1 to 192.168.48.1
+    // with 255.255.255.0
+    // P2P is 192.168.49.1 and 255.255.255.0
+    private static final String[] DHCP_DEFAULT_RANGE = {
+        "192.168.42.2", "192.168.42.254", "192.168.43.2", "192.168.43.254",
+        "192.168.44.2", "192.168.44.254", "192.168.45.2", "192.168.45.254",
+        "192.168.46.2", "192.168.46.254", "192.168.47.2", "192.168.47.254",
+        "192.168.48.2", "192.168.48.254", "192.168.49.2", "192.168.49.254",
+    };
+
+    private final String[] DEFAULT_IPV4_DNS = {"8.8.4.4", "8.8.8.8"};
+
+    public final String[] tetherableUsbRegexs;
+    public final String[] tetherableWifiRegexs;
+    public final String[] tetherableBluetoothRegexs;
+    public final boolean isDunRequired;
+    public final Collection<Integer> preferredUpstreamIfaceTypes;
+    public final String[] dhcpRanges;
+    public final String[] defaultIPv4DNS;
+
+    public TetheringConfiguration(Context ctx) {
+        tetherableUsbRegexs = ctx.getResources().getStringArray(
+                com.android.internal.R.array.config_tether_usb_regexs);
+        tetherableWifiRegexs = ctx.getResources().getStringArray(
+                com.android.internal.R.array.config_tether_wifi_regexs);
+        tetherableBluetoothRegexs = ctx.getResources().getStringArray(
+                com.android.internal.R.array.config_tether_bluetooth_regexs);
+
+        isDunRequired = checkDunRequired(ctx);
+        preferredUpstreamIfaceTypes = getUpstreamIfaceTypes(ctx, isDunRequired);
+
+        dhcpRanges = getDhcpRanges(ctx);
+        defaultIPv4DNS = copy(DEFAULT_IPV4_DNS);
+    }
+
+    public boolean isUsb(String iface) {
+        return matchesDownstreamRegexs(iface, tetherableUsbRegexs);
+    }
+
+    public boolean isWifi(String iface) {
+        return matchesDownstreamRegexs(iface, tetherableWifiRegexs);
+    }
+
+    public boolean isBluetooth(String iface) {
+        return matchesDownstreamRegexs(iface, tetherableBluetoothRegexs);
+    }
+
+    private static boolean checkDunRequired(Context ctx) {
+        final TelephonyManager tm = ctx.getSystemService(TelephonyManager.class);
+        final int secureSetting =
+                (tm != null) ? tm.getTetherApnRequired() : DUN_UNSPECIFIED;
+        return (secureSetting == DUN_REQUIRED);
+    }
+
+    private static Collection<Integer> getUpstreamIfaceTypes(Context ctx, boolean requiresDun) {
+        final int ifaceTypes[] = ctx.getResources().getIntArray(
+                com.android.internal.R.array.config_tether_upstream_types);
+        final ArrayList<Integer> upstreamIfaceTypes = new ArrayList<>(ifaceTypes.length);
+        for (int i : ifaceTypes) {
+            switch (i) {
+                case TYPE_MOBILE:
+                case TYPE_MOBILE_HIPRI:
+                    if (requiresDun) continue;
+                    break;
+                case TYPE_MOBILE_DUN:
+                    if (!requiresDun) continue;
+                    break;
+            }
+            upstreamIfaceTypes.add(i);
+        }
+
+        // Fix up upstream interface types for DUN or mobile. NOTE: independent
+        // of the value of |requiresDun|, cell data of one form or another is
+        // *always* an upstream, regardless of the upstream interface types
+        // specified by configuration resources.
+        if (requiresDun) {
+            if (!upstreamIfaceTypes.contains(TYPE_MOBILE_DUN)) {
+                upstreamIfaceTypes.add(TYPE_MOBILE_DUN);
+            }
+        } else {
+            if (!upstreamIfaceTypes.contains(TYPE_MOBILE)) {
+                upstreamIfaceTypes.add(TYPE_MOBILE);
+            }
+            if (!upstreamIfaceTypes.contains(TYPE_MOBILE_HIPRI)) {
+                upstreamIfaceTypes.add(TYPE_MOBILE_HIPRI);
+            }
+        }
+
+        return upstreamIfaceTypes;
+    }
+
+    private static boolean matchesDownstreamRegexs(String iface, String[] regexs) {
+        for (String regex : regexs) {
+            if (iface.matches(regex)) return true;
+        }
+        return false;
+    }
+
+    private static String[] getDhcpRanges(Context ctx) {
+        final String[] fromResource = ctx.getResources().getStringArray(
+                com.android.internal.R.array.config_tether_dhcp_range);
+        if ((fromResource.length > 0) && (fromResource.length % 2 == 0)) {
+            return fromResource;
+        }
+        return copy(DHCP_DEFAULT_RANGE);
+    }
+
+    private static String[] copy(String[] strarray) {
+        return Arrays.copyOf(strarray, strarray.length);
+    }
+}