/*
 * Copyright (C) 2011 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;

import static android.Manifest.permission.BIND_VPN_SERVICE;
import static android.net.ConnectivityManager.NETID_UNSET;
import static android.net.RouteInfo.RTN_THROW;
import static android.net.RouteInfo.RTN_UNREACHABLE;

import android.Manifest;
import android.annotation.NonNull;
import android.annotation.Nullable;
import android.annotation.UserIdInt;
import android.app.AppGlobals;
import android.app.AppOpsManager;
import android.app.Notification;
import android.app.NotificationManager;
import android.app.PendingIntent;
import android.content.BroadcastReceiver;
import android.content.ComponentName;
import android.content.Context;
import android.content.Intent;
import android.content.IntentFilter;
import android.content.ServiceConnection;
import android.content.pm.PackageManager;
import android.content.pm.PackageManager.NameNotFoundException;
import android.content.pm.ResolveInfo;
import android.content.pm.UserInfo;
import android.net.ConnectivityManager;
import android.net.INetworkManagementEventObserver;
import android.net.IpPrefix;
import android.net.LinkAddress;
import android.net.LinkProperties;
import android.net.LocalSocket;
import android.net.LocalSocketAddress;
import android.net.Network;
import android.net.NetworkAgent;
import android.net.NetworkCapabilities;
import android.net.NetworkInfo;
import android.net.NetworkInfo.DetailedState;
import android.net.NetworkMisc;
import android.net.RouteInfo;
import android.net.UidRange;
import android.net.Uri;
import android.os.Binder;
import android.os.FileUtils;
import android.os.IBinder;
import android.os.INetworkManagementService;
import android.os.Looper;
import android.os.Parcel;
import android.os.ParcelFileDescriptor;
import android.os.PatternMatcher;
import android.os.Process;
import android.os.RemoteException;
import android.os.SystemClock;
import android.os.SystemService;
import android.os.UserHandle;
import android.os.UserManager;
import android.provider.Settings;
import android.security.Credentials;
import android.security.KeyStore;
import android.text.TextUtils;
import android.util.ArraySet;
import android.util.Log;

import com.android.internal.R;
import com.android.internal.annotations.GuardedBy;
import com.android.internal.annotations.VisibleForTesting;
import com.android.internal.messages.nano.SystemMessageProto.SystemMessage;
import com.android.internal.net.LegacyVpnInfo;
import com.android.internal.net.VpnConfig;
import com.android.internal.net.VpnInfo;
import com.android.internal.net.VpnProfile;
import com.android.internal.notification.SystemNotificationChannels;
import com.android.server.DeviceIdleController;
import com.android.server.LocalServices;
import com.android.server.net.BaseNetworkObserver;

import libcore.io.IoUtils;

import java.io.File;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.net.Inet4Address;
import java.net.Inet6Address;
import java.net.InetAddress;
import java.nio.charset.StandardCharsets;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collection;
import java.util.Collections;
import java.util.List;
import java.util.Set;
import java.util.SortedSet;
import java.util.TreeSet;
import java.util.concurrent.atomic.AtomicInteger;

/**
 * @hide
 */
public class Vpn {
    private static final String NETWORKTYPE = "VPN";
    private static final String TAG = "Vpn";
    private static final boolean LOGD = true;

    // Length of time (in milliseconds) that an app hosting an always-on VPN is placed on
    // the device idle whitelist during service launch and VPN bootstrap.
    private static final long VPN_LAUNCH_IDLE_WHITELIST_DURATION = 60 * 1000;

    // TODO: create separate trackers for each unique VPN to support
    // automated reconnection

    private Context mContext;
    private NetworkInfo mNetworkInfo;
    private String mPackage;
    private int mOwnerUID;
    private String mInterface;
    private Connection mConnection;
    private LegacyVpnRunner mLegacyVpnRunner;
    private PendingIntent mStatusIntent;
    private volatile boolean mEnableTeardown = true;
    private final INetworkManagementService mNetd;
    private VpnConfig mConfig;
    private NetworkAgent mNetworkAgent;
    private final Looper mLooper;
    private final NetworkCapabilities mNetworkCapabilities;
    private final SystemServices mSystemServices;

    /**
     * Whether to keep the connection active after rebooting, or upgrading or reinstalling. This
     * only applies to {@link VpnService} connections.
     */
    private boolean mAlwaysOn = false;

    /**
     * Whether to disable traffic outside of this VPN even when the VPN is not connected. System
     * apps can still bypass by choosing explicit networks. Has no effect if {@link mAlwaysOn} is
     * not set.
     */
    private boolean mLockdown = false;

    /**
     * List of UIDs that are set to use this VPN by default. Normally, every UID in the user is
     * added to this set but that can be changed by adding allowed or disallowed applications. It
     * is non-null iff the VPN is connected.
     *
     * Unless the VPN has set allowBypass=true, these UIDs are forced into the VPN.
     *
     * @see VpnService.Builder#addAllowedApplication(String)
     * @see VpnService.Builder#addDisallowedApplication(String)
     */
    @GuardedBy("this")
    private Set<UidRange> mVpnUsers = null;

    /**
     * List of UIDs for which networking should be blocked until VPN is ready, during brief periods
     * when VPN is not running. For example, during system startup or after a crash.
     * @see mLockdown
     */
    @GuardedBy("this")
    private Set<UidRange> mBlockedUsers = new ArraySet<>();

    // Handle of user initiating VPN.
    private final int mUserHandle;

    // Listen to package remove and change event in this user
    private final BroadcastReceiver mPackageIntentReceiver = new BroadcastReceiver() {
        @Override
        public void onReceive(Context context, Intent intent) {
            final Uri data = intent.getData();
            final String packageName = data == null ? null : data.getSchemeSpecificPart();
            if (packageName == null) {
                return;
            }

            synchronized (Vpn.this) {
                // Avoid race that always-on package has been unset
                if (!packageName.equals(getAlwaysOnPackage())) {
                    return;
                }

                final String action = intent.getAction();
                Log.i(TAG, "Received broadcast " + action + " for always-on package " + packageName
                        + " in user " + mUserHandle);

                switch(action) {
                    case Intent.ACTION_PACKAGE_REPLACED:
                        // Start vpn after app upgrade
                        startAlwaysOnVpn();
                        break;
                    case Intent.ACTION_PACKAGE_REMOVED:
                        final boolean isPackageRemoved = !intent.getBooleanExtra(
                                Intent.EXTRA_REPLACING, false);
                        if (isPackageRemoved) {
                            setAlwaysOnPackage(null, false);
                        }
                        break;
                }
            }
        }
    };

    private boolean mIsPackageIntentReceiverRegistered = false;

    public Vpn(Looper looper, Context context, INetworkManagementService netService,
            @UserIdInt int userHandle) {
        this(looper, context, netService, userHandle, new SystemServices(context));
    }

    @VisibleForTesting
    protected Vpn(Looper looper, Context context, INetworkManagementService netService,
            int userHandle, SystemServices systemServices) {
        mContext = context;
        mNetd = netService;
        mUserHandle = userHandle;
        mLooper = looper;
        mSystemServices = systemServices;

        mPackage = VpnConfig.LEGACY_VPN;
        mOwnerUID = getAppUid(mPackage, mUserHandle);

        try {
            netService.registerObserver(mObserver);
        } catch (RemoteException e) {
            Log.wtf(TAG, "Problem registering observer", e);
        }

        mNetworkInfo = new NetworkInfo(ConnectivityManager.TYPE_VPN, 0, NETWORKTYPE, "");
        // TODO: Copy metered attribute and bandwidths from physical transport, b/16207332
        mNetworkCapabilities = new NetworkCapabilities();
        mNetworkCapabilities.addTransportType(NetworkCapabilities.TRANSPORT_VPN);
        mNetworkCapabilities.removeCapability(NetworkCapabilities.NET_CAPABILITY_NOT_VPN);

        loadAlwaysOnPackage();
    }

    /**
     * Set if this object is responsible for watching for {@link NetworkInfo}
     * teardown. When {@code false}, teardown is handled externally by someone
     * else.
     */
    public void setEnableTeardown(boolean enableTeardown) {
        mEnableTeardown = enableTeardown;
    }

    /**
     * Update current state, dispaching event to listeners.
     */
    @VisibleForTesting
    protected void updateState(DetailedState detailedState, String reason) {
        if (LOGD) Log.d(TAG, "setting state=" + detailedState + ", reason=" + reason);
        mNetworkInfo.setDetailedState(detailedState, reason, null);
        if (mNetworkAgent != null) {
            mNetworkAgent.sendNetworkInfo(mNetworkInfo);
        }
        updateAlwaysOnNotification(detailedState);
    }

    /**
     * Configures an always-on VPN connection through a specific application.
     * This connection is automatically granted and persisted after a reboot.
     *
     * <p>The designated package should exist and declare a {@link VpnService} in its
     *    manifest guarded by {@link android.Manifest.permission.BIND_VPN_SERVICE},
     *    otherwise the call will fail.
     *
     * @param packageName the package to designate as always-on VPN supplier.
     * @param lockdown whether to prevent traffic outside of a VPN, for example while connecting.
     * @return {@code true} if the package has been set as always-on, {@code false} otherwise.
     */
    public synchronized boolean setAlwaysOnPackage(String packageName, boolean lockdown) {
        enforceControlPermissionOrInternalCaller();

        if (setAlwaysOnPackageInternal(packageName, lockdown)) {
            saveAlwaysOnPackage();
            return true;
        }
        return false;
    }

    /**
     * Configures an always-on VPN connection through a specific application, the same as
     * {@link #setAlwaysOnPackage}.
     *
     * Does not perform permission checks. Does not persist any of the changes to storage.
     *
     * @param packageName the package to designate as always-on VPN supplier.
     * @param lockdown whether to prevent traffic outside of a VPN, for example while connecting.
     * @return {@code true} if the package has been set as always-on, {@code false} otherwise.
     */
    @GuardedBy("this")
    private boolean setAlwaysOnPackageInternal(String packageName, boolean lockdown) {
        if (VpnConfig.LEGACY_VPN.equals(packageName)) {
            Log.w(TAG, "Not setting legacy VPN \"" + packageName + "\" as always-on.");
            return false;
        }

        if (packageName != null) {
            // Pre-authorize new always-on VPN package.
            if (!setPackageAuthorization(packageName, true)) {
                return false;
            }
            mAlwaysOn = true;
        } else {
            packageName = VpnConfig.LEGACY_VPN;
            mAlwaysOn = false;
        }

        mLockdown = (mAlwaysOn && lockdown);
        if (isCurrentPreparedPackage(packageName)) {
            updateAlwaysOnNotification(mNetworkInfo.getDetailedState());
        } else {
            // Prepare this app. The notification will update as a side-effect of updateState().
            prepareInternal(packageName);
        }
        maybeRegisterPackageChangeReceiverLocked(packageName);
        setVpnForcedLocked(mLockdown);
        return true;
    }

    private static boolean isNullOrLegacyVpn(String packageName) {
        return packageName == null || VpnConfig.LEGACY_VPN.equals(packageName);
    }

    private void unregisterPackageChangeReceiverLocked() {
        // register previous intent filter
        if (mIsPackageIntentReceiverRegistered) {
            mContext.unregisterReceiver(mPackageIntentReceiver);
            mIsPackageIntentReceiverRegistered = false;
        }
    }

    private void maybeRegisterPackageChangeReceiverLocked(String packageName) {
        // Unregister IntentFilter listening for previous always-on package change
        unregisterPackageChangeReceiverLocked();

        if (!isNullOrLegacyVpn(packageName)) {
            mIsPackageIntentReceiverRegistered = true;

            IntentFilter intentFilter = new IntentFilter();
            // Protected intent can only be sent by system. No permission required in register.
            intentFilter.addAction(Intent.ACTION_PACKAGE_REPLACED);
            intentFilter.addAction(Intent.ACTION_PACKAGE_REMOVED);
            intentFilter.addDataScheme("package");
            intentFilter.addDataSchemeSpecificPart(packageName, PatternMatcher.PATTERN_LITERAL);
            mContext.registerReceiverAsUser(
                    mPackageIntentReceiver, UserHandle.of(mUserHandle), intentFilter, null, null);
        }
    }

    /**
     * @return the package name of the VPN controller responsible for always-on VPN,
     *         or {@code null} if none is set or always-on VPN is controlled through
     *         lockdown instead.
     * @hide
     */
    public synchronized String getAlwaysOnPackage() {
        enforceControlPermissionOrInternalCaller();
        return (mAlwaysOn ? mPackage : null);
    }

    /**
     * Save the always-on package and lockdown config into Settings.Secure
     */
    @GuardedBy("this")
    private void saveAlwaysOnPackage() {
        final long token = Binder.clearCallingIdentity();
        try {
            mSystemServices.settingsSecurePutStringForUser(Settings.Secure.ALWAYS_ON_VPN_APP,
                    getAlwaysOnPackage(), mUserHandle);
            mSystemServices.settingsSecurePutIntForUser(Settings.Secure.ALWAYS_ON_VPN_LOCKDOWN,
                    (mLockdown ? 1 : 0), mUserHandle);
        } finally {
            Binder.restoreCallingIdentity(token);
        }
    }

    /**
     * Load the always-on package and lockdown config from Settings.Secure
     */
    @GuardedBy("this")
    private void loadAlwaysOnPackage() {
        final long token = Binder.clearCallingIdentity();
        try {
            final String alwaysOnPackage = mSystemServices.settingsSecureGetStringForUser(
                    Settings.Secure.ALWAYS_ON_VPN_APP, mUserHandle);
            final boolean alwaysOnLockdown = mSystemServices.settingsSecureGetIntForUser(
                    Settings.Secure.ALWAYS_ON_VPN_LOCKDOWN, 0 /*default*/, mUserHandle) != 0;
            setAlwaysOnPackageInternal(alwaysOnPackage, alwaysOnLockdown);
        } finally {
            Binder.restoreCallingIdentity(token);
        }
    }

    /**
     * @return {@code true} if the service was started, the service was already connected, or there
     *         was no always-on VPN to start. {@code false} otherwise.
     */
    public boolean startAlwaysOnVpn() {
        final String alwaysOnPackage;
        synchronized (this) {
            alwaysOnPackage = getAlwaysOnPackage();
            // Skip if there is no service to start.
            if (alwaysOnPackage == null) {
                return true;
            }
            // Skip if the service is already established. This isn't bulletproof: it's not bound
            // until after establish(), so if it's mid-setup onStartCommand will be sent twice,
            // which may restart the connection.
            if (getNetworkInfo().isConnected()) {
                return true;
            }
        }

        // Tell the OS that background services in this app need to be allowed for
        // a short time, so we can bootstrap the VPN service.
        final long oldId = Binder.clearCallingIdentity();
        try {
            DeviceIdleController.LocalService idleController =
                    LocalServices.getService(DeviceIdleController.LocalService.class);
            idleController.addPowerSaveTempWhitelistApp(Process.myUid(), alwaysOnPackage,
                    VPN_LAUNCH_IDLE_WHITELIST_DURATION, mUserHandle, false, "vpn");

            // Start the VPN service declared in the app's manifest.
            Intent serviceIntent = new Intent(VpnConfig.SERVICE_INTERFACE);
            serviceIntent.setPackage(alwaysOnPackage);
            try {
                return mContext.startServiceAsUser(serviceIntent, UserHandle.of(mUserHandle)) != null;
            } catch (RuntimeException e) {
                Log.e(TAG, "VpnService " + serviceIntent + " failed to start", e);
                return false;
            }
        } finally {
            Binder.restoreCallingIdentity(oldId);
        }
    }

    /**
     * Prepare for a VPN application. This method is designed to solve
     * race conditions. It first compares the current prepared package
     * with {@code oldPackage}. If they are the same, the prepared
     * package is revoked and replaced with {@code newPackage}. If
     * {@code oldPackage} is {@code null}, the comparison is omitted.
     * If {@code newPackage} is the same package or {@code null}, the
     * revocation is omitted. This method returns {@code true} if the
     * operation is succeeded.
     *
     * Legacy VPN is handled specially since it is not a real package.
     * It uses {@link VpnConfig#LEGACY_VPN} as its package name, and
     * it can be revoked by itself.
     *
     * Note: when we added VPN pre-consent in http://ag/522961 the names oldPackage
     * and newPackage become misleading, because when an app is pre-consented, we
     * actually prepare oldPackage, not newPackage.
     *
     * Their meanings actually are:
     *
     * - oldPackage non-null, newPackage null: App calling VpnService#prepare().
     * - oldPackage null, newPackage non-null: ConfirmDialog calling prepareVpn().
     * - oldPackage null, newPackage=LEGACY_VPN: Used internally to disconnect
     *   and revoke any current app VPN and re-prepare legacy vpn.
     *
     * TODO: Rename the variables - or split this method into two - and end this confusion.
     * TODO: b/29032008 Migrate code from prepare(oldPackage=non-null, newPackage=LEGACY_VPN)
     * to prepare(oldPackage=null, newPackage=LEGACY_VPN)
     *
     * @param oldPackage The package name of the old VPN application
     * @param newPackage The package name of the new VPN application
     *
     * @return true if the operation is succeeded.
     */
    public synchronized boolean prepare(String oldPackage, String newPackage) {
        if (oldPackage != null) {
            // Stop an existing always-on VPN from being dethroned by other apps.
            if (mAlwaysOn && !isCurrentPreparedPackage(oldPackage)) {
                return false;
            }

            // Package is not same or old package was reinstalled.
            if (!isCurrentPreparedPackage(oldPackage)) {
                // The package doesn't match. We return false (to obtain user consent) unless the
                // user has already consented to that VPN package.
                if (!oldPackage.equals(VpnConfig.LEGACY_VPN) && isVpnUserPreConsented(oldPackage)) {
                    prepareInternal(oldPackage);
                    return true;
                }
                return false;
            } else if (!oldPackage.equals(VpnConfig.LEGACY_VPN)
                    && !isVpnUserPreConsented(oldPackage)) {
                // Currently prepared VPN is revoked, so unprepare it and return false.
                prepareInternal(VpnConfig.LEGACY_VPN);
                return false;
            }
        }

        // Return true if we do not need to revoke.
        if (newPackage == null || (!newPackage.equals(VpnConfig.LEGACY_VPN) &&
                isCurrentPreparedPackage(newPackage))) {
            return true;
        }

        // Check that the caller is authorized.
        enforceControlPermission();

        // Stop an existing always-on VPN from being dethroned by other apps.
        if (mAlwaysOn && !isCurrentPreparedPackage(newPackage)) {
            return false;
        }

        prepareInternal(newPackage);
        return true;
    }

    private boolean isCurrentPreparedPackage(String packageName) {
        // We can't just check that packageName matches mPackage, because if the app was uninstalled
        // and reinstalled it will no longer be prepared. Instead check the UID.
        return getAppUid(packageName, mUserHandle) == mOwnerUID;
    }

    /** Prepare the VPN for the given package. Does not perform permission checks. */
    private void prepareInternal(String newPackage) {
        long token = Binder.clearCallingIdentity();
        try {
            // Reset the interface.
            if (mInterface != null) {
                mStatusIntent = null;
                agentDisconnect();
                jniReset(mInterface);
                mInterface = null;
                mVpnUsers = null;
            }

            // Revoke the connection or stop LegacyVpnRunner.
            if (mConnection != null) {
                try {
                    mConnection.mService.transact(IBinder.LAST_CALL_TRANSACTION,
                            Parcel.obtain(), null, IBinder.FLAG_ONEWAY);
                } catch (Exception e) {
                    // ignore
                }
                mContext.unbindService(mConnection);
                mConnection = null;
            } else if (mLegacyVpnRunner != null) {
                mLegacyVpnRunner.exit();
                mLegacyVpnRunner = null;
            }

            try {
                mNetd.denyProtect(mOwnerUID);
            } catch (Exception e) {
                Log.wtf(TAG, "Failed to disallow UID " + mOwnerUID + " to call protect() " + e);
            }

            Log.i(TAG, "Switched from " + mPackage + " to " + newPackage);
            mPackage = newPackage;
            mOwnerUID = getAppUid(newPackage, mUserHandle);
            try {
                mNetd.allowProtect(mOwnerUID);
            } catch (Exception e) {
                Log.wtf(TAG, "Failed to allow UID " + mOwnerUID + " to call protect() " + e);
            }
            mConfig = null;

            updateState(DetailedState.IDLE, "prepare");
        } finally {
            Binder.restoreCallingIdentity(token);
        }
    }

    /**
     * Set whether a package has the ability to launch VPNs without user intervention.
     */
    public boolean setPackageAuthorization(String packageName, boolean authorized) {
        // Check if the caller is authorized.
        enforceControlPermissionOrInternalCaller();

        int uid = getAppUid(packageName, mUserHandle);
        if (uid == -1 || VpnConfig.LEGACY_VPN.equals(packageName)) {
            // Authorization for nonexistent packages (or fake ones) can't be updated.
            return false;
        }

        long token = Binder.clearCallingIdentity();
        try {
            AppOpsManager appOps =
                    (AppOpsManager) mContext.getSystemService(Context.APP_OPS_SERVICE);
            appOps.setMode(AppOpsManager.OP_ACTIVATE_VPN, uid, packageName,
                    authorized ? AppOpsManager.MODE_ALLOWED : AppOpsManager.MODE_IGNORED);
            return true;
        } catch (Exception e) {
            Log.wtf(TAG, "Failed to set app ops for package " + packageName + ", uid " + uid, e);
        } finally {
            Binder.restoreCallingIdentity(token);
        }
        return false;
    }

    private boolean isVpnUserPreConsented(String packageName) {
        AppOpsManager appOps =
                (AppOpsManager) mContext.getSystemService(Context.APP_OPS_SERVICE);

        // Verify that the caller matches the given package and has permission to activate VPNs.
        return appOps.noteOpNoThrow(AppOpsManager.OP_ACTIVATE_VPN, Binder.getCallingUid(),
                packageName) == AppOpsManager.MODE_ALLOWED;
    }

    private int getAppUid(String app, int userHandle) {
        if (VpnConfig.LEGACY_VPN.equals(app)) {
            return Process.myUid();
        }
        PackageManager pm = mContext.getPackageManager();
        int result;
        try {
            result = pm.getPackageUidAsUser(app, userHandle);
        } catch (NameNotFoundException e) {
            result = -1;
        }
        return result;
    }

    public NetworkInfo getNetworkInfo() {
        return mNetworkInfo;
    }

    public int getNetId() {
        return mNetworkAgent != null ? mNetworkAgent.netId : NETID_UNSET;
    }

    private LinkProperties makeLinkProperties() {
        boolean allowIPv4 = mConfig.allowIPv4;
        boolean allowIPv6 = mConfig.allowIPv6;

        LinkProperties lp = new LinkProperties();

        lp.setInterfaceName(mInterface);

        if (mConfig.addresses != null) {
            for (LinkAddress address : mConfig.addresses) {
                lp.addLinkAddress(address);
                allowIPv4 |= address.getAddress() instanceof Inet4Address;
                allowIPv6 |= address.getAddress() instanceof Inet6Address;
            }
        }

        if (mConfig.routes != null) {
            for (RouteInfo route : mConfig.routes) {
                lp.addRoute(route);
                InetAddress address = route.getDestination().getAddress();
                allowIPv4 |= address instanceof Inet4Address;
                allowIPv6 |= address instanceof Inet6Address;
            }
        }

        if (mConfig.dnsServers != null) {
            for (String dnsServer : mConfig.dnsServers) {
                InetAddress address = InetAddress.parseNumericAddress(dnsServer);
                lp.addDnsServer(address);
                allowIPv4 |= address instanceof Inet4Address;
                allowIPv6 |= address instanceof Inet6Address;
            }
        }

        if (!allowIPv4) {
            lp.addRoute(new RouteInfo(new IpPrefix(Inet4Address.ANY, 0), RTN_UNREACHABLE));
        }
        if (!allowIPv6) {
            lp.addRoute(new RouteInfo(new IpPrefix(Inet6Address.ANY, 0), RTN_UNREACHABLE));
        }

        // Concatenate search domains into a string.
        StringBuilder buffer = new StringBuilder();
        if (mConfig.searchDomains != null) {
            for (String domain : mConfig.searchDomains) {
                buffer.append(domain).append(' ');
            }
        }
        lp.setDomains(buffer.toString().trim());

        // TODO: Stop setting the MTU in jniCreate and set it here.

        return lp;
    }

    private void agentConnect() {
        LinkProperties lp = makeLinkProperties();

        if (lp.hasIPv4DefaultRoute() || lp.hasIPv6DefaultRoute()) {
            mNetworkCapabilities.addCapability(NetworkCapabilities.NET_CAPABILITY_INTERNET);
        } else {
            mNetworkCapabilities.removeCapability(NetworkCapabilities.NET_CAPABILITY_INTERNET);
        }

        mNetworkInfo.setDetailedState(DetailedState.CONNECTING, null, null);

        NetworkMisc networkMisc = new NetworkMisc();
        networkMisc.allowBypass = mConfig.allowBypass && !mLockdown;

        long token = Binder.clearCallingIdentity();
        try {
            mNetworkAgent = new NetworkAgent(mLooper, mContext, NETWORKTYPE,
                    mNetworkInfo, mNetworkCapabilities, lp, 0, networkMisc) {
                            @Override
                            public void unwanted() {
                                // We are user controlled, not driven by NetworkRequest.
                            }
                        };
        } finally {
            Binder.restoreCallingIdentity(token);
        }

        mVpnUsers = createUserAndRestrictedProfilesRanges(mUserHandle,
                mConfig.allowedApplications, mConfig.disallowedApplications);
        mNetworkAgent.addUidRanges(mVpnUsers.toArray(new UidRange[mVpnUsers.size()]));

        mNetworkInfo.setIsAvailable(true);
        updateState(DetailedState.CONNECTED, "agentConnect");
    }

    private boolean canHaveRestrictedProfile(int userId) {
        long token = Binder.clearCallingIdentity();
        try {
            return UserManager.get(mContext).canHaveRestrictedProfile(userId);
        } finally {
            Binder.restoreCallingIdentity(token);
        }
    }

    private void agentDisconnect(NetworkAgent networkAgent) {
        if (networkAgent != null) {
            NetworkInfo networkInfo = new NetworkInfo(mNetworkInfo);
            networkInfo.setIsAvailable(false);
            networkInfo.setDetailedState(DetailedState.DISCONNECTED, null, null);
            networkAgent.sendNetworkInfo(networkInfo);
        }
    }

    private void agentDisconnect() {
        if (mNetworkInfo.isConnected()) {
            mNetworkInfo.setIsAvailable(false);
            updateState(DetailedState.DISCONNECTED, "agentDisconnect");
            mNetworkAgent = null;
        }
    }

    /**
     * Establish a VPN network and return the file descriptor of the VPN
     * interface. This methods returns {@code null} if the application is
     * revoked or not prepared.
     *
     * @param config The parameters to configure the network.
     * @return The file descriptor of the VPN interface.
     */
    public synchronized ParcelFileDescriptor establish(VpnConfig config) {
        // Check if the caller is already prepared.
        UserManager mgr = UserManager.get(mContext);
        if (Binder.getCallingUid() != mOwnerUID) {
            return null;
        }
        // Check to ensure consent hasn't been revoked since we were prepared.
        if (!isVpnUserPreConsented(mPackage)) {
            return null;
        }
        // Check if the service is properly declared.
        Intent intent = new Intent(VpnConfig.SERVICE_INTERFACE);
        intent.setClassName(mPackage, config.user);
        long token = Binder.clearCallingIdentity();
        try {
            // Restricted users are not allowed to create VPNs, they are tied to Owner
            UserInfo user = mgr.getUserInfo(mUserHandle);
            if (user.isRestricted()) {
                throw new SecurityException("Restricted users cannot establish VPNs");
            }

            ResolveInfo info = AppGlobals.getPackageManager().resolveService(intent,
                                                                        null, 0, mUserHandle);
            if (info == null) {
                throw new SecurityException("Cannot find " + config.user);
            }
            if (!BIND_VPN_SERVICE.equals(info.serviceInfo.permission)) {
                throw new SecurityException(config.user + " does not require " + BIND_VPN_SERVICE);
            }
        } catch (RemoteException e) {
                throw new SecurityException("Cannot find " + config.user);
        } finally {
            Binder.restoreCallingIdentity(token);
        }

        // Save the old config in case we need to go back.
        VpnConfig oldConfig = mConfig;
        String oldInterface = mInterface;
        Connection oldConnection = mConnection;
        NetworkAgent oldNetworkAgent = mNetworkAgent;
        mNetworkAgent = null;
        Set<UidRange> oldUsers = mVpnUsers;

        // Configure the interface. Abort if any of these steps fails.
        ParcelFileDescriptor tun = ParcelFileDescriptor.adoptFd(jniCreate(config.mtu));
        try {
            updateState(DetailedState.CONNECTING, "establish");
            String interfaze = jniGetName(tun.getFd());

            // TEMP use the old jni calls until there is support for netd address setting
            StringBuilder builder = new StringBuilder();
            for (LinkAddress address : config.addresses) {
                builder.append(" " + address);
            }
            if (jniSetAddresses(interfaze, builder.toString()) < 1) {
                throw new IllegalArgumentException("At least one address must be specified");
            }
            Connection connection = new Connection();
            if (!mContext.bindServiceAsUser(intent, connection,
                    Context.BIND_AUTO_CREATE | Context.BIND_FOREGROUND_SERVICE,
                    new UserHandle(mUserHandle))) {
                throw new IllegalStateException("Cannot bind " + config.user);
            }

            mConnection = connection;
            mInterface = interfaze;

            // Fill more values.
            config.user = mPackage;
            config.interfaze = mInterface;
            config.startTime = SystemClock.elapsedRealtime();
            mConfig = config;

            // Set up forwarding and DNS rules.
            agentConnect();

            if (oldConnection != null) {
                mContext.unbindService(oldConnection);
            }
            // Remove the old tun's user forwarding rules
            // The new tun's user rules have already been added so they will take over
            // as rules are deleted. This prevents data leakage as the rules are moved over.
            agentDisconnect(oldNetworkAgent);
            if (oldInterface != null && !oldInterface.equals(interfaze)) {
                jniReset(oldInterface);
            }

            try {
                IoUtils.setBlocking(tun.getFileDescriptor(), config.blocking);
            } catch (IOException e) {
                throw new IllegalStateException(
                        "Cannot set tunnel's fd as blocking=" + config.blocking, e);
            }
        } catch (RuntimeException e) {
            IoUtils.closeQuietly(tun);
            agentDisconnect();
            // restore old state
            mConfig = oldConfig;
            mConnection = oldConnection;
            mVpnUsers = oldUsers;
            mNetworkAgent = oldNetworkAgent;
            mInterface = oldInterface;
            throw e;
        }
        Log.i(TAG, "Established by " + config.user + " on " + mInterface);
        return tun;
    }

    private boolean isRunningLocked() {
        return mNetworkAgent != null && mInterface != null;
    }

    // Returns true if the VPN has been established and the calling UID is its owner. Used to check
    // that a call to mutate VPN state is admissible.
    private boolean isCallerEstablishedOwnerLocked() {
        return isRunningLocked() && Binder.getCallingUid() == mOwnerUID;
    }

    // Note: Return type guarantees results are deduped and sorted, which callers require.
    private SortedSet<Integer> getAppsUids(List<String> packageNames, int userHandle) {
        SortedSet<Integer> uids = new TreeSet<Integer>();
        for (String app : packageNames) {
            int uid = getAppUid(app, userHandle);
            if (uid != -1) uids.add(uid);
        }
        return uids;
    }

    /**
     * Creates a {@link Set} of non-intersecting {@link UidRange} objects including all UIDs
     * associated with one user, and any restricted profiles attached to that user.
     *
     * <p>If one of {@param allowedApplications} or {@param disallowedApplications} is provided,
     * the UID ranges will match the app whitelist or blacklist specified there. Otherwise, all UIDs
     * in each user and profile will be included.
     *
     * @param userHandle The userId to create UID ranges for along with any of its restricted
     *                   profiles.
     * @param allowedApplications (optional) whitelist of applications to include.
     * @param disallowedApplications (optional) blacklist of applications to exclude.
     */
    @VisibleForTesting
    Set<UidRange> createUserAndRestrictedProfilesRanges(@UserIdInt int userHandle,
            @Nullable List<String> allowedApplications,
            @Nullable List<String> disallowedApplications) {
        final Set<UidRange> ranges = new ArraySet<>();

        // Assign the top-level user to the set of ranges
        addUserToRanges(ranges, userHandle, allowedApplications, disallowedApplications);

        // If the user can have restricted profiles, assign all its restricted profiles too
        if (canHaveRestrictedProfile(userHandle)) {
            final long token = Binder.clearCallingIdentity();
            List<UserInfo> users;
            try {
                users = UserManager.get(mContext).getUsers(true);
            } finally {
                Binder.restoreCallingIdentity(token);
            }
            for (UserInfo user : users) {
                if (user.isRestricted() && (user.restrictedProfileParentId == userHandle)) {
                    addUserToRanges(ranges, user.id, allowedApplications, disallowedApplications);
                }
            }
        }
        return ranges;
    }

    /**
     * Updates a {@link Set} of non-intersecting {@link UidRange} objects to include all UIDs
     * associated with one user.
     *
     * <p>If one of {@param allowedApplications} or {@param disallowedApplications} is provided,
     * the UID ranges will match the app whitelist or blacklist specified there. Otherwise, all UIDs
     * in the user will be included.
     *
     * @param ranges {@link Set} of {@link UidRange}s to which to add.
     * @param userHandle The userId to add to {@param ranges}.
     * @param allowedApplications (optional) whitelist of applications to include.
     * @param disallowedApplications (optional) blacklist of applications to exclude.
     */
    @VisibleForTesting
    void addUserToRanges(@NonNull Set<UidRange> ranges, @UserIdInt int userHandle,
            @Nullable List<String> allowedApplications,
            @Nullable List<String> disallowedApplications) {
        if (allowedApplications != null) {
            // Add ranges covering all UIDs for allowedApplications.
            int start = -1, stop = -1;
            for (int uid : getAppsUids(allowedApplications, userHandle)) {
                if (start == -1) {
                    start = uid;
                } else if (uid != stop + 1) {
                    ranges.add(new UidRange(start, stop));
                    start = uid;
                }
                stop = uid;
            }
            if (start != -1) ranges.add(new UidRange(start, stop));
        } else if (disallowedApplications != null) {
            // Add all ranges for user skipping UIDs for disallowedApplications.
            final UidRange userRange = UidRange.createForUser(userHandle);
            int start = userRange.start;
            for (int uid : getAppsUids(disallowedApplications, userHandle)) {
                if (uid == start) {
                    start++;
                } else {
                    ranges.add(new UidRange(start, uid - 1));
                    start = uid + 1;
                }
            }
            if (start <= userRange.stop) ranges.add(new UidRange(start, userRange.stop));
        } else {
            // Add all UIDs for the user.
            ranges.add(UidRange.createForUser(userHandle));
        }
    }

    // Returns the subset of the full list of active UID ranges the VPN applies to (mVpnUsers) that
    // apply to userHandle.
    private List<UidRange> uidRangesForUser(int userHandle) {
        final UidRange userRange = UidRange.createForUser(userHandle);
        final List<UidRange> ranges = new ArrayList<UidRange>();
        for (UidRange range : mVpnUsers) {
            if (userRange.containsRange(range)) {
                ranges.add(range);
            }
        }
        return ranges;
    }

    private void removeVpnUserLocked(int userHandle) {
        if (mVpnUsers == null) {
            throw new IllegalStateException("VPN is not active");
        }
        final List<UidRange> ranges = uidRangesForUser(userHandle);
        if (mNetworkAgent != null) {
            mNetworkAgent.removeUidRanges(ranges.toArray(new UidRange[ranges.size()]));
        }
        mVpnUsers.removeAll(ranges);
    }

    public void onUserAdded(int userHandle) {
        // If the user is restricted tie them to the parent user's VPN
        UserInfo user = UserManager.get(mContext).getUserInfo(userHandle);
        if (user.isRestricted() && user.restrictedProfileParentId == mUserHandle) {
            synchronized(Vpn.this) {
                if (mVpnUsers != null) {
                    try {
                        addUserToRanges(mVpnUsers, userHandle, mConfig.allowedApplications,
                                mConfig.disallowedApplications);
                        if (mNetworkAgent != null) {
                            final List<UidRange> ranges = uidRangesForUser(userHandle);
                            mNetworkAgent.addUidRanges(ranges.toArray(new UidRange[ranges.size()]));
                        }
                    } catch (Exception e) {
                        Log.wtf(TAG, "Failed to add restricted user to owner", e);
                    }
                }
                if (mAlwaysOn) {
                    setVpnForcedLocked(mLockdown);
                }
            }
        }
    }

    public void onUserRemoved(int userHandle) {
        // clean up if restricted
        UserInfo user = UserManager.get(mContext).getUserInfo(userHandle);
        if (user.isRestricted() && user.restrictedProfileParentId == mUserHandle) {
            synchronized(Vpn.this) {
                if (mVpnUsers != null) {
                    try {
                        removeVpnUserLocked(userHandle);
                    } catch (Exception e) {
                        Log.wtf(TAG, "Failed to remove restricted user to owner", e);
                    }
                }
                if (mAlwaysOn) {
                    setVpnForcedLocked(mLockdown);
                }
            }
        }
    }

    /**
     * Called when the user associated with this VPN has just been stopped.
     */
    public synchronized void onUserStopped() {
        // Switch off networking lockdown (if it was enabled)
        setVpnForcedLocked(false);
        mAlwaysOn = false;

        unregisterPackageChangeReceiverLocked();
        // Quit any active connections
        agentDisconnect();
    }

    /**
     * Restrict network access from all UIDs affected by this {@link Vpn}, apart from the VPN
     * service app itself, to only sockets that have had {@code protect()} called on them. All
     * non-VPN traffic is blocked via a {@code PROHIBIT} response from the kernel.
     *
     * The exception for the VPN UID isn't technically necessary -- setup should use protected
     * sockets -- but in practice it saves apps that don't protect their sockets from breaking.
     *
     * Calling multiple times with {@param enforce} = {@code true} will recreate the set of UIDs to
     * block every time, and if anything has changed update using {@link #setAllowOnlyVpnForUids}.
     *
     * @param enforce {@code true} to require that all traffic under the jurisdiction of this
     *                {@link Vpn} goes through a VPN connection or is blocked until one is
     *                available, {@code false} to lift the requirement.
     *
     * @see #mBlockedUsers
     */
    @GuardedBy("this")
    private void setVpnForcedLocked(boolean enforce) {
        final Set<UidRange> removedRanges = new ArraySet<>(mBlockedUsers);
        if (enforce) {
            final Set<UidRange> addedRanges = createUserAndRestrictedProfilesRanges(mUserHandle,
                    /* allowedApplications */ null,
                    /* disallowedApplications */ Collections.singletonList(mPackage));

            removedRanges.removeAll(addedRanges);
            addedRanges.removeAll(mBlockedUsers);

            setAllowOnlyVpnForUids(false, removedRanges);
            setAllowOnlyVpnForUids(true, addedRanges);
        } else {
            setAllowOnlyVpnForUids(false, removedRanges);
        }
    }

    /**
     * Either add or remove a list of {@link UidRange}s to the list of UIDs that are only allowed
     * to make connections through sockets that have had {@code protect()} called on them.
     *
     * @param enforce {@code true} to add to the blacklist, {@code false} to remove.
     * @param ranges {@link Collection} of {@link UidRange}s to add (if {@param enforce} is
     *               {@code true}) or to remove.
     * @return {@code true} if all of the UIDs were added/removed. {@code false} otherwise,
     *         including added ranges that already existed or removed ones that didn't.
     */
    @GuardedBy("this")
    private boolean setAllowOnlyVpnForUids(boolean enforce, Collection<UidRange> ranges) {
        if (ranges.size() == 0) {
            return true;
        }
        final UidRange[] rangesArray = ranges.toArray(new UidRange[ranges.size()]);
        try {
            mNetd.setAllowOnlyVpnForUids(enforce, rangesArray);
        } catch (RemoteException | RuntimeException e) {
            Log.e(TAG, "Updating blocked=" + enforce
                    + " for UIDs " + Arrays.toString(ranges.toArray()) + " failed", e);
            return false;
        }
        if (enforce) {
            mBlockedUsers.addAll(ranges);
        } else {
            mBlockedUsers.removeAll(ranges);
        }
        return true;
    }

    /**
     * Return the configuration of the currently running VPN.
     */
    public VpnConfig getVpnConfig() {
        enforceControlPermission();
        return mConfig;
    }

    @Deprecated
    public synchronized void interfaceStatusChanged(String iface, boolean up) {
        try {
            mObserver.interfaceStatusChanged(iface, up);
        } catch (RemoteException e) {
            // ignored; target is local
        }
    }

    private INetworkManagementEventObserver mObserver = new BaseNetworkObserver() {
        @Override
        public void interfaceStatusChanged(String interfaze, boolean up) {
            synchronized (Vpn.this) {
                if (!up && mLegacyVpnRunner != null) {
                    mLegacyVpnRunner.check(interfaze);
                }
            }
        }

        @Override
        public void interfaceRemoved(String interfaze) {
            synchronized (Vpn.this) {
                if (interfaze.equals(mInterface) && jniCheck(interfaze) == 0) {
                    mStatusIntent = null;
                    mVpnUsers = null;
                    mConfig = null;
                    mInterface = null;
                    if (mConnection != null) {
                        mContext.unbindService(mConnection);
                        mConnection = null;
                        agentDisconnect();
                    } else if (mLegacyVpnRunner != null) {
                        mLegacyVpnRunner.exit();
                        mLegacyVpnRunner = null;
                    }
                }
            }
        }
    };

    private void enforceControlPermission() {
        mContext.enforceCallingPermission(Manifest.permission.CONTROL_VPN, "Unauthorized Caller");
    }

    private void enforceControlPermissionOrInternalCaller() {
        // Require caller to be either an application with CONTROL_VPN permission or a process
        // in the system server.
        mContext.enforceCallingOrSelfPermission(Manifest.permission.CONTROL_VPN,
                "Unauthorized Caller");
    }

    private class Connection implements ServiceConnection {
        private IBinder mService;

        @Override
        public void onServiceConnected(ComponentName name, IBinder service) {
            mService = service;
        }

        @Override
        public void onServiceDisconnected(ComponentName name) {
            mService = null;
        }
    }

    private void prepareStatusIntent() {
        final long token = Binder.clearCallingIdentity();
        try {
            mStatusIntent = VpnConfig.getIntentForStatusPanel(mContext);
        } finally {
            Binder.restoreCallingIdentity(token);
        }
    }

    public synchronized boolean addAddress(String address, int prefixLength) {
        if (!isCallerEstablishedOwnerLocked()) {
            return false;
        }
        boolean success = jniAddAddress(mInterface, address, prefixLength);
        mNetworkAgent.sendLinkProperties(makeLinkProperties());
        return success;
    }

    public synchronized boolean removeAddress(String address, int prefixLength) {
        if (!isCallerEstablishedOwnerLocked()) {
            return false;
        }
        boolean success = jniDelAddress(mInterface, address, prefixLength);
        mNetworkAgent.sendLinkProperties(makeLinkProperties());
        return success;
    }

    public synchronized boolean setUnderlyingNetworks(Network[] networks) {
        if (!isCallerEstablishedOwnerLocked()) {
            return false;
        }
        if (networks == null) {
            mConfig.underlyingNetworks = null;
        } else {
            mConfig.underlyingNetworks = new Network[networks.length];
            for (int i = 0; i < networks.length; ++i) {
                if (networks[i] == null) {
                    mConfig.underlyingNetworks[i] = null;
                } else {
                    mConfig.underlyingNetworks[i] = new Network(networks[i].netId);
                }
            }
        }
        return true;
    }

    public synchronized Network[] getUnderlyingNetworks() {
        if (!isRunningLocked()) {
            return null;
        }
        return mConfig.underlyingNetworks;
    }

    /**
     * This method should only be called by ConnectivityService. Because it doesn't
     * have enough data to fill VpnInfo.primaryUnderlyingIface field.
     */
    public synchronized VpnInfo getVpnInfo() {
        if (!isRunningLocked()) {
            return null;
        }

        VpnInfo info = new VpnInfo();
        info.ownerUid = mOwnerUID;
        info.vpnIface = mInterface;
        return info;
    }

    public synchronized boolean appliesToUid(int uid) {
        if (!isRunningLocked()) {
            return false;
        }
        for (UidRange uidRange : mVpnUsers) {
            if (uidRange.contains(uid)) {
                return true;
            }
        }
        return false;
    }

    /**
     * @return {@code true} if {@param uid} is blocked by an always-on VPN.
     *         A UID is blocked if it's included in one of the mBlockedUsers ranges and the VPN is
     *         not connected, or if the VPN is connected but does not apply to the UID.
     *
     * @see #mBlockedUsers
     */
    public synchronized boolean isBlockingUid(int uid) {
        if (!mLockdown) {
            return false;
        }

        if (mNetworkInfo.isConnected()) {
            return !appliesToUid(uid);
        } else {
            for (UidRange uidRange : mBlockedUsers) {
                if (uidRange.contains(uid)) {
                    return true;
                }
            }
            return false;
        }
    }

    private void updateAlwaysOnNotification(DetailedState networkState) {
        final boolean visible = (mAlwaysOn && networkState != DetailedState.CONNECTED);

        final UserHandle user = UserHandle.of(mUserHandle);
        final long token = Binder.clearCallingIdentity();
        try {
            final NotificationManager notificationManager = NotificationManager.from(mContext);
            if (!visible) {
                notificationManager.cancelAsUser(TAG, SystemMessage.NOTE_VPN_DISCONNECTED, user);
                return;
            }
            final Intent intent = new Intent(Settings.ACTION_VPN_SETTINGS);
            final PendingIntent configIntent = mSystemServices.pendingIntentGetActivityAsUser(
                    intent, PendingIntent.FLAG_IMMUTABLE | PendingIntent.FLAG_UPDATE_CURRENT, user);
            final Notification.Builder builder =
                    new Notification.Builder(mContext, SystemNotificationChannels.VPN)
                            .setSmallIcon(R.drawable.vpn_connected)
                            .setContentTitle(mContext.getString(R.string.vpn_lockdown_disconnected))
                            .setContentText(mContext.getString(R.string.vpn_lockdown_config))
                            .setContentIntent(configIntent)
                            .setCategory(Notification.CATEGORY_SYSTEM)
                            .setVisibility(Notification.VISIBILITY_PUBLIC)
                            .setOngoing(true)
                            .setColor(mContext.getColor(R.color.system_notification_accent_color));
            notificationManager.notifyAsUser(TAG, SystemMessage.NOTE_VPN_DISCONNECTED,
                    builder.build(), user);
        } finally {
            Binder.restoreCallingIdentity(token);
        }
    }

    /**
     * Facade for system service calls that change, or depend on, state outside of
     * {@link ConnectivityService} and have hard-to-mock interfaces.
     *
     * @see com.android.server.connectivity.VpnTest
     */
    @VisibleForTesting
    public static class SystemServices {
        private final Context mContext;

        public SystemServices(@NonNull Context context) {
            mContext = context;
        }

        /**
         * @see PendingIntent#getActivityAsUser()
         */
        public PendingIntent pendingIntentGetActivityAsUser(
                Intent intent, int flags, UserHandle user) {
            return PendingIntent.getActivityAsUser(mContext, 0 /*request*/, intent, flags,
                    null /*options*/, user);
        }

        /**
         * @see Settings.Secure#putStringForUser
         */
        public void settingsSecurePutStringForUser(String key, String value, int userId) {
            Settings.Secure.putStringForUser(mContext.getContentResolver(), key, value, userId);
        }

        /**
         * @see Settings.Secure#putIntForUser
         */
        public void settingsSecurePutIntForUser(String key, int value, int userId) {
            Settings.Secure.putIntForUser(mContext.getContentResolver(), key, value, userId);
        }

        /**
         * @see Settings.Secure#getStringForUser
         */
        public String settingsSecureGetStringForUser(String key, int userId) {
            return Settings.Secure.getStringForUser(mContext.getContentResolver(), key, userId);
        }

        /**
         * @see Settings.Secure#getIntForUser
         */
        public int settingsSecureGetIntForUser(String key, int def, int userId) {
            return Settings.Secure.getIntForUser(mContext.getContentResolver(), key, def, userId);
        }
    }

    private native int jniCreate(int mtu);
    private native String jniGetName(int tun);
    private native int jniSetAddresses(String interfaze, String addresses);
    private native void jniReset(String interfaze);
    private native int jniCheck(String interfaze);
    private native boolean jniAddAddress(String interfaze, String address, int prefixLen);
    private native boolean jniDelAddress(String interfaze, String address, int prefixLen);

    private static RouteInfo findIPv4DefaultRoute(LinkProperties prop) {
        for (RouteInfo route : prop.getAllRoutes()) {
            // Currently legacy VPN only works on IPv4.
            if (route.isDefaultRoute() && route.getGateway() instanceof Inet4Address) {
                return route;
            }
        }

        throw new IllegalStateException("Unable to find IPv4 default gateway");
    }

    /**
     * Start legacy VPN, controlling native daemons as needed. Creates a
     * secondary thread to perform connection work, returning quickly.
     *
     * Should only be called to respond to Binder requests as this enforces caller permission. Use
     * {@link #startLegacyVpnPrivileged(VpnProfile, KeyStore, LinkProperties)} to skip the
     * permission check only when the caller is trusted (or the call is initiated by the system).
     */
    public void startLegacyVpn(VpnProfile profile, KeyStore keyStore, LinkProperties egress) {
        enforceControlPermission();
        long token = Binder.clearCallingIdentity();
        try {
            startLegacyVpnPrivileged(profile, keyStore, egress);
        } finally {
            Binder.restoreCallingIdentity(token);
        }
    }

    /**
     * Like {@link #startLegacyVpn(VpnProfile, KeyStore, LinkProperties)}, but does not check
     * permissions under the assumption that the caller is the system.
     *
     * Callers are responsible for checking permissions if needed.
     */
    public void startLegacyVpnPrivileged(VpnProfile profile, KeyStore keyStore,
            LinkProperties egress) {
        UserManager mgr = UserManager.get(mContext);
        UserInfo user = mgr.getUserInfo(mUserHandle);
        if (user.isRestricted() || mgr.hasUserRestriction(UserManager.DISALLOW_CONFIG_VPN,
                    new UserHandle(mUserHandle))) {
            throw new SecurityException("Restricted users cannot establish VPNs");
        }

        final RouteInfo ipv4DefaultRoute = findIPv4DefaultRoute(egress);
        final String gateway = ipv4DefaultRoute.getGateway().getHostAddress();
        final String iface = ipv4DefaultRoute.getInterface();

        // Load certificates.
        String privateKey = "";
        String userCert = "";
        String caCert = "";
        String serverCert = "";
        if (!profile.ipsecUserCert.isEmpty()) {
            privateKey = Credentials.USER_PRIVATE_KEY + profile.ipsecUserCert;
            byte[] value = keyStore.get(Credentials.USER_CERTIFICATE + profile.ipsecUserCert);
            userCert = (value == null) ? null : new String(value, StandardCharsets.UTF_8);
        }
        if (!profile.ipsecCaCert.isEmpty()) {
            byte[] value = keyStore.get(Credentials.CA_CERTIFICATE + profile.ipsecCaCert);
            caCert = (value == null) ? null : new String(value, StandardCharsets.UTF_8);
        }
        if (!profile.ipsecServerCert.isEmpty()) {
            byte[] value = keyStore.get(Credentials.USER_CERTIFICATE + profile.ipsecServerCert);
            serverCert = (value == null) ? null : new String(value, StandardCharsets.UTF_8);
        }
        if (privateKey == null || userCert == null || caCert == null || serverCert == null) {
            throw new IllegalStateException("Cannot load credentials");
        }

        // Prepare arguments for racoon.
        String[] racoon = null;
        switch (profile.type) {
            case VpnProfile.TYPE_L2TP_IPSEC_PSK:
                racoon = new String[] {
                    iface, profile.server, "udppsk", profile.ipsecIdentifier,
                    profile.ipsecSecret, "1701",
                };
                break;
            case VpnProfile.TYPE_L2TP_IPSEC_RSA:
                racoon = new String[] {
                    iface, profile.server, "udprsa", privateKey, userCert,
                    caCert, serverCert, "1701",
                };
                break;
            case VpnProfile.TYPE_IPSEC_XAUTH_PSK:
                racoon = new String[] {
                    iface, profile.server, "xauthpsk", profile.ipsecIdentifier,
                    profile.ipsecSecret, profile.username, profile.password, "", gateway,
                };
                break;
            case VpnProfile.TYPE_IPSEC_XAUTH_RSA:
                racoon = new String[] {
                    iface, profile.server, "xauthrsa", privateKey, userCert,
                    caCert, serverCert, profile.username, profile.password, "", gateway,
                };
                break;
            case VpnProfile.TYPE_IPSEC_HYBRID_RSA:
                racoon = new String[] {
                    iface, profile.server, "hybridrsa",
                    caCert, serverCert, profile.username, profile.password, "", gateway,
                };
                break;
        }

        // Prepare arguments for mtpd.
        String[] mtpd = null;
        switch (profile.type) {
            case VpnProfile.TYPE_PPTP:
                mtpd = new String[] {
                    iface, "pptp", profile.server, "1723",
                    "name", profile.username, "password", profile.password,
                    "linkname", "vpn", "refuse-eap", "nodefaultroute",
                    "usepeerdns", "idle", "1800", "mtu", "1400", "mru", "1400",
                    (profile.mppe ? "+mppe" : "nomppe"),
                };
                break;
            case VpnProfile.TYPE_L2TP_IPSEC_PSK:
            case VpnProfile.TYPE_L2TP_IPSEC_RSA:
                mtpd = new String[] {
                    iface, "l2tp", profile.server, "1701", profile.l2tpSecret,
                    "name", profile.username, "password", profile.password,
                    "linkname", "vpn", "refuse-eap", "nodefaultroute",
                    "usepeerdns", "idle", "1800", "mtu", "1400", "mru", "1400",
                };
                break;
        }

        VpnConfig config = new VpnConfig();
        config.legacy = true;
        config.user = profile.key;
        config.interfaze = iface;
        config.session = profile.name;

        config.addLegacyRoutes(profile.routes);
        if (!profile.dnsServers.isEmpty()) {
            config.dnsServers = Arrays.asList(profile.dnsServers.split(" +"));
        }
        if (!profile.searchDomains.isEmpty()) {
            config.searchDomains = Arrays.asList(profile.searchDomains.split(" +"));
        }
        startLegacyVpn(config, racoon, mtpd);
    }

    private synchronized void startLegacyVpn(VpnConfig config, String[] racoon, String[] mtpd) {
        stopLegacyVpnPrivileged();

        // Prepare for the new request.
        prepareInternal(VpnConfig.LEGACY_VPN);
        updateState(DetailedState.CONNECTING, "startLegacyVpn");

        // Start a new LegacyVpnRunner and we are done!
        mLegacyVpnRunner = new LegacyVpnRunner(config, racoon, mtpd);
        mLegacyVpnRunner.start();
    }

    /** Stop legacy VPN. Permissions must be checked by callers. */
    public synchronized void stopLegacyVpnPrivileged() {
        if (mLegacyVpnRunner != null) {
            mLegacyVpnRunner.exit();
            mLegacyVpnRunner = null;

            synchronized (LegacyVpnRunner.TAG) {
                // wait for old thread to completely finish before spinning up
                // new instance, otherwise state updates can be out of order.
            }
        }
    }

    /**
     * Return the information of the current ongoing legacy VPN.
     */
    public synchronized LegacyVpnInfo getLegacyVpnInfo() {
        // Check if the caller is authorized.
        enforceControlPermission();
        return getLegacyVpnInfoPrivileged();
    }

    /**
     * Return the information of the current ongoing legacy VPN.
     * Callers are responsible for checking permissions if needed.
     */
    public synchronized LegacyVpnInfo getLegacyVpnInfoPrivileged() {
        if (mLegacyVpnRunner == null) return null;

        final LegacyVpnInfo info = new LegacyVpnInfo();
        info.key = mConfig.user;
        info.state = LegacyVpnInfo.stateFromNetworkInfo(mNetworkInfo);
        if (mNetworkInfo.isConnected()) {
            info.intent = mStatusIntent;
        }
        return info;
    }

    public VpnConfig getLegacyVpnConfig() {
        if (mLegacyVpnRunner != null) {
            return mConfig;
        } else {
            return null;
        }
    }

    /**
     * Bringing up a VPN connection takes time, and that is all this thread
     * does. Here we have plenty of time. The only thing we need to take
     * care of is responding to interruptions as soon as possible. Otherwise
     * requests will be piled up. This can be done in a Handler as a state
     * machine, but it is much easier to read in the current form.
     */
    private class LegacyVpnRunner extends Thread {
        private static final String TAG = "LegacyVpnRunner";

        private final String[] mDaemons;
        private final String[][] mArguments;
        private final LocalSocket[] mSockets;
        private final String mOuterInterface;
        private final AtomicInteger mOuterConnection =
                new AtomicInteger(ConnectivityManager.TYPE_NONE);

        private long mTimer = -1;

        /**
         * Watch for the outer connection (passing in the constructor) going away.
         */
        private final BroadcastReceiver mBroadcastReceiver = new BroadcastReceiver() {
            @Override
            public void onReceive(Context context, Intent intent) {
                if (!mEnableTeardown) return;

                if (intent.getAction().equals(ConnectivityManager.CONNECTIVITY_ACTION)) {
                    if (intent.getIntExtra(ConnectivityManager.EXTRA_NETWORK_TYPE,
                            ConnectivityManager.TYPE_NONE) == mOuterConnection.get()) {
                        NetworkInfo info = (NetworkInfo)intent.getExtra(
                                ConnectivityManager.EXTRA_NETWORK_INFO);
                        if (info != null && !info.isConnectedOrConnecting()) {
                            try {
                                mObserver.interfaceStatusChanged(mOuterInterface, false);
                            } catch (RemoteException e) {}
                        }
                    }
                }
            }
        };

        public LegacyVpnRunner(VpnConfig config, String[] racoon, String[] mtpd) {
            super(TAG);
            mConfig = config;
            mDaemons = new String[] {"racoon", "mtpd"};
            // TODO: clear arguments from memory once launched
            mArguments = new String[][] {racoon, mtpd};
            mSockets = new LocalSocket[mDaemons.length];

            // This is the interface which VPN is running on,
            // mConfig.interfaze will change to point to OUR
            // internal interface soon. TODO - add inner/outer to mconfig
            // TODO - we have a race - if the outer iface goes away/disconnects before we hit this
            // we will leave the VPN up.  We should check that it's still there/connected after
            // registering
            mOuterInterface = mConfig.interfaze;

            if (!TextUtils.isEmpty(mOuterInterface)) {
                final ConnectivityManager cm = ConnectivityManager.from(mContext);
                for (Network network : cm.getAllNetworks()) {
                    final LinkProperties lp = cm.getLinkProperties(network);
                    if (lp != null && lp.getAllInterfaceNames().contains(mOuterInterface)) {
                        final NetworkInfo networkInfo = cm.getNetworkInfo(network);
                        if (networkInfo != null) mOuterConnection.set(networkInfo.getType());
                    }
                }
            }

            IntentFilter filter = new IntentFilter();
            filter.addAction(ConnectivityManager.CONNECTIVITY_ACTION);
            mContext.registerReceiver(mBroadcastReceiver, filter);
        }

        public void check(String interfaze) {
            if (interfaze.equals(mOuterInterface)) {
                Log.i(TAG, "Legacy VPN is going down with " + interfaze);
                exit();
            }
        }

        public void exit() {
            // We assume that everything is reset after stopping the daemons.
            interrupt();
            agentDisconnect();
            try {
                mContext.unregisterReceiver(mBroadcastReceiver);
            } catch (IllegalArgumentException e) {}
        }

        @Override
        public void run() {
            // Wait for the previous thread since it has been interrupted.
            Log.v(TAG, "Waiting");
            synchronized (TAG) {
                Log.v(TAG, "Executing");
                try {
                    execute();
                    monitorDaemons();
                    interrupted(); // Clear interrupt flag if execute called exit.
                } catch (InterruptedException e) {
                } finally {
                    for (LocalSocket socket : mSockets) {
                        IoUtils.closeQuietly(socket);
                    }
                    // This sleep is necessary for racoon to successfully complete sending delete
                    // message to server.
                    try {
                        Thread.sleep(50);
                    } catch (InterruptedException e) {
                    }
                    for (String daemon : mDaemons) {
                        SystemService.stop(daemon);
                    }
                }
                agentDisconnect();
            }
        }

        private void checkpoint(boolean yield) throws InterruptedException {
            long now = SystemClock.elapsedRealtime();
            if (mTimer == -1) {
                mTimer = now;
                Thread.sleep(1);
            } else if (now - mTimer <= 60000) {
                Thread.sleep(yield ? 200 : 1);
            } else {
                updateState(DetailedState.FAILED, "checkpoint");
                throw new IllegalStateException("Time is up");
            }
        }

        private void execute() {
            // Catch all exceptions so we can clean up few things.
            boolean initFinished = false;
            try {
                // Initialize the timer.
                checkpoint(false);

                // Wait for the daemons to stop.
                for (String daemon : mDaemons) {
                    while (!SystemService.isStopped(daemon)) {
                        checkpoint(true);
                    }
                }

                // Clear the previous state.
                File state = new File("/data/misc/vpn/state");
                state.delete();
                if (state.exists()) {
                    throw new IllegalStateException("Cannot delete the state");
                }
                new File("/data/misc/vpn/abort").delete();
                initFinished = true;

                // Check if we need to restart any of the daemons.
                boolean restart = false;
                for (String[] arguments : mArguments) {
                    restart = restart || (arguments != null);
                }
                if (!restart) {
                    agentDisconnect();
                    return;
                }
                updateState(DetailedState.CONNECTING, "execute");

                // Start the daemon with arguments.
                for (int i = 0; i < mDaemons.length; ++i) {
                    String[] arguments = mArguments[i];
                    if (arguments == null) {
                        continue;
                    }

                    // Start the daemon.
                    String daemon = mDaemons[i];
                    SystemService.start(daemon);

                    // Wait for the daemon to start.
                    while (!SystemService.isRunning(daemon)) {
                        checkpoint(true);
                    }

                    // Create the control socket.
                    mSockets[i] = new LocalSocket();
                    LocalSocketAddress address = new LocalSocketAddress(
                            daemon, LocalSocketAddress.Namespace.RESERVED);

                    // Wait for the socket to connect.
                    while (true) {
                        try {
                            mSockets[i].connect(address);
                            break;
                        } catch (Exception e) {
                            // ignore
                        }
                        checkpoint(true);
                    }
                    mSockets[i].setSoTimeout(500);

                    // Send over the arguments.
                    OutputStream out = mSockets[i].getOutputStream();
                    for (String argument : arguments) {
                        byte[] bytes = argument.getBytes(StandardCharsets.UTF_8);
                        if (bytes.length >= 0xFFFF) {
                            throw new IllegalArgumentException("Argument is too large");
                        }
                        out.write(bytes.length >> 8);
                        out.write(bytes.length);
                        out.write(bytes);
                        checkpoint(false);
                    }
                    out.write(0xFF);
                    out.write(0xFF);
                    out.flush();

                    // Wait for End-of-File.
                    InputStream in = mSockets[i].getInputStream();
                    while (true) {
                        try {
                            if (in.read() == -1) {
                                break;
                            }
                        } catch (Exception e) {
                            // ignore
                        }
                        checkpoint(true);
                    }
                }

                // Wait for the daemons to create the new state.
                while (!state.exists()) {
                    // Check if a running daemon is dead.
                    for (int i = 0; i < mDaemons.length; ++i) {
                        String daemon = mDaemons[i];
                        if (mArguments[i] != null && !SystemService.isRunning(daemon)) {
                            throw new IllegalStateException(daemon + " is dead");
                        }
                    }
                    checkpoint(true);
                }

                // Now we are connected. Read and parse the new state.
                String[] parameters = FileUtils.readTextFile(state, 0, null).split("\n", -1);
                if (parameters.length != 7) {
                    throw new IllegalStateException("Cannot parse the state");
                }

                // Set the interface and the addresses in the config.
                mConfig.interfaze = parameters[0].trim();

                mConfig.addLegacyAddresses(parameters[1]);
                // Set the routes if they are not set in the config.
                if (mConfig.routes == null || mConfig.routes.isEmpty()) {
                    mConfig.addLegacyRoutes(parameters[2]);
                }

                // Set the DNS servers if they are not set in the config.
                if (mConfig.dnsServers == null || mConfig.dnsServers.size() == 0) {
                    String dnsServers = parameters[3].trim();
                    if (!dnsServers.isEmpty()) {
                        mConfig.dnsServers = Arrays.asList(dnsServers.split(" "));
                    }
                }

                // Set the search domains if they are not set in the config.
                if (mConfig.searchDomains == null || mConfig.searchDomains.size() == 0) {
                    String searchDomains = parameters[4].trim();
                    if (!searchDomains.isEmpty()) {
                        mConfig.searchDomains = Arrays.asList(searchDomains.split(" "));
                    }
                }

                // Add a throw route for the VPN server endpoint, if one was specified.
                String endpoint = parameters[5];
                if (!endpoint.isEmpty()) {
                    try {
                        InetAddress addr = InetAddress.parseNumericAddress(endpoint);
                        if (addr instanceof Inet4Address) {
                            mConfig.routes.add(new RouteInfo(new IpPrefix(addr, 32), RTN_THROW));
                        } else if (addr instanceof Inet6Address) {
                            mConfig.routes.add(new RouteInfo(new IpPrefix(addr, 128), RTN_THROW));
                        } else {
                            Log.e(TAG, "Unknown IP address family for VPN endpoint: " + endpoint);
                        }
                    } catch (IllegalArgumentException e) {
                        Log.e(TAG, "Exception constructing throw route to " + endpoint + ": " + e);
                    }
                }

                // Here is the last step and it must be done synchronously.
                synchronized (Vpn.this) {
                    // Set the start time
                    mConfig.startTime = SystemClock.elapsedRealtime();

                    // Check if the thread is interrupted while we are waiting.
                    checkpoint(false);

                    // Check if the interface is gone while we are waiting.
                    if (jniCheck(mConfig.interfaze) == 0) {
                        throw new IllegalStateException(mConfig.interfaze + " is gone");
                    }

                    // Now INetworkManagementEventObserver is watching our back.
                    mInterface = mConfig.interfaze;
                    prepareStatusIntent();

                    agentConnect();

                    Log.i(TAG, "Connected!");
                }
            } catch (Exception e) {
                Log.i(TAG, "Aborting", e);
                updateState(DetailedState.FAILED, e.getMessage());
                exit();
            }
        }

        /**
         * Monitor the daemons we started, moving to disconnected state if the
         * underlying services fail.
         */
        private void monitorDaemons() throws InterruptedException{
            if (!mNetworkInfo.isConnected()) {
                return;
            }
            while (true) {
                Thread.sleep(2000);
                for (int i = 0; i < mDaemons.length; i++) {
                    if (mArguments[i] != null && SystemService.isStopped(mDaemons[i])) {
                        return;
                    }
                }
            }
        }
    }
}