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/*
* 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 android.net;
import static android.system.OsConstants.AF_INET;
import static android.system.OsConstants.AF_INET6;
import android.annotation.RequiresPermission;
import android.annotation.SystemApi;
import android.app.Activity;
import android.app.PendingIntent;
import android.app.Service;
import android.content.Context;
import android.content.Intent;
import android.content.pm.IPackageManager;
import android.content.pm.PackageManager;
import android.os.Binder;
import android.os.IBinder;
import android.os.Parcel;
import android.os.ParcelFileDescriptor;
import android.os.RemoteException;
import android.os.ServiceManager;
import android.os.UserHandle;
import com.android.internal.net.VpnConfig;
import java.net.DatagramSocket;
import java.net.Inet4Address;
import java.net.Inet6Address;
import java.net.InetAddress;
import java.net.Socket;
import java.util.ArrayList;
import java.util.List;
/**
* VpnService is a base class for applications to extend and build their
* own VPN solutions. In general, it creates a virtual network interface,
* configures addresses and routing rules, and returns a file descriptor
* to the application. Each read from the descriptor retrieves an outgoing
* packet which was routed to the interface. Each write to the descriptor
* injects an incoming packet just like it was received from the interface.
* The interface is running on Internet Protocol (IP), so packets are
* always started with IP headers. The application then completes a VPN
* connection by processing and exchanging packets with the remote server
* over a tunnel.
*
* Letting applications intercept packets raises huge security concerns.
* A VPN application can easily break the network. Besides, two of them may
* conflict with each other. The system takes several actions to address
* these issues. Here are some key points:
*
* - User action is required the first time an application creates a VPN
* connection.
* - There can be only one VPN connection running at the same time. The
* existing interface is deactivated when a new one is created.
* - A system-managed notification is shown during the lifetime of a
* VPN connection.
* - A system-managed dialog gives the information of the current VPN
* connection. It also provides a button to disconnect.
* - The network is restored automatically when the file descriptor is
* closed. It also covers the cases when a VPN application is crashed
* or killed by the system.
*
*
* There are two primary methods in this class: {@link #prepare} and
* {@link Builder#establish}. The former deals with user action and stops
* the VPN connection created by another application. The latter creates
* a VPN interface using the parameters supplied to the {@link Builder}.
* An application must call {@link #prepare} to grant the right to use
* other methods in this class, and the right can be revoked at any time.
* Here are the general steps to create a VPN connection:
*
* - When the user presses the button to connect, call {@link #prepare}
* and launch the returned intent, if non-null.
* - When the application becomes prepared, start the service.
* - Create a tunnel to the remote server and negotiate the network
* parameters for the VPN connection.
* - Supply those parameters to a {@link Builder} and create a VPN
* interface by calling {@link Builder#establish}.
* - Process and exchange packets between the tunnel and the returned
* file descriptor.
* - When {@link #onRevoke} is invoked, close the file descriptor and
* shut down the tunnel gracefully.
*
*
* Services extending this class need to be declared with an appropriate
* permission and intent filter. Their access must be secured by
* {@link android.Manifest.permission#BIND_VPN_SERVICE} permission, and
* their intent filter must match {@link #SERVICE_INTERFACE} action. Here
* is an example of declaring a VPN service in {@code AndroidManifest.xml}:
*
* <service android:name=".ExampleVpnService"
* android:permission="android.permission.BIND_VPN_SERVICE">
* <intent-filter>
* <action android:name="android.net.VpnService"/>
* </intent-filter>
* </service>
*
* The Android system starts a VPN in the background by calling
* {@link android.content.Context#startService startService()}. In Android 8.0
* (API level 26) and higher, the system places VPN apps on the temporary
* whitelist for a short period so the app can start in the background. The VPN
* app must promote itself to the foreground after it's launched or the system
* will shut down the app.
*
* @see Builder
*/
public class VpnService extends Service {
/**
* The action must be matched by the intent filter of this service. It also
* needs to require {@link android.Manifest.permission#BIND_VPN_SERVICE}
* permission so that other applications cannot abuse it.
*/
public static final String SERVICE_INTERFACE = VpnConfig.SERVICE_INTERFACE;
/**
* Key for boolean meta-data field indicating whether this VpnService supports always-on mode.
*
*
For a VPN app targeting {@link android.os.Build.VERSION_CODES#N API 24} or above, Android
* provides users with the ability to set it as always-on, so that VPN connection is
* persisted after device reboot and app upgrade. Always-on VPN can also be enabled by device
* owner and profile owner apps through
* {@link android.app.admin.DevicePolicyManager#setAlwaysOnVpnPackage}.
*
*
VPN apps not supporting this feature should opt out by adding this meta-data field to the
* {@code VpnService} component of {@code AndroidManifest.xml}. In case there is more than one
* {@code VpnService} component defined in {@code AndroidManifest.xml}, opting out any one of
* them will opt out the entire app. For example,
*
{@code
*
*
*
*
*
* }
*
* This meta-data field defaults to {@code true} if absent. It will only have effect on
* {@link android.os.Build.VERSION_CODES#O_MR1} or higher.
*/
public static final String SERVICE_META_DATA_SUPPORTS_ALWAYS_ON =
"android.net.VpnService.SUPPORTS_ALWAYS_ON";
/**
* Use IConnectivityManager since those methods are hidden and not
* available in ConnectivityManager.
*/
private static IConnectivityManager getService() {
return IConnectivityManager.Stub.asInterface(
ServiceManager.getService(Context.CONNECTIVITY_SERVICE));
}
/**
* Prepare to establish a VPN connection. This method returns {@code null}
* if the VPN application is already prepared or if the user has previously
* consented to the VPN application. Otherwise, it returns an
* {@link Intent} to a system activity. The application should launch the
* activity using {@link Activity#startActivityForResult} to get itself
* prepared. The activity may pop up a dialog to require user action, and
* the result will come back via its {@link Activity#onActivityResult}.
* If the result is {@link Activity#RESULT_OK}, the application becomes
* prepared and is granted to use other methods in this class.
*
*
Only one application can be granted at the same time. The right
* is revoked when another application is granted. The application
* losing the right will be notified via its {@link #onRevoke}. Unless
* it becomes prepared again, subsequent calls to other methods in this
* class will fail.
*
*
The user may disable the VPN at any time while it is activated, in
* which case this method will return an intent the next time it is
* executed to obtain the user's consent again.
*
* @see #onRevoke
*/
public static Intent prepare(Context context) {
try {
if (getService().prepareVpn(context.getPackageName(), null, context.getUserId())) {
return null;
}
} catch (RemoteException e) {
// ignore
}
return VpnConfig.getIntentForConfirmation();
}
/**
* Version of {@link #prepare(Context)} which does not require user consent.
*
*
Requires {@link android.Manifest.permission#CONTROL_VPN} and should generally not be
* used. Only acceptable in situations where user consent has been obtained through other means.
*
*
Once this is run, future preparations may be done with the standard prepare method as this
* will authorize the package to prepare the VPN without consent in the future.
*
* @hide
*/
@SystemApi
@RequiresPermission(android.Manifest.permission.CONTROL_VPN)
public static void prepareAndAuthorize(Context context) {
IConnectivityManager cm = getService();
String packageName = context.getPackageName();
try {
// Only prepare if we're not already prepared.
int userId = context.getUserId();
if (!cm.prepareVpn(packageName, null, userId)) {
cm.prepareVpn(null, packageName, userId);
}
cm.setVpnPackageAuthorization(packageName, userId, true);
} catch (RemoteException e) {
// ignore
}
}
/**
* Protect a socket from VPN connections. After protecting, data sent
* through this socket will go directly to the underlying network,
* so its traffic will not be forwarded through the VPN.
* This method is useful if some connections need to be kept
* outside of VPN. For example, a VPN tunnel should protect itself if its
* destination is covered by VPN routes. Otherwise its outgoing packets
* will be sent back to the VPN interface and cause an infinite loop. This
* method will fail if the application is not prepared or is revoked.
*
*
The socket is NOT closed by this method.
*
* @return {@code true} on success.
*/
public boolean protect(int socket) {
return NetworkUtils.protectFromVpn(socket);
}
/**
* Convenience method to protect a {@link Socket} from VPN connections.
*
* @return {@code true} on success.
* @see #protect(int)
*/
public boolean protect(Socket socket) {
return protect(socket.getFileDescriptor$().getInt$());
}
/**
* Convenience method to protect a {@link DatagramSocket} from VPN
* connections.
*
* @return {@code true} on success.
* @see #protect(int)
*/
public boolean protect(DatagramSocket socket) {
return protect(socket.getFileDescriptor$().getInt$());
}
/**
* Adds a network address to the VPN interface.
*
* Both IPv4 and IPv6 addresses are supported. The VPN must already be established. Fails if the
* address is already in use or cannot be assigned to the interface for any other reason.
*
* Adding an address implicitly allows traffic from that address family (i.e., IPv4 or IPv6) to
* be routed over the VPN. @see Builder#allowFamily
*
* @throws IllegalArgumentException if the address is invalid.
*
* @param address The IP address (IPv4 or IPv6) to assign to the VPN interface.
* @param prefixLength The prefix length of the address.
*
* @return {@code true} on success.
* @see Builder#addAddress
*
* @hide
*/
public boolean addAddress(InetAddress address, int prefixLength) {
check(address, prefixLength);
try {
return getService().addVpnAddress(address.getHostAddress(), prefixLength);
} catch (RemoteException e) {
throw new IllegalStateException(e);
}
}
/**
* Removes a network address from the VPN interface.
*
* Both IPv4 and IPv6 addresses are supported. The VPN must already be established. Fails if the
* address is not assigned to the VPN interface, or if it is the only address assigned (thus
* cannot be removed), or if the address cannot be removed for any other reason.
*
* After removing an address, if there are no addresses, routes or DNS servers of a particular
* address family (i.e., IPv4 or IPv6) configured on the VPN, that DOES NOT block that
* family from being routed. In other words, once an address family has been allowed, it stays
* allowed for the rest of the VPN's session. @see Builder#allowFamily
*
* @throws IllegalArgumentException if the address is invalid.
*
* @param address The IP address (IPv4 or IPv6) to assign to the VPN interface.
* @param prefixLength The prefix length of the address.
*
* @return {@code true} on success.
*
* @hide
*/
public boolean removeAddress(InetAddress address, int prefixLength) {
check(address, prefixLength);
try {
return getService().removeVpnAddress(address.getHostAddress(), prefixLength);
} catch (RemoteException e) {
throw new IllegalStateException(e);
}
}
/**
* Sets the underlying networks used by the VPN for its upstream connections.
*
*
Used by the system to know the actual networks that carry traffic for apps affected by
* this VPN in order to present this information to the user (e.g., via status bar icons).
*
*
This method only needs to be called if the VPN has explicitly bound its underlying
* communications channels — such as the socket(s) passed to {@link #protect(int)} —
* to a {@code Network} using APIs such as {@link Network#bindSocket(Socket)} or
* {@link Network#bindSocket(DatagramSocket)}. The VPN should call this method every time
* the set of {@code Network}s it is using changes.
*
*
{@code networks} is one of the following:
*
* - a non-empty array: an array of one or more {@link Network}s, in
* decreasing preference order. For example, if this VPN uses both wifi and mobile (cellular)
* networks to carry app traffic, but prefers or uses wifi more than mobile, wifi should appear
* first in the array.
* - an empty array: a zero-element array, meaning that the VPN has no
* underlying network connection, and thus, app traffic will not be sent or received.
* - null: (default) signifies that the VPN uses whatever is the system's
* default network. I.e., it doesn't use the {@code bindSocket} or {@code bindDatagramSocket}
* APIs mentioned above to send traffic over specific channels.
*
*
* This call will succeed only if the VPN is currently established. For setting this value
* when the VPN has not yet been established, see {@link Builder#setUnderlyingNetworks}.
*
* @param networks An array of networks the VPN uses to tunnel traffic to/from its servers.
*
* @return {@code true} on success.
*/
public boolean setUnderlyingNetworks(Network[] networks) {
try {
return getService().setUnderlyingNetworksForVpn(networks);
} catch (RemoteException e) {
throw new IllegalStateException(e);
}
}
/**
* Return the communication interface to the service. This method returns
* {@code null} on {@link Intent}s other than {@link #SERVICE_INTERFACE}
* action. Applications overriding this method must identify the intent
* and return the corresponding interface accordingly.
*
* @see Service#onBind
*/
@Override
public IBinder onBind(Intent intent) {
if (intent != null && SERVICE_INTERFACE.equals(intent.getAction())) {
return new Callback();
}
return null;
}
/**
* Invoked when the application is revoked. At this moment, the VPN
* interface is already deactivated by the system. The application should
* close the file descriptor and shut down gracefully. The default
* implementation of this method is calling {@link Service#stopSelf()}.
*
*
Calls to this method may not happen on the main thread
* of the process.
*
* @see #prepare
*/
public void onRevoke() {
stopSelf();
}
/**
* Use raw Binder instead of AIDL since now there is only one usage.
*/
private class Callback extends Binder {
@Override
protected boolean onTransact(int code, Parcel data, Parcel reply, int flags) {
if (code == IBinder.LAST_CALL_TRANSACTION) {
onRevoke();
return true;
}
return false;
}
}
/**
* Private method to validate address and prefixLength.
*/
private static void check(InetAddress address, int prefixLength) {
if (address.isLoopbackAddress()) {
throw new IllegalArgumentException("Bad address");
}
if (address instanceof Inet4Address) {
if (prefixLength < 0 || prefixLength > 32) {
throw new IllegalArgumentException("Bad prefixLength");
}
} else if (address instanceof Inet6Address) {
if (prefixLength < 0 || prefixLength > 128) {
throw new IllegalArgumentException("Bad prefixLength");
}
} else {
throw new IllegalArgumentException("Unsupported family");
}
}
/**
* Helper class to create a VPN interface. This class should be always
* used within the scope of the outer {@link VpnService}.
*
* @see VpnService
*/
public class Builder {
private final VpnConfig mConfig = new VpnConfig();
private final List mAddresses = new ArrayList();
private final List mRoutes = new ArrayList();
public Builder() {
mConfig.user = VpnService.this.getClass().getName();
}
/**
* Set the name of this session. It will be displayed in
* system-managed dialogs and notifications. This is recommended
* not required.
*/
public Builder setSession(String session) {
mConfig.session = session;
return this;
}
/**
* Set the {@link PendingIntent} to an activity for users to
* configure the VPN connection. If it is not set, the button
* to configure will not be shown in system-managed dialogs.
*/
public Builder setConfigureIntent(PendingIntent intent) {
mConfig.configureIntent = intent;
return this;
}
/**
* Set the maximum transmission unit (MTU) of the VPN interface. If
* it is not set, the default value in the operating system will be
* used.
*
* @throws IllegalArgumentException if the value is not positive.
*/
public Builder setMtu(int mtu) {
if (mtu <= 0) {
throw new IllegalArgumentException("Bad mtu");
}
mConfig.mtu = mtu;
return this;
}
/**
* Add a network address to the VPN interface. Both IPv4 and IPv6
* addresses are supported. At least one address must be set before
* calling {@link #establish}.
*
* Adding an address implicitly allows traffic from that address family
* (i.e., IPv4 or IPv6) to be routed over the VPN. @see #allowFamily
*
* @throws IllegalArgumentException if the address is invalid.
*/
public Builder addAddress(InetAddress address, int prefixLength) {
check(address, prefixLength);
if (address.isAnyLocalAddress()) {
throw new IllegalArgumentException("Bad address");
}
mAddresses.add(new LinkAddress(address, prefixLength));
mConfig.updateAllowedFamilies(address);
return this;
}
/**
* Convenience method to add a network address to the VPN interface
* using a numeric address string. See {@link InetAddress} for the
* definitions of numeric address formats.
*
* Adding an address implicitly allows traffic from that address family
* (i.e., IPv4 or IPv6) to be routed over the VPN. @see #allowFamily
*
* @throws IllegalArgumentException if the address is invalid.
* @see #addAddress(InetAddress, int)
*/
public Builder addAddress(String address, int prefixLength) {
return addAddress(InetAddress.parseNumericAddress(address), prefixLength);
}
/**
* Add a network route to the VPN interface. Both IPv4 and IPv6
* routes are supported.
*
* Adding a route implicitly allows traffic from that address family
* (i.e., IPv4 or IPv6) to be routed over the VPN. @see #allowFamily
*
* @throws IllegalArgumentException if the route is invalid.
*/
public Builder addRoute(InetAddress address, int prefixLength) {
check(address, prefixLength);
int offset = prefixLength / 8;
byte[] bytes = address.getAddress();
if (offset < bytes.length) {
for (bytes[offset] <<= prefixLength % 8; offset < bytes.length; ++offset) {
if (bytes[offset] != 0) {
throw new IllegalArgumentException("Bad address");
}
}
}
mRoutes.add(new RouteInfo(new IpPrefix(address, prefixLength), null));
mConfig.updateAllowedFamilies(address);
return this;
}
/**
* Convenience method to add a network route to the VPN interface
* using a numeric address string. See {@link InetAddress} for the
* definitions of numeric address formats.
*
* Adding a route implicitly allows traffic from that address family
* (i.e., IPv4 or IPv6) to be routed over the VPN. @see #allowFamily
*
* @throws IllegalArgumentException if the route is invalid.
* @see #addRoute(InetAddress, int)
*/
public Builder addRoute(String address, int prefixLength) {
return addRoute(InetAddress.parseNumericAddress(address), prefixLength);
}
/**
* Add a DNS server to the VPN connection. Both IPv4 and IPv6
* addresses are supported. If none is set, the DNS servers of
* the default network will be used.
*
* Adding a server implicitly allows traffic from that address family
* (i.e., IPv4 or IPv6) to be routed over the VPN. @see #allowFamily
*
* @throws IllegalArgumentException if the address is invalid.
*/
public Builder addDnsServer(InetAddress address) {
if (address.isLoopbackAddress() || address.isAnyLocalAddress()) {
throw new IllegalArgumentException("Bad address");
}
if (mConfig.dnsServers == null) {
mConfig.dnsServers = new ArrayList();
}
mConfig.dnsServers.add(address.getHostAddress());
return this;
}
/**
* Convenience method to add a DNS server to the VPN connection
* using a numeric address string. See {@link InetAddress} for the
* definitions of numeric address formats.
*
* Adding a server implicitly allows traffic from that address family
* (i.e., IPv4 or IPv6) to be routed over the VPN. @see #allowFamily
*
* @throws IllegalArgumentException if the address is invalid.
* @see #addDnsServer(InetAddress)
*/
public Builder addDnsServer(String address) {
return addDnsServer(InetAddress.parseNumericAddress(address));
}
/**
* Add a search domain to the DNS resolver.
*/
public Builder addSearchDomain(String domain) {
if (mConfig.searchDomains == null) {
mConfig.searchDomains = new ArrayList();
}
mConfig.searchDomains.add(domain);
return this;
}
/**
* Allows traffic from the specified address family.
*
* By default, if no address, route or DNS server of a specific family (IPv4 or IPv6) is
* added to this VPN, then all outgoing traffic of that family is blocked. If any address,
* route or DNS server is added, that family is allowed.
*
* This method allows an address family to be unblocked even without adding an address,
* route or DNS server of that family. Traffic of that family will then typically
* fall-through to the underlying network if it's supported.
*
* {@code family} must be either {@code AF_INET} (for IPv4) or {@code AF_INET6} (for IPv6).
* {@link IllegalArgumentException} is thrown if it's neither.
*
* @param family The address family ({@code AF_INET} or {@code AF_INET6}) to allow.
*
* @return this {@link Builder} object to facilitate chaining of method calls.
*/
public Builder allowFamily(int family) {
if (family == AF_INET) {
mConfig.allowIPv4 = true;
} else if (family == AF_INET6) {
mConfig.allowIPv6 = true;
} else {
throw new IllegalArgumentException(family + " is neither " + AF_INET + " nor " +
AF_INET6);
}
return this;
}
private void verifyApp(String packageName) throws PackageManager.NameNotFoundException {
IPackageManager pm = IPackageManager.Stub.asInterface(
ServiceManager.getService("package"));
try {
pm.getApplicationInfo(packageName, 0, UserHandle.getCallingUserId());
} catch (RemoteException e) {
throw new IllegalStateException(e);
}
}
/**
* Adds an application that's allowed to access the VPN connection.
*
* If this method is called at least once, only applications added through this method (and
* no others) are allowed access. Else (if this method is never called), all applications
* are allowed by default. If some applications are added, other, un-added applications
* will use networking as if the VPN wasn't running.
*
* A {@link Builder} may have only a set of allowed applications OR a set of disallowed
* ones, but not both. Calling this method after {@link #addDisallowedApplication} has
* already been called, or vice versa, will throw an {@link UnsupportedOperationException}.
*
* {@code packageName} must be the canonical name of a currently installed application.
* {@link PackageManager.NameNotFoundException} is thrown if there's no such application.
*
* @throws PackageManager.NameNotFoundException If the application isn't installed.
*
* @param packageName The full name (e.g.: "com.google.apps.contacts") of an application.
*
* @return this {@link Builder} object to facilitate chaining method calls.
*/
public Builder addAllowedApplication(String packageName)
throws PackageManager.NameNotFoundException {
if (mConfig.disallowedApplications != null) {
throw new UnsupportedOperationException("addDisallowedApplication already called");
}
verifyApp(packageName);
if (mConfig.allowedApplications == null) {
mConfig.allowedApplications = new ArrayList();
}
mConfig.allowedApplications.add(packageName);
return this;
}
/**
* Adds an application that's denied access to the VPN connection.
*
* By default, all applications are allowed access, except for those denied through this
* method. Denied applications will use networking as if the VPN wasn't running.
*
* A {@link Builder} may have only a set of allowed applications OR a set of disallowed
* ones, but not both. Calling this method after {@link #addAllowedApplication} has already
* been called, or vice versa, will throw an {@link UnsupportedOperationException}.
*
* {@code packageName} must be the canonical name of a currently installed application.
* {@link PackageManager.NameNotFoundException} is thrown if there's no such application.
*
* @throws PackageManager.NameNotFoundException If the application isn't installed.
*
* @param packageName The full name (e.g.: "com.google.apps.contacts") of an application.
*
* @return this {@link Builder} object to facilitate chaining method calls.
*/
public Builder addDisallowedApplication(String packageName)
throws PackageManager.NameNotFoundException {
if (mConfig.allowedApplications != null) {
throw new UnsupportedOperationException("addAllowedApplication already called");
}
verifyApp(packageName);
if (mConfig.disallowedApplications == null) {
mConfig.disallowedApplications = new ArrayList();
}
mConfig.disallowedApplications.add(packageName);
return this;
}
/**
* Allows all apps to bypass this VPN connection.
*
* By default, all traffic from apps is forwarded through the VPN interface and it is not
* possible for apps to side-step the VPN. If this method is called, apps may use methods
* such as {@link ConnectivityManager#bindProcessToNetwork} to instead send/receive
* directly over the underlying network or any other network they have permissions for.
*
* @return this {@link Builder} object to facilitate chaining of method calls.
*/
public Builder allowBypass() {
mConfig.allowBypass = true;
return this;
}
/**
* Sets the VPN interface's file descriptor to be in blocking/non-blocking mode.
*
* By default, the file descriptor returned by {@link #establish} is non-blocking.
*
* @param blocking True to put the descriptor into blocking mode; false for non-blocking.
*
* @return this {@link Builder} object to facilitate chaining method calls.
*/
public Builder setBlocking(boolean blocking) {
mConfig.blocking = blocking;
return this;
}
/**
* Sets the underlying networks used by the VPN for its upstream connections.
*
* @see VpnService#setUnderlyingNetworks
*
* @param networks An array of networks the VPN uses to tunnel traffic to/from its servers.
*
* @return this {@link Builder} object to facilitate chaining method calls.
*/
public Builder setUnderlyingNetworks(Network[] networks) {
mConfig.underlyingNetworks = networks != null ? networks.clone() : null;
return this;
}
/**
* Create a VPN interface using the parameters supplied to this
* builder. The interface works on IP packets, and a file descriptor
* is returned for the application to access them. Each read
* retrieves an outgoing packet which was routed to the interface.
* Each write injects an incoming packet just like it was received
* from the interface. The file descriptor is put into non-blocking
* mode by default to avoid blocking Java threads. To use the file
* descriptor completely in native space, see
* {@link ParcelFileDescriptor#detachFd()}. The application MUST
* close the file descriptor when the VPN connection is terminated.
* The VPN interface will be removed and the network will be
* restored by the system automatically.
*
* To avoid conflicts, there can be only one active VPN interface
* at the same time. Usually network parameters are never changed
* during the lifetime of a VPN connection. It is also common for an
* application to create a new file descriptor after closing the
* previous one. However, it is rare but not impossible to have two
* interfaces while performing a seamless handover. In this case, the
* old interface will be deactivated when the new one is created
* successfully. Both file descriptors are valid but now outgoing
* packets will be routed to the new interface. Therefore, after
* draining the old file descriptor, the application MUST close it
* and start using the new file descriptor. If the new interface
* cannot be created, the existing interface and its file descriptor
* remain untouched.
*
*
An exception will be thrown if the interface cannot be created
* for any reason. However, this method returns {@code null} if the
* application is not prepared or is revoked. This helps solve
* possible race conditions between other VPN applications.
*
* @return {@link ParcelFileDescriptor} of the VPN interface, or
* {@code null} if the application is not prepared.
* @throws IllegalArgumentException if a parameter is not accepted
* by the operating system.
* @throws IllegalStateException if a parameter cannot be applied
* by the operating system.
* @throws SecurityException if the service is not properly declared
* in {@code AndroidManifest.xml}.
* @see VpnService
*/
public ParcelFileDescriptor establish() {
mConfig.addresses = mAddresses;
mConfig.routes = mRoutes;
try {
return getService().establishVpn(mConfig);
} catch (RemoteException e) {
throw new IllegalStateException(e);
}
}
}
}