Java tutorial
/* * 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.NonNull; import android.annotation.Nullable; import android.annotation.RequiresPermission; import android.annotation.SystemApi; import android.annotation.UnsupportedAppUsage; import android.app.Activity; import android.app.PendingIntent; import android.app.Service; import android.app.admin.DevicePolicyManager; import android.content.ComponentName; 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; import java.util.Set; /** * 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. * * <p>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: * <ul> * <li>User action is required the first time an application creates a VPN * connection.</li> * <li>There can be only one VPN connection running at the same time. The * existing interface is deactivated when a new one is created.</li> * <li>A system-managed notification is shown during the lifetime of a * VPN connection.</li> * <li>A system-managed dialog gives the information of the current VPN * connection. It also provides a button to disconnect.</li> * <li>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.</li> * </ul> * * <p>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: * <ol> * <li>When the user presses the button to connect, call {@link #prepare} * and launch the returned intent, if non-null.</li> * <li>When the application becomes prepared, start the service.</li> * <li>Create a tunnel to the remote server and negotiate the network * parameters for the VPN connection.</li> * <li>Supply those parameters to a {@link Builder} and create a VPN * interface by calling {@link Builder#establish}.</li> * <li>Process and exchange packets between the tunnel and the returned * file descriptor.</li> * <li>When {@link #onRevoke} is invoked, close the file descriptor and * shut down the tunnel gracefully.</li> * </ol> * * <p>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}: * <pre> * <service android:name=".ExampleVpnService" * android:permission="android.permission.BIND_VPN_SERVICE"> * <intent-filter> * <action android:name="android.net.VpnService"/> * </intent-filter> * </service></pre> * * <p> 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. * * <h3>Developer's guide</h3> * * <p>To learn more about developing VPN apps, read the * <a href="{@docRoot}guide/topics/connectivity/vpn">VPN developer's guide</a>. * * @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. * * <p>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 DevicePolicyManager#setAlwaysOnVpnPackage}. * * <p>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, * <pre> {@code * <service android:name=".ExampleVpnService" * android:permission="android.permission.BIND_VPN_SERVICE"> * <intent-filter> * <action android:name="android.net.VpnService"/> * </intent-filter> * <meta-data android:name="android.net.VpnService.SUPPORTS_ALWAYS_ON" * android:value=false/> * </service> * } </pre> * * <p>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. * * <p>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. * * <p>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. * * <p>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. * * <p>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. * * <p class="note">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 <b>DOES NOT</b> 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. * * <p>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). * * <p>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. * * <p>{@code networks} is one of the following: * <ul> * <li><strong>a non-empty array</strong>: 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.</li> * <li><strong>an empty array</strong>: a zero-element array, meaning that the VPN has no * underlying network connection, and thus, app traffic will not be sent or received.</li> * <li><strong>null</strong>: (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.</li> * </ul> * * <p>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); } } /** * Returns whether the service is running in always-on VPN mode. In this mode the system ensures * that the service is always running by restarting it when necessary, e.g. after reboot. * * @see DevicePolicyManager#setAlwaysOnVpnPackage(ComponentName, String, boolean, Set) */ public final boolean isAlwaysOn() { try { return getService().isCallerCurrentAlwaysOnVpnApp(); } catch (RemoteException e) { throw e.rethrowFromSystemServer(); } } /** * Returns whether the service is running in always-on VPN lockdown mode. In this mode the * system ensures that the service is always running and that the apps aren't allowed to bypass * the VPN. * * @see DevicePolicyManager#setAlwaysOnVpnPackage(ComponentName, String, boolean, Set) */ public final boolean isLockdownEnabled() { try { return getService().isCallerCurrentAlwaysOnVpnLockdownApp(); } catch (RemoteException e) { throw e.rethrowFromSystemServer(); } } /** * 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()}. * * <p class="note">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(); @UnsupportedAppUsage private final List<LinkAddress> mAddresses = new ArrayList<LinkAddress>(); @UnsupportedAppUsage private final List<RouteInfo> mRoutes = new ArrayList<RouteInfo>(); 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. */ @NonNull public Builder setSession(@NonNull 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. */ @NonNull public Builder setConfigureIntent(@NonNull 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. */ @NonNull public Builder setMtu(int mtu) { if (mtu <= 0) { throw new IllegalArgumentException("Bad mtu"); } mConfig.mtu = mtu; return this; } /** * Sets an HTTP proxy for the VPN network. This proxy is only a recommendation * and it is possible that some apps will ignore it. */ @NonNull public Builder setHttpProxy(@NonNull ProxyInfo proxyInfo) { mConfig.proxyInfo = proxyInfo; 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. */ @NonNull public Builder addAddress(@NonNull 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) */ @NonNull public Builder addAddress(@NonNull 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. */ @NonNull public Builder addRoute(@NonNull 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) */ @NonNull public Builder addRoute(@NonNull 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. */ @NonNull public Builder addDnsServer(@NonNull InetAddress address) { if (address.isLoopbackAddress() || address.isAnyLocalAddress()) { throw new IllegalArgumentException("Bad address"); } if (mConfig.dnsServers == null) { mConfig.dnsServers = new ArrayList<String>(); } 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) */ @NonNull public Builder addDnsServer(@NonNull String address) { return addDnsServer(InetAddress.parseNumericAddress(address)); } /** * Add a search domain to the DNS resolver. */ @NonNull public Builder addSearchDomain(@NonNull String domain) { if (mConfig.searchDomains == null) { mConfig.searchDomains = new ArrayList<String>(); } 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. */ @NonNull 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. */ @NonNull public Builder addAllowedApplication(@NonNull 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<String>(); } 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. */ @NonNull public Builder addDisallowedApplication(@NonNull 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<String>(); } 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. */ @NonNull 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. */ @NonNull 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. */ @NonNull public Builder setUnderlyingNetworks(@Nullable Network[] networks) { mConfig.underlyingNetworks = networks != null ? networks.clone() : null; return this; } /** * Marks the VPN network as metered. A VPN network is classified as metered when the user is * sensitive to heavy data usage due to monetary costs and/or data limitations. In such * cases, you should set this to {@code true} so that apps on the system can avoid doing * large data transfers. Otherwise, set this to {@code false}. Doing so would cause VPN * network to inherit its meteredness from its underlying networks. * * <p>VPN apps targeting {@link android.os.Build.VERSION_CODES#Q} or above will be * considered metered by default. * * @param isMetered {@code true} if VPN network should be treated as metered regardless of * underlying network meteredness * @return this {@link Builder} object to facilitate chaining method calls * @see #setUnderlyingNetworks(Networks[]) * @see ConnectivityManager#isActiveNetworkMetered() */ @NonNull public Builder setMetered(boolean isMetered) { mConfig.isMetered = isMetered; 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. * * <p>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. * * <p>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 */ @Nullable public ParcelFileDescriptor establish() { mConfig.addresses = mAddresses; mConfig.routes = mRoutes; try { return getService().establishVpn(mConfig); } catch (RemoteException e) { throw new IllegalStateException(e); } } } }