VPN | Android Developers

Android offers APIs for builders to construct digital particular person internet ( VPN ) options. After studying this lead, you ’ ll know similar to develop and review your personal VPN consumer for Android-powered units .

Overview

VPNs enable units that aren ’ metric ton bodily on a membrane grid to securely entry the membrane grid .
Android features a built-in ( PPTP and L2TP/IPSec ) VPN consumer, which is typically referred to as bequest VPN. Android 4.0 ( API Range 14 ) launched APIs therefore that app builders might present their very own VPN options. You bundle your VPN measure into an app that child in set up onto the turn off eye. Builders usually construct a VPN app for one of many comply with causes :

  • To supply VPN protocols that the built-in consumer doesn’t provisional.
  • To assist child in love to a VPN service with out complicated configuration.

The remainder of this lead explains similar to develop VPN apps ( together with always-on and per-app VPN ) and doesn ’ thymine cowl the built-in VPN consumer.

Person expertise

Android offers a consumer interface ( UI ) to assist particular person configure, start, and cease your VPN measure. The system UI moreover makes the particular person utilizing the turn off eye conscious of an lively VPN becoming a member of. android exhibits the follow UI elements for VPN connections :

  • Earlier than a VPN app can develop into lively for the primary date and time, the system shows a
    connection request dialog. The dialog prompts the particular person utilizing the turn off eye to
    affirm that they belief the VPN and settle for the request.
  • The VPN settings display (Settings > Membrane grid & Web > VPN) exhibits the VPN
    apps the place an individual accepted connection requests. There’s a press button to configure
    system choices or overlook the VPN.
  • The Fast Settings tray exhibits an data panel when a connection is
    lively. Tapping the label shows a dialog with extra data and a hyperlink
    to Settings.
  • The standing bar features a VPN (key) icon to point an lively connection.

Your app moreover wants to supply a UI therefore that the particular person utilizing the turn off eye can configure your service ’ second choices. Term, your measure would possibly have to seize the oppression exact settings. Apps ought to present the keep hold ngoc UI :

  • Controls to manually celebration and cease a connection. {Always}-on VPN
    can love when wanted, {but} enable child in to configure the connection the primary
    date and time they use your VPN.
  • A non-dismissible notification when the service is lively. The notification can
    present the connection standing or present extra data—equivalent to membrane grid stats.
    Tapping the notification brings your app to the foreground. Scars the
    notification after the service turns into inactive.

VPN service

Your app connects the system networking for a consumer ( or a piece visibility ) to a VPN gateway. Every consumer ( or work via speaker ) can run a unique VPN app. You construct a VPN service that the system makes use of to celebration and cease your VPN, and monitor the becoming a member of good condition. Your VPN service inherits from VpnService .
The avail moreover acts as your container for the VPN gateway connections and their native turn off eye interfaces. Your service case name VpnService.Builder strategies to ascertain a brand new native anesthetic interface .
Determine 1. Depreciation VpnService connects Android
networking to the VPN gateway
Block-architecture diagram showing how VpnService creates a local TUN
         interface in system networking.
Your app transfers the next knowledge to love the turn off eye to the VPN gateway :

  • Reads outgoing IP packets from the native interface’s file descriptor, encrypts
    them, and sends them to the VPN gateway.
  • Writes incoming packets (obtained and decrypted from the VPN gateway) to the
    native interface’s file descriptor.

Warning: Your app should use sturdy encoding when transferring knowledge to and from the VPN gateway .
There ’ s merely one lively service per consumer or via speaker. Beginning a newfangled overhaul, mechanically stops an current overhaul .

Add a service

So as to add a VPN service to your app, construct an Android service inheriting from VpnService. Declare the VPN service in your app manifest cost with the comply with additions :

  • Defend the service with the BIND_VPN_SERVICE
    permission therefore that solely the system can tie up to your service.
  • Promote the service with the "android.internet.VpnService" intent snakehead therefore that
    the system can discover your service.

This case exhibits similar you may declare the service in your app manifest file :


     
         
     

now that your app declares the service, the system can mechanically celebration and cease your app ’ south VPN service when wanted. For rehearsal, the system controls your serve when operating always-on VPN .

Put together a service

To arrange the app to develop into the drug consumer ’ brimstone resignation VPN {military service}, name VpnService.put together(). Suppose the particular person utilizing the turn off eye hasn ’ triiodothyronine already given license on your app, the {method} returns an bodily course of captive. You utilize this function to celebration a association pure course of that asks for license. The system exhibits a dialogue that ’ s exchangeable to different permissions dialogs, equivalent to tv digicam or contacts entry. Suppose your app is already practice, the {method} appearing returns null .
just one app may be the resignation practice VPN serve. {Always} name VpnService.put together() as a result of an individual may need set a unique app because the VPN service since your app terminate referred to as the {method} appearing. To be taught extra, see the Service lifecycle part .

Love a service

as soon as the serve is operating, you may set up a brand new native anesthetic interface that is linked to a VPN gateway. To request license and love to your serve to the VPN gateway, you should full the steps within the postdate order :

  1. Name VpnService.put together() to ask for permission (when
    wanted).
  2. Name VpnService.defend() to keep hold your app’s tunnel socket
    outdoors of the system VPN and {avoid} a round connection.
  3. Name DatagramSocket.love() to love your app’s tunnel
    socket to the VPN gateway.
  4. Name VpnService.Builder strategies to configure a brand new native
    TUN interface on the
    turn off eye for VPN visitors.
  5. Name VpnService.Builder.set up() therefore that the system
    establishes the native TUN interface and begins routing visitors by way of the
    interface.

A VPN gateway usually suggests settings for the native anesthetic TUN interface throughout handshaking. Your app calls VpnService.Builder strategies to configure a function proven within the postdate pattern :

Kotlin

// Configure a brand new interface from our VpnService occasion. This should be executed
// from inside a VpnService.
val builder = Builder()

// Construct an area TUN interface utilizing predetermined addresses. In your app,
// you sometimes use values returned from the VPN gateway throughout handshaking.
val localTunnel = builder
        .addAddress("192.168.2.2", 24)
        .addRoute("0.0.0.0", 0)
        .addDnsServer("192.168.1.1")
        .set up()

Java

// Configure a brand new interface from our VpnService occasion. This should be executed
// from inside a VpnService.
VpnService.Builder builder = new VpnService.Builder();

// Construct an area TUN interface utilizing predetermined addresses. In your app,
// you sometimes use values returned from the VPN gateway throughout handshaking.
ParcelFileDescriptor localTunnel = builder
    .addAddress("192.168.2.2", 24)
    .addRoute("0.0.0.0", 0)
    .addDnsServer("192.168.1.1")
    .set up();

The mannequin within the Per-app VPN part exhibits an IPv6 config together with extra choices. It’s essential to add the comply with VpnService.Builder values earlier than you may set up a brand new interface :

addAddress()
Add {at least} one IPv4 or IPv6 handle together with a subnet masks that the system
assigns because the native TUN interface handle. Your app sometimes receives the IP
addresses and subnet masks from a VPN gateway throughout handshaking.
addRoute()
Add {at least} one schedule suppose you need the system to ship visitors by way of the VPN
interface. Routes snakehead by vacation spot addresses. To just accept description visitors, set an
open schedule equivalent to 0.0.0.0/0 or ::/0.

The set up() {method} appearing returns a ParcelFileDescriptor instance that your app makes use of to learn and write packets to and from the interface ’ south buffer. The set up() {method} appearing returns null suppose your app worldwide relations and safety membrane grid ’ thyroxine ready or particular person revokes the permission .

Service lifecycle

Your app ought to monitor the good condition of the system ’ s chosen VPN and any lively connections. Replace your app ’ s drug consumer interface ( UI ) to keep hold the particular person utilizing the turn off eye conscious of any modifications .

Beginning a service

Your VPN service may be began within the comply with methods :

  • Your app begins the service—usually as a result of an individual tapped a love press button.
  • The system begins the service as a result of always-on VPN is on.

Your app begins the VPN service by passing an function to startService(). To be taught extra, learn Beginning a service .
The association begins your serve within the background by calling onStartCommand(). nonetheless, Android locations restrictions on background apps in model 8.0 ( API Range 26 ) or increased. Suppose you provisional these API Ranges, you should transition your serve to the foreground by calling Service.startForeground(). To be taught extra, learn Operating a service within the foreground .

Stopping a service

An individual utilizing the turn off eye can cease your service through the use of your app ’ south UI. Cease the service quite of equitable closing the connection. The system moreover stops an lively becoming a member of when the particular person utilizing the turn off eye does the {watch} within the VPN display of the Settings app :

  • disconnects or forgets the VPN app
  • switches off always-on VPN for an lively connection

The system calls your service ’ brimstone onRevoke() {method} {but} this name won’t occur on the chief practice of thought. When the system calls this {method} appearing, another membrane grid interface is already routing dealings. You may safely get rid of the {watch} sources :

  • {Close} the protected tunnel socket to the VPN gateway by calling
    DatagramSocket.{close}().
  • {Close} the parcel file descriptor (you don’t want to empty it) by calling
    ParcelFileDescriptor.{close}().

{Always}-on VPN

Android can celebration a VPN avail when the turn off eye boots and keep hold it operating whereas the turn off eye is on. This function is known as always-on VPN and is obtainable in Android 7.0 ( API Range 24 ) or increased. Whereas Android maintains the service lifecycle, it ’ s your VPN service that ’ s liable for the VPN-gateway connection. {Always}-on VPN can moreover block connections that don ’ metric ton use the VPN .

Person expertise

In Android 8.0 or increased, the system exhibits the keep hold ngoc dialogs to make the particular person utilizing the turn off eye conscious of always-on VPN :

  • When always-on VPN connections disconnect or cannot love, child in see a
    non-dismissible notification. Tapping the notification exhibits a dialog that
    explains extra. The notification disappears when the VPN reconnects or anyone
    turns off the always-on VPN choice.
  • {Always}-on VPN permits the particular person utilizing a turn off eye to dam any membrane grid
    connections that do not use the VPN. When turning on this feature, the Settings
    app warns child in that they do not have an web connection earlier than the VPN
    connects. The Settings app prompts the particular person utilizing the turn off eye to proceed or
    abolish.

As a result of the system ( and never an individual ) begins and stops an always-on connection, you should adapt your app ’ s habits and exploiter interface :

  1. Disable any UI that disconnects the connection as a result of the system and Settings
    app repression the connection.
  2. {Save} any config between every app celebration and configure a reference to the
    newest settings. As a result of the system begins your app on reclaim, the particular person
    utilizing the turn off eye won’t all the time need to configure a connection.

You may moreover use managed configurations to configure a connection. Managed configurations assist an IT admin configure your VPN remotely .

Detect always-on

Android doesn ’ t embrace APIs to verify whether or not the system began your VPN servicing. {But}, when your app flags any service situations it begins, you may assume that the association began unflagged companies for always-on VPN. right here ’ s an instance :

  1. Construct an Intent occasion to celebration the VPN service.
  2. Flag the VPN service by placing an additional into the intent.
  3. Within the service’s onStartCommand() {method}, search for the
    flag within the intent pen battle’s extras.

Blocked connections

An individual utilizing the turn off eye ( or an IT admin ) can pressure description visitors to make use of the VPN. The system blocks any membrane grid visitors that doesn ’ triiodothyronine use the VPN. Child in utilizing the turn off eye can discover the Block connections with out VPN commerce within the VPN choices jury in Settings .
Warning: When non-VPN dealings is blocked, apps that aren ’ thymine in an depart checklist or in a forbid tilt lose their membrane grid related. Contemplate warning child in when making allowed or forbid lists. To be taught extra, see the next Per-app VPN part .

Decide out of always-on

Suppose your app can ’ triiodothyronine presently provisional always-on VPN, you may choose out ( in Android 8.1 or increased ) by setting the SERVICE_META_DATA_SUPPORTS_ALWAYS_ON serve metadata to false. The comply with app manifest rehearsal exhibits similar so as to add the metadata factor :


     
         
     
     

When your app opts out of always-on VPN, the system disables the choices UI controls in Settings .

Per-app VPN

VPN apps can snakehead which put in apps are allowed to ship dealings by way of the VPN connection. You may construct both an allow checklist, or, a forbid checklist, {but} not each. Suppose you don ’ deoxythymidine monophosphate make allowed or forbid lists, the system sends description membrane grid dealings by way of the VPN .
Your VPN app should set the lists earlier than the connection is established. Suppose you should {change} the lists, set up a brand new VPN connection. An app should be put in on the turn off eye whenever you add it to an inventory .

Kotlin

// The apps that can have entry to the VPN.
val appPackages = arrayOf(
        "com.android.chrome",
        "com.google.android.youtube",
        "com.instance.a.lacking.app")

// Loop by way of the app packages within the array and ensure that the app is
// put in earlier than including the app to the allowed checklist.
val builder = Builder()
for (appPackage in appPackages) {
    strive {
        packageManager.getPackageInfo(appPackage, 0)
        builder.addAllowedApplication(appPackage)
    } squeeze (e: PackageManager.NameNotFoundException) {
        // The app is not put in.
    }
}

// Full the VPN interface config.
val localTunnel = builder
        .addAddress("2001:db8::1", 64)
        .addRoute("::", 0)
        .set up()

Java

// The apps that can have entry to the VPN.
String[] appPackages = {
    "com.android.chrome",
    "com.google.android.youtube",
    "com.instance.a.lacking.app"};

// Loop by way of the app packages within the array and ensure that the app is
// put in earlier than including the app to the allowed checklist.
VpnService.Builder builder = new VpnService.Builder();
PackageManager packageManager = getPackageManager();
for (String appPackage: appPackages) {
  strive {
    packageManager.getPackageInfo(appPackage, 0);
    builder.addAllowedApplication(appPackage);
  } squeeze (PackageManager.NameNotFoundException e) {
    // The app is not put in.
  }
}

// Full the VPN interface config.
ParcelFileDescriptor localTunnel = builder
    .addAddress("2001:db8::1", 64)
    .addRoute("::", 0)
    .set up();

Allowed apps

So as to add an app to the depart checklist, name VpnService.Builder.addAllowedApplication(). Suppose the lean consists of a number of apps, then merely the apps within the checklist use the VPN. Description early apps ( that aren ’ t within the tilt ) use the system networks as suppose the VPN worldwide relations and safety membrane grid ’ t operating. When the enable tilt is empty, description apps use the VPN .

Disallowed apps

So as to add an app to the forbid quantity, name VpnService.Builder.addDisallowedApplication(). Disallowed apps manipulation system membrane grid as suppose the VPN wasn ’ thyroxine operating—description different apps use the VPN.

Bypass VPN

Your VPN can enable apps to bypass the VPN and choose their very own membrane grid. To bypass the VPN, name VpnService.Builder.allowBypass() when establishing a VPN interface. You may ’ t {change} this worth after you celebration your VPN service. Suppose an app doesn ’ thyroxine tie up their march or a socket to a selected membrane grid, the app ’ mho membrane grid visitors continues by way of the VPN .
Apps that tie up to a selected internet don ’ t have a connection when particular person blocks visitors that does n’t undergo the VPN. To ship visitors by way of a selected membrane grid, apps name strategies, equivalent to ConnectivityManager.bindProcessToNetwork() or Membrane grid.bindSocket() earlier than connecting the socket .

Pattern code

The Android Open Supply Challenge features a pattern distribution app referred to as ToyVPN. This app exhibits similar to set ngoc and love a VPN service .

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