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VPN Hotspot

README.md

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VPN Hotspot

(Pre-release channel)

Connecting things to your VPN made simple. Share your VPN connection over hotspot or repeater. (root required)

This app is useful for:

  • Connecting things that don't support VPN like Chromecasts behind corporate firewalls;
  • Setting up gapps behind corporate firewalls;
  • Connecting to your mobile hotspot but you're not bothered to set up VPN on your device;
  • Identifying, monitoring and blocking (unwanted) clients;
  • Bypassing tethering limits by:
    • (recommended) Use this app with a real VPN/socksifier;
    • Use this app with some adblock/DNS apps that uses system VPN service APIs, i.e. fake VPNs; (troubleshooting/a list of apps that work)
    • Try your luck and simply use this app.

P.S. You can also do the similar on Windows, Mac, and iOS.

Features That Requires System App Installation

The following features in the app requires it to be installed under /system/priv-app since some restricted permissions are required. One way to do this is to use App systemizer for Magisk.

  • (Android 8-10, since app v2.4.0) android.permission.OVERRIDE_WIFI_CONFIG: Read/write system Wi-Fi hotspot configuration. (#117)

Installing as system app also has the side benefit of launching root daemon less frequently due to having privileged permissions listed below.

  • android.permission.CONNECTIVITY_USE_RESTRICTED_NETWORKS
  • android.permission.LOCAL_MAC_ADDRESS
  • android.permission.MANAGE_USB
  • android.permission.OVERRIDE_WIFI_CONFIG
  • android.permission.READ_WIFI_CREDENTIAL
  • android.permission.TETHER_PRIVILEGED
  • android.permission.WRITE_SECURE_SETTINGS
  • Other system-app exclusive features that are not gated by permissions.

Whenever you install an app update, if there was a new protected permission addition (last updated in v2.17.1), you should update the app installed in system as well to make the system grant the privileged permission.

Q & A

Search the issue tracker for more.

What changes exactly can this app do to my system? (and how to revert them)

  1. If you change repeater credentials in unsafe mode, this feature will modify /data/misc/wifi/p2p_supplicant.conf or /data/vendor/wifi/wpa/p2p_supplicant.conf. If things stopped working after you use this feature, simply delete this file and everything should start working again.
  2. If you edited the system Wi-Fi hotspot configuration through this app, those changes will also persist. Undo those changes if you face any issues.
  3. If you toggle tethering hardware offload through this app, the Android global tether_offload_disabled setting will persist. Toggle it back in this app or the matching Developer options setting to revert it.

Routing, firewall, addresses, and daemon/service state managed by this app are cleaned up when stopped, by Clean, or upon reboot.

No root?

Failed to create group due to internal error/repeater shuts down after a while?

This could caused by the Wi-Fi channel you selected is no longer available, due to:

  1. Your device doesn't support operating on this channel, or
  2. There is some nearby Wi-Fi direct device that broadcasted that it can't operate on the channel you picked.

For maximum stability, you need to set channel = 0 so that your device will pick a channel automatically. You can also use WPS to connect your 2.4GHz-only device to force the repeater to switch from 5GHz to 2.4GHz for this time.

Private APIs used / Assumptions for Android customizations

a.k.a. things that can go wrong if this app doesn't work.

This is a list of stuff that might impact this app's functionality if unavailable. This is only meant to be an index. You can read more in the source code. API restrictions are updated up to SHA-256 checksum 9102af02fe6ab68b92464bdff5e5b09f3bd62c65d1130aaf85d3296f17d38074.

Greylisted/blacklisted APIs or internal constants: (some constants are hardcoded or implicitly used)

  • (prior to API 30) Landroid/net/ConnectivityManager;->getLastTetherError(Ljava/lang/String;)I,max-target-r
  • (prior to API 30) Landroid/net/ConnectivityManager;->EXTRA_ACTIVE_LOCAL_ONLY:Ljava/lang/String;,lo-prio,max-target-o
  • (prior to API 30) Landroid/net/ConnectivityManager;->EXTRA_ACTIVE_TETHER:Ljava/lang/String;,max-target-r
  • (prior to API 30) Landroid/net/ConnectivityManager;->EXTRA_AVAILABLE_TETHER:Ljava/lang/String;,max-target-r
  • (prior to API 30) Landroid/net/ConnectivityManager;->ACTION_TETHER_STATE_CHANGED:Ljava/lang/String;,max-target-r
  • (prior to API 30) Landroid/net/ConnectivityManager;->EXTRA_ERRORED_TETHER:Ljava/lang/String;,max-target-r
  • (since API 30) Landroid/net/ConnectivityModuleConnector;->IN_PROCESS_SUFFIX:Ljava/lang/String;
  • (since API 31) Landroid/net/INetd$Stub;->asInterface(Landroid/os/IBinder;)Landroid/net/INetd;
  • (since API 31) Landroid/net/INetd;->ipSecUpdateSecurityPolicy(IIILjava/lang/String;Ljava/lang/String;IIII)V
  • (since API 30) Landroid/net/IIntResultListener$Stub;-><init>()V,blocked
  • (since API 30) Landroid/net/IIntResultListener;->onResult(I)V,blocked
  • (since API 30) Landroid/net/ITetheringConnector;->stopTethering(ILjava/lang/String;Landroid/net/IIntResultListener;)V,blocked
  • (since API 30) Landroid/net/ITetheringConnector;->stopTethering(ILjava/lang/String;Ljava/lang/String;Landroid/net/IIntResultListener;)V,blocked
  • (since API 30) Landroid/net/TetheringManager$ConnectorConsumer;->onConnectorAvailable(Landroid/net/ITetheringConnector;)V,blocked
  • (since API 30) Landroid/net/TetheringManager$TetheringEventCallback;->onTetherableInterfaceRegexpsChanged(Landroid/net/TetheringManager$TetheringInterfaceRegexps;)V,blocked
  • (since API 31) Landroid/net/TetheringManager$TetheringEventCallback;->onSupportedTetheringTypes(Ljava/util/Set;)V,blocked
  • (since API 30) Landroid/net/TetheringManager;->getConnector(Landroid/net/TetheringManager$ConnectorConsumer;)V,blocked
  • Landroid/net/TetheringManager;->TETHER_ERROR_*:I,blocked
  • (since API 30) Landroid/net/TetheringManager;->TETHERING_VIRTUAL:I,blocked
  • (since API 31) Landroid/net/IpSecManager;->DIRECTION_FWD:I,blocked
  • (since API 31) Landroid/net/IpSecManager;->INVALID_SECURITY_PARAMETER_INDEX:I,blocked
  • (since API 31) Landroid/net/wifi/SoftApCapability;->getCountryCode()Ljava/lang/String;,blocked
  • (since API 33) Landroid/net/wifi/SoftApConfiguration$Builder;->setRandomizedMacAddress(Landroid/net/MacAddress;)Landroid/net/wifi/SoftApConfiguration$Builder;,blocked
  • (since API 31) Landroid/net/wifi/SoftApConfiguration;->BAND_TYPES:[I,blocked
  • (since API 31) Landroid/net/wifi/SoftApInfo;->getApInstanceIdentifier()Ljava/lang/String;,blocked
  • (since API 31) Landroid/net/wifi/WifiClient;->getApInstanceIdentifier()Ljava/lang/String;,blocked
  • (prior to API 30) Landroid/net/wifi/WifiConfiguration$KeyMgmt;->FT_PSK:I,lo-prio,max-target-o
  • (prior to API 30) Landroid/net/wifi/WifiConfiguration$KeyMgmt;->WPA_PSK_SHA256:I,blocked
  • (prior to API 30) Landroid/net/wifi/WifiConfiguration;->AP_BAND_2GHZ:I,lo-prio,max-target-o
  • (prior to API 30) Landroid/net/wifi/WifiConfiguration;->AP_BAND_5GHZ:I,lo-prio,max-target-o
  • (prior to API 30) Landroid/net/wifi/WifiConfiguration;->AP_BAND_ANY:I,lo-prio,max-target-o
  • (prior to API 30) Landroid/net/wifi/WifiConfiguration;->apBand:I,unsupported
  • (prior to API 30) Landroid/net/wifi/WifiConfiguration;->apChannel:I,unsupported
  • (since API 30) Landroid/net/wifi/WifiContext;->ACTION_RESOURCES_APK:Ljava/lang/String;,blocked
  • (prior to API 30) Landroid/net/wifi/WifiManager$SoftApCallback;->onNumClientsChanged(I)V,greylist-max-o
  • Landroid/net/wifi/WifiManager;->cancelLocalOnlyHotspotRequest()V,unsupported
  • Landroid/net/wifi/p2p/WifiP2pConfig$Builder;->MAC_ANY_ADDRESS:Landroid/net/MacAddress;,blocked
  • Landroid/net/wifi/p2p/WifiP2pConfig$Builder;->mNetworkName:Ljava/lang/String;,blocked
  • (since API 30) Landroid/net/wifi/p2p/WifiP2pGroup;->interfaceAddress:[B,unsupported
  • Landroid/net/wifi/p2p/WifiP2pManager;->startWps(Landroid/net/wifi/p2p/WifiP2pManager$Channel;Landroid/net/wifi/WpsInfo;Landroid/net/wifi/p2p/WifiP2pManager$ActionListener;)V,unsupported
  • (prior to API 30) Landroid/provider/Settings$Global;->SOFT_AP_TIMEOUT_ENABLED:Ljava/lang/String;,lo-prio,max-target-o
  • (on API 34) Landroid/service/quicksettings/TileService;->mToken:Landroid/os/IBinder;,lo-prio,max-target-o
  • (prior to API 30) Lcom/android/internal/R$array;->config_tether_bluetooth_regexs:I,max-target-q
  • (prior to API 30) Lcom/android/internal/R$array;->config_tether_usb_regexs:I,max-target-q
  • (prior to API 30) Lcom/android/internal/R$array;->config_tether_wifi_regexs:I,max-target-q
  • (on API 29) Lcom/android/internal/R$bool;->config_wifi_p2p_mac_randomization_supported:I,blacklist
  • (prior to API 30) Lcom/android/internal/R$integer;->config_wifi_framework_soft_ap_timeout_delay:I,greylist-max-o
  • Lcom/android/internal/R$string;->config_ethernet_iface_regex:I,lo-prio,max-target-o
  • Lcom/android/server/wifi/p2p/WifiP2pServiceImpl;->ANONYMIZED_DEVICE_ADDRESS:Ljava/lang/String;
  • (since API 30) Lcom/android/server/SystemServer;->TETHERING_CONNECTOR_CLASS:Ljava/lang/String;
  • (since API 33) Ldalvik/system/BaseDexClassLoader;->pathList:Ldalvik/system/DexPathList;,unsupported
  • (since API 33) Ldalvik/system/DexPathList;->nativeLibraryDirectories:Ljava/util/List;,unsupported
  • (prior to API 33) Ljava/lang/invoke/MethodHandles$Lookup;-><init>(Ljava/lang/Class;I)V,unsupported
  • (prior to API 33) Ljava/lang/invoke/MethodHandles$Lookup;->ALL_MODES:I,lo-prio,max-target-o

See mobile/src/hiddenApiStubs for hidden whitelisted/system APIs as well as partial SDK-class stubs.

Nonexported system resources:

  • (since API 30) @com.android.networkstack.tethering:array/config_tether_bluetooth_regexs
  • (since API 30) @com.android.networkstack.tethering:array/config_tether_ncm_regexs
  • (since API 30) @com.android.networkstack.tethering:array/config_tether_usb_regexs
  • (since API 30) @com.android.networkstack.tethering:array/config_tether_wifi_p2p_regexs
  • (since API 30) @com.android.networkstack.tethering:array/config_tether_wifi_regexs
  • (since API 30) @com.android.networkstack.tethering:array/config_tether_wigig_regexs
  • (since API 30) @com.android.wifi.resources:bool/config_wifi_p2p_mac_randomization_supported
  • (since API 31) @com.android.wifi.resources:integer/config_wifiFrameworkSoftApShutDownIdleInstanceInBridgedModeTimeoutMillisecond
  • (since API 30) @com.android.wifi.resources:integer/config_wifiFrameworkSoftApShutDownTimeoutMilliseconds

Other:

  • (prior to API 30) Activity com.android.settings/.Settings$TetherSettingsActivity is assumed to be exported.
  • IPv6 NAT mode depends on the iptables TPROXY and NFQUEUE targets and transparent sockets. ICMPv6 Echo interception uses app-owned queue 30000 and assumes queued downstream packets expose six-byte source hardware-address metadata through NFQA_HWADDR.
  • (since API 30) Relevant tethering APEX classes used here, including android.net.ITetheringConnector, may be jarjar-relocated under the optional prefixes android.net.connectivity or com.android.connectivity.
  • (since API 31) Relevant netd APEX classes used here, including android.net.INetd*, may be jarjar-relocated under the optional prefixes android.net.connectivity or com.android.connectivity.
  • (since API 30) When runtime TetheringEventCallback.onLocalOnlyInterfacesChanged is present, AOSP dispatches startup tether-state callbacks from one executor.execute { ... } block in onCallbackStarted, and later tether-state updates from one executor.execute { ... } block in onTetherStatesChanged.
  • The Rust DNS proxy submits upstream queries through android_res_nsend/android_res_nresult. To keep daemon tasks nonblocking while still using android_res_nresult as the public result reader/closer, it waits for dnsproxyd to close the one-shot resnsend client socket before reading the result. This assumes resnsend writes the complete resolver result before returning and the socket receive buffer can hold that result until the framework socket listener closes the client socket.
  • For ip rule priorities, AOSP local-network/tethering priorities are assumed to be 17000/18000 on API 29..30 and 20000/21000 on API 31+. VPNHotspot uses the 17500..17900 or 20500..20900 gap between them.
  • For route-table numbers, Android interface tables are assumed to start at ifindex + 1000; IPv6 NAT TPROXY uses table 900 to stay below that range and away from AOSP fixed tables 97..99 and kernel built-ins.
  • Clean flushes table 900 because that table is reserved by VPNHotspot. IPv6 NAT also adds its deterministic ULA /64 route to Android's shared local_network table; Clean never flushes that table and only deletes VPNHotspot prefixes reconstructed from current interface names.
  • For packet marks, Android fwmark is assumed to use low bits for netId and routing metadata.
  • IPv6 NAT fwmark fallback for TPROXY uses masked high reserved bits 0x10000000/0x10000000. That fallback is expected on only kernels without effective FRA_IP_PROTO policy-rule support, which upstream Linux added in 4.17.
  • Daemon reply sockets use the AOSP local-network protected mark 0x00030063, which assumes LOCAL_NET_ID = 99 plus the explicitlySelected and protectedFromVpn fwmark bits.

System/root command assumptions:

The following Android system binaries are assumed to be bundled and executable:

  • /system/bin/dumpsys (ipsec);
  • /system/bin/iptables-restore, /system/bin/ip6tables-restore (-w --noflush, restore input commands including -I, -D, -N, -nvx -L <chain>);
  • /system/bin/ndc (ipfwd, nat);
  • /system/bin/settings (put global);
  • /system/bin/linker, /system/bin/linker64 (path.zip!/program).

Wi-Fi driver wpa_supplicant: