Local Network Permission

Devices on a LAN can be accessed by any app that has the INTERNET permission. This makes it easy for apps to connect to local devices, but also carries privacy implications such as forming a fingerprint of the user and being a proxy for location.

The Local Network Protections project aims to protect the user's privacy by gating access to the local network behind a new runtime permission.

Impact

During Android 16, this permission is an opt-in feature which means only the apps that opt-in will be affected. The goal of the opt-in is for app developers to understand which parts of their app depend on implicit local network access such that they can prepare to permission guard them on a future Android release.

Apps will be affected if they access the user's local network using:

  • Direct or library use of raw sockets on local network addresses (e.g. mDNS or SSDP service discovery protocol)
  • Use of framework level classes that access the local network (e.g. NsdManager)

Details of Impact

Traffic to and from a local network address requires local network access permission. The following table lists some common cases:

App Low Level Network Operation Local Network Permission Required
Making an outgoing TCP connection yes
Accepting an incoming TCP connection yes
Sending a UDP unicast, multicast, broadcast yes
Receiving a incoming UDP unicast, multicast, broadcast yes

These restrictions are implemented deep in the networking stack, and thus they apply to all networking APIs. This includes sockets created in the platform or managed code, networking libraries like Cronet and OkHttp, and any APIs implemented on top of those. Trying to resolve services on the local network (i.e. those with a .local suffix) will require local network permission.

Exceptions to the preceding rules:

  • If a device's DNS server is on a local network, traffic to / from it (at port 53) doesn't require local network access permission.
  • Applications using Output Switcher as their in-app picker won't need local network permissions (more guidance to come at a later release).

Guidance

To opt into local network restrictions, do the following:

  1. Flash your device to a build with Android 16 Beta 3 or later
  2. Install the app to be tested

  3. Toggle the Appcompat config by using adb

    adb shell am compat enable RESTRICT_LOCAL_NETWORK <package_name>

  4. Reboot the device

Now your app's access to the local network is restricted and any attempt to access the local network will lead to socket errors. If you are using APIs that perform local network operations outside of your app process (Ex: NsdManager), they won't be impacted during the opt-in.

To restore access, you must grant your app permission to NEARBY_WIFI_DEVICES.

  • Ensure the app declares the NEARBY_WIFI_DEVICES permission in its manifest.
  • Go to Settings > Apps > [Application Name] > Permissions > Nearby devices > Allow

Now your app's access to the local network should be restored and all your scenarios should work as they did prior to opting the app in. Here is how the app network traffic will be impacted.

Permission Outbound LAN Request Outbound/Inbound Internet Request Inbound LAN Request
Granted Works Works Works
Not Granted Fails Works Fails

Use the following command to toggle-off the Appcompat config

adb shell am compat disable RESTRICT_LOCAL_NETWORK <package_name>

Errors

Errors arising from these restrictions will be returned to the calling socket whenever it invokes send or a send variant to a local network address.

Example errors:

sendto failed: EPERM (Operation not permitted)

sendto failed: ECONNABORTED (Operation not permitted)

Bugs

Submit bugs and feedback for:

  • Discrepancies in LAN access (you don't think a certain access should be considered "local network" access)
  • Bugs where LAN access should be blocked but isn't
  • Bugs where LAN access shouldn't be blocked but is

The following should be unaffected by this change:

  • Access to the Internet
  • Mobile Network