Limiting concurrent sessions (Simultaneous-Use)

Simultaneous-Use is a FreeRADIUS feature that restricts how many sessions a user can keep active at the same time. When the maximum limit is reached and the user attempts to start another session from a different client device, the authorization is rejected with the following RADIUS reply message:

You are already logged in - access denied

FreeRADIUS can enforce this check through its sql module, but that's not multi-tenant aware: this can cause issues when a user belongs to multiple organizations with different session limits, potentially resulting in wrong limits being applied.

To address this, OpenWISP RADIUS provides a multi-tenant aware Simultaneous-Use check in its authorization REST API endpoint.

Configuring Simultaneous-Use Check

Add the Simultaneous-Use RADIUS check to the desired RADIUS group by following these steps:

  1. In the admin interface, navigate to RADIUS in the left-hand menu.

  2. Go to Groups.

  3. Select the group you want to configure.

  4. In the GROUP CHECKS section, click on Add another Group check.

  5. Fill in the fields as follows:

    • Attribute: Simultaneous-Use

    • Operator: :=

    • Value: 1 (or any number greater than 0; 1 limits users to one concurrent session)

    Example of setting Idle-Timeout to 240

Important

When using Simultaneous-Use, it is recommended to add an Idle-Timeout RADIUS reply to the same RADIUS group, with a low value (below 300 seconds). This ensures inactive sessions are cleared quickly, preventing users from being blocked due to stale sessions.

  1. For the same radius group, in the GROUP REPLIES section, click on Add another Group reply.

  2. Fill in the fields as follows:

    • Attribute: Idle-Timeout

    • Operator: =

    • Value: 240

    Example of setting Idle-Timeout to 240

  3. Click on Save and continue editing at the bottom of the page.

Disabling the Simultaneous-Use check

The Simultaneous-Use feature is enabled by default.

It can be disabled with the OPENWISP_RADIUS_SIMULTANEOUS_USE_ENABLED setting.

This is useful if you already rely on another FreeRADIUS module to enforce Simultaneous-Use and do not need the OpenWISP implementation.