Troubleshooting Tip: FortiProxy fails to delete loopback interface with error: 'unregister_netdevice: waiting for loopback to become free'

Description

This article describes an issue where FortiProxy fails to delete a loopback interface and continuously logs the message unregister_netdevice: waiting for <loopback-interface> to become free. As a result, the interface deletion operation remains incomplete and the CMDB becomes locked, preventing further configuration changes.

Scope

FortiProxy v7.4 and v7.6.

Solution

When attempting to delete a loopback interface, FortiProxy may become stuck waiting for the interface to be released by the kernel. The console and crash log may show messages similar to the following:

unregister_netdevice: waiting for loopback1 to become free. Usage count = 1

Or:

unregister_netdevice: waiting for loopback1 to become free. Usage count = 2

To identify whether the affected loopback interfaces are present, verify the interface configuration and IP address list:

config system interface
    edit "lo1"
        set vdom "root"
        set type loopback
        set snmp-index 12
    next
    edit "lo2"
        set vdom "root"
        set type loopback
        set snmp-index 13
    next
end

An example output from the command:

diagnose ip address list

IP=127.0.0.1->127.0.0.1/255.0.0.0 index=1 devname=lo
IP=192.168.1.99->192.168.1.99/255.255.255.0 index=3 devname=port1
IP=127.0.0.1->127.0.0.1/255.0.0.0 index=33 devname=lo1
IP=127.0.0.1->127.0.0.1/255.0.0.0 index=34 devname=lo2

When deleting one of the loopback interfaces:

FortiProxy # config system interface
FortiProxy (interface) # delete lo1
[  365.389997] unregister_netdevice: waiting for lo1 to become free. Usage count = 1 

The message may repeat continuously and the interface is not removed. In some cases, the CMDB becomes locked, preventing configuration objects from being created, modified, or deleted.

The issue has been identified and resolved in the following FortiProxy releases:

• FortiProxy v7.4.14 and later (Release Notes).

• FortiProxy v7.6.7 and later (scheduled for release in August 2026).