KB44479 - "Nfqueue is full and dropping packets. (kernel) critical." event is seen on Pulse Connect Secure 9.1R5 with a noticeable performance impact (i.e. high cpu usage)

This article describes an issue where "Nfqueue is full and dropping packets. (kernel) critical." event is seen on Pulse Connect Secure 9.1R5 with a noticeable performance impact (i.e. high cpu usage).

NFQUEUE is a kernel and user mode module for managing network packets in iptables.  The following event is seen along with a noticeable impact on system resources especially on PCS 9.1R5 and in some rare cases may show up on any PCS version from 9.0R1 onwards as well.
 

2020-05-12 01:31:40 - PSA7000 - [127.0.0.1] System()[] - Nfqueue is full and dropping packets. (kernel).

This issue is known to occur on PCS versions that support FQDN ACLs irrespective of it being configured or not.

This feature to configure "FQDN Resources" under Users -> Resource Policies -> VPN Tunneling Access Control, was introduced in Pulse Connect Secure 9.0R1. 

The issue is occurs with Pulse Connect Secure 9.1R5 as the maximum supported FQDN length does not meet RFC requirements. 

To resolve this problem, Pulse Secure is strongly advising to upgrade to 9.1R6 and above which is now available for download via https://my.pulsesecure.net/

For the other impacted PCS versions, Pulse Secure is working on a solution and will keep this KB updated as and when we make progress.