Bug ID 783125: iRule drop command on DNS traffic without Datagram-LB may cause TMM crash

Last Modified: Jan 04, 2022

Bug Tracker

Affected Product:  See more info
BIG-IP DNS, LTM(all modules)

Known Affected Versions:
11.6.0, 11.6.0 HF1, 11.6.0 HF2, 11.6.0 HF3, 11.6.0 HF4, 11.6.0 HF5, 11.6.0 HF6, 11.6.0 HF7, 11.6.0 HF8, 11.6.1, 11.6.1 HF1, 11.6.1 HF2, 11.6.2, 11.6.2 HF1, 11.6.3,,,,, 11.6.4, 11.6.5,,,, 12.0.0, 12.0.0 HF1, 12.0.0 HF2, 12.0.0 HF3, 12.0.0 HF4, 12.1.0, 12.1.0 HF1, 12.1.0 HF2, 12.1.1, 12.1.1 HF1, 12.1.1 HF2, 12.1.2, 12.1.2 HF1, 12.1.2 HF2, 12.1.3,,,,,,,, 12.1.4,, 12.1.5,,,, 12.1.6, 13.0.0, 13.0.0 HF1, 13.0.0 HF2, 13.0.0 HF3, 13.0.1, 13.1.0,,,,,,,,, 13.1.1,,,,, 13.1.3,,,,, 14.0.0,,,,,, 14.0.1,, 14.1.0,,,,,, 14.1.2,,,,,,,, 15.0.0, 15.0.1,,,,, 15.1.0,,,,,, 16.0.0,

Fixed In:
16.1.0, 16.0.1, 15.1.1,,

Opened: May 17, 2019
Severity: 2-Critical


The TMM may crash and restart when an iRule on a DNS virtual server performs the 'drop' command while the BIG-IP system is handling both a DNS request and DNS response at the same time for the same DNS client IP and port without UDP Datagram-LB.


TMM crash or restart. Traffic impacted. Traffic disrupted while tmm restarts.


-- The BIG-IP instance has two or more TMM processes as a result of having two or more physical cores or virtual CPUs. -- A virtual server with both DNS and UDP profiles and one or more iRules. -- The UDP profile has Datagram LB disabled. -- The iRules have a 'drop' command. -- The iRules have a DNS_REQUEST and/or DNS_RESPONSE event with an iRule command that require coordinating data with another TMM on the system, such as the 'table' command.


F5 strongly recommends using a UDP profile with Datagram-LB enabled for DNS UDP virtual servers. Alternatively, replace the 'drop' command with DNS::drop in DNS_REQUEST and DNS_RESPONSE events, or with UDP::drop in other iRule events. See the respective references pages for DNS::drop and UDP::drop for the Valid Events each iRule command is available in: https://clouddocs.f5.com/api/irules/DNS__drop.html https://clouddocs.f5.com/api/irules/UDP__drop.html

Fix Information


Behavior Change