Bug ID 1099373: Virtual Servers may reply with a three-way handshake when disabled or when processing iRules

Last Modified: Sep 29, 2022

Bug Tracker

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

Known Affected Versions:
15.1.0, 15.1.0.1, 15.1.0.2, 15.1.0.3, 15.1.0.4, 15.1.0.5, 15.1.1, 15.1.2, 15.1.2.1, 15.1.3, 15.1.3.1, 15.1.4, 15.1.4.1, 15.1.5, 15.1.5.1, 15.1.6, 15.1.6.1, 15.1.7, 16.1.0, 16.1.1, 16.1.2, 16.1.2.1, 16.1.2.2, 16.1.3, 16.1.3.1, 16.1.3.2

Opened: Apr 14, 2022
Severity: 3-Major

Symptoms

Virtual servers may complete a three-way handshake before resetting a connection when they are disabled or when iRules process traffic for disabled virtual servers.

Impact

When a virtual server is marked as disabled and a client attempts to connect to it, tmm will normally send a reset to the first SYN packet. However, if you then administratively disable the pool ( disabled pool members - Not forced offline) tmm will complete the three-way handshake before sending resets. Additionally, when in this state, iRules will process and can pass traffic to pools if the iRule is configured to do that even though the virtual server status is disabled.

Conditions

-- Virtual Server with a pool assigned -- Pool is disabled administratively

Workaround

Avoid marking pools disabled or use forced offline for virtual servers that you want to administratively disable.

Fix Information

None

Behavior Change