Bug ID 812693: Connection in FIN_WAIT_2 state may fail to be removed

Last Modified: Nov 15, 2019

Bug Tracker

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

Known Affected Versions:
13.1.0, 13.1.0.1, 13.1.0.2, 13.1.0.3, 13.1.0.4, 13.1.0.5, 13.1.0.6, 13.1.0.7, 13.1.0.8, 13.1.1, 13.1.1.1, 13.1.1.2, 13.1.1.3, 13.1.1.4, 13.1.1.5, 13.1.3, 13.1.3.1, 13.1.3.2, 14.0.0, 14.0.0.1, 14.0.0.2, 14.0.0.3, 14.0.0.4, 14.0.0.5, 14.0.1, 14.0.1.1, 14.1.0, 14.1.0.1, 14.1.0.2, 14.1.0.3, 14.1.0.4, 14.1.0.5, 14.1.0.6, 14.1.2, 14.1.2.1, 14.1.2.2, 15.0.0, 15.0.1

Opened: Aug 06, 2019
Severity: 3-Major

Symptoms

If a connection that has a fully closed client-side, but a server-side still in FIN_WAIT_2, receives a SYN matching the same connflow, the idle time is reset. This can result in the fin-wait-2-timeout never being reached. The SYN will be responded to with a RST - 'TCP Closed'

Impact

Connection may fail to be removed in a timely manner. New connection attempts are RST with 'TCP Closed'

Conditions

- Client side connection has been fully closed. This may occur if a client SSL profile is in use and an 'Encrypted Alert' has been received. - Server side has sent a FIN which has been ACK'd, but no FIN has been received from the server. - SYN received matching the existing connflow before the FIN-WAIT-2-timeout has been reached (300 default).

Workaround

You can use either of the following: -- Ensure servers are sending FIN's so as not to leave the connection in a FIN_WAIT_2 state. -- Mitigate the issue by lowering the FIN-WAIT-2-timeout to a smaller value, e.g., FIN-WAIT-2-timeout 10.

Fix Information

None

Behavior Change