Bug ID 591828: For unmatched connection, TCP RST may not be sent for data packet

Last Modified: Apr 10, 2019

Bug Tracker

Affected Product:  See more info
BIG-IP AFM, ASM(all modules)

Known Affected Versions:
11.5.1, 11.5.1 HF1, 11.5.1 HF10, 11.5.1 HF11, 11.5.1 HF2, 11.5.1 HF3, 11.5.1 HF4, 11.5.1 HF5, 11.5.1 HF6, 11.5.1 HF7, 11.5.1 HF8, 11.5.1 HF9, 11.5.2, 11.5.2 HF1, 11.5.3, 11.5.3 HF1, 11.5.3 HF2, 11.5.4, 11.5.4 HF1, 11.5.4 HF2, 11.5.4 HF3, 11.5.4 HF4, 11.5.5, 11.5.6, 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, 11.6.3.1, 11.6.3.2, 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

Fixed In:
13.0.0, 12.1.3.1, 11.6.3.3, 11.5.7

Opened: May 06, 2016
Severity: 3-Major
Related AskF5 Article:
K52750813

Symptoms

When TCP connection times out (no entry in 'show sys conn'), and subsequent data packet comes in (not SYN), The BIG-IP system does not send a RST to the client to reset the connection.

Impact

Client retransmits several times and then terminates TCP connection. There is no RST sent from BIG-IP to client for unmatched connection.

Conditions

This issue occurs if AFM is provisioned. Additionally, in BIG-IP v12.1.0 and above, it occurs if ASM is provisioned (regardless of AFM provisioning). -- Packets other than SYN with no entry in the connection table arrive. This can occur either after a failover (when mirroring is disabled) when traffic arrives at the newly-active system, or can occur if the relevant virtual server has 'reset-on-timeout' disabled.

Workaround

Enable the reset on timeout option to send TCP RST to client when connection times out. Note: This workaround does not address the circumstances where a newly-active BIG-IP system receives traffic (e.g. after a failover or system reboot).

Fix Information

The BIG-IP system now sends a TCP RST for unknown connections so the clients and backend servers can start a new connection.

Behavior Change