Bug ID 483539: With fastL4, incorrect MSS value might be used if SYN has options without MSS specified

Last Modified: Apr 28, 2025

Affected Product(s):
BIG-IP LTM(all modules)

Known Affected Versions:
11.3.0, 11.5.1, 11.5.1 HF1, 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, 11.5.1 HF10, 11.5.1 HF11, 11.5.2, 11.5.2 HF1, 11.6.0, 11.6.0 HF1, 11.6.0 HF2, 11.6.0 HF3, 11.6.0 HF4

Fixed In:
12.0.0, 11.6.0 HF5, 11.5.3

Opened: Oct 08, 2014

Severity: 3-Major

Related Article: K16814

Symptoms

Due to the incorrect MSS value, TMM might core because based on the MSS value the outgoing packet attempts to use TSO, which is not correct. This can result in a crash.

Impact

If this issue occurs, then TMM will core resulting in a failover/reboot of the system.

Conditions

A virtual using fastL4 where a SYN packet with options is received, but the SYN packet does not contain an MSS option.

Workaround

None.

Fix Information

The correct MSS value is now used when SYN has options without MSS specified, so TMM no longer cores.

Behavior Change

Guides & references

K10134038: F5 Bug Tracker Filter Names and Tips