Bug ID 521556: Assertion "valid pcb" in TCP4 with ICAP adaptation

Last Modified: Apr 28, 2025

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

Known Affected Versions:
11.3.0, 11.4.0, 11.4.1, 11.5.0, 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, 11.5.3, 11.5.3 HF1, 11.6.0, 11.6.0 HF1, 11.6.0 HF2, 11.6.0 HF3, 11.6.0 HF4, 11.6.0 HF5

Fixed In:
12.0.0, 11.6.0 HF6, 11.5.3 HF2, 11.4.1 HF10

Opened: May 05, 2015

Severity: 2-Critical

Symptoms

TMM crashes with assertion "valid pcb" in tcp4.c

Impact

Intermittent crash under load. Traffic disrupted while tmm restarts.

Conditions

Virtual server with request-adapt or response-adapt profile. Congested client or TCP small window (flow-control is active). Multiple HTTP requests in a single client connection. More likely with iRules that park.

Workaround

None

Fix Information

Assertion "valid pcb" does not occur.

Behavior Change

Guides & references

K10134038: F5 Bug Tracker Filter Names and Tips