Bug ID 648316: Flows using DEFLATE decompresion can generate error message during flow tear-down.

Last Modified: Jun 30, 2021

Bug Tracker

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

Known Affected Versions:
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

Fixed In:
13.1.0, 11.6.2

Opened: Mar 01, 2017
Severity: 3-Major
Related AskF5 Article:


Repeated entries in the ltm log will show a completion-code error (comp_code=4) as in the following: Zip engine ctx eviction (comp_code=4): ctx dropped.


False errors can appear: o In fields of tmctl rst_cause_stat table, false stats counters will increment for compression and packet errors. o Log entries with the "Zip engine... (comp_code=4)" appear in ltm log. Monitors observing the ltm log or stats in the tmctl rst_cause_stat table will see false positives.


The problem occurs when a flow that requests DEFLATE decompression is terminated when the compression engine is still in the middle of working on an incomplete DEFLATE block.


Disable hardware acceleration.

Fix Information

A new tcl variable, nitrox::comp_suppress_itrunc, was added. It defaults to NO which yields legacy behavior. Setting it to YES causes comp_code=4 (ITRUNC) errors to not propagate as an error. To enable the feature, add the following line to /config/tmm_init.tcl: nitrox::comp_suppress_itrunc yes You will have to restart tmm for the change to take effect.

Behavior Change