Bug ID 757357: Tmm crashes when using virtio direct descriptors and packets 2 KB or larger

Last Modified: Mar 21, 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, 14.0.0, 14.0.0.1, 14.0.0.2, 14.0.0.3, 14.0.0.4, 14.1.0, 14.1.0.1, 14.1.0.2, 14.1.0.3

Opened: Feb 01, 2019
Severity: 2-Critical

Symptoms

Some virtio backend implementations send large packets (2 KB or larger) even when LRO is disabled. If the backend uses direct descriptors, this combination might lead to a tmm core. The standard KVM implementation of virtio does not have this behavior.

Impact

Tmm may restart. Traffic disrupted while tmm restarts.

Conditions

-- BIG-IP Virtual Edition (VE) using virtio interfaces with direct descriptors. -- A 2 KB or larger packet is delivered to the virtio interface.

Workaround

Disable direct descriptors in the virtio backend.

Fix Information

None

Behavior Change