Bug ID 512119: Improved UDP DNS packet truncation

Last Modified: Sep 13, 2023

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

Known Affected Versions:
11.6.0, 12.1.0 HF1, 12.1.0 HF2, 12.1.1 HF1, 12.1.1 HF2, 12.1.2 HF1, 12.1.2 HF2

Fixed In:
12.0.0, 11.6.1, 11.5.4 HF3

Opened: Mar 12, 2015

Severity: 3-Major

Symptoms

UDP responses from the DNS cache were not truncated properly. This is primarily seen in DNS tools, such as dig or Wireshark that would mark the response as malformed. Regular resolver clients handled the responses correctly noting the tc bit in the response header.

Impact

Packets may be flagged as malformed by DNS packet analyzers. There are no known issues with regular DNS client resolvers.

Conditions

UDP DNS responses larger than the size requested by the client, typically 512 bytes.

Workaround

None

Fix Information

The DNS Cache now properly fills in response data and handles truncation as expected.

Behavior Change

Guides & references

K10134038: F5 Bug Tracker Filter Names and Tips