Bug ID 1122377: If-Modified-Since always returns 304 response if there is no last-modified header in the server response

Last Modified: Aug 04, 2022

Bug Tracker

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

Known Affected Versions:
15.1.0, 15.1.0.1, 15.1.0.2, 15.1.0.3, 15.1.0.4, 15.1.0.5, 15.1.1, 15.1.2, 15.1.2.1, 15.1.3, 15.1.3.1, 15.1.4, 15.1.4.1, 15.1.5, 15.1.5.1, 15.1.6, 15.1.6.1_RELEASE

Opened: Jun 28, 2022
Severity: 4-Minor

Symptoms

Requests sent with an If-Modified-Since header always return a 304 Not Modified response

Impact

When the Last Modified header is not present in the response, its default value i.e., Thu, 01 Jan 1970 00:00:00 GMT, is used and 304 Not Modified is sent to the client.

Conditions

The Last Modified header is not included in the origin server response headers.

Workaround

Add the Last-Modified header to the response headers using iRule when HTTP_RESPONSE priority 1 { set time [clock format [clock seconds] -gmt 1 -format "%a, %d %b %Y %H:%M:%S %Z"] HTTP::header insert Last-Modified $time log local0.debug "Inserting Last-Modified header as $time" }

Fix Information

None

Behavior Change