87844 - conditional requests generate an if-modified-since from previous response's Date

Status: RESOLVED DUPLICATE of bug 86265

(Core :: Networking: HTTP, defect)

Description

[Mark Nottingham]

From Bugzilla Helper:
User-Agent: Mozilla/5.0 (X11; U; Linux 2.4.5 i686; en-US; rv:0.9.1) Gecko/20010607
BuildID:    2001060713

Mozilla seems to generate an If-Modified-Since header (from the previous
response's Date header) in requests for cached entities when there is no
Last-Modified in the previous response.

While normally this would be harmless, a HTTP/1.0 intermediary cache will
misinterpret this, and serve a response from its cache (LM/IMS semantics in 1.0
were ill-defined, and this was allowed behaviour). Effectively, Mozilla is
mixing HTTP/1.1 mechanisms (ETag validation, etc. to enable storage of the
entity in cache) and HTTP/1.0 lazy LM/IMS behaviour. This is bad. 

Specifically, I have an application that generates strong ETags in responses,
but not last-modified times, as weak validators aren't acceptable. Mozilla will
insert an IMS into subseqent requests, causing an upstream intermediary to
return a cached entity (which is legal for a HTTP/1.0 cache).

Reproducible: Always
Steps to Reproduce:
1. send mozilla a response with an ETag, no Last-Modified, no other cache
headers (e.g., Cache-Control, Expires)
2. reload the resource, causing a request
3. note the request headers

Actual Results:  
> GET http://www.example.com/ HTTP/1.1
> Host: www.example.com
> User-Agent: Mozilla/5.0 (X11; U; Linux 2.4.5 i686; en-US; rv:0.9.1) Gecko/20010607
> Accept: text/xml, application/xml, application/xhtml+xml, text/html;q=0.9,
image/png, image/jpeg, image/gif;q=0.2, text/plain;q=0.8, text/css, */*;q=0.1
> Accept-Language: en-us
> Accept-Encoding: gzip,deflate,compress,identity
> Accept-Charset: ISO-8859-1, utf-8; q=0.667, *; q=0.667
> Keep-Alive: 300
> Connection: keep-alive
> If-Modified-Since: Tue, 26 Jun 2001 05:01:01 GMT
> If-None-Match: "IP0Wpf+E53v0/1TnlM9nyg=="

Expected Results:  Same request, without If-Modified-Since

Comment 1

[Bradley Baetz (:bbaetz)]

Dupe of 86265

*** This bug has been marked as a duplicate of 86265 ***