1.3.x if-none-match only works if las-modified set

[Maxim Dounin]

Hello!

On Mon, Mar 11, 2013 at 01:04:32PM -0400, Brian Akins wrote:

> in ngx_http_not_modified_header_filter
> 
> if (r->headers_out.status != NGX_HTTP_OK
> 	|| r != r->main
> 	|| r->headers_out.last_modified_time == -1)
>     {
> 
> So, it only checks if-match or if-none-match if last-modified is set.
> Is this on purpose?  I'm just wondering if we want to be able to check
> etime without checking last-modified.

The following commit log suggests it was done intentionally,
http://trac.nginx.org/nginx/changeset/4745/nginx:

: Note that the "r->headers_out.last_modified_time == -1" check in the not
: modified filter is left as is intentionally.  It's to prevent handling
: of If-* headers in case of proxy without cache (much like currently
: done with If-Modified-Since).

Changing the code to work with ETag from cache without 
Last-Modified being present in a cached response should be 
possible, but it will require some additional changes.

-- 
Maxim Dounin
http://nginx.org/en/donation.html