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From Allan Edwards <a...@us.ibm.com>
Subject mod_include strangeness
Date Wed, 01 Dec 2004 23:44:27 GMT
Seems that mod_include can pass empty bucket brigades
down the filter chain. For instance if the first line in
an SSI is  <!--#include... then SPLIT_AND_PASS_PRETAG_BUCKETS
will pass an empty brigade as the first brigade.

This causes problems with the logic in mod_deflate which
attempts to bypass deflate when a response has zero
body length (e.g. proxied 304's)

What happens is that this empty brigade gets passed down
the filter chain and ap_http_header_filter is called before
the Content-Encoding header has been set (mod_deflate is
holding off setting this until it knows it has some
content).

As a defensive move, mod_deflate could just check for
APR_BRIGADE_EMPTY and immediately return APR_SUCCESS.
Or we could put checks in mod_include to prevent passing
empty buckets in the first place (I think there was such
a check at one time but were taken out for performance
improving reasons?).

The latter might avoid problems with other modules
but being defensive is probably a good idea also.

Comments?

Allan


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