Due to ap_http_header_filter():
/* This is a hack, but I can't find anyway around it. The idea is that
* we don't want to send out 0 Content-Lengths if it is a head request.
* This happens when modules try to outsmart the server, and return
* if they see a HEAD request. Apache 1.3 handlers were supposed to
* just return in that situation, and the core handled the HEAD. In
* 2.0, if a handler returns, then the core sends an EOS bucket down
* the filter stack, and the content-length filter computes a C-L of
* zero and that gets put in the headers, and we end up sending a
* zero C-L to the client. We can't just remove the C-L filter,
* because well behaved 2.0 handlers will send their data down the stack,
* and we will compute a real C-L for the head request. RBB
*
* Allow modification of this behavior through the
* HttpContentLengthHeadZero directive.
*
* The default (unset) behavior is to squelch the C-L in this case.
*/
if (r->header_only
&& (clheader = apr_table_get(r->headers_out, "Content-Length"))
&& !strcmp(clheader, "0")
&& conf->http_cl_head_zero != AP_HTTP_CL_HEAD_ZERO_ENABLE) {
apr_table_unset(r->headers_out, "Content-Length");
}
I find this workaround a bit too much hacky because "Content-Length:
0" could be the real one for the corresponding GET request, either
given by a module or forwarded from a backend.
Hence how about removing this whole block (is there any module today
"outsmarting" httpd that cannot be considered as buggy?) or least
disable it for forwarded responses, eg:
Index: modules/http/http_filters.c
===================================================================
--- modules/http/http_filters.c (revision 1676716)
+++ modules/http/http_filters.c (working copy)
@@ -1292,6 +1292,7 @@ AP_CORE_DECLARE_NONSTD(apr_status_t) ap_http_heade
* The default (unset) behavior is to squelch the C-L in this case.
*/
if (r->header_only
+ && !r->proxyreq
&& (clheader = apr_table_get(r->headers_out, "Content-Length"))
&& !strcmp(clheader, "0")
&& conf->http_cl_head_zero != AP_HTTP_CL_HEAD_ZERO_ENABLE) {
--
?
