There have been a number of glitches with our canned error message support
(ap_send_error_response) which are caused by us trying to use two different
request_recs to send them, believe it or not. We get into this situation when
an ErrorDocument specifies an internal redirect to a bad URI. Current external
symptoms include the wrong Content-Type if the ErrorDocument URI points to a bad
CGI, and garbled canned error text on ebcdic boxes due to ascii data being sent
thru a charset-lite filter which expects ebcdic input.
When ap_die detects a recursive error caused by an internal redirect to an
ErrorDocument, it saves and processes the recursive error status code, backs up
to the request_rec for the first error, and passes that to
ap_send_error_response. We then initialize this request_rec as appropriate for
a canned error message. But just before we start emitting the text of the
message, we switch to the newest request_rec by chasing r->next, which gets us
out of sync. It looks like this code was added to be compatible with similar
code in ap_finalize_request_protocol.
I can't tell from the commit logs why the code to chase r->next was added to
ap_finalize_request_protocol (rev 1.207 of modules/http/http_protocol.c). It
takes away the caller's ability to back out to an earlier request_rec after an
internal redirect failure. Is that important? Dunno, but we support in 1.3 and
I see no reason to remove that support. It's probably why the r->prev and
r->next pointers exist.
We need to send the canned error text on the same request_rec that we initialize
for that purpose in order to fix the glitches. This patch chooses to
consistantly use the request_rec passed into ap_send_error_message to be
compatible with 1.3. In order for that to work properly, the filter chains must
be updated to point to the earlier request_rec, backing out the changes done by
internal_internal_redirect.
Comments?
Thanks,
Greg
Index: modules/http/http_protocol.c
===================================================================
RCS file: /home/cvs/httpd-2.0/modules/http/http_protocol.c,v
retrieving revision 1.453
diff -u -d -b -r1.453 http_protocol.c
--- modules/http/http_protocol.c 8 Aug 2002 20:39:15 -0000 1.453
+++ modules/http/http_protocol.c 12 Aug 2002 13:41:07 -0000
@@ -2301,16 +2301,6 @@
const char *title = status_lines[idx];
const char *h1;
- /* XXX This is a major hack that should be fixed cleanly. The
- * problem is that we have the information we need in a previous
- * request, but the text of the page must be sent down the last
- * request_rec's filter stack. rbb
- */
- request_rec *rlast = r;
- while (rlast->next) {
- rlast = rlast->next;
- }
-
/* Accept a status_line set by a module, but only if it begins
* with the 3 digit status code
*/
@@ -2331,24 +2321,24 @@
* so do ebcdic->ascii translation explicitly (if needed)
*/
- ap_rvputs_proto_in_ascii(rlast,
+ ap_rvputs_proto_in_ascii(r,
DOCTYPE_HTML_2_0
"<html><head>\n<title>", title,
"</title>\n</head><body>\n<h1>", h1, "</h1>\n",
NULL);
- ap_rvputs_proto_in_ascii(rlast,
+ ap_rvputs_proto_in_ascii(r,
get_canned_error_string(status, r, location),
NULL);
if (recursive_error) {
- ap_rvputs_proto_in_ascii(rlast, "<p>Additionally, a ",
+ ap_rvputs_proto_in_ascii(r, "<p>Additionally, a ",
status_lines[ap_index_of_response(recursive_error)],
"\nerror was encountered while trying to use an "
"ErrorDocument to handle the request.</p>\n", NULL);
}
- ap_rvputs_proto_in_ascii(rlast, ap_psignature("<hr />\n", r), NULL);
- ap_rvputs_proto_in_ascii(rlast, "</body></html>\n", NULL);
+ ap_rvputs_proto_in_ascii(r, ap_psignature("<hr />\n", r), NULL);
+ ap_rvputs_proto_in_ascii(r, "</body></html>\n", NULL);
}
ap_finalize_request_protocol(r);
}
Index: modules/http/http_request.c
===================================================================
RCS file: /home/cvs/httpd-2.0/modules/http/http_request.c,v
retrieving revision 1.151
diff -u -d -b -r1.151 http_request.c
--- modules/http/http_request.c 27 Jun 2002 04:40:47 -0000 1.151
+++ modules/http/http_request.c 12 Aug 2002 13:41:07 -0000
@@ -96,6 +96,23 @@
* Mainline request processing...
*/
+/* XXX A cleaner and faster way to do this might be to pass the request_rec
+ * down the filter chain as a parameter. It would need to change for
+ * subrequest vs. main request filters; perhaps the subrequest filter could
+ * make the switch.
+ */
+static void update_r_in_filters(ap_filter_t *f,
+ request_rec *from,
+ request_rec *to)
+{
+ while (f) {
+ if (f->r == from) {
+ f->r = to;
+ }
+ f = f->next;
+ }
+}
+
AP_DECLARE(void) ap_die(int type, request_rec *r)
{
int error_index = ap_index_of_response(type);
@@ -124,6 +141,20 @@
while (r_1st_err->prev && (r_1st_err->prev->status != HTTP_OK))
r_1st_err = r_1st_err->prev; /* Get back to original error */
+ if (r_1st_err != r) {
+ /* The recursive error was caused by an ErrorDocument specifying
+ * an internal redirect to a bad URI. ap_internal_redirect has
+ * changed the filter chains to point to the ErrorDocument's
+ * request_rec. Back out those changes so we can safely use the
+ * original failing request_rec to send the canned error message.
+ *
+ * ap_send_error_response gets rid of existing resource filters
+ * on the output side, so we can skip those.
+ */
+ update_r_in_filters(r_1st_err->proto_output_filters, r, r_1st_err);
+ update_r_in_filters(r_1st_err->input_filters, r, r_1st_err);
+ }
+
custom_response = NULL; /* Do NOT retry the custom thing! */
}
@@ -301,7 +332,6 @@
static request_rec *internal_internal_redirect(const char *new_uri,
request_rec *r) {
int access_status;
- ap_filter_t *f;
request_rec *new = (request_rec *) apr_pcalloc(r->pool,
sizeof(request_rec));
@@ -367,21 +397,8 @@
new->output_filters = new->proto_output_filters;
new->input_filters = new->proto_input_filters;
- f = new->input_filters;
- while (f) {
- if (f->r == r) {
- f->r = new;
- }
- f = f->next;
- }
-
- f = new->output_filters;
- while (f) {
- if (f->r == r) {
- f->r = new;
- }
- f = f->next;
- }
+ update_r_in_filters(new->input_filters, r, new);
+ update_r_in_filters(new->output_filters, r, new);
apr_table_setn(new->subprocess_env, "REDIRECT_STATUS",
apr_itoa(r->pool, r->status));
Index: server/protocol.c
===================================================================
RCS file: /home/cvs/httpd-2.0/server/protocol.c,v
retrieving revision 1.114
diff -u -d -b -r1.114 protocol.c
--- server/protocol.c 17 Jul 2002 13:50:26 -0000 1.114
+++ server/protocol.c 12 Aug 2002 13:41:07 -0000
@@ -1101,10 +1101,6 @@
{
(void) ap_discard_request_body(r);
- while (r->next) {
- r = r->next;
- }
-
/* tell the filter chain there is no more content coming */
if (!r->eos_sent) {
end_output_stream(r);
