Copy regex unnamed captures to cloned subrequests

[Roman Arutyunyan]

details:   https://hg.nginx.org/nginx/rev/81d49f85afed
branches:  
changeset: 7427:81d49f85afed
user:      Roman Arutyunyan <arut at nginx.com>
date:      Tue Dec 11 13:09:00 2018 +0300
description:
Copy regex unnamed captures to cloned subrequests.

Previously, unnamed regex captures matched in the parent request, were not
available in a cloned subrequest.  Now 3 fields related to unnamed captures
are copied to a cloned subrequest: r->ncaptures, r->captures and
r->captures_data.  Since r->captures cannot be changed by either request after
creating a clone, a new flag r->realloc_captures is introduced to force
reallocation of r->captures.

The issue was reported as a proxy_cache_background_update misbehavior in
http://mailman.nginx.org/pipermail/nginx/2018-December/057251.html.

diffstat:

 src/http/ngx_http_core_module.c |  8 ++++++++
 src/http/ngx_http_request.h     |  4 ++++
 src/http/ngx_http_variables.c   |  4 +++-
 3 files changed, 15 insertions(+), 1 deletions(-)

diffs (47 lines):

diff -r 4722b4b8aa93 -r 81d49f85afed src/http/ngx_http_core_module.c
--- a/src/http/ngx_http_core_module.c	Tue Dec 11 13:12:35 2018 +0300
+++ b/src/http/ngx_http_core_module.c	Tue Dec 11 13:09:00 2018 +0300
@@ -2386,6 +2386,14 @@ ngx_http_subrequest(ngx_http_request_t *
         sr->phase_handler = r->phase_handler;
         sr->write_event_handler = ngx_http_core_run_phases;
 
+#if (NGX_PCRE)
+        sr->ncaptures = r->ncaptures;
+        sr->captures = r->captures;
+        sr->captures_data = r->captures_data;
+        sr->realloc_captures = 1;
+        r->realloc_captures = 1;
+#endif
+
         ngx_http_update_location_config(sr);
     }
 
diff -r 4722b4b8aa93 -r 81d49f85afed src/http/ngx_http_request.h
--- a/src/http/ngx_http_request.h	Tue Dec 11 13:12:35 2018 +0300
+++ b/src/http/ngx_http_request.h	Tue Dec 11 13:09:00 2018 +0300
@@ -499,6 +499,10 @@ struct ngx_http_request_s {
     unsigned                          gzip_vary:1;
 #endif
 
+#if (NGX_PCRE)
+    unsigned                          realloc_captures:1;
+#endif
+
     unsigned                          proxy:1;
     unsigned                          bypass_cache:1;
     unsigned                          no_cache:1;
diff -r 4722b4b8aa93 -r 81d49f85afed src/http/ngx_http_variables.c
--- a/src/http/ngx_http_variables.c	Tue Dec 11 13:12:35 2018 +0300
+++ b/src/http/ngx_http_variables.c	Tue Dec 11 13:09:00 2018 +0300
@@ -2504,7 +2504,9 @@ ngx_http_regex_exec(ngx_http_request_t *
     if (re->ncaptures) {
         len = cmcf->ncaptures;
 
-        if (r->captures == NULL) {
+        if (r->captures == NULL || r->realloc_captures) {
+            r->realloc_captures = 0;
+
             r->captures = ngx_palloc(r->pool, len * sizeof(int));
             if (r->captures == NULL) {
                 return NGX_ERROR;