mod_cache: Ensure that we don't attempt to replace a cached response

with an older response as per RFC2616 13.12.


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@1479966 13f79535-47bb-0310-9956-ffa450edef68

1 files changed, 19 insertions, 0 deletions

diff --git a/modules/cache/mod_cache.c b/modules/cache/mod_cache.c
index 90a4efa670..e183b3a257 100644
--- a/modules/cache/mod_cache.c
+++ b/modules/cache/mod_cache.c
@@ -1089,6 +1089,25 @@ static apr_status_t cache_save_filter(ap_filter_t *f, apr_bucket_brigade *in)
         /* or we've been asked not to cache it above */
         reason = "r->no_cache present";
     }
+    else if (cache->stale_handle
+            && APR_DATE_BAD
+                    != (date = apr_date_parse_http(
+                            apr_table_get(r->headers_out, "Date")))
+            && date < cache->stale_handle->cache_obj->info.date) {
+
+        /**
+         * 13.12 Cache Replacement:
+         *
+         * Note: a new response that has an older Date header value than
+         * existing cached responses is not cacheable.
+         */
+        reason = "updated entity is older than cached entity";
+
+        /* while this response is not cacheable, the previous response still is */
+        ap_log_rerror(APLOG_MARK, APLOG_DEBUG, 0, r, APLOGNO(00770)
+                "cache: Removing CACHE_REMOVE_URL filter.");
+        ap_remove_output_filter(cache->remove_url_filter);
+    }
     else if (r->status == HTTP_NOT_MODIFIED && cache->stale_handle) {
         apr_table_t *left = cache->stale_handle->resp_hdrs;
         apr_table_t *right = r->headers_out;