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Upstream: fixed X-Accel-Expires/Cache-Control/Expires handling. 

Previously, if caching was disabled due to Expires in the past, nginx
failed to cache the response even if it was cacheable as per subsequently
parsed Cache-Control header (ticket #964).

Similarly, if caching was disabled due to Expires in the past,
"Cache-Control: no-cache" or "Cache-Control: max-age=0", caching was not
used if it was cacheable as per subsequently parsed X-Accel-Expires header.

Fix is to avoid disabling caching immediately after parsing Expires in
the past or Cache-Control, but rather set flags which are later checked by
ngx_http_upstream_process_headers() (and cleared by "Cache-Control: max-age"
and X-Accel-Expires).

Additionally, now X-Accel-Expires does not prevent parsing of cache control
extensions, notably stale-while-revalidate and stale-if-error.  This
ensures that order of the X-Accel-Expires and Cache-Control headers is not
important.

Prodded by Vadim Fedorenko and Yugo Horie.
This commit is contained in:
Maxim Dounin 2022-06-07 00:07:12 +03:00
parent e571a75ba4
commit bb4d3b091d
2 changed files with 24 additions and 7 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

29
src/http/ngx_http_upstream.c
View File

@ -2702,6 +2702,10 @@ ngx_http_upstream_intercept_errors(ngx_http_request_t *r,
if (r->cache) {
if (u->headers_in.no_cache || u->headers_in.expired) {
u->cacheable = 0;
}
if (u->cacheable) {
time_t valid;
@ -2796,6 +2800,10 @@ ngx_http_upstream_process_headers(ngx_http_request_t *r, ngx_http_upstream_t *u)
umcf = ngx_http_get_module_main_conf(r, ngx_http_upstream_module);
if (u->headers_in.no_cache || u->headers_in.expired) {
u->cacheable = 0;
}
if (u->headers_in.x_accel_redirect
&& !(u->conf->ignore_headers & NGX_HTTP_UPSTREAM_IGN_XA_REDIRECT))
{
@ -4791,18 +4799,18 @@ ngx_http_upstream_process_cache_control(ngx_http_request_t *r,
return NGX_OK;
}
if (r->cache->valid_sec != 0 && u->headers_in.x_accel_expires != NULL) {
return NGX_OK;
}
start = h->value.data;
last = start + h->value.len;
if (r->cache->valid_sec != 0 && u->headers_in.x_accel_expires != NULL) {
goto extensions;
}
if (ngx_strlcasestrn(start, last, (u_char *) "no-cache", 8 - 1) != NULL
|| ngx_strlcasestrn(start, last, (u_char *) "no-store", 8 - 1) != NULL
|| ngx_strlcasestrn(start, last, (u_char *) "private", 7 - 1) != NULL)
{
u->cacheable = 0;
u->headers_in.no_cache = 1;
return NGX_OK;
}
@ -4832,13 +4840,16 @@ ngx_http_upstream_process_cache_control(ngx_http_request_t *r,
}
if (n == 0) {
u->cacheable = 0;
u->headers_in.no_cache = 1;
return NGX_OK;
}
r->cache->valid_sec = ngx_time() + n;
u->headers_in.expired = 0;
}
extensions:
p = ngx_strlcasestrn(start, last, (u_char *) "stale-while-revalidate=",
23 - 1);
@ -4932,7 +4943,7 @@ ngx_http_upstream_process_expires(ngx_http_request_t *r, ngx_table_elt_t *h,
expires = ngx_parse_http_time(h->value.data, h->value.len);
if (expires == NGX_ERROR || expires < ngx_time()) {
u->cacheable = 0;
u->headers_in.expired = 1;
return NGX_OK;
}
@ -4996,6 +5007,8 @@ ngx_http_upstream_process_accel_expires(ngx_http_request_t *r,
default:
r->cache->valid_sec = ngx_time() + n;
u->headers_in.no_cache = 0;
u->headers_in.expired = 0;
return NGX_OK;
}
}
@ -5007,6 +5020,8 @@ ngx_http_upstream_process_accel_expires(ngx_http_request_t *r,
if (n != NGX_ERROR) {
r->cache->valid_sec = n;
u->headers_in.no_cache = 0;
u->headers_in.expired = 0;
}
}
#endif

2
src/http/ngx_http_upstream.h
View File

@ -293,6 +293,8 @@ typedef struct {
unsigned connection_close:1;
unsigned chunked:1;
unsigned no_cache:1;
unsigned expired:1;
} ngx_http_upstream_headers_in_t;