# HG changeset patch
# User Vadim Fedorenko <vadim.fedorenko@cdnnow.ru>
# Date 1650406016 -10800
# Wed Apr 20 01:06:56 2022 +0300
# Node ID e04dac22328020cf8d8abcc4863b982b513b0c80
# Parent a736a7a613ea6e182ff86fbadcb98bb0f8891c0b
Upstream: prioritise X-Accel-Expire over Cache-Control and Expire

RFC7234 explicitly says that cache recipient MUST ignore Expires
header if response includes Cache-Control header with max-age or
s-maxage directives. Previously Cache-Control was ignored if it
was after Expires in reply headers.

At the same time documentation states that there is special header
X-Accel-Expires that controls the behavior of nginx and should be
prioritized over other cache-specific headers and this patch
implements this priority.

More informantion could be found in ticket #964.
---
src/http/ngx_http_upstream.c | 62 +++++++++++++++++++++++++-----------
src/http/ngx_http_upstream.h | 6 ++++
2 files changed, 50 insertions(+), 18 deletions(-)

diff -r a736a7a613ea -r e04dac223280 src/http/ngx_http_upstream.c
--- a/src/http/ngx_http_upstream.c Tue Feb 08 17:35:27 2022 +0300
+++ b/src/http/ngx_http_upstream.c Wed Apr 20 01:06:56 2022 +0300
@@ -2350,6 +2350,32 @@


static void
+ngx_http_upstream_validate_cache_headers(ngx_http_request_t *r, ngx_http_upstream_t *u)
+{
+ ngx_http_upstream_headers_in_t *uh = &u->headers_in;
+ if (uh->x_accel_expires != NULL &&
+ !(u->conf->ignore_headers & NGX_HTTP_UPSTREAM_IGN_XA_EXPIRES)) {
+ u->cacheable = uh->x_accel_expires_c;
+ r->cache->valid_sec = uh->x_accel_expires_n;
+ return;
+ }
+
+ if (uh->cache_control.elts != NULL &&
+ !(u->conf->ignore_headers & NGX_HTTP_UPSTREAM_IGN_CACHE_CONTROL)) {
+ u->cacheable = uh->cache_control_c;
+ r->cache->valid_sec = uh->cache_control_n;
+ return;
+ }
+
+ if (uh->expires != NULL &&
+ !(u->conf->ignore_headers & NGX_HTTP_UPSTREAM_IGN_EXPIRES)) {
+ u->cacheable = uh->expires_c;
+ r->cache->valid_sec = uh->expires_n;
+ }
+}
+
+
+static void
ngx_http_upstream_process_header(ngx_http_request_t *r, ngx_http_upstream_t *u)
{
ssize_t n;
@@ -2468,6 +2494,11 @@

continue;
}
+#if (NGX_HTTP_CACHE)
+ if (u->cacheable) {
+ ngx_http_upstream_validate_cache_headers(r, u);
+ }
+#endif

break;
}
@@ -4735,10 +4766,6 @@
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;

@@ -4746,7 +4773,7 @@
|| 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.cache_control_c = 0;
return NGX_OK;
}

@@ -4771,16 +4798,15 @@
continue;
}

- u->cacheable = 0;
return NGX_OK;
}

if (n == 0) {
- u->cacheable = 0;
return NGX_OK;
}

- r->cache->valid_sec = ngx_time() + n;
+ u->headers_in.cache_control_c = 1;
+ u->headers_in.cache_control_n = ngx_time() + n;
}

p = ngx_strlcasestrn(start, last, (u_char *) "stale-while-revalidate=",
@@ -4856,18 +4882,18 @@
return NGX_OK;
}

- if (r->cache->valid_sec != 0) {
+ expires = ngx_parse_http_time(h->value.data, h->value.len);
+
+ if (expires == NGX_ERROR || expires < ngx_time()) {
return NGX_OK;
}

- expires = ngx_parse_http_time(h->value.data, h->value.len);
-
- if (expires == NGX_ERROR || expires < ngx_time()) {
- u->cacheable = 0;
- return NGX_OK;
- }
-
- r->cache->valid_sec = expires;
+ if (u->headers_in.expires_c) {
+ expires = ngx_min(expires, u->headers_in.expires_n);
+ }
+ u->headers_in.expires_n = expires;
+ u->headers_in.expires_c = 1;
+
}
#endif

@@ -4906,14 +4932,12 @@

switch (n) {
case 0:
- u->cacheable = 0;
- /* fall through */
-
case NGX_ERROR:
return NGX_OK;

default:
- r->cache->valid_sec = ngx_time() + n;
+ u->headers_in.x_accel_expires_c = 1;
+ u->headers_in.x_accel_expires_n = ngx_time() + n;
return NGX_OK;
}
}
@@ -4924,7 +4948,8 @@
n = ngx_atoi(p, len);

if (n != NGX_ERROR) {
- r->cache->valid_sec = n;
+ u->headers_in.x_accel_expires_c = 1;
+ u->headers_in.x_accel_expires_n = ngx_time() + n;
}
}
#endif
diff -r a736a7a613ea -r e04dac223280 src/http/ngx_http_upstream.h
--- a/src/http/ngx_http_upstream.h Tue Feb 08 17:35:27 2022 +0300
+++ b/src/http/ngx_http_upstream.h Wed Apr 20 01:06:56 2022 +0300
@@ -294,9 +294,15 @@

off_t content_length_n;
time_t last_modified_time;
+ ngx_int_t cache_control_n;
+ ngx_int_t expires_n;
+ ngx_int_t x_accel_expires_n;

unsigned connection_close:1;
unsigned chunked:1;
+ unsigned cache_control_c;
+ unsigned expires_c;
+ unsigned x_accel_expires_c;
} ngx_http_upstream_headers_in_t;


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