Upstream: fixed proxy_no_cache when caching errors. Caching errors, notably intercepted errors and internally generated 502/504 errors, as well as handling of cache revalidation with 304, did not take into account u->conf->no_cache predicates configured. As a result, an error might be cached even if configuration explicitly says not to. Fix is to check u->conf->no_cache in these cases. To simplify usage in multiple places, checking u->conf->no_cache is now done in a separate function. As a minor optimization, u->conf->no_cache is only checked if u->cacheable is set. As a side effect, this change also fixes caching errors after proxy_cache_bypass. Also, during cache revalidation u->cacheable is now tested, so 304 responses which disable caching won't extend cacheability of stored responses. Additionally, when caching internally generated 502/504 errors u->cacheable is now explicitly updated from u->headers_in.no_cache and u->headers_in.expired, restoring the behaviour before 8041:0784ab86ad08 (1.23.0) when an error happens while reading the response headers. Reported by Kirill A. Korinsky, https://freenginx.org/pipermail/nginx/2024-April/000082.html

/*
 * Copyright (C) Igor Sysoev
 * Copyright (C) Nginx, Inc.
 */


#ifndef _NGX_SHMEM_H_INCLUDED_
#define _NGX_SHMEM_H_INCLUDED_


#include <ngx_config.h>
#include <ngx_core.h>


typedef struct {
    u_char      *addr;
    size_t       size;
    ngx_str_t    name;
    ngx_log_t   *log;
    ngx_uint_t   exists;   /* unsigned  exists:1;  */
} ngx_shm_t;


ngx_int_t ngx_shm_alloc(ngx_shm_t *shm);
void ngx_shm_free(ngx_shm_t *shm);


#endif /* _NGX_SHMEM_H_INCLUDED_ */