view src/core/ngx_buf.h @ 5992:174512857ccf

Cache: do not inherit last_modified and etag from stale response. When replacing a stale cache entry, its last_modified and etag could be inherited from the old entry if the response code is not 200 or 206. Moreover, etag could be inherited with any response code if it's missing in the new response. As a result, the cache entry is left with invalid last_modified or etag which could lead to broken revalidation. For example, when a file is deleted from backend, its last_modified is copied to the new 404 cache entry and is used later for revalidation. Once the old file appears again with its original timestamp, revalidation succeeds and the cached 404 response is sent to client instead of the file. The problem appeared with etags in 44b9ab7752e3 (1.7.3) and affected last_modified in 1573fc7875fa (1.7.9).
author Roman Arutyunyan <arut@nginx.com>
date Mon, 02 Mar 2015 19:47:13 +0300
parents 0f234ee664f7
children 1fdba317ee6d
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/*
 * Copyright (C) Igor Sysoev
 * Copyright (C) Nginx, Inc.
 */


#ifndef _NGX_BUF_H_INCLUDED_
#define _NGX_BUF_H_INCLUDED_


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


typedef void *            ngx_buf_tag_t;

typedef struct ngx_buf_s  ngx_buf_t;

struct ngx_buf_s {
    u_char          *pos;
    u_char          *last;
    off_t            file_pos;
    off_t            file_last;

    u_char          *start;         /* start of buffer */
    u_char          *end;           /* end of buffer */
    ngx_buf_tag_t    tag;
    ngx_file_t      *file;
    ngx_buf_t       *shadow;


    /* the buf's content could be changed */
    unsigned         temporary:1;

    /*
     * the buf's content is in a memory cache or in a read only memory
     * and must not be changed
     */
    unsigned         memory:1;

    /* the buf's content is mmap()ed and must not be changed */
    unsigned         mmap:1;

    unsigned         recycled:1;
    unsigned         in_file:1;
    unsigned         flush:1;
    unsigned         sync:1;
    unsigned         last_buf:1;
    unsigned         last_in_chain:1;

    unsigned         last_shadow:1;
    unsigned         temp_file:1;

    /* STUB */ int   num;
};


struct ngx_chain_s {
    ngx_buf_t    *buf;
    ngx_chain_t  *next;
};


typedef struct {
    ngx_int_t    num;
    size_t       size;
} ngx_bufs_t;


typedef struct ngx_output_chain_ctx_s  ngx_output_chain_ctx_t;

typedef ngx_int_t (*ngx_output_chain_filter_pt)(void *ctx, ngx_chain_t *in);

#if (NGX_HAVE_FILE_AIO)
typedef void (*ngx_output_chain_aio_pt)(ngx_output_chain_ctx_t *ctx,
    ngx_file_t *file);
#endif

struct ngx_output_chain_ctx_s {
    ngx_buf_t                   *buf;
    ngx_chain_t                 *in;
    ngx_chain_t                 *free;
    ngx_chain_t                 *busy;

    unsigned                     sendfile:1;
    unsigned                     directio:1;
#if (NGX_HAVE_ALIGNED_DIRECTIO)
    unsigned                     unaligned:1;
#endif
    unsigned                     need_in_memory:1;
    unsigned                     need_in_temp:1;
#if (NGX_HAVE_FILE_AIO)
    unsigned                     aio:1;

    ngx_output_chain_aio_pt      aio_handler;
#if (NGX_HAVE_AIO_SENDFILE)
    ssize_t                    (*aio_preload)(ngx_buf_t *file);
#endif
#endif

    off_t                        alignment;

    ngx_pool_t                  *pool;
    ngx_int_t                    allocated;
    ngx_bufs_t                   bufs;
    ngx_buf_tag_t                tag;

    ngx_output_chain_filter_pt   output_filter;
    void                        *filter_ctx;
};


typedef struct {
    ngx_chain_t                 *out;
    ngx_chain_t                **last;
    ngx_connection_t            *connection;
    ngx_pool_t                  *pool;
    off_t                        limit;
} ngx_chain_writer_ctx_t;


#define NGX_CHAIN_ERROR     (ngx_chain_t *) NGX_ERROR


#define ngx_buf_in_memory(b)        (b->temporary || b->memory || b->mmap)
#define ngx_buf_in_memory_only(b)   (ngx_buf_in_memory(b) && !b->in_file)

#define ngx_buf_special(b)                                                   \
    ((b->flush || b->last_buf || b->sync)                                    \
     && !ngx_buf_in_memory(b) && !b->in_file)

#define ngx_buf_sync_only(b)                                                 \
    (b->sync                                                                 \
     && !ngx_buf_in_memory(b) && !b->in_file && !b->flush && !b->last_buf)

#define ngx_buf_size(b)                                                      \
    (ngx_buf_in_memory(b) ? (off_t) (b->last - b->pos):                      \
                            (b->file_last - b->file_pos))

ngx_buf_t *ngx_create_temp_buf(ngx_pool_t *pool, size_t size);
ngx_chain_t *ngx_create_chain_of_bufs(ngx_pool_t *pool, ngx_bufs_t *bufs);


#define ngx_alloc_buf(pool)  ngx_palloc(pool, sizeof(ngx_buf_t))
#define ngx_calloc_buf(pool) ngx_pcalloc(pool, sizeof(ngx_buf_t))

ngx_chain_t *ngx_alloc_chain_link(ngx_pool_t *pool);
#define ngx_free_chain(pool, cl)                                             \
    cl->next = pool->chain;                                                  \
    pool->chain = cl



ngx_int_t ngx_output_chain(ngx_output_chain_ctx_t *ctx, ngx_chain_t *in);
ngx_int_t ngx_chain_writer(void *ctx, ngx_chain_t *in);

ngx_int_t ngx_chain_add_copy(ngx_pool_t *pool, ngx_chain_t **chain,
    ngx_chain_t *in);
ngx_chain_t *ngx_chain_get_free_buf(ngx_pool_t *p, ngx_chain_t **free);
void ngx_chain_update_chains(ngx_pool_t *p, ngx_chain_t **free,
    ngx_chain_t **busy, ngx_chain_t **out, ngx_buf_tag_t tag);

off_t ngx_chain_coalesce_file(ngx_chain_t **in, off_t limit);

ngx_chain_t *ngx_chain_update_sent(ngx_chain_t *in, off_t sent);

#endif /* _NGX_BUF_H_INCLUDED_ */