Nginx write new module as filter.

[Walter Dal Mut]

Hi everybody I am new to nginx and actually I am interested on nginx
extensions.

I need to write a new module for nginx and compile a version with this
module. I don't want to write down an handler but a filter, I need to work
on headers.

For that reason I start my module using gzip as a base and cut different
part that I don't want use.

I compile nginx with my module and all works fine. After that I start the
server with my personal configuration (corley on;) in the main conf file and
the server start correctly. The problem is that my module seems never used.
The filter functionality is pretty simple, I want to force text/plain
header.

I don't understand why my module is never called. Any one can help me?

The main filename is: *ngx_http_corley_filter_module.c*
The configuration filename is:* config*
*
*
The config content:
*
*
ngx_addon_name=ngx_http_corley_filter_module
HTTP_MODULES="$HTTP_MODULES ngx_http_corley_filter_module"
NGX_ADDON_SRCS="$NGX_ADDON_SRCS
$ngx_addon_dir/ngx_http_corley_filter_module.c"


The ngx_http_corley_filter_module.c content:

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

typedef struct {
   ngx_flag_t           enable;
} ngx_http_corley_conf_t;

static ngx_int_t ngx_http_corley_filter_init(ngx_conf_t *cf);
static void * ngx_http_corley_create_conf(ngx_conf_t *cf);
static char * ngx_http_corley_merge_conf(ngx_conf_t *cf, void *parent, void
*child);
static void * ngx_http_corley_create_conf(ngx_conf_t *cf);

static ngx_command_t  ngx_http_corley_filter_commands[] = {

   { ngx_string("corley"),

 NGX_HTTP_MAIN_CONF|NGX_HTTP_SRV_CONF|NGX_HTTP_LOC_CONF|NGX_HTTP_LIF_CONF|NGX_CONF_FLAG,
     ngx_conf_set_flag_slot,
     NGX_HTTP_LOC_CONF_OFFSET,
     offsetof(ngx_http_corley_conf_t, enable),
     NULL },

     ngx_null_command
};


static ngx_http_module_t  ngx_http_corley_filter_module_ctx = {
   NULL,                                  /* preconfiguration */
   ngx_http_corley_filter_init,           /* postconfiguration */
   NULL,                                  /* create main configuration */
   NULL,                                  /* init main configuration */
   NULL,                                  /* create server configuration */
   NULL,                                  /* merge server configuration */
   ngx_http_corley_create_conf,           /* create location configuration
*/
   ngx_http_corley_merge_conf             /* merge location configuration */
};


ngx_module_t  ngx_http_corley_filter_module = {
   NGX_MODULE_V1,
   &ngx_http_corley_filter_module_ctx,      /* module context */
   ngx_http_corley_filter_commands,         /* module directives */
   NGX_HTTP_MODULE,                       /* module type */
   NULL,                                  /* init master */
   NULL,                                  /* init module */
   NULL,                                  /* init process */
   NULL,                                  /* init thread */
   NULL,                                  /* exit thread */
   NULL,                                  /* exit process */
   NULL,                                  /* exit master */
   NGX_MODULE_V1_PADDING
};


static ngx_http_output_header_filter_pt  ngx_http_next_header_filter;
static ngx_http_output_body_filter_pt    ngx_http_next_body_filter;


*static ngx_int_t
ngx_http_corley_header_filter(ngx_http_request_t *r)
{
   ngx_http_corley_conf_t  *conf;
   conf = ngx_http_get_module_loc_conf(r, ngx_http_corley_filter_module);

   ngx_table_elt_t       *h;

   h = ngx_list_push(&r->headers_out.headers);
   if (h == NULL) {
       return NGX_ERROR;
   }

   h->hash = 1;
   ngx_str_set(&h->key, "Content-Encoding");
   ngx_str_set(&h->value, "text/plain");

   r->headers_out.content_encoding = h;

   r->main_filter_need_in_memory = 1;

   ngx_http_clear_content_length(r);
   ngx_http_clear_accept_ranges(r);


   return ngx_http_next_header_filter(r);
}
*

static ngx_int_t
ngx_http_corley_body_filter(ngx_http_request_t *r, ngx_chain_t *in)
{
   ngx_log_error(NGX_LOG_ERR, r->connection->log, 0,
             "not well formed XML document");
   return ngx_http_next_body_filter(r, in);
}

static void *
ngx_http_corley_create_conf(ngx_conf_t *cf)
{
   ngx_http_corley_conf_t  *conf;

   conf = ngx_pcalloc(cf->pool, sizeof(ngx_http_corley_conf_t));
   if (conf == NULL) {
       return NULL;
   }

   /*
    * set by ngx_pcalloc():
    *
    *     conf->bufs.num = 0;
    *     conf->types = { NULL };
    *     conf->types_keys = NULL;
    */

   conf->enable = NGX_CONF_UNSET;

   return conf;
}


static char *
ngx_http_corley_merge_conf(ngx_conf_t *cf, void *parent, void *child)
{
   ngx_http_corley_conf_t *prev = parent;
   ngx_http_corley_conf_t *conf = child;

   ngx_conf_merge_value(conf->enable, prev->enable, 0);

   return NGX_CONF_OK;
}

static ngx_int_t
ngx_http_corley_filter_init(ngx_conf_t *cf)
{
   ngx_http_next_header_filter = ngx_http_top_header_filter;
   ngx_http_top_header_filter = ngx_http_corley_header_filter;

   ngx_http_next_body_filter = ngx_http_top_body_filter;
   ngx_http_top_body_filter = ngx_http_corley_body_filter;

   return NGX_OK;
}

Thanks to all.
Walter
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