Request Processing in Apache 2.0請求的處理過程

Apache中HTTP Request的程序主要是request.c中的函數來處理，這個函數是ap_process_request_internal，所有的請求都由它處理，包含子請求(subrequest)和轉向(redirect)。

其程式碼如下所示：

/* This is the master logic for processing requests.  Do NOT duplicate
* this logic elsewhere, or the security model will be broken by future
* API changes.  Each phase must be individually optimized to pick up
* redundant/duplicate calls by subrequests, and redirects.
*/
AP_DECLARE(int) ap_process_request_internal(request_rec *r)
{
   int file_req = (r->main && r->filename);
   int access_status;

   /* Ignore embedded %2F's in path for proxy requests */
   if (!r->proxyreq && r->parsed_uri.path) {
       core_dir_config *d;
       d = ap_get_module_config(r->per_dir_config, &core_module);
       if (d->allow_encoded_slashes) {
           access_status = ap_unescape_url_keep2f(r->parsed_uri.path);
       }
       else {
           access_status = ap_unescape_url(r->parsed_uri.path);
       }
       if (access_status) {
           if (access_status == HTTP_NOT_FOUND) {
               if (! d->allow_encoded_slashes) {
                   ap_log_rerror(APLOG_MARK, APLOG_INFO, 0, r,
                                 "found %%2f (encoded '/') in URI "
                                 "(decoded='%s'), returning 404",
                                 r->parsed_uri.path);
               }
           }
           return access_status;
       }
   }

   ap_getparents(r->uri);     /* OK --- shrinking transformations... */

   /* All file subrequests are a huge pain... they cannot bubble through the
    * next several steps.  Only file subrequests are allowed an empty uri,
    * otherwise let translate_name kill the request.
    */
   if (!file_req) {
       if ((access_status = ap_location_walk(r))) {
           return access_status;
       }

       if ((access_status = ap_run_translate_name(r))) {
           return decl_die(access_status, "translate", r);
       }
   }

   /* Reset to the server default config prior to running map_to_storage
    */
   r->per_dir_config = r->server->lookup_defaults;

   if ((access_status = ap_run_map_to_storage(r))) {
       /* This request wasn't in storage (e.g. TRACE) */
       return access_status;
   }

   /* Rerun the location walk, which overrides any map_to_storage config.
    */
   if ((access_status = ap_location_walk(r))) {
       return access_status;
   }

   /* Only on the main request! */
   if (r->main == NULL) {
       if ((access_status = ap_run_header_parser(r))) {
           return access_status;
       }
   }

   /* Skip authn/authz if the parent or prior request passed the authn/authz,
    * and that configuration didn't change (this requires optimized _walk()
    * functions in map_to_storage that use the same merge results given
    * identical input.)  If the config changes, we must re-auth.
    */
   if (r->main && (r->main->per_dir_config == r->per_dir_config)) {
       r->user = r->main->user;
       r->ap_auth_type = r->main->ap_auth_type;
   }
   else if (r->prev && (r->prev->per_dir_config == r->per_dir_config)) {
       r->user = r->prev->user;
       r->ap_auth_type = r->prev->ap_auth_type;
   }
   else {
       switch (ap_satisfies(r)) {
       case SATISFY_ALL:
       case SATISFY_NOSPEC:
           if ((access_status = ap_run_access_checker(r)) != 0) {
               return decl_die(access_status, "check access", r);
           }

           if (ap_some_auth_required(r)) {
               if (((access_status = ap_run_check_user_id(r)) != 0)
                   || !ap_auth_type(r)) {
                   return decl_die(access_status, ap_auth_type(r)
                                 ? "check user.  No user file?"
                                 : "perform authentication. AuthType not set!",
                                 r);
               }

               if (((access_status = ap_run_auth_checker(r)) != 0)
                   || !ap_auth_type(r)) {
                   return decl_die(access_status, ap_auth_type(r)
                                 ? "check access.  No groups file?"
                                 : "perform authentication. AuthType not set!",
                                  r);
               }
           }
           break;

       case SATISFY_ANY:
           if (((access_status = ap_run_access_checker(r)) != 0)) {
               if (!ap_some_auth_required(r)) {
                   return decl_die(access_status, "check access", r);
               }

               if (((access_status = ap_run_check_user_id(r)) != 0)
                   || !ap_auth_type(r)) {
                   return decl_die(access_status, ap_auth_type(r)
                                 ? "check user.  No user file?"
                                 : "perform authentication. AuthType not set!",
                                 r);
               }

               if (((access_status = ap_run_auth_checker(r)) != 0)
                   || !ap_auth_type(r)) {
                   return decl_die(access_status, ap_auth_type(r)
                                 ? "check access.  No groups file?"
                                 : "perform authentication. AuthType not set!",
                                 r);
               }
           }
           break;
       }
   }
   /* XXX Must make certain the ap_run_type_checker short circuits mime
    * in mod-proxy for r->proxyreq && r->parsed_uri.scheme
    *                              && !strcmp(r->parsed_uri.scheme, "http")
    */
   if ((access_status = ap_run_type_checker(r)) != 0) {
       return decl_die(access_status, "find types", r);
   }

   if ((access_status = ap_run_fixups(r)) != 0) {
       return access_status;
   }

   return OK;
}