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From <oh...@cox.net>
Subject Re: Confused about modules processing order...
Date Thu, 01 Jan 1970 00:00:00 GMT

---- Sorin Manolache <sorinm@gmail.com> wrote: 
> On 2012-06-26 03:49, ohaya@cox.net wrote:
> >
> > Hi,
> >
> > I have my small prototype module, which I implemented starting with the mod_headers.c
source, working.  The changes that I did to the original source were to add some code in the
insert_filter hook to inject an additional header into the request.
> >
> > That seems to work ok with a "vanilla" Apache configuration.
> >
> > I want to be able to make my modified module work together with another module,
provided by Oracle (the Oracle Access Manager webgate, aka "webgate").
> >
> > However, after I add the directives into the Apache httpd.conf to enable the webgate,
it appears that, on incoming requests, the webgate processing occurs, but my code in the modified
mod_headers module is not called at all :(!!
> >
> >
> > Here's the last part of my modified mod_headers.c:
> >
> > static void register_hooks(apr_pool_t *p)
> > {
> >      printf("mod_headers-jl V0.13 - use LIBCURL instead of OAM ASDK-process response
from callCurl\n");
> >      printf("In register_hooks\n");
> >      ap_register_output_filter("FIXUP_HEADERS_OUT", ap_headers_output_filter,
> >                                NULL, AP_FTYPE_CONTENT_SET);
> >      ap_register_output_filter("FIXUP_HEADERS_ERR", ap_headers_error_filter,
> >                                NULL, AP_FTYPE_CONTENT_SET);
> >      ap_hook_pre_config(header_pre_config,NULL,NULL,APR_HOOK_MIDDLE);
> >      ap_hook_post_config(header_post_config,NULL,NULL,APR_HOOK_MIDDLE);
> >      ap_hook_insert_filter(ap_headers_insert_output_filter, NULL, NULL, APR_HOOK_LAST);
> >      ap_hook_insert_error_filter(ap_headers_insert_error_filter,
> >                                  NULL, NULL, APR_HOOK_LAST);
> >      ap_hook_fixups(ap_headers_fixup, NULL, NULL, APR_HOOK_LAST);
> >      ap_hook_post_read_request(ap_headers_early, NULL, NULL, APR_HOOK_FIRST);
> > }
> >
> > module AP_MODULE_DECLARE_DATA headers_module =
> > {
> >      STANDARD20_MODULE_STUFF,
> >      create_headers_dir_config,  /* dir config creater */
> >      merge_headers_config,       /* dir merger --- default is to override */
> >      NULL,                       /* server config */
> >      NULL,                       /* merge server configs */
> >      headers_cmds,               /* command apr_table_t */
> >      register_hooks              /* register hooks */
> > };
> >
> >
> > The code I added is in the "ap_headers_insert_output_filter()" function.
> >
> >
> > I did an "export SHOW_HOOKS=1" and ran the Apache, and I see this for the modified
mod_headers:
> >
> > Registering hooks for mod_headers.c
> > mod_headers-jl V0.13 - use LIBCURL instead of OAM ASDK-process response from callCurl
> > In register_hooks
> >    Hooked pre_config
> >    Hooked post_config
> >    Hooked insert_filter
> >    Hooked insert_error_filter
> >    Hooked fixups
> >    Hooked post_read_request
> >
> >
> > And for webgate, I see:
> >
> > Registering hooks for apache2entry_web_gate.cpp
> >    Hooked post_config
> >    Hooked handler
> >    Hooked check_user_id
> >    Hooked auth_checker
> >
> >
> > I thought that the handler functions are called almost last part of the processing
(content generation), and my code is hooked to insert_filter, which I thought occurs earlier
than content generation, so shouldn't my code get processed BEFORE Apache attempts to process
the webgate functions?
> >
> > How can I get my code to process before the webgate does?
> >
> 
> insert_filter is run between the fixups and the handler hooks.
> 
> Try to identify who is producing the variables that you need, in which 
> phase they are available at the earliest. Then identify which part of 
> web_gate hijacks the processing such that your code is not executed 
> anymore. I suppose it is one of web_gate's auth_checker or 
> check_user_id. If it was the web_gate handler then your code would have 
> run before.
> 
> Sorin


Hi Sorin,

I posted a later msg that I've been trying do something along the lines that you said:

"I've been doing more testing, and it appears that the insert_filter hook (the 
"ap_headers_insert_output_filter()" function) is the only place where I can put 
my code where it has access to the variables that it needs to do the processing 
that I'm doing. 
 
The problem is that if that other Oracle module is enabled in the Apache, it 
runs before my code, and I can't get the insert_filter hook (my function) to get 
processed before the Oracle module "


What I've been doing is to put a dump_headers() call into various hooks that are configured
in the mod_headers, but so far, none of them have the SSL vars, which is what my code needs.


Jim

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