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Date: Tue, 26 Jun 2012 7:55:09 -0400
From: <ohaya@cox.net>
To: modules-dev@httpd.apache.org
Subject: Re: Confused about modules processing order...
Cc: Sorin Manolache <sorinm@gmail.com>
In-Reply-To: <4FE9A148.2050501@gmail.com>
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---- Sorin Manolache <sorinm@gmail.com> wrote: 
> On 2012-06-26 13:14, ohaya@cox.net wrote:
> >
> > ---- 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 "
> 
> The SSL variables are set in the fixups hook by mod_ssl. The fixups hook 
> is run _after_ check_user_id and auth_checker. So you cannot rely on 
> mod_ssl to populate the environment with the variables. I guess you'll 
> have to get those variables yourself, before Oracle's check_user_id and 
> auth_checker hooks.
> 
> Sorin


Hi,

The original mod_headers code has a hook for fixups.  If I added an "after" string in the code that registers my fixup function, with the name of the webgate, would that cause my modified mod_headers to run before the webgate?

Also can you clarify/expand on what you mean by " you'll have to get those variables yourself"?  I think that I'm currently getting them using env->setproc or something like that.

Jim