config/2996: Dynamically Loaded module gets unloaded

[Alok Agrawal <aa...@us.oracle.com>]

>Number:         2996
>Category:       config
>Synopsis:       Dynamically Loaded module gets unloaded
>Confidential:   no
>Severity:       critical
>Priority:       medium
>Responsible:    apache
>State:          open
>Class:          sw-bug
>Submitter-Id:   apache
>Arrival-Date:   Fri Sep 11 13:10:00 PDT 1998
>Last-Modified:
>Originator:     aagrawal@us.oracle.com
>Organization:
apache
>Release:        1.3.1
>Environment:
OS SunOS aagrawal-sun 5.5.1 Generic_103640-20 sun4u sparc SUNW,Ultra-1
Compiler - gcc
Apache version 1.3.1
>Description:
The problem is related to Apache's tendency to call read
the configuration information twice and the way mod_so.c is behaving.

I am using the core as SHARED_CORE on Solaris. I have written a custom
module and the module is not loaded in the final childprocess
as it is initially loaded and the eventually unloaded.
I am including a trace of some printf statements I put in.


The custom module I wrote is called "ndwfapd.c"

I have piped all printfs to stderr so I initially see some errors
on the screen and after a file they are directed to the error log.
I am just shoing the concatenated version here.

mod_so.c (load_module)
1 Loading module /home/aagrawal/apache_1.3.1/src/modules/extra/ndwfapd.so ows_module

http_config.c (ap_add_module)
Adding modules ndwfapd.c Adding module before mod_setenvif.c

http_config.c
Doing  init for module ndwfapd.c
ndwfapd.c
Calling the init routine
http_config.c
Doing  init for module mod_setenvif.c
Doing  init for module mod_so.c
Doing  init for module mod_auth.c
Doing  init for module mod_access.c
Doing  init for module mod_alias.c
Doing  init for module mod_userdir.c
Doing  init for module mod_actions.c
Doing  init for module mod_imap.c
Doing  init for module mod_asis.c
Doing  init for module mod_cgi.c
Doing  init for module mod_dir.c
Doing  init for module mod_autoindex.c
Doing  init for module mod_include.c
Doing  init for module mod_negotiation.c
Doing  init for module mod_mime.c
Doing  init for module mod_log_config.c
Doing  init for module mod_env.c
Doing  init for module http_core.c

mod_so.c unload_module
Removing loaded module ndwfapd.c
http_config.c
Remove module ndwfapd.c

mod_so.c - load_module (Notice that the module is being loaded again)
2 Loading module /home/aagrawal/apache_1.3.1/src/modules/extra/ndwfapd.s
http_config.c (ap_add_module)
Adding modules ndwfapd.c

But the new module is not added the next time beacsue the code
in ap_add_module checks for (m->next == NULL) which is not
the case any more since the code that removes the module
never sets it back to NULL (in ap_remove_module).
The code just sets m->module_index to -1

I have a fundamental problem with you guys reading the configuration
information twice. Eventhough I have
1 LoadModule statment in httpd.conf, the call load_module (the handler
for LoadModule in mod_so.c) is called twice. This just creates
a lot of  problems.

The call ap_read_config (which eventually calls the handelers) is being
called twice. Once from the main program and then again from 
stanalone_main.
>How-To-Repeat:
It is failry easy to reproduce the problem.
Compile the server with a shared code and mod_so enabled.
Then write a dummy module and manually edit the httpd.conf
file and add the LoadModule call. The module will not
worl.
>Fix:
Yes. Either read the configuration information once or set 
m->next = NULL in ap_remove_module (in http_config.c)
>Audit-Trail:
>Unformatted:
[In order for any reply to be added to the PR database, ]
[you need to include <ap...@Apache.Org> in the Cc line ]
[and leave the subject line UNCHANGED.  This is not done]
[automatically because of the potential for mail loops. ]
[If you do not include this Cc, your reply may be ig-   ]
[nored unless you are responding to an explicit request ]
[from a developer.                                      ]
[Reply only with text; DO NOT SEND ATTACHMENTS!         ]