[PATCH] Guarantee that an output module is loaded at most once.

[Christopher Brannon]

Since we now support the autodetection of output modules,
it is feasible that a module could be both requested by the
configuration file and autodetected at the same time.
We now insure that the same module is not loaded twice.  See the
comments in the code for my well-justified definition of "same".
---
 src/server/module.c |   57 ++++++++++++++++++++++++++++++++++++++++++++++++++-
 1 files changed, 56 insertions(+), 1 deletions(-)

diff --git a/src/server/module.c b/src/server/module.c
index be3fff6..bebc922 100644
--- a/src/server/module.c
+++ b/src/server/module.c
@@ -437,6 +437,48 @@ int output_module_nodebug(OutputModule * module)
 static GList *requested_modules = NULL;
 
 /*
+ * module_already_requested: determine whether we have already received
+ * a load request for a given module.
+ * Parameters:
+ * module_name: the name of the module.
+ * module_cmd: name of the binary associated with this module.
+ * module_cfgfile: the name of the module's configuration file.
+ *
+ * Returns:
+ * TRUE if the module was previously requested, FALSE otherwise.
+ *
+ * A module is previously requested if:
+ * 1. module_name is the same as some other module in the list of load
+ * requests.  We select a given output module using its name, so names
+ * must be unique.
+ * 2. The name of the executable and the name of the configuration file
+ * are exactly the same as those of another module.
+ * It is acceptable to load the same module binary multiple times, where
+ * each instance uses a different configuration file.  In fact, this is
+ * how sd_generic works.  The instances are differentiated by module_name.
+ * However, it is not reasonable to load multiple instances, all of which
+ * use the same (binary, config file) pair.
+ * These two rules should cover all cases adequately.
+ *
+ */
+gboolean
+module_already_requested(char *module_name, char *module_cmd,
+                        char *module_cfgfile)
+{
+       GList *lp;
+
+       for (lp = requested_modules; lp != NULL; lp = lp->next) {
+               char **params = lp->data;
+               if (!strcmp(module_name, params[0]) ||
+                   (!strcmp(module_cmd, params[1]) &&
+                    !strcmp(module_cfgfile, params[2])))
+                       return TRUE;
+       }
+
+       return FALSE;
+}
+
+/*
  * module_add_load_request - request that a module be loaded.
  * In other words, add it to the list of modules which will be loaded
  * by module_load_requested_modules.
@@ -454,7 +496,20 @@ void
 module_add_load_request(char *module_name, char *module_cmd,
                        char *module_cfgfile, char *module_dbgfile)
 {
-       char **module_params = g_malloc(4 * sizeof(char *));
+       char **module_params = NULL;
+
+       if (module_already_requested(module_name, module_cmd, module_cfgfile)) {
+               MSG(1,
+                   "Load request for module %s with command %s and 
configuration file %s was previously received; ignoring the second one.",
+                   module_name, module_cmd, module_cfgfile);
+               g_free(module_name);
+               g_free(module_cmd);
+               g_free(module_cfgfile);
+               g_free(module_dbgfile);
+               return;
+       }
+
+       module_params = g_malloc(4 * sizeof(char *));
        module_params[0] = module_name;
        module_params[1] = module_cmd;
        module_params[2] = module_cfgfile;
-- 
1.7.3.4