main/cdr: Allow modules to modify CDR fields before dispatching them

This patch adds the functions

	ast_cdr_modifier_register()
	ast_cdr_modifier_unregister()

That work much like ast_cdr_register() and ast_cdr_unregister().

Modules registered will be given a chance to modify (or to do whatever
they want) CDR fields just before they are passed to registered engines.

Thus, for instance, if a module change the "userfield" field of a CDR,
the modified value will be passed to every registered CDR backend for
logging.

ASTERISK-25479 #close

Change-Id: If11d8fd19ef89b1a66ecacf1201e10fcf86ccd56

include/asterisk/cdr.h

@@ -535,6 +535,36 @@ int ast_cdr_backend_suspend(const char *name);
  */
 int ast_cdr_backend_unsuspend(const char *name);
 
+/*!
+ * \brief Register a CDR modifier
+ * \param name name associated with the particular CDR modifier
+ * \param desc description of the CDR modifier
+ * \param be function pointer to a CDR modifier
+ *
+ * Used to register a Call Detail Record modifier.
+ *
+ * This gives modules a chance to modify CDR fields before they are dispatched
+ * to registered backends (odbc, syslog, etc).
+ *
+ * \note The *modified* CDR will be passed to **all** registered backends for
+ * logging. For instance, if cdr_manager changes the CDR data, cdr_adaptive_odbc
+ * will also get the modified CDR.
+ *
+ * \retval 0 on success.
+ * \retval -1 on error
+ */
+int ast_cdr_modifier_register(const char *name, const char *desc, ast_cdrbe be);
+
+/*!
+ * \brief Unregister a CDR modifier
+ * \param name name of CDR modifier to unregister
+ * Unregisters a CDR modifier by its name
+ *
+ * \retval 0 The modifier unregistered successfully
+ * \retval -1 The modifier could not be unregistered at this time
+ */
+int ast_cdr_modifier_unregister(const char *name);
+
 /*!
  * \brief Disposition to a string
  * \param disposition input binary form

main/cdr.c

@@ -297,6 +297,9 @@ struct cdr_beitem {
 /*! \brief List of registered backends */
 static AST_RWLIST_HEAD_STATIC(be_list, cdr_beitem);
 
+/*! \brief List of registered modifiers */
+static AST_RWLIST_HEAD_STATIC(mo_list, cdr_beitem);
+
 /*! \brief Queued CDR waiting to be batched */
 struct cdr_batch_item {
 	struct ast_cdr *cdr;
@@ -2678,7 +2681,7 @@ int ast_cdr_backend_unsuspend(const char *name)
 	return success;
 }
 
-int ast_cdr_register(const char *name, const char *desc, ast_cdrbe be)
+static int cdr_generic_register(struct be_list *generic_list, const char *name, const char *desc, ast_cdrbe be)
 {
 	struct cdr_beitem *i = NULL;
 
@@ -2690,11 +2693,11 @@ int ast_cdr_register(const char *name, const char *desc, ast_cdrbe be)
 		return -1;
 	}
 
-	AST_RWLIST_WRLOCK(&be_list);
-	AST_RWLIST_TRAVERSE(&be_list, i, list) {
+	AST_RWLIST_WRLOCK(generic_list);
+	AST_RWLIST_TRAVERSE(generic_list, i, list) {
 		if (!strcasecmp(name, i->name)) {
 			ast_log(LOG_WARNING, "Already have a CDR backend called '%s'\n", name);
-			AST_RWLIST_UNLOCK(&be_list);
+			AST_RWLIST_UNLOCK(generic_list);
 			return -1;
 		}
 	}
@@ -2706,40 +2709,50 @@ int ast_cdr_register(const char *name, const char *desc, ast_cdrbe be)
 	ast_copy_string(i->name, name, sizeof(i->name));
 	ast_copy_string(i->desc, desc, sizeof(i->desc));
 
-	AST_RWLIST_INSERT_HEAD(&be_list, i, list);
-	AST_RWLIST_UNLOCK(&be_list);
+	AST_RWLIST_INSERT_HEAD(generic_list, i, list);
+	AST_RWLIST_UNLOCK(generic_list);
 
 	return 0;
 }
 
-int ast_cdr_unregister(const char *name)
+int ast_cdr_register(const char *name, const char *desc, ast_cdrbe be)
+{
+	return cdr_generic_register(&be_list, name, desc, be);
+}
+
+int ast_cdr_modifier_register(const char *name, const char *desc, ast_cdrbe be)
+{
+	return cdr_generic_register((struct be_list *)&mo_list, name, desc, be);
+}
+
+static int ast_cdr_generic_unregister(struct be_list *generic_list, const char *name)
 {
 	struct cdr_beitem *match = NULL;
 	int active_count;
 
-	AST_RWLIST_WRLOCK(&be_list);
-	AST_RWLIST_TRAVERSE(&be_list, match, list) {
+	AST_RWLIST_WRLOCK(generic_list);
+	AST_RWLIST_TRAVERSE(generic_list, match, list) {
 		if (!strcasecmp(name, match->name)) {
 			break;
 		}
 	}
 
 	if (!match) {
-		AST_RWLIST_UNLOCK(&be_list);
+		AST_RWLIST_UNLOCK(generic_list);
 		return 0;
 	}
 
 	active_count = ao2_container_count(active_cdrs_by_channel);
 
 	if (!match->suspended && active_count != 0) {
-		AST_RWLIST_UNLOCK(&be_list);
+		AST_RWLIST_UNLOCK(generic_list);
 		ast_log(AST_LOG_WARNING, "Unable to unregister CDR backend %s; %d CDRs are still active\n",
 			name, active_count);
 		return -1;
 	}
 
-	AST_RWLIST_REMOVE(&be_list, match, list);
-	AST_RWLIST_UNLOCK(&be_list);
+	AST_RWLIST_REMOVE(generic_list, match, list);
+	AST_RWLIST_UNLOCK(generic_list);
 
 	ast_verb(2, "Unregistered '%s' CDR backend\n", name);
 	ast_free(match);
@@ -2747,6 +2760,16 @@ int ast_cdr_unregister(const char *name)
 	return 0;
 }
 
+int ast_cdr_unregister(const char *name)
+{
+	return ast_cdr_generic_unregister(&be_list, name);
+}
+
+int ast_cdr_modifier_unregister(const char *name)
+{
+	return ast_cdr_generic_unregister((struct be_list *)&mo_list, name);
+}
+
 struct ast_cdr *ast_cdr_dup(struct ast_cdr *cdr)
 {
 	struct ast_cdr *newcdr;
@@ -3262,6 +3285,13 @@ static void post_cdr(struct ast_cdr *cdr)
 			continue;
 		}
 
+		/* Modify CDR's */
+		AST_RWLIST_RDLOCK(&mo_list);
+		AST_RWLIST_TRAVERSE(&mo_list, i, list) {
+			i->be(cdr);
+		}
+		AST_RWLIST_UNLOCK(&mo_list);
+
 		if (ast_test_flag(cdr, AST_CDR_FLAG_DISABLE)) {
 			continue;
 		}