loader: Create ast_module_running_ref.

This function returns NULL if the module in question is not running.  I
did not change ast_module_ref as most callers do not check the result
and they always call ast_module_unref.

Make use of this function when running registered items from:
* app_stack API's
* bridge technologies
* CLI commands
* File formats
* Manager Actions
* RTP engines
* Sorcery Wizards
* Timing Interfaces
* Translators
* AGI Commands
* Fax Technologies

ASTERISK-20346 #close

Change-Id: Ia16fd28e188b2fc0b9d18b8a5d9cacc31df73fcc

2 files changed, 20 insertions, 17 deletions

diff --git a/res/res_agi.c b/res/res_agi.c
index 85914c018..393a50351 100644
--- a/res/res_agi.c
+++ b/res/res_agi.c
@@ -4040,14 +4040,19 @@ static enum agi_result agi_handle_command(struct ast_channel *chan, AGI *agi, ch
 
 	parse_args(buf, &argc, argv);
 	c = find_command(argv, 0);
-	if (c && (!dead || (dead && c->dead))) {
-		/* if this command wasn't registered by res_agi, be sure to usecount
-		the module we are using */
-		if (c->mod != ast_module_info->self)
-			ast_module_ref(c->mod);
+	if (!c || !ast_module_running_ref(c->mod)) {
+		ami_res = "Invalid or unknown command";
+		resultcode = 510;
+
+		ast_agi_send(agi->fd, chan, "%d %s\n", resultcode, ami_res);
+
+		publish_async_exec_end(chan, command_id, ami_cmd, resultcode, ami_res);
+
+		return AGI_RESULT_SUCCESS;
+	}
+
+	if (!dead || (dead && c->dead)) {
 		res = c->handler(chan, agi, argc, argv);
-		if (c->mod != ast_module_info->self)
-			ast_module_unref(c->mod);
 		switch (res) {
 		case RESULT_SHOWUSAGE:
 			ami_res = "Usage";
@@ -4094,21 +4099,15 @@ static enum agi_result agi_handle_command(struct ast_channel *chan, AGI *agi, ch
 
 			break;
 		}
-	} else if (c) {
+	} else {
 		ami_res = "Command Not Permitted on a dead channel or intercept routine";
 		resultcode = 511;
 
 		ast_agi_send(agi->fd, chan, "%d %s\n", resultcode, ami_res);
 
 		publish_async_exec_end(chan, command_id, ami_cmd, resultcode, ami_res);
-	} else {
-		ami_res = "Invalid or unknown command";
-		resultcode = 510;
-
-		ast_agi_send(agi->fd, chan, "%d %s\n", resultcode, ami_res);
-
-		publish_async_exec_end(chan, command_id, ami_cmd, resultcode, ami_res);
 	}
+	ast_module_unref(c->mod);
 
 	return AGI_RESULT_SUCCESS;
 }
diff --git a/res/res_fax.c b/res/res_fax.c
index 093845246..4be5aee75 100644
--- a/res/res_fax.c
+++ b/res/res_fax.c
@@ -1161,8 +1161,10 @@ static struct ast_fax_session *fax_session_reserve(struct ast_fax_session_detail
 		if ((faxmod->tech->caps & details->caps) != details->caps) {
 			continue;
 		}
+		if (!ast_module_running_ref(faxmod->tech->module)) {
+			continue;
+		}
 		ast_debug(4, "Reserving a FAX session from '%s'.\n", faxmod->tech->description);
-		ast_module_ref(faxmod->tech->module);
 		s->tech = faxmod->tech;
 		break;
 	}
@@ -1279,8 +1281,10 @@ static struct ast_fax_session *fax_session_new(struct ast_fax_session_details *d
 			if ((faxmod->tech->caps & details->caps) != details->caps) {
 				continue;
 			}
+			if (!ast_module_running_ref(faxmod->tech->module)) {
+				continue;
+			}
 			ast_debug(4, "Requesting a new FAX session from '%s'.\n", faxmod->tech->description);
-			ast_module_ref(faxmod->tech->module);
 			if (reserved) {
 				/* Balance module ref from reserved session */
 				ast_module_unref(reserved->tech->module);