rc: don't check if DDNS IP matches nvram content when DDNS set to use…

… external checks

Otherwise, this would constantly try to update the DDNS when in a dual NAT
or CGNAT situation where local WAN IP != real public IP.

We'd need to implement remote IP checks, however I'm not confortable
with having the watchdog constantly poll a remote server to check
the current IP, so for now external checks won't be monitored by
watchdog.

release/src/router/rc/watchdog.c

@@ -5023,6 +5023,9 @@ void regular_ddns_check(void)
 	struct in_addr ip_addr;
 	struct hostent *hostinfo;
 
+	if (nvram_get_int("ddns_ipcheck") != 0)	// Not relying on local wan0_ipaddr content
+		return;
+
 	//_dprintf("regular_ddns_check...\n");
 
 	hostinfo = gethostbyname(nvram_get("ddns_hostname_x"));