R7000 Inbound Filtering

R7000 Inbound Filtering - This morning it was confirmed to me by Netgear support that the R7000 is not capable of inbound filtering. IE. Open a port, that port is accessible from anywhere in the world - awesome security, I can see my clients loving that. Obviously I need to fix this or change routers. Can anyone confirm whether inbound filtering is supported in DD-WRT version and whether they would regard that version as stable enough to use on a client site. Thanks.