iOS XMPP Framework blocking/privacy options?

I am developing a XMPP based chat client for iOS. One of the requirements is the ability to "block" users. The XMPP specifications have a few options (XEP-0016, XEP-0191) however I have yet to be able to find any extensions for the XMPP Framework that are already available? It seems like this would be a pretty basic feature? I could always go the easy route and just save a list of blocked JIDs locally and filter out incoming messages, however it will not transfer between devices this way. The other option is to write an extension, which might be out of the budget/time frame requirements. Am I missing something here? Is there a built in way to do this o开发者_JAVA百科r an extension already out there?

It may be a basic feature, but no one that has needed it has contributed an implementation to the project.