I've started working on a XEP-198 implementation at https://github.com/flowdalic/smack/tree/xep198 since the Smack codebase is now able to support it. As of now the code is completely untested.

Stream Management can only be implemented if the state of the connection is kept after a disconnect, be it a clean disconnect or a forced one.

I implemented this for the Guardian project. You are welcome to adapt the code to be a more integral part of smack. My design minimized the change to smack (actually asmack).

https://github.com/guardianproject/Gibberbot/pull/116
https://github.com/guardianproject/asmack/pull/5

Contributions are welcome, but design discussions and the like should probably be brought up in the forums, open_chat or private messages.

I am interested in writing some code for this. As I read the standard, it requires access to some internals of XMPPConnection, like counting the incoming and outgoing stanzas and keeping a list of the unacknowledged ones that have been sent and might need retransmission.

Should this be implemented inside of XMPPConnection or as an external module, creating additional interfaces when the existing ones are insufficient? Maybe even by subclassing XMPPConnection?