kerberos keyring ccache

[Steve French]

This discussion on using the infrastructure for caching kerberos tickets 
sounds promising, but I am missing some background information on what 
has been added.   Are there pointers to background information on the topic?

The needs for cifs client (and presumably non-kernel samba client code 
eventually) would be:
1) identify whether current (perhaps current->fsuid) already has a krb5 
service ticket for a particular server/service
2) if no service ticket, request a service ticket for current
3) if ticket is expired, refresh the service ticket
4) upcall to samba tooling (similar to Samba's ntlm_auth used by some 
apache modules etc.) to SPNEGO authenticate with that ticket if SMB/CIFS 
session is not authenticated

Parts of the first three items seem like they relate to the earlier 
discussion thread - but I am not sure where to look to get up to speed 
on what has been done already for the somewhat similar cases for nfsv4 
and afs on the first three items