using multiple credential cache files in a server

[Rick Macklem]

A gssd daemon for an NFS client needs to be able to use the GSS API call
gss_init_sec_context() on behalf of different users (uids). I can see two
ways of doing this:
1 - fork off a separate child that does setuid(user_uid) to get context for
     that user (seems inefficient)
OR
2 - Get Initiator credentials for the principal and use those in the
     gss_init_sec_context() call. This seems preferable, but requires that
     the server switch to the credentials cache file for the appropriate uid
     associated with that principal. (At least it seems that a credentials
     cache file with the correct tgt is required to get Initiator Credentials.)

This leads me to my question:
How do you get the Kerberos libraries to switch to a different credential cache
file whenever you want to get Initiator Credentials for a different uid?

Thanks in advance for any help, rick