NFS4_CALLBACK
.pg_prog = NFS4_CALLBACK, /* RPC service number */
status = nfs4_proc_setclientid(clp, NFS4_CALLBACK, port, cred, &clid);
.cb_program = NFS4_CALLBACK,
status = nfs4_proc_setclientid(clp, NFS4_CALLBACK, port, cred, &clid);