gnutls_certificate_client_set_retrieve_function() and application "cookies"

Hi,

me again ;) I have (potentially) different certificate stores for
different sessions. I do not (yet) have a readily accessible list of
session identifiers. Is there any way to pass a void* pointer to
GnuTLS that will be passed back to me when the callback is called? I
see that there is no direct way to do it, but can I store this pointer
e.g. somehow inside the GnuTLS session data structure?

If I am not able to do that, I need to go long (and inefficient!) ways
to look up my session information based on the GnuTLS session handle I
receive. I hope I can avoid this.

Feedback is deeply appreciated.

Thanks,
Rainer