The B<SSL_psk_find_session_cb_func> callback should return 1 on success or 0 on
failure. In the event of failure the connection setup fails.
+=head1 NOTES
+
+There are no known security issues with sharing the same PSK between TLSv1.2 (or
+below) and TLSv1.3. However the RFC has this note of caution:
+
+"While there is no known way in which the same PSK might produce related output
+in both versions, only limited analysis has been done. Implementations can
+ensure safety from cross-protocol related output by not reusing PSKs between
+TLS 1.3 and TLS 1.2."
+
=head1 SEE ALSO
L<SSL_CTX_set_psk_use_session_callback(3)>,