* after the client's side of the handshake is complete. That is,
* it can be used to send data before gnutls_handshake() completes
* (i.e., before the peer's Finished message is received)
- * and reduce the handshake to a single round-trip.
+ * and reduce the handshake to a single round-trip. The callback
+ * must only be used to send data using gnutls_record_send().
*
* This callback must return 0 on success or a gnutls error code to
* terminate the handshake. Typically it should include a call to