rfc6803_calc_KDF_FEEDBACK_CMAC
ret = rfc6803_calc_KDF_FEEDBACK_CMAC(krb5, protocol_key, &prfconstant,
.calc_Kc = rfc6803_calc_KDF_FEEDBACK_CMAC,
.calc_Ke = rfc6803_calc_KDF_FEEDBACK_CMAC,
.calc_Ki = rfc6803_calc_KDF_FEEDBACK_CMAC,