pub unsafe extern "C" fn ssl_tls_prf(
    prf: tls_prf_types,
    secret: *const c_uchar,
    slen: size_t,
    label: *const c_char,
    random: *const c_uchar,
    rlen: size_t,
    dstbuf: *mut c_uchar,
    dlen: size_t
) -> c_int