ossl_quic_channel_get_tx_key_epoch
uint64_t ossl_quic_channel_get_tx_key_epoch(QUIC_CHANNEL *ch);
int64_t txke = (int64_t)ossl_quic_channel_get_tx_key_epoch(ch);
uint64_t txke = ossl_quic_channel_get_tx_key_epoch(ch);