TCP_CS_OFFSET
#define UDP_TCP_CS_OFFSET_DIFF (TCP_CS_OFFSET - UDP_CS_OFFSET)
if (lso || ((csStuff - csStart) == TCP_CS_OFFSET))
pTxPkt->tx_info.tcp_pseudo_csum = ntohs(*((u16_t *)&pL4Hdr[TCP_CS_OFFSET]));