ETH_TX_BD_FLAGS_L4_CSUM
ETH_TX_BD_FLAGS_L4_CSUM);
tx_start_bd->bd_flags.as_bitfield |= ETH_TX_BD_FLAGS_L4_CSUM;
tx_start_bd->bd_flags.as_bitfield |= (ETH_TX_BD_FLAGS_L4_CSUM |