simple checksum computation and/or verification, indeed most cards can do (sometimes with restrictions: not for IPv6, not for VLAN...) the other kind of offloa

simple checksum computation and/or verification, indeed most cards can do (sometimes with restrictions: not for IPv6, not for VLAN...) the other kind of offloading that the kernel can use is TCP Segmentation Offload (TSO), which is much more complex to implement in hardware, and you won't find it on cheap NIC (like Realtek)