question about nic driver implementation(about TCP checksum offload )

[Gang Lei (雷刚)]

Hi All:

I want to build TOE(tcp checksum offload engine) in our hardware to improve the overall performance of NIC, however, i met a problem as follow:
AS you know, the TCP checksum protect the TCP pseudo header+TCP header+Data,  if TCP packet is fragmented into many fragments, the hardware will have not enough information to generate tcp checksum for the whole TCP PDU, how to overcome this problem?

I searched in NIC driver source code of different vendor, found that TOE is generally used, I wonder whether the kernel will calculate the TCP checksum even we set features of this device as NETIF_F_IP_CSUM when fragmentation happens.

Can anyone throw some lights on this problem?

Thanks a lot.


Rick.


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