I'm trying to understand something related to checksum offloading. when using partial checksum offloading, the checksum on the pseudo header is calculated in the host, and put into the udp checksum field, to be use in the full calculation inside the NIC. but the pseudo header checksum can be more than 16-bit, so how do it supposed to be fold into its 16-bit checksum field? when the entire calculation is done in the host, the checksum value from the pseudo header is used as is, which means regular folding (like the one the being done at the end of the full checksum - add top half and bottom half) is not good here, as it change the value. it looks like there is an option to fold the checksum from 32/64 bits to 16, without loosing its "value" to the entire calculation, but I can't find anything about it online.
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