# TCP checksum calculation



## bsd_newbie (Mar 24, 2009)

Can someone point me to the code that tries to redo tcp checksum as a result of mucking up with the ip source addrees.


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## hydra (Mar 24, 2009)

Check out: /usr/src/sys/netinet. The checksum calculation is platform specific, the amd64 algorithm is for example located in: /usr/src/sys/amd64/amd64/in_cksum.c.


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