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SubjectRe: seq numbers and checksum in tcp
   Date: 	Sun, 17 Jan 1999 23:51:41 -0600
From: Ayman El-Khashab <>

for some research that i am working on, i am doing some experiments
with the linux kernel and some tcpip stuff in particular. In any
case, in the tcp_rcv function, i have been able to get most of the
information that i need. Now i need to modify the sequence number
of the packet and then recompute the checksum, but i am not sure
how to go about this. I have expermimented for a while and turned
up nothing.

basically, i want to just modify the th->seq and then recompute
the tcp checksum and i suspect the skb checksum.

Why do you need to recompute the checksum on incoming packets, at
tcp_rcv() the checksum has already been validated as correct and is
never checked again? ie. nobody else cares about the checksum

David S. Miller

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