>Reassembled fragments still need to yield a checksum-valid frame. For a 32bit checksum changing data will give you a 1 in 4,294,967,296 chance of being correc

>Reassembled fragments still need to yield a checksum-valid frame. For a 32bit checksum changing data will give you a 1 in 4,294,967,296 chance of being correct. So just keep bit twiddling some unimportant portion of the frame until you obtain a valid checksum. 4,294,967,296 is not a large number for a modern computer. These frame checksums are only intended for accidental bit flips. They aren't protection against someone creating fake frames with valid checksums.