TCP checksums are fairly simple; a TCP stack basically just sums up the 16-bit words in a packet and stores the result in the checksum field; this will not dete

TCP checksums are fairly simple; a TCP stack basically just sums up the 16-bit words in a packet and stores the result in the checksum field; this will not detect 16-bit words being swapped around. My guess is that the load balancer tried to invalidate the header while preserving the TCP checksum.