caused by:
commit 2626419ad5be1a054d350786b684b41d23de1538
Author: David S. Miller <davem@davemloft.net>
Date: Thu Apr 8 11:32:30 2010 -0700
tcp: Set CHECKSUM_UNNECESSARY in tcp_init_nondata_skb
it will make sshd server, telnet server and vnc server doesn't respond
connecting request anymore.
YH
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