commit 1ac530b3553e0b4dc1e18a32bed57cfa84cd57cb
author Wei Yongjun <yjwei@cn.fujitsu.com> Wed Jun 24 22:29:31 2009 +0000
committer David S. Miller <davem@davemloft.net> Thu Jun 25 20:03:15 2009 -0700
tree cc0198945aeee7b60ea06c1699fc72268efc26f7
parent d8146bb23ea045fb75c56b4e3b53f0964eed4076

tcp: missing check ACK flag of received segment in FIN-WAIT-2 state

RFC0793 defined that in FIN-WAIT-2 state if the ACK bit is off drop
the segment and return[Page 72]. But this check is missing in function
tcp_timewait_state_process(). This cause the segment with FIN flag but
no ACK has two diffent action:

Case 1:
    Node A                      Node B
              <-------------    FIN,ACK
                                (enter FIN-WAIT-1)
    ACK       ------------->
                                (enter FIN-WAIT-2)
    FIN       ------------->    discard
                                (move sk to tw list)

Case 2:
    Node A                      Node B
              <-------------    FIN,ACK
                                (enter FIN-WAIT-1)
    ACK       ------------->
                                (enter FIN-WAIT-2)
                                (move sk to tw list)
    FIN       ------------->

              <-------------    ACK

This patch fixed the problem.

Signed-off-by: Wei Yongjun <yjwei@cn.fujitsu.com>
Signed-off-by: David S. Miller <davem@davemloft.net>