Hi, all.
   When I tested 2.6.20.16, found something strange. The following is
the test case:
1. Establish a connection between client and server [Client and Server
in EST state]
2. Power down server [ client in EST state ]
3. CTL+C the client. client should invoke close() API, and send FIN. [
FW state]
4. client retransmit the FIN due to timeout [ Now, FW -> LAST_ACK ]
Here the bug happens. FW is a active close state, but LAST_ACK is a
passive close state. The correct state is FW -> FW. The ip_conntrack TCP
state is wrong!

Also I looked the kernel source. And found the bug.
ip_conntrack_proto_tcp.c at line 201

/*fin*/    { sIV, sIV, sFW, sFW, sLA, sLA, sLA, sTW, sCL, sIV },
/*
*      sNO -> sIV      Too late and no reason to do anything...
*      sSS -> sIV      Client migth not send FIN in this state:
*                      we enforce waiting for a SYN/ACK reply first.
*      sSR -> sFW      Close started.
*      sES -> sFW
*      sFW -> sLA      FIN seen in both directions, waiting for
*                      the last ACK.
*                      Migth be a retransmitted FIN as well... [ Wrong
state!!!]

It's easy to check a FIN packet is a restransmitted packet or not, but
we need check every TCP packet in tcp_packet() function, Its performance
is too bad. I don't like this. Anyone can give a good solution?

Thanks in advance :)

BR. Wei Dong