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Commit 1ac530b3 authored by Wei Yongjun's avatar Wei Yongjun Committed by David S. Miller
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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: default avatarWei Yongjun <yjwei@cn.fujitsu.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent d8146bb2

net/ipv4/tcp_minisocks.c

+2 −1
Original line number Diff line number Diff line
@@ -128,7 +128,8 @@ tcp_timewait_state_process(struct inet_timewait_sock *tw, struct sk_buff *skb, 
			goto kill_with_rst;



		/* Dup ACK? */

		if (!after(TCP_SKB_CB(skb)->end_seq, tcptw->tw_rcv_nxt) ||

		if (!th->ack ||

		    !after(TCP_SKB_CB(skb)->end_seq, tcptw->tw_rcv_nxt) ||

		    TCP_SKB_CB(skb)->end_seq == TCP_SKB_CB(skb)->seq) {

			inet_twsk_put(tw);

			return TCP_TW_SUCCESS;