From 1ac530b3553e0b4dc1e18a32bed57cfa84cd57cb Mon Sep 17 00:00:00 2001 From: Wei Yongjun Date: Wed, 24 Jun 2009 22:29:31 +0000 Subject: [PATCH] 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 Signed-off-by: David S. Miller --- net/ipv4/tcp_minisocks.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/net/ipv4/tcp_minisocks.c b/net/ipv4/tcp_minisocks.c index 43bbba7926ee..f8d67ccc64f3 100644 --- a/net/ipv4/tcp_minisocks.c +++ b/net/ipv4/tcp_minisocks.c @@ -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; -- 2.20.1