netdev - Re: Why network stack not reply RST

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Message-Id: <201112291117.23886.zrpeng@linx-info.com>
Date:	Thu, 29 Dec 2011 11:17:23 +0800
From:	zrpeng <zrpeng@...x-info.com>
To:	Zhen-Hua Li <lizhenhua.dev@...il.com>
Cc:	netdev@...r.kernel.org
Subject: Re: Why network stack not reply RST

Hi:
   It is my error. After returned from the judgement, the network stack will 
send RST according to return value.

   Thank you very much! And Happy New Year!
   Best Regards.

   Peng Zhaoran from Linx-Info Tech.

www.linx-info.com

在 Thursday 29 December 2011 11:04:10，Zhen-Hua Li 写道：
> Hi,
>     Are you sure your client did not called fork() ?  If it has
> subprocess, there may be such problems.
>
> On Tue, Dec 27, 2011 at 4:31 PM, zrpeng <zrpeng@...x-info.com> wrote:
> > Hi:
> >    Why network stack not reply RST?
> >    I am doing test recently based on kernel 2.6.32. In my case:
> >    1) The server application closed the established socket, the network
> > stack sent FIN to client. The socket status in kernel's network stack was
> > TCP_FIN_WAIT1.
> >    2) The client sent out a tcp packet with ACK bit set for the server's
> > FIN, the packet also took new data.
> >    3) When the server received the packet, network stack entered "step 5"
> > in function "tcp_rcv_state_process".
> >    4) Then came to 'case TCP_FIN_WAIT1:'
> >    5) Then came to judgement
> > if (tp->linger2 < 0 ||
> >                                            (TCP_SKB_CB(skb)->end_seq !=
> > TCP_SKB_CB(skb)->seq && after(TCP_SKB_CB(skb)->end_seq - th->fin,
> > tp->rcv_nxt))) { .....
> > }
> >    6) Because the previous packet took data and ACK (for the FIN), it
> > entered the judgement. So, the socket is deleted in function
> > 'tcp_done(sk)'. 7) No TCP message was sent back to client side from then
> > on, and client was left in LAST_ACK status.
> >
> >    My questions are:
> >    1) Is this process correct? I think the server should sent RST to
> > client, is this correct?
> >    2) What's the using of judgement
> >  (TCP_SKB_CB(skb)->end_seq != TCP_SKB_CB(skb)->seq &&
> >                                            
> > after(TCP_SKB_CB(skb)->end_seq - th->fin, tp->rcv_nxt)
> >
> >       The code exists from kernel 2.3.41 and 2.3.42.
> >
> >    Thank you very much!
> >    Best Regards.
> >
> >    Peng Zhaoran from Linx-Info Tech.
> >
> >    www.linx-info.com
> > --
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