On Fri, 31 Jan 2020 22:55:34 -0500 Neal Cardwell <ncardwell@xxxxxxxxxx> wrote: > On Fri, Jan 31, 2020 at 5:18 PM SeongJae Park <sj38.park@xxxxxxxxx> wrote: > > > > On Fri, 31 Jan 2020 17:11:35 -0500 Neal Cardwell <ncardwell@xxxxxxxxxx> wrote: > > > > > On Fri, Jan 31, 2020 at 1:12 PM Eric Dumazet <eric.dumazet@xxxxxxxxx> wrote: > > > > > > > > > > > > > > > > On 1/31/20 7:10 AM, Neal Cardwell wrote: > > > > > On Fri, Jan 31, 2020 at 7:25 AM <sjpark@xxxxxxxxxx> wrote: > > > > >> > > > > >> From: SeongJae Park <sjpark@xxxxxxxxx> > > > > >> > > > > >> When closing a connection, the two acks that required to change closing > > > > >> socket's status to FIN_WAIT_2 and then TIME_WAIT could be processed in > > > > >> reverse order. This is possible in RSS disabled environments such as a > > > > >> connection inside a host. > > [...] > > > > > > I looked into fixing this, but my quick reading of the Linux > > > tcp_rcv_state_process() code is that it should behave correctly and > > > that a connection in FIN_WAIT_1 that receives a FIN/ACK should move to > > > TIME_WAIT. > > > > > > SeongJae, do you happen to have a tcpdump trace of the problematic > > > sequence where the "process A" ends up in FIN_WAIT_2 when it should be > > > in TIME_WAIT? > > > > Hi Neal, > > > > > > Yes, I have. You can get it from the previous discussion for this patchset > > (https://lore.kernel.org/bpf/20200129171403.3926-1-sjpark@xxxxxxxxxx/). As it > > also has a reproducer program and how I got the tcpdump trace, I believe you > > could get your own trace, too. If you have any question or need help, feel > > free to let me know. :) > > Great. Thank you for the pointer. > > I had one quick question: in the message: > https://lore.kernel.org/bpf/20200129171403.3926-1-sjpark@xxxxxxxxxx/ > ... it showed a trace with the client sending a RST/ACK, but this > email thread shows a FIN/ACK. I am curious about the motivation for > the difference? RST/ACK is traced if LINGER socket option is applied in the reproduce program, and FIN/ACK is traced if it is not applied. LINGER applied version shows the spikes more frequently, but the main problem logic has no difference. I confirmed this by testing both of the two versions. In the previous discussion, I showed the LINGER applied trace. However, as many other documents are using FIN/ACK, I changed the trace to FIN/ACK version in this patchset for better understanding. I will comment that it doesn't matter whether it is FIN/ACK or RST/ACK in the next spin. Thanks, SeongJae Park > > Anyway, thanks for the report, and thanks to Eric for further clarifying! > > neal >
