On Fri, 31 Jan 2020 22:55:34 -0500 Neal Cardwell ncardwell@google.com wrote:
On Fri, Jan 31, 2020 at 5:18 PM SeongJae Park sj38.park@gmail.com wrote:
On Fri, 31 Jan 2020 17:11:35 -0500 Neal Cardwell ncardwell@google.com wrote:
On Fri, Jan 31, 2020 at 1:12 PM Eric Dumazet eric.dumazet@gmail.com wrote:
On 1/31/20 7:10 AM, Neal Cardwell wrote:
On Fri, Jan 31, 2020 at 7:25 AM sjpark@amazon.com wrote:
From: SeongJae Park sjpark@amazon.de
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@amazon.com/). 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@amazon.com/ ... 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