linux-kernel - Re: [PATCH v5 4/4] ipv4: Namespaceify tcp_fastopen_blackhole

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Date:   Thu, 28 Sep 2017 10:48:01 -0700 (PDT)
From:   David Miller <davem@...emloft.net>
To:     yanhaishuang@...s.chinamobile.com
Cc:     kuznet@....inr.ac.ru, edumazet@...gle.com, weiwan@...gle.com,
        lucab@...ian.org, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v5 4/4] ipv4: Namespaceify
 tcp_fastopen_blackhole_timeout knob

From: Haishuang Yan <yanhaishuang@...s.chinamobile.com>
Date: Wed, 27 Sep 2017 11:35:43 +0800

> Different namespace application might require different time period in
> second to disable Fastopen on active TCP sockets.
> 
> Tested:
> Simulate following similar situation that the server's data gets dropped
> after 3WHS.
> C ---- syn-data ---> S
> C <--- syn/ack ----- S
> C ---- ack --------> S
> S (accept & write)
> C?  X <- data ------ S
> 	[retry and timeout]
> 
> And then print netstat of TCPFastOpenBlackhole, the counter increased as
> expected when the firewall blackhole issue is detected and active TFO is
> disabled.
> # cat /proc/net/netstat | awk '{print $91}'
> TCPFastOpenBlackhole
> 1
> 
> Signed-off-by: Haishuang Yan <yanhaishuang@...s.chinamobile.com>

Applied.