netdev - Re: TCP connection will hang in FIN_WAIT1 after closing if zero window is advertised

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Message-ID: <CADVnQym0NmF-Cqz=OEpVBmMAe6T-G1jmoq=fbVWtL7_Ny-wn3w@mail.gmail.com>
Date:	Mon, 15 Sep 2014 15:43:27 -0400
From:	Neal Cardwell <ncardwell@...gle.com>
To:	Andrey Dmitrov <andrey.dmitrov@...etlabs.ru>
Cc:	Netdev <netdev@...r.kernel.org>,
	"Alexandra N. Kossovsky" <Alexandra.Kossovsky@...etlabs.ru>,
	Konstantin Ushakov <kostik@...etlabs.ru>
Subject: Re: TCP connection will hang in FIN_WAIT1 after closing if zero
 window is advertised

On Mon, Sep 15, 2014 at 12:11 PM, Andrey Dmitrov
<andrey.dmitrov@...etlabs.ru> wrote:
> It is possible to create a lot of connections in the same manner which will be in FIN_WAIT1 state forever.
...
> After ~10 minutes you will see 500 connections in the FIN_WAIT1 state on the host_A:
> netstat | grep FIN_WAIT1 | wc -l
> 500

Thanks for the report. In your tests, have you ever seen the number of
such connections exceed net.ipv4.tcp_max_orphans?

Can you set net.ipv4.tcp_max_orphans to a low value and verify that it
limits the number of such connections? AFAICT it should.

thanks,
neal
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