netdev - Re: orphan sockets

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Message-ID: <CAEnQRZDWZzCCeL3auoLJ=sK5V9yi_Zxs+HgtPoeLFRUV8b0m-Q@mail.gmail.com>
Date:	Fri, 8 Jul 2011 19:28:27 +0300
From:	Daniel Baluta <daniel.baluta@...il.com>
To:	Denys Fedoryshchenko <denys@...p.net.lb>
Cc:	netdev@...r.kernel.org
Subject: Re: orphan sockets

On Fri, Jul 8, 2011 at 6:13 PM, Denys Fedoryshchenko <denys@...p.net.lb> wrote:
> Hi
>
> Just after digging orphan sockets problem, that was causing "Address already
> in use" for bind(),i found that in documentation is mentioned:
>
> tcp_orphan_retries - INTEGER
>        This value influences the timeout of a locally closed TCP connection,
>        when RTO retransmissions remain unacknowledged.
>        See tcp_retries2 for more details.
>
>        The default value is 7.
>        If your machine is a loaded WEB server,
>        you should think about lowering this value, such sockets
>        may consume significant resources. Cf. tcp_max_orphans.

This should be 8. tcp(7) got it wright.

> But all servers i have, i notice that  tcp_orphan_retries = 0 by default, i
> check in code, and found that:
>        if (retries == 0 && alive)
>                retries = 8;
> is a bit confusing, that tcp_orphan_retries = 0, is in fact = 8, or to be
> more exact is 8 if socket has rto < RTO_MAX. But nothing like 7 mentioned in
> documentation, i guess it is wrong?. My english too bad to edit that, but
> maybe someone will take a look :-)

I guess 0 means, let the operating system to choose the default value for this.
Basically, what we should do here is replace 7 with 8 in
Documentation/networking/ip-sysctl.txt
I can try to make a patch for this if you want.

thanks,
Daniel.
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