linux-kernel - Re: [ 059/143] sysctl net: Keep tcp_syn

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Date:	Sat, 21 Jun 2014 00:58:27 +0200
From:	Willy Tarreau <w@....eu>
To:	"Eric W. Biederman" <ebiederm@...ssion.com>
Cc:	Luis Henriques <luis.henriques@...onical.com>,
	linux-kernel@...r.kernel.org, stable@...r.kernel.org,
	Michal Tesar <mtesar@...hat.com>,
	"David S. Miller" <davem@...emloft.net>, tyler.hicks@...onical.com
Subject: Re: [ 059/143] sysctl net: Keep tcp_syn_retries inside the boundary

Hi Eric,

On Fri, Jun 20, 2014 at 03:16:07PM -0700, Eric W. Biederman wrote:
> Willy Tarreau <w@....eu> writes:
> 
> > Hi Luis,
> >
> > On Thu, Jun 12, 2014 at 01:55:53PM +0100, Luis Henriques wrote:
> >> I was finally able to spend some more time with this and tried (a
> >> modified) Tyler's patch on top of 2.6.32.62, and it seems to work.
> >> Although I haven't done any extended testing, I don't see the two
> >> stack traces and the /proc/sys/net/ipv4/ directory seems to be
> >> correctly populated.
> >> 
> >> I'm attaching the patch I've used, based on Tyler's.
> >
> > Would any of you or Tyler please kindly pass me a signed-off-by with
> > a commit message ? That would be great. Alternately I'd do it myself
> > and mention you authored them.
> 
> If my memory serves it is possibe in 2.6.32 to set 
> .ctl_name = CTL_UNNEEDED
> 
> and not need to implement a .strategy routine at all.

Ah that's quite interesting, thanks for the tip!

> Given the fact that most people got the strategy routines
> slightly wrong and that sys_sysctl is effectively unused
> a strategy where you don't implement code that no-one
> will use in a backport I would be preferable.

OK.

> Since you have mentioned this has come up a couple of times if something
> else this will be something to think about for next time.

I'm keeping your e-mail where I manage patches, hoping to recognize
this case next time.

> I am puzzled why .ctl_name was populated in a backport at all.

Oh it's simply because I didn't know it did not have to be there,
and among the few reviewers, I guess that it's not common to know
what version uses what semantics.

Thank you for the exaplanation, it's really helpful. We're not used
to backport sysctl changes but here I got caught a few times and have
found some sysctl.conf with bogus values in field a few times, so it
was really important to backport this one.

Best regards,
Willy

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