netdev - Re: [PATCH] sctp: properly latch and use autoclose value from sock to association

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Message-ID: <20131206162931.GC1426@hmsreliant.think-freely.org>
Date:	Fri, 6 Dec 2013 11:29:31 -0500
From:	Neil Horman <nhorman@...driver.com>
To:	David Laight <David.Laight@...LAB.COM>
Cc:	linux-sctp@...r.kernel.org, Wang Weidong <wangweidong1@...wei.com>,
	David Miller <davem@...emloft.net>,
	Vlad Yasevich <vyasevich@...il.com>, netdev@...r.kernel.org
Subject: Re: [PATCH] sctp: properly latch and use autoclose value from sock
 to association

On Fri, Dec 06, 2013 at 03:46:31PM -0000, David Laight wrote:
> > From: Neil Horman
> > Currently, sctp associations latch a sockets autoclose value to an association
> > at association init time, subject to capping constraints from the max_autoclose
> > sysctl value.  This leads to an odd situation where an application may set a
> > socket level autoclose timeout, but sliently sctp will limit the autoclose
> > timeout to something less than that.
> > 
> > Fix this by modifying the autoclose setsockopt function to check the limit, cap
> > it and warn the user via syslog that the timeout is capped.  This will allow
> > getsockopt to return valid autoclose timeout values that reflect what subsequent
> > associations actually use.
> ...
> > +	if (sp->autoclose > net->sctp.max_autoclose) {
> > +		pr_warn("Capping autoclose value %d to defined maximum of %lu\n",
> > +			sp->autoclose, net->sctp.max_autoclose);
> > +		sp->autoclose = net->sctp.max_autoclose;
> > +	}
> 
> Is it really reasonable to allow a user to spam syslog this way?
> 
> 	David
> 
> 
Actually, I think its ok, or at least common.  Theres lots of pr_messages
checking common user errors in the various setockopt paths.  We should probably
undertake a larger effort to convert those all to printk_ratelimited with some
level of sctp shared state.
Neil

> 
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