netdev - Re: [PATCH] tcp FRTO: in-order-only "TCP proxy" fragility workaround

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20080911143006.2f516569@tux>
Date:	Thu, 11 Sep 2008 14:30:06 -0300
From:	Dâniel Fraga <fragabr@...il.com>
To:	"Ilpo Järvinen" <ilpo.jarvinen@...sinki.fi>
Cc:	David Miller <davem@...emloft.net>, thomas.jarosch@...ra2net.com,
	billfink@...dspring.com, Netdev <netdev@...r.kernel.org>,
	Patrick Hardy <kaber@...sh.net>,
	netfilter-devel@...r.kernel.org, kadlec@...ckhole.kfki.hu
Subject: Re: [PATCH] tcp FRTO: in-order-only "TCP proxy" fragility
 workaround

On Thu, 11 Sep 2008 16:44:20 +0300 (EEST)
"Ilpo Järvinen" <ilpo.jarvinen@...sinki.fi> wrote:

> ...I guess it would be possible to remove SCHED_FEAT_HRTICK from
> /proc/sys/kernel/sched_features then while keeping the hrtimers
> otherwise enabled to test this.
> 
> It's possible that hrtimers just affect on how easy it is to trigger
> but at least it seems an useful lead until proven otherwise.

	You're right Ilpo. After days and days without the problem,
today it triggered (but I wasn't online at the time, so I couldn't grab
any data).

	So, you're correct. HRtimers just affect on how easy it is to
trigger the issue. In other words: with high resolution timer enabled,
the problem appears more frequently.

	At least if we discovered a way how to trigger this, we could
test it more easily. The problem is to wait a long time for it to
happen.

	Just a curiosity: on your servers, do you use x86_64? It seems
this problem is very specific to x86_64 or appear more often on x86_64
than x86_32. It never happens on my x86_32 bit servers.

	


-- 
--
To unsubscribe from this list: send the line "unsubscribe netdev" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html