From mboxrd@z Thu Jan 1 00:00:00 1970 From: Neil Horman Subject: Re: BSD 4.2 style TCP keepalives Date: Fri, 8 Jan 2010 20:22:27 -0500 Message-ID: <20100109012227.GA2762@localhost.localdomain> References: <20100105.163911.10233438.davem@davemloft.net> <20100108124033.GA28782@hmsreliant.think-freely.org> <20100108.132107.38069748.davem@davemloft.net> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: netdev@vger.kernel.org, ilpo.jarvinen@helsinki.fi To: David Miller Return-path: Received: from charlotte.tuxdriver.com ([70.61.120.58]:60816 "EHLO smtp.tuxdriver.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753538Ab0AIBWf (ORCPT ); Fri, 8 Jan 2010 20:22:35 -0500 Content-Disposition: inline In-Reply-To: <20100108.132107.38069748.davem@davemloft.net> Sender: netdev-owner@vger.kernel.org List-ID: On Fri, Jan 08, 2010 at 01:21:07PM -0800, David Miller wrote: > From: Neil Horman > Date: Fri, 8 Jan 2010 07:40:33 -0500 > > > Dave, sorry about this, but it looks like we can scrap this, I just > > looked at the initial tcpdump this was reported in, and apparently > > w2k doesn't compute the checksum properly on these old style > > keepalives. > > Thanks for the update. Nothing to be sorry about, this is actually a > relief and we learned a lot about keepalives and zero-window probes in > the process :-) > I'm trying to do some independent computation on it, but its looking like this may have been a combination of old software (win2k) and a bad corner case in hardware. I think the reporter has a NIC that doesn't do TCO properly on these old style keepalives, which would explain why it wasn't reproducable outside of the reporters environment. I'm trying to figure out which card/hw revision of NIC they were using. It might be worth coding an errata check into the appropriate driver if this all turns out to be accurate to disable TCO affectecd hw. Neil