From mboxrd@z Thu Jan 1 00:00:00 1970 From: Gilad Ben-Yossef Subject: Re: [PATCH] [RFC] IPv4 TCP fails to send window scale option when window scale is zero Date: Thu, 01 Oct 2009 11:39:43 +0200 Message-ID: <4AC478DF.2060401@codefidence.com> References: <4AC22250.7060301@codefidence.com> <4AC241BA.8040608@gmail.com> <4AC2FA7C.6030901@codefidence.com> <4AC305BF.6080306@gmail.com> <4AC357D3.7080606@gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: =?ISO-8859-1?Q?Ilpo_J=E4rvinen?= , Netdev , Ori Finkalman To: Eric Dumazet Return-path: Received: from xenbox.codefidence.com ([92.48.73.16]:45029 "EHLO xenbox.codefidence.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750706AbZJAJjm (ORCPT ); Thu, 1 Oct 2009 05:39:42 -0400 In-Reply-To: <4AC357D3.7080606@gmail.com> Sender: netdev-owner@vger.kernel.org List-ID: Eric Dumazet wrote: > >>> >>> Your version slows down the tcp_options_write() function, once per tx packet. >>> >> Are you serious that anding would cost that much? :-/ >> > > Not really :) > LOL I was trying very hard to understand why you thought this was such an issue. My head was flying into all sorts of weird directions like cache effects and the like... ;-) > Yes, wscale 0 is RFC valid, but are we sure some equipment wont play funny games > with such value ? At least sending "wscale 1-14" must be working... > Well, there at least used to be routers that would actually zeroed the WS value in transit while leaving the option set, but this is another issue of course. Anyway, I know Vista at least does set the window scale TCP option by default. One assumes they occasionally send a zero value scale. Not that Vista is such a good benchmark to compare Linux to but at least I tend to believe the issue would have popped up if it is common enough. I can craft a patch to introduce a route table option to set TCP window scale minimum and maximum sizes, similar to window size route option, if you there is a need for that. Personally, I think it is just overkill. > > My quick&dirty patch was only for discussion, I have no strong opinion on it, > only that was on one place to patch instead of two/three/four I dont know yet. > > So please Gilad & Ori send us a new patch :) > > Revised patch follows in next email. Gilad -- Gilad Ben-Yossef Chief Coffee Drinker & CTO Codefidence Ltd. Web: http://codefidence.com Cell: +972-52-8260388 Skype: gilad_codefidence Tel: +972-8-9316883 ext. 201 Fax: +972-8-9316884 Email: gilad@codefidence.com Check out our Open Source technology and training blog - http://tuxology.net "Now the world has gone to bed Darkness won't engulf my head I can see by infra-red How I hate the night."