From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932771Ab2HWL6v (ORCPT ); Thu, 23 Aug 2012 07:58:51 -0400 Received: from mail.linlab.net ([89.244.147.154]:43371 "EHLO mail.linlab.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755101Ab2HWL6r (ORCPT ); Thu, 23 Aug 2012 07:58:47 -0400 X-DKIM: OpenDKIM Filter v2.5.1 mail.linlab.net q7NBwXaj023354 Message-ID: <50361AEA.6010807@linlab.net> Date: Thu, 23 Aug 2012 13:58:34 +0200 From: Alex Bergmann User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:14.0) Gecko/20120713 Thunderbird/14.0 MIME-Version: 1.0 To: "H.K. Jerry Chu" CC: davem@davemloft.net, netdev@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 1/1] tcp: Wrong timeout for SYN segments References: <503419D3.1080700@linlab.net> In-Reply-To: Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit X-Greylist: Sender succeeded STARTTLS authentication, not delayed by milter-greylist-4.2.6 (mail.linlab.net [IPv6:2001:470:7142:a0::3]); Thu, 23 Aug 2012 13:58:39 +0200 (CEST) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 08/22/2012 06:41 PM, H.K. Jerry Chu wrote: > On Tue, Aug 21, 2012 at 4:29 PM, Alex Bergmann > wrote: > > Hi David, > > I'm not 100% sure, but it looks like I found an RFC mismatch with the > current default values of the TCP implementation. > > Alex > > From 8b854a525eb45f64ad29dfab16f9d9f681e84495 Mon Sep 17 00:00:00 2001 > From: Alexander Bergmann > > Date: Wed, 22 Aug 2012 00:29:08 +0200 > Subject: [PATCH 1/1] tcp: Wrong timeout for SYN segments > > Commit 9ad7c049 changed the initRTO from 3secs to 1sec in accordance to > RFC6298 (former RFC2988bis). This introduced a gap with RFC1122 that > defines a minimum retransmission window for SYN segments of at least > 180secs. > > Prior to 9ad7c049 the timeout was defined with 189secs. Now we have only > a timeout of 63secs. > > ((2 << 5) - 1) * 3 secs = 189 secs > ((2 << 5) - 1) * 1 secs = 63 secs > > To fulfill the MUST constraint in RFC1122 section 4.2.3.5 about R2 for > SYN segments, the values of TCP_SYN_RETRIES and TCP_SYNACK_RETRIES must > be changed to 7 reties. > > ((2 << 7) - 1) * 1 secs = 255 secs > > This would result in an ETIMEDOUT of 4 minutes 15 seconds. > > > This issue occurred to me right after I submitted the patch for RFC6298. > I did not commit any more change because RFC compliance aside, 180secs > just seem like eternity in the Internet age. > > (See my past post on this at > http://marc.info/?l=linux-netdev&m=130759078118866&w=2) Okay, I missed that post during my search about the current situation. Thanks, Alex > Jerry > > > Signed-off-by: Alexander Bergmann > > --- > include/net/tcp.h | 4 ++-- > 1 files changed, 2 insertions(+), 2 deletions(-) > > diff --git a/include/net/tcp.h b/include/net/tcp.h > index 1f000ff..7eaae19 100644 > --- a/include/net/tcp.h > +++ b/include/net/tcp.h > @@ -98,10 +98,10 @@ extern void tcp_time_wait(struct sock *sk, int > state, int timeo); > * 15 is ~13-30min depending on RTO. > */ > > -#define TCP_SYN_RETRIES 5 /* number of times to retry > active opening a > +#define TCP_SYN_RETRIES 7 /* number of times to retry > active opening a > * connection: ~180sec is RFC > minimum */ > > -#define TCP_SYNACK_RETRIES 5 /* number of times to retry passive > opening a > +#define TCP_SYNACK_RETRIES 7 /* number of times to retry passive > opening a > * connection: ~180sec is RFC > minimum */ > > #define TCP_TIMEWAIT_LEN (60*HZ) /* how long to wait to destroy > TIME-WAIT > -- > 1.7.8.6 > > -- > To unsubscribe from this list: send the line "unsubscribe netdev" in > the body of a message to majordomo@vger.kernel.org > > More majordomo info at http://vger.kernel.org/majordomo-info.html > > -- |. _ | _ |_ _ _ _|_ ||| ||(_||_).| |(/_ | email/sip/xmpp: alex@linlab.net phone/enum: +49 2871 2355378