From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752596Ab2HVKAI (ORCPT ); Wed, 22 Aug 2012 06:00:08 -0400 Received: from mail-bk0-f46.google.com ([209.85.214.46]:33192 "EHLO mail-bk0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751490Ab2HVKAE (ORCPT ); Wed, 22 Aug 2012 06:00:04 -0400 Subject: Re: [PATCH 1/1] tcp: Wrong timeout for SYN segments From: Eric Dumazet To: Alex Bergmann Cc: davem@davemloft.net, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, Jerry Chu , Neal Cardwell , Nandita Dukkipati In-Reply-To: <5034A678.3040207@linlab.net> References: <503419D3.1080700@linlab.net> <1345622798.5158.717.camel@edumazet-glaptop> <50349CC5.3050601@linlab.net> <1345625910.5158.793.camel@edumazet-glaptop> <5034A678.3040207@linlab.net> Content-Type: text/plain; charset="UTF-8" Date: Wed, 22 Aug 2012 11:59:57 +0200 Message-ID: <1345629597.5158.924.camel@edumazet-glaptop> Mime-Version: 1.0 X-Mailer: Evolution 2.28.3 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 2012-08-22 at 11:29 +0200, Alex Bergmann wrote: > Actual 6 SYN frames are sent. The initial one and 5 retries. > first one had a t0 + 0 delay. How can it count ??? > The kernel is waiting another 32 seconds for a SYN+ACK and then gives > the ETIMEDOUT back to userspace. > > Do you mean that we have to send another SYN packet after the 3 minutes? > First SYN is not a retransmit R2 = time_of_last_SYN - time_of_initial_SYN (t0) = 31 If you read RFC it states : "In particular, R2 for a SYN segment MUST be set large enough to provide retransmission of the segment for at least 3 minutes." That means that the last _retransmit_ MUST happen after 180 seconds. And not : Send all the restransmits at t0 + 1, then wait 180 seconds before giving connect() a timeout indication.