From owner-freebsd-current@FreeBSD.ORG Sun Nov 4 12:16:01 2012 Return-Path: Delivered-To: freebsd-current@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [69.147.83.52]) by hub.freebsd.org (Postfix) with ESMTP id D176EB7C; Sun, 4 Nov 2012 12:16:01 +0000 (UTC) (envelope-from w8hdkim@gmail.com) Received: from mail-vc0-f182.google.com (mail-vc0-f182.google.com [209.85.220.182]) by mx1.freebsd.org (Postfix) with ESMTP id 59CA78FC0A; Sun, 4 Nov 2012 12:16:01 +0000 (UTC) Received: by mail-vc0-f182.google.com with SMTP id fw7so6674439vcb.13 for ; Sun, 04 Nov 2012 04:16:01 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=mime-version:date:message-id:subject:from:to:cc:content-type; bh=qblL1B5AQsZj5ioS+a0waQ85TYKIqibksI6+34EOsNg=; b=IXa57ApSO7PlbzdE8mJUpctbLNzam19+RTvDKiAGBHRz9JLc6Gfg+t1rhEx09FS8Es se4BmEayPdkepxgBgpGFjJVZ4iMDbKJlulcC4bHrAKUupNinxEF0Fb9c3qQQOv2sh3uU dLfKf5muMZ50ctsYN8K9lRmV1CeeS3JT6TzSwn+bDclpi4rZQATxll2biR3VD8GOdxDe VoQ7i/jleOT422wCKoSmi8X/koVGAn6GP+oG/w4wT4vNJxdrUwtQAyT2pN40V33NLvwn xZcGcqcWz/wB6GOI+FA1C1/Ng10UVi9aljGFyAfX9NbgXPpRZMim2XNwVhPF+vpGFkft YP/Q== MIME-Version: 1.0 Received: by 10.58.155.169 with SMTP id vx9mr6938122veb.45.1352031361131; Sun, 04 Nov 2012 04:16:01 -0800 (PST) Received: by 10.58.226.163 with HTTP; Sun, 4 Nov 2012 04:16:01 -0800 (PST) Date: Sun, 4 Nov 2012 07:16:01 -0500 Message-ID: Subject: Re: weird network problems on current since 10/28/2012 From: Kim Culhan To: Dimitry Andric Content-Type: text/plain; charset=ISO-8859-1 X-Content-Filtered-By: Mailman/MimeDel 2.1.14 Cc: Adrian Chadd , freebsd-current@freebsd.org, Andre Oppermann X-BeenThere: freebsd-current@freebsd.org X-Mailman-Version: 2.1.14 Precedence: list List-Id: Discussions about the use of FreeBSD-current List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Sun, 04 Nov 2012 12:16:02 -0000 On Sun, November 4, 2012 6:21 am, Dimitry Andric wrote: > On 2012-11-04 02:13, Manfred Antar wrote: >> At 03:29 PM 11/3/2012, Adrian Chadd wrote: >>> On 3 November 2012 10:40, Manfred Antar wrote: >>>> i have problem connecting to freebsd box on local network since last sunday. >>>> the last kernel that works: >>>> FreeBSD 10.0-CURRENT #0: Sun Oct 28 12:14:38 PDT 2012 >>>> anything after that, sometimes i can connect, other times just hangs. >>>> any network connection hangs ===== pop httpd ssh etc etc. >>>> anyone have any ideas ? >>>> i can checkout different sources and see if i can locate the changes that cause >>>> this. >>> >>> Please do! > ... >> Here is what I found doing : >> setenv CVSROOT /usr/home/ncvs >> >> cvs co -D"October 28, 2012 12:14:38 PDT" sys >> >> A kernel from that time works fine. >> >> doing: >> >> cvs up -D"October 28, 2012 13:14:38 PDT" sys 1 hour later >> the following files were changed: >> sys/netinet/tcp_input.c >> sys/netinet/tcp_timer.c >> sys/netinet/tcp_var.h >> >> Building a kernel from these new files is when the problem starts. > > So, your problems seem to have been introduced by this commit by Andre: > > http://svn.freebsd.org/changeset/base/242266 > > Increase the initial CWND to 10 segments as defined in IETF TCPM > draft-ietf-tcpm-initcwnd-05. It explains why the increased initial > window improves the overall performance of many web services without > risking congestion collapse. > > As long as it remains a draft it is placed under a sysctl marking it > as experimental: > net.inet.tcp.experimental.initcwnd10 = 1 > When it becomes an official RFC soon the sysctl will be changed to > the RFC number and moved to net.inet.tcp. > > This implementation differs from the RFC draft in that it is a bit > more conservative in the case of packet loss on SYN or SYN|ACK because > we haven't reduced the default RTO to 1 second yet. Also the restart > window isn't yet increased as allowed. Both will be adjusted with > upcoming changes. > > Is is enabled by default. In Linux it is enabled since kernel 3.0. > > After the commit, there was a small discussion thread on svn-src-head@ > about the possible problems with the approach. Maybe you are > experiencing those? > > As the commit message says, you should be able to turn the feature off > using: > > sysctl net.inet.tcp.experimental.initcwnd10=0 > > Can you please try that, and see if the problems go away? FWIW this did not make the problem go away here. thanks -kim --