From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-04-ewr.dyndns.com (mxout-039-ewr.mailhop.org [216.146.33.39]) by lists.bufferbloat.net (Postfix) with ESMTP id 7D9652E00F5 for ; Mon, 14 Mar 2011 12:55:07 -0700 (PDT) Received: from scan-02-ewr.mailhop.org (scan-02-ewr.local [10.0.141.224]) by mail-04-ewr.dyndns.com (Postfix) with ESMTP id 617527E6FD9 for ; Mon, 14 Mar 2011 19:55:06 +0000 (UTC) X-Spam-Score: -1.0 (-) X-Mail-Handler: MailHop by DynDNS X-Originating-IP: 209.85.215.171 Received: from mail-ey0-f171.google.com (mail-ey0-f171.google.com [209.85.215.171]) by mail-04-ewr.dyndns.com (Postfix) with ESMTP id 1E5907E6FD0; Mon, 14 Mar 2011 19:55:05 +0000 (UTC) Received: by eydd26 with SMTP id d26so2002329eyd.16 for ; Mon, 14 Mar 2011 12:55:04 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=gamma; h=domainkey-signature:subject:mime-version:content-type:from :in-reply-to:date:cc:content-transfer-encoding:message-id:references :to:x-mailer; bh=LFEyKvFOBFNgY/Yo9qXXIWcSHHBu3jjmV5K9JyKSk3k=; b=juKJCUpWpsy2loLxvD/ay+PIAmHjAnM24PnNbLOyspPEMJ48vWCZg0qrl9yeknvJG1 O9i4IyYQDDlOaeY/QMwNqo4iMIWF9C7238k/6WyAFzyZdb6JgmwSfLW31ihAoB3Dbcq0 S2NuqnIAqIGdcmzBLGGw5xdTPBWkaCdpk58LM= DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=subject:mime-version:content-type:from:in-reply-to:date:cc :content-transfer-encoding:message-id:references:to:x-mailer; b=bwpyGmqded7bAEd/wzR7oITaZdof+SuEodZD4INn/BAv5Zzv027RWp5r3Fo2Bipe7A dRXqdBaujamOqW7gzX2zwnnilAErOfTOG9UTo+3zE9yRl9N6AsQCSIFaLO8pCojoqx2o lVGg3Jzdn3UWcRM/oyC1/QzRYK1NKu+c88W1I= Received: by 10.213.35.132 with SMTP id p4mr1643898ebd.108.1300132504395; Mon, 14 Mar 2011 12:55:04 -0700 (PDT) Received: from [192.168.239.42] (xdsl-83-150-84-172.nebulazone.fi [83.150.84.172]) by mx.google.com with ESMTPS id b52sm6252178eei.19.2011.03.14.12.55.03 (version=TLSv1/SSLv3 cipher=OTHER); Mon, 14 Mar 2011 12:55:03 -0700 (PDT) Subject: Re: [Bloat] shaper team forming up Mime-Version: 1.0 (Apple Message framework v1082) Content-Type: text/plain; charset=iso-8859-1 From: Jonathan Morton In-Reply-To: <87wrk1a4gx.fsf@cruithne.co.teklibre.org> Date: Mon, 14 Mar 2011 21:55:01 +0200 Content-Transfer-Encoding: quoted-printable Message-Id: <5BC42741-852B-4699-BA5D-D70B8D610D96@gmail.com> References: <87wrk1a4gx.fsf@cruithne.co.teklibre.org> To: d@taht.net (=?iso-8859-1?Q?Dave_T=E4ht?=) X-Mailer: Apple Mail (2.1082) X-Mailman-Approved-At: Mon, 14 Mar 2011 13:00:49 -0700 Cc: bloat-devel , bloat X-BeenThere: bloat-devel@lists.bufferbloat.net X-Mailman-Version: 2.1.13 Precedence: list List-Id: "Developers working on AQM, device drivers, and networking stacks" List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 14 Mar 2011 19:55:07 -0000 On 14 Mar, 2011, at 9:26 pm, Dave T=E4ht wrote: > Over the weekend, Dan Siemons uncovered a possible bad interaction > between ECN and the default pfifo_fast qdisc in Linux. >=20 > http://www.coverfire.com/archives/2011/03/13/pfifo_fast-and-ecn/ This seems to be more complicated that it appears. It looks as though = Linux has re-used the LSB of the old TOS field for some "link local" = flag which is used by routing. It's not immediately obvious whether pfifo_fast is using this new = interpretation though. If it isn't, the fix should be to remove the = RTO_ONLINK bit from the mask it's using on the tos field. The other = half of the mask correctly excludes the ECN bits from the field. - Jonathan