From: Jonathan Morton <chromatix99@gmail.com>
To: d@taht.net (Dave Täht)
Cc: bloat-devel <bloat-devel@lists.bufferbloat.net>,
bloat <bloat@lists.bufferbloat.net>
Subject: Re: [Bloat] shaper team forming up
Date: Mon, 14 Mar 2011 21:55:01 +0200 [thread overview]
Message-ID: <5BC42741-852B-4699-BA5D-D70B8D610D96@gmail.com> (raw)
In-Reply-To: <87wrk1a4gx.fsf@cruithne.co.teklibre.org>
On 14 Mar, 2011, at 9:26 pm, Dave Täht wrote:
> Over the weekend, Dan Siemons uncovered a possible bad interaction
> between ECN and the default pfifo_fast qdisc in Linux.
>
> 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
next prev parent reply other threads:[~2011-03-14 19:55 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-03-14 19:26 Dave Täht
2011-03-14 19:55 ` Jonathan Morton [this message]
2011-03-14 20:24 ` [Bloat] " Eric Dumazet
[not found] ` <1300164166.2649.70.camel@edumazet-laptop>
[not found] ` <87ipvlosvz.fsf_-_@cruithne.co.teklibre.org>
[not found] ` <1300169749.2649.142.camel@edumazet-laptop>
[not found] ` <3D05C1F1-B75E-426B-8267-6DB5323A839D@gmail.com>
[not found] ` <1300213714.2927.37.camel@edumazet-laptop>
2011-03-15 18:37 ` ECN + pfifo_fast borked? Dave Täht
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