[Codel] [RFCv2 PATCH] iproute2: Add ecn_target option to codel and fq_codel

[Eric Dumazet]

On Sun, 2012-06-24 at 22:00 -0700, Dave Täht wrote:
> From: Dave Taht <dave.taht at bufferbloat.net>
> 
> ECN was not part of the original codel design and adding support
> for it revealed problems in two areas. 1) ECN can be gamed.
> 2) Dropping packets under overload more rapidly frees up
> bandwidth than marking packets.
> 
> Two possible scenarios of use - on egress from a network,
> ecn_target could be set low, to drop more often, to
> ensure lowest latency for other packets.
> 
> On ingress, it could be set high to mark packets more often,
> to lower data loss while still signalling the end application
> that bandwidth is a problem.
> 
> ecn_target is not engaged until after codel enters a dropping
> state overall.

I would suggest 'drop_above' instead of ecn_target, since its quite
different than the 'target'

(And dont display/output it if ecn is not set, no need to confuse users
who didn't enable ecn on CoDel)