From owner-freebsd-net@freebsd.org  Mon May 16 07:03:48 2016
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Date: Mon, 16 May 2016 00:03:41 -0700 (PDT)
From: Don Lewis <truckman@FreeBSD.org>
Subject: changing net.inet.tcp.ecn.enable=1 to a three-way knob
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I posted a patch here: <https://reviews.freebsd.org/D6386> to change
net.inet.tcp.ecn.enable from a binary off/on knob to a three way knob
that adds a setting allow incoming TCP connections to negotiate ECN
while outgoing connections don't request ECN.  Always requesting ECN on
outgoing connections can be troublesome because of the number of broken
middle-boxes that block ECN connections (though we do have a fallback to
turning off ECN if the initial connection request fails).

I'd like to get this into HEAD before the code slush.