From: Jakub Kicinski <jakub.kicinski@netronome.com>
Date: Tue, 16 Jan 2018 23:08:50 +0000 (-0800)
Subject: tc: red: allow setting th_min and th_max to the same value
X-Git-Tag: v4.16.0~86
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=e0850bdedc22ccc536039b1cb832cf383cafc6f8;p=thirdparty%2Fiproute2.git

tc: red: allow setting th_min and th_max to the same value

Setting th_min and th_max to the same value may be useful for DCTCP
deployments.  The original DCTCP paper describes it as a simplest way
of achieving simple ECN threshold marking.  Indeed, there doesn't seem
to be any simpler qdisc in Linux which would allow such a setup today.

Signed-off-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Reviewed-by: Dirk van der Merwe <dirk.vandermerwe@netronome.com>
Signed-off-by: David Ahern <dsahern@gmail.com>
---

diff --git a/tc/tc_red.c b/tc/tc_red.c
index 1f82ef1ae..178fe088f 100644
--- a/tc/tc_red.c
+++ b/tc/tc_red.c
@@ -30,7 +30,9 @@ int tc_red_eval_P(unsigned int qmin, unsigned int qmax, double prob)
 {
 	int i = qmax - qmin;
 
-	if (i <= 0)
+	if (!i)
+		return 0;
+	if (i < 0)
 		return -1;
 
 	prob /= i;