netdev - [PATCH] net_sched: fix ip

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Date:	Wed, 16 Mar 2011 00:56:07 +0100
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	David Miller <davem@...emloft.net>
Cc:	chromatix99@...il.com, d@...t.net, netdev@...r.kernel.org,
	Dan Siemon <dan@...erfire.com>
Subject: [PATCH] net_sched: fix ip_tos2prio

From: Dan Siemon <dan@...erfire.com>

ECN support incorrectly maps ECN BESTEFFORT packets to TC_PRIO_FILLER
(1) instead of TC_PRIO_BESTEFFORT (0)

This means ECN enabled flows are placed in pfifo_fast/prio low priority
band, giving ECN enabled flows [ECT(0) and CE codepoints] higher drop
probabilities.

This is rather unfortunate, given we would like ECN being more widely
used.

Ref : http://www.coverfire.com/archives/2011/03/13/pfifo_fast-and-ecn/

Signed-off-by: Dan Siemon <dan@...erfire.com>
Signed-off-by: Eric Dumazet <eric.dumazet@...il.com>
Cc: Dave Täht <d@...t.net>
Cc: Jonathan Morton <chromatix99@...il.com>
---
Note: I left TC_PRIO_FILLER definition, this can be removed later.

 net/ipv4/route.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/ipv4/route.c b/net/ipv4/route.c
index 209989c..870b518 100644
--- a/net/ipv4/route.c
+++ b/net/ipv4/route.c
@@ -204,7 +204,7 @@ static struct dst_ops ipv4_dst_ops = {
 
 const __u8 ip_tos2prio[16] = {
 	TC_PRIO_BESTEFFORT,
-	ECN_OR_COST(FILLER),
+	ECN_OR_COST(BESTEFFORT),
 	TC_PRIO_BESTEFFORT,
 	ECN_OR_COST(BESTEFFORT),
 	TC_PRIO_BULK,


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