From 2867e1eac61016f59b3d730e3f7aa488e186e917 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Toke=20H=C3=B8iland-J=C3=B8rgensen?= <toke@redhat.com>
Date: Mon, 30 Nov 2020 19:37:05 +0100
Subject: [PATCH] inet_ecn: Fix endianness of checksum update when setting
ECT(1)
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit
When adding support for propagating ECT(1) marking in IP headers it seems I
suffered from endianness-confusion in the checksum update calculation: In
fact the ECN field is in the *lower* bits of the first 16-bit word of the
IP header when calculating in network byte order. This means that the
addition performed to update the checksum field was wrong; let's fix that.
Fixes: b723748750ec ("tunnel: Propagate ECT(1) when decapsulating as recommended by RFC6040")
Reported-by: Jonathan Morton <chromatix99@gmail.com>
Tested-by: Pete Heist <pete@heistp.net>
Signed-off-by: Toke Høiland-Jørgensen <toke@redhat.com>
Link: https://lore.kernel.org/r/20201130183705.17540-1-toke@redhat.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
---
include/net/inet_ecn.h | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/include/net/inet_ecn.h b/include/net/inet_ecn.h
index e1eaf17802889d..563457fec557ef 100644
--- a/include/net/inet_ecn.h
+++ b/include/net/inet_ecn.h
@@ -107,7 +107,7 @@ static inline int IP_ECN_set_ect1(struct iphdr *iph)
if ((iph->tos & INET_ECN_MASK) != INET_ECN_ECT_0)
return 0;
- check += (__force u16)htons(0x100);
+ check += (__force u16)htons(0x1);
iph->check = (__force __sum16)(check + (check>=0xFFFF));
iph->tos ^= INET_ECN_MASK;
--
GitLab