Natty SRU: ipv6: restore correct ECN handling on TCP xmit

[Tim Gardner]

>From d8130742ea8e3c0f8f4a3fca3db54f16e335b443 Mon Sep 17 00:00:00 2001
From: Steinar H. Gunderson <sgunderson at bigfoot.com>
Date: Fri, 6 May 2011 23:44:46 +0000
Subject: [PATCH] ipv6: restore correct ECN handling on TCP xmit

BugLink: http://bugs.launchpad.net/bugs/872179

Since commit e9df2e8fd8fbc9 (Use appropriate sock tclass setting for
routing lookup) we lost ability to properly add ECN codemarks to ipv6
TCP frames.

It seems like TCP_ECN_send() calls INET_ECN_xmit(), which only sets the
ECN bit in the IPv4 ToS field (inet_sk(sk)->tos), but after the patch,
what's checked is inet6_sk(sk)->tclass, which is a completely different
field.

Close bug https://bugzilla.kernel.org/show_bug.cgi?id=34322

[Eric Dumazet] : added the INET_ECN_dontxmit() fix and replace macros
by inline functions for clarity.

Signed-off-by: Steinar H. Gunderson <sgunderson at bigfoot.com>
Signed-off-by: Eric Dumazet <eric.dumazet at gmail.com>
Cc: YOSHIFUJI Hideaki <yoshfuji at linux-ipv6.org>
Cc: Andrew Morton <akpm at linux-foundation.org>
Signed-off-by: David S. Miller <davem at davemloft.net>
(cherry picked from commit ca06707022d6ba4744198a8ebbe4994786b0c613)

Signed-off-by: Tim Gardner <tim.gardner at canonical.com>
---
 include/net/inet_ecn.h |   16 +++++++++++++---
 1 files changed, 13 insertions(+), 3 deletions(-)

diff --git a/include/net/inet_ecn.h b/include/net/inet_ecn.h
index 88bdd01..2fa8d13 100644
--- a/include/net/inet_ecn.h
+++ b/include/net/inet_ecn.h
@@ -38,9 +38,19 @@ static inline __u8 INET_ECN_encapsulate(__u8 outer, __u8 inner)
 	return outer;
 }
 
-#define	INET_ECN_xmit(sk) do { inet_sk(sk)->tos |= INET_ECN_ECT_0; } while (0)
-#define	INET_ECN_dontxmit(sk) \
-	do { inet_sk(sk)->tos &= ~INET_ECN_MASK; } while (0)
+static inline void INET_ECN_xmit(struct sock *sk)
+{
+	inet_sk(sk)->tos |= INET_ECN_ECT_0;
+	if (inet6_sk(sk) != NULL)
+		inet6_sk(sk)->tclass |= INET_ECN_ECT_0;
+}
+
+static inline void INET_ECN_dontxmit(struct sock *sk)
+{
+	inet_sk(sk)->tos &= ~INET_ECN_MASK;
+	if (inet6_sk(sk) != NULL)
+		inet6_sk(sk)->tclass &= ~INET_ECN_MASK;
+}
 
 #define IP6_ECN_flow_init(label) do {		\
       (label) &= ~htonl(INET_ECN_MASK << 20);	\
-- 
1.7.0.4