From: Michal Kubecek <mkubecek@suse.cz>
Date: Mon, 4 Jun 2018 11:36:05 +0200
Subject: ipv6: omit traffic class when calculating flow hash
Patch-mainline: v4.18-rc1
Git-commit: fa1be7e01ea863e911349e30456706749518eeab
References: bsc#1095042

Some of the code paths calculating flow hash for IPv6 use flowlabel member
of struct flowi6 which, despite its name, encodes both flow label and
traffic class. If traffic class changes within a TCP connection (as e.g.
ssh does), ECMP route can switch between path. It's also inconsistent with
other code paths where ip6_flowlabel() (returning only flow label) is used
to feed the key.

Use only flow label everywhere, including one place where hash key is set
using ip6_flowinfo().

Fixes: 51ebd3181572 ("ipv6: add support of equal cost multipath (ECMP)")
Fixes: f70ea018da06 ("net: Add functions to get skb->hash based on flow structures")
Signed-off-by: Michal Kubecek <mkubecek@suse.cz>
Signed-off-by: David S. Miller <davem@davemloft.net>

---
 include/net/ipv6.h        | 5 +++++
 net/core/flow_dissector.c | 4 ++--
 2 files changed, 7 insertions(+), 2 deletions(-)

--- a/include/net/ipv6.h
+++ b/include/net/ipv6.h
@@ -859,6 +859,11 @@ static inline __be32 ip6_make_flowinfo(unsigned int tclass, __be32 flowlabel)
 	return htonl(tclass << IPV6_TCLASS_SHIFT) | flowlabel;
 }
 
+static inline __be32 flowi6_get_flowlabel(const struct flowi6 *fl6)
+{
+	return fl6->flowlabel & IPV6_FLOWLABEL_MASK;
+}
+
 /*
  *	Prototypes exported by ipv6
  */
--- a/net/core/flow_dissector.c
+++ b/net/core/flow_dissector.c
@@ -1012,7 +1012,7 @@ __u32 __skb_get_hash_flowi6(struct sk_buff *skb, const struct flowi6 *fl6)
 	keys.ports.src = fl6->fl6_sport;
 	keys.ports.dst = fl6->fl6_dport;
 	keys.keyid.keyid = fl6->fl6_gre_key;
-	keys.tags.flow_label = (__force u32)fl6->flowlabel;
+	keys.tags.flow_label = (__force u32)flowi6_get_flowlabel(fl6);
 	keys.basic.ip_proto = fl6->flowi6_proto;
 
 	__skb_set_sw_hash(skb, flow_hash_from_keys(&keys),
@@ -1125,7 +1125,7 @@ __u32 __get_hash_from_flowi6(const struct flowi6 *fl6, struct flow_keys *keys)
 	keys->ports.src = fl6->fl6_sport;
 	keys->ports.dst = fl6->fl6_dport;
 	keys->keyid.keyid = fl6->fl6_gre_key;
-	keys->tags.flow_label = (__force u32)fl6->flowlabel;
+	keys->tags.flow_label = (__force u32)flowi6_get_flowlabel(fl6);
 	keys->basic.ip_proto = fl6->flowi6_proto;
 
 	return flow_hash_from_keys(keys);