netdev - [PATCH net-next 2/4] ipv6: Use a 31-bit multipath hash

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Message-Id: <20180109144028.30133-3-idosch@mellanox.com>
Date:   Tue,  9 Jan 2018 16:40:26 +0200
From:   Ido Schimmel <idosch@...lanox.com>
To:     netdev@...r.kernel.org
Cc:     davem@...emloft.net, dsahern@...il.com, roopa@...ulusnetworks.com,
        nikolay@...ulusnetworks.com, pch@...bogen.com, jkbs@...hat.com,
        yoshfuji@...ux-ipv6.org, mlxsw@...lanox.com,
        Ido Schimmel <idosch@...lanox.com>
Subject: [PATCH net-next 2/4] ipv6: Use a 31-bit multipath hash

The hash thresholds assigned to IPv6 nexthops are in the range of
[-1, 2^31 - 1], where a negative value is assigned to nexthops that
should not be considered during multipath selection.

Therefore, in a similar fashion to IPv4, we need to use the upper
31-bits of the multipath hash for multipath selection.

Signed-off-by: Ido Schimmel <idosch@...lanox.com>
---
 net/ipv6/route.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/net/ipv6/route.c b/net/ipv6/route.c
index ced2c9bed10b..09e8e10b101d 100644
--- a/net/ipv6/route.c
+++ b/net/ipv6/route.c
@@ -1833,10 +1833,10 @@ u32 rt6_multipath_hash(const struct flowi6 *fl6, const struct sk_buff *skb)
 
 	if (skb) {
 		ip6_multipath_l3_keys(skb, &hash_keys);
-		return flow_hash_from_keys(&hash_keys);
+		return flow_hash_from_keys(&hash_keys) >> 1;
 	}
 
-	return get_hash_from_flowi6(fl6);
+	return get_hash_from_flowi6(fl6) >> 1;
 }
 
 void ip6_route_input(struct sk_buff *skb)
-- 
2.14.3