From 6862234238e84648c305526af2edd98badcad1e0 Mon Sep 17 00:00:00 2001
From: Chema Gonzalez <chema@google.com>
Date: Fri, 7 Sep 2012 13:40:50 +0000
Subject: net: small bug on rxhash calculation
In the current rxhash calculation function, while the
sorting of the ports/addrs is coherent (you get the
same rxhash for packets sharing the same 4-tuple, in
both directions), ports and addrs are sorted
independently. This implies packets from a connection
between the same addresses but crossed ports hash to
the same rxhash.
For example, traffic between A=S:l and B=L:s is hashed
(in both directions) from {L, S, {s, l}}. The same
rxhash is obtained for packets between C=S:s and D=L:l.
This patch ensures that you either swap both addrs and ports,
or you swap none. Traffic between A and B, and traffic
between C and D, get their rxhash from different sources
({L, S, {l, s}} for A<->B, and {L, S, {s, l}} for C<->D)
The patch is co-written with Eric Dumazet <edumazet@google.com>
Signed-off-by: Chema Gonzalez <chema@google.com>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
---
net/core/dev.c | 11 ++++++-----
1 file changed, 6 insertions(+), 5 deletions(-)
(limited to 'net/core/dev.c')
diff --git a/net/core/dev.c b/net/core/dev.c
index 83988362805e..d7fe32c946c1 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -2647,15 +2647,16 @@ void __skb_get_rxhash(struct sk_buff *skb)
if (!skb_flow_dissect(skb, &keys))
return;
- if (keys.ports) {
- if ((__force u16)keys.port16[1] < (__force u16)keys.port16[0])
- swap(keys.port16[0], keys.port16[1]);
+ if (keys.ports)
skb->l4_rxhash = 1;
- }
/* get a consistent hash (same value on both flow directions) */
- if ((__force u32)keys.dst < (__force u32)keys.src)
+ if (((__force u32)keys.dst < (__force u32)keys.src) ||
+ (((__force u32)keys.dst == (__force u32)keys.src) &&
+ ((__force u16)keys.port16[1] < (__force u16)keys.port16[0]))) {
swap(keys.dst, keys.src);
+ swap(keys.port16[0], keys.port16[1]);
+ }
hash = jhash_3words((__force u32)keys.dst,
(__force u32)keys.src,
--
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