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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>
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1 changed files with 6 additions and 5 deletions
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@ -2647,15 +2647,16 @@ void __skb_get_rxhash(struct sk_buff *skb)
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if (!skb_flow_dissect(skb, &keys))
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return;
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if (keys.ports) {
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if ((__force u16)keys.port16[1] < (__force u16)keys.port16[0])
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swap(keys.port16[0], keys.port16[1]);
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if (keys.ports)
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skb->l4_rxhash = 1;
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}
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/* get a consistent hash (same value on both flow directions) */
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if ((__force u32)keys.dst < (__force u32)keys.src)
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if (((__force u32)keys.dst < (__force u32)keys.src) ||
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(((__force u32)keys.dst == (__force u32)keys.src) &&
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((__force u16)keys.port16[1] < (__force u16)keys.port16[0]))) {
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swap(keys.dst, keys.src);
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swap(keys.port16[0], keys.port16[1]);
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}
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hash = jhash_3words((__force u32)keys.dst,
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(__force u32)keys.src,
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