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ipv6: use a stronger hash for tcp

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It looks like its possible to open thousands of TCP IPv6
sessions on a server, all landing in a single slot of TCP hash
table. Incoming packets have to lookup sockets in a very
long list.

We should hash all bits from foreign IPv6 addresses, using
a salt and hash mix, not a simple XOR.

inet6_ehashfn() can also separately use the ports, instead
of xoring them.

Reported-by: Neal Cardwell <ncardwell@google.com>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Yuchung Cheng <ycheng@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Eric Dumazet 2013-02-21 12:18:52 +00:00 • committed by David S. Miller
parent 0ab8a9f5fa
commit 08dcdbf6a7
4 changed files with 24 additions and 6 deletions
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8
include/net/inet6_hashtables.h
View file

@ -28,16 +28,16 @@
struct inet_hashinfo;
/* I have no idea if this is a good hash for v6 or not. -DaveM */
static inline unsigned int inet6_ehashfn(struct net *net,
const struct in6_addr *laddr, const u16 lport,
const struct in6_addr *faddr, const __be16 fport)
{
u32 ports = (lport ^ (__force u16)fport);
u32 ports = (((u32)lport) << 16) | (__force u32)fport;
return jhash_3words((__force u32)laddr->s6_addr32[3],
(__force u32)faddr->s6_addr32[3],
ports, inet_ehash_secret + net_hash_mix(net));
ipv6_addr_jhash(faddr),
ports,
inet_ehash_secret + net_hash_mix(net));
}
static inline int inet6_sk_ehashfn(const struct sock *sk)