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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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12
include/net/ipv6.h
View file

@ -15,6 +15,7 @@
#include <linux/ipv6.h>
#include <linux/hardirq.h>
#include <linux/jhash.h>
#include <net/if_inet6.h>
#include <net/ndisc.h>
#include <net/flow.h>
@ -514,6 +515,17 @@ static inline u32 ipv6_addr_hash(const struct in6_addr *a)
#endif
}
/* more secured version of ipv6_addr_hash() */
static inline u32 ipv6_addr_jhash(const struct in6_addr *a)
{
u32 v = (__force u32)a->s6_addr32[0] ^ (__force u32)a->s6_addr32[1];
return jhash_3words(v,
(__force u32)a->s6_addr32[2],
(__force u32)a->s6_addr32[3],
ipv6_hash_secret);
}
static inline bool ipv6_addr_loopback(const struct in6_addr *a)
{
#if defined(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS) && BITS_PER_LONG == 64