From: Eric Dumazet <dada1@cosmosbay•com>
To: David Miller <davem@davemloft•net>, nikb@webmaster•com
Cc: netdev@vger•kernel.org
Subject: Re: RFC: Established connections hash function
Date: Thu, 22 Mar 2007 23:03:04 +0100 [thread overview]
Message-ID: <4602FD18.7060902@cosmosbay.com> (raw)
In-Reply-To: <20070322.135834.74723088.davem@davemloft.net>
David Miller a écrit :
> From: "Nikolaos D. Bougalis" <nikb@webmaster•com>
> Date: Thu, 22 Mar 2007 12:44:09 -0700
>
>> People _have_ had problems. _I_ have had problems. And when
>> someone with a few thousand drones under his control hoses your
>> servers because he can do math and he leaves you with 20000-item
>> long chains, _you_ will have problems.
>
> No need to further argue this point, the people that matter
> (ie. me :-) understand it, don't worry..
Yes, I recall having one big server hit two years ago by an attack on tcp hash
function. David sent me the patch to use jhash. It's performing well :)
Welcome to the club :)
===== net/ipv4/tcp_ipv4.c 1.114 vs edited =====
--- 1.114/net/ipv4/tcp_ipv4.c 2005-03-26 15:04:35 -08:00
+++ edited/net/ipv4/tcp_ipv4.c 2005-04-05 13:39:52 -07:00
@@ -103,14 +103,15 @@
*/
int sysctl_local_port_range[2] = { 1024, 4999 };
int tcp_port_rover = 1024 - 1;
+static u32 tcp_v4_hash_rand;
static __inline__ int tcp_hashfn(__u32 laddr, __u16 lport,
__u32 faddr, __u16 fport)
{
- int h = (laddr ^ lport) ^ (faddr ^ fport);
- h ^= h >> 16;
- h ^= h >> 8;
- return h & (tcp_ehash_size - 1);
+ return jhash_2words(laddr ^ faddr,
+ (lport << 16) | fport,
+ tcp_v4_hash_rand) &
+ (tcp_ehash_size - 1);
}
> static __inline__ int tcp_sk_hashfn(struct sock *sk)
> @@ -2626,6 +2627,9 @@
> panic("Failed to create the TCP control socket.\n");
> tcp_socket->sk->sk_allocation = GFP_ATOMIC;
> inet_sk(tcp_socket->sk)->uc_ttl = -1;
> +
> + get_random_bytes(&tcp_v4_hash_rand, 4);
> + tcp_v4_hash_rand ^= jiffies;
>
> /* Unhash it so that IP input processing does not even
> * see it, we do not wish this socket to see incoming
>
>
next prev parent reply other threads:[~2007-03-22 22:03 UTC|newest]
Thread overview: 34+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-03-22 15:39 RFC: Established connections hash function Nikolaos D. Bougalis
2007-03-22 15:52 ` Evgeniy Polyakov
2007-03-22 17:32 ` Nikolaos D. Bougalis
2007-03-22 18:21 ` Evgeniy Polyakov
2007-03-22 19:44 ` Nikolaos D. Bougalis
2007-03-22 19:56 ` Evgeniy Polyakov
2007-03-22 20:53 ` Nikolaos D. Bougalis
2007-03-23 7:52 ` Evgeniy Polyakov
2007-03-22 20:58 ` David Miller
2007-03-22 22:03 ` Eric Dumazet [this message]
2007-03-23 7:11 ` David Miller
2007-03-23 8:00 ` Eric Dumazet
2007-03-23 18:46 ` David Miller
2007-03-23 8:07 ` Evgeniy Polyakov
2007-03-23 8:17 ` Eric Dumazet
2007-03-23 8:33 ` Evgeniy Polyakov
2007-03-23 9:10 ` Evgeniy Polyakov
2007-03-23 11:58 ` XOR hash beauty solved [Was: RFC: Established connections hash function] Evgeniy Polyakov
2007-03-23 12:51 ` Nikolaos D. Bougalis
2007-03-23 12:45 ` RFC: Established connections hash function Nikolaos D. Bougalis
2007-03-27 14:11 ` Andi Kleen
2007-03-28 5:01 ` Nikolaos D. Bougalis
2007-03-28 6:29 ` David Miller
2007-03-28 9:29 ` Andi Kleen
2007-03-28 10:45 ` Evgeniy Polyakov
2007-03-28 14:14 ` Andi Kleen
2007-03-28 13:50 ` Eric Dumazet
2007-03-28 14:52 ` Andi Kleen
2007-03-29 9:18 ` Evgeniy Polyakov
2007-03-28 14:17 ` RFC: Established connections hash function II Andi Kleen
2007-03-28 19:04 ` RFC: Established connections hash function David Miller
2007-03-28 20:12 ` Andi Kleen
-- strict thread matches above, loose matches on Subject: below --
2007-03-24 12:26 linux
2007-03-24 13:29 ` Evgeniy Polyakov
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