netdev - Re: ipv4: Simplify ARP hash function.

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Fri, 08 Jul 2011 16:47:51 -0700 (PDT)
From:	David Miller <davem@...emloft.net>
To:	shemminger@...tta.com
Cc:	roland@...estorage.com, johnwheffner@...il.com, mj@....cz,
	netdev@...r.kernel.org
Subject: Re: ipv4: Simplify ARP hash function.

From: Stephen Hemminger <shemminger@...tta.com>
Date: Fri, 8 Jul 2011 16:41:28 -0700

> What about using murmur hash which has a four byte pass as well.
>   https://sites.google.com/site/murmurhash/

I'm trying to avoid multiplies that are not done in hardware on some
cpus.

Right now I'm looking at one of Thomas Wang's hashes, referenced on
Bob Jenkin's hash analysis page:

u32 hashint(u32 a)
{
	a += ~(a<<15);
	a ^=  (a>>10);
	a +=  (a<<3);
	a ^=  (a>>6);
	a += ~(a<<11);
	a ^=  (a>>16);

	return a;
}

It's 15 instructions, and produces better entropy in the low bits of
the result than the high bits, which is fine for how we'll use this
thing.
--
To unsubscribe from this list: send the line "unsubscribe netdev" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html