From: David Miller <davem@davemloft.net>
To: shemminger@vyatta.com
Cc: jesse@nicira.com, chrisw@redhat.com, netdev@vger.kernel.org
Subject: Re: [PATCHv5 net-next] vxlan: virtual extensible lan
Date: Thu, 27 Sep 2012 18:47:40 -0400 (EDT) [thread overview]
Message-ID: <20120927.184740.975766966558033959.davem@davemloft.net> (raw)
In-Reply-To: <20120925150957.78591205@nehalam.linuxnetplumber.net>
From: Stephen Hemminger <shemminger@vyatta.com>
Date: Tue, 25 Sep 2012 15:09:57 -0700
> +/* Hash Ethernet address */
> +static u32 eth_hash(const unsigned char *addr)
> +{
> + /* could be optimized for unaligned access */
> + u32 a = addr[5] << 8 | addr[4];
> + u32 b = addr[3] << 24 | addr[2] << 16 | addr[1] << 8 | addr[0];
> +
> + return jhash_2words(a, b, vxlan_salt);
> +}
> +
> +/* Hash chain to use given mac address */
> +static inline struct hlist_head *vxlan_fdb_head(struct vxlan_dev *vxlan,
> + const u8 *mac)
> +{
> + return &vxlan->fdb_head[hash_32(eth_hash(mac), FDB_HASH_BITS)];
> +}
This hashing is way overkill, and in fact is a mis-use of Jenkins.
Jenkins can work fine with power-of-two hash sizes, so using hash_32()
on the Jenkins hash result is nothing short of silly.
I would go one step further and change this to:
(a ^ b) * vxlan_salt
much like how we hash IP addresses in the ipv4 ARP tables. That
function is a universal hash, and therefore provides whatever kind
of protection you're trying to obtain using the salt.
But I wonder if this matters at all, the administrator controls
the contents of this table, rather than external entitites.
next prev parent reply other threads:[~2012-09-27 22:47 UTC|newest]
Thread overview: 43+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-09-24 18:43 [PATCH net-next 0/3] VXLAN driver Stephen Hemminger
2012-09-24 18:43 ` [PATCH net-next 1/3] netlink: add attributes to fdb interface Stephen Hemminger
2012-09-24 18:43 ` [PATCH net-next 2/3] igmp: export symbol ip_mc_leave_group Stephen Hemminger
2012-09-24 18:43 ` [PATCH net-next 3/3] vxlan: virtual extensible lan Stephen Hemminger
2012-09-24 19:33 ` Eric Dumazet
2012-09-24 19:39 ` Eric Dumazet
2012-09-24 19:46 ` [PATCHv2 " Stephen Hemminger
2012-09-24 19:55 ` Eric Dumazet
2012-09-24 20:02 ` [PATCHv3 " Stephen Hemminger
2012-09-24 20:24 ` John Fastabend
2012-09-24 20:27 ` Stephen Hemminger
2012-09-24 23:17 ` John Fastabend
2012-09-24 20:09 ` [PATCHv2 " Eric Dumazet
2012-09-24 20:26 ` Stephen Hemminger
2012-09-24 20:41 ` Eric Dumazet
2012-09-24 20:58 ` [PATCH " Chris Wright
2012-09-24 21:11 ` Stephen Hemminger
2012-09-24 21:22 ` Chris Wright
2012-09-24 21:44 ` [RFC] gre: conform to RFC6040 ECN progogation Stephen Hemminger
2012-09-24 22:25 ` Eric Dumazet
2012-09-24 22:30 ` Stephen Hemminger
2012-09-25 5:17 ` Eric Dumazet
2012-10-01 15:55 ` Ben Hutchings
2012-10-01 15:56 ` Stephen Hemminger
2012-10-01 16:49 ` Ben Hutchings
2012-10-01 17:13 ` Eric Dumazet
2012-10-01 21:21 ` Stephen Hemminger
2012-09-24 21:50 ` [PATCHv4 net-next] vxlan: virtual extensible lan Stephen Hemminger
2012-09-25 21:55 ` Jesse Gross
2012-09-25 22:03 ` Stephen Hemminger
2012-09-25 22:09 ` [PATCHv5 " Stephen Hemminger
2012-09-27 22:47 ` David Miller [this message]
2012-09-27 23:00 ` Stephen Hemminger
2012-09-27 23:12 ` David Miller
2012-10-01 20:57 ` [PATCHv6 " Stephen Hemminger
2012-10-01 22:07 ` David Miller
2012-10-01 22:23 ` Stephen Hemminger
2012-10-01 22:30 ` Stephen Hemminger
2012-10-01 22:34 ` David Miller
[not found] ` <20121001140206.2bbf9c41@nehalam.linuxnetplumber.net>
2012-10-01 21:02 ` [PATCH 2/2] iproute2: manage VXLAN forwarding entries Stephen Hemminger
2012-10-01 21:02 ` [PATCH 1/2] iproute2: vxlan support Stephen Hemminger
2012-09-26 4:36 ` [PATCHv4 net-next] vxlan: virtual extensible lan Stephen Hemminger
2012-09-27 17:20 ` Jesse Gross
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