From: Jakub Kicinski <kuba@kernel.org>
To: Jarod Wilson <jarod@redhat.com>
Cc: linux-kernel@vger.kernel.org, Jay Vosburgh <j.vosburgh@gmail.com>,
Veaceslav Falico <vfalico@gmail.com>,
Andy Gospodarek <andy@greyhouse.net>,
"David S. Miller" <davem@davemloft.net>,
Thomas Davis <tadavis@lbl.gov>,
netdev@vger.kernel.org
Subject: Re: [PATCH net-next v2] bonding: add a vlan+mac tx hashing option
Date: Thu, 14 Jan 2021 13:23:14 -0800 [thread overview]
Message-ID: <20210114132314.2c484e9f@kicinski-fedora-pc1c0hjn.dhcp.thefacebook.com> (raw)
In-Reply-To: <20210114211141.GH1171031@redhat.com>
On Thu, 14 Jan 2021 16:11:41 -0500 Jarod Wilson wrote:
> In truth, this code started out as a copy of bond_eth_hash(), which also
> only uses the last byte, though of both source and destination macs. In
> the typical use case for the requesting user, the bond is formed from two
> onboard NICs, which typically have adjacent mac addresses, i.e.,
> AA:BB:CC:DD:EE:01 and AA:BB:CC:DD:EE:02, so only the last byte is really
> relevant to hash differently, but in thinking about it, a replacement NIC
> because an onboard one died could have the same last byte, and maybe we
> ought to just go full source mac right off the go here.
>
> Something like this instead maybe:
>
> static u32 bond_vlan_srcmac_hash(struct sk_buff *skb)
> {
> struct ethhdr *mac_hdr = (struct ethhdr *)skb_mac_header(skb);
> u32 srcmac = 0;
> u16 vlan;
> int i;
>
> for (i = 0; i < ETH_ALEN; i++)
> srcmac = (srcmac << 8) | mac_hdr->h_source[i];
>
> if (!skb_vlan_tag_present(skb))
> return srcmac;
>
> vlan = skb_vlan_tag_get(skb);
>
> return vlan ^ srcmac;
> }
>
> Then the documentation is spot-on, and we're future-proof, though
> marginally less performant in calculating the hash, which may have been a
> consideration when the original function was written, but is probably
> basically irrelevant w/modern systems...
No preference, especially if bond_eth_hash() already uses the last byte.
Just make sure the choice is explained in the commit message.
next prev parent reply other threads:[~2021-01-14 21:24 UTC|newest]
Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-12-18 19:30 [RFC PATCH net-next] bonding: add a vlan+srcmac tx hashing option Jarod Wilson
2020-12-19 0:18 ` Jay Vosburgh
2021-01-08 0:03 ` Jarod Wilson
2021-01-12 21:12 ` Jarod Wilson
2021-01-12 21:39 ` Jay Vosburgh
2021-01-12 22:32 ` Jarod Wilson
2020-12-28 10:11 ` Jiri Pirko
2021-01-07 23:58 ` Jarod Wilson
2021-01-08 13:12 ` Jiri Pirko
2021-01-08 15:21 ` Jarod Wilson
2021-01-15 2:02 ` question about bonding mode 4 moyufeng
2021-01-23 6:10 ` moyufeng
2021-01-29 19:11 ` Jay Vosburgh
2021-01-30 9:41 ` moyufeng
2021-01-13 22:35 ` [PATCH net-next v2] bonding: add a vlan+mac tx hashing option Jarod Wilson
2021-01-13 23:41 ` [PATCH iproute2] bond: support xmit_hash_policy=vlan+mac Jarod Wilson
2021-01-15 15:12 ` Jarod Wilson
2021-01-15 19:21 ` [PATCH iproute2 v2] bond: support xmit_hash_policy=vlan+srcmac Jarod Wilson
2021-01-23 18:35 ` David Ahern
2021-01-14 1:58 ` [PATCH net-next v2] bonding: add a vlan+mac tx hashing option Jakub Kicinski
2021-01-14 21:11 ` Jarod Wilson
2021-01-14 21:23 ` Jakub Kicinski [this message]
2021-01-14 21:42 ` Jarod Wilson
2021-01-14 21:54 ` Jay Vosburgh
2021-01-15 15:08 ` Jarod Wilson
2021-01-15 19:21 ` [PATCH net-next v3] bonding: add a vlan+srcmac " Jarod Wilson
2021-01-18 23:10 ` David Ahern
2021-01-19 1:04 ` Jarod Wilson
2021-01-19 1:09 ` [PATCH net-next v4] " Jarod Wilson
2021-01-20 6:10 ` patchwork-bot+netdevbpf
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