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Date: Tue, 17 May 2011 17:57:36 -0700
From: Jay Vosburgh <fubar@...ibm.com>
To: John <linux@...2.net>
cc: netdev@...r.kernel.org
Subject: Re: [PATCH] IPv6 transmit hashing for bonding driver
John <linux@...2.net> wrote:
>Currently the "bonding" driver does not support load balancing outgoing
>traffic in LACP mode for IPv6 traffic. IPv4 (and TCP over IPv4) are
>currently supported; this patch adds transmit hashing for IPv6 (and TCP
>over IPv6), bringing IPv6 up to par with IPv4 support in the bonding
>driver.
>
>The algorithm chosen (xor'ing the bottom three quads and then xor'ing that
>down into the bottom byte) was chosen after testing almost 400,000 unique
>IPv6 addresses harvested from server logs. This algorithm had the most
>even distribution for both big- and little-endian architectures while
>still using few instructions.
>
>This patch also adds missing configuration information the MODULE_PARM_DESC.
>
>Patch has been tested on various machines and performs as expected. Thanks
>to Stephen Hemminger and Andy Gospodarek for advice and guidance.
This looks reasonable at first glance, with a few comments
below. You'll need to supply a Signed-Off-By at some point.
It would also be useful to include an update bonding.txt to
describe the IPv6 algorithm; I'd word that something like the following
(filling in the missing bits) for the layer3+4 section, applying similar
changes to the layer2+3 section:
--- net-next-2.6/Documentation/networking/bonding.txt 2011-05-09 17:53:03.000000000 -0700
+++ net-next-2.6/Documentation/networking/bonding.txt.new 2011-05-17 17:53:46.000000000 -0700
@@ -733,21 +733,26 @@
slaves, although a single connection will not span
multiple slaves.
- The formula for unfragmented TCP and UDP packets is
+ The formula for unfragmented IPv4 TCP and UDP packets is
((source port XOR dest port) XOR
((source IP XOR dest IP) AND 0xffff)
modulo slave count
- For fragmented TCP or UDP packets and all other IP
+ The formula for unfragmented IPv6 TCP and UDP packets is
+
+ [ your formula here ]
+
+ For fragmented TCP or UDP packets and all other IP or IPv6
protocol traffic, the source and destination port
- information is omitted. For non-IP traffic, the
+ information is omitted. For non-IP/IPv6 traffic, the
formula is the same as for the layer2 transmit hash
policy.
- This policy is intended to mimic the behavior of
- certain switches, notably Cisco switches with PFC2 as
- well as some Foundry and IBM products.
+ The IPv4 behavior is intended to mimic the behavior of
+ certain switches, notably Cisco switches with PFC2 as well
+ as some Foundry and IBM products. The IPv6 behavior was
+ determined by [ your rationale here ].
This algorithm is not fully 802.3ad compliant. A
single TCP or UDP conversation containing both
>John
>
>--- drivers/net/bonding/bond_main.c.orig 2011-04-18 17:23:09.202894000 -0700
>+++ drivers/net/bonding/bond_main.c 2011-04-19 18:12:30.287929000 -0700
>@@ -152,7 +152,7 @@
> MODULE_PARM_DESC(ad_select, "803.ad aggregation selection logic: stable (0, default), bandwidth (1), count (2)");
> module_param(xmit_hash_policy, charp, 0);
> MODULE_PARM_DESC(xmit_hash_policy, "XOR hashing method: 0 for layer 2 (default)"
>- ", 1 for layer 3+4");
>+ ", 1 for layer 3+4, 2 for layer 2+3");
> module_param(arp_interval, int, 0);
> MODULE_PARM_DESC(arp_interval, "arp interval in milliseconds");
> module_param_array(arp_ip_target, charp, NULL, 0);
>@@ -3720,11 +3720,20 @@
> static int bond_xmit_hash_policy_l23(struct sk_buff *skb, int count)
> {
> struct ethhdr *data = (struct ethhdr *)skb->data;
>- struct iphdr *iph = ip_hdr(skb);
>
> if (skb->protocol == htons(ETH_P_IP)) {
>+ struct iphdr *iph = ip_hdr(skb);
> return ((ntohl(iph->saddr ^ iph->daddr) & 0xffff) ^
> (data->h_dest[5] ^ data->h_source[5])) % count;
>+ } else if (skb->protocol == htons(ETH_P_IPV6)) {
>+ struct ipv6hdr *ipv6h = ipv6_hdr(skb);
>+ u32 v6hash = (
>+ (ipv6h->saddr.s6_addr32[1] ^ ipv6h->daddr.s6_addr32[1]) ^
>+ (ipv6h->saddr.s6_addr32[2] ^ ipv6h->daddr.s6_addr32[2]) ^
>+ (ipv6h->saddr.s6_addr32[3] ^ ipv6h->daddr.s6_addr32[3])
>+ );
Style nit: I don't believe the outermost parentheses are
necessary. Since you do this twice, perhaps make a small inline
function to handle it.
>+ v6hash = (v6hash >> 16) ^ (v6hash >> 8) ^ v6hash;
>+ return (v6hash ^ data->h_dest[5] ^ data->h_source[5]) % count;
> }
>
> return (data->h_dest[5] ^ data->h_source[5]) % count;
>@@ -3738,11 +3747,11 @@
> static int bond_xmit_hash_policy_l34(struct sk_buff *skb, int count)
> {
> struct ethhdr *data = (struct ethhdr *)skb->data;
>- struct iphdr *iph = ip_hdr(skb);
>- __be16 *layer4hdr = (__be16 *)((u32 *)iph + iph->ihl);
>- int layer4_xor = 0;
>+ u32 layer4_xor = 0;
>
> if (skb->protocol == htons(ETH_P_IP)) {
>+ struct iphdr *iph = ip_hdr(skb);
>+ __be16 *layer4hdr = (__be16 *)((u32 *)iph + iph->ihl);
> if (!(iph->frag_off & htons(IP_MF|IP_OFFSET)) &&
> (iph->protocol == IPPROTO_TCP ||
> iph->protocol == IPPROTO_UDP)) {
>@@ -3750,7 +3759,18 @@
> }
> return (layer4_xor ^
> ((ntohl(iph->saddr ^ iph->daddr)) & 0xffff)) % count;
>-
>+ } else if (skb->protocol == htons(ETH_P_IPV6)) {
>+ struct ipv6hdr *ipv6h = ipv6_hdr(skb);
>+ __be16 *layer4hdrv6 = (__be16 *)((u8 *)ipv6h + sizeof(*ipv6h));
>+ if (ipv6h->nexthdr == IPPROTO_TCP || ipv6h->nexthdr == IPPROTO_UDP) {
For fragmented datagrams, the above will keep all fragments
together, which is good, but are there other header types that should be
skipped over to find the UDP/TCP header for hashing purposes?
>+ layer4_xor = (*layer4hdrv6 ^ *(layer4hdrv6 + 1));
>+ }
>+ layer4_xor ^= (
>+ (ipv6h->saddr.s6_addr32[1] ^ ipv6h->daddr.s6_addr32[1]) ^
>+ (ipv6h->saddr.s6_addr32[2] ^ ipv6h->daddr.s6_addr32[2]) ^
>+ (ipv6h->saddr.s6_addr32[3] ^ ipv6h->daddr.s6_addr32[3])
>+ );
Parentheses / maybe inline again.
>+ return ((layer4_xor >> 16) ^ (layer4_xor >> 8) ^ layer4_xor) % count;
> }
>
> return (data->h_dest[5] ^ data->h_source[5]) % count;
-J
---
-Jay Vosburgh, IBM Linux Technology Center, fubar@...ibm.com
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