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Date: Wed, 03 Feb 2010 12:09:53 -0800
From: Jay Vosburgh <fubar@...ibm.com>
To: Stephen Hemminger <shemminger@...tta.com>
cc: David Miller <davem@...emloft.net>, Jiri Pirko <jpirko@...hat.com>,
bonding-devel@...ts.sourceforge.net, netdev@...r.kernel.org
Subject: Re: [RFC] bonding: better transmit hash
Stephen Hemminger <shemminger@...tta.com> wrote:
>This is a prototype of improved bonding link hashing. It adds a couple
>of things:
> * support IPV6 addresses for L3/L4
> * support other protocols beside TCP/UDP
> * use all of mac address (not just last byte)
> * use jhash for better mixing
> * use skb header field access to handle vlan's etc properly
>
>It no longer is a pure xor, does that matter?
Maybe.
The layer3+4 algorithm in particular was set up to purposely
mimic the algorithm on specific switches. I'm not sure if there are
users who have dependencies on any of the algorithms being a precise
match for a switch's algorithm (in order to have both directions of a
given flow end up on the same slave).
Will the jhash preserve 802.3ad packet ordering requirements for
the layer2 and layer2+3 options (this is the property that all packets
for a given flow will be sent over the same slave)?
How does the computational expense for the jhash compare to the
existing XOR stuff?
I also noted one line, below, that removes whitespace.
-J
>--- a/drivers/net/bonding/bond_main.c 2010-02-03 10:42:50.998328499 -0800
>+++ b/drivers/net/bonding/bond_main.c 2010-02-03 11:08:35.034851960 -0800
>@@ -3587,17 +3587,28 @@ void bond_unregister_arp(struct bonding
> * Hash for the output device based upon layer 2 and layer 3 data. If
> * the packet is not IP mimic bond_xmit_hash_policy_l2()
> */
>-static int bond_xmit_hash_policy_l23(struct sk_buff *skb, int count)
>+static int bond_xmit_hash_policy_l23(const struct sk_buff *skb, int count)
> {
>- struct ethhdr *data = (struct ethhdr *)skb->data;
>- struct iphdr *iph = ip_hdr(skb);
>+ u32 h;
>
>- if (skb->protocol == htons(ETH_P_IP)) {
>- return ((ntohl(iph->saddr ^ iph->daddr) & 0xffff) ^
>- (data->h_dest[5] ^ data->h_source[5])) % count;
>+ switch (skb->protocol) {
>+ case htons(ETH_P_IP):
>+ {
>+ const struct iphdr *iph = ip_hdr(skb);
>+ h = iph->daddr ^ iph->saddr ^ iph->protocol;
>+ break;
>+ }
>+ case htons(ETH_P_IPV6):
>+ {
>+ const struct ipv6hdr *iph = ipv6_hdr(skb);
>+ h = iph->saddr.s6_addr32[3] ^ iph->daddr.s6_addr32[3];
>+ break;
>+ }
>+ default:
>+ h = skb->protocol;
> }
>
>- return (data->h_dest[5] ^ data->h_source[5]) % count;
>+ return jhash(eth_hdr(skb), 2*ETH_ALEN, h) % count;
> }
>
> /*
>@@ -3605,35 +3616,55 @@ static int bond_xmit_hash_policy_l23(str
> * the packet is a frag or not TCP or UDP, just use layer 3 data. If it is
> * altogether not IP, mimic bond_xmit_hash_policy_l2()
> */
>-static int bond_xmit_hash_policy_l34(struct sk_buff *skb, int count)
>+static int bond_xmit_hash_policy_l34(const 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 h;
>+
>+ switch (skb->protocol) {
>+ case htons(ETH_P_IP):
>+ {
>+ const struct iphdr *iph = ip_hdr(skb);
>+ h = iph->saddr ^ iph->daddr;
>
>- if (skb->protocol == htons(ETH_P_IP)) {
>- if (!(iph->frag_off & htons(IP_MF|IP_OFFSET)) &&
>+ if (!(iph->frag_off&htons(IP_MF|IP_OFFSET)) &&
Why squeeze out the spaces here?
> (iph->protocol == IPPROTO_TCP ||
>- iph->protocol == IPPROTO_UDP)) {
>- layer4_xor = ntohs((*layer4hdr ^ *(layer4hdr + 1)));
>- }
>- return (layer4_xor ^
>- ((ntohl(iph->saddr ^ iph->daddr)) & 0xffff)) % count;
>+ iph->protocol == IPPROTO_UDP ||
>+ iph->protocol == IPPROTO_UDPLITE ||
>+ iph->protocol == IPPROTO_SCTP ||
>+ iph->protocol == IPPROTO_DCCP ||
>+ iph->protocol == IPPROTO_ESP))
>+ h ^= *(((u32*)iph) + iph->ihl);
>
>+ break;
>+ }
>+ case htons(ETH_P_IPV6):
>+ {
>+ const struct ipv6hdr *iph = ipv6_hdr(skb);
>+ h = iph->daddr.s6_addr32[3] ^
>+ iph->saddr.s6_addr32[3] ^ iph->nexthdr;
>+ if (iph->nexthdr == IPPROTO_TCP ||
>+ iph->nexthdr == IPPROTO_UDP ||
>+ iph->nexthdr == IPPROTO_UDPLITE ||
>+ iph->nexthdr == IPPROTO_SCTP ||
>+ iph->nexthdr == IPPROTO_DCCP ||
>+ iph->nexthdr == IPPROTO_ESP)
>+ h ^= *(u32*)&iph[1];
>+ break;
>+ }
>+ default:
>+ h = ntohs(skb->protocol);
> }
>
>- return (data->h_dest[5] ^ data->h_source[5]) % count;
>+ return jhash(eth_hdr(skb), 2*ETH_ALEN, h) % count;
> }
>
> /*
> * Hash for the output device based upon layer 2 data
> */
>-static int bond_xmit_hash_policy_l2(struct sk_buff *skb, int count)
>+static int bond_xmit_hash_policy_l2(const struct sk_buff *skb, int count)
> {
>- struct ethhdr *data = (struct ethhdr *)skb->data;
>-
>- return (data->h_dest[5] ^ data->h_source[5]) % count;
>+ return jhash(eth_hdr(skb), 2*ETH_ALEN,
>+ ntohs(skb->protocol)) % count;
> }
>
> /*-------------------------- Device entry points ----------------------------*/
>--- a/drivers/net/bonding/bonding.h 2010-02-03 11:07:43.694540137 -0800
>+++ b/drivers/net/bonding/bonding.h 2010-02-03 11:07:59.294853950 -0800
>@@ -204,7 +204,7 @@ struct bonding {
> #endif /* CONFIG_PROC_FS */
> struct list_head bond_list;
> struct dev_mc_list *mc_list;
>- int (*xmit_hash_policy)(struct sk_buff *, int);
>+ int (*xmit_hash_policy)(const struct sk_buff *, int);
> __be32 master_ip;
> u16 flags;
> u16 rr_tx_counter;
>--
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