Subject: [RFC] bonding: better transmit hash

From: Stephen Hemminger <[email-masked]>
Date: Wed, 3 Feb 2010 11:13:37 -0800

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?

--- 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)) &&
 		    (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;