bonding: support for IPv6 transmit hashing

Currently the "bonding" driver does not support load balancing outgoing
traffic in LACP mode for IPv6 traffic. IPv4 (and TCP or UDP over IPv4)
are currently supported; this patch adds transmit hashing for IPv6 (and
TCP or UDP over IPv6), bringing IPv6 up to par with IPv4 support in the
bonding driver. In addition, bounds checking has been added to all
transmit hashing functions.

The algorithm chosen (xor'ing the bottom three quads of the source and
destination addresses together, then xor'ing each byte of that result into
the bottom byte, finally xor'ing with the last bytes of the MAC addresses)
was selected 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. Its
behavior also attempts to closely match that of the IPv4 algorithm.

The IPv6 flow label was intentionally not included in the hash as it appears
to be unset in the vast majority of IPv6 traffic sampled, and the current
algorithm not using the flow label already offers a very even distribution.

Fragmented IPv6 packets are handled the same way as fragmented IPv4 packets,
ie, they are not balanced based on layer 4 information. Additionally,
IPv6 packets with intermediate headers are not balanced based on layer
4 information. In practice these intermediate headers are not common and
this should not cause any problems, and the alternative (a packet-parsing
loop and look-up table) seemed slow and complicated for little gain.

Tested-by: John Eaglesham <linux@8192.net>
Signed-off-by: John Eaglesham <linux@8192.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 63 insertions, 26 deletions

diff --git a/drivers/net/bonding/bond_main.c b/drivers/net/bonding/bond_main.c
index a86174c9fed1..b24ce257ac7b 100644
--- a/drivers/net/bonding/bond_main.c
+++ b/drivers/net/bonding/bond_main.c
@@ -3352,56 +3352,93 @@ static struct notifier_block bond_netdev_notifier = {
 /*---------------------------- Hashing Policies -----------------------------*/
 
 /*
+ * Hash for the output device based upon layer 2 data
+ */
+static int bond_xmit_hash_policy_l2(struct sk_buff *skb, int count)
+{
+	struct ethhdr *data = (struct ethhdr *)skb->data;
+
+	if (skb_headlen(skb) >= offsetof(struct ethhdr, h_proto))
+		return (data->h_dest[5] ^ data->h_source[5]) % count;
+
+	return 0;
+}
+
+/*
  * 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()
+ * the packet is not IP, fall back on bond_xmit_hash_policy_l2()
  */
 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;
+	struct ipv6hdr *ipv6h;
+	u32 v6hash;
+	__be32 *s, *d;
+
+	if (skb->protocol == htons(ETH_P_IP) &&
+	    skb_network_header_len(skb) >= sizeof(*iph)) {
+		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) &&
+		   skb_network_header_len(skb) >= sizeof(*ipv6h)) {
+		ipv6h = ipv6_hdr(skb);
+		s = &ipv6h->saddr.s6_addr32[0];
+		d = &ipv6h->daddr.s6_addr32[0];
+		v6hash = (s[1] ^ d[1]) ^ (s[2] ^ d[2]) ^ (s[3] ^ d[3]);
+		v6hash ^= (v6hash >> 24) ^ (v6hash >> 16) ^ (v6hash >> 8);
+		return (v6hash ^ data->h_dest[5] ^ data->h_source[5]) % count;
 	}
 
-	return (data->h_dest[5] ^ data->h_source[5]) % count;
+	return bond_xmit_hash_policy_l2(skb, count);
 }
 
 /*
  * Hash for the output device based upon layer 3 and layer 4 data. If
  * 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()
+ * altogether not IP, fall back on bond_xmit_hash_policy_l2()
  */
 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;
-
-	if (skb->protocol == htons(ETH_P_IP)) {
+	u32 layer4_xor = 0;
+	struct iphdr *iph;
+	struct ipv6hdr *ipv6h;
+	__be32 *s, *d;
+	__be16 *layer4hdr;
+
+	if (skb->protocol == htons(ETH_P_IP) &&
+	    skb_network_header_len(skb) >= sizeof(*iph)) {
+		iph = ip_hdr(skb);
 		if (!ip_is_fragment(iph) &&
 		    (iph->protocol == IPPROTO_TCP ||
-		     iph->protocol == IPPROTO_UDP)) {
-			layer4_xor = ntohs((*layer4hdr ^ *(layer4hdr + 1)));
+		     iph->protocol == IPPROTO_UDP) &&
+		    (skb_headlen(skb) - skb_network_offset(skb) >=
+		     iph->ihl * sizeof(u32) + sizeof(*layer4hdr) * 2)) {
+			layer4hdr = (__be16 *)((u32 *)iph + iph->ihl);
+			layer4_xor = ntohs(*layer4hdr ^ *(layer4hdr + 1));
 		}
 		return (layer4_xor ^
 			((ntohl(iph->saddr ^ iph->daddr)) & 0xffff)) % count;
-
+	} else if (skb->protocol == htons(ETH_P_IPV6) &&
+		   skb_network_header_len(skb) >= sizeof(*ipv6h)) {
+		ipv6h = ipv6_hdr(skb);
+		if ((ipv6h->nexthdr == IPPROTO_TCP ||
+		     ipv6h->nexthdr == IPPROTO_UDP) &&
+		    (skb_headlen(skb) - skb_network_offset(skb) >=
+		     sizeof(*ipv6h) + sizeof(*layer4hdr) * 2)) {
+			layer4hdr = (__be16 *)(ipv6h + 1);
+			layer4_xor = ntohs(*layer4hdr ^ *(layer4hdr + 1));
+		}
+		s = &ipv6h->saddr.s6_addr32[0];
+		d = &ipv6h->daddr.s6_addr32[0];
+		layer4_xor ^= (s[1] ^ d[1]) ^ (s[2] ^ d[2]) ^ (s[3] ^ d[3]);
+		layer4_xor ^= (layer4_xor >> 24) ^ (layer4_xor >> 16) ^
+			       (layer4_xor >> 8);
+		return layer4_xor % count;
 	}
 
-	return (data->h_dest[5] ^ data->h_source[5]) % count;
-}
-
-/*
- * Hash for the output device based upon layer 2 data
- */
-static int bond_xmit_hash_policy_l2(struct sk_buff *skb, int count)
-{
-	struct ethhdr *data = (struct ethhdr *)skb->data;
-
-	return (data->h_dest[5] ^ data->h_source[5]) % count;
+	return bond_xmit_hash_policy_l2(skb, count);
 }
 
 /*-------------------------- Device entry points ----------------------------*/