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Message-ID: <18390.1341272010@death.nxdomain>
Date: Mon, 02 Jul 2012 16:33:30 -0700
From: Jay Vosburgh <fubar@...ibm.com>
To: John Eaglesham <linux@...2.net>
cc: netdev@...r.kernel.org
Subject: Re: [PATCH v6] bonding support for IPv6 transmit hashing
John Eaglesham <linux@...2.net> wrote:
>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.
>
>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.
>
>This is an update to prior patches I submitted. This version includes:
>* Updated and clarified description
>* IPv6 algorithm more closely matches that of IPv4
>* Thorough bounds checking on all xmit functions
>* Consolidate layer 2 hashing logic into one function
>* Update style as per Jay Vosburgh and David Miller
>* Patches against net-next as one patch
>
>Patch has been tested and performs as expected.
>
>John Eaglesham
>
>---
> Documentation/networking/bonding.txt | 32 +++++++++++--
> drivers/net/bonding/bond_main.c | 91 +++++++++++++++++++++++++-----------
> 2 files changed, 92 insertions(+), 31 deletions(-)
>
>diff --git a/Documentation/networking/bonding.txt b/Documentation/networking/bonding.txt
>index bfea8a3..3851dad 100644
>--- a/Documentation/networking/bonding.txt
>+++ b/Documentation/networking/bonding.txt
>@@ -752,12 +752,23 @@ xmit_hash_policy
> protocol information to generate the hash.
>
> Uses XOR of hardware MAC addresses and IP addresses to
>- generate the hash. The formula is
>+ generate the hash. The IPv4 formula is
>
> (((source IP XOR dest IP) AND 0xffff) XOR
> ( source MAC XOR destination MAC ))
> modulo slave count
>
>+ The IPv6 formula is
>+
>+ hash =
>+ (source ip quad 2 XOR dest IP quad 2) XOR
>+ (source ip quad 3 XOR dest IP quad 3) XOR
>+ (source ip quad 4 XOR dest IP quad 4)
>+
>+ (((hash >> 24) XOR (hash >> 16) XOR (hash >> 8) XOR hash)
>+ (source MAC XOR destination MAC))
>+ modulo slave count
This seems to be missing an XOR, between the end of "XOR hash)"
and the start of "(source MAC".
>+
> This algorithm will place all traffic to a particular
> network peer on the same slave. For non-IP traffic,
> the formula is the same as for the layer2 transmit
>@@ -778,19 +789,30 @@ xmit_hash_policy
> 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
>- protocol traffic, the source and destination port
>+ The formula for unfragmented IPv6 TCP and UDP packets is
>+
>+ hash =
>+ (source ip quad 2 XOR dest IP quad 2) XOR
>+ (source ip quad 3 XOR dest IP quad 3) XOR
>+ (source ip quad 4 XOR dest IP quad 4)
>+
>+ ((source port XOR dest port) XOR
>+ (hash >> 24) XOR (hash >> 16) XOR (hash >> 8) XOR hash)
>+ modulo slave count
>+
>+ For fragmented TCP or UDP packets and all other IPv4 and
>+ IPv6 protocol traffic, the source and destination port
> information is omitted. For non-IP traffic, the
> formula is the same as for the layer2 transmit hash
> policy.
>
>- This policy is intended to mimic the behavior of
>+ The IPv4 policy is intended to mimic the behavior of
> certain switches, notably Cisco switches with PFC2 as
> well as some Foundry and IBM products.
>
>diff --git a/drivers/net/bonding/bond_main.c b/drivers/net/bonding/bond_main.c
>index f5a40b9..c733d55 100644
>--- a/drivers/net/bonding/bond_main.c
>+++ b/drivers/net/bonding/bond_main.c
>@@ -3345,56 +3345,95 @@ 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(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) &&
>+ skb_network_header_len(skb) >= sizeof(struct ipv6hdr)) {
>+ 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;
>+ u32 layer4_xor = 0;
>+ struct iphdr *iph;
>+ struct ipv6hdr *ipv6h;
>+ __be32 *s, *d;
>+ __be16 *layer4hdr;
>
> if (skb->protocol == htons(ETH_P_IP)) {
>+ iph = ip_hdr(skb);
> if (!ip_is_fragment(iph) &&
>- (iph->protocol == IPPROTO_TCP ||
>- iph->protocol == IPPROTO_UDP)) {
>+ (iph->protocol == IPPROTO_TCP ||
>+ iph->protocol == IPPROTO_UDP)) {
Why did these two lines change?
>+ layer4hdr = (__be16 *)((u32 *)iph + iph->ihl);
>+ if (iph->ihl * sizeof(u32) + sizeof(__be16) * 2 >
>+ skb_headlen(skb) - skb_network_offset(skb))
>+ goto short_header;
> layer4_xor = ntohs((*layer4hdr ^ *(layer4hdr + 1)));
>+ } else if (skb_network_header_len(skb) < sizeof(struct iphdr)) {
>+ goto short_header;
> }
>- return (layer4_xor ^
>- ((ntohl(iph->saddr ^ iph->daddr)) & 0xffff)) % count;
>-
>+ return (layer4_xor ^ ((ntohl(iph->saddr ^ iph->daddr)) & 0xffff)) % count;
This line runs past 80 columns. There are a few more of these
further down.
>+ } else if (skb->protocol == htons(ETH_P_IPV6)) {
>+ ipv6h = ipv6_hdr(skb);
>+ if (ipv6h->nexthdr == IPPROTO_TCP || ipv6h->nexthdr == IPPROTO_UDP) {
>+ layer4hdr = (__be16 *)((u8 *)ipv6h + sizeof(struct ipv6hdr));
Could this be written as
layer4hdr = (__be16 *)(ipv6h + 1);
instead?
-J
>+ if (sizeof(struct ipv6hdr) + sizeof(__be16) * 2 >
>+ skb_headlen(skb) - skb_network_offset(skb))
>+ goto short_header;
>+ layer4_xor = (*layer4hdr ^ *(layer4hdr + 1));
>+ } else if (skb_network_header_len(skb) < sizeof(struct ipv6hdr)) {
>+ goto short_header;
>+ }
>+ 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;
>+short_header:
>+ return bond_xmit_hash_policy_l2(skb, count);
> }
>
> /*-------------------------- Device entry points ----------------------------*/
>--
>1.7.11
---
-Jay Vosburgh, IBM Linux Technology Center, fubar@...ibm.com
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