Re: Bonding driver has bad load balancing for forwarded traffic,3.7+
From: Eric Dumazet
Date: Mon Apr 15 2013 - 23:03:34 EST
From: Eric Dumazet <edumazet@xxxxxxxxxx>
On Mon, 2013-04-15 at 17:37 -0700, Eric Dumazet wrote:
> On Mon, 2013-04-15 at 16:57 +0300, Vitaly V. Bursov wrote:
> > Hello,
> >
> > I have a bonding device (mode=802.3ad xmit_hash_policy=layer2+3 miimon=300) and
> > for kernels <3.7 forwarded IPv4 traffic distributed fine across multiple physical
> > links. Ethernet cards are Intel 82576 with igb driver (various versions).
> >
> > 3.7 and 3.8 kernels tend to fully utilize only one link and leave the others almost idling.
> >
> > Replacing bond_xmit_hash_policy_* functions with older ones (3.6 kernel) looks like
> > resolves the issue (but I haven't tested it thoroughly).
> >
> > So, I added
> > printk(KERN_INFO "hash_policy: protocol = %d, skb_network_header_len = %d, %d %d\n",
> > skb->protocol, skb_network_header_len(skb),
> > skb_headlen(skb), skb_network_offset(skb));
> > to bond_xmit_hash_policy_l23() of bond_main.c
> >
> > and got this:
> > [ 65.280831] hash_policy: protocol = 8, skb_network_header_len = 0, 74 14
> > [ 65.280835] hash_policy: protocol = 8, skb_network_header_len = 0, 74 14
> > [ 65.280839] hash_policy: protocol = 8, skb_network_header_len = 0, 74 14
> > [ 65.280843] hash_policy: protocol = 8, skb_network_header_len = 0, 74 14
> > [ 65.280847] hash_policy: protocol = 8, skb_network_header_len = 0, 74 14
> > [ 65.280851] hash_policy: protocol = 8, skb_network_header_len = 0, 74 14
> >
> > It's clear that the new check condition (skb_network_header_len(skb) >= sizeof(*iph))
> > fails here and hash policy fallbacks to l2 balancing.
> >
> > I have no idea how to fix this besides removing this check completely, any
> > help would be appreciated.
> >
>
> Thanks for your report.
>
> CC netdev
>
> I guess that for forwarding setup, we don't set skb->transport_header
>
> Please try following fix :
Here is a more complete patch, please test it.
Thanks !
[PATCH] bonding: fix l23 and l34 load balancing in forwarding path
Since commit 6b923cb7188d46 (bonding: support for IPv6 transmit hashing)
bonding doesn't properly hash traffic in forwarding setups.
Vitaly V. Bursov diagnosed that skb_network_header_len() returned 0 in
this case.
More generally, the transport header might not be in the skb head.
Use pskb_may_pull() & skb_header_pointer() to get it right, and use
proto_ports_offset() in bond_xmit_hash_policy_l34() to get support for
more protocols than TCP and UDP.
Reported-by: Vitaly V. Bursov <vitalyb@xxxxxxxxxxxxx>
Signed-off-by: Eric Dumazet <edumazet@xxxxxxxxxx>
Cc: Jay Vosburgh <fubar@xxxxxxxxxx>
Cc: Andy Gospodarek <andy@xxxxxxxxxxxxx>
Cc: John Eaglesham <linux@xxxxxxxx>
---
drivers/net/bonding/bond_main.c | 55 ++++++++++++++++--------------
1 file changed, 30 insertions(+), 25 deletions(-)
diff --git a/drivers/net/bonding/bond_main.c b/drivers/net/bonding/bond_main.c
index 07401a3..d9ff09a 100644
--- a/drivers/net/bonding/bond_main.c
+++ b/drivers/net/bonding/bond_main.c
@@ -3286,20 +3286,22 @@ static int bond_xmit_hash_policy_l2(struct sk_buff *skb, int count)
*/
static int bond_xmit_hash_policy_l23(struct sk_buff *skb, int count)
{
- struct ethhdr *data = (struct ethhdr *)skb->data;
- struct iphdr *iph;
- struct ipv6hdr *ipv6h;
+ const struct ethhdr *data;
+ const struct iphdr *iph;
+ const struct ipv6hdr *ipv6h;
u32 v6hash;
- __be32 *s, *d;
+ const __be32 *s, *d;
if (skb->protocol == htons(ETH_P_IP) &&
- skb_network_header_len(skb) >= sizeof(*iph)) {
+ pskb_network_may_pull(skb, sizeof(*iph))) {
iph = ip_hdr(skb);
+ data = (struct ethhdr *)skb->data;
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)) {
+ pskb_network_may_pull(skb, sizeof(*ipv6h))) {
ipv6h = ipv6_hdr(skb);
+ data = (struct ethhdr *)skb->data;
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]);
@@ -3318,33 +3320,36 @@ static int bond_xmit_hash_policy_l23(struct sk_buff *skb, int count)
static int bond_xmit_hash_policy_l34(struct sk_buff *skb, int count)
{
u32 layer4_xor = 0;
- struct iphdr *iph;
- struct ipv6hdr *ipv6h;
- __be32 *s, *d;
- __be16 *layer4hdr;
+ const struct iphdr *iph;
+ const struct ipv6hdr *ipv6h;
+ const __be32 *s, *d;
+ const __be16 *l4 = NULL;
+ __be16 _l4[2];
+ int noff = skb_network_offset(skb);
+ int poff;
if (skb->protocol == htons(ETH_P_IP) &&
- skb_network_header_len(skb) >= sizeof(*iph)) {
+ pskb_may_pull(skb, noff + sizeof(*iph))) {
iph = ip_hdr(skb);
- if (!ip_is_fragment(iph) &&
- (iph->protocol == IPPROTO_TCP ||
- 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));
+ poff = proto_ports_offset(iph->protocol);
+
+ if (!ip_is_fragment(iph) && poff >= 0) {
+ l4 = skb_header_pointer(skb, noff + (iph->ihl << 2) + poff,
+ sizeof(_l4), &_l4);
+ if (l4)
+ layer4_xor = ntohs(l4[0] ^ l4[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)) {
+ pskb_may_pull(skb, noff + 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));
+ poff = proto_ports_offset(ipv6h->nexthdr);
+ if (poff >= 0) {
+ l4 = skb_header_pointer(skb, noff + sizeof(*ipv6h) + poff,
+ sizeof(_l4), &_l4);
+ if (l4)
+ layer4_xor = ntohs(l4[0] ^ l4[1]);
}
s = &ipv6h->saddr.s6_addr32[0];
d = &ipv6h->daddr.s6_addr32[0];
--
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