Patchwork Bonding driver has bad load balancing for forwarded traffic, 3.7+

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Submitter Eric Dumazet
Date April 16, 2013, 3:03 a.m.
Message ID <1366081404.4459.127.camel@edumazet-glaptop>
Download mbox | patch
Permalink /patch/236831/
State Accepted
Delegated to: David Miller
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Comments

Eric Dumazet - April 16, 2013, 3:03 a.m.
From: Eric Dumazet <edumazet@google.com>

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@telenet.dn.ua>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Jay Vosburgh <fubar@us.ibm.com>
Cc: Andy Gospodarek <andy@greyhouse.net>
Cc: John Eaglesham <linux@8192.net>
---
 drivers/net/bonding/bond_main.c |   55 ++++++++++++++++--------------
 1 file changed, 30 insertions(+), 25 deletions(-)



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Vitaly V. Bursov - April 16, 2013, 9:01 a.m.
16.04.2013 06:03, Eric Dumazet пишет:
> From: Eric Dumazet <edumazet@google.com>
>
> 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 !

Testing under real load for almost 2 hours now, works as expected.
xmit_hash_policy=layer3+4

I made a few simple test with layer2+3 policy too, looks OK.

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@telenet.dn.ua>
> Signed-off-by: Eric Dumazet <edumazet@google.com>
> Cc: Jay Vosburgh <fubar@us.ibm.com>
> Cc: Andy Gospodarek <andy@greyhouse.net>
> Cc: John Eaglesham <linux@8192.net>
> ---
>   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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Eric Dumazet - April 16, 2013, 1:51 p.m.
On Tue, 2013-04-16 at 12:01 +0300, Vitaly V. Bursov wrote:

> Testing under real load for almost 2 hours now, works as expected.
> xmit_hash_policy=layer3+4
> 
> I made a few simple test with layer2+3 policy too, looks OK.
> 
> Thanks!

Perfect, thanks a lot for all this !

Tested-by: Vitaly V. Bursov <vitalyb@telenet.dn.ua>



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Eric Dumazet - April 16, 2013, 2:25 p.m.
On Tue, 2013-04-16 at 06:51 -0700, Eric Dumazet wrote:

> Perfect, thanks a lot for all this !
> 
> Tested-by: Vitaly V. Bursov <vitalyb@telenet.dn.ua>
> 
> 

By the way, we probably should use skb_flow_dissect() to get proper
hashing for tunnels users.



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David Miller - April 16, 2013, 8:39 p.m.
From: Eric Dumazet <eric.dumazet@gmail.com>
Date: Tue, 16 Apr 2013 07:25:17 -0700

> On Tue, 2013-04-16 at 06:51 -0700, Eric Dumazet wrote:
> 
>> Perfect, thanks a lot for all this !
>> 
>> Tested-by: Vitaly V. Bursov <vitalyb@telenet.dn.ua>
>> 
>> 
> 
> By the way, we probably should use skb_flow_dissect() to get proper
> hashing for tunnels users.

Agreed but that's net-next material.
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David Miller - April 18, 2013, 7:09 p.m.
From: Eric Dumazet <eric.dumazet@gmail.com>
Date: Mon, 15 Apr 2013 20:03:24 -0700

> [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@telenet.dn.ua>
> Signed-off-by: Eric Dumazet <edumazet@google.com>

Applied and queued up for -stable, but:

> +						sizeof(_l4), &_l4);						
                                                                   ^^^^^^^^^^^^^^^^^^^^^^^^^

That's some rather amazing trailing whitespace.  Are you trying to break
free of earth's atmosphere? :-)
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Eric Dumazet - April 18, 2013, 7:33 p.m.
On Thu, 2013-04-18 at 15:09 -0400, David Miller wrote:

> Applied and queued up for -stable, but:
> 
> > +						sizeof(_l4), &_l4);						
>                                                                    ^^^^^^^^^^^^^^^^^^^^^^^^^
> 
> That's some rather amazing trailing whitespace.  Are you trying to break
> free of earth's atmosphere? :-)

Ah, sorry for this ;)

Thanks


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Patch

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];