Subject: Re: [PATCH] bonding: L2L3 xmit doesn't support IPv6

From: Jay Vosburgh <[email-masked]>
Date: Tue, 11 Oct 2011 08:58:59 -0700

Andy Gospodarek <[email-masked]> wrote:

>On Fri, Oct 07, 2011 at 10:36:45PM -0700, Yinglin Sun wrote:
>> Add IPv6 support in L2L3 xmit policy.
>> L3L4 doesn't support IPv6 either, and I'll try to fix that later.
>> 
>> Signed-off-by: Yinglin Sun <[email-masked]>
>> ---
>>  drivers/net/bonding/bond_main.c |    7 +++++++
>>  1 files changed, 7 insertions(+), 0 deletions(-)
>> 
>> diff --git a/drivers/net/bonding/bond_main.c b/drivers/net/bonding/bond_main.c
>> index 6d79b78..d6fd282 100644
>> --- a/drivers/net/bonding/bond_main.c
>> +++ b/drivers/net/bonding/bond_main.c
>> @@ -41,8 +41,10 @@
>>  #include <linux/ptrace.h>
>>  #include <linux/ioport.h>
>>  #include <linux/in.h>
>> +#include <linux/in6.h>
>>  #include <net/ip.h>
>>  #include <linux/ip.h>
>> +#include <linux/ipv6.h>
>>  #include <linux/tcp.h>
>>  #include <linux/udp.h>
>>  #include <linux/slab.h>
>> @@ -3372,10 +3374,15 @@ 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);
>> +	struct ipv6hdr *ipv6h = ipv6_hdr(skb);
>>  
>>  	if (skb->protocol == htons(ETH_P_IP)) {
>>  		return ((ntohl(iph->saddr ^ iph->daddr) & 0xffff) ^
>>  			(data->h_dest[5] ^ data->h_source[5])) % count;
>> +	} else if (skb->protocol == htons(ETH_P_IPV6)) {
>> +		return ((ntohl(ipv6h->saddr.s6_addr32[3] ^
>> +			       ipv6h->daddr.s6_addr32[3]) & 0xffff) ^
>> +			(data->h_dest[5] ^ data->h_source[5])) % count;
>>  	}
>>  
>
>There have been some attempts to add support for ipv6 hashing this in
>the past, but none have been committed.  The best one I had seen was one
>that did some extensive testing one a wide variety of ipv6 traffic and
>it showed nice traffic distribution.  I'm not sure if it was ever posted
>upstream, so I will see if I can dig it up.
>
>Can you quantify how traffic was distributed with this algorithm?

	As I recall, the IPv6 issues had to do with the "layer3+4" hash,
because the IPv6 TCP or UDP port numbers can be harder to get at than in
IPv4 (which typically has a fixed size header).  The above is just for
layer 2, so it only hits the IPv6 addresses, which don't move around.

	That said, I believe that many IPv6 addresses are derived from
the MAC address, the autoconf addresses in particular, so s6_addr32[3]
may not show a lot more variation than just the MAC address.  I don't
know for sure though, since I haven't tested it.

	I don't recall seeing the patch you mention, Andy, that checks
ipv6 traffic; can you post it?

	-J

---
	-Jay Vosburgh, IBM Linux Technology Center, [email-masked]