Le 15/01/2010 03:22, Changli Gao a écrit :
> On Fri, Jan 15, 2010 at 5:56 AM, Tom Herbert <therbert@xxxxxxxxxx> wrote:
>> +
>> + if (skb->rxhash)
>> + goto got_hash; /* Skip hash computation on packet header */
>> +
>> + switch (skb->protocol) {
>> + case __constant_htons(ETH_P_IP):
>> + if (!pskb_may_pull(skb, sizeof(*ip)))
>> + goto done;
>> +
>> + ip = (struct iphdr *) skb->data;
>> + ip_proto = ip->protocol;
>> + addr1 = ip->saddr;
>> + addr2 = ip->daddr;
>> + ihl = ip->ihl;
>> + break;
>> + case __constant_htons(ETH_P_IPV6):
>> + if (!pskb_may_pull(skb, sizeof(*ip6)))
>> + goto done;
>> +
>> + ip6 = (struct ipv6hdr *) skb->data;
>> + ip_proto = ip6->nexthdr;
> This code can't work, when there are extra headers. ipv6_skip_exthdr()
> can be used to get the l4 header.
Could you give exact code please ?
>
>> + addr1 = ip6->saddr.s6_addr32[3];
>> + addr2 = ip6->daddr.s6_addr32[3];
>> + ihl = (40 >> 2);
>> + break;
>> + default:
>> + goto done;
>> + }
>> + ports = 0;
>> + switch (ip_proto) {
>> + case IPPROTO_TCP:
>> + case IPPROTO_UDP:
>> + case IPPROTO_DCCP:
>> + case IPPROTO_ESP:
>> + case IPPROTO_AH:
>> + case IPPROTO_SCTP:
>> + case IPPROTO_UDPLITE:
>> + if (pskb_may_pull(skb, (ihl * 4) + 4))
>> + ports = *((u32 *) (skb->data + (ihl * 4)));
>> + break;
>> +
>> + default:
>> + break;
>> + }
>> +
>> + skb->rxhash = jhash_3words(addr1, addr2, ports, hashrnd);
> For connection based packet processing, such as netfilter,
> distributing the packets in two directions into one CPU will reduce
> cache miss, when NAT isn't used. I think the code bellow will help:
> if (addr1 > addr2)
> swap(addr1, addr2);
Yes, I already gave this hint in a previous review, but this adds a test
and I suspect Google is not using NAT :)
>
>> + if (!skb->rxhash)
>> + skb->rxhash = 1;
>
> Why not put the above code into a new function, and add more protocols
> support, such as 802.1Q. Though rxhash is based on 4-tuple, I think
> netfilter will benefit from it.
>
Sure, this can be done in a followup patch.
Thanks
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