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.
> + 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);
> + 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.
--
Regards，
Changli Gao(xiaosuo@xxxxxxxxx)
��.n��������+%������w��{.n����z�����n�r������&��z�ޗ�zf���h���~����������_��+v���)ߣ�m
