net: Improve simple_tx_hash().
Based upon feedback from Eric Dumazet and Andi Kleen. Cure several deficiencies in simple_tx_hash() by using jhash + reciprocol multiply. 1) Eliminates expensive modulus operation. 2) Makes hash less attackable by using random seed. 3) Eliminates endianness hash distribution issues. Signed-off-by: David S. Miller <davem@davemloft.net>
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@ -124,6 +124,8 @@
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#include <linux/ip.h>
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#include <linux/ipv6.h>
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#include <linux/in.h>
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#include <linux/jhash.h>
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#include <linux/random.h>
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#include "net-sysfs.h"
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@ -1668,34 +1670,37 @@ out_kfree_skb:
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* --BLG
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*/
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static u32 simple_tx_hashrnd;
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static int simple_tx_hashrnd_initialized = 0;
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static u16 simple_tx_hash(struct net_device *dev, struct sk_buff *skb)
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{
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u32 *addr, *ports, hash, ihl;
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u32 addr1, addr2, ports;
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u32 hash, ihl;
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u8 ip_proto;
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int alen;
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if (unlikely(!simple_tx_hashrnd_initialized)) {
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get_random_bytes(&simple_tx_hashrnd, 4);
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simple_tx_hashrnd_initialized = 1;
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}
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switch (skb->protocol) {
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case __constant_htons(ETH_P_IP):
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ip_proto = ip_hdr(skb)->protocol;
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addr = &ip_hdr(skb)->saddr;
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addr1 = ip_hdr(skb)->saddr;
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addr2 = ip_hdr(skb)->daddr;
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ihl = ip_hdr(skb)->ihl;
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alen = 2;
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break;
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case __constant_htons(ETH_P_IPV6):
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ip_proto = ipv6_hdr(skb)->nexthdr;
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addr = &ipv6_hdr(skb)->saddr.s6_addr32[0];
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addr1 = ipv6_hdr(skb)->saddr.s6_addr32[3];
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addr2 = ipv6_hdr(skb)->daddr.s6_addr32[3];
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ihl = (40 >> 2);
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alen = 8;
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break;
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default:
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return 0;
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}
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ports = (u32 *) (skb_network_header(skb) + (ihl * 4));
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hash = 0;
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while (alen--)
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hash ^= *addr++;
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switch (ip_proto) {
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case IPPROTO_TCP:
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@ -1705,14 +1710,17 @@ static u16 simple_tx_hash(struct net_device *dev, struct sk_buff *skb)
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case IPPROTO_AH:
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case IPPROTO_SCTP:
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case IPPROTO_UDPLITE:
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hash ^= *ports;
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ports = *((u32 *) (skb_network_header(skb) + (ihl * 4)));
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break;
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default:
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ports = 0;
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break;
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}
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return hash % dev->real_num_tx_queues;
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hash = jhash_3words(addr1, addr2, ports, simple_tx_hashrnd);
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return (u16) (((u64) hash * dev->real_num_tx_queues) >> 32);
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}
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static struct netdev_queue *dev_pick_tx(struct net_device *dev,
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