diff options
| author | David S. Miller <davem@davemloft.net> | 2008-07-21 09:48:06 -0700 |
|---|---|---|
| committer | David S. Miller <davem@davemloft.net> | 2008-07-21 10:10:48 -0700 |
| commit | b6b2fed1f4802b8fcc9d7548a8f785225d38f9a3 (patch) | |
| tree | eebdc34112d617524b762c585b79b2eaab3386ae /net/core | |
| parent | c3ee84163e5bc0dc2e1ccf1d3fc412debca73bab (diff) | |
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>
Diffstat (limited to 'net/core')
| -rw-r--r-- | net/core/dev.c | 34 |
1 files changed, 21 insertions, 13 deletions
diff --git a/net/core/dev.c b/net/core/dev.c index 2eed17bcb2d..7e2d5274333 100644 --- a/net/core/dev.c +++ b/net/core/dev.c @@ -124,6 +124,8 @@ #include <linux/ip.h> #include <linux/ipv6.h> #include <linux/in.h> +#include <linux/jhash.h> +#include <linux/random.h> #include "net-sysfs.h" @@ -1668,34 +1670,37 @@ out_kfree_skb: * --BLG */ +static u32 simple_tx_hashrnd; +static int simple_tx_hashrnd_initialized = 0; + static u16 simple_tx_hash(struct net_device *dev, struct sk_buff *skb) { - u32 *addr, *ports, hash, ihl; + u32 addr1, addr2, ports; + u32 hash, ihl; u8 ip_proto; - int alen; + + if (unlikely(!simple_tx_hashrnd_initialized)) { + get_random_bytes(&simple_tx_hashrnd, 4); + simple_tx_hashrnd_initialized = 1; + } switch (skb->protocol) { case __constant_htons(ETH_P_IP): ip_proto = ip_hdr(skb)->protocol; - addr = &ip_hdr(skb)->saddr; + addr1 = ip_hdr(skb)->saddr; + addr2 = ip_hdr(skb)->daddr; ihl = ip_hdr(skb)->ihl; - alen = 2; break; case __constant_htons(ETH_P_IPV6): ip_proto = ipv6_hdr(skb)->nexthdr; - addr = &ipv6_hdr(skb)->saddr.s6_addr32[0]; + addr1 = ipv6_hdr(skb)->saddr.s6_addr32[3]; + addr2 = ipv6_hdr(skb)->daddr.s6_addr32[3]; ihl = (40 >> 2); - alen = 8; break; default: return 0; } - ports = (u32 *) (skb_network_header(skb) + (ihl * 4)); - - hash = 0; - while (alen--) - hash ^= *addr++; switch (ip_proto) { case IPPROTO_TCP: @@ -1705,14 +1710,17 @@ static u16 simple_tx_hash(struct net_device *dev, struct sk_buff *skb) case IPPROTO_AH: case IPPROTO_SCTP: case IPPROTO_UDPLITE: - hash ^= *ports; + ports = *((u32 *) (skb_network_header(skb) + (ihl * 4))); break; default: + ports = 0; break; } - return hash % dev->real_num_tx_queues; + hash = jhash_3words(addr1, addr2, ports, simple_tx_hashrnd); + + return (u16) (((u64) hash * dev->real_num_tx_queues) >> 32); } static struct netdev_queue *dev_pick_tx(struct net_device *dev, |