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[NET]: Slightly optimize ethernet address comparison. 

We know the thing is at least 2-byte aligned, so take
advantage of that instead of invoking memcmp() which
results in truly horrifically inefficient code because
it can't assume anything about alignment.

Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
David S. Miller 2005-09-27 16:03:05 -07:00
parent 2fab35d78f
commit ba645c1602
1 changed files with 21 additions and 10 deletions
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31
net/ethernet/eth.c
View File

@ -146,6 +146,19 @@ int eth_rebuild_header(struct sk_buff *skb)
return 0;
}
static inline unsigned int compare_eth_addr(const unsigned char *__a, const unsigned char *__b)
{
const unsigned short *dest = (unsigned short *) __a;
const unsigned short *devaddr = (unsigned short *) __b;
unsigned int res;
BUILD_BUG_ON(ETH_ALEN != 6);
res = ((dest[0] ^ devaddr[0]) |
(dest[1] ^ devaddr[1]) |
(dest[2] ^ devaddr[2])) != 0;
return res;
}
/*
* Determine the packet's protocol ID. The rule here is that we
@ -158,16 +171,15 @@ __be16 eth_type_trans(struct sk_buff *skb, struct net_device *dev)
struct ethhdr *eth;
unsigned char *rawp;
skb->mac.raw=skb->data;
skb->mac.raw = skb->data;
skb_pull(skb,ETH_HLEN);
eth = eth_hdr(skb);
if(*eth->h_dest&1)
{
if(memcmp(eth->h_dest,dev->broadcast, ETH_ALEN)==0)
skb->pkt_type=PACKET_BROADCAST;
if (*eth->h_dest&1) {
if (!compare_eth_addr(eth->h_dest, dev->broadcast))
skb->pkt_type = PACKET_BROADCAST;
else
skb->pkt_type=PACKET_MULTICAST;
skb->pkt_type = PACKET_MULTICAST;
}
/*
@ -178,10 +190,9 @@ __be16 eth_type_trans(struct sk_buff *skb, struct net_device *dev)
* seems to set IFF_PROMISC.
*/
else if(1 /*dev->flags&IFF_PROMISC*/)
{
if(memcmp(eth->h_dest,dev->dev_addr, ETH_ALEN))
skb->pkt_type=PACKET_OTHERHOST;
else if(1 /*dev->flags&IFF_PROMISC*/) {
if (unlikely(!compare_eth_addr(eth->h_dest, dev->dev_addr)))
skb->pkt_type = PACKET_OTHERHOST;
}
if (ntohs(eth->h_proto) >= 1536)