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Commit ba645c16 authored by David S. Miller's avatar David S. Miller
Browse files

[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: default avatarDavid S. Miller <davem@davemloft.net>
parent 2fab35d7

net/ethernet/eth.c

+21 −10
Original line number Diff line number Diff line
@@ -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
@@ -162,9 +175,8 @@ __be16 eth_type_trans(struct sk_buff *skb, struct net_device *dev) 
	skb_pull(skb,ETH_HLEN);

	eth = eth_hdr(skb);

	

	if(*eth->h_dest&1)

	{

		if(memcmp(eth->h_dest,dev->broadcast, ETH_ALEN)==0)

	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;
@@ -178,9 +190,8 @@ __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))

	else if(1 /*dev->flags&IFF_PROMISC*/) {

		if (unlikely(!compare_eth_addr(eth->h_dest, dev->dev_addr)))

			skb->pkt_type = PACKET_OTHERHOST;

	}