[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>

1 files changed, 21 insertions, 10 deletions

diff --git a/net/ethernet/eth.c b/net/ethernet/eth.c
index 87a052a9a84f..8b299cc82060 100644
--- a/net/ethernet/eth.c
+++ b/net/ethernet/eth.c
@@ -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)