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Merge branch 'eth_type_trans'

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Alexander Duyck says:

====================
A few minor clean-ups to eth_type_trans

This series addresses a few minor issues I found in eth_type_trans that
that allow us to gain back something like 3 or more cycles per packet.

The first change is to drop the byte swap since it isn't necessary.  On x86
we could just check the first byte and compare that against the upper 8
bits of the Ethertype to determine if we are dealing with a size value or
not.

The second makes it so that the value we read in to test for multicast can
be used for the address comparison.  This allows us to avoid a second read
of the destination address.

The final change is to avoid some unneeded instructions in computing the
Ethernet header pointer.  When we start the call the Ethernet header is at
skb->data, so we just use that rather than computing mac_header, and then
adding that back to skb->head.
====================

Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
David S. Miller 2015-05-03 22:30:36 -04:00
commit 7a852021a4
2 changed files with 28 additions and 5 deletions
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24
include/linux/etherdevice.h
View File

@ -110,7 +110,29 @@ static inline bool is_zero_ether_addr(const u8 *addr)
*/
static inline bool is_multicast_ether_addr(const u8 *addr)
{
return 0x01 & addr[0];
#if defined(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS)
u32 a = *(const u32 *)addr;
#else
u16 a = *(const u16 *)addr;
#endif
#ifdef __BIG_ENDIAN
return 0x01 & (a >> ((sizeof(a) * 8) - 8));
#else
return 0x01 & a;
#endif
}
static inline bool is_multicast_ether_addr_64bits(const u8 addr[6+2])
{
#if defined(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS) && BITS_PER_LONG == 64
#ifdef __BIG_ENDIAN
return 0x01 & ((*(const u64 *)addr) >> 56);
#else
return 0x01 & (*(const u64 *)addr);
#endif
#else
return is_multicast_ether_addr(addr);
#endif
}
/**

9
net/ethernet/eth.c
View File

@ -156,10 +156,11 @@ __be16 eth_type_trans(struct sk_buff *skb, struct net_device *dev)
skb->dev = dev;
skb_reset_mac_header(skb);
skb_pull_inline(skb, ETH_HLEN);
eth = eth_hdr(skb);
if (unlikely(is_multicast_ether_addr(eth->h_dest))) {
eth = (struct ethhdr *)skb->data;
skb_pull_inline(skb, ETH_HLEN);
if (unlikely(is_multicast_ether_addr_64bits(eth->h_dest))) {
if (ether_addr_equal_64bits(eth->h_dest, dev->broadcast))
skb->pkt_type = PACKET_BROADCAST;
else
@ -178,7 +179,7 @@ __be16 eth_type_trans(struct sk_buff *skb, struct net_device *dev)
if (unlikely(netdev_uses_dsa(dev)))
return htons(ETH_P_XDSA);
if (likely(ntohs(eth->h_proto) >= ETH_P_802_3_MIN))
if (likely((eth->h_proto & htons(0xFF00)) >= htons(ETH_P_802_3_MIN)))
return eth->h_proto;
/*