netdev - [PATCH 1/3] etherdev: Avoid unnecessary byte swap in check for Ethertype

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Message-ID: <20150430215348.1798.15509.stgit@ahduyck-vm-fedora22>
Date:	Thu, 30 Apr 2015 14:53:48 -0700
From:	Alexander Duyck <alexander.h.duyck@...hat.com>
To:	netdev@...r.kernel.org
Cc:	davem@...emloft.net
Subject: [PATCH 1/3] etherdev: Avoid unnecessary byte swap in check for
 Ethertype

This change takes advantage of the fact that ETH_P_802_3_MIN is aligned to
512 so as a result we can actually ignore the lower 8b when comparing the
Ethertype to ETH_P_802_3_MIN.  This allows us to avoid a byte swap by simply
masking the value and comparing it to the byte swapped value for
ETH_P_802_3_MIN.

Signed-off-by: Alexander Duyck <alexander.h.duyck@...hat.com>
---
 net/ethernet/eth.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/ethernet/eth.c b/net/ethernet/eth.c
index f3bad41d725f..60069318d5d1 100644
--- a/net/ethernet/eth.c
+++ b/net/ethernet/eth.c
@@ -178,7 +178,7 @@ __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;
 
 	/*

--
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