netdev - bridge: faster compare for link local addresses

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Message-ID: <20070312162015.5d22cd68@dxpl.pdx.osdl.net>
Date:	Mon, 12 Mar 2007 16:20:15 -0700
From:	Stephen Hemminger <shemminger@...ux-foundation.org>
To:	David Miller <davem@...emloft.net>
Cc:	netdev@...r.kernel.org
Subject: bridge: faster compare for link local addresses

Use logic operations rather than memcmp() to compare destination
address with link local multicast addresses.

Signed-off-by: Stephen Hemminger <shemminger@...ux-foundation.org>

---
 net/bridge/br_input.c |    6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

--- netem-dev.orig/net/bridge/br_input.c
+++ netem-dev/net/bridge/br_input.c
@@ -112,7 +112,11 @@ static int br_handle_local_finish(struct
  */
 static inline int is_link_local(const unsigned char *dest)
 {
-	return memcmp(dest, br_group_address, 5) == 0 && (dest[5] & 0xf0) == 0;
+	const u16 *a = (const u16 *) dest;
+	static const u16 *const b = (const u16 *const ) br_group_address;
+	static const u16 m = __constant_cpu_to_be16(0xfff0);
+
+	return ((a[0] ^ b[0]) | (a[1] ^ b[1]) | ((a[2] ^ b[2]) & m)) == 0;
 }
 
 /*
-
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