Subject: [PATCH] Avoid extra calculation in ip_route_input_common

From: Michael Wang <[email-masked]>
Date: Wed, 21 Dec 2011 13:12:03 +0800

From: Michael Wang <[email-masked]>

If previous condition doesn't meet, the later check will be cancelled.
So we don't need to do all the calculation.

Signed-off-by: Michael Wang <[email-masked]>
---
 net/ipv4/route.c |    8 ++++----
 1 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/net/ipv4/route.c b/net/ipv4/route.c
index f30112f..2872bfb 100644
--- a/net/ipv4/route.c
+++ b/net/ipv4/route.c
@@ -2362,10 +2362,10 @@ int ip_route_input_common(struct sk_buff *skb, __be32 daddr, __be32 saddr,
 
 	for (rth = rcu_dereference(rt_hash_table[hash].chain); rth;
 	     rth = rcu_dereference(rth->dst.rt_next)) {
-		if ((((__force u32)rth->rt_key_dst ^ (__force u32)daddr) |
-		     ((__force u32)rth->rt_key_src ^ (__force u32)saddr) |
-		     (rth->rt_route_iif ^ iif) |
-		     (rth->rt_key_tos ^ tos)) == 0 &&
+		if (((__force u32)rth->rt_key_dst ^ (__force u32)daddr) == 0 &&
+		    ((__force u32)rth->rt_key_src ^ (__force u32)saddr) == 0 &&
+		    rth->rt_route_iif == iif &&
+		    rth->rt_key_tos == tos &&
 		    rth->rt_mark == skb->mark &&
 		    net_eq(dev_net(rth->dst.dev), net) &&
 		    !rt_is_expired(rth)) {
-- 
1.7.4.1