IPV4: use xor rather than multiple ands for route compare

The comparison in ip_route_input is a hot path, by recoding the C
"and" as bit operations, fewer conditional branches get generated
so the code should be faster. Maybe someday Gcc will be smart
enough to do this?

Signed-off-by: Stephen Hemminger <shemminger@vyatta.com>
Acked-by: Eric Dumazet <dada1@cosmosbay.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/ipv4/route.c b/net/ipv4/route.c
index a1c5b8dbdfed403d8a1adbeb43962887c2f62550..139799f8a8a125f9113e7fed020c87ac0947f4e8 100644 (file)
--- a/net/ipv4/route.c
+++ b/net/ipv4/route.c
@@ -2077,12 +2077,12 @@ int ip_route_input(struct sk_buff *skb, __be32 daddr, __be32 saddr,
        rcu_read_lock();
        for (rth = rcu_dereference(rt_hash_table[hash].chain); rth;
             rth = rcu_dereference(rth->u.dst.rt_next)) {
-               if (rth->fl.fl4_dst == daddr &&
-                   rth->fl.fl4_src == saddr &&
-                   rth->fl.iif == iif &&
-                   rth->fl.oif == 0 &&
+               if (((rth->fl.fl4_dst ^ daddr) |
+                    (rth->fl.fl4_src ^ saddr) |
+                    (rth->fl.iif ^ iif) |
+                    rth->fl.oif |
+                    (rth->fl.fl4_tos ^ tos)) == 0 &&
                    rth->fl.mark == skb->mark &&
-                   rth->fl.fl4_tos == tos &&
                    net_eq(dev_net(rth->u.dst.dev), net) &&
                    rth->rt_genid == atomic_read(&rt_genid)) {
                        dst_use(&rth->u.dst, jiffies);