[BRIDGE]: Properly dereference the br_should_route_hook

This hook is protected with the RCU, so simple

	if (br_should_route_hook)
		br_should_route_hook(...)

is not enough on some architectures.

Use the rcu_dereference/rcu_assign_pointer in this case.

Fixed Stephen's comment concerning using the typeof().

Signed-off-by: Pavel Emelyanov <xemul@openvz.org>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
diff --git a/net/bridge/br_input.c b/net/bridge/br_input.c
index 3cedd4e..0ee79a7 100644
--- a/net/bridge/br_input.c
+++ b/net/bridge/br_input.c
@@ -122,6 +122,7 @@
 struct sk_buff *br_handle_frame(struct net_bridge_port *p, struct sk_buff *skb)
 {
 	const unsigned char *dest = eth_hdr(skb)->h_dest;
+	int (*rhook)(struct sk_buff *skb);
 
 	if (!is_valid_ether_addr(eth_hdr(skb)->h_source))
 		goto drop;
@@ -147,9 +148,9 @@
 
 	switch (p->state) {
 	case BR_STATE_FORWARDING:
-
-		if (br_should_route_hook) {
-			if (br_should_route_hook(skb))
+		rhook = rcu_dereference(br_should_route_hook);
+		if (rhook != NULL) {
+			if (rhook(skb))
 				return skb;
 			dest = eth_hdr(skb)->h_dest;
 		}