ipmr: RCU protection for mfc_cache_array

Use RCU & RTNL protection for mfc_cache_array[]

ipmr_cache_find() is called under rcu_read_lock();

Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/include/linux/mroute.h b/include/linux/mroute.h
index fa04b24..0fa7a3a 100644
--- a/include/linux/mroute.h
+++ b/include/linux/mroute.h
@@ -213,6 +213,7 @@
 			unsigned char ttls[MAXVIFS];	/* TTL thresholds		*/
 		} res;
 	} mfc_un;
+	struct rcu_head	rcu;
 };
 
 #define MFC_STATIC		1