batman-adv: Make orig_node->router an rcu protected pointer

The rcu protected macros rcu_dereference() and rcu_assign_pointer()
for the orig_node->router need to be used, as well as spin/rcu locking.
Otherwise we might end up using a router pointer pointing to already
freed memory.

Therefore this commit introduces the safe getter method
orig_node_get_router().

Signed-off-by: Linus Lüssing <linus.luessing@web.de>
Signed-off-by: Marek Lindner <lindner_marek@yahoo.de>
Signed-off-by: Sven Eckelmann <sven@narfation.org>
diff --git a/net/batman-adv/originator.h b/net/batman-adv/originator.h
index 5cc0110..e1d641f 100644
--- a/net/batman-adv/originator.h
+++ b/net/batman-adv/originator.h
@@ -34,6 +34,7 @@
 				   uint8_t *neigh,
 				   struct hard_iface *if_incoming);
 void neigh_node_free_ref(struct neigh_node *neigh_node);
+struct neigh_node *orig_node_get_router(struct orig_node *orig_node);
 int orig_seq_print_text(struct seq_file *seq, void *offset);
 int orig_hash_add_if(struct hard_iface *hard_iface, int max_if_num);
 int orig_hash_del_if(struct hard_iface *hard_iface, int max_if_num);