mac80211: don't initiate path discovery when forwarding frame with unknown DA

We used to initiate a path discovery when receiving a frame for which
there is no forwarding information. To cut down on PREQ spam, just send
a (gated) PERR in response.

Also separate path discovery logic from nexthop querying. This patch
means we no longer queue frames when forwarding, so kill the PERR TX
stuff in discard_frame().

Signed-off-by: Thomas Pedersen <thomas@cozybit.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
diff --git a/net/mac80211/mesh.h b/net/mac80211/mesh.h
index 622cc96..bd14bd2 100644
--- a/net/mac80211/mesh.h
+++ b/net/mac80211/mesh.h
@@ -233,6 +233,8 @@
 /* Mesh paths */
 int mesh_nexthop_lookup(struct sk_buff *skb,
 		struct ieee80211_sub_if_data *sdata);
+int mesh_nexthop_resolve(struct sk_buff *skb,
+			 struct ieee80211_sub_if_data *sdata);
 void mesh_path_start_discovery(struct ieee80211_sub_if_data *sdata);
 struct mesh_path *mesh_path_lookup(u8 *dst,
 		struct ieee80211_sub_if_data *sdata);