llc: use a device based hash table to speed up multicast delivery

This patch adds a per SAP device based hash table to solve the
multicast delivery scalability issue when we have large number of
interfaces and a large number of sockets bound to the same SAP.

Signed-off-by: Octavian Purdila <opurdila@ixiacom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/include/net/llc_conn.h b/include/net/llc_conn.h
index fe982fd..2f97d8d 100644
--- a/include/net/llc_conn.h
+++ b/include/net/llc_conn.h
@@ -77,6 +77,7 @@
 					      received and caused sending FRMR.
 					      Used for resending FRMR */
 	u32		    cmsg_flags;
+	struct hlist_node   dev_hash_node;
 };
 
 static inline struct llc_sock *llc_sk(const struct sock *sk)