[LLC]: allow applications to get copy of kernel datagrams

It is legal for an application to bind to a SAP that is also being
used by the kernel. This happens if the bridge module binds to the
STP SAP, and the user wants to have a daemon for STP as well.
It is possible to have kernel doing STP on one bridge, but
let application do RSTP on another bridge.
Signed-off-by: NStephen Hemminger <shemminger@osdl.org>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/llc/llc_input.c

@@ -173,8 +173,10 @@ int llc_rcv(struct sk_buff *skb, struct net_device *dev,
 	 */
 	rcv = rcu_dereference(sap->rcv_func);
 	if (rcv) {
+ 		struct sk_buff *cskb = skb_clone(skb, GFP_ATOMIC);
+ 		if (cskb)
+ 			rcv(cskb, dev, pt, orig_dev);
 		rcv(skb, dev, pt, orig_dev);
-		goto out_put;
 	}
 	dest = llc_pdu_type(skb);
 	if (unlikely(!dest || !llc_type_handlers[dest - 1]))