tipc: eliminate unnecessary skb expansion during retransmission

We increase the allocated headroom for the buffer copies to be
retransmitted. This eliminates the need for the lower stack levels
(UDP/IP/L2) to expand the headroom in order to add their own headers.
Signed-off-by: Jon Maloy <jon.maloy@ericsson.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/tipc/link.c

@@ -1125,7 +1125,7 @@ static int tipc_link_bc_retrans(struct tipc_link *l, struct tipc_link *r,
 				continue;
 			TIPC_SKB_CB(skb)->nxt_retr = jiffies + TIPC_BC_RETR_LIM;
 		}
-		_skb = __pskb_copy(skb, MIN_H_SIZE, GFP_ATOMIC);
+		_skb = __pskb_copy(skb, LL_MAX_HEADER + MIN_H_SIZE, GFP_ATOMIC);
 		if (!_skb)
 			return 0;
 		hdr = buf_msg(_skb);