Revert "net: Remove unused neighbour layer ops."

This reverts commit 5c3ddec73d01a1fae9409c197078cb02c42238c3.

S390 qeth driver actually still uses the setup ops.

Reported-by: Frank Blaschka <blaschka@linux.vnet.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/linux/netdevice.h

@@ -974,6 +974,7 @@ struct net_device_ops {
 	int			(*ndo_set_features)(struct net_device *dev,
 						    netdev_features_t features);
 	int			(*ndo_neigh_construct)(struct neighbour *n);
+	void			(*ndo_neigh_destroy)(struct neighbour *n);
 };
 
 /*

include/net/neighbour.h

@@ -43,6 +43,7 @@ struct neigh_parms {
 #endif
 	struct net_device *dev;
 	struct neigh_parms *next;
+	int	(*neigh_setup)(struct neighbour *);
 	void	(*neigh_cleanup)(struct neighbour *);
 	struct neigh_table *tbl;
 

net/core/neighbour.c

@@ -497,6 +497,13 @@ struct neighbour *neigh_create(struct neigh_table *tbl, const void *pkey,
 		}
 	}
 
+	/* Device specific setup. */
+	if (n->parms->neigh_setup &&
+	    (error = n->parms->neigh_setup(n)) < 0) {
+		rc = ERR_PTR(error);
+		goto out_neigh_release;
+	}
+
 	n->confirmed = jiffies - (n->parms->base_reachable_time << 1);
 
 	write_lock_bh(&tbl->lock);
@@ -710,6 +717,9 @@ void neigh_destroy(struct neighbour *neigh)
 	skb_queue_purge(&neigh->arp_queue);
 	neigh->arp_queue_len_bytes = 0;
 
+	if (dev->netdev_ops->ndo_neigh_destroy)
+		dev->netdev_ops->ndo_neigh_destroy(neigh);
+
 	dev_put(dev);
 	neigh_parms_put(neigh->parms);