net: Add ->neigh_lookup() operation to dst_ops

In the future dst entries will be neigh-less. In that environment we
need to have an easy transition point for current users of
dst->neighbour outside of the packet output fast path.

Signed-off-by: David S. Miller <[e-mail]>

include/net/arp.h

···
 	return n;
 }
 
-static inline struct neighbour *ipv4_neigh_lookup(struct neigh_table *tbl, struct net_device *dev, const __be32 *pkey)
-{
-	struct neighbour *n = __ipv4_neigh_lookup(tbl, dev,
-						  *(__force u32 *)pkey);
-	if (n)
-		return n;
-	return neigh_create(tbl, pkey, dev);
-}
-
 extern void	arp_init(void);
 extern int	arp_find(unsigned char *haddr, struct sk_buff *skb);
 extern int	arp_ioctl(struct net *net, unsigned int cmd, void __user *arg);

include/net/dst.h

···
 	}
 }
 
+static inline struct neighbour *dst_neigh_lookup(const struct dst_entry *dst, const void *daddr)
+{
+	return dst->ops->neigh_lookup(dst, daddr);
+}
+
 static inline void dst_link_failure(struct sk_buff *skb)
 {
 	struct dst_entry *dst = skb_dst(skb);

include/net/dst_ops.h

···
 	void			(*link_failure)(struct sk_buff *);
 	void			(*update_pmtu)(struct dst_entry *dst, u32 mtu);
 	int			(*local_out)(struct sk_buff *skb);
+	struct neighbour *	(*neigh_lookup)(const struct dst_entry *dst, const void *daddr);
 
 	struct kmem_cache	*kmem_cachep;
 

net/bridge/br_netfilter.c

···
 	return NULL;
 }
 
+static struct neighbour *fake_neigh_lookup(const struct dst_entry *dst, const void *daddr)
+{
+	return NULL;
+}
+
 static struct dst_ops fake_dst_ops = {
 	.family =		AF_INET,
 	.protocol =		cpu_to_be16(ETH_P_IP),
 	.update_pmtu =		fake_update_pmtu,
 	.cow_metrics =		fake_cow_metrics,
+	.neigh_lookup =		fake_neigh_lookup,
 };
 
 /*

net/decnet/dn_route.c

···
 static struct dst_entry *dn_dst_negative_advice(struct dst_entry *);
 static void dn_dst_link_failure(struct sk_buff *);
 static void dn_dst_update_pmtu(struct dst_entry *dst, u32 mtu);
+static struct neighbour *dn_dst_neigh_lookup(const struct dst_entry *dst, const void *daddr);
 static int dn_route_input(struct sk_buff *);
 static void dn_run_flush(unsigned long dummy);
 
···
 	.negative_advice =	dn_dst_negative_advice,
 	.link_failure =		dn_dst_link_failure,
 	.update_pmtu =		dn_dst_update_pmtu,
+	.neigh_lookup =		dn_dst_neigh_lookup,
 };
 
 static void dn_dst_destroy(struct dst_entry *dst)
···
 static unsigned int dn_dst_default_mtu(const struct dst_entry *dst)
 {
 	return dst->dev->mtu;
+}
+
+static struct neighbour *dn_dst_neigh_lookup(const struct dst_entry *dst, const void *daddr)
+{
+	return __neigh_lookup_errno(&dn_neigh_table, daddr, dst->dev);
 }
 
 static int dn_rt_set_next_hop(struct dn_route *rt, struct dn_fib_res *res)

net/ipv4/route.c

···
 	return p;
 }
 
+static struct neighbour *ipv4_neigh_lookup(const struct dst_entry *dst, const void *daddr);
+
 static struct dst_ops ipv4_dst_ops = {
 	.family =		AF_INET,
 	.protocol =		cpu_to_be16(ETH_P_IP),
···
 	.link_failure =		ipv4_link_failure,
 	.update_pmtu =		ip_rt_update_pmtu,
 	.local_out =		__ip_local_out,
+	.neigh_lookup =		ipv4_neigh_lookup,
 };
 
 #define ECN_OR_COST(class)	TC_PRIO_##class
···
 	return length >> FRACT_BITS;
 }
 
-static int rt_bind_neighbour(struct rtable *rt)
+static struct neighbour *ipv4_neigh_lookup(const struct dst_entry *dst, const void *daddr)
 {
-	static const __be32 inaddr_any = 0;
-	struct net_device *dev = rt->dst.dev;
 	struct neigh_table *tbl = &arp_tbl;
-	const __be32 *nexthop;
+	static const __be32 inaddr_any = 0;
+	struct net_device *dev = dst->dev;
+	const __be32 *pkey = daddr;
 	struct neighbour *n;
 
 #if defined(CONFIG_ATM_CLIP) || defined(CONFIG_ATM_CLIP_MODULE)
 	if (dev->type == ARPHRD_ATM)
 		tbl = clip_tbl_hook;
 #endif
-	nexthop = &rt->rt_gateway;
 	if (dev->flags & (IFF_LOOPBACK | IFF_POINTOPOINT))
-		nexthop = &inaddr_any;
-	n = ipv4_neigh_lookup(tbl, dev, nexthop);
+		pkey = &inaddr_any;
+
+	n = __ipv4_neigh_lookup(tbl, dev, *(__force u32 *)pkey);
+	if (n)
+		return n;
+	return neigh_create(tbl, pkey, dev);
+}
+
+static int rt_bind_neighbour(struct rtable *rt)
+{
+	struct neighbour *n = ipv4_neigh_lookup(&rt->dst, &rt->rt_gateway);
 	if (IS_ERR(n))
 		return PTR_ERR(n);
 	dst_set_neighbour(&rt->dst, n);
···
 	.default_advmss		=	ipv4_default_advmss,
 	.update_pmtu		=	ipv4_rt_blackhole_update_pmtu,
 	.cow_metrics		=	ipv4_rt_blackhole_cow_metrics,
+	.neigh_lookup		=	ipv4_neigh_lookup,
 };
 
 struct dst_entry *ipv4_blackhole_route(struct net *net, struct dst_entry *dst_orig)

net/ipv6/route.c

···
 	return p;
 }
 
+static struct neighbour *ip6_neigh_lookup(const struct dst_entry *dst, const void *daddr)
+{
+	return __neigh_lookup_errno(&nd_tbl, daddr, dst->dev);
+}
+
 static struct dst_ops ip6_dst_ops_template = {
 	.family			=	AF_INET6,
 	.protocol		=	cpu_to_be16(ETH_P_IPV6),
···
 	.link_failure		=	ip6_link_failure,
 	.update_pmtu		=	ip6_rt_update_pmtu,
 	.local_out		=	__ip6_local_out,
+	.neigh_lookup		=	ip6_neigh_lookup,
 };
 
 static unsigned int ip6_blackhole_default_mtu(const struct dst_entry *dst)
···
 	.default_advmss		=	ip6_default_advmss,
 	.update_pmtu		=	ip6_rt_blackhole_update_pmtu,
 	.cow_metrics		=	ip6_rt_blackhole_cow_metrics,
+	.neigh_lookup		=	ip6_neigh_lookup,
 };
 
 static const u32 ip6_template_metrics[RTAX_MAX] = {

net/xfrm/xfrm_policy.c

···
 	return dst_mtu(dst->path);
 }
 
+static struct neighbour *xfrm_neigh_lookup(const struct dst_entry *dst, const void *daddr)
+{
+	return dst_neigh_lookup(dst->path, daddr);
+}
+
 int xfrm_policy_register_afinfo(struct xfrm_policy_afinfo *afinfo)
 {
 	struct net *net;
···
 			dst_ops->negative_advice = xfrm_negative_advice;
 		if (likely(dst_ops->link_failure == NULL))
 			dst_ops->link_failure = xfrm_link_failure;
+		if (likely(dst_ops->neigh_lookup == NULL))
+			dst_ops->neigh_lookup = xfrm_neigh_lookup;
 		if (likely(afinfo->garbage_collect == NULL))
 			afinfo->garbage_collect = __xfrm_garbage_collect;
 		xfrm_policy_afinfo[afinfo->family] = afinfo;