net: Consolidate common blackhole dst ops

Move generic blackhole dst ops to the core and use them from both
ipv4_dst_blackhole_ops and ip6_dst_blackhole_ops where possible. No
functional change otherwise. We need these also in other locations
and having to define them over and over again is not great.
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/net/dst.h

@@ -550,4 +550,15 @@ static inline void skb_dst_update_pmtu_no_confirm(struct sk_buff *skb, u32 mtu)
 		dst->ops->update_pmtu(dst, NULL, skb, mtu, false);
 }
 
+struct dst_entry *dst_blackhole_check(struct dst_entry *dst, u32 cookie);
+void dst_blackhole_update_pmtu(struct dst_entry *dst, struct sock *sk,
+			       struct sk_buff *skb, u32 mtu, bool confirm_neigh);
+void dst_blackhole_redirect(struct dst_entry *dst, struct sock *sk,
+			    struct sk_buff *skb);
+u32 *dst_blackhole_cow_metrics(struct dst_entry *dst, unsigned long old);
+struct neighbour *dst_blackhole_neigh_lookup(const struct dst_entry *dst,
+					     struct sk_buff *skb,
+					     const void *daddr);
+unsigned int dst_blackhole_mtu(const struct dst_entry *dst);
+
 #endif /* _NET_DST_H */

net/core/dst.c

@@ -237,6 +237,44 @@ void __dst_destroy_metrics_generic(struct dst_entry *dst, unsigned long old)
 }
 EXPORT_SYMBOL(__dst_destroy_metrics_generic);
 
+struct dst_entry *dst_blackhole_check(struct dst_entry *dst, u32 cookie)
+{
+	return NULL;
+}
+
+u32 *dst_blackhole_cow_metrics(struct dst_entry *dst, unsigned long old)
+{
+	return NULL;
+}
+
+struct neighbour *dst_blackhole_neigh_lookup(const struct dst_entry *dst,
+					     struct sk_buff *skb,
+					     const void *daddr)
+{
+	return NULL;
+}
+
+void dst_blackhole_update_pmtu(struct dst_entry *dst, struct sock *sk,
+			       struct sk_buff *skb, u32 mtu,
+			       bool confirm_neigh)
+{
+}
+EXPORT_SYMBOL_GPL(dst_blackhole_update_pmtu);
+
+void dst_blackhole_redirect(struct dst_entry *dst, struct sock *sk,
+			    struct sk_buff *skb)
+{
+}
+EXPORT_SYMBOL_GPL(dst_blackhole_redirect);
+
+unsigned int dst_blackhole_mtu(const struct dst_entry *dst)
+{
+	unsigned int mtu = dst_metric_raw(dst, RTAX_MTU);
+
+	return mtu ? : dst->dev->mtu;
+}
+EXPORT_SYMBOL_GPL(dst_blackhole_mtu);
+
 static struct dst_ops md_dst_ops = {
 	.family =		AF_UNSPEC,
 };

net/ipv4/route.c

@@ -2687,44 +2687,15 @@ struct rtable *ip_route_output_key_hash_rcu(struct net *net, struct flowi4 *fl4,
 	return rth;
 }
 
-static struct dst_entry *ipv4_blackhole_dst_check(struct dst_entry *dst, u32 cookie)
-{
-	return NULL;
-}
-
-static unsigned int ipv4_blackhole_mtu(const struct dst_entry *dst)
-{
-	unsigned int mtu = dst_metric_raw(dst, RTAX_MTU);
-
-	return mtu ? : dst->dev->mtu;
-}
-
-static void ipv4_rt_blackhole_update_pmtu(struct dst_entry *dst, struct sock *sk,
-					  struct sk_buff *skb, u32 mtu,
-					  bool confirm_neigh)
-{
-}
-
-static void ipv4_rt_blackhole_redirect(struct dst_entry *dst, struct sock *sk,
-				       struct sk_buff *skb)
-{
-}
-
-static u32 *ipv4_rt_blackhole_cow_metrics(struct dst_entry *dst,
-					  unsigned long old)
-{
-	return NULL;
-}
-
 static struct dst_ops ipv4_dst_blackhole_ops = {
-	.family			=	AF_INET,
-	.check			=	ipv4_blackhole_dst_check,
-	.mtu			=	ipv4_blackhole_mtu,
-	.default_advmss		=	ipv4_default_advmss,
-	.update_pmtu		=	ipv4_rt_blackhole_update_pmtu,
-	.redirect		=	ipv4_rt_blackhole_redirect,
-	.cow_metrics		=	ipv4_rt_blackhole_cow_metrics,
-	.neigh_lookup		=	ipv4_neigh_lookup,
+	.family			= AF_INET,
+	.default_advmss		= ipv4_default_advmss,
+	.neigh_lookup		= ipv4_neigh_lookup,
+	.check			= dst_blackhole_check,
+	.cow_metrics		= dst_blackhole_cow_metrics,
+	.update_pmtu		= dst_blackhole_update_pmtu,
+	.redirect		= dst_blackhole_redirect,
+	.mtu			= dst_blackhole_mtu,
 };
 
 struct dst_entry *ipv4_blackhole_route(struct net *net, struct dst_entry *dst_orig)

net/ipv6/route.c

@@ -260,34 +260,16 @@ static struct dst_ops ip6_dst_ops_template = {
 	.confirm_neigh		=	ip6_confirm_neigh,
 };
 
-static unsigned int ip6_blackhole_mtu(const struct dst_entry *dst)
-{
-	unsigned int mtu = dst_metric_raw(dst, RTAX_MTU);
-
-	return mtu ? : dst->dev->mtu;
-}
-
-static void ip6_rt_blackhole_update_pmtu(struct dst_entry *dst, struct sock *sk,
-					 struct sk_buff *skb, u32 mtu,
-					 bool confirm_neigh)
-{
-}
-
-static void ip6_rt_blackhole_redirect(struct dst_entry *dst, struct sock *sk,
-				      struct sk_buff *skb)
-{
-}
-
 static struct dst_ops ip6_dst_blackhole_ops = {
-	.family			=	AF_INET6,
-	.destroy		=	ip6_dst_destroy,
-	.check			=	ip6_dst_check,
-	.mtu			=	ip6_blackhole_mtu,
-	.default_advmss		=	ip6_default_advmss,
-	.update_pmtu		=	ip6_rt_blackhole_update_pmtu,
-	.redirect		=	ip6_rt_blackhole_redirect,
-	.cow_metrics		=	dst_cow_metrics_generic,
-	.neigh_lookup		=	ip6_dst_neigh_lookup,
+	.family			= AF_INET6,
+	.default_advmss		= ip6_default_advmss,
+	.neigh_lookup		= ip6_dst_neigh_lookup,
+	.check			= ip6_dst_check,
+	.destroy		= ip6_dst_destroy,
+	.cow_metrics		= dst_cow_metrics_generic,
+	.update_pmtu		= dst_blackhole_update_pmtu,
+	.redirect		= dst_blackhole_redirect,
+	.mtu			= dst_blackhole_mtu,
 };
 
 static const u32 ip6_template_metrics[RTAX_MAX] = {