[NET]: Eliminate duplicate copies of dst_discard

We have a number of copies of dst_discard scattered around the place
which all do the same thing, namely free a packet on the input or
output paths.

This patch deletes all of them except dst_discard and points all the
users to it.

The only non-trivial bit is decnet where it returns an error.
However, conceptually this is identical to the blackhole functions
used in IPv4 and IPv6 which do not return errors.  So they should
either all return errors or all return zero.  For now I've stuck with
the majority and picked zero as the return value.

It doesn't really matter in practice since few if any driver would
react differently depending on a zero return value or NET_RX_DROP.
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/net/dst.h

@@ -179,6 +179,7 @@ static inline struct dst_entry *dst_pop(struct dst_entry *dst)
 	return child;
 }
 
+extern int dst_discard(struct sk_buff *skb);
 extern void * dst_alloc(struct dst_ops * ops);
 extern void __dst_free(struct dst_entry * dst);
 extern struct dst_entry *dst_destroy(struct dst_entry * dst);

net/core/dst.c

@@ -153,11 +153,12 @@ static void dst_gc_task(struct work_struct *work)
 #endif
 }
 
-static int dst_discard(struct sk_buff *skb)
+int dst_discard(struct sk_buff *skb)
 {
 	kfree_skb(skb);
 	return 0;
 }
+EXPORT_SYMBOL(dst_discard);
 
 void * dst_alloc(struct dst_ops * ops)
 {

net/decnet/dn_route.c

@@ -764,17 +764,6 @@ static int dn_forward(struct sk_buff *skb)
 	return NET_RX_DROP;
 }
 
-/*
- * Drop packet. This is used for endnodes and for
- * when we should not be forwarding packets from
- * this dest.
- */
-static int dn_blackhole(struct sk_buff *skb)
-{
-	kfree_skb(skb);
-	return NET_RX_DROP;
-}
-
 /*
  * Used to catch bugs. This should never normally get
  * called.
@@ -1396,7 +1385,7 @@ static int dn_route_input_slow(struct sk_buff *skb)
 		default:
 		case RTN_UNREACHABLE:
 		case RTN_BLACKHOLE:
-			rt->u.dst.input = dn_blackhole;
+			rt->u.dst.input = dst_discard;
 	}
 	rt->rt_flags = flags;
 	if (rt->u.dst.dev)

net/ipv4/route.c

@@ -92,6 +92,7 @@
 #include <linux/jhash.h>
 #include <linux/rcupdate.h>
 #include <linux/times.h>
+#include <net/dst.h>
 #include <net/net_namespace.h>
 #include <net/protocol.h>
 #include <net/ip.h>
@@ -2357,12 +2358,6 @@ static struct dst_ops ipv4_dst_blackhole_ops = {
 };
 
 
-static int ipv4_blackhole_output(struct sk_buff *skb)
-{
-	kfree_skb(skb);
-	return 0;
-}
-
 static int ipv4_dst_blackhole(struct rtable **rp, struct flowi *flp, struct sock *sk)
 {
 	struct rtable *ort = *rp;
@@ -2374,8 +2369,8 @@ static int ipv4_dst_blackhole(struct rtable **rp, struct flowi *flp, struct sock
 
 		atomic_set(&new->__refcnt, 1);
 		new->__use = 1;
-		new->input = ipv4_blackhole_output;
-		new->output = ipv4_blackhole_output;
+		new->input = dst_discard;
+		new->output = dst_discard;
 		memcpy(new->metrics, ort->u.dst.metrics, RTAX_MAX*sizeof(u32));
 
 		new->dev = ort->u.dst.dev;

net/ipv6/exthdrs.c

@@ -32,6 +32,7 @@
 #include <linux/in6.h>
 #include <linux/icmpv6.h>
 
+#include <net/dst.h>
 #include <net/sock.h>
 #include <net/snmp.h>
 
@@ -318,18 +319,8 @@ void __init ipv6_destopt_init(void)
 		printk(KERN_ERR "ipv6_destopt_init: Could not register protocol\n");
 }
 
-/********************************
-  NONE header. No data in packet.
- ********************************/
-
-static int ipv6_nodata_rcv(struct sk_buff *skb)
-{
-	kfree_skb(skb);
-	return 0;
-}
-
 static struct inet6_protocol nodata_protocol = {
-	.handler	=	ipv6_nodata_rcv,
+	.handler	=	dst_discard,
 	.flags		=	INET6_PROTO_NOPOLICY,
 };
 

net/ipv6/route.c

@@ -152,7 +152,6 @@ struct rt6_info ip6_null_entry = {
 
 static int ip6_pkt_prohibit(struct sk_buff *skb);
 static int ip6_pkt_prohibit_out(struct sk_buff *skb);
-static int ip6_pkt_blk_hole(struct sk_buff *skb);
 
 struct rt6_info ip6_prohibit_entry = {
 	.u = {
@@ -181,8 +180,8 @@ struct rt6_info ip6_blk_hole_entry = {
 			.obsolete	= -1,
 			.error		= -EINVAL,
 			.metrics	= { [RTAX_HOPLIMIT - 1] = 255, },
-			.input		= ip6_pkt_blk_hole,
-			.output		= ip6_pkt_blk_hole,
+			.input		= dst_discard,
+			.output		= dst_discard,
 			.ops		= &ip6_dst_ops,
 			.path		= (struct dst_entry*)&ip6_blk_hole_entry,
 		}
@@ -782,12 +781,6 @@ struct dst_entry * ip6_route_output(struct sock *sk, struct flowi *fl)
 
 EXPORT_SYMBOL(ip6_route_output);
 
-static int ip6_blackhole_output(struct sk_buff *skb)
-{
-	kfree_skb(skb);
-	return 0;
-}
-
 int ip6_dst_blackhole(struct sock *sk, struct dst_entry **dstp, struct flowi *fl)
 {
 	struct rt6_info *ort = (struct rt6_info *) *dstp;
@@ -800,8 +793,8 @@ int ip6_dst_blackhole(struct sock *sk, struct dst_entry **dstp, struct flowi *fl
 
 		atomic_set(&new->__refcnt, 1);
 		new->__use = 1;
-		new->input = ip6_blackhole_output;
-		new->output = ip6_blackhole_output;
+		new->input = dst_discard;
+		new->output = dst_discard;
 
 		memcpy(new->metrics, ort->u.dst.metrics, RTAX_MAX*sizeof(u32));
 		new->dev = ort->u.dst.dev;
@@ -1811,12 +1804,6 @@ static int ip6_pkt_prohibit_out(struct sk_buff *skb)
 	return ip6_pkt_drop(skb, ICMPV6_ADM_PROHIBITED, IPSTATS_MIB_OUTNOROUTES);
 }
 
-static int ip6_pkt_blk_hole(struct sk_buff *skb)
-{
-	kfree_skb(skb);
-	return 0;
-}
-
 #endif
 
 /*