[IPV6] SNMP: Fix {In,Out}NoRoutes statistics.

A packet which is being discarded because of no routes in the
forwarding path should not be counted as OutNoRoutes but as
InNoRoutes.
Additionally, on this occasion, a packet whose destinaion is
not valid should be counted as InAddrErrors separately.

Based on patch from Mitsuru Chinen <mitch@linux.vnet.ibm.com>.

Signed-off-by: YOSHIFUJI Hideaki <yoshfuji@linux-ipv6.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/ipv6/route.c

@@ -1766,13 +1766,22 @@ int ipv6_route_ioctl(unsigned int cmd, void __user *arg)
  *	Drop the packet on the floor
  */
 
-static inline int ip6_pkt_drop(struct sk_buff *skb, int code)
-{
-	int type = ipv6_addr_type(&skb->nh.ipv6h->daddr);
-	if (type == IPV6_ADDR_ANY || type == IPV6_ADDR_RESERVED)
-		IP6_INC_STATS(ip6_dst_idev(skb->dst), IPSTATS_MIB_INADDRERRORS);
-
-	IP6_INC_STATS(ip6_dst_idev(skb->dst), IPSTATS_MIB_OUTNOROUTES);
+static inline int ip6_pkt_drop(struct sk_buff *skb, int code,
+			       int ipstats_mib_noroutes)
+{
+	int type;
+	switch (ipstats_mib_noroutes) {
+	case IPSTATS_MIB_INNOROUTES:
+		type = ipv6_addr_type(&skb->nh.ipv6h->daddr);
+		if (type == IPV6_ADDR_ANY || type == IPV6_ADDR_RESERVED) {
+			IP6_INC_STATS(ip6_dst_idev(skb->dst), IPSTATS_MIB_INADDRERRORS);
+			break;
+		}
+		/* FALLTHROUGH */
+	case IPSTATS_MIB_OUTNOROUTES:
+		IP6_INC_STATS(ip6_dst_idev(skb->dst), ipstats_mib_noroutes);
+		break;
+	}
 	icmpv6_send(skb, ICMPV6_DEST_UNREACH, code, 0, skb->dev);
 	kfree_skb(skb);
 	return 0;
@@ -1780,26 +1789,26 @@ static inline int ip6_pkt_drop(struct sk_buff *skb, int code)
 
 static int ip6_pkt_discard(struct sk_buff *skb)
 {
-	return ip6_pkt_drop(skb, ICMPV6_NOROUTE);
+	return ip6_pkt_drop(skb, ICMPV6_NOROUTE, IPSTATS_MIB_INNOROUTES);
 }
 
 static int ip6_pkt_discard_out(struct sk_buff *skb)
 {
 	skb->dev = skb->dst->dev;
-	return ip6_pkt_discard(skb);
+	return ip6_pkt_drop(skb, ICMPV6_NOROUTE, IPSTATS_MIB_OUTNOROUTES);
 }
 
 #ifdef CONFIG_IPV6_MULTIPLE_TABLES
 
 static int ip6_pkt_prohibit(struct sk_buff *skb)
 {
-	return ip6_pkt_drop(skb, ICMPV6_ADM_PROHIBITED);
+	return ip6_pkt_drop(skb, ICMPV6_ADM_PROHIBITED, IPSTATS_MIB_INNOROUTES);
 }
 
 static int ip6_pkt_prohibit_out(struct sk_buff *skb)
 {
 	skb->dev = skb->dst->dev;
-	return ip6_pkt_prohibit(skb);
+	return ip6_pkt_drop(skb, ICMPV6_ADM_PROHIBITED, IPSTATS_MIB_OUTNOROUTES);
 }
 
 static int ip6_pkt_blk_hole(struct sk_buff *skb)