[IPV4]: Snmpv2 Mib IP counter ipInAddrErrors support

I followed Thomas' proposal to see every martian destination as a case
where the ipInAddrErrors counter has to be incremented. There are
two advantages by doing so: (1) The relation between the ipInReceive
counter and all the other ipInXXX counters is more accurate in the
case the RTN_UNICAST code check fails and (2) it makes the code in
ip_route_input_slow easier.

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

net/ipv4/ip_input.c

···
 {
 	struct net_device *dev = skb->dev;
 	struct iphdr *iph = skb->nh.iph;
+	int err;
 
 	/*
 	 *	Initialise the virtual path cache for the packet. It describes
 	 *	how the packet travels inside Linux networking.
 	 */ 
 	if (skb->dst == NULL) {
-		if (ip_route_input(skb, iph->daddr, iph->saddr, iph->tos, dev))
+		if ((err = ip_route_input(skb, iph->daddr, iph->saddr, iph->tos, dev))) {
+			if (err == -EHOSTUNREACH)
+				IP_INC_STATS_BH(IPSTATS_MIB_INADDRERRORS);
 			goto drop; 
+		}
 	}
 
 #ifdef CONFIG_NET_CLS_ROUTE

net/ipv4/route.c

···
 	 */
 	if ((err = fib_lookup(&fl, &res)) != 0) {
 		if (!IN_DEV_FORWARD(in_dev))
-			goto e_inval;
+			goto e_hostunreach;
 		goto no_route;
 	}
 	free_res = 1;
···
 	}
 
 	if (!IN_DEV_FORWARD(in_dev))
-		goto e_inval;
+		goto e_hostunreach;
 	if (res.type != RTN_UNICAST)
 		goto martian_destination;
 
···
 			"%u.%u.%u.%u, dev %s\n",
 			NIPQUAD(daddr), NIPQUAD(saddr), dev->name);
 #endif
+
+e_hostunreach:
+        err = -EHOSTUNREACH;
+        goto done;
+
 e_inval:
 	err = -EINVAL;
 	goto done;