[IPV4] SNMP: Support InNoRoutes

An IP datagram which is being discarded because of no routes in the
forwarding path should be counted as InNoRoutes.
Signed-off-by: NMitsuru Chinen <mitch@linux.vnet.ibm.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/ipv4/ip_input.c

@@ -340,6 +340,8 @@ static inline int ip_rcv_finish(struct sk_buff *skb)
 		if (unlikely(err)) {
 			if (err == -EHOSTUNREACH)
 				IP_INC_STATS_BH(IPSTATS_MIB_INADDRERRORS);
+			else if (err == -ENETUNREACH)
+				IP_INC_STATS_BH(IPSTATS_MIB_INNOROUTES);
 			goto drop;
 		}
 	}