[IPV6]: Add IPv6 routing table statistic: fib_discarded_routes.

include/net/ip6_fib.h

@@ -114,6 +114,7 @@ struct rt6_statistics {
 	__u32		fib_rt_alloc;		/* permanent routes	*/
 	__u32		fib_rt_entries;		/* rt entries in table	*/
 	__u32		fib_rt_cache;		/* cache routes		*/
+	__u32		fib_discarded_routes;
 };
 
 #define RTN_TL_ROOT	0x0001

net/ipv6/ip6_fib.c

@@ -896,6 +896,7 @@ static void fib6_del_route(struct fib6_node *fn, struct rt6_info **rtp,
 	*rtp = rt->u.next;
 	rt->rt6i_node = NULL;
 	rt6_stats.fib_rt_entries--;
+	rt6_stats.fib_discarded_routes++;
 
 	/* Adjust walkers */
 	read_lock(&fib6_walker_lock);

net/ipv6/route.c

@@ -1786,11 +1786,12 @@ extern struct rt6_statistics rt6_stats;
 
 static int rt6_stats_seq_show(struct seq_file *seq, void *v)
 {
-	seq_printf(seq, "%04x %04x %04x %04x %04x %04x\n",
+	seq_printf(seq, "%04x %04x %04x %04x %04x %04x %04x\n",
 		      rt6_stats.fib_nodes, rt6_stats.fib_route_nodes,
 		      rt6_stats.fib_rt_alloc, rt6_stats.fib_rt_entries,
 		      rt6_stats.fib_rt_cache,
-		      atomic_read(&ip6_dst_ops.entries));
+		      atomic_read(&ip6_dst_ops.entries),
+		      rt6_stats.fib_discarded_routes);
 
 	return 0;
 }