ipv6: Set default hoplimit as zero.

Commit a02e4b7d(Demark default hoplimit as zero) only changes the
hoplimit checking condition and default value in ip6_dst_hoplimit, not
zeros all hoplimit default value.

Keep the zeroing ip6_template_metrics[RTAX_HOPLIMIT - 1] to force it as
const, cause as a37e6e34(net: force dst_default_metrics to const
section)
Signed-off-by: NLi RongQing <roy.qing.li@gmail.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/ipv6/route.c

@@ -219,7 +219,7 @@ static struct dst_ops ip6_dst_blackhole_ops = {
 };
 
 static const u32 ip6_template_metrics[RTAX_MAX] = {
-	[RTAX_HOPLIMIT - 1] = 255,
+	[RTAX_HOPLIMIT - 1] = 0,
 };
 
 static const struct rt6_info ip6_null_entry_template = {
@@ -1232,7 +1232,7 @@ struct dst_entry *icmp6_dst_alloc(struct net_device *dev,
 	rt->rt6i_dst.addr = fl6->daddr;
 	rt->rt6i_dst.plen = 128;
 	rt->rt6i_idev     = idev;
-	dst_metric_set(&rt->dst, RTAX_HOPLIMIT, 255);
+	dst_metric_set(&rt->dst, RTAX_HOPLIMIT, 0);
 
 	spin_lock_bh(&icmp6_dst_lock);
 	rt->dst.next = icmp6_dst_gc_list;