ip6_tunnel: fix setting hop_limit value for ipv6 tunnel

Similar to vxlan/geneve tunnel, if hop_limit is zero, it should fall
back to ip6_dst_hoplimt().

Signed-off-by: Haishuang Yan <yanhaishuang@cmss.chinamobile.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/ipv6/ip6_tunnel.c b/net/ipv6/ip6_tunnel.c
index 3a0ba2a..10a693a 100644
--- a/net/ipv6/ip6_tunnel.c
+++ b/net/ipv6/ip6_tunnel.c
@@ -1184,6 +1184,7 @@ int ip6_tnl_xmit(struct sk_buff *skb, struct net_device *dev, __u8 dsfield,
 		init_tel_txopt(&opt, encap_limit);
 		ipv6_push_frag_opts(skb, &opt.ops, &proto);
 	}
+	hop_limit = hop_limit ? : ip6_dst_hoplimit(dst);
 
 	/* Calculate max headroom for all the headers and adjust
 	 * needed_headroom if necessary.