net: use inet6_iif instead of IP6CB()->iif

Signed-off-by: Duan Jiong <duanj.fnst@cn.fujitsu.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/ipv4/ping.c b/net/ipv4/ping.c
index 044a0dd..a3c59a0 100644
--- a/net/ipv4/ping.c
+++ b/net/ipv4/ping.c
@@ -911,7 +911,7 @@
 				sin6->sin6_flowinfo = ip6_flowinfo(ip6);
 			sin6->sin6_scope_id =
 				ipv6_iface_scope_id(&sin6->sin6_addr,
-						    IP6CB(skb)->iif);
+						    inet6_iif(skb));
 			*addr_len = sizeof(*sin6);
 		}