Compile error: 'nf_skb_duplicated' undeclared (first use in this function)

Hi,

I just got:

net/ipv4/netfilter/nf_dup_ipv4.c: In function ‘nf_dup_ipv4’:
net/ipv4/netfilter/nf_dup_ipv4.c:72:16: error: ‘nf_skb_duplicated’
undeclared (first use in this function)
  if (this_cpu_read(nf_skb_duplicated))
                ^
net/ipv4/netfilter/nf_dup_ipv4.c:72:16: note: each undeclared
identifier is reported only once for each function it appears in

And the following patch could fix it, but I haven't looked into it
yet, maybe some Kconfig symbol dependency issue too.

diff --git a/net/ipv4/netfilter/nf_dup_ipv4.c b/net/ipv4/netfilter/nf_dup_ipv4.c
index b5bb375..2d79e6e 100644
--- a/net/ipv4/netfilter/nf_dup_ipv4.c
+++ b/net/ipv4/netfilter/nf_dup_ipv4.c

@@ -13,6 +13,7 @@
 #include <linux/percpu.h>
 #include <linux/route.h>
 #include <linux/skbuff.h>
+#include <linux/netfilter.h>
 #include <net/checksum.h>
 #include <net/icmp.h>
 #include <net/ip.h>

diff --git a/net/ipv6/netfilter/nf_dup_ipv6.c b/net/ipv6/netfilter/nf_dup_ipv6.c
index d8ab654..89c2624 100644
--- a/net/ipv6/netfilter/nf_dup_ipv6.c
+++ b/net/ipv6/netfilter/nf_dup_ipv6.c

@@ -11,6 +11,7 @@
 #include <linux/module.h>
 #include <linux/percpu.h>
 #include <linux/skbuff.h>
+#include <linux/netfilter.h>
 #include <net/ipv6.h>
 #include <net/ip6_route.h>
 #include <net/netfilter/ipv6/nf_dup_ipv6.h>