netfilter: fix compilation when conntrack is disabled but tproxy is enabled

The IPv6 tproxy patches split IPv6 defragmentation off of conntrack, but
failed to update the #ifdef stanzas guarding the defragmentation related
fields and code in skbuff and conntrack related code in nf_defrag_ipv6.c.

This patch adds the required #ifdefs so that IPv6 tproxy can truly be used
without connection tracking.

Original report:
http://marc.info/?l=linux-netdev&m=129010118516341&w=2

Reported-by: Randy Dunlap <randy.dunlap@oracle.com>
Acked-by: Randy Dunlap <randy.dunlap@oracle.com>
Signed-off-by: KOVACS Krisztian <hidden@balabit.hu>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index 20ec0a64..bf221d6 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -255,6 +255,11 @@
 typedef unsigned char *sk_buff_data_t;
 #endif
 
+#if defined(CONFIG_NF_DEFRAG_IPV4) || defined(CONFIG_NF_DEFRAG_IPV4_MODULE) || \
+    defined(CONFIG_NF_DEFRAG_IPV6) || defined(CONFIG_NF_DEFRAG_IPV6_MODULE)
+#define NET_SKBUFF_NF_DEFRAG_NEEDED 1
+#endif
+
 /** 
  *	struct sk_buff - socket buffer
  *	@next: Next buffer in list
@@ -362,6 +367,8 @@
 	void			(*destructor)(struct sk_buff *skb);
 #if defined(CONFIG_NF_CONNTRACK) || defined(CONFIG_NF_CONNTRACK_MODULE)
 	struct nf_conntrack	*nfct;
+#endif
+#ifdef NET_SKBUFF_NF_DEFRAG_NEEDED
 	struct sk_buff		*nfct_reasm;
 #endif
 #ifdef CONFIG_BRIDGE_NETFILTER
@@ -2057,6 +2064,8 @@
 	if (nfct)
 		atomic_inc(&nfct->use);
 }
+#endif
+#ifdef NET_SKBUFF_NF_DEFRAG_NEEDED
 static inline void nf_conntrack_get_reasm(struct sk_buff *skb)
 {
 	if (skb)
@@ -2085,6 +2094,8 @@
 #if defined(CONFIG_NF_CONNTRACK) || defined(CONFIG_NF_CONNTRACK_MODULE)
 	nf_conntrack_put(skb->nfct);
 	skb->nfct = NULL;
+#endif
+#ifdef NET_SKBUFF_NF_DEFRAG_NEEDED
 	nf_conntrack_put_reasm(skb->nfct_reasm);
 	skb->nfct_reasm = NULL;
 #endif
@@ -2101,6 +2112,8 @@
 	dst->nfct = src->nfct;
 	nf_conntrack_get(src->nfct);
 	dst->nfctinfo = src->nfctinfo;
+#endif
+#ifdef NET_SKBUFF_NF_DEFRAG_NEEDED
 	dst->nfct_reasm = src->nfct_reasm;
 	nf_conntrack_get_reasm(src->nfct_reasm);
 #endif
@@ -2114,6 +2127,8 @@
 {
 #if defined(CONFIG_NF_CONNTRACK) || defined(CONFIG_NF_CONNTRACK_MODULE)
 	nf_conntrack_put(dst->nfct);
+#endif
+#ifdef NET_SKBUFF_NF_DEFRAG_NEEDED
 	nf_conntrack_put_reasm(dst->nfct_reasm);
 #endif
 #ifdef CONFIG_BRIDGE_NETFILTER