netfilter: nfnetlink_queue: fix compilation with CONFIG_NF_NAT=m and CONFIG_NF_CT_NETLINK=y

LD init/built-in.o
net/built-in.o:(.data+0x4408): undefined reference to `nf_nat_tcp_seq_adjust'
make: *** [vmlinux] Error 1

This patch adds a new pointer hook (nfq_ct_nat_hook) similar to other existing
in Netfilter to solve our complicated configuration dependencies.

Reported-by: Valdis Kletnieks <[e-mail]>
Signed-off-by: Pablo Neira Ayuso <[e-mail]>

include/linux/netfilter.h

···
 	size_t (*build_size)(const struct nf_conn *ct);
 	int (*build)(struct sk_buff *skb, struct nf_conn *ct);
 	int (*parse)(const struct nlattr *attr, struct nf_conn *ct);
+};
+extern struct nfq_ct_hook __rcu *nfq_ct_hook;
+
+struct nfq_ct_nat_hook {
 	void (*seq_adjust)(struct sk_buff *skb, struct nf_conn *ct,
 			   u32 ctinfo, int off);
 };
-extern struct nfq_ct_hook __rcu *nfq_ct_hook;
+extern struct nfq_ct_nat_hook __rcu *nfq_ct_nat_hook;
 #else
 static inline void nf_ct_attach(struct sk_buff *new, struct sk_buff *skb) {}
 #endif

net/ipv4/netfilter/nf_nat_core.c

···
 	.expectfn	= nf_nat_follow_master,
 };
 
+static struct nfq_ct_nat_hook nfq_ct_nat = {
+	.seq_adjust	= nf_nat_tcp_seq_adjust,
+};
+
 static int __init nf_nat_init(void)
 {
 	size_t i;
···
 			   nfnetlink_parse_nat_setup);
 	BUG_ON(nf_ct_nat_offset != NULL);
 	RCU_INIT_POINTER(nf_ct_nat_offset, nf_nat_get_offset);
+	RCU_INIT_POINTER(nfq_ct_nat_hook, &nfq_ct_nat);
 	return 0;
 
  cleanup_extend:
···
 	RCU_INIT_POINTER(nf_nat_seq_adjust_hook, NULL);
 	RCU_INIT_POINTER(nfnetlink_parse_nat_setup_hook, NULL);
 	RCU_INIT_POINTER(nf_ct_nat_offset, NULL);
+	RCU_INIT_POINTER(nfq_ct_nat_hook, NULL);
 	synchronize_net();
 }
 

net/netfilter/core.c

···
 struct nfq_ct_hook __rcu *nfq_ct_hook __read_mostly;
 EXPORT_SYMBOL_GPL(nfq_ct_hook);
 
+struct nfq_ct_nat_hook __rcu *nfq_ct_nat_hook __read_mostly;
+EXPORT_SYMBOL_GPL(nfq_ct_nat_hook);
+
 #endif /* CONFIG_NF_CONNTRACK */
 
 #ifdef CONFIG_PROC_FS

net/netfilter/nf_conntrack_netlink.c

···
 	.build_size	= ctnetlink_nfqueue_build_size,
 	.build		= ctnetlink_nfqueue_build,
 	.parse		= ctnetlink_nfqueue_parse,
-#ifdef CONFIG_NF_NAT_NEEDED
-	.seq_adjust	= nf_nat_tcp_seq_adjust,
-#endif
 };
 #endif /* CONFIG_NETFILTER_NETLINK_QUEUE_CT */
 

net/netfilter/nfnetlink_queue_ct.c

···
 void nfqnl_ct_seq_adjust(struct sk_buff *skb, struct nf_conn *ct,
 			 enum ip_conntrack_info ctinfo, int diff)
 {
-	struct nfq_ct_hook *nfq_ct;
+	struct nfq_ct_nat_hook *nfq_nat_ct;
 
-	nfq_ct = rcu_dereference(nfq_ct_hook);
-	if (nfq_ct == NULL)
+	nfq_nat_ct = rcu_dereference(nfq_ct_nat_hook);
+	if (nfq_nat_ct == NULL)
 		return;
 
 	if ((ct->status & IPS_NAT_MASK) && diff)
-		nfq_ct->seq_adjust(skb, ct, ctinfo, diff);
+		nfq_nat_ct->seq_adjust(skb, ct, ctinfo, diff);
 }