netfilter: nf_tables: merge ipv4 and ipv6 nat chain types

Merge the ipv4 and ipv6 nat chain type. This is the last
missing piece which allows to provide inet family support
for nat in a follow patch.

The kconfig knobs for ipv4/ipv6 nat chain are removed, the
nat chain type will be built unconditionally if NFT_NAT
expression is enabled.

Before:
   text	   data	    bss	    dec	    hex	filename
   1576     896       0    2472     9a8 nft_chain_nat_ipv4.ko
   1697     896       0    2593     a21 nft_chain_nat_ipv6.ko

After:
   text	   data	    bss	    dec	    hex	filename
   1832     896       0    2728     aa8 nft_chain_nat.ko

Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

3 files changed, 111 insertions, 0 deletions

diff --git a/net/netfilter/Kconfig b/net/netfilter/Kconfig
index 537f23a8ed52..d43ffb09939b 100644
--- a/net/netfilter/Kconfig
+++ b/net/netfilter/Kconfig
@@ -550,6 +550,7 @@ config NFT_REDIR
 config NFT_NAT
 	depends on NF_CONNTRACK
 	select NF_NAT
+	depends on NF_TABLES_IPV4 || NF_TABLES_IPV6
 	tristate "Netfilter nf_tables nat module"
 	help
 	  This option adds the "nat" expression that you can use to perform
diff --git a/net/netfilter/Makefile b/net/netfilter/Makefile
index c7910706f8dd..4894a85cdd0b 100644
--- a/net/netfilter/Makefile
+++ b/net/netfilter/Makefile
@@ -110,6 +110,8 @@ obj-$(CONFIG_NFT_OSF)		+= nft_osf.o
 obj-$(CONFIG_NFT_TPROXY)	+= nft_tproxy.o
 obj-$(CONFIG_NFT_XFRM)		+= nft_xfrm.o
 
+obj-$(CONFIG_NFT_NAT)		+= nft_chain_nat.o
+
 # nf_tables netdev
 obj-$(CONFIG_NFT_DUP_NETDEV)	+= nft_dup_netdev.o
 obj-$(CONFIG_NFT_FWD_NETDEV)	+= nft_fwd_netdev.o
diff --git a/net/netfilter/nft_chain_nat.c b/net/netfilter/nft_chain_nat.c
new file mode 100644
index 000000000000..ee4852088d50
--- /dev/null
+++ b/net/netfilter/nft_chain_nat.c
@@ -0,0 +1,108 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#include <linux/module.h>
+#include <linux/netfilter/nf_tables.h>
+#include <net/netfilter/nf_nat.h>
+#include <net/netfilter/nf_tables.h>
+#include <net/netfilter/nf_tables_ipv4.h>
+#include <net/netfilter/nf_tables_ipv6.h>
+
+static unsigned int nft_nat_do_chain(void *priv, struct sk_buff *skb,
+				     const struct nf_hook_state *state)
+{
+	struct nft_pktinfo pkt;
+
+	nft_set_pktinfo(&pkt, skb, state);
+
+	switch (state->pf) {
+#ifdef CONFIG_NF_TABLES_IPV4
+	case NFPROTO_IPV4:
+		nft_set_pktinfo_ipv4(&pkt, skb);
+		break;
+#endif
+#ifdef CONFIG_NF_TABLES_IPV6
+	case NFPROTO_IPV6:
+		nft_set_pktinfo_ipv6(&pkt, skb);
+		break;
+#endif
+	default:
+		break;
+	}
+
+	return nft_do_chain(&pkt, priv);
+}
+
+#ifdef CONFIG_NF_TABLES_IPV4
+static const struct nft_chain_type nft_chain_nat_ipv4 = {
+	.name		= "nat",
+	.type		= NFT_CHAIN_T_NAT,
+	.family		= NFPROTO_IPV4,
+	.owner		= THIS_MODULE,
+	.hook_mask	= (1 << NF_INET_PRE_ROUTING) |
+			  (1 << NF_INET_POST_ROUTING) |
+			  (1 << NF_INET_LOCAL_OUT) |
+			  (1 << NF_INET_LOCAL_IN),
+	.hooks		= {
+		[NF_INET_PRE_ROUTING]	= nft_nat_do_chain,
+		[NF_INET_POST_ROUTING]	= nft_nat_do_chain,
+		[NF_INET_LOCAL_OUT]	= nft_nat_do_chain,
+		[NF_INET_LOCAL_IN]	= nft_nat_do_chain,
+	},
+	.ops_register = nf_nat_ipv4_register_fn,
+	.ops_unregister = nf_nat_ipv4_unregister_fn,
+};
+#endif
+
+#ifdef CONFIG_NF_TABLES_IPV6
+static const struct nft_chain_type nft_chain_nat_ipv6 = {
+	.name		= "nat",
+	.type		= NFT_CHAIN_T_NAT,
+	.family		= NFPROTO_IPV6,
+	.owner		= THIS_MODULE,
+	.hook_mask	= (1 << NF_INET_PRE_ROUTING) |
+			  (1 << NF_INET_POST_ROUTING) |
+			  (1 << NF_INET_LOCAL_OUT) |
+			  (1 << NF_INET_LOCAL_IN),
+	.hooks		= {
+		[NF_INET_PRE_ROUTING]	= nft_nat_do_chain,
+		[NF_INET_POST_ROUTING]	= nft_nat_do_chain,
+		[NF_INET_LOCAL_OUT]	= nft_nat_do_chain,
+		[NF_INET_LOCAL_IN]	= nft_nat_do_chain,
+	},
+	.ops_register		= nf_nat_ipv6_register_fn,
+	.ops_unregister		= nf_nat_ipv6_unregister_fn,
+};
+#endif
+
+static int __init nft_chain_nat_init(void)
+{
+#ifdef CONFIG_NF_TABLES_IPV6
+	nft_register_chain_type(&nft_chain_nat_ipv6);
+#endif
+#ifdef CONFIG_NF_TABLES_IPV4
+	nft_register_chain_type(&nft_chain_nat_ipv4);
+#endif
+
+	return 0;
+}
+
+static void __exit nft_chain_nat_exit(void)
+{
+#ifdef CONFIG_NF_TABLES_IPV4
+	nft_unregister_chain_type(&nft_chain_nat_ipv4);
+#endif
+#ifdef CONFIG_NF_TABLES_IPV6
+	nft_unregister_chain_type(&nft_chain_nat_ipv6);
+#endif
+}
+
+module_init(nft_chain_nat_init);
+module_exit(nft_chain_nat_exit);
+
+MODULE_LICENSE("GPL");
+#ifdef CONFIG_NF_TABLES_IPV4
+MODULE_ALIAS_NFT_CHAIN(AF_INET, "nat");
+#endif
+#ifdef CONFIG_NF_TABLES_IPV6
+MODULE_ALIAS_NFT_CHAIN(AF_INET6, "nat");
+#endif