netfilter: x_tables: merge ip and ipv6 masquerade modules

No need to have separate modules for this.
before:
 text    data   bss    dec  filename
 2038    1168     0   3206  net/ipv4/netfilter/ipt_MASQUERADE.ko
 1526    1024     0   2550  net/ipv6/netfilter/ip6t_MASQUERADE.ko
after:
 text    data   bss    dec  filename
 2521    1296     0   3817  net/netfilter/xt_MASQUERADE.ko

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

3 files changed, 158 insertions, 0 deletions

diff --git a/net/netfilter/Kconfig b/net/netfilter/Kconfig
index f4384c096d0d..02b281d3c167 100644
--- a/net/netfilter/Kconfig
+++ b/net/netfilter/Kconfig
@@ -997,6 +997,20 @@ config NETFILTER_XT_TARGET_REDIRECT
 
 	To compile it as a module, choose M here. If unsure, say N.
 
+config NETFILTER_XT_TARGET_MASQUERADE
+	tristate "MASQUERADE target support"
+	depends on NF_NAT
+	default m if NETFILTER_ADVANCED=n
+	select NF_NAT_MASQUERADE
+	help
+	  Masquerading is a special case of NAT: all outgoing connections are
+	  changed to seem to come from a particular interface's address, and
+	  if the interface goes down, those connections are lost.  This is
+	  only useful for dialup accounts with dynamic IP address (ie. your IP
+	  address will be different on next dialup).
+
+	  To compile it as a module, choose M here.  If unsure, say N.
+
 config NETFILTER_XT_TARGET_TEE
 	tristate '"TEE" - packet cloning to alternate destination'
 	depends on NETFILTER_ADVANCED
diff --git a/net/netfilter/Makefile b/net/netfilter/Makefile
index afbf475e02b2..72cca6b48960 100644
--- a/net/netfilter/Makefile
+++ b/net/netfilter/Makefile
@@ -148,6 +148,7 @@ obj-$(CONFIG_NETFILTER_XT_TARGET_NFLOG) += xt_NFLOG.o
 obj-$(CONFIG_NETFILTER_XT_TARGET_NFQUEUE) += xt_NFQUEUE.o
 obj-$(CONFIG_NETFILTER_XT_TARGET_RATEEST) += xt_RATEEST.o
 obj-$(CONFIG_NETFILTER_XT_TARGET_REDIRECT) += xt_REDIRECT.o
+obj-$(CONFIG_NETFILTER_XT_TARGET_MASQUERADE) += xt_MASQUERADE.o
 obj-$(CONFIG_NETFILTER_XT_TARGET_SECMARK) += xt_SECMARK.o
 obj-$(CONFIG_NETFILTER_XT_TARGET_TPROXY) += xt_TPROXY.o
 obj-$(CONFIG_NETFILTER_XT_TARGET_TCPMSS) += xt_TCPMSS.o
diff --git a/net/netfilter/xt_MASQUERADE.c b/net/netfilter/xt_MASQUERADE.c
new file mode 100644
index 000000000000..96d884718749
--- /dev/null
+++ b/net/netfilter/xt_MASQUERADE.c
@@ -0,0 +1,143 @@
+/* Masquerade.  Simple mapping which alters range to a local IP address
+   (depending on route). */
+
+/* (C) 1999-2001 Paul `Rusty' Russell
+ * (C) 2002-2006 Netfilter Core Team <coreteam@netfilter.org>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+#include <linux/module.h>
+#include <linux/netfilter/x_tables.h>
+#include <net/netfilter/nf_nat.h>
+#include <net/netfilter/nf_nat_masquerade.h>
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Netfilter Core Team <coreteam@netfilter.org>");
+MODULE_DESCRIPTION("Xtables: automatic-address SNAT");
+
+/* FIXME: Multiple targets. --RR */
+static int masquerade_tg_check(const struct xt_tgchk_param *par)
+{
+	const struct nf_nat_ipv4_multi_range_compat *mr = par->targinfo;
+
+	if (mr->range[0].flags & NF_NAT_RANGE_MAP_IPS) {
+		pr_debug("bad MAP_IPS.\n");
+		return -EINVAL;
+	}
+	if (mr->rangesize != 1) {
+		pr_debug("bad rangesize %u\n", mr->rangesize);
+		return -EINVAL;
+	}
+	return nf_ct_netns_get(par->net, par->family);
+}
+
+static unsigned int
+masquerade_tg(struct sk_buff *skb, const struct xt_action_param *par)
+{
+	struct nf_nat_range2 range;
+	const struct nf_nat_ipv4_multi_range_compat *mr;
+
+	mr = par->targinfo;
+	range.flags = mr->range[0].flags;
+	range.min_proto = mr->range[0].min;
+	range.max_proto = mr->range[0].max;
+
+	return nf_nat_masquerade_ipv4(skb, xt_hooknum(par), &range,
+				      xt_out(par));
+}
+
+static void masquerade_tg_destroy(const struct xt_tgdtor_param *par)
+{
+	nf_ct_netns_put(par->net, par->family);
+}
+
+#if IS_ENABLED(CONFIG_IPV6)
+static unsigned int
+masquerade_tg6(struct sk_buff *skb, const struct xt_action_param *par)
+{
+	return nf_nat_masquerade_ipv6(skb, par->targinfo, xt_out(par));
+}
+
+static int masquerade_tg6_checkentry(const struct xt_tgchk_param *par)
+{
+	const struct nf_nat_range2 *range = par->targinfo;
+
+	if (range->flags & NF_NAT_RANGE_MAP_IPS)
+		return -EINVAL;
+
+	return nf_ct_netns_get(par->net, par->family);
+}
+#endif
+
+static struct xt_target masquerade_tg_reg[] __read_mostly = {
+	{
+#if IS_ENABLED(CONFIG_IPV6)
+		.name		= "MASQUERADE",
+		.family		= NFPROTO_IPV6,
+		.target		= masquerade_tg6,
+		.targetsize	= sizeof(struct nf_nat_range),
+		.table		= "nat",
+		.hooks		= 1 << NF_INET_POST_ROUTING,
+		.checkentry	= masquerade_tg6_checkentry,
+		.destroy	= masquerade_tg_destroy,
+		.me		= THIS_MODULE,
+	}, {
+#endif
+		.name		= "MASQUERADE",
+		.family		= NFPROTO_IPV4,
+		.target		= masquerade_tg,
+		.targetsize	= sizeof(struct nf_nat_ipv4_multi_range_compat),
+		.table		= "nat",
+		.hooks		= 1 << NF_INET_POST_ROUTING,
+		.checkentry	= masquerade_tg_check,
+		.destroy	= masquerade_tg_destroy,
+		.me		= THIS_MODULE,
+	}
+};
+
+static int __init masquerade_tg_init(void)
+{
+	int ret;
+
+	ret = xt_register_targets(masquerade_tg_reg,
+				  ARRAY_SIZE(masquerade_tg_reg));
+	if (ret)
+		return ret;
+
+	ret = nf_nat_masquerade_ipv4_register_notifier();
+	if (ret) {
+		xt_unregister_targets(masquerade_tg_reg,
+				      ARRAY_SIZE(masquerade_tg_reg));
+		return ret;
+	}
+
+#if IS_ENABLED(CONFIG_IPV6)
+	ret = nf_nat_masquerade_ipv6_register_notifier();
+	if (ret) {
+		xt_unregister_targets(masquerade_tg_reg,
+				      ARRAY_SIZE(masquerade_tg_reg));
+		nf_nat_masquerade_ipv4_unregister_notifier();
+		return ret;
+	}
+#endif
+	return ret;
+}
+
+static void __exit masquerade_tg_exit(void)
+{
+	xt_unregister_targets(masquerade_tg_reg, ARRAY_SIZE(masquerade_tg_reg));
+	nf_nat_masquerade_ipv4_unregister_notifier();
+#if IS_ENABLED(CONFIG_IPV6)
+	nf_nat_masquerade_ipv6_unregister_notifier();
+#endif
+}
+
+module_init(masquerade_tg_init);
+module_exit(masquerade_tg_exit);
+#if IS_ENABLED(CONFIG_IPV6)
+MODULE_ALIAS("ip6t_MASQUERADE");
+#endif
+MODULE_ALIAS("ipt_MASQUERADE");