1 /* NETMAP - static NAT mapping of IP network addresses (1:1).
2 * The mapping can be applied to source (POSTROUTING),
3 * destination (PREROUTING), or both (with separate rules).
6 /* (C) 2000-2001 Svenning Soerensen <svenning@post5.tele.dk>
8 * This program is free software; you can redistribute it and/or modify
9 * it under the terms of the GNU General Public License version 2 as
10 * published by the Free Software Foundation.
14 #include <linux/module.h>
15 #include <linux/netdevice.h>
16 #include <linux/netfilter.h>
17 #include <linux/netfilter_ipv4.h>
18 #include <linux/netfilter/x_tables.h>
19 #include <net/netfilter/nf_nat_rule.h>
21 MODULE_LICENSE("GPL");
22 MODULE_AUTHOR("Svenning Soerensen <svenning@post5.tele.dk>");
23 MODULE_DESCRIPTION("iptables 1:1 NAT mapping of IP networks target");
26 check(const char *tablename,
28 const struct xt_target *target,
30 unsigned int hook_mask)
32 const struct nf_nat_multi_range_compat *mr = targinfo;
34 if (!(mr->range[0].flags & IP_NAT_RANGE_MAP_IPS)) {
35 pr_debug("NETMAP:check: bad MAP_IPS.\n");
38 if (mr->rangesize != 1) {
39 pr_debug("NETMAP:check: bad rangesize %u.\n", mr->rangesize);
46 target(struct sk_buff **pskb,
47 const struct net_device *in,
48 const struct net_device *out,
50 const struct xt_target *target,
54 enum ip_conntrack_info ctinfo;
55 __be32 new_ip, netmask;
56 const struct nf_nat_multi_range_compat *mr = targinfo;
57 struct nf_nat_range newrange;
59 NF_CT_ASSERT(hooknum == NF_IP_PRE_ROUTING
60 || hooknum == NF_IP_POST_ROUTING
61 || hooknum == NF_IP_LOCAL_OUT);
62 ct = nf_ct_get(*pskb, &ctinfo);
64 netmask = ~(mr->range[0].min_ip ^ mr->range[0].max_ip);
66 if (hooknum == NF_IP_PRE_ROUTING || hooknum == NF_IP_LOCAL_OUT)
67 new_ip = ip_hdr(*pskb)->daddr & ~netmask;
69 new_ip = ip_hdr(*pskb)->saddr & ~netmask;
70 new_ip |= mr->range[0].min_ip & netmask;
72 newrange = ((struct nf_nat_range)
73 { mr->range[0].flags | IP_NAT_RANGE_MAP_IPS,
75 mr->range[0].min, mr->range[0].max });
77 /* Hand modified range to generic setup. */
78 return nf_nat_setup_info(ct, &newrange, hooknum);
81 static struct xt_target target_module __read_mostly = {
85 .targetsize = sizeof(struct nf_nat_multi_range_compat),
87 .hooks = (1 << NF_IP_PRE_ROUTING) | (1 << NF_IP_POST_ROUTING) |
88 (1 << NF_IP_LOCAL_OUT),
93 static int __init ipt_netmap_init(void)
95 return xt_register_target(&target_module);
98 static void __exit ipt_netmap_fini(void)
100 xt_unregister_target(&target_module);
103 module_init(ipt_netmap_init);
104 module_exit(ipt_netmap_fini);