1 /* Masquerade. Simple mapping which alters range to a local IP address
2 (depending on route). */
3
4 /* (C) 1999-2001 Paul `Rusty' Russell
5 * (C) 2002-2006 Netfilter Core Team <coreteam@netfilter.org>
6 *
7 * This program is free software; you can redistribute it and/or modify
8 * it under the terms of the GNU General Public License version 2 as
9 * published by the Free Software Foundation.
10 */
11 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
12 #include <linux/types.h>
13 #include <linux/inetdevice.h>
14 #include <linux/ip.h>
15 #include <linux/timer.h>
16 #include <linux/module.h>
17 #include <linux/netfilter.h>
18 #include <net/protocol.h>
19 #include <net/ip.h>
20 #include <net/checksum.h>
21 #include <net/route.h>
22 #include <net/netfilter/nf_nat_rule.h>
23 #include <linux/netfilter_ipv4.h>
24 #include <linux/netfilter/x_tables.h>
25
26 MODULE_LICENSE("GPL");
27 MODULE_AUTHOR("Netfilter Core Team <coreteam@netfilter.org>");
28 MODULE_DESCRIPTION("Xtables: automatic-address SNAT");
29
30 /* FIXME: Multiple targets. --RR */
masquerade_tg_check(const struct xt_tgchk_param * par)31 static int masquerade_tg_check(const struct xt_tgchk_param *par)
32 {
33 const struct nf_nat_multi_range_compat *mr = par->targinfo;
34
35 if (mr->range[0].flags & IP_NAT_RANGE_MAP_IPS) {
36 pr_debug("bad MAP_IPS.\n");
37 return -EINVAL;
38 }
39 if (mr->rangesize != 1) {
40 pr_debug("bad rangesize %u\n", mr->rangesize);
41 return -EINVAL;
42 }
43 return 0;
44 }
45
46 static unsigned int
masquerade_tg(struct sk_buff * skb,const struct xt_action_param * par)47 masquerade_tg(struct sk_buff *skb, const struct xt_action_param *par)
48 {
49 struct nf_conn *ct;
50 struct nf_conn_nat *nat;
51 enum ip_conntrack_info ctinfo;
52 struct nf_nat_range newrange;
53 const struct nf_nat_multi_range_compat *mr;
54 const struct rtable *rt;
55 __be32 newsrc;
56
57 NF_CT_ASSERT(par->hooknum == NF_INET_POST_ROUTING);
58
59 ct = nf_ct_get(skb, &ctinfo);
60 nat = nfct_nat(ct);
61
62 NF_CT_ASSERT(ct && (ctinfo == IP_CT_NEW || ctinfo == IP_CT_RELATED ||
63 ctinfo == IP_CT_RELATED + IP_CT_IS_REPLY));
64
65 /* Source address is 0.0.0.0 - locally generated packet that is
66 * probably not supposed to be masqueraded.
67 */
68 if (ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.src.u3.ip == 0)
69 return NF_ACCEPT;
70
71 mr = par->targinfo;
72 rt = skb_rtable(skb);
73 newsrc = inet_select_addr(par->out, rt->rt_gateway, RT_SCOPE_UNIVERSE);
74 if (!newsrc) {
75 pr_info("%s ate my IP address\n", par->out->name);
76 return NF_DROP;
77 }
78
79 nat->masq_index = par->out->ifindex;
80
81 /* Transfer from original range. */
82 newrange = ((struct nf_nat_range)
83 { mr->range[0].flags | IP_NAT_RANGE_MAP_IPS,
84 newsrc, newsrc,
85 mr->range[0].min, mr->range[0].max });
86
87 /* Hand modified range to generic setup. */
88 return nf_nat_setup_info(ct, &newrange, IP_NAT_MANIP_SRC);
89 }
90
91 static int
device_cmp(struct nf_conn * i,void * ifindex)92 device_cmp(struct nf_conn *i, void *ifindex)
93 {
94 const struct nf_conn_nat *nat = nfct_nat(i);
95
96 if (!nat)
97 return 0;
98
99 return nat->masq_index == (int)(long)ifindex;
100 }
101
masq_device_event(struct notifier_block * this,unsigned long event,void * ptr)102 static int masq_device_event(struct notifier_block *this,
103 unsigned long event,
104 void *ptr)
105 {
106 const struct net_device *dev = ptr;
107 struct net *net = dev_net(dev);
108
109 if (event == NETDEV_DOWN) {
110 /* Device was downed. Search entire table for
111 conntracks which were associated with that device,
112 and forget them. */
113 NF_CT_ASSERT(dev->ifindex != 0);
114
115 nf_ct_iterate_cleanup(net, device_cmp,
116 (void *)(long)dev->ifindex);
117 }
118
119 return NOTIFY_DONE;
120 }
121
masq_inet_event(struct notifier_block * this,unsigned long event,void * ptr)122 static int masq_inet_event(struct notifier_block *this,
123 unsigned long event,
124 void *ptr)
125 {
126 struct net_device *dev = ((struct in_ifaddr *)ptr)->ifa_dev->dev;
127 return masq_device_event(this, event, dev);
128 }
129
130 static struct notifier_block masq_dev_notifier = {
131 .notifier_call = masq_device_event,
132 };
133
134 static struct notifier_block masq_inet_notifier = {
135 .notifier_call = masq_inet_event,
136 };
137
138 static struct xt_target masquerade_tg_reg __read_mostly = {
139 .name = "MASQUERADE",
140 .family = NFPROTO_IPV4,
141 .target = masquerade_tg,
142 .targetsize = sizeof(struct nf_nat_multi_range_compat),
143 .table = "nat",
144 .hooks = 1 << NF_INET_POST_ROUTING,
145 .checkentry = masquerade_tg_check,
146 .me = THIS_MODULE,
147 };
148
masquerade_tg_init(void)149 static int __init masquerade_tg_init(void)
150 {
151 int ret;
152
153 ret = xt_register_target(&masquerade_tg_reg);
154
155 if (ret == 0) {
156 /* Register for device down reports */
157 register_netdevice_notifier(&masq_dev_notifier);
158 /* Register IP address change reports */
159 register_inetaddr_notifier(&masq_inet_notifier);
160 }
161
162 return ret;
163 }
164
masquerade_tg_exit(void)165 static void __exit masquerade_tg_exit(void)
166 {
167 xt_unregister_target(&masquerade_tg_reg);
168 unregister_netdevice_notifier(&masq_dev_notifier);
169 unregister_inetaddr_notifier(&masq_inet_notifier);
170 }
171
172 module_init(masquerade_tg_init);
173 module_exit(masquerade_tg_exit);
174