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
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 /* Lock protects masq region inside conntrack */
31 static DEFINE_RWLOCK(masq_lock);
32
33 /* FIXME: Multiple targets. --RR */
34 static bool
35 masquerade_tg_check(const char *tablename, const void *e,
36 const struct xt_target *target, void *targinfo,
37 unsigned int hook_mask)
38 {
39 const struct nf_nat_multi_range_compat *mr = targinfo;
40
41 if (mr->range[0].flags & IP_NAT_RANGE_MAP_IPS) {
42 pr_debug("masquerade_check: bad MAP_IPS.\n");
43 return false;
44 }
45 if (mr->rangesize != 1) {
46 pr_debug("masquerade_check: bad rangesize %u\n", mr->rangesize);
47 return false;
48 }
49 return true;
50 }
51
52 static unsigned int
53 masquerade_tg(struct sk_buff *skb, const struct net_device *in,
54 const struct net_device *out, unsigned int hooknum,
55 const struct xt_target *target, const void *targinfo)
56 {
57 struct nf_conn *ct;
58 struct nf_conn_nat *nat;
59 enum ip_conntrack_info ctinfo;
60 struct nf_nat_range newrange;
61 const struct nf_nat_multi_range_compat *mr;
62 const struct rtable *rt;
63 __be32 newsrc;
64
65 NF_CT_ASSERT(hooknum == NF_INET_POST_ROUTING);
66
67 ct = nf_ct_get(skb, &ctinfo);
68 nat = nfct_nat(ct);
69
70 NF_CT_ASSERT(ct && (ctinfo == IP_CT_NEW || ctinfo == IP_CT_RELATED
71 || ctinfo == IP_CT_RELATED + IP_CT_IS_REPLY));
72
73 /* Source address is 0.0.0.0 - locally generated packet that is
74 * probably not supposed to be masqueraded.
75 */
76 if (ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.src.u3.ip == 0)
77 return NF_ACCEPT;
78
79 mr = targinfo;
80 rt = (struct rtable *)skb->dst;
81 newsrc = inet_select_addr(out, rt->rt_gateway, RT_SCOPE_UNIVERSE);
82 if (!newsrc) {
83 printk("MASQUERADE: %s ate my IP address\n", out->name);
84 return NF_DROP;
85 }
86
87 write_lock_bh(&masq_lock);
88 nat->masq_index = out->ifindex;
89 write_unlock_bh(&masq_lock);
90
91 /* Transfer from original range. */
92 newrange = ((struct nf_nat_range)
93 { mr->range[0].flags | IP_NAT_RANGE_MAP_IPS,
94 newsrc, newsrc,
95 mr->range[0].min, mr->range[0].max });
96
97 /* Hand modified range to generic setup. */
98 return nf_nat_setup_info(ct, &newrange, IP_NAT_MANIP_SRC);
99 }
100
101 static int
102 device_cmp(struct nf_conn *i, void *ifindex)
103 {
104 const struct nf_conn_nat *nat = nfct_nat(i);
105 int ret;
106
107 if (!nat)
108 return 0;
109
110 read_lock_bh(&masq_lock);
111 ret = (nat->masq_index == (int)(long)ifindex);
112 read_unlock_bh(&masq_lock);
113
114 return ret;
115 }
116
117 static int masq_device_event(struct notifier_block *this,
118 unsigned long event,
119 void *ptr)
120 {
121 const struct net_device *dev = ptr;
122
123 if (dev->nd_net != &init_net)
124 return NOTIFY_DONE;
125
126 if (event == NETDEV_DOWN) {
127 /* Device was downed. Search entire table for
128 conntracks which were associated with that device,
129 and forget them. */
130 NF_CT_ASSERT(dev->ifindex != 0);
131
132 nf_ct_iterate_cleanup(device_cmp, (void *)(long)dev->ifindex);
133 }
134
135 return NOTIFY_DONE;
136 }
137
138 static int masq_inet_event(struct notifier_block *this,
139 unsigned long event,
140 void *ptr)
141 {
142 const struct net_device *dev = ((struct in_ifaddr *)ptr)->ifa_dev->dev;
143
144 if (event == NETDEV_DOWN) {
145 /* IP address was deleted. Search entire table for
146 conntracks which were associated with that device,
147 and forget them. */
148 NF_CT_ASSERT(dev->ifindex != 0);
149
150 nf_ct_iterate_cleanup(device_cmp, (void *)(long)dev->ifindex);
151 }
152
153 return NOTIFY_DONE;
154 }
155
156 static struct notifier_block masq_dev_notifier = {
157 .notifier_call = masq_device_event,
158 };
159
160 static struct notifier_block masq_inet_notifier = {
161 .notifier_call = masq_inet_event,
162 };
163
164 static struct xt_target masquerade_tg_reg __read_mostly = {
165 .name = "MASQUERADE",
166 .family = AF_INET,
167 .target = masquerade_tg,
168 .targetsize = sizeof(struct nf_nat_multi_range_compat),
169 .table = "nat",
170 .hooks = 1 << NF_INET_POST_ROUTING,
171 .checkentry = masquerade_tg_check,
172 .me = THIS_MODULE,
173 };
174
175 static int __init masquerade_tg_init(void)
176 {
177 int ret;
178
179 ret = xt_register_target(&masquerade_tg_reg);
180
181 if (ret == 0) {
182 /* Register for device down reports */
183 register_netdevice_notifier(&masq_dev_notifier);
184 /* Register IP address change reports */
185 register_inetaddr_notifier(&masq_inet_notifier);
186 }
187
188 return ret;
189 }
190
191 static void __exit masquerade_tg_exit(void)
192 {
193 xt_unregister_target(&masquerade_tg_reg);
194 unregister_netdevice_notifier(&masq_dev_notifier);
195 unregister_inetaddr_notifier(&masq_inet_notifier);
196 }
197
198 module_init(masquerade_tg_init);
199 module_exit(masquerade_tg_exit);
200
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