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1da177e4 LT |
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) 2002-2004 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/config.h> | |
13 | #include <linux/types.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 <linux/netfilter_ipv4.h> | |
22 | #include <linux/netfilter_ipv4/ip_nat_rule.h> | |
23 | #include <linux/netfilter_ipv4/ip_tables.h> | |
24 | ||
25 | MODULE_LICENSE("GPL"); | |
26 | MODULE_AUTHOR("Netfilter Core Team <coreteam@netfilter.org>"); | |
27 | MODULE_DESCRIPTION("iptables MASQUERADE target module"); | |
28 | ||
29 | #if 0 | |
30 | #define DEBUGP printk | |
31 | #else | |
32 | #define DEBUGP(format, args...) | |
33 | #endif | |
34 | ||
35 | /* Lock protects masq region inside conntrack */ | |
e45b1be8 | 36 | static DEFINE_RWLOCK(masq_lock); |
1da177e4 LT |
37 | |
38 | /* FIXME: Multiple targets. --RR */ | |
39 | static int | |
40 | masquerade_check(const char *tablename, | |
41 | const struct ipt_entry *e, | |
42 | void *targinfo, | |
43 | unsigned int targinfosize, | |
44 | unsigned int hook_mask) | |
45 | { | |
46 | const struct ip_nat_multi_range_compat *mr = targinfo; | |
47 | ||
48 | if (strcmp(tablename, "nat") != 0) { | |
49 | DEBUGP("masquerade_check: bad table `%s'.\n", tablename); | |
50 | return 0; | |
51 | } | |
52 | if (targinfosize != IPT_ALIGN(sizeof(*mr))) { | |
53 | DEBUGP("masquerade_check: size %u != %u.\n", | |
54 | targinfosize, sizeof(*mr)); | |
55 | return 0; | |
56 | } | |
57 | if (hook_mask & ~(1 << NF_IP_POST_ROUTING)) { | |
58 | DEBUGP("masquerade_check: bad hooks %x.\n", hook_mask); | |
59 | return 0; | |
60 | } | |
61 | if (mr->range[0].flags & IP_NAT_RANGE_MAP_IPS) { | |
62 | DEBUGP("masquerade_check: bad MAP_IPS.\n"); | |
63 | return 0; | |
64 | } | |
65 | if (mr->rangesize != 1) { | |
66 | DEBUGP("masquerade_check: bad rangesize %u.\n", mr->rangesize); | |
67 | return 0; | |
68 | } | |
69 | return 1; | |
70 | } | |
71 | ||
72 | static unsigned int | |
73 | masquerade_target(struct sk_buff **pskb, | |
74 | const struct net_device *in, | |
75 | const struct net_device *out, | |
76 | unsigned int hooknum, | |
77 | const void *targinfo, | |
78 | void *userinfo) | |
79 | { | |
80 | struct ip_conntrack *ct; | |
81 | enum ip_conntrack_info ctinfo; | |
82 | const struct ip_nat_multi_range_compat *mr; | |
83 | struct ip_nat_range newrange; | |
84 | struct rtable *rt; | |
85 | u_int32_t newsrc; | |
86 | ||
87 | IP_NF_ASSERT(hooknum == NF_IP_POST_ROUTING); | |
88 | ||
1da177e4 LT |
89 | ct = ip_conntrack_get(*pskb, &ctinfo); |
90 | IP_NF_ASSERT(ct && (ctinfo == IP_CT_NEW || ctinfo == IP_CT_RELATED | |
91 | || ctinfo == IP_CT_RELATED + IP_CT_IS_REPLY)); | |
92 | ||
adcb5ad1 PM |
93 | /* Source address is 0.0.0.0 - locally generated packet that is |
94 | * probably not supposed to be masqueraded. | |
95 | */ | |
96 | if (ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.src.ip == 0) | |
97 | return NF_ACCEPT; | |
98 | ||
1da177e4 LT |
99 | mr = targinfo; |
100 | rt = (struct rtable *)(*pskb)->dst; | |
101 | newsrc = inet_select_addr(out, rt->rt_gateway, RT_SCOPE_UNIVERSE); | |
102 | if (!newsrc) { | |
103 | printk("MASQUERADE: %s ate my IP address\n", out->name); | |
104 | return NF_DROP; | |
105 | } | |
106 | ||
e45b1be8 | 107 | write_lock_bh(&masq_lock); |
1da177e4 | 108 | ct->nat.masq_index = out->ifindex; |
e45b1be8 | 109 | write_unlock_bh(&masq_lock); |
1da177e4 LT |
110 | |
111 | /* Transfer from original range. */ | |
112 | newrange = ((struct ip_nat_range) | |
113 | { mr->range[0].flags | IP_NAT_RANGE_MAP_IPS, | |
114 | newsrc, newsrc, | |
115 | mr->range[0].min, mr->range[0].max }); | |
116 | ||
117 | /* Hand modified range to generic setup. */ | |
118 | return ip_nat_setup_info(ct, &newrange, hooknum); | |
119 | } | |
120 | ||
121 | static inline int | |
122 | device_cmp(struct ip_conntrack *i, void *ifindex) | |
123 | { | |
124 | int ret; | |
125 | ||
e45b1be8 | 126 | read_lock_bh(&masq_lock); |
1da177e4 | 127 | ret = (i->nat.masq_index == (int)(long)ifindex); |
e45b1be8 | 128 | read_unlock_bh(&masq_lock); |
1da177e4 LT |
129 | |
130 | return ret; | |
131 | } | |
132 | ||
133 | static int masq_device_event(struct notifier_block *this, | |
134 | unsigned long event, | |
135 | void *ptr) | |
136 | { | |
137 | struct net_device *dev = ptr; | |
138 | ||
139 | if (event == NETDEV_DOWN) { | |
140 | /* Device was downed. Search entire table for | |
141 | conntracks which were associated with that device, | |
142 | and forget them. */ | |
143 | IP_NF_ASSERT(dev->ifindex != 0); | |
144 | ||
145 | ip_ct_iterate_cleanup(device_cmp, (void *)(long)dev->ifindex); | |
146 | } | |
147 | ||
148 | return NOTIFY_DONE; | |
149 | } | |
150 | ||
151 | static int masq_inet_event(struct notifier_block *this, | |
152 | unsigned long event, | |
153 | void *ptr) | |
154 | { | |
155 | struct net_device *dev = ((struct in_ifaddr *)ptr)->ifa_dev->dev; | |
156 | ||
157 | if (event == NETDEV_DOWN) { | |
158 | /* IP address was deleted. Search entire table for | |
159 | conntracks which were associated with that device, | |
160 | and forget them. */ | |
161 | IP_NF_ASSERT(dev->ifindex != 0); | |
162 | ||
163 | ip_ct_iterate_cleanup(device_cmp, (void *)(long)dev->ifindex); | |
164 | } | |
165 | ||
166 | return NOTIFY_DONE; | |
167 | } | |
168 | ||
169 | static struct notifier_block masq_dev_notifier = { | |
170 | .notifier_call = masq_device_event, | |
171 | }; | |
172 | ||
173 | static struct notifier_block masq_inet_notifier = { | |
174 | .notifier_call = masq_inet_event, | |
175 | }; | |
176 | ||
177 | static struct ipt_target masquerade = { | |
178 | .name = "MASQUERADE", | |
179 | .target = masquerade_target, | |
180 | .checkentry = masquerade_check, | |
181 | .me = THIS_MODULE, | |
182 | }; | |
183 | ||
184 | static int __init init(void) | |
185 | { | |
186 | int ret; | |
187 | ||
188 | ret = ipt_register_target(&masquerade); | |
189 | ||
190 | if (ret == 0) { | |
191 | /* Register for device down reports */ | |
192 | register_netdevice_notifier(&masq_dev_notifier); | |
193 | /* Register IP address change reports */ | |
194 | register_inetaddr_notifier(&masq_inet_notifier); | |
195 | } | |
196 | ||
197 | return ret; | |
198 | } | |
199 | ||
200 | static void __exit fini(void) | |
201 | { | |
202 | ipt_unregister_target(&masquerade); | |
203 | unregister_netdevice_notifier(&masq_dev_notifier); | |
204 | unregister_inetaddr_notifier(&masq_inet_notifier); | |
205 | } | |
206 | ||
207 | module_init(init); | |
208 | module_exit(fini); |