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 <linux/netfilter_ipv4.h>
23 #include <linux/netfilter/x_tables.h>
24 #include <net/netfilter/nf_nat.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_ipv4_multi_range_compat *mr = par->targinfo;
34
35 if (mr->range[0].flags & NF_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_ipv4_multi_range_compat *mr;
54 const struct rtable *rt;
55 __be32 newsrc, nh;
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_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 nh = rt_nexthop(rt, ip_hdr(skb)->daddr);
74 newsrc = inet_select_addr(par->out, nh, RT_SCOPE_UNIVERSE);
75 if (!newsrc) {
76 pr_info("%s ate my IP address\n", par->out->name);
77 return NF_DROP;
78 }
79
80 nat->masq_index = par->out->ifindex;
81
82 /* Transfer from original range. */
83 memset(&newrange.min_addr, 0, sizeof(newrange.min_addr));
84 memset(&newrange.max_addr, 0, sizeof(newrange.max_addr));
85 newrange.flags = mr->range[0].flags | NF_NAT_RANGE_MAP_IPS;
86 newrange.min_addr.ip = newsrc;
87 newrange.max_addr.ip = newsrc;
88 newrange.min_proto = mr->range[0].min;
89 newrange.max_proto = mr->range[0].max;
90
91 /* Hand modified range to generic setup. */
92 return nf_nat_setup_info(ct, &newrange, NF_NAT_MANIP_SRC);
93 }
94
95 static int
device_cmp(struct nf_conn * i,void * ifindex)96 device_cmp(struct nf_conn *i, void *ifindex)
97 {
98 const struct nf_conn_nat *nat = nfct_nat(i);
99
100 if (!nat)
101 return 0;
102 if (nf_ct_l3num(i) != NFPROTO_IPV4)
103 return 0;
104 return nat->masq_index == (int)(long)ifindex;
105 }
106
masq_device_event(struct notifier_block * this,unsigned long event,void * ptr)107 static int masq_device_event(struct notifier_block *this,
108 unsigned long event,
109 void *ptr)
110 {
111 const struct net_device *dev = ptr;
112 struct net *net = dev_net(dev);
113
114 if (event == NETDEV_DOWN) {
115 /* Device was downed. Search entire table for
116 conntracks which were associated with that device,
117 and forget them. */
118 NF_CT_ASSERT(dev->ifindex != 0);
119
120 nf_ct_iterate_cleanup(net, device_cmp,
121 (void *)(long)dev->ifindex);
122 }
123
124 return NOTIFY_DONE;
125 }
126
masq_inet_event(struct notifier_block * this,unsigned long event,void * ptr)127 static int masq_inet_event(struct notifier_block *this,
128 unsigned long event,
129 void *ptr)
130 {
131 struct net_device *dev = ((struct in_ifaddr *)ptr)->ifa_dev->dev;
132 return masq_device_event(this, event, dev);
133 }
134
135 static struct notifier_block masq_dev_notifier = {
136 .notifier_call = masq_device_event,
137 };
138
139 static struct notifier_block masq_inet_notifier = {
140 .notifier_call = masq_inet_event,
141 };
142
143 static struct xt_target masquerade_tg_reg __read_mostly = {
144 .name = "MASQUERADE",
145 .family = NFPROTO_IPV4,
146 .target = masquerade_tg,
147 .targetsize = sizeof(struct nf_nat_ipv4_multi_range_compat),
148 .table = "nat",
149 .hooks = 1 << NF_INET_POST_ROUTING,
150 .checkentry = masquerade_tg_check,
151 .me = THIS_MODULE,
152 };
153
masquerade_tg_init(void)154 static int __init masquerade_tg_init(void)
155 {
156 int ret;
157
158 ret = xt_register_target(&masquerade_tg_reg);
159
160 if (ret == 0) {
161 /* Register for device down reports */
162 register_netdevice_notifier(&masq_dev_notifier);
163 /* Register IP address change reports */
164 register_inetaddr_notifier(&masq_inet_notifier);
165 }
166
167 return ret;
168 }
169
masquerade_tg_exit(void)170 static void __exit masquerade_tg_exit(void)
171 {
172 xt_unregister_target(&masquerade_tg_reg);
173 unregister_netdevice_notifier(&masq_dev_notifier);
174 unregister_inetaddr_notifier(&masq_inet_notifier);
175 }
176
177 module_init(masquerade_tg_init);
178 module_exit(masquerade_tg_exit);
179