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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
26MODULE_LICENSE("GPL");
27MODULE_AUTHOR("Netfilter Core Team <coreteam@netfilter.org>");
28MODULE_DESCRIPTION("Xtables: automatic-address SNAT");
29
30
31static 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
46static unsigned int
47masquerade_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
66
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
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
92 return nf_nat_setup_info(ct, &newrange, NF_NAT_MANIP_SRC);
93}
94
95static int
96device_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
107static 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
116
117
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
127static 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
135static struct notifier_block masq_dev_notifier = {
136 .notifier_call = masq_device_event,
137};
138
139static struct notifier_block masq_inet_notifier = {
140 .notifier_call = masq_inet_event,
141};
142
143static 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
154static 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
162 register_netdevice_notifier(&masq_dev_notifier);
163
164 register_inetaddr_notifier(&masq_inet_notifier);
165 }
166
167 return ret;
168}
169
170static 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
177module_init(masquerade_tg_init);
178module_exit(masquerade_tg_exit);
179
