1 /* (C) 1999-2001 Paul `Rusty' Russell
2 * (C) 2002-2006 Netfilter Core Team <coreteam@netfilter.org>
3 *
4 * This program is free software; you can redistribute it and/or modify
5 * it under the terms of the GNU General Public License version 2 as
6 * published by the Free Software Foundation.
7 */
8
9 /* Everything about the rules for NAT. */
10 #include <linux/types.h>
11 #include <linux/ip.h>
12 #include <linux/netfilter.h>
13 #include <linux/netfilter_ipv4.h>
14 #include <linux/module.h>
15 #include <linux/kmod.h>
16 #include <linux/skbuff.h>
17 #include <linux/proc_fs.h>
18 #include <net/checksum.h>
19 #include <net/route.h>
20 #include <linux/bitops.h>
21
22 #include <linux/netfilter_ipv4/ip_tables.h>
23 #include <net/netfilter/nf_nat.h>
24 #include <net/netfilter/nf_nat_core.h>
25 #include <net/netfilter/nf_nat_rule.h>
26
27 #define NAT_VALID_HOOKS ((1 << NF_INET_PRE_ROUTING) | \
28 (1 << NF_INET_POST_ROUTING) | \
29 (1 << NF_INET_LOCAL_OUT))
30
31 static struct
32 {
33 struct ipt_replace repl;
34 struct ipt_standard entries[3];
35 struct ipt_error term;
36 } nat_initial_table __initdata = {
37 .repl = {
38 .name = "nat",
39 .valid_hooks = NAT_VALID_HOOKS,
40 .num_entries = 4,
41 .size = sizeof(struct ipt_standard) * 3 + sizeof(struct ipt_error),
42 .hook_entry = {
43 [NF_INET_PRE_ROUTING] = 0,
44 [NF_INET_POST_ROUTING] = sizeof(struct ipt_standard),
45 [NF_INET_LOCAL_OUT] = sizeof(struct ipt_standard) * 2
46 },
47 .underflow = {
48 [NF_INET_PRE_ROUTING] = 0,
49 [NF_INET_POST_ROUTING] = sizeof(struct ipt_standard),
50 [NF_INET_LOCAL_OUT] = sizeof(struct ipt_standard) * 2
51 },
52 },
53 .entries = {
54 IPT_STANDARD_INIT(NF_ACCEPT), /* PRE_ROUTING */
55 IPT_STANDARD_INIT(NF_ACCEPT), /* POST_ROUTING */
56 IPT_STANDARD_INIT(NF_ACCEPT), /* LOCAL_OUT */
57 },
58 .term = IPT_ERROR_INIT, /* ERROR */
59 };
60
61 static struct xt_table __nat_table = {
62 .name = "nat",
63 .valid_hooks = NAT_VALID_HOOKS,
64 .lock = RW_LOCK_UNLOCKED,
65 .me = THIS_MODULE,
66 .af = AF_INET,
67 };
68 static struct xt_table *nat_table;
69
70 /* Source NAT */
71 static unsigned int ipt_snat_target(struct sk_buff *skb,
72 const struct net_device *in,
73 const struct net_device *out,
74 unsigned int hooknum,
75 const struct xt_target *target,
76 const void *targinfo)
77 {
78 struct nf_conn *ct;
79 enum ip_conntrack_info ctinfo;
80 const struct nf_nat_multi_range_compat *mr = targinfo;
81
82 NF_CT_ASSERT(hooknum == NF_INET_POST_ROUTING);
83
84 ct = nf_ct_get(skb, &ctinfo);
85
86 /* Connection must be valid and new. */
87 NF_CT_ASSERT(ct && (ctinfo == IP_CT_NEW || ctinfo == IP_CT_RELATED ||
88 ctinfo == IP_CT_RELATED + IP_CT_IS_REPLY));
89 NF_CT_ASSERT(out);
90
91 return nf_nat_setup_info(ct, &mr->range[0], IP_NAT_MANIP_SRC);
92 }
93
94 /* Before 2.6.11 we did implicit source NAT if required. Warn about change. */
95 static void warn_if_extra_mangle(__be32 dstip, __be32 srcip)
96 {
97 static int warned = 0;
98 struct flowi fl = { .nl_u = { .ip4_u = { .daddr = dstip } } };
99 struct rtable *rt;
100
101 if (ip_route_output_key(&init_net, &rt, &fl) != 0)
102 return;
103
104 if (rt->rt_src != srcip && !warned) {
105 printk("NAT: no longer support implicit source local NAT\n");
106 printk("NAT: packet src %u.%u.%u.%u -> dst %u.%u.%u.%u\n",
107 NIPQUAD(srcip), NIPQUAD(dstip));
108 warned = 1;
109 }
110 ip_rt_put(rt);
111 }
112
113 static unsigned int ipt_dnat_target(struct sk_buff *skb,
114 const struct net_device *in,
115 const struct net_device *out,
116 unsigned int hooknum,
117 const struct xt_target *target,
118 const void *targinfo)
119 {
120 struct nf_conn *ct;
121 enum ip_conntrack_info ctinfo;
122 const struct nf_nat_multi_range_compat *mr = targinfo;
123
124 NF_CT_ASSERT(hooknum == NF_INET_PRE_ROUTING ||
125 hooknum == NF_INET_LOCAL_OUT);
126
127 ct = nf_ct_get(skb, &ctinfo);
128
129 /* Connection must be valid and new. */
130 NF_CT_ASSERT(ct && (ctinfo == IP_CT_NEW || ctinfo == IP_CT_RELATED));
131
132 if (hooknum == NF_INET_LOCAL_OUT &&
133 mr->range[0].flags & IP_NAT_RANGE_MAP_IPS)
134 warn_if_extra_mangle(ip_hdr(skb)->daddr,
135 mr->range[0].min_ip);
136
137 return nf_nat_setup_info(ct, &mr->range[0], IP_NAT_MANIP_DST);
138 }
139
140 static bool ipt_snat_checkentry(const char *tablename,
141 const void *entry,
142 const struct xt_target *target,
143 void *targinfo,
144 unsigned int hook_mask)
145 {
146 struct nf_nat_multi_range_compat *mr = targinfo;
147
148 /* Must be a valid range */
149 if (mr->rangesize != 1) {
150 printk("SNAT: multiple ranges no longer supported\n");
151 return false;
152 }
153 return true;
154 }
155
156 static bool ipt_dnat_checkentry(const char *tablename,
157 const void *entry,
158 const struct xt_target *target,
159 void *targinfo,
160 unsigned int hook_mask)
161 {
162 struct nf_nat_multi_range_compat *mr = targinfo;
163
164 /* Must be a valid range */
165 if (mr->rangesize != 1) {
166 printk("DNAT: multiple ranges no longer supported\n");
167 return false;
168 }
169 return true;
170 }
171
172 unsigned int
173 alloc_null_binding(struct nf_conn *ct, unsigned int hooknum)
174 {
175 /* Force range to this IP; let proto decide mapping for
176 per-proto parts (hence not IP_NAT_RANGE_PROTO_SPECIFIED).
177 Use reply in case it's already been mangled (eg local packet).
178 */
179 __be32 ip
180 = (HOOK2MANIP(hooknum) == IP_NAT_MANIP_SRC
181 ? ct->tuplehash[IP_CT_DIR_REPLY].tuple.dst.u3.ip
182 : ct->tuplehash[IP_CT_DIR_REPLY].tuple.src.u3.ip);
183 struct nf_nat_range range
184 = { IP_NAT_RANGE_MAP_IPS, ip, ip, { 0 }, { 0 } };
185
186 pr_debug("Allocating NULL binding for %p (%u.%u.%u.%u)\n",
187 ct, NIPQUAD(ip));
188 return nf_nat_setup_info(ct, &range, HOOK2MANIP(hooknum));
189 }
190
191 unsigned int
192 alloc_null_binding_confirmed(struct nf_conn *ct, unsigned int hooknum)
193 {
194 __be32 ip
195 = (HOOK2MANIP(hooknum) == IP_NAT_MANIP_SRC
196 ? ct->tuplehash[IP_CT_DIR_REPLY].tuple.dst.u3.ip
197 : ct->tuplehash[IP_CT_DIR_REPLY].tuple.src.u3.ip);
198 __be16 all
199 = (HOOK2MANIP(hooknum) == IP_NAT_MANIP_SRC
200 ? ct->tuplehash[IP_CT_DIR_REPLY].tuple.dst.u.all
201 : ct->tuplehash[IP_CT_DIR_REPLY].tuple.src.u.all);
202 struct nf_nat_range range
203 = { IP_NAT_RANGE_MAP_IPS, ip, ip, { all }, { all } };
204
205 pr_debug("Allocating NULL binding for confirmed %p (%u.%u.%u.%u)\n",
206 ct, NIPQUAD(ip));
207 return nf_nat_setup_info(ct, &range, HOOK2MANIP(hooknum));
208 }
209
210 int nf_nat_rule_find(struct sk_buff *skb,
211 unsigned int hooknum,
212 const struct net_device *in,
213 const struct net_device *out,
214 struct nf_conn *ct)
215 {
216 int ret;
217
218 ret = ipt_do_table(skb, hooknum, in, out, nat_table);
219
220 if (ret == NF_ACCEPT) {
221 if (!nf_nat_initialized(ct, HOOK2MANIP(hooknum)))
222 /* NUL mapping */
223 ret = alloc_null_binding(ct, hooknum);
224 }
225 return ret;
226 }
227
228 static struct xt_target ipt_snat_reg __read_mostly = {
229 .name = "SNAT",
230 .target = ipt_snat_target,
231 .targetsize = sizeof(struct nf_nat_multi_range_compat),
232 .table = "nat",
233 .hooks = 1 << NF_INET_POST_ROUTING,
234 .checkentry = ipt_snat_checkentry,
235 .family = AF_INET,
236 };
237
238 static struct xt_target ipt_dnat_reg __read_mostly = {
239 .name = "DNAT",
240 .target = ipt_dnat_target,
241 .targetsize = sizeof(struct nf_nat_multi_range_compat),
242 .table = "nat",
243 .hooks = (1 << NF_INET_PRE_ROUTING) | (1 << NF_INET_LOCAL_OUT),
244 .checkentry = ipt_dnat_checkentry,
245 .family = AF_INET,
246 };
247
248 int __init nf_nat_rule_init(void)
249 {
250 int ret;
251
252 nat_table = ipt_register_table(&init_net, &__nat_table,
253 &nat_initial_table.repl);
254 if (IS_ERR(nat_table))
255 return PTR_ERR(nat_table);
256 ret = xt_register_target(&ipt_snat_reg);
257 if (ret != 0)
258 goto unregister_table;
259
260 ret = xt_register_target(&ipt_dnat_reg);
261 if (ret != 0)
262 goto unregister_snat;
263
264 return ret;
265
266 unregister_snat:
267 xt_unregister_target(&ipt_snat_reg);
268 unregister_table:
269 ipt_unregister_table(nat_table);
270
271 return ret;
272 }
273
274 void nf_nat_rule_cleanup(void)
275 {
276 xt_unregister_target(&ipt_dnat_reg);
277 xt_unregister_target(&ipt_snat_reg);
278 ipt_unregister_table(nat_table);
279 }
280
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