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1 /*
2 * Stateless NAT actions
3 *
4 * Copyright (c) 2007 Herbert Xu <herbert@gondor.apana.org.au>
5 *
6 * This program is free software; you can redistribute it and/or modify it
7 * under the terms of the GNU General Public License as published by the Free
8 * Software Foundation; either version 2 of the License, or (at your option)
9 * any later version.
10 */
11
12 #include <linux/errno.h>
13 #include <linux/init.h>
14 #include <linux/kernel.h>
15 #include <linux/module.h>
16 #include <linux/netfilter.h>
17 #include <linux/rtnetlink.h>
18 #include <linux/skbuff.h>
19 #include <linux/slab.h>
20 #include <linux/spinlock.h>
21 #include <linux/string.h>
22 #include <linux/tc_act/tc_nat.h>
23 #include <net/act_api.h>
24 #include <net/icmp.h>
25 #include <net/ip.h>
26 #include <net/netlink.h>
27 #include <net/tc_act/tc_nat.h>
28 #include <net/tcp.h>
29 #include <net/udp.h>
30
31
32 #define NAT_TAB_MASK 15
33
34 static struct tcf_hashinfo nat_hash_info;
35
36 static const struct nla_policy nat_policy[TCA_NAT_MAX + 1] = {
37 [TCA_NAT_PARMS] = { .len = sizeof(struct tc_nat) },
38 };
39
40 static int tcf_nat_init(struct net *net, struct nlattr *nla, struct nlattr *est,
41 struct tc_action *a, int ovr, int bind)
42 {
43 struct nlattr *tb[TCA_NAT_MAX + 1];
44 struct tc_nat *parm;
45 int ret = 0, err;
46 struct tcf_nat *p;
47 struct tcf_common *pc;
48
49 if (nla == NULL)
50 return -EINVAL;
51
52 err = nla_parse_nested(tb, TCA_NAT_MAX, nla, nat_policy);
53 if (err < 0)
54 return err;
55
56 if (tb[TCA_NAT_PARMS] == NULL)
57 return -EINVAL;
58 parm = nla_data(tb[TCA_NAT_PARMS]);
59
60 pc = tcf_hash_check(parm->index, a, bind);
61 if (!pc) {
62 pc = tcf_hash_create(parm->index, est, a, sizeof(*p), bind);
63 if (IS_ERR(pc))
64 return PTR_ERR(pc);
65 ret = ACT_P_CREATED;
66 } else {
67 if (bind)
68 return 0;
69 tcf_hash_release(pc, bind, a->ops->hinfo);
70 if (!ovr)
71 return -EEXIST;
72 }
73 p = to_tcf_nat(pc);
74
75 spin_lock_bh(&p->tcf_lock);
76 p->old_addr = parm->old_addr;
77 p->new_addr = parm->new_addr;
78 p->mask = parm->mask;
79 p->flags = parm->flags;
80
81 p->tcf_action = parm->action;
82 spin_unlock_bh(&p->tcf_lock);
83
84 if (ret == ACT_P_CREATED)
85 tcf_hash_insert(pc, a->ops->hinfo);
86
87 return ret;
88 }
89
90 static int tcf_nat_cleanup(struct tc_action *a, int bind)
91 {
92 struct tcf_nat *p = a->priv;
93
94 return tcf_hash_release(&p->common, bind, &nat_hash_info);
95 }
96
97 static int tcf_nat(struct sk_buff *skb, const struct tc_action *a,
98 struct tcf_result *res)
99 {
100 struct tcf_nat *p = a->priv;
101 struct iphdr *iph;
102 __be32 old_addr;
103 __be32 new_addr;
104 __be32 mask;
105 __be32 addr;
106 int egress;
107 int action;
108 int ihl;
109 int noff;
110
111 spin_lock(&p->tcf_lock);
112
113 p->tcf_tm.lastuse = jiffies;
114 old_addr = p->old_addr;
115 new_addr = p->new_addr;
116 mask = p->mask;
117 egress = p->flags & TCA_NAT_FLAG_EGRESS;
118 action = p->tcf_action;
119
120 bstats_update(&p->tcf_bstats, skb);
121
122 spin_unlock(&p->tcf_lock);
123
124 if (unlikely(action == TC_ACT_SHOT))
125 goto drop;
126
127 noff = skb_network_offset(skb);
128 if (!pskb_may_pull(skb, sizeof(*iph) + noff))
129 goto drop;
130
131 iph = ip_hdr(skb);
132
133 if (egress)
134 addr = iph->saddr;
135 else
136 addr = iph->daddr;
137
138 if (!((old_addr ^ addr) & mask)) {
139 if (skb_cloned(skb) &&
140 !skb_clone_writable(skb, sizeof(*iph) + noff) &&
141 pskb_expand_head(skb, 0, 0, GFP_ATOMIC))
142 goto drop;
143
144 new_addr &= mask;
145 new_addr |= addr & ~mask;
146
147 /* Rewrite IP header */
148 iph = ip_hdr(skb);
149 if (egress)
150 iph->saddr = new_addr;
151 else
152 iph->daddr = new_addr;
153
154 csum_replace4(&iph->check, addr, new_addr);
155 } else if ((iph->frag_off & htons(IP_OFFSET)) ||
156 iph->protocol != IPPROTO_ICMP) {
157 goto out;
158 }
159
160 ihl = iph->ihl * 4;
161
162 /* It would be nice to share code with stateful NAT. */
163 switch (iph->frag_off & htons(IP_OFFSET) ? 0 : iph->protocol) {
164 case IPPROTO_TCP:
165 {
166 struct tcphdr *tcph;
167
168 if (!pskb_may_pull(skb, ihl + sizeof(*tcph) + noff) ||
169 (skb_cloned(skb) &&
170 !skb_clone_writable(skb, ihl + sizeof(*tcph) + noff) &&
171 pskb_expand_head(skb, 0, 0, GFP_ATOMIC)))
172 goto drop;
173
174 tcph = (void *)(skb_network_header(skb) + ihl);
175 inet_proto_csum_replace4(&tcph->check, skb, addr, new_addr, 1);
176 break;
177 }
178 case IPPROTO_UDP:
179 {
180 struct udphdr *udph;
181
182 if (!pskb_may_pull(skb, ihl + sizeof(*udph) + noff) ||
183 (skb_cloned(skb) &&
184 !skb_clone_writable(skb, ihl + sizeof(*udph) + noff) &&
185 pskb_expand_head(skb, 0, 0, GFP_ATOMIC)))
186 goto drop;
187
188 udph = (void *)(skb_network_header(skb) + ihl);
189 if (udph->check || skb->ip_summed == CHECKSUM_PARTIAL) {
190 inet_proto_csum_replace4(&udph->check, skb, addr,
191 new_addr, 1);
192 if (!udph->check)
193 udph->check = CSUM_MANGLED_0;
194 }
195 break;
196 }
197 case IPPROTO_ICMP:
198 {
199 struct icmphdr *icmph;
200
201 if (!pskb_may_pull(skb, ihl + sizeof(*icmph) + noff))
202 goto drop;
203
204 icmph = (void *)(skb_network_header(skb) + ihl);
205
206 if ((icmph->type != ICMP_DEST_UNREACH) &&
207 (icmph->type != ICMP_TIME_EXCEEDED) &&
208 (icmph->type != ICMP_PARAMETERPROB))
209 break;
210
211 if (!pskb_may_pull(skb, ihl + sizeof(*icmph) + sizeof(*iph) +
212 noff))
213 goto drop;
214
215 icmph = (void *)(skb_network_header(skb) + ihl);
216 iph = (void *)(icmph + 1);
217 if (egress)
218 addr = iph->daddr;
219 else
220 addr = iph->saddr;
221
222 if ((old_addr ^ addr) & mask)
223 break;
224
225 if (skb_cloned(skb) &&
226 !skb_clone_writable(skb, ihl + sizeof(*icmph) +
227 sizeof(*iph) + noff) &&
228 pskb_expand_head(skb, 0, 0, GFP_ATOMIC))
229 goto drop;
230
231 icmph = (void *)(skb_network_header(skb) + ihl);
232 iph = (void *)(icmph + 1);
233
234 new_addr &= mask;
235 new_addr |= addr & ~mask;
236
237 /* XXX Fix up the inner checksums. */
238 if (egress)
239 iph->daddr = new_addr;
240 else
241 iph->saddr = new_addr;
242
243 inet_proto_csum_replace4(&icmph->checksum, skb, addr, new_addr,
244 0);
245 break;
246 }
247 default:
248 break;
249 }
250
251 out:
252 return action;
253
254 drop:
255 spin_lock(&p->tcf_lock);
256 p->tcf_qstats.drops++;
257 spin_unlock(&p->tcf_lock);
258 return TC_ACT_SHOT;
259 }
260
261 static int tcf_nat_dump(struct sk_buff *skb, struct tc_action *a,
262 int bind, int ref)
263 {
264 unsigned char *b = skb_tail_pointer(skb);
265 struct tcf_nat *p = a->priv;
266 struct tc_nat opt = {
267 .old_addr = p->old_addr,
268 .new_addr = p->new_addr,
269 .mask = p->mask,
270 .flags = p->flags,
271
272 .index = p->tcf_index,
273 .action = p->tcf_action,
274 .refcnt = p->tcf_refcnt - ref,
275 .bindcnt = p->tcf_bindcnt - bind,
276 };
277 struct tcf_t t;
278
279 if (nla_put(skb, TCA_NAT_PARMS, sizeof(opt), &opt))
280 goto nla_put_failure;
281 t.install = jiffies_to_clock_t(jiffies - p->tcf_tm.install);
282 t.lastuse = jiffies_to_clock_t(jiffies - p->tcf_tm.lastuse);
283 t.expires = jiffies_to_clock_t(p->tcf_tm.expires);
284 if (nla_put(skb, TCA_NAT_TM, sizeof(t), &t))
285 goto nla_put_failure;
286
287 return skb->len;
288
289 nla_put_failure:
290 nlmsg_trim(skb, b);
291 return -1;
292 }
293
294 static struct tc_action_ops act_nat_ops = {
295 .kind = "nat",
296 .hinfo = &nat_hash_info,
297 .type = TCA_ACT_NAT,
298 .owner = THIS_MODULE,
299 .act = tcf_nat,
300 .dump = tcf_nat_dump,
301 .cleanup = tcf_nat_cleanup,
302 .init = tcf_nat_init,
303 };
304
305 MODULE_DESCRIPTION("Stateless NAT actions");
306 MODULE_LICENSE("GPL");
307
308 static int __init nat_init_module(void)
309 {
310 int err = tcf_hashinfo_init(&nat_hash_info, NAT_TAB_MASK);
311 if (err)
312 return err;
313 return tcf_register_action(&act_nat_ops);
314 }
315
316 static void __exit nat_cleanup_module(void)
317 {
318 tcf_unregister_action(&act_nat_ops);
319 tcf_hashinfo_destroy(&nat_hash_info);
320 }
321
322 module_init(nat_init_module);
323 module_exit(nat_cleanup_module);