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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 | static struct tcf_common *tcf_nat_ht[NAT_TAB_MASK + 1]; |
34 | static u32 nat_idx_gen; |
35 | static DEFINE_RWLOCK(nat_lock); |
36 | |
37 | static struct tcf_hashinfo nat_hash_info = { |
38 | .htab = tcf_nat_ht, |
39 | .hmask = NAT_TAB_MASK, |
40 | .lock = &nat_lock, |
41 | }; |
42 | |
43 | static const struct nla_policy nat_policy[TCA_NAT_MAX + 1] = { |
44 | [TCA_NAT_PARMS] = { .len = sizeof(struct tc_nat) }, |
45 | }; |
46 | |
47 | static int tcf_nat_init(struct nlattr *nla, struct nlattr *est, |
48 | struct tc_action *a, int ovr, int bind) |
49 | { |
50 | struct nlattr *tb[TCA_NAT_MAX + 1]; |
51 | struct tc_nat *parm; |
52 | int ret = 0, err; |
53 | struct tcf_nat *p; |
54 | struct tcf_common *pc; |
55 | |
56 | if (nla == NULL) |
57 | return -EINVAL; |
58 | |
59 | err = nla_parse_nested(tb, TCA_NAT_MAX, nla, nat_policy); |
60 | if (err < 0) |
61 | return err; |
62 | |
63 | if (tb[TCA_NAT_PARMS] == NULL) |
64 | return -EINVAL; |
65 | parm = nla_data(tb[TCA_NAT_PARMS]); |
66 | |
67 | pc = tcf_hash_check(parm->index, a, bind, &nat_hash_info); |
68 | if (!pc) { |
69 | pc = tcf_hash_create(parm->index, est, a, sizeof(*p), bind, |
70 | &nat_idx_gen, &nat_hash_info); |
71 | if (IS_ERR(pc)) |
72 | return PTR_ERR(pc); |
73 | p = to_tcf_nat(pc); |
74 | ret = ACT_P_CREATED; |
75 | } else { |
76 | p = to_tcf_nat(pc); |
77 | if (!ovr) { |
78 | tcf_hash_release(pc, bind, &nat_hash_info); |
79 | return -EEXIST; |
80 | } |
81 | } |
82 | |
83 | spin_lock_bh(&p->tcf_lock); |
84 | p->old_addr = parm->old_addr; |
85 | p->new_addr = parm->new_addr; |
86 | p->mask = parm->mask; |
87 | p->flags = parm->flags; |
88 | |
89 | p->tcf_action = parm->action; |
90 | spin_unlock_bh(&p->tcf_lock); |
91 | |
92 | if (ret == ACT_P_CREATED) |
93 | tcf_hash_insert(pc, &nat_hash_info); |
94 | |
95 | return ret; |
96 | } |
97 | |
98 | static int tcf_nat_cleanup(struct tc_action *a, int bind) |
99 | { |
100 | struct tcf_nat *p = a->priv; |
101 | |
102 | return tcf_hash_release(&p->common, bind, &nat_hash_info); |
103 | } |
104 | |
105 | static int tcf_nat(struct sk_buff *skb, struct tc_action *a, |
106 | struct tcf_result *res) |
107 | { |
108 | struct tcf_nat *p = a->priv; |
109 | struct iphdr *iph; |
110 | __be32 old_addr; |
111 | __be32 new_addr; |
112 | __be32 mask; |
113 | __be32 addr; |
114 | int egress; |
115 | int action; |
116 | int ihl; |
117 | |
118 | spin_lock(&p->tcf_lock); |
119 | |
120 | p->tcf_tm.lastuse = jiffies; |
121 | old_addr = p->old_addr; |
122 | new_addr = p->new_addr; |
123 | mask = p->mask; |
124 | egress = p->flags & TCA_NAT_FLAG_EGRESS; |
125 | action = p->tcf_action; |
126 | |
127 | p->tcf_bstats.bytes += qdisc_pkt_len(skb); |
128 | p->tcf_bstats.packets++; |
129 | |
130 | spin_unlock(&p->tcf_lock); |
131 | |
132 | if (unlikely(action == TC_ACT_SHOT)) |
133 | goto drop; |
134 | |
135 | if (!pskb_may_pull(skb, sizeof(*iph))) |
136 | goto drop; |
137 | |
138 | iph = ip_hdr(skb); |
139 | |
140 | if (egress) |
141 | addr = iph->saddr; |
142 | else |
143 | addr = iph->daddr; |
144 | |
145 | if (!((old_addr ^ addr) & mask)) { |
146 | if (skb_cloned(skb) && |
147 | !skb_clone_writable(skb, sizeof(*iph)) && |
148 | pskb_expand_head(skb, 0, 0, GFP_ATOMIC)) |
149 | goto drop; |
150 | |
151 | new_addr &= mask; |
152 | new_addr |= addr & ~mask; |
153 | |
154 | /* Rewrite IP header */ |
155 | iph = ip_hdr(skb); |
156 | if (egress) |
157 | iph->saddr = new_addr; |
158 | else |
159 | iph->daddr = new_addr; |
160 | |
161 | csum_replace4(&iph->check, addr, new_addr); |
162 | } |
163 | |
164 | ihl = iph->ihl * 4; |
165 | |
166 | /* It would be nice to share code with stateful NAT. */ |
167 | switch (iph->frag_off & htons(IP_OFFSET) ? 0 : iph->protocol) { |
168 | case IPPROTO_TCP: |
169 | { |
170 | struct tcphdr *tcph; |
171 | |
172 | if (!pskb_may_pull(skb, ihl + sizeof(*tcph)) || |
173 | (skb_cloned(skb) && |
174 | !skb_clone_writable(skb, ihl + sizeof(*tcph)) && |
175 | pskb_expand_head(skb, 0, 0, GFP_ATOMIC))) |
176 | goto drop; |
177 | |
178 | tcph = (void *)(skb_network_header(skb) + ihl); |
179 | inet_proto_csum_replace4(&tcph->check, skb, addr, new_addr, 1); |
180 | break; |
181 | } |
182 | case IPPROTO_UDP: |
183 | { |
184 | struct udphdr *udph; |
185 | |
186 | if (!pskb_may_pull(skb, ihl + sizeof(*udph)) || |
187 | (skb_cloned(skb) && |
188 | !skb_clone_writable(skb, ihl + sizeof(*udph)) && |
189 | pskb_expand_head(skb, 0, 0, GFP_ATOMIC))) |
190 | goto drop; |
191 | |
192 | udph = (void *)(skb_network_header(skb) + ihl); |
193 | if (udph->check || skb->ip_summed == CHECKSUM_PARTIAL) { |
194 | inet_proto_csum_replace4(&udph->check, skb, addr, |
195 | new_addr, 1); |
196 | if (!udph->check) |
197 | udph->check = CSUM_MANGLED_0; |
198 | } |
199 | break; |
200 | } |
201 | case IPPROTO_ICMP: |
202 | { |
203 | struct icmphdr *icmph; |
204 | |
205 | if (!pskb_may_pull(skb, ihl + sizeof(*icmph) + sizeof(*iph))) |
206 | goto drop; |
207 | |
208 | icmph = (void *)(skb_network_header(skb) + ihl); |
209 | |
210 | if ((icmph->type != ICMP_DEST_UNREACH) && |
211 | (icmph->type != ICMP_TIME_EXCEEDED) && |
212 | (icmph->type != ICMP_PARAMETERPROB)) |
213 | break; |
214 | |
215 | iph = (void *)(icmph + 1); |
216 | if (egress) |
217 | addr = iph->daddr; |
218 | else |
219 | addr = iph->saddr; |
220 | |
221 | if ((old_addr ^ addr) & mask) |
222 | break; |
223 | |
224 | if (skb_cloned(skb) && |
225 | !skb_clone_writable(skb, |
226 | ihl + sizeof(*icmph) + sizeof(*iph)) && |
227 | pskb_expand_head(skb, 0, 0, GFP_ATOMIC)) |
228 | goto drop; |
229 | |
230 | icmph = (void *)(skb_network_header(skb) + ihl); |
231 | iph = (void *)(icmph + 1); |
232 | |
233 | new_addr &= mask; |
234 | new_addr |= addr & ~mask; |
235 | |
236 | /* XXX Fix up the inner checksums. */ |
237 | if (egress) |
238 | iph->daddr = new_addr; |
239 | else |
240 | iph->saddr = new_addr; |
241 | |
242 | inet_proto_csum_replace4(&icmph->checksum, skb, addr, new_addr, |
243 | 1); |
244 | break; |
245 | } |
246 | default: |
247 | break; |
248 | } |
249 | |
250 | return action; |
251 | |
252 | drop: |
253 | spin_lock(&p->tcf_lock); |
254 | p->tcf_qstats.drops++; |
255 | spin_unlock(&p->tcf_lock); |
256 | return TC_ACT_SHOT; |
257 | } |
258 | |
259 | static int tcf_nat_dump(struct sk_buff *skb, struct tc_action *a, |
260 | int bind, int ref) |
261 | { |
262 | unsigned char *b = skb_tail_pointer(skb); |
263 | struct tcf_nat *p = a->priv; |
264 | struct tc_nat *opt; |
265 | struct tcf_t t; |
266 | int s; |
267 | |
268 | s = sizeof(*opt); |
269 | |
270 | /* netlink spinlocks held above us - must use ATOMIC */ |
271 | opt = kzalloc(s, GFP_ATOMIC); |
272 | if (unlikely(!opt)) |
273 | return -ENOBUFS; |
274 | |
275 | opt->old_addr = p->old_addr; |
276 | opt->new_addr = p->new_addr; |
277 | opt->mask = p->mask; |
278 | opt->flags = p->flags; |
279 | |
280 | opt->index = p->tcf_index; |
281 | opt->action = p->tcf_action; |
282 | opt->refcnt = p->tcf_refcnt - ref; |
283 | opt->bindcnt = p->tcf_bindcnt - bind; |
284 | |
285 | NLA_PUT(skb, TCA_NAT_PARMS, s, opt); |
286 | t.install = jiffies_to_clock_t(jiffies - p->tcf_tm.install); |
287 | t.lastuse = jiffies_to_clock_t(jiffies - p->tcf_tm.lastuse); |
288 | t.expires = jiffies_to_clock_t(p->tcf_tm.expires); |
289 | NLA_PUT(skb, TCA_NAT_TM, sizeof(t), &t); |
290 | |
291 | kfree(opt); |
292 | |
293 | return skb->len; |
294 | |
295 | nla_put_failure: |
296 | nlmsg_trim(skb, b); |
297 | kfree(opt); |
298 | return -1; |
299 | } |
300 | |
301 | static struct tc_action_ops act_nat_ops = { |
302 | .kind = "nat", |
303 | .hinfo = &nat_hash_info, |
304 | .type = TCA_ACT_NAT, |
305 | .capab = TCA_CAP_NONE, |
306 | .owner = THIS_MODULE, |
307 | .act = tcf_nat, |
308 | .dump = tcf_nat_dump, |
309 | .cleanup = tcf_nat_cleanup, |
310 | .lookup = tcf_hash_search, |
311 | .init = tcf_nat_init, |
312 | .walk = tcf_generic_walker |
313 | }; |
314 | |
315 | MODULE_DESCRIPTION("Stateless NAT actions"); |
316 | MODULE_LICENSE("GPL"); |
317 | |
318 | static int __init nat_init_module(void) |
319 | { |
320 | return tcf_register_action(&act_nat_ops); |
321 | } |
322 | |
323 | static void __exit nat_cleanup_module(void) |
324 | { |
325 | tcf_unregister_action(&act_nat_ops); |
326 | } |
327 | |
328 | module_init(nat_init_module); |
329 | module_exit(nat_cleanup_module); |
330 |
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