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b4219952 HX |
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 int tcf_nat_init(struct rtattr *rta, struct rtattr *est, | |
44 | struct tc_action *a, int ovr, int bind) | |
45 | { | |
46 | struct rtattr *tb[TCA_NAT_MAX]; | |
47 | struct tc_nat *parm; | |
48 | int ret = 0; | |
49 | struct tcf_nat *p; | |
50 | struct tcf_common *pc; | |
51 | ||
52 | if (rta == NULL || rtattr_parse_nested(tb, TCA_NAT_MAX, rta) < 0) | |
53 | return -EINVAL; | |
54 | ||
55 | if (tb[TCA_NAT_PARMS - 1] == NULL || | |
56 | RTA_PAYLOAD(tb[TCA_NAT_PARMS - 1]) < sizeof(*parm)) | |
57 | return -EINVAL; | |
58 | parm = RTA_DATA(tb[TCA_NAT_PARMS - 1]); | |
59 | ||
60 | pc = tcf_hash_check(parm->index, a, bind, &nat_hash_info); | |
61 | if (!pc) { | |
62 | pc = tcf_hash_create(parm->index, est, a, sizeof(*p), bind, | |
63 | &nat_idx_gen, &nat_hash_info); | |
64 | if (unlikely(!pc)) | |
65 | return -ENOMEM; | |
66 | p = to_tcf_nat(pc); | |
67 | ret = ACT_P_CREATED; | |
68 | } else { | |
69 | p = to_tcf_nat(pc); | |
70 | if (!ovr) { | |
71 | tcf_hash_release(pc, bind, &nat_hash_info); | |
72 | return -EEXIST; | |
73 | } | |
74 | } | |
75 | ||
76 | spin_lock_bh(&p->tcf_lock); | |
77 | p->old_addr = parm->old_addr; | |
78 | p->new_addr = parm->new_addr; | |
79 | p->mask = parm->mask; | |
80 | p->flags = parm->flags; | |
81 | ||
82 | p->tcf_action = parm->action; | |
83 | spin_unlock_bh(&p->tcf_lock); | |
84 | ||
85 | if (ret == ACT_P_CREATED) | |
86 | tcf_hash_insert(pc, &nat_hash_info); | |
87 | ||
88 | return ret; | |
89 | } | |
90 | ||
91 | static int tcf_nat_cleanup(struct tc_action *a, int bind) | |
92 | { | |
93 | struct tcf_nat *p = a->priv; | |
94 | ||
95 | return tcf_hash_release(&p->common, bind, &nat_hash_info); | |
96 | } | |
97 | ||
98 | static int tcf_nat(struct sk_buff *skb, struct tc_action *a, | |
99 | struct tcf_result *res) | |
100 | { | |
101 | struct tcf_nat *p = a->priv; | |
102 | struct iphdr *iph; | |
103 | __be32 old_addr; | |
104 | __be32 new_addr; | |
105 | __be32 mask; | |
106 | __be32 addr; | |
107 | int egress; | |
108 | int action; | |
109 | int ihl; | |
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 | p->tcf_bstats.bytes += skb->len; | |
121 | p->tcf_bstats.packets++; | |
122 | ||
123 | spin_unlock(&p->tcf_lock); | |
124 | ||
125 | if (unlikely(action == TC_ACT_SHOT)) | |
126 | goto drop; | |
127 | ||
128 | if (!pskb_may_pull(skb, sizeof(*iph))) | |
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)) && | |
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 | nf_csum_replace4(&iph->check, addr, new_addr); | |
155 | } | |
156 | ||
157 | ihl = iph->ihl * 4; | |
158 | ||
159 | /* It would be nice to share code with stateful NAT. */ | |
160 | switch (iph->frag_off & htons(IP_OFFSET) ? 0 : iph->protocol) { | |
161 | case IPPROTO_TCP: | |
162 | { | |
163 | struct tcphdr *tcph; | |
164 | ||
165 | if (!pskb_may_pull(skb, ihl + sizeof(*tcph)) || | |
166 | (skb_cloned(skb) && | |
167 | !skb_clone_writable(skb, ihl + sizeof(*tcph)) && | |
168 | pskb_expand_head(skb, 0, 0, GFP_ATOMIC))) | |
169 | goto drop; | |
170 | ||
171 | tcph = (void *)(skb_network_header(skb) + ihl); | |
172 | nf_proto_csum_replace4(&tcph->check, skb, addr, new_addr, 1); | |
173 | break; | |
174 | } | |
175 | case IPPROTO_UDP: | |
176 | { | |
177 | struct udphdr *udph; | |
178 | ||
179 | if (!pskb_may_pull(skb, ihl + sizeof(*udph)) || | |
180 | (skb_cloned(skb) && | |
181 | !skb_clone_writable(skb, ihl + sizeof(*udph)) && | |
182 | pskb_expand_head(skb, 0, 0, GFP_ATOMIC))) | |
183 | goto drop; | |
184 | ||
185 | udph = (void *)(skb_network_header(skb) + ihl); | |
186 | if (udph->check || skb->ip_summed == CHECKSUM_PARTIAL) { | |
187 | nf_proto_csum_replace4(&udph->check, skb, addr, | |
188 | new_addr, 1); | |
189 | if (!udph->check) | |
190 | udph->check = CSUM_MANGLED_0; | |
191 | } | |
192 | break; | |
193 | } | |
194 | case IPPROTO_ICMP: | |
195 | { | |
196 | struct icmphdr *icmph; | |
197 | ||
198 | if (!pskb_may_pull(skb, ihl + sizeof(*icmph) + sizeof(*iph))) | |
199 | goto drop; | |
200 | ||
201 | icmph = (void *)(skb_network_header(skb) + ihl); | |
202 | ||
203 | if ((icmph->type != ICMP_DEST_UNREACH) && | |
204 | (icmph->type != ICMP_TIME_EXCEEDED) && | |
205 | (icmph->type != ICMP_PARAMETERPROB)) | |
206 | break; | |
207 | ||
208 | iph = (void *)(icmph + 1); | |
209 | if (egress) | |
210 | addr = iph->daddr; | |
211 | else | |
212 | addr = iph->saddr; | |
213 | ||
214 | if ((old_addr ^ addr) & mask) | |
215 | break; | |
216 | ||
217 | if (skb_cloned(skb) && | |
218 | !skb_clone_writable(skb, | |
219 | ihl + sizeof(*icmph) + sizeof(*iph)) && | |
220 | pskb_expand_head(skb, 0, 0, GFP_ATOMIC)) | |
221 | goto drop; | |
222 | ||
223 | icmph = (void *)(skb_network_header(skb) + ihl); | |
224 | iph = (void *)(icmph + 1); | |
225 | ||
226 | new_addr &= mask; | |
227 | new_addr |= addr & ~mask; | |
228 | ||
229 | /* XXX Fix up the inner checksums. */ | |
230 | if (egress) | |
231 | iph->daddr = new_addr; | |
232 | else | |
233 | iph->saddr = new_addr; | |
234 | ||
235 | nf_proto_csum_replace4(&icmph->checksum, skb, addr, new_addr, | |
236 | 1); | |
237 | break; | |
238 | } | |
239 | default: | |
240 | break; | |
241 | } | |
242 | ||
243 | return action; | |
244 | ||
245 | drop: | |
246 | spin_lock(&p->tcf_lock); | |
247 | p->tcf_qstats.drops++; | |
248 | spin_unlock(&p->tcf_lock); | |
249 | return TC_ACT_SHOT; | |
250 | } | |
251 | ||
252 | static int tcf_nat_dump(struct sk_buff *skb, struct tc_action *a, | |
253 | int bind, int ref) | |
254 | { | |
255 | unsigned char *b = skb_tail_pointer(skb); | |
256 | struct tcf_nat *p = a->priv; | |
257 | struct tc_nat *opt; | |
258 | struct tcf_t t; | |
259 | int s; | |
260 | ||
261 | s = sizeof(*opt); | |
262 | ||
263 | /* netlink spinlocks held above us - must use ATOMIC */ | |
264 | opt = kzalloc(s, GFP_ATOMIC); | |
265 | if (unlikely(!opt)) | |
266 | return -ENOBUFS; | |
267 | ||
268 | opt->old_addr = p->old_addr; | |
269 | opt->new_addr = p->new_addr; | |
270 | opt->mask = p->mask; | |
271 | opt->flags = p->flags; | |
272 | ||
273 | opt->index = p->tcf_index; | |
274 | opt->action = p->tcf_action; | |
275 | opt->refcnt = p->tcf_refcnt - ref; | |
276 | opt->bindcnt = p->tcf_bindcnt - bind; | |
277 | ||
278 | RTA_PUT(skb, TCA_NAT_PARMS, s, opt); | |
279 | t.install = jiffies_to_clock_t(jiffies - p->tcf_tm.install); | |
280 | t.lastuse = jiffies_to_clock_t(jiffies - p->tcf_tm.lastuse); | |
281 | t.expires = jiffies_to_clock_t(p->tcf_tm.expires); | |
282 | RTA_PUT(skb, TCA_NAT_TM, sizeof(t), &t); | |
283 | ||
284 | kfree(opt); | |
285 | ||
286 | return skb->len; | |
287 | ||
288 | rtattr_failure: | |
289 | nlmsg_trim(skb, b); | |
290 | kfree(opt); | |
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 | .capab = TCA_CAP_NONE, | |
299 | .owner = THIS_MODULE, | |
300 | .act = tcf_nat, | |
301 | .dump = tcf_nat_dump, | |
302 | .cleanup = tcf_nat_cleanup, | |
303 | .lookup = tcf_hash_search, | |
304 | .init = tcf_nat_init, | |
305 | .walk = tcf_generic_walker | |
306 | }; | |
307 | ||
308 | MODULE_DESCRIPTION("Stateless NAT actions"); | |
309 | MODULE_LICENSE("GPL"); | |
310 | ||
311 | static int __init nat_init_module(void) | |
312 | { | |
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 | } | |
320 | ||
321 | module_init(nat_init_module); | |
322 | module_exit(nat_cleanup_module); |