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 static unsigned int nat_net_id;
33 static struct tc_action_ops act_nat_ops;
34
35 static const struct nla_policy nat_policy[TCA_NAT_MAX + 1] = {
36 [TCA_NAT_PARMS] = { .len = sizeof(struct tc_nat) },
37 };
38
tcf_nat_init(struct net * net,struct nlattr * nla,struct nlattr * est,struct tc_action ** a,int ovr,int bind,bool rtnl_held,struct netlink_ext_ack * extack)39 static int tcf_nat_init(struct net *net, struct nlattr *nla, struct nlattr *est,
40 struct tc_action **a, int ovr, int bind,
41 bool rtnl_held, struct netlink_ext_ack *extack)
42 {
43 struct tc_action_net *tn = net_generic(net, nat_net_id);
44 struct nlattr *tb[TCA_NAT_MAX + 1];
45 struct tc_nat *parm;
46 int ret = 0, err;
47 struct tcf_nat *p;
48
49 if (nla == NULL)
50 return -EINVAL;
51
52 err = nla_parse_nested(tb, TCA_NAT_MAX, nla, nat_policy, NULL);
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 err = tcf_idr_check_alloc(tn, &parm->index, a, bind);
61 if (!err) {
62 ret = tcf_idr_create(tn, parm->index, est, a,
63 &act_nat_ops, bind, false);
64 if (ret) {
65 tcf_idr_cleanup(tn, parm->index);
66 return ret;
67 }
68 ret = ACT_P_CREATED;
69 } else if (err > 0) {
70 if (bind)
71 return 0;
72 if (!ovr) {
73 tcf_idr_release(*a, bind);
74 return -EEXIST;
75 }
76 } else {
77 return err;
78 }
79 p = to_tcf_nat(*a);
80
81 spin_lock_bh(&p->tcf_lock);
82 p->old_addr = parm->old_addr;
83 p->new_addr = parm->new_addr;
84 p->mask = parm->mask;
85 p->flags = parm->flags;
86
87 p->tcf_action = parm->action;
88 spin_unlock_bh(&p->tcf_lock);
89
90 if (ret == ACT_P_CREATED)
91 tcf_idr_insert(tn, *a);
92
93 return ret;
94 }
95
tcf_nat_act(struct sk_buff * skb,const struct tc_action * a,struct tcf_result * res)96 static int tcf_nat_act(struct sk_buff *skb, const struct tc_action *a,
97 struct tcf_result *res)
98 {
99 struct tcf_nat *p = to_tcf_nat(a);
100 struct iphdr *iph;
101 __be32 old_addr;
102 __be32 new_addr;
103 __be32 mask;
104 __be32 addr;
105 int egress;
106 int action;
107 int ihl;
108 int noff;
109
110 spin_lock(&p->tcf_lock);
111
112 tcf_lastuse_update(&p->tcf_tm);
113 old_addr = p->old_addr;
114 new_addr = p->new_addr;
115 mask = p->mask;
116 egress = p->flags & TCA_NAT_FLAG_EGRESS;
117 action = p->tcf_action;
118
119 bstats_update(&p->tcf_bstats, skb);
120
121 spin_unlock(&p->tcf_lock);
122
123 if (unlikely(action == TC_ACT_SHOT))
124 goto drop;
125
126 noff = skb_network_offset(skb);
127 if (!pskb_may_pull(skb, sizeof(*iph) + noff))
128 goto drop;
129
130 iph = ip_hdr(skb);
131
132 if (egress)
133 addr = iph->saddr;
134 else
135 addr = iph->daddr;
136
137 if (!((old_addr ^ addr) & mask)) {
138 if (skb_try_make_writable(skb, sizeof(*iph) + noff))
139 goto drop;
140
141 new_addr &= mask;
142 new_addr |= addr & ~mask;
143
144 /* Rewrite IP header */
145 iph = ip_hdr(skb);
146 if (egress)
147 iph->saddr = new_addr;
148 else
149 iph->daddr = new_addr;
150
151 csum_replace4(&iph->check, addr, new_addr);
152 } else if ((iph->frag_off & htons(IP_OFFSET)) ||
153 iph->protocol != IPPROTO_ICMP) {
154 goto out;
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) + noff) ||
166 skb_try_make_writable(skb, ihl + sizeof(*tcph) + noff))
167 goto drop;
168
169 tcph = (void *)(skb_network_header(skb) + ihl);
170 inet_proto_csum_replace4(&tcph->check, skb, addr, new_addr,
171 true);
172 break;
173 }
174 case IPPROTO_UDP:
175 {
176 struct udphdr *udph;
177
178 if (!pskb_may_pull(skb, ihl + sizeof(*udph) + noff) ||
179 skb_try_make_writable(skb, ihl + sizeof(*udph) + noff))
180 goto drop;
181
182 udph = (void *)(skb_network_header(skb) + ihl);
183 if (udph->check || skb->ip_summed == CHECKSUM_PARTIAL) {
184 inet_proto_csum_replace4(&udph->check, skb, addr,
185 new_addr, true);
186 if (!udph->check)
187 udph->check = CSUM_MANGLED_0;
188 }
189 break;
190 }
191 case IPPROTO_ICMP:
192 {
193 struct icmphdr *icmph;
194
195 if (!pskb_may_pull(skb, ihl + sizeof(*icmph) + noff))
196 goto drop;
197
198 icmph = (void *)(skb_network_header(skb) + ihl);
199
200 if ((icmph->type != ICMP_DEST_UNREACH) &&
201 (icmph->type != ICMP_TIME_EXCEEDED) &&
202 (icmph->type != ICMP_PARAMETERPROB))
203 break;
204
205 if (!pskb_may_pull(skb, ihl + sizeof(*icmph) + sizeof(*iph) +
206 noff))
207 goto drop;
208
209 icmph = (void *)(skb_network_header(skb) + ihl);
210 iph = (void *)(icmph + 1);
211 if (egress)
212 addr = iph->daddr;
213 else
214 addr = iph->saddr;
215
216 if ((old_addr ^ addr) & mask)
217 break;
218
219 if (skb_try_make_writable(skb, ihl + sizeof(*icmph) +
220 sizeof(*iph) + noff))
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 inet_proto_csum_replace4(&icmph->checksum, skb, addr, new_addr,
236 false);
237 break;
238 }
239 default:
240 break;
241 }
242
243 out:
244 return action;
245
246 drop:
247 spin_lock(&p->tcf_lock);
248 p->tcf_qstats.drops++;
249 spin_unlock(&p->tcf_lock);
250 return TC_ACT_SHOT;
251 }
252
tcf_nat_dump(struct sk_buff * skb,struct tc_action * a,int bind,int ref)253 static int tcf_nat_dump(struct sk_buff *skb, struct tc_action *a,
254 int bind, int ref)
255 {
256 unsigned char *b = skb_tail_pointer(skb);
257 struct tcf_nat *p = to_tcf_nat(a);
258 struct tc_nat opt = {
259 .old_addr = p->old_addr,
260 .new_addr = p->new_addr,
261 .mask = p->mask,
262 .flags = p->flags,
263
264 .index = p->tcf_index,
265 .action = p->tcf_action,
266 .refcnt = refcount_read(&p->tcf_refcnt) - ref,
267 .bindcnt = atomic_read(&p->tcf_bindcnt) - bind,
268 };
269 struct tcf_t t;
270
271 if (nla_put(skb, TCA_NAT_PARMS, sizeof(opt), &opt))
272 goto nla_put_failure;
273
274 tcf_tm_dump(&t, &p->tcf_tm);
275 if (nla_put_64bit(skb, TCA_NAT_TM, sizeof(t), &t, TCA_NAT_PAD))
276 goto nla_put_failure;
277
278 return skb->len;
279
280 nla_put_failure:
281 nlmsg_trim(skb, b);
282 return -1;
283 }
284
tcf_nat_walker(struct net * net,struct sk_buff * skb,struct netlink_callback * cb,int type,const struct tc_action_ops * ops,struct netlink_ext_ack * extack)285 static int tcf_nat_walker(struct net *net, struct sk_buff *skb,
286 struct netlink_callback *cb, int type,
287 const struct tc_action_ops *ops,
288 struct netlink_ext_ack *extack)
289 {
290 struct tc_action_net *tn = net_generic(net, nat_net_id);
291
292 return tcf_generic_walker(tn, skb, cb, type, ops, extack);
293 }
294
tcf_nat_search(struct net * net,struct tc_action ** a,u32 index,struct netlink_ext_ack * extack)295 static int tcf_nat_search(struct net *net, struct tc_action **a, u32 index,
296 struct netlink_ext_ack *extack)
297 {
298 struct tc_action_net *tn = net_generic(net, nat_net_id);
299
300 return tcf_idr_search(tn, a, index);
301 }
302
303 static struct tc_action_ops act_nat_ops = {
304 .kind = "nat",
305 .type = TCA_ACT_NAT,
306 .owner = THIS_MODULE,
307 .act = tcf_nat_act,
308 .dump = tcf_nat_dump,
309 .init = tcf_nat_init,
310 .walk = tcf_nat_walker,
311 .lookup = tcf_nat_search,
312 .size = sizeof(struct tcf_nat),
313 };
314
nat_init_net(struct net * net)315 static __net_init int nat_init_net(struct net *net)
316 {
317 struct tc_action_net *tn = net_generic(net, nat_net_id);
318
319 return tc_action_net_init(tn, &act_nat_ops);
320 }
321
nat_exit_net(struct list_head * net_list)322 static void __net_exit nat_exit_net(struct list_head *net_list)
323 {
324 tc_action_net_exit(net_list, nat_net_id);
325 }
326
327 static struct pernet_operations nat_net_ops = {
328 .init = nat_init_net,
329 .exit_batch = nat_exit_net,
330 .id = &nat_net_id,
331 .size = sizeof(struct tc_action_net),
332 };
333
334 MODULE_DESCRIPTION("Stateless NAT actions");
335 MODULE_LICENSE("GPL");
336
nat_init_module(void)337 static int __init nat_init_module(void)
338 {
339 return tcf_register_action(&act_nat_ops, &nat_net_ops);
340 }
341
nat_cleanup_module(void)342 static void __exit nat_cleanup_module(void)
343 {
344 tcf_unregister_action(&act_nat_ops, &nat_net_ops);
345 }
346
347 module_init(nat_init_module);
348 module_exit(nat_cleanup_module);
349
