1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /*
3 * Stateless NAT actions
4 *
5 * Copyright (c) 2007 Herbert Xu <herbert@gondor.apana.org.au>
6 */
7
8 #include <linux/errno.h>
9 #include <linux/init.h>
10 #include <linux/kernel.h>
11 #include <linux/module.h>
12 #include <linux/netfilter.h>
13 #include <linux/rtnetlink.h>
14 #include <linux/skbuff.h>
15 #include <linux/slab.h>
16 #include <linux/spinlock.h>
17 #include <linux/string.h>
18 #include <linux/tc_act/tc_nat.h>
19 #include <net/act_api.h>
20 #include <net/pkt_cls.h>
21 #include <net/icmp.h>
22 #include <net/ip.h>
23 #include <net/netlink.h>
24 #include <net/tc_act/tc_nat.h>
25 #include <net/tcp.h>
26 #include <net/udp.h>
27
28
29 static unsigned int nat_net_id;
30 static struct tc_action_ops act_nat_ops;
31
32 static const struct nla_policy nat_policy[TCA_NAT_MAX + 1] = {
33 [TCA_NAT_PARMS] = { .len = sizeof(struct tc_nat) },
34 };
35
tcf_nat_init(struct net * net,struct nlattr * nla,struct nlattr * est,struct tc_action ** a,int ovr,int bind,bool rtnl_held,struct tcf_proto * tp,u32 flags,struct netlink_ext_ack * extack)36 static int tcf_nat_init(struct net *net, struct nlattr *nla, struct nlattr *est,
37 struct tc_action **a, int ovr, int bind,
38 bool rtnl_held, struct tcf_proto *tp,
39 u32 flags, struct netlink_ext_ack *extack)
40 {
41 struct tc_action_net *tn = net_generic(net, nat_net_id);
42 struct nlattr *tb[TCA_NAT_MAX + 1];
43 struct tcf_chain *goto_ch = NULL;
44 struct tc_nat *parm;
45 int ret = 0, err;
46 struct tcf_nat *p;
47 u32 index;
48
49 if (nla == NULL)
50 return -EINVAL;
51
52 err = nla_parse_nested_deprecated(tb, TCA_NAT_MAX, nla, nat_policy,
53 NULL);
54 if (err < 0)
55 return err;
56
57 if (tb[TCA_NAT_PARMS] == NULL)
58 return -EINVAL;
59 parm = nla_data(tb[TCA_NAT_PARMS]);
60 index = parm->index;
61 err = tcf_idr_check_alloc(tn, &index, a, bind);
62 if (!err) {
63 ret = tcf_idr_create(tn, index, est, a,
64 &act_nat_ops, bind, false, 0);
65 if (ret) {
66 tcf_idr_cleanup(tn, index);
67 return ret;
68 }
69 ret = ACT_P_CREATED;
70 } else if (err > 0) {
71 if (bind)
72 return 0;
73 if (!ovr) {
74 tcf_idr_release(*a, bind);
75 return -EEXIST;
76 }
77 } else {
78 return err;
79 }
80 err = tcf_action_check_ctrlact(parm->action, tp, &goto_ch, extack);
81 if (err < 0)
82 goto release_idr;
83 p = to_tcf_nat(*a);
84
85 spin_lock_bh(&p->tcf_lock);
86 p->old_addr = parm->old_addr;
87 p->new_addr = parm->new_addr;
88 p->mask = parm->mask;
89 p->flags = parm->flags;
90
91 goto_ch = tcf_action_set_ctrlact(*a, parm->action, goto_ch);
92 spin_unlock_bh(&p->tcf_lock);
93 if (goto_ch)
94 tcf_chain_put_by_act(goto_ch);
95
96 return ret;
97 release_idr:
98 tcf_idr_release(*a, bind);
99 return err;
100 }
101
tcf_nat_act(struct sk_buff * skb,const struct tc_action * a,struct tcf_result * res)102 static int tcf_nat_act(struct sk_buff *skb, const struct tc_action *a,
103 struct tcf_result *res)
104 {
105 struct tcf_nat *p = to_tcf_nat(a);
106 struct iphdr *iph;
107 __be32 old_addr;
108 __be32 new_addr;
109 __be32 mask;
110 __be32 addr;
111 int egress;
112 int action;
113 int ihl;
114 int noff;
115
116 spin_lock(&p->tcf_lock);
117
118 tcf_lastuse_update(&p->tcf_tm);
119 old_addr = p->old_addr;
120 new_addr = p->new_addr;
121 mask = p->mask;
122 egress = p->flags & TCA_NAT_FLAG_EGRESS;
123 action = p->tcf_action;
124
125 bstats_update(&p->tcf_bstats, skb);
126
127 spin_unlock(&p->tcf_lock);
128
129 if (unlikely(action == TC_ACT_SHOT))
130 goto drop;
131
132 noff = skb_network_offset(skb);
133 if (!pskb_may_pull(skb, sizeof(*iph) + noff))
134 goto drop;
135
136 iph = ip_hdr(skb);
137
138 if (egress)
139 addr = iph->saddr;
140 else
141 addr = iph->daddr;
142
143 if (!((old_addr ^ addr) & mask)) {
144 if (skb_try_make_writable(skb, sizeof(*iph) + noff))
145 goto drop;
146
147 new_addr &= mask;
148 new_addr |= addr & ~mask;
149
150 /* Rewrite IP header */
151 iph = ip_hdr(skb);
152 if (egress)
153 iph->saddr = new_addr;
154 else
155 iph->daddr = new_addr;
156
157 csum_replace4(&iph->check, addr, new_addr);
158 } else if ((iph->frag_off & htons(IP_OFFSET)) ||
159 iph->protocol != IPPROTO_ICMP) {
160 goto out;
161 }
162
163 ihl = iph->ihl * 4;
164
165 /* It would be nice to share code with stateful NAT. */
166 switch (iph->frag_off & htons(IP_OFFSET) ? 0 : iph->protocol) {
167 case IPPROTO_TCP:
168 {
169 struct tcphdr *tcph;
170
171 if (!pskb_may_pull(skb, ihl + sizeof(*tcph) + noff) ||
172 skb_try_make_writable(skb, ihl + sizeof(*tcph) + noff))
173 goto drop;
174
175 tcph = (void *)(skb_network_header(skb) + ihl);
176 inet_proto_csum_replace4(&tcph->check, skb, addr, new_addr,
177 true);
178 break;
179 }
180 case IPPROTO_UDP:
181 {
182 struct udphdr *udph;
183
184 if (!pskb_may_pull(skb, ihl + sizeof(*udph) + noff) ||
185 skb_try_make_writable(skb, ihl + sizeof(*udph) + noff))
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, true);
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 (!icmp_is_err(icmph->type))
207 break;
208
209 if (!pskb_may_pull(skb, ihl + sizeof(*icmph) + sizeof(*iph) +
210 noff))
211 goto drop;
212
213 icmph = (void *)(skb_network_header(skb) + ihl);
214 iph = (void *)(icmph + 1);
215 if (egress)
216 addr = iph->daddr;
217 else
218 addr = iph->saddr;
219
220 if ((old_addr ^ addr) & mask)
221 break;
222
223 if (skb_try_make_writable(skb, ihl + sizeof(*icmph) +
224 sizeof(*iph) + noff))
225 goto drop;
226
227 icmph = (void *)(skb_network_header(skb) + ihl);
228 iph = (void *)(icmph + 1);
229
230 new_addr &= mask;
231 new_addr |= addr & ~mask;
232
233 /* XXX Fix up the inner checksums. */
234 if (egress)
235 iph->daddr = new_addr;
236 else
237 iph->saddr = new_addr;
238
239 inet_proto_csum_replace4(&icmph->checksum, skb, addr, new_addr,
240 false);
241 break;
242 }
243 default:
244 break;
245 }
246
247 out:
248 return action;
249
250 drop:
251 spin_lock(&p->tcf_lock);
252 p->tcf_qstats.drops++;
253 spin_unlock(&p->tcf_lock);
254 return TC_ACT_SHOT;
255 }
256
tcf_nat_dump(struct sk_buff * skb,struct tc_action * a,int bind,int ref)257 static int tcf_nat_dump(struct sk_buff *skb, struct tc_action *a,
258 int bind, int ref)
259 {
260 unsigned char *b = skb_tail_pointer(skb);
261 struct tcf_nat *p = to_tcf_nat(a);
262 struct tc_nat opt = {
263 .index = p->tcf_index,
264 .refcnt = refcount_read(&p->tcf_refcnt) - ref,
265 .bindcnt = atomic_read(&p->tcf_bindcnt) - bind,
266 };
267 struct tcf_t t;
268
269 spin_lock_bh(&p->tcf_lock);
270 opt.old_addr = p->old_addr;
271 opt.new_addr = p->new_addr;
272 opt.mask = p->mask;
273 opt.flags = p->flags;
274 opt.action = p->tcf_action;
275
276 if (nla_put(skb, TCA_NAT_PARMS, sizeof(opt), &opt))
277 goto nla_put_failure;
278
279 tcf_tm_dump(&t, &p->tcf_tm);
280 if (nla_put_64bit(skb, TCA_NAT_TM, sizeof(t), &t, TCA_NAT_PAD))
281 goto nla_put_failure;
282 spin_unlock_bh(&p->tcf_lock);
283
284 return skb->len;
285
286 nla_put_failure:
287 spin_unlock_bh(&p->tcf_lock);
288 nlmsg_trim(skb, b);
289 return -1;
290 }
291
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)292 static int tcf_nat_walker(struct net *net, struct sk_buff *skb,
293 struct netlink_callback *cb, int type,
294 const struct tc_action_ops *ops,
295 struct netlink_ext_ack *extack)
296 {
297 struct tc_action_net *tn = net_generic(net, nat_net_id);
298
299 return tcf_generic_walker(tn, skb, cb, type, ops, extack);
300 }
301
tcf_nat_search(struct net * net,struct tc_action ** a,u32 index)302 static int tcf_nat_search(struct net *net, struct tc_action **a, u32 index)
303 {
304 struct tc_action_net *tn = net_generic(net, nat_net_id);
305
306 return tcf_idr_search(tn, a, index);
307 }
308
309 static struct tc_action_ops act_nat_ops = {
310 .kind = "nat",
311 .id = TCA_ID_NAT,
312 .owner = THIS_MODULE,
313 .act = tcf_nat_act,
314 .dump = tcf_nat_dump,
315 .init = tcf_nat_init,
316 .walk = tcf_nat_walker,
317 .lookup = tcf_nat_search,
318 .size = sizeof(struct tcf_nat),
319 };
320
nat_init_net(struct net * net)321 static __net_init int nat_init_net(struct net *net)
322 {
323 struct tc_action_net *tn = net_generic(net, nat_net_id);
324
325 return tc_action_net_init(net, tn, &act_nat_ops);
326 }
327
nat_exit_net(struct list_head * net_list)328 static void __net_exit nat_exit_net(struct list_head *net_list)
329 {
330 tc_action_net_exit(net_list, nat_net_id);
331 }
332
333 static struct pernet_operations nat_net_ops = {
334 .init = nat_init_net,
335 .exit_batch = nat_exit_net,
336 .id = &nat_net_id,
337 .size = sizeof(struct tc_action_net),
338 };
339
340 MODULE_DESCRIPTION("Stateless NAT actions");
341 MODULE_LICENSE("GPL");
342
nat_init_module(void)343 static int __init nat_init_module(void)
344 {
345 return tcf_register_action(&act_nat_ops, &nat_net_ops);
346 }
347
nat_cleanup_module(void)348 static void __exit nat_cleanup_module(void)
349 {
350 tcf_unregister_action(&act_nat_ops, &nat_net_ops);
351 }
352
353 module_init(nat_init_module);
354 module_exit(nat_cleanup_module);
355
