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11#include <linux/types.h>
12#include <linux/module.h>
13#include <linux/skbuff.h>
14#include <linux/ip.h>
15#include <linux/icmp.h>
16#include <linux/netfilter.h>
17#include <linux/netfilter_ipv4.h>
18#include <net/secure_seq.h>
19#include <net/checksum.h>
20#include <net/route.h>
21#include <net/ip.h>
22
23#include <net/netfilter/nf_conntrack_core.h>
24#include <net/netfilter/nf_conntrack.h>
25#include <net/netfilter/nf_nat_core.h>
26#include <net/netfilter/nf_nat_l3proto.h>
27#include <net/netfilter/nf_nat_l4proto.h>
28
29static const struct nf_nat_l3proto nf_nat_l3proto_ipv4;
30
31#ifdef CONFIG_XFRM
32static void nf_nat_ipv4_decode_session(struct sk_buff *skb,
33 const struct nf_conn *ct,
34 enum ip_conntrack_dir dir,
35 unsigned long statusbit,
36 struct flowi *fl)
37{
38 const struct nf_conntrack_tuple *t = &ct->tuplehash[dir].tuple;
39 struct flowi4 *fl4 = &fl->u.ip4;
40
41 if (ct->status & statusbit) {
42 fl4->daddr = t->dst.u3.ip;
43 if (t->dst.protonum == IPPROTO_TCP ||
44 t->dst.protonum == IPPROTO_UDP ||
45 t->dst.protonum == IPPROTO_UDPLITE ||
46 t->dst.protonum == IPPROTO_DCCP ||
47 t->dst.protonum == IPPROTO_SCTP)
48 fl4->fl4_dport = t->dst.u.all;
49 }
50
51 statusbit ^= IPS_NAT_MASK;
52
53 if (ct->status & statusbit) {
54 fl4->saddr = t->src.u3.ip;
55 if (t->dst.protonum == IPPROTO_TCP ||
56 t->dst.protonum == IPPROTO_UDP ||
57 t->dst.protonum == IPPROTO_UDPLITE ||
58 t->dst.protonum == IPPROTO_DCCP ||
59 t->dst.protonum == IPPROTO_SCTP)
60 fl4->fl4_sport = t->src.u.all;
61 }
62}
63#endif
64
65static bool nf_nat_ipv4_in_range(const struct nf_conntrack_tuple *t,
66 const struct nf_nat_range *range)
67{
68 return ntohl(t->src.u3.ip) >= ntohl(range->min_addr.ip) &&
69 ntohl(t->src.u3.ip) <= ntohl(range->max_addr.ip);
70}
71
72static u32 nf_nat_ipv4_secure_port(const struct nf_conntrack_tuple *t,
73 __be16 dport)
74{
75 return secure_ipv4_port_ephemeral(t->src.u3.ip, t->dst.u3.ip, dport);
76}
77
78static bool nf_nat_ipv4_manip_pkt(struct sk_buff *skb,
79 unsigned int iphdroff,
80 const struct nf_nat_l4proto *l4proto,
81 const struct nf_conntrack_tuple *target,
82 enum nf_nat_manip_type maniptype)
83{
84 struct iphdr *iph;
85 unsigned int hdroff;
86
87 if (!skb_make_writable(skb, iphdroff + sizeof(*iph)))
88 return false;
89
90 iph = (void *)skb->data + iphdroff;
91 hdroff = iphdroff + iph->ihl * 4;
92
93 if (!l4proto->manip_pkt(skb, &nf_nat_l3proto_ipv4, iphdroff, hdroff,
94 target, maniptype))
95 return false;
96 iph = (void *)skb->data + iphdroff;
97
98 if (maniptype == NF_NAT_MANIP_SRC) {
99 csum_replace4(&iph->check, iph->saddr, target->src.u3.ip);
100 iph->saddr = target->src.u3.ip;
101 } else {
102 csum_replace4(&iph->check, iph->daddr, target->dst.u3.ip);
103 iph->daddr = target->dst.u3.ip;
104 }
105 return true;
106}
107
108static void nf_nat_ipv4_csum_update(struct sk_buff *skb,
109 unsigned int iphdroff, __sum16 *check,
110 const struct nf_conntrack_tuple *t,
111 enum nf_nat_manip_type maniptype)
112{
113 struct iphdr *iph = (struct iphdr *)(skb->data + iphdroff);
114 __be32 oldip, newip;
115
116 if (maniptype == NF_NAT_MANIP_SRC) {
117 oldip = iph->saddr;
118 newip = t->src.u3.ip;
119 } else {
120 oldip = iph->daddr;
121 newip = t->dst.u3.ip;
122 }
123 inet_proto_csum_replace4(check, skb, oldip, newip, true);
124}
125
126static void nf_nat_ipv4_csum_recalc(struct sk_buff *skb,
127 u8 proto, void *data, __sum16 *check,
128 int datalen, int oldlen)
129{
130 const struct iphdr *iph = ip_hdr(skb);
131 struct rtable *rt = skb_rtable(skb);
132
133 if (skb->ip_summed != CHECKSUM_PARTIAL) {
134 if (!(rt->rt_flags & RTCF_LOCAL) &&
135 (!skb->dev || skb->dev->features & NETIF_F_V4_CSUM)) {
136 skb->ip_summed = CHECKSUM_PARTIAL;
137 skb->csum_start = skb_headroom(skb) +
138 skb_network_offset(skb) +
139 ip_hdrlen(skb);
140 skb->csum_offset = (void *)check - data;
141 *check = ~csum_tcpudp_magic(iph->saddr, iph->daddr,
142 datalen, proto, 0);
143 } else {
144 *check = 0;
145 *check = csum_tcpudp_magic(iph->saddr, iph->daddr,
146 datalen, proto,
147 csum_partial(data, datalen,
148 0));
149 if (proto == IPPROTO_UDP && !*check)
150 *check = CSUM_MANGLED_0;
151 }
152 } else
153 inet_proto_csum_replace2(check, skb,
154 htons(oldlen), htons(datalen), true);
155}
156
157#if IS_ENABLED(CONFIG_NF_CT_NETLINK)
158static int nf_nat_ipv4_nlattr_to_range(struct nlattr *tb[],
159 struct nf_nat_range *range)
160{
161 if (tb[CTA_NAT_V4_MINIP]) {
162 range->min_addr.ip = nla_get_be32(tb[CTA_NAT_V4_MINIP]);
163 range->flags |= NF_NAT_RANGE_MAP_IPS;
164 }
165
166 if (tb[CTA_NAT_V4_MAXIP])
167 range->max_addr.ip = nla_get_be32(tb[CTA_NAT_V4_MAXIP]);
168 else
169 range->max_addr.ip = range->min_addr.ip;
170
171 return 0;
172}
173#endif
174
175static const struct nf_nat_l3proto nf_nat_l3proto_ipv4 = {
176 .l3proto = NFPROTO_IPV4,
177 .in_range = nf_nat_ipv4_in_range,
178 .secure_port = nf_nat_ipv4_secure_port,
179 .manip_pkt = nf_nat_ipv4_manip_pkt,
180 .csum_update = nf_nat_ipv4_csum_update,
181 .csum_recalc = nf_nat_ipv4_csum_recalc,
182#if IS_ENABLED(CONFIG_NF_CT_NETLINK)
183 .nlattr_to_range = nf_nat_ipv4_nlattr_to_range,
184#endif
185#ifdef CONFIG_XFRM
186 .decode_session = nf_nat_ipv4_decode_session,
187#endif
188};
189
190int nf_nat_icmp_reply_translation(struct sk_buff *skb,
191 struct nf_conn *ct,
192 enum ip_conntrack_info ctinfo,
193 unsigned int hooknum)
194{
195 struct {
196 struct icmphdr icmp;
197 struct iphdr ip;
198 } *inside;
199 enum ip_conntrack_dir dir = CTINFO2DIR(ctinfo);
200 enum nf_nat_manip_type manip = HOOK2MANIP(hooknum);
201 unsigned int hdrlen = ip_hdrlen(skb);
202 const struct nf_nat_l4proto *l4proto;
203 struct nf_conntrack_tuple target;
204 unsigned long statusbit;
205
206 NF_CT_ASSERT(ctinfo == IP_CT_RELATED || ctinfo == IP_CT_RELATED_REPLY);
207
208 if (!skb_make_writable(skb, hdrlen + sizeof(*inside)))
209 return 0;
210 if (nf_ip_checksum(skb, hooknum, hdrlen, 0))
211 return 0;
212
213 inside = (void *)skb->data + hdrlen;
214 if (inside->icmp.type == ICMP_REDIRECT) {
215 if ((ct->status & IPS_NAT_DONE_MASK) != IPS_NAT_DONE_MASK)
216 return 0;
217 if (ct->status & IPS_NAT_MASK)
218 return 0;
219 }
220
221 if (manip == NF_NAT_MANIP_SRC)
222 statusbit = IPS_SRC_NAT;
223 else
224 statusbit = IPS_DST_NAT;
225
226
227 if (dir == IP_CT_DIR_REPLY)
228 statusbit ^= IPS_NAT_MASK;
229
230 if (!(ct->status & statusbit))
231 return 1;
232
233 l4proto = __nf_nat_l4proto_find(NFPROTO_IPV4, inside->ip.protocol);
234 if (!nf_nat_ipv4_manip_pkt(skb, hdrlen + sizeof(inside->icmp),
235 l4proto, &ct->tuplehash[!dir].tuple, !manip))
236 return 0;
237
238 if (skb->ip_summed != CHECKSUM_PARTIAL) {
239
240 inside = (void *)skb->data + hdrlen;
241 inside->icmp.checksum = 0;
242 inside->icmp.checksum =
243 csum_fold(skb_checksum(skb, hdrlen,
244 skb->len - hdrlen, 0));
245 }
246
247
248 nf_ct_invert_tuplepr(&target, &ct->tuplehash[!dir].tuple);
249 l4proto = __nf_nat_l4proto_find(NFPROTO_IPV4, 0);
250 if (!nf_nat_ipv4_manip_pkt(skb, 0, l4proto, &target, manip))
251 return 0;
252
253 return 1;
254}
255EXPORT_SYMBOL_GPL(nf_nat_icmp_reply_translation);
256
257unsigned int
258nf_nat_ipv4_fn(const struct nf_hook_ops *ops, struct sk_buff *skb,
259 const struct nf_hook_state *state,
260 unsigned int (*do_chain)(const struct nf_hook_ops *ops,
261 struct sk_buff *skb,
262 const struct nf_hook_state *state,
263 struct nf_conn *ct))
264{
265 struct nf_conn *ct;
266 enum ip_conntrack_info ctinfo;
267 struct nf_conn_nat *nat;
268
269 enum nf_nat_manip_type maniptype = HOOK2MANIP(ops->hooknum);
270
271
272
273
274 NF_CT_ASSERT(!ip_is_fragment(ip_hdr(skb)));
275
276 ct = nf_ct_get(skb, &ctinfo);
277
278
279
280
281
282 if (!ct)
283 return NF_ACCEPT;
284
285
286 if (nf_ct_is_untracked(ct))
287 return NF_ACCEPT;
288
289 nat = nf_ct_nat_ext_add(ct);
290 if (nat == NULL)
291 return NF_ACCEPT;
292
293 switch (ctinfo) {
294 case IP_CT_RELATED:
295 case IP_CT_RELATED_REPLY:
296 if (ip_hdr(skb)->protocol == IPPROTO_ICMP) {
297 if (!nf_nat_icmp_reply_translation(skb, ct, ctinfo,
298 ops->hooknum))
299 return NF_DROP;
300 else
301 return NF_ACCEPT;
302 }
303
304 case IP_CT_NEW:
305
306
307
308 if (!nf_nat_initialized(ct, maniptype)) {
309 unsigned int ret;
310
311 ret = do_chain(ops, skb, state, ct);
312 if (ret != NF_ACCEPT)
313 return ret;
314
315 if (nf_nat_initialized(ct, HOOK2MANIP(ops->hooknum)))
316 break;
317
318 ret = nf_nat_alloc_null_binding(ct, ops->hooknum);
319 if (ret != NF_ACCEPT)
320 return ret;
321 } else {
322 pr_debug("Already setup manip %s for ct %p\n",
323 maniptype == NF_NAT_MANIP_SRC ? "SRC" : "DST",
324 ct);
325 if (nf_nat_oif_changed(ops->hooknum, ctinfo, nat,
326 state->out))
327 goto oif_changed;
328 }
329 break;
330
331 default:
332
333 NF_CT_ASSERT(ctinfo == IP_CT_ESTABLISHED ||
334 ctinfo == IP_CT_ESTABLISHED_REPLY);
335 if (nf_nat_oif_changed(ops->hooknum, ctinfo, nat, state->out))
336 goto oif_changed;
337 }
338
339 return nf_nat_packet(ct, ctinfo, ops->hooknum, skb);
340
341oif_changed:
342 nf_ct_kill_acct(ct, ctinfo, skb);
343 return NF_DROP;
344}
345EXPORT_SYMBOL_GPL(nf_nat_ipv4_fn);
346
347unsigned int
348nf_nat_ipv4_in(const struct nf_hook_ops *ops, struct sk_buff *skb,
349 const struct nf_hook_state *state,
350 unsigned int (*do_chain)(const struct nf_hook_ops *ops,
351 struct sk_buff *skb,
352 const struct nf_hook_state *state,
353 struct nf_conn *ct))
354{
355 unsigned int ret;
356 __be32 daddr = ip_hdr(skb)->daddr;
357
358 ret = nf_nat_ipv4_fn(ops, skb, state, do_chain);
359 if (ret != NF_DROP && ret != NF_STOLEN &&
360 daddr != ip_hdr(skb)->daddr)
361 skb_dst_drop(skb);
362
363 return ret;
364}
365EXPORT_SYMBOL_GPL(nf_nat_ipv4_in);
366
367unsigned int
368nf_nat_ipv4_out(const struct nf_hook_ops *ops, struct sk_buff *skb,
369 const struct nf_hook_state *state,
370 unsigned int (*do_chain)(const struct nf_hook_ops *ops,
371 struct sk_buff *skb,
372 const struct nf_hook_state *state,
373 struct nf_conn *ct))
374{
375#ifdef CONFIG_XFRM
376 const struct nf_conn *ct;
377 enum ip_conntrack_info ctinfo;
378 int err;
379#endif
380 unsigned int ret;
381
382
383 if (skb->len < sizeof(struct iphdr) ||
384 ip_hdrlen(skb) < sizeof(struct iphdr))
385 return NF_ACCEPT;
386
387 ret = nf_nat_ipv4_fn(ops, skb, state, do_chain);
388#ifdef CONFIG_XFRM
389 if (ret != NF_DROP && ret != NF_STOLEN &&
390 !(IPCB(skb)->flags & IPSKB_XFRM_TRANSFORMED) &&
391 (ct = nf_ct_get(skb, &ctinfo)) != NULL) {
392 enum ip_conntrack_dir dir = CTINFO2DIR(ctinfo);
393
394 if ((ct->tuplehash[dir].tuple.src.u3.ip !=
395 ct->tuplehash[!dir].tuple.dst.u3.ip) ||
396 (ct->tuplehash[dir].tuple.dst.protonum != IPPROTO_ICMP &&
397 ct->tuplehash[dir].tuple.src.u.all !=
398 ct->tuplehash[!dir].tuple.dst.u.all)) {
399 err = nf_xfrm_me_harder(skb, AF_INET);
400 if (err < 0)
401 ret = NF_DROP_ERR(err);
402 }
403 }
404#endif
405 return ret;
406}
407EXPORT_SYMBOL_GPL(nf_nat_ipv4_out);
408
409unsigned int
410nf_nat_ipv4_local_fn(const struct nf_hook_ops *ops, struct sk_buff *skb,
411 const struct nf_hook_state *state,
412 unsigned int (*do_chain)(const struct nf_hook_ops *ops,
413 struct sk_buff *skb,
414 const struct nf_hook_state *state,
415 struct nf_conn *ct))
416{
417 const struct nf_conn *ct;
418 enum ip_conntrack_info ctinfo;
419 unsigned int ret;
420 int err;
421
422
423 if (skb->len < sizeof(struct iphdr) ||
424 ip_hdrlen(skb) < sizeof(struct iphdr))
425 return NF_ACCEPT;
426
427 ret = nf_nat_ipv4_fn(ops, skb, state, do_chain);
428 if (ret != NF_DROP && ret != NF_STOLEN &&
429 (ct = nf_ct_get(skb, &ctinfo)) != NULL) {
430 enum ip_conntrack_dir dir = CTINFO2DIR(ctinfo);
431
432 if (ct->tuplehash[dir].tuple.dst.u3.ip !=
433 ct->tuplehash[!dir].tuple.src.u3.ip) {
434 err = ip_route_me_harder(skb, RTN_UNSPEC);
435 if (err < 0)
436 ret = NF_DROP_ERR(err);
437 }
438#ifdef CONFIG_XFRM
439 else if (!(IPCB(skb)->flags & IPSKB_XFRM_TRANSFORMED) &&
440 ct->tuplehash[dir].tuple.dst.protonum != IPPROTO_ICMP &&
441 ct->tuplehash[dir].tuple.dst.u.all !=
442 ct->tuplehash[!dir].tuple.src.u.all) {
443 err = nf_xfrm_me_harder(skb, AF_INET);
444 if (err < 0)
445 ret = NF_DROP_ERR(err);
446 }
447#endif
448 }
449 return ret;
450}
451EXPORT_SYMBOL_GPL(nf_nat_ipv4_local_fn);
452
453static int __init nf_nat_l3proto_ipv4_init(void)
454{
455 int err;
456
457 err = nf_nat_l4proto_register(NFPROTO_IPV4, &nf_nat_l4proto_icmp);
458 if (err < 0)
459 goto err1;
460 err = nf_nat_l3proto_register(&nf_nat_l3proto_ipv4);
461 if (err < 0)
462 goto err2;
463 return err;
464
465err2:
466 nf_nat_l4proto_unregister(NFPROTO_IPV4, &nf_nat_l4proto_icmp);
467err1:
468 return err;
469}
470
471static void __exit nf_nat_l3proto_ipv4_exit(void)
472{
473 nf_nat_l3proto_unregister(&nf_nat_l3proto_ipv4);
474 nf_nat_l4proto_unregister(NFPROTO_IPV4, &nf_nat_l4proto_icmp);
475}
476
477MODULE_LICENSE("GPL");
478MODULE_ALIAS("nf-nat-" __stringify(AF_INET));
479
480module_init(nf_nat_l3proto_ipv4_init);
481module_exit(nf_nat_l3proto_ipv4_exit);
482
