1 /* NAT for netfilter; shared with compatibility layer. */
3 /* (C) 1999-2001 Paul `Rusty' Russell
4 * (C) 2002-2006 Netfilter Core Team <coreteam@netfilter.org>
6 * This program is free software; you can redistribute it and/or modify
7 * it under the terms of the GNU General Public License version 2 as
8 * published by the Free Software Foundation.
11 #include <linux/module.h>
12 #include <linux/types.h>
13 #include <linux/timer.h>
14 #include <linux/skbuff.h>
15 #include <linux/vmalloc.h>
16 #include <net/checksum.h>
19 #include <net/tcp.h> /* For tcp_prot in getorigdst */
20 #include <linux/icmp.h>
21 #include <linux/udp.h>
22 #include <linux/jhash.h>
24 #include <linux/netfilter_ipv4.h>
25 #include <net/netfilter/nf_conntrack.h>
26 #include <net/netfilter/nf_conntrack_core.h>
27 #include <net/netfilter/nf_nat.h>
28 #include <net/netfilter/nf_nat_protocol.h>
29 #include <net/netfilter/nf_nat_core.h>
30 #include <net/netfilter/nf_nat_helper.h>
31 #include <net/netfilter/nf_conntrack_helper.h>
32 #include <net/netfilter/nf_conntrack_l3proto.h>
33 #include <net/netfilter/nf_conntrack_l4proto.h>
38 #define DEBUGP(format, args...)
41 static DEFINE_RWLOCK(nf_nat_lock
);
43 static struct nf_conntrack_l3proto
*l3proto
= NULL
;
45 /* Calculated at init based on memory size */
46 static unsigned int nf_nat_htable_size
;
48 static struct list_head
*bysource
;
50 #define MAX_IP_NAT_PROTO 256
51 static struct nf_nat_protocol
*nf_nat_protos
[MAX_IP_NAT_PROTO
];
53 static inline struct nf_nat_protocol
*
54 __nf_nat_proto_find(u_int8_t protonum
)
56 return nf_nat_protos
[protonum
];
59 struct nf_nat_protocol
*
60 nf_nat_proto_find_get(u_int8_t protonum
)
62 struct nf_nat_protocol
*p
;
64 /* we need to disable preemption to make sure 'p' doesn't get
65 * removed until we've grabbed the reference */
67 p
= __nf_nat_proto_find(protonum
);
68 if (!try_module_get(p
->me
))
69 p
= &nf_nat_unknown_protocol
;
74 EXPORT_SYMBOL_GPL(nf_nat_proto_find_get
);
77 nf_nat_proto_put(struct nf_nat_protocol
*p
)
81 EXPORT_SYMBOL_GPL(nf_nat_proto_put
);
83 /* We keep an extra hash for each conntrack, for fast searching. */
84 static inline unsigned int
85 hash_by_src(const struct nf_conntrack_tuple
*tuple
)
87 /* Original src, to ensure we map it consistently if poss. */
88 return jhash_3words((__force u32
)tuple
->src
.u3
.ip
, tuple
->src
.u
.all
,
89 tuple
->dst
.protonum
, 0) % nf_nat_htable_size
;
92 /* Noone using conntrack by the time this called. */
93 static void nf_nat_cleanup_conntrack(struct nf_conn
*conn
)
95 struct nf_conn_nat
*nat
;
96 if (!(conn
->status
& IPS_NAT_DONE_MASK
))
100 write_lock_bh(&nf_nat_lock
);
101 list_del(&nat
->info
.bysource
);
102 write_unlock_bh(&nf_nat_lock
);
105 /* Is this tuple already taken? (not by us) */
107 nf_nat_used_tuple(const struct nf_conntrack_tuple
*tuple
,
108 const struct nf_conn
*ignored_conntrack
)
110 /* Conntrack tracking doesn't keep track of outgoing tuples; only
111 incoming ones. NAT means they don't have a fixed mapping,
112 so we invert the tuple and look for the incoming reply.
114 We could keep a separate hash if this proves too slow. */
115 struct nf_conntrack_tuple reply
;
117 nf_ct_invert_tuplepr(&reply
, tuple
);
118 return nf_conntrack_tuple_taken(&reply
, ignored_conntrack
);
120 EXPORT_SYMBOL(nf_nat_used_tuple
);
122 /* If we source map this tuple so reply looks like reply_tuple, will
123 * that meet the constraints of range. */
125 in_range(const struct nf_conntrack_tuple
*tuple
,
126 const struct nf_nat_range
*range
)
128 struct nf_nat_protocol
*proto
;
130 proto
= __nf_nat_proto_find(tuple
->dst
.protonum
);
131 /* If we are supposed to map IPs, then we must be in the
132 range specified, otherwise let this drag us onto a new src IP. */
133 if (range
->flags
& IP_NAT_RANGE_MAP_IPS
) {
134 if (ntohl(tuple
->src
.u3
.ip
) < ntohl(range
->min_ip
) ||
135 ntohl(tuple
->src
.u3
.ip
) > ntohl(range
->max_ip
))
139 if (!(range
->flags
& IP_NAT_RANGE_PROTO_SPECIFIED
) ||
140 proto
->in_range(tuple
, IP_NAT_MANIP_SRC
,
141 &range
->min
, &range
->max
))
148 same_src(const struct nf_conn
*ct
,
149 const struct nf_conntrack_tuple
*tuple
)
151 const struct nf_conntrack_tuple
*t
;
153 t
= &ct
->tuplehash
[IP_CT_DIR_ORIGINAL
].tuple
;
154 return (t
->dst
.protonum
== tuple
->dst
.protonum
&&
155 t
->src
.u3
.ip
== tuple
->src
.u3
.ip
&&
156 t
->src
.u
.all
== tuple
->src
.u
.all
);
159 /* Only called for SRC manip */
161 find_appropriate_src(const struct nf_conntrack_tuple
*tuple
,
162 struct nf_conntrack_tuple
*result
,
163 const struct nf_nat_range
*range
)
165 unsigned int h
= hash_by_src(tuple
);
166 struct nf_conn_nat
*nat
;
169 read_lock_bh(&nf_nat_lock
);
170 list_for_each_entry(nat
, &bysource
[h
], info
.bysource
) {
171 ct
= (struct nf_conn
*)((char *)nat
- offsetof(struct nf_conn
, data
));
172 if (same_src(ct
, tuple
)) {
173 /* Copy source part from reply tuple. */
174 nf_ct_invert_tuplepr(result
,
175 &ct
->tuplehash
[IP_CT_DIR_REPLY
].tuple
);
176 result
->dst
= tuple
->dst
;
178 if (in_range(result
, range
)) {
179 read_unlock_bh(&nf_nat_lock
);
184 read_unlock_bh(&nf_nat_lock
);
188 /* For [FUTURE] fragmentation handling, we want the least-used
189 src-ip/dst-ip/proto triple. Fairness doesn't come into it. Thus
190 if the range specifies 1.2.3.4 ports 10000-10005 and 1.2.3.5 ports
191 1-65535, we don't do pro-rata allocation based on ports; we choose
192 the ip with the lowest src-ip/dst-ip/proto usage.
195 find_best_ips_proto(struct nf_conntrack_tuple
*tuple
,
196 const struct nf_nat_range
*range
,
197 const struct nf_conn
*ct
,
198 enum nf_nat_manip_type maniptype
)
202 u_int32_t minip
, maxip
, j
;
204 /* No IP mapping? Do nothing. */
205 if (!(range
->flags
& IP_NAT_RANGE_MAP_IPS
))
208 if (maniptype
== IP_NAT_MANIP_SRC
)
209 var_ipp
= &tuple
->src
.u3
.ip
;
211 var_ipp
= &tuple
->dst
.u3
.ip
;
213 /* Fast path: only one choice. */
214 if (range
->min_ip
== range
->max_ip
) {
215 *var_ipp
= range
->min_ip
;
219 /* Hashing source and destination IPs gives a fairly even
220 * spread in practice (if there are a small number of IPs
221 * involved, there usually aren't that many connections
222 * anyway). The consistency means that servers see the same
223 * client coming from the same IP (some Internet Banking sites
224 * like this), even across reboots. */
225 minip
= ntohl(range
->min_ip
);
226 maxip
= ntohl(range
->max_ip
);
227 j
= jhash_2words((__force u32
)tuple
->src
.u3
.ip
,
228 (__force u32
)tuple
->dst
.u3
.ip
, 0);
229 *var_ipp
= htonl(minip
+ j
% (maxip
- minip
+ 1));
232 /* Manipulate the tuple into the range given. For NF_IP_POST_ROUTING,
233 * we change the source to map into the range. For NF_IP_PRE_ROUTING
234 * and NF_IP_LOCAL_OUT, we change the destination to map into the
235 * range. It might not be possible to get a unique tuple, but we try.
236 * At worst (or if we race), we will end up with a final duplicate in
237 * __ip_conntrack_confirm and drop the packet. */
239 get_unique_tuple(struct nf_conntrack_tuple
*tuple
,
240 const struct nf_conntrack_tuple
*orig_tuple
,
241 const struct nf_nat_range
*range
,
243 enum nf_nat_manip_type maniptype
)
245 struct nf_nat_protocol
*proto
;
247 /* 1) If this srcip/proto/src-proto-part is currently mapped,
248 and that same mapping gives a unique tuple within the given
251 This is only required for source (ie. NAT/masq) mappings.
252 So far, we don't do local source mappings, so multiple
253 manips not an issue. */
254 if (maniptype
== IP_NAT_MANIP_SRC
) {
255 if (find_appropriate_src(orig_tuple
, tuple
, range
)) {
256 DEBUGP("get_unique_tuple: Found current src map\n");
257 if (!nf_nat_used_tuple(tuple
, ct
))
262 /* 2) Select the least-used IP/proto combination in the given
264 *tuple
= *orig_tuple
;
265 find_best_ips_proto(tuple
, range
, ct
, maniptype
);
267 /* 3) The per-protocol part of the manip is made to map into
268 the range to make a unique tuple. */
270 proto
= nf_nat_proto_find_get(orig_tuple
->dst
.protonum
);
272 /* Only bother mapping if it's not already in range and unique */
273 if ((!(range
->flags
& IP_NAT_RANGE_PROTO_SPECIFIED
) ||
274 proto
->in_range(tuple
, maniptype
, &range
->min
, &range
->max
)) &&
275 !nf_nat_used_tuple(tuple
, ct
)) {
276 nf_nat_proto_put(proto
);
280 /* Last change: get protocol to try to obtain unique tuple. */
281 proto
->unique_tuple(tuple
, range
, maniptype
, ct
);
283 nf_nat_proto_put(proto
);
287 nf_nat_setup_info(struct nf_conn
*ct
,
288 const struct nf_nat_range
*range
,
289 unsigned int hooknum
)
291 struct nf_conntrack_tuple curr_tuple
, new_tuple
;
292 struct nf_conn_nat
*nat
= nfct_nat(ct
);
293 struct nf_nat_info
*info
= &nat
->info
;
294 int have_to_hash
= !(ct
->status
& IPS_NAT_DONE_MASK
);
295 enum nf_nat_manip_type maniptype
= HOOK2MANIP(hooknum
);
297 NF_CT_ASSERT(hooknum
== NF_IP_PRE_ROUTING
||
298 hooknum
== NF_IP_POST_ROUTING
||
299 hooknum
== NF_IP_LOCAL_IN
||
300 hooknum
== NF_IP_LOCAL_OUT
);
301 BUG_ON(nf_nat_initialized(ct
, maniptype
));
303 /* What we've got will look like inverse of reply. Normally
304 this is what is in the conntrack, except for prior
305 manipulations (future optimization: if num_manips == 0,
307 conntrack->tuplehash[IP_CT_DIR_ORIGINAL].tuple) */
308 nf_ct_invert_tuplepr(&curr_tuple
,
309 &ct
->tuplehash
[IP_CT_DIR_REPLY
].tuple
);
311 get_unique_tuple(&new_tuple
, &curr_tuple
, range
, ct
, maniptype
);
313 if (!nf_ct_tuple_equal(&new_tuple
, &curr_tuple
)) {
314 struct nf_conntrack_tuple reply
;
316 /* Alter conntrack table so will recognize replies. */
317 nf_ct_invert_tuplepr(&reply
, &new_tuple
);
318 nf_conntrack_alter_reply(ct
, &reply
);
320 /* Non-atomic: we own this at the moment. */
321 if (maniptype
== IP_NAT_MANIP_SRC
)
322 ct
->status
|= IPS_SRC_NAT
;
324 ct
->status
|= IPS_DST_NAT
;
327 /* Place in source hash if this is the first time. */
329 unsigned int srchash
;
331 srchash
= hash_by_src(&ct
->tuplehash
[IP_CT_DIR_ORIGINAL
].tuple
);
332 write_lock_bh(&nf_nat_lock
);
333 list_add(&info
->bysource
, &bysource
[srchash
]);
334 write_unlock_bh(&nf_nat_lock
);
338 if (maniptype
== IP_NAT_MANIP_DST
)
339 set_bit(IPS_DST_NAT_DONE_BIT
, &ct
->status
);
341 set_bit(IPS_SRC_NAT_DONE_BIT
, &ct
->status
);
345 EXPORT_SYMBOL(nf_nat_setup_info
);
347 /* Returns true if succeeded. */
349 manip_pkt(u_int16_t proto
,
350 struct sk_buff
**pskb
,
351 unsigned int iphdroff
,
352 const struct nf_conntrack_tuple
*target
,
353 enum nf_nat_manip_type maniptype
)
356 struct nf_nat_protocol
*p
;
358 if (!skb_make_writable(pskb
, iphdroff
+ sizeof(*iph
)))
361 iph
= (void *)(*pskb
)->data
+ iphdroff
;
363 /* Manipulate protcol part. */
364 p
= nf_nat_proto_find_get(proto
);
365 if (!p
->manip_pkt(pskb
, iphdroff
, target
, maniptype
)) {
371 iph
= (void *)(*pskb
)->data
+ iphdroff
;
373 if (maniptype
== IP_NAT_MANIP_SRC
) {
374 nf_csum_replace4(&iph
->check
, iph
->saddr
, target
->src
.u3
.ip
);
375 iph
->saddr
= target
->src
.u3
.ip
;
377 nf_csum_replace4(&iph
->check
, iph
->daddr
, target
->dst
.u3
.ip
);
378 iph
->daddr
= target
->dst
.u3
.ip
;
383 /* Do packet manipulations according to nf_nat_setup_info. */
384 unsigned int nf_nat_packet(struct nf_conn
*ct
,
385 enum ip_conntrack_info ctinfo
,
386 unsigned int hooknum
,
387 struct sk_buff
**pskb
)
389 enum ip_conntrack_dir dir
= CTINFO2DIR(ctinfo
);
390 unsigned long statusbit
;
391 enum nf_nat_manip_type mtype
= HOOK2MANIP(hooknum
);
393 if (mtype
== IP_NAT_MANIP_SRC
)
394 statusbit
= IPS_SRC_NAT
;
396 statusbit
= IPS_DST_NAT
;
398 /* Invert if this is reply dir. */
399 if (dir
== IP_CT_DIR_REPLY
)
400 statusbit
^= IPS_NAT_MASK
;
402 /* Non-atomic: these bits don't change. */
403 if (ct
->status
& statusbit
) {
404 struct nf_conntrack_tuple target
;
406 /* We are aiming to look like inverse of other direction. */
407 nf_ct_invert_tuplepr(&target
, &ct
->tuplehash
[!dir
].tuple
);
409 if (!manip_pkt(target
.dst
.protonum
, pskb
, 0, &target
, mtype
))
414 EXPORT_SYMBOL_GPL(nf_nat_packet
);
416 /* Dir is direction ICMP is coming from (opposite to packet it contains) */
417 int nf_nat_icmp_reply_translation(struct nf_conn
*ct
,
418 enum ip_conntrack_info ctinfo
,
419 unsigned int hooknum
,
420 struct sk_buff
**pskb
)
426 struct nf_conntrack_tuple inner
, target
;
427 int hdrlen
= (*pskb
)->nh
.iph
->ihl
* 4;
428 enum ip_conntrack_dir dir
= CTINFO2DIR(ctinfo
);
429 unsigned long statusbit
;
430 enum nf_nat_manip_type manip
= HOOK2MANIP(hooknum
);
432 if (!skb_make_writable(pskb
, hdrlen
+ sizeof(*inside
)))
435 inside
= (void *)(*pskb
)->data
+ (*pskb
)->nh
.iph
->ihl
*4;
437 /* We're actually going to mangle it beyond trivial checksum
438 adjustment, so make sure the current checksum is correct. */
439 if (nf_ip_checksum(*pskb
, hooknum
, hdrlen
, 0))
442 /* Must be RELATED */
443 NF_CT_ASSERT((*pskb
)->nfctinfo
== IP_CT_RELATED
||
444 (*pskb
)->nfctinfo
== IP_CT_RELATED
+IP_CT_IS_REPLY
);
446 /* Redirects on non-null nats must be dropped, else they'll
447 start talking to each other without our translation, and be
449 if (inside
->icmp
.type
== ICMP_REDIRECT
) {
450 /* If NAT isn't finished, assume it and drop. */
451 if ((ct
->status
& IPS_NAT_DONE_MASK
) != IPS_NAT_DONE_MASK
)
454 if (ct
->status
& IPS_NAT_MASK
)
458 DEBUGP("icmp_reply_translation: translating error %p manp %u dir %s\n",
459 *pskb
, manip
, dir
== IP_CT_DIR_ORIGINAL
? "ORIG" : "REPLY");
461 if (!nf_ct_get_tuple(*pskb
,
462 (*pskb
)->nh
.iph
->ihl
*4 + sizeof(struct icmphdr
),
463 (*pskb
)->nh
.iph
->ihl
*4 +
464 sizeof(struct icmphdr
) + inside
->ip
.ihl
*4,
469 __nf_ct_l4proto_find((u_int16_t
)PF_INET
,
470 inside
->ip
.protocol
)))
473 /* Change inner back to look like incoming packet. We do the
474 opposite manip on this hook to normal, because it might not
475 pass all hooks (locally-generated ICMP). Consider incoming
476 packet: PREROUTING (DST manip), routing produces ICMP, goes
477 through POSTROUTING (which must correct the DST manip). */
478 if (!manip_pkt(inside
->ip
.protocol
, pskb
,
479 (*pskb
)->nh
.iph
->ihl
*4 + sizeof(inside
->icmp
),
480 &ct
->tuplehash
[!dir
].tuple
,
484 if ((*pskb
)->ip_summed
!= CHECKSUM_PARTIAL
) {
485 /* Reloading "inside" here since manip_pkt inner. */
486 inside
= (void *)(*pskb
)->data
+ (*pskb
)->nh
.iph
->ihl
*4;
487 inside
->icmp
.checksum
= 0;
488 inside
->icmp
.checksum
=
489 csum_fold(skb_checksum(*pskb
, hdrlen
,
490 (*pskb
)->len
- hdrlen
, 0));
493 /* Change outer to look the reply to an incoming packet
494 * (proto 0 means don't invert per-proto part). */
495 if (manip
== IP_NAT_MANIP_SRC
)
496 statusbit
= IPS_SRC_NAT
;
498 statusbit
= IPS_DST_NAT
;
500 /* Invert if this is reply dir. */
501 if (dir
== IP_CT_DIR_REPLY
)
502 statusbit
^= IPS_NAT_MASK
;
504 if (ct
->status
& statusbit
) {
505 nf_ct_invert_tuplepr(&target
, &ct
->tuplehash
[!dir
].tuple
);
506 if (!manip_pkt(0, pskb
, 0, &target
, manip
))
512 EXPORT_SYMBOL_GPL(nf_nat_icmp_reply_translation
);
514 /* Protocol registration. */
515 int nf_nat_protocol_register(struct nf_nat_protocol
*proto
)
519 write_lock_bh(&nf_nat_lock
);
520 if (nf_nat_protos
[proto
->protonum
] != &nf_nat_unknown_protocol
) {
524 nf_nat_protos
[proto
->protonum
] = proto
;
526 write_unlock_bh(&nf_nat_lock
);
529 EXPORT_SYMBOL(nf_nat_protocol_register
);
531 /* Noone stores the protocol anywhere; simply delete it. */
532 void nf_nat_protocol_unregister(struct nf_nat_protocol
*proto
)
534 write_lock_bh(&nf_nat_lock
);
535 nf_nat_protos
[proto
->protonum
] = &nf_nat_unknown_protocol
;
536 write_unlock_bh(&nf_nat_lock
);
538 /* Someone could be still looking at the proto in a bh. */
541 EXPORT_SYMBOL(nf_nat_protocol_unregister
);
543 #if defined(CONFIG_IP_NF_CONNTRACK_NETLINK) || \
544 defined(CONFIG_IP_NF_CONNTRACK_NETLINK_MODULE)
546 nf_nat_port_range_to_nfattr(struct sk_buff
*skb
,
547 const struct nf_nat_range
*range
)
549 NFA_PUT(skb
, CTA_PROTONAT_PORT_MIN
, sizeof(__be16
),
550 &range
->min
.tcp
.port
);
551 NFA_PUT(skb
, CTA_PROTONAT_PORT_MAX
, sizeof(__be16
),
552 &range
->max
.tcp
.port
);
559 EXPORT_SYMBOL_GPL(nf_nat_port_nfattr_to_range
);
562 nf_nat_port_nfattr_to_range(struct nfattr
*tb
[], struct nf_nat_range
*range
)
566 /* we have to return whether we actually parsed something or not */
568 if (tb
[CTA_PROTONAT_PORT_MIN
-1]) {
570 range
->min
.tcp
.port
=
571 *(__be16
*)NFA_DATA(tb
[CTA_PROTONAT_PORT_MIN
-1]);
574 if (!tb
[CTA_PROTONAT_PORT_MAX
-1]) {
576 range
->max
.tcp
.port
= range
->min
.tcp
.port
;
579 range
->max
.tcp
.port
=
580 *(__be16
*)NFA_DATA(tb
[CTA_PROTONAT_PORT_MAX
-1]);
585 EXPORT_SYMBOL_GPL(nf_nat_port_range_to_nfattr
);
588 static int __init
nf_nat_init(void)
592 /* Leave them the same for the moment. */
593 nf_nat_htable_size
= nf_conntrack_htable_size
;
595 /* One vmalloc for both hash tables */
596 bysource
= vmalloc(sizeof(struct list_head
) * nf_nat_htable_size
);
600 /* Sew in builtin protocols. */
601 write_lock_bh(&nf_nat_lock
);
602 for (i
= 0; i
< MAX_IP_NAT_PROTO
; i
++)
603 nf_nat_protos
[i
] = &nf_nat_unknown_protocol
;
604 nf_nat_protos
[IPPROTO_TCP
] = &nf_nat_protocol_tcp
;
605 nf_nat_protos
[IPPROTO_UDP
] = &nf_nat_protocol_udp
;
606 nf_nat_protos
[IPPROTO_ICMP
] = &nf_nat_protocol_icmp
;
607 write_unlock_bh(&nf_nat_lock
);
609 for (i
= 0; i
< nf_nat_htable_size
; i
++) {
610 INIT_LIST_HEAD(&bysource
[i
]);
613 /* FIXME: Man, this is a hack. <SIGH> */
614 NF_CT_ASSERT(nf_conntrack_destroyed
== NULL
);
615 nf_conntrack_destroyed
= &nf_nat_cleanup_conntrack
;
617 /* Initialize fake conntrack so that NAT will skip it */
618 nf_conntrack_untracked
.status
|= IPS_NAT_DONE_MASK
;
620 l3proto
= nf_ct_l3proto_find_get((u_int16_t
)AF_INET
);
624 /* Clear NAT section of all conntracks, in case we're loaded again. */
625 static int clean_nat(struct nf_conn
*i
, void *data
)
627 struct nf_conn_nat
*nat
= nfct_nat(i
);
631 memset(nat
, 0, sizeof(nat
));
632 i
->status
&= ~(IPS_NAT_MASK
| IPS_NAT_DONE_MASK
| IPS_SEQ_ADJUST
);
636 static void __exit
nf_nat_cleanup(void)
638 nf_ct_iterate_cleanup(&clean_nat
, NULL
);
639 nf_conntrack_destroyed
= NULL
;
641 nf_ct_l3proto_put(l3proto
);
644 MODULE_LICENSE("GPL");
646 module_init(nf_nat_init
);
647 module_exit(nf_nat_cleanup
);