1 // SPDX-License-Identifier: GPL-2.0-only
2 /* Helper handling for netfilter. */
4 /* (C) 1999-2001 Paul `Rusty' Russell
5 * (C) 2002-2006 Netfilter Core Team <coreteam@netfilter.org>
6 * (C) 2003,2004 USAGI/WIDE Project <http://www.linux-ipv6.org>
7 * (C) 2006-2012 Patrick McHardy <kaber@trash.net>
10 #include <linux/types.h>
11 #include <linux/netfilter.h>
12 #include <linux/module.h>
13 #include <linux/skbuff.h>
14 #include <linux/vmalloc.h>
15 #include <linux/stddef.h>
16 #include <linux/random.h>
17 #include <linux/err.h>
18 #include <linux/kernel.h>
19 #include <linux/netdevice.h>
20 #include <linux/rculist.h>
21 #include <linux/rtnetlink.h>
23 #include <net/netfilter/nf_conntrack.h>
24 #include <net/netfilter/nf_conntrack_core.h>
25 #include <net/netfilter/nf_conntrack_ecache.h>
26 #include <net/netfilter/nf_conntrack_extend.h>
27 #include <net/netfilter/nf_conntrack_helper.h>
28 #include <net/netfilter/nf_conntrack_l4proto.h>
29 #include <net/netfilter/nf_log.h>
31 static DEFINE_MUTEX(nf_ct_helper_mutex
);
32 struct hlist_head
*nf_ct_helper_hash __read_mostly
;
33 EXPORT_SYMBOL_GPL(nf_ct_helper_hash
);
34 unsigned int nf_ct_helper_hsize __read_mostly
;
35 EXPORT_SYMBOL_GPL(nf_ct_helper_hsize
);
36 static unsigned int nf_ct_helper_count __read_mostly
;
38 static bool nf_ct_auto_assign_helper __read_mostly
= false;
39 module_param_named(nf_conntrack_helper
, nf_ct_auto_assign_helper
, bool, 0644);
40 MODULE_PARM_DESC(nf_conntrack_helper
,
41 "Enable automatic conntrack helper assignment (default 0)");
43 static DEFINE_MUTEX(nf_ct_nat_helpers_mutex
);
44 static struct list_head nf_ct_nat_helpers __read_mostly
;
46 /* Stupid hash, but collision free for the default registrations of the
47 * helpers currently in the kernel. */
48 static unsigned int helper_hash(const struct nf_conntrack_tuple
*tuple
)
50 return (((tuple
->src
.l3num
<< 8) | tuple
->dst
.protonum
) ^
51 (__force __u16
)tuple
->src
.u
.all
) % nf_ct_helper_hsize
;
54 static struct nf_conntrack_helper
*
55 __nf_ct_helper_find(const struct nf_conntrack_tuple
*tuple
)
57 struct nf_conntrack_helper
*helper
;
58 struct nf_conntrack_tuple_mask mask
= { .src
.u
.all
= htons(0xFFFF) };
61 if (!nf_ct_helper_count
)
64 h
= helper_hash(tuple
);
65 hlist_for_each_entry_rcu(helper
, &nf_ct_helper_hash
[h
], hnode
) {
66 if (nf_ct_tuple_src_mask_cmp(tuple
, &helper
->tuple
, &mask
))
72 struct nf_conntrack_helper
*
73 __nf_conntrack_helper_find(const char *name
, u16 l3num
, u8 protonum
)
75 struct nf_conntrack_helper
*h
;
78 for (i
= 0; i
< nf_ct_helper_hsize
; i
++) {
79 hlist_for_each_entry_rcu(h
, &nf_ct_helper_hash
[i
], hnode
) {
80 if (strcmp(h
->name
, name
))
83 if (h
->tuple
.src
.l3num
!= NFPROTO_UNSPEC
&&
84 h
->tuple
.src
.l3num
!= l3num
)
87 if (h
->tuple
.dst
.protonum
== protonum
)
93 EXPORT_SYMBOL_GPL(__nf_conntrack_helper_find
);
95 struct nf_conntrack_helper
*
96 nf_conntrack_helper_try_module_get(const char *name
, u16 l3num
, u8 protonum
)
98 struct nf_conntrack_helper
*h
;
102 h
= __nf_conntrack_helper_find(name
, l3num
, protonum
);
103 #ifdef CONFIG_MODULES
106 if (request_module("nfct-helper-%s", name
) == 0) {
108 h
= __nf_conntrack_helper_find(name
, l3num
, protonum
);
114 if (h
!= NULL
&& !try_module_get(h
->me
))
116 if (h
!= NULL
&& !refcount_inc_not_zero(&h
->refcnt
)) {
125 EXPORT_SYMBOL_GPL(nf_conntrack_helper_try_module_get
);
127 void nf_conntrack_helper_put(struct nf_conntrack_helper
*helper
)
129 refcount_dec(&helper
->refcnt
);
130 module_put(helper
->me
);
132 EXPORT_SYMBOL_GPL(nf_conntrack_helper_put
);
134 static struct nf_conntrack_nat_helper
*
135 nf_conntrack_nat_helper_find(const char *mod_name
)
137 struct nf_conntrack_nat_helper
*cur
;
140 list_for_each_entry_rcu(cur
, &nf_ct_nat_helpers
, list
) {
141 if (!strcmp(cur
->mod_name
, mod_name
)) {
146 return found
? cur
: NULL
;
150 nf_nat_helper_try_module_get(const char *name
, u16 l3num
, u8 protonum
)
152 struct nf_conntrack_helper
*h
;
153 struct nf_conntrack_nat_helper
*nat
;
154 char mod_name
[NF_CT_HELPER_NAME_LEN
];
158 h
= __nf_conntrack_helper_find(name
, l3num
, protonum
);
164 nat
= nf_conntrack_nat_helper_find(h
->nat_mod_name
);
166 snprintf(mod_name
, sizeof(mod_name
), "%s", h
->nat_mod_name
);
168 request_module(mod_name
);
171 nat
= nf_conntrack_nat_helper_find(mod_name
);
178 if (!try_module_get(nat
->module
))
184 EXPORT_SYMBOL_GPL(nf_nat_helper_try_module_get
);
186 void nf_nat_helper_put(struct nf_conntrack_helper
*helper
)
188 struct nf_conntrack_nat_helper
*nat
;
190 nat
= nf_conntrack_nat_helper_find(helper
->nat_mod_name
);
191 if (WARN_ON_ONCE(!nat
))
194 module_put(nat
->module
);
196 EXPORT_SYMBOL_GPL(nf_nat_helper_put
);
198 struct nf_conn_help
*
199 nf_ct_helper_ext_add(struct nf_conn
*ct
, gfp_t gfp
)
201 struct nf_conn_help
*help
;
203 help
= nf_ct_ext_add(ct
, NF_CT_EXT_HELPER
, gfp
);
205 INIT_HLIST_HEAD(&help
->expectations
);
207 pr_debug("failed to add helper extension area");
210 EXPORT_SYMBOL_GPL(nf_ct_helper_ext_add
);
212 static struct nf_conntrack_helper
*
213 nf_ct_lookup_helper(struct nf_conn
*ct
, struct net
*net
)
215 if (!net
->ct
.sysctl_auto_assign_helper
) {
216 if (net
->ct
.auto_assign_helper_warned
)
218 if (!__nf_ct_helper_find(&ct
->tuplehash
[IP_CT_DIR_REPLY
].tuple
))
220 pr_info("nf_conntrack: default automatic helper assignment "
221 "has been turned off for security reasons and CT-based "
222 " firewall rule not found. Use the iptables CT target "
223 "to attach helpers instead.\n");
224 net
->ct
.auto_assign_helper_warned
= 1;
228 return __nf_ct_helper_find(&ct
->tuplehash
[IP_CT_DIR_REPLY
].tuple
);
232 int __nf_ct_try_assign_helper(struct nf_conn
*ct
, struct nf_conn
*tmpl
,
235 struct nf_conntrack_helper
*helper
= NULL
;
236 struct nf_conn_help
*help
;
237 struct net
*net
= nf_ct_net(ct
);
239 /* We already got a helper explicitly attached. The function
240 * nf_conntrack_alter_reply - in case NAT is in use - asks for looking
241 * the helper up again. Since now the user is in full control of
242 * making consistent helper configurations, skip this automatic
243 * re-lookup, otherwise we'll lose the helper.
245 if (test_bit(IPS_HELPER_BIT
, &ct
->status
))
249 help
= nfct_help(tmpl
);
251 helper
= help
->helper
;
252 set_bit(IPS_HELPER_BIT
, &ct
->status
);
256 help
= nfct_help(ct
);
258 if (helper
== NULL
) {
259 helper
= nf_ct_lookup_helper(ct
, net
);
260 if (helper
== NULL
) {
262 RCU_INIT_POINTER(help
->helper
, NULL
);
268 help
= nf_ct_helper_ext_add(ct
, flags
);
272 /* We only allow helper re-assignment of the same sort since
273 * we cannot reallocate the helper extension area.
275 struct nf_conntrack_helper
*tmp
= rcu_dereference(help
->helper
);
277 if (tmp
&& tmp
->help
!= helper
->help
) {
278 RCU_INIT_POINTER(help
->helper
, NULL
);
283 rcu_assign_pointer(help
->helper
, helper
);
287 EXPORT_SYMBOL_GPL(__nf_ct_try_assign_helper
);
289 /* appropriate ct lock protecting must be taken by caller */
290 static int unhelp(struct nf_conn
*ct
, void *me
)
292 struct nf_conn_help
*help
= nfct_help(ct
);
294 if (help
&& rcu_dereference_raw(help
->helper
) == me
) {
295 nf_conntrack_event(IPCT_HELPER
, ct
);
296 RCU_INIT_POINTER(help
->helper
, NULL
);
299 /* We are not intended to delete this conntrack. */
303 void nf_ct_helper_destroy(struct nf_conn
*ct
)
305 struct nf_conn_help
*help
= nfct_help(ct
);
306 struct nf_conntrack_helper
*helper
;
310 helper
= rcu_dereference(help
->helper
);
311 if (helper
&& helper
->destroy
)
317 static LIST_HEAD(nf_ct_helper_expectfn_list
);
319 void nf_ct_helper_expectfn_register(struct nf_ct_helper_expectfn
*n
)
321 spin_lock_bh(&nf_conntrack_expect_lock
);
322 list_add_rcu(&n
->head
, &nf_ct_helper_expectfn_list
);
323 spin_unlock_bh(&nf_conntrack_expect_lock
);
325 EXPORT_SYMBOL_GPL(nf_ct_helper_expectfn_register
);
327 void nf_ct_helper_expectfn_unregister(struct nf_ct_helper_expectfn
*n
)
329 spin_lock_bh(&nf_conntrack_expect_lock
);
330 list_del_rcu(&n
->head
);
331 spin_unlock_bh(&nf_conntrack_expect_lock
);
333 EXPORT_SYMBOL_GPL(nf_ct_helper_expectfn_unregister
);
335 /* Caller should hold the rcu lock */
336 struct nf_ct_helper_expectfn
*
337 nf_ct_helper_expectfn_find_by_name(const char *name
)
339 struct nf_ct_helper_expectfn
*cur
;
342 list_for_each_entry_rcu(cur
, &nf_ct_helper_expectfn_list
, head
) {
343 if (!strcmp(cur
->name
, name
)) {
348 return found
? cur
: NULL
;
350 EXPORT_SYMBOL_GPL(nf_ct_helper_expectfn_find_by_name
);
352 /* Caller should hold the rcu lock */
353 struct nf_ct_helper_expectfn
*
354 nf_ct_helper_expectfn_find_by_symbol(const void *symbol
)
356 struct nf_ct_helper_expectfn
*cur
;
359 list_for_each_entry_rcu(cur
, &nf_ct_helper_expectfn_list
, head
) {
360 if (cur
->expectfn
== symbol
) {
365 return found
? cur
: NULL
;
367 EXPORT_SYMBOL_GPL(nf_ct_helper_expectfn_find_by_symbol
);
370 void nf_ct_helper_log(struct sk_buff
*skb
, const struct nf_conn
*ct
,
371 const char *fmt
, ...)
373 const struct nf_conn_help
*help
;
374 const struct nf_conntrack_helper
*helper
;
375 struct va_format vaf
;
383 /* Called from the helper function, this call never fails */
384 help
= nfct_help(ct
);
386 /* rcu_read_lock()ed by nf_hook_thresh */
387 helper
= rcu_dereference(help
->helper
);
389 nf_log_packet(nf_ct_net(ct
), nf_ct_l3num(ct
), 0, skb
, NULL
, NULL
, NULL
,
390 "nf_ct_%s: dropping packet: %pV ", helper
->name
, &vaf
);
394 EXPORT_SYMBOL_GPL(nf_ct_helper_log
);
396 int nf_conntrack_helper_register(struct nf_conntrack_helper
*me
)
398 struct nf_conntrack_tuple_mask mask
= { .src
.u
.all
= htons(0xFFFF) };
399 unsigned int h
= helper_hash(&me
->tuple
);
400 struct nf_conntrack_helper
*cur
;
403 BUG_ON(me
->expect_policy
== NULL
);
404 BUG_ON(me
->expect_class_max
>= NF_CT_MAX_EXPECT_CLASSES
);
405 BUG_ON(strlen(me
->name
) > NF_CT_HELPER_NAME_LEN
- 1);
407 if (me
->expect_policy
->max_expected
> NF_CT_EXPECT_MAX_CNT
)
410 mutex_lock(&nf_ct_helper_mutex
);
411 for (i
= 0; i
< nf_ct_helper_hsize
; i
++) {
412 hlist_for_each_entry(cur
, &nf_ct_helper_hash
[i
], hnode
) {
413 if (!strcmp(cur
->name
, me
->name
) &&
414 (cur
->tuple
.src
.l3num
== NFPROTO_UNSPEC
||
415 cur
->tuple
.src
.l3num
== me
->tuple
.src
.l3num
) &&
416 cur
->tuple
.dst
.protonum
== me
->tuple
.dst
.protonum
) {
423 /* avoid unpredictable behaviour for auto_assign_helper */
424 if (!(me
->flags
& NF_CT_HELPER_F_USERSPACE
)) {
425 hlist_for_each_entry(cur
, &nf_ct_helper_hash
[h
], hnode
) {
426 if (nf_ct_tuple_src_mask_cmp(&cur
->tuple
, &me
->tuple
,
433 refcount_set(&me
->refcnt
, 1);
434 hlist_add_head_rcu(&me
->hnode
, &nf_ct_helper_hash
[h
]);
435 nf_ct_helper_count
++;
437 mutex_unlock(&nf_ct_helper_mutex
);
440 EXPORT_SYMBOL_GPL(nf_conntrack_helper_register
);
442 static bool expect_iter_me(struct nf_conntrack_expect
*exp
, void *data
)
444 struct nf_conn_help
*help
= nfct_help(exp
->master
);
445 const struct nf_conntrack_helper
*me
= data
;
446 const struct nf_conntrack_helper
*this;
448 if (exp
->helper
== me
)
451 this = rcu_dereference_protected(help
->helper
,
452 lockdep_is_held(&nf_conntrack_expect_lock
));
456 void nf_conntrack_helper_unregister(struct nf_conntrack_helper
*me
)
458 mutex_lock(&nf_ct_helper_mutex
);
459 hlist_del_rcu(&me
->hnode
);
460 nf_ct_helper_count
--;
461 mutex_unlock(&nf_ct_helper_mutex
);
463 /* Make sure every nothing is still using the helper unless its a
464 * connection in the hash.
468 nf_ct_expect_iterate_destroy(expect_iter_me
, NULL
);
469 nf_ct_iterate_destroy(unhelp
, me
);
471 /* Maybe someone has gotten the helper already when unhelp above.
472 * So need to wait it.
476 EXPORT_SYMBOL_GPL(nf_conntrack_helper_unregister
);
478 void nf_ct_helper_init(struct nf_conntrack_helper
*helper
,
479 u16 l3num
, u16 protonum
, const char *name
,
480 u16 default_port
, u16 spec_port
, u32 id
,
481 const struct nf_conntrack_expect_policy
*exp_pol
,
482 u32 expect_class_max
,
483 int (*help
)(struct sk_buff
*skb
, unsigned int protoff
,
485 enum ip_conntrack_info ctinfo
),
486 int (*from_nlattr
)(struct nlattr
*attr
,
488 struct module
*module
)
490 helper
->tuple
.src
.l3num
= l3num
;
491 helper
->tuple
.dst
.protonum
= protonum
;
492 helper
->tuple
.src
.u
.all
= htons(spec_port
);
493 helper
->expect_policy
= exp_pol
;
494 helper
->expect_class_max
= expect_class_max
;
496 helper
->from_nlattr
= from_nlattr
;
498 snprintf(helper
->nat_mod_name
, sizeof(helper
->nat_mod_name
),
499 NF_NAT_HELPER_PREFIX
"%s", name
);
501 if (spec_port
== default_port
)
502 snprintf(helper
->name
, sizeof(helper
->name
), "%s", name
);
504 snprintf(helper
->name
, sizeof(helper
->name
), "%s-%u", name
, id
);
506 EXPORT_SYMBOL_GPL(nf_ct_helper_init
);
508 int nf_conntrack_helpers_register(struct nf_conntrack_helper
*helper
,
514 for (i
= 0; i
< n
; i
++) {
515 err
= nf_conntrack_helper_register(&helper
[i
]);
523 nf_conntrack_helpers_unregister(helper
, i
);
526 EXPORT_SYMBOL_GPL(nf_conntrack_helpers_register
);
528 void nf_conntrack_helpers_unregister(struct nf_conntrack_helper
*helper
,
532 nf_conntrack_helper_unregister(&helper
[n
]);
534 EXPORT_SYMBOL_GPL(nf_conntrack_helpers_unregister
);
536 void nf_nat_helper_register(struct nf_conntrack_nat_helper
*nat
)
538 mutex_lock(&nf_ct_nat_helpers_mutex
);
539 list_add_rcu(&nat
->list
, &nf_ct_nat_helpers
);
540 mutex_unlock(&nf_ct_nat_helpers_mutex
);
542 EXPORT_SYMBOL_GPL(nf_nat_helper_register
);
544 void nf_nat_helper_unregister(struct nf_conntrack_nat_helper
*nat
)
546 mutex_lock(&nf_ct_nat_helpers_mutex
);
547 list_del_rcu(&nat
->list
);
548 mutex_unlock(&nf_ct_nat_helpers_mutex
);
550 EXPORT_SYMBOL_GPL(nf_nat_helper_unregister
);
552 static const struct nf_ct_ext_type helper_extend
= {
553 .len
= sizeof(struct nf_conn_help
),
554 .align
= __alignof__(struct nf_conn_help
),
555 .id
= NF_CT_EXT_HELPER
,
558 void nf_conntrack_helper_pernet_init(struct net
*net
)
560 net
->ct
.auto_assign_helper_warned
= false;
561 net
->ct
.sysctl_auto_assign_helper
= nf_ct_auto_assign_helper
;
564 int nf_conntrack_helper_init(void)
567 nf_ct_helper_hsize
= 1; /* gets rounded up to use one page */
569 nf_ct_alloc_hashtable(&nf_ct_helper_hsize
, 0);
570 if (!nf_ct_helper_hash
)
573 ret
= nf_ct_extend_register(&helper_extend
);
575 pr_err("nf_ct_helper: Unable to register helper extension.\n");
579 INIT_LIST_HEAD(&nf_ct_nat_helpers
);
582 kvfree(nf_ct_helper_hash
);
586 void nf_conntrack_helper_fini(void)
588 nf_ct_extend_unregister(&helper_extend
);
589 kvfree(nf_ct_helper_hash
);