1 /* Helper handling for netfilter. */
3 /* (C) 1999-2001 Paul `Rusty' Russell
4 * (C) 2002-2006 Netfilter Core Team <coreteam@netfilter.org>
5 * (C) 2003,2004 USAGI/WIDE Project <http://www.linux-ipv6.org>
6 * (C) 2006-2012 Patrick McHardy <kaber@trash.net>
8 * This program is free software; you can redistribute it and/or modify
9 * it under the terms of the GNU General Public License version 2 as
10 * published by the Free Software Foundation.
13 #include <linux/types.h>
14 #include <linux/netfilter.h>
15 #include <linux/module.h>
16 #include <linux/skbuff.h>
17 #include <linux/vmalloc.h>
18 #include <linux/stddef.h>
19 #include <linux/random.h>
20 #include <linux/err.h>
21 #include <linux/kernel.h>
22 #include <linux/netdevice.h>
23 #include <linux/rculist.h>
24 #include <linux/rtnetlink.h>
26 #include <net/netfilter/nf_conntrack.h>
27 #include <net/netfilter/nf_conntrack_l3proto.h>
28 #include <net/netfilter/nf_conntrack_l4proto.h>
29 #include <net/netfilter/nf_conntrack_helper.h>
30 #include <net/netfilter/nf_conntrack_core.h>
31 #include <net/netfilter/nf_conntrack_extend.h>
32 #include <net/netfilter/nf_log.h>
34 static DEFINE_MUTEX(nf_ct_helper_mutex
);
35 struct hlist_head
*nf_ct_helper_hash __read_mostly
;
36 EXPORT_SYMBOL_GPL(nf_ct_helper_hash
);
37 unsigned int nf_ct_helper_hsize __read_mostly
;
38 EXPORT_SYMBOL_GPL(nf_ct_helper_hsize
);
39 static unsigned int nf_ct_helper_count __read_mostly
;
41 static bool nf_ct_auto_assign_helper __read_mostly
= false;
42 module_param_named(nf_conntrack_helper
, nf_ct_auto_assign_helper
, bool, 0644);
43 MODULE_PARM_DESC(nf_conntrack_helper
,
44 "Enable automatic conntrack helper assignment (default 0)");
47 static struct ctl_table helper_sysctl_table
[] = {
49 .procname
= "nf_conntrack_helper",
50 .data
= &init_net
.ct
.sysctl_auto_assign_helper
,
51 .maxlen
= sizeof(unsigned int),
53 .proc_handler
= proc_dointvec
,
58 static int nf_conntrack_helper_init_sysctl(struct net
*net
)
60 struct ctl_table
*table
;
62 table
= kmemdup(helper_sysctl_table
, sizeof(helper_sysctl_table
),
67 table
[0].data
= &net
->ct
.sysctl_auto_assign_helper
;
69 /* Don't export sysctls to unprivileged users */
70 if (net
->user_ns
!= &init_user_ns
)
71 table
[0].procname
= NULL
;
73 net
->ct
.helper_sysctl_header
=
74 register_net_sysctl(net
, "net/netfilter", table
);
76 if (!net
->ct
.helper_sysctl_header
) {
77 pr_err("nf_conntrack_helper: can't register to sysctl.\n");
88 static void nf_conntrack_helper_fini_sysctl(struct net
*net
)
90 struct ctl_table
*table
;
92 table
= net
->ct
.helper_sysctl_header
->ctl_table_arg
;
93 unregister_net_sysctl_table(net
->ct
.helper_sysctl_header
);
97 static int nf_conntrack_helper_init_sysctl(struct net
*net
)
102 static void nf_conntrack_helper_fini_sysctl(struct net
*net
)
105 #endif /* CONFIG_SYSCTL */
107 /* Stupid hash, but collision free for the default registrations of the
108 * helpers currently in the kernel. */
109 static unsigned int helper_hash(const struct nf_conntrack_tuple
*tuple
)
111 return (((tuple
->src
.l3num
<< 8) | tuple
->dst
.protonum
) ^
112 (__force __u16
)tuple
->src
.u
.all
) % nf_ct_helper_hsize
;
115 static struct nf_conntrack_helper
*
116 __nf_ct_helper_find(const struct nf_conntrack_tuple
*tuple
)
118 struct nf_conntrack_helper
*helper
;
119 struct nf_conntrack_tuple_mask mask
= { .src
.u
.all
= htons(0xFFFF) };
122 if (!nf_ct_helper_count
)
125 h
= helper_hash(tuple
);
126 hlist_for_each_entry_rcu(helper
, &nf_ct_helper_hash
[h
], hnode
) {
127 if (nf_ct_tuple_src_mask_cmp(tuple
, &helper
->tuple
, &mask
))
133 struct nf_conntrack_helper
*
134 __nf_conntrack_helper_find(const char *name
, u16 l3num
, u8 protonum
)
136 struct nf_conntrack_helper
*h
;
139 for (i
= 0; i
< nf_ct_helper_hsize
; i
++) {
140 hlist_for_each_entry_rcu(h
, &nf_ct_helper_hash
[i
], hnode
) {
141 if (strcmp(h
->name
, name
))
144 if (h
->tuple
.src
.l3num
!= NFPROTO_UNSPEC
&&
145 h
->tuple
.src
.l3num
!= l3num
)
148 if (h
->tuple
.dst
.protonum
== protonum
)
154 EXPORT_SYMBOL_GPL(__nf_conntrack_helper_find
);
156 struct nf_conntrack_helper
*
157 nf_conntrack_helper_try_module_get(const char *name
, u16 l3num
, u8 protonum
)
159 struct nf_conntrack_helper
*h
;
163 h
= __nf_conntrack_helper_find(name
, l3num
, protonum
);
164 #ifdef CONFIG_MODULES
167 if (request_module("nfct-helper-%s", name
) == 0) {
169 h
= __nf_conntrack_helper_find(name
, l3num
, protonum
);
175 if (h
!= NULL
&& !try_module_get(h
->me
))
177 if (h
!= NULL
&& !refcount_inc_not_zero(&h
->refcnt
)) {
186 EXPORT_SYMBOL_GPL(nf_conntrack_helper_try_module_get
);
188 void nf_conntrack_helper_put(struct nf_conntrack_helper
*helper
)
190 refcount_dec(&helper
->refcnt
);
191 module_put(helper
->me
);
193 EXPORT_SYMBOL_GPL(nf_conntrack_helper_put
);
195 struct nf_conn_help
*
196 nf_ct_helper_ext_add(struct nf_conn
*ct
,
197 struct nf_conntrack_helper
*helper
, gfp_t gfp
)
199 struct nf_conn_help
*help
;
201 help
= nf_ct_ext_add(ct
, NF_CT_EXT_HELPER
, gfp
);
203 INIT_HLIST_HEAD(&help
->expectations
);
205 pr_debug("failed to add helper extension area");
208 EXPORT_SYMBOL_GPL(nf_ct_helper_ext_add
);
210 static struct nf_conntrack_helper
*
211 nf_ct_lookup_helper(struct nf_conn
*ct
, struct net
*net
)
213 if (!net
->ct
.sysctl_auto_assign_helper
) {
214 if (net
->ct
.auto_assign_helper_warned
)
216 if (!__nf_ct_helper_find(&ct
->tuplehash
[IP_CT_DIR_REPLY
].tuple
))
218 pr_info("nf_conntrack: default automatic helper assignment "
219 "has been turned off for security reasons and CT-based "
220 " firewall rule not found. Use the iptables CT target "
221 "to attach helpers instead.\n");
222 net
->ct
.auto_assign_helper_warned
= 1;
226 return __nf_ct_helper_find(&ct
->tuplehash
[IP_CT_DIR_REPLY
].tuple
);
230 int __nf_ct_try_assign_helper(struct nf_conn
*ct
, struct nf_conn
*tmpl
,
233 struct nf_conntrack_helper
*helper
= NULL
;
234 struct nf_conn_help
*help
;
235 struct net
*net
= nf_ct_net(ct
);
237 /* We already got a helper explicitly attached. The function
238 * nf_conntrack_alter_reply - in case NAT is in use - asks for looking
239 * the helper up again. Since now the user is in full control of
240 * making consistent helper configurations, skip this automatic
241 * re-lookup, otherwise we'll lose the helper.
243 if (test_bit(IPS_HELPER_BIT
, &ct
->status
))
247 help
= nfct_help(tmpl
);
249 helper
= help
->helper
;
250 set_bit(IPS_HELPER_BIT
, &ct
->status
);
254 help
= nfct_help(ct
);
256 if (helper
== NULL
) {
257 helper
= nf_ct_lookup_helper(ct
, net
);
258 if (helper
== NULL
) {
260 RCU_INIT_POINTER(help
->helper
, NULL
);
266 help
= nf_ct_helper_ext_add(ct
, helper
, flags
);
270 /* We only allow helper re-assignment of the same sort since
271 * we cannot reallocate the helper extension area.
273 struct nf_conntrack_helper
*tmp
= rcu_dereference(help
->helper
);
275 if (tmp
&& tmp
->help
!= helper
->help
) {
276 RCU_INIT_POINTER(help
->helper
, NULL
);
281 rcu_assign_pointer(help
->helper
, helper
);
285 EXPORT_SYMBOL_GPL(__nf_ct_try_assign_helper
);
287 /* appropriate ct lock protecting must be taken by caller */
288 static int unhelp(struct nf_conn
*ct
, void *me
)
290 struct nf_conn_help
*help
= nfct_help(ct
);
292 if (help
&& rcu_dereference_raw(help
->helper
) == me
) {
293 nf_conntrack_event(IPCT_HELPER
, ct
);
294 RCU_INIT_POINTER(help
->helper
, NULL
);
297 /* We are not intended to delete this conntrack. */
301 void nf_ct_helper_destroy(struct nf_conn
*ct
)
303 struct nf_conn_help
*help
= nfct_help(ct
);
304 struct nf_conntrack_helper
*helper
;
308 helper
= rcu_dereference(help
->helper
);
309 if (helper
&& helper
->destroy
)
315 static LIST_HEAD(nf_ct_helper_expectfn_list
);
317 void nf_ct_helper_expectfn_register(struct nf_ct_helper_expectfn
*n
)
319 spin_lock_bh(&nf_conntrack_expect_lock
);
320 list_add_rcu(&n
->head
, &nf_ct_helper_expectfn_list
);
321 spin_unlock_bh(&nf_conntrack_expect_lock
);
323 EXPORT_SYMBOL_GPL(nf_ct_helper_expectfn_register
);
325 void nf_ct_helper_expectfn_unregister(struct nf_ct_helper_expectfn
*n
)
327 spin_lock_bh(&nf_conntrack_expect_lock
);
328 list_del_rcu(&n
->head
);
329 spin_unlock_bh(&nf_conntrack_expect_lock
);
331 EXPORT_SYMBOL_GPL(nf_ct_helper_expectfn_unregister
);
333 /* Caller should hold the rcu lock */
334 struct nf_ct_helper_expectfn
*
335 nf_ct_helper_expectfn_find_by_name(const char *name
)
337 struct nf_ct_helper_expectfn
*cur
;
340 list_for_each_entry_rcu(cur
, &nf_ct_helper_expectfn_list
, head
) {
341 if (!strcmp(cur
->name
, name
)) {
346 return found
? cur
: NULL
;
348 EXPORT_SYMBOL_GPL(nf_ct_helper_expectfn_find_by_name
);
350 /* Caller should hold the rcu lock */
351 struct nf_ct_helper_expectfn
*
352 nf_ct_helper_expectfn_find_by_symbol(const void *symbol
)
354 struct nf_ct_helper_expectfn
*cur
;
357 list_for_each_entry_rcu(cur
, &nf_ct_helper_expectfn_list
, head
) {
358 if (cur
->expectfn
== symbol
) {
363 return found
? cur
: NULL
;
365 EXPORT_SYMBOL_GPL(nf_ct_helper_expectfn_find_by_symbol
);
368 void nf_ct_helper_log(struct sk_buff
*skb
, const struct nf_conn
*ct
,
369 const char *fmt
, ...)
371 const struct nf_conn_help
*help
;
372 const struct nf_conntrack_helper
*helper
;
373 struct va_format vaf
;
381 /* Called from the helper function, this call never fails */
382 help
= nfct_help(ct
);
384 /* rcu_read_lock()ed by nf_hook_thresh */
385 helper
= rcu_dereference(help
->helper
);
387 nf_log_packet(nf_ct_net(ct
), nf_ct_l3num(ct
), 0, skb
, NULL
, NULL
, NULL
,
388 "nf_ct_%s: dropping packet: %pV ", helper
->name
, &vaf
);
392 EXPORT_SYMBOL_GPL(nf_ct_helper_log
);
394 int nf_conntrack_helper_register(struct nf_conntrack_helper
*me
)
396 struct nf_conntrack_tuple_mask mask
= { .src
.u
.all
= htons(0xFFFF) };
397 unsigned int h
= helper_hash(&me
->tuple
);
398 struct nf_conntrack_helper
*cur
;
401 BUG_ON(me
->expect_policy
== NULL
);
402 BUG_ON(me
->expect_class_max
>= NF_CT_MAX_EXPECT_CLASSES
);
403 BUG_ON(strlen(me
->name
) > NF_CT_HELPER_NAME_LEN
- 1);
405 if (me
->expect_policy
->max_expected
> NF_CT_EXPECT_MAX_CNT
)
408 mutex_lock(&nf_ct_helper_mutex
);
409 for (i
= 0; i
< nf_ct_helper_hsize
; i
++) {
410 hlist_for_each_entry(cur
, &nf_ct_helper_hash
[i
], hnode
) {
411 if (!strcmp(cur
->name
, me
->name
) &&
412 (cur
->tuple
.src
.l3num
== NFPROTO_UNSPEC
||
413 cur
->tuple
.src
.l3num
== me
->tuple
.src
.l3num
) &&
414 cur
->tuple
.dst
.protonum
== me
->tuple
.dst
.protonum
) {
421 /* avoid unpredictable behaviour for auto_assign_helper */
422 if (!(me
->flags
& NF_CT_HELPER_F_USERSPACE
)) {
423 hlist_for_each_entry(cur
, &nf_ct_helper_hash
[h
], hnode
) {
424 if (nf_ct_tuple_src_mask_cmp(&cur
->tuple
, &me
->tuple
,
431 refcount_set(&me
->refcnt
, 1);
432 hlist_add_head_rcu(&me
->hnode
, &nf_ct_helper_hash
[h
]);
433 nf_ct_helper_count
++;
435 mutex_unlock(&nf_ct_helper_mutex
);
438 EXPORT_SYMBOL_GPL(nf_conntrack_helper_register
);
440 void nf_conntrack_helper_unregister(struct nf_conntrack_helper
*me
)
442 struct nf_conntrack_expect
*exp
;
443 const struct hlist_node
*next
;
446 mutex_lock(&nf_ct_helper_mutex
);
447 hlist_del_rcu(&me
->hnode
);
448 nf_ct_helper_count
--;
449 mutex_unlock(&nf_ct_helper_mutex
);
451 /* Make sure every nothing is still using the helper unless its a
452 * connection in the hash.
456 /* Get rid of expectations */
457 spin_lock_bh(&nf_conntrack_expect_lock
);
458 for (i
= 0; i
< nf_ct_expect_hsize
; i
++) {
459 hlist_for_each_entry_safe(exp
, next
,
460 &nf_ct_expect_hash
[i
], hnode
) {
461 struct nf_conn_help
*help
= nfct_help(exp
->master
);
462 if ((rcu_dereference_protected(
464 lockdep_is_held(&nf_conntrack_expect_lock
)
465 ) == me
|| exp
->helper
== me
))
466 nf_ct_remove_expect(exp
);
469 spin_unlock_bh(&nf_conntrack_expect_lock
);
471 nf_ct_iterate_destroy(unhelp
, me
);
473 EXPORT_SYMBOL_GPL(nf_conntrack_helper_unregister
);
475 void nf_ct_helper_init(struct nf_conntrack_helper
*helper
,
476 u16 l3num
, u16 protonum
, const char *name
,
477 u16 default_port
, u16 spec_port
, u32 id
,
478 const struct nf_conntrack_expect_policy
*exp_pol
,
479 u32 expect_class_max
,
480 int (*help
)(struct sk_buff
*skb
, unsigned int protoff
,
482 enum ip_conntrack_info ctinfo
),
483 int (*from_nlattr
)(struct nlattr
*attr
,
485 struct module
*module
)
487 helper
->tuple
.src
.l3num
= l3num
;
488 helper
->tuple
.dst
.protonum
= protonum
;
489 helper
->tuple
.src
.u
.all
= htons(spec_port
);
490 helper
->expect_policy
= exp_pol
;
491 helper
->expect_class_max
= expect_class_max
;
493 helper
->from_nlattr
= from_nlattr
;
496 if (spec_port
== default_port
)
497 snprintf(helper
->name
, sizeof(helper
->name
), "%s", name
);
499 snprintf(helper
->name
, sizeof(helper
->name
), "%s-%u", name
, id
);
501 EXPORT_SYMBOL_GPL(nf_ct_helper_init
);
503 int nf_conntrack_helpers_register(struct nf_conntrack_helper
*helper
,
509 for (i
= 0; i
< n
; i
++) {
510 err
= nf_conntrack_helper_register(&helper
[i
]);
518 nf_conntrack_helpers_unregister(helper
, i
);
521 EXPORT_SYMBOL_GPL(nf_conntrack_helpers_register
);
523 void nf_conntrack_helpers_unregister(struct nf_conntrack_helper
*helper
,
527 nf_conntrack_helper_unregister(&helper
[n
]);
529 EXPORT_SYMBOL_GPL(nf_conntrack_helpers_unregister
);
531 static const struct nf_ct_ext_type helper_extend
= {
532 .len
= sizeof(struct nf_conn_help
),
533 .align
= __alignof__(struct nf_conn_help
),
534 .id
= NF_CT_EXT_HELPER
,
537 int nf_conntrack_helper_pernet_init(struct net
*net
)
539 net
->ct
.auto_assign_helper_warned
= false;
540 net
->ct
.sysctl_auto_assign_helper
= nf_ct_auto_assign_helper
;
541 return nf_conntrack_helper_init_sysctl(net
);
544 void nf_conntrack_helper_pernet_fini(struct net
*net
)
546 nf_conntrack_helper_fini_sysctl(net
);
549 int nf_conntrack_helper_init(void)
552 nf_ct_helper_hsize
= 1; /* gets rounded up to use one page */
554 nf_ct_alloc_hashtable(&nf_ct_helper_hsize
, 0);
555 if (!nf_ct_helper_hash
)
558 ret
= nf_ct_extend_register(&helper_extend
);
560 pr_err("nf_ct_helper: Unable to register helper extension.\n");
566 nf_ct_free_hashtable(nf_ct_helper_hash
, nf_ct_helper_hsize
);
570 void nf_conntrack_helper_fini(void)
572 nf_ct_extend_unregister(&helper_extend
);
573 nf_ct_free_hashtable(nf_ct_helper_hash
, nf_ct_helper_hsize
);