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1 | /* Helper handling for netfilter. */ | |
2 | ||
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 | * | |
7 | * This program is free software; you can redistribute it and/or modify | |
8 | * it under the terms of the GNU General Public License version 2 as | |
9 | * published by the Free Software Foundation. | |
10 | */ | |
11 | ||
12 | #include <linux/types.h> | |
13 | #include <linux/netfilter.h> | |
14 | #include <linux/module.h> | |
15 | #include <linux/skbuff.h> | |
16 | #include <linux/vmalloc.h> | |
17 | #include <linux/stddef.h> | |
18 | #include <linux/random.h> | |
19 | #include <linux/err.h> | |
20 | #include <linux/kernel.h> | |
21 | #include <linux/netdevice.h> | |
22 | #include <linux/rculist.h> | |
23 | #include <linux/rtnetlink.h> | |
24 | ||
25 | #include <net/netfilter/nf_conntrack.h> | |
26 | #include <net/netfilter/nf_conntrack_l3proto.h> | |
27 | #include <net/netfilter/nf_conntrack_l4proto.h> | |
28 | #include <net/netfilter/nf_conntrack_helper.h> | |
29 | #include <net/netfilter/nf_conntrack_core.h> | |
30 | #include <net/netfilter/nf_conntrack_extend.h> | |
31 | ||
32 | static DEFINE_MUTEX(nf_ct_helper_mutex); | |
33 | static struct hlist_head *nf_ct_helper_hash __read_mostly; | |
34 | static unsigned int nf_ct_helper_hsize __read_mostly; | |
35 | static unsigned int nf_ct_helper_count __read_mostly; | |
36 | static int nf_ct_helper_vmalloc; | |
37 | ||
38 | ||
39 | /* Stupid hash, but collision free for the default registrations of the | |
40 | * helpers currently in the kernel. */ | |
41 | static unsigned int helper_hash(const struct nf_conntrack_tuple *tuple) | |
42 | { | |
43 | return (((tuple->src.l3num << 8) | tuple->dst.protonum) ^ | |
44 | (__force __u16)tuple->src.u.all) % nf_ct_helper_hsize; | |
45 | } | |
46 | ||
47 | static struct nf_conntrack_helper * | |
48 | __nf_ct_helper_find(const struct nf_conntrack_tuple *tuple) | |
49 | { | |
50 | struct nf_conntrack_helper *helper; | |
51 | struct nf_conntrack_tuple_mask mask = { .src.u.all = htons(0xFFFF) }; | |
52 | struct hlist_node *n; | |
53 | unsigned int h; | |
54 | ||
55 | if (!nf_ct_helper_count) | |
56 | return NULL; | |
57 | ||
58 | h = helper_hash(tuple); | |
59 | hlist_for_each_entry_rcu(helper, n, &nf_ct_helper_hash[h], hnode) { | |
60 | if (nf_ct_tuple_src_mask_cmp(tuple, &helper->tuple, &mask)) | |
61 | return helper; | |
62 | } | |
63 | return NULL; | |
64 | } | |
65 | ||
66 | struct nf_conntrack_helper * | |
67 | __nf_conntrack_helper_find(const char *name, u16 l3num, u8 protonum) | |
68 | { | |
69 | struct nf_conntrack_helper *h; | |
70 | struct hlist_node *n; | |
71 | unsigned int i; | |
72 | ||
73 | for (i = 0; i < nf_ct_helper_hsize; i++) { | |
74 | hlist_for_each_entry_rcu(h, n, &nf_ct_helper_hash[i], hnode) { | |
75 | if (!strcmp(h->name, name) && | |
76 | h->tuple.src.l3num == l3num && | |
77 | h->tuple.dst.protonum == protonum) | |
78 | return h; | |
79 | } | |
80 | } | |
81 | return NULL; | |
82 | } | |
83 | EXPORT_SYMBOL_GPL(__nf_conntrack_helper_find); | |
84 | ||
85 | struct nf_conntrack_helper * | |
86 | nf_conntrack_helper_try_module_get(const char *name, u16 l3num, u8 protonum) | |
87 | { | |
88 | struct nf_conntrack_helper *h; | |
89 | ||
90 | h = __nf_conntrack_helper_find(name, l3num, protonum); | |
91 | #ifdef CONFIG_MODULES | |
92 | if (h == NULL) { | |
93 | if (request_module("nfct-helper-%s", name) == 0) | |
94 | h = __nf_conntrack_helper_find(name, l3num, protonum); | |
95 | } | |
96 | #endif | |
97 | if (h != NULL && !try_module_get(h->me)) | |
98 | h = NULL; | |
99 | ||
100 | return h; | |
101 | } | |
102 | EXPORT_SYMBOL_GPL(nf_conntrack_helper_try_module_get); | |
103 | ||
104 | struct nf_conn_help *nf_ct_helper_ext_add(struct nf_conn *ct, gfp_t gfp) | |
105 | { | |
106 | struct nf_conn_help *help; | |
107 | ||
108 | help = nf_ct_ext_add(ct, NF_CT_EXT_HELPER, gfp); | |
109 | if (help) | |
110 | INIT_HLIST_HEAD(&help->expectations); | |
111 | else | |
112 | pr_debug("failed to add helper extension area"); | |
113 | return help; | |
114 | } | |
115 | EXPORT_SYMBOL_GPL(nf_ct_helper_ext_add); | |
116 | ||
117 | int __nf_ct_try_assign_helper(struct nf_conn *ct, struct nf_conn *tmpl, | |
118 | gfp_t flags) | |
119 | { | |
120 | struct nf_conntrack_helper *helper = NULL; | |
121 | struct nf_conn_help *help; | |
122 | int ret = 0; | |
123 | ||
124 | if (tmpl != NULL) { | |
125 | help = nfct_help(tmpl); | |
126 | if (help != NULL) | |
127 | helper = help->helper; | |
128 | } | |
129 | ||
130 | help = nfct_help(ct); | |
131 | if (helper == NULL) | |
132 | helper = __nf_ct_helper_find(&ct->tuplehash[IP_CT_DIR_REPLY].tuple); | |
133 | if (helper == NULL) { | |
134 | if (help) | |
135 | rcu_assign_pointer(help->helper, NULL); | |
136 | goto out; | |
137 | } | |
138 | ||
139 | if (help == NULL) { | |
140 | help = nf_ct_helper_ext_add(ct, flags); | |
141 | if (help == NULL) { | |
142 | ret = -ENOMEM; | |
143 | goto out; | |
144 | } | |
145 | } else { | |
146 | memset(&help->help, 0, sizeof(help->help)); | |
147 | } | |
148 | ||
149 | rcu_assign_pointer(help->helper, helper); | |
150 | out: | |
151 | return ret; | |
152 | } | |
153 | EXPORT_SYMBOL_GPL(__nf_ct_try_assign_helper); | |
154 | ||
155 | static inline int unhelp(struct nf_conntrack_tuple_hash *i, | |
156 | const struct nf_conntrack_helper *me) | |
157 | { | |
158 | struct nf_conn *ct = nf_ct_tuplehash_to_ctrack(i); | |
159 | struct nf_conn_help *help = nfct_help(ct); | |
160 | ||
161 | if (help && help->helper == me) { | |
162 | nf_conntrack_event(IPCT_HELPER, ct); | |
163 | rcu_assign_pointer(help->helper, NULL); | |
164 | } | |
165 | return 0; | |
166 | } | |
167 | ||
168 | void nf_ct_helper_destroy(struct nf_conn *ct) | |
169 | { | |
170 | struct nf_conn_help *help = nfct_help(ct); | |
171 | struct nf_conntrack_helper *helper; | |
172 | ||
173 | if (help) { | |
174 | rcu_read_lock(); | |
175 | helper = rcu_dereference(help->helper); | |
176 | if (helper && helper->destroy) | |
177 | helper->destroy(ct); | |
178 | rcu_read_unlock(); | |
179 | } | |
180 | } | |
181 | ||
182 | int nf_conntrack_helper_register(struct nf_conntrack_helper *me) | |
183 | { | |
184 | unsigned int h = helper_hash(&me->tuple); | |
185 | ||
186 | BUG_ON(me->expect_policy == NULL); | |
187 | BUG_ON(me->expect_class_max >= NF_CT_MAX_EXPECT_CLASSES); | |
188 | BUG_ON(strlen(me->name) > NF_CT_HELPER_NAME_LEN - 1); | |
189 | ||
190 | mutex_lock(&nf_ct_helper_mutex); | |
191 | hlist_add_head_rcu(&me->hnode, &nf_ct_helper_hash[h]); | |
192 | nf_ct_helper_count++; | |
193 | mutex_unlock(&nf_ct_helper_mutex); | |
194 | ||
195 | return 0; | |
196 | } | |
197 | EXPORT_SYMBOL_GPL(nf_conntrack_helper_register); | |
198 | ||
199 | static void __nf_conntrack_helper_unregister(struct nf_conntrack_helper *me, | |
200 | struct net *net) | |
201 | { | |
202 | struct nf_conntrack_tuple_hash *h; | |
203 | struct nf_conntrack_expect *exp; | |
204 | const struct hlist_node *n, *next; | |
205 | const struct hlist_nulls_node *nn; | |
206 | unsigned int i; | |
207 | ||
208 | /* Get rid of expectations */ | |
209 | for (i = 0; i < nf_ct_expect_hsize; i++) { | |
210 | hlist_for_each_entry_safe(exp, n, next, | |
211 | &net->ct.expect_hash[i], hnode) { | |
212 | struct nf_conn_help *help = nfct_help(exp->master); | |
213 | if ((help->helper == me || exp->helper == me) && | |
214 | del_timer(&exp->timeout)) { | |
215 | nf_ct_unlink_expect(exp); | |
216 | nf_ct_expect_put(exp); | |
217 | } | |
218 | } | |
219 | } | |
220 | ||
221 | /* Get rid of expecteds, set helpers to NULL. */ | |
222 | hlist_nulls_for_each_entry(h, nn, &net->ct.unconfirmed, hnnode) | |
223 | unhelp(h, me); | |
224 | for (i = 0; i < net->ct.htable_size; i++) { | |
225 | hlist_nulls_for_each_entry(h, nn, &net->ct.hash[i], hnnode) | |
226 | unhelp(h, me); | |
227 | } | |
228 | } | |
229 | ||
230 | void nf_conntrack_helper_unregister(struct nf_conntrack_helper *me) | |
231 | { | |
232 | struct net *net; | |
233 | ||
234 | mutex_lock(&nf_ct_helper_mutex); | |
235 | hlist_del_rcu(&me->hnode); | |
236 | nf_ct_helper_count--; | |
237 | mutex_unlock(&nf_ct_helper_mutex); | |
238 | ||
239 | /* Make sure every nothing is still using the helper unless its a | |
240 | * connection in the hash. | |
241 | */ | |
242 | synchronize_rcu(); | |
243 | ||
244 | rtnl_lock(); | |
245 | spin_lock_bh(&nf_conntrack_lock); | |
246 | for_each_net(net) | |
247 | __nf_conntrack_helper_unregister(me, net); | |
248 | spin_unlock_bh(&nf_conntrack_lock); | |
249 | rtnl_unlock(); | |
250 | } | |
251 | EXPORT_SYMBOL_GPL(nf_conntrack_helper_unregister); | |
252 | ||
253 | static struct nf_ct_ext_type helper_extend __read_mostly = { | |
254 | .len = sizeof(struct nf_conn_help), | |
255 | .align = __alignof__(struct nf_conn_help), | |
256 | .id = NF_CT_EXT_HELPER, | |
257 | }; | |
258 | ||
259 | int nf_conntrack_helper_init(void) | |
260 | { | |
261 | int err; | |
262 | ||
263 | nf_ct_helper_hsize = 1; /* gets rounded up to use one page */ | |
264 | nf_ct_helper_hash = nf_ct_alloc_hashtable(&nf_ct_helper_hsize, | |
265 | &nf_ct_helper_vmalloc, 0); | |
266 | if (!nf_ct_helper_hash) | |
267 | return -ENOMEM; | |
268 | ||
269 | err = nf_ct_extend_register(&helper_extend); | |
270 | if (err < 0) | |
271 | goto err1; | |
272 | ||
273 | return 0; | |
274 | ||
275 | err1: | |
276 | nf_ct_free_hashtable(nf_ct_helper_hash, nf_ct_helper_vmalloc, | |
277 | nf_ct_helper_hsize); | |
278 | return err; | |
279 | } | |
280 | ||
281 | void nf_conntrack_helper_fini(void) | |
282 | { | |
283 | nf_ct_extend_unregister(&helper_extend); | |
284 | nf_ct_free_hashtable(nf_ct_helper_hash, nf_ct_helper_vmalloc, | |
285 | nf_ct_helper_hsize); | |
286 | } |