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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 | } |
287 |
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