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/slab.h>
19 #include <linux/random.h>
20 #include <linux/err.h>
21 #include <linux/kernel.h>
22 #include <linux/netdevice.h>
23
24 #include <net/netfilter/nf_conntrack.h>
25 #include <net/netfilter/nf_conntrack_l3proto.h>
26 #include <net/netfilter/nf_conntrack_l4proto.h>
27 #include <net/netfilter/nf_conntrack_helper.h>
28 #include <net/netfilter/nf_conntrack_core.h>
29 #include <net/netfilter/nf_conntrack_extend.h>
30
31 static DEFINE_MUTEX(nf_ct_helper_mutex);
32 static struct hlist_head *nf_ct_helper_hash __read_mostly;
33 static unsigned int nf_ct_helper_hsize __read_mostly;
34 static unsigned int nf_ct_helper_count __read_mostly;
35 static int nf_ct_helper_vmalloc;
36
37
38 /* Stupid hash, but collision free for the default registrations of the
39 * helpers currently in the kernel. */
40 static unsigned int helper_hash(const struct nf_conntrack_tuple *tuple)
41 {
42 return (((tuple->src.l3num << 8) | tuple->dst.protonum) ^
43 (__force __u16)tuple->src.u.all) % nf_ct_helper_hsize;
44 }
45
46 struct nf_conntrack_helper *
47 __nf_ct_helper_find(const struct nf_conntrack_tuple *tuple)
48 {
49 struct nf_conntrack_helper *helper;
50 struct nf_conntrack_tuple_mask mask = { .src.u.all = htons(0xFFFF) };
51 struct hlist_node *n;
52 unsigned int h;
53
54 if (!nf_ct_helper_count)
55 return NULL;
56
57 h = helper_hash(tuple);
58 hlist_for_each_entry_rcu(helper, n, &nf_ct_helper_hash[h], hnode) {
59 if (nf_ct_tuple_src_mask_cmp(tuple, &helper->tuple, &mask))
60 return helper;
61 }
62 return NULL;
63 }
64 EXPORT_SYMBOL_GPL(__nf_ct_helper_find);
65
66 struct nf_conntrack_helper *
67 __nf_conntrack_helper_find_byname(const char *name)
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 return h;
77 }
78 }
79 return NULL;
80 }
81 EXPORT_SYMBOL_GPL(__nf_conntrack_helper_find_byname);
82
83 struct nf_conn_help *nf_ct_helper_ext_add(struct nf_conn *ct, gfp_t gfp)
84 {
85 struct nf_conn_help *help;
86
87 help = nf_ct_ext_add(ct, NF_CT_EXT_HELPER, gfp);
88 if (help)
89 INIT_HLIST_HEAD(&help->expectations);
90 else
91 pr_debug("failed to add helper extension area");
92 return help;
93 }
94 EXPORT_SYMBOL_GPL(nf_ct_helper_ext_add);
95
96 static inline int unhelp(struct nf_conntrack_tuple_hash *i,
97 const struct nf_conntrack_helper *me)
98 {
99 struct nf_conn *ct = nf_ct_tuplehash_to_ctrack(i);
100 struct nf_conn_help *help = nfct_help(ct);
101
102 if (help && help->helper == me) {
103 nf_conntrack_event(IPCT_HELPER, ct);
104 rcu_assign_pointer(help->helper, NULL);
105 }
106 return 0;
107 }
108
109 int nf_conntrack_helper_register(struct nf_conntrack_helper *me)
110 {
111 unsigned int h = helper_hash(&me->tuple);
112
113 BUG_ON(me->timeout == 0);
114
115 mutex_lock(&nf_ct_helper_mutex);
116 hlist_add_head_rcu(&me->hnode, &nf_ct_helper_hash[h]);
117 nf_ct_helper_count++;
118 mutex_unlock(&nf_ct_helper_mutex);
119
120 return 0;
121 }
122 EXPORT_SYMBOL_GPL(nf_conntrack_helper_register);
123
124 void nf_conntrack_helper_unregister(struct nf_conntrack_helper *me)
125 {
126 struct nf_conntrack_tuple_hash *h;
127 struct nf_conntrack_expect *exp;
128 struct hlist_node *n, *next;
129 unsigned int i;
130
131 mutex_lock(&nf_ct_helper_mutex);
132 hlist_del_rcu(&me->hnode);
133 nf_ct_helper_count--;
134 mutex_unlock(&nf_ct_helper_mutex);
135
136 /* Make sure every nothing is still using the helper unless its a
137 * connection in the hash.
138 */
139 synchronize_rcu();
140
141 spin_lock_bh(&nf_conntrack_lock);
142
143 /* Get rid of expectations */
144 for (i = 0; i < nf_ct_expect_hsize; i++) {
145 hlist_for_each_entry_safe(exp, n, next,
146 &nf_ct_expect_hash[i], hnode) {
147 struct nf_conn_help *help = nfct_help(exp->master);
148 if ((help->helper == me || exp->helper == me) &&
149 del_timer(&exp->timeout)) {
150 nf_ct_unlink_expect(exp);
151 nf_ct_expect_put(exp);
152 }
153 }
154 }
155
156 /* Get rid of expecteds, set helpers to NULL. */
157 hlist_for_each_entry(h, n, &unconfirmed, hnode)
158 unhelp(h, me);
159 for (i = 0; i < nf_conntrack_htable_size; i++) {
160 hlist_for_each_entry(h, n, &nf_conntrack_hash[i], hnode)
161 unhelp(h, me);
162 }
163 spin_unlock_bh(&nf_conntrack_lock);
164 }
165 EXPORT_SYMBOL_GPL(nf_conntrack_helper_unregister);
166
167 static struct nf_ct_ext_type helper_extend __read_mostly = {
168 .len = sizeof(struct nf_conn_help),
169 .align = __alignof__(struct nf_conn_help),
170 .id = NF_CT_EXT_HELPER,
171 };
172
173 int nf_conntrack_helper_init(void)
174 {
175 int err;
176
177 nf_ct_helper_hsize = 1; /* gets rounded up to use one page */
178 nf_ct_helper_hash = nf_ct_alloc_hashtable(&nf_ct_helper_hsize,
179 &nf_ct_helper_vmalloc);
180 if (!nf_ct_helper_hash)
181 return -ENOMEM;
182
183 err = nf_ct_extend_register(&helper_extend);
184 if (err < 0)
185 goto err1;
186
187 return 0;
188
189 err1:
190 nf_ct_free_hashtable(nf_ct_helper_hash, nf_ct_helper_vmalloc,
191 nf_ct_helper_hsize);
192 return err;
193 }
194
195 void nf_conntrack_helper_fini(void)
196 {
197 nf_ct_extend_unregister(&helper_extend);
198 nf_ct_free_hashtable(nf_ct_helper_hash, nf_ct_helper_vmalloc,
199 nf_ct_helper_hsize);
200 }
201
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