IPv6: fix race between cleanup and add/delete address
[linux-2.6.git] / net / netfilter / xt_helper.c
1 /* iptables module to match on related connections */
2 /*
3  * (C) 2001 Martin Josefsson <gandalf@wlug.westbo.se>
4  *
5  * This program is free software; you can redistribute it and/or modify
6  * it under the terms of the GNU General Public License version 2 as
7  * published by the Free Software Foundation.
8  */
9
10 #include <linux/module.h>
11 #include <linux/skbuff.h>
12 #include <linux/netfilter.h>
13 #include <net/netfilter/nf_conntrack.h>
14 #include <net/netfilter/nf_conntrack_core.h>
15 #include <net/netfilter/nf_conntrack_helper.h>
16 #include <linux/netfilter/x_tables.h>
17 #include <linux/netfilter/xt_helper.h>
18
19 MODULE_LICENSE("GPL");
20 MODULE_AUTHOR("Martin Josefsson <gandalf@netfilter.org>");
21 MODULE_DESCRIPTION("Xtables: Related connection matching");
22 MODULE_ALIAS("ipt_helper");
23 MODULE_ALIAS("ip6t_helper");
24
25
26 static bool
27 helper_mt(const struct sk_buff *skb, const struct xt_match_param *par)
28 {
29         const struct xt_helper_info *info = par->matchinfo;
30         const struct nf_conn *ct;
31         const struct nf_conn_help *master_help;
32         const struct nf_conntrack_helper *helper;
33         enum ip_conntrack_info ctinfo;
34         bool ret = info->invert;
35
36         ct = nf_ct_get(skb, &ctinfo);
37         if (!ct || !ct->master)
38                 return ret;
39
40         master_help = nfct_help(ct->master);
41         if (!master_help)
42                 return ret;
43
44         /* rcu_read_lock()ed by nf_hook_slow */
45         helper = rcu_dereference(master_help->helper);
46         if (!helper)
47                 return ret;
48
49         if (info->name[0] == '\0')
50                 ret = !ret;
51         else
52                 ret ^= !strncmp(helper->name, info->name,
53                                 strlen(helper->name));
54         return ret;
55 }
56
57 static bool helper_mt_check(const struct xt_mtchk_param *par)
58 {
59         struct xt_helper_info *info = par->matchinfo;
60
61         if (nf_ct_l3proto_try_module_get(par->family) < 0) {
62                 printk(KERN_WARNING "can't load conntrack support for "
63                                     "proto=%u\n", par->family);
64                 return false;
65         }
66         info->name[29] = '\0';
67         return true;
68 }
69
70 static void helper_mt_destroy(const struct xt_mtdtor_param *par)
71 {
72         nf_ct_l3proto_module_put(par->family);
73 }
74
75 static struct xt_match helper_mt_reg __read_mostly = {
76         .name       = "helper",
77         .revision   = 0,
78         .family     = NFPROTO_UNSPEC,
79         .checkentry = helper_mt_check,
80         .match      = helper_mt,
81         .destroy    = helper_mt_destroy,
82         .matchsize  = sizeof(struct xt_helper_info),
83         .me         = THIS_MODULE,
84 };
85
86 static int __init helper_mt_init(void)
87 {
88         return xt_register_match(&helper_mt_reg);
89 }
90
91 static void __exit helper_mt_exit(void)
92 {
93         xt_unregister_match(&helper_mt_reg);
94 }
95
96 module_init(helper_mt_init);
97 module_exit(helper_mt_exit);