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 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
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, struct xt_action_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_thresh */
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 int helper_mt_check(const struct xt_mtchk_param *par)
58 {
59 struct xt_helper_info *info = par->matchinfo;
60 int ret;
61
62 ret = nf_ct_netns_get(par->net, par->family);
63 if (ret < 0) {
64 pr_info("cannot load conntrack support for proto=%u\n",
65 par->family);
66 return ret;
67 }
68 info->name[sizeof(info->name) - 1] = '\0';
69 return 0;
70 }
71
72 static void helper_mt_destroy(const struct xt_mtdtor_param *par)
73 {
74 nf_ct_netns_put(par->net, par->family);
75 }
76
77 static struct xt_match helper_mt_reg __read_mostly = {
78 .name = "helper",
79 .revision = 0,
80 .family = NFPROTO_UNSPEC,
81 .checkentry = helper_mt_check,
82 .match = helper_mt,
83 .destroy = helper_mt_destroy,
84 .matchsize = sizeof(struct xt_helper_info),
85 .me = THIS_MODULE,
86 };
87
88 static int __init helper_mt_init(void)
89 {
90 return xt_register_match(&helper_mt_reg);
91 }
92
93 static void __exit helper_mt_exit(void)
94 {
95 xt_unregister_match(&helper_mt_reg);
96 }
97
98 module_init(helper_mt_init);
99 module_exit(helper_mt_exit);
100
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