1 // SPDX-License-Identifier: GPL-2.0-only
2 /* iptables module to match on related connections */
3 /*
4 * (C) 2001 Martin Josefsson <gandalf@wlug.westbo.se>
5 */
6 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
7 #include <linux/module.h>
8 #include <linux/skbuff.h>
9 #include <linux/netfilter.h>
10 #include <net/netfilter/nf_conntrack.h>
11 #include <net/netfilter/nf_conntrack_core.h>
12 #include <net/netfilter/nf_conntrack_helper.h>
13 #include <linux/netfilter/x_tables.h>
14 #include <linux/netfilter/xt_helper.h>
15
16 MODULE_LICENSE("GPL");
17 MODULE_AUTHOR("Martin Josefsson <gandalf@netfilter.org>");
18 MODULE_DESCRIPTION("Xtables: Related connection matching");
19 MODULE_ALIAS("ipt_helper");
20 MODULE_ALIAS("ip6t_helper");
21
22
23 static bool
24 helper_mt(const struct sk_buff *skb, struct xt_action_param *par)
25 {
26 const struct xt_helper_info *info = par->matchinfo;
27 const struct nf_conn *ct;
28 const struct nf_conn_help *master_help;
29 const struct nf_conntrack_helper *helper;
30 enum ip_conntrack_info ctinfo;
31 bool ret = info->invert;
32
33 ct = nf_ct_get(skb, &ctinfo);
34 if (!ct || !ct->master)
35 return ret;
36
37 master_help = nfct_help(ct->master);
38 if (!master_help)
39 return ret;
40
41 /* rcu_read_lock()ed by nf_hook_thresh */
42 helper = rcu_dereference(master_help->helper);
43 if (!helper)
44 return ret;
45
46 if (info->name[0] == '\0')
47 ret = !ret;
48 else
49 ret ^= !strncmp(helper->name, info->name,
50 strlen(helper->name));
51 return ret;
52 }
53
54 static int helper_mt_check(const struct xt_mtchk_param *par)
55 {
56 struct xt_helper_info *info = par->matchinfo;
57 int ret;
58
59 ret = nf_ct_netns_get(par->net, par->family);
60 if (ret < 0) {
61 pr_info_ratelimited("cannot load conntrack support for proto=%u\n",
62 par->family);
63 return ret;
64 }
65 info->name[sizeof(info->name) - 1] = '\0';
66 return 0;
67 }
68
69 static void helper_mt_destroy(const struct xt_mtdtor_param *par)
70 {
71 nf_ct_netns_put(par->net, par->family);
72 }
73
74 static struct xt_match helper_mt_reg __read_mostly = {
75 .name = "helper",
76 .revision = 0,
77 .family = NFPROTO_UNSPEC,
78 .checkentry = helper_mt_check,
79 .match = helper_mt,
80 .destroy = helper_mt_destroy,
81 .matchsize = sizeof(struct xt_helper_info),
82 .me = THIS_MODULE,
83 };
84
85 static int __init helper_mt_init(void)
86 {
87 return xt_register_match(&helper_mt_reg);
88 }
89
90 static void __exit helper_mt_exit(void)
91 {
92 xt_unregister_match(&helper_mt_reg);
93 }
94
95 module_init(helper_mt_init);
96 module_exit(helper_mt_exit);
97
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