| 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_ratelimited("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); |