| 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 net_device *in, |
| 28 | const struct net_device *out, const struct xt_match *match, |
| 29 | const void *matchinfo, int offset, unsigned int protoff, |
| 30 | bool *hotdrop) |
| 31 | { |
| 32 | const struct xt_helper_info *info = matchinfo; |
| 33 | const struct nf_conn *ct; |
| 34 | const struct nf_conn_help *master_help; |
| 35 | const struct nf_conntrack_helper *helper; |
| 36 | enum ip_conntrack_info ctinfo; |
| 37 | bool ret = info->invert; |
| 38 | |
| 39 | ct = nf_ct_get(skb, &ctinfo); |
| 40 | if (!ct || !ct->master) |
| 41 | return ret; |
| 42 | |
| 43 | master_help = nfct_help(ct->master); |
| 44 | if (!master_help) |
| 45 | return ret; |
| 46 | |
| 47 | /* rcu_read_lock()ed by nf_hook_slow */ |
| 48 | helper = rcu_dereference(master_help->helper); |
| 49 | if (!helper) |
| 50 | return ret; |
| 51 | |
| 52 | if (info->name[0] == '\0') |
| 53 | ret = !ret; |
| 54 | else |
| 55 | ret ^= !strncmp(helper->name, info->name, |
| 56 | strlen(helper->name)); |
| 57 | return ret; |
| 58 | } |
| 59 | |
| 60 | static bool |
| 61 | helper_mt_check(const char *tablename, const void *inf, |
| 62 | const struct xt_match *match, void *matchinfo, |
| 63 | unsigned int hook_mask) |
| 64 | { |
| 65 | struct xt_helper_info *info = matchinfo; |
| 66 | |
| 67 | if (nf_ct_l3proto_try_module_get(match->family) < 0) { |
| 68 | printk(KERN_WARNING "can't load conntrack support for " |
| 69 | "proto=%u\n", match->family); |
| 70 | return false; |
| 71 | } |
| 72 | info->name[29] = '\0'; |
| 73 | return true; |
| 74 | } |
| 75 | |
| 76 | static void helper_mt_destroy(const struct xt_match *match, void *matchinfo) |
| 77 | { |
| 78 | nf_ct_l3proto_module_put(match->family); |
| 79 | } |
| 80 | |
| 81 | static struct xt_match helper_mt_reg[] __read_mostly = { |
| 82 | { |
| 83 | .name = "helper", |
| 84 | .family = NFPROTO_IPV4, |
| 85 | .checkentry = helper_mt_check, |
| 86 | .match = helper_mt, |
| 87 | .destroy = helper_mt_destroy, |
| 88 | .matchsize = sizeof(struct xt_helper_info), |
| 89 | .me = THIS_MODULE, |
| 90 | }, |
| 91 | { |
| 92 | .name = "helper", |
| 93 | .family = NFPROTO_IPV6, |
| 94 | .checkentry = helper_mt_check, |
| 95 | .match = helper_mt, |
| 96 | .destroy = helper_mt_destroy, |
| 97 | .matchsize = sizeof(struct xt_helper_info), |
| 98 | .me = THIS_MODULE, |
| 99 | }, |
| 100 | }; |
| 101 | |
| 102 | static int __init helper_mt_init(void) |
| 103 | { |
| 104 | return xt_register_matches(helper_mt_reg, ARRAY_SIZE(helper_mt_reg)); |
| 105 | } |
| 106 | |
| 107 | static void __exit helper_mt_exit(void) |
| 108 | { |
| 109 | xt_unregister_matches(helper_mt_reg, ARRAY_SIZE(helper_mt_reg)); |
| 110 | } |
| 111 | |
| 112 | module_init(helper_mt_init); |
| 113 | module_exit(helper_mt_exit); |