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net/netfilter/xt_helper.c
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/* iptables module to match on related connections */
/*
* (C) 2001 Martin Josefsson <gandalf@wlug.westbo.se>
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation.
*/
#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
#include <linux/module.h>
#include <linux/skbuff.h>
#include <linux/netfilter.h>
#include <net/netfilter/nf_conntrack.h>
#include <net/netfilter/nf_conntrack_core.h>
#include <net/netfilter/nf_conntrack_helper.h>
#include <linux/netfilter/x_tables.h>
#include <linux/netfilter/xt_helper.h>
MODULE_LICENSE("GPL");
MODULE_AUTHOR("Martin Josefsson <gandalf@netfilter.org>");
MODULE_DESCRIPTION("Xtables: Related connection matching");
MODULE_ALIAS("ipt_helper");
MODULE_ALIAS("ip6t_helper");
static bool
helper_mt(const struct sk_buff *skb, struct xt_action_param *par)
{
const struct xt_helper_info *info = par->matchinfo;
const struct nf_conn *ct;
const struct nf_conn_help *master_help;
const struct nf_conntrack_helper *helper;
enum ip_conntrack_info ctinfo;
bool ret = info->invert;
ct = nf_ct_get(skb, &ctinfo);
if (!ct || !ct->master)
return ret;
master_help = nfct_help(ct->master);
if (!master_help)
return ret;
/* rcu_read_lock()ed by nf_hook_thresh */
helper = rcu_dereference(master_help->helper);
if (!helper)
return ret;
if (info->name[0] == '\0')
ret = !ret;
else
ret ^= !strncmp(helper->name, info->name,
strlen(helper->name));
return ret;
}
static int helper_mt_check(const struct xt_mtchk_param *par)
{
struct xt_helper_info *info = par->matchinfo;
int ret;
ret = nf_ct_netns_get(par->net, par->family);
if (ret < 0) {
pr_info("cannot load conntrack support for proto=%u
",
par->family);
return ret;
}
info->name[sizeof(info->name) - 1] = '\0';
return 0;
}
static void helper_mt_destroy(const struct xt_mtdtor_param *par)
{
nf_ct_netns_put(par->net, par->family);
}
static struct xt_match helper_mt_reg __read_mostly = {
.name = "helper",
.revision = 0,
.family = NFPROTO_UNSPEC,
.checkentry = helper_mt_check,
.match = helper_mt,
.destroy = helper_mt_destroy,
.matchsize = sizeof(struct xt_helper_info),
.me = THIS_MODULE,
};
static int __init helper_mt_init(void)
{
return xt_register_match(&helper_mt_reg);
}
static void __exit helper_mt_exit(void)
{
xt_unregister_match(&helper_mt_reg);
}
module_init(helper_mt_init);
module_exit(helper_mt_exit);
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