// SPDX-License-Identifier: GPL-2.0-only
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/* iptables module to match on related connections */
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/*
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* (C) 2001 Martin Josefsson <gandalf@wlug.westbo.se>
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*/
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#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
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#include <linux/module.h>
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#include <linux/skbuff.h>
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#include <linux/netfilter.h>
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#include <net/netfilter/nf_conntrack.h>
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#include <net/netfilter/nf_conntrack_core.h>
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#include <net/netfilter/nf_conntrack_helper.h>
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#include <linux/netfilter/x_tables.h>
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#include <linux/netfilter/xt_helper.h>
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MODULE_LICENSE("GPL");
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MODULE_AUTHOR("Martin Josefsson <gandalf@netfilter.org>");
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MODULE_DESCRIPTION("Xtables: Related connection matching");
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MODULE_ALIAS("ipt_helper");
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MODULE_ALIAS("ip6t_helper");
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static bool
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helper_mt(const struct sk_buff *skb, struct xt_action_param *par)
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{
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const struct xt_helper_info *info = par->matchinfo;
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const struct nf_conn *ct;
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const struct nf_conn_help *master_help;
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const struct nf_conntrack_helper *helper;
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enum ip_conntrack_info ctinfo;
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bool ret = info->invert;
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ct = nf_ct_get(skb, &ctinfo);
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if (!ct || !ct->master)
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return ret;
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master_help = nfct_help(ct->master);
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if (!master_help)
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return ret;
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/* rcu_read_lock()ed by nf_hook_thresh */
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helper = rcu_dereference(master_help->helper);
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if (!helper)
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return ret;
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if (info->name[0] == '\0')
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ret = !ret;
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else
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ret ^= !strncmp(helper->name, info->name,
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strlen(helper->name));
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return ret;
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}
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static int helper_mt_check(const struct xt_mtchk_param *par)
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{
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struct xt_helper_info *info = par->matchinfo;
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int ret;
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ret = nf_ct_netns_get(par->net, par->family);
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if (ret < 0) {
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pr_info_ratelimited("cannot load conntrack support for proto=%u\n",
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par->family);
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return ret;
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}
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info->name[sizeof(info->name) - 1] = '\0';
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return 0;
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}
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static void helper_mt_destroy(const struct xt_mtdtor_param *par)
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{
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nf_ct_netns_put(par->net, par->family);
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}
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static struct xt_match helper_mt_reg __read_mostly = {
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.name = "helper",
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.revision = 0,
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.family = NFPROTO_UNSPEC,
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.checkentry = helper_mt_check,
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.match = helper_mt,
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.destroy = helper_mt_destroy,
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.matchsize = sizeof(struct xt_helper_info),
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.me = THIS_MODULE,
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};
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static int __init helper_mt_init(void)
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{
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return xt_register_match(&helper_mt_reg);
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}
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static void __exit helper_mt_exit(void)
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{
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xt_unregister_match(&helper_mt_reg);
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}
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module_init(helper_mt_init);
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module_exit(helper_mt_exit);
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