LXR linux/net/netfilter/xt

   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
  16MODULE_LICENSE("GPL");
  17MODULE_AUTHOR("Martin Josefsson <gandalf@netfilter.org>");
  18MODULE_DESCRIPTION("Xtables: Related connection matching");
  19MODULE_ALIAS("ipt_helper");
  20MODULE_ALIAS("ip6t_helper");
  21
  22
  23static bool
  24helper_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
  54static 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
  69static void helper_mt_destroy(const struct xt_mtdtor_param *par)
  70{
  71        nf_ct_netns_put(par->net, par->family);
  72}
  73
  74static 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
  85static int __init helper_mt_init(void)
  86{
  87        return xt_register_match(&helper_mt_reg);
  88}
  89
  90static void __exit helper_mt_exit(void)
  91{
  92        xt_unregister_match(&helper_mt_reg);
  93}
  94
  95module_init(helper_mt_init);
  96module_exit(helper_mt_exit);
  97