LXR linux/net/netfilter/xt

   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
  19MODULE_LICENSE("GPL");
  20MODULE_AUTHOR("Martin Josefsson <gandalf@netfilter.org>");
  21MODULE_DESCRIPTION("Xtables: Related connection matching");
  22MODULE_ALIAS("ipt_helper");
  23MODULE_ALIAS("ip6t_helper");
  24
  25
  26static bool
  27helper_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
  57static 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_l3proto_try_module_get(par->family);
  63        if (ret < 0) {
  64                pr_info("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
  72static void helper_mt_destroy(const struct xt_mtdtor_param *par)
  73{
  74        nf_ct_l3proto_module_put(par->family);
  75}
  76
  77static 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
  88static int __init helper_mt_init(void)
  89{
  90        return xt_register_match(&helper_mt_reg);
  91}
  92
  93static void __exit helper_mt_exit(void)
  94{
  95        xt_unregister_match(&helper_mt_reg);
  96}
  97
  98module_init(helper_mt_init);
  99module_exit(helper_mt_exit);
 100