LXR linux/net/netfilter/nf_conntrack

   1// SPDX-License-Identifier: GPL-2.0-or-later
   2/*
   3 *      SNMP service broadcast connection tracking helper
   4 *
   5 *      (c) 2011 Jiri Olsa <jolsa@redhat.com>
   6 */
   7#include <linux/kernel.h>
   8#include <linux/module.h>
   9#include <linux/init.h>
  10#include <linux/in.h>
  11
  12#include <net/netfilter/nf_conntrack.h>
  13#include <net/netfilter/nf_conntrack_helper.h>
  14#include <net/netfilter/nf_conntrack_expect.h>
  15#include <linux/netfilter/nf_conntrack_snmp.h>
  16
  17#define SNMP_PORT       161
  18
  19MODULE_AUTHOR("Jiri Olsa <jolsa@redhat.com>");
  20MODULE_DESCRIPTION("SNMP service broadcast connection tracking helper");
  21MODULE_LICENSE("GPL");
  22MODULE_ALIAS_NFCT_HELPER("snmp");
  23
  24static unsigned int timeout __read_mostly = 30;
  25module_param(timeout, uint, 0400);
  26MODULE_PARM_DESC(timeout, "timeout for master connection/replies in seconds");
  27
  28int (*nf_nat_snmp_hook)(struct sk_buff *skb,
  29                        unsigned int protoff,
  30                        struct nf_conn *ct,
  31                        enum ip_conntrack_info ctinfo);
  32EXPORT_SYMBOL_GPL(nf_nat_snmp_hook);
  33
  34static int snmp_conntrack_help(struct sk_buff *skb, unsigned int protoff,
  35                               struct nf_conn *ct,
  36                               enum ip_conntrack_info ctinfo)
  37{
  38        typeof(nf_nat_snmp_hook) nf_nat_snmp;
  39
  40        nf_conntrack_broadcast_help(skb, ct, ctinfo, timeout);
  41
  42        nf_nat_snmp = rcu_dereference(nf_nat_snmp_hook);
  43        if (nf_nat_snmp && ct->status & IPS_NAT_MASK)
  44                return nf_nat_snmp(skb, protoff, ct, ctinfo);
  45
  46        return NF_ACCEPT;
  47}
  48
  49static struct nf_conntrack_expect_policy exp_policy = {
  50        .max_expected   = 1,
  51};
  52
  53static struct nf_conntrack_helper helper __read_mostly = {
  54        .name                   = "snmp",
  55        .tuple.src.l3num        = NFPROTO_IPV4,
  56        .tuple.src.u.udp.port   = cpu_to_be16(SNMP_PORT),
  57        .tuple.dst.protonum     = IPPROTO_UDP,
  58        .me                     = THIS_MODULE,
  59        .help                   = snmp_conntrack_help,
  60        .expect_policy          = &exp_policy,
  61};
  62
  63static int __init nf_conntrack_snmp_init(void)
  64{
  65        exp_policy.timeout = timeout;
  66        return nf_conntrack_helper_register(&helper);
  67}
  68
  69static void __exit nf_conntrack_snmp_fini(void)
  70{
  71        nf_conntrack_helper_unregister(&helper);
  72}
  73
  74module_init(nf_conntrack_snmp_init);
  75module_exit(nf_conntrack_snmp_fini);
  76