LXR linux/net/netfilter/nf_conntrack

   1/*
   2 *      SNMP service broadcast connection tracking helper
   3 *
   4 *      (c) 2011 Jiri Olsa <jolsa@redhat.com>
   5 *
   6 *      This program is free software; you can redistribute it and/or
   7 *      modify it under the terms of the GNU General Public License
   8 *      as published by the Free Software Foundation; either version
   9 *      2 of the License, or (at your option) any later version.
  10 */
  11#include <linux/kernel.h>
  12#include <linux/module.h>
  13#include <linux/init.h>
  14#include <linux/in.h>
  15
  16#include <net/netfilter/nf_conntrack.h>
  17#include <net/netfilter/nf_conntrack_helper.h>
  18#include <net/netfilter/nf_conntrack_expect.h>
  19#include <linux/netfilter/nf_conntrack_snmp.h>
  20
  21#define SNMP_PORT       161
  22
  23MODULE_AUTHOR("Jiri Olsa <jolsa@redhat.com>");
  24MODULE_DESCRIPTION("SNMP service broadcast connection tracking helper");
  25MODULE_LICENSE("GPL");
  26MODULE_ALIAS_NFCT_HELPER("snmp");
  27
  28static unsigned int timeout __read_mostly = 30;
  29module_param(timeout, uint, 0400);
  30MODULE_PARM_DESC(timeout, "timeout for master connection/replies in seconds");
  31
  32int (*nf_nat_snmp_hook)(struct sk_buff *skb,
  33                        unsigned int protoff,
  34                        struct nf_conn *ct,
  35                        enum ip_conntrack_info ctinfo);
  36EXPORT_SYMBOL_GPL(nf_nat_snmp_hook);
  37
  38static int snmp_conntrack_help(struct sk_buff *skb, unsigned int protoff,
  39                               struct nf_conn *ct,
  40                               enum ip_conntrack_info ctinfo)
  41{
  42        typeof(nf_nat_snmp_hook) nf_nat_snmp;
  43
  44        nf_conntrack_broadcast_help(skb, ct, ctinfo, timeout);
  45
  46        nf_nat_snmp = rcu_dereference(nf_nat_snmp_hook);
  47        if (nf_nat_snmp && ct->status & IPS_NAT_MASK)
  48                return nf_nat_snmp(skb, protoff, ct, ctinfo);
  49
  50        return NF_ACCEPT;
  51}
  52
  53static struct nf_conntrack_expect_policy exp_policy = {
  54        .max_expected   = 1,
  55};
  56
  57static struct nf_conntrack_helper helper __read_mostly = {
  58        .name                   = "snmp",
  59        .tuple.src.l3num        = NFPROTO_IPV4,
  60        .tuple.src.u.udp.port   = cpu_to_be16(SNMP_PORT),
  61        .tuple.dst.protonum     = IPPROTO_UDP,
  62        .me                     = THIS_MODULE,
  63        .help                   = snmp_conntrack_help,
  64        .expect_policy          = &exp_policy,
  65};
  66
  67static int __init nf_conntrack_snmp_init(void)
  68{
  69        exp_policy.timeout = timeout;
  70        return nf_conntrack_helper_register(&helper);
  71}
  72
  73static void __exit nf_conntrack_snmp_fini(void)
  74{
  75        nf_conntrack_helper_unregister(&helper);
  76}
  77
  78module_init(nf_conntrack_snmp_init);
  79module_exit(nf_conntrack_snmp_fini);
  80