linux/net/netfilter/nf_conntrack_snmp.c
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   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, S_IRUSR);
  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, enum ip_conntrack_info ctinfo)
  40{
  41        typeof(nf_nat_snmp_hook) nf_nat_snmp;
  42
  43        nf_conntrack_broadcast_help(skb, protoff, ct, ctinfo, timeout);
  44
  45        nf_nat_snmp = rcu_dereference(nf_nat_snmp_hook);
  46        if (nf_nat_snmp && ct->status & IPS_NAT_MASK)
  47                return nf_nat_snmp(skb, protoff, ct, ctinfo);
  48
  49        return NF_ACCEPT;
  50}
  51
  52static struct nf_conntrack_expect_policy exp_policy = {
  53        .max_expected   = 1,
  54};
  55
  56static struct nf_conntrack_helper helper __read_mostly = {
  57        .name                   = "snmp",
  58        .tuple.src.l3num        = NFPROTO_IPV4,
  59        .tuple.src.u.udp.port   = cpu_to_be16(SNMP_PORT),
  60        .tuple.dst.protonum     = IPPROTO_UDP,
  61        .me                     = THIS_MODULE,
  62        .help                   = snmp_conntrack_help,
  63        .expect_policy          = &exp_policy,
  64};
  65
  66static int __init nf_conntrack_snmp_init(void)
  67{
  68        exp_policy.timeout = timeout;
  69        return nf_conntrack_helper_register(&helper);
  70}
  71
  72static void __exit nf_conntrack_snmp_fini(void)
  73{
  74        nf_conntrack_helper_unregister(&helper);
  75}
  76
  77module_init(nf_conntrack_snmp_init);
  78module_exit(nf_conntrack_snmp_fini);
  79
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