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
  20#define SNMP_PORT       161
  21
  22MODULE_AUTHOR("Jiri Olsa <jolsa@redhat.com>");
  23MODULE_DESCRIPTION("SNMP service broadcast connection tracking helper");
  24MODULE_LICENSE("GPL");
  25MODULE_ALIAS_NFCT_HELPER("snmp");
  26
  27static unsigned int timeout __read_mostly = 30;
  28module_param(timeout, uint, S_IRUSR);
  29MODULE_PARM_DESC(timeout, "timeout for master connection/replies in seconds");
  30
  31int (*nf_nat_snmp_hook)(struct sk_buff *skb,
  32                        unsigned int protoff,
  33                        struct nf_conn *ct,
  34                        enum ip_conntrack_info ctinfo);
  35EXPORT_SYMBOL_GPL(nf_nat_snmp_hook);
  36
  37static int snmp_conntrack_help(struct sk_buff *skb, unsigned int protoff,
  38                struct nf_conn *ct, enum ip_conntrack_info ctinfo)
  39{
  40        typeof(nf_nat_snmp_hook) nf_nat_snmp;
  41
  42        nf_conntrack_broadcast_help(skb, protoff, ct, ctinfo, timeout);
  43
  44        nf_nat_snmp = rcu_dereference(nf_nat_snmp_hook);
  45        if (nf_nat_snmp && ct->status & IPS_NAT_MASK)
  46                return nf_nat_snmp(skb, protoff, ct, ctinfo);
  47
  48        return NF_ACCEPT;
  49}
  50
  51static struct nf_conntrack_expect_policy exp_policy = {
  52        .max_expected   = 1,
  53};
  54
  55static struct nf_conntrack_helper helper __read_mostly = {
  56        .name                   = "snmp",
  57        .tuple.src.l3num        = NFPROTO_IPV4,
  58        .tuple.src.u.udp.port   = cpu_to_be16(SNMP_PORT),
  59        .tuple.dst.protonum     = IPPROTO_UDP,
  60        .me                     = THIS_MODULE,
  61        .help                   = snmp_conntrack_help,
  62        .expect_policy          = &exp_policy,
  63};
  64
  65static int __init nf_conntrack_snmp_init(void)
  66{
  67        exp_policy.timeout = timeout;
  68        return nf_conntrack_helper_register(&helper);
  69}
  70
  71static void __exit nf_conntrack_snmp_fini(void)
  72{
  73        nf_conntrack_helper_unregister(&helper);
  74}
  75
  76module_init(nf_conntrack_snmp_init);
  77module_exit(nf_conntrack_snmp_fini);
  78
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