blob: b8e0a22ca1a9fd580d00b7ca46c93f2d096cde81 [file] [log] [blame]
* SNMP service broadcast connection tracking helper
* (c) 2011 Jiri Olsa <>
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License
* as published by the Free Software Foundation; either version
* 2 of the License, or (at your option) any later version.
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/init.h>
#include <linux/in.h>
#include <net/netfilter/nf_conntrack.h>
#include <net/netfilter/nf_conntrack_helper.h>
#include <net/netfilter/nf_conntrack_expect.h>
#include <linux/netfilter/nf_conntrack_snmp.h>
#define SNMP_PORT 161
MODULE_AUTHOR("Jiri Olsa <>");
MODULE_DESCRIPTION("SNMP service broadcast connection tracking helper");
static unsigned int timeout __read_mostly = 30;
module_param(timeout, uint, 0400);
MODULE_PARM_DESC(timeout, "timeout for master connection/replies in seconds");
int (*nf_nat_snmp_hook)(struct sk_buff *skb,
unsigned int protoff,
struct nf_conn *ct,
enum ip_conntrack_info ctinfo);
static int snmp_conntrack_help(struct sk_buff *skb, unsigned int protoff,
struct nf_conn *ct,
enum ip_conntrack_info ctinfo)
typeof(nf_nat_snmp_hook) nf_nat_snmp;
nf_conntrack_broadcast_help(skb, ct, ctinfo, timeout);
nf_nat_snmp = rcu_dereference(nf_nat_snmp_hook);
if (nf_nat_snmp && ct->status & IPS_NAT_MASK)
return nf_nat_snmp(skb, protoff, ct, ctinfo);
return NF_ACCEPT;
static struct nf_conntrack_expect_policy exp_policy = {
.max_expected = 1,
static struct nf_conntrack_helper helper __read_mostly = {
.name = "snmp",
.tuple.src.l3num = NFPROTO_IPV4,
.tuple.src.u.udp.port = cpu_to_be16(SNMP_PORT),
.tuple.dst.protonum = IPPROTO_UDP,
.help = snmp_conntrack_help,
.expect_policy = &exp_policy,
static int __init nf_conntrack_snmp_init(void)
exp_policy.timeout = timeout;
return nf_conntrack_helper_register(&helper);
static void __exit nf_conntrack_snmp_fini(void)