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