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
23 MODULE_AUTHOR("Jiri Olsa <jolsa@redhat.com>");
24 MODULE_DESCRIPTION("SNMP service broadcast connection tracking helper");
25 MODULE_LICENSE("GPL");
26 MODULE_ALIAS_NFCT_HELPER("snmp");
27
28 static unsigned int timeout __read_mostly = 30;
29 module_param(timeout, uint, S_IRUSR);
30 MODULE_PARM_DESC(timeout, "timeout for master connection/replies in seconds");
31
32 int (*nf_nat_snmp_hook)(struct sk_buff *skb,
33 unsigned int protoff,
34 struct nf_conn *ct,
35 enum ip_conntrack_info ctinfo);
36 EXPORT_SYMBOL_GPL(nf_nat_snmp_hook);
37
snmp_conntrack_help(struct sk_buff * skb,unsigned int protoff,struct nf_conn * ct,enum ip_conntrack_info ctinfo)38 static 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
52 static struct nf_conntrack_expect_policy exp_policy = {
53 .max_expected = 1,
54 };
55
56 static 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
nf_conntrack_snmp_init(void)66 static int __init nf_conntrack_snmp_init(void)
67 {
68 exp_policy.timeout = timeout;
69 return nf_conntrack_helper_register(&helper);
70 }
71
nf_conntrack_snmp_fini(void)72 static void __exit nf_conntrack_snmp_fini(void)
73 {
74 nf_conntrack_helper_unregister(&helper);
75 }
76
77 module_init(nf_conntrack_snmp_init);
78 module_exit(nf_conntrack_snmp_fini);
79