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
22 MODULE_AUTHOR("Jiri Olsa <jolsa@redhat.com>");
23 MODULE_DESCRIPTION("SNMP service broadcast connection tracking helper");
24 MODULE_LICENSE("GPL");
25 MODULE_ALIAS_NFCT_HELPER("snmp");
26
27 static unsigned int timeout __read_mostly = 30;
28 module_param(timeout, uint, S_IRUSR);
29 MODULE_PARM_DESC(timeout, "timeout for master connection/replies in seconds");
30
31 int (*nf_nat_snmp_hook)(struct sk_buff *skb,
32 unsigned int protoff,
33 struct nf_conn *ct,
34 enum ip_conntrack_info ctinfo);
35 EXPORT_SYMBOL_GPL(nf_nat_snmp_hook);
36
snmp_conntrack_help(struct sk_buff * skb,unsigned int protoff,struct nf_conn * ct,enum ip_conntrack_info ctinfo)37 static 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
51 static struct nf_conntrack_expect_policy exp_policy = {
52 .max_expected = 1,
53 };
54
55 static 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
nf_conntrack_snmp_init(void)65 static int __init nf_conntrack_snmp_init(void)
66 {
67 exp_policy.timeout = timeout;
68 return nf_conntrack_helper_register(&helper);
69 }
70
nf_conntrack_snmp_fini(void)71 static void __exit nf_conntrack_snmp_fini(void)
72 {
73 nf_conntrack_helper_unregister(&helper);
74 }
75
76 module_init(nf_conntrack_snmp_init);
77 module_exit(nf_conntrack_snmp_fini);
78