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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 | ||
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 | ||
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 | ||
65 | static int __init nf_conntrack_snmp_init(void) | |
66 | { | |
67 | exp_policy.timeout = timeout; | |
68 | return nf_conntrack_helper_register(&helper); | |
69 | } | |
70 | ||
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); |