1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /*
3 * SNMP service broadcast connection tracking helper
4 *
5 * (c) 2011 Jiri Olsa <jolsa@redhat.com>
6 */
7 #include <linux/kernel.h>
8 #include <linux/module.h>
9 #include <linux/init.h>
10 #include <linux/in.h>
11
12 #include <net/netfilter/nf_conntrack.h>
13 #include <net/netfilter/nf_conntrack_helper.h>
14 #include <net/netfilter/nf_conntrack_expect.h>
15 #include <linux/netfilter/nf_conntrack_snmp.h>
16
17 #define SNMP_PORT 161
18
19 MODULE_AUTHOR("Jiri Olsa <jolsa@redhat.com>");
20 MODULE_DESCRIPTION("SNMP service broadcast connection tracking helper");
21 MODULE_LICENSE("GPL");
22 MODULE_ALIAS_NFCT_HELPER("snmp");
23
24 static unsigned int timeout __read_mostly = 30;
25 module_param(timeout, uint, 0400);
26 MODULE_PARM_DESC(timeout, "timeout for master connection/replies in seconds");
27
28 int (*nf_nat_snmp_hook)(struct sk_buff *skb,
29 unsigned int protoff,
30 struct nf_conn *ct,
31 enum ip_conntrack_info ctinfo);
32 EXPORT_SYMBOL_GPL(nf_nat_snmp_hook);
33
snmp_conntrack_help(struct sk_buff * skb,unsigned int protoff,struct nf_conn * ct,enum ip_conntrack_info ctinfo)34 static int snmp_conntrack_help(struct sk_buff *skb, unsigned int protoff,
35 struct nf_conn *ct,
36 enum ip_conntrack_info ctinfo)
37 {
38 typeof(nf_nat_snmp_hook) nf_nat_snmp;
39
40 nf_conntrack_broadcast_help(skb, ct, ctinfo, timeout);
41
42 nf_nat_snmp = rcu_dereference(nf_nat_snmp_hook);
43 if (nf_nat_snmp && ct->status & IPS_NAT_MASK)
44 return nf_nat_snmp(skb, protoff, ct, ctinfo);
45
46 return NF_ACCEPT;
47 }
48
49 static struct nf_conntrack_expect_policy exp_policy = {
50 .max_expected = 1,
51 };
52
53 static struct nf_conntrack_helper helper __read_mostly = {
54 .name = "snmp",
55 .tuple.src.l3num = NFPROTO_IPV4,
56 .tuple.src.u.udp.port = cpu_to_be16(SNMP_PORT),
57 .tuple.dst.protonum = IPPROTO_UDP,
58 .me = THIS_MODULE,
59 .help = snmp_conntrack_help,
60 .expect_policy = &exp_policy,
61 };
62
nf_conntrack_snmp_init(void)63 static int __init nf_conntrack_snmp_init(void)
64 {
65 exp_policy.timeout = timeout;
66 return nf_conntrack_helper_register(&helper);
67 }
68
nf_conntrack_snmp_fini(void)69 static void __exit nf_conntrack_snmp_fini(void)
70 {
71 nf_conntrack_helper_unregister(&helper);
72 }
73
74 module_init(nf_conntrack_snmp_init);
75 module_exit(nf_conntrack_snmp_fini);
76