net/netfilter/nf_conntrack_snmp.c

0001 // SPDX-License-Identifier: GPL-2.0-or-later
0002 /*
0003  *      SNMP service broadcast connection tracking helper
0004  *
0005  *      (c) 2011 Jiri Olsa <jolsa@redhat.com>
0006  */
0007 #include <linux/kernel.h>
0008 #include <linux/module.h>
0009 #include <linux/init.h>
0010 #include <linux/in.h>
0011
0012 #include <net/netfilter/nf_conntrack.h>
0013 #include <net/netfilter/nf_conntrack_helper.h>
0014 #include <net/netfilter/nf_conntrack_expect.h>
0015 #include <linux/netfilter/nf_conntrack_snmp.h>
0016
0017 #define SNMP_PORT   161
0018
0019 MODULE_AUTHOR("Jiri Olsa <jolsa@redhat.com>");
0020 MODULE_DESCRIPTION("SNMP service broadcast connection tracking helper");
0021 MODULE_LICENSE("GPL");
0022 MODULE_ALIAS_NFCT_HELPER("snmp");
0023
0024 static unsigned int timeout __read_mostly = 30;
0025 module_param(timeout, uint, 0400);
0026 MODULE_PARM_DESC(timeout, "timeout for master connection/replies in seconds");
0027
0028 int (*nf_nat_snmp_hook)(struct sk_buff *skb,
0029             unsigned int protoff,
0030             struct nf_conn *ct,
0031             enum ip_conntrack_info ctinfo);
0032 EXPORT_SYMBOL_GPL(nf_nat_snmp_hook);
0033
0034 static int snmp_conntrack_help(struct sk_buff *skb, unsigned int protoff,
0035                    struct nf_conn *ct,
0036                    enum ip_conntrack_info ctinfo)
0037 {
0038     typeof(nf_nat_snmp_hook) nf_nat_snmp;
0039
0040     nf_conntrack_broadcast_help(skb, ct, ctinfo, timeout);
0041
0042     nf_nat_snmp = rcu_dereference(nf_nat_snmp_hook);
0043     if (nf_nat_snmp && ct->status & IPS_NAT_MASK)
0044         return nf_nat_snmp(skb, protoff, ct, ctinfo);
0045
0046     return NF_ACCEPT;
0047 }
0048
0049 static struct nf_conntrack_expect_policy exp_policy = {
0050     .max_expected   = 1,
0051 };
0052
0053 static struct nf_conntrack_helper helper __read_mostly = {
0054     .name           = "snmp",
0055     .tuple.src.l3num    = NFPROTO_IPV4,
0056     .tuple.src.u.udp.port   = cpu_to_be16(SNMP_PORT),
0057     .tuple.dst.protonum = IPPROTO_UDP,
0058     .me         = THIS_MODULE,
0059     .help           = snmp_conntrack_help,
0060     .expect_policy      = &exp_policy,
0061 };
0062
0063 static int __init nf_conntrack_snmp_init(void)
0064 {
0065     exp_policy.timeout = timeout;
0066     return nf_conntrack_helper_register(&helper);
0067 }
0068
0069 static void __exit nf_conntrack_snmp_fini(void)
0070 {
0071     nf_conntrack_helper_unregister(&helper);
0072 }
0073
0074 module_init(nf_conntrack_snmp_init);
0075 module_exit(nf_conntrack_snmp_fini);