net/netfilter/nf_conntrack_snmp.c

   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
  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
  63 static int __init nf_conntrack_snmp_init(void)
  64 {
  65         exp_policy.timeout = timeout;
  66         return nf_conntrack_helper_register(&helper);
  67 }
  68
  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);