net/netfilter/nf_conntrack_snmp.c

   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 #include <linux/netfilter/nf_conntrack_snmp.h>
  20
  21 #define SNMP_PORT       161
  22
  23 MODULE_AUTHOR("Jiri Olsa <jolsa@redhat.com>");
  24 MODULE_DESCRIPTION("SNMP service broadcast connection tracking helper");
  25 MODULE_LICENSE("GPL");
  26 MODULE_ALIAS_NFCT_HELPER("snmp");
  27
  28 static unsigned int timeout __read_mostly = 30;
  29 module_param(timeout, uint, 0400);
  30 MODULE_PARM_DESC(timeout, "timeout for master connection/replies in seconds");
  31
  32 int (*nf_nat_snmp_hook)(struct sk_buff *skb,
  33                         unsigned int protoff,
  34                         struct nf_conn *ct,
  35                         enum ip_conntrack_info ctinfo);
  36 EXPORT_SYMBOL_GPL(nf_nat_snmp_hook);
  37
  38 static int snmp_conntrack_help(struct sk_buff *skb, unsigned int protoff,
  39                                struct nf_conn *ct,
  40                                enum ip_conntrack_info ctinfo)
  41 {
  42         typeof(nf_nat_snmp_hook) nf_nat_snmp;
  43
  44         nf_conntrack_broadcast_help(skb, ct, ctinfo, timeout);
  45
  46         nf_nat_snmp = rcu_dereference(nf_nat_snmp_hook);
  47         if (nf_nat_snmp && ct->status & IPS_NAT_MASK)
  48                 return nf_nat_snmp(skb, protoff, ct, ctinfo);
  49
  50         return NF_ACCEPT;
  51 }
  52
  53 static struct nf_conntrack_expect_policy exp_policy = {
  54         .max_expected   = 1,
  55 };
  56
  57 static struct nf_conntrack_helper helper __read_mostly = {
  58         .name                   = "snmp",
  59         .tuple.src.l3num        = NFPROTO_IPV4,
  60         .tuple.src.u.udp.port   = cpu_to_be16(SNMP_PORT),
  61         .tuple.dst.protonum     = IPPROTO_UDP,
  62         .me                     = THIS_MODULE,
  63         .help                   = snmp_conntrack_help,
  64         .expect_policy          = &exp_policy,
  65 };
  66
  67 static int __init nf_conntrack_snmp_init(void)
  68 {
  69         exp_policy.timeout = timeout;
  70         return nf_conntrack_helper_register(&helper);
  71 }
  72
  73 static void __exit nf_conntrack_snmp_fini(void)
  74 {
  75         nf_conntrack_helper_unregister(&helper);
  76 }
  77
  78 module_init(nf_conntrack_snmp_init);
  79 module_exit(nf_conntrack_snmp_fini);