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); 80