1/* 2 * NetBIOS name service broadcast connection tracking helper 3 * 4 * (c) 2005 Patrick McHardy <kaber@trash.net> 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/* 12 * This helper tracks locally originating NetBIOS name service 13 * requests by issuing permanent expectations (valid until 14 * timing out) matching all reply connections from the 15 * destination network. The only NetBIOS specific thing is 16 * actually the port number. 17 */ 18#include <linux/kernel.h> 19#include <linux/module.h> 20#include <linux/init.h> 21#include <linux/skbuff.h> 22#include <linux/netdevice.h> 23#include <linux/inetdevice.h> 24#include <linux/if_addr.h> 25#include <linux/in.h> 26#include <linux/ip.h> 27#include <linux/netfilter.h> 28#include <net/route.h> 29 30#include <net/netfilter/nf_conntrack.h> 31#include <net/netfilter/nf_conntrack_helper.h> 32#include <net/netfilter/nf_conntrack_expect.h> 33 34#define NMBD_PORT 137 35 36MODULE_AUTHOR("Patrick McHardy <kaber@trash.net>"); 37MODULE_DESCRIPTION("NetBIOS name service broadcast connection tracking helper"); 38MODULE_LICENSE("GPL"); 39MODULE_ALIAS("ip_conntrack_netbios_ns"); 40MODULE_ALIAS_NFCT_HELPER("netbios_ns"); 41 42static unsigned int timeout __read_mostly = 3; 43module_param(timeout, uint, 0400); 44MODULE_PARM_DESC(timeout, "timeout for master connection/replies in seconds"); 45 46static int help(struct sk_buff *skb, unsigned int protoff, 47 struct nf_conn *ct, enum ip_conntrack_info ctinfo) 48{ 49 struct nf_conntrack_expect *exp; 50 struct iphdr *iph = ip_hdr(skb); 51 struct rtable *rt = skb_rtable(skb); 52 struct in_device *in_dev; 53 __be32 mask = 0; 54 55 /* we're only interested in locally generated packets */ 56 if (skb->sk == NULL) 57 goto out; 58 if (rt == NULL || !(rt->rt_flags & RTCF_BROADCAST)) 59 goto out; 60 if (CTINFO2DIR(ctinfo) != IP_CT_DIR_ORIGINAL) 61 goto out; 62 63 rcu_read_lock(); 64 in_dev = __in_dev_get_rcu(rt->dst.dev); 65 if (in_dev != NULL) { 66 for_primary_ifa(in_dev) { 67 if (ifa->ifa_broadcast == iph->daddr) { 68 mask = ifa->ifa_mask; 69 break; 70 } 71 } endfor_ifa(in_dev); 72 } 73 rcu_read_unlock(); 74 75 if (mask == 0) 76 goto out; 77 78 exp = nf_ct_expect_alloc(ct); 79 if (exp == NULL) 80 goto out; 81 82 exp->tuple = ct->tuplehash[IP_CT_DIR_REPLY].tuple; 83 exp->tuple.src.u.udp.port = htons(NMBD_PORT); 84 85 exp->mask.src.u3.ip = mask; 86 exp->mask.src.u.udp.port = htons(0xFFFF); 87 88 exp->expectfn = NULL; 89 exp->flags = NF_CT_EXPECT_PERMANENT; 90 exp->class = NF_CT_EXPECT_CLASS_DEFAULT; 91 exp->helper = NULL; 92 93 nf_ct_expect_related(exp); 94 nf_ct_expect_put(exp); 95 96 nf_ct_refresh(ct, skb, timeout * HZ); 97out: 98 return NF_ACCEPT; 99} 100 101static struct nf_conntrack_expect_policy exp_policy = { 102 .max_expected = 1, 103}; 104 105static struct nf_conntrack_helper helper __read_mostly = { 106 .name = "netbios-ns", 107 .tuple.src.l3num = AF_INET, 108 .tuple.src.u.udp.port = cpu_to_be16(NMBD_PORT), 109 .tuple.dst.protonum = IPPROTO_UDP, 110 .me = THIS_MODULE, 111 .help = help, 112 .expect_policy = &exp_policy, 113}; 114 115static int __init nf_conntrack_netbios_ns_init(void) 116{ 117 exp_policy.timeout = timeout; 118 return nf_conntrack_helper_register(&helper); 119} 120 121static void __exit nf_conntrack_netbios_ns_fini(void) 122{ 123 nf_conntrack_helper_unregister(&helper); 124} 125 126module_init(nf_conntrack_netbios_ns_init); 127module_exit(nf_conntrack_netbios_ns_fini); 128