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"); 40 41static unsigned int timeout __read_mostly = 3; 42module_param(timeout, uint, 0400); 43MODULE_PARM_DESC(timeout, "timeout for master connection/replies in seconds"); 44 45static int help(struct sk_buff **pskb, unsigned int protoff, 46 struct nf_conn *ct, enum ip_conntrack_info ctinfo) 47{ 48 struct nf_conntrack_expect *exp; 49 struct iphdr *iph = ip_hdr(*pskb); 50 struct rtable *rt = (struct rtable *)(*pskb)->dst; 51 struct in_device *in_dev; 52 __be32 mask = 0; 53 54 /* we're only interested in locally generated packets */ 55 if ((*pskb)->sk == NULL) 56 goto out; 57 if (rt == NULL || !(rt->rt_flags & RTCF_BROADCAST)) 58 goto out; 59 if (CTINFO2DIR(ctinfo) != IP_CT_DIR_ORIGINAL) 60 goto out; 61 62 rcu_read_lock(); 63 in_dev = __in_dev_get_rcu(rt->u.dst.dev); 64 if (in_dev != NULL) { 65 for_primary_ifa(in_dev) { 66 if (ifa->ifa_broadcast == iph->daddr) { 67 mask = ifa->ifa_mask; 68 break; 69 } 70 } endfor_ifa(in_dev); 71 } 72 rcu_read_unlock(); 73 74 if (mask == 0) 75 goto out; 76 77 exp = nf_conntrack_expect_alloc(ct); 78 if (exp == NULL) 79 goto out; 80 81 exp->tuple = ct->tuplehash[IP_CT_DIR_REPLY].tuple; 82 exp->tuple.src.u.udp.port = htons(NMBD_PORT); 83 84 exp->mask.src.u3.ip = mask; 85 exp->mask.src.u.udp.port = htons(0xFFFF); 86 exp->mask.dst.u3.ip = htonl(0xFFFFFFFF); 87 exp->mask.dst.u.udp.port = htons(0xFFFF); 88 exp->mask.dst.protonum = 0xFF; 89 90 exp->expectfn = NULL; 91 exp->flags = NF_CT_EXPECT_PERMANENT; 92 exp->helper = NULL; 93 94 nf_conntrack_expect_related(exp); 95 nf_conntrack_expect_put(exp); 96 97 nf_ct_refresh(ct, *pskb, timeout * HZ); 98out: 99 return NF_ACCEPT; 100} 101 102static struct nf_conntrack_helper helper __read_mostly = { 103 .name = "netbios-ns", 104 .tuple.src.l3num = AF_INET, 105 .tuple.src.u.udp.port = __constant_htons(NMBD_PORT), 106 .tuple.dst.protonum = IPPROTO_UDP, 107 .mask.src.l3num = 0xFFFF, 108 .mask.src.u.udp.port = __constant_htons(0xFFFF), 109 .mask.dst.protonum = 0xFF, 110 .max_expected = 1, 111 .me = THIS_MODULE, 112 .help = help, 113}; 114 115static int __init nf_conntrack_netbios_ns_init(void) 116{ 117 helper.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