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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 | |
36 | MODULE_AUTHOR("Patrick McHardy <kaber@trash.net>"); |
37 | MODULE_DESCRIPTION("NetBIOS name service broadcast connection tracking helper"); |
38 | MODULE_LICENSE("GPL"); |
39 | MODULE_ALIAS("ip_conntrack_netbios_ns"); |
40 | MODULE_ALIAS_NFCT_HELPER("netbios_ns"); |
41 | |
42 | static unsigned int timeout __read_mostly = 3; |
43 | module_param(timeout, uint, 0400); |
44 | MODULE_PARM_DESC(timeout, "timeout for master connection/replies in seconds"); |
45 | |
46 | static 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->u.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); |
97 | out: |
98 | return NF_ACCEPT; |
99 | } |
100 | |
101 | static struct nf_conntrack_expect_policy exp_policy = { |
102 | .max_expected = 1, |
103 | }; |
104 | |
105 | static 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 | |
115 | static int __init nf_conntrack_netbios_ns_init(void) |
116 | { |
117 | exp_policy.timeout = timeout; |
118 | return nf_conntrack_helper_register(&helper); |
119 | } |
120 | |
121 | static void __exit nf_conntrack_netbios_ns_fini(void) |
122 | { |
123 | nf_conntrack_helper_unregister(&helper); |
124 | } |
125 | |
126 | module_init(nf_conntrack_netbios_ns_init); |
127 | module_exit(nf_conntrack_netbios_ns_fini); |
128 |
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