1 /*
2  *      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 #include <linux/module.h>
13 #include <linux/ip.h>
14 #include <net/route.h>
15 #include <linux/inetdevice.h>
16 #include <linux/skbuff.h>
17 
18 #include <net/netfilter/nf_conntrack.h>
19 #include <net/netfilter/nf_conntrack_helper.h>
20 #include <net/netfilter/nf_conntrack_expect.h>
21 
22 int nf_conntrack_broadcast_help(struct sk_buff *skb,
23 				struct nf_conn *ct,
24 				enum ip_conntrack_info ctinfo,
25 				unsigned int timeout)
26 {
27 	struct nf_conntrack_expect *exp;
28 	struct iphdr *iph = ip_hdr(skb);
29 	struct rtable *rt = skb_rtable(skb);
30 	struct in_device *in_dev;
31 	struct nf_conn_help *help = nfct_help(ct);
32 	__be32 mask = 0;
33 
34 	/* we're only interested in locally generated packets */
35 	if (skb->sk == NULL)
36 		goto out;
37 	if (rt == NULL || !(rt->rt_flags & RTCF_BROADCAST))
38 		goto out;
39 	if (CTINFO2DIR(ctinfo) != IP_CT_DIR_ORIGINAL)
40 		goto out;
41 
42 	in_dev = __in_dev_get_rcu(rt->dst.dev);
43 	if (in_dev != NULL) {
44 		for_primary_ifa(in_dev) {
45 			if (ifa->ifa_broadcast == iph->daddr) {
46 				mask = ifa->ifa_mask;
47 				break;
48 			}
49 		} endfor_ifa(in_dev);
50 	}
51 
52 	if (mask == 0)
53 		goto out;
54 
55 	exp = nf_ct_expect_alloc(ct);
56 	if (exp == NULL)
57 		goto out;
58 
59 	exp->tuple                = ct->tuplehash[IP_CT_DIR_REPLY].tuple;
60 	exp->tuple.src.u.udp.port = help->helper->tuple.src.u.udp.port;
61 
62 	exp->mask.src.u3.ip       = mask;
63 	exp->mask.src.u.udp.port  = htons(0xFFFF);
64 
65 	exp->expectfn             = NULL;
66 	exp->flags                = NF_CT_EXPECT_PERMANENT;
67 	exp->class		  = NF_CT_EXPECT_CLASS_DEFAULT;
68 	exp->helper               = NULL;
69 
70 	nf_ct_expect_related(exp);
71 	nf_ct_expect_put(exp);
72 
73 	nf_ct_refresh(ct, skb, timeout * HZ);
74 out:
75 	return NF_ACCEPT;
76 }
77 EXPORT_SYMBOL_GPL(nf_conntrack_broadcast_help);
78 
79 MODULE_LICENSE("GPL");
80