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
22int nf_conntrack_broadcast_help(struct sk_buff *skb,
23				unsigned int protoff,
24				struct nf_conn *ct,
25				enum ip_conntrack_info ctinfo,
26				unsigned int timeout)
27{
28	struct nf_conntrack_expect *exp;
29	struct iphdr *iph = ip_hdr(skb);
30	struct rtable *rt = skb_rtable(skb);
31	struct in_device *in_dev;
32	struct nf_conn_help *help = nfct_help(ct);
33	__be32 mask = 0;
34
35	/* we're only interested in locally generated packets */
36	if (skb->sk == NULL)
37		goto out;
38	if (rt == NULL || !(rt->rt_flags & RTCF_BROADCAST))
39		goto out;
40	if (CTINFO2DIR(ctinfo) != IP_CT_DIR_ORIGINAL)
41		goto out;
42
43	rcu_read_lock();
44	in_dev = __in_dev_get_rcu(rt->dst.dev);
45	if (in_dev != NULL) {
46		for_primary_ifa(in_dev) {
47			if (ifa->ifa_broadcast == iph->daddr) {
48				mask = ifa->ifa_mask;
49				break;
50			}
51		} endfor_ifa(in_dev);
52	}
53	rcu_read_unlock();
54
55	if (mask == 0)
56		goto out;
57
58	exp = nf_ct_expect_alloc(ct);
59	if (exp == NULL)
60		goto out;
61
62	exp->tuple                = ct->tuplehash[IP_CT_DIR_REPLY].tuple;
63	exp->tuple.src.u.udp.port = help->helper->tuple.src.u.udp.port;
64
65	exp->mask.src.u3.ip       = mask;
66	exp->mask.src.u.udp.port  = htons(0xFFFF);
67
68	exp->expectfn             = NULL;
69	exp->flags                = NF_CT_EXPECT_PERMANENT;
70	exp->class		  = NF_CT_EXPECT_CLASS_DEFAULT;
71	exp->helper               = NULL;
72
73	nf_ct_expect_related(exp);
74	nf_ct_expect_put(exp);
75
76	nf_ct_refresh(ct, skb, timeout * HZ);
77out:
78	return NF_ACCEPT;
79}
80EXPORT_SYMBOL_GPL(nf_conntrack_broadcast_help);
81
82MODULE_LICENSE("GPL");
83