1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /*
3  *      broadcast connection tracking helper
4  *
5  *      (c) 2005 Patrick McHardy <kaber@trash.net>
6  */
7 
8 #include <linux/module.h>
9 #include <linux/ip.h>
10 #include <net/route.h>
11 #include <linux/inetdevice.h>
12 #include <linux/skbuff.h>
13 
14 #include <net/netfilter/nf_conntrack.h>
15 #include <net/netfilter/nf_conntrack_helper.h>
16 #include <net/netfilter/nf_conntrack_expect.h>
17 
nf_conntrack_broadcast_help(struct sk_buff * skb,struct nf_conn * ct,enum ip_conntrack_info ctinfo,unsigned int timeout)18 int nf_conntrack_broadcast_help(struct sk_buff *skb,
19 				struct nf_conn *ct,
20 				enum ip_conntrack_info ctinfo,
21 				unsigned int timeout)
22 {
23 	struct nf_conntrack_expect *exp;
24 	struct iphdr *iph = ip_hdr(skb);
25 	struct rtable *rt = skb_rtable(skb);
26 	struct in_device *in_dev;
27 	struct nf_conn_help *help = nfct_help(ct);
28 	__be32 mask = 0;
29 
30 	/* we're only interested in locally generated packets */
31 	if (skb->sk == NULL || !net_eq(nf_ct_net(ct), sock_net(skb->sk)))
32 		goto out;
33 	if (rt == NULL || !(rt->rt_flags & RTCF_BROADCAST))
34 		goto out;
35 	if (CTINFO2DIR(ctinfo) != IP_CT_DIR_ORIGINAL)
36 		goto out;
37 
38 	in_dev = __in_dev_get_rcu(rt->dst.dev);
39 	if (in_dev != NULL) {
40 		const struct in_ifaddr *ifa;
41 
42 		in_dev_for_each_ifa_rcu(ifa, in_dev) {
43 			if (ifa->ifa_flags & IFA_F_SECONDARY)
44 				continue;
45 
46 			if (ifa->ifa_broadcast == iph->daddr) {
47 				mask = ifa->ifa_mask;
48 				break;
49 			}
50 		}
51 	}
52 
53 	if (mask == 0)
54 		goto out;
55 
56 	exp = nf_ct_expect_alloc(ct);
57 	if (exp == NULL)
58 		goto out;
59 
60 	exp->tuple                = ct->tuplehash[IP_CT_DIR_REPLY].tuple;
61 	exp->tuple.src.u.udp.port = help->helper->tuple.src.u.udp.port;
62 
63 	exp->mask.src.u3.ip       = mask;
64 	exp->mask.src.u.udp.port  = htons(0xFFFF);
65 
66 	exp->expectfn             = NULL;
67 	exp->flags                = NF_CT_EXPECT_PERMANENT;
68 	exp->class		  = NF_CT_EXPECT_CLASS_DEFAULT;
69 	exp->helper               = NULL;
70 
71 	nf_ct_expect_related(exp, 0);
72 	nf_ct_expect_put(exp);
73 
74 	nf_ct_refresh(ct, skb, timeout * HZ);
75 out:
76 	return NF_ACCEPT;
77 }
78 EXPORT_SYMBOL_GPL(nf_conntrack_broadcast_help);
79 
80 MODULE_LICENSE("GPL");
81