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 
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 	const struct nf_conntrack_helper *helper;
24 	struct nf_conntrack_expect *exp;
25 	struct iphdr *iph = ip_hdr(skb);
26 	struct rtable *rt = skb_rtable(skb);
27 	struct in_device *in_dev;
28 	struct nf_conn_help *help = nfct_help(ct);
29 	__be32 mask = 0;
30 
31 	/* we're only interested in locally generated packets */
32 	if (skb->sk == NULL || !net_eq(nf_ct_net(ct), sock_net(skb->sk)))
33 		goto out;
34 	if (rt == NULL || !(rt->rt_flags & RTCF_BROADCAST))
35 		goto out;
36 	if (CTINFO2DIR(ctinfo) != IP_CT_DIR_ORIGINAL)
37 		goto out;
38 
39 	in_dev = __in_dev_get_rcu(rt->dst.dev);
40 	if (in_dev != NULL) {
41 		const struct in_ifaddr *ifa;
42 
43 		in_dev_for_each_ifa_rcu(ifa, in_dev) {
44 			if (ifa->ifa_flags & IFA_F_SECONDARY)
45 				continue;
46 
47 			if (ifa->ifa_broadcast == iph->daddr) {
48 				mask = ifa->ifa_mask;
49 				break;
50 			}
51 		}
52 	}
53 
54 	if (mask == 0)
55 		goto out;
56 
57 	exp = nf_ct_expect_alloc(ct);
58 	if (exp == NULL)
59 		goto out;
60 
61 	exp->tuple                = ct->tuplehash[IP_CT_DIR_REPLY].tuple;
62 
63 	helper = rcu_dereference(help->helper);
64 	if (helper)
65 		exp->tuple.src.u.udp.port = helper->tuple.src.u.udp.port;
66 
67 	exp->mask.src.u3.ip       = mask;
68 	exp->mask.src.u.udp.port  = htons(0xFFFF);
69 
70 	exp->expectfn             = NULL;
71 	exp->flags                = NF_CT_EXPECT_PERMANENT;
72 	exp->class		  = NF_CT_EXPECT_CLASS_DEFAULT;
73 	exp->helper               = NULL;
74 
75 	nf_ct_expect_related(exp, 0);
76 	nf_ct_expect_put(exp);
77 
78 	nf_ct_refresh(ct, skb, timeout * HZ);
79 out:
80 	return NF_ACCEPT;
81 }
82 EXPORT_SYMBOL_GPL(nf_conntrack_broadcast_help);
83 
84 MODULE_LICENSE("GPL");
85