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