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 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
