nf_conntrack_broadcast.c

 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
18int 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 net *net = read_pnet(&ct->ct_net);
25	struct nf_conntrack_expect *exp;
26	struct iphdr *iph = ip_hdr(skb);
27	struct rtable *rt = skb_rtable(skb);
28	struct in_device *in_dev;
29	struct nf_conn_help *help = nfct_help(ct);
30	__be32 mask = 0;
31
32	/* we're only interested in locally generated packets */
33	if (skb->sk == NULL || !net_eq(nf_ct_net(ct), sock_net(skb->sk)))
34		goto out;
35	if (rt == NULL || !(rt->rt_flags & RTCF_BROADCAST))
36		goto out;
37	if (CTINFO2DIR(ctinfo) != IP_CT_DIR_ORIGINAL)
38		goto out;
39
40	in_dev = __in_dev_get_rcu(rt->dst.dev);
41	if (in_dev != NULL) {
42		const struct in_ifaddr *ifa;
43
44		in_dev_for_each_ifa_rcu(ifa, in_dev) {
45			if (ifa->ifa_flags & IFA_F_SECONDARY)
46				continue;
47
48			if (ifa->ifa_broadcast == iph->daddr) {
49				mask = ifa->ifa_mask;
50				break;
51			}
52		}
53	}
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
64	helper = rcu_dereference(help->helper);
65	if (helper)
66		exp->tuple.src.u.udp.port = helper->tuple.src.u.udp.port;
67
68	exp->mask.src.u3.ip       = mask;
69	exp->mask.src.u.udp.port  = htons(0xFFFF);
70
71	exp->expectfn             = NULL;
72	exp->flags                = NF_CT_EXPECT_PERMANENT;
73	exp->class		  = NF_CT_EXPECT_CLASS_DEFAULT;
74	rcu_assign_pointer(exp->helper, helper);
75	write_pnet(&exp->net, net);
76#ifdef CONFIG_NF_CONNTRACK_ZONES
77	exp->zone = ct->zone;
78#endif
79	nf_ct_expect_related(exp, 0);
80	nf_ct_expect_put(exp);
81
82	nf_ct_refresh(ct, timeout * HZ);
83out:
84	return NF_ACCEPT;
85}
86EXPORT_SYMBOL_GPL(nf_conntrack_broadcast_help);
87
88MODULE_LICENSE("GPL");
89MODULE_DESCRIPTION("Broadcast connection tracking helper");