1/* (C) 1999-2001 Paul `Rusty' Russell
2 * (C) 2002-2004 Netfilter Core Team <coreteam@netfilter.org>
3 *
4 * This program is free software; you can redistribute it and/or modify
5 * it under the terms of the GNU General Public License version 2 as
6 * published by the Free Software Foundation.
7 */
8
9#include <linux/types.h>
10#include <linux/ip.h>
11#include <linux/netfilter.h>
12#include <linux/module.h>
13#include <linux/skbuff.h>
14#include <net/netns/generic.h>
15#include <net/route.h>
16#include <net/ip.h>
17
18#include <linux/netfilter_bridge.h>
19#include <linux/netfilter_ipv4.h>
20#include <net/netfilter/ipv4/nf_defrag_ipv4.h>
21#if IS_ENABLED(CONFIG_NF_CONNTRACK)
22#include <net/netfilter/nf_conntrack.h>
23#endif
24#include <net/netfilter/nf_conntrack_zones.h>
25
26static DEFINE_MUTEX(defrag4_mutex);
27
28static int nf_ct_ipv4_gather_frags(struct net *net, struct sk_buff *skb,
29 u_int32_t user)
30{
31 int err;
32
33 local_bh_disable();
34 err = ip_defrag(net, skb, user);
35 local_bh_enable();
36
37 if (!err)
38 skb->ignore_df = 1;
39
40 return err;
41}
42
43static enum ip_defrag_users nf_ct_defrag_user(unsigned int hooknum,
44 struct sk_buff *skb)
45{
46 u16 zone_id = NF_CT_DEFAULT_ZONE_ID;
47#if IS_ENABLED(CONFIG_NF_CONNTRACK)
48 if (skb_nfct(skb)) {
49 enum ip_conntrack_info ctinfo;
50 const struct nf_conn *ct = nf_ct_get(skb, &ctinfo);
51
52 zone_id = nf_ct_zone_id(nf_ct_zone(ct), CTINFO2DIR(ctinfo));
53 }
54#endif
55 if (nf_bridge_in_prerouting(skb))
56 return IP_DEFRAG_CONNTRACK_BRIDGE_IN + zone_id;
57
58 if (hooknum == NF_INET_PRE_ROUTING)
59 return IP_DEFRAG_CONNTRACK_IN + zone_id;
60 else
61 return IP_DEFRAG_CONNTRACK_OUT + zone_id;
62}
63
64static unsigned int ipv4_conntrack_defrag(void *priv,
65 struct sk_buff *skb,
66 const struct nf_hook_state *state)
67{
68 struct sock *sk = skb->sk;
69
70 if (sk && sk_fullsock(sk) && (sk->sk_family == PF_INET) &&
71 inet_sk(sk)->nodefrag)
72 return NF_ACCEPT;
73
74#if IS_ENABLED(CONFIG_NF_CONNTRACK)
75#if !IS_ENABLED(CONFIG_NF_NAT)
76 /* Previously seen (loopback)? Ignore. Do this before
77 fragment check. */
78 if (skb_nfct(skb) && !nf_ct_is_template((struct nf_conn *)skb_nfct(skb)))
79 return NF_ACCEPT;
80#endif
81 if (skb->_nfct == IP_CT_UNTRACKED)
82 return NF_ACCEPT;
83#endif
84 /* Gather fragments. */
85 if (ip_is_fragment(ip_hdr(skb))) {
86 enum ip_defrag_users user =
87 nf_ct_defrag_user(state->hook, skb);
88
89 if (nf_ct_ipv4_gather_frags(state->net, skb, user))
90 return NF_STOLEN;
91 }
92 return NF_ACCEPT;
93}
94
95static const struct nf_hook_ops ipv4_defrag_ops[] = {
96 {
97 .hook = ipv4_conntrack_defrag,
98 .pf = NFPROTO_IPV4,
99 .hooknum = NF_INET_PRE_ROUTING,
100 .priority = NF_IP_PRI_CONNTRACK_DEFRAG,
101 },
102 {
103 .hook = ipv4_conntrack_defrag,
104 .pf = NFPROTO_IPV4,
105 .hooknum = NF_INET_LOCAL_OUT,
106 .priority = NF_IP_PRI_CONNTRACK_DEFRAG,
107 },
108};
109
110static void __net_exit defrag4_net_exit(struct net *net)
111{
112 if (net->nf.defrag_ipv4) {
113 nf_unregister_net_hooks(net, ipv4_defrag_ops,
114 ARRAY_SIZE(ipv4_defrag_ops));
115 net->nf.defrag_ipv4 = false;
116 }
117}
118
119static struct pernet_operations defrag4_net_ops = {
120 .exit = defrag4_net_exit,
121};
122
123static int __init nf_defrag_init(void)
124{
125 return register_pernet_subsys(&defrag4_net_ops);
126}
127
128static void __exit nf_defrag_fini(void)
129{
130 unregister_pernet_subsys(&defrag4_net_ops);
131}
132
133int nf_defrag_ipv4_enable(struct net *net)
134{
135 int err = 0;
136
137 might_sleep();
138
139 if (net->nf.defrag_ipv4)
140 return 0;
141
142 mutex_lock(&defrag4_mutex);
143 if (net->nf.defrag_ipv4)
144 goto out_unlock;
145
146 err = nf_register_net_hooks(net, ipv4_defrag_ops,
147 ARRAY_SIZE(ipv4_defrag_ops));
148 if (err == 0)
149 net->nf.defrag_ipv4 = true;
150
151 out_unlock:
152 mutex_unlock(&defrag4_mutex);
153 return err;
154}
155EXPORT_SYMBOL_GPL(nf_defrag_ipv4_enable);
156
157module_init(nf_defrag_init);
158module_exit(nf_defrag_fini);
159
160MODULE_LICENSE("GPL");
161