1 // SPDX-License-Identifier: GPL-2.0-only
2 /* (C) 1999-2001 Paul `Rusty' Russell
3 * (C) 2002-2004 Netfilter Core Team <coreteam@netfilter.org>
4 */
5
6 #include <linux/types.h>
7 #include <linux/ip.h>
8 #include <linux/netfilter.h>
9 #include <linux/module.h>
10 #include <linux/rcupdate.h>
11 #include <linux/skbuff.h>
12 #include <net/netns/generic.h>
13 #include <net/route.h>
14 #include <net/ip.h>
15
16 #include <linux/netfilter_bridge.h>
17 #include <linux/netfilter_ipv4.h>
18 #include <net/netfilter/ipv4/nf_defrag_ipv4.h>
19 #if IS_ENABLED(CONFIG_NF_CONNTRACK)
20 #include <net/netfilter/nf_conntrack.h>
21 #endif
22 #include <net/netfilter/nf_conntrack_zones.h>
23
24 static DEFINE_MUTEX(defrag4_mutex);
25
26 static int nf_ct_ipv4_gather_frags(struct net *net, struct sk_buff *skb,
27 u_int32_t user)
28 {
29 int err;
30
31 local_bh_disable();
32 err = ip_defrag(net, skb, user);
33 local_bh_enable();
34
35 if (!err)
36 skb->ignore_df = 1;
37
38 return err;
39 }
40
41 static enum ip_defrag_users nf_ct_defrag_user(unsigned int hooknum,
42 struct sk_buff *skb)
43 {
44 u16 zone_id = NF_CT_DEFAULT_ZONE_ID;
45 #if IS_ENABLED(CONFIG_NF_CONNTRACK)
46 if (skb_nfct(skb)) {
47 enum ip_conntrack_info ctinfo;
48 const struct nf_conn *ct = nf_ct_get(skb, &ctinfo);
49
50 zone_id = nf_ct_zone_id(nf_ct_zone(ct), CTINFO2DIR(ctinfo));
51 }
52 #endif
53 if (nf_bridge_in_prerouting(skb))
54 return IP_DEFRAG_CONNTRACK_BRIDGE_IN + zone_id;
55
56 if (hooknum == NF_INET_PRE_ROUTING)
57 return IP_DEFRAG_CONNTRACK_IN + zone_id;
58 else
59 return IP_DEFRAG_CONNTRACK_OUT + zone_id;
60 }
61
62 static unsigned int ipv4_conntrack_defrag(void *priv,
63 struct sk_buff *skb,
64 const struct nf_hook_state *state)
65 {
66 struct sock *sk = skb->sk;
67
68 if (sk && sk_fullsock(sk) && (sk->sk_family == PF_INET) &&
69 inet_test_bit(NODEFRAG, sk))
70 return NF_ACCEPT;
71
72 #if IS_ENABLED(CONFIG_NF_CONNTRACK)
73 #if !IS_ENABLED(CONFIG_NF_NAT)
74 /* Previously seen (loopback)? Ignore. Do this before
75 fragment check. */
76 if (skb_nfct(skb) && !nf_ct_is_template((struct nf_conn *)skb_nfct(skb)))
77 return NF_ACCEPT;
78 #endif
79 if (skb->_nfct == IP_CT_UNTRACKED)
80 return NF_ACCEPT;
81 #endif
82 /* Gather fragments. */
83 if (ip_is_fragment(ip_hdr(skb))) {
84 enum ip_defrag_users user =
85 nf_ct_defrag_user(state->hook, skb);
86
87 if (nf_ct_ipv4_gather_frags(state->net, skb, user))
88 return NF_STOLEN;
89 }
90 return NF_ACCEPT;
91 }
92
93 static const struct nf_hook_ops ipv4_defrag_ops[] = {
94 {
95 .hook = ipv4_conntrack_defrag,
96 .pf = NFPROTO_IPV4,
97 .hooknum = NF_INET_PRE_ROUTING,
98 .priority = NF_IP_PRI_CONNTRACK_DEFRAG,
99 },
100 {
101 .hook = ipv4_conntrack_defrag,
102 .pf = NFPROTO_IPV4,
103 .hooknum = NF_INET_LOCAL_OUT,
104 .priority = NF_IP_PRI_CONNTRACK_DEFRAG,
105 },
106 };
107
108 static void __net_exit defrag4_net_exit(struct net *net)
109 {
110 if (net->nf.defrag_ipv4_users) {
111 nf_unregister_net_hooks(net, ipv4_defrag_ops,
112 ARRAY_SIZE(ipv4_defrag_ops));
113 net->nf.defrag_ipv4_users = 0;
114 }
115 }
116
117 static const struct nf_defrag_hook defrag_hook = {
118 .owner = THIS_MODULE,
119 .enable = nf_defrag_ipv4_enable,
120 .disable = nf_defrag_ipv4_disable,
121 };
122
123 static struct pernet_operations defrag4_net_ops = {
124 .exit = defrag4_net_exit,
125 };
126
127 static int __init nf_defrag_init(void)
128 {
129 int err;
130
131 err = register_pernet_subsys(&defrag4_net_ops);
132 if (err)
133 return err;
134
135 rcu_assign_pointer(nf_defrag_v4_hook, &defrag_hook);
136 return err;
137 }
138
139 static void __exit nf_defrag_fini(void)
140 {
141 rcu_assign_pointer(nf_defrag_v4_hook, NULL);
142 unregister_pernet_subsys(&defrag4_net_ops);
143 }
144
145 int nf_defrag_ipv4_enable(struct net *net)
146 {
147 int err = 0;
148
149 mutex_lock(&defrag4_mutex);
150 if (net->nf.defrag_ipv4_users == UINT_MAX) {
151 err = -EOVERFLOW;
152 goto out_unlock;
153 }
154
155 if (net->nf.defrag_ipv4_users) {
156 net->nf.defrag_ipv4_users++;
157 goto out_unlock;
158 }
159
160 err = nf_register_net_hooks(net, ipv4_defrag_ops,
161 ARRAY_SIZE(ipv4_defrag_ops));
162 if (err == 0)
163 net->nf.defrag_ipv4_users = 1;
164
165 out_unlock:
166 mutex_unlock(&defrag4_mutex);
167 return err;
168 }
169 EXPORT_SYMBOL_GPL(nf_defrag_ipv4_enable);
170
171 void nf_defrag_ipv4_disable(struct net *net)
172 {
173 mutex_lock(&defrag4_mutex);
174 if (net->nf.defrag_ipv4_users) {
175 net->nf.defrag_ipv4_users--;
176 if (net->nf.defrag_ipv4_users == 0)
177 nf_unregister_net_hooks(net, ipv4_defrag_ops,
178 ARRAY_SIZE(ipv4_defrag_ops));
179 }
180
181 mutex_unlock(&defrag4_mutex);
182 }
183 EXPORT_SYMBOL_GPL(nf_defrag_ipv4_disable);
184
185 module_init(nf_defrag_init);
186 module_exit(nf_defrag_fini);
187
188 MODULE_LICENSE("GPL");
189 MODULE_DESCRIPTION("IPv4 defragmentation support");
190
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