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