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/route.h>
15 #include <net/ip.h>
16 
17 #include <linux/netfilter_bridge.h>
18 #include <linux/netfilter_ipv4.h>
19 #include <net/netfilter/ipv4/nf_defrag_ipv4.h>
20 #if IS_ENABLED(CONFIG_NF_CONNTRACK)
21 #include <net/netfilter/nf_conntrack.h>
22 #endif
23 #include <net/netfilter/nf_conntrack_zones.h>
24 
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 	skb_orphan(skb);
31 
32 	local_bh_disable();
33 	err = ip_defrag(net, skb, user);
34 	local_bh_enable();
35 
36 	if (!err) {
37 		ip_send_check(ip_hdr(skb));
38 		skb->ignore_df = 1;
39 	}
40 
41 	return err;
42 }
43 
44 static enum ip_defrag_users nf_ct_defrag_user(unsigned int hooknum,
45 					      struct sk_buff *skb)
46 {
47 	u16 zone_id = NF_CT_DEFAULT_ZONE_ID;
48 #if IS_ENABLED(CONFIG_NF_CONNTRACK)
49 	if (skb->nfct) {
50 		enum ip_conntrack_info ctinfo;
51 		const struct nf_conn *ct = nf_ct_get(skb, &ctinfo);
52 
53 		zone_id = nf_ct_zone_id(nf_ct_zone(ct), CTINFO2DIR(ctinfo));
54 	}
55 #endif
56 	if (nf_bridge_in_prerouting(skb))
57 		return IP_DEFRAG_CONNTRACK_BRIDGE_IN + zone_id;
58 
59 	if (hooknum == NF_INET_PRE_ROUTING)
60 		return IP_DEFRAG_CONNTRACK_IN + zone_id;
61 	else
62 		return IP_DEFRAG_CONNTRACK_OUT + zone_id;
63 }
64 
65 static unsigned int ipv4_conntrack_defrag(void *priv,
66 					  struct sk_buff *skb,
67 					  const struct nf_hook_state *state)
68 {
69 	struct sock *sk = skb->sk;
70 
71 	if (sk && sk_fullsock(sk) && (sk->sk_family == PF_INET) &&
72 	    inet_sk(sk)->nodefrag)
73 		return NF_ACCEPT;
74 
75 #if IS_ENABLED(CONFIG_NF_CONNTRACK)
76 #if !IS_ENABLED(CONFIG_NF_NAT)
77 	/* Previously seen (loopback)?  Ignore.  Do this before
78 	   fragment check. */
79 	if (skb->nfct && !nf_ct_is_template((struct nf_conn *)skb->nfct))
80 		return NF_ACCEPT;
81 #endif
82 #endif
83 	/* Gather fragments. */
84 	if (ip_is_fragment(ip_hdr(skb))) {
85 		enum ip_defrag_users user =
86 			nf_ct_defrag_user(state->hook, skb);
87 
88 		if (nf_ct_ipv4_gather_frags(state->net, skb, user))
89 			return NF_STOLEN;
90 	}
91 	return NF_ACCEPT;
92 }
93 
94 static struct nf_hook_ops ipv4_defrag_ops[] = {
95 	{
96 		.hook		= ipv4_conntrack_defrag,
97 		.pf		= NFPROTO_IPV4,
98 		.hooknum	= NF_INET_PRE_ROUTING,
99 		.priority	= NF_IP_PRI_CONNTRACK_DEFRAG,
100 	},
101 	{
102 		.hook           = ipv4_conntrack_defrag,
103 		.pf             = NFPROTO_IPV4,
104 		.hooknum        = NF_INET_LOCAL_OUT,
105 		.priority       = NF_IP_PRI_CONNTRACK_DEFRAG,
106 	},
107 };
108 
109 static int __init nf_defrag_init(void)
110 {
111 	return nf_register_hooks(ipv4_defrag_ops, ARRAY_SIZE(ipv4_defrag_ops));
112 }
113 
114 static void __exit nf_defrag_fini(void)
115 {
116 	nf_unregister_hooks(ipv4_defrag_ops, ARRAY_SIZE(ipv4_defrag_ops));
117 }
118 
119 void nf_defrag_ipv4_enable(void)
120 {
121 }
122 EXPORT_SYMBOL_GPL(nf_defrag_ipv4_enable);
123 
124 module_init(nf_defrag_init);
125 module_exit(nf_defrag_fini);
126 
127 MODULE_LICENSE("GPL");
128