1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3  * (C) 1999-2001 Paul `Rusty' Russell
4  * (C) 2002-2006 Netfilter Core Team <coreteam@netfilter.org>
5  * Copyright (c) 2011 Patrick McHardy <kaber@trash.net>
6  *
7  * Based on Rusty Russell's IPv4 REDIRECT target. Development of IPv6
8  * NAT funded by Astaro.
9  */
10 
11 #include <linux/if.h>
12 #include <linux/inetdevice.h>
13 #include <linux/ip.h>
14 #include <linux/kernel.h>
15 #include <linux/netdevice.h>
16 #include <linux/netfilter.h>
17 #include <linux/types.h>
18 #include <linux/netfilter_ipv4.h>
19 #include <linux/netfilter_ipv6.h>
20 #include <linux/netfilter/x_tables.h>
21 #include <net/addrconf.h>
22 #include <net/checksum.h>
23 #include <net/protocol.h>
24 #include <net/netfilter/nf_nat.h>
25 #include <net/netfilter/nf_nat_redirect.h>
26 
27 unsigned int
nf_nat_redirect_ipv4(struct sk_buff * skb,const struct nf_nat_ipv4_multi_range_compat * mr,unsigned int hooknum)28 nf_nat_redirect_ipv4(struct sk_buff *skb,
29 		     const struct nf_nat_ipv4_multi_range_compat *mr,
30 		     unsigned int hooknum)
31 {
32 	struct nf_conn *ct;
33 	enum ip_conntrack_info ctinfo;
34 	__be32 newdst;
35 	struct nf_nat_range2 newrange;
36 
37 	WARN_ON(hooknum != NF_INET_PRE_ROUTING &&
38 		hooknum != NF_INET_LOCAL_OUT);
39 
40 	ct = nf_ct_get(skb, &ctinfo);
41 	WARN_ON(!(ct && (ctinfo == IP_CT_NEW || ctinfo == IP_CT_RELATED)));
42 
43 	/* Local packets: make them go to loopback */
44 	if (hooknum == NF_INET_LOCAL_OUT) {
45 		newdst = htonl(0x7F000001);
46 	} else {
47 		const struct in_device *indev;
48 
49 		newdst = 0;
50 
51 		indev = __in_dev_get_rcu(skb->dev);
52 		if (indev) {
53 			const struct in_ifaddr *ifa;
54 
55 			ifa = rcu_dereference(indev->ifa_list);
56 			if (ifa)
57 				newdst = ifa->ifa_local;
58 		}
59 
60 		if (!newdst)
61 			return NF_DROP;
62 	}
63 
64 	/* Transfer from original range. */
65 	memset(&newrange.min_addr, 0, sizeof(newrange.min_addr));
66 	memset(&newrange.max_addr, 0, sizeof(newrange.max_addr));
67 	newrange.flags	     = mr->range[0].flags | NF_NAT_RANGE_MAP_IPS;
68 	newrange.min_addr.ip = newdst;
69 	newrange.max_addr.ip = newdst;
70 	newrange.min_proto   = mr->range[0].min;
71 	newrange.max_proto   = mr->range[0].max;
72 
73 	/* Hand modified range to generic setup. */
74 	return nf_nat_setup_info(ct, &newrange, NF_NAT_MANIP_DST);
75 }
76 EXPORT_SYMBOL_GPL(nf_nat_redirect_ipv4);
77 
78 static const struct in6_addr loopback_addr = IN6ADDR_LOOPBACK_INIT;
79 
80 unsigned int
nf_nat_redirect_ipv6(struct sk_buff * skb,const struct nf_nat_range2 * range,unsigned int hooknum)81 nf_nat_redirect_ipv6(struct sk_buff *skb, const struct nf_nat_range2 *range,
82 		     unsigned int hooknum)
83 {
84 	struct nf_nat_range2 newrange;
85 	struct in6_addr newdst;
86 	enum ip_conntrack_info ctinfo;
87 	struct nf_conn *ct;
88 
89 	ct = nf_ct_get(skb, &ctinfo);
90 	if (hooknum == NF_INET_LOCAL_OUT) {
91 		newdst = loopback_addr;
92 	} else {
93 		struct inet6_dev *idev;
94 		struct inet6_ifaddr *ifa;
95 		bool addr = false;
96 
97 		idev = __in6_dev_get(skb->dev);
98 		if (idev != NULL) {
99 			read_lock_bh(&idev->lock);
100 			list_for_each_entry(ifa, &idev->addr_list, if_list) {
101 				newdst = ifa->addr;
102 				addr = true;
103 				break;
104 			}
105 			read_unlock_bh(&idev->lock);
106 		}
107 
108 		if (!addr)
109 			return NF_DROP;
110 	}
111 
112 	newrange.flags		= range->flags | NF_NAT_RANGE_MAP_IPS;
113 	newrange.min_addr.in6	= newdst;
114 	newrange.max_addr.in6	= newdst;
115 	newrange.min_proto	= range->min_proto;
116 	newrange.max_proto	= range->max_proto;
117 
118 	return nf_nat_setup_info(ct, &newrange, NF_NAT_MANIP_DST);
119 }
120 EXPORT_SYMBOL_GPL(nf_nat_redirect_ipv6);
121