1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3 * This is the 1999 rewrite of IP Firewalling, aiming for kernel 2.3.x.
4 *
5 * Copyright (C) 1999 Paul `Rusty' Russell & Michael J. Neuling
6 * Copyright (C) 2000-2004 Netfilter Core Team <coreteam@netfilter.org>
7 */
8 #include <linux/module.h>
9 #include <linux/netfilter_ipv4/ip_tables.h>
10 #include <linux/netdevice.h>
11 #include <linux/skbuff.h>
12 #include <linux/slab.h>
13 #include <net/sock.h>
14 #include <net/route.h>
15 #include <linux/ip.h>
16 #include <net/ip.h>
17
18 MODULE_LICENSE("GPL");
19 MODULE_AUTHOR("Netfilter Core Team <coreteam@netfilter.org>");
20 MODULE_DESCRIPTION("iptables mangle table");
21
22 #define MANGLE_VALID_HOOKS ((1 << NF_INET_PRE_ROUTING) | \
23 (1 << NF_INET_LOCAL_IN) | \
24 (1 << NF_INET_FORWARD) | \
25 (1 << NF_INET_LOCAL_OUT) | \
26 (1 << NF_INET_POST_ROUTING))
27
28 static const struct xt_table packet_mangler = {
29 .name = "mangle",
30 .valid_hooks = MANGLE_VALID_HOOKS,
31 .me = THIS_MODULE,
32 .af = NFPROTO_IPV4,
33 .priority = NF_IP_PRI_MANGLE,
34 };
35
36 static unsigned int
ipt_mangle_out(void * priv,struct sk_buff * skb,const struct nf_hook_state * state)37 ipt_mangle_out(void *priv, struct sk_buff *skb, const struct nf_hook_state *state)
38 {
39 unsigned int ret;
40 const struct iphdr *iph;
41 u_int8_t tos;
42 __be32 saddr, daddr;
43 u_int32_t mark;
44 int err;
45
46 /* Save things which could affect route */
47 mark = skb->mark;
48 iph = ip_hdr(skb);
49 saddr = iph->saddr;
50 daddr = iph->daddr;
51 tos = iph->tos;
52
53 ret = ipt_do_table(priv, skb, state);
54 /* Reroute for ANY change. */
55 if (ret != NF_DROP && ret != NF_STOLEN) {
56 iph = ip_hdr(skb);
57
58 if (iph->saddr != saddr ||
59 iph->daddr != daddr ||
60 skb->mark != mark ||
61 iph->tos != tos) {
62 err = ip_route_me_harder(state->net, state->sk, skb, RTN_UNSPEC);
63 if (err < 0)
64 ret = NF_DROP_ERR(err);
65 }
66 }
67
68 return ret;
69 }
70
71 /* The work comes in here from netfilter.c. */
72 static unsigned int
iptable_mangle_hook(void * priv,struct sk_buff * skb,const struct nf_hook_state * state)73 iptable_mangle_hook(void *priv,
74 struct sk_buff *skb,
75 const struct nf_hook_state *state)
76 {
77 if (state->hook == NF_INET_LOCAL_OUT)
78 return ipt_mangle_out(priv, skb, state);
79 return ipt_do_table(priv, skb, state);
80 }
81
82 static struct nf_hook_ops *mangle_ops __read_mostly;
iptable_mangle_table_init(struct net * net)83 static int iptable_mangle_table_init(struct net *net)
84 {
85 struct ipt_replace *repl;
86 int ret;
87
88 repl = ipt_alloc_initial_table(&packet_mangler);
89 if (repl == NULL)
90 return -ENOMEM;
91 ret = ipt_register_table(net, &packet_mangler, repl, mangle_ops);
92 kfree(repl);
93 return ret;
94 }
95
iptable_mangle_net_pre_exit(struct net * net)96 static void __net_exit iptable_mangle_net_pre_exit(struct net *net)
97 {
98 ipt_unregister_table_pre_exit(net, "mangle");
99 }
100
iptable_mangle_net_exit(struct net * net)101 static void __net_exit iptable_mangle_net_exit(struct net *net)
102 {
103 ipt_unregister_table_exit(net, "mangle");
104 }
105
106 static struct pernet_operations iptable_mangle_net_ops = {
107 .pre_exit = iptable_mangle_net_pre_exit,
108 .exit = iptable_mangle_net_exit,
109 };
110
iptable_mangle_init(void)111 static int __init iptable_mangle_init(void)
112 {
113 int ret = xt_register_template(&packet_mangler,
114 iptable_mangle_table_init);
115 if (ret < 0)
116 return ret;
117
118 mangle_ops = xt_hook_ops_alloc(&packet_mangler, iptable_mangle_hook);
119 if (IS_ERR(mangle_ops)) {
120 xt_unregister_template(&packet_mangler);
121 ret = PTR_ERR(mangle_ops);
122 return ret;
123 }
124
125 ret = register_pernet_subsys(&iptable_mangle_net_ops);
126 if (ret < 0) {
127 xt_unregister_template(&packet_mangler);
128 kfree(mangle_ops);
129 return ret;
130 }
131
132 return ret;
133 }
134
iptable_mangle_fini(void)135 static void __exit iptable_mangle_fini(void)
136 {
137 unregister_pernet_subsys(&iptable_mangle_net_ops);
138 xt_unregister_template(&packet_mangler);
139 kfree(mangle_ops);
140 }
141
142 module_init(iptable_mangle_init);
143 module_exit(iptable_mangle_fini);
144