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 <[email protected]>
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 <[email protected]>");
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, verdict;
40 const struct iphdr *iph;
41 __be32 saddr, daddr;
42 u32 mark;
43 int err;
44 u8 tos;
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 verdict = ret & NF_VERDICT_MASK;
55 /* Reroute for ANY change. */
56 if (verdict != NF_DROP && verdict != NF_STOLEN) {
57 iph = ip_hdr(skb);
58
59 if (iph->saddr != saddr ||
60 iph->daddr != daddr ||
61 skb->mark != mark ||
62 iph->tos != tos) {
63 err = ip_route_me_harder(state->net, state->sk, skb, RTN_UNSPEC);
64 if (err < 0)
65 ret = NF_DROP_ERR(err);
66 }
67 }
68
69 return ret;
70 }
71
72 /* The work comes in here from netfilter.c. */
73 static unsigned int
iptable_mangle_hook(void * priv,struct sk_buff * skb,const struct nf_hook_state * state)74 iptable_mangle_hook(void *priv,
75 struct sk_buff *skb,
76 const struct nf_hook_state *state)
77 {
78 if (state->hook == NF_INET_LOCAL_OUT)
79 return ipt_mangle_out(priv, skb, state);
80 return ipt_do_table(priv, skb, state);
81 }
82
83 static struct nf_hook_ops *mangle_ops __read_mostly;
iptable_mangle_table_init(struct net * net)84 static int iptable_mangle_table_init(struct net *net)
85 {
86 struct ipt_replace *repl;
87 int ret;
88
89 repl = ipt_alloc_initial_table(&packet_mangler);
90 if (repl == NULL)
91 return -ENOMEM;
92 ret = ipt_register_table(net, &packet_mangler, repl, mangle_ops);
93 kfree(repl);
94 return ret;
95 }
96
iptable_mangle_net_pre_exit(struct net * net)97 static void __net_exit iptable_mangle_net_pre_exit(struct net *net)
98 {
99 ipt_unregister_table_pre_exit(net, "mangle");
100 }
101
iptable_mangle_net_exit(struct net * net)102 static void __net_exit iptable_mangle_net_exit(struct net *net)
103 {
104 ipt_unregister_table_exit(net, "mangle");
105 }
106
107 static struct pernet_operations iptable_mangle_net_ops = {
108 .pre_exit = iptable_mangle_net_pre_exit,
109 .exit = iptable_mangle_net_exit,
110 };
111
iptable_mangle_init(void)112 static int __init iptable_mangle_init(void)
113 {
114 int ret = xt_register_template(&packet_mangler,
115 iptable_mangle_table_init);
116 if (ret < 0)
117 return ret;
118
119 mangle_ops = xt_hook_ops_alloc(&packet_mangler, iptable_mangle_hook);
120 if (IS_ERR(mangle_ops)) {
121 xt_unregister_template(&packet_mangler);
122 ret = PTR_ERR(mangle_ops);
123 return ret;
124 }
125
126 ret = register_pernet_subsys(&iptable_mangle_net_ops);
127 if (ret < 0) {
128 xt_unregister_template(&packet_mangler);
129 kfree(mangle_ops);
130 return ret;
131 }
132
133 return ret;
134 }
135
iptable_mangle_fini(void)136 static void __exit iptable_mangle_fini(void)
137 {
138 unregister_pernet_subsys(&iptable_mangle_net_ops);
139 xt_unregister_template(&packet_mangler);
140 kfree(mangle_ops);
141 }
142
143 module_init(iptable_mangle_init);
144 module_exit(iptable_mangle_fini);
145