1 /*
2 * This is the 1999 rewrite of IP Firewalling, aiming for kernel 2.3.x.
3 *
4 * Copyright (C) 1999 Paul `Rusty' Russell & Michael J. Neuling
5 * Copyright (C) 2000-2004 Netfilter Core Team <coreteam@netfilter.org>
6 *
7 * This program is free software; you can redistribute it and/or modify
8 * it under the terms of the GNU General Public License version 2 as
9 * published by the Free Software Foundation.
10 */
11 #include <linux/module.h>
12 #include <linux/netfilter_ipv4/ip_tables.h>
13 #include <linux/netdevice.h>
14 #include <linux/skbuff.h>
15 #include <linux/slab.h>
16 #include <net/sock.h>
17 #include <net/route.h>
18 #include <linux/ip.h>
19 #include <net/ip.h>
20
21 MODULE_LICENSE("GPL");
22 MODULE_AUTHOR("Netfilter Core Team <coreteam@netfilter.org>");
23 MODULE_DESCRIPTION("iptables mangle table");
24
25 #define MANGLE_VALID_HOOKS ((1 << NF_INET_PRE_ROUTING) | \
26 (1 << NF_INET_LOCAL_IN) | \
27 (1 << NF_INET_FORWARD) | \
28 (1 << NF_INET_LOCAL_OUT) | \
29 (1 << NF_INET_POST_ROUTING))
30
31 static const struct xt_table packet_mangler = {
32 .name = "mangle",
33 .valid_hooks = MANGLE_VALID_HOOKS,
34 .me = THIS_MODULE,
35 .af = NFPROTO_IPV4,
36 .priority = NF_IP_PRI_MANGLE,
37 };
38
39 static unsigned int
ipt_mangle_out(struct sk_buff * skb,const struct nf_hook_state * state)40 ipt_mangle_out(struct sk_buff *skb, const struct nf_hook_state *state)
41 {
42 unsigned int ret;
43 const struct iphdr *iph;
44 u_int8_t tos;
45 __be32 saddr, daddr;
46 u_int32_t mark;
47 int err;
48
49 /* root is playing with raw sockets. */
50 if (skb->len < sizeof(struct iphdr) ||
51 ip_hdrlen(skb) < sizeof(struct iphdr))
52 return NF_ACCEPT;
53
54 /* Save things which could affect route */
55 mark = skb->mark;
56 iph = ip_hdr(skb);
57 saddr = iph->saddr;
58 daddr = iph->daddr;
59 tos = iph->tos;
60
61 ret = ipt_do_table(skb, state, state->net->ipv4.iptable_mangle);
62 /* Reroute for ANY change. */
63 if (ret != NF_DROP && ret != NF_STOLEN) {
64 iph = ip_hdr(skb);
65
66 if (iph->saddr != saddr ||
67 iph->daddr != daddr ||
68 skb->mark != mark ||
69 iph->tos != tos) {
70 err = ip_route_me_harder(state->net, skb, RTN_UNSPEC);
71 if (err < 0)
72 ret = NF_DROP_ERR(err);
73 }
74 }
75
76 return ret;
77 }
78
79 /* The work comes in here from netfilter.c. */
80 static unsigned int
iptable_mangle_hook(void * priv,struct sk_buff * skb,const struct nf_hook_state * state)81 iptable_mangle_hook(void *priv,
82 struct sk_buff *skb,
83 const struct nf_hook_state *state)
84 {
85 if (state->hook == NF_INET_LOCAL_OUT)
86 return ipt_mangle_out(skb, state);
87 if (state->hook == NF_INET_POST_ROUTING)
88 return ipt_do_table(skb, state,
89 state->net->ipv4.iptable_mangle);
90 /* PREROUTING/INPUT/FORWARD: */
91 return ipt_do_table(skb, state, state->net->ipv4.iptable_mangle);
92 }
93
94 static struct nf_hook_ops *mangle_ops __read_mostly;
95
iptable_mangle_net_init(struct net * net)96 static int __net_init iptable_mangle_net_init(struct net *net)
97 {
98 struct ipt_replace *repl;
99
100 repl = ipt_alloc_initial_table(&packet_mangler);
101 if (repl == NULL)
102 return -ENOMEM;
103 net->ipv4.iptable_mangle =
104 ipt_register_table(net, &packet_mangler, repl);
105 kfree(repl);
106 return PTR_ERR_OR_ZERO(net->ipv4.iptable_mangle);
107 }
108
iptable_mangle_net_exit(struct net * net)109 static void __net_exit iptable_mangle_net_exit(struct net *net)
110 {
111 ipt_unregister_table(net, net->ipv4.iptable_mangle);
112 }
113
114 static struct pernet_operations iptable_mangle_net_ops = {
115 .init = iptable_mangle_net_init,
116 .exit = iptable_mangle_net_exit,
117 };
118
iptable_mangle_init(void)119 static int __init iptable_mangle_init(void)
120 {
121 int ret;
122
123 ret = register_pernet_subsys(&iptable_mangle_net_ops);
124 if (ret < 0)
125 return ret;
126
127 /* Register hooks */
128 mangle_ops = xt_hook_link(&packet_mangler, iptable_mangle_hook);
129 if (IS_ERR(mangle_ops)) {
130 ret = PTR_ERR(mangle_ops);
131 unregister_pernet_subsys(&iptable_mangle_net_ops);
132 }
133
134 return ret;
135 }
136
iptable_mangle_fini(void)137 static void __exit iptable_mangle_fini(void)
138 {
139 xt_hook_unlink(&packet_mangler, mangle_ops);
140 unregister_pernet_subsys(&iptable_mangle_net_ops);
141 }
142
143 module_init(iptable_mangle_init);
144 module_exit(iptable_mangle_fini);
145