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
18MODULE_LICENSE("GPL");
19MODULE_AUTHOR("Netfilter Core Team <coreteam@netfilter.org>");
20MODULE_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
28static 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
36static unsigned int
37ipt_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. */
73static unsigned int
74iptable_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
83static struct nf_hook_ops *mangle_ops __read_mostly;
84static 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
97static void __net_exit iptable_mangle_net_pre_exit(struct net *net)
98{
99	ipt_unregister_table_pre_exit(net, "mangle");
100}
101
102static void __net_exit iptable_mangle_net_exit(struct net *net)
103{
104	ipt_unregister_table_exit(net, "mangle");
105}
106
107static struct pernet_operations iptable_mangle_net_ops = {
108	.pre_exit = iptable_mangle_net_pre_exit,
109	.exit = iptable_mangle_net_exit,
110};
111
112static 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
136static 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
143module_init(iptable_mangle_init);
144module_exit(iptable_mangle_fini);
145