// SPDX-License-Identifier: GPL-2.0-only
/*
* This is the 1999 rewrite of IP Firewalling, aiming for kernel 2.3.x.
*
* Copyright (C) 1999 Paul `Rusty' Russell & Michael J. Neuling
* Copyright (C) 2000-2004 Netfilter Core Team <[email protected]>
*/
#include <linux/module.h>
#include <linux/netfilter_ipv4/ip_tables.h>
#include <linux/netdevice.h>
#include <linux/skbuff.h>
#include <linux/slab.h>
#include <net/sock.h>
#include <net/route.h>
#include <linux/ip.h>
#include <net/ip.h>
MODULE_LICENSE("GPL");
MODULE_AUTHOR("Netfilter Core Team <[email protected]>");
MODULE_DESCRIPTION("iptables mangle table");
#define MANGLE_VALID_HOOKS ((1 << NF_INET_PRE_ROUTING) | \
(1 << NF_INET_LOCAL_IN) | \
(1 << NF_INET_FORWARD) | \
(1 << NF_INET_LOCAL_OUT) | \
(1 << NF_INET_POST_ROUTING))
static const struct xt_table packet_mangler = {
.name = "mangle",
.valid_hooks = MANGLE_VALID_HOOKS,
.me = THIS_MODULE,
.af = NFPROTO_IPV4,
.priority = NF_IP_PRI_MANGLE,
};
static unsigned int
ipt_mangle_out(void *priv, struct sk_buff *skb, const struct nf_hook_state *state)
{
unsigned int ret, verdict;
const struct iphdr *iph;
__be32 saddr, daddr;
u32 mark;
int err;
u8 tos;
/* Save things which could affect route */
mark = skb->mark;
iph = ip_hdr(skb);
saddr = iph->saddr;
daddr = iph->daddr;
tos = iph->tos;
ret = ipt_do_table(priv, skb, state);
verdict = ret & NF_VERDICT_MASK;
/* Reroute for ANY change. */
if (verdict != NF_DROP && verdict != NF_STOLEN) {
iph = ip_hdr(skb);
if (iph->saddr != saddr ||
iph->daddr != daddr ||
skb->mark != mark ||
iph->tos != tos) {
err = ip_route_me_harder(state->net, state->sk, skb, RTN_UNSPEC);
if (err < 0)
ret = NF_DROP_ERR(err);
}
}
return ret;
}
/* The work comes in here from netfilter.c. */
static unsigned int
iptable_mangle_hook(void *priv,
struct sk_buff *skb,
const struct nf_hook_state *state)
{
if (state->hook == NF_INET_LOCAL_OUT)
return ipt_mangle_out(priv, skb, state);
return ipt_do_table(priv, skb, state);
}
static struct nf_hook_ops *mangle_ops __read_mostly;
static int iptable_mangle_table_init(struct net *net)
{
struct ipt_replace *repl;
int ret;
repl = ipt_alloc_initial_table(&packet_mangler);
if (repl == NULL)
return -ENOMEM;
ret = ipt_register_table(net, &packet_mangler, repl, mangle_ops);
kfree(repl);
return ret;
}
static void __net_exit iptable_mangle_net_pre_exit(struct net *net)
{
ipt_unregister_table_pre_exit(net, "mangle");
}
static void __net_exit iptable_mangle_net_exit(struct net *net)
{
ipt_unregister_table_exit(net, "mangle");
}
static struct pernet_operations iptable_mangle_net_ops = {
.pre_exit = iptable_mangle_net_pre_exit,
.exit = iptable_mangle_net_exit,
};
static int __init iptable_mangle_init(void)
{
int ret = xt_register_template(&packet_mangler,
iptable_mangle_table_init);
if (ret < 0)
return ret;
mangle_ops = xt_hook_ops_alloc(&packet_mangler, iptable_mangle_hook);
if (IS_ERR(mangle_ops)) {
xt_unregister_template(&packet_mangler);
ret = PTR_ERR(mangle_ops);
return ret;
}
ret = register_pernet_subsys(&iptable_mangle_net_ops);
if (ret < 0) {
xt_unregister_template(&packet_mangler);
kfree(mangle_ops);
return ret;
}
return ret;
}
static void __exit iptable_mangle_fini(void)
{
unregister_pernet_subsys(&iptable_mangle_net_ops);
xt_unregister_template(&packet_mangler);
kfree(mangle_ops);
}
module_init(iptable_mangle_init);
module_exit(iptable_mangle_fini);