ip6table_mangle.c

  1// SPDX-License-Identifier: GPL-2.0-only
  2/*
  3 * IPv6 packet mangling table, a port of the IPv4 mangle table to IPv6
  4 *
  5 * Copyright (C) 2000-2001 by Harald Welte <laforge@gnumonks.org>
  6 * Copyright (C) 2000-2004 Netfilter Core Team <coreteam@netfilter.org>
  7 */
  8#include <linux/module.h>
  9#include <linux/netfilter_ipv6/ip6_tables.h>
 10#include <linux/slab.h>
 11#include <net/ipv6.h>
 12
 13MODULE_LICENSE("GPL");
 14MODULE_AUTHOR("Netfilter Core Team <coreteam@netfilter.org>");
 15MODULE_DESCRIPTION("ip6tables mangle table");
 16
 17#define MANGLE_VALID_HOOKS ((1 << NF_INET_PRE_ROUTING) | \
 18			    (1 << NF_INET_LOCAL_IN) | \
 19			    (1 << NF_INET_FORWARD) | \
 20			    (1 << NF_INET_LOCAL_OUT) | \
 21			    (1 << NF_INET_POST_ROUTING))
 22
 23static const struct xt_table packet_mangler = {
 24	.name		= "mangle",
 25	.valid_hooks	= MANGLE_VALID_HOOKS,
 26	.me		= THIS_MODULE,
 27	.af		= NFPROTO_IPV6,
 28	.priority	= NF_IP6_PRI_MANGLE,
 29};
 30
 31static unsigned int
 32ip6t_mangle_out(void *priv, struct sk_buff *skb, const struct nf_hook_state *state)
 33{
 34	struct in6_addr saddr, daddr;
 35	unsigned int ret, verdict;
 36	u32 flowlabel, mark;
 37	u8 hop_limit;
 38	int err;
 39
 40	/* save source/dest address, mark, hoplimit, flowlabel, priority,  */
 41	memcpy(&saddr, &ipv6_hdr(skb)->saddr, sizeof(saddr));
 42	memcpy(&daddr, &ipv6_hdr(skb)->daddr, sizeof(daddr));
 43	mark = skb->mark;
 44	hop_limit = ipv6_hdr(skb)->hop_limit;
 45
 46	/* flowlabel and prio (includes version, which shouldn't change either */
 47	flowlabel = *((u_int32_t *)ipv6_hdr(skb));
 48
 49	ret = ip6t_do_table(priv, skb, state);
 50	verdict = ret & NF_VERDICT_MASK;
 51
 52	if (verdict != NF_DROP && verdict != NF_STOLEN &&
 53	    (!ipv6_addr_equal(&ipv6_hdr(skb)->saddr, &saddr) ||
 54	     !ipv6_addr_equal(&ipv6_hdr(skb)->daddr, &daddr) ||
 55	     skb->mark != mark ||
 56	     ipv6_hdr(skb)->hop_limit != hop_limit ||
 57	     flowlabel != *((u_int32_t *)ipv6_hdr(skb)))) {
 58		err = ip6_route_me_harder(state->net, state->sk, skb);
 59		if (err < 0)
 60			ret = NF_DROP_ERR(err);
 61	}
 62
 63	return ret;
 64}
 65
 66/* The work comes in here from netfilter.c. */
 67static unsigned int
 68ip6table_mangle_hook(void *priv, struct sk_buff *skb,
 69		     const struct nf_hook_state *state)
 70{
 71	if (state->hook == NF_INET_LOCAL_OUT)
 72		return ip6t_mangle_out(priv, skb, state);
 73	return ip6t_do_table(priv, skb, state);
 74}
 75
 76static struct nf_hook_ops *mangle_ops __read_mostly;
 77static int ip6table_mangle_table_init(struct net *net)
 78{
 79	struct ip6t_replace *repl;
 80	int ret;
 81
 82	repl = ip6t_alloc_initial_table(&packet_mangler);
 83	if (repl == NULL)
 84		return -ENOMEM;
 85	ret = ip6t_register_table(net, &packet_mangler, repl, mangle_ops);
 86	kfree(repl);
 87	return ret;
 88}
 89
 90static void __net_exit ip6table_mangle_net_pre_exit(struct net *net)
 91{
 92	ip6t_unregister_table_pre_exit(net, "mangle");
 93}
 94
 95static void __net_exit ip6table_mangle_net_exit(struct net *net)
 96{
 97	ip6t_unregister_table_exit(net, "mangle");
 98}
 99
100static struct pernet_operations ip6table_mangle_net_ops = {
101	.pre_exit = ip6table_mangle_net_pre_exit,
102	.exit = ip6table_mangle_net_exit,
103};
104
105static int __init ip6table_mangle_init(void)
106{
107	int ret = xt_register_template(&packet_mangler,
108				       ip6table_mangle_table_init);
109
110	if (ret < 0)
111		return ret;
112
113	mangle_ops = xt_hook_ops_alloc(&packet_mangler, ip6table_mangle_hook);
114	if (IS_ERR(mangle_ops)) {
115		xt_unregister_template(&packet_mangler);
116		return PTR_ERR(mangle_ops);
117	}
118
119	ret = register_pernet_subsys(&ip6table_mangle_net_ops);
120	if (ret < 0) {
121		xt_unregister_template(&packet_mangler);
122		kfree(mangle_ops);
123		return ret;
124	}
125
126	return ret;
127}
128
129static void __exit ip6table_mangle_fini(void)
130{
131	unregister_pernet_subsys(&ip6table_mangle_net_ops);
132	xt_unregister_template(&packet_mangler);
133	kfree(mangle_ops);
134}
135
136module_init(ip6table_mangle_init);
137module_exit(ip6table_mangle_fini);