ip6t_mh.c

 1// SPDX-License-Identifier: GPL-2.0-only
 2/*
 3 * Copyright (C)2006 USAGI/WIDE Project
 4 *
 5 * Author:
 6 *	Masahide NAKAMURA @USAGI <masahide.nakamura.cz@hitachi.com>
 7 *
 8 * Based on net/netfilter/xt_tcpudp.c
 9 */
10#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
11#include <linux/types.h>
12#include <linux/module.h>
13#include <net/ip.h>
14#include <linux/ipv6.h>
15#include <net/ipv6.h>
16#include <net/mip6.h>
17
18#include <linux/netfilter/x_tables.h>
19#include <linux/netfilter_ipv6/ip6t_mh.h>
20
21MODULE_DESCRIPTION("Xtables: IPv6 Mobility Header match");
22MODULE_LICENSE("GPL");
23
24/* Returns 1 if the type is matched by the range, 0 otherwise */
25static inline bool
26type_match(u_int8_t min, u_int8_t max, u_int8_t type, bool invert)
27{
28	return (type >= min && type <= max) ^ invert;
29}
30
31static bool mh_mt6(const struct sk_buff *skb, struct xt_action_param *par)
32{
33	struct ip6_mh _mh;
34	const struct ip6_mh *mh;
35	const struct ip6t_mh *mhinfo = par->matchinfo;
36
37	/* Must not be a fragment. */
38	if (par->fragoff != 0)
39		return false;
40
41	mh = skb_header_pointer(skb, par->thoff, sizeof(_mh), &_mh);
42	if (mh == NULL) {
43		/* We've been asked to examine this packet, and we
44		   can't.  Hence, no choice but to drop. */
45		pr_debug("Dropping evil MH tinygram.\n");
46		par->hotdrop = true;
47		return false;
48	}
49
50	if (mh->ip6mh_proto != IPPROTO_NONE) {
51		pr_debug("Dropping invalid MH Payload Proto: %u\n",
52			 mh->ip6mh_proto);
53		par->hotdrop = true;
54		return false;
55	}
56
57	return type_match(mhinfo->types[0], mhinfo->types[1], mh->ip6mh_type,
58			  !!(mhinfo->invflags & IP6T_MH_INV_TYPE));
59}
60
61static int mh_mt6_check(const struct xt_mtchk_param *par)
62{
63	const struct ip6t_mh *mhinfo = par->matchinfo;
64
65	/* Must specify no unknown invflags */
66	return (mhinfo->invflags & ~IP6T_MH_INV_MASK) ? -EINVAL : 0;
67}
68
69static struct xt_match mh_mt6_reg __read_mostly = {
70	.name		= "mh",
71	.family		= NFPROTO_IPV6,
72	.checkentry	= mh_mt6_check,
73	.match		= mh_mt6,
74	.matchsize	= sizeof(struct ip6t_mh),
75	.proto		= IPPROTO_MH,
76	.me		= THIS_MODULE,
77};
78
79static int __init mh_mt6_init(void)
80{
81	return xt_register_match(&mh_mt6_reg);
82}
83
84static void __exit mh_mt6_exit(void)
85{
86	xt_unregister_match(&mh_mt6_reg);
87}
88
89module_init(mh_mt6_init);
90module_exit(mh_mt6_exit);