1/* ipv6header match - matches IPv6 packets based
2   on whether they contain certain headers */
3
4/* Original idea: Brad Chapman
5 * Rewritten by: Andras Kis-Szabo <kisza@sch.bme.hu> */
6
7/* (C) 2001-2002 Andras Kis-Szabo <kisza@sch.bme.hu>
8 *
9 * This program is free software; you can redistribute it and/or modify
10 * it under the terms of the GNU General Public License version 2 as
11 * published by the Free Software Foundation.
12 */
13
14#include <linux/module.h>
15#include <linux/skbuff.h>
16#include <linux/ipv6.h>
17#include <linux/types.h>
18#include <net/checksum.h>
19#include <net/ipv6.h>
20
21#include <linux/netfilter/x_tables.h>
22#include <linux/netfilter_ipv6/ip6_tables.h>
23#include <linux/netfilter_ipv6/ip6t_ipv6header.h>
24
25MODULE_LICENSE("GPL");
26MODULE_DESCRIPTION("Xtables: IPv6 header types match");
27MODULE_AUTHOR("Andras Kis-Szabo <kisza@sch.bme.hu>");
28
29static bool
30ipv6header_mt6(const struct sk_buff *skb, struct xt_action_param *par)
31{
32	const struct ip6t_ipv6header_info *info = par->matchinfo;
33	unsigned int temp;
34	int len;
35	u8 nexthdr;
36	unsigned int ptr;
37
38	/* Make sure this isn't an evil packet */
39
40	/* type of the 1st exthdr */
41	nexthdr = ipv6_hdr(skb)->nexthdr;
42	/* pointer to the 1st exthdr */
43	ptr = sizeof(struct ipv6hdr);
44	/* available length */
45	len = skb->len - ptr;
46	temp = 0;
47
48	while (ip6t_ext_hdr(nexthdr)) {
49		const struct ipv6_opt_hdr *hp;
50		struct ipv6_opt_hdr _hdr;
51		int hdrlen;
52
53		/* No more exthdr -> evaluate */
54		if (nexthdr == NEXTHDR_NONE) {
55			temp |= MASK_NONE;
56			break;
57		}
58		/* Is there enough space for the next ext header? */
59		if (len < (int)sizeof(struct ipv6_opt_hdr))
60			return false;
61		/* ESP -> evaluate */
62		if (nexthdr == NEXTHDR_ESP) {
63			temp |= MASK_ESP;
64			break;
65		}
66
67		hp = skb_header_pointer(skb, ptr, sizeof(_hdr), &_hdr);
68		BUG_ON(hp == NULL);
69
70		/* Calculate the header length */
71		if (nexthdr == NEXTHDR_FRAGMENT)
72			hdrlen = 8;
73		else if (nexthdr == NEXTHDR_AUTH)
74			hdrlen = (hp->hdrlen + 2) << 2;
75		else
76			hdrlen = ipv6_optlen(hp);
77
78		/* set the flag */
79		switch (nexthdr) {
80		case NEXTHDR_HOP:
81			temp |= MASK_HOPOPTS;
82			break;
83		case NEXTHDR_ROUTING:
84			temp |= MASK_ROUTING;
85			break;
86		case NEXTHDR_FRAGMENT:
87			temp |= MASK_FRAGMENT;
88			break;
89		case NEXTHDR_AUTH:
90			temp |= MASK_AH;
91			break;
92		case NEXTHDR_DEST:
93			temp |= MASK_DSTOPTS;
94			break;
95		default:
96			return false;
97		}
98
99		nexthdr = hp->nexthdr;
100		len -= hdrlen;
101		ptr += hdrlen;
102		if (ptr > skb->len)
103			break;
104	}
105
106	if (nexthdr != NEXTHDR_NONE && nexthdr != NEXTHDR_ESP)
107		temp |= MASK_PROTO;
108
109	if (info->modeflag)
110		return !((temp ^ info->matchflags ^ info->invflags)
111			 & info->matchflags);
112	else {
113		if (info->invflags)
114			return temp != info->matchflags;
115		else
116			return temp == info->matchflags;
117	}
118}
119
120static int ipv6header_mt6_check(const struct xt_mtchk_param *par)
121{
122	const struct ip6t_ipv6header_info *info = par->matchinfo;
123
124	/* invflags is 0 or 0xff in hard mode */
125	if ((!info->modeflag) && info->invflags != 0x00 &&
126	    info->invflags != 0xFF)
127		return -EINVAL;
128
129	return 0;
130}
131
132static struct xt_match ipv6header_mt6_reg __read_mostly = {
133	.name		= "ipv6header",
134	.family		= NFPROTO_IPV6,
135	.match		= ipv6header_mt6,
136	.matchsize	= sizeof(struct ip6t_ipv6header_info),
137	.checkentry	= ipv6header_mt6_check,
138	.destroy	= NULL,
139	.me		= THIS_MODULE,
140};
141
142static int __init ipv6header_mt6_init(void)
143{
144	return xt_register_match(&ipv6header_mt6_reg);
145}
146
147static void __exit ipv6header_mt6_exit(void)
148{
149	xt_unregister_match(&ipv6header_mt6_reg);
150}
151
152module_init(ipv6header_mt6_init);
153module_exit(ipv6header_mt6_exit);
154