ip6t_rt.c

  1// SPDX-License-Identifier: GPL-2.0-only
  2/* Kernel module to match ROUTING parameters. */
  3
  4/* (C) 2001-2002 Andras Kis-Szabo <kisza@sch.bme.hu>
  5 */
  6#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  7#include <linux/module.h>
  8#include <linux/skbuff.h>
  9#include <linux/ipv6.h>
 10#include <linux/types.h>
 11#include <net/checksum.h>
 12#include <net/ipv6.h>
 13
 14#include <asm/byteorder.h>
 15
 16#include <linux/netfilter/x_tables.h>
 17#include <linux/netfilter_ipv6/ip6_tables.h>
 18#include <linux/netfilter_ipv6/ip6t_rt.h>
 19
 20MODULE_LICENSE("GPL");
 21MODULE_DESCRIPTION("Xtables: IPv6 Routing Header match");
 22MODULE_AUTHOR("Andras Kis-Szabo <kisza@sch.bme.hu>");
 23
 24/* Returns 1 if the id is matched by the range, 0 otherwise */
 25static inline bool
 26segsleft_match(u_int32_t min, u_int32_t max, u_int32_t id, bool invert)
 27{
 28	return (id >= min && id <= max) ^ invert;
 29}
 30
 31static bool rt_mt6(const struct sk_buff *skb, struct xt_action_param *par)
 32{
 33	struct ipv6_rt_hdr _route;
 34	const struct ipv6_rt_hdr *rh;
 35	const struct ip6t_rt *rtinfo = par->matchinfo;
 36	unsigned int temp;
 37	unsigned int ptr = 0;
 38	unsigned int hdrlen = 0;
 39	bool ret = false;
 40	struct in6_addr _addr;
 41	const struct in6_addr *ap;
 42	int err;
 43
 44	err = ipv6_find_hdr(skb, &ptr, NEXTHDR_ROUTING, NULL, NULL);
 45	if (err < 0) {
 46		if (err != -ENOENT)
 47			par->hotdrop = true;
 48		return false;
 49	}
 50
 51	rh = skb_header_pointer(skb, ptr, sizeof(_route), &_route);
 52	if (rh == NULL) {
 53		par->hotdrop = true;
 54		return false;
 55	}
 56
 57	hdrlen = ipv6_optlen(rh);
 58	if (skb->len - ptr < hdrlen) {
 59		/* Pcket smaller than its length field */
 60		return false;
 61	}
 62
 63	ret = (segsleft_match(rtinfo->segsleft[0], rtinfo->segsleft[1],
 64			      rh->segments_left,
 65			      !!(rtinfo->invflags & IP6T_RT_INV_SGS))) &&
 66	      (!(rtinfo->flags & IP6T_RT_LEN) ||
 67	       ((rtinfo->hdrlen == hdrlen) ^
 68		!!(rtinfo->invflags & IP6T_RT_INV_LEN))) &&
 69	      (!(rtinfo->flags & IP6T_RT_TYP) ||
 70	       ((rtinfo->rt_type == rh->type) ^
 71		!!(rtinfo->invflags & IP6T_RT_INV_TYP)));
 72
 73	if (ret && (rtinfo->flags & IP6T_RT_RES)) {
 74		const u_int32_t *rp;
 75		u_int32_t _reserved;
 76		rp = skb_header_pointer(skb,
 77					ptr + offsetof(struct rt0_hdr,
 78						       reserved),
 79					sizeof(_reserved),
 80					&_reserved);
 81		if (!rp) {
 82			par->hotdrop = true;
 83			return false;
 84		}
 85
 86		ret = (*rp == 0);
 87	}
 88
 89	if (!(rtinfo->flags & IP6T_RT_FST)) {
 90		return ret;
 91	} else if (rtinfo->flags & IP6T_RT_FST_NSTRICT) {
 92		if (rtinfo->addrnr > (unsigned int)((hdrlen - 8) / 16)) {
 93			return false;
 94		} else {
 95			unsigned int i = 0;
 96
 97			for (temp = 0;
 98			     temp < (unsigned int)((hdrlen - 8) / 16);
 99			     temp++) {
100				ap = skb_header_pointer(skb,
101							ptr
102							+ sizeof(struct rt0_hdr)
103							+ temp * sizeof(_addr),
104							sizeof(_addr),
105							&_addr);
106
107				if (ap == NULL) {
108					par->hotdrop = true;
109					return false;
110				}
111
112				if (ipv6_addr_equal(ap, &rtinfo->addrs[i]))
113					i++;
114				if (i == rtinfo->addrnr)
115					break;
116			}
117			if (i == rtinfo->addrnr)
118				return ret;
119			else
120				return false;
121		}
122	} else {
123		if (rtinfo->addrnr > (unsigned int)((hdrlen - 8) / 16)) {
124			return false;
125		} else {
126			for (temp = 0; temp < rtinfo->addrnr; temp++) {
127				ap = skb_header_pointer(skb,
128							ptr
129							+ sizeof(struct rt0_hdr)
130							+ temp * sizeof(_addr),
131							sizeof(_addr),
132							&_addr);
133				if (ap == NULL) {
134					par->hotdrop = true;
135					return false;
136				}
137
138				if (!ipv6_addr_equal(ap, &rtinfo->addrs[temp]))
139					break;
140			}
141			if (temp == rtinfo->addrnr &&
142			    temp == (unsigned int)((hdrlen - 8) / 16))
143				return ret;
144			else
145				return false;
146		}
147	}
148
149	return false;
150}
151
152static int rt_mt6_check(const struct xt_mtchk_param *par)
153{
154	const struct ip6t_rt *rtinfo = par->matchinfo;
155
156	if (rtinfo->invflags & ~IP6T_RT_INV_MASK) {
157		pr_debug("unknown flags %X\n", rtinfo->invflags);
158		return -EINVAL;
159	}
160	if (rtinfo->addrnr > IP6T_RT_HOPS) {
161		pr_debug("too many addresses specified\n");
162		return -EINVAL;
163	}
164	if ((rtinfo->flags & (IP6T_RT_RES | IP6T_RT_FST_MASK)) &&
165	    (!(rtinfo->flags & IP6T_RT_TYP) ||
166	     (rtinfo->rt_type != 0) ||
167	     (rtinfo->invflags & IP6T_RT_INV_TYP))) {
168		pr_debug("`--rt-type 0' required before `--rt-0-*'");
169		return -EINVAL;
170	}
171
172	return 0;
173}
174
175static struct xt_match rt_mt6_reg __read_mostly = {
176	.name		= "rt",
177	.family		= NFPROTO_IPV6,
178	.match		= rt_mt6,
179	.matchsize	= sizeof(struct ip6t_rt),
180	.checkentry	= rt_mt6_check,
181	.me		= THIS_MODULE,
182};
183
184static int __init rt_mt6_init(void)
185{
186	return xt_register_match(&rt_mt6_reg);
187}
188
189static void __exit rt_mt6_exit(void)
190{
191	xt_unregister_match(&rt_mt6_reg);
192}
193
194module_init(rt_mt6_init);
195module_exit(rt_mt6_exit);