// SPDX-License-Identifier: GPL-2.0-only
/* Kernel module to match ROUTING parameters. */

/* (C) 2001-2002 Andras Kis-Szabo <kisza@sch.bme.hu>
 */
#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
#include <linux/module.h>
#include <linux/skbuff.h>
#include <linux/ipv6.h>
#include <linux/types.h>
#include <net/checksum.h>
#include <net/ipv6.h>

#include <asm/byteorder.h>

#include <linux/netfilter/x_tables.h>
#include <linux/netfilter_ipv6/ip6_tables.h>
#include <linux/netfilter_ipv6/ip6t_rt.h>

MODULE_LICENSE("GPL");
MODULE_DESCRIPTION("Xtables: IPv6 Routing Header match");
MODULE_AUTHOR("Andras Kis-Szabo <kisza@sch.bme.hu>");

/* Returns 1 if the id is matched by the range, 0 otherwise */
static inline bool
segsleft_match(u_int32_t min, u_int32_t max, u_int32_t id, bool invert)
{
	return (id >= min && id <= max) ^ invert;
}

static bool rt_mt6(const struct sk_buff *skb, struct xt_action_param *par)
{
	struct ipv6_rt_hdr _route;
	const struct ipv6_rt_hdr *rh;
	const struct ip6t_rt *rtinfo = par->matchinfo;
	unsigned int temp;
	unsigned int ptr = 0;
	unsigned int hdrlen = 0;
	bool ret = false;
	struct in6_addr _addr;
	const struct in6_addr *ap;
	int err;

	err = ipv6_find_hdr(skb, &ptr, NEXTHDR_ROUTING, NULL, NULL);
	if (err < 0) {
		if (err != -ENOENT)
			par->hotdrop = true;
		return false;
	}

	rh = skb_header_pointer(skb, ptr, sizeof(_route), &_route);
	if (rh == NULL) {
		par->hotdrop = true;
		return false;
	}

	hdrlen = ipv6_optlen(rh);
	if (skb->len - ptr < hdrlen) {
		/* Pcket smaller than its length field */
		return false;
	}

	ret = (segsleft_match(rtinfo->segsleft[0], rtinfo->segsleft[1],
			      rh->segments_left,
			      !!(rtinfo->invflags & IP6T_RT_INV_SGS))) &&
	      (!(rtinfo->flags & IP6T_RT_LEN) ||
	       ((rtinfo->hdrlen == hdrlen) ^
		!!(rtinfo->invflags & IP6T_RT_INV_LEN))) &&
	      (!(rtinfo->flags & IP6T_RT_TYP) ||
	       ((rtinfo->rt_type == rh->type) ^
		!!(rtinfo->invflags & IP6T_RT_INV_TYP)));

	if (ret && (rtinfo->flags & IP6T_RT_RES)) {
		const u_int32_t *rp;
		u_int32_t _reserved;
		rp = skb_header_pointer(skb,
					ptr + offsetof(struct rt0_hdr,
						       reserved),
					sizeof(_reserved),
					&_reserved);
		if (!rp) {
			par->hotdrop = true;
			return false;
		}

		ret = (*rp == 0);
	}

	if (!(rtinfo->flags & IP6T_RT_FST)) {
		return ret;
	} else if (rtinfo->flags & IP6T_RT_FST_NSTRICT) {
		if (rtinfo->addrnr > (unsigned int)((hdrlen - 8) / 16)) {
			return false;
		} else {
			unsigned int i = 0;

			for (temp = 0;
			     temp < (unsigned int)((hdrlen - 8) / 16);
			     temp++) {
				ap = skb_header_pointer(skb,
							ptr
							+ sizeof(struct rt0_hdr)
							+ temp * sizeof(_addr),
							sizeof(_addr),
							&_addr);

				if (ap == NULL) {
					par->hotdrop = true;
					return false;
				}

				if (ipv6_addr_equal(ap, &rtinfo->addrs[i]))
					i++;
				if (i == rtinfo->addrnr)
					break;
			}
			if (i == rtinfo->addrnr)
				return ret;
			else
				return false;
		}
	} else {
		if (rtinfo->addrnr > (unsigned int)((hdrlen - 8) / 16)) {
			return false;
		} else {
			for (temp = 0; temp < rtinfo->addrnr; temp++) {
				ap = skb_header_pointer(skb,
							ptr
							+ sizeof(struct rt0_hdr)
							+ temp * sizeof(_addr),
							sizeof(_addr),
							&_addr);
				if (ap == NULL) {
					par->hotdrop = true;
					return false;
				}

				if (!ipv6_addr_equal(ap, &rtinfo->addrs[temp]))
					break;
			}
			if (temp == rtinfo->addrnr &&
			    temp == (unsigned int)((hdrlen - 8) / 16))
				return ret;
			else
				return false;
		}
	}

	return false;
}

static int rt_mt6_check(const struct xt_mtchk_param *par)
{
	const struct ip6t_rt *rtinfo = par->matchinfo;

	if (rtinfo->invflags & ~IP6T_RT_INV_MASK) {
		pr_debug("unknown flags %X\n", rtinfo->invflags);
		return -EINVAL;
	}
	if ((rtinfo->flags & (IP6T_RT_RES | IP6T_RT_FST_MASK)) &&
	    (!(rtinfo->flags & IP6T_RT_TYP) ||
	     (rtinfo->rt_type != 0) ||
	     (rtinfo->invflags & IP6T_RT_INV_TYP))) {
		pr_debug("`--rt-type 0' required before `--rt-0-*'");
		return -EINVAL;
	}

	return 0;
}

static struct xt_match rt_mt6_reg __read_mostly = {
	.name		= "rt",
	.family		= NFPROTO_IPV6,
	.match		= rt_mt6,
	.matchsize	= sizeof(struct ip6t_rt),
	.checkentry	= rt_mt6_check,
	.me		= THIS_MODULE,
};

static int __init rt_mt6_init(void)
{
	return xt_register_match(&rt_mt6_reg);
}

static void __exit rt_mt6_exit(void)
{
	xt_unregister_match(&rt_mt6_reg);
}

module_init(rt_mt6_init);
module_exit(rt_mt6_exit);