net/ipv6/netfilter/ip6t_eui64.c

// SPDX-License-Identifier: GPL-2.0-only
/* Kernel module to match EUI64 address parameters. */

/* (C) 2001-2002 Andras Kis-Szabo <kisza@sch.bme.hu>
 */

#include <linux/module.h>
#include <linux/skbuff.h>
#include <linux/ipv6.h>
#include <linux/if_ether.h>

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

MODULE_DESCRIPTION("Xtables: IPv6 EUI64 address match");
MODULE_LICENSE("GPL");
MODULE_AUTHOR("Andras Kis-Szabo <kisza@sch.bme.hu>");

static bool
eui64_mt6(const struct sk_buff *skb, struct xt_action_param *par)
{
	unsigned char eui64[8];

	if (!(skb_mac_header(skb) >= skb->head &&
	      skb_mac_header(skb) + ETH_HLEN <= skb->data) &&
	    par->fragoff != 0) {
		par->hotdrop = true;
		return false;
	}

	memset(eui64, 0, sizeof(eui64));

	if (eth_hdr(skb)->h_proto == htons(ETH_P_IPV6)) {
		if (ipv6_hdr(skb)->version == 0x6) {
			memcpy(eui64, eth_hdr(skb)->h_source, 3);
			memcpy(eui64 + 5, eth_hdr(skb)->h_source + 3, 3);
			eui64[3] = 0xff;
			eui64[4] = 0xfe;
			eui64[0] ^= 0x02;

			if (!memcmp(ipv6_hdr(skb)->saddr.s6_addr + 8, eui64,
				    sizeof(eui64)))
				return true;
		}
	}

	return false;
}

static struct xt_match eui64_mt6_reg __read_mostly = {
	.name		= "eui64",
	.family		= NFPROTO_IPV6,
	.match		= eui64_mt6,
	.matchsize	= sizeof(int),
	.hooks		= (1 << NF_INET_PRE_ROUTING) | (1 << NF_INET_LOCAL_IN) |
			  (1 << NF_INET_FORWARD),
	.me		= THIS_MODULE,
};

static int __init eui64_mt6_init(void)
{
	return xt_register_match(&eui64_mt6_reg);
}

static void __exit eui64_mt6_exit(void)
{
	xt_unregister_match(&eui64_mt6_reg);
}

module_init(eui64_mt6_init);
module_exit(eui64_mt6_exit);