// 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->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);