xt_ipaddr.c

#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/skbuff.h>
#include <linux/netfilter.h>
#include <linux/netfilter/x_tables.h>
#include <net/ipv6.h>
#include <linux/ipv6.h>
#include <linux/ip.h>

#include "xt_ipaddr.h"

MODULE_AUTHOR("Me and <my@address.com>");
MODULE_DESCRIPTION("Xtables: Match source/destination address");
MODULE_LICENSE("GPL");
MODULE_ALIAS("ip6t_ipaddr"); 

static bool ipaddr_mt(const struct sk_buff *skb,
		      struct xt_action_param *par)
{
	const struct xt_ipaddr_mtinfo *info = par->matchinfo;
	const struct ipv6hdr *iph = ipv6_hdr(skb);

	pr_info("xt_ipaddr: IN=%s OUT=%s "
		"SRC=%pI6 DST=%pI6 "
		"IPSRC=%pI6 IPDST=%pI6\n",
		(par->in != NULL) ? par->in->name : "",
		(par->out != NULL) ? par->out->name : "",
		&iph->saddr, &iph->daddr,
		&info->src, &info->dst);

	if (info->flags & XT_IPADDR_SRC)
		if ((ipv6_addr_cmp(&iph->saddr, &info->src.in6) != 0) ^
			!!(info->flags & XT_IPADDR_INV_SRC)) {
			pr_notice("src IP - no match\n");
			return false;
		}

	if (info->flags & XT_IPADDR_DST)
		if ((ipv6_addr_cmp(&iph->daddr, &info->dst.in6) != 0) ^
			!!(info->flags & XT_IPADDR_INV_DST)) {
			pr_info("dst IP - no match\n");
			return false;
		}

	return true;
}

static int ipaddr_mt_check(const struct xt_mtchk_param *par)
{
	const struct xt_ipaddr_mtinfo *info = par->matchinfo;

	if(!(info->flags & (XT_IPADDR_SRC | XT_IPADDR_DST))) {
		pr_info("not testing anything\n");
		return -EINVAL;
	}

	if (ntohl(info->src.ip6[0]) == 0x20010DB8) {
		/* Disallow test network 2001:db8::/32 */
		pr_info("I'm sorry, Dave. "
			"I'm afraid I can't let you do that.\n");
		return -EPERM;
	}

	return 0;
}

static void ipaddr_mt_destroy(const struct xt_mtdtor_param *par)
{
	const struct xt_ipaddr_mtinfo *info = par->matchinfo;
	
	pr_info("Test for address %pI6 removed\n",
		&info->src.ip6);
}

static bool ipaddr_mt4(const struct sk_buff *skb,
		       struct xt_action_param *par)
{
	const struct xt_ipaddr_mtinfo *info = par->matchinfo;
	const struct iphdr *iph = ip_hdr(skb);

	if (info->flags & XT_IPADDR_SRC)
		if ((iph->saddr != info->src.ip) ^
			!!(info->flags & XT_IPADDR_INV_SRC))
			return false;

	if (info->flags & XT_IPADDR_DST)
		if ((iph->daddr != info->dst.ip) ^
				!! (info->flags & XT_IPADDR_INV_SRC))
			return false;

	return true;
}

static struct xt_match ipaddr_mt4_reg __read_mostly = {
	.name = "ipaddr",
	.revision = 0,
	.family = NFPROTO_IPV6,
	.match = ipaddr_mt4,
	.matchsize = sizeof(struct xt_ipaddr_mtinfo),
	.me = THIS_MODULE,
};

static struct xt_match ipaddr_mt_reg __read_mostly = {
	.name = "ipaddr",
	.revision = 0,
	.family = NFPROTO_IPV6,
	.match = ipaddr_mt,
	.checkentry = ipaddr_mt_check,
	.destroy = ipaddr_mt_destroy,
	.matchsize = sizeof(struct xt_ipaddr_mtinfo),
	.me = THIS_MODULE,
};

static int __init ipaddr_mt_init(void)
{
	int ret;

	ret =  xt_register_match(&ipaddr_mt_reg);
	if (ret < 0)
		return ret;

	ret =  xt_register_match(&ipaddr_mt4_reg);
	if (ret < 0) {
		xt_unregister_match(&ipaddr_mt_reg);
		return ret;
	}

	return 0;
}

static void __exit ipaddr_mt_exit(void)
{
	xt_unregister_match(&ipaddr_mt_reg);
	xt_unregister_match(&ipaddr_mt4_reg);
}

module_init(ipaddr_mt_init);
module_exit(ipaddr_mt_exit);