[deliverable/linux.git] / net / ipv4 / netfilter / arpt_mangle.c

/* module that allows mangling of the arp payload */
#include <linux/module.h>
#include <linux/netfilter.h>
#include <linux/netfilter_arp/arpt_mangle.h>
#include <net/sock.h>

MODULE_LICENSE("GPL");
MODULE_AUTHOR("Bart De Schuymer <bdschuym@pandora.be>");
MODULE_DESCRIPTION("arptables arp payload mangle target");

static unsigned int
target(struct sk_buff *skb,
       const struct net_device *in, const struct net_device *out,
       unsigned int hooknum, const struct xt_target *target,
       const void *targinfo)
{
	const struct arpt_mangle *mangle = targinfo;
	struct arphdr *arp;
	unsigned char *arpptr;
	int pln, hln;

	if (skb_make_writable(skb, skb->len))
		return NF_DROP;

	arp = arp_hdr(skb);
	arpptr = skb_network_header(skb) + sizeof(*arp);
	pln = arp->ar_pln;
	hln = arp->ar_hln;
	/* We assume that pln and hln were checked in the match */
	if (mangle->flags & ARPT_MANGLE_SDEV) {
		if (ARPT_DEV_ADDR_LEN_MAX < hln ||
		   (arpptr + hln > skb_tail_pointer(skb)))
			return NF_DROP;
		memcpy(arpptr, mangle->src_devaddr, hln);
	}
	arpptr += hln;
	if (mangle->flags & ARPT_MANGLE_SIP) {
		if (ARPT_MANGLE_ADDR_LEN_MAX < pln ||
		   (arpptr + pln > skb_tail_pointer(skb)))
			return NF_DROP;
		memcpy(arpptr, &mangle->u_s.src_ip, pln);
	}
	arpptr += pln;
	if (mangle->flags & ARPT_MANGLE_TDEV) {
		if (ARPT_DEV_ADDR_LEN_MAX < hln ||
		   (arpptr + hln > skb_tail_pointer(skb)))
			return NF_DROP;
		memcpy(arpptr, mangle->tgt_devaddr, hln);
	}
	arpptr += hln;
	if (mangle->flags & ARPT_MANGLE_TIP) {
		if (ARPT_MANGLE_ADDR_LEN_MAX < pln ||
		   (arpptr + pln > skb_tail_pointer(skb)))
			return NF_DROP;
		memcpy(arpptr, &mangle->u_t.tgt_ip, pln);
	}
	return mangle->target;
}

static bool
checkentry(const char *tablename, const void *e, const struct xt_target *target,
	   void *targinfo, unsigned int hook_mask)
{
	const struct arpt_mangle *mangle = targinfo;

	if (mangle->flags & ~ARPT_MANGLE_MASK ||
	    !(mangle->flags & ARPT_MANGLE_MASK))
		return false;

	if (mangle->target != NF_DROP && mangle->target != NF_ACCEPT &&
	   mangle->target != ARPT_CONTINUE)
		return false;
	return true;
}

static struct arpt_target arpt_mangle_reg __read_mostly = {
	.name		= "mangle",
	.target		= target,
	.targetsize	= sizeof(struct arpt_mangle),
	.checkentry	= checkentry,
	.me		= THIS_MODULE,
};

static int __init arpt_mangle_init(void)
{
	if (arpt_register_target(&arpt_mangle_reg))
		return -EINVAL;

	return 0;
}

static void __exit arpt_mangle_fini(void)
{
	arpt_unregister_target(&arpt_mangle_reg);
}

module_init(arpt_mangle_init);
module_exit(arpt_mangle_fini);
Commit	Line	Data
1da177e4 LT	1	/* module that allows mangling of the arp payload */
1da177e4 LT	2	#include <linux/module.h>
2ca7b0ac	3	#include <linux/netfilter.h>
1da177e4 LT	4	#include <linux/netfilter_arp/arpt_mangle.h>
	5	#include <net/sock.h>
	6
	7	MODULE_LICENSE("GPL");
	8	MODULE_AUTHOR("Bart De Schuymer <bdschuym@pandora.be>");
	9	MODULE_DESCRIPTION("arptables arp payload mangle target");
	10
	11	static unsigned int
3db05fea	12	target(struct sk_buff *skb,
c4986734 PM	13	const struct net_device in, const struct net_device out,
c4986734 PM	14	unsigned int hooknum, const struct xt_target *target,
fe1cb108	15	const void *targinfo)
1da177e4 LT	16	{
	17	const struct arpt_mangle *mangle = targinfo;
	18	struct arphdr *arp;
	19	unsigned char *arpptr;
	20	int pln, hln;
	21
3db05fea	22	if (skb_make_writable(skb, skb->len))
2ca7b0ac	23	return NF_DROP;
1da177e4	24
3db05fea HX	25	arp = arp_hdr(skb);
3db05fea HX	26	arpptr = skb_network_header(skb) + sizeof(*arp);
1da177e4 LT	27	pln = arp->ar_pln;
	28	hln = arp->ar_hln;
	29	/* We assume that pln and hln were checked in the match */
	30	if (mangle->flags & ARPT_MANGLE_SDEV) {
	31	if (ARPT_DEV_ADDR_LEN_MAX < hln \|\|
3db05fea	32	(arpptr + hln > skb_tail_pointer(skb)))
1da177e4 LT	33	return NF_DROP;
	34	memcpy(arpptr, mangle->src_devaddr, hln);
	35	}
	36	arpptr += hln;
	37	if (mangle->flags & ARPT_MANGLE_SIP) {
	38	if (ARPT_MANGLE_ADDR_LEN_MAX < pln \|\|
3db05fea	39	(arpptr + pln > skb_tail_pointer(skb)))
1da177e4 LT	40	return NF_DROP;
	41	memcpy(arpptr, &mangle->u_s.src_ip, pln);
	42	}
	43	arpptr += pln;
	44	if (mangle->flags & ARPT_MANGLE_TDEV) {
	45	if (ARPT_DEV_ADDR_LEN_MAX < hln \|\|
3db05fea	46	(arpptr + hln > skb_tail_pointer(skb)))
1da177e4 LT	47	return NF_DROP;
	48	memcpy(arpptr, mangle->tgt_devaddr, hln);
	49	}
	50	arpptr += hln;
	51	if (mangle->flags & ARPT_MANGLE_TIP) {
	52	if (ARPT_MANGLE_ADDR_LEN_MAX < pln \|\|
3db05fea	53	(arpptr + pln > skb_tail_pointer(skb)))
1da177e4 LT	54	return NF_DROP;
	55	memcpy(arpptr, &mangle->u_t.tgt_ip, pln);
	56	}
	57	return mangle->target;
	58	}
	59
e1931b78	60	static bool
c4986734	61	checkentry(const char tablename, const void e, const struct xt_target *target,
e905a9ed	62	void *targinfo, unsigned int hook_mask)
1da177e4 LT	63	{
	64	const struct arpt_mangle *mangle = targinfo;
	65
	66	if (mangle->flags & ~ARPT_MANGLE_MASK \|\|
	67	!(mangle->flags & ARPT_MANGLE_MASK))
e1931b78	68	return false;
1da177e4 LT	69
	70	if (mangle->target != NF_DROP && mangle->target != NF_ACCEPT &&
	71	mangle->target != ARPT_CONTINUE)
e1931b78 JE	72	return false;
e1931b78 JE	73	return true;
1da177e4 LT	74	}
1da177e4 LT	75
9f15c530	76	static struct arpt_target arpt_mangle_reg __read_mostly = {
aa83c1ab PM	77	.name = "mangle",
	78	.target = target,
	79	.targetsize = sizeof(struct arpt_mangle),
	80	.checkentry = checkentry,
	81	.me = THIS_MODULE,
1da177e4 LT	82	};
1da177e4 LT	83
65b4b4e8	84	static int __init arpt_mangle_init(void)
1da177e4 LT	85	{
	86	if (arpt_register_target(&arpt_mangle_reg))
	87	return -EINVAL;
	88
	89	return 0;
	90	}
	91
65b4b4e8	92	static void __exit arpt_mangle_fini(void)
1da177e4 LT	93	{
	94	arpt_unregister_target(&arpt_mangle_reg);
	95	}
	96
65b4b4e8 AM	97	module_init(arpt_mangle_init);
65b4b4e8 AM	98	module_exit(arpt_mangle_fini);