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/net/bridge/netfilter/ebt_arpreply.c

http://github.com/mirrors/linux
C | 103 lines | 77 code | 15 blank | 11 comment | 19 complexity | f0bdccf018ec4ca5f67da45b6f82e8ef MD5 | raw file
  1// SPDX-License-Identifier: GPL-2.0-only
  2/*
  3 *  ebt_arpreply
  4 *
  5 *	Authors:
  6 *	Grzegorz Borowiak <grzes@gnu.univ.gda.pl>
  7 *	Bart De Schuymer <bdschuym@pandora.be>
  8 *
  9 *  August, 2003
 10 *
 11 */
 12#include <linux/if_arp.h>
 13#include <net/arp.h>
 14#include <linux/module.h>
 15#include <linux/netfilter/x_tables.h>
 16#include <linux/netfilter_bridge/ebtables.h>
 17#include <linux/netfilter_bridge/ebt_arpreply.h>
 18
 19static unsigned int
 20ebt_arpreply_tg(struct sk_buff *skb, const struct xt_action_param *par)
 21{
 22	const struct ebt_arpreply_info *info = par->targinfo;
 23	const __be32 *siptr, *diptr;
 24	__be32 _sip, _dip;
 25	const struct arphdr *ap;
 26	struct arphdr _ah;
 27	const unsigned char *shp;
 28	unsigned char _sha[ETH_ALEN];
 29
 30	ap = skb_header_pointer(skb, 0, sizeof(_ah), &_ah);
 31	if (ap == NULL)
 32		return EBT_DROP;
 33
 34	if (ap->ar_op != htons(ARPOP_REQUEST) ||
 35	    ap->ar_hln != ETH_ALEN ||
 36	    ap->ar_pro != htons(ETH_P_IP) ||
 37	    ap->ar_pln != 4)
 38		return EBT_CONTINUE;
 39
 40	shp = skb_header_pointer(skb, sizeof(_ah), ETH_ALEN, &_sha);
 41	if (shp == NULL)
 42		return EBT_DROP;
 43
 44	siptr = skb_header_pointer(skb, sizeof(_ah) + ETH_ALEN,
 45				   sizeof(_sip), &_sip);
 46	if (siptr == NULL)
 47		return EBT_DROP;
 48
 49	diptr = skb_header_pointer(skb,
 50				   sizeof(_ah) + 2 * ETH_ALEN + sizeof(_sip),
 51				   sizeof(_dip), &_dip);
 52	if (diptr == NULL)
 53		return EBT_DROP;
 54
 55	arp_send(ARPOP_REPLY, ETH_P_ARP, *siptr,
 56		 (struct net_device *)xt_in(par),
 57		 *diptr, shp, info->mac, shp);
 58
 59	return info->target;
 60}
 61
 62static int ebt_arpreply_tg_check(const struct xt_tgchk_param *par)
 63{
 64	const struct ebt_arpreply_info *info = par->targinfo;
 65	const struct ebt_entry *e = par->entryinfo;
 66
 67	if (BASE_CHAIN && info->target == EBT_RETURN)
 68		return -EINVAL;
 69	if (e->ethproto != htons(ETH_P_ARP) ||
 70	    e->invflags & EBT_IPROTO)
 71		return -EINVAL;
 72	if (ebt_invalid_target(info->target))
 73		return -EINVAL;
 74
 75	return 0;
 76}
 77
 78static struct xt_target ebt_arpreply_tg_reg __read_mostly = {
 79	.name		= "arpreply",
 80	.revision	= 0,
 81	.family		= NFPROTO_BRIDGE,
 82	.table		= "nat",
 83	.hooks		= (1 << NF_BR_NUMHOOKS) | (1 << NF_BR_PRE_ROUTING),
 84	.target		= ebt_arpreply_tg,
 85	.checkentry	= ebt_arpreply_tg_check,
 86	.targetsize	= sizeof(struct ebt_arpreply_info),
 87	.me		= THIS_MODULE,
 88};
 89
 90static int __init ebt_arpreply_init(void)
 91{
 92	return xt_register_target(&ebt_arpreply_tg_reg);
 93}
 94
 95static void __exit ebt_arpreply_fini(void)
 96{
 97	xt_unregister_target(&ebt_arpreply_tg_reg);
 98}
 99
100module_init(ebt_arpreply_init);
101module_exit(ebt_arpreply_fini);
102MODULE_DESCRIPTION("Ebtables: ARP reply target");
103MODULE_LICENSE("GPL");