// SPDX-License-Identifier: GPL-2.0-only
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/*
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* ebt_arpreply
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*
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* Authors:
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* Grzegorz Borowiak <grzes@gnu.univ.gda.pl>
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* Bart De Schuymer <bdschuym@pandora.be>
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*
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* August, 2003
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*
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*/
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#include <linux/if_arp.h>
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#include <net/arp.h>
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#include <linux/module.h>
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#include <linux/netfilter/x_tables.h>
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#include <linux/netfilter_bridge/ebtables.h>
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#include <linux/netfilter_bridge/ebt_arpreply.h>
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static unsigned int
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ebt_arpreply_tg(struct sk_buff *skb, const struct xt_action_param *par)
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{
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const struct ebt_arpreply_info *info = par->targinfo;
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const __be32 *siptr, *diptr;
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__be32 _sip, _dip;
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const struct arphdr *ap;
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struct arphdr _ah;
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const unsigned char *shp;
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unsigned char _sha[ETH_ALEN];
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ap = skb_header_pointer(skb, 0, sizeof(_ah), &_ah);
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if (ap == NULL)
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return EBT_DROP;
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if (ap->ar_op != htons(ARPOP_REQUEST) ||
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ap->ar_hln != ETH_ALEN ||
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ap->ar_pro != htons(ETH_P_IP) ||
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ap->ar_pln != 4)
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return EBT_CONTINUE;
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shp = skb_header_pointer(skb, sizeof(_ah), ETH_ALEN, &_sha);
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if (shp == NULL)
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return EBT_DROP;
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siptr = skb_header_pointer(skb, sizeof(_ah) + ETH_ALEN,
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sizeof(_sip), &_sip);
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if (siptr == NULL)
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return EBT_DROP;
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diptr = skb_header_pointer(skb,
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sizeof(_ah) + 2 * ETH_ALEN + sizeof(_sip),
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sizeof(_dip), &_dip);
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if (diptr == NULL)
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return EBT_DROP;
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arp_send(ARPOP_REPLY, ETH_P_ARP, *siptr,
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(struct net_device *)xt_in(par),
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*diptr, shp, info->mac, shp);
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return info->target;
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}
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static int ebt_arpreply_tg_check(const struct xt_tgchk_param *par)
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{
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const struct ebt_arpreply_info *info = par->targinfo;
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const struct ebt_entry *e = par->entryinfo;
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if (BASE_CHAIN && info->target == EBT_RETURN)
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return -EINVAL;
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if (e->ethproto != htons(ETH_P_ARP) ||
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e->invflags & EBT_IPROTO)
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return -EINVAL;
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if (ebt_invalid_target(info->target))
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return -EINVAL;
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return 0;
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}
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static struct xt_target ebt_arpreply_tg_reg __read_mostly = {
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.name = "arpreply",
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.revision = 0,
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.family = NFPROTO_BRIDGE,
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.table = "nat",
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.hooks = (1 << NF_BR_NUMHOOKS) | (1 << NF_BR_PRE_ROUTING),
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.target = ebt_arpreply_tg,
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.checkentry = ebt_arpreply_tg_check,
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.targetsize = sizeof(struct ebt_arpreply_info),
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.me = THIS_MODULE,
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};
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static int __init ebt_arpreply_init(void)
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{
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return xt_register_target(&ebt_arpreply_tg_reg);
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}
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static void __exit ebt_arpreply_fini(void)
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{
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xt_unregister_target(&ebt_arpreply_tg_reg);
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}
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module_init(ebt_arpreply_init);
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module_exit(ebt_arpreply_fini);
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MODULE_DESCRIPTION("Ebtables: ARP reply target");
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MODULE_LICENSE("GPL");
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