98 lines
2.3 KiB
C
98 lines
2.3 KiB
C
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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/netfilter_bridge/ebtables.h>
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#include <linux/netfilter_bridge/ebt_arpreply.h>
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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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static int ebt_target_reply(struct sk_buff **pskb, unsigned int hooknr,
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const struct net_device *in, const struct net_device *out,
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const void *data, unsigned int datalen)
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{
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struct ebt_arpreply_info *info = (struct ebt_arpreply_info *)data;
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u32 _sip, *siptr, _dip, *diptr;
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struct arphdr _ah, *ap;
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unsigned char _sha[ETH_ALEN], *shp;
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struct sk_buff *skb = *pskb;
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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, (struct net_device *)in,
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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_target_reply_check(const char *tablename, unsigned int hookmask,
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const struct ebt_entry *e, void *data, unsigned int datalen)
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{
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struct ebt_arpreply_info *info = (struct ebt_arpreply_info *)data;
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if (datalen != EBT_ALIGN(sizeof(struct ebt_arpreply_info)))
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return -EINVAL;
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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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CLEAR_BASE_CHAIN_BIT;
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if (strcmp(tablename, "nat") || hookmask & ~(1 << NF_BR_PRE_ROUTING))
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return -EINVAL;
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return 0;
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}
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static struct ebt_target reply_target =
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{
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.name = EBT_ARPREPLY_TARGET,
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.target = ebt_target_reply,
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.check = ebt_target_reply_check,
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.me = THIS_MODULE,
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};
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static int __init init(void)
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{
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return ebt_register_target(&reply_target);
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}
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static void __exit fini(void)
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{
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ebt_unregister_target(&reply_target);
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}
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module_init(init);
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module_exit(fini);
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MODULE_LICENSE("GPL");
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