98 lines
2.2 KiB
C
98 lines
2.2 KiB
C
/*
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* ebt_snat
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*
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* Authors:
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* Bart De Schuymer <bdschuym@pandora.be>
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*
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* June, 2002
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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_nat.h>
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#include <linux/module.h>
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#include <net/sock.h>
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#include <linux/if_arp.h>
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#include <net/arp.h>
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static int ebt_target_snat(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_nat_info *info = (struct ebt_nat_info *) data;
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if (skb_shared(*pskb) || skb_cloned(*pskb)) {
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struct sk_buff *nskb;
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nskb = skb_copy(*pskb, GFP_ATOMIC);
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if (!nskb)
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return NF_DROP;
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if ((*pskb)->sk)
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skb_set_owner_w(nskb, (*pskb)->sk);
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kfree_skb(*pskb);
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*pskb = nskb;
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}
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memcpy(eth_hdr(*pskb)->h_source, info->mac, ETH_ALEN);
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if (!(info->target & NAT_ARP_BIT) &&
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eth_hdr(*pskb)->h_proto == htons(ETH_P_ARP)) {
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struct arphdr _ah, *ap;
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ap = skb_header_pointer(*pskb, 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_hln != ETH_ALEN)
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goto out;
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if (skb_store_bits(*pskb, sizeof(_ah), info->mac,ETH_ALEN))
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return EBT_DROP;
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}
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out:
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return info->target | ~EBT_VERDICT_BITS;
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}
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static int ebt_target_snat_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_nat_info *info = (struct ebt_nat_info *) data;
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int tmp;
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if (datalen != EBT_ALIGN(sizeof(struct ebt_nat_info)))
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return -EINVAL;
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tmp = info->target | ~EBT_VERDICT_BITS;
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if (BASE_CHAIN && tmp == EBT_RETURN)
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return -EINVAL;
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CLEAR_BASE_CHAIN_BIT;
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if (strcmp(tablename, "nat"))
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return -EINVAL;
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if (hookmask & ~(1 << NF_BR_POST_ROUTING))
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return -EINVAL;
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if (tmp < -NUM_STANDARD_TARGETS || tmp >= 0)
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return -EINVAL;
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tmp = info->target | EBT_VERDICT_BITS;
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if ((tmp & ~NAT_ARP_BIT) != ~NAT_ARP_BIT)
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return -EINVAL;
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return 0;
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}
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static struct ebt_target snat =
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{
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.name = EBT_SNAT_TARGET,
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.target = ebt_target_snat,
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.check = ebt_target_snat_check,
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.me = THIS_MODULE,
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};
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static int __init ebt_snat_init(void)
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{
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return ebt_register_target(&snat);
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}
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static void __exit ebt_snat_fini(void)
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{
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ebt_unregister_target(&snat);
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}
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module_init(ebt_snat_init);
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module_exit(ebt_snat_fini);
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MODULE_LICENSE("GPL");
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