net/bridge/netfilter/ebt_snat.c

   1 /*
   2  *  ebt_snat
   3  *
   4  *      Authors:
   5  *      Bart De Schuymer <bdschuym@pandora.be>
   6  *
   7  *  June, 2002
   8  *
   9  */
  10
  11 #include <linux/netfilter_bridge/ebtables.h>
  12 #include <linux/netfilter_bridge/ebt_nat.h>
  13 #include <linux/module.h>
  14 #include <net/sock.h>
  15
  16 static int ebt_target_snat(struct sk_buff **pskb, unsigned int hooknr,
  17    const struct net_device *in, const struct net_device *out,
  18    const void *data, unsigned int datalen)
  19 {
  20         struct ebt_nat_info *info = (struct ebt_nat_info *) data;
  21
  22         if (skb_shared(*pskb) || skb_cloned(*pskb)) {
  23                 struct sk_buff *nskb;
  24
  25                 nskb = skb_copy(*pskb, GFP_ATOMIC);
  26                 if (!nskb)
  27                         return NF_DROP;
  28                 if ((*pskb)->sk)
  29                         skb_set_owner_w(nskb, (*pskb)->sk);
  30                 kfree_skb(*pskb);
  31                 *pskb = nskb;
  32         }
  33         memcpy(eth_hdr(*pskb)->h_source, info->mac, ETH_ALEN);
  34         return info->target;
  35 }
  36
  37 static int ebt_target_snat_check(const char *tablename, unsigned int hookmask,
  38    const struct ebt_entry *e, void *data, unsigned int datalen)
  39 {
  40         struct ebt_nat_info *info = (struct ebt_nat_info *) data;
  41
  42         if (datalen != EBT_ALIGN(sizeof(struct ebt_nat_info)))
  43                 return -EINVAL;
  44         if (BASE_CHAIN && info->target == EBT_RETURN)
  45                 return -EINVAL;
  46         CLEAR_BASE_CHAIN_BIT;
  47         if (strcmp(tablename, "nat"))
  48                 return -EINVAL;
  49         if (hookmask & ~(1 << NF_BR_POST_ROUTING))
  50                 return -EINVAL;
  51         if (INVALID_TARGET)
  52                 return -EINVAL;
  53         return 0;
  54 }
  55
  56 static struct ebt_target snat =
  57 {
  58         .name           = EBT_SNAT_TARGET,
  59         .target         = ebt_target_snat,
  60         .check          = ebt_target_snat_check,
  61         .me             = THIS_MODULE,
  62 };
  63
  64 static int __init ebt_snat_init(void)
  65 {
  66         return ebt_register_target(&snat);
  67 }
  68
  69 static void __exit ebt_snat_fini(void)
  70 {
  71         ebt_unregister_target(&snat);
  72 }
  73
  74 module_init(ebt_snat_init);
  75 module_exit(ebt_snat_fini);
  76 MODULE_LICENSE("GPL");